Separation of hydrogen isotopes

Separation of Hydrogen Isotopes H o w a r d K . Rae, EDITOR Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068...

Author: Howard K. Rae

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Separation of Hydrogen Isotopes H o w a r d K . Rae,

EDITOR

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.fw001

Atomic Energy of Canada, Limited

A symposium co-sponsored by the Physical Chemistry Division of the Chemical Institute of Canada and the Canadian Society for Chemical Engineering at the 2nd Joint Conference of the Chemical Institute of Canada and the American Chemical Society, Montreal, May 30-June 1,

1977.

ACS SYMPOSIUM SERIES 68

AMERICAN

CHEMICAL

WASHINGTON, D. C.

SOCIETY 1978

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.fw001

Library of Congress CIP Data Main entry under title: Separation of hydrogen isotopes. (ACS symposium series; 68 ISSN 0097-6156) Includes bibliographies and index. 1. Deuterium oxide—Congresses. 2. Hydrogen—Isotopes—Congresses. 3. Isotope separation—Congresses. 4. Heavy water reactors—Congresses. I. Rae, Howard K . , 1925. II. Chemical Institute of Canada. Physical Chemistry Division. III. Canadian Society for Chemical Engineering. IV. Series: American Chemical Society. ACS symposium series; 68. TK9350.S46 ISBN 0-8412-0420-9

661'.08 ASCMC8

68

78-760 1-184 1978

Copyright © 1978 American Chemical Society A l l Rights Reserved. The appearance of the code at the bottom of the first page of each article in this volume indicates the copyright owner's consent that reprographic copies of the article may be made for personal or internal use or for the personal or internal use of specific clients. This consent is given on the condition, however, that the copier pay the stated per copy fee through the Copyright Clearance Center, Inc. for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. This consent does not extend to copying or transmission by any means—graphic or electronic—for any other purpose, such as for general distribution, for advertising or promotional purposes, for creating new collective works, for resale, or for information storage and retrieval systems. The citation of trade names and/or names of manufacturers in this publication is not to be construed as an endorsement or as approval by ACS of the commercial products or services referenced herein; nor should the mere reference herein to any drawing, specification, chemical process, or other data be regarded as a license or as a conveyance of any right or permission, to the holder, reader, or any other person or corporation, to manufacture, reproduce, use, or sell any patented invention or copyrighted work that may in any way be related thereto. PRINTED IN T H E UNITED

STATES

OF

AMERICA

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ACS Symposium Series

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.fw001

Robert F. G o u l d , Editor

Advisory Board Kenneth B. Bischoff

Nina I. McClelland

Donald G. Crosby

John B. Pfeiffer

Jeremiah P. Freeman

Joseph V. Rodricks

E. Desmond Goddard

F. Sherwood Rowland

Jack Halpern

Alan C. Sartorelli

Robert A. Hofstader

Raymond B. Seymour

James P. Lodge

Roy L. Whistler

John L. Margrave

Aaron Wold

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.fw001

FOREWORD The ACS SYMPOSIUM SERIES was founded in 1974 to provide

a medium for publishing symposia quickly in book form. The format of the SERIES parallels that of the continuing ADVANCES IN CHEMISTRY SERIES except that in order to save time the papers are not typeset but are reproduced as they are submitted by the authors in camera-ready form. As a further means of saving time, the papers are not edited or reviewed except by the symposium chairman, who becomes editor of the book. Papers published in the ACS SYMPOSIUM SERIES are original contributions not published elsewhere in whole or major part and include reports of research as well as reviews since symposia may embrace both types of presentation.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.pr001

PREFACE '"phis volume describes process development and plant performance -•- for the separation of deuterium from hydrogen, tritium from hydrogen, and tritium from deuterium. All of the important processes that are recognized today are included although not necessarily in equal detail or appropriate relative emphasis. Nonetheless, this volume forms a valuable, up-to-date report on the status of hydrogen isotope separation. Obviously heavy water production is essential to a program of nuclear power production that is based on natural uranium-fueled and heavy water-moderated reactors. Canada and India have selected this route to nuclear power, and both are establishing an industrial heavy water production capability. The Canadian design of a heavy water power reactor, the C A N D U design, requires 0.85 Mg of heavy water per electrical M W of installed capacity. The heavy water is not consumed by reactor operation so that the demand for heavy water is set by the rate at which new nuclear power stations are built. A small make-up of less than 1% of the inventory per year is needed to replace losses by leakage. With 4000 M W of nuclear-electric generating capacity in operation and with 15,000 M W committed for operation by 1988, Canada has a very substantial demand for heavy water. Several large production plants are in operation and more are being built. Thus, it is not surprising that one-half of the papers in this volume are from Canada; the chapters report on plant performance and on the development of alternative processes to the established water-hydrogen-sulfide exchange method. Tritium is produced by neutron capture in deuterium and by uranium fission. Thus, heavy water in reactors contains a gradually increasing concentration of T D O , and aqueous wastes from any water-cooled reactor and from fuel reprocessing contain T H O . Tritium recovery from these sources is desirable to minimize the release of tritium to the biosphere, and such tritium separation plants will become increasingly common. Tritium separation on a much larger scale will be necessary when fusion reactors are developed successfully. Atomic Energy of Canada, Limited Ontario, Canada December, 1977

HOWARD K . R A E

vii

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1 Selecting Heavy Water Processes H . K . RAE

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

Chalk River Nuclear Laboratories, Atomic Energy of Canada Ltd., Chalk River, Ontario, Canada K0J 1J0

Hundreds o f methods have been proposed f o r the p r o d u c t i o n o f heavy water, b u t o n l y a few show any real promise. This paper will d i s c u s s the important characteristics which define relative process a t t r a c t i v e n e s s and will compare s e v e r a l chemical exchange and distillation processes. In this way it will show why the GS ( G i r d l e r - S u l f i d e ) process has dominated heavy water p r o d u c t i o n f o r 25 y e a r s . I t will a l s o review the c u r r e n t s t a t u s o f s e v e r a l promising alternatives. A brief review o f heavy water process development and heavy water p r o d u c t i o n will s e t the background. Deuterium was first separated by the fractional e v a p o r a t i o n o f hydrogen in 1932 by Urey, Brickwedde and Murphy (1). Over the next few years water electrolysis, water distillation and hydrogen distillation were i n v e s t i g a t e d as hydrogen-deuterium s e p a r a t i o n methods. During World War II in the USA, and t o l e s s e r extent in Germany, there was a very l a r g e e f f o r t t o evaluate and develop methods f o r heavy water p r o d u c t i o n ( 2 , 3 ) . Two p r o m i s i n g chemical exchange p r o cesses were defined—water-hydrogen and w a t e r - h y d r o g e n - s u l f i d e . The former was the b a s i s o f the first heavy water p r o d u c t i o n a t a reasonable c o s t from industrial s c a l e p l a n t s . The latter eventu ally became known as the GS p r o c e s s , and the b a s i s o f all l a r g e heavy water p l a n t s . Throughout the f i f t i e s and the s i x t i e s hundreds o f methods were c o n s i d e r e d , dozens were i n v e s t i g a t e d in the l a b o r a t o r y and in p i l o t p l a n t s , but o n l y a handful were used in p r o d u c t i o n (4_) . Major research and development to i n v e s t i g a t e heavy water p r o cesses (A) was done in n e a r l y a l l the c o u n t r i e s t h a t b u i l t p r o t o type heavy water power r e a c t o r s : Canada, F r a n c e , Germany, I n d i a , I t a l y , Sweden, S w i t z e r l a n d and U n i t e d Kingdom. Despite this l a r g e e f f o r t i n v o l v i n g hundreds o f man-years by chemists, p h y s i c i s t s and e n g i n e e r s , no other method has reached the stage where it can challenge the GS process as the major source o f heavy water.

©

0-8412-0420-9/78/47-068-001$10.00/0

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

2

SEPARATION O F

HYDROGEN

ISOTOPES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

Heavy Water Plants So f a r p l a n t o p e r a t i n g experience has been obtained with f i v e processes, as shown in Table I. Monothermal water-vapour-hydrogen exchange, with the e n r i c h e d hydrogen r e f l u x p r o v i d e d by e l e c t r o l y s i s , was used a t T r a i l in Canada (5) and in Norway (5); the l a t t e r p l a n t i s s t i l l in o p e r a t i o n . An improved v e r s i o n o f this process using exchange with l i q u i d water i s d e s c r i b e d by Hammerli (<S) and r e f e r r e d to as combined e l e c t r o l y s i s and chemical exchange (CECE). The o r i g i n a l p l a n t in Norway simply used e l e c t r o l y s i s to produce heavy water. Water-hydrogen exchange u n i t s were being added to the p l a n t in 1943 d u r i n g the German occupation o f Norway when it was destroyed by A l l i e d r a i d s ; the p l a n t was r e b u i l t and expanded a f t e r the war. Water distillation was used as a p r o d u c t i o n method b r i e f l y in three s m a l l p l a n t s during World War II (2). In the USA in 1950 there was a need f o r a l a r g e heavy water p r o d u c t i o n c a p a c i t y and the GS process was chosen as the p r e f e r red method (7). Two 500 Mg/a p l a n t s were b u i l t . One t h i r d of the Savannah R i v e r p l a n t i s s t i l l o p e r a t i n g a f t e r twenty-five y e a r s . The GS process was adopted in Canada in the m i d - s i x t i e s to supply the CANDU* power r e a c t o r program. Current o p e r a t i n g c a p a c i t y in Canada i s 1600 Mg/a in three p l a n t s and three more are being b u i l t (8). In I n d i a a 100 Mg/a GS p l a n t i s a t an advanced stage o f c o n s t r u c t i o n . F i v e small hydrogen distillation p l a n t s have been operated. The p l a n t in I n d i a , of 13 Mg/a c a p a c i t y , continues in o p e r a t i o n (9). The s i z e of the Russian p l a n t has not been reported; it a l s o probably continues in o p e r a t i o n . A 25 Mg/a ammonia-hydrogen p l a n t operated f o r s e v e r a l years in France (10) . The first o f three Indian ammonia-hydrogen p l a n t s , each about 65 Mg/a, (11,12) i s being commissioned. Heavy Water Production The cumulative world production o f heavy water to May 1977 i s 11 Gg (excluding USSR and China). This i s d i s t r i b u t e d by process as f o l l o w s : GS - 93.2%, H2O/H2 exchange - 4.4%, H D i s t i l l a t i o n - 1.3%, NH /H exchange - 0.9% and H 0 D i s t i l l a t i o n - 0.2%. By country, 59% has been produced in the USA, 35% in Canada, 4% in Norway, 1% in India and 1% in France. By about 1982 the Canadian heavy water p r o d u c t i o n c a p a c i t y will be 4000 Mg/a. This will c o n s i s t o f the three o p e r a t i n g p l a n t s — P o r t Hawkesbury in Nova S c o t i a with a nominal design c a p a c i t y o f 400 Mg/a, Bruce A in Ontario o f 800 Mg/a and Glace Bay in Nova S c o t i a o f 400 Mg/a—and three p l a n t s now being b u i l t 2

3

2

2

*Canada Deuterium Uranium

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1.

RAE

Selecting

Heavy

Water

3

Processes

B r u c e Β a n d D, e a c h o f 800 Mg/a n o m i n a l c a p a c i t y , a n d L a P r a d e in Quebec o f 800 Mg/a. T h i s c a p a c i t y i s e x p e c t e d t o meet demands u n t i l a b o u t 1990 (8).

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

General Process

Characteristics

Before c o n s i d e r i n g the v a r i o u s i n d i v i d u a l processes and c o m p a r i n g t h e i r c h a r a c t e r i s t i c s , it i s i m p o r t a n t t o l o o k a t t h e g e n e r a l nature o f the deuterium-hydrogen s e p a r a t i o n problem which d e r i v e s from the low d e u t e r i u m c o n t e n t o f a l l p o t e n t i a l s o u r c e materials. The c o n s e q u e n c e s o f this f o r a n y p r o c e s s c a n be r e a d i l y s e e n in t e r m s o f i t s a f f e c t o n t h e d e s i g n o f GS h e a v y water p l a n t s . T h i s v e r y l o w v a l u e o f t h e d e u t e r i u m - t o - h y d r o g e n r a t i o in n a t u r e *of a b o u t 150 ppm i s t h e m a i n f a c t o r r e s p o n s i b l e f o r t h e h i g h c o s t o f heavy water. I t i s necessary t o process a t l e a s t 8000 m o i s o f f e e d p e r m o l o f p r o d u c t f o r a l l p r o c e s s e s , a n d f o r t h e GS p r o c e s s t h e r a t i o o f f e e d t o p r o d u c t i s n e a r l y 40,000 t o 1. R e a c t o r g r a d e h e a v y w a t e r i s 99.75 m o l % D2O. Thus, the o v e r a l l c o n c e n t r a t i o n r a t i o from feed t o p r o d u c t i s about 3 x l O . T h i s means t h a t h u n d r e d s o f s e p a r a t i v e e l e m e n t s in s e r i e s a r e n e e d e d t o go f r o m n a t u r a l w a t e r t o r e a c t o r g r a d e h e a v y w a t e r . The c o m b i n a t i o n o f a v e r y l a r g e f e e d f l o w a n d a v e r y l a r g e number o f s e p a r a t i v e e l e m e n t s means t h a t h e a v y w a t e r p l a n t s a r e v e r y l a r g e in r e l a t i o n t o most o t h e r c h e m i c a l p l a n t s . A s a consequence heavy water i s an e x t r e m e l y c a p i t a l i n t e n s i v e p r o d u c t . F i g u r e 1 shows t h e G l a c e Bay Heavy Water P l a n t . The first s t a g e t o w e r s a r e a b o u t 7 m in d i a m e t e r a n d 60 m h i g h . F e e d w a t e r goes t o s i x o f t h e s e t o w e r s in p a r a l l e l a t a t o t a l f l o w r a t e o f a b o u t 40,000 m /d ( 1 0 US g a l l o n s / d a y ) . T o t a l h e a t r e j e c t i o n b y t h e p l a n t i s 300 t h e r m a l MW, m a i n l y b y c o o l i n g t o w e r s a t t h e r i g h t o f the photograph. The e f f l u e n t w a t e r i s c o o l e d b y s p r a y m o d u l e s in the e f f l u e n t channel a t the l e f t o f the photograph. The c o m b i n a t i o n o f a d i l u t e f e e d a n d a l a r g e o v e r a l l c o n c e n t r a t i o n r a t i o means t h a t c a s c a d i n g c o n f e r s v e r y i m p o r t a n t a d v a n tages. F i g u r e 2 i l l u s t r a t e s three cascade arrangements f o r a t y p i c a l GS p r o c e s s d e s i g n . I n e a c h c a s e t h e p r o d u c t i s 2 0 % D2O. I n t h e t w o - s t a g e a r r a n g e m e n t t h e first s t a g e g i v e s a t e n - f o l d enrichment. I n the t h r e e - s t a g e arrangement the first stage gives a f o u r - f o l d enrichment w h i l e the second stage p r o v i d e s a f u r t h e r s i x - f o l d enrichment. The r e l a t i v e t o w e r v o l u m e s show a 30% decrease f o r the two-stage case and a f u r t h e r 10% r e d u c t i o n f o r t h e t h r e e - s t a g e c a s e . The change in h e a v y w a t e r i n v e n t o r y i s more d r a m a t i c . I n the s i n g l e stage case the i n v e n t o r y approaches t h e a n n u a l p l a n t c a p a c i t y . F o r two s t a g e s this i s r e d u c e d b y a n o r d e r o f magnitude and f o r t h r e e stages i s reduced f u r t h e r by a f a c t o r o f two. A d d i n g more s t a g e s i s n o t w o r t h w h i l e s i n c e e a c h s t a g e adds e x t r a e q u i p m e n t a n d i n c r e a s e s p l a n t c o m p l e x i t y . I n a l l c a s e s t h e first s t a g e d o m i n a t e s p l a n t c o s t s . Thus, when c o m p a r i n g p r o c e s s e s it i s g e n e r a l l y o n l y this first stage 6

3

7

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

4

SEPARATION OF HYDROGEN ISOTOPES

Table I HEAVY WATER PRODUCTION PLANTS

First Plant

Operating Capacity 1977 Mg/a

19 34

30

Number o f P l a n t s Process

H 0/H 2

Country

P

e r a

. 9

l n

Being Built

NOR.,* CAN

2

H2O D i s t n

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

Shut Down

GS H2 D i s t n

USA

1944

USA, CAN, IND

1952

1800

W. GER, RUS FR, SWIT, IND

1958

>13

NH3/H2

FR,

* electrolysis

1968

IND

o n l y u n t i l 1948.

Figure 1.

Glace Bay heavy water plant

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1.

RAE

Selecting

Heavy

Water

5

Processes

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

t h a t needs t o be c o n s i d e r e d . F i g u r e 3 i l l u s t r a t e s a t h r e e - s t a g e GS p r o c e s s d e s i g n s h o w i n g t h e r e l a t i v e m o l a r f l o w r a t e s o f w a t e r a n d h y d r o g e n s u l f i d e in e a c h s t a g e a n d t h e v a r i o u s i n t e r s t a g e c o n n e c t i o n s . The r e l a t i v e tower s i z e s a r e a l s o i l l u s t r a t e d . Because o f t h e v e r y l a r g e f l o w s r e q u i r e d in t h e first s t a g e it i s n e c e s s a r y t o have s e v e r a l l a r g e t o w e r s in p a r a l l e l ; t h r e e a r e shown in this e x a m p l e . The p r o d u c t f r o m t h e t h i r d GS s t a g e i s 2 0 % D2O. I t i s b r o u g h t t o r e a c t o r grade by water distillation w h i c h i s a much s i m p l e r p r o cess o p e r a t i n g a t low p r e s s u r e w i t h a low p o t e n t i a l f o r leakage. T h i s f i n a l e n r i c h m e n t u n i t r e p r e s e n t s l e s s t h a n 5% o f t h e t o t a l p l a n t i n v e s t m e n t . N e a r l y a l l h e a v y w a t e r p l a n t s have b e e n designed w i t h d i f f e r e n t p r o c e s s e s f o r p r i m a r y enrichment and f i n a l enrichment (13). Types o f P r o c e s s e s Table I I i s a p a r t i a l l i s t o f the types o f processes t h a t have been c o n s i d e r e d f o r heavy w a t e r p r o d u c t i o n . D i s t i l l a t i o n i s one o f t h e s i m p l e s t . However, t o w e r volume i s e x c e s s i v e f o r a l l p o t e n t i a l working substances except hydrogen itself. The most p r o m i s i n g p r o c e s s e s a r e b a s e d o n c h e m i c a l e x c h a n g e . I r r e v e r s i b l e p r o c e s s e s l i k e d i f f u s i o n have h i g h e n e r g y c o s t s and v e r y l a r g e membrane o r b a r r i e r a r e a s a r e n e e d e d . B o t h e l e c t r o l y s i s and g r a v i t a t i o n a l processes, w h i l e o f f e r i n g f a i r l y h i g h s e p a r a t i o n f a c t o r s , a r e v e r y e n e r g y i n t e n s i v e a n d f o r this r e a s o n unattractive. Adsorption processes are not p a r t i c u l a r l y s e l e c t i v e f o r deuterium and t h e r e f o r e r e q u i r e v e r y l a r g e volumes o f a d s o r b e n t . B i o l o g i c a l p r o c e s s e s have t h e same s h o r t c o m i n g s a s a d s o r p t i o n ,

Table I I POSSIBLE HEAVY WATER PROCESSES P r o c e s s Type Distillation C h e m i c a l Exchange Diffusion Electrolysis Gravitational Adsorption Biological Crystallization S e l e c t i v e Photochemical

Status S i z e E x c e s s i v e E x c e p t H2 Most P r o m i s i n g B a r r i e r o r Membrane C o s t s E x c e s s i v e ; High Energy E x c e s s i v e Energy E x c e s s i v e Energy H i g h A d s o r b e n t Volume E x c e s s i v e Volume I m p r a c t i c a l on Large S c a l e Promising i f S e l e c t i v i t y A p p r o a c h e s 10

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

SEPARATION O F H Y D R O G E N ISOTOPES

SINGLE STAGE

TWO STAGES

THREE STAGES

RELATIVE TOWER VOLUME

1

0.7

0.6

RELATIVE PROCESS INVENTORY

1

0.12

Figure 2.

0.05

GS process cascades

Figure 3.

GS flowsheet

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1.

RAE

Selecting

Heavy

Water

7

Processes

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

and h e n c e r e q u i r e t h e p r o d u c t i o n o f e x c e s s i v e amounts o f deuterium-depleted organisms. C o u n t e r c u r r e n t c r y s t a l i z a t i o n systems ( i c e - w a t e r ) c a n con c e i v a b l y h a v e v e r y l a r g e numbers o f s e p a r a t i n g e l e m e n t s in a r e a s o n a b l e volume a n d h a v e a l o w e n e r g y r e q u i r e m e n t ; h o w e v e r , a r e a s o n a b l e p r o c e s s i n g r a t e c a n o n l y be a c h i e v e d w i t h an i m practically small crystal size (14). S e l e c t i v e photochemical processes are a t too e a r l y a stage to assess p r o p e r l y . I f s u c c e s s i s t o be a c h i e v e d f o r d e u t e r i u m hydrogen s e p a r a t i o n , a v e r y h i g h s e l e c t i v i t y i s needed t o o f f s e t t h e d i s a d v a n t a g e o f t h e low n a t u r a l abundance o f d e u t e r i u m . The r e m a i n d e r o f t h e p a p e r will r e v i e w distillation and c h e m i c a l e x c h a n g e p r o c e s s e s in more d e t a i l . Separation Factor One o f t h e m o s t i m p o r t a n t p a r a m e t e r s in d e f i n i n g t h e a t t r a c t i v e n e s s o f a process i s the s e p a r a t i o n f a c t o r . It is d e f i n e d as α = (D/H) /(D/H) Β A

where A a n d Β a r e e n r i c h e d a n d d e p l e t e d s t r e a m s f r o m a s e p a r a t i n g d e v i c e , a r e t w o p h a s e s in p h y s i c a l e q u i l i b r i u m , o r a r e two com p o u n d s in c h e m i c a l e q u i l i b r i u m . The s e p a r a t i o n f a c t o r i s f r e q u e n t l y t h e first p a r a m e t e r t o be d e t e r m i n e d in s t u d y i n g a new h e a v y w a t e r p r o c e s s . Values r a n g e f r o m u n i t y (no s e p a r a t i o n ) t o a b o u t 30 (low t e m p e r a t u r e e l e c t r o l y s i s o f ammonia). Distillation T a b l e I I I compares f o u r distillation p r o c e s s e s based on h y d r o g e n , methane, ammonia a n d w a t e r . I n e a c h c a s e optimum c o n d i t i o n s have been s e l e c t e d . For water the pressure i s h i g h e r than i s used f o r f i n a l enrichment. T h i s i s because the p r o c e s s , as o p t i m i z e d f o r p r i m a r y e n r i c h m e n t , i s b a s e d o n v a p o u r recom p r e s s i o n t o conserve energy. The l o w s e p a r a t i o n f a c t o r s f o r t h e

Table I I I D I S T I L L A T I O N PROCESSES Temperature k Hydrogen Methane Ammonia Water

24 112 2 39 378

Pressure kPa 250 100 100 120

Separation Factor 1.5 1.00 35 1.036 1.024

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

8

SEPARATION

O F HYDROGEN

ISOTOPES

three substances other than hydrogen are an overwhelming d i s advantage. This can be seen by comparing tower volumes. The r e l a t i v e tower volume i s p r o p o r t i o n a l t o TP" (ot-1) " m~ f o r a given gas v e l o c i t y and HETP (height e q u i v a l e n t to a t h e o r e t i c a l p l a t e ) where Τ i s absolute temperature, Ρ i s pressure, α i s s e p a r a t i o n f a c t o r and m i s the number o f hydrogen atoms p e r molecule. C l e a r l y ( a - l ) ~ dominates this expression. F i g u r e 4 shows this r e l a t i v e tower volume as a f u n c t i o n o f p r e s s u r e . There i s a three t o four orders o f magnitude d i f f e r e n c e in tower volume between the compounds o f hydrogen and molecular hydrogen itself. The c a p i t a l c o s t a s s o c i a t e d with the former as d i s t i l l a t i o n working substance would be f a r too high f o r these t o be a t t r a c t i v e heavy water production processes. However, as already i n d i c a t e d , water distillation i s used e x t e n s i v e l y f o r f i n a l en richment from a D/H r a t i o o f about 0.1. Hydrogen distillation, on the other hand, i s a p o t e n t i a l l y a t t r a c t i v e process. As will be d i s c u s s e d l a t e r , it i s c l o s e t o being competitive with the GS process. 1

2

1

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

2

Chemical Exchange The GS process i s the archetype o f chemical exchange pro cesses. Deuterium i s t r a n s f e r r e d from a water molecule t o a hydrogen s u l f i d e molecule and v i s a - v e r s a : H 0 + H D S ^ ± H D O + H S. 2

2

The s e p a r a t i o n f a c t o r i s roughly equal t o the e q u i l i b r i u m con s t a n t f o r this r e a c t i o n . At 303 Κ α = 2.33 and a t 403 Κ it i s 1.82. T h i s d i f f e r e n c e i s the b a s i s o f the b i t h e r m a l concentra t i o n process t o be d e s c r i b e d l a t e r . The l a r g e flows and l a r g e energy input have already been d i s c u s s e d q u a l i t a t i v e l y . F o r the GS process the feed r a t e p e r kg D 0 i s 35 Mg and the energy r e q u i r e d per kg D 0 i s 25 GJ o f thermal energy and 700 kWh o f e l e c t r i c a l energy. The three other chemical exchange processes d i s c u s s e d in this paper are water-hydrogen, ammonia-hydrogen and aminehydrogen: 2

2

H 0 + HD ^ HDO + H , NH + H D ^ N H D + H , CH NH + HD^CH NHD + H . 2

2

3

3

2

2

3

2

2

In each case the gas i s hydrogen and the other component i s the liquid. F i g u r e 5 i l l u s t r a t e s the simplest chemical exchange flow sheet - that f o r monothermal exchange as used in Norway o r a t Trail. The l i q u i d feed i s enriched in deuterium as it flows down the tower and encounters p r o g r e s s i v e l y r i c h e r gas. A t the bottom o f the tower the l i q u i d i s t o t a l l y converted t o the gas,

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1.

RAE

Selecting

E

Heavy 10

Water

9

Processes

E

ο- 1 0 ' h

S

10 h 4

< oc

1

0

AMMONIA

3

Ρ Η , Ο = Pc D

10

2

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

Q

2

Ο ÛC

ÛH 0 =1

ONE

ATM -H

10

D

HYDROGEN

OC

0.1 1

10

10

2

10

3

10

4

10

5

PRESSURE, kPa Figure 4.

Relative tower volume for

Figure 5.

distilhtion

Simple monothermal process

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

10

SEPARATION OF HYDROGEN ISOTOPES

e x c e p t f o r t h a t f r a c t i o n which forms the f e e d t o h i g h e r s t a g e s in t h e c a s c a d e . T h i s phase c o n v e r t e r i s analogous t o a r e b o i l e r in distillation. P h a s e c o n v e r s i o n i s e x p e n s i v e in m o s t e x c h a n g e systems. However, w a t e r e l e c t r o l y s i s u s e d f o r c o m m e r c i a l h y d r o gen p r o d u c t i o n c a n be a s p e c i a l c a s e . Then h e a v y w a t e r r e c o v e r y becomes a b y p r o d u c t o p e r a t i o n . O t h e r h y d r o g e n p r o d u c t i o n t e c h n i q u e s c a n f u n c t i o n in a s i m i l a r manner ( 1 5 ) . Ammonia-hydrogen e x c h a n g e i s most r e a d i l y a d a p t e d t o monothermal o p e r a t i o n because the heat o f f o r m a t i o n from hydrogen and n i t r o g e n i s r e l a t i v e l y l o w . I n this c a s e ammonia s y n t h e s i s gas i s t h e d e u t e r i u m s o u r c e , so t h e f e e d i s a g a s . The ammonia e x c h a n g e l i q u i d i s n o t o n l y c r a c k e d in t h e p h a s e c o n v e r t e r a t t h e b o t t o m o f t h e e x c h a n g e c o l u m n as in F i g u r e 5, b u t i s a l s o s y n t h e s i z e d f o r r e f l u x a t t h e t o p o f t h e c o l u m n - in this f o r m the monothermal f l o w s h e e t i s c o m p l e t e l y analogous t o a d i s t i l l a t i o n process. S u c h a m o n o t h e r m a l ammonia-hydrogen e x c h a n g e p r o c e s s was first u s e d a t M a z i n g a r b e in F r a n c e and i s t h e b a s i s o f two p l a n t s in I n d i a ( 1 1 ) . P r a c t i c a l monothermal p r o c e s s e s a r e u n f o r t u n a t e l y r a r e because phase c o n v e r s i o n i s g e n e r a l l y too complex o r too c o s t l y . I n s t e a d , t h e b i t h e r m a l a r r a n g e m e n t i s u s e d as i l l u s t r a t e d in F i g u r e 6 f o r t h e GS p r o c e s s . The p h a s e c o n v e r t e r o f F i g u r e 5 i s r e p l a c e d by a h o t t o w e r . I n this i l l u s t r a t i o n , and in s e v e r a l o f t h e GS p l a n t s , t h e h o t and c o l d t o w e r s a r e c o m b i n e d in a single vessel: t h e y a r e t h e n r e f e r r e d t o as h o t and c o l d t o w e r sections. I n t h e GS p r o c e s s t h e w a t e r i s e n r i c h e d in d e u t e r i u m in t h e c o l d s e c t i o n and i s d e p l e t e d in t h e h o t s e c t i o n . The w a t e r c o n t a c t s t h e same gas a t t h e t o p o f t h e c o l d s e c t i o n as a t t h e b o t t o m o f t h e h o t s e c t i o n , and t h e f l o w s a r e c o n t r o l l e d s o gas and w a t e r t e n d t o a p p r o a c h e q u i l i b r i u m w i t h e a c h o t h e r a t t h e s e two l o c a t i o n s . T h e r e f o r e , the deuterium-to-hydrogen r a t i o in t h e d e p l e t e d e f f l u e n t w a t e r a p p r o a c h e s a v a l u e e q u a l t o o t h / o t c (~0.8 f o r t h e GS p r o c e s s ) o f t h a t in t h e f e e d . The c o u n t e r c u r r e n t gas and w a t e r f l o w s , i f a p p r o p r i a t e l y c o n t r o l l e d a t c l o s e t o t h e c o r r e c t f l o w r a t i o , c a u s e a n e t t r a n s p o r t o f d e u t e r i u m up t h e h o t s e c t i o n and down t h e . c o l d s e c t i o n t o p r o v i d e e n r i c h e d gas and w a t e r a t t h e c e n t r e o f t h e t o w e r . Here a s m a l l e n r i c h e d s t r e a m i s f e d f o r w a r d t o a n o t h e r t o w e r w o r k i n g in a h i g h e r c o n c e n t r a t i o n r a n g e (a h i g h e r s t a g e ) and i s m a t c h e d by a p a r t i a l l y d e p l e t e d r e t u r n i n g stream. The n e t t r a n s p o r t o f d e u t e r i u m t o the h i g h e r stage i s c o n t r o l l e d t o equal the e x t r a c t i o n r a t e from the feed water. The c o n n e c t i o n b e t w e e n t h e first s t a g e and t h e h i g h e r s t a g e c a n be gas as in F i g u r e 6, o r w a t e r o r b o t h . The h o t t o w e r o f t h e b i t h e r m a l p r o c e s s c a n be t h o u g h t o f as a n a l o g o u s t o an i m p e r f e c t r e b o i l e r , and so p r o v i d e s gas t o t h e c o l d tower a t a c o n s i d e r a b l y lower deuterium c o n c e n t r a t i o n than i s a c h i e v e d by the phase c o n v e r t e r o f the monothermal p r o c e s s . As a c o n s e q u e n c e , n o t o n l y does t h e h o t t o w e r and i t s a s s o c i a t e d h e a t i n g and c o o l i n g e q u i p m e n t o f t h e b i t h e r m a l p r o c e s s r e p l a c e the phase c o n v e r t e r o f the monothermal p r o c e s s , b u t the

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1.

RAE

Selecting

Heavy

Water

11

Processes

b i t h e r m a l p r o c e s s r e q u i r e s a much l a r g e r c o l d t o w e r . The m o n o t h e r m a l a n d b i t h e r m a l p r o c e s s a r r a n g e m e n t s a r e com p a r e d i n F i g u r e 7 i n t h e f o r m o f M c C a b e - T h i e l e d i a g r a m s . The e q u i l i b r i u m l i n e s h a v e s l o p e s o f 1/ot. The o p e r a t i n g l i n e f o r the monothermal case has a s l o p e o f u n i t y , e q u a l t o t h e l i q u i d to-gas f l o w r a t i o (L/G). The l a r g e d i v e r g e n c e b e t w e e n t h e o p e r a t i n g and e q u i l i b r i u m l i n e s a l l o w s a s u b s t a n t i a l enrichment (e.g. 5 times t h e f e e d c o n c e n t r a t i o n ) t o be reached w i t h o n l y a few t h e o r e t i c a l t r a y s . The d i f f e r e n c e i n d e u t e r i u m c o n c e n t r a t i o n b e t w e e n t h e f e e d (F) a n d t h e w a s t e (W), i . e . t h e r e c o v e r y f r o m t h e f e e d , c a n be l a r g e ; a s a f r a c t i o n i t a p p r o a c h e s (α-1)/α. F o r t h e b i t h e r m a l c a s e L/G, t h e s l o p e o f t h e o p e r a t i n g l i n e s , m u s t be b e t w e e n l / a a n d 1/oth. C o n s e q u e n t l y , b o t h h o t and c o l d c o l u m n s a r e s e v e r e l y p i n c h e d a n d many t h e o r e t i c a l t r a y s a r e r e q u i r e d f o r t h e same f i v e - f o l d e n r i c h m e n t . The r e c o v e r y , as a l r e a d y n o t e d , i s s m a l l ; l e s s t h a n ( a - a h ) / o t . Thus, t h e p e n a l t y f o r c i r c u m v e n t i n g t h e need f o r phase c o n v e r s i o n i s a l a r g e i n c r e a s e i n f l o w s a n d a n e v e n l a r g e r i n c r e a s e i n column v o l u m e . N o n e t h e l e s s , b i t h e r m a l i s g e n e r a l l y t h e more a t t r a c t i v e a r r a n g e m e n t t o s e l e c t b e c a u s e f e a s i b l e r e a c t i o n s f o r a monothermal process a r e r a r e and r e q u i r e l a r g e energy i n p u t s . A l t h o u g h t h e s i m p l e f l o w s h e e t s d i s c u s s e d so f a r have l i m i t e d r e c o v e r i e s s e t b y t h e above r e l a t i o n s h i p s , i t i s p o s s i b l e t o add s t r i p p i n g s e c t i o n s t o t h e process and achieve h i g h r e coveries approaching u n i t y i n the l i m i t . T h i s means a d d i n g more c o l u m n volume a s shown i n F i g u r e 8, f o r a g a s - f e d b i t h e r m a l p r o cess. T h i s i s t h e arrangement o f t h e amine-hydrogen p r o c e s s w h i c h h a s been s t u d i e d e x t e n s i v e l y b y A t o m i c Energy o f Canada L i m i t e d ( 1 6 ) . To s t r i p t h e g a s t o a l o w d e u t e r i u m c o n t e n t r e q u i r e s a l i q u i d s u f f i c i e n t l y l e a n i n deuterium. This i s pro d u c e d b y r e c y c l i n g some l e a n g a s t o t h e h o t t o w e r a n d l e n g t h e n i n g the h o t tower c o r r e s p o n d i n g l y . I n t h e simple case w i t h o u t s t r i p p i n g , t h e gas feed would e n t e r t h e bottom o f t h e h o t tower and n o t r e q u i r e a g a s r e c y c l e . A n o t h e r v e r s i o n o f a g a s - f e d b i t h e r m a l flowsheet w i t h s t r i p p i n g i s d e s c r i b e d by N i t s c h k e ( 1 2 ) . F i g u r e 9 d e s c r i b e s the s e p a r a t i o n f a c t o r as a f u n c t i o n o f temperature f o r t h e f o u r systems b e i n g c o n s i d e r e d . The l a r g e r a b s o l u t e v a l u e s f o r t h e hydrogen-based systems a r e e v i d e n t , as a r e t h e p o s s i b i l i t i e s o f much l a r g e r v a l u e s o f o t / a n . non-aqueous s y s t e m s c a n r e a c h v e r y l o w t e m p e r a t u r e s w i t h a c o n sequent l a r g e i n c r e a s e i n s e p a r a t i o n f a c t o r . In this respect t h e amine s y s t e m (17) i s p a r t i c u l a r l y a t t r a c t i v e . Relative to t h e GS s y s t e m , t h e much l a r g e r s e p a r a t i o n f a c t o r s f o r t h e h y d r o g e n - b a s e d s y s t e m s mean t h a t r e c o v e r i e s a r e h i g h e r , f l o w s per u n i t product lower and fewer t h e o r e t i c a l t r a y s a r e r e q u i r e d . A l l these advantages c o u l d l e a d t o s u b s t a n t i a l l y s m a l l e r tower volume f o r t h e h y d r o g e n - b a s e d p r o c e s s e s , b u t t h i s c a n o n l y b e a s s e s s e d a f t e r r a t e s o f exchange a r e c o n s i d e r e d which r e l a t e actual trays to theoretical trays.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

c

c

c

T

n

c

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

e

t

w

o

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

12

SEPARATION OF HYDROGEN ISOTOPES

Figure 6.

Exchange tower with gas feed forward

Figure 7.

McCabe-Thiele

diagrams

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

1.

RAE

Selecting

Heavy

Figure

ι

ι

Water

8.

Gas-fed bithermal stripping

I

ι ι

13

Processes

1 1 ι

-

\H -CH

" Η

2

2

- Ν Η ^ Λ

:

>

ι

N

I

process with

I

ι ι ι ι

11 1 1

I

1 1 11

—

2

H

ν

H

2

- H

2

-

0

H

2

S - H

2

0

o°c 1 1 1 1 200

11

250

1 ι

ι I 300

ι

ι ι

ι

1

100°C I 1 I I I I

350

400

I

I

I

450

TEMPERATURE,°K Figure 9.

Liquid^gas separation factors

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

14

SEPARATION O F

HYDROGEN ISOTOPES

Because exchange r a t e s are g e n e r a l l y f a s t a t h o t tower con d i t i o n s f o r a l l four processes being c o n s i d e r e d , the important mass t r a n s f e r and k i n e t i c l i m i t a t i o n s o c c u r i n t h e c o l d t o w e r . These w i l l now be d i s c u s s e d i n some d e t a i l . The f i r s t s t e p i n c o m p a r i n g r a t e s o f d e u t e r i u m e x c h a n g e i s t o d e f i n e p r a c t i c a l p r o c e s s c o n d i t i o n s f o r e a c h s y s t e m , and t h i s i s done i n T a b l e IV. B e c a u s e o f t h e low s o l u b i l i t y o f h y d r o g e n , g i v e n as t h e r e c i p r o c a l o f H e n r y ' s Law c o n s t a n t i n t h e T a b l e , the hydrogen-based processes operate a t high p r e s s u r e . The t e m p e r a t u r e r a n g e s a r e p r i m a r i l y d i c t a t e d by v a p o u r p r e s s u r e f o r t h e u p p e r v a l u e and by a minimum p r a c t i c a l e x c h a n g e r a t e f o r t h e l o w e r v a l u e . The amine p r o c e s s i s r e s t r i c t e d i n h o t t o w e r t e m p e r a t u r e by t h e r m a l s t a b i l i t y o f t h e c a t a l y s t (16_). The GS p r o c e s s i s r e s t r i c t e d i n c o l d t o w e r t e m p e r a t u r e by t h e f o r m a t i o n of a s o l i d hydrate. Each o f the hydrogen-based p r o c e s s e s r e q u i r e s a c a t a l y s t - homogeneous f o r t h e non-aqueous o n e s and heterogeneous for'water-hydrogen. Even so t h e v a l u e s o f t h e k i n e t i c r a t e c o n s t a n t s w h i c h can be a c h i e v e d a r e low (18, 1 9 ) . The v a l u e g i v e n i n T a b l e IV f o r w a t e r - h y d r o g e n i s f o r t h e c a t a l y s t as a c o l l o i d a l s l u r r y (20) ; h i g h e r e f f e c t i v e r a t e s can be a c h i e v e d w i t h a f i x e d - b e d c a t a l y s t as w i l l be d i s c u s s e d l a t e r . F o r the purposes o f comparison exchange r a t e s are e v a l u a t e d h e r e f o r g a s - l i q u i d c o n t a c t i n g on a s i e v e t r a y , even t h o u g h t h i s i s n o t t h e most p r a c t i c a l c o l d t o w e r c o n t a c t i n g e q u i p m e n t f o r a l l four processes. As i l l u s t r a t e d s c h e m a t i c a l l y i n F i g u r e 10, t h e gas f l o w s up t h e t o w e r t h r o u g h a m u l t i t u d e o f h o l e s i n e a c h t r a y . The l i q u i d f l o w s a c r o s s e a c h t r a y , o v e r a w e i r and down t o t h e n e x t t r a y ; t h e gas p r e s s u r e d r o p a c r o s s a t r a y h o l d s t h e l i q u i d on t h e t r a y . Thus, t h e r e i s c o n t i n u o u s , m u l t i - c o n t a c t , c o u n t e r c u r r e n t o p e r a t i o n . The g a s - l i q u i d m i x i n g on e a c h t r a y g e n e r a t e s a l a r g e i n t e r f a c i a l a r e a b e t w e e n them i n t h e f o r m o f b u b b l e and d r o p l e t s u r f a c e s . The gas and l i q u i d t h e n must s e p a r a t e b e f o r e each phase passes t o i t s subsequent t r a y .

Table

IV

CHEMICAL EXCHANGE PROCESSES GS

7 230 330

2

H 0/H 2

and a p r a c t i c a l v a l u e o f

catalyst

Catalyst Rate Constant* s" Gas S o l u b i l i t y * mol/(m .MPa) *at c o l d tower temperature concentration.

7 220 315

3

15 10

2 30 3 400

3

NH /H

10 300 440 Pt/C 1 8

P r e s s u r e MPa Temperature Κ

1

Amine

-

5000 830

CH3NHK

130 24

NH2K

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

2

1.

RAE

Selecting

Heavy

Water

15

Processes

I n s i m p l e t e r m s t h e t o w e r volume i s g i v e n b y : Volume = GRTN/(PK a) G where G i s the gas f l o w i n m o l s / s , R i s the gas law c o n s t a n t (MPa.m /(mol.Κ)), Τ i s t h e t e m p e r a t u r e i n Κ, Ν i s t h e number o f t h e o r e t i c a l t r a y s , Ρ i s t h e p r e s s u r e i n MPa, K G i s t h e o v e r a l l mass t r a n s f e r c o e f f i c i e n t i n m/s a n d a i s t h e i n t e r f a c i a l a r e a p e r u n i t volume ( m / m ) . The o v e r a l l mass t r a n s f e r c o e f f i c i e n t can be r e l a t e d t o t h e g a s p h a s e mass t r a n s f e r c o e f f i c i e n t , k^, and t h e l i q u i d p h a s e mass t r a n s f e r c o e f f i c i e n t , k , b y : 3

2

3

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

L

1__ Κ G

=

1_ k G

H k RT L 3

where H i s t h e H e n r y ' s Law c o n s t a n t (MPa.m /mol). For a s o l u b l e gas l i k e hydrogen s u l f i d e the v a l u e o f H i s s m a l l ( T a b l e IV) a n d t h e g a s p h a s e r e s i s t a n c e i s i m p o r t a n t a n d p o s s i b l y c o n t r o l l i n g . F o r h y d r o g e n H i s l a r g e r b y two o r d e r s o f magnitude and k g i s a l s o i n c r e a s e d ; t h u s , o n l y the l i q u i d phase r e s i s t a n c e need be c o n s i d e r e d . The v a l u e o f k L depends o n b o t h mass t r a n s f e r a n d c h e m i c a l r e a c t i o n s o t h a t t h e k i n e t i c r a t e constant, k , enters i n t o i t s determination. I t i s beyond the scope o f t h i s paper t o t r e a t the e v a l u a t i o n o f k i n any d e t a i l . F o l l o w i n g the e x p o s i t i o n o f A s t a r i t a (21), F i g u r e 11 shows how k L , t h e mass t r a n s f e r c o e f f i c i e n t f o r t h e l i q u i d phase f o r combined a b s o r p t i o n and c h e m i c a l r e a c t i o n , i s r e l a t e d t o kg, the l i q u i d phase c o e f f i c i e n t f o r p h y s i c a l ab s o r p t i o n w i t h o u t r e a c t i o n , as a f u n c t i o n o f k . I n e x p r e s s i n g t h i s f u n c t i o n t h e r a t i o o f k / s i s u s e d where s i s t h e f r a c t i o n a l rate o f surface renewal ( s " ) . A t y p i c a l value o f s for a sieve t r a y i s 50 s " . I f D i s the d i f f u s i v i t y o f the d i s s o l v e d gas ( m / s ) , t h e n k g = (Ds)°« . The p a r a m e t e r i n t h i s f i g u r e , e s ° * / a D - , a l l o w s f o r t h e e f f e c t o f t h e volume f r a c t i o n o f l i q u i d c o n t a i n e d i n t h e t o t a l u n i t v o l u m e , ε, w h i c h i s i m p o r t a n t i n the slow r e a c t i o n regime. I n t h e s l o w r e a c t i o n r e g i m e i n F i g u r e 11, t h e e x c h a n g e r e a c t i o n occurs i n the bulk l i q u i d . k i s l e s s than k g and equals ek /a. I n t h e c a s e o f t h e e j e c t o r c o n t a c t o r (15) where a i s very l a r g e and s i s l i k e l y a l s o i n c r e a s e d r e l a t i v e t o a s i e v e t r a y , t h e low v a l u e o f e s ° - / a D - c o u l d b r i n g b o t h t h e w a t e r - h y d r o g e n a n d t h e ammonia-hydrogen s y s t e m s i n t o t h e s l o w r e a c t i o n regime. When k s k g t h e e x c h a n g e r a t e i s c o n t r o l l e d p r i m a r i l y b y physical absorption. This i s a t r a n s i t i o n r e g i o n o r the d i f f u s i o n r e g i m e w h e r e k < s . The r e a c t i o n o c c u r s p r i m a r i l y i n t h e bulk l i q u i d , but s u f f i c i e n t l y r a p i d l y that p h y s i c a l absorption i s the r a t e c o n t r o l l i n g s t e p . Both the s l u r r y - c a t a l y z e d w a t e r h y d r o g e n s y s t e m a n d t h e ammonia-hydrogen s y s t e m a r e i n t h i s r e g i o n f o r c o n t a c t i n g on a s i e v e t r a y . r

L

r

r

1

1

2

5

5

0

5

L

r

5

0

5

L

r

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

16

SEPARATION O F H Y D R O G E N ISOTOPES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

COLD

SECTION O F E X C H A N G E

WATER

Figure 10.

Figure 11.

TOWER

E N R I C H E D IN D E U T E R I U M

Sieve tray operation

Cold tower mass transfer coefficients

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1.

RAE

Selecting

Heavy

Water

17

Processes

The f a s t r e a c t i o n r e g i m e i n F i g u r e 11 b e g i n s when k > k^, and c h e m i c a l r e a c t i o n e n h a n c e s t h e mass t r a n s f e r r a t e . Once k / s e x c e e d s a b o u t 3, t h e n k]^ i s e q u a l t o ( k D ) - . Here t h e r e a c t i o n zone i s l i m i t e d t o f r e s h e l e m e n t s o f l i q u i d b r o u g h t t o the i n t e r f a c i a l s u r f a c e by t u r b u l e n t e d d i e s ; d i f f u s i o n and r e a c t i o n o c c u r s i m u l t a n e o u s l y a t the s u r f a c e w h i l e the b u l k l i q u i d i s a l w a y s a t e q u i l i b r i u m . The a m i n e - h y d r o g e n p r o c e s s i s c l e a r l y i n t h i s regime. F o r a n y g i v e n c o n t a c t o r s y s t e m t h e f a s t r e a c t i o n r e g i m e ends once t h e g a s p h a s e mass t r a n s f e r r a t e b e g i n s t o c o n t r o l ; t h i s i s t h e i n s t a n t a n e o u s r e a c t i o n r e g i m e . A s shown i n F i g u r e 11 t h e GS p r o c e s s i s a l m o s t i n t h i s r e g i m e . The v a l u e o f k f o r t h i s s y s t e m g i v e n i n T a b l e IV i s o n l y a p p r o x i m a t e ; no r e l i a b l e measurement h a s b e e n made. However, 5000 s " p r o b a b l y i s a lower l i m i t . A s d i s c u s s e d above t h e l o w v a l u e o f H f o r t h e H2O-H2S s y s t e m means t h e g a s p h a s e r e s i s t a n c e must be c o n s i d e r e d e v e n a t modest v a l u e s f o r k . P i l o t p l a n t d a t a f o r GS s i e v e t r a y e f f i c i e n c y a r e c o n s i s t e n t w i t h kgH/RTkg e q u a l t o 6. The d o t t e d l i n e i n F i g u r e 11 r e p r e s e n t s KçH/RTk^ when k H / R T k ° = 6 f o r v a r i o u s v a l u e s o f k and hence k . U s i n g t h e d a t a i n T a b l e I V a n d F i g u r e 11, t h e o v e r a l l v o l u m e t i c mass t r a n s f e r c o e f f i c i e n t s , Kça, a n d t h e t o w e r v o l u m e s have b e e n e s t i m a t e d a s shown i n T a b l e V a s s u m i n g a * 300 m" f o r L

0

r

5

r

r

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

1

r

G

r

L

1

H2O-H2S a n d H2O-H2,

1

a n d a * 600 m"

f o r NH3-H2 a n d C H N H - H . 3

2

2

F o r t h e p r o c e s s e s b a s e d on h y d r o g e n t h e low v a l u e s o f Kça a r e c o m p e n s a t e d f o r b y t h e f e w e r number o f t h e o r e t i c a l t r a y s , t h e h i g h e r p r e s s u r e and the lower gas f l o w r a t e . Thus, f o r t h e amine p r o c e s s t h e t o w e r volume i s l e s s t h a n f o r t h e GS p r o c e s s . However, t h e h i g h e r p r e s s u r e f o r t h e f o r m e r r e s u l t s i n a v e s s e l w e i g h t w h i c h i s s i m i l a r t o t h a t f o r t h e GS p r o c e s s . K^a c a n be enhanced by u s i n g mechanical energy t o i n c r e a s e the i n t e r f a c i a l area very c o n s i d e r a b l y , as i n the e j e c t o r c o n t a c t o r (15), and so t o r e d u c e t o w e r volume s i g n i f i c a n t l y a t t h e e x p e n s e o f c o m p l e x and c o s t l y i n t e r n a l s . The o v e r a l l e x c h a n g e r a t e i s o f c o u r s e d e p e n d e n t o n c a t a l y s t c o n c e n t r a t i o n a n d on t h e f o r m o f c a t a l y s t u s e d . F o r t h e w a t e r h y d r o g e n p r o c e s s t h e v a l u e s o f Kça g i v e n i n T a b l e V a r e f o r a hydrophobic p l a t i n u m c a t a l y s t supported on the s u r f a c e o f a p a c k i n g i n a t r i c k l e - b e d r e a c t o r (22) . T h i s new c a t a l y s t d e v e l o p e d b y A t o m i c E n e r g y o f Canada L i m i t e d p r o v i d e s a h i g h e r v o l u m e t r i c mass t r a n s f e r r a t e t h a n t h e s l u r r y c a t a l y s t r e f e r r e d to e a r l i e r . The b i t h e r m a l p r o c e s s a r r a n g e m e n t r e q u i r e s a h i g h p r e s s u r e (10 MPa) s o t h a t K^a i s l o w a n d t h e t o w e r volume i s large. F o r t h e m o n o t h e r m a l CECE a r r a n g e m e n t t h e p r e s s u r e i s l o w e r (1.5 MPa) a n d Kça i s a n o r d e r o f m a g n i t u d e h i g h e r g i v i n g a somewhat l a r g e r v a l u e f o r PKça; t h e much s m a l l e r t o w e r volume r e s u l t s m a i n l y f r o m t h e r e d u c t i o n i n Ν a n d G. The same a d v a n t a g e f o r t h e m o n o t h e r m a l f l o w s h e e t c a n a l s o be s e e n f o r t h e ammoniahydrogen system.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

18

SEPARATION O F

HYDROGEN ISOTOPES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

T u r n i n g now t o c o n s i d e r h o t t o w e r v o l u m e s , t h e r e i s no l o n g e r a p r o b l e m o f low exchange r a t e s . F o r t h e GS p r o c e s s t h e r a t e s i n t h e c o l d and h o t t o w e r s a r e r o u g h l y s i m i l a r , b o t h c o n trolled by mass t r a n s f e r i n t h e gas p h a s e . F o r the hydrogenb a s e d p r o c e s s e s t h e r a t e s o f e x c h a n g e a r e much f a s t e r i n t h e h o t tower than i n the c o l d tower. Thus, i n p r i n c i p l e the h o t tower v o l u m e s f o r t h e s e p r o c e s s e s c o u l d be s m a l l e r t h a n f o r t h e GS p r o c e s s . However, i n p r a c t i c e t h e b i t h e r m a l d e s i g n i n t h e s e c a s e s i s o p t i m i z e d t o c o n c e n t r a t e s e p a r a t i v e work i n t h e h o t t o w e r and so l i m i t demands on t h e c o l d t o w e r ; as a r e s u l t b o t h t e n d t o have a b o u t t h e same v o l u m e . The v a l u e s o f Ν u s e d i n T a b l e V r e f l e c t t h i s o p t i m i z i n g p r o c e s s , and so t h e r e l a t i v e c o l d tower volumes a r e r e p r e s e n t a t i v e o f the r e l a t i v e t o t a l tower volumes f o r t h e b i t h e r m a l f l o w s h e e t s . Transfer Processes A s p e c i a l c a t e g o r y o f c h e m i c a l exchange r e a c t i o n i s h i g h temperature p r o c e s s e s which t r a n s f e r deuterium from a source m a t e r i a l a v a i l a b l e as l a r g e s i n g l e s t r e a m s , s u c h as w a t e r o r methane, t o h y d r o g e n . Thus, the v e r y l a r g e s c a l e p o s s i b l e w i t h t h e s e s o u r c e m a t e r i a l s c a n be c o m b i n e d w i t h t h e i n h e r e n t a d vantages o f u s i n g a hydrogen-based p r o c e s s w h i c h can c o n c e n t r a t e d e u t e r i u m more e f f i c i e n t l y . H y d r o g e n i t s e l f i s an a b u n d a n t s o u r c e ( w o r l d p r o d u c t i o n e q u i v a l e n t t o 30,000 Mg D20/a b u t i t i s d e r i v e d f r o m a v a s t number o f i n d i v i d u a l u n i t s , w i t h a t y p i c a l l a r g e u n i t b e i n g e q u i v a l e n t t o o n l y 70 Mg D20/a. The s t e a m - h y d r o g e n p r o c e s s i l l u s t r a t e d i n F i g u r e 12 l i n k s a w a t e r f e e d t o t h e amine-hydrogen p r o c e s s . Water i s e v a p o r a t e d i n t o d e p l e t e d h y d r o g e n and t h e m i x t u r e i s h e a t e d t o 870 Κ where the exchange r e a c t i o n o c c u r s o v e r a n i c k e l o x i d e c a t a l y s t t o t r a n s f e r d e u t e r i u m from t h e steam t o the hydrogen. The s t e a m i s c o n d e n s e d and t h e h y d r o g e n r e t u r n e d t o t h e b i t h e r m a l a m i n e hydrogen u n i t . Two s t e a m - h y d r o g e n e q u i l i b r a t i o n s i n s e r i e s a r e r e q u i r e d , and e v e n so t h e d e u t e r i u m c o n t e n t o f t h e r e p l e n i s h e d h y d r o g e n i s s i g n i f i c a n t l y b e l o w n a t u r a l . F l o w s a r e l a r g e and energy requirements are h i g h ; the steam-hydrogen t r a n s f e r p r o c e s s by i t s e l f i s e q u i v a l e n t i n c o s t p e r k g o f h e a v y w a t e r e x t r a c t e d t o more t h a n h a l f t h e c o s t o f t h e h e a v y w a t e r p r o d u c e d by t h e GS p r o c e s s . A l t h o u g h some i m p r o v e m e n t s i n t h i s t r a n s f e r p r o c e s s may be p o s s i b l e , i t w i l l be d i f f i c u l t t o a c h i e v e a c o m p e t i t i v e combination w i t h amine-hydrogen o r o t h e r hydrogen-based p r o c e s s . A s i m i l a r t r a n s f e r p r o c e s s w h i c h c a n be u s e d t o e x t r a c t d e u t e r i u m f r o m methane (2_3) has b e e n s t u d i e d a t t h e G u l f R e s e a r c h and D e v e l o p m e n t Company. D e p l e t e d h y d r o g e n i s m i x e d w i t h methane f e e d and t h e e x c h a n g e r e a c t i o n i s c a r r i e d o u t o v e r a c a t a l y s t a t a b o u t 1000 K. The two components a r e s e p a r a t e d by l i q u e f y i n g t h e methane. The r e p l e n i s h e d h y d r o g e n f e e d s a d i s t i l l a t i o n u n i t which separates the deuterium. T h i s p r o c e s s com b i n a t i o n i s i l l u s t r a t e d i n F i g u r e 13. A g a i n two e q u i l i b r a t i o n s

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

RAE

Selecting

Heavy Water

Processes

Table V RELATIVE COLD TOWER VOLUMES Gas F l o w Theoretical k m o l / m o l D2O Trays H 0 -H2S

74

2

CH3NH2

-

H

24

2

;

Kça s^ 1

Relative Volume 1

27

0.9

1

10

0.04

0.6

5 10

0.008 0.008

0.9 4

0.08* 0.008^

0.3 5

NH3-H2

14 31

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

monothermal bithermal H 0 - H CECE bithermal 2

2

*For a 4 - f o l d 2

3

9 50 enrichment.

V o l u m e = GNT/PK a; s e e T a b l e I V f o r Ρ a n d Τ e x c e p t f o r CECE w h i c h h a s Ρ =1.5 MPa. G

3

Weighted average f o r s t r i p p i n g and e n r i c h i n g (see F i g u r e 8 ) .

*For t h e f i x e d - b e d

columns

hydrophobic platinum c a t a l y s t .

Figure 12.

Steam-Η

-amine process

2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

20

SEPARATION OF HYDROGEN ISOTOPES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

with countercurrent flow o f hydrogen and methane between them are needed. Energy consumption i s h i g h , most o f i t f o r r e f r i g e r a t i o n . The methane-hydrogen p a r t o f the process i s probably s i m i l a r i n cost t o steam-hydrogen t r a n s f e r . I t should be noted t h a t s e l e c t i v e photochemical processes based on the use o f l a s e r s w i l l r e q u i r e a s i m i l a r t r a n s f e r step to l i n k the s e p a r a t i o n process t o an abundant feed. Depending on the molecules i n v o l v e d , high temperature may not be needed t o achieve a s e p a r a t i o n f a c t o r near u n i t y f o r the t r a n s f e r r e a c t i o n , but unusually low p r e s s u r e s may be a requirement. C e r t a i n l y , t h i s can be a c o s t l y o p e r a t i o n because o f the l a r g e volume o f m a t e r i a l t o be handled and the n e c e s s i t y t o recover the r e c i r c u l a t i n g deuterium c a r r i e r from the waste stream with a h i g h efficiency . Process

Comparison

While the s e p a r a t i o n f a c t o r i s a key p r o p e r t y f o r r a n k i n g the economic a t t r a c t i v e n e s s o f p r o c e s s e s , energy consumption i s almost o f equal importance. A convenient c h a r t to i l l u s t r a t e t h i s i s shown i n Figure 14. An expanded s c a l e o f l o g ( a - l ) i s used f o r the s e p a r a t i o n f a c t o r . E l e c t r i c a l o r mechanical energy i s converted t o e q u i v a l e n t thermal energy u s i n g 40% e f f i c i e n c y and added t o the a c t u a l thermal energy requirement t o give t o t a l e q u i v a l e n t thermal energy i n GJ/kg. The GS process r e q u i r e s 30 GJ/kg which i s e q u i v a l e n t to about 5 b a r r e l s o f o i l per kilogram. The energy consumption f o r a process i s d i f f i c u l t t o d e f i n e without a d e t a i l e d d e s i g n . I t depends on the degree o f energy recovery which i n turn depends on such f a c t o r s as the i n g e n u i t y of the designer, the r e l a t i v e cost o f energy and c a p i t a l equipment, and how the p l a n t i s t o be f i n a n c e d . T o t a l energy i f o f t e n under-estimated i n p r e l i m i n a r y process e v a l u a t i o n s because o f the s i m p l i f y i n g assumptions that are u s u a l l y made. Processes i n the uneconomic region o f Figure 14 have too low a s e p a r a t i o n f a c t o r (water c r y s t a l l i z a t i o n ) , too high an energy consumption (hydrogen d i f f u s i o n ) o r both (water d i s t i l l a t i o n ) . E l e c t r o l y s i s ranks h i g h e s t i n s e p a r a t i o n f a c t o r and h i g h e s t i n energy consumption unless i t i s undertaken f o r hydrogen production. In t h a t case about one t h i r d o f the deuterium cont a i n e d i n the feed water can be recovered as a hydrogen stream enriched t o three times n a t u r a l a t p r a c t i c a l l y zero c o s t (9_) . The G u l f process (23) i s d e s c r i b e d i n F i g u r e 13; while i t s energy consumption i s high, i t has many i n h e r e n t advantages which are l i k e l y t o permit an a t t r a c t i v e l y low c a p i t a l c o s t . However, not only i s i t s energy consumption about twice t h a t o f the GS process, but t h i s energy i s p r i m a r i l y mechanical and t h e r e f o r e expensive. Under e s p e c i a l l y favourable circumstances the G u l f process might become competitive with GS.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

Selecting

Heavy

Water

Processes

Figure 13.

C,-H

2

process

Figure 14

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

22

SEPARATION

O F HYDROGEN

The CECE process i s shown twice - a t the high energy con sumption f o r the case where there i s no market f o r the e l e c t r o l y t i c hydrogen and a t the low energy consumption where the heavy water i s a by-product o f the hydrogen p r o d u c t i o n . The l a t t e r i s a p a r t i c u l a r l y favourable s i t u a t i o n . The value o f α used i n F i g u r e 14 f o r the s e p a r a t i o n f a c t o r of the b i t h e r m a l exchange processes i s α / α ^ i n order t o c h a r a c t e r i z e each o f them by a s i n g l e v a l u e . The GS process has a lower s e p a r a t i o n f a c t o r and a h i g h e r energy consumption than s i x other processes i n Figure 14. I t even has the d i s t i n c t l y u n d e s i r a b l e f e a t u r e o f using hydrogen s u l f i d e which i s c o r r o s i v e , smelly and t o x i c . Yet the GS process dominates heavy water p r o d u c t i o n and i s s t i l l the p r e f e r r e d method o f p r o d u c t i o n . Why? Table VI compares i t with two o f i t s p o t e n t i a l competitors: - the GS process uses an abundant feed and t h e r e f o r e enjoys the advantage o f a l a r g e s c a l e ; hydrogen-fed p l a n t s are l i m i t e d to l e s s than 100 Mg/a c a p a c i t y and the hydrogenbased processes are expensive t o l i n k to water o r methane, - while the GS process energy consumption i s higher than the other two, i t i s not e x c e s s i v e , - the GS process enjoys f a s t mass t r a n s f e r r a t e s , b u t so does hydrogen d i s t i l l a t i o n , - the temperature which c o n t r o l s GS process energy i n p u t i s moderate, whereas both hydrogen d i s t i l l a t i o n and aminehydrogen r e q u i r e expensive r e f r i g e r a t i o n , - the GS process pressure i s not high enough t o i n c u r a large cost penalty, - while the GS process s e p a r a t i o n f a c t o r i s not as h i g h as f o r the other processes, i t i s reasonable. The major reason f o r the success o f the GS process i s the s c a l e effect. α

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

ISOTOPES

Table VI PROCESS COMPARISON GS Feed Energy GJ/kg D 2 O Mass T r a n s f e r Temperature* Κ Pressure MPa Separation F a c t o r

H0 30 Fast 400 2 1.3 2

Amine

Hydrogen Distillation

H2

H2

11 Slow 220 7 2.2

22 Fast 24 0.25 1.5

C o n t r o l l i n g major energy i n p u t

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

1.

RAE

Selecting

Heavy Water Processes

Figure 15.

Key factors in process evaluation

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

23

24

SEPARATION O F HYDROGEN ISOTOPES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

The k e y f a c t o r s i n p r o c e s s e v a l u a t i o n a r e o u t l i n e d i n F i g u r e 15. The i n h e r e n t p r o c e s s c o n d i t i o n s a n d p r o p e r t i e s o f p r e s s u r e , t e m p e r a t u r e , mass t r a n s f e r r a t e and s e p a r a t i o n f a c t o r a r e a l l i m p o r t a n t . P r e s s u r e and t e m p e r a t u r e c a n be v a r i e d t o o p t i m i z e the c o n d i t i o n s , b u t u s u a l l y o n l y a r e l a t i v e l y narrow range i s p r a c t i c a l . These c o n d i t i o n s s e t t h e v a l u e s o f α a n d Kça. Knowing α i t i s p o s s i b l e t o s e l e c t t h e r e c o v e r y , t h e f l o w r a t e , G, a n d t h e number o f t r a n s f e r u n i t s o r t h e o r e t i c a l t r a y s , N. The p r e s s u r e and t e m p e r a t u r e s e t t h e a l l o w a b l e v e l o c i t y , V. Then G, N, Kça and V combine t o d e f i n e t o w e r v o l u m e . The m a j o r p a r a m e t e r s d e t e r m i n i n g e n e r g y c o n s u m p t i o n a r e f l o w and t e m p e r a t u r e , b u t as a l r e a d y n o t e d t h e d e t a i l e d p r o c e s s f l o w s h e e t i s important here. Summary The GS p r o c e s s i s t h e o n l y l a r g e - s c a l e i n d e p e n d e n t p r o c e s s w i t h a d i r e c t w a t e r f e e d and t h i s i s l a r g e l y r e s p o n s i b l e f o r i t s p r e - e m i n e n t p o s i t i o n i n heavy w a t e r p r o d u c t i o n . Water-hydrogen exchange i s o n l y a t t r a c t i v e i n c o m b i n a t i o n w i t h e l e c t r o l y t i c hydrogen p r o d u c t i o n - t h e combined e l e c t r o l y s i s and c a t a l y t i c exchange (CECE) p r o c e s s . T h r e e h y d r o g e n - b a s e d p r o c e s s e s , a m i n e - h y d r o g e n , ammoniah y d r o g e n and h y d r o g e n d i s t i l l a t i o n , a r e a l l c l o s e t o b e i n g comp e t i t i v e w i t h t h e GS p r o c e s s . Of t h e s e , a m i n e - h y d r o g e n i s l i k e l y t o be t h e c h e a p e s t . H y d r o g e n d i s t i l l a t i o n l i n k e d t o n a t u r a l gas as t h e d e u t e r i u m s o u r c e , w h i l e d i s t i n c t l y e n e r g y i n t e n s i v e , may be a n e a r c o m p e t i t o r u n d e r some c i r c u m s t a n c e s . Hydrogen i s a p o t e n t i a l l y abundant heavy w a t e r s o u r c e , b u t i n d i v i d u a l p l a n t s are small. However, h y d r o g e n - b a s e d h e a v y w a t e r p l a n t s a r e b e i n g b u i l t a n d more w i l l be c o m m i t t e d . N o n e t h e l e s s , t h e GS p r o c e s s w i l l c o n t i n u e as t h e d o m i n a n t one f o r a n o t h e r 10 o r 20 y e a r s . Nomenclature a D (D/H) G H G KQ

~ -

k kg

-

k

-

k

L

L

r

-

i n t e r f a c i a l a r e a p e r u n i t volume o f m i x e d p h a s e s , m" d i f f u s i v i t y o f d i s s o l v e d g a s , m /s atom r a t i o o f d e u t e r i u m t o h y d r o g e n gas f l o w r a t e , mol/s H e n r y ' s Law c o n s t a n t , MPa.m /kmol 9 p h a s e mass t r a n s f e r c o e f f i c i e n t , m/s o v e r a l l mass t r a n s f e r c o e f f i c i e n t b a s e d on gas p h a s e c o n c e n t r a t i o n s , m/s l i q u i d p h a s e mass t r a n s f e r c o e f f i c i e n t , m/s l i q u i d p h a s e mass t r a n s f e r c o e f f i c i e n t f o r p h y s i c a l a b s o r p t i o n , m/s psuedo f i r s t o r d e r r a t e c o n s t a n t f o r c o n v e r s i o n o f m o n o d e u t e r a t e d d i s s o l v e d gas t o m o n o d e u t e r a t e d s o l v e n t , s " l i q u i d f l o w r a t e , mol/s 2

3

a s

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1

1.

Selecting

RAE

m Ν Ρ R s Τ V

α ε

Water

-

25

Processes

number o f hydrogen atoms i n the molecule number o f t h e o r e t i c a l t r a y s p r e s s u r e , MPa gas law constant = 8.2 χ 10"" m .MPa/ (kmol .K) f r a c t i o n a l r a t e o f surface renewal, s " temperature, Κ gas v e l o c i t y based on the a c t i v e area o f the t r a y , i . e . tower cross s e c t i o n a l area minus t o t a l downcomer area, m/s - deuterium s e p a r a t i o n f a c t o r - volume f r a c t i o n o f l i q u i d on a t r a y

Subscripts : Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

Heavy

3

3

1

c - c o l d tower;

h - h o t tower

Literature Cited (1) (2) (3) (4) (5) (6)

(7)

(8)

(9)

(10) (11)

(12)

Urey, H . C . , Brickwedde, F . G . , Murphy, G.M., Phys. Rev., (1932), 39, 164. Murphy, G.M., Urey, H . C . , Kirshenbaum, I . , "Production of Heavy Water", McGraw-Hill Book Co., Inc., New York, 1955. Clusius, K . , et al., "Nuclear Physics and Cosmic Rays, Part II", FIAT Rev. Ger. S c i . , (1948), p.182-188. Lavrencic, D . , Comitato Nazionale Energia Nucleare Report RT/ING(74)9, (1974), Rome. Benedict, M . , Pigford, T . H . , "Nuclear Chemical Engineering", McGraw-Hill Book Co., Inc., New York, 1957. Hammerli, Μ., Stevens, W.H., Butler, J.P., "Separation of Hydrogen Isotopes", p.110, American Chemical Society, Washington, 1978. Bebbington, W.P., Proctor, J.F., Scotten, W.C., Thayer, V.R., Third United Nations International Conference on the Peace ful Uses of Atomic Energy, (1964), Proceedings 12, 334 United Nations, Geneva. Dahlinger, Α . , Lockerby, W.E., Rae, H . K . , IAEA Inter national Conference on Nuclear Power and i t s Fuel Cycle, (1977), Salzbury, Austria, Paper IAEA-CN-36/183; Atomic Energy of Canada Limited Report 5710 (1977). Gami, D . C . , Rapial, A . S . , Third United Nations Inter national Conference on the Peaceful Uses of Atomic Energy, (1964), Proceedings 12, 421 United Nations, Geneva. Roth, E., Bedhome, Α . , Lefrancois, B . , LeChatelier, J., Tillol, Α . , Energie Nucleaire, (1968), 10, 214. Roth, Ε . , Traourouder, R., V i r a t e l l e , J., Lefrancois, B . , Fourth United Nations Conference on the Peaceful Uses of Atomic Energy, (1971), Proceedings 9, 69, United Nations, Geneva. Nitschke, E., Ilgner, H . , Walter, S., "Separation of Hydrogen Isotopes", p. 77, American Chemical Society, Washington, 1978.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

SEPARATION OF HYDROGEN ISOTOPES

26

(13) (14) (15) (16)

(17)

(18)

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch001

(19) (20) (21) (22)

(23)

Nitschke, E., Atomwirtschaft, (1973), 18, 297. Kuhn, W., Thurkauf, Μ., Helv. Chem. Acta, (1958), 41, 938. Wynn, N.P., "Separation of Hydrogen Isotopes", p. , American Chemical Society, Washington, 1978. Holtslander, W . J . , Lockerby, W.E., "Separation of Hydrogen Isotopes", p. 4 0 , American Chemical Society, Washington, 1978. Rolston, J.H., Butler, J.P., Denhartog, J., "A Deter mination of the Isotopic Separation Factor Between Hydrogen and Liquid Methylamine", to be published. Bourke, P.J., Lee, J.C., Trans. Inst. Chem. Engrs., (1961), 39, 280. Kalra, H . , Otto, F . D . , Can. J. Chem. Eng., (1974), 52, 258. Becker, E.W., Hubener, R., Kessler, R., Chemie Ing. Tech., (1958), 30, 288. Astarita, G . , "Mass Transfer with Chemical Reaction", Elsevier, 1967. Butler, J.P., Rolston, J.H., Stevens, W.H., "Separation of Hydrogen Isotopes", p. 9 3 , American Chemical Society, Washington, 1978. Pachaly, R.W., "Process for Obtaining Deuterium from Hydrogen-Containing Compounds and the Production of Heavy Water Therefrom", Canadian Patent 943742, (1974).

RECEIVED December 16, 1977

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

2 Bruce Heavy Water Plant Performance G. D. DAVIDSON

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002

Bruce Heavy Water Plant, Ontario Hydro, Box 2000, Triverton, Ontario, CanadaN0G2T0

To satisfy the Canadian demand f o r heavy water which is used as a moderator and heat t r a n s p o r t medium in CANDU r e a c t o r s , Atomic Energy o f Canada L i m i t e d c o n t r a c t e d the Lummus Company o f Canada L i m i t e d in 1969 t o d e s i g n and c o n s t r u c t Bruce Heavy Water P l a n t ' A ' a t the Bruce N u c l e a r Power Development. The 9.5 square k i l o m e t e r (2300 a c r e s ) s i t e had p r e v i o u s l y been p u r c h a s e d by O n t a r i o Hydro f o r the Douglas P o i n t N u c l e a r G e n e r a t i n g S t a t i o n . I t is l o c a t e d in the County o f Bruce on the e a s t e r n shore o f Lake Huron, midway between the towns o f K i n c a r d i n e and P o r t Elgin, a p p r o x i m a t e l y 240 k i l o m e t e r s (150 m i l e s ) northwest o f T o r o n t o . O n t a r i o Hydro was r e s p o n s i b l e f o r commissioning and o p e r a t i n g the p l a n t which has a d e s i g n c a p a c i t y o f 96.6 k g / h o f 99.75% purity heavy water (D2O). Commissioning o f P l a n t ' Α ' commenced in 1971 and proceeded w i t h o u t any major difficulty t h r o u g h 1972 and 1973. On 28 June, 1973, O n t a r i o Hydro p u r c h a s e d the p l a n t from AECL and d e c l a r e d the p l a n t in-service. D e s i g n p r o d u c t i o n c a p a c i t y was r e a c h e d in April, 1974 after e l e v e n months o f o p e r a t i o n . Production rates and c a p a c i t y f a c t o r s have s t e a d i l y been i n c r e a s e d such t h a t the official capacity was i n c r e a s e d t o 100.6 k g / h in 1976. As a r e s u l t o f t h e e a r l y o p e r a t i n g s u c c e s s o f BHWP A, O n t a r i o Hydro announced t h e c o n s t r u c t i o n o f t h r e e a d d i t i o n a l and e s s e n t i a l l y i d e n t i c a l heavy water p l a n t s a t Bruce (BHWP B, C and D ) . A c u t b a c k in t h e N u c l e a r G e n e r a t i o n c o n s t r u c t i o n program in 1976 r e s u l t e d in one o f t h e s e , BHWP C, b e i n g c a n c e l l e d and the s c h e d u l e f o r a n o t h e r , BHWP D, b e i n g d e f e r r e d by two y e a r s . ©

0-8412-0420-9/78/47-068-027$05.00/0

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

28

SEPARATION O F H Y D R O G E N

ISOTOPES

Bruce Heavy Water Plant uses the proven Dual Temperature Hydrogen Sulphide - Water Exchange Process to separate deuterium. This process has been in use on a commercial scale in North America f o r 25 years. Following a b r i e f d e s c r i p t i o n of the production process, BHWP A performance from in-service to the end of 1976 is described in terms of the following key performance c r i t e r i a : Employee Safety, Care of the Environment, R e l i a b i l i t y and Manpower Development. F i n a l l y , commissioning progress to date of BHWP Β is described.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002

Production Process Water is pumped from Lake Huron (see "Figure 1") with a deuterium i s o t o p i c content of 148 mg/kg. I t is f i l t e r e d to remove s o l i d s and preheated to 29°C. The pH is lowered to 3.8 - 4.2 by the addition of sulphuric acid to decompose carbonates, the water is degassed of oxygen and carbon dioxide, and then the pH is raised to 6.0 - 6.5 by the addition of caustic to avoid corrosion to carbon s t e e l processing equipment. This treated water is then fed to the Enriching Units. Each of the heavy water plants consists of two i d e n t i c a l enriching units and one f i n i s h i n g u n i t . Each Enriching Unit can be divided broadly into three sections: the absorption and desorption section, the extraction section and the enriching section. The absorption and desorption section serves two functions: removal of H2S from the depleted water be fore i t is returned to the lake, and removal of H2S in the purge gas before i t is f l a r e d . As the feed water passes through t h i s section, i t is p a r t i a l l y saturated with H2S. In the extraction section (see "Figure 2") water passes counter-current to a r e c i r c u l a t i n g stream of hydrogen sulphide (H2S) gas in three large sieve tray towers operating in p a r a l l e l which are the f i r s t stage. By making use of a two temperature exchange reaction (see "Figure 3") between hydrogen sulphide (H2S) and water - at 30°C deuterium is concentrated in the l i q u i d phase and a t 130°C deuterium is concentrated in the gas phase. The three f i r s t stage towers (see "Figure 2") each have two d i s t i n c t process temperature sections the top being a cold section and the bottom being a hot section. Deuterium is c a r r i e d forward to the second stage only in the gas phase while anything not extracted from the water is returned to the lake from the f i r s t stage a f t e r i t has been stripped of H2S and cooled. I f H2S in the e f f l u e n t is not within the

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

2.

DAVIDSON

Bruce

Heavy Water Plant

29

Performance

Water Treating

D

2

0

Enrichingj 20-30% D

2

0

Finishing 99.73% Product

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002

Treating

Candu Reactors

Figure 1.

BHWP-AD 0

Figure 2.

2

production

Enriching section

30°C H

2

0

(i> +

P D S (g) ^

±

P D O

(£) +

H

2

S

(g)

130°C

Figure 3.

GS process

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

SEPARATION OF HYDROGEN ISOTOPES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002

30

r e g u l a t o r y l i m i t s i t is d i v e r t e d t o a e r a t e d lagoons where the gas is removed and the water is s e n t t o t h e lake. One p a r t in 7000 coming o u t o f t h e l a k e is deuterium. But i t is o n l y e c o n o m i c a l t o remove about 20% or one p a r t in 35000. The second and t h i r d s t a g e s o n l y e n r i c h o r conc e n t r a t e t h e d e u t e r i u m which has been e x t r a c t e d . The second s t a g e is a s i n g l e tower whose o p e r a t i o n is s i m i l a r t o t h e f i r s t s t a g e towers. However, t h e r e is no h e a t i n g s e c t i o n a t the bottom o f the h o t tower as the gas is a l r e a d y hot coming forward from the f i r s t stage. To m a i n t a i n l i q u i d c i r c u l a t i o n in the second s t a g e , water is pumped from t h e bottom o f the h o t tower, t h r o u g h a c o o l e r t o t h e top o f the c o l d tower. The t h i r d s t a g e c o n s i s t s o f two s e p a r a t e towers - one c o l d tower, t h e o t h e r a hot tower. T h i r d s t a g e o p e r a t i o n a l s o d i f f e r s from the p r e v i o u s two. Enriched l i q u i d from the bottom o f t h e c o l d tower is t a k e n f o r ward f o r f u r t h e r p r o c e s s i n g . The H 2 S in t h i s e n r i c h i n g u n i t l i q u i d p r o d u c t is s t r i p p e d out and r e t u r n e d t o t h e t h i r d s t a g e gas l o o p . E n r i c h e d water a t 20 - 30% D 0 c o n c e n t r a t i o n from b o t h e n r i c h i n g u n i t s is f e d t o t h e f i n i s h i n g u n i t . The f i n i s h i n g u n i t is a t h r e e s t a g e , f o u r tower steam vacuum d i s t i l l a t i o n system t h a t c o n c e n t r a t e s t h e p r o d u c t from t h e e n r i c h i n g u n i t s i n t o the f i n a l r e a c t o r grade heavy water. A l l f i n i s h i n g u n i t towers c o n t a i n sieve trays. The heavy water is then t r e a t e d in e i t h e r o f two p o t a s s i u m permanganate b a t c h k e t t l e s t o o x i d i z e o r g a n i c impurities. The p r o d u c t is e i t h e r drummed o r s h i p p e d in b u l k t o CANDU r e a c t o r s . T r a n s l a t e d i n t o r e a l i t y , the process u n i t s a r e shown in t h e a e r i a l view o f BHWP (see " F i g u r e 4 " ) . BHWP A water i n t a k e is shared w i t h the Douglas P o i n t Nuclear Generating S t a t i o n . The f i g u r e shows t h e b u i l d i n g h o u s i n g t h e sand f i l t e r s , t h e d e g a s s i n g towe r s , the main s w i t c h y a r d , t h e steam s u p p l y from Douglas P o i n t N u c l e a r G e n e r a t i n g S t a t i o n and t h e Bruce Steam P l a n t , t h e H S s t o r a g e b u l l e t s , t h e f l a r e (145 m or 475 f e e t above g r a d e ) , t h e l a g o o n s , t h e a b s o r p t i o n and d e s o r p t i o n s e c t i o n c o n s i s t i n g o f an Absorber tower, Purge tower and an E f f l u e n t S t r i p p e r tower, t h e t h r e e f i r s t s t a g e towers, the second s t a g e tower, the t h i r d s t a g e and t h e f o u r tower, t h r e e s t a g e F i n i s h i n g U n i t . The f i g u r e a l s o shows the bank o f heat exchangers a c r o s s the f r o n t o f each u n i t , used t o a c h i e v e t h e two p r o c e s s temperatures and o p t i m i z e steam u t i l i z a tion . 2

2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

2.

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Safety

One m a j o r d i s a d v a n t a g e o f t h e D u a l T e m p e r a t u r e Hydrogen S u l p h i d e - Water Exchange Process i s t h e t o x i c i t y o f the H2Sgas and the p o t e n t i a l s a f e t y hazards i t poses. The g r e a t e s t d a n g e r f r o m t h e i n h a l a t i o n o f hydrogen sulphide i s from i t s acute e f f e c t s ; i t i s n o tcumulative i n a c t i o n . Exposure t o moderate c o n c e n t r a t i o n s causes headaches, d i z z i n e s s , nausea and vomiting i n that order. C o n t i n u e d e x p o s u r e may c a u s e l o s s o f consciousness, r e s p i r a t o r y f a i l u r e and death i f the gas c o n c e n t r a t i o n i s h i g h enough. Hydrogen S u l phide i s a l s o flammable and i n c e r t a i n mixtures w i t h a i r i t c a nbe e x p l o s i v e . From t h e o u t s e t , O n t a r i o Hydro o p e r a t i n g s t a f f e s t a b l i s h e d rigorous s a f e t y p o l i c i e s and procedures f o r a l l a s p e c t s o f c o m m i s s i o n i n g a n d o p e r a t i n g P l a n t A, w i t h s p e c i a l emphasis on the h a n d l i n g o f H2S and equipment c o n t a i n i n g i t . S a f e t y p e r f o r m a n c e a t B r u c e Heavy Water P l a n t i s p r e s e n t e d i n terms o f "H2S I n c i d e n t s " (see " F i g u r e 5") o r t h e number o f e m p l o y e e s t e m p o r a r i l y a f f e c t e d b y t h e t o x i c o l o g i c a l p r o p e r t i e s o f h y d r o g e n s u l p h i d e , number of l o s t time accidents and l o s t time accident frequency (see " F i g u r e 6"). "H2S I n c i d e n t s " are d e f i n e d as "sub-acute" o r "acute". B r i e f l y , a "sub-acute" i n c i d e n t i s one i n w h i c h a p e r s o n e x p o s e d t o H y d r o g e n S u l p h i d e shows s i g n s of b e i n g a f f e c t e d b u t does n o tr e q u i r e r e s u s c i t a t i o n or a s s i s t a n c e t o e x i t from the area a f f e c t e d by H2S, w h i l e an "acute" i n c i d e n t i s one i n which a person overcome by Hydrogen S u l p h i d e r e q u i r e s r e s u s c i t a t i o n and/or a s s i s t a n c e t o e x i t from the area a f f e c t e d by Hydrogen S u l p h i d e . Only one H2S I n c i d e n t has r e s u l t e d i na l o s t time a c c i d e n t ( i n 1975) when t h e a f f e c t s o f H 2 S c a u s e d a n employee t o f a l l and b r u i s e h i s r i b s . I n t h e t w o y e a r p e r i o d f r o m May 1 9 7 2 t o May 1 9 7 4 , w h i c h c o v e r e d t h e b u l k o f c o m m i s s i o n i n g , t h e r e was n o t a s i n g l e l o s t time accident. The two l o s t t i m e a c c i d e n t s i n 1976 were b o t h b a c k i n j u r i e s c a u s e d b y improper l i f t i n g techniques. F a c t o r s c o n t r i b u t i n g t o BHWP s a f e w o r k p e r f o r m a n c e ( s e e " F i g u r e 7") h a v e b e e n g r o u p e d u n d e r t h e b r o a d h e a d i n g s o f Management P o l i c i e s , S a f e t y T r a i n i n g , General T r a i n i n g , Procedures, Employee R e l a t i o n s , P l a n t I n t e g r i t y , P e r s o n a l P r o t e c t i v e Equipment and S a f e t y Equipment. A l l a r eimportant t o a successful s a f e t y program. A t no t i m e d u r i n g the h i s t o r y o f B r u c e Heavy Water

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002

SEPARATION OF HYDROGEN ISOTOPES

Figure 4. Aerial view of BHWP

1973

74

75

76

Figures. BHWP—History of H S incidents t

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

2.

3

Bruce

DAVIDSON

Heavy

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33

·

Lost T i m e

ι:·:·:·:·:.·ι :

Accidents

Frequency (/10

6

Rate

Manhours)

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1 ·

Manhours

1973

74

75

76

772,575

737,906

965,870

1,230,626

Figure 6.

1.

Management

BHWP—Safety

4.

Policies

- the b u d d y s y s t e m

environment

- training

- work on H2S systems

- procedural approach

- control of work - equipment inspections.

- plant m o d i f i c a t i o n c o n t r o l - equipment

maintenance

5.

Safety

- communications.

orientation 6.

- emergency procedures

Plant

Integrity

- b u d d y training

- isolating circuits a n d devices

- r e s c u e training

- equipment design

- p r o t e c t i o n training - fire,

- e m e r g e n c y p o w e r , s t e a m , w a t e r a n d air - equipment inspections.

c h e m i c a l , electrical, etc. - W o r k Protection C o d e

7.

Personal Protective

- t a n k c a r repairs

- conventional

- v e s s e l entry

- breathing

- first aid

- rescue stations.

- regular m e e t i n g s . 3.

Relations

- Personal Hygiene

Training

- new employee

Employee - Medicals

- event reporting. 2.

Procedures - plant a c c e s s control

- n u m b e r 1 priority - work

performance

8.

Safety

Equipment

equipment

Equipment

General Training

- fire f i g h t i n g

- science fundamentals

- H2S detectors and monitors

- e q u i p m e n t / s y s t e m s principles

- gas detectors

- plant s y s t e m s

- rescue vehicle

- field skills.

- survey vehicles - first aid r o o m .

Figure 7.

Factors contributing to safe work performance

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

34

SEPARATION

P l a n t has i t s o p e r a t i o n p r e s e n t e d and s a f e t y o f the p u b l i c . Care o f t h e

O F HYDROGEN

a r i s k t o the

health

Environment

Bruce Heavy Water P l a n t has two major e n v i r o n mental c o n s i d e r a t i o n s - H 2 S e m i s s i o n s t o atmosphere and H 2 S e m i s s i o n s t o water. On the f i r s t o f t h e s e , Hydrogen S u l p h i d e i s an odourous m a t e r i a l . I f concent r a t i o n s r e a c h more than 2 0 0 yg/m (micrograms per metre cubed) H 2 S can be s m e l l e d by most p e o p l e and i s c o n s i d e r e d by v i r t u a l l y a l l as an u n a c c e p t a b l e odour. The p l a n t i s s i t u a t e d i n a r u r a l and summer r e s o r t area. C o m p l a i n t s o f odour s t a r t e d t o be r e c e i v e d s h o r t l y a f t e r H S was i n t r o d u c e d i n t o the u n i t s i n 1973. By y e a r end, a t o t a l o f 56 c o m p l a i n t s were r e g i s t e r e d (see " F i g u r e 8"). A t a s k f o r c e was formed to r e c t i f y t h i s u n s a t i s f a c t o r y s i t u a t i o n . Several a c t i o n s were t a k e n : e f f o r t s were d i r e c t e d toward r e d u c i n g the amount o f H 2 S r e l e a s e d ; s t e p s were taken t o i n s u r e a c o m b u s t i b l e m i x t u r e o f s t a c k gas a t a l l t i m e s ; d r a i n water t o be s t r i p p e d o f H 2 S was m i n i m i z e d ; r e l e a s e s o f steam o r n i t r o g e n and o t h e r i n e r t s t o t h e f l a r e were accompanied by i n c r e a s e d propane f l o w s t o the f l a r e . In 1974, t h r e e odour r e p o r t s came i n , i n 1975 f o u r odour r e p o r t s were r e c e i v e d and i n 1976 t h e r e were two. R e l a t i o n s w i t h t h e p u b l i c a r e no l o n g e r a problem as f a r as H 2 S odours a r e c o n c e r n e d . An H 2 S r e c o v e r y system t o m i n i m i z e H 2 S and p r o pane usage i s b e i n g b u i l t as p a r t o f t h e p l a n t expansion. As a r e s u l t , H 2 S r e l e a s e s t o the f l a r e w i l l be f u r t h e r r e d u c e d . On the second e n v i r o n m e n t a l c o n s i d e r a t i o n , H 2 S e m i s s i o n s t o water, a l l water streams c o n t a i n i n g H 2 S must be s t r i p p e d o f i t b e f o r e the water i s r e t u r n e d to the l a k e . " F i g u r e 8" shows the number o f times the r e g u l a t o r y l i m i t f o r hydrogen s u l p h i d e i n water was exceeded by y e a r . U n s t a b l e f l o w s i n the towers were q u i t e f r e q u e n t i n 1973. T h i s i n s t a b i l i t y caused the e f f l u e n t s t r i p p e r operating conditions to f l u c t u a t e d e t e r r i n g i t s e f f e c t i v e n e s s . P h y s i c a l changes t o tower t r a y w e i r s and the a d d i t i o n o f a n t i f o a m t o t h e p r o c e s s water s t e a d i e d o p e r a t i n g c o n d i t i o n s and t h e r e f o r e improved the e f f e c t i v e n e s s o f the s t r i p p e r . Replacement o f u n r e l i a b l e i n s t r u m e n t a t i o n and b e t t e r p r o c e s s c o n t r o l d u r i n g s t a r t u p s and shutdowns have improved performance. A continuous H2S-in-water m o n i t o r which has p r o v e n r e l i a b l e w i t h q u i c k r e s p o n s e was i n s t a l l e d on the s t r i p p e r o u t l e t . This monitor p l u s o t h e r e f f l u e n t s t r i p p e r p r o c e s s parameters o f 3

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ISOTOPES

2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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f e e d temperature, l e v e l and p r e s s u r e have a l l been interlocked to automatically d i v e r t e f f l u e n t to the lagoons i f a p r e s e t c o n c e n t r a t i o n o f H 2 S i s exceeded o r t h e measured v a r i a b l e s exceed d e f i n e d l i m i t s .

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002

Reliability The r e l i a b i l i t y o f BHWP A has g e n e r a l l y been good f o r a p l a n t o f i t s s i z e w i t h m i n i m a l redundancy i n i t s o p e r a t i n g equipment. " F i g u r e 9" shows downtime e x p e r i e n c e t o d a t e . P l a n n e d u n i t t u r n - a r o u n d s have been r e d u c e d from 10 weeks i n 1973 t o 4 weeks i n 1975. An outage p l a n n e d f o r September, 1976 was advanced t o t a k e advantage o f an unplanned outage i n J u l y . Another f a c t o r o f r e l i a b i l i t y i s production r a t e . " F i g u r e 10" shows i n s t a n t a n e o u s p r o d u c t i o n r a t e s i n k i l o g r a m s p e r hour t h a t t h e p l a n t was o p e r a t i n g , i . e . shutdown p e r i o d s have been e x c l u d e d . The o r i g i n a l Des i g n C a p a c i t y was 48.3 kg/h f o r each e n r i c h i n g u n i t . F o l l o w i n g s t a r t up i n 1973, t r a y f l o o d i n g problems caused by foaminess o f t h e p r o c e s s and a d e f i c i e n c y i n t r a y d e s i g n were e x p e r i e n c e d . C o r r e c t i o n o f these problems by t h e a d d i t i o n o f a n t i f o a m t o t h e feedwater and m o d i f i c a t i o n o f t h e t r a y s r e s u l t e d i n d r a m a t i c improvements i n p r o d u c t i o n r a t e s . P r o d u c t i o n r a t e s have c o n t i n u e d t o improve, r e s u l t i n g i n a r e - r a t i n g o f t h e p l a n t c a p a c i t y i n 1976 t o 100.6 kg/h. C a p a c i t y F a c t o r s (based on D e s i g n C a p a c i t y f o r 1973 t o 1975 and based on Demonstrated C a p a c i t y f o r 1976) and a n n u a l p r o d u c t i o n a r e shown i n " F i g u r e 11". These do n o t i n c l u d e about 99 Mg t h a t were " e n r i c h e d " t o 20% i s o t o p i c p u r i t y d u r i n g 1974/1975/1976, o f which 31 Mg were " f i n i s h e d " t o r e a c t o r grade elsewhere i n 1975 and 42 Mg were " f i n i s h e d " elsewhere i n " 1976. I f t h e s e " f i n i s h e d " q u a n t i t i e s were c o m p l e t e l y c r e d i t e d t o BHWP A, t h e apparent C a p a c i t y F a c t o r s i n 1975 and 1976 would be 71.7% and 90.9% r e s p e c t i v e l y . Manpower Development The purpose o f t r a i n i n g i s t o e n s u r e t h a t each p o s i t i o n i n t h e p l a n t i s f i l l e d by a p e r s o n w i t h a p p r o p r i a t e knowledge and s k i l l s so t h a t t h e p l a n t i s o p e r a t e d s a f e l y , e f f e c t i v e l y and e f f i c i e n t l y . T r a i n i n g i s therefore a part o f the plant's p e r f o r mance o b j e c t i v e s . Formal t r a i n i n g i s p r o v i d e d by l e c t u r e d c o u r s e s and demonstrated s k i l l s i n t h e c l a s s r o o m and t h e f i e l d . F o r each j o b , t h e l e v e l and p r o f i c i e n c y which must be

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

36

SEPARATION

O F HYDROGEN

Odour

ΓΤ!Τ·!·!·!·!·!·!:!:Ι

i.'.',.„'.'.'.'.'.'|

ι

ISOTOPES

Reports

•!

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002

H2S E m i s s i o n s t o W a t e r

mam Figure 8.

%

rnmrn

74

1973

75

76

Environmental performance to date

Downtime

Enriching

Finishing

Units

Planned E$:$:$:3 F o r c e d

Unit

V////A T o t a l

Outages

Outages

Outages

ρ

m ϋ m

S 1973

74 Figure 9.

75

76

BHWP—Reliability

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002

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Performance

37

a t t a i n e d are s p e c i f i e d i n each o f the f o l l o w i n g : Management, S c i e n c e Fundamentals, Equipment and System P r i n c i p l e s , F i e l d S k i l l s , S p e c i f i c P l a n t Systems, AECB Operating License, Protection T r a i n i n g . T r a i n i n g i s p r o v i d e d by the N u c l e a r T r a i n i n g De partment o f O n t a r i o Hydro a t R o l p h t o n , by the Manpower Development Department o f O n t a r i o Hydro a t O r a n g e v i l l e , by the Bruce T r a i n i n g C e n t r e a t the s i t e and by the BHWP T r a i n i n g S e c t i o n . BHWP T r a i n i n g S e c t i o n i s s t a f f e d by e i g h t T r a i n i n g T e c h n i c i a n s , two e n g i n e e r s and a T r a i n i n g O f f i c e r . BHWP o p e r a t e s a f i v e s h i f t system i n s t e a d o f t h e t r a d i t i o n a l f o u r , so t h a t o p e r a t o r s , m a i n t a i n e r s and c o n t r o l t e c h n i c i a n s on s h i f t spend t e n t o f o u r t e e n p e r c e n t o f t h e i r time i n t r a i n i n g . I n 1975 t h e r e were 6,822 man c o u r s e s g i v e n and i n 1976 t h e r e were 11,400 man c o u r s e s g i v e n a t BHWP. Commissioning P r o g r e s s Report - BHWP Β A s s e m b l i n g a commissioning team o f e n g i n e e r s , o p e r a t o r s , m a i n t a i n e r s and c o n t r o l t e c h n i c i a n s f o r P l a n t Β began i n 1975. A nucleus o f personnel with o p e r a t i n g e x p e r i e n c e i n P l a n t A i s b e i n g augmented w i t h new employees. The commissioning group i s p r e p a r i n g commissioning e s t i m a t e s and p r o c e d u r e s , and i n s p e c t i n g and w i t n e s s i n g equipment t e s t s as the p l a n t i s being b u i l t . T h i s group i s commissioning and o p e r a t i n g the v a r i o u s p l a n t systems as t h e y a r e t u r n e d o v e r from c o n s t r u c t i o n . The a i r compressor system f o r P l a n t Β and t h e u t i l i t i e s f o r F i n i s h i n g U n i t F2 were t u r n e d o v e r from c o n s t r u c t i o n and commissioned i n the l a s t q u a r t e r o f 1976. The l a s t t u r n o v e r o f the F i n i s h i n g U n i t p r o c e s s system was on 6 J a n u a r y , 1977. P r e - s t a r t u p checks o f equipment and i n s t r u m e n t a t i o n were completed by 18 F e b r u a r y , 1977. O p e r a t i o n o f F2 on d e m i n e r a l i z e d water f o l l o w e d and t h i s program was completed by the end o f A p r i l . Equipment i n s p e c t i o n s f o l l o w i n g t h i s run and minor d e f i c i e n c y c o r r e c t i o n s were completed by 10 May, 1977 and s t a r t u p on i n t e r m e d i a t e p r o d u c t from P l a n t A commenced. F i r s t r e a c t o r grade p r o d u c t from F2 was produced on 23 May, 1977. The p l a n (see " F i g u r e 12") shows l a s t t u r n o v e r o f E n r i c h i n g U n i t E4 equipment f o r commissioning 1 May, 1978. E n r i c h i n g U n i t E3 l a s t t u r n o v e r i s s c h e d u l e d f o r 15 December, 1978. T h i s p l a n a l s o shows P l a n t D F i n i s h i n g U n i t F4 l a s t t u r n o v e r f o r commissioning a t the end o f September, 1979 w i t h E n r i c h i n g U n i t s 7 and

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

38

SEPARATION

OF

HYDROGEN

ISOTOPES

Extraction kg D 0 / h 2

60· Hot Tower

Clarifier Tests Alum Addition June 74

40<

^

^

: Q u e n c h W a t e r ·:·

1 s t A n t ifo a m

: Addition

Addition May

Temp.

Raised J a n .7 6

Stopped

June

'73 E1 W e i r :

Starts 75

Cuts:

Sept. 7 3

:

:

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002

20

1973

74

10.

Figure

76

75

Enriching

unit extraction

D 0/h)

(kg

2

Production Megagrams

Capacitor Factor % 57

249

1974

76

640

1975

68

574

1976

86

758

74

2221

1973

(6 mo.)

Figure

11.

BHWP-A

BHWP Β

E4

<3>—©

F2

E3

First R / G

D

2

Φ

0

®Φ-®

BHWP D

E7 φ

Last Turnover ( L u m m u s to O . H . )

@

First E x t r a c t i o n o f D 0

F4

E8

( § ) First R e a c t o r G r a d e @

1976

-®

2

D 0 2

First R / G

D

2

0

In S e r v i c e

77

Figure

78

12.

Commissioning

79

80

milestones

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

81

2.

DAVIDSON

Bruce Heavy

Water

Plant

Performance

8 t o f o l l o w i n 1980. Conclusion The c o - o p e r a t i o n o f AECL and O n t a r i o Hydro has brought s u c c e s s t o Bruce Heavy Water P l a n t t o d a t e . Comparable r e s u l t s a r e expected i n t h e f u t u r e . September

12, 1977

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch002

RECEIVED

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

3 Hydrogen-Amine Process for Heavy Water Production W. J. HOLTSLANDER Atomic Energy of Canada Ltd., Chemical Engineering Branch, Chalk River Nuclear Laboratories, Chalk River, Ontario W. E . LOCKERBY

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003

Atomic Energy of Canada Ltd., Heavy Water Projects, Tunney's Pasture, Ottawa, Ontario

Ammonia-hydrogen or amine-hydrogen exchange is one of the three major chemical systems considered u s e f u l f o r deuterium enrichment processes. The other two being the water-hydrogen sulfide system (GS process) p r e s e n t l y being used to produce the major f r a c t i o n o f the w o r l d ' s heavy water supply and the hydrogen -water system which is c u r r e n t l y under a c t i v e development. Heavy water p l a n t s based on ammonia-hydrogen exchange have operated in France and are being commissioned in I n d i a . The usefulness of amines in place of ammonia was shown by B a r - E l i and K l e i n (_1) in 1962. This work showed amines, p a r t i c u l a r l y methylamine had f a s t e r exchange r a t e s than the comparable ammonia-based system. A t Chalk R i v e r , a f t e r work w i t h the ammonia-hydrogen system showed a water-fed p l a n t d i d not o f f e r any advantage over the GS p r o c e s s , development was s t a r t e d on the amine-hydrogen system. A p a r a l l e l development program f o r the amine process was a l s o i n i t i a t e d by the Commissariat a L ' E n e r g i e Atomique in France and d e t a i l s of the exchange r e a c t i o n work were reported by Rochard and Ravoire ( 2 ) . The amine chosen was methylamine (MA). The advan tages of methylamine over ammonia are f a s t e r deuterium exchange r a t e s , higher hydrogen s o l u b i l i t y and a low vapour pressure. The choice of methylamine over other amines was discussed in d e t a i l by Bancroft and Rae ( 3 ) . The o r i g i n a l c a t a l y s t was the potassium s a l t of methylamine, potassium methylamide (PMA), because of i t s favourable exchange r a t e coupled w i t h reasonable c o s t . Subsequent work forced a m o d i f i c a t i o n o f the c a t a l y s t and the reasons f o r t h i s w i l l be d i s c u s s e d . T h e d e v e l o p m e n t o f t h e amine p r o c e s s a t CRNL p r o c e e d e d in three major areas: c o n t a c t o r development, p r o c e s s c h e m i s t r y and p r o c e s s d e s i g n . Development o f e f f i c i e n t g a s - l i q u i d c o n t a c t o r s was r e q u i r e d t o p r o v i d e h i g h mass t r a n s f e r r a t e s p e r u n i t volume in t h e c o l d t o w e r s (-50°C) where t h e e x c h a n g e r e a c t i o n r a t e is r e l a t i v e l y slow. T h i s program evolved through a s e r i e s o f p i l o t p l a n t c o n t a c t o r s r a n g i n g in s i z e f r o m 5 t o 15 cm d i a m e t e r a t l o w

©

0-8412-0420-9/78/47-068-040$05.00/0

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

3.

HOLTSLANDER

AND

LOCKERBY

Hydro gen-Amine

Process

41

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003

p r e s s u r e in g l a s s t o a 25 cm s t a i n l e s s s t e e l c o n t a c t o r t h a t o p e r a t e d a t 2 MPa (300 p s i ) f o r b o t h c o l d t o w e r a n d h o t t o w e r testing. F u r t h e r i n f o r m a t i o n on c o n t a c t o r development and process d e s i g n was o b t a i n e d in c o o p e r a t i o n w i t h S u l z e r B r o s . , S w i t z e r l a n d who h a d i n d e p e n d e n t l y c o n s t r u c t e d a p i l o t p l a n t u s i n g a f u l l s c a l e contactor operating a t f u l l process pressure (4). E x t e n s i v e p r o c e s s d e s i g n work and economic e v a l u a t i o n s were done a t CRNL a n d u n d e r c o n t r a c t w i t h i n d u s t r i a l e n g i n e e r i n g f irms. The v e r y e x t e n s i v e c h e m i s t r y p r o g r a m c o n s i s t e d o f d e t e r m i n ing the p h y s i c a l and chemical p r o p e r t i e s o f the system, d e v e l o p i n g h a n d l i n g and a n a l y t i c a l t e c h n i q u e s , d e t e r m i n i n g the r e a c t i v i t y o f the system w i t h p o t e n t i a l i m p u r i t i e s , examining f a c t o r s which a f f e c t the deuterium exchange r a t e , l o o k i n g f o r b e t t e r c a t a l y s t s t o improve the exchange r a t e and s t u d y i n g the s t a b i l i t y o f the c a t a l y s t s o l u t i o n a t process c o n d i t i o n s . This p r o g r a m was v e r y much o f a p i o n e e r i n g one b e c a u s e o f t h e s c a r c i t y o f i n f o r m a t i o n o n s o l u t i o n s o f a l k a l i m e t a l a l k y l a m i d e in a m i n e s in t h e l i t e r a t u r e . I t was n e c e s s a r y t o f i r s t d e v e l o p s u i t a b l e l a b o r a t o r y t e c h n i q u e s t o handle such a r e a c t i v e system s a f e l y and in t h e a b s e n c e o f a t m o s p h e r i c c o n t a m i n a n t s t o o b t a i n meaningful q u a n t i t a t i v e data. The a b s e n c e o f p r e v i o u s l y p u b l i s h e d i n f o r m a t i o n o n r e l a t e d s y s t e m s meant t h a t l i t t l e g u i d a n c e was a v a i l a b l e f o r p r e d i c t i o n o f t h e c h e m i c a l b e h a v i o u r and a l l a s p e c t s o f t h e w o r k had t o b e e x p e r i m e n t a l l y d e t e r m i n e d . D e v e l o p m e n t o f a c o m p l e t e r a n g e o f a n a l y t i c a l m e t h o d s was a m a j o r component o f t h e p r o g r a m . W i t h t h i s l a c k o f b a c k g r o u n d i n f o r m a t i o n , u n f o r e s e e n r e s u l t s were o f t e n observed. A prime e x a m p l e in t h i s w o r k was t h e d i s c o v e r y t h a t h y d r o g e n a t p r o c e s s p r e s s u r e is a r e a c t i v e s p e c i e s ; n o t o n l y in t h e d e u t e r i u m e x c h a n g e r e a c t i o n b u t a l s o c h e m i c a l l y . T h i s is n o t s oint h e c o m p a r a b l e ammonia s y s t e m and was t o t a l l y u n e x p e c t e d . I t was t h i s d i s c o v e r y t h a t n e c e s s i t a t e d t h e d e v e l o p m e n t o f a new c a t a l y s t t o make t h e p r o c e s s v i a b l e . Because the process operates a t h i g h p r e s s u r e (6-13 MPa, d i c t a t e d b y t h e h o s t ammonia p l a n t ) t o o b t a i n e f f e c t i v e mass t r a n s f e r r a t e s , much o f t h e c h e m i s t r y h a d t o b e done a t c o n d i t i o n s w h i c h s i m u l a t e d t h e p r o c e s s . T h i s added t h e c o m p l i c a t i o n o f having t o develop s p e c i a l experimental techniques. T h i s w o r k i l l u s t r a t e s t h e i m p o r t a n c e o f c h e m i s t r y s t u d i e s in p r o c e s s d e v e l o p m e n t . A l t h o u g h d e u t e r i u m e x c h a n g e is t h e c e n t r a l f e a t u r e o f a heavy water process, s u c c e s s f u l development r e q u i r e s d e t a i l e d knowledge o f a l l a s p e c t s o f p r o c e s s c h e m i s t r y . I n many c a s e s t h e s e a r e l a r g e l y unknown b e f o r e h a n d . The c h e m i s t r y w o r k was done b y a number o f g r o u p s a t CRNL and t h r o u g h c o n t r a c t s w i t h t h e U n i v e r s i t y o f A l b e r t a , T r e n t U n i v e r s i t y , R a y l o C h e m i c a l s L t d . in A l b e r t a a n d C h e m i c a l P r o j e c t s L t d . in T o r o n t o . A more d e t a i l e d r e v i e w o f t h i s c h e m i c a l w o r k forms the major p o r t i o n o f t h i s paper.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

42

S E P A R A T I O N O F H Y D R O G E N ISOTOPES

Process

Chemistry

The p r o c e s s l i q u i d , m e t h y l a m i n e , must c o n t a i n a d i s s o l v e d c a t a l y s t t o p r o v i d e an a c c e p t a b l e d e u t e r i u m e x c h a n g e r a t e . This c a t a l y s t is p r e p a r e d b y d i s s o l v i n g p o t a s s i u m m e t a l in t h e m e t h y l amine. The p o t a s s i u m s l o w l y d i s s o l v e s t o g i v e a b l u e s o l u t i o n t y p i c a l o f a l k a l i m e t a l s in ammonia o r a m i n e s . Blue

Yellow +

Κ + C H N H + K , K~, e" - + KNHCH + % H 3 2 * ' solv 3 2

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003

0

0

0

I n a m i n e s w i t h p o t a s s i u m F l e t c h e r e t a l Ç5,6) a t CRNL h a v e shown t h i s c o l o u r t o be due t o a n e q u i l i b r i u m b e t w e e n p o t a s s i u m a n i o n s and s o l v a t e d e l e c t i o n i o n p a i r s . The b l u e c o l o u r e d s o l u t i o n s l o w l y decomposes t o g i v e t h e y e l l o w p o t a s s i u m m e t h y l a m i d e s o l u t i o n and hydrogen. A l k a l i m e t a l a l k y l a m i d e s d i s s o l v e d in a m i n e s a r e s t r o n g b a s e s and a r e v e r y r e a c t i v e c h e m i c a l l y . They r e a c t v i g o r o u s l y w i t h a i r and w a t e r s o t h a t s p e c i a l t e c h n i q u e s a r e r e q u i r e d when h a n d l i n g and s t u d y i n g t h e s e s y s t e m s . Some o f t h e more i m p o r t a n t r e a c t i o n s w i t h i m p u r i t i e s e n c o u n t e r e d in t h e p r o c e s s a r e l i s t e d below. CH^NHK + H 0

CH NH

2

CH^NHK + 0

3

2

+ ΚΟΗΨ

-> KCN+, CH NCH=NCH , ΚΟΗΨ

2

3

3

Κ Potassium D ime t h y 1 f ο rmamid i d e 0

π CH NHK + CO

CH^NHK + C 0

HC-lji- CH Ψ ( p o t a s s i u m N - m e t h y l f ormamide) Κ 0 2

-> C^NHC-ΟΚΨ(carbamate) 0

2CH NH 3

2

+ C0

CH NHK + N H 3

0

2

3

·> CH NHC-O CH NH®(carbamate) 3

-> C H N H 3

3

2

+ KNH^

A l l o f t h e s e r e a c t i o n s h a v e b e e n s t u d i e d in v a r y i n g d e g r e e s o f d e t a i l t o d e t e r m i n e t h e i d e n t i t y o f t h e p r o d u c t s and t h e e f f e c t t h e y h a v e on t h e p r o c e s s . The m a j o r c o n s e q u e n c e o f t h e s e r e a c t i o n s is d e s t r u c t i o n o f c a t a l y s t t h u s r e d u c i n g t h e e x c h a n g e r a t e , and p r o d u c i n g i n s o l u b l e s o l i d s t h a t may c a u s e d e p o s i t i o n

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

3.

HOLTSLANDER

H y dro gen-Amine

A N D LOCKERBY

Process

43

and b l o c k a g e o f e q u i p m e n t . I t is t h e r e f o r e a r e q u i r e m e n t t h a t t h e s e i m p u r i t i e s b e m a i n t a i n e d a t an a c c e p t a b l y l o w l e v e l in t h e process t o a v o i d these problems. An a r e a o f p r o c e s s c h e m i s t r y t h a t was e x t e n s i v e l y s t u d i e d b o t h a t C h a l k R i v e r and by S a n f o r d , P r e s c o t t and Lemieux a t Raylo C h e m i c a l s , Edmonton was t h e t h e r m a l s t a b i l i t y o f t h e PMA-MA system. Thermal decomposition occurs t o y i e l d t h r e e major p r o d u c t s : h y d r o g e n , p o t a s s i u m d i m e t h y l f o r m a m i d i d e (PDMFA) a n d ammonia, 2CH NH

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003

3

2

+ CH^NHK + 2 H + CH N=CHNKCH + N H ^ 2

3

3

The r a t e o f t h i s r e a c t i o n h a s b e e n d e t e r m i n e d o v e r t h e r a n g e of p r o c e s s c o n d i t i o n s . A s a r e s u l t t h e optimum h o t t o w e r t e m p e r a t u r e o r i g i n a l l y s e t a t 70°C ( 3 ) b a s e d on p r e l i m i n a r y d e c o m p o s i t i o n d a t a was r e d u c e d t o 40^C. The d e c o m p o s i t i o n r e a c t i o n h a s two p r o c e s s e f f e c t s ; i t r e s u l t s in a l o s s o f c a t a l y s t t h a t r e q u i r e s make-up and i t p r o d u c e s ammonia and PDMFA b o t h o f w h i c h must be removed. The ammonia must b e removed b e c a u s e o f i t s r e a c t i o n w i t h PMA f o r m i n g p o t a s s i u m amide w h i c h h a s a l i m i t e d s o l u b i l i t y (0.06 mmoles/g). Removal o f PDMFA is o f l e s s importance b u t i t w i l l e v e n t u a l l y b u i l d up t o a c o n c e n t r a t i o n t h a t e x c e e d s i t s s o l u b i l i t y (3.3 mmoles/g @ -40°C) a n d w i l l p r e c i p i t a t e . I n t h e s t u d y o f ways t o r e d u c e t h e d e c o m p o s i t i o n r a t e a n u n e x p e c t e d s i d e r e a c t i o n was d i s c o v e r e d . S i n c e h y d r o g e n was a p r o d u c t o f t h e d e c o m p o s i t i o n , one o f t h e p o s t u l a t e d f i r s t s t e p s w a s d e h y d r o g e n a t i o n o f t h e PMA t o a m e t h y l e n i m i n e , CH NHK t CH =NK + 3

2

I f t h i s p o s t u l a t e d i n t e r m e d i a t e s t e p was r e v e r s i b l e t h e n a h i g h hydrogen p a r t i a l p r e s s u r e might i n h i b i t t h e d e c o m p o s i t i o n . Since t h e p r o c e s s o p e r a t e s most e f f e c t i v e l y a t h i g h h y d r o g e n p r e s s u r e i t was e s s e n t i a l t o i n v e s t i g a t e t h e d e c o m p o s i t i o n r e a c t i o n o v e r t h e f u l l p r e s s u r e range. High hydrogen p r e s s u r e d i d reduce t h e d e c o m p o s i t i o n r a t e b u t t h e r e s u l t s were v e r y e r r a t i c and t h e e x p e r i m e n t s were p l a g u e d b y t h e i r r e p r o d u c i b l e a p p e a r a n c e a n d disappearance of white p r e c i p i t a t e s . Workers a t Raylo Chemicals showed t h e h y d r o g e n was r e a c t i n g w i t h t h e PMA-MA s o l u t i o n t o g i v e p o t a s s i u m h y d r i d e w h i c h was i n s o l u b l e . CH NHK + H 3

2

t CH NH 3

2

+ ΚΗΨ

The a p p a r e n t r e d u c t i o n in t h e r m a l d e c o m p o s i t i o n r a t e was due t o r e m o v a l o f PMA f r o m s o l u t i o n . T h i s r e a c t i o n t o f o r m KH does n o t o c c u r in t h e ammonia s y s t e m and was n o t e x p e c t e d in m e t h y l a m i n e . A r e a c t i o n b e t w e e n KNH2 a n d h y d r o g e n d o e s o c c u r in ammonia a t v e r y h i g h hydrogen p r e s s u r e , b u t g i v e s t h e s o l v a t e d e l e c t r o n (the b l u e s o l u t i o n ) r a t h e r than a h y d r i d e p r e c i p i t a t e (7,8).

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003

44

SEPARATION

OF

HYDROGEN

ISOTOPES

The gas l i q u i d c o n t a c t o r w o r k a t C h a l k R i v e r was done a t 2 MPa and m i s s e d t h e h y d r i d e r e a c t i o n . A l o w p r e s s u r e c o n t a c t o r was u s e d b e c a u s e t h e mass t r a n s f e r c o e f f i c i e n t was l i q u i d phase c o n t r o l l e d and c o u l d be r e l i a b l y e x t r a p o l a t e d t o h i g h e r p r e s s u r e s . I t was o n l y through the chemistry study the r e a c t i v i t y of hydrogen w i t h p o t a s s i u m m e t h y l a m i d e came t o l i g h t . The h y d r i d e r e a c t i o n had m a j o r p r o c e s s i m p l i c a t i o n s . B e c a u s e o f t h e l o w KH s o l u b i l i t y t h e n e t r e a c t i o n a t p r o c e s s h y d r o g e n p r e s s u r e s was t o t h e r i g h t so t h a t t h e m a j o r p o r t i o n o f t h e c a t a l y s t was t a k e n o u t o f s o l u t i o n as t h e h y d r i d e . T h i s is shown in F i g u r e 1. T h e r e is l i t t l e t e m p e r a t u r e e f f e c t on t h e r e a c t i o n , w h i c h o c c u r s t o g i v e a s i m i l a r shape o f s o l u b i l i t y v e r s u s p r e s s u r e f r o m -30°C t o +50°C. The e f f e c t o f t h e l o w maximum c a t a l y s t s o l u b i l i t y in s o l u t i o n s a t p r o c e s s p r e s s u r e was t o r e d u c e t h e c o l d t o w e r e x c h a n g e e f f i c i e n c y t o a b o u t h a l f t h a t m e a s u r e d a t 2 MPa. A f t e r d i s c o v e r y o f t h e h y d r i d e r e a c t i o n an e x t e n s i v e p r o g r a m was i n i t i a t e d t o f i n d a method o f i n h i b i t i n g t h e r e a c t i o n . A v e r y l a r g e number o f c h e m i c a l a d d i t i v e s and a l t e r n a t i v e s y s t e m s were investigated. Work a t C h a l k R i v e r showed t h e a n a l o g o u s r e a c t i o n o c c u r r e d w i t h s o d i u m m e t h y l a m i d e in m e t h y l a m i n e and w i t h s o d i u m and p o t a s s i u m d i m e t h y l a m i d e in d i m e t h y l a m i n e . I t d i d not occur w i t h l i t h i u m methylamide or w i t h cesium methylamide, but l i t h i u m m e t h y l a m i d e is a v e r y p o o r c a t a l y s t f o r d e u t e r i u m e x c h a n g e and c e s i u m is e x p e n s i v e . I t was f o u n d , h o w e v e r , t h a t when l i t h i u m was added t o PMA in m e t h y l a m i n e t h e r e a c t i o n w i t h h y d r o g e n d i d n o t o c c u r , a t l e a s t in t h e r a n g e o f h y d r o g e n p a r t i a l p r e s s u r e s o f i n t e r e s t to the heavy water p r o c e s s . T h i s is shown in F i g u r e 2 where PLMA r e p r e s e n t s e q u i m o l a r p o t a s s i u m - l i t h i u m m e t h y l a m i d e . T h i s d i s c o v e r y s o l v e d one o f t h e m a j o r p r o c e s s p r o b l e m s b u t r e q u i r e d t h e answer t o many q u e s t i o n s s u c h as t h e e f f e c t o f added l i t h i u m on t h e e x c h a n g e r e a c t i o n , t h e r e a c t i o n s w i t h i m p u r i t i e s , t h e t h e r m a l d e c o m p o s i t i o n r e a c t i o n , and t h e optimum l i t h i u m concentration. E x c h a n g e r a t e s w e r e s t u d i e d in t h e l a b o r a t o r y a t C h a l k R i v e r u s i n g a s m a l l r a p i d l y s t i r r e d e x c h a n g e c e l l where t h e t r a n s f e r o f d e u t e r i u m f r o m h y d r o g e n t o m e t h y l a m i n e was m o n i t o r e d w i t h an onl i n e mass s p e c t r o m e t e r . L a r g e - s c a l e e x c h a n g e w o r k was done in t h e 25 cm p i l o t p l a n t c o n t a c t o r . K i n e t i c e x c h a n g e d a t a u s i n g a s i n g l e - s p h e r e a b s o r b e r was a l s o o b t a i n e d by P r o f e s s o r F.D. O t t o a t t h e U n i v e r s i t y o f A l b e r t a . I n i t i a l w o r k showed t h e PLMA e x c h a n g e c a t a l y s t gave e q u a l o r somewhat h i g h e r r a t e c o n s t a n t s and t r a y e f f i c i e n c i e s t h a n PMA. However, s u b s e q u e n t more d e t a i l e d w o r k has shown t h e e x c h a n g e r a t e c o n s t a n t is d e p e n d e n t on t h e amount o f l i t h i u m added and d e c r e a s e s w i t h i n c r e a s i n g l i t h i u m c o n c e n t r a t i o n . T h i s is shown in F i g u r e 3. The t e m p e r a t u r e c o e f f i c i e n t o f t h e e x c h a n g e r e a c t i o n was f o u n d t o be t h e same f o r b o t h t h e PMA and PLMA s y s t e m s w i t h an a c t i v a t i o n e n e r g y o f 28 k j o u l e s / m o l e , t h e same a s was f o u n d e a r l i e r by R o c h a r d f o r t h e PMA s y s t e m ( 2 ) .

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

3.

HOLTSLANDER

Hydrogen-Amine

A N D LOCKERBY

45

Process

MAXIMUM CATALYST CONCENTRATION

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003

(m moles/g)

8

10

12

14

16

18

20

22

24

26

28

30

PRESSURE (MPa)

Figure 1.

Effect of hydrogen on PMA solutions at 296°Κ

MAXIMUM CATALYST CONCENTRATION (m moles/g)

12

14

16

18

20

22

24

26

28

30

PRESSURE (MPa)

Figure 2.

Effect of hydrogen on PMA and PLMA

catalyst solutions at 296°Κ

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003

46

SEPARATION O F H Y D R O G E N ISOTOPES

Figure 3.

Effect of lithium-potassium mole ratio on exchange rate. Stirred exchange cell at 203°K.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003

3.

HOLTSLANDER

AND

LOCKERBY

Hydrogen-Amine

Process

47

A s e c o n d exchange r e a c t i o n t h a t o c c u r s in b o t h t h e PMA and PLMA s y s t e m is d e u t e r i u m e x c h a n g e b e t w e e n t h e amino- and m e t h y l groups o f methylamine. T h i s r e a c t i o n was s t u d i e d in d e t a i l b y H a l l i d a y and B i n d n e r (9) a t CRNL and is more t h a n 1000 t i m e s s l o w e r than the amino-group-molecular hydrogen exchange. W h i l e i t d o e s r e s u l t in a s l o w b u i l d u p o f d e u t e r i u m in t h e m e t h y l g r o u p o f t h e p r o c e s s l i q u i d , i t does n o t c o n s t i t u t e a p r o c e s s p r o b l e m . The s o l u b i l i t y - t e m p e r a t u r e r e l a t i o n s h i p o f PLMA ( F i g u r e 4) is o p p o s i t e t o t h a t o f e i t h e r PMA o r LMA ( l i t h i u m m e t h y l a m i d e ) , s h o w i n g a somewhat l o w e r s o l u b i l i t y a t t h e l o w t e m p e r a t u r e and a much h i g h e r s o l u b i l i t y a t h i g h t e m p e r a t u r e s . The s o l u b i l i t y is a l s o m a r k e d l y d e p e n d e n t on t h e l i t h i u m c o n c e n t r a t i o n a s shown in F i g u r e 5. A s t h e amount o f l i t h i u m i n c r e a s e s t h e t o t a l s o l u b i l i t y increases rapidly. I n f a c t systems w i t h h i g h l i t h i u m r a t i o s y i e l d e d c l e a r s o l u t i o n s w i t h a s a l t c o n t e n t c l o s e t o 30% by w e i g h t . The e f f e c t o f added l i t h i u m on t h e t h e r m a l s t a b i l i t y o f t h e s o l u t i o n is shown in F i g u r e 6. The s o l u t i o n is more s t a b l eint h e presence of l i t h i u m w i t h the h a l f - l i f e f o r an equimolar potassiuml i t h i u m s o l u t i o n b e i n g h i g h e r (100 d a y s ) a t 40°C t h a n a PMA s o l u t i o n (25 d a y s ) . I n t h e h e a v y w a t e r p r o c e s s w h e r e t h e s o l u t i o n is c i r c u l a t i n g b e t w e e n c o l d and h o t t o w e r s t h e t i m e s p e n t a t 40°C is o n l y a f r a c t i o n o f a c t u a l t i m e in t h e p r o c e s s so t h a t t h e p r a c t i c a l h a l f - l i f e o f t h e s o l u t i o n is g r e a t e r t h a n t h e 100 d a y s m e a s u r e d in t h e l a b o r a t o r y . The p r o d u c t s o f d e c o m p o s i t i o n a r e t h e same as f r o m PMA w i t h t h e a d d i t i o n o f l i t h i u m d i m e t h y l f o r m a m i d i d e . The ammonia formed r e a c t s i n d i s c r i m i n a t e l y w i t h l i t h i u m and p o t a s s i u m s a l t s t o p r e c i p i t a t e L i N H 2 and KNH2. I n a d d i t i o n , i t was f o u n d t h a t t h e amide s a l t s c o - p r e c i p i t a t e d m e t h y l a m i d e a l o n g w i t h them t h u s f u r t h e r r e m o v i n g a c t i v e c a t a l y s t f r o m t h e s o l u t i o n . F o r t h i s r e a s o n t h e p u r i f i c a t i o n s y s t e m m u s t m a i n t a i n t h e ammonia a t a c o n c e n t r a t i o n b e l o w 0.06 mmole/g w h i c h c o r r e s p o n d s t o t h e amide s o l u b i l i t y . S a n f o r d a t R a y l o has demonstrated a s i m p l e p u r i f i c a t i o n method b a s e d o n d i s t i l l a t i o n o f a s i d e s t r e a m t o remove ammonia and c o n v e r t a m i d e s b a c k t o m e t h y l a m i d e s . MNH

+ CH NH

2

3

2

-> CH^NHM + N H ^

From t h e f u n d a m e n t a l p o i n t o f v i e w t h e q u e s t i o n a r i s e s o f how l i t h i u m m o d i f i e s t h e p r o p e r t i e s o f t h e s o l u t i o n . L i t h i u m m e t h y l a m i d e b y i t s e l f in m e t h y l a m i n e s o l u t i o n is a v e r y p o o r c a t a l y s t w i t h a n e x c h a n g e r a t e l e s s t h a n 1% o f t h a t o f PMA. The w o r k r e p o r t e d in t h i s p a p e r s u g g e s t s t h a t p o t a s s i u m and l i t h i u m m e t h y l a m i d e e x i s t in s o l u t i o n a s a c o m p l e x r a t h e r t h a n a s i m p l e m i x t u r e o f t h e two s a l t s in s o l u t i o n . S u c h a c o m p l e x in e q u i l i b r i u m w i t h t h e two m e t h y l a m i d e s is shown b e l o w . K Li (NHCH ) ^±2KNHCH 2

2

3

4

3

+ 2LiNHCH

2

E v i d e n c e f o r s u c h a c o m p l e x in s o l u t i o n is s u m m a r i z e d in F i g u r e 7. The t o t a l l y o p p o s i t e s o l u b i l i t y - t e m p e r a t u r e r e l a t i o n s h i p

American Chemfcar

Society Library

1155 of Hydrogen 16th St.Isotopes; N. w.Rae, H.; In Separation ACS Symposium Series; American Chemical Washington, DC, 1978. Washington, D. C.Society: 20038

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003

SEPARATION O F HYDROGEN ISOTOPES

Figure 4.

Solubility of methylamides

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Hydrogen-Amine

A N D LOCKERBY

Process

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003

HOLTSLANDER

Figure

5. Solubility

of

potassium-lithium methylamine

methylamide

in

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

SEPARATION

O F HYDROGEN ISOTOPES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003

1000

Figure 7.

Evidence that PLMA is a complex

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

3.

HOLTSLANDER

AND

LOCKERBY

Hydrogen

Amine

Process

51

i n d i c a t e s a c o m p l e x r a t h e r t h a n a m i x t u r e . The I R a n d X - r a y s p e c t r a obtained i n Glinthard's l a b o r a t o r y i n t h e Swiss F e d e r a l I n s t i t u t e o f T e c h n o l o g y u n d e r c o n t r a c t t o S u l z e r shows u n i q u e s p e c t r a f o r PLMA r a t h e r t h a n a sum o f a l l t h e l i n e s f r o m PMA a n d LMA. C o n d u c t i v i t y d a t a o b t a i n e d a t CRNL shows a d i f f e r e n t t e m p e r a t u r e b e h a v i o u r f o r PLMA t h a n f o r PMA o r LMA. The r e a c t i v i t y i s d i f f e r e n t t h a n PMA a n d t h e v a p o u r p r e s s u r e d a t a o b t a i n e d b y Sanford a t Raylo Chemicals i n d i c a t e s a d i f f e r e n t species i n s o l u t i o n t h a n e i t h e r o f t h e two component s a l t s . A l l o f these o b s e r v a t i o n s a r e c o n s i s t e n t w i t h a complex r a t h e r than a s i m p l e mixture.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003

Conclusion I t h a s been demonstrated t h a t p o t a s s i u m - l i t h i u m methylamide i s a s u p e r i o r c a t a l y s t f o r t h e amine-hydrogen heavy water p r o c e s s . I t does n o t r e a c t w i t h hydrogen, and I t has a f a v o u r a b l e deuterium e x c h a n g e r a t e , good s o l u b i l i t y a n d a n a c c e p t a b l e t h e r m a l decomposition rate. A p a t e n t h a s b e e n g r a n t e d f o r t h i s new c a t a l y s t (10). The a m i n e - h y d r o g e n p r o c e s s i s r i c h i n c h e m i s t r y , much o f i t p r e v i o u s l y unknown. The p r a c t i c a l a s p e c t s o f t h e c h e m i s t r y w h i c h d i r e c t l y affect theprocess, i . e . , the preparation of catalyst, t h e r e a c t i v i t y o f t h ec a t a l y s t s o l u t i o n w i t h process ingredients and p r o c e s s i m p u r i t i e s , t h e d e u t e r i u m e x c h a n g e p r o p e r t i e s , t h e t h e r m a l s t a b i l i t y have been t h o r o u g h l y i n v e s t i g a t e d . The p r o c e s s c h e m i s t r y s t u d i e s p r o v i d e a f i r m b a s i s f o r t h e p r o c e s s , however t h e r e i s s t i l l many f u n d a m e n t a l a s p e c t s o f c h e m i s t r y o f t h e s y s t e m w h i c h c o u l d be a f e r t i l e a r e a f o r f u r t h e r b a s i c r e s e a r c h . As a r e s u l t o f t h e s u c c e s s a c h i e v e d i n t h e t h r e e a r e a s o f development, t h a t o f g a s - l i q u i d c o n t a c t o r s , p r o c e s s c h e m i s t r y and p r o c e s s d e s i g n , t h e amine-hydrogen heavy water p r o c e s s h i s reached t h e p o s i t i o n w h e r e t h e n e x t s t a g e i s commitment o f a p r o t o t y p e p l a n t , and t h u s i s now b e i n g p u r s u e d . Acknowledgement s We a c k n o w l e d g e t h e c o n t r i b u t i o n s o f D r . H.K. Rae a n d A.R. B a n c r o f t who d i r e c t e d t h e p r o c e s s d e v e l o p m e n t p r o g r a m a n d for t h e i r review of t h i s manuscript. We a l s o a c k n o w l e d g e D r s . J . F . P r e s c o t t a n d E.C. S a n f o r d a t R a y l o C h e m i c a l s a n d R.E. J o h n s o n a n d R.P. D e n a u l t o f t h e C h e m i c a l E n g i n e e r i n g B r a n c h , CRNL f o r t h e i r m a j o r c o n t r i b u t i o n t o t h e e x p e r i m e n t a l w o r k a n d t o D r . J.P. M i s l a n a n d c o - w o r k e r s o f t h e G e n e r a l C h e m i s t r y B r a n c h , CRNL, who d i d much o f t h e a n a l y t i c a l m e t h o d s d e v e l o p m e n t .

Abstract The hydrogen-amine process f o r heavy water p r o d u c t i o n employs a deuterium i s o t o p e exchange r e a c t i o n between hydrogen and m e t h y l amine c o n t a i n i n g a d i s s o l v e d alkali metal methylamide c a t a l y s t .

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

52

SEPARATION OF HYDROGEN ISOTOPES

This system is c h e m i c a l l y v e r y r e a c t i v e and a d e t a i l e d understand ing o f all aspects of the process chemistry was r e q u i r e d . T h i s understanding was made more difficult by the l a c k of i n f o r m a t i o n in the literature on this o r similar systems. The m a j o r i t y of the work was of a p i o n e e r i n g n a t u r e . For example, a h i t h e r t o unknown s i d e r e a c t i o n of hydrogen at process pressure w i t h the original exchange c a t a l y s t was d i s c o v e r e d . The s u c c e s s f u l development of a new c a t a l y s t r e s t o r e d the viability of the process so that commercial a p p l i c a t i o n is now f e a s i b l e and is being pursued. Literature

Cited

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch003

(1) (2)

Bar-Eli, K . and Klein, F.S., J. Chem. S o c . , 3803, (1962). Rochard, E . and R a v o i r e , J., J. Chem. P h y s . , 68, 1183, (1971). (3) B a n c r o f t , A . R . and Rae, H.K., Atomic Energy of Canada L i m i t e d , Report AECL-3684, (1970). (4) Wynn, Ν . , paper no. 57 Isotope Separation Symposium ACS/CIC C o n f . , (June 1977). (5) F l e t c h e r , J.W., Seddon, W . A . , Jevcak, J. and Sopchyshyn, F.C., Chem. Phys. Lett., 18, 592, (1973). (6) F l e t c h e r , J.W., Seddon, W.A. and Sopchyshyn, F.C., Can. J. Chem., 51, 2975, (1973). (7) K i r s c h k e , E.J. and Jolly, W . L . , I n o r g . Chem. 6, 855, (1967). (8) Bödddeker, K . W . , Land, G . , and Schindewolf, U., Angew Chem. ( I n t . E d . ) 8, 138, (1969). (9) H a l l i d a y , J.D. and B i n d n e r , P.E., Can. J. Chem. 54, 3775 (1967). (10) H o l t s l a n d e r , W.J., and Johnson, R.E., U n i t e d States P a t e n t , 3995017, (November 30, 1976). RECEIVED September 7, 1977

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

4 AECL-Sulzer Amine Process for Heavy Water N. P. WYNN

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004

Sulzer Brothers Ltd., P.O. Box 210, Pointe Claire, Quebec, Canada H9R

4N9

The purpose o f t h i s paper is t o o u t l i n e the d e s i g n o f the AECL - S u l z e r amine p r o c e s s f o r heavy water, t o demonstrate why the p r o c e s s is a t t r a c t i v e compared t o e x i s t i n g p r o c e s s e s and t o summarise the s t e p s which have been taken t o p r e p a r e the p r o c e s s f o r commercial exploitation. Work on p r o c e s s development was s t a r t e d independ e n t l y by Atomic Energy o f Canada and by S u l z e r B r o t h e r s . AECL were e v a l u a t i n g a l t e r n a t i v e s t o the e s t a b l i s h e d GS s e p a r a t i o n p r o c e s s and conducted experiments to compare exchange r a t e s f o r ammonia-hydrogen and amine-hydrogen. S u l z e r were i n t e r e s t e d in the amine-hydrogen p r o c e s s as a s u c c e s s o r t o the s e r i e s o f hydrogen f e d heavy water p l a n t s w i t h which they had been inv o l v e d . T h i s i n v o l v e m e n t had s t a r t e d in 1956 w i t h the c o n s t r u c t i o n o f a p l a n t u s i n g l i q u e f a c t i o n and d i s t i l l a t i o n o f e l e c t r o l y t i c hydrogen a t Ems in S w i t z e r l a n d (1) and has c o n t i n u e d w i t h the c o n s t r u c t i o n o f t h r e e p l a n t s u s i n g the monothermal ammonia-hydrogen p r o c e s s . The p r o t o t y p e p l a n t was b u i l t a t Mazingarbe (2/3,4) in F r a n c e in 1967 and was f o l l o w e d by two p l a n t s s u p p l i e d to I n d i a by the GELPRA c o n s o r t i u m (5,6). The f i r s t o f t h e s e p l a n t s , a t Baroda, is c u r r e n t l y b e i n g s t a r t e d up and the second, a t T u t i c o r i n , is in the f i n a l s t a g e o f c o n s t r u c t i o n . The o t h e r ammonia-hydrogen p l a n t a t T a l c h e r (6), a l s o in I n d i a , uses a f i n a l enrichment system d e s i g n e d and s u p p l i e d by S u l z e r and is a l s o in the l a t t e r s t a g e s o f c o n s t r u c t i o n . S i m i l a r f i n a l enr i c h m e n t systems u s i n g vacuum d i s t i l l a t i o n o f water have been s u p p l i e d by S u l z e r f o r a m a j o r i t y o f the Can a d i a n GS heavy water p l a n t s {J)In 1973 S u l z e r and AECL agreed t o exchange i n f o r mation on amine p r o c e s s development. A heavy water p r o c e s s was d e s i g n e d u s i n g a f l o w s h e e t development from S u l z e r s e x p e r i e n c e w i t h the f i v e ammonia p l a n t based 1

© 0-8412-0420-9/78/47-068-053$05.00/0

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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heavy water p l a n t s ment, oned above t o g e t h e r w i t h the AECL owned c a t a l y s t d e v e l o p e d a t C h a l k R i v e r N u c l e a r l a b o r a t o r i e s . Advantages o v e r e x i s t i n g p r o c e s s e s were a p p a r e n t and s u f f i c i e n t f o r S u l z e r t o commit themselves to d e v e l o p the p r o c e s s t o a s t a g e a t which a t u r n k e y p l a n t c o u l d be b u i l t w i t h known c o s t s and guaranteed performance. The s t i m u l u s b e h i n d t h i s development was the r e c o g n i t i o n t h a t the p r o c e s s can produce heavy water u s i n g c o n s i d e r a b l y l e s s equipment and l e s s energy than e x i s t i n g p r o c e s s e s . There a r e two p r i n c i p a l reasons f o r t h i s . The f i r s t depends on the d e u t e r i u m exchange p r o p e r t i e s o f methylamine and hydrogen and can b e s t be i l l u s t r a t e d by comparing t h i s c h e m i c a l exchange p a i r w i t h the two o t h e r exchange p a i r s commonly used in ind u s t r i a l heavy water p l a n t s : hydrogen s u l p h i d e - w a t e r and ammonia-hydrogen (8,9). The second f a c t o r is t i e d up w i t h the use o f hydrogen, in the form o f ammonia s y n t h e s i s gas, as d e u t e r i u m f e e d s t o c k . T h i s w i l l be dem o n s t r a t e d by d i s c u s s i n g the way in which the heavy water p l a n t is c o u p l e d w i t h the s y n t h e s i s gas product i o n system o f the ammonia p l a n t . B i t h e r m a l Enrichment u s i n g Amine-Hydrogen Exchange Most o f the d e u t e r i u m s e p a r a t i o n in the amine-hydrogen p r o c e s s is a c h i e v e d u s i n g the b i t h e r m a l (dual temperature) enrichment t e c h n i q u e (10). T h i s t e c h n i q u e is a l s o used in the GS p l a n t s and in the ammonia-hydrogen p l a n t b e i n g b u i l t a t T a l c h e r (6). The t e c h n i q u e makes use o f a temperature dependent d e u t e r i u m exchange r e a c t i o n between a l i q u i d and a gas. In the amine-hydrogen p r o c e s s d e u t e r i u m is exchanged between the amino group o f l i q u i d monomethylamine and gaseous hydrogen a c c o r d i n g t o the r e a c t i o n :

A s i m p l e gas f e d b i t h e r m a l enrichment l o o p is shown in F i g u r e 1. Feed gas is s u c c e s s i v e l y passed through hot and c o l d exchange towers in c o u n t e r c u r r e n t to a c l o s e d l o o p o f l i q u i d . In t h e h o t tower the e q u i l i b r i u m f o r the above r e a c t i o n is t o the l e f t , t h e r e f o r e d e u t e r i u m passes from the l i q u i d t o the gas. In the c o l d tower the e q u i l i b r i u m s h i f t s t o the r i g h t so t h a t d e u t e r i u m passes from the gas t o the l i q u i d . The gas l e a v i n g the h o t tower is e n r i c h e d in d e u t e r i u m and a p o r t i o n o f i t is used as f e e d f o r a h i g h e r enrichment s t a g e . T h i s gas r e t u r n s d e p l e t e d and j o i n s the main stream o f gas which is d e u t e r i u m s t r i p p e d in the c o l d

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tower. The s e p a r a t i o n power o f such a b i t h e r m a l l o o p depends on the d i f f e r e n c e in the exchange e q u i l i b r i a in the h o t and c o l d towers. The s e p a r a t i o n f a c t o r , is d e f i n e d as the r a t i o o f D/D+H in l i q u i d t o D/D+H in the gas. E f f i c i e n t d e u t e r i u m e x t r a c t i o n and e n r i c h m e n t is a c h i e v e d w i t h a low v a l u e o f t h e s e p a r a t i o n f a c t o r in the h o t tower i ^ ) and a h i g h v a l u e in the c o l d tower (oCç). The s i m p l e s t s t a n d a r d o f comparison f o r b i t h e r m a l e n r i c h m e n t p r o c e s s e s is t h e maximum r e c o v e r y a v a i l a b l e u s i n g a s i n g l e e n r i c h m e n t l o o p w i t h an i n f i n i t e number o f t h e o r e t i c a l p l a t e s in h o t and c o l d towers, g i v e n by the term l-oCh/<=*c. T h i s v a l u e is a rough i n d i c a t i o n o f t h e amount o f p r o d u c t heavy water s e p a r a t e d by p l a n t s p r o c e s s i n g the same molar q u a n t i t y o f f e e d s t o c k , be i t water o r hydrogen. F o r the same p r o d u c t i o n r a t e t h e r e f o r e , the f e e d s t o c k q u a n t i t y t o be p r o c e s s e d is r o u g h l y p r o p o r t i o n a l t o t h e r e c i p r o c a l o f t h i s number. The s e p a r a t i o n f a c t o r s t h a t can be r e a l i s e d in a b i t h e r m a l l o o p depend upon the p r o p e r t i e s o f the exchange p a r t n e r s . F i g u r e 2 shows t h e v a r i a t i o n in the s e p a r a t i o n f a c t o r , * * , as a f u n c t i o n o f t e m p e r a t u r e f o r the f o l l o w i n g exchange r e a c t i o n s :

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004

0

1

HDO

+ HS

«=-t

2

HD

+ NH

4 = £ H

3

HD

+ CH NH

2

3

3

2

i=?

H0

H

2

+

HDS

2

+ NH D

2

+ CH^HD

2

The c u r v e s a r e o n l y shown f o r the temperature range in which an i n d u s t r i a l heavy water p r o c e s s can o p e r a t e w e l l . F o r the GS p r o c e s s the h o t tower o p e r a t e s a t 130 °C t o l i m i t t h e amount o f water vapour in the gas phase. C o l d tower temperature i g l i m i t e d by the f o r m a t i o n o f a s o l i d h y d r a t e a t 28 C. F o r the ammonia-hydrogen p r o c e s s a h o t tower temperature around 60 °C l i m i t s the ammonia vapour c o n c e n t r a t i o n in t h e gas phase. C o l d tower t e m p e r a t u r e is l i m i t e d t o about -25 °C by the poor k i n e t i c s o f the exchange a t low t e m p e r a t u r e s . Amine-hydrogen h o t tower t e m p e r a t u r e is l i m i t e d t o +40 °C t o m i n i m i s e the r a t e o f c a t a l y s t d e c o m p o s i t i o n . The c o l d tower can o p e r a t e a t -50 C however, because o f the f a r s u p e r i o r k i n e t i c s o f the c h e m i c a l exchange r e a c t i o n , compared w i t h ammonia-hydrogen exchange. However, the use o f s p e c i a l g a s - l i q u i d c o n t a c t o r s is n e c e s s a r y t o t a k e f u l l advantages o f the amine-hydrogen exchange k i n e t i c s a t -50 C. L i s t e d below a r e the h o t and c o l d tower o p e r a t i n g

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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DEPLETED GAS

LIQUID

ICOLDj GAS RETURN FROM NEXT STAGE

ENRICHED GAS

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004

TO NEXT STAGE HOT

Jf FEED GAS Figure 1.

Gas-fed bithermal enrichment stage

SEPARATION FACTOR dC 10

Figure 2.

Deuterium exchange equilibria for bithermal enrichment processes

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c o n d i t i o n s , s e p a r a t i o n f a c t o r s and maximum p o s s i b l e y i e l d f o r the t h r e e systems. System

H S/H 0 2

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004

c o l d tower o p e r a t i n g temperature (°C) c o l d tower s e p a r a t i o n factor hot tower o p e r a t i n g temperature (°C) hot tower s e p a r a t i o n factor maximum p o s s i b l e y i e l d

2

NH /H 3

2

CH NH /H 3

2

+ 30

-25

-50

2.22

5.3

7.9

+130

+60

+40

1.76 0.21

2.9 0.45

3.6 0.55

T h i s s i m p l e comparison i n d i c a t e s t h a t f o r t h e same d e u t e r i u m e x t r a c t i o n t h e ammonia-hydrogen system o n l y needs t o p r o c e s s about h a l f as much f e e d s t o c k as the GS system and the amine-hydrogen system o n l y about 40 % as much. A more r e a l i s t i c comparison is t o l o o k a t t h e performance o f t h e systems w i t h a f i n i t e number o f t h e o r e t i c a l s t a g e s in the exchange towers. A t t a i n m e n t of t h e h i g h s e p a r a t i o n f a c t o r in the c o l d towers o f the hydrogen based p r o c e s s e s is n e c e s s a r y t o a c h i e v e a h i g h y i e l d . T h i s can o n l y be a c h i e v e d by o p e r a t i n g a t low c o l d tower t e m p e r a t u r e s where the slow i s o t o p i c exchange r e q u i r e s the use o f s p e c i a l c o n t a c t i n g d e v i c e s to a c h i e v e r e a s o n a b l e t r a y e f f i c i e n c i e s . Each o f t h e s e s p e c i a l c o n t a c t o r s r e q u i r e s more tower volume t h a n a s i e v e t r a y which g i v e s a r e a s o n a b l e t r a y e f f i c i e n c y in the GS c o l d towers. C o n s e q u e n t l y , f o r t h e same o u t l a y in equipment, l e s s t h e o r e t i c a l s t a g e s w i l l be a v a i l a b l e in the c o l d towers o f the hydrogen based p r o c e s s e s . F i g u r e 3 compares the performance o f t h e t h r e e b i t h e r m a l systems u s i n g a f i n i t e number o f t r a n s f e r s t a ges in the h o t and c o l d exchange columns. GS p e r f o r mance has been computed f o r h o t and c o l d towers each with f i f t y sieve trays using tray e f f i c i e n c i e s reported in the l i t e r a t u r e (11). The performance o f t h e amine-hydrogen and ammonia hydrogen system has been computed f o r h o t towers w i t h f i f t y s i e v e t r a y s and c o l d towers w i t h f i v e s p e c i a l c o l d c o n t a c t o r s . Stage e f f i c i e n c i e s a r e based on S u l z e r and AECL p i l o t t e s t s . The c o l d towers w i t h f i v e c o l d c o n t a c t o r s r o u g h l y c o r r e s p o n d in tower h e i g h t t o the f i f t y s i e v e t r a y s used in the GS c o l d tower c o n s i d e r e d h e r e . Hence the comparison is f o r enrichment l o o p s w i t h r o u g h l y s i m i l a r equipment c o s t s , b u t o p e r a t i n g w i t h d i f f e r e n t exchange fluids.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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The performance o f t h e s e systems cannot a c c u r a t e l y be compared u s i n g t h e s i n g l e v a r i a b l e o f d e u t e r i u m r e c o v e r y s i n c e t h i s is dependent on t h e e n r i c h m e n t p r o d u c e d . F i g u r e 3 shows t h e e n r i c h m e n t / y i e l d c h a r a c t e r i s t i c s f o r t h e t h r e e systems. A t an e n r i c h m e n t f a c t o r o f 1 (no e n richment) t h e y i e l d s a r e t h e maximum t h e o r e t i c a l v a l ues o f l - c * h / c * c . As t h e e n r i c h m e n t f a c t o r i n c r e a s e s the y i e l d is r e d u c e d . T h i s e f f e c t is more marked f o r the hydrogen based p r o c e s s e s because l e s s c o n t a c t i n g s t a g e s a r e a v a i l a b l e in t h e c o l d tower. T h i s is t h e p e n a l t y f o r t h e c o m p a r a t i v e l y poor exchange k i n e t i c s o f the hydrogen based p r o c e s s e s a t low t e m p e r a t u r e s . An e n r i c h m e n t f a c t o r o f about f o u r c o r r e s p o n d s t o o p e r a t i n g c o n d i t i o n s in t h e GS p l a n t s (11) and in t h e amine-hydrogen p r o c e s s . A t t h i s p o i n t t h e y i e l d f o r the ammonia-hydrogen l o o p is no more than t h a t f o r t h e GS l o o p . The y i e l d from t h e amine-hydrogen l o o p is howe v e r t w i c e as g r e a t , i . e . u n i t p r o d u c t from t h e aminehydrogen l o o p r e q u i r e s o n l y h a l f t h e amount o f f e e d s t o c k o f t h e o t h e r two p r o c e s s e s . The amount o f f l u i d r e q u i r i n g p r o c e s s i n g is a key parameter in d e t e r m i n i n g t h e c o s t o f a p r o c e s s . Heavy water is e x p e n s i v e because huge q u a n t i t i e s o f f e e d s t o c k r e q u i r e p r o c e s s i n g t o produce a r e l a t i v e l y s m a l l amount o f p r o d u c t . A p r o c e s s b u i l t from a c a s c a d e o f h i g h y i e l d e n r i c h m e n t l o o p s is l i k e l y t o be c h e a p e r . Not o n l y tower volumes b u t equipment and energy c o s t s f o r p u r i f i c a t i o n , h u m i d i f i c a t i o n and d e - h u m i d f i c a t i o n a r e all p r o p o r t i o n a l t o t h e amount o f gas and l i q u i d r e q u i r i n g p r o c e s s i n g in t h e e n r i c h m e n t l o o p s . The p r o c e s s i n g c o s t s p e r mole o f c i r c u l a t i n g gas a r e d i f f i c u l t t o compare f o r t h e amine-hydrogen and GS p r o c e s s e s a s t h e problems a r e o f a d i f f e r e n t n a t u r e . Problems o f c o r r o s i o n and t h e t o x i c p r o p e r t i e s o f hydrogen s u l p h i d e add t o t h e c o s t s o f t h e GS p r o c e s s . I n the amine p r o c e s s c o s t s a r i s e from t h e use o f low temp e r a t u r e r e f r i g e r a t i o n and low t e m p e r a t u r e s t e e l s . Comparison between ammonia-hydrogen and amine-hydrogen is e a s i e r . These p r o c e s s e s o p e r a t e a t s i m i l a r p r e s s u r e s and use s i m i l a r equipment. The amine p r o c e s s o p e r a t e s a t a lower temperature so r e f r i g e r a t i o n is more expens i v e . On t h e o t h e r hand l e s s r e f r i g e r a t i o n is r e q u i r e d p e r mole o f hydrogen c i r c u l a t e d because t h e vapour p r e s s u r e o f amine is o n l y h a l f t h a t o f ammonia. T h e r e f o r e l e s s r e f r i g e r a t i o n is r e q u i r e d f o r d e h u m i d i f y i n g the c i r c u l a t i n g gas. P r o c e s s i n g c o s t s p e r mole o f gas c i r c u l a t e d a r e u n l i k e l y t o be s i g n i f i c a n t l y d i f f e r e n t . The above comparison u s i n g t h e d e u t e r i u m exchange p r o p e r t i e s o f t h e t h r e e systems shows t h a t an aminehydrogen b i t h e r m a l l o o p need o n l y be h a l f t h e s i z e o f

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an ammonia-hydrogen l o o p o f e q u i v a l e n t performance. T h i s is one o f the key reasons f o r the economy o f the amine-hydrogen p r o c e s s and i t has p r o v i d e d the s t i m u l u s f o r S u l z e r t o s h i f t development from the ammonia-hydrogen t o the amine-hydrogen p r o c e s s .

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004

Special Cold Contactors The achievement o f h i g h i s o t o p i c exchange e f f i c i e n c i e s a t low temperature was the f i r s t g o a l o f the amine-hydrogen p r o c e s s development program. E a r l y t e s t s made by AECL show a s i e v e t r a y e f f i c i e n c y o f o n l y 0.7 % a t -50 °C (.12). Subsequent development work has produced c o n t a c t o r s w i t h e f f i c i e n c i e s r a n g i n g up to 70 % a t t h i s temperature. Success in t h i s key a r e a l e d t o a more g e n e r a l development e f f o r t which has brought the p r o c e s s t o i t s c u r r e n t mature s t a t e . Deuterium exchange between methylamine and hydrogen o c c u r s v i a the c a t a l y s t d i s s o l v e d in the l i q u i d phase. In p r i n c i p l e the r a t e o f i s o t o p i c exchange is dependent on both the i n t r i n s i c c h e m i c a l k i n e t i c s o f the exchange r e a c t i o n and the r a t e o f d i f f u s i o n a l mass t r a n s f e r o f r e a c t a n t s and p r o d u c t s . Because o f the low s o l u b i l i t y o f hydrogen in amine and the h i g h a c t i v i t y o f the c a t a l y s t , even a t the low c o l d tower tempe r a t u r e o f -50 °C, the r e a c t i o n is in the f a s t regime (11). T h i s means t h a t s i m u l t a n e o u s mass t r a n s f e r and c h e m i c a l r e a c t i o n o c c u r o n l y in f r e s h elements o f l i q u i d brought near the g a s - l i q u i d i n t e r f a c e . I n c r e a s e s in exchange r a t e have been produced by i n c r e a s i n g both the g a s - l i q u i d i n t e r f a c i a l a r e a and the r a t e o f s u r f a c e renewal by p r o d u c i n g a t u r b u l e n t gas l i q u i d m i x t u r e . Exchange e f f i c i e n c i e s in the s p e c i a l l y d e v e l o p e d c o n t a c t o r s a r e a l s o h i g h e r than f o r the s i e v e t r a y because o f g r e a t e r r e s i d e n c e time, i . e . the cont a c t o r s c o n t a i n more l i q u i d in which exchange is o c c u r r i n g . F i g u r e 4 shows two s u i t a b l e low temperature cont a c t o r s . The c o c u r r e n t bed c o n t a c t o r is b a s i c a l l y a deep s i e v e t r a y which is f i l l e d w i t h a k n i t t e d mesh p a c k i n g t o reduce bubble c o a l e s c e n c e . The f l o w p a t t e r n is m a i n l y c o n c u r r e n t because o f the h i g h o v e r f l o w w e i r . T h i s c o n t a c t o r has been d e v e l o p e d by Chalk R i v e r Nuc l e a r L a b o r a t o r i e s (11,13). The e j e c t o r c o n t a c t o r , shown s c h e m a t i c a l l y in F i g u r e 4, was d e v e l o p e d by S u l z e r o r i g i n a l l y f o r use in the monothermal ammonia heavy water p r o c e s s (14,4). In each s t a g e gas is expanded through n o z z l e s and l i q u i d is sucked i n t o the h i g h v e l o c i t y gas stream g i v i n g a v e r y i n t i m a t e g a s / l i q u i d m i x t u r e . The m i x t u r e passes up a r e a c t i o n tube and is then s e p a r a t e d in a c e n t r i -

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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SEPARATION O F HYDROGEN ISOTOPES

Figure 3.

Comparison of bithermal enrichment fluids

Figure 4.

Cold-contacting devices

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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f u g a l s e p a r a t o r , gas p a s s i n g on t o t h e n e x t s t a g e and l i q u i d b e i n g r e c y c l e d t o t h e e j e c t o r s . The l i q u i d throughput in t h e tower is pumped from s t a g e t o s t a g e t o overcome t h e p r e s s u r e d i f f e r e n c e caused by t h e p r e s s u r e drop in t h e e j e c t o r d r i v i n g n o z z l e . The d e s i g n f e a t u r e s and performance o f t h e s p e c i a l c o n t a c t o r s on amine-hydrogen exchange a t -50 C a r e c o n t r a s t e d w i t h t h o s e o f a normal s i e v e t r a y below: contactor type ^ ^ ^ - ^

property

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004

flow p a t t e r n gas phase residence

superficial (s)

time,u,

sieve tray

packed bed

ejector

cross current

cocurrent

recycle co-current 7.6

1

6.7

s p e c i f i c energy dissipation (watts/liter)

1

1

10

stage e f f i c i e n c y

0.7

22

70

(%)

r a t i o o f mass transfer rates i n t e r f a c i a l area

1 2 3 (m /m )

250

5.7 1300

23 6000

The packed bed c o n t a c t o r d e v e l o p e d by AECL p e r f o r m s b e t t e r than t h e s i e v e t r a y f o r two r e a s o n s . F i r s t l y the packed bed is deeper so t h e gas phase r e s i d e n c e time is h i g h e r . S e c o n d l y t h e r a t e o f mass t r a n s f e r in the m i x t u r e is h i g h e r . T h i s is a t t r i b u t a b l e t o t h e high voidage packing i n c r e a s i n g g a s - l i q u i d i n t e r f a c i a l a r e a by p r e v e n t i n g b u b b l e c o a l e s c e n c e . I t is a l s o p r o b a b l e t h a t t h e upper r e g i o n s o f t h e s i e v e t r a y were o p e r a t i n g in t h e s p r a y regime where l i q u i d phase t u r b u l e n c e would be r e l a t i v e l y p o o r . The s p e c i f i c energy d i s s i p a t i o n is d e f i n e d as t h e gas phase p r e s s u r e d r o p m u l t i p l i e d by t h e gas f l o w r a t e and d i v i d e d by t h e r e a c t i o n m i x t u r e volume. Both t h e s i e v e t r a y and t h e packed bed a r e d e s i g n e d t o keep t h e p r e s s u r e drop a c r o s s t h e s i e v e p l a t e low so as t o reduce l i q u i d backup in t h e downcomers and r e d u c e t r a y s p a c i n g . T h i s r e s u l t s in t h e s p e c i f i c energy d i s s i p a t i o n b e i n g low and s i m i l a r f o r both d e v i c e s . The e j e c t o r shows more than a t h r e e f o l d improvement in e f f i c i e n c y compared t o t h e packed bed. The r e s i d e n c e times f o r t h e two d e v i c e s a r e s i m i l a r . The

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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S E P A R A T I O N O F H Y D R O G E N ISOTOPES

b e t t e r performance is a t t r i b u t a b l e t o t h e h i g h e r r a t e o f energy d i s s i p a t i o n in t h e e j e c t o r p r o d u c i n g a much more i n t i m a t e g a s - l i q u i d m i x t u r e . The h i g h e r energy input is caused by t h e p r e s s u r e drop in t h e gas n o z z l e s o f t h e e j e c t o r which r e q u i r e s t h e use o f pumps f o r p a s s i n g l i q u i d s t a g e w i s e down t h e tower. The r e d u c t i o n in tower volume by a f a c t o r o f o v e r t h r e e when u s i n g the e j e c t o r more than makes up f o r t h e c o s t o f t h e s e pumps. Energy c o s t s in t h e form o f i n c r e a s e d gas stream p r e s s u r e drop a r e s m a l l . In f a c t t h e e j e c t o r c o n t a c t o r s use l e s s energy than t h e s i e v e t r a y s f o r a g i v e n mass t r a n s f e r d u t y . Though t h e r a t e o f energy d i s s i p a t i o n p e r u n i t r e a c t i o n volume f o r t h e e j e c t o r is h i g h e r than f o r t h e s i e v e t r a y , a tower u s i n g e j e c t o r s w i l l r e q u i r e o n l y 75 % o f t h e energy in t h e form o f p r e s s u r e drop compared w i t h a s i e v e t r a y tower o f equal performance. There a r e o t h e r advantages in u s i n g t h e e j e c t o r contactor. Multiple units consisting of nozzles, eject o r s , r e a c t i o n tubes and s e p a r a t o r s a r e i n s t a l l e d in p a r a l l e l i n s i d e each s t a g e o f t h e c o l d tower. P i l o t t e s t i n g o f one f u l l s i z e u n i t e l i m i n a t e s t h e n e c e s s i t y f o r and a v o i d s t h e r i s k s o f s c a l e - u p . A n o t h e r advantage is t h a t gas and l i q u i d a r e mixed and s e p a r a t e d u s i n g i n e r t i a l f o r c e s . These a r e l a r g e compared t o t h e normal i n t e r f a c i a l f o r c e s a c t i n g in a two phase m i x t u r e . V a r i a t i o n s in t h e foaminess o f t h e p r o c e s s l i q u i d s c a u s e d by a c o n c e n t r a t i o n o f i m p u r i t i e s a r e l e s s l i k e l y t o a f f e c t t h e h y d r a u l i c performance o f t h e e j e c t o r s . The use o f t h e s e s p e c i a l c o n t a c t o r s is t o a l a r g e e x t e n t r e s p o n s i b l e f o r t h e p o t e n t i a l o f t h e amine p r o c e s s . Because o f t h e s t r o n g temperature dependence o f the exchange e f f i c i e n c y , t h e i r use e f f e c t i v e l y lowers the optimum c o l d tower temperature a l l o w i n g t h e p r o c e s s the economies o f h i g h d e u t e r i u m r e c o v e r y mentioned earlier. Link-Up w i t h t h e Ammonia

Plant

Ammonia p l a n t s y n t h e s i s gas has been used as f e e d s t o c k f o r a number o f heavy water p l a n t s (6,15). The gas is s t r i p p e d o f d e u t e r i u m in t h e heavy water p l a n t and r e t u r n e d t o t h e s y n t h e s i s l o o p o f t h e ammonia p l a n t . One advantage o f u s i n g s y n t h e s i s gas is t h a t the gas is r e l a t i v e l y p u r e . The main contaminant, n i t r o g e n , is i n e r t and does n o t i n t e r f e r e w i t h t h e heavy water p r o c e s s . The main d i s a d v a n t a g e o f u s i n g s y n t h e s i s gas as a d e u t e r i u m s o u r c e is t h a t t h e s i z e o f t h e heavy water p l a n t is l i m i t e d by t h e s i z e o f t h e ammonia p l a n t t o which i t is c o n n e c t e d . S y n t h e s i s gas

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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from a one thousand t o n p e r day ammonia p l a n t c a n o n l y y i e l d about 65 t o n s p e r y e a r o f heavy water. T h i s l i m i t s t h e s c a l e economies p o s s i b l e f o r t h e heavy water plant. C o n n e c t i o n o f t h e amine-hydrogen p r o c e s s t o t h e ammonia p l a n t has been d e s i g n e d so t h a t a p r e - e n r i c h ment in d e u t e r i u m o c c u r s b e f o r e t h e s y n t h e s i s gas r e a c h e s t h e heavy water p l a n t , so r e d u c i n g t h e e n r i c h ment n e c e s s a r y in t h e heavy water p l a n t i t s e l f . T h i s is the second r e a s o n why t h e amine-hydrogen p r o c e s s is a b l e t o produce heavy water c h e a p l y . In an o p e r a t i n g ammonia p l a n t t h e hydrogen in t h e s y n t h e s i s gas has a d e u t e r i u m c o n c e n t r a t i o n w e l l below the average v a l u e o f t h a t o f t h e hydrogen in t h e f e e d s t o c k , which is n o r m a l l y around 130 ppm. The s y n t h e s i s gas is d e p l e t e d in d e u t e r i u m by t h e l a r g e e x c e s s o f steam r e q u i r e d in t h e r e f o r m e r s where t h e s y n t h e s i s gas is produced. A t t h e h i g h temperatures r e q u i r e d t h e steam and p r o d u c t hydrogen r e a c h i s o t o p i c e q u i l i b r i u m ; the e q u i l i b r i u m p r o d u c i n g a d e u t e r i u m enrichment in t h e steam and a d e p l e t i o n in t h e hydrogen g a s . When t h e unr e a c t e d steam is condensed o u t o f t h e gas and dumped the d e u t e r i u m c o n t e n t is l o s t . The d i s t r i b u t i o n o f d e u t e r i u m in t h e main p r o c e s s streams o f an ammonia p l a n t is shown in F i g u r e 5. Most ammonia p l a n t s which have been c o u p l e d w i t h heavy water p l a n t s have been m o d i f i e d t o a v o i d t h i s d e u t e r i u m d e p l e t i o n in t h e s y n t h e s i s g a s . Two methods have been used, b o t h e f f e c t i v e l y r e c y c l i n g d e u t e r i u m from t h e e n r i c h e d p r o c e s s condensate back i n t o t h e r e f o r m e r steam s u p p l y . F i g u r e 6 shows one o f t h e s e methods. The steam d e s t i n e d f o r t h e r e f o r m e r s is passed t h r o u g h a column in c o u n t e r c u r r e n t t o t h e p r o c e s s cond e n s a t e and s t r i p s o u t t h e e n r i c h e d w a t e r . The o t h e r method is t o use t h e e n r i c h e d condensate, a f t e r s u i t a b l e t r e a t m e n t , as feedwater f o r t h e b o i l e r which g e n e r a t e s r e f o r m e r steam. A f l o w s h e e t has been used f o r t h e amine-hydrogen p r o c e s s which goes one s t e p f u r t h e r ; i n s t e a d o f r e s t o r i n g t h e d e u t e r i u m c o n t e n t in t h e s y n t h e s i s gas t o i t s natural l e v e l i t increases i t s t i l l further. This p r e - e n r i c h m e n t r e d u c e s s u b s t a n t i a l l y t h e number o f b i t h e r m a l enrichment s t a g e s r e q u i r e d in t h e r e s t o f t h e p l a n t . F i g u r e 7 shows in p r i n c i p l e how t h i s is done. Some o f t h e d e u t e r i u m e x t r a c t e d from t h e s y n t h e s i s gas stream is t r a n s f e r r e d v i a a s e r i e s o f i s o t o p i c exchange columns t o t h e r e f o r m e r steam f e e d t o g e t h e r w i t h t h e d e u t e r i u m from t h e e n r i c h e d p r o c e s s condensate. In t h e f i r s t t r a n s f e r column, t h e t o p one in the f i g u r e , d e u t e r i u m is t r a n s f e r r e d i n t o c a t a l y s t

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

SEPARATION O F H Y D R O G E N ISOTOPES

AMMONIA SYNTHESIS LOOP

AMMONIA PRODUCT

CONDENSATE

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004

AIR

GAS

|SYNTHESI9| GAS jGENERAT. STEAM

Ν = 135 PPM D/D + H (ALBERTA)

Figure 5. Deuterium concentrations in an ammonia plant

Figure 6.

Concentrations with deuterium recycle from condensate

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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l a d e n l i q u i d methy1amine. In the n e x t column the deut e r i u m e n r i c h e d amine is t r a n s f e r r e d i n t o an amine vapor stream. In the t h i r d column d e u t e r i u m is t r a n s f e r r e d from amine vapor t o water which is p a s s e d , t o g e t h e r w i t h the e n r i c h e d p r o c e s s condensate, i n t o the condensate s t r i p p i n g column. T h i s e n r i c h e s the r e f o r m e r steam which in t u r n e n r i c h e s the s y n t h e s i s gas produced in the r e f o r m e r . Deuterium t r a n s f e r from the hydrogen in the s y n t h e s i s gas back t o the r e f o r m e r steam is p o s s i b l e because the s e p a r a t i o n f a c t o r between water and hydrogen is g r e a t e r than 1. I f water and hydrogen o f e q u a l deut e r i u m c o n c e n t r a t i o n a r e brought i n t o i s o t o p i c e q u i l i brium t h e n d e u t e r i u m w i l l pass from the hydrogen t o the water. The d e u t e r i u m in the hydrogen is, in e f f e c t , more a v a i l a b l e . I f hydrogen is produced from t h i s water by removing oxygen, t h e n i t w i l l a l s o be e n r i c h e d and can s e r v e t o e n r i c h more water by i s o t o p i c exchange. T h i s is the monothermal o r d e c o m p o s i t i o n enrichment t e c h n i q u e which has been used w i t h water and hydrogen in the heavy water p l a n t s a t T r a i l and Rjukan and w i t h ammonia and hydrogen in t h e p l a n t s a t Mazingarbe, Baroda and T u t i c o r i n (5). The d i s a d v a n t a g e o f the p r o c e s s is the c o s t o f the d e c o m p o s i t i o n s t e p ; e l e c t r o l y s i s o f water o r t h e r m a l c r a c k i n g o f ammonia (15). However, in the amine-hydrogen p r o c e s s the d e c o m p o s i t i o n s t e p o c c u r s in the r e f o r m e r s o f the ammonia p l a n t . Where s y n t h e s i s gas is used as a d e u t e r i u m s o u r c e the ammonia p l a n t is n o r m a l l y m o d i f i e d t o r e c y c l e d e u t e r i u m from the p r o c e s s condensate t o the r e f o r m e r steam. The e x t r a c o s t o f r e c y c l i n g d e u t e r i u m from the s y n t h e s i s gas t o the r e f o r m e r steam is s m a l l . D e t a i l e d d e s i g n o f the l i n k - u p depends on the des i g n o f the ammonia p l a n t . K e l l o g g Canada have c o l l a b o r a t e d w i t h S u l z e r in t h i s a r e a and the d e s i g n package f o r the 65 t o n s p e r y e a r heavy water p l a n t is spec i f i c a l l y t a i l o r e d t o the K e l l o g g ammonia p l a n t d e s i g n . The degree o f p r e - e n r i c h m e n t p o s s i b l e u s i n g such a system is l i m i t e d by the l e a k s o f steam, water and s y n t h e s i s gas o c c u r r i n g in the ammonia p l a n t r e f o r m e r s . However, s u f f i c i e n t p r e - e n r i c h m e n t can be a c h i e v e d t o more than h a l v e the amount o f equipment used in the subsequent b i t h e r m a l amine-hydrogen enrichment s e c t i o n o f the heavy water p l a n t . Deuterium Enrichment

System

F i g u r e 8 shows s c h e m a t i c a l l y the i s o t o p i c e n r i c h ment scheme used in the p r o c e s s . A c a s c a d e o f two amine-hydrogen b i t h e r m a l enrichment l o o p s is used

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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Figure 7.

Figure 8.

O F HYDROGEN ISOTOPES

Concentrations with deuterium recycle from condensate and synthesis gas

Isotopic enrichment scheme

HEAVY WATER

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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c o u p l e d w i t h f i n a l enrichment by water d i s t i l l a t i o n . T h i s scheme is used t o reduce l o s s e s o f d e u t e r i u m enr i c h e d s u b s t a n c e s and t o m i n i m i z e the d e u t e r i u m i n v e n t o r y o f the p l a n t . P r e - e n r i c h e d s y n t h e s i s gas from the ammonia p l a n t is t r e a t e d t o remove water and c a r b o n o x i d e s and t h e n fed t h r o u g h the main b i t h e r m a l enrichment l o o p . Dep l e t e d amine from the h o t tower is f u r t h e r s t r i p p e d by the p r e - e n r i c h m e n t d e u t e r i u m t r a n s f e r column b e f o r e b e i n g f e d t o the f i r s t s t a g e c o l d column. The f i r s t stage e n r i c h e s gas t o about 20 t i m e s n a t u r a l c o n c e n t r a t i o n . E n r i c h e d l i q u i d is b l e d from between the c o l d and h o t columns and f e d t o the second b i t h e r m a l enrichment stage. The second s t a g e e n r i c h e s gas t o about 300 t i m e s n a t u r a l c o n c e n t r a t i o n g i v i n g a deuterium concentration in methylamine o f about f o u r t e e n p e r c e n t . Condensed amine vapor from the second s t a g e d e h u m i d i f i e r is cont a c t e d w i t h water in a t r a n s f e r column. T h i s e n r i c h e d water is then d i s t i l l e d under vacuum t o g i v e the heavy water p r o d u c t o f 99.8 % d e u t e r i u m c o n c e n t r a t i o n . Process Status The amine-hydrogen p r o c e s s f o r heavy water o u t l i n e d here has been d e v e l o p e d o v e r t h e p a s t t e n y e a r s , s t a r t i n g w i t h bench t e s t s o f amine-hydrogen d e u t e r i u m exchange by Atomic Energy o f Canada L i m i t e d (16) and c u l m i n a t i n g in the g e n e r a t i o n by S u l z e r o f a complete d e s i g n package f o r a 65 t o n s p e r y e a r p l a n t l i n k e d t o an ammonia p l a n t in A l b e r t a . L a b o r a t o r y work has c e n t r e d around i m p r o v i n g the low temperature k i n e t i c s o f the amine-hydrogen exchange r e a c t i o n . Three f u l l s c a l e e j e c t o r c o n t a c t o r s have been p i l o t e d and s u c c e s s i v e m o d i f i c a t i o n s have improved exchange e f f i c i e n c y by a f a c t o r o f f o u r . A l l o t h e r u n i t p r o c e s s e s n o t used in i n d u s t r i a l heavy water p l a n t have been p i l o t e d e i t h e r by AECL o r by S u l z e r . AECL have d e v e l o p e d the homogeneous c a t a l y s t used to promote exchange and have measured r a t e s o f c a t a l y s t d e c o m p o s i t i o n (17). S u l z e r have p i l o t e d p r o c e s s e s t o remove t h e s e d e c o m p o s i t i o n p r o d u c t s from the p l a n t inventory. P r o c e s s d e s i g n has p r o g r e s s e d from the g e n e r a l o u t l i n e o f the p r o c e s s g i v e n above t o d e t a i l e d h e a t , mass and i s o t o p i c b a l a n c e s f o r the complete p r o c e s s . D e s i g n is based on equipment performance d e t e r m i n e d d u r i n g p i l o t t e s t s o r on m a n u f a c t u r e r s ' quoted guarant e e s f o r s t a n d a r d equipment i t e m s . The s e n s i t i v i t y o f the p r o c e s s t o equipment m a l f u n c t i o n o r o p e r a t i n g

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e r r o r s has been a s s e s s e d by computer m o d e l l i n g and s u i t a b l e d e s i g n margins i n c o r p o r a t e d . In g e n e r a l t h e p r o c e s s is much l e s s s e n s i t i v e t o such d i s t u r b a n c e s than o t h e r b i t h e r m a l heavy water p r o c e s s e s because o f the b i g d i f f e r e n c e in h o t and c o l d tower s e p a r a t i o n factors (11). E n g i n e e r i n g d e s i g n has been pursued s i m u l t a n e o u s l y w i t h t h e above a c t i v i t i e s . Equipment items have been s p e c i f i e d and b i d s r e c e i v e d from s e l e c t e d v e n d o r s . P r e l i m i n a r y d e s i g n o f c i v i l work has been c o n c l u d e d by l o c a l companies. A s a f e t y r e p o r t has been p r e p a r e d as a guide t o s i t e s e l e c t i o n . The p l a n t c a p i t a l c o s t has been c a l c u l a t e d based on b i d s f o r equipment and e n g i n eering. Conclusion Amine-hydrogen p r o c e s s development was t r i g g e r e d by p r o c e s s c o n s i d e r a t i o n s i n d i c a t i n g c o n s i d e r a b l e a d vantages o v e r e s t a b l i s h e d p r o d u c t i o n p r o c e s s e s (16). S u c c e s s f u l development, i n c l u d i n g l a b o r a t o r y and p i l o t work, has in t u r n s t i m u l a t e d t h e g e n e r a t i o n by S u l z e r of a complete d e s i g n package f o r a 65 t o n / y r heavy water p l a n t a t t a c h e d t o a K e l l o g g ammonia p l a n t in Western Canada. E s t i m a t e s o f heavy water p r o d u c t i o n c o s t from t h i s p l a n t a r e based on a s o l i d f o u n d a t i o n and f a v o u r t h e e x p l o i t a t i o n o f t h e p r o c e s s in t h e near future. Abstract A heavy water p r o c e s s based on isotopic exchange between hydrogen and methylamine and methylamine and water has been d e v e l o p e d by S u l z e r and Atomic Energy of Canada. Deuterium s o u r c e is the s y n t h e s i s gas stream of an ammonia p l a n t . Deuterium enrichment is a c h i e v e d by b i t h e r m a l amine-hydrogen exchange, however, p r e l i m i nary enrichment is made t o o c c u r in the r e f o r m e r s o f the ammonia p l a n t by u s i n g the steam r e f o r m i n g p r o c e s s as the d e c o m p o s i t i o n s t e p o f a monothermal enrichment s t a g e . T h i s f e a t u r e , c o u p l e d w i t h the h i g h v a l u e o f the s e p a r a t i o n f a c t o r a c h i e v a b l e w i t h hydrogen-amine exchange, a l l o w s a h i g h d e u t e r i u m yield w i t h o u t the use of hydrogen r e c y c l e in the e x t r a c t i o n s t a g e . D e s i g n work has been based on pilot t e s t s o f the key p r o c e s s steps using industrial c o n t a c t i n g equipment. Literature 1 Haenny

Cited J.,

"A Low-Temperature P l a n t f o r the Production

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

4.

WYNN

2

3

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4

5

6 7

8

9

10

11 12 13

14 15

AECL-Sulzer Amine Process

69

o f Heavy Water", S u l z e r T e c h n i c a l Review (1960) 42, 9 Roth E., Bedhome Α., L e f r a n c o i s B . L e C h a t e l i e r J. and Tillol Α., "Mazingarbe Heavy Water P l a n t " , E n e r gie Nucleaire (1968) 10, 214 Roth E., " I s o t o p i c Exchange o f Deuterium Between Ammonia and Hydrogen - A New Method o f P r o d u c i n g Heavy Water", Bull. d ' I n f o r m a t i o n S c i e n t i q u e s e t Technique de C o m m i s s a r i a t a L ' E n e r g i e Atomique (1968) 123, 3 L e f r a n c o i s Β., "Mazingarbe Heavy Water P l a n t , Des cription and O p e r a t i o n " , T e c n i c a ed Economia della P r o d u z i o n e de Acque P e s a n t e , p . 199, Comitato N a z i o n a l e E n e r g i a N u c l e a r e Rome (1971) Roth E., T r a o u r o u d e r R., Viratelle J. and L e f r a n c o i s B., " S t u d i e s o f P r o d u c t i o n P r o c e s s e s and Heavy Water P l a n t s U s i n g the F r e n c h P r o c e s s " , F o u r t h U n i t e d N a t i o n s Conference on the P e a c e f u l Uses o f Atomic E n e r g y , P r o c e e d i n g s 9, 69 U n i t e d N a t i o n s , Geneva (1971). N i t s c h k e E., "Processes and Research in the Produc tion o f Heavy Water", A t o m w i r t s c h a f t 18 (1973) 297 Zmasek R., " S u l z e r R e c t i f y i n g P l a n t s f o r E n r i c h i n g Heavy Water", S u l z e r T e c h n i c a l Review S p e c i a l I s s u e f o r Nuclex 72 (1972) S c h i n d e w o l f U . and Lang G . " O p t i m i z a t i o n o f a Heavy Water P r o d u c t i o n P l a n t w i t h the Ammonia-Hydrogen Dual Temperature Exchange System", T e c n i c a ed E c o n o mia della P r o d u z i o n e de Acque P e s a n t e , p . 75, Comi t a t o N a z i o n a l e E n e r g i a N u c l e a r e , Rome (1971) W a l t e r S. and N i t s c h k e E., "Problems o f the D e s i g n and C o n s t r u c t i o n o f a P l a n t f o r Heavy Water Produc tion U s i n g the Dual Temperature Ammonia-Hydrogen Exchange System" T e c n i c a ed Economia della P r o d u z i o n e di Acque P e s a n t e , p . 173, Comitato N a z i o n a l e E n e r g i a N u c l e a r e , Rome (1971). B e n e d i c t M. and P i g f o r d T.H., "Nuclear C h e m i c a l E n g i n e e r i n g " , M c G r a w - H i l l Book C o . Inc., New York (1957) Rae H.K., "Mass T r a n s f e r in Heavy Water P r o d u c t i o n " , paper p r e s e n t e d a t 25th Canadian C h e m i c a l E n g i n e e r i n g C o n f e r e n c e , M o n t r e a l (November 1975). L o c k e r b y W.E., private communication. Miller A.I. and Voyer R.D., "Improved G a s - L i q u i d C o n t a c t i n g in C o - C u r r e n t F l o w " , C a n . J. Chem. E n g . (1968), 46, 355 Hartmann F. and Roeck G., Chemie Ingen. T e c h . (1965) 37, 294 Miller A.I. and Rae H.K., "The S e a r c h f o r an Im proved Heavy Water P r o c e s s " , paper p r e s e n t e d a t 24th

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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Canadian Chemical Engineering Conference (October 1974). 16 Bancroft A.R. a n d R a e H.K., " H e a v y W a t e r Production by Amine-Hydrogen E x c h a n g e " , Tecnica ed Economia della P r o d u z i o n e di A c q u a Pesante, p . 47, C o m i t a t o Nazionale Energia Nucleare, Rome (1971); a n d Atomic E n e r g y of C a n a d a Limited Report, AECL-3684 (1970). 17 Holtslander W.J. and Lockerby W.E., "Chemistry of the H y d r o g e n - A m i n e Process for H e a v y W a t e r Produc tion", t o be published.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch004

RECEIVED September 6, 1977

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

5 Heavy Water Production by Isotopic Exchange between Hydrogen and Methylamine M. BRIEC, J. RAVOIRE, M. ROSTAING, and E . ROTH Commissariat à l'Energie Atomique, Division de Chimie, Centre D'Études Nucléaires De Saclay, République Française B. LEFRANCOIS

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch005

Sté. Chimique des Charbonnages

Isotopic exchange between water and hydrogen sulphide was the f i r s t chemical process used on a large scale for the production of heavy water, and is still employed in the big Canadian plants. Isotopic exchange between liquid ammonia and hydrogen, discovered by Wilmarth and Dayton(1) which offers a much higher separation factor than the former process, has been studied in French CEA laboratory, since 1956, and developed using available sources of hydrogen in the ammonia industry. However, to extract deuterium from hydrogen, especially from NH3 synthesis gases, Bar-Eli and Klein (2) then J. Ravoire and E . Rochard (3 and 4)studied the exchange between hydrogen and a primary or secondary amine, catalysed by an alkaline derivative of the amine used. Kinetic measurements showed that the exchange is much faster than that between hydrogen and ammonia, the separation factors being similar (7 at - 6 0 ° C and 3.5 at +30° C). The hydrogen-monomethylamine system (MMA) can thus be used for productions of the same order as those of the NH -H exchange process, as shown by detailed studies on a laboratory, p i l o t unit and plant project scale. 3

2

Laboratory Studies I t is easy t o imagine the use o f the amine-H exchange in a dual-temperature process, t u r n i n g t o account the v a r i a t i o n in the separation f a c t o r α with temperature. Once the α values were determined the p o i n t s t o be s t u d i e d were as f o l l o w s : 2

1. Exchange K i n e t i c s . The exchange is c a t a l y s e d by a l k a l i n e methylamides, the most e f f i c i e n t being C H 3 N H K ; the chemical r a t e is much f a s t e r than in the case o f ammonia under the same temperature and c a t a l y s t c o n c e n t r a t i o n c o n d i t i o n s .

© 0-8412-0420-9/78/47-068-071$05.00/0

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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2. S o l u b i l i t y o f Hydrogen. Hydrogen is more s o l u b l e in monomethylamine (MMA) than in ammonia (2.5 times a t -50° C ) . T h i s helps t o speed up the exchange r a t e .

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch005

3. Thermal S t a b i l i t y o f the C a t a l y s t . Potassium methylamide is s t a b l e a t low temperatures, but in s o l u t i o n a t high temperature i t is thermolysed and converted t o a potassium s a l t of Ν,Ν'-dimethylformamidine, s o l u b l e in MMA. By long duration t e s t s in p i l o t u n i t s , the s t a b i l i t y was proved s a t i s f a c t o r y under present working c o n d i t i o n s . 4. S o l u b i l i t y o f the C a t a l y s t . I t s s o l u b i l i t y decreases as the temperature r i s e s . In the presence o f hydrogen the con c e n t r a t i o n o f potassium methylamide is l i m i t e d by the formation of potassium hydride: CH NHK + H 3

2

*

>

CH NH 3

2

+ HK.

The methylamide concentration a t e q u i l i b r i u m is i n v e r s e l y p r o p o r t i o n a l t o the hydrogen pressure and is about 0.1 mol/kg amine f o r a hydrogen pressure o f 50 bars. The e q u i l i b r i u m depends l i t t l e on temperature; i t is s e t up slowly and the hydride formation r a t e is bound up with the nature o f the con tainer walls. 5. Adjuvant E f f e c t o f Trimethylamine (TMA). I t was discovered t h a t a n o n - c a t a l y t i c a d d i t i v e t o the c a t a l y s t can speed up the exchange r a t e ; thus, a m u l t i p l i c a t i o n f a c t o r o f 1.7 was obtained by a d d i t i o n o f about 7% (molar) o f TMA t o the MMA. P i l o t Plant

Tests

The c h i e f problem was t o f i n d a h i g h l y e f f i c i e n t contact system. F i n e l y p e r f o r a t e d p l a t e s , with s u i t a b l e heights o f l i q u i d , are s a t i s f a c t o r y s i n c e a 60 cm spacing is enough f o r the p l a t e s t o f u n c t i o n w e l l . P r e l i m i n a r y D r a f t o f a Factory (in c o l l a b o r a t i o n with l a Société Chimique des Charbonnages) 1. D e s c r i p t i o n o f the Process. The r e s u l t s presented here concern research on the p r e l i m i n a r y d r a f t o f a 60 Τ p e r year heavy water p l a n t attached t o a 1000 Τ per day ammonium s y t h e s i s u n i t ; the exchange takes place by a dual temperature process, as mentioned above, t o avoid any chemical transformation o f the amine. As shown on Figure 1, the synthesis mixture (N + 3 H ) , f r e e d o f oxygenated i m p u r i t i e s by hydrogénation (A), dehydration (B) and f i n a l l y by washing in the tower (C), t r a n s f e r s i t s deuterium t o a c u r r e n t o f MMA in a low-temperature TT tower (the only tower t o c o n t a i n a nitrogen-hydrogen mixture, enabling 2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

2

B R i E C ET AL.

and

Methyhmine

Isotopic

Exchange

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch005

Hydrogen

A

methanation

TF2

cold

BB'

dehydration

TC2

h o t tower

(2nd

stage) stage)

CC

1

TT

purification transfer

tower

DD'

deamination

TEP

s t r i p p i n g tower

(1st stage)

TEN

enrichment

TC

hot toner ( 1 s t sta^e)

tower

TH

humidification

tower

(2nd

r

compressor(2nd

F

f i n i s h i n g plant

abed

hydrogen

efgh

liquid

stage)

loop (1st stage)

loop (1st stage)

(1st stage)

tower

(1st stage)

Figure 1.

Heavy water production unit

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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HYDROGEN ISOTOPES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch005

p u r e h y d r o g e n t o be u s e d in t h e r e s t o f t h e s y s t e m ) . After r e c u p e r a t i o n of the methylamine t h e gas is s e n t t o t h e ammonia s y n t h e s i s u n i t . The l i q u i d is f e d t h r o u g h a s e r i e s o f h o t and c o l d t o w e r s in w h i c h i t a c c u m u l a t e s d e u t e r i u m a g a i n s t t h e c o u n t e r - f l o w o f a h y d r o g e n l o o p . The p r o c e s s i n v o l v e s two e n r i c h m e n t s t a g e s b e f o r e a f i n i s h i n g p l a n t w h i c h can be e i t h e r a h y d r o g e n r e c t i f i c a t i o n o r a w a t e r r e c t i f i c a t i o n a f t e r e x c h a n g e b e t w e e n t h e w a t e r and t h e amine. 2. D e t e r m i n a t i o n o f W o r k i n g C o n d i t i o n s . The p r e s s u r e and t e m p e r a t u r e c o n d i t i o n s were d e t e r m i n e d on t h e b a s i s o f p h y s i c o - c h e m i c a l f a c t o r s s u c h as t h e r m a l s t a b i l i t y o f t h e c a t a l y s t , s o l u b i l i t y in t h e p r e s e n c e o f h y d r o g e n , f a c t o r s r e l a t i v e t o a s s o c i a t i o n w i t h ammonia s y s t h e s i s s u c h as t h e a v a i l a b l e p r e s s u r e o f f e e d - g a s , and e c o n o m i c c o n s i d e r a t i o n s . The c h o i c e o f t h e p r e s s u r e is t h e r e s u l t o f many c o m p r o m i s e s ; t h e p r e s s u r e must be l o w enough t o a l l o w a r e a s o n a b l e c a t a l y s t c o n c e n t r a t i o n , so as t o o b t a i n good p l a t e e f f i c i e n c i e s and t h e use o f more c o n v e n t i o n a l m a t e r i a l t h a n in h i g h p r e s s u r e ammonia s y n t h e s i s ; on t h e o t h e r hand i t must be f a i r l y h i g h in o r d e r t o a v o i d undue gas r e c o m p r e s s i o n and t o m a i n t a i n t h e l o w MMA v a p o u r p r e s s u r e w h i c h a f f e c t s t h e e n e r g y consump t i o n (amine s a t u r a t i o n o f t h e gas and c o n d e n s a t i o n o f t h i s amine b e t w e e n t h e h o t a n d c o l d t o w e r s ) . The h i g h e r t e m p e r a t u r e c h o s e n is l o w enough t o r e t a i n s a t i s f a c t o r y b e h a v i o u r o f t h e catalyst. I n c h o o s i n g t h e c o l d t e m p e r a t u r e i t was n e c e s s a r y t o d e c i d e b e t w e e n l o w e r f l o w s a t l o w e r t e m p e r a t u r e on t h e one hand and l e s s f a v o u r a b l e k i n e t i c s , h i g h e r c o o l i n g c o s t s and more e l a b o r a t e s t e e l s on t h e o t h e r . A f t e r a d e t a i l e d e c o n o m i c s t u d y a c o l d t e m p e r a t u r e o f -50° C was a d o p t e d . 3. Economy o f t h e P r o c e s s . T a b l e I shows t h e m a i n s p e c i f i c a t i o n s o f the u n i t : dimensions o f the i s o t o p i c exchange towers, d i s t r i b u t i o n of investments according t o the d i f f e r e n t i t e m s , and p r i n c i p a l c o n s u m p t i o n s . Where i n v e s t m e n t s a r e c o n c e r n e d t h e two m a i n i t e m s o f e x p e n s e a r e t h e h e a t t r a n s f e r e q u i p m e n t ( c o o l i n g s t a t i o n + e x c h a n g e r s + i n s u l a t i o n ) and t h e exchange towers equipped w i t h t h e i r p l a t e s . The c a p i t a l c o s t f o r t h i s p r o c e s s r e p r e s e n t s $460 p e r k g o f h e a v y w a t e r p e r y e a r . The p r e s s u r e b e l o w t h a t o f t h e s y n t h e s i s c a n i n v o l v e an i n c r e a s e o f gas r e c o m p r e s s i o n c o s t s and o f c e r t a i n c o o l i n g costs. I n s p i t e o f a l l t h e s e f a c t o r s the energy expenses are lower than those o f o t h e r p r o c e s s e s , H S - H 0 f o r example, u n d e r t h e e c o n o m i c c o n d i t i o n s p u b l i s h e d f o r t h e P o r t Hawkesbury and B r u c e s i t e s {5) (where 60% o f t h e e n e r g y is r e c o v e r e d ) . The c o n s u m p t i o n s f o r o u r p r o c e s s a r e 0.7 Τ s t e a m (60 p s i ^ k g D 0 and 700 k W h A g a g a i n s t 11 Τ s t e a m (330 p s i ) / k g D 0 and 550 kWh/kg. 2

2

2

2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1000 T/day N2 + 3H2 (H2) = 1,4

piping + valves e l e c t r i c i t y + control compressors + pumps b u i l d i n g , engineering H2preparation tanks + catalyst preparation 2nd stage dehydration + deamination c o o l i n g s t a t i o n + exchanger + insulation towers + p l a t e s 18, 46% 17, 34%

1 1 , 30% 13, 60%

r

10, 00%

7, 18% 4,44% 5, 59%

1 1 , 98%

Coolant water:

Steam

o f which

Electricity

1164 m /hour

2292 : 1 s t stage com pressors 2245 : c o o l i n g s t a t i o n 6 tons/hour

5893 kWh

Consumptions

75 73,8 51 55,5 2 χ 49,8 28

2,35 2,44 2,44 2,94 1,22 1,47 Principal

h e i g h t (m)

130 ppm

Diameter (m)

Deuterium content o f the hydrogen:

t r a n s f e r tower s t r i p p i n g tower enrichment tower hot tower c o l d tower hot tower

D i s t r i b u t i o n o f investments (%)

2nd tower

1 s t stage:

1000 (25 f o r the 1 s t stage)

Tower dimension

Enrichment:

Loop gas flow-rate/supply gas f l o w - r a t e

Feeding r a t e :

Main s p e c i f i c a t i o n s o f the heavy water p r o d u c t i o n p l a n t (production: 58,5 T/year)

TABLE I

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch005

76

SEPARATION OF HYDROGEN ISOTOPES

Conclusion The exchange r a t e s in the H -MMA system are extremely f a s t in view o f the a c t i v i t y o f the c a t a l y s t and the s o l u b i l i t y of hydrogen. The development o f a s u f f i c i e n t l y s t a b l e and s o l u b l e c a t a l y s t means t h a t the c o n s t r u c t i o n o f heavy water p l a n t s is f e a s i b l e under f i n a n c i a l l y competitive c o n d i t i o n s . The production o f appreciable q u a n t i t i e s o f heavy water from the hydrogen used f o r synthesis o f ammonia is now p o s s i b l e in many c o u n t r i e s . I f the use o f hydrogen in the future as an energy v e c t o r is developed, the MMA-hydrogen process w i l l p r o f i t from the s c a l e e f f e c t in the b u i l d i n g o f u n i t s , and the low p r i c e s o f thermal and e l e c t r i c a l s u p p l i e s a v a i l a b l e a t the proximity o f hydrogen chemical-nuclear generators.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch005

2

Literature Cited (1) (2) (3) (4) (5)

Wilmarth, W . , . and Dayton, J.C., JACS (1953) 75.4553. B a r - E l i , Ε . , and Klein, F . S . , J. Chem. Soc. (1962) 3083. Rochard, E., and Ravoire, J., Rapport C . E . A . (1969) 3835. Rochard, Ε., and Ravoire, J., J. Chem. Phys. (1971) 1183. Rae, H . K . , "Heavy Water", Atomic Energy of Canada Limited Report No. 3866, Geneva, 1971.

RECEIVED October 17, 1977

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

6 U H D E Process for the Recovery of Heavy Water from Synthesis Gas E. NITSCHKE, H. ILGNER, and S. WALTER

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006

Friedrich Uhde GmbH, Dortmund, West Germany

Heavy water, or deuterium o x i d e , has been used up t o now, on an industrial s c a l e , only as a moderator in nuclear r e a c t o r s . Due to the good utilization of neutrons in heavy water r e a c t o r s , n a t u r a l uranium can be used as f u e l . A t the end o f the fifties, when the feasibility of the v a r i o u s types o f r e a c t o r s was examined, the heavy water r e a c t o r was found t o have very good prospects. Heavy water r e a c t o r s are of particular i n t e r e s t to c o u n t r i e s which have uranium d e p o s i t s , but do not have t h e i r own uranium enrichment p l a n t s . Canada has c o n s i s t e n t l y centred the development of the nuclear energy generation on heavy water and has assumed a l e a d i n g r o l e in this field (1). A l s o , in I n d i a , A r g e n t i n a and P a k i s t a n heavy water r e a c t o r s are used as nuclear power p l a n t s . Deuterium can a l s o be used as f u e l f o r f u s i o n r e a c t o r s . Intensive research is being made i n t o the development of these r e a c t o r s , but there are still s e v e r a l fundamental p h y s i c a l and t e c h n i c a l problems t o be s o l v e d . There are f o r e c a s t s t h a t some time in the f u t u r e , the f u s i o n r e a c t o r will supersede the fission r e a c t o r in energy p r o d u c t i o n . However, it is difficult to p r e d i c t when this will happen. The h e a v y w a t e r r e q u i r e m e n t o f a h e a v y w a t e r r e a c t o r is 0.7 t D2O/MW; in o t h e r w o r d s , a 600 MW f i s s i o n r e a c t o r r e q u i r e s a p p r o x i m a t e l y 400 t D 0 a s a n i n i t i a l c h a r g e . L o s s e s o f one t o two p e r c e n t p e r y e a r o f t h e i n i t i a l c h a r g e c a n be e x p e c t e d , i . e . the make-up r e q u i r e m e n t is 4 - 8 t D2O p e r y e a r . I n t h e c a s e o f f u s i o n r e a c t o r s , t h e a n n u a l heavy water r e q u i r e m e n t f o r a t y p i c a l 2000 MW f u s i o n r e a c t o r w o u l d be no more t h a n a f e w t D2O. There a r e two f u n d a m e n t a l c o n c e p t s t o s e p a r a t e t h e d e u t e r i u m isotope: one i n v o l v i n g t h e p h y s i c a l c h a r a c t e r i s t i c s o f h y d r o g e n and w a t e r a n d t h e o t h e r , t h e c h e m i c a l i s o t o p e e x c h a n g e c h a r a c t e r i s t i c s w h i c h o f f e r some f a v o u r a b l e f a c t o r s f o r c o m m e r c i a l plant design. Under t h i s c a t e g o r y t h r e e s y s t e m s h a v e b e e n a p p l i e d f o r commercial a p p l i c a t i o n : hydrogen s u l f i d e system, h y d r o g e n - w a t e r e x c h a n g e , a n d t h e hydrogen-ammonia e x c h a n g e . 2

© 0-8412-0420-9/78/47-068-077$05.00/0

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

SEPARATION OF

78

HYDROGEN ISOTOPES

The H2O/H2S p r o c e s s u s e s w a t e r a s a f e e d s t o c k and is u s e d f o r i n d u s t r i a l h e a v y w a t e r p l a n t s in t h e U.S.A. and in Canada. The f e a s i b l e s i z e o f a p l a n t is a t a p r o d u c t i o n o f more t h a n 200 t p e r y e a r . I n c o n t r a s t t o t h i s , t h e H / H 0 and H / NH systems are b a s e d on h y d r o g e n . When u s i n g h y d r o g e n t h e p r o d u c t i o n c a p a c i t y is l i m i t e d by t h e amount o f h y d r o g e n a v a i l a b l e . T h i s l i m i t a t i o n was o f t e n c o n s i d e r e d as a p r i n c i p a l d i s a d v a n t a g e . T h i s argument is n o t v a l i d any more, a s t h e c a p a c i t y o f i n d u s t r i a l h y d r o g e n p r o d u c t i o n p l a n t s , f o r e x a m p l e ammonia s y n t h e s i s , has i n c r e a s e d in r e c e n t y e a r s by a f a c t o r o f 5 - 10. A 1500 t p e r day NH s y n t h e s i s p l a n t is c a p a b l e o f p r o d u c i n g more t h a n 100 t p e r y e a r D 0 a t a y i e l d o f 80%. 2

2

2

3

3

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006

2

P r i n c i p l e s of Isotope

Separation

The a t t a i n a b l e e l e m e n t a r y s e p a r a t i o n f a c t o r is s m a l l in c h e m i c a l i s o t o p e e x c h a n g e . The n e c e s s a r y m u l t i p l i c a t i o n o f t h e e l e m e n t a r y s e p a r a t i o n f a c t o r by c o u n t e r c u r r e n t o f t h e l i q u i d and t h e g a s e o u s p h a s e c a n be a c h i e v e d by v a r i o u s schemes (2) . The p r i n c i p a l schemes a r e shown in F i g u r e 1. Schemes a and b c o m p r i s e o n l y one c o l u m n , w h i c h is c o u p l e d t o a s o - c a l l e d p h a s e conversion unit. I n a r e c t i f i c a t i o n p r o c e s s p h a s e c o n v e r s i o n is a c h i e v e d in a r e l a t i v e l y s i m p l e way, by means o f , r e s p e c t i v e l y , t h e r e b o i l e r and t h e o v e r h e a d c o n d e n s e r . F o r c h e m i c a l s y s t e m s s u c h p h a s e c o n v e r s i o n i n v o l v e s a more c o m p l i c a t e d s t e p - i n a water/hydrogen system, f o r instance, a water e l e c t r o l y s i s . In an ammonia/hydrogen s y s t e m , p h a s e c o n v e r s i o n w o u l d be e f f e c t e d by t h e s y n t h e s i s o f t h e ammonia o r t h e c r a c k i n g o f ammonia t o h y d r o g e n and n i t r o g e n . T h i s i n v o l v e s c o n s i d e r a b l e p r o b l e m s f r o m t h e d e s i g n and o p e r a t i o n p o i n t o f v i e w , as t h e c a t a l y s t must be s e p a r a t e d and f e d b a c k t o t h e t o p o f t h e e n r i c h m e n t column. Ammonia c r a c k i n g means a r e l a t i v e l y h i g h a d d i t i o n a l i n v e s t ment and e n e r g y c o n s u m p t i o n , as t h e e n e r g y r e l e a s e d d u r i n g s y n t h e s i s is o b t a i n e d a t a d i f f e r e n t l e v e l f r o m t h e e n e r g y w h i c h is r e q u i r e d f o r ammonia c r a c k i n g . When u s i n g t h e h o t - c o l d p r i n c i p l e , t h e p h a s e - c o n v e r s i o n is r e p l a c e d by a h o t c o l u m n ( F i g u r e 1 c ) . Due t o n e g a t i v e d e p e n dence o f the e q u i l i b r i u m c o n s t a n t , t h e d i r e c t i o n o f the i s o t o p e t r a n s p o r t is r e s e r v e d . H o t - c o l d processes are a l s o c a l l e d b i t h e r m a l o r d u a l t e m p e r a t u r e exchange p r o c e s s e s . The maximum y i e l d w h i c h is t h e o r e t i c a l l y p o s s i b l e is shown in t h e f i r s t l i n e o f t h e d i a g r a m . F o r t h e b i t h e r m a l s y s t e m , t h e y i e l d is l i m i t e d by t h e g i v e n s e p a r a t i o n f a c t o r s a t t h e o p e r a t i n g t e m p e r a t u r e o f t h e h o t and c o l d c o l u m n . The y i e l d c a n be i n c r e a s e d by a d d i n g a s t r i p p i n g system. Such a s t r i p p i n g s y s t e m is a r e v e r s e h o t c o l d s y s t e m , i . e . a c o l d c o l u m n is f o l l o w e d by a h o t column ( F i g u r e I d ) . F o r t h i s p u r p o s e i t is n e c e s s a r y t o c i r c u l a t e an a d d i t i o n a l gas and l i q u i d s t r e a m t h r o u g h t h e s y s t e m .

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

^«1

LIT

4"

a

Ρο

c

o

2

τ«

Ρ,

u

2

Τ, α ,

Pi

Τ,or

Figure 1.

C o n d l f i o n s

Principal schemes for chemical isotope exchange

T£

m

n

s

Λ* double phase conversion. c- Hot-coldsystem d-Hot-coldsystem with, e Hot-colasystem with Stripping system Transfer column A - depleted stream ^ ^^ f ^ / RU^phase-conversbn catalyst separation ^conditions of fyof columns

P.U.

Τι«ι

pu.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006

SEPARATION O F

80

H Y D R O G E N ISOTOPES

I n t h e b i t h e r m a l s y s t e m t h e t e m p e r a t u r e o f t h e h o t column is l i m i t e d f o r p r o c e s s and e c o n o m i c r e a s o n s - t h e p a r t i a l p r e s s u r e o f t h e l i q u i d p h a s e in t h e h o t column s h o u l d be s m a l l in r e l a t i o n t o t h e t o t a l p r e s s u r e ; h i g h p r e s s u r e o f a b o u t 300 k g / c m is t h e r e f o r e r e q u e s t e d in t h e s y s t e m . T h e r e f o r e , i f t h e f e e d m a t e r i a l , h y d r o g e n , is o n l y a v a i l a b l e a t a r e l a t i v e l y l o w p r e s s u r e (100 - 200 k g / c m ) , one c a n add a t r a n s f e r column w h i c h o p e r a t e s a t a low temperature upstream o f the enrichment system (Figure l e ) . The e n r i c h m e n t s y s t e m i t s e l f is t h e n c o u p l e d t o t h e t r a n s f e r column o n l y v i a t h e l i q u i d p h a s e . A t r a n s f e r column a l s o g i v e s a d d i t i o n a l a d v a n t a g e s w h i c h w i l l be shown l a t e r . The UHDE p r o c e s s is a c o m b i n a t i o n o f a s t r i p p i n g s y s t e m w i t h a t r a n s f e r column ( F i g u r e 2 ) . F e a s i b i l i t y s t u d i e s o f t h e s y s t e m have c l e a r l y shown t h a t due t o t h e i m p r o v e d r e c o v e r y , t h e i n c r e a s e in c a p a c i t y more t h a n compensates f o r t h e e x t r a c o s t o f t h e s t r i p p i n g s y s t e m . The e c o n o m i c optimum is a p p r o x i m a t e l y 80% y i e l d . L i k e t h e w a t e r / h y d r o g e n s y s t e m , t h e ammonia/hydrogen s y s t e m a l s o r e q u i r e s a c a t a l y s t f o r the d e u t e r i u m exchange. Potassium amide (KNH2) is a c a t a l y s t s u i t a b l e f o r t h i s p u r p o s e . T h i s c a t a l y s t has t h e s p e c i a l a d v a n t a g e t h a t i t is h o m o g e n e o u s l y d i s s o l v e d in ammonia. A number o f o t h e r c a t a l y s t s and c a t a l y s t g r o u p s have been t e s t e d , b u t up t o now i t is t h e o n l y c a t a l y s t u s e d in t h e c o m m e r c i a l a p p l i c a t i o n . 2

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006

2

D e s i g n o f Heavy Water P l a n t The p l a n t a s shown on t h e s i m p l i f i e d f l o w d i a g r a m ( F i g u r e 3) c o n s i s t s o f f i v e e s s e n t i a l s e c t i o n s , t h e gas p u r i f i c a t i o n s e c t i o n w i t h t r a n s f e r column, the f i r s t stage w i t h s t r i p p i n g system, t h e s e c o n d a n d t h i r d s t a g e and l a s t l y , t h e f i n a l c o n c e n t r a t i o n s e c t i o n c o m p r i s i n g t h e exchange column and t h e w a t e r d i s t i l l a t i o n section. A n o t h e r i m p o r t a n t p l a n t s e c t i o n n o t shown on t h e f l o w d i a grams is t h e r e f r i g e r a t i o n u n i t . The r e f r i g e r a t i o n c o m p r e s s o r w i t h two d i f f e r e n t t e m p e r a t u r e l e v e l s is d r i v e n by a s t e a m t u r b i n e o f t h e e x t r a c t i o n c o n d e n s i n g t y p e . B a c k - p r e s s u r e steam is u s e d f o r h e a t i n g and s a t u r a t i n g t h e gas o r l i q u i d s t r e a m s . D e p e n d i n g on t h e c o o l i n g w a t e r c o n d i t i o n s t h e t u r b i n e c a n a l s o be o p e r a t e d w i t h o u t t h e c o n d e n s i n g p a r t . P u r i f i c a t i o n System. The s y n t h e s i s gas p a s s e s t h r o u g h a gas p u r i f i c a t i o n s e c t i o n in w h i c h a l l o x y g e n - b e a r i n g gas comp o n e n t s s u c h as H2O, C 0 , CO and 0 a r e removed (<5) . A l l t h e s e s u b s t a n c e s r e a c t w i t h t h e p o t a s s i u m amide, f o r m i n g s u b s t a n c e s w h i c h a r e i n s o l u b l e in l i q u i d ammonia. T h i s w o u l d r e s u l t n o t o n l y in a r e d u c t i o n o f t h e c a t a l y s t e f f i c i e n c y , b u t a l s o i n t r o d u c e s t h e r i s k o f c l o g g i n g in t h e c o l u m n . Water a n d c a r b o n d i o x i d e a r e removed in a f i r s t s t a g e by l i q u i d ammonia s c r u b b i n g . The ammonia is t a k e n f r o m t h e ammonia 2

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In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006

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s y n t h e s i s u n i t and r e t u r n e d t o i t a f t e r p a s s i n g t h e p u r i f i c a t i o n unit. C a r b o n monoxide and a l s o o x y g e n , i f t h e l a t t e r is p r e s e n t in t h e g a s , a r e removed b y s c r u b b i n g w i t h p o t a s s i u m amide solution. A special design o f the trays eliminates the r i s k o f c l o g g i n g . The r e a c t i o n p r o d u c t s f o r m e d in t h i s s t a g e a r e r e moved o u t s i d e t h e c o l u m n and t h e p o t a s s i u m amide s o l u t i o n is f e d to t h e t o p a g a i n . T r a n s f e r Column. The g a s t h e n p a s s e s t h r o u g h t h e t r a n s f e r c o l u m n where t h e d e u t e r i u m is t r a n s f e r r e d t o t h e ammonia a n d t h e s y n g a s is r e t u r n e d t o t h e ammonia s y n t h e s i s u n i t . I n washing t r a y s a t t h e t o p o f t h e t r a n s f e r column e n t r a i n e d p o t a s s i u m amide is removed. The e n r i c h e d ammonia l e a v i n g t h e b o t t o m o f t h e t r a n s f e r c o l u m n is p r e s s u r i z e d t o t h e p r e s s u r e o f t h e downstream f i r s t stage. F i r s t S t a g e a n d S t r i p p i n g System. The f i r s t s t a g e c o n s i s t s o f t h e b i t h e r m a l s e c t i o n p r o p e r a n d t h e s t r i p p i n g s y s t e m . The o p e r a t i o n o f t h e i n d i v i d u a l s e c t i o n s o f t h e f i r s t stage might b e s t be e x p l a i n e d w i t h t h e a i d o f t h e M c C a b e - T h i e l e diagrams ( F i g u r e 4 ) . H e r e , N ( 0 ) is t h e c o n c e n t r a t i o n o f t h e l i q u i d ammonia f e d f r o m t h e b o t t o m o f t h e t r a n s f e r c o l u m n t o t h e t o p o f t h e c o l d column o f t h e e n r i c h m e n t s y s t e m . In t h e c o l d c o l u m n , d e u t e r i u m is t r a n s f e r r e d f r o m t h e g a s t o t h e l i q u i d ; in o t h e r w o r d s , we a r e g o i n g up t h e w o r k i n g l i n e . A t t h e b o t t o m o f t h e c o l d c o l u m n , d e u t e r i u m - b e a r i n g h y d r o g e n is removed a n d t r a n s f e r r e d t o t h e n e x t s t a g e a n d a c o r r e s p o n d i n g s t r e a m is r e t u r n e d ; h o w e v e r , w i t h a l o w e r d e u t e r i u m c o n c e n t r a tion. The c o n c e n t r a t i o n c h a n g e s f r o m N ( z ) t o N ( z ) a n d we f o l l o w the w o r k i n g l i n e o f t h e h o t column as f a r as t o t h e bottom o f t h e h o t c o l u m n . Here t h e g a s s t r e a m is s p l i t . On t h e McCabeT h i e l e d i a g r a m , t h i s means a change in t h e s l o p e o f t h e w o r k i n g line. I n t h e h o t s t r i p p i n g c o l u m n d e u t e r i u m c o n t i n u e s t o be t r a n s f e r r e d t o t h e gas and t h e l o w e s t deuterium c o n c e n t r a t i o n N ( Z ) is f i n a l l y r e a c h e d a t t h e b o t t o m o f t h e h o t s t r i p p i n g column. P r i o r t o e n t e r i n g t h e c o l d s t r i p p i n g column, t h e ammonia, w h i c h is b e i n g r e t u r n e d t o t h e t o p o f t h e t r a n s f e r column, is removed. T h i s a l t e r s t h e s l o p e o f t h e w o r k i n g l i n e a g a i n a n d in t h e c o l d s t r i p p i n g c o l u m n we come b a c k t o t h e feeding point. T h i s d i a g r a m a l s o shows t h a t t h e s l o p e o f t h e w o r k i n g l i n e is l i m i t e d b y t h e s l o p e o f t h e two e q u i l i b r i u m l i n e s a t t h e t e m p e r a t u r e o f t h e h o t a n d c o l d c o l u m n . When d e s i g n i n g t h e p l a n t , t h e s l o p e o f t h e w o r k i n g l i n e s must be d e t e r m i n e d in s u c h a way t h a t o n l y a minimum o f t r a y s is r e quired. As t h e t r a y e f f i c i e n c y in t h e h o t and c o l d c o l u m n s is d i f f e r e n t , t h i s minimum r e f e r s t o t h e number o f a c t u a l t r a y s ; in o t h e r w o r d s , t h e c o l u m n volume o f t h e s y s t e m is t o be m i n i m i z e d . 1

2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978. Figure 4.

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Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006

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I n t h e f i r s t s t a g e t h e r e a r e two s u p e r i m p o s e d gas c y c l e s . However, o n l y one c i r c u l a t i n g c o m p r e s s o r is s u f f i c i e n t as t h e d i f f e r e n t p r e s s u r e d r o p s in b o t h c y c l e s c a n be u s e d f o r c o n t r o l l i n g t h e gas r a t e s . When b e i n g t r a n s f e r r e d f r o m t h e h o t c o l u m n t o t h e c o l d c o l u m n and v i c e v e r s a , t h e gas and l i q u i d s t r e a m s are h e a t e d and c o o l e d r e s p e c t i v e l y . I t is o b v i o u s t h a t t h i s must be done in a way t o c o n s e r v e t h e h e a t in o r d e r t o r e d u c e t h e energy consumption. F i g u r e 5 shows t h e e n t h a l p y / t e m p e r a t u r e d i a g r a m f o r s y n t h e s i s gas w h i c h is s a t u r a t e d w i t h ammonia and t h e a r r a n g e m e n t of the h e a t exchanges f o r c o o l i n g t h e s y n t h e s i s gas from the h o t column. Downstream o f a d i r e c t h e a t e x c h a n g e r , w h i c h is a r r a n g e d i n s i d e t h e h o t c o l u m n , t h e h e a t is t r a n s f e r r e d t o l i q u i d ammonia a t a r e l a t i v e l y h i g h t e m p e r a t u r e w h i c h t h e n t r a n s f e r s t h i s h e a t t o t h e gas f o r s a t u r a t i o n . The gas t h e n f l o w s t h r o u g h a water c o o l e r and t h e n t h r o u g h a gas/gas exchanger. The r e m a i n i n g gap t o come down t o t h e t e m p e r a t u r e o f t h e c o l d c o l u m n is p r o v i d e d by t h e r e f r i g e r a t i o n p l a n t and t r a n s f e r r e d f r o m the gas in two h e a t e x c h a n g e r s , c o n n e c t e d in s e r i e s . These o p e r a t e a t d i f f e r e n t t e m p e r a t u r e s in o r d e r t o r e d u c e t h e e n e r g y consumption f o r the r e f r i g e r a t i o n compressor. Altogether, a l m o s t 70% o f t h e h e a t r e l e a s e d d u r i n g c o o l i n g is u t i l i z e d . The a r r a n g e m e n t o f t h e h e a t e x c h a n g e r s and t h e d e t e r m i n a t i o n o f t h e w o r k i n g r a n g e is n o t a r b i t r a r y , b u t is d e t e r m i n e d by t h e e n e r g y c o s t s and t h e c a p i t a l i n v e s t m e n t f o r h e a t e x c h a n g e r s , t a k i n g i n t o account the s p e c i a l c o n d i t i o n s a t the s i t e . T h i s p r o b l e m o f o p t i m i z a t i o n was r e s o l v e d s i m u l t a n e o u s l y w i t h t h e p r o b l e m o f m i n i m i z i n g t h e c o l u m n v o l u m e by s e t t i n g up a p p r o p r i a t e computer programs. T h i s work was done in a v e r y c l o s e c o o p e r a t i o n w i t h the I n s t i t u t e f o r Nuclear Technology a t K a r l s r u h e U n i v e r s i t y (4). The c o o p e r a t i o n is n o t c o n f i n e d t o t h i s s u b j e c t b u t a l s o t o s o l v i n g o t h e r p r o b l e m s , in p a r t i c u l a r the p e r f o r m a n c e o f p i l o t p l a n t t e s t s w h i c h s u p p l i e d t h e r e s u l t s on w h i c h t h e d e s i g n o f t h e p r o c e s s is b a s e d ( 3 ) , C5) . Second and T h i r d S t a g e . The a r r a n g e m e n t o f t h e s e c o n d and t h i r d s t a g e is a n a l o g u e t o t h e f i r s t s t a g e . I n e a c h s t a g e t h e d e u t e r i u m c o n t e n t is i n c r e a s e d by a f a c t o r a r o u n d 9. Ammonia w h i c h h a s b e e n e n r i c h e d t o 15-20% d e u t e r i u m c a n t h e n be t a k e n o u t b e t w e e n t h e h o t and c o l d c o l u m n o f t h e t h i r d and l a s t s t a g e . Since the streams are s m a l l e r , i . e . i n v e r s e l y p r o p o r t i o n a l t o the e n r i c h m e n t f a c t o r , t h e h e a t r e c o v e r y s y s t e m b e t w e e n h o t and c o l d c o l u m n is made s i m p l e r . F i n a l C o n c e n t r a t i o n . A f t e r c a r e f u l e x a m i n a t i o n Uhde d e c i d e d f o r a w a t e r d i s t i l l a t i o n as f i n a l c o n c e n t r a t i o n . W a t e r d i s t i l l a t i o n is a w e l l - p r o v e n p r o c e s s and c a n be o p e r a t e d u n d e r n o r m a l p r e s s u r e and t e m p e r a t u r e . F o r t h i s , i t is n e c e s s a r y t o t r a n s f e r t h e d e u t e r i u m f r o m the ammonia t o w a t e r . The e n r i c h e d ammonia w h i c h h a d b e e n

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

SEPARATION OF HYDROGEN ISOTOPES

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86

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In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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s e p a r a t e d f r o m t h e c a t a l y s t t h r o u g h e v a p o r a t i o n , is t h u s b r o u g h t i n t o contact w i t h water. Both r e a c t i o n p a r t n e r s a r e separated a g a i n in a d i s t i l l a t i o n s e c t i o n a t t o p and b o t t o m o f t h e c o l u m n , t h e ammonia is f e d b a c k t o t h e t h i r d s t a g e . The e n r i c h e d w a t e r is f e d t o a s i n g l e - s t a g e d i s t i l l a t i o n c o l u m n . The h e a v y w a t e r w i t h a c o n t e n t o f o v e r 9 9 . 8 % D 0 c a n f i n a l l y be w i t h d r a w n f r o m the bottom o f t h e d i s t i l l a t i o n column. B a s e d on t h i s c o n s i d e r a t i o n t h e f i n a l c o n c e n t r a t i o n h a s b e e n d e s i g n e d and s u p p l i e d by S u l z e r B r o s . , W i n t e r t h u r .

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006

2

O p e r a t i o n o f t h e P l a n t . The d i f f e r e n t s e c t i o n s o f t h e p l a n t - t h e gas p u r i f i c a t i o n s e c t i o n w i t h t r a n s f e r column, t h e f i r s t s t a g e w i t h s t r i p p i n g s y s t e m , t h e s e c o n d and t h i r d s t a g e and l a s t l y , t h e f i n a l p u r i f i c a t i o n s e c t i o n , c a n be o p e r a t e d i n d e p e n d e n t l y ; t h a t means i f one o f them h a s t o be s h u t down, t h e o t h e r s c a n still be o p e r a t e d . This reduces the process c o n t r o l p r o b l e m s and i n c r e a s e s p l a n t r e l i a b i l i t y . I t is a c h a r a c t e r i s t i c f e a t u r e o f the process t h a t the steady s t a t e c o n d i t i o n s , i . e . t h e f i n a l c o n c e n t r a t i o n p r o f i l e in t h e c o l u m n s , a r e r e a c h e d o n l y a f t e r a p e r i o d o f a few d a y s . Also therefore e a c h s e c t i o n is p r o v i d e d w i t h a s e p a r a t e c o l l e c t i n g t a n k f o r t h e l i q u i d h o l d up in o r d e r t o a v o i d m i x i n g o f l i q u i d s w i t h d i f f e r e n t i s o t o p e c o n c e n t r a t i o n s , and so t o f a c i l i t a t e r e - s t a r t i n g . Engineering

Problems

Apart from q u e s t i o n s d e a l i n g w i t h t h e process d e s i g n e n g i n e e r i n g t h e r e were a l s o s e v e r a l m e c h a n i c a l e n g i n e e r i n g p r o b l e m s t o be s o l v e d . The p l a n t is d e s i g n e d f o r much t h e same p r e s s u r e a n d t e m p e r a t u r e r a n g e as an ammonia s y n t h e s i s p l a n t ; c o n s e q u e n t l y , t h e same s o r t o f t e c h n i q u e s c a n be u s e d for the design. This a p p l i e s p a r t i c u l a r l y t o the heat exchangers as w e l l as t h e c h o i c e o f o t h e r equipment. The h i g h - p r e s s u r e c o l u m n s i n v o l v e new p r o b l e m s . The d i a m e t e r o f t h e c o l d c o l u m n in t h e f i r s t s t a g e is 2 m and t h e d i a m e t e r o f t h e c o r r e s p o n d i n g h o t c o l u m n s is l a r g e r still due t o t h e g r e a t e r g a s and l i q u i d l o a d . The c o l u m n s a r e up t o 40 m h i g h . The c o l d c o l u m n s o f t h e e n r i c h m e n t s y s t e m a n d o f t h e t r a n s f e r s e c t i o n a r e d i v i d e d in two p a r t s in s e r i e s . A t an o p e r a t i n g p r e s s u r e o f 325 k g / c m t h e c o l u m n w e i g h t is c o n s i d e r a b l e . The l a r g e s t c o l u m n , w h i c h h a s a d e a d w e i g h t o f 270 t , must be t r a n s p o r t e d t o t h e p l a n t s i t e in one p i e c e and e r e c t e d t h e r e . T h e r e f o r e t h e t r a n s p o r t a t i o n c o n d i t i o n s s h o u l d be r e v i e w e d c a r e f u l l y b e f o r e d e c i d i n g o n t h e l o c a t i o n f o r a plant of this kind. A l l towers are equipped w i t h s i e v e t r a y s , which p r o v i d e a good mass t r a n s f e r b e t w e e n t h e p h a s e s . A c c o r d i n g t o t h e s p e c i a l f e a t u r e s o f the system w i t h regard t o the k i n e t i c s o f the r e a c t i o n and t h e h y d r o d y n a m i c c h a r a c t e r i s t i c s o f t h e f l u i d s , t h e d e s i g n o f t h e s i e v e t r a y s d i f f e r s from t h e d e s i g n n o r m a l l y used 2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006

for

d i s t i l l a t i o n or a b s o r p t i o n towers. O x y g e n - b e a r i n g s u b s t a n c e s a r e c o m p l e t e l y removed f r o m t h e gas due t o t h e p r e s e n c e o f p o t a s s i u m amide. I t is w e l l known t h a t hydrogen o f extreme p u r i t y reduces the n o t c h impact s t r e n g t h of high-grade s t e e l s . T e s t s have shown, h o w e v e r , t h a t s u c h a r i s k is u n l i k e l y u n d e r t h e c o n d i t i o n s p r e v a i l i n g h e r e . For s a f e t y r e a s o n s s t e e l s a r e p r e f e r r e d , w h i c h h a v e a r e l a t i v e l y low s t r e n g t h and good d u c t i l i t y , e v e n a t low t e m p e r a t u r e s , a s is t h e case f o r higher n i c k e l - a l l o y e d s t e e l s . P o t a s s i u m amide in ammonia a c t s v e r y s t r o n g l y on o r g a n i c m a t e r i a l s , so e v e n m a t e r i a l s l i k e T e f l o n c o r r o d e w i t h i n a short time. A v a r i e t y o f m a t e r i a l s were e x a m i n e d in a u t o c l a v e t e s t s in o r d e r t o f i n d m a t e r i a l s w h i c h a r e r e s i s t a n t t c p o t a s s i u m amide a t t h e p r e v a i l i n g o p e r a t i n g c o n d i t i o n s . L a t e r t h e s e m a t e r i a l s a r e t e s t e d u n d e r o p e r a t i n g c o n d i t i o n s in a s p e c i a l facility. Even t o d a y t h i s is done t o t e s t m a t e r i a l f o r pump s e a l s and s t u f f i n g b o x e s w h i c h a r e new on t h e m a r k e t . A l l t h e s e q u e s t i o n s have b e e n e x a m i n e d v e r y c a r e f u l l y , f i r s t on a l a b o r a t o r y s c a l e and t h e n on a p i l o t - p l a n t s c a l e in o r d e r t o f i n d a r e l i a b l e s o l u t i o n f o r the design of a commercial p l a n t . I n t e g r a t i o n o f Heavy W a t e r P l a n t and Ammonia

Synthesis

T h i s p r o c e s s is b a s e d on h y d r o g e n as t h e s o u r c e o f d e u t e r i u m . T h i s h y d r o g e n can be o b t a i n e d f o r example f r o m t h e g a s i f i c a t i o n u n i t o f t h e ammonia p l a n t . The h e a v y w a t e r p l a n t is s t r i p p i n g t h e d e u t e r i u m f r o m t h e s y n g a s , w h i c h is t h e n r e t u r n e d t o t h e ammonia s y n t h e s i s l o o p . T h i s c o u p l i n g is o f v i t a l i m p o r t a n c e f o r t h e o p e r a t i o n o f ammonia p l a n t s . I t must be c e r t a i n t h a t t h e p r o d u c t i o n and a l s o t h e o n - s t r e a m t i m e o f t h e ammonia p l a n t are not a f f e c t e d . F i g u r e 6 shows t h e scheme o f i n t e g r a t i o n o f a h e a v y w a t e r p l a n t w i t h an ammonia p l a n t . 1.

2.

The s y n t h e s i s gas p r o d u c e d in t h e g a s i f i c a t i o n s e c t i o n is p u r i f i e d in t h e u s u a l way and f e d t o t h e s y n t h e s i s gas c o m p r e s s o r , where i t is b r o u g h t up t o t h e p r e s s u r e o f t h e ammonia s y n t h e s i s u n i t and a d m i x e d t o t h e s y n t h e s i s gas c y c l e as f e e d g a s . A f t e r the l a s t stage o f the syngas c o m p r e s s o r , t h e s y n t h e s i s gas is d i v e r t e d t o t h e h e a v y w a t e r p l a n t . The s y n t h e s i s gas w h i c h is d e p l e t e d o f d e u t e r i u m is t h e n r e t u r n e d t o t h e ammonia s y n t h e s i s u n i t . The h e a v y w a t e r p l a n t in f a c t c o n s t i t u t e s a b y - p a s s t o t h e ammonia s y n t h e s i s u n i t . The s y n t h e s i s gas p a s s e s o n l y t h r o u g h t h e gas p u r i f i c a t i o n c o l u m n and t h e t r a n s f e r column o f t h e h e a v y w a t e r p l a n t r e s u l t i n g in a c e r t a i n p r e s s u r e d r o p . T h i s p r e s s u r e d r o p w o u l d have t o be made up by t h e s y n t h e s i s gas c o m p r e s s o r . However, i t is b e t t e r t o i n s t a l l an a d d i t i o n a l b o o s t e r comp r e s s o r w h i c h compensates f o r t h i s p r e s s u r e drop. In the

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978. Figure 6.

Integration of heavy water plant with ammonia plant

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006

CD

92

es S?

Ci

-* ο

ft

>

w

90

SEPARATION OF

HYDROGEN ISOTOPES

e v e n t o f f a i l u r e o f t h e NH s y n t h e s i s u n i t , t h e gas p u r i f i c a t i o n c o l u m n and t h e t r a n s f e r c o l u m n can be o p e r a t e d in a closed c i r c u i t . A l s o in t h i s c a s e t h e r e is no n e e d f o r a v a l v e in t h e b y - p a s s l i n e , t h u s e s t a b l i s h i n g an open bypass. I n t h e c a s e o f f l u c t u a t i o n in t h e gas f l o w t h e h e a v y water p l a n t runs under c o n s t a n t c o n d i t i o n s ; o n l y the d i r e c t i o n f l o w in t h e b y - p a s s l i n e w i l l be c h a n g e d . The f l o w can s l o w l y be a d j u s t e d t o new c o n d i t i o n s a c c o r d i n g l y . The same is t h e c a s e i f t h e r e a r e d i s t u r b a n c e s in t h e h e a v y water p l a n t . The s y n t h e s i s gas w h i c h is r e t u r n e d t o t h e s y n t h e s i s u n i t is s a t u r a t e d w i t h ammonia a t a dew p o i n t o f -28° C c o r r e sponding t o the temperature a t the top o f the c o l d t r a n s f e r c o l u m n . A t a p r e s s u r e o f 200 k g / c m in t h e s y n t h e s i s u n i t , t h e ammonia c o n t e n t o f t h i s s t r e a m is t h u s a p p r o x i m a t e l y 1.2%. I f t h i s gas is a d m i x e d t o t h e r e c y c l e gas o f t h e s y n t h e s i s u n i t u p s t r e a m o f t h e f i r s t s e p a r a t o r , i t has no e f f e c t on t h e s y n t h e s i s c y c l e . However, i f t h e gas is f e d t o t h e r e c y c l e gas d i r e c t l y u p s t r e a m o f t h e c o n v e r t e r , as is t h e c a s e sometimes in s y n t h e s i s u n i t s where n i t r o g e n s c r u b b i n g is u s e d f o r gas p u r i f i c a t i o n , t h e gas e n t e r i n g t h e c o n v e r t e r w o u l d have a s l i g h t l y h i g h e r ammonia c o n t e n t and t h i s w o u l d r e s u l t in a c o r r e s p o n d i n g d e c r e a s e in t h e N H 3 c o n v e r s i o n r a t e in t h e c o n v e r t e r . T h i s can be compens a t e d by i n c r e a s i n g t h e p r e s s u r e o f t h e s y n t h e s i s l o o p , b u t i t is b e t t e r t o compensate t h i s h i g h e r ammonia c o n t e n t by s l i g h t l y i n c r e a s i n g t h e c o l d d u t y o f t h e l a s t s e p a r a t o r o f t h e ammonia s y n t h e s i s u n i t , in o r d e r t o k e e p t h e d e s i g n c o n d i t i o n s of the converter constant. The t e m p e r a t u r e o f t h e r e t u r n gas is l o w e r t h a n t h a t o f t h e f e e d g a s , b e c a u s e t h e h e a t e x c h a n g e r must have a c e r t a i n temperature gradient. F u r t h e r m o r e , t h e gas c o n t a i n s no t r a c e s o f e i t h e r CO o r o x y g e n w h i c h u s u a l l y have a d e t r i m e n t a l e f f e c t on t h e ammonia c a t a l y s t . The l a s t two f a c t o r s m e n t i o n e d have a f a v o u r a b l e e f f e c t on t h e o p e r a t i o n o f t h e ammonia s y n t h e s i s u n i t , a l t h o u g h t h e b e n e f i t s c a n n o t be d e f i n e d q u a n t i t a t i v e l y . An e s s e n t i a l p o i n t o f t h e i n t e g r a t i o n c o n c e r n s t h e g a s i f i c a t i o n s e c t i o n . The gas p u r i f i c a t i o n s h o u l d be d e s i g n e d in s u c h a way as t o k e e p t h e c o n t e n t o f o x y g e n - b e a r i n g i m p u r i t i e s as low as p o s s i b l e in o r d e r t o r e d u c e t h e l o a d on t h e gas p u r i f i c a t i o n s e c t i o n o f t h e h e a v y w a t e r p l a n t . However, t h e d e u t e r i u m c o n t e n t in t h e gas is more i m p o r t a n t and s h o u l d , o f c o u r s e , be k e p t as h i g h as p o s s i b l e . The d e u t e r i u m c o n t e n t is d e t e r m i n e d by t h e d e u t e r i u m c o n t e n t o f t h e f e e d s t o c k s u s e d f o r t h e ammonia, e.g. methane and w a t e r ; b u t , as we h a v e s e e n f r o m numerous measurements o f the d e u t e r i u m content o f samples taken a t v a r i o u s p a r t s o f ammonia p l a n t s , i t c a n be n e g a t i v e l y i n f l u e n c e d by p r o c e s s e s w i t h i n t h e g a s i f i c a t i o n s e c t i o n . A d e u t e r i u m e x c h a n g e can 3

3.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006

2

4.

5.

6.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006

NiTscHKE ET AL.

Figure 7.

UHDE

Process

Model of a heavy water plant (capacity 631/yr)

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch006

92

SEPARATION OF HYDROGEN ISOTOPES

take p l a c e between the hydrogen and the excess steam i n the CO s h i f t conversion,the deuterium being t r a n s f e r r e d t o the steam. The hydrogen thus becomes depleted o f deuterium and the steam becomes e n r i c h e d . This steam i s condensed upstream o f the CO2 scrubbing u n i t and i s discharged from the p l a n t . The condensate i s u s u a l l y not returned t o the p l a n t and the deuterium contained i n i t would be l o s t and t h i s would r e s u l t i n a p r o p o r t i o n a t e r e d u c t i o n i n the p r o d u c t i o n o f the heavy water p l a n t . These l o s s e s can be avoided i f t h i s enriched condensate i s transformed t o steam and t h i s steam i s then used as process steam i n the steam reformer. However, t h i s i n v o l v e s a g r e a t e r load on the steam system o f the ammonia p l a n t which cannot be r e a l i z e d i n the case o f e x i s t i n g ammonia p l a n t s . This problem can be avoided by an isotope exchange o f the enriched condensate with the process steam which i s being fed t o the steam reformer o r t o the s h i f t conversion. The e q u i l i b r i u m between water and water vapour i s n e a r l y equal t o u n i t y ; t h a t means the condensate l e a v i n g the exchange system has the normal deuterium c o n c e n t r a t i o n again. These p o i n t s show t h a t an ammonia p l a n t and a heavy water p l a n t can be i n t e g r a t e d without any p a r t i c u l a r d i f f i c u l t i e s . Conclusion A heavy water p l a n t with a c a p a c i t y o f 63 t D 0 p e r year w i l l be b u i l t a t T a l c h e r / I n d i a . The p l a n t i s coupled w i t h a 900 t per day ammonia p l a n t and w i l l be put on stream beginning 1978. F i g u r e 7 i s a photo o f the model. A comparison o f the p r o d u c t i o n costs based on the c a l c u l a t i o n f o r t h i s p l a n t shows with regard t o the investment as w e l l as t o the o p e r a t i n g c o s t s t h a t t h i s process can compete with other processes o r may even be s u p e r i o r . 2

Literature (1) (2) (3)

(4)

(5) (6)

Cited

Lumb, P.B.; J. B r . N u c l . Energy Soc. (1976) 15, pp. 35-46. Becker, E . W . ; IAEA R e v . , S e r i e s No. 21 (1962) V i e n n a . W a l t e r , S., N i t s c h k e , E.; "Tecnica ed Economia d e l l a Produzione d i Acqua Pesante", p . 173, Comitato Nazionale Energia Nucleare, Rome (1971). Schindewolf, U., Lang, G.; "Tecnica ed Economia d e l l a Produzione d i Acqua Pesante", p . 75, Comitato Nazionale Energia N u c l e a r e , Rome (1971). Walter, S., Schindewolf, U . ; Chem. Ing. Techn. (1965), 37, pp. 1185-91. Schindewolf, U., Hornke, S . ; Chem. Ing. Techn. (1969), 41, p p . 645-648.

RECEIVED October 28, 1977

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

7 Novel Catalysts for Isotopic Exchange between Hydrogen and Liquid Water J. P. BUTLER, J. H . ROLSTON, and W. H . STEVENS

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007

Atomic Energy of Canada Ltd., Chalk River Nuclear Laboratories, Physical Chemistry Branch, Chalk River, Ontario K0J 1J0

Canada's atomic power program r e q u i r e s l a r g e q u a n t i t i e s o f heavy water t h a t a r e c u r r e n t l y produced by t h e G i r d l e r - S u l p h i d e o r GS p r o c e s s . This process i s based on exchange o f hydrogen i s o t o p e s between hydrogen s u l p h i d e gas and l i q u i d w a t e r as g i v e n by t h e f o l l o w i n g c h e m i c a l exchange r e a c t i o n : HDS

g

+ H 0,. s liq

N

HDO . + H S l i q g

z 2

n

(1)

z 2

At Chalk R i v e r we have a s t r o n g i n t e r e s t i n t r y i n g t o d e v e l o p new and more e f f i c i e n t p r o c e s s e s f o r t h e p r o d u c t i o n o f heavy w a t e r . A v e r y a t t r a c t i v e p r o c e s s and one w i t h many i n h e r e n t p o t e n t i a l advantages i s based on t h e h y d r o g e n - l i q u i d w a t e r i s o t o p i c exchange reaction. HD + H 0 2

l i q

N

^

H

D

0

H

l i q

+ 2

(2>

The hydrogen-water i s o t o p i c exchange r e a c t i o n i s more a t t r a c t i v e p r i m a r i l y because i t has a h i g h e r s e p a r a t i o n f a c t o r , a , d e f i n e d i n terms o f t h e d e u t e r i u m (D) to p r o t i u m (H) atom r a t i o s i n t h e two s p e c i e s a t equilibrium. α

= (D/H)

l i q

j/(D/H)

(3)

g

A t low d e u t e r i u m c o n c e n t r a t i o n s , α i s e q u a l t o t h e e q u i l i b r i u m c o n s t a n t f o r b o t h o f t h e s e exchange reactions. Figure 1 gives the separation f a c t o r f o r the h y d r o g e n - l i q u i d water (1) and t h e hydrogen s u l p h i d e l i q u i d water (2) exchange r e a c t i o n s i n t h e temperature range 0-200°C. Over t h e e n t i r e temperature range, t h e s e p a r a t i o n f a c t o r , a , f o r t h e H - H 0 system i s about a f a c t o r o f 2 h i g h e r than t h a t f o r t h e H S - H 0 2

2

2

©

2

0-8412-0420-9/78/47-068-093$05.00/0

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007

SEPARATION O F HYDROGEN ISOTOPES

Figure 1.

Separation factor, a, as a function of temperature for the hydrogen-water and hydrogen sulfide—water systems

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

7.

BUTLER ET

AL.

Novel

Catalysts

for

Isotopic

Exchange

95

exchange r e a c t i o n . As a r e s u l t , a p r o c e s s based on the H 2 - H 2 O r e a c t i o n w i l l have a h i g h e r r e c o v e r y o f d e u t e r i u m from n a t u r a l w a t e r and, as a consequence, a s m a l l e r p l a n t w i l l be r e q u i r e d . T h e o r e t i c a l r e c o v e r i e s o f 50% are p o s s i b l e f o r a b i t h e r m a l p r o c e s s based on the hydrogen-water r e a c t i o n compared t o 21% f o r the GS p r o c e s s .

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007

C a t a l y s t Development A l t h o u g h the hydrogen-water i s o t o p i c exchange r e a c t i o n i s v e r y d e s i r a b l e f o r the s e p a r a t i o n o f hydrogen i s o t o p e s , the d i f f i c u l t y has been t o o b t a i n a c a t a l y s t t h a t can o p e r a t e e f f i c i e n t l y i n the p r e s e n c e o f l i q u i d w a t e r (3) . E f f e c t i v e n o b l e metal c a t a l y s t s f o r the vapour exchange r e a c t i o n have been known f o r many y e a r s b u t t h e s e c a t a l y s t s l o s e t h e i r a c t i v i t y i n contact with water. Our new approach i s t o use a c a t a l y s t s u i t a b l e f o r the vapour exchange r e a c t i o n , such as h i g h l y d i s p e r s e d p l a t i n u m metal d e p o s i t e d on γ-alumina, and t o c o a t the c a t a l y s t body w i t h a v e r y t h i n l a y e r o f a water r e p e l l e n t m a t e r i a l , such as a s i l i c o n e polymer, t o p r e v e n t w e t t i n g (4) . To i l l u s t r a t e the e f f e c t i v e ness o f the s i l i c o n e w e t p r o o f i n g , F i g u r e 2 shows what happens when c a t a l y s t p e l l e t s o f p l a t i n u m on alumina, a commercial c a t a l y s t produced by E n g e l h a r d I n d u s t r i e s , a r e immersed i n water. The u n t r e a t e d p e l l e t s r e l e a s e a stream o f s m a l l b u b b l e s o f a i r as w a t e r immediately e n t e r s the p o r e s o f the alumina. The p e l l e t s become j e t b l a c k , i n d i c a t i n g t h a t the s u r f a c e i s completely wetted. In c o n t r a s t , the s i l i c o n e t r e a t e d p e l l e t s shown i n F i g u r e 3 have l a r g e gas b u b b l e s a d h e r i n g t o t h e i r s u r f a c e and the s u r f a c e remains l i g h t grey i n c o l o u r , which i s c h a r a c t e r i s t i c o f the w e t p r o o f i n g a c t i o n o f the s i l i c o n e . These s i l i c o n e t r e a t e d , o r w e t p r o o f e d , c a t a l y s t s are q u i t e e f f e c t i v e f o r the h y d r o g e n - l i q u i d water i s o t o p i c exchange r e a c t i o n . S u b s e q u e n t l y , c a t a l y s t s were p r e p a r e d by d e p o s i t i n g p l a t i n u m on porous p o l y t e t r a f l u o r o e t h y l e n e i n an attempt t o p r o v i d e an improved h y d r o p h o b i c environment f o r t h e p l a t i n u m c r y s t a l l i t e s (5) . A more s u c c e s s f u l approach has been t o d e p o s i t p l a t i n u m on h i g h s u r f a c e a r e a carbon and t o bond the p l a t i n i z e d carbon t o a v a r i e t y o f column p a c k i n g s o r c a r r i e r s u s i n g T e f l o n as b o t h the b o n d i n g and the w e t p r o o f i n g agent. These l a i t t e r c a t a l y s t s have proven v e r y e f f e c t i v e f o r the h y d r o g e n - l i q u i d w a t e r exchange r e a c t i o n .

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

96

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SEPARATION O F H Y D R O G E N ISOTOPES

Figure

2.

Untreated 0.5% Pt-Al O Engelhard mersed in water 2

s

catalyst im-

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007

BUTLER E T A L .

Figure 3.

0.5%

Novel

Catalysts for Isotopic

Exchange

Pt-Al 0 Engelhard catalyst treated with Dow 773 Silicone and immersed in water 2

3

Corning

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

98

SEPARATION O F H Y D R O G E N ISOTOPES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007

C a t a l y s t Performance To measure the performance, o r the a c t i v i t y , o f t h e s e c a t a l y s t s we have used a s i n g l e pass t r i c k l e bed r e a c t o r shown d i a g r a m m a t i c a l l y i n F i g u r e 4. A known q u a n t i t y o f c a t a l y s t i s packed i n a 2.5 cm d i a m e t e r g l a s s column t o depths v a r y i n g from 5 t o 75 cm. About 15 cm o f n o n - c a t a l y t i c p a c k i n g i s p l a c e d d i r e c t l y below the c a t a l y s t bed t o a i d i n e s t a b l i s h i n g u n i f o r m gas flow p a t t e r n s through the bed. The e n t i r e p a c k i n g i s s u p p o r t e d on a s t a i n l e s s s t e e l s c r e e n (mesh s i z e , 40 χ 40). N a t u r a l w a t e r (D/H = 144 ppm) i s i n t r o d u c e d a t the top o f the column through a w a t e r d i s t r i b u t o r and flows downward through the c a t a l y s t bed assembly. P u r i f i e d d r y hydrogen, e n r i c h e d i n d e u t e r i u m (D/H = 300 ppm), flows c o u n t e r c u r r e n t l y upward through the h u m i d i f i e r where i t becomes s a t u r a t e d w i t h w a t e r vapour which i s i n i s o t o p i c e q u i l i b r i u m w i t h the l i q u i d water l e a v i n g the c a t a l y s t bed. The gas and water vapour then c o n t i n u e upward t h r o u g h the c a t a l y s t bed. The d e u t e r i u m c o n c e n t r a t i o n i n the i n l e t and o u t l e t hydrogen gas streams i s measured w i t h an on l i n e mass s p e c t r o m e t e r {6) . F o r the o p e r a t i n g con d i t i o n s d e s c r i b e d , the e n r i c h e d hydrogen gas becomes d e p l e t e d i n d e u t e r i u m i n p a s s i n g through the column w h i l e the n a t u r a l water f e e d i s e n r i c h e d . For example, f o r a g i v e n c a t a l y s t o p e r a t i n g a t 25°C where the s e p a r a t i o n f a c t o r , a, i s 3.81, the hydrogen gas s t r e a m l e a v i n g the top o f the column may have a D/H = 150 ppm, w h i l e i f e q u i l i b r i u m had been e s t a b l i s h e d between the two phases the c o n c e n t r a t i o n would be 37.8 ppm. The a c t i v i t y o f the v a r i o u s c a t a l y s t s f o r the i s o t o p i c exchange r e a c t i o n i n the hydrogen-water system i s d e t e r m i n e d by the nearness o f approach t o i s o t o p i c e q u i l i b r i u m between the two phases a f t e r p a s s i n g through the column. T h i s degree o f approach i s e x p r e s s e d i n terms o f a column e f f i c i e n c y , η , d e f i n e d as the r a t i o o f the a c t u a l change i n the d e u t e r i u m c o n c e n t r a t i o n o f the hydrogen t o the change t h a t would have o c c u r r e d had the hydrogen gas stream r e a c h e d e q u i l i b r i u m w i t h the f e e d water. With m i x t u r e s o f hydrogen and water a t low d e u t e r i u m i s o t o p i c c o m p o s i t i o n , the column e f f i c i e n c y , η , f o r the c a t a l y s t bed i s g i v e n by the e x p r e s s i o n η = F r a c t i o n a l Approach t o E q u i l i b r i u m Between the Two Phases

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

7.

BUTLER ET AL.

Novel

Catalysts

for Isotopic

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007

NATURAL WATER FEED (D/H)=l44ppm > WATER DISTRIBUTOR

—

PACKED CATALYST BED

—

NON-CATALYTIC PACKING

—

H

2°LIQ Ψ

Exchange

H -(D/H)=l50ppm 2

(AT EQUIL= 37.8ppm)

T=

25°C

a= 3.806

H - SATURATED WITH H 0 H (D/H)= 300ppm 2

ι

2

V A P

2

PACKED BED HUMIDIFIER

—

PURIFIED^DRY ENRICHED

H

2

(D/H)=300ppm

Figure 4. Trickle bed reactor used for hydrogenliquid water isotopic exchange studies

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

99

100

SEPARATION O F H Y D R O G E N ISOTOPES

(D/H),

-

(D/H)

(D/H)^ "

(D/H)

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007

b

t

(4) eq

where (D/H) i s the atom r a t i o and the s u b s c r i p t s , b and t , r e f e r t o the i n l e t and o u t l e t hydrogen gas streams a t the bottom and top r e s p e c t i v e l y o f the exchange column. The s u b s c r i p t , eq, r e f e r s t o the d e u t e r i u m c o n c e n t r a t i o n o f the hydrogen i n e q u i l i b r i u m w i t h the l i q u i d w a t e r . From a measurement o f the column e f f i c i e n c y , η , the o v e r a l l t r a n s f e r o f d e u t e r i u m from hydrogen t o l i q u i d w a t e r can be calculated. F o r hydrogen and water f l o w i n g c o u n t e r c u r r e n t l y i n a packed column, the t r a n s f e r o f d e u t e r i u m from the hydrogen t o the w a t e r i s c h a r a c t e r i z e d by an o v e r a l l gas-phase mass t r a n s f e r c o e f f i c i e n t , Tya, e x p r e s s e d i n gram atoms p e r u n i t t i m e , p e r u n i t volume o f bed, f o r u n i t d i s p l a c e m e n t o f the d e u t e r i u m mole f r a c t i o n from the e q u i l i b r i u m value. F o r a s m a l l t e s t r e a c t o r where the concen t r a t i o n o f d e u t e r i u m i n the water does n o t v a r y s i g n i f i c a n t l y t h r o u g h o u t the r e a c t o r , the r a t e o f d e u t e r i u m t r a n s f e r from the gas t o the l i q u i d phase i n a s m a l l volume element o f the r e a c t o r , dV, o f c r o s s s e c t i o n a l a r e a A and h e i g h t dh, i s g i v e n by the following d i f f e r e n t i a l equation: -G-A-dy = T a ( y - y*)A-dh y

(5)

where G i s the molar f l o w r a t e o f hydrogen p e r second p e r u n i t a r e a , y i s the a c t u a l mole f r a c t i o n o f d e u t e r i u m i n the hydrogen a t a g i v e n h e i g h t , h , and y* i s the v a l u e a t e q u i l i b r i u m w i t h the l i q u i d w a t e r . I n t e g r a t i n g e q u a t i o n 5 o v e r the h e i g h t o f the c a t a l y s t bed, h, g i v e s (6) Τ a = = g £-ln(l - n) y S i n c e gas flow r a t e s are n o r m a l l y measured i n terms o f volume, we have found i t c o n v e n i e n t t o use a volume t r a n s f e r c o e f f i c i e n t , Κ a g i v e n by the e x p r e s s i o n K a y

= ~

I -ln(l

-

n)

(7)

where F

- s u p e r f i c i a l hydrogen flow r a t e , m-s a t STP h - h e i g h t o f the c a t a l y s t bed, m Κ a - gas-phase volume t r a n s f e r c o e f f i c i e n t , m (of H at STP)-s" -m" (of c a t a l y s t bed). Y

1

3

2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

:

BUTLER ET AL.

7.

Novel

Catalysts

for

Isotopic

Exchange

101

The r a t e o f the o v e r a l l i s o t o p i c exchange r e a c t i o n i s f i r s t o r d e r i n the approach o f the d e u t e r i u m concent r a t i o n o f any o f the s p e c i e s t o i t s f i n a l e q u i l i b r i u m v a l u e and thus Kya i s a f i r s t o r d e r r a t e c o n s t a n t and d i m e n s i o n a l l y i t has the u n i t s o f s " . We have s t u d i e d the e f f e c t o f many parameters on the a c t i v i t y o f the c a t a l y s t , Kya, and F i g u r e 5 shows the e f f e c t o f hydrogen gas flow r a t e and temperature f o r a 0.37% P t - C - T e f l o n c a t a l y s t on 6.1 mm c e r a m i c spheres. F o r t h i s c a t a l y s t , Kya i n c r e a s e s a p p r o x i mately as the 0.3 power o f the hydrogen flow r a t e i n the range 0.05 t o 1.4 m/s a t STP. We a r e d e a l i n g h e r e w i t h a v e r y f a s t i s o t o p i c exchange r e a c t i o n : f o r example, a t a temperature o f 25°C and a hydrogen flow r a t e o f 1.0 m/s a t STP, Kya = 1.2. This i s equivalent t o a h a l f - t i m e f o r the exchange r e a c t i o n o f 0.18 s. The h a l f - t i m e i s c a l c u l a t e d u s i n g the a c t u a l hydrogen f l o w r a t e which i s 3.1 times the s u p e r f i c i a l flow r a t e f o r t h i s p a r t i c u l a r c a t a l y s t bed assembly (the volume f r a c t i o n o f gas i n the o p e r a t i n g column i s 0.32). The s o l i d p o i n t s i n F i g u r e 5 were o b t a i n e d u s i n g e n r i c h e d hydrogen (D/H = 250 ppm), where the d e u t e r i u m i s t r a n s f e r r e d from the hydrogen gas t o the l i q u i d w a t e r , w h i l e the open p o i n t s were o b t a i n e d u s i n g e n r i c h e d water (D/H = 1130 ppm),where d e u t e r i u m i s t r a n s f e r r e d from the l i q u i d water t o the hydrogen gas. From the d a t a no d i f f e r e n c e can be d e t e c t e d i n the r a t e o f d e u t e r i u m t r a n s f e r f o r the n e t r e a c t i o n o c c u r r i n g i n either direction. The e f f e c t o f temperature on the a c t i v i t y o f the c a t a l y s t i s a l s o i l l u s t r a t e d i n F i g u r e 5. F o r an i n c r e a s e i n temperature from 25° t o 60°C, K a i n c r e a s e s by a f a c t o r o f 2.4. The temperature c o e f f i c i e n t o f Kya f o r t h i s c a t a l y s t i n the range 15° t o 60°C i s e q u i v a l e n t t o an A r r h e n i u s a c t i v a t i o n energy o f 21 k J - m o l " o r about 5 k c a l - m o l " . The e f f e c t o f p l a t i n u m m e t a l s u r f a c e a r e a on the a c t i v i t y o f the c a t a l y s t i s shown i n F i g u r e 6 where Kya, the volume t r a n s f e r r a t e c o n s t a n t , i s p l o t t e d a g a i n s t the p l a t i n u m m e t a l s u r f a c e a r e a , measured by hydrogen c h e m i s o r p t i o n , and e x p r e s s e d as m p e r cm of packed bed. A l t h o u g h Kya i n c r e a s e s w i t h m e t a l a r e a , the i n c r e a s e i s not d i r e c t l y p r o p o r t i o n a l t o the a r e a . F o r m e t a l areas below 0.06 m -cm" , Kya i n c r e a s e s as the 0.75 power o f the m e t a l s u r f a c e a r e a and a t h i g h e r m e t a l areas the r a t e o f i n c r e a s e o f Kya i s l e s s . The curve appears t o be a p p r o a c h i n g a maximum v a l u e . These r e s u l t s i n d i c a t e t h a t a n o t h e r r e a c t i o n b e s i d e s the c a t a l y t i c one i s l i m i t i n g the o v e r a l l exchange reaction rate.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007

1

y

1

1

2

2

3

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

3

102

SEPARATION

O F HYDROGEN

-

-

6

*

0

^ ^ ^ - P - 4 5

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007

C

°

e

C

^0 • ^

-

2

5

^

OOo-—°*

-

CARRIER

-

6 . 1 mm C E R A M I C

SPHERES

CATALYST BED

0. 5

HEIGHT

-

20.3

cm

AREA

-

4.80

cm*

PRESSURE

-

106 k P a

H 0 2

FLOW -

2. 1 k g - m (60

•

m

ο

•

1 0.2

A

1 0 . 4 HYDROGEN

Figure

^

5.

ENRICHED Η ENRICHED

2

- °/H

Η 0 2

0 . 6 . 0.8 FLOW

RATE

= 2 5 0 ppm

- D/H

1

1

· $•'

2

g/m i n )

= 1 1 3 0 ppm

1

1

1.0

1.2

- m/s ( A T

1.4

STP)

Effect of hydrogen gas flow rate and temperature on the activity, K a , of α 0.37% Pt-C-Teflon y

catalyst

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ISOTOPES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007

7.

BUTLER ET AL.

Figure 6.

Novel Catalysts

for Isotopic

Exchange

103

Dependence of the transfer rate constant, K a, on the platinum metal area o) Pt-C-Teflon catalysts y

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

104

SEPARATION

O F HYDROGEN

ISOTOPES

Mechanism o f the Exchange R e a c t i o n As a f i r s t a p p r o x i m a t i o n , t h e o v e r a l l r a t e o f transfer of d e u t e r i u m between streams o f hydrogen and l i q u i d water o v e r these w e t p r o o f e d c a t a l y s t s can be c o n s i d e r e d i n terms o f two t r a n s f e r s t e p s . The f i r s t corresponds t o the c a t a l y t i c r a t e o f t r a n s f e r o f d e u t e r i u m from an e n r i c h e d hydrogen stream t o water vapour and t h e second c o r r e s p o n d s t o the t r a n s f e r r a t e from water vapour t o l i q u i d as shown i n e q u a t i o n s [8] and [ 9 ] .

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007

HD HDO

vap

+ H zo O

vap

+

Ηz

2

Ο

η

.

liq

ν

^

N

s

HDO

vap

HDO,.

l i q

+

+ Hz

(8)

H 0 z

(9)

2

2

vap

The c a t a l y t i c r e a c t i o n [8] o c c u r s on a c t i v e c a t a l y s t s i t e s w h i l e t h e v a p o u r - l i q u i d t r a n s f e r r e a c t i o n [9] o c c u r s on any s u r f a c e . The l a t t e r t r a n s f e r s t e p can be c o n s i d e r e d as a c o n d e n s a t i o n - e v a p o r a t i o n r e a c t i o n . Techniques have been d e v e l o p e d so t h a t , i n a t r i c k l e bed r e a c t o r , t h e o v e r a l l r a t e and t h e i n d i v i d u a l t r a n s f e r r a t e s ( r e a c t i o n s [8] and [9]) can be d e t e r mined s i m u l t a n e o u s l y (7) . The magnitudes o f t h e s e s e p a r a t e d r a t e s a r e b o t h about a f a c t o r o f 2 l a r g e r than v a l u e s from d i r e c t measurements made on these two r e a c t i o n s i n d e p e n d e n t l y . These r e s u l t s have l e d to t h e c o n c l u s i o n t h a t t h e o v e r a l l mechanism f o r t h e exchange r e a c t i o n i s n o t as s i m p l e as f i r s t assumed and t h a t t h e r e i s a t h i r d p r o c e s s independent o f t h e w a t e r vapour i n v o l v e d i n the t r a n s f e r o f deuterium from hydrogen gas t o l i q u i d w a t e r . The e x a c t n a t u r e of t h i s t h i r d p r o c e s s i s n o t y e t known. S t u d i e s have been made o f t h e e f f e c t o f some 20 d i f f e r e n t parameters on t h e a c t i v i t y o f t h e c a t a l y s t s and t h e s e w i l l be d i s c u s s e d i n f u t u r e p u b l i c a t i o n s . Improvements i n C a t a l y s t Performance I n n o v a t i o n s r e s u l t i n g i n improved c a t a l y s t p e r formance a r e summarized i n T a b l e 1. The a c t i v i t y , Kya, o f each c a t a l y s t i n a t r i c k l e bed r e a c t o r i s g i v e n f o r a column o p e r a t i n g a t 25°C, a t about 1 atmosphere p r e s s u r e (0.106 MPa) and a s u p e r f i c i a l hydrogen gas flow r a t e o f 1.0 m/s a t STP. A l s o l i s t e d i n T a b l e 1 i s t h e s p e c i f i c a c t i v i t y o f each c a t a l y s t , Kya*, d e f i n e d as t h e o v e r a l l t r a n s f e r r a t e per u n i t c o n c e n t r a t i o n o f platinum i n the c a t a l y s t bed,

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

0.14% P t - C - T e f l o n

0.087% P t - C - T e f l o n 0.39% P t - C - T e f l o n Ordered Packing

6.

7. 8.

0.98 2.40

1.20

0.58

0.20

0.22

0.005

0.017

K^a m^'S 1 ·itT3

C a l c u l a t e d from d a t a g i v e n i n r e f e r e n c e

0.4% P t - C - T e f l o n

5.

Teflon

0.4% P t - P o r o u s

3

4.

2

0.5% P t - A l 0 S i l i c o n e Treated

3

3.

2

0.05% P t - A l 0 Untreated

2.

Taylor

Pt-Charcoal,

1.

Catalyst

(8) .

a

2.18 2.84

1.44

0.146

0.064

0.046

0.0011

0.0022

K

Performance

a

y * m3*s~Mkg Pt)"^-

Improvement i n C a t a l y s t

TABLE 1

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007

1980 2580

1300

133

58

42

1.0

2.0

Rel. Specific Activity

106

SEPARATION

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007

/

O F HYDROGEN

ISOTOPES

Κ a* = (10) kg P t p e r m bed y The s p e c i f i c a c t i v i t y g i v e s a measure o f how e f f e c t i v e l y t h e p l a t i n u m i s b e i n g used i n a g i v e n c a t a l y s t . The l a s t column g i v e s t h e s p e c i f i c a c t i v i t y r e l a t i v e t o c a t a l y s t #2, an u n t r e a t e d , 0 . 5 % P t c a t a l y s t on 3.2 mm p e l l e t s o f γ-alumina. C a t a l y s t #1, p l a t i n u m on powdered c h a r c o a l , was p a t e n t e d by T a y l o r f o r t h i s exchange r e a c t i o n i n 1954 (8) . Treatment o f c a t a l y s t #2 w i t h s i l i c o n e (Cat. #3) improved t h e performance by a f a c t o r o f 40. In an attempt t o f u r t h e r improve t h e h y d r o p h o b i c environment o f t h e p l a t i n u m c r y s t a l l i t e s , p l a t i n u m was d e p o s i t e d on porous T e f l o n (Cat. #4) and t h i s enhanced the a c t i v i t y s l i g h t l y . Depositing p l a t i n u m on h i g h s u r f a c e a r e a carbon and b o n d i n g t h i s t o a c a r r i e r w i t h T e f l o n (Cat. #5) made a s i g n i f i c a n t improvement i n the s p e c i f i c a c t i v i t y . By d e c r e a s i n g the p l a t i n u m l o a d i n g and i n c r e a s i n g i t s d i s p e r s i o n on the carbon b l a c k (Cat. #6) t h e r e l a t i v e s p e c i f i c a c t i v i t y was i n c r e a s e d by a f a c t o r o f 10. By f u r t h e r d e c r e a s i n g t h e p l a t i n u m l o a d i n g t o 0.0 87% (Cat. #7) a f u r t h e r i n c r e a s e was o b t a i n e d . This l a t t e r c a t a l y s t has a s p e c i f i c a c t i v i t y about 2000 times h i g h e r than the u n t r e a t e d 0.5% P t - A l 0 c a t a l y s t , #3, and i s about 1000 times more a c t i v e than the c a t a l y s t p a t e n t e d by T a y l o r (8) f o r t h i s exchange r e a c t i o n (Cat. #1). In c a t a l y s t #8, the p l a t i n i z e d carbon was bonded w i t h T e f l o n t o c o r r u g a t e d m e t a l s h e e t s a r r a n g e d i n an o r d e r e d f a s h i o n i n t h e exchange column. A l t h o u g h t h i s c a t a l y s t has a h i g h e r p l a t i n u m c o n t e n t , 0.39%, t h e c o n c e n t r a t i o n o f p l a t i n u m p e r u n i t volume o f b e d i s e s s e n t i a l l y the same as c a t a l y s t #6. However as a r e s u l t o f t h e improved g e o m e t r i c c o n f i g u r a t i o n o f t h e c a t a l y s t , b o t h t h e a c t i v i t y and t h e s p e c i f i c a c t i v i t y are t w i c e t h a t o f c a t a l y s t #6. S i n c e the h e i g h t o f the column r e q u i r e d f o r a g i v e n s e p a r a t i o n i s i n v e r s e l y p r o p o r t i o n a l t o Kya, t h e s p e c t a c u l a r improvements i n c a t a l y s t a c t i v i t y r e p o r t e d here make a hydrogen-water exchange p r o c e s s f o r d e u t e r i u m e n r i c h ment l o o k v e r y p r o m i s i n g . 3

2

Process

3

F e a t u r e s o f Hydrogen-Water Exchange

P r o c e s s e s based on the hydrogen-water exchange r e a c t i o n p o t e n t i a l l y have many a t t r a c t i v e f e a t u r e s f o r t h e s e p a r a t i o n o f hydrogen i s o t o p e s r e l a t i v e t o the GS p r o c e s s .

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

7.

BUTLER ET AL.

Novel Catalysts

for Isotopic

Exchange

107

ADVANTAGES OF HYDROGEN-WATER PROCESSES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007

1. 2. 3. 4. 5. 6. 7. 8. 9.

HIGHER SEPARATION FACTOR HIGHER RECOVERY LOWER WATER AND GAS FLOWS SMALLER EXCHANGE COLUMNS SIMPLE CHEMISTRY NON-CORROSIVE SYSTEM NON-TOXIC LOW ENVIRONMENTAL IMPACT, POLLUTION-NIL USES ONLY ONE EXCHANGE REACTION

These g e n e r i c advantages a r e g e n e r a l l y a p p l i c a b l e t o any p r o c e s s based on the hydrogen-water exchange r e a c t i o n and a r e p a r t i c u l a r l y r e l e v a n t t o t h e Combined Electrolysis C a t a l y t i c Exchange (CECE) p r o c e s s . The CECE p r o c e s s which c o u p l e s a hydrogen-water c a t a l y t i c exchange column t o the hydrogen gas stream from an e l e c t r o l y s i s c e l l o f f e r s a v e r y e f f e c t i v e system f o r the enrichment o f deuterium. The p r o c e s s i s d i s c u s s e d i n more d e t a i l by Hammerli, e t a^L. (9) i n the next paper. S i n c e t h e s e p a r a t i o n f a c t o r , a , f o r the hydrogen-water exchange r e a c t i o n i s h i g h e r than t h a t f o r the GS system, a h i g h e r deuterium r e c o v e r y i s p o s s i b l e , 70% from n a t u r a l water compared t o 19% f o r the GS p r o c e s s . H i g h e r r e c o v e r y p e r m i t s lower water and gas flow r a t e s i n t h e p l a n t . The v e r y a c t i v e c a t a l y s t s t h a t have been d e v e l o p e d mean t h a t the exchange columns w i l l be q u i t e s m a l l . A l t h o u g h most o f t h e s e p a r a t o r y work i s a c c o m p l i s h e d i n these columns, t h e i r volume would o n l y be about 4% o r 1/25 o f t h e exchange volume i n c u r r e n t GS p l a n t s f o r t h e same p r o d u c t i o n o f heavy water. The c h e m i s t r y o f the hydrogen-water system i s s i m p l e and o p e r a t i n g c o n d i t i o n s o f the CECE p r o c e s s are n e a r ambient. The system i s n o n - c o r r o s i v e , an i m p o r t a n t f e a t u r e s i n c e many o f the shut-downs i n GS p l a n t s r e s u l t from c o r r o s i o n . The system i s nont o x i c and n o n - p o l l u t i n g and would have a v e r y low e n v i r o n m e n t a l impact. The CECE p r o c e s s y i e l d s two v a l u a b l e p r o d u c t s - heavy water and l a r g e q u a n t i t i e s o f hydrogen, a v e r y u s e f u l c h e m i c a l . Electrolytic oxygen may a l s o be c o n s i d e r e d as an a d d i t i o n a l product. F i n a l l y the p r o c e s s u t i l i z e s o n l y one exchange r e a c t i o n f o r t h e complete enrichment o f d e u t e r i u m from n a t u r a l water t o r e a c t o r grade heavy w a t e r , 99.8% D 0 . T h i s removes many o f the comp l e x i t i e s o f o t h e r heavy water p r o c e s s e s which r e q u i r e d i f f e r e n t processes a t various stages i n the enrichment. 2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

108

SEPARATION OF HYDROGEN ISOTOPES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007

The major d i s a d v a n t a g e s o f t h e p r o c e s s a r e t h a t i t r e q u i r e s a l a r g e amount o f e l e c t r i c a l power f o r t h e e l e c t r o l y s i s c e l l s and i t r e q u i r e s a s t a b l e p l a t i n u m c a t a l y s t which i s somewhat e x p e n s i v e . However a c t i v e c a t a l y s t s have been d e v e l o p e d w i t h low p l a t i n u m l o a d i n g s so t h a t the p l a t i n u m r e p r e s e n t s o n l y about 30% o f the c o s t o f t h e f i n i s h e d c a t a l y s t . Further, the amount o f c a t a l y s t r e q u i r e d i s s m a l l and i t has been e s t i m a t e d t h a t t h e c a t a l y s t c o s t w i l l be o n l y a v e r y s m a l l p e r c e n t a g e o f the t o t a l c a p i t a l c o s t o f a heavy water p l a n t . L i k e w i s e c a t a l y s t replacement i s n o t e x p e c t e d t o add s i g n i f i c a n t l y t o t h e o p e r a t i n g costs. Acknowledgements We thank J. den H a r t o g and F.W. Molson f o r t h e i r a s s i s t a n c e i n t h e development o f these w e t p r o o f e d catalysts. We e x p r e s s o u r thanks t o W.M. T h u r s t o n f o r the development o f an a u t o m a t i c mass s p e c t r o m e t e r system f o r o n - l i n e a n a l y s i s o f d e u t e r i u m i n hydrogen gas streams, a t n e a r n a t u r a l abundance. Only w i t h h i s equipment and a s s i s t a n c e i n the a n a l y s i s o f thousands o f gas samples has t h i s r e s e a r c h been feasible. Abstract Catalytic i s o t o p i c exchange between hydrogen and liquid water o f f e r s many i n h e r e n t p o t e n t i a l advantages f o r the s e p a r a t i o n o f hydrogen i s o t o p e s which i s o f g r e a t importance i n the Canadian n u c l e a r program. Active catalysts for isotopic exchange between hydrogen and water vapour have l o n g been a v a i l a b l e , but these c a t a l y s t s are essentially i n a c t i v e i n the presence o f liquid w a t e r . New, water r e p e l l e n t p l a t i n u m c a t a l y s t s have been p r e p a r e d b y : 1) t r e a t i n g supported c a t a l y s t s with silicone, 2) d e p o s i t i n g p l a t i n u m on i n h e r e n t l y hydrophobic polymeric s u p p o r t s , and 3) t r e a t i n g platinized carbon with T e f l o n and b o n d i n g to a carrier. The activity of these c a t a l y s t s f o r i s o t o p i c exchange between c o u n t e r - c u r r e n t streams o f liquid water and hydrogen s a t u r a t e d w i t h water vapour has been measured in a packed trickle bed integral reactor. The performance o f t h e s e h y d r o p h o b i c c a t a l y s t s i s compared w i t h non-wetproofed catalysts. The mechanism o f the overall exchange r e a c t i o n i s briefly discussed.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

7.

BUTLER ET AL.

Literature 1. 2. 3.

4.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch007

5. 6. 7.

8. 9.

Novel

Catalysts

for Isotopic

Exchange

109

Cited

R o l s t o n , J.H., den H a r t o g , J. and B u t l e r , J.P., J. Phys. Chem., (1976), 80, 1064. P o h l , H.Α., J. Chem. & E n g . D a t a , (1961), 6, (4), 515. Murphy, G.M., U r e y , H . C . and Kirshenbaum, I., Editors, " P r o d u c t i o n o f Heavy Water, N a t i o n a l Energy S e r i e s " , C h a p t e r 2, p . 16, M c G r a w - H i l l , New Y o r k , 1955. S t e v e n s , W . H . , Canadian P a t e n t No. 907,292, August 15, 1972. Rolston, J.H., den H a r t o g , J. and B u t l e r , J.P., U . S . P a t e n t No. 4 , 0 2 5 , 5 6 0 , May 24, 1977. T h u r s t o n , W . M . , Rev. Sci. I n s t r u m e n t s , (1970), 41, 963 and (1971), 42, 700. Butler, J.P., den H a r t o g , J., G o o d a l e , J.W. and Rolston, J.H., "Proceedings o f the S i x t h I n t e r n a t i o n a l Congress on Catalysis, London 1976", Vol. 2, p . 747, The C h e m i c a l S o c i e t y , London, 1977. T a y l o r , H.S., U . S . P a t e n t No. 2 , 6 9 0 , 3 8 0 , September 28, 1954. Hammerli, Μ . , S t e v e n s , W . H . , and Butler, J.P., P r o c e e d i n g s o f the Symposium on " S e p a r a t i o n o f Hydrogen I s o t o p e s " , M o n t r e a l 1977, p . 110 , American Chemical S o c i e t y , Washington, 1977.

RECEIVED October 10, 1977

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

8 Combined Electrolysis Catalytic Exchange (CECE) Process for Hydrogen Isotope Separation M. HAMMERLI, W. H . STEVENS, and J. P. BUTLER

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008

Atomic Energy of Canada Ltd., Chalk River Nuclear Laboratories, Chalk River, Ontario, Canada K0J 1J0

In t h e p r e c e d i n g p a p e r ( J ) a n o v e l p l a t i n u m - c a r b o n - T e f l o n c a t a l y s t for e f f i c i e n t s e p a r a t i o n o f the hydro gen i s o t o p e s i n t h e p r e s e n c e o f l i q u i d w a t e r has been discussed. T h i s p a p e r d e a l s w i t h the Combined E l e c t r o l y s i s C a t a l y t i c E x c h a n g e (CECE) p r o c e s s e s w h i c h use t h i s c a t a l y s t f o r s e p a r a t i n g t h e h y d r o g e n i s o t o p e s , n a m e l y t h e CECE-HWP ( - H e a v y W a t e r p r o c e s s ) and t h e CECE-TRP ( - T j i t i u m R e c o v e r y p r o c e s s ) . The i s o t o p i c s e p a r a t i o n p r i n c i p l e s i n h e r e n t i n the CECE p r o c e s s e s are: (a) the e q u i l i b r i u m i s o t o p e e f f e c t i n r e a c t i o n s o f the type : H D

and

gas

+

i t s isotopic

H

*

0

l i q u i d ^ % a s

+

H

D

0

l i q u i d

analogues, and

™

(b) the k i n e t i c isotope e f f e c t (2) i n h e r e n t i n t h e e l e c t r o l y t i c hydrogen e v o l u t i o n r e a c t i o n . There are thus two r e l a t i v e l y large isotopic separation factors i n v o l v e d i n t h e s e p r o c e s s e s w h i c h , as we m i g h t e x p e c t , l e a d t o many o f t h e i r a d v a n t a g e s , d i s c u s s e d later. Both s e p a r a t i o n f a c t o r s favour c o n c e n t r a t i o n o f the heavier isotope i n the l i q u i d water r e l a t i v e to the hydrogen g a s . T h e CECE-HWP i s a n e w , y e t o l d p r o c e s s , f o r i t u t i l i z e s t h e same b a s i c p r i n c i p l e s as C a n a d a ' s first i n d u s t r i a l heavy w a t e r p l a n t o p e r a t e d by C o n s o l i d a t e d M i n i n g a n d S m e l t i n g Company f r o m 1 9 4 3 t o 1956 a t T r a i l , B.C. (J3 ) . The T r a i l p r o c e s s was a l s o a c o m b i n a t i o n o f e l e c t r o l y s i s and hydrogen-water exchange, but the e x c h a n g e r e a c t i o n h a d t o be c a r r i e d o u t i n t h e gas phase because l i q u i d water p o i s o n e d the c a t a l y s t . In the e x c h a n g e c o l u m n , d e u t e r i u m was t r a n s f e r r e d from hydrogen to water vapour i n a heated c a t a l y s t bed, and then a p a i r o f bubble cap t r a y s promoted d e u t e r i u m ©

0-8412-0420-9/78/47-068-110$05.00/0

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008

8.

HAMMERLI ET AL.

Combined

Electrolysis

Catalytic

Exchange

111

exchange between the w a t e r vapour and l i q u i d w a t e r . T h i s s e q u e n c e w a s r e p e a t e d many t i m e s t h r o u g h o u t t h e column. Heavy w a t e r p r o d u c e d by t h e T r a i l p r o c e s s was too c o s t l y because o f the s i z e and c o m p l e x i t y o f t h e exchange columns and t h e e x c e s s i v e energy r e q u i r e d f o r the steam preheaters t o r e p e a t e d l y v a p o u r i z e any l i q u i d w a t e r i n the gas s t r e a m . I t s h o u l d be n o t e d t h a t t h e c a t a l y s t beds o c c u p i e d o n l y 4 p e r c e n t o f t h e t o t a l volume o f the t o w e r s . If a catalyst c o u l d be d e v e l o p e d t h a t w o u l d remain a c t i v e i n the presence of l i q u i d w a t e r , the need f o r t h e c o m p l e x T r a i l - t y p e c o l u m n s c o u l d be e l i m i n a t e d , a n d p a c k e d l i q u i d - v a p o u r c o n t a c t o r s c o u l d be u s e d . Becker and c o - w o r k e r s (£) developed a s l u r r y c a t a l y s t cons i s t i n g o f p l a t i n u m on f i n e l y d i v i d e d c h a r c o a l f o r t h e hydrogen l i q u i d water exchange r e a c t i o n . The e x c h a n g e r a t e f o r t h e i r c a t a l y s t d e p e n d e d p r i m a r i l y on t h e d i s s o l v e d hydrogen c o n c e n t r a t i o n so t h a t t h e c a t a l y s t c o u l d o n l y be u s e d a t v e r y h i g h p r e s s u r e s , 20 M P a . Low c a t a l y s t a c t i v i t y , h i g h i n v e n t o r y o f p l a t i n u m and l o s s e s of the f i n e l y d i v i d e d c a t a l y s t are t h e main reasons the process proved uneconomic. With Stevens' i n v e n t i o n of the wetproofed catalyst (5>) , i t b e c a m e p o s s i b l e t o e f f e c t a v e r y efficient d e u t e r i u m exchange between hydrogen and l i q u i d w a t e r a t low p r e s s u r e s , t h i s c a t a l y s t allows the very close c o u p l i n g o f t h e two e x c h a n g e r e a c t i o n s . Preheaters and b u b b l e cap t r a y s become u n n e c e s s a r y and t h e e x c h a n g e c o l u m n c a n be o p e r a t e d a t l o w e r ( a m b i e n t ) temperatures where the s e p a r a t i o n f a c t o r i s l a r g e r ( 6 ) . Thus t h e v o l u m e o f t h e c o l u m n f o r t h e CECE-HWP i s r e d u c e d b y a f a c t o r o f a b o u t 20 r e l a t i v e to the T r a i l process. B e c a u s e t h e w e t p r o o f e d c a t a l y s t i n t h e CECE-HWP has d r a s t i c a l l y a l t e r e d t h e e x c h a n g e column o f t h e T r a i l - t y p e p r o c e s s , t h e d e s i g n a t i o n CECE w i l l only apply t o processes i n c o r p o r a t i n g t h i s type o f c a t a l y s t , e v e n t h o u g h t h e same b a s i c i s o t o p e s e p a r a t i o n p r i n c i p l e s a p p l y to b o t h . B e f o r e d i s c u s s i n g t h e CECE-HWP i n m o r e d e t a i l , i t is worth mentioning that this process involves three p r o d u c t s , H , D 0 and 0 , o f w h i c h t h e f i r s t two have considerable commercial value at present. The l a r g e amount o f e l e c t r i c a l e n e r g y r e q u i r e d t o p r o d u c e one k i l o g r a m o f r e a c t o r g r a d e h e a v y w a t e r can be o f f s e t s o m e w h a t b y t h e v a l u e o f t h e h y d r o g e n , e i t h e r as a c h e m i c a l o r as a f u e l (equivalent t o ^ 2 0 MWh/kg D 0 ) . N e v e r t h e l e s s , i t m u s t be u n d e r s t o o d a t t h e o u t s e t that t h e m a j o r d i s a d v a n t a g e o f t h e CECE-HWP i s i t s r e l a tively l a r g e s p e c i f i c e n e r g y r e q u i r e m e n t ( ^ 5 0 MWh/kg D 0), t h e energy b e i n g o f the h i g h e s t grade and c o s t . 2

2

2

2

2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

112

SEPARATION OF

H Y D R O G E N ISOTOPES

T h e CECE-HWP w i l l b e c o m e i n c r e a s i n g l y m o r e attractive f o r the l a r g e s c a l e p r o d u c t i o n of D 0 from n a t u r a l water, to the degree t h a t the c o s t of f o s s i l fuels escalates f a s t e r t h a n t h e c o s t o f CANDU* n u c l e a r p o w e r . 2

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008

The

CECE-HWP

B a s i c D e s c r i p t i o n of the P r o c e s s . I n t h e CECE-HWP (see F i g u r e 1) t h e e l e c t r o l y t i c h y d r o a e n , already depleted in deuterium r e l a t i v e to the e l e c t r o l y t e by v i r t u e o f the k i n e t i c i s o t o p e e f f e c t i n h e r e n t i n the hydrogen e v o l u t i o n r e a c t i o n , s t e a d i l y loses most of its r e m a i n i n g d e u t e r i u m as i t m o v e s up t h e c a t a l y s t column in c o u n t e r - c u r r e n t flow w i t h the feed water t r i c k l i n g down i n t o t h e e l e c t r o l y s i s c e l l . The w a t e r becomes e n r i c h e d i n d e u t e r i u m a c c o r d i n g t o r e a c t i o n 1 as it p a s s e s down t h e c a t a l y s t b e d . The o v e r a l l deuterium p r o f i l e i s one i n w h i c h t h e d e u t e r i u m c o n c e n t r a t i o n in the w a t e r i n c r e a s e s a l o n g t h e l e n g t h o f the column from top to b o t t o m , w h i l e i n the gas phase t h e deuterium concentration decreases from the bottom to top. The d e h u m i d i f i e r i s n e c e s s a r y i f t h e depleted h y d r o g e n g a s m u s t be d r y . This unit also transfers the d e u t e r i u m i n t h e w a t e r v a p o u r c a r r i e d by t h e hydroaen gas to the f e e d w a t e r . The s c r u b b e r b e t w e e n t h e c a t a l y s t c o l u m n and t h e e l e c t r o l y s i s c e l l serves the f o l l o w i n g f u n c t i o n s : (a) removes e n t r a i n e d e l e c t r o l y t e i n t h e hydrogen g a s , (b) a d j u s t s the h u m i d i t y of the h y d r o g e n gas to t h e c o n d i t i o n s p r e v a i l i n g i n t h e c o l u m n , w h i c h n e e d n o t be t h e same as t h o s e i n t h e cell, (c) t h e r m o s t a t s t h e h u m i d i f i e d gas t o t h e c o l u m n t e m perature, and (d) t r a n s f e r s deuterium from the w a t e r vapour e n t r a i n e d i n t h e h y d r o g e n gas to the l i q u i d water. The l a t t e r f u n c t i o n i s v e r y i m p o r t a n t s i n c e the deuterium c o n c e n t r a t i o n of the water vapour in the h y d r o g e n gas s t r e a m l e a v i n g t h e e l e c t r o l y s i s cell c o u l d e a s i l y be a b o u t 3 t o 10 t i m e s l a r g e r t h a n that in the w a t e r at the b o t t o m o f the e x c h a n q e c o l u m n . T h i s d i f f e r e n c e i s m a i n l y d e p e n d e n t on t h e m a g n i t u d e o f t h e e f f e c t i v e e l e c t r o l y t i c H/D s e p a r a t i o n f a c t o r , which i n t u r n d e p e n d s on t h e c a t h o d e m a t e r i a l a n d t h e o p e r a ting conditions of the e l e c t r o l y s i s cell. Any t y p e o f e l e c t r o l y s i s c e l l i n c o r p o r a t i n g a s e p a r a t o r between the anode and c a t h o d e compartments may b e u s e d i n t h e C E C E - H W P . If the c e l l contains a l i q u i d e l e c t r o l y t e , s u c h as 2 5 w e i g h t % s o l u t i o n o f K O H , t h e s a l t o f t h e e l e c t r o l y t e m u s t be r e m o v e d f r o m t h e w

*CANada

Deuterium

I U r a n i urn

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Combined

HAMMERLI ET AL.

Electrolysis

FEED WATER

Catalytic

Exchange

HYDROGEN GAS TO f s T Ô R AGF ÔVENÊRGY '

[l48 ppm]

DEHUMIDIFIER

CONVERTER ETC.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008

1 H /H 0 DEUTERIUM EXCHANGE CATALYST TOWER 2

OXYGEN GAS TO STORAGEJDR ENERGY CONVERTER ETC.

2

~! SCRUBBER

DRYER

H0 2

τ. ,H 2

1

ELECTROLYS IS CELLS ANODE COMPARTMENT , 1

CATHODE COMPARTMENT

SALT OF ELECTROLYTE

ELECTROLYTE SEPARATOR DEUTERIUM ENRICHED WATER TO HEAVY WATER PLANT Figure 1.

Combined Electrolysis Catalytic Exchange-Heavy "Process (CECE-HWP)

Water

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

114

SEPARATION O F HYDROGEN ISOTOPES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008

p r o d u c t s t r e a m b e f o r e i t c a n be f e d t o t h e n e x t h i g h e r stage. Electrolyte r e m o v a l may b e s t b e a c c o m p l i s h e d b y f l a s h e v a p o r a t i o n (_7) * w h i c h w o u l d a l s o remove s i m u l t a n e o u s l y the excess heat generated in the c e l l . It i s i m p o r t a n t t o dry the c o - l i b e r a t e d oxygen b e c a u s e t h e f i r s t s t a g e p r o d u c t c o u l d e a s i l y be a b o u t 20 t i m e s r i c h e r i n d e u t e r i u m t h a n t h e f e e d w a t e r a t the top o f the column ( 8j , so t h a t l o s s e s w o u l d o t h e r w i s e be i n t o l e r a b l e . Results from L a b o r a t o r y U n i t . The s m a l l labora t o r y u n i t used to demonstrate the p r i n c i p l e s of the CECE-HWP c o n s i s t s o f a c a t a l y s t c o l u m n , 36 cm l o n g a n d 2 . 5 4 cm i n d i a m e t e r , a n d a G . E . e l e c t r o l y s i s module containing 2-unit c e l l s . The a p p a r a t u s i s shown s c h e m a t i c a l l y in Figure 2. Because the G.E. e l e c t r o l y s i s module c o n t a i n s a s o l i d polymer electrolyte (SPE), the e l e c t r o l y t e s e p a r a t o r (see F i g u r e 1) i s n o t r e q u i r e d . The e l e c t r o l y s i s c e l l was o p e r a t e d a t a c u r r e n t o f 2 χ 2 0 = 40 A . With o p e r a t i n g c o n d i t i o n s such that the feed water r a t e i s a d j u s t e d t o e q u a l t h e e l e c t r o l y s i s r a t e and no p r o d u c t i s w i t h d r a w n ( t o t a l r e f l u x ) , one w o u l d e x p e c t to see a l i n e a r i n c r e a s e i n the deuterium concentration i n t h e c e l l - w a t e r c i r c u i t as a f u n c t i o n o f e l e c t r o l y s i s time p r o v i d i n g the f o l l o w i n g c o n d i t i o n s p e r t a i n : (a) t h e c e l l c u r r e n t remains constant, (b) t h e d e u t e r i u m c o n c e n t r a t i o n s i n both t h e feed w a t e r and t h e e f f l u e n t h y d r o g e n r e m a i n c o n s t a n t , and (c) t h e r e are no e x t r a n e o u s d e u t e r i u m l o s s e s i n t h e system. C o n d i t i o n (a) i s e a s i l y s a t i s f i e d w i t h a c o n s t a n t c u r r e n t power s u p p l y . The d e u t e r i u m c o n c e n t r a t i o n i n the f e e d w a t e r i s a l s o easy to keep c o n s t a n t , b u t t h a t i n t h e e f f l u e n t h y d r o g e n gas i s a f u n c t i o n o f the c o l u m n p a r a m e t e r s i n c l u d i n g c a t a l y s t a c t i v i t y , as w e l l as t h e d e u t e r i u m c o n c e n t r a t i o n i n t h e e l e c t r o l y t i c hydrogen. However, the c a t a l y s t bed parameters were c h o s e n so t h a t t h e column o p e r a t e d a t n e a r 100% e f f i c i e n c y f o r a p r o d u c t c o n c e n t r a t i o n up t o a b o u t 0 . 1 % . T h i s c a n be s e e n b y t h e a l m o s t h o r i z o n t a l l i n e f o r t h e d e u t e r i u m c o n c e n t r a t i o n i n t h e d e p l e t e d h y d r o q e n gas i n F i g u r e 3. The d e v i a t i o n o f t h e d e u t e r i u m b u i l d - u p i n the w a t e r from the t h e o r e t i c a l l i n e i s thus mainly a t t r i b u t a b l e to l o s s e s a s s o c i a t e d w i t h incomplete d r y i n g o f the oxygen g a s . These l o s s e s naturally b e c o m e l a r g e r as t h e d e u t e r i u m c o n c e n t r a t i o n increases in the c e l l water. The s l o p e o f t h e c a l c u l a t e d l i q u i d p h a s e l i n e i n F i g u r e 3 i s a f u n c t i o n o f t h e volume o f w a t e r i n the

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Laboratory CECE-HWP demonstration unit. The unit incorporates a General Electric solid polymer electrolyte electrolysis module.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008

SEPARATION O F HYDROGEN ISOTOPES

Figure 3. Deuterium concentration in the electrolysis cell water circuit as a function of electrolysis time. The feed water flow rate equals the electrolysis rate, and the product flow rate is zero. The dashed line is calculated assuming no deuterium loss from the system (see text).

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

8.

HAMMERLI ET AL.

Combined

Electrolysis

Catalytic

Exchange

117

c e l l - w a t e r c i r c u i t , the deuterium concentration i n the feed water, the operating temperature o f the column, and t h e r a t e o f e l e c t r o l y s i s . Thus i t h a s no f u n d a mental significance. It i s worth e m p h a s i z i n g that both t h e w a t e r and h y d r o g e n l i n e a r f l o w r a t e s a r e a b o u t two o r d e r s o f magnitude s m a l l e r than t h e optimum flow rates f o r t h e 2 . 5 4 cm d i a m e t e r c o l u m n , b e c a u s e o f t h e l o w c u r r e n t , 40 A , i n t h e e l e c t r o l y s i s c e l l . L i n e a r hydroaen flow r a t e s o f 1 to 2 m - s " at S . T . P . appear optimum f o r e f f i c i e n t u t i l i z a t i o n o f the novel c a t a l y s t Q ) for a column o p e r a t i n g at near a t m o s p h e r i c p r e s s u r e . This c o l u m n w o u l d r e q u i r e an e l e c t r o l y s i s c u r r e n t o f 4 , 3 6 5 A to 8,730 A t o produce t h e r e q u i r e d l i n e a r hydrogen flow rates. These f i g u r e s p o i n t to t h e f a c t t h a t t h e e l e c t r o l y s i s p l a n t w i l l be c o n s i d e r a b l y l a r g e r t h a n t h e c o r r e s p o n d i n g c a t a l y s t c o l u m n i n an o p t i m u m C E C E - H W P pi ant.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008

1

De u t e r i urn R e c o v e r y . In t h e CECE-HWP, t h e theoretical f r a c t i o n o f t h e d e u t e r i u m w h i c h c a n be r e c o v e r e d from t h e f e e d w a t e r i s g o v e r n e d s o l e l y by t h e v a l u e o f t h e e q u i l i b r i u m c o n s t a n t o f r e a c t i o n 1, and hence t h e t e m p e r a t u r e o f t h e top o f t h e c o l u m n . I t may be e x p r e s s e d i n t e r m s o f t h e s e p a r a t i o n f a c t o r f o r t h e column, aç, which i s i d e n t i c a l to the e q u i l i b r i u m cons t a n t , as f o l 1 o w s : Theoretical

Recovery

=

D

p

-

D /a p

c

(2)

w h e r e Dp i s t h e d e u t e r i u m c o n c e n t r a t i o n i n t h e f e e d wate r. In p r a c t i c e , i t i s p r u d e n t t o c h o o s e a d e u t e r i u m c o n c e n t r a t i o n i n the e f f l u e n t hydrogen gas which i s a b o u t 10% l a r g e r than t h e c a l c u l a t e d e q u i l i b r i u m v a l u e , Dp/aQ. Then c a t a l y s t r e q u i r e m e n t s , w h i c h w o u l d otherwise approach i n f i n i t y , are reasonable. The p r a c t i c a l range of deuterium recoveries f o r t h e CECE-HWP w i l l probably be i n t h e r a n g e 6 6 - 7 5 % c o r r e s p o n d i n g t o a t e m p e r a t u r e range o f about 60°C t o 15°C r e s p e c t i v e l y . This i s a h i g h r e c o v e r y f o r a d e u t e r i u m p r o d u c t i o n p r o c e s s (9). S y n e r q i s t i c Ε f fe c t s . Several synergistic effects r e s u l t from combining e l e c t r o l y s i s with H /H 0 deuterium exchange r e l a t i v e t o e i t h e r cascaded conventional e l e c t r o l y s i s alone or cascaded H /H 0 exchange alone. In t h e l a t t e r c a s e , a b i t h e r m a l e x c h a n g e p r o c e s s m u s t be u s e d , s i m i l a r i n p r i n c i p l e t o t h e p r e s e n t GirdlerS u l p h i d e ( G S ) p r o c e s s (9) b a s e d on t h e H S / H 0 e x c h a n g e 2

2

2

2

2

2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

118

SEPARATION O F

HYDROGEN ISOTOPES

re a c t i o n . The s y n e r g i s t i c e f f e c t s o f t h e CECE-HWP a r e s u m m a r i z e d i n T a b l e s I and II. I n T a b l e I, e l e c t r o l y s i s a l o n e , o p e r a t i n g a s an i d e a l c a s c a d e , i s c o m p a r e d to e l e c t r o l y s i s i n the CECE-HWP a s s u m i n g t h e e l e c t r o l y t i c H/D s e p a r a t i o n f a c t o r , CL£ is 6 for both. This value is certainly attainable in p r a c t i c e . For e x a m p l e , the electrolytic h e a v y w a t e r U p g r a d i n a P l a n t a t CRNL h a s o p e r a t e d for s e v e r a l y e a r s w i t h an e f f e c t i v e a p o f 8 t o 9 a t cell t e m p e r a t u r e s f r o m 35°C t o 25°C r e s p e c t i v e l y . However, these c e l l s incorporate mild steel cathodes and operate at lower temperatures than i s the current p r a c t i c e in commercial c e l l s . S i n c e the t r e n d is to w a r d s h i g h e r o p e r a t i n g t e m p e r a t u r e s and o t h e r cathode m a t e r i a l s * , i n c l u d i n g p r e c i o u s m e t a l s , an a£ o f s a y , 3, m i g h t be m o r e r e a l i s t i c i n t h e f u t u r e . A n y v a l u e o f ap less than 6 w o u l d , of c o u r s e , i n c r e a s e the differences in Table I. The f a c t o r s w h i c h l e a d t o a r e d u c t i o n i n catalyst r e q u i r e m e n t s f o r t h e CECE-HWP v e r s u s t h e b i t h e r m a l H / H 0-HWP are t a b u l a t e d i n T a b l e II. S i n c e the s p e c i f i c c a t a l y s t r e q u i r e m e n t (amount o f c a t a l y s t r e q u i r e d p e r unit of D 0 production per unit of time) is directly p r o p o r t i o n a l to t h e gas f l o w r a t e but t h e deuterium p r o d u c t i o n i s d i r e c t l y p r o p o r t i o n a l to the l i q u i d flow r a t e , i n c r e a s i n g t h e L/G r a t i o ( L a n d G a r e t h e m o l a r w a t e r and gas f l o w r a t e s r e s p e c t i v e l y ) decreases the catalyst requirement d i r e c t l y . D a t a i n T a b l e II serve to i l l u s t r a t e the e f f e c t s of the d i f f e r e n t parameters on t h e c a t a l y s t v o l u m e f o r a g i v e n D 0 p r o d u c t i o n rate and are n o t n e c e s s a r i l y optimum v a l u e s . For the b i t h e r m a l H /H 0-HWP, the d e u t e r i u m r e c o v e r y i s l i m i t e d by t h e d i f f e r e n c e i n t h e practical c o l d and hot column t e m p e r a t u r e a t t a i n a b l e , s i n c e it i s b a s e d on t h e t e m p e r a t u r e c o e f f i c i e n t o f α ς . For a g i v e n d e u t e r i u m c o n c e n t r a t i o n i n the f e e d , the specific v o l u m e o f w a t e r w h i c h m u s t be p r o c e s s e d p e r u n i t o f D 0 p r o d u c e d i s d i r e c t l y d e p e n d e n t on t h e recovery. The t h i r d p a r a m e t e r w h i c h i s c o m p a r e d i n T a b l e II i s the number of t r a n s f e r u n i t s ( N . T . U . ) r e q u i r e d f o r a deuterium c o n c e n t r a t i o n in the product of 0.1% [ 1 0 0 0 ppm D/(H + D ) ] w h e n a£ = 6 , a n d t h e f e e d w a t e r con t a i n s 1 4 8 ppm d e u t e r i u m , w h i c h c o i n c i d e s w i t h the Great Lakes w a t e r s ( 1 0 ) . The s p e c i f i c c a t a l y s t volume f o r a g i v e n c a t a l y s t i s d i r e c t l y d e p e n d e n t on t h e N.T.U.'s (£). It i s i m p o r t a n t to p o i n t out that only

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008

9

2

2

2

2

2

2

2

* I r o n o r m i l d s t e e 1 c a t h o d e s y i e l d t h e l a r g e s t aE values f o r a given set of operating conditions relat i ve t o o t h e r m e t a l s .

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

a

F

No.

of

Reflux,

F

Stages

n

Parameter

Cascade 1.7

^17

Ideal

Electrolysis

Compared

CECE-HWP

3

1.0

CECE-HWP

Cascade)

CECE-HWP

OF THE

I

Size of electrolysis plant not affected

the

(Ideal

in

EFFECTS

Size of electrolysis plant d i r e c t l y dependent on ac

Conventional

SYNERGISTIC

Table

in plant volume increases a s α^· d e c r e a s e s

complicated Catalyst somewhat

Less

costs

reduction

Remarks

Electrolysis

energy

^70%

to

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

for

the

cold

FACTOR

^1

=

6

MPa

7.4

^66

1

CECE-HWP

E

the

Bithermal

since = 265

the ppm

^24

^2

Λ

^15

deuterium instead of

1 .66

2

2.3

C a t a l y s t R e d u c t i on Factor

versus

CECE-HWP

CECE-HWP

THE

^ T h e N . T . U . ' s f o r t h e CECE-HWP a r e r e d u c e d by t h i s f a c t o r c o n c e n t r a t i o n i n t h e c o l u m n l i q u i d p r o d u c t n e e d s o n l y be 1 0 0 0 ppm i f a is 6 instead of unity.

on1y

REDUCTION

Calculated

TOTAL column

12.3*

^33

Nil

Separation

2

0.43

2

H /H 0-HWP

Electrolytic

ppm

OF

II

Requirements f o r the H2/H2O-HWP

Bithermal

Catalyst

7 MP a

1000

in

EFFECTS

Pressure

for

Recovery

N.T.U.

%

L/G

Ρ aramete r

Reduction

SYNERGISTIC

Table

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008

8.

HAMMERLI ET AL.

Combined

Electrolysis

Catalytic

Exchange

121

catalyst f o r t h e c o l d column i n the b i t h e r m a l process is considered here. A d d i t i o n a l c a t a l y s t would of c o u r s e be r e q u i r e d f o r t h e h o t c o l u m n i n t h e b i t h e r m a l p r o c e s s b u t n o t i n t h e CECE-HWP. On t h e o t h e r h a n d , e l e c t r o l y s i s c e l l s a r e r e q u i r e d i n t h e CECE-HWP. The b i t h e r m a l p r o c e s s must o p e r a t e a t h i g h p r e s s u r e s t o a v o i d an e x c e s s i v e l y l a r g e h o t c o l u m n a s a r e s u l t o f t h e vapour l o a d a t t h e hot column t e m p e r a ture (^200°C). On t h e o t h e r h a n d , t h e c a t a l y s t column i n t h e CECE-HWP c o u l d o p e r a t e a t a b o u t a t m o s p h e r i c p r e s s u r e , a l t h o u g h 1 t o 2 M P a may b e p r e f e r a b l e i n t h e 1st stage. S e v e r a l p r e s s u r e e f f e c t s combine t o produce t h e a p p r o x i m a t e f a c t o r shown i n T a b l e II. A s s u m i n g f o r t h e m o m e n t t h a t ot£ i s u n i t y , a v a l u e w h i c h w o u l d be a p p r o a c h e d i n a h i g h temperature (~1000°C) e l e c t r o l y s i s c e l l , t h e c a t a l y s t requirements f o r t h e C E C E - H W P w o u l d be a b o u t 1 5 t i m e s l e s s t h a n that f o r only t h e c o l d column of the b i t h e r m a l H /H 0-HWP. I f aE i s 6 , t h e o v e r a l l catalyst reduction factor is approximately 24. In the above a n a l y s i s , t h e 2nd and 3 r d s t a g e s have been i g n o r e d . This i s j u s t i f i a b l e s i n c e t h e s e s t a g e s w o u l d t o g e t h e r r e q u i r e o n l y 10% a d d i t i o n a l c a t a l y s t o r l e s s d e p e n d i n g on t h e d e u t e r i u m c o n c e n t r a t i o n o f t h e 1 s t s t a g e p r o d u c t (8;). 2

Applications

o f t h e CECE-HWP

2

and CECE-TRP

T h e d e v e l o p m e n t o f b o t h t h e CECE-HWP a n d t h e CECE-TRP i s b a s e d m a i n l y on a b o u t 7 y e a r s o f l a b o r a t o r y r e s e a r c h (]_). The r e s u l t s f r o m t h i s w o r k h a v e l e d t o commitments o f s m a l l p i l o t p l a n t s f o r both p r o c e s s e s . T h e CECE-HWP p i l o t p l a n t w i l l b e l o c a t e d a t C h a l k River Nuclear Laboratories (CRNL). The CECE-TRP p i l o t plant i s a c o o p e r a t i v e p r o j e c t b e t w e e n CRNL a n d t h e E n e r g y Research and D e v e l o p m e n t A d m i n i s t r a t i o n (ERDA) o f t h e U.S. G o v e r n m e n t , and i s l o c a t e d at t h e Mound L a b o r a t o r y , Miamisburg, Ohio. P r e l i m i n a r y r e s u l t s f r o m t h e Mound p i l o t p l a n t have been r e p o r t e d by Rogers e t a l . ( Π ) . D e s p i t e t h e s u c c e s s a c h i e v e d i n t h e c a t a l ys t H J e v e l o p m e n t p r o g r a m , we h a v e n o t y e t p r e p a r e d a p l a t i n u m carbon-TefIon catalyst (J_) w i t h s u f f i c i e n t a c t i v i t y t o make a f u l l s c a l e b i t h e r m a l H - H 0 h e a v y w a t e r p l a n t economically feasible. With our present catalysts the amount r e q u i r e d w o u l d be t o o l a r g e . Furthermore, a s a t i s f a c t o r y h y d r o p h o b i c c a t a l y s t f o r the h o t column has n o t been d e v e l o p e d . Our present c a t a l y s t s are s u f f i c i e n t l y a c t i v e , however, to perform e f f e c t i v e l y i n t h e CECE-HWP w h e r e t h e c a t a l y s t r e q u i r e m e n t s a r e r e l a t i v e l y s m a l l , o n l y a b o u t 4% o f t h a t r e q u i r e d i n t h e c o l d column o f a b i t h e r m a l p l a n t . Several small scale 2

2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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a p p l i c a t i o n s o f t h e CECE-HWP a n d t h e C E C E - T R P that c o u l d now b e u s e d i n t h e n u c l e a r p o w e r i n d u s t r y are outlined below. (1) U p g r a d i n g o f D 0 - T h e h e a v y w a t e r u s e d i n CANDU reactors as m o d e r a t o r a n d c o o l a n t t h a t h a s b e c o m e d o w n g r a d e d w i t h l i g h t w a t e r c a n be r e - e n r i c h e d t o reactor g r a d e , 9 9 . 8 % D 0 , by t h e C E C E - H W P . (2) F i n a l E n r i c h m e n t S t a g e f o r GS P l a n t s - T h e GS system produces 10-20% D 0 which i s c u r r e n t l y e n r i c h e d to r e a c t o r g r a d e by w a t e r d i s t i l l a t i o n . T h i s c o u l d be done more e f f e c t i v e l y by t h e CECE-HWP. (3) Recovery o f T r i t i u m f r o m t h e D 0 i n CANDU R e a c t o r s T r i t i u m b u i l d s up i n t h e h e a v y w a t e r d u r i n g t h e operat i o n o f CANDU r e a c t o r s . The r e c o v e r y of this tritium w o u l d r e d u c e t h e r a d i a t i o n f i e l d i n some a r e a s of the p o w e r s t a t i o n and i t s r e m o v a l may b e c o m e an e n v i r o n mental n e c e s s i t y . T r i t i u m may a l s o b e c o m e a s a l e a b l e commodity f o r the d e v e l o p m e n t o f e x p e r i m e n t a l nuclear fusion reactors. (4) T r i t i u m Recovery f r o m L i g h t W a t e r - T r i t i u m c a n be recovered from l i g h t water wastes f r o m ERDA contractors in the U.S.A. As a l r e a d y n o t e d , p i l o t s t u d i e s o f this a p p l i c a t i o n a r e b e i n g made a t t h e M o u n d L a b o r a t o r y (11). This a p p l i c a t i o n w i l l a l s o be r e q u i r e d i n n u c l e a r fuel reprocessing plants since t r i t i u m is a product of the fission process. The d i s a d v a n t a g e o f t h e h i g h e n e r g y requirement for t h e f u l l s c a l e p r o d u c t i o n o f h e a v y w a t e r by t h e CECEHWP d o e s n o t a p p l y t o t h e s e a p p l i c a t i o n s , p r i m a r i l y b e c a u s e o f t h e much s m a l l e r l i q u i d f l o w s . F o r t h e CECE-HWP a p p l i c a t i o n s 1 a n d 2 , t h e overall separation required is considerably less (enrichment f a c t o r of ^10) than t h a t r e q u i r e d to p r o d u c e pure D 0 from natural water (enrichment f a c t o r 'WOOO ) . Thus the e l e c t r o l y s i s energy r e q u i r e d i s r e d u c e d by a f a c t o r of a b o u t 7 0 0 f r o m 50 MWh t o 70 kWh p e r k i l o g r a m o f D 0. F o r the CECE-TRP a p p l i c a t i o n s 3 and 4, t h e water f l o w s w i l l be a t l e a s t a t h o u s a n d t i m e s s m a l l e r than f o r a f u l l s c a l e heavy w a t e r p l a n t . Furthermore, the energy requirements f o r the CECE-TRP are s m a l l e r than f o r other processes c u r r e n t l y being c o n s i d e r e d , such as w a t e r and h y d r o g e n d i s t i l l a t i o n , because the separation factors are larger. L a r g e r s c a l e a p p l i c a t i o n s o f t h e CECE-HWP, i f pilot plant studies warrant these, would i n c l u d e : (1) Small D 0 Plant - A s m a l l ('WO Mg/a) complete D 0 p l a n t w o u l d be e c o n o m i c a l l y f e a s i b l e w h e r e a m a r k e t e x i s t s f o r the e l e c t r o l y t i c h y d r o g e n and the heavy water. (2) S i m u l t a n e o u s D 0 and P e a k P o w e r P r o d u c t i o n - The CECE-HWP c o u l d be c o u p l e d w i t h e i t h e r H / 0 gas turbine2

2

2

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008

2

2

2

2

2

2

2

2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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Exchange

123

generators or fuel c e l l s through appropriate H and 0 s t o r a g e f a c i l i t i e s to produce D 0 ( d u r i n g the off-peak periods) and peak p o w e r . This load l e v e l l i n g scheme (8.) i s b e i n g c o n s i d e r e d b y O n t a r i o H y d r o , Canada's l a r g e s t e l e c t r i c u t i l i t y , as o n e a l t e r n a t i v e for their future load-level l i n g requi rements. (3) E l e c t r o l y t i c H as N a t u r a l G a s S u p p l e m e n t or C h e m i c a l - I t m i g h t be f e a s i b l e t o u s e e x c e s s hydro e l e c t r i c power, w h e r e v e r i t e x i s t s , to produce hydrogen and D 0 u s i n g t h e CECE-HWP. T h e h y d r o g e n c o u l d be u s e d as a n a t u r a l gas s u p p l e m e n t i n a p i p e l i n e and a f e a s i b i l i t y s t u d y o f a 1 0 0 MW p r o t o t y p e p l a n t i s underway. A l t e r n a t i v e l y t h e h y d r o g e n c o u l d b e u s e d as a c h e m i c a l , e . g . hydrogénation o f bitumen or chemical intermediate, e . g . m e t h a n o l p r o d u c t i o n w h i c h c o u l d s e r v e as a g a s o line supplement. 2

2

2

2

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008

2

A l l of the above p o t e n t i a l a p p l i c a t i o n s must a w a i t p i l o t p l a n t s t u d i e s b e f o r e p l a n t s c a n be c o m m i t t e d . Furthermore, the r e l a t i v e economics of electrolytic hydrogen versus hydrogen produced from f o s s i l fuels w i l l p l a y a m a j o r r o l e i n any d e c i s i o n t o p r o c e e d in each of these a p p l i c a t i o n s . The c u r r e n t v a l u e o f the D 0 by-product w i l l a l s o be i m p o r t a n t a n d t o a l e s s e r e x t e n t , the v a l u e and m a r k e t a b i l i t y o f the co-liberated oxygen. I t n e e d h a r d l y be s a i d t h a t s u c c e s s f u l development of e f f i c i e n t , r e l a t i v e l y low c o s t electrol y z e r s i s a l s o a key r e q u i r e m e n t f o r these larger applications. Moreover, c u r r e n t emphasis to conserve a l l our non-renewable resources w i l l increase the s t i m u l u s t o d e v e l o p t h e CECE p r o c e s s o v e r t h e next decade or s o . When f o s s i l r e s o u r c e s become s u f f i c i e n t l y s c a r c e , a n d / o r e x p e n s i v e , t h e move t o w a r d s a hybrid h y d r o g e n - e l e c t r i c e c o n o m y w i l l be a c c e l e r a t e d and c o n s e q u e n t l y l a r g e r amounts o f b y - p r o d u c t heavy w a t e r c o u l d be p r o d u c e d b y t h e C E C E - H W P . 2

Summary The CECE p r o c e s s i s a v e r y e f f i c i e n t m e t h o d f o r the s e p a r a t i o n of hydrogen i s o t o p e s . The catalytic exchange columns where most o f the s e p a r a t o r y work is a c c o m p l i s h e d w o u l d be v e r y s m a l l c o m p a r e d t o t h e e x change column used i n e i t h e r a b i t h e r m a l H / H 0 p r o c e s s o r t h e p r e s e n t b i t h e r m a l H S / H 0 (GS) process. Laborat o r y s t u d i e s have d e m o n s t r a t e d the s a l i e n t f e a t u r e s of t h e CECE p r o c e s s a n d i f p i l o t p l a n t s t u d i e s a t CRNL and Mound L a b o r a t o r y are s u c c e s s f u l , the process w i l l und o u b t e d l y be u s e d i n t h e n u c l e a r p o w e r i n d u s t r y i n a number of the s m a l l s c a l e a p p l i c a t i o n s d i s c u s s e d i n this paper. As l a r g e h y d r o g e n g a s s t r e a m s become 2

2

2

2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

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ISOTOPES

a v a i l a b l e t h e p r o c e s s c o u l d a l s o be u s e d f o r t h e f u l l s c a l e p r o d u c t i o n o f l a r g e q u a n t i t i e s , 70-100 M g / a , o f heavy w a t e r . Acknowledgements

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch008

We t h a n k A . S . D e n o v a n f o r t e c h n i c a l a s s i s t a n c e i n operatinq the laboratory demonstration unit of the CECE p r o c e s s a n d f o r p e r f o r m i n g t h e d e u t e r i u m a n a l y s e s i n gas and w a t e r s a m p l e s . We a l s o t h a n k W.M. T h u r s t o n and M.W.D. James f o r c o n s t r u c t i n g and m a i n t a i n i n g t h e mass- and i n f r a r e d - s p e c t r o m e t e r s y s t e m s used f o r the d e u t e r i urn an a l y s e s .

Abstract Hydrogen i s o t o p e s can be s e p a r a t e d efficiently by a process which combines an electrolysis c e l l with a trickle bed column packed with a hydrophobic p l a t i n u m catalyst. The column e f f e c t s i s o t o p i c exchange between c o u n t e r - c u r r e n t streams o f electrolytic hydrogen and liquid water w h i l e the electrolysis c e l l contributes to i s o t o p e s e p a r a t i o n by v i r t u e of the k i n e t i c i s o t o p e e f f e c t i n h e r e n t i n the hydrogen e v o l u t i o n r e a c t i o n . The main f e a t u r e s of the CECE process f o r heavy water p r o d u c t i o n are p r e s e n t e d as w e l l as a d i s c u s s i o n of the i n h e r e n t p o s i t i v e s y n e r g i s t i c effects, and o t h e r advantages and disadvantages of the p r o c e s s . S e v e r a l p o t e n t i a l a p p l i c a t i o n s o f the process in the n u c l e a r power i n d u s t r y are d i s c u s s e d . Literature 1.

2. 3. 4.

5.

Cited

B u t l e r , J.P., R o l s t o n , J.H. and S t e v e n s , W.H., Proceedings of the Symposium on " S e p a r a t i o n of Hydrogen I s o t o p e s " , Montreal 1977, p. 93 , American Chemical S o c i e t y , Washington, 1977. Hammerli, M., M i s l a n , J.P. and Olmstead, W.J., J. E l e c t r o c h e m . Soc., ( 1 9 7 0 ) , 117, 751 (and references t h e r e i n ) . B a r l o w , E . A , Atomic Energy of Canada r e p o r t no. CRE-374, March 8, 1948; D e c l a s s i f i e d and r e i s s u e d as r e p o r t no. A E C L - 1 6 3 , February 22, 1955. B e c k e r , H . W . , Bier, K . , Hubener, R . P . and K e s s e l e r , R.W., " P r o c e e d i n g s of 2nd I n t e r n a t i o n a l Conference on P e a c e f u l Uses of Atomic E n e r g y " , ( 1 9 5 9 ) , 4, 543, U n i t e d N a t i o n s . S t e v e n s , W.H., U . S . Patent no. 3 , 8 8 8 , 9 7 4 , June 10, 1975.

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8.

6. 7. 8. 9. 10.

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125

Rolston, J.H., den H a r t o g , J. and B u t l e r , J.P., J. Phys. Chem., (1976), 80, 1064. Winter, E.E., p r i v a t e communications. Hammerli, Μ., S t e v e n s , W.H., B r a d l e y , W.J. and Butler, J.P., Atomic Energy of Canada r e p o r t no. AECL-5512, A p r i l 1976. Rae, H . K . , Proceedings of the Symposium on " S e p a r a t i o n o f Hydrogen I s o t o p e s " , Montreal 1977, p. 1 , American Chemical S o c i e t y , Washington, 1977. Brown, R . M . , R o b e r t s o n , E . and T h u r s t o n , W.M., Atomic Energy of Canada L t d . r e p o r t no. AECL-3800, January 1971. Rogers, M.L., Lamberger, P.H., Ellis, R . E . and Mills, T.K., Proceedings of the Symposium on " S e p a r a t i o n of Hydrogen I s o t o p e s " , Montreal 1977, p. 171, American Chemical S o c i e t y , Washington, 1977.

RECEIVED October 18, 1977

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

9 Heavy Water Distillation G. M. KEYSER, D. B. McCONNELL, N. ANYAS-WEISS, and P. KIRKBY

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch009

Ontario Hydro Research Div., 800 Kipling Ave., Toronto, Canada

The m o t i v a t i o n f o r t h e c u r r e n t heavy water r e s e a r c h program a t O n t a r i o Hydro comes from o u r growing dependence on CANDU-based n u c l e a r power p l a n t s . About 15% o f t h e c a p i t a l c o s t o f t h e s e p l a n t s i s f o r t h e heavy water moderator and c o o l a n t . We hope t o be a b l e to p r o v i d e e c o n o m i c a l l y and t e c h n i c a l l y v i a b l e o p t i o n s f o r heavy water p r o d u c t i o n i n t h e 1990 s by d e v e l o p i n g a l t e r n a t i v e p r o d u c t i o n methods t o an i n d u s t r i a l l y usef u l degree by t h a t t i m e . The Heavy Water Group a t Hydro Research D i v i s i o n has a s s i s t e d i n e s t a b l i s h i n g t h e s c i e n t i f i c feasibili t y o f two heavy water p r o d u c t i o n methods : l a s e r i n d u c e d d i s s o c i a t i o n o f formaldehyde, and low-temperat u r e water d i s t i l l a t i o n u s i n g waste h e a t and hopes t o c o n t i n u e development o f b o t h t h e s e methods. In t h i s t a l k , I w i l l d e s c r i b e t h e experiments c a r r i e d o u t t o demonstrate t h e f e a s i b i l i t y o f lowtemperature d i s t i l l a t i o n w i t h a p a r a l l e l - s h e e t p a c k i n g d e v e l o p e d a t t h e Research D i v i s i o n . The c o s t e n v i r o n ment o f heavy water d i s t i l l a t i o n w i l l a l s o be d i s cussed. 1

Distillation

Systems

- Physical

To r e f r e s h your memory, I w i l l show i n F i g u r e 1 (a) a s c h e m a t i c r e p r e s e n t a t i o n o f a d i s t i l l a t i o n system. The main f e a t u r e s o f t h e system a r e upward moving v a pour streams and f a l l i n g l i q u i d f i l m s i n c l o s e p r o x i m i t y , m a i n t a i n e d by a temperature g r a d i e n t between t h e h e a t s o u r c e ( b o i l e r ) a t t h e bottom and t h e heat s i n k (condenser) a t t h e t o p o f t h e system. A c o n v e n i e n t way o f b r i n g i n g t h e c o u n t e r - f l o w i n g phases c l o s e t o each o t h e r i s t o p r o v i d e v e r t i c a l s h e e t s o f m a t e r i a l o v e r which t h e l i q u i d f l o w s as a t h i n f i l m , w h i l e t h e vapour r i s e s i n narrow c h a n n e l s between t h e s h e e t s , as ©

0-8412-0420-9/78/47-068-126$05.00/0

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

9.

KEYSER ET AL.

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Water

127

Distillation

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch009

shown i n F i g u r e 1 ( b ) . What makes a heavy water system " d i f f e r e n t " i s t h a t the component t o be s e p a r a t e d o u t , HDO, i s p r e s e n t i n v e r y low c o n c e n t r a t i o n , about one p a r t i n 3500, i n n a t u r a l water f e d t o the system, so t h a t enormous v o l umes o f vapour must be p a s s e d t h r o u g h the s e p a r a t i n g system t o e x t r a c t s u f f i c i e n t HDO. C o s t Components. From our e s t i m a t e (and those o f many p r i o r workers) o f the c o s t o f heavy water from a d i s t i l l a t i o n p l a n t , i f we were t o pay f o r f o s s i l f u e l s , or i f we used the heat from a n u c l e a r r e a c t o r which would o t h e r w i s e be g e n e r a t i n g e l e c t r i c i t y , the c o s t o f t h i s energy would i t s e l f amount t o w e l l o v e r the c u r r e n t c o s t o f heavy water. S i n c e t h e r m a l g e n e r a t i n g s t a t i o n s are o n l y about 40% e f f i c i e n t i n c o n v e r t i n g the t h e r m a l energy r e l e a s e d from f u e l i n t o e l e c t r i c i t y , ~ 6 0 % o f i t i s a v a i l a b l e as low grade heat (water a t about 26°C) c o s t i n g o n l y the p r i c e o f t r a n s p o r t i n g i t t o the p o i n t o f use. Our o b j e c t i v e , t h e n , has been t o u t i l i z e t h i s waste h e a t , by o p e r a t i n g between about 26°C and the l a k e water temperature which i s t y p i c a l l y 20° lower. I f we can u t i l i z e waste h e a t , then the r e m a i n i n g h i g h c o s t components a r e the m a t e r i a l , o r p a c k i n g , used t o b r i n g the l i q u i d and vapour i n t o c l o s e p r o x i m i t y , the s t r u c t u r e s (vacuum b u i l d i n g s ) used t o house the packi n g , and the h e a t exchangers and b o i l e r s f o r m a i n t a i n i n g the f l o w o f h e a t t h r o u g h the system. The r e l a t i v e magnitudes o f t h e s e components, based on D 0 a t $200/kg i s shown i n F i g u r e 2. The g r e a t e s t c o s t component, by f a r , i s the p a c k i n g f o r the columns. 2

400 Ton P l a n t C o n c e p t i o n F i g u r e 3 shows our p r e s e n t c o n c e p t i o n o f a lowtemperature d i s t i l l a t i o n p l a n t c a p a b l e o f p r o d u c i n g 400 tons o f heavy water per y e a r . I t i s d i v i d e d i n t o s e v e r a l hundred u n i t s housed i n s e p a r a t e towers, each o p e r a t i n g i n d e p e n d e n t l y to d i s t i l l the heavy water out o f c l e a n l a k e water and b r i n g i t t o a c o n c e n t r a t i o n o f about 1%. The subsequent c o n c e n t r a t i o n s t e p t o 99.8% f o r r e a c t o r use c o s t s o n l y 15% t o 20% t h a t o f p e r f o r m i n g the f i r s t s t e p , and i s c a r r i e d o u t i n a s e p a r a t e d i s t i l l a t i o n "finishing" unit. Experimental Packing The major gap i n the p l a n t c o n c e p t was the p a c k i n g . Heavy Water d i s t i l l a t i o n p a c k i n g s f o r the low-tempera-

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

SEPARATION OF HYDROGEN ISOTOPES H E A T SINK AT T E M P E R A T U R E T

2

DIFFUSIVE DEUTERIUM TRANSPORT FROM VAPOR T O LIQUID

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch009

FALLING LIQUID

RISING VAPOUR

HEAT SOURCE A T T E M P E R A T U R E T,

(a)

(b)

Figure 1.

Elements of a distilhtion system

COMPONENT WASTE

RELATIVE COST $ / k g D2O 6.5

HEAT

COOLING

20

V A C U U M BUILDINGS AND PLUMBING

5.5

CONDENSERS AND BOILERS

14

PACKING AND SUPPORTING STRUCTURES OPERATION AND MISCELLANEOUS*

96

58 200

•WATER CLEANUP, COMMISSIONING

Figure 2.

INSTRUMENTATION,

CONSTRUCTION LABOR,

Rehtive component costs in heavy water distilhtion

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

9.

KEYSER ET AL.

Heavy

Water

129

Distillation

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch009

GENERATING STATION (3000 MW)

COOLING W A T E R FROM L A K E 35 - 5 0 ° F 150 ppm 0O 125 rn /s

REJECT HEAT TO LAKE * ~ 55 - 7 0 ° F 149 ppm

X

9

3

60°F

90°F

HEATING OUT

COOLING

HEATING IN

IN

COOLING

OUT

DISTILLATION PLANT

S E V E R A L HUNDRED TOWERS W O R K I N G V O L U M E - 3 0 000 m F O R 400 T O N N E S / Y E A R 3

\\%

D 0 2

τ

FINISHER

Τ PRODUCT (45 Kg/h ) REACTOR GRADE

Figure 3.

0 0 £

Concept for a heavy water distillation plant using waste heat from a generating station. 400 tonne/year D 0 plant. 2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

SEPARATION OF HYDROGEN ISOTOPES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch009

130

t u r e and p r e s s u r e regime had not been developed com mercially. A t h e o r y o f the p r o c e s s p r e d i c t e d t h a t a u s e f u l degree o f s e p a r a t i v e power c o u l d be a c h i e v e d u s i n g simple p a r a l l e l s h e e t s c a r r y i n g downward-moving water f i l m s , w i t h upward-moving vapour between them. The p a c k i n g developed a t the Research D i v i s i o n i s based on t h i s concept, and i s shown s c h e m a t i c a l l y i n F i g u r e 4. A s e r i e s of tubes c a r r i e s condensed water t o the tops of the s h e e t s t o f l o w downward over t h e i r s u r f a c e s , w h i l e vapour moves up between them. The s h e e t s used t o date have been n y l o n f a b r i c under t e n s i o n , w i t h a s u r f a c e treatment t o improve the u n i f o r m i t y o f the water f i l m . The performance of t h i s module i s expected t o depend on the two mass and d e u t e r i u m f l o w parameters, the v e l o c i t y , and the d i f f u s i o n time i n each phase. P a c k i n g Performance -

Experimental

The b a s i c mechanism which causes i s o t o p i c s e p a r a t i o n i n d i s t i l l a t i o n systems i s the d i f f e r e n c e i n v a pour p r e s s u r e of H 0 and HDO, a t the same temperature. In d i s t i l l a t i o n , the r a t i o o f the e q u i l i b r i u m vapour p r e s s u r e s of H 0 and HDO i s c a l l e d a, as shown i n F i g u r e 5. 2

2

P

a(T) =

H- 0 , HDO 1

t y p i c a l l y , α i s around 1.08 i n t h i s temperature r e g i o n , r i s i n g a t lower temperatures towards 1.10.

We can gauge the performance by measuring the i s o t o p i c enrichment o f the water f l o w i n g out the bottom Bottonw the d e p l e t i o n o f the vapour l e a v i n g at. the top Or/op' t a k i n g the n a t u r a l l o g a r i t h m o f t h e i r r a t i o and d i v i d i n g by the n a t u r a l l o g a r i t h m of the average α v a l u e f o r the system; t h i s i s a measure of the num ber o f s t a g e s , each c a r r y i n g out a s e p a r a t i o n o f a, i n the column. The number o f such s t a g e s per metre of column h e i g h t i s a performance parameter f o r the pack ing : ~ In In [I ^Bottomjl / H l n a , where Η i s Ν (number of stages/m) « c

C

\ T"Top o p // the column h e i g h t . C u r r e n t e x p e r i m e n t a l v a l u e s o f Ν run from 2.5 t o over 3 s t a g e s per metre. U s i n g t h i s parameter, and the c o r r e s p o n d i n g mass flow r a t e , we can e s t i m a t e the t o t a l s u r f a c e a r e a o f the s h e e t s r e q u i r e d t o produce 400 tons of D 0 per year. The f i g u r e a l s o shows the " e a r n i n g power" o f our e x p e r i m e n t a l p a c k i n g and the t h e o r e t i c a l l i m i t t o i t as a f u n c t i o n o f the F-number ( r e l a t e d t o the mass 2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Heavy

Water

Distillation

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch009

KEYSER ET AL.

Figure 4.

Parallel plate packing module (without glass envelope)

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

132

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch009

SEPARATION O F HYDROGEN ISOTOPES

Figure 5.

Earning power of two experimental packings

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

9.

KEYSER ET AL.

Heavy

Water

Distillation

133

flow) i n t h e system. Each square metre o f p a c k i n g can be c o n s i d e r e d t o produce about 0 . 2 k i l o g r a m s ( - 4 0 d o l l a r s worth) o f D 0 p e r y e a r . The upper c u r v e i s t h e p r e d i c t e d maximum e a r n i n g power f o r t h i s type o f packi n g system. As you can see, o u r r e s u l t s w h i l e showing t h a t t h e system works, c a n s t i l l be c o n s i d e r a b l y improved. The t r i a n g l e s show more r e c e n t work w i t h a d i f f e r e n t m a t e r i a l ; as o u r u n d e r s t a n d i n g o f t h e d e s i r a b l e and u n d e s i r a b l e f e a t u r e s o f t h e s e m a t e r i a l s grows, we b e l i e v e we c a n come s t i l l c l o s e r t o t h e t h e o r e t i cal limit. T h i s would b r i n g our heavy water c o s t e s t i m a t e down towards $2 0 0 / k g . F u r t h e r work on a l a r g e r s c a l e would a l s o be r e q u i r e d t o study how w e l l t h e p a c k i n g u n i t c a n be s c a l e d up t o an i n d u s t r i a l l y useful size.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch009

2

Summary I c a n summarize what we have l e a r n e d as f o l l o w s : r e c e n t work a t t h e R e s e a r c h D i v i s i o n has demonstrated the f e a s i b i l i t y o f p e r f o r m i n g heavy water s e p a r a t i o n by d i s t i l l a t i o n a t low t e m p e r a t u r e , u s i n g a newly dev e l o p e d p a c k i n g system. We b e l i e v e t h a t t h e c u r r e n t performance can be c o n s i d e r a b l y improved, and t h a t t h e c o s t o f heavy water from d i s t i l l a t i o n can be made comp a r a b l e t o t h a t from t h e c u r r e n t p r o d u c t i o n method. T e s t s on a l a r g e r s c a l e w i l l be r e q u i r e d t o demons t r a t e t h a t t h i s performance can be s u c c e s s f u l l y s c a l e d up t o an i n d u s t r i a l l y u s e f u l d e g r e e . Abstract A review of distillation as a heavy water separation method has identified a r e a s o f h i g h c o s t : energy and p a c k i n g material. A t t e m p e r a t u r e s around 2 5 ° C , l a r g e amounts o f energy are a v a i l a b l e as waste heat from t h e r m a l g e n e r a t i n g s t a t i o n s . I f a s u i t a b l e low- c o s t p a c k i n g can be d e v e l o p e d f o r use i n this temperature r e g i o n , distillation c o u l d become e c o n o m i c a l l y competitive. Results of theoretical p a c k i n g work, and e x p e r i ments on a p r o t o t y p e p a c k i n g f o r heavy water p l a n t s are d i s c u s s e d . RECEIVED August 30, 1977

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

10 Deuterium Isotope Separation via Vibrationally Enhanced Deuterium Halide—Olefin Addition Reactions J. B . M A R L I N G and J. R. S I M P S O N University of California, Lawrence Livermore Laboratory, Livermore, C A

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

M. M . M I L L E R Francis Bitter National Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, M A

Over t h e past few y e a r s , t h e r e has been much excitement i n the s c i e n t i f i c community about the prospects f o r e f f i c i e n t sep a r a t i o n o f i s o t o p e s , p a r t i c u l a r l y uranium-235 and deuterium, using l a s e r techniques. Of t h e v a r i o u s l a s e r methods which have been suggested, those which i n v o l v e t h e use o f IR photons t o enhance t h e r a t e o f i s o t o p i c a l l y s e l e c t i v e photochemical r e a c t i o n s have r e c e i v e d much a t t e n t i o n , and t h i s paper d i s c u s s e s one e x a m p l e — v i b r a t i o n a l l y enhanced gas phase deuterium h a l i d e a d d i t i o n i n t o o l e f i n s . The i n c e n t i v e f o r u s i n g IR photons i s c l e a r ; t o quote from a recent review a r t i c l e (l_) : "The a t t r a c t i v e f e a t u r e o f v i b r a t i o n a l photochemistry f o r i s o t o p e s e p a r a t i o n i s the promise o f u s i n g low energy IR photons from an e f f i c i e n t molecular l a s e r t o get a good y i e l d o f product. Since 1 mole of photons at 3000 cm" i s 1 0 kwh and some IR l a s e r s are about 10 per cent e f f i c i e n t , p r o c e s s i n g o f b u l k chemicals might even be economic." Thus, a deuterium s e p a r a t i o n process w i t h 1% quantum e f f i c i e n c y t h a t u t i l i z e d 2000 cm" photons from a 10 per cent e f f i c i e n t CO l a s e r would r e q u i r e a l a s e r process energy o f 6 . 6 kwh/mole D, e q u i v a l e n t t o a l a s e r o p e r a t i n g cost o f 13^/mole D Ξ $13/kg D 0, assuming e l e c t r i c i t y at 20 m i l l s per kwh. The s p e c i f i c l a s e r c a p i t a l investment, assuming a p r i c e o f $20 per o p t i c a l watt o f 10 per cent e f f i c i e n t l a s e r power, would be roughly $152/kg D 0/yr., e q u i v a l e n t t o approximately $30/kg D 0 at a c a p i t a l charge r a t e o f 20 per cent/year. To put these numbers i n p e r s p e c t i v e , we note t h a t t h e current Canadian p r i c e f o r heavy water made by the H S/H 0 exchange (G-S) process i s about $150/kilogram, o f which 60 per cent i s due t o c a p i t a l charges, 25 per cent due t o energy, and 15 per cent f o r operations and maintenance (2). Since heavy water i s a much cheaper commod i t y than U-235, t h i s approximate c a l c u l a t i o n i l l u s t r a t e s t h e challenge i n developing a l a s e r deuterium s e p a r a t i o n process which i s economically c o m p e t i t i v e w i t h the e x i s t i n g technology ( 3_). In t h i s paper we i l l u s t r a t e t h e problems and prospects i n v o l v e d by examining i n some d e t a i l a s p e c i f i c deuterium separation process based on deuterium h a l i d e - o l e f i n a d d i t i o n 1

- 2

1

2

2

2

2

©

2

0-8412-0420-9/78/47-068-134$05.00/0

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

10.

MARLING ET AL.

Deuterium

Isotope

Separation

135

r e a c t i o n s . I n S e c t i o n I I we describe t h e b a s i c r e a c t i o n mechan ism, w i t h p a r t i c u l a r a t t e n t i o n t o the problem o f e x c i t i n g t h e deuterium h a l i d e w i t h e x i s t i n g l a s e r s . S e c t i o n I I I i s devoted t o t h e c r u c i a l question o f the expected e f f e c t i v e n e s s o f v i b r a t i o n a l e x c i t a t i o n f o r t h i s c l a s s o f r e a c t i o n s . I n S e c t i o n IV, we focus on t h e "back-end" o f t h i s separation scheme i n the context of a p o s s i b l e flow-sheet f o r t h e o v e r a l l process. We conclude w i t h a summary o f our r e s u l t s and the i m p l i c a t i o n s t h e r e o f i n S e c t i o n V.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

II.

Hydrogen H a l i d e - O l e f i n A d d i t i o n Reactions

An i d e a l i s o t o p i c a l l y s e l e c t i v e l a s e r photochemical process would use a s i n g l e IR photon t o e x c i t e t h e fundamental mode o f the i s o t o p i c molecule o f i n t e r e s t , f o l l o w e d by a gas phase, v i b r a t i o n a l l y - e n h a n c e d b i m o l e c u l a r r e a c t i o n , l e a d i n g t o an i s o t o p i c a l l y enriched r e a c t i o n product which could e a s i l y be separated. A primary c o n s i d e r a t i o n i n t h e choice o f r e a c t i o n i s the a c t i v a t i o n energy. I t must be high enough t o minimize t h e (thermal) r e a c t i o n r a t e i n t h e absence o f v i b r a t i o n a l e x c i t a t i o n , but low enough so that t h e r e a c t i o n r a t e o f the v i b r a t i o n a l l y e x c i t e d species exceeds t h e r a t e o f scrambling r e a c t i o n s , e.g., V-V and V-T energy t r a n s f e r s , which l e a d t o the l o s s o f i s o t o p i c s e l e c t i v i t y . I n t h i s s e c t i o n we d i s c u s s a c l a s s o f r e a c t i o n s , deuterium h a l i d e - o l e f i n a d d i t i o n s , w i t h thermal e q u i l i b r i u m a c t i v a t i o n energies i n the range 15-^0 kcal/mole. The i n i t i a l step o f t h i s process i n v o l v e s s e q u e n t i a l absorp t i o n o f s e v e r a l quanta near 5 microns from a pulsed CO l a s e r t o e x c i t e DBr o r DC1 up t h e i r v i b r a t i o n a l ladders t o t h e ν >_ 3 v i b r a t i o n a l l e v e l . A l t e r n a t e l y , a pulsed DF l a s e r near h microns can s e q u e n t i a l l y e x c i t e DF or EDO t o ν > 3. I n pure DX, c o l l i sions o f the type DX(v = l ) + DX(v = l ) •> DX(v = 2) + DX(v = 0) can a l s o e x c i t e higher v i b r a t i o n a l l e v e l s , but t h i s mechanism i s not f e a s i b l e i n n a t u r a l HX c o n t a i n i n g only 0.015% DX. The v i b r a t i o n a l l y e x c i t e d DX molecule (X = B r , C l , F, OH) then w i l l p r e f e r e n t i a l l y r e a c t w i t h unsaturated hydrocarbons ( f o r example, DBr r e a c t i n g w i t h ethylene) t o y i e l d a deuterium-tagged a d d i t i o n product, e.g., e t h y l bromide-d}. These steps may be w r i t t e n DX + nhv + DX* (v=n) η >_ 3 (pulsed CO o r DF l a s e r e x c i t a t i o n ) DX* +

(R

(1)

(2)

l5

R

2

= H, CH , CH=CH , etc.) 3

2

This type o f a d d i t i o n r e a c t i o n i n t o unsaturated hydrocarbons i n t h e gas phase occurs by a homogeneous, b i m o l e c u l a r , f o u r - o r s i x - c e n t e r process (^,5.). Both the forward r e a c t i o n (2) and t h e

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

SEPARATION OF HYDROGEN ISOTOPES

136

reverse r e a c t i o n (unimolecular e l i m i n a t i o n o f HX) have been very w e l l s t u d i e d i n the gas p h a s e ( 6 l ) . K i n e t i c parameters f o r the gas phase thermal a d d i t i o n r e a c t i o n are w e l l represented by the Arrhenius r a t e e x p r e s s i o n , -E /RT k(sec ) = [C]-Ae (3) 9

a

where

[c] = o l e f i n c o n c e n t r a t i o n ( m o l e s / l i t e r ) A = frequency f a c t o r ( l i t e r / m o l e - s e c ) Ε = thermal a c t i v a t i o n energy (kcal/mole) a

A r r h e n i u s parameters f o r HX a d d i t i o n i n t o simple and con jugated o l e f i n s are given i n Table I , which i l l u s t r a t e s the v a r i a t i o n o f a c t i v a t i o n energy E and frequency f a c t o r A, according t o the choice o f reagents. Examination o f Table I r e v e a l s t h a t a c t i v a t i o n energies i n the range 10-50 kcal/mole are a v a i l a b l e , depending on the choice o f reagents. Lowest a c t i v a t i o n energies occur f o r HI a d d i t i o n w i t h i n c r e a s i n g a c t i v a t i o n energy f o r l i g h t e r HX, such t h a t E ( H l ) < E ( H B r ) < E (HCl) < E (HF) < E ( H 0 ) . Table I a l s o shows t h a t a c t i v a t i o n energy decreases w i t h i n c r e a s i n g s u b s t i t u t i o n , w i t h E decreasing by about 5 kcal/mole per methyl (-CH3) group and by about 9 kcal/mole per v i n y l (-CH=CH2) group on the a- or h a l o g e n - r e c e i v i n g carbon atom. Among olefins, 2-methylpropene and 1,3-butadiene have n e a r l y i d e n t i c a l a c t i v a t i o n e n e r g i e s , but 1,3-butadiene i s a f a r s u p e r i o r reagent choice because of i t s approximately 2 0 0 - f o l d higher frequency f a c t o r (A v a l u e ) . Although HI has the lowest a c t i v a t i o n energies f o r r e a c t i o n , i t i s probably not an acceptable choice i n a l a r g e s c a l e process because of i t s tendency t o decompose. HF and H 0 are probably r e l a t i v e l y u n a t t r a c t i v e , s i n c e they have s i g n i f i c a n t l y higher a c t i v a t i o n e n e r g i e s ; t h i s l e a v e s HBr or HC1 as the most l i k e l y reagent c h o i c e . A l s o , use of HF or H 0 would r e q u i r e e x c i t a t i o n by a DF chemical l a s e r , which i s an i n h e r e n t l y more expensive and l e s s e f f i c i e n t device than the CO l a s e r , p r i m a r i l y due t o the cost of r e g e n e r a t i n g the f l u o r i n e . The CO l a s e r i s an e f f i c i e n t , well-developed device ( l l ) which i s q u i t e s u i t a b l e f o r a l a r g e - s c a l e i n d u s t r i a l process. To evaluate the s u i t a b i l i t y o f the CO l a s e r f o r e x c i t a t i o n o f DBr or DC1, a computer comparison was made o f the c a l c u l a t e d wavelengths of CO emission l i n e s and DBr or DC1 a b s o r p t i o n l i n e s . For these diatomic molecules, accurate frequencies may be gener ated from a Dunham equation f o r the energy l e v e l s :

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

a

a

a

a

a

a

2

a

2

2

kj j+i

*™ = Z\*K)\î

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

(u)

10.

MARLING ET AL.

Deuterium

Isotope

137

Separation

TABLE I A r r h e n i u s Parameters Olefins: Frequency Factor

Unsaturated Hydrocarbon

LogipA

propylene^

3

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

t

2-methylpropene Phenyl e t h y l e n e

X = I , B r , C l , F, OH A c t i v a t i o n Energy Ε (kcal/mole) a HBr HCl HF HI H 0 tot7

2

8.3°

ethylene

f o r HX A d d i t i o n t o

28.5

ko

50

57

U5

52

7.9

C

23.5

28.5

3k

6.5

C

18.5

23.5

28

20

2k

30

13

1,3-butadiene 2-methyl-l,3butadiene 1 5 3-pentadiene

3k

18.7

1

Q.k

h

7-7

I5

s

1

26

g

20

1

25

s

2k 20

f

ih.T

h

2-methyl-l,3 . pentadiene

l.k*

11

16

21

H-methyl-1,3-. pentadiene

6.3

10

15

20

J

U n i t s o f A are l i t e r s - m o l e f o r a l l HX compounds. b

Ε

a

l e

38

29

1

e

kg

sec \

L o g A i s constant ± 0 . 3 10

values from Reference 6.

c Reference k. d Computed from A o f back r e a c t i o n .

See Reference 7 ·

Reference 8. Computed from k i n e t i c data o f Reference 5 . Computed from k i n e t i c s o f back r e a c t i o n .

See Reference 9 ·

Reference 1 0 . Estimated Ε

value.

Probable accuracy:

Estimated v a l u e f o r L o g ^ A .

± 2 kcal/mole.

Probable accuracy: ± O.k.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

SEPARATION OF HYDROGEN ISOTOPES

138

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

For normal and i s o t o p i c y i e l d computed emission (Ref. 12) or even a few measured values f o r the

carbon monoxide, the c o e f f i c i e n t s Y frequencies accurate t o 0.001 cm" megahertz (13). For D ^ ^ c i , d i r e c t l y Υ „ were a v a i l a b l e ( l U ) . For D^Tci the £k ntr — Y were computed from D ^ C l u s i n g the Dunham i s o t o p e r e l a t i o n s (15) and the a p p r o p r i a t e atomic reduced masses ( l 6 ) . For D^^Br and D^lBr the e a r l i e r r e p o r t e d a b s o r p t i o n f r e q u e n c i e s (IT) were not s u f f i c i e n t l y accurate. T h e r e f o r e , accurate Y were generated f o r HBr u s i n g the accurate r o t a t i o n a l constants (l8) and recent higher l e v e l v i b r a t i o n a l constants (19.). The a p p r o p r i a t e reduced masses (l6) and Dunham i s o t o p e relation§^(15) then were used t o d e r i v e a l l Y except Y ^ f o r D Br and D Br. Y-|_Q was then f i x e d by r e q u i r i n g the computed 1-0 band t o be 0.25 cm" higher than i t s measured value (17) > according t o the c o r r e c t i o n suggested i n Ref. 20. The d e r i v e d Dunham c o e f f i c i e n t s f o r DC1 and DBr thus p r o v i d e d c a l c u l a t e d a b s o r p t i o n l i n e center frequencies f o r a computer search t o f i n d near-coincidences w i t h CO l a s e r emission f r e q u e n c i e s . For each near c o i n c i d e n c e , the a b s o r p t i o n co e f f i c i e n t was computed u s i n g a standard Lorentz l i n e shape f o r mula, equation (5)> which a l s o i n c l u d e d the temperature depen dence o f the r o t a t i o n a l l e v e l p o p u l a t i o n : -3m(m+l)/kT 1

Λ

1

α ( Δ ν )

= lV

(Λν/0. Ρ) 5Ύ

( 5 ) 2

In equation ( 5 ) , α(Δν) i s the a b s o r p t i o n ( i n cm" ) at a d i s t a n c e Av(cm~l) from DX l i n e center at a pressure o f Ρ atmospheres. The values f o r the pressure-broadened l i n e w i d t h γ(cm atm" ) depend on r o t a t i o n a l number m, and were taken from Ref. 21_ f o r DC1 broadening by HC1. The r o t a t i o n a l number i s m = J - l f o r R-branch and m = J f o r P-branch t r a n s i t i o n s . DBr values f o r γ were d e r i v e d from the r e p o r t e d values f o r HBr(22). The parameters Κ and 3 i n equation (5) were a d j u s t e d t o match the r e p o r t e d DC1 a b s o r p t i o n l i n e s t r e n g t h s ( 2 3 ) , and DBr values f o r Κ and 3 were d e r i v e d from the HBr values (22) by assuming K(DBr) = l/k K(HBr) and 3(DBr) Ξ 2 3(HBr), assumptions found t o be reasonable f o r the DC1/HC1 data (23). Equation (5) thus permits reasonably accurate e s t i m a t i o n of a b s o r p t i o n i n the 1-0 band o f DC1 and DBr by CO l a s e r l i n e s . A b s o r p t i o n s t r e n g t h of the higher v i b r a t i o n a l bands (2-1 through 5-U i n t h i s study) w i l l i n c r e a s e approximately p r o p o r t i o n a l t o ν (Réf. 2*0, but decrease due t o the d i s t r i b u t i o n o f p o p u l a t i o n over the s e v e r a l l e v e l s . As a f i r s t approximation, a b s o r p t i o n s t r e n g t h f o r higher v i b r a t i o n a l bands was thus taken t o be the same as the 1-0 band. Tables I I and I I I summarize the computed a b s o r p t i o n o f -^C-^O l a s e r emission l i n e s by the v a r i o u s i s o t o p e s of DC1 and DBr. Data f o r Tables I I and I I I were computed f o r atmospheric pressure and room temperature (298°K), and i l l u s t r a t e the ease 1

-1

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1

10.

MARLING ET AL.

Deuterium

Isotope

139

Separation

TABLE I I ABSORPTION OF

C O

DC1 T r a n s i t i o n * · ν ( cm" )

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

1

1-0 1-0 1-0 1-0 2-1 2-1 2-1 2-1 3-2 3-2 3-2 3-2 U-3 h-3 h-3 h-3 5-U

P(T) P(3)37 P(T)37 P(U) P(2) p(n) P(U) 3 5

3 5

3 5

3 5

3 7

2011.Ohl 2055-1^6 2008.282 20U6.609 2016.033 1909.678 1991.iih

R(3) 2077.3k0 P(2) 1963.IUO P(ll) 1858.853 P(6) 1918.799 P(2) 1960.51^ P ( 5 ) 5 1878.238 R(5) 1986.873 P(2) 1910.507 P(3) 1897.518 P ( 7 ) 5 I80U.358 p(i) 1868.160 3 5

3 5

3 5

3 5

3 7

3

3 5

3 5

3 7

3

5-U 5-U R ( 2 )

3 5

3 7

1903.939

LASER LINES BY D ^ C l and D^'Cl, a t P=l ATM.

1 2

l 6

c o LASER LINE 5-h P ( 7 ) 3-2 P ( 9 ) 3-2 P ( 2 0 ) 3-2 P ( l l ) 2 - 1 F(2k) 6-5 P ( 2 5 ) 5-U P ( 1 2 ) 2 - 1 P(10) 7-6 P ( 6 ) 1 0 - 9 P(13) 7-6 P ( 1 7 ) h-3 P ( 2 5 ) 10-9 P(8) 5-U P ( 1 3 ) 7-6 P ( 1 9 ) 7-6 P ( 2 2 ) 12-11 P(lU) 9-8 P ( 1 7 ) 9-8 P(8)

v

Vi- co

( c n r l )

ABSORPTION COEF. (cm" )

-0.0i+9 -0.012 -O.I38 -0.3^9 0.007 -0.001 0.090 0.201 0.058 -O.Okh -0.179 0.103 -O.OI7 -0.037 -0.02U -0.101 0.026 0.03U 0.058

* S u b s c r i p t 35 o r 37 r e f e r s t o D ^ C l o r D respectively.

1

11.8 l.U 1.1 12.6 5.1 3.0 2.9 8.7 3.6

3Λ 1.7 18.5 15.2 11.8 2.3 Ik.k 6.0 3.7

Cltransitions,

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

SEPARATION OF HYDROGEN ISOTOPES

140

TABLE I I I ABSORPTION OF

1 2

C

l 6

0 LASER LINES BY D

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

TRANSITION*

v ( cm*" ) 1

B r and D

C C 0 LASER LINE 1 2

DBr

T 9

8 l

B r a t P=l ATM.

1 6

v

v

DBr- C0

( c m

"

1 )

ABSORPTION (cm" ) 1

1-0

R ( 2 ) 81

1863.999

9-8

P(l8)

0.011

3.2

1-0

R(3) 79

18T2.3T8

8-7

P(22)

0.0U8

2.5

1-0

P(9) 79

1757.851

lU-13 P(13)

1-0

P(3) 81

1813.573

11-10

2-1

R ( 6 ] 81

I8U7.I63

9-8

2-1

P(8] 81

1722.606

2-1

R ( 9 ! 79

1867.966

8-7

2-1

P ( 9 ! 79

1713.U97

15-lh

3-2

P(6) 81

1696.517

3-2

R ( 2 ; 81

3-2

P(l8)

2.1 0.057

1.9

P(22)

0.0U6

3.0

16-15 P(9)

0.003

3.8

-0.032

2.0

P(l8)

-0.0U6

2.0

16-15

P(l6)

0.008

h.3

1771.3h3

13-12

P(l6)

0.017

3.1

P ( 9 l 79

1669.172

18-17

P(10)

0.07^

1.3

h-3

p(u; 81

1669.H5

18-17

P(10)

0.017

3.7

h-3

R(3

79

1732.808

15-lU P(13)

0.0U3

2.7

5-U

P(T ) g

1598.386

21-20 P ( 9 )

0.016

u.o

5-U

P(T '81

1597.983

20-19

P(l6)

0.0^9

2.9

Br o r D

Br t r a n s i t i o n s ,

7

* S u b s c r i p t 79 o r 8 l r e f e r s t o D

P(23)

respectively.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

10.

MARLING ET AL.

Deuterium

Isotope

141

Separation

i n a c h i e v i n g s e q u e n t i a l a b s o r p t i o n o f CO l a s e r quanta t o e x c i t e DC1 o r DBr up t h e i r v i b r a t i o n a l l a d d e r s t o ν - 5· Examination o f Table I I i n d i c a t e s t h a t the best matches o f 12^1 ο l a s e r emission w i t h D^^ci y i e l d a b s o r p t i o n c o e f f i c i e n t s of about 12 cm" a t 1 atmosphere. S i m i l a r l y , the best CO laser-DBr a b s o r p t i o n c o e f f i c i e n t s are about 3 cm" . At higher p r e s s u r e s , r a d i a t i o n from CO l a s e r l i n e s i s e a s i l y absorbed w i t h out need f o r CO l a s e r l i n e s e l e c t i o n . For example, a t 5 atmo spheres pressure any CO l a s e r l i n e i n the U.9—5·1 micron r e g i o n i s c a l c u l a t e d t o experience an average DC1 a b s o r p t i o n c o e f f i c i e n t of 2 cm" f o r the 1-0 band, which i n c r e a s e s t o about 10 cm" when a b s o r p t i o n from DC1 v i b r a t i o n a l l y e x c i t e d s t a t e s i s i n c l u d ed. Only the "best" matches were given i n Tables I I and I I I f o r each l e v e l o f v i b r a t i o n a l e x c i t a t i o n . Table I I shows t h a t most DC1 a b s o r p t i o n o f C " 0 l a s e r emission w i l l occur i n the U . 9 micron r e g i o n , and u s e f u l DBr a b s o r p t i o n w i l l occur i n the 5.^-6.2 micron r e g i o n . At n a t u r a l deuterium abundance, t h e 1/e a b s o r p t i o n depth would be about 5 meters f o r DC1 and 20 meters f o r DBr. Since a t y p i c a l r e a c t i o n mixture would a l s o c o n t a i n an o l e f i n a t near-atmospheric p r e s s u r e , i t would be important t o i n s u r e t h a t the o l e f i n i s s u f f i c i e n t l y t r a n s p a r e n t a t these wavelengths (a < 0.1 m e t e r " ) . This i s e s s e n t i a l t o a l l o w the CO l a s e r emission t o e x c i t e p r i m a r i l y DBr o r DC1, and not waste photons by o p t i c a l l y h e a t i n g the o l e f i n . Examination o f simple and conjugated o l e f i n a b s o r p t i o n bands (25) i n the 5-6 micron r e g i o n r e v e a l s q u i t e strong C = C s t r e t c h a b s o r p t i o n a t 6.0-6.2 micron. P o t e n t i a l l y troublesome combination band a b s o r p t i o n occurs a t 5·1*Μ and e s p e c i a l l y a t 5 · 6 μ i n 1,3-butadiene and i s o prene, probably the best reagent choices from Table I . Gas phase a b s o r p t i o n s p e c t r a were examined and showed an a b s o r p t i o n c o e f f i c i e n t ( t o base e) o f about 0 . 5 cm" A t m f o r both 1,3-butadiene and isoprene near 5 · 6 micron. This i s about 2-3 orders o f magnitude stronger than n a t u r a l l y o c c u r r i n g DBr a b s o r p t i o n , r e n d e r i n g photon e f f i c i e n t e x c i t a t i o n o f DBr i m p o s s i b l e . The s i t u a t i o n i s somewhat improved a t 5·1 micron, where the a b s o r p t i o n c o e f f i c i e n t s o f these two o l e f i n s are about 0.05 cm"" atm" , s t i l l about an order o f magnitude stronger than DC1 a b s o r p t i o n a t n a t u r a l abundance. T h i s suggests t h a t l i n e a r conjugated o l e f i n s w i l l be e x c e s s i v e l y absorbing, and prevent e f f i c i e n t CO-laser e x c i t a t i o n o f DC1 and e s p e c i a l l y DBr. Cyclopentadiene and 1 , 3 - c y c l o h e x a d i e n e should a l s o e x h i b i t low a c t i v a t i o n energies f o r hydrogen h a l i d e a d d i t i o n , s i m i l a r t o the l i n e a r conjugated o l e f i n s l i s t e d i n Table I , and o p t i c a l a b s o r p t i o n s p e c t r a are somewhat more promising. Cyclopentadiene (26) appears t r a n s p a r e n t i n the 5 . 0 - 5 . 3 μ r e g i o n , p o t e n t i a l l y s u i t able f o r use w i t h DC1, and 1 , 3 - c y c l o h e x a d i e n e (27) appears t r a n s p a r e n t i n the 5 · ^ - 5 · 7 5 y r e g i o n , making i t p o t e n t i a l l y s u i t a b l e f o r use w i t h DBr. E l i m i n a t i o n of o l e f i n absorption w i l l be e s s e n t i a l f o r e f f i c i e n t photon u t i l i z a t i o n a t low deuterium Ό

1

1

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

1

1

1 2

1

1

1

1

1

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

- 1

SEPARATION OF HYDROGEN ISOTOPES

142

c o n c e n t r a t i o n s . Only ethylene (25) shows extreme t r a n s p a r e n c y , w i t h no d e t e c t a b l e a b s o r p t i o n from 1550 cm- t o 1750 cm"" , making i t o p t i c a l l y s u i t a b l e f o r use w i t h DBr. Non-reactive quenching o f v i b r a t i o n a l l y e x c i t e d deuterium h a l i d e w i l l be an important p r o c e s s , as i t competes w i t h r e a c t i v e a d d i t i o n o f t h e e x c i t e d s p e c i e s i n t o t h e o l e f i n . The r e a c t i o n e f f i c i e n c y φ w i l l be simply t h e r a t i o o f r e a c t i v e quenching t o t o t a l quenching, or 1

1

R [c] v

φ

=

( V Q ) [ c ] + Q [x] c

(6)

x

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

where [c] = Olefin concentration [x] = Hydrogen h a l i d e c o n c e n t r a t i o n R = Deuterium h a l i d e r e a c t i v i t y i n vibrational level ν Q = Quenching r a t e / u n i t c o n c e n t r a t i o n ° of olefin Q = Quenching r a t e / u n i t c o n c e n t r a t i o n of hydrogen h a l i d e In a d d i t i o n t o r e a c t i o n , t h e v i b r a t i o n a l l y e x c i t e d deuterium h a l i d e w i l l experience n o n - r e a c t i v e v i b r a t i o n a l quenching by both t h e o l e f i n and t h e hydrogen h a l i d e . Q denotes v i b r a t i o n a l quenching o f deuterium h a l i d e by hydrogen h a l i d e and has been measured f o r quenching o f t h e DX v = l l e v e l (28-31). For DBr, a value o f Q = 0.2 (μsec · atm)" was d e t e r mined (28) f o r quenching by HBr. For DC1 quenching by HC1, a value of Q = O.h {\isec · atm)"" may be i n f e r r e d (29). Nonr e a c t i v e v i b r a t i o n a l quenching by t h e o l e f i n may be 10-100 times f a s t e r than these r a t e s , based on t h e observed r a p i d quenching of HBr ( 3 0 ) , HC1 (31) and DC1 (31) by water and methane. Quenching r a t e s o f higher DX v i b r a t i o n a l l e v e l s w i l l be f a s t e r than f o r the v = l l e v e l , r i s i n g approximately p r o p o r t i o n a l t o ν (Ref. 2 9 ) . Thus, equation (6) reduces t o a simpler form when the o l e f i n c o n c e n t r a t i o n [θ] i s r a i s e d t o o p t i m i z e φ, x

1

x

1

x

φ ifc R /(R +Q ) i f [C] % [X] v

v

c

and Q » Q c χ

(7)

since v i b r a t i o n a l quenching by HX i s slow compared t o t h e expected o l e f i n quenching r a t e s . The upper l i m i t o f t h e DX r e a c t i o n r a t e w i t h a given o l e f i n i s simply the frequency A (Table I ) and i s expected t o be approached as t h e DX l a s e r s u p p l i e d v i b r a t i o n a l energy exceeds t h e r e a c t i o n - a c t i v a t i o n energy Ε . T h i s assumption was examined f o r other r e a c t i o n systems ( 3 2 ) , and i s d i s c u s s e d f u r t h e r i n S e c t i o n I I I . T h i s p l a c e s an upper l i m i t on t h e r e a c t i o n e f f i c i e n c y

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

10.

MARLING ET AL.

Deuterium

Isotope

143

Separation

(8)

max

when one assumes (32) t h a t A f o r a b i m o l e c u l a r r e a c t i o n i s i n d e pendent o f reagent v i b r a t i o n a l e x c i t a t i o n . The best value o f A from Table I occurs f o r 1 , 3 - b u t a d i e n e , A - 25 (μsec•atm) . I f o l e f i n n o n - r e a c t i v e v i b r a t i o n a l quenching i s comparable t o HX quenching r a t e s by methane ( 3 j 0 , 3 l ) , o r Q = 10-60 (μεβο •atm)*"" , then the maximum r e a c t i o n e f f i c i e n c y , from equation ( 8 ) , c o u l d l i e i n the range 0.1%-50%, w i t h the higher r e a c t i o n e f f i c i e n c i e s corresponding t o use o f o l e f i n s w i t h h i g h values o f A, such as 1,3-butadiene o r ethylene. The problem o f n o n - r e a c t i v e quenching o f v i b r a t i o n a l l y e x c i t e d DX by the o l e f i n i s r e l a t e d t o the problem o f e x c e s s i v e o p t i c a l a b s o r p t i o n by the o l e f i n , namely the presence o f o l e f i n energy resonances near DX a b s o r p t i o n f r e q u e n c i e s . DX v i b r a t i o n a l quenching by v-v energy t r a n s f e r processes becomes very r a p i d near energy resonance (30,33), but should drop t o acceptably low v a l u e s , i f the nearest resonances have an energy discrepancy o f more than about 1000 cm" . Lower n o n - r e a c t i v e quenching can be achieved by u s i n g f u l l y halogenated o l e f i n s (3*0, which may a l s o y i e l d h i g h o l e f i n transparency a t DX a b s o r p t i o n f r e q u e n c i e s . However, t y p i c a l f l u o r i n a t e d o l e f i n reagent c h o i c e s , such as h e x a f l u o r o - l , 3 - b u t a d i e n e (35.), hexafluoropropene (36), o r f l u o r i n a t e d ethylenes (36) have e x c e s s i v e o p t i c a l a b s o r p t i o n i n the 5-6 micron r e g i o n (35.,36) , and hence are not s u i t a b l e . But when i n the course o f t h i s work t e t r a c h l o r o e t h y l e n e o p t i c a l a b s o r p t i o n was examined i n the gas phase, i t was found t o be h i g h l y transparent i n the H.2-5-2 μ r e g i o n , and i s thus poten t i a l l y s u i t a b l e f o r use w i t h HC1. Experimental k i n e t i c data on a c t i v a t i o n energies are not r e p o r t e d , but c a l c u l a t e d values o f E f o r HF o r HC1 r e a c t i n g w i t h perhalogenated ethylene are 5 kcal/mole lower than w i t h normal ethylene (6). Some p e r f l u o r i n a t e d o l e f i n s are v e r y t o x i c ( 3T_), and p e r c h l o r i n a t e d o l e f i n s r e q u i r e o p e r a t i n g temperatures 100-200°C higher than normal o l e f i n s t o achieve u s e f u l vapor pressure. N e v e r t h e l e s s , t h e p o t e n t i a l f o r h i g h IR transparency and low v i b r a t i o n a l quenching makes t h i s c l a s s o f reagents (and t e t r a c h l o r o e t h y l e n e i n p a r t i c u l a r ) a t t r a c t i v e t o c o n s i d e r f o r a p r a c t i c a l process. There i s p r e s e n t l y very l i t t l e experimental data on l a s e r e x c i t e d HX a d d i t i o n i n t o o l e f i n s . However, r e a c t i o n was observed between 2-methylpropene and HCl(v=6) produced by i n t r a c a v i t y dye l a s e r e x c i t a t i o n o f the HC1 f i f t h overtone ( 3 8 ) . Quantum y i e l d s f o r r e a c t i o n were estimated (38.) t o l i e i n the range 0.01-0.1%, c o n s i s t e n t w i t h the very l o w frequency f a c t o r f o r t h i s o l e f i n (see Table I ) . Use o f 1,3-butadiene i n t h i s same experiement ( i n s t e a d o f 2-methylpropene) was not t r i e d , but should have y i e l d e d a r e a c t i o n quantum y i e l d o f 2-20%, based on i t s 2 0 0 - f o l d higher frequency f a c t o r . Economic a n a l y s i s o f l a s e r - r e l a t e d c o s t s i n heavy water p r o d u c t i o n by the D X - o l e f i n process l

1

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

c

1

a

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

SEPARATION OF HYDROGEN ISOTOPES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

144

d i s c u s s e d here i n d i c a t e t h a t r e a c t i o n e f f i c i e n c i e s must exceed 5% f o r t h i s process t o be economically v i a b l e (39)· Additional c o s t s due t o the "back-end" of t h i s process (see S e c t i o n IV) w i l l probably set a p r a c t i c a l lower l i m i t of 10% f o r an acceptable r e a c t i o n e f f i c i e n c y . In t h i s c o n t e x t , the c l a s s i c a l quantum e f f i c i e n c y i s the r e a c t i o n e f f i c i e n c y φ d i v i d e d by n, the average number of absorbed quanta per DX molecule. The assumption of η = 5 p l a c e s an approximate lower l i m i t of 2% on an economically acceptable quantum e f f i c i e n c y f o r deuterium h a l i d e a d d i t i o n i n t o o l e f i n s as a p o t e n t i a l photochemical route t o heavy water pro duction. In t h i s s e c t i o n we have shown t h a t the CO l a s e r permits s e q u e n t i a l e x c i t a t i o n of DBr or DC1 up the v i b r a t i o n a l ladder t o at l e a s t the ν = 5 v i b r a t i o n a l l e v e l . At n a t u r a l deuterium abundance, the l / e a b s o r p t i o n depth f o r s e l e c t e d CO l a s e r l i n e r a d i a t i o n i s about 5 meters f o r DC1 and about 20 meters f o r DBr, at a hydrogen h a l i d e o p e r a t i n g pressure of one atmosphere. At 5 atmospheres o p e r a t i n g p r e s s u r e , u n r e s t r i c t e d m u l t i l i n e opera t i o n of the CO l a s e r i s s u f f i c i e n t , but some l i n e t u n i n g (according t o Tables I I and I I I ) f a c i l i t a t e s DX a b s o r p t i o n at one atmosphere pressure. Troublesome o l e f i n o p t i c a l a b s o r p t i o n and v i b r a t i o n a l quenching may be reduced by u s i n g t e t r a c h l o r o e t h y l e n e . Unwanted o l e f i n o p t i c a l a b s o r p t i o n may a l s o be avoided by u s i n g e t h y l e n e , cyclopentadiene, or 1,3-cyclohexadiene. The l a r g e choice of Arrhenius parameters a v a i l a b l e f o r t y p i c a l reagent choices (Table I ) permits reagent o p t i m i z a t i o n f o r acceptable process r e a c t i o n e f f i c i e n c y . Experimental e v a l u a t i o n of the deuterium h a l i d e / o l e f i n process f o r heavy water p r o d u c t i o n i s i n progress at the Lawrence Livermore Laboratory. I I I . E f f e c t i v e n e s s of V i b r a t i o n a l E x c i t a t i o n In the preceding s e c t i o n , we have shown t h a t e x c i t a t i o n of l o w - l y i n g v i b r a t i o n a l l e v e l s of deuterated h a l i d e s should l e a d t o s i g n i f i c a n t enrichments v i a i s o t o p i c a l l y s e l e c t i v e a d d i t i o n r e a c t i o n s , I f the h a l i d e v i b r a t i o n and r e a c t i o n coordinates are e s s e n t i a l l y i d e n t i c a l . That v i b r a t i o n a l e x c i t a t i o n of hydrogen h a l i d e s l e a d s t o enhanced r a t e s f o r diatomic-atom exchange r e a c t i o n s of the type K f

A + BC

t

t

AB

+ C

(9)

have been e x p e r i m e n t a l l y confirmed; perhaps the most s t r i k i n g example i s the f a c t t h a t HC1 (v = 2) was found t o r e a c t w i t h bromine approximately 1 0 times f a s t e r than HC1 (ν = 0) (kO). The t h e o r e t i c a l e x p l a n a t i o n o f these r a t e enhancements runs as f o l l o w s : Since the forward, exoergic r e a c t i o n leaves the product AB i n a h i g h l y v i b r a t i o n a l l y e x c i t e d s t a t e (AB ), then 1 1

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

10.

MARLING ET AL.

Deuterium

Isotope

145

Separation

microscopic r e v e r s i b i l i t y a t the same t o t a l energy i m p l i e s t h a t the r a t e o f the r e v e r s e , endoergic r e a c t i o n - w i l l be enhanced more e f f e c t i v e l y when energy i s put i n t o AB v i b r a t i o n r a t h e r than i n t o r e l a t i v e t r a n s l a t i o n o f AB and C. I n c o n s i d e r i n g more general r e a c t i o n s i n v o l v i n g v i b r a t i o n a l l y e x c i t e d reagents, i t i s impor t a n t t o note t h a t the r e v e r s i b i l i t y argument can be a p p l i e d inde pendent o f whether the r e a c t i o n which leads t o a v i b r a t i o n a l l y e x c i t e d product i s endoergic o r exoergic. We s t r e s s t h i s because, w h i l e i t i s g e n e r a l l y b e l i e v e d t h a t t h e endoergic r e a c t i o n s u t i l i z e v i b r a t i o n a l energy more e f f e c t i v e l y than exoergic r e a c t i o n s (hi), t h e e x i s t i n g experimental evidence, as analyzed by B i r e l y and Lyman (32.) does not show any strong c o r r e l a t i o n between the e f f e c t i v e n e s s o f reagent v i b r a t i o n i n lowering the a c t i v a t i o n energy and r e a c t i o n e x o e r g i c i t y . I t f o l l o w s t h a t i n s i g h t i n t o the e f f e c t o f v i b r a t i o n a l e x c i t a t i o n o f hydrogen h a l i d e s on the r a t e o f exoergic a d d i t i o n r e a c t i o n s can best be gleaned from t h e experimental data on the energy d i s p o s a l o f the reverse r e a c t i o n s , i . e . , unimolecular hydrogen h a l i d e e l i m i n a t i o n s from, e.g., h a l o alkanes and h a l o o l e f i n s , f o l l o w i n g chemical o r photochemical a c t i v a t i o n . There i s an extensive l i t e r a t u r e i n t h i s area: The experimental evidence i s summarized by Berry (h2) who concludes t h a t , i r r e s p e c t i v e o f the a c t i v a t i o n mechanism, the t o t a l a v a i l able energy ( E ) , o r t h e molecular complexity o f the r e a c t a n t , a l l HX e l i m i n a t i o n products acquire ^ 15-h0% o f t h e p o t e n t i a l energy (E ) a v a i l a b l e t o t h e r e a c t a n t s (defined as t h e t h r e s h h o l d energy fo? HX e l i m i n a t i o n minus t h e r e a c t i o n e n d o e r g i c i t y ) as v i b r a t i o n a l energy. The remaining energy i s channeled i n t o HX r o t a t i o n , o l e f i n product r o t a t i o n and v i b r a t i o n and r e l a t i v e t r a n s l a t i o n a l energy o f t h e r e c o i l i n g products. We note t h a t a l l t h e data per t a i n s t o experiments i n which E^ >> Ε . Of g r e a t e r relevance as f a r as e f f e c t i v e n e s s o f HX v i b r a t i o n §n t h e r a t e o f t h e i n v e r s e a d d i t i o n would be data on HX e l i m i n a t i o n s f o r which E - Ε . Τ ρ Nevertheless, t h e a v a i l a b i l i t y o f many i n t e r n a l degrees o f f r e e dom o f t h e product o l e f i n makes i t improbable t h a t r a t e enhance ments f o r HX a d d i t i o n r e a c t i o n comparable t o those f o r HX-atom exchange r e a c t i o n s can be achieved. Experiments t o t e s t t h i s conjecture are i n progress a t t h e Lawrence Livermore Laboratory. IV. "Back-End" o f the Separation Cycle

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

5

T

m

In common w i t h most other deuterium separation schemes, t h e economic v i a b i l i t y o f an enrichment process based on l a s e r enhanced deuterium h a l i d e a d d i t i o n r e a c t i o n s n e c e s s i t a t e s p r o v i s i o n f o r r e c y c l i n g t h e working f l u i d . That i s , i t i s not f e a s i b l e t o use, e.g., h y d r o c h l o r i c a c i d , on a once-through b a s i s as feed f o r a deuterium separation p l a n t since even i f a l l t h e D i n n a t u r a l HC1 ( n a t u r a l abundance - 1 . 5 x 10" ) were removed w i t h 100% e f f i c i e n c y , t h e HC1 feed cost alone would be 4

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

SEPARATION OF HYDROGEN ISOTOPES

146

$0.1

36

kgHCl

kg mole HC1 1 mole D 0

kg HC1

(1)

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

2 mole DC1

$2U00/kg

20 kg

2

X

^

'

to

D_0

2

kg mole D 0 2

assuming HC1 c o s t s 10φ p e r k i l o g r a m . Thus, t h e economic v i a b i l i t y o f t h i s process depends on the a b i l i t y t o redeuterate t h e HC1 which has been depleted o f D by t h e i s o t o p i c a l l y s e l e c t i v e a d d i t i o n r e a c t i o n . The "obvious" way t o accomplish t h e r e d e u t e r a t i o n i s by i s o t o p i c exchange o f HC1 w i t h n a t u r a l water (k3). For s p e c i f i c i t y , we d i s c u s s t h i s r e f l u x o p e r a t i o n i n t h e context o f the prototype system shown i n F i g u r e 1. The deuterated product of t h e a d d i t i o n r e a c t i o n (DACl) i s t h e r m a l l y d i s s o c i a t e d t o p r o duce i s o t o p i c a l l y pure DC1 (and e v e n t u a l l y D2O through exchange with n a t u r a l water), while the o l e f i n i s r e c i r c u l a t e d t o the l a s e r i r r a d i a t i o n area. The m a t e r i a l flows i n t h e r e f l u x tower assume e q u i l i b r i u m o p e r a t i o n a t 108°C (hh). At t h i s temperature the s e p a r a t i o n f a c t o r α f o r t h e exchange r e a c t i o n DC1 + H 0 $ HC1 + HDO

(2)

2

is

(U3)

(H)H^O 2

(I)

1.9

Ή01

Besides t h e f a c t t h a t a l l t h e hydrogen h a l i d e - w a t e r exchange r e a c t i o n s are c h a r a c t e r i z e d by an unfavorable e q u i l i b r i u m as f a r as r e f l e x i s concerned, i . e . , t h e deuterium tends t o concentrate i n the water, t h e r e a r e two other p r a c t i c a l d i f f i c u l t i e s a s s o c i a t e d w i t h t h e use o f these systems: ( l ) they are h i g h l y c o r r o s i v e , n e c e s s i t a t i n g t h e use o f s p e c i a l m a t e r i a l s , e.g., Monel, and, (2) they form constant b o i l i n g ( a z e o t r o p i c ) mixtures. The s i g n i f i c a n c e o f t h e l a t t e r i s t h a t i t i s i m p o s s i b l e by s u c c e s s i v e d i s t i l l a t i o n s a t a given pressure (or a t a given temperature) t o o b t a i n both components as pure products from a hydrogen halide-water mixture. At some p o i n t i n t h e d i s t i l l a t i o n p r o c e s s , the a z e o t r o p i c c o n c e n t r a t i o n w i l l be reached (kk) ; when t h i s a z e o t r o p i c feed i s p a r t i a l l y v a p o r i z e d , t h e vapor has t h e same composition as t h e l i q u i d and no f u r t h e r s e p a r a t i o n o f com ponents i s p o s s i b l e . One convenient way t o break t h e azeotrope and separate t h e phases a f t e r t h e i s o t o p i c exchange process has been completed i s t o make use o f t h e s o - c a l l e d " s a l t e f f e c t " i n v a p o r - l i q u i d e q u i l i b r i u m . The a d d i t i o n o f a n o n - v o l a t i l e s a l t such as c a l c i u m c h l o r i d e , CaCl2, t o t h e HCl/H 0 mixture has t h e e f f e c t o f s i m u l t a n e o u s l y i n c r e a s i n g t h e vapor pressure o f t h e HC1 v i a t h e common i o n effect, and decreasing t h e vapor pressure o f the water, thus generating vapor o f higher HC1 c o n c e n t r a t i o n than t h a t c h a r a c t e r i s t i c o f t h e azeotrope. We have not been able t o 2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

10.

MARLING ET AL.

Deuterium

Isotope

147

Separation

1mA

DC1 + A

1 m DAC1 DAC1

addition

dissociation

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

Carbon monoxide laser

13,500 m HC1 1 m DC1

1 m DC1 +

13,500

m HC1 13,501

HC1 reflux

| l m HC1

m HC1

D

2°

production

0.5m D 0 2

t

Feed: 3500 m n a t u r a l H^O

Waste : 3500 m H 0 2

Feed: 0.5 m n a t u r a l H^O

LEGEND : m = Mole A = Olefin DAC1 = DC1 + O l e f i n a d d i t i o n product Figure 1.

Process flow diagram for DO production by laser-augmented deuteriumchloride addition into olefins

American Chemfcaf

Society Library 1155 16th St. N. W. In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Washington, DC, 1978. 1. D. C.Society: 20038

SEPARATION O F HYDROGEN ISOTOPES

148

f i n d i n f o r m a t i o n i n the l i t e r a t u r e on t h e HCl/H O/CaCl^ system; however, from data on Isopropanol/H^O/CaCl^ (^5.) and HCl/H^O/H^SO^ mixtures (U6_)(HpS0^, w h i l e not a common i o n , be haves s i m i l a r l y t o a n o n - v o l a t i l e s a l t i n reducing the vapor pressure o f H^O), we c o n j e c t u r e t h a t t h e c o n c e n t r a t i o n o f CaCl^ r e q u i r e d w i l l be approximately 2-k wt.%. A d e t a i l e d d i s c u s s i o n o f t h e design o f t h e HC1/H 0 exchange process i n c o r p o r a t i n g t h e equipment necessary t o generate r e deuterated, anhydrous HC1 f o r r e f l u x t o the l a s e r tower would c a r r y us too f a r a f i e l d (Vf) ; however, t h e b a s i c concept i s as f o l l o w s . The i s o t o p i c exchange takes p l a c e on a s e r i e s o f t r a y s w i t h the HC1 bubbling up and H 0 f l o w i n g down i n a countereurrent f a s h i o n . The l i q u i d stream from t h e exchange column, and a s a l t s o l u t i o n are f e d t o a concentrated s t r i p p e r which produces vapor of h i g h p u r i t y (> 99 mole % H C l ) ; t h i s i s r e c y c l e d t o t h e bottom o f t h e i s o t o p i c exchange column. The l i q u i d from t h e concentra ted s t r i p p e r , having a c o n c e n t r a t i o n lower than t h e azeotrope, passes t o an evaporator where t h e s a l t i s recovered f o r r e c y c l e to t h e concentrated s t r i p p e r , and vapor i s produced which i s subsequently s t r i p p e d t o produce two streams: a water stream which i s washed before d i s c h a r g e , and an a z e o t r o p i c HC1/H 0 mixture. The l a t t e r , mixed w i t h incoming f r e s h water, i s f e d t o the t o p o f t h e i s o t o p i c exchange column. Many v a r i a t i o n s o f t h e above are probably f e a s i b l e ; our main p o i n t here i s t o i n d i c a t e t h a t w h i l e t h e use o f hydrogen h a l i d e s i n t r o d u c e s c o m p l i c a t i o n s i n the design o f the "back-end" o f t h e s e p a r a t i o n scheme, these can be overcome. 2

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

2

2

V.

Conclusion

O p t i c a l p r o d u c t i o n o f heavy water i s beginning t o r e c e i v e s e r i o u s c o n s i d e r a t i o n . L a b o r a t o r y - s c a l e photochemical s e p a r a t i o n of deuterium v i a d i s s o c i a t i o n o f deuterated formaldehyde (HDCO)to y i e l d HD and CO has a l r e a d y been demonstrated i n t h e UV(3_) u s i n g a s i n g l e photon, and i n t h e IR at 10.6 microns u s i n g multi-photon a b s o r p t i o n (kO). To be economically v i a b l e , t h e former process awaits e f f i c i e n t low cost tunable u l t r a v i o l e t l a s e r s near 3^0 nm (39,^9) w h i l e the l a t t e r process r e q u i r e s s i g n i f i c a n t improve ment i n photon u t i l i z a t i o n (^ 1 0 photons are p r e s e n t l y r e q u i r e d per separated HD {kQ)). A l l photochemical deuterium enrichment processes w i l l probably r e q u i r e deuterium o p t i c a l i s o t o p i c s e l e c t i v i t y o f 1000-fold or b e t t e r f o r e f f i c i e n t photon u t i l i z a t i o n (3£,^9), about an order o f magnitude higher than has been demonstrated (3,^8). The deuterium s e p a r a t i o n process j u s t presented proposes t o u t i l i z e e x i s t i n g , e f f i c i e n t , h i g h average power CO l a s e r t e c h nology t o promote deuterium h a l i d e a d d i t i o n i n t o unsaturated hydrocarbons. Spectroscopic s t u d i e s o f CO l a s e r s and deuterium h a l i d e s have shown t h a t both DC1 and DBr can be s e q u e n t i a l l y e x c i t e d by t h e CO l a s e r near 5-6 microns t o a t l e a s t the ν = 5 9

6

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

10.

MARLING E T A L .

Deuterium

Isotope

149

Separation

l e v e l , as summarized i n Tables I I and I I I . A d d i t i o n i n t o unsaturated hydrocarbons should occur w i t h a c t i v a t i o n energies i n the range of 15-^0 kcal/mole u s i n g HC1 or HBr as the working gas, as i n d i c a t e d i n Table I . The e f f e c t i v e n e s s of hydrogen h a l i d e v i b r a t i o n a l energy toward l o w e r i n g the a d d i t i o n r e a c t i o n a c t i v a t i o n b a r r i e r is not known, but probably l i e s i n the range of 30-100%, suggesting t h a t perhaps 5-8 quanta of DX v i b r a t i o n a l e x c i t a t i o n w i l l be r e q u i r e d f o r u s e f u l l y f a s t r e a c t i o n t o occur. Two s i g n i f i c a n t problems t o be r e s o l v e d are photon l o s s by o l e f i n combination band absorption i n the 5 - 6 micron r e g i o n and p o t e n t i a l l y low r e a c t i o n quantum y i e l d s due t o non-reactive v i b r a t i o n a l quenching by the o l e f i n . These problems appear s o l v a b l e by s u i t a b l e o l e f i n s t r u c t u r a l design. The problems a t the "back-end" of t h e s e p a r a t i o n c y c l e , s p e c i f i c a l l y the breaking of the HX/H 0 azeotrope, a l s o appear s o l v a b l e . Research c u r r e n t l y underway w i l l examine the e f f e c t i v e n e s s of v i b r a t i o n a l c a t a l y s i s on the r e a c t i o n r a t e and r e a c t i o n quantum y i e l d as a f u n c t i o n of o l e f i n s t r u c t u r e . 2

Acknowledgement One of the authors (M.M.M.) would l i k e t o thank M. Benedict and J. E. V i v i a n f o r h e l p f u l d i s c u s s i o n .

Professors

Abstract The feasibility of a gas phase deuterium s e p a r a t i o n process is examined which would use IR l a s e r s t o augment a d d i t i o n re actions between HX (X = Br, Cl, F , OH) and unsaturated hydro carbons. High vibrational levels (V ≥ 4) of DF or HDO may be e x c i t e d by a p u l s e d DF laser. S i m i l a r h i g h vibrational excitation of DCl o r DBr may be achieved by a p u l s e d CO laser and s p e c t r o scopic d e t a i l s f o r excitation up t o V = 5 are examined. The thermal r e a c t i o n between HX and unsaturated hydrocarbons is c h a r a c t e r i z e d by activation exergies between 15 and 57 k c a l / m o l e , depending on olefin s t r u c t u r e and choice of HX. The e f f e c t i v e n e s s of HX/DX vibrational energy in l o w e r i n g the r e a c t i o n b a r r i e r is d i s c u s s e d . Primary emphasis is g i v e n t o an overall deuterium s e p a r a t i o n process utilizing HCl as a c l o s e d c y c l e working gas w i t h aqueous phase r e d e u t e r a t i o n . P r e f e r r e d olefin reagents are i n d i c a t e d compatible w i t h CO laser e x c i t a t i o n of DCl at a wave l e n g t h of 4.9-5.3 m i c r o n . Literature Cited 1. 2.

Letokhov, V . S . and Moore, C.B., Sov. J. Quant. E l e c t r o n (1976) 6, 129 and 259. Miller, A . I. and Rae, H.K., Chemistry in Canada (1975), 27, 25. We note t h a t ERDA's current (April, 1977) p r i c e f o r heavy water is $213/kg, a p r i c e i n c r e a s e due t o the

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

150

3.

4.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

17. 18. 19. 20. 21. 22. 23.

SEPARATION OF HYDROGEN ISOTOPES

diseconomy of small s c a l e p r o d u c t i o n . N e v e r t h e l e s s , a heavy water cost of approximately $200/kg f o r d e l i v e r y in 1980 is probably a conservative estimate. The possibility of deuterium separation via photopredissociation of formaldehyde has been demonstrated by J. B . M a r l i n g . See J. B . M a r l i n g , "Laser Isotope Separation of Deuterium," Chem. Phys. Lett., (1974) 34, 84, and "Isotope Separation of Oxygen-17, Oxygen-18, Carbon-13, and Deuterium by Ion Laser Induced Formaldehyde P h o t o p r e d i s s o c i a t i o n , " J. Chem. Phys. (1977) 66, 4200. Benson, S. W., and Bose, A . N., J. Chem. Phys. (1963), 39 3463. Gorton, P . J., and Walsh, R., J. Chem. Soc. Chem. Comm. (London) (1972), 782. Tschuikow-Roux, Ε., and Maltman, F . R., I n t . J. Chem. Kin. (1975), Vol. VII, 363. Benson, S. W., and O ' N e a l , Η. Ε., " K i n e t i c Data on Gas Phase Unimolecular R e a c t i o n s , " (1970), NSRDS-NBS 21. Kubota, Η . , Rev. Phys. Chem., Japan (1967) 37, 25, and (1967) 37, 32. Harding, C. J., M a c c o l l , Α., and Ross, R. Α., J. Chem. Soc. B, (1969), 634. Egger, K. W . , and Benson, S. W., J. Phys. Chem. (1967), 71, 1933. Boness, M. J. W . , and Center, R. E., J. A p p l . Phys. (1977), 48, 2705. See a l s o Sobolev, Ν. Ν., and Sokovikov, V . V., Sov. J. Quant. E l e c t r o n . (1973), 2, 305. Todd, T. R., C l a y t o n , C. Μ . , Telfair, W. Β., McCubbin, Τ. Κ . , Jr., and Pliva, J., J. M o l . Spect. (1976), 62, 201. Ross, A . H . M., Eng, R. S., and Kildal, Η . , Opt. Comm. (1974), 12, 433. Rank, D. Η . , Eastman, D. P., Rao, B . S., and Wiggins, Τ. Α., J. Opt. Soc. Am. (1962), 52, 1. Dunham, J. L., Phys. Rev. (1932), 41, 721. Townes, C. Η . , and Shawlow, A . L., "Microwave Spectroscopy," p. 644, McGraw-Hill Brook Company, Inc., New York, New York (1955). Keller, F . L., and N i e l s e n , A . H., J. Chem. Phys. (1954), 22, 294. Rank, D. Η . , F i n k , Uwe, and Wiggins, Τ. Α., J. M o l . Spect. (1965), 18, 170. Bernage, P., N i a y , P., Bockuet, Η . , and Houdart, R., Revue de Phys. A p p l . (1973), 8, 333. Mould, Η. Μ., Price, W. C., and W i l k i n s o n , G. R., S p e c t r o chimica A c t a (1960), 16, 479. James, T. C., and T h i b a u l t , R. J., J. Chem. Phys. (1964), 40, 534. Babrov, H. J., J. Chem. Phys. (1964), 40, 831. B e n e d i c t , W. S., Herman, R., and S i l v e r m a n , S., J. Chem. Phys. (1957), 26, 1671.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

10.

MARLING ET AL.

Deuterium

Isotope

24. Smith, F. G., J. Quant. Spectrosc. R a d i a t . T r a n s f e r 13, 25.

151

Separation

(1973),

717.

26.

Rasmussen, R.S.,and Brattain, R. R., J. Chem. Phys. ( 1 9 4 7 ) , 120 and 131. Gallinella, Ε., F o r t u n a t o , Β., and Mirone, P., J. Mol. Spect.

27. 28.

DiLauro, C., and Neto, N., J. Mol. S t r u c t u r e ( 1 9 6 9 ) , 3, 219. Chen, M. Y.-D., and Chen, H. -L., J. Chem. Phys. ( 1 9 7 2 ) ,

29.

Weitz, Ε., and F l y n n , G., Ann. Rev. Phys. Chem. ( 1 9 7 4 ) , 25,

15,

(1967),

56,

24, 345.

3315.

275.

30. Hopkins, Β. M., and Chen, H. -L., J. Chem. Phys. ( 1 9 7 3 ) , 5 9 , 1495.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch010

31.

Zittel,

P. F., and Moore, C. B.,J.Chem. Phys. ( 1 9 7 3 ) ,

58,

2004. 32. Birely, J. H., and Lyman, J. L., J. Photochem. ( 1 9 7 5 ) , 4, 2 6 9 . 33. Zittel, P. F., and Moore, C. B., J. Chem. Phys. ( 1 9 7 3 ) , 5 8 , 2922.

34. Moore, C. Β., private communication. 35. A l b r i g h t , J. C., and N i e l s o n , J. R., J. Chem. Phys. 36.

26,

(1957),

370.

N i e l s o n , J. R., C l a s s e n , H. H., and Smith, D. C., J. Chem. Phys. ( 1 9 5 0 ) , 1 8 , 485 and 8 1 2 ; ibid ( 1 9 5 2 ) , 2 0 , 1 9 1 6 . 37. C l a y t o n , J. W., Jr., Fluorine Chem. Rev. ( 1 9 6 7 ) , 1, 197. 38. B e r r y , M. J., paper presented a t t h e T h i r d Winter Colloquium on Laser Induced Chemistry, Park City, Utah, Feb. 14-16, 1977. 39. M a r l i n g , J. Β., Wood, L. L., and Daugherty, J. D., "The LaserR e l a t e d Costs of Some Approaches to Laser Isotope S e p a r a t i o n of Deuterium," Univ. Calif. Lawrence Livermore Laboratory I n t e r n a l Document, Feb., 1977. 40. Arnoldi, D., Kaufmann, Κ., and Wolfrum, J., Phys. Rev. L e t t . (1975),

34, 1 5 9 7 .

41. See, e.g., L e v i n e , R. D., and Manz, J., J. Chem. Phys. 63,

(1975),

4280.

42.

B e r r y , M. J., J. Chem. Phys. (1974), 61, 3114, and r e f e r e n c e s cited t h e r e i n . 43. B e n e d i c t , Μ., and Pigford, Τ. Η., "Nuclear Chemical Engineer i n g , " p. 454, Table II-9, McGraw-Hill, New York, New York (1957).

44. For HCl/H O the constant boiling mixture is 11.13 mole%HCl. It boils at 108.5°C under a pressure of one atmosphere. 45. Ohe, S., Japan Chem. Quart. ( 1 9 6 9 ) , 4, 2 0 . 46. Chu, J u Chin, e tal.,"Vapor L i q u i d E q u i l i b r i u m Data," 2nd Edition, p. 6 3 9 , Edwards, Ann Arbor ( 1 9 5 6 ) . 47. A d e t a i l e d f l o w sheet is a v a i l a b l e from one of the authors (M.M.M.). 48. Koren, G., Oppenheim,P.,Tal,D., Okon, Μ., and W e i l , R., A p p l . Phys. L e t t . ( 1 9 7 6 ) , 2 9 , 40. 49. Vanderleeden, J. C., "Laser S e p a r a t i o n of Deuterium," Laser Focus (June, 1 9 7 7 ) , 1 3 , 51. 2

RECEIVED September 12, 1977

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

11 Proposed H / D / T Separations Based on Laser-Augmented A + B = C Reactions S. H . BAUER

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011

Department of Chemistry, Cornell University, Ithaca, NY 14853

The separationofH/D/T by laser photolysisofselected congeners in the infrared does not require high spectral resolution but does depend on the retentionofselective excitation and rapid reactionofthe species which initially absorb the photolyzing radiation. Except for the vibra tion augmentationofthree center abstraction reactions [A + B*C — AB + C], all isotope fractionations achieved to date involving polyatomics are based on fragmentationofthe irradiated species by co herent absorption of a large numberofphotons under essentially colli sion free conditions, to excited states considerably above the critical level for dissociation. A thermodynamic and kinetic analysis, which constitutes the first partofthis report indicates that the inverse process i.e. the bimolecular association should also be isotopically selective. In the second partofthis report several specific cases are proposed for testing this concept. The emphasis hereison chemical properties, not on spectroscopy, sinceitappears that the required irradiating frequen cies are either available now or shortly will be from sufficiently power ful lasers. All the systems considered are presumed to beinthe gas phase at pressures sufficiently low such that individually each species behaves ideally. Whileinsome respects the analysis appears elemen tary,itisbasic and merits formulation in a consistent manner. Thermodynamic and Kinetic Relations Consider the direct synthesisofan adduct: A + Β < " >.

C

(M)

v

(1)

C

Reference to Figure 1 provides definitionsofthe conventional symbols used. For a system whichisinstatistical equilibrium N^. ( E , T) represent a normalized Boltzmann distributionofpopulationsofthe reactants; the hashed levels represent the weighted mean energies of B

©

0-8412-0420-9/78/47-068-152$05.00/0

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

11.

BAUER

Proposed

H/D/T

153

Separations

the reactants, transition state, and products. The zero of energy for each species, per convention, is measured from the corresponding zeropoint level. Thus, 00

Δ

Τ =

Ε

Δ

Ε

ο

JΟ

+

00

E

< '

A; Β A; Β

Ε

N

"J

T) d E

ΔΗ° = (ΔΕ° - RT) < 0

;

E

N

C

ο

( E

C

'

T ) d E

( 2 )

Δβ° < 0

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011

These are thermodynamically favored reactions.

K

p,eq ' Ρ

=

4

?V

μ

}

Α Ί

=

E

eq

"

L

E

X

P { - | A S ° | /

R

|ΔΕ°|/ΚΤ}

+

1

(«») -1 \ = (RT) — ·

X

2 —

-1 3 -1 The units of κ-^ and ^ * molecule cm s . Clearly, on raising the temperature, i.e. for T^ > T,both distribution functions get steeper and eq( l> eq< >For a system which is in statistical equilibrium at the temperature T, except for a steady burning of a hole at level Eg and maintenance of an overpopulation at E ^ , most of the reactant populations are unchanged, Figure 2. The magnitude of the second term in the right member of (2) is obviously increased and K^(T) is greater than Kp q(T). The reverse applies when the hole in the population is burned at fe and the over population established at Ε . These qualitative relations apply inde pendentlyofthe magnitude of E , which can be positive or zero. For example, the steady state irradiation of a mixture of B(CH3>3 and N H with a C O 2 laser should increase the magnitude of the "perturbed equili brium constant" for the reaction (1), a

K

T

r

e

n

T

e

p

σ

a

3

NH* + B ( C H ) 3

3

* (CH ) B:NH 3

3

AR°

3

QQ

=

-14.2 kcal/mole (unirradiated)

even though the adduct is presumed to be generated without an activation energy. A similar argument applies to the adsorption of gases onto a solid surface, where the amount adsorbed under steady state irradiation should increase when either the adsorber or the adsorbate undergo a resonant transition which is matched by the irradiating frequency. Here, the equivalent of the condition κ Ι Μ ι * P i d intrasurface-layer vibrational relaxation. 2

>

κ

s

r a

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011

SEPARATION OF HYDROGEN ISOTOPES

Figure 2. Change in population distribution at steady state because of pumping by β -> « = (E — Ε )/1ι or + = (Ε — E )/h, assuming the statistical temperature remains at Τ a

β

Vp

σ

σ

p

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

11.

BAUER

Proposed H/D/T

155

Separations

The kinetic formulation provides addition details for the above analysis. To eliminate the dependence on [M] we must stipulate that X2ÎM] > κ ^ . Then the unidirectional rate of production of from the reagent is determined by the product of the individual state densities and the cross sections for association: j) P

(i) (J) A B

at stat. equil. *

P

Γ A B &

/

&

V

E

° A , BL lQ Q: e x p v - " k F ~ ) J o 7- o A

(4)

B M

B

P

A B P

i,3 -1

with

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011

-1

r ψ « ι/L ( 1 +

(5)

skT /

where s is the equivalent number of classical oscillators assigned to the transition state (C*) and,

ν* = Π u . ( Π +

C

1=1

ι \j i =

ν* ) 3 /

Similar expressions apply to the second step in the conversion. Hence for a system at steady state, with a hole burned at E and overpopulated Q

se Β ρ ' is the molecular density at Eg at statistical equilibrium. Because the perturbed system is generated by direct pumping, the increments in densities at a and 3 are equal but of opposite sign; however, < κ£°^ and (R^-R^) > 0. The net rate (fà^-ift.j) is larger than ( ^ - i ^ ) since the reverse rate is minimally affected by pumping β — a; recall Ή^[Μ.] > κ ^ . Note that the sign of the increment in the unidirectional flux is determined by the perturbed population, again, irrespective of the magnitude of E . However, the size of the increment depends on (κ^-κ^) which is small when Eg > E (2). Clearly, to maintain the spiked distribution at the steady state, with out allowing the system temperature to rise indefinitely, one must continually remove as much energy as is pumped into it by radiation. Imagine that the reactants and the reactor s walls are initially at a uni form temperature, T < T . Upon turning on the radiation there will be a transient condition wherein, on a time scale of T(vib) (transi), the reactant temperature rises, but on a longer time scale ( T ) it levels off, due to conduction and convection, to the operating temperature Τ which a

R

T

Q

r

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

156

SEPARATION OF HYDROGEN ISOTOPES

is determined by the rate of heat transfer to the walls, maintained at Τ . Thus the gas temperature tends toward, but does not attain a uniform distribution (3). The steady state populationinlevel a is established by the balance between the pumping rate and the combined loss by relaxation and reaction. The efficiency of any LIS will be determined by the selectivity and intensity of pumping (β — a) and limited by v(i) v(3) transfer efficiencies among the congeners, as well as by ν —• R, Τ pro cesses which raise the operating temperature.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011

Classification of Adduct Production To select suitable systems for isotope separations based on the above relations a broad range of criteria must be considered, but the principal step is to find conditions under which laser radiation does augment the rate of adduct production. In many cases the apparently simple reaction indicated in Eq. (1) proves to follow a much more complex mechanism. Toward this end it is useful to compile proposed reactions according to the magnitudes of their activation energies (E ). Values of (30-40) kcal/mole are typical for the additionofmineral acids, water and hydro gen sulfide to olefins (4); these are the inverse of (α, β) eliminations. The additionofmineral acids or water to aldehydes and ketones require (12-18) kcal/mole. Also the additionofHBr and HI to conjugated dienes are in this group. Lewis acid-base adducts and hydrogen bonded com plexes are generated with little or no activation energy (0-5 kcal/mole). A small sub-s et of the first group which is the largest and the most extensively investigated, is the addition of HF to H C = C F and other variously substituted fluoroethylenes, illustrated in Figure 3. Many lower activation energy pairs in this category are cited by Marling (5). Numerical values for the pertinent energy parameters for the HF/ethylene additions are listed in Table I. The estimated lowest activation energy is that for H F / C F ^ . Indeed, one may anticipate that excitation of H F would accelerate its addition across the double bondinview of the ob served vibrationally excited HF generated from mixtures of C H 3 and CF^ radicals. However, it appears (6) that of the 72 kcal/mole which the a

2

2

2

level], about 30 kcal/mole are statistically distributed prior to H F * elimination. Hence the application of detailed balance suggest that C H F ^ excitation may be just as essential as that of the H F to promote significant enhancement of the rate. Indeed we reached that conclusion after obtaining negative results by simply exposing mixtures of HF and various olefins to a pulsed HF laser with the cell at room temperature (Table H). Thus, the conditions outlinedinthe preceeding section are necessary but not sufficient, particularly for combinations which consist of a sizeable polyatomic acceptor and a strongly bonded intruder (HF; 2

n

n

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

11.

BAUER

Proposed

H/D/T

TABLE I. HF/Ethylene

x

-1

kcal mol

57

11

31

46

-93

62

24

33

38

CH FCH F

89.6

62

10

28

52

CH CF

99

69

27

30

42

92

71

-28

21

43

91

69

-26

22

43

94

72

-40

22

31

2

2

3

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011

2

e

kcal mol

kcal mol

88

2

3

Ε

kcal mol * kcal mol

CH CH F CH CHF

Values of Parameters for Figure 3

D(C-C)

Adduct 3

157

Separations

3

CH FCF 2

3

CHF CHF 2

CHF CF 2

2

3

T A B L E II. Attempts to Augment HF Addition HF laser operation: pulsed, 2/s; & 150 mj/p ο

p(HF)/p(substrate):

3/1 to 1/3; 10 pulses

P(HF) = 0.5 torr; cell temp f\

/TTT.v

c

n

±

^

Γ

25°

^

C

(low

^

T)

Mass spectral analysis for products Compounds tested, no reaction with H F * C F 2

<*,h); C H = C F (H); H ^ - C H - C O O E t (h)

4

2

2

C H - c p d (h); C H -allene (ft); H CC=CH (*) 5

6

3

6

3

c - C H O (h); c - C H 0 4

g

4

6

2

(h); COC^ (*,h) 2

SiH (h); C D (h); HC£CF (h) 4

HF

4

2

reacts with the following, on mixing

;

Ο H C=CO 1

H C=CH* OCH 0

Q

\ Ο

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

158

SEPARATION OF HYDROGEN ISOTOPES

H 0 ; CHgOH). Then vibrational activation of the acceptor is probably essential for significant augmentation of the rate of addition across the double bond. An interesting combination of reagents which is related to, but is not strictly a member of, the first category involves an (a, a) elimi nation of DCS. from OC&C F . This is diagramed in Figure 4 and conceived as a by-pass attached to a polyfluoroethylene production plant (7). There are relatively few members of the second group of addition reactions. Also only sparse data are available on their thermochemistry and kinetic behavior. We looked for combinations which fitted the following criteria as closely as possible: (a) One or both of the combining reagents (if one uses two irradiation frequencies) should have strong ir absorption bands in the region of currently developed, high powered lasers. (b) The thermal recombination rate should be limited by an activation energy which equals the equivalent of a few photons of the#irradiating frequency, such that addition of DX* would be favored strongly over HX. (c) The adduct can be separated from the mixture rapidly enough to avoid H/D exchange with the residual X H . (d) The system is scalable for large throughput. This implies that the H/D carrier can be readily equilibrated with a natural source of deuterium (natural gas or water). We found several combinations which satisfy criteria (a) and (b) and thus constitute good candidates for laser augmented rate trials, but as yet no such tests have been made. The equilibrium constants at room temper ature for the addition of HF to tetrahydrofurane [C^HgO] is substantial (1.1 χ 10 , M " ) ; addition to dimethylformamide [Me NCHO] is even larger, 4. 6 χ 10** M * ; however, no kinetic data are available. It has been reported that perfluorocyclobutanon [ C 4 F 4 O ] readily adds H F but only qualitative observations have been mde. We selected for our initial experiments the production of gaseous hydrates of perfluoroacetone and trifluoroacetaldehyde. Their infrared spectra are shown in Figures 5 and 6, respectively. These compounds do satisfy criterion (a). Several rates of hydration and of decomposition of the adducts were measured (8) to check whether these comply with criterion (b). 2

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011

2

3

1

2

-

For:

H

F.C-CHO + H O

* -,

> FC-CH(OH)

Q

a

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

BAUER

Proposed

H/D/T

Separations

H3C+CF3 ^ = = : Radicals by

generated

Photolysis F

3

of

C ^

H Ç = ÇF 2

-HF(4) 2

H--F D(C-C)

— HF(3)

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011

—

HF(2)

-HF(I)

H C = CF + 2

ΙΛΠ

HF(0)

-r

L

H3C-CF3

Figure 3.

2

Energy level diagram for pairs

HF/ethylene

ν selected

to d e c o m p o s e

D C I C F 2 but not H C I C F 2

HF—η

CHCI -4 3

[CDCI j^ 3

PHOTOLYTIC

C F

CELL

2

4

STRIPPER

Figure 4. Flow chart for selective laser photolysis of DCICF to generate DCl from natural abundance of D in chloroform, incorporated in a perfiuoroethylene plant. Based on the total annual C>F production (USA), an optimum yield of 400 tons of D 0 could be developed. Recirculation of CF F F , and F to generate larger supplies of chloroform (via HCl) would be energy intensive. 2

h

2

2

h

lï}

12

23

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

SEPARATION OF HYDROGEN ISOTOPES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011

fui W

Figure 5.

IR transmission spectra of perfiuoroacetone, its mono-and hemihy drat es

6

7

8

9

10

12

15

WAVELENGTH

Figure 6.

IR transmission spectra of trifluoroacetaldehyde and its monohydrate

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

11.

BAUER

k k

a d

Proposed

2

3

S

1

Ε (77°C) = 6.23 χ 10~

s"

1

3

(137°C) = 3.75 χ 10~

s"

1

3

a

1

4

(F C) CO

k

161

Separations

(75°C) - 1.3 χ 10 mole c m

For:

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011

H/D/T

2

+

Ε

H 0

a d

= 19 ± 3 kcal/mole = 29.2 ± 1 kcal/mole

(F C) C(OH)

2

3

(25°C) = 1.5 χ 10 mole c m s 3

1

3

2

2

1

Measurement of laser augmented rates will be made after our low pressure intracavity reactor (9) has been modified to minimize adsorp tion of these reagents on the cell walls. We anticipate that the rates of adduct production in the third category, characterized by very low activation energies, would be slightly if at all augmented by laser irradiation of the precursors but the "perturbed equilibrium" composition of the adduct (at steady state, Figure 2) should be reduced upon its irradiation. Conceptually this can be utilized for an H/D separation in the following scheme, wherein the particular Lewis acid and base shown are examples selected from a large class of possible combinations (1) :

Β Me

k < " >

+ MeNH ο

Δ

GaEt + MeNH 3 2 0

κ

<

t

Me B:NH Me S

> k 2 2

Δ

Et Ga NH Me 3 2 :

ΔΗ°

=-18.2 kcal/mole

oUU

= -19.8

Whereas both k^ and ko are presumed to be large (?^10 mole c m s and temperature insensitive, the reverse steps are much slower since and k have Arrhenius exponential factors with (-18.2/RT) and (-19.9/RT), respectively. Thus, were an equilibrium mixture of methylamine, the two Lewis acids, and the corresponding adducts in equilibrium, exposed to radiation which is selectively absorbed by EtgGa:NHDMe, the deuterium would be selectively trapped as MegBHDMe, possibly for a sufficient time to achieve separation. Other means for trapping laser shifted concentrations of dissociation products are conceivable. For example, the irradiation of matrix isolated samples followed by adjusted diffusion rates of the products (careful 12

2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

1

3

162

SEPARATION O F HYDROGEN ISOTOPES

temperature control) but these applications appear of little practical utility. Abstract Thermodynamic and kinetic analyses of adduct production:

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch011

indicate how the steady state composition and rates (forward vs reverse) can be perturbed by absorbable radiation which generates a "spiked" steady state population distribution for one of the species. Three classes of reactions were considered, wherein E ranges from (30-40) kcal/mole; (12-16) kcal/mole; and (0-5) kcal/mole. These are of particular interest for H/D/T separation, in that one of the adducts can be water, a mineral acid (which rapidly equilibrates with water) or hydrogen. Our analysis and preliminary experiments indicate that the intermediate case ( E ~ 15 kcal/mole) is particularly attractive for LIS. a

a

Literature Cited 1.

2. 3. 4.

5. 6. 7. 8.

9.

Drago, R. S., Vogel, G. C. and Needham, T . E., J. Am. Chem. Soc (1971) 93, 6014, have compiled extensive tables of enthalpies for adduct formation. Levine, R. D. and Manz, J., J. Chem. Phys. (1975) 63, 4280. Shaub, W. and Bauer, S. Η . , Int. J. Chem. Kin. (1975) 7, 509. Tschuikow-Roux, E . and Maltman, Κ. A., Int. J. Chem. Kin. (1975) 7, 363, have compiled extensive tables for the inverse processes. Marling, J. Β., Joint Conference CIC and ACS, Montreal, 1977, Physical Chemistry Division, Abst. 081. Clough, P. N., Polanyi, J. C. and Tagudu, R. Τ., Can. J. Chem. (1970) 48, 2919. Data from Petrochemical Handbood, 1976. Bell, R. P. and McDougall, Α. Ο . , Trans. Farad. Soc. (1960) 56, 1285 give useful data on hydration equilibria of aldehydes and ketones. My sincere thanks to Dr. Kuei-Ru Chien for performing measure ments on the perfluoro compounds. Lory, E . R . , Manuccia, T . and Bauer, S. H., J. Phys. Chem. (1975) 79, 545.

RECEIVED

August 31, 1977

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

12 Operating Experience with the Tritium and Hydrogen Extraction Plant at the Laue—Langevin Institute PH.

PAUTROT

Institute Max Von Laue-Paul Langevin, 38000, Grenoble, France M. DAMIANI

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch012

Sulzer Brothers L t d . , Dept. 6162, CH-8401 Winterthur, Switzerland

The I n s t i t u t e Max Von LAUE - P a u l LANGEVIN in GRENOBLE is a s o c i e t y founded in 1967 by a government agreement between FRANCE and GERMANY. In 1974 GREAT BRITAIN a l s o j o i n e d the I n s t i t u t e . The I n s t i t u t e o p e r a t e s the High F l u x R e a c t o r whose purpose is a l a r g e programme of n u c l e a r p h y s i c s r e s e a r c h u s i n g the n e u t r o n s produced by the r e a c t o r . T h i s High F l u x R e a c t o r has a t h e r m a l performance of 57 MW w i t h a s i n g l e heavy water c o o l e d and moderated circuit. Heavy water h o l d - u p is about 40 m . The mean f l u x of t h e r m a l n e u t r o n s in the heavy water is e q u a l t o 1,8 . 10 n / c m s e c , which l e a d s t o f o r m a t i o n of tritium w i t h a s a t u r a t i o n activity of more than 80 C u r i e per litre ( a f t e r 10 y e a r s about 30 Curie/1). T h i s is s i m i l a r t o the v a l u e e x p e c t e d in the moderator circuit of the CANDU type r e a c t o r . For s a f e t y r e a s o n s , tritium c o n c e n t r a t i o n in heavy water s h o u l d not exceed 3 C u r i e per litre and in o r d e r t o m a i n t a i n moderator efficiency of heavy w a t e r , its fractional c o n c e n t r a t i o n s h o u l d not be lower than 99,6 mol %. The installation fulfilling the mentioned d u t i e s was built by CCM/SULZER* in c l o s e c o - o p e r a t i o n w i t h the C.E.A. (Commissariat ā l'Energie A t o m i q u e ) . SULZER a l r e a d y had e x p e r i e n c e in the low temperature distillation of hydrogen from a s m a l l heavy water p l a n t in EMS S w i t z e r l a n d . The installation a t the LAUE-LANGEVIN I n s t i t u t e on the Grenoble N u c l e a r C e n t r e site is the first known p l a n t in o p e r a t i o n f o r the s i m u l t a n e o u s e x t r a c t i o n of hydrogen and tritium from heavy w a t e r . 3

14

*

is L i c e n s e e process

of

©

2

a patent

owned by the CEA for t h i s

0-8412-0420-9/78/47-068-163$05.00/0

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

164

SEPARATION OF HYDROGEN ISOTOPES

Design Data. - T r i t i u m c o n c e n t r a t i o n of heavy water has t o be s t a b i l i z e d a t 1,7 C i / 1 by an annual e x t r a c t i o n of 160 000 C u r i e , e q u i v a l e n t t o about 60 N l of pure t r i t i u m . - C o n t e n t of heavy water has t o be m a i n t a i n e d a t 99,6 mol % by an a n n u a l e x t r a c t i o n of 160 l i t r e s of l i g h t water, e q u i v a l e n t t o about 2 00 Nm of hydrogen. 3

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch012

P r i n c i p l e of O p e r a t i o n . F i g u r e 1 shows the mass f l o w s w i t h the c o r r e s p o n d i n g c o n t e n t s a t normal opera t i o n c o n d i t i o n s in 1976, and f u r t h e r m o r e , t h a t the p l a n t is made up of two main p a r t s : 1.

C a t a l y t i c exchange between heavy water vapour and d e u t e r i u m gas a t 200°C and about 1,2 b a r , which a l l o w s the mass t r a n s f e r of hydrogen and t r i t i u m from heavy water t o d e u t e r i u m t o r e a c h e q u i l i b r i u m a c c o r d i n g t o the f o l l o w i n g r e a c t i o n s :

HDO

+ D2

D2O

+

HD

2.

Low temperature r e c t i f i c a t i o n of the hydrogen i s o t o p e s HD/D2/DT/T2 a t about 1,5 bar in two columns w i t h e x t r a c t i o n of HD a t the top of the f i r s t column and pure t r i t i u m a t the bottom of the second column. The f l o w s h e e t F i g . 2 shows t h a t the heavy water coming from the r e a c t o r is e v a p o r a t e d , s u p e r h e a t e d , and mixed w i t h the d e u t e r i u m t o pass through the c a t a l y t i c r e a c t o r where the i s o t o p i c exchange r e a c t i o n s o c c u r ; it is then recondensed t o be s e p a r a t e d from the d e u t e r i u m and t r a n s f e r r e d t o the second and then t o the t h i r d s t a g e of the c a t a l y t i c exchange. The d e u t e r i u m coming out of the c a t a l y t i c exchange is d r i e d and p u r i f i e d b e f o r e b e i n g s e n t i n t o a d i s t i l l a t i o n column c o n t a i n i n g S u l z e r p a c k i n g s . The p a r t i a l l y t r i t i u m and hydrogen s t r i p p e d d e u t e r i u m coming out of the column r e t u r n s t o the c a t a l y t i c exchange t h r o u g h an e x p a n s i o n v e s s e l . The d e u t e r i u m h y d r i d e drawn o f f w i t h a c o n t e n t of about 80 mol % a t the head is s e n t to a burner. The t r i t i a t e d d e u t e r i u m a t the f o o t of the column is s e n t t o a second column w i t h d i x o n r i n g packing. In the m i d d l e of t h i s column, DT is w i t h drawn in a tank t o g e t t r i t i u m a c c o r d i n g t o e q u i l i b r i u m r e a c t i o n 2 DT
In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

D2

HDO +

2

D

+

DTO

= ^ ·

XHDO

10"'

+

D 0

HYDROGEN

TRITIUM

DEUTERIUM

2

+

2

Nm*.h Nr^.h-

D 0

45 45

EXCHANGE

FLOW OW

CATALYTIC

- 1.34.

XDTO

;

Ci I

2.15

ACTIVITY ;

2

D 0

21 I h "

;

FLOW

INPUT

1

2

D 0

HD

DT

Ι J

M<^y COMPRESSOR

(f^.

D

T

=

XHO=

X

XHD^9

XHO=0.01

11

0,69 1

0" 3

6

10-

10 "

XQJ ΖΟ,Μ 10 '

«02=0,996

2

5,6.ΙΟ

10-

APPOINT D =2Nm /we*k

XH

3

Ci I -

X T O =. 0.3S

ACTIVITY ; 0.56

OUTPUT .

Figure 1

165 I h"'

COLUMN

θ 2

N°1

=0,8

=a2

CIRCULATOR

XHD

χ

=*0

6

10-

X Q T = 1β0.10"»

XQT

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch012

T

X 2 = 0,9β

~ 2 Ν I /week

COLUMN N°2

STORAGE -••"j DP AWING OFF OF TRITIUM

S*

a

H

C*l

-* ο

ft

> > 3

ο

> Ο

Η

Η

» ο

>

SEPARATION O F HYDROGEN ISOTOPES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch012

166

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

12.

PAUTROT AND DAMiANi

Tritium

and

Hydrogen

Extraction

Plant

167

R e f r i g e r a t i o n power r e q u i r e d t o l i q u i f y d e u t e r i u m is o b t a i n e d by an a u x i l i a r y h e l i u m c i r c u i t . Helium is compressed t o 15 bar and then expanded t o 4 bar through a gas expansion t u r b i n e w i t h o i l b e a r i n g s .

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch012

P l a n t S a f e t y P r e c a u t i o n s . The r i s k s of e x p l o s i o n and r a d i o a c t i v e c o n t a m i n a t i o n formed the b a s i c c r i t e r i a f o r the d e s i g n , c o n s t r u c t i o n and o p e r a t i o n of the installation. Very s t r i c t measures were adopted: 1.

L o c a t i o n of the i n s t a l l a t i o n o u t s i d e of the r e a c t o r but n o t in the open a i r . The e x t e r n a l w a l l s of the b u i l d i n g are blowable t o an open a r e a t o l i m i t e x p l o s i o n damage.

2.

C o n s t r u c t i o n of the p l a n t a c c o r d i n g t o standards".

3.

C o n s t a n t v e n t i l a t i o n of the p r e m i s e s .

4.

C o n s t a n t t r i t i u m and d e u t e r i u m c o n t r o l of the a t m o s p h e r i c a i r of the p r e m i s e s .

5.

Oxygen c o n t e n t in d e u t e r i u m c i r c u i t is permanently r e g i s t e r e d a t the i n l e t t o the d i s t i l l a t i o n column in o r d e r t o have an i n d i c a t i o n about the q u a n t i t y of ozone which c o u l d be formed by β - r a d i a t i o n of oxygen. Ozone in l i q u i d or s o l i d phase may decom pose in an e x p l o s i v e manner.

6.

In case of a l a r m from d e u t e r i u m o r t r i t i u m l e a k a g e , the p l a n t is stopped and i s o l a t e d in f i v e p a r t s . Each of t h e s e can be e v a c u a t e d and r i n s e d auto m a t i c a l l y by n i t r o g e n b e f o r e r e p a i r works s t a r t .

7.

A two stage membrane compressor can draw o f f the d e u t e r i u m hold-up and f i l l i n t o b o t t l e s under 200 bar.

8.

Some main alarms and a main s w i t c h are r e p e a t e d in the main c o n t r o l p a n e l of the r e a c t o r .

"hydrogen

S t a r t - U p of the P l a n t and O p e r a t i n g E x p e r i e n c e The f i r s t t e s t s w i t h hydrogen began in August 1971. S t a r t - u p w i t h d e u t e r i u m and n o n t r i t i a t e d heavy water f o l l o w e d q u i c k l y and s e p a r a t i o n performances between hydrogen and d e u t e r i u m were c o n t r o l l e d . I t was o n l y in August 1972 t h a t the f i r s t i n t r o d u c t i o n of t r i t i a t e d heavy water from the High F l u x R e a c t o r was t r e a t e d .

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch012

168

SEPARATION OF HYDROGEN ISOTOPES

By J u l y 19 73 the a c c u m u l a t i o n of t r i t i u m o n l y r e a c h e d 5 000 C u r i e . By the end of 1976 t h e r e was a t r i t i u m hold-up of 220 000 C u r i e in the p l a n t and 230 000 l i t r e s of heavy water had been t r e a t e d . About 85 000 C u r i e of pure t r i t i u m w i t h an average molar c o n t e n t of 98% had been e x t r a c t e d in gaseous phase. S i n c e t r i t i u m p r o d u c t i o n of the r e a c t o r is about 35 % lower and the a d m i s s i b l e t r i t i u m c o n c e n t r a t i o n is now about 10 % h i g h e r compared w i t h d e s i g n d a t a , and f u r t h e r m o r e p l a n t performance c o u l d be i n c r e a s e d by about 25 % by v a r i a t i o n of the r a t i o between heavy water and d e u t e r i u m streams in the c a t a l y t i c exchange, the p l a n t is a b l e t o f u l f i l r e a c t o r r e q u i r e m e n t s in o n l y f i v e months per y e a r . That means p l a n t o v e r c a p a c i t y a l l o w s the treatment of t r i t i a t e d water from other r e a c t o r s . The I n s t i t u t e has a l r e a d y t r e a t e d about 16 000 1 of heavy water w i t h a c o n c e n t r a t i o n of about 6 C u r i e per l i t r e f o r a F r e n c h c l i e n t . A t p r e s e n t , p l a n t performance r e a c h e s an e x t r a c t i o n of 240 000 C u r i e per y e a r s t a r t i n g from a f e e d c o n c e n t r a t i o n of 2 C u r i e per l i t r e . Tritium analysis made on the r e c t i f i c a t i o n columns showed t h a t about 400 t h e o r e t i c a l s t a g e s are i n s t a l l e d . S i n c e leakage of l i g h t water i n t o the heavy water c i r c u i t is s m a l l e r than presumed, the heavy water molar c o n t e n t has n o t reached 99,6 % up t o now, and conseq u e n t l y l i g h t water e x t r a c t i o n has been s m a l l e r than 160 l i t r e s per y e a r . D i f f i c u l t i e s Encountered

During

Operation

C o n c e r n i n g the p r i n c i p a l r u n n i n g of t h i s p r o c e s s c a t a l y t i c exchange w i t h d e u t e r i u m r e c t i f i c a t i o n - no p a r t i c u l a r d i f f i c u l t i e s have been encountered. The main d i f f i c u l t i e s which o c c u r r e d d u r i n g opera t i o n were: Two t e c h n o l o g i c a l i n c i d e n t s on the h e l i u m c i r c u i t , the major b e i n g an a c c i d e n t a l d i s p l a c e m e n t of the m o l e c u l a r s i e v e , w i t h subsequent d i s t r i b u t i o n of i t s c o n s t i t u e n t s through the whole h e l i u m c i r c u i t . T h i s r e q u i r e d complete c l e a n i n g of the h e l i u m c i r c u i t , p a r t i c u l a r l y of the heat exchangers and caused a p l a n t shutdown of s e v e r a l months. The o t h e r i n c i d e n t was the p r e s e n c e of mud and o r g a n i c a l g a e in the r i v e r water, which c l o g g e d the h e l i u m water c o o l e r . C h l o r i n a t i o n in the c o o l i n g water k i l l e d o f f the a l g a e , but r e s u l t e d in c o r r o s i o n

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

PAUTROT AND D A M i A N i

Tritium

and

Hydrogen

Extraction

Plant

169

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch012

of the welds on the carbon s t e e l h e l i u m c o o l e r s , so t h a t leakages of h e l i u m and i n g r e s s of water p r e vented the r e q u i r e d r e f r i g e r a t i o n power b e i n g reached. F i n a l l y , new s t a i n l e s s s t e e l c o o l e r s and a c l o s e d c o o l i n g water c i r c u i t were i n s t a l l e d t o get s a t i s f a c t o r y c o n d i t i o n s . The presence of alumina p a r t i c l e s in the heavy water a r r i v i n g from the r e a c t o r s e r v e d as s u p p o r t f o r a c t i v a t i o n p r o d u c t s - m a i n l y c o b a l t and chrome - and r e s u l t e d in h i g h a c t i v i t y in the e n t r a n c e of the c a t a l y t i c exchange. The alumina p a r t i c l e s have a s i z e of 0,01 t o 0, lM and pass through e x i s t i n g 0,22 ΛΑ f i l t e r . To p r e v e n t the presence of t h e s e a c t i v a t e d alumina p a r t i c l e s in t r i t i u m e x t r a c t i o n p l a n t , a supplementary s e p a r a t i o n p l a n t has been i n s t a l l e d in the r e a c t o r . T h i s p l a n t was put i n t o o p e r a t i o n s a t i s f a c t o r i l y some months ago. F i s s u r e phenomena have appeared in the p i p i n g work c o n t a i n i n g heavy water vapor a t the e n t r a n c e in the f i r s t stage of c a t a l y t i c exchange. The o r i g i n of t h e s e c o r r o s i o n s is not e x a c t l y known. Different e x p e r t s t h i n k t h a t these c o r r o s i o n s are due t o the a c t i o n of m e c h a n i c a l f o r c e s , caused by v i b r a t i o n and t h e r m a l e x p a n s i o n , a c t i n g in c o n j u n c t i o n w i t h a c o r r o s i v e agent p r e s e n t in the heavy water. This agent may be c h l o r i n e . However, t h i s f a c t is not yet proved. At the b e g i n n i n g n i t r o g e n was used as c o v e r gas in the r e a c t o r . N i t r o g e n d i s s o l v e d in heavy water passed even through a c t i v a t e d c h a r c o a l a d s o r b e r and was c o n c e n t r a t e d in the column e v a p o r a t o r r e d u c i n g d e u t e r i u m vapor l o a d due t o d e t e r i o r a t i o n in heat transfer. Furthermore, a pH v a l u e of about 1 was noted in the heavy water l e a v i n g the b u r n e r , caused by n i t r i c a c i d formed due t o the presence of n i t r o gen coming from the n i t r o g e n a d s o r b e r d u r i n g i t s regeneration cycle. These i n c o n v e n i e n c e s were r e s o l v e d by r e p l a c i n g n i t r o g e n by h e l i u m as r e a c t o r cover gas. D u r i n g commissioning, d i f f e r e n t r e g u l a t i o n systems c o u l d be improved but none of t h e s e improvements r e s u l t e d from major problems. A f t e r about 23 000 hours of o p e r a t i o n of the p l a n t , the e f f i c i e n c y of c a t a l y s t s has s t i l l n o t d e c r e a s e d .

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch012

170

SEPARATION OF HYDROGEN ISOTOPES

In t h e f o l l o w i n g I w i l l i n d i c a t e some o p e r a t i o n conditions : P l a n t o p e r a t i o n is semiautomatic. P e r s o n n e l a r e r e q u i r e d t o c a r r y o u t v a r i o u s adjustments and mainten ance concerned w i t h t h e movement of heavy water and r e g e n e r a t i o n of t h e a d s o r b e r s and c a r r y i n g o u t v a r i o u s analyses. D u r i n g working h o u r s , o p e r a t i o n is ensured by f o u r p e r s o n s ; o u t s i d e working hours r e q u i r e d super v i s i o n is t r a n s f e r r e d t o t h e r e a c t o r main c o n t r o l room. A t a s t o p , p l a n t goes a u t o m a t i c a l l y i n t o a s a f e t y p o s i tion. O p e r a t i o n of t h e p l a n t is c o n t i n u o u s , s t a r t up l a s t s about 12 hours and another 3 o r 4 days a r e r e q u i r e d t o reach steady s t a t e c o n d i t i o n s before t r e a t i n g t r i t i a t e d heavy water. The main consumptions a r e : - Electricity - C o o l i n g water - Deuterium - Compressed

air

800 KW 25 m /h 2 Nm /week a t todays conditions 50 Nm /h 3

3

3

Hold-ups : 1 000 l i t r e s of 85 Nm of 200 000 C i of 35 Nm of 3

3

Bibliography:

heavy water deuterium tritium helium

(1) PAUTROT, P h . , ARNAULD, J.P. American N u c l e a r S o c i e t y , (1975) V o l 20, 202-205 (2) DAMIANI, M . , GETRAUD, R., SENN, Α., S u l z e r T e c h . Revue, (1972) V o l 4

RECEIVED August 22, 1977

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

13 Catalytic Detritiation of Water M. L. ROGERS, P. H . LAMBERGER, R. E . ELLIS, and T. K. MILLS

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch013

Monsanto Research Corp., Mound Laboratory*, Miamisburg, O H 45342

Mound L a b o r a t o r y has, d u r i n g t h e p a s t f o u r y e a r s , been a c t i v e l y i n v o l v e d i n the development o f methods t o c o n t a i n and c o n t r o l t r i t i u m d u r i n g i t s p r o c e s s i n g and t o r e c o v e r i t from waste s t r e a m s . I n i t i a l b e n c h - s c a l e r e s e a r c h was d i r e c t e d m a i n l y toward removal o f t r i t i u m from gaseous e f f l u e n t s t r e a m s . The gaseous e f f l u e n t i n v e s t i g a t i o n has p r o g r e s s e d t h r o u g h t h e development s t a g e and has been implemented i n r o u t i n e o p e r a t i o n s . A t e s t l a b o r a t o r y embodying many o f t h e r e s u l t s o f t h e r e s e a r c h phase has been d e s i g n e d and i t s c o n s t r u c t i o n has been completed. As t h e program a t Mound L a b o r a t o r y has p r o g r e s s e d , the scope o f t h e e f f o r t has been expanded t o i n c l u d e r e s e a r c h c o n c e r n e d w i t h h a n d l i n g t r i t i a t e d l i q u i d s as well. A program i s p r e s e n t l y under way t o i n v e s t i g a t e the d e t r i t i a t i o n o f aqueous wastes u s i n g the Combined E l e c t r o l y s i s C a t a l y t i c Exchange (CECE) p r o c e s s , a p r o c e s s v e r y s i m i l a r t o the CECE-TRP p r o c e s s d i s c u s s e d a t t h i s symposium by Dr. Hammerli. As i n the CECE-TRP p r o c e s s , the key t o o u r CECE p r o c e s s i s a p r e c i o u s m e t a l h y d r o p h o b i c c a t a l y s t d e v e l o p e d by Dr. John B u t l e r a t Chalk R i v e r . Dr. B u t l e r , who d i s c u s s e d t h i s t y p e o f c a t a l y s t e a r l i e r i n the symposium, made t h e c a t a l y s t f o r our system. Catalytic

Exchange

The c a t a l y t i c c e n t e r s around two arranged i n s e r i e s and lower s e c t i o n s

exchange s e c t i o n o f the p r o c e s s c a t a l y s t - p a c k e d columns, which a r e t o o p e r a t e as i f they were t h e upper o f a s i n g l e column. (See F i g u r e 1.)

*Mound L a b o r a t o r y is o p e r a t e d by Monsanto R e s e a r c h C o r p o r a t i o n f o r t h e U.S. Energy R e s e a r c h and Development A d m i n i s t r a t i o n under C o n t r a c t No. EY-76-C-04-0053. ©

0-8412-0420-9/78/47-068-171$05.00/0

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

SEPARATION

172

O F HYDROGEN ISOTOPES

Each column i s 7.5 m i n l e n g t h and has an i n s i d e diame t e r o f 2.5 cm, which r e s u l t s i n a s u p e r f i c i a l c r o s s s e c t i o n a l a r e a o f 5 cm and a g r o s s column volume o f 3800 cm . The p a c k i n g i n each column c o n s i s t s o f 4300 g o f 0.6-cm d i a m e t e r c a t a l y s t s p h e r e s . L i q u i d r e d i s t r i b u t i o n r i n g s a r e p l a c e d a t 45-cm i n t e r v a l s t h r o u g h out the l e n g t h o f each column t o l i m i t c h a n n e l i n g i n the packed s e c t i o n s . In o p e r a t i o n , the l i q u i d t o be d e t r i t i a t e d i s s u p p l i e d a t a p p r o x i m a t e l y 5 cm /min. I t i s combined w i t h the l i q u i d stream e x i t i n g the upper column, and i n t r o d u c e d a t the t o p o f the lower column. The 10 cm / min l i q u i d stream from the bottom o f the lower column i s r o u t e d t o the e l e c t r o l y s i s s e c t i o n o f the p r o c e s s where i t i s used as f e e d . C u r r e n t l y , the l i q u i d stream e n t e r i n g a t the top o f the upper column i s made up o f d i s t i l l e d water, s u p p l i e d from o u t s i d e the p r o c e s s . U l t i m a t e l y , however, t h i s stream i s e x p e c t e d t o be a r e f l u x stream, p r o v i d e d by a recombiner o r f u e l c e l l which would i n t u r n be f e d by the hydrogen p r o d u c t from the upper column. The hydrogen stream from t h e e l e c t r o l y s i s s e c t i o n i s f e d t o the bottom o f the lower column and t h e n i s r o u t e d t o t h e bottom o f the upper column. Upon e x i t i n g t h e upper column, i t i s c u r r e n t l y v e n t e d t o the a t mosphere t h r o u g h a s t a c k . As mentioned p r e v i o u s l y , however, i t i s a n t i c i p a t e d t h a t t h i s stream w i l l l a t e r be f e d t o e i t h e r a f u e l c e l l o r a recombiner t o p r o v i d e r e f l u x t o the p r o c e s s and a d e t r i t i a t e d l i q u i d p r o d u c t . C o n t r o l o f the c a t a l y t i c exchange s e c t i o n o f the p r o c e s s c o n s i s t s o f f i v e l o o p s , s e r v i c e d by a s i n g l e microprocessor. In each o f the l o o p s t h e c o n t r o l element i s a m e t e r i n g v a l v e , d r i v e n by a s t e p p i n g motor. F o r the gas stream p a s s i n g through the columns, the s e n s i n g element i s a t u r b i n e meter l o c a t e d downstream from the columns. The two l i q u i d f e e d s t o the p r o c e s s are sensed by h o t - w i r e anemometers, and the l e v e l s m a i n t a i n e d i n the bottom o f each column a r e m o n i t o r e d by c a p a c i t i v e l e v e l s e n s o r s . A l t h o u g h not used i n the c o n t r o l o f the p r o c e s s , t r i t i u m c o n c e n t r a t i o n s a r e m o n i t o r e d a t v a r i o u s p o i n t s by l i q u i d s c i n t i l l a t i o n c o u n t e r s f o r l i q u i d streams and i o n chambers f o r gas streams. 2

3

3

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch013

3

Electrolysis The p r i n c i p a l items o f equipment i n the e l e c t r o l y s i s s e c t i o n are f o u r G e n e r a l E l e c t r i c e l e c t r o l y s i s stacks. (See F i g u r e 2.) Each s t a c k c o n s i s t s o f e i g h t c e l l s , each o f which has an a c t i v e a r e a o f 46.45 cm .

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

13.

ROGERS

E T

Catalytic

AL.

Detritiation

of

173

Water

DEPLETED H TO STACK 2

DISTILLED WATER

ENRICHED H FROM ELECTROLYSIS

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch013

2

TRITIATED LIQUID FEED

ENRICHED LIQUID T O ELECTROLYSIS

Figure 1.

Catalytic exchange section

PHASE SEPARATOR

ENRICHED LIQUID _ FROM CATALYTIC EXCHANGE

OXYGEN TO EX HAUST

Ho TO PHASE SEPARATOR

ft ι

I I ι

cb

-

DEIONIZER

\ |ELECTROLYSIS| CELLS

Figure 2. Electrolysis section

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

CATALYTIC EXCHANGE

174

SEPARATION O F

HYDROGEN

ISOTOPES

C u r r e n t d e n s i t y i s 1.076 amp/cm f o r the maximum r a t e d c u r r e n t o f 50 amps. Rated s t a c k v o l t a g e i s 16.8 VDC. O p e r a t i n g a t t h e s e c o n d i t i o n s , each s t a c k e l e c t r o l y z e s 2.45 cm water/min t o produce a p p r o x i m a t e l y 3000 cm hydrogen/min and 1500 cm oxygen/min. The maximum p r e s s u r e i s 100 p s i g and the upper l i m i t temperature i s 66°C. Proper s t a c k o p e r a t i o n r e q u i r e s t h a t f e e d water r e s i s t i v i t y be m a i n t a i n e d a t g r e a t e r than 500,000 ohmcm, and t h a t a water c i r c u l a t i o n r a t e o f a p p r o x i m a t e l y 400 cm /min p e r 8 - c e l l s t a c k be m a i n t a i n e d . Feed t o the e l e c t r o l y s i s s e c t i o n i s s u p p l i e d from a f e e d tank, which a l s o p r o v i d e s r e c i r c u l a t i o n capacity. From the f e e d tank, the water i s pumped through a d e i o n i z e r , and then t o the c e l l s . From the c e l l s , the hydrogen stream p a s s e s through a c o o l e r and a phase s e p a r a t o r , and i s r e t u r n e d t o the c a t a l y t i c exchange s e c t i o n . The oxygen stream, a f t e r b e i n g r o u t e d through a c o o l e r and a phase s e p a r a t o r , i s c u r r e n t l y s e n t t o the a i r d e t r i t i a t i o n system f o r p u r i f i c a t i o n and d i s p o s a l . I t i s a n t i c i p a t e d , however, t h a t t h i s stream w i l l u l t i m a t e l y be f e d t o a recombiner o r a f u e l c e l l s u p p l y i n g r e f l u x t o the c a t a l y t i c exchange columns. The water removed from both the oxygen and hydrogen streams i n the phase s e p a r a t o r s i s mixed w i t h the f r e s h f e e d upstream from the d e i o n i z e r , and r e c i r c u l a t e d through the system. 3

3

3

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch013

3

Preliminary

Results

The CECE system was r e c e n t l y o p e r a t e d c o n t i n u o u s l y f o r a p e r i o d o f a p p r o x i m a t e l y 48 h r . Water was f e d both t o the top o f the f i r s t column and i n between the columns, each a t a r a t e o f 3 cm /min. The top f e e d had a c o n c e n t r a t i o n o f 0.028 y C i / l i t e r w h i l e the mid-column f e e d , which can be c o n s i d e r e d the "hot" f e e d , had a t r i t i u m c o n c e n t r a t i o n o f 304 y C i / l i t e r . The t o t a l e l e c t r o l y s i s stream, 7.2 l i t e r s / m i n , was r e t u r n e d t o the bottom o f the second column. The d e p l e t e d hydrogen stream e x i t s the system a t the top o f t h e f i r s t column, where a p o r t i o n o f t h i s stream i s o x i d i z e d t o water, c o l l e c t e d i n an e t h y l e n e g l y c o l " b u b b l e r " , and a n a l y z e d f o r t r i t i u m u s i n g l i q u i d s c i n t i l l a t i o n counting. A t the end of t h i s 48-hr r u n , the water formed from t h i s d e p l e t e d hydrogen had a c o n c e n t r a t i o n o f 0.006 y C i / l i t e r , w h i l e the e l e c t r o l y s i s water l o o p had been e n r i c h e d t o 386 y C i / l i t e r . These r e s u l t s a r e summarized i n F i g u r e 3. 3

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

ROGERS

E T

Catalytic

AL.

H 0 3 cm /min 0.028 MCi/liter

Detritiation

of

Water

2

3

H (depleted in T ) 7.2 liter/min (6 cm /min H 0) burn ^ 100 cm /min to water and sample 2

2

3

2

3

After ^28 ^39 ^42 ^46

hr hr hr hr

0.021 juCi/liter 0.012 MCi/liter 0.011 MCi/liter 0.006 MCi/liter

Equilibrium value 0.004

μΟ\/\\Χβτ

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch013

7.5-m Stripping Section

HTO 3 cm /min 304 MCi/liter 3

7.5-m Enriching Section

HTO

Electrolysis Cells 0 to Stack via Air Detritiation System 2

HTO in Cell Loop 386 MCi/liter After 48 hr Equilibrium Value ν 2 Ci/liter Figure 3.

Preliminary results combined electrolysis catalytic exchange sys tem (CECE)

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

176

Future

SEPARATION

O F HYDROGEN ISOTOPES

Plans

The p i l o t CECE system w i l l c o n t i n u e t o be operated with goals of obtaining operating experience, d e t e r m i n i n g s c a l e - u p parameters, and i m p r o v i n g system dependability. Mound L a b o r a t o r y a l s o t e n t a t i v e l y p l a n s t o b u i l d a l a r g e r system b e g i n n i n g i n l a t e 1 9 7 8 . T h i s system would be used t o t r e a t aqueous t r i t i a t e d waste f o r ERDA.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ch013

Abstract A pilot-scale system has been used a t Mound L a b o r a t o r y t o i n v e s t i g a t e the catalytic detritiation of w a t e r . A hydrophobic, precious metal c a t a l y s t i s used t o promote the exchange o f tritium between liquid water and gaseous h y d r o g e n . T h i s c a t a l y s t was d e v e l o p e d a t C h a l k R i v e r N u c l e a r L a b o r a t o r i e s and i s operated at 6 0 ° C . The catalyst i s packed in two columns, each 7.5 m l o n g by 2 . 5 cm i.d. Water flow i s 5 - 1 0 c m / m i n and c o u n t e r c u r r e n t hydrogen flow i s 9 0 0 0 12,000 cm /min. The equipment, e x c e p t f o r the columns, is housed i n an inert atmosphere glovebox and i s computer controlled. The hydrogen i s o b t a i n e d by electrolysis of a p o r t i o n o f the water s t r e a m . E n r i c h e d gaseous tritium i s withdrawn f o r f u r t h e r enrichment. T h i s paper d e s c r i b e s the system and o u t l i n e s its o p e r a t i o n , i n c l u d i n g e x p e r i m e n t a l d a t a . 3

3

RECEIVED August 10, 1977

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

INDEX A Absorption of C 0 laser lines 139,140 Absorption coefficients, C O laser-DBr 141 Acids, mineral 156 Addition reactions, deuterium isotope separation via vibrationally enhanced deuterium halide olefin 134 Adduct production, classification of .. 156 Adsorption 5 AECL—Sulzer amine process 53 Algae, presence of mud and organic .. 168 Alumina, catalyst pellets of platinum on 95 Alumina particles, presence of 169 Amine-hydrogen exchange 8, 40 bithermal enrichment using 54 Amine-hydrogen process 11, 17, 40, 53, 63 Amine, steam hydrogen 19 Amino groups of methylamine 47 Ammonia advantages of methylamine over .... 40 catalyst 90 cracking 78 exchange, hydrogen8-10, 40, 77 and hydrogen, isotopic exchange between liquid 71 hydrogen process 15,53,58,80 plant 63,67,89 deuterium concentrations in an .. 64 link-up with the 62 synthesis 88 system 43 Argentina 77 Arrhenius parameters for H X addition 136 Atmosphere, H S emissions to 34

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ix001

1 2

1 6

2

Β Back-end of the separation cycle Bed contactor, packed Bed reactor, trickle BHWP aerial view II,S incidents reliability safety performance training section BHWP-A deuterium production reliability of

145 61 99 32 32 36 33 37 38 29 35

BIIWP-B 37 Bimolecular association 152 Bimolecular reaction 143 Biological 5 Bithermal enrichment using amine-hydrogen exchange 54 enrichment fluids 60 enrichment process 54—56 exchange processes 78 hydrogen-water— H W P 118 process 10-13,121 systems 57 Bruce heavy water plant 27, 28 "Bubbler," ethylene glycol 174

Canada 1, 2, 53, 77, 78, 93, 110 Canada Deuterium Uranium power reactor program ( C A N D U ) 2 C A N D U reactors 27-30, 122, 163 Capacity factors 35 Carbamate 42 Carbon monoxide absorption coefficients 141 Carbon-Teflon catalyst, platinum 121 Catalyst(s) 44 activity, effect of hydrogen gas flow rate and temperature on 102 ammonia 90 concentration 17 development 95 effect of platinum metal surface area on the activity of the 101 efficiency of 169 Engelhard 96 for isotopic exchange between hydrogen and liquid water, novel 93 metal hydrophobic 171 pellets of platinum on alumina 95 performance 98, 104, 105 platinum carbon-Teflon catalyst .... 121 solubility of the 72 thermal stability of the 72 Catalytic detritiation of water 171 Catalytic exchange 171-173 between heavy water vapor and deuterium gas 164

177

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

SEPARATION O F HYDROGEN ISOTOPES

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ix001

178 Catalytic exchange process, com bined electrolysis ( C E C E ) 110 Cesium methylamide 44 Chalk River 40 Chemical exchange 5—8 combined electrolysis and ( C E C E ) 2 processes 1, 14 China 2 Cold principle, hot— 78 Column efficiency 100 Combined electrolysis and chemical exchange ( C E C E ) 2, 110, 175 arrangement, monothermal 17 HWP 112 applications of the 121 block diagram of the 113 demonstration unit laboratory .... 115 synergistic effects of the 119, 120 process 22,171 T R P , applications of the 121 Commissioning progress report 37 Components, cost 127,128 Concentration in an ammonia plant, deuterium .... 64 catalyst 17 in the electrolysis cell water circuit, deuterium 116 Condensate and synthesis gas, deuterium recycle from 66 Conditions, determination of working 74 Coefficients, mass transfer 16 Contacting devices, cold 60 Contactons) development 40 ejector 61, 62 packed bed 61 sieve tray 61 special cold 59 Countercurrent crystallization systems 7 Crystallization 5 systems, countercurrent 7 water 20 Cycle, back-end of the separation 145 D D.O in C A N D U reactors, recovery of tritium from the and peak power production, simultaneous plant, small upgrading of Decomposition, thermal Design data Detritiation of water, catalytic Deuterium concentrations in an ammonia plant

Deuterium (continued) concentration in the electrolysis cell water circuit 116 enrichment system 65 exchange between hydrogen and liquid water Ill between the water vapor and liquid water Ill equilibria 56 properties 54, 58 rate 14,42 gas, catalytic exchange between heavy water vapor and 164 halide, vibrationally excited 142 -to-hydrogen ratio 3,10 isotope separation via vibrationally enhanced deuterium halide olefin addition reactions 134 plant 82 production, B H W P - A 29 recovery 117 recycle from condensate and synthesis gas 66 separation methods, hydrogen 1 uranium power reactor program, Canada ( C A N D U ) 2 Development, reliability and manpower 28 Diagram, enthalpy-temperature 85, 86 Diagram, McCabe-Thiele 11, 83, 84 Diffusion 5 hydrogen 20 D i e t h y l a m i d e , potassium 44 Dimethylformamidide, lithium 47 Dimethylformamidide ( P D M F A ) , potassium 42, 43 Distillation 5-9 component costs in heavy water .... 128 heavy water 126 system, elements of a 128 systems—physical 126 water 20 Draft of a factory, preliminary 72 Dunham isotope relations 138

Ε 122 122 122 122 43 164 171 64

Effects of the C E C E - H W P , synergistic 119, 120 Effects, synergistic 117 Ejector contactor 61, 62 Electrolysis 5, 172,173 catalytic exchange process, combined ( C E C E ) 2, 110 cell water circuit, deuterium concentration in the 116 Elimination of H X , unimolecular 136

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

179

INDEX

Emissions to atmosphere, IL.S 34 Emissions to water, H »S 34 Energy consumption 20 Energy diagram, potential 154 Engineering problems 87 Enrichment system 81 Enthalpy-temperature diagram 85, 86 Environment, care of the 28, 34 Environmental performance 36 Equilibrium constant, perturbed 153 isotope effect 110 perturbed 161 statistical 152 Ethylene 142 additions, H F 156 pairs, H F 195 Exchange amine-hydrogen 8,40 ammonia-hydrogen 8-10, 40 between heavy water vapor and deutrium gas, catalytic 164 between hydrogen and liquid water, deuterium Ill between hydrogen and liquid water, novel catalysts for isotopic 93 between hydrogen and methyl amine, isotopic 71 between liquid ammonia and hydrogen, isotopic 71 between water and hydrogen sulfide, isotopic 71 between the water vapor and liquid water, deuterium 111 bithermal enrichment using amine-hydrogen 54 catalytic 171-173 chemical 5-8 combined electrolysis and chemical (CECE) 2 efficiencies, isotopic 59 equilibria, deuterium 56 hydrogen-ammonia 77 of HC1 with natural water, isotopic 146 isotope 79 kinetics 71 process ( es) bithermal 78 chemical 1, 14 combined electrolysis catalytic (CECE) 110 design of the H C l - H . O 148 dual temperature 78 features of hydrogen-water 106 hydrogen sulfide-water 31 water 28 properties, deuterium 54, 58 rate, deuterium 14,42

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ix001

L

Exchange (continued) rate, effect of lithium-potassium mole ratio on reaction, hydrogen halide-water ... reaction, mechanism of the water-hydrogen water-hydrogen sulfide water-vapor—hydrogen Excitation, effectiveness of vibrational Extraction plant, operating experience with the tritium hydrogen

46 146 104 2,8 8 2 144 163

F Factors, capacity 35 Factory, preliminary draft of a 72 Fissure phenomena 169 Flash evaporation 114 Fluoroethylenes 156 Fragmentation 152 France 1,2,10,40,53,163 G Gas catalytic exchange between heavy water vapor and deuterium .... 164 deuterium recycle from condensate and synthesis 66 fed bithermal process 11 flow rate and temperature on catalyst activity, effect of hydrogen 102 reactor cover 169 supplement, electrolytic H as natural 123 synthesis 62, 63, 85 Gaseous effluent streams, removal of tritium from 171 Germany 1, 163 Girdler-Sulfide ( G S ) plants, final enrichment stage for 122 GS process 1-10,14,17-22, 29, 55-58, 93 Glace Bay heavy water plant 3, 4 Glycol 'limbbler," ethylene 174 Gravitational 5 Great Britain 163 Gulf process 20 2

H

H C l - Η . , Ο exchange process, design of the 148 H F addition 156, 157 HF-ethylene pairs 159 H S emissions 34 H S incidents 31 H X addition, Arrhenius parameters for 136, 137 H X , unimolecular elimination of 136 2 2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ix001

180

SEPARATION O F HYDROGEN ISOTOPES

Halide-olefin addition reactions .134, 135 Halide, vibrationally excited deuterium 142 Heavy water plant applications of the C E C E 121 bithermal Η - , - Η , Ο 118 block diagram of the C E C E 113 Bruce 27,28 CECE 112 demonstration unit, laboratory CECE 115 design of 80 Glace Bay 3, 4 model of a 91 synergistic effects of the CECE 119,120 processes 1 production 2 from synthesis gas, U H D E process for the recovery of 77 Henry's Law 14, 15 Hot-cold principle 78 Hydrates of perfluoroacetone, gaseous 158 Hydrates of trifluoroacetaldehyde, gaseous 158 Hydrogen 7, 42, 43 amine process 40 amine, steam19 ammonia exchange 77 ammonia systems 15 -based processes 14, 18 deuterium separation methods 1 deuterium-tritium separations based on laser augmented A - f B = C reactions proposed 152 diffusion 20 exchange amine 8, 40 ammonia 8-10. 40 bithermal enrichment using amine54 water 2, 8 extraction plant, operating experi ence with the tritium and 163 gas flow rate and temperature on catalyst activity, effect of 102 halide-olefin addition reactions 135 halide-water exchange reactions .... 146 isotopic exchange between liquid ammonia and 71 and liquid water, deuterium exchange between Ill and liquid water, novel catalysts for isotopic exchange between 93 and methylamine, isotopic exchange between 71 monomethylamine system ( M M A ) 71

Hydrogen (continued) as natural gas supplement, electrolytic 123 on P L M A solutions, effect of 45 on P M A solutions, effect of 45 process amine 11, 17,18, 53-58, 63-67 ammonia 53, 58 methane 20,21 steam 18 water 1 ratio, deuterium-to3, 10 solubility of 72 sufide dual temperature 28 exchange, water 8 isotope exchange between water and 71 process, water 1 system 77 water 40 toxicologic^ properties of 31 water exchange process 31 water system 94 system, ammonia80 system, water14, 15, 80, 94 transfer, steam 20 water exchange 77 water-HWP, bithermal 118 water processes, advantages of 107 Hydrophobic catalyst, metal 171

Ice-water systems 7 Impurities, oxygen-bearing 90 Incidents, I L S 31 India 1, 2, 10, 40, 53, 77 IR photons 134 Institute, Laue-Langevin 163 Isotope effect, equilibrium 110 enrichment 66 exchange 79 of HC1 with natural water 146 between hydrogen and liquid water, novel catalysts for 93 between hydrogen and methylamine 71 between liquid ammonia and hydrogen 71 between water and hydrogen sulfide 71 relations, Dunham 138 separation, principles of 78 separation via vibrationally enhanced deuterium halide olefin addition reactions 134 Italy 1

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

181

INDEX

Κ Kinetics, exchange

71

Monothermal process M u d and organic algae, presence of .. Ν

L Laboratory unit, results from 114 Lake Huron 28 Laser augmented A + Β = C reactions, proposed H / D / T separation based on 152 lines, absorption of C O 139, 140 methods 134 photolysis 159 Laue-Langevin Institute 163 Law, Henry's 14,15 Cithium 47 dimethylformamidide 47 methylamide 44 potassium 44 solubility of potassium 49 potassium mole ratio on exchange rate, effect of 46

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ix001

1 2

9-11 168

Natural gas supplement, electrolytic H as North America Norway 2

123 28 2,8

Ο

i e

M Manpower development, reliability and 28,35 McCabe-Thiele diagrams 11,12, 83, 84 Metal hydrophobic catalyst 171 surface area on the activity of the catalyst, effect of platinum 101 transfer rate constant dependence on platinum 103 Methane 7 -hydrogen process 20 Methyl groups of methylamine 47 Methylamide cesium 44 lithium 44 potassium-lithium 44 sodium 44 solubility of 48, 49 solution, potassium 42 Methylamine 42-44, 65 amino groups of 47 over ammonia, advantages of 40 isotopic exchange between hydrogen and 71 methyl groups of 47 Methylenimine 43 N-Methylformamide, potassium 42 Mineral acids 156 Molecular sieve, displacement of the 168 Monomethylamine system, hydrogen (MMA) 71 Monothermal C E C E arrangement .... 17

Olefin addition reactions, hydrogen halide 134,135 Olefins, Arrhenius parameters for H X addition to 137 Operating experience 167 Operation, difficulties encountered during 168 Operation, principle of 164 Oxygen-bearing impurities 90 Ρ

Packed bed contactor 61 Packing(s) earning power of two experimental 132 experimental 127 performance—experimental 130 Sulzer 164 Pakistan 77 Perfluoroacetone 160 Photochemical, selective 5 Photolysis, laser 159 Photons, ir 134 Pilot plant tests 72 Plant(s) ammonia 63-67, 89 Bruce heavy water 28 conception, 400 ton 127 design of heavy water 80 deuterium 82 concentration in an ammonia 64 final enrichment stage for GS 122 Glace Bay heavy water 3 heavy water 2 link-up with the ammonia 62 model of a heavy water 91 operating experience with the tritium and hydrogen extraction 163 operation of the 87 packing module, parallel 131 performance, Bruce heavy water .... 27 polyfluoroethylene production 158 safety precautions 164 small DX> 122 start-up of the 167 400-ton 129

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

182

SEPARATION O F HYDROGEN

Platinum on alumina, catalyst pellets of 95 carbon-Teflon catalyst 121 metal surface area on the activity of the catalyst, effect of 101 metal, transfer rate constant dependence on 103 PLMA 44-50 Polyfluoroethylene production plant.. 158 Potassium amide ( K N H ) 80 Potassium dimethylamide 44 Potassium dimethylformamidide (PDMFA) 42,43 Potassium hydride 43 Potassium-lithium methylamide 44, 49 Potassium methylamide ( P M A ) 40-47 Potassium N-methylformamide 42 Potassium mole ratio on exchange rate, effect of lithium 46 Potential energy diagram 154 Power of experimental packings 132 production, simultaneous D 0 and peak 122 reactor program, Canada deuterium uranium ( C A N D U ) 2 Principle, hot-cold 78 Problems, engineering 87 Process (es) advantages of hydrogen water 107 amine-hydrogen .11,17,18, 53-58, 63-67 basic description of the 112 bithermal 10-13, 121 enrichment 56 exchange 78 CECE 22, 171 characteristics, general 3 chemical exchange 1,14 chemistry 40-42 comparison 20-22 design 40,67 GS 3 of the H C 1 - H 0 exchange 148 development 41 dual temperature exchange 78 economy of the 74 evaluation 23,24 features of hydrogen-water exchange 106 gas-fed bithermal 11 Girdler-Sulfide ( GS ) 1, 5-10,17-22, 29, 55-59,93 gulf 20 heavy water 1 hydrogen-amine 40 hydrogen-based 14,18 hydrogen sulfide—water exchange 31 methane-hydrogen 20, 21

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ix001

2

2

2

ISOTOPES

Process ( es ) ( continued ) monothermal 10,11 production 28 for the recovery of heavy water from synthesis gas, U H D E .. 77 steam-hydrogen 18 transfer 18 types of 5 water exchange 28 water—hydrogen 1 Production heavy water 2 process 28 rate 35 unit diagram 73 Program, Canada deuterium uranium power reactor ( C A N D U ) 2 Properties, deuterium exchange 54 Properties of hydrogen sulfide, toxicological 31 Purification system 80

Q Quenching, vibrational

142

R Rate(s) constant dependence on platinum metal, transfer 103 deuterium exchange 14, 42 effect of lithium—potassium mole ratio on exchange 46 expression, Arrhenius 136 of methylamide solutions, thermolysis 50 production 35 and temperature on catalyst activity, effect of hydrogen gas flow 102 Ratio, deuterium-to-hydrogen 3, 10 Reaction(s) bimolecular 143 deuterium isotope separation via vibrationally enhanced deuterium halide olefin addition .... 134 hydrogen halide—water exchange . . . 146 mechanism of the exchange 104 proposed H / D / T separations based on laser augmented A + B = C 152 Reactor C A N D U type 27-30, 163 cover gas 169 high flux 163 program ( C A N D U ) 2 trickle bed 99 Recovery of heavy water from synthesis gas, U H D E process for the .... 77

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

183

INDEX

Reliability of B H W P - A Reliability and manpower development Results, preliminary Russia

35 28 172 2

S Safety, employee 28—31 Safety performance, B H W P 33 Safety precautions, plant 167 Selective photochemical 5 Separation(s) based on laser augmented A -f- Β = C reactions, proposed H/D/T 152 cycle, back-end of the 145 factors 7-13, 20, 57, 65, 71, 93 94 methods, hydrogen-deuterium 1 Sieve displacement of the molecular 168 tray(s) 87 contactor 61 operation 16 Silicone-treated pellets 95 Sodium methylamide 44 Solubility 44 of the catalyst 72 of hydrogen 72 Stability of the catalyst, thermal 72 Statistical equilibrium 152 Steady state 154 Steam-hydrogen-amine 19 Steam-hydrogen process 18 Steam-hydrogen transfer 20 Stripping system 81—83 Sulfide dual temperature hydrogen 28 process, Girdler-Sulfide (GS) 1 process, water-hydrogen 1 system, hydrogen 77 system, water-hydrogen 40 toxicological properties of hydrogen 31 water exchange process, hydrogen .. 31 Sulzer packings 164 Surfaoe area on the activity of the catalyst, effect of platinum metal 101 Sweden 1 Switzerland 1, 41, 163 Synergistic effects 117-120 Synthesis, ammonia 88 Synthesis gas 62r-67, 80, 85, 90 deuterium recycle from condensate and 66 U H D E process for the recovery of heavy water from 77 System ammonia hydrogen 80 deuterium enrichment 65

System (continued) elements of a distillation enrichment GS hydrogen—monomethylamine (MMA) hydrogen—sulfide hydrogen sulfide-water hydrogen-water physical, distillation purification stripping transfer water-hydrogen water-hydrogen sulfide

71 77 94 94 126 80 81-83 81 80 40

Τ

;

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ix001

128 81 11

Teflon catalyst, platinum carbon 121 Temperature on catalyst activity, effect of hydrogen gas flow rate and .... 102 diagram, enthalpy 85, 86 dual 31 exchange processes, dual 78 hydrogen sulfide, dual 28 Tetrahydrofurane, addition of H F to 158 Thermal decomposition 43 Thermal stability of the catalyst 72 Thermodynamic and kinetic relations 152 Thermolysis rate of methylamide solutions 50 Thiele diagrams, M c C a b e 11, 83, 84 Thylene glycol "bubbler" 174 Toxicological properties of hydrogen sulfide 31 Training section, B H W P 37 Transfer coefficients, mass 16 column 83 processes 18 rate constant dependence on platinum metal 103 steam—hydrogen 20 system 81 Trays, sieve 16, 87 Trickle bed reactor 99 Trifluoroacetaldehyde 160 Trimethylamine ( T M A ) , adjuvant effect of 72 Tritium from the D 0 in C A N D U reactors, recovery of 122 from gaseous effluent streams, removal of 171 and hydrogen extraction plant, operating experience with the . 163 recovery from light water 122 T R P , applications of the C E C E 121 2

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.

184

SEPARATION O F HYDROGEN ISOTOPES

u U H D E process for the recovery of heavy water from synthesis gas .. 77 United Kingdom 1 Uranium power reactor program, Canada deuterium ( C A N D U ) .... 2 USA 2,77 USSR 2

Water (continued) exchange hydrogen— 77 process 28 design of the H C 1 148 features of hydrogen106 hydrogen sulfide31 reactions, hydrogen halide146 H W P , bithermal H 118 H S emissions to 34 hydrogen 14, 15 exchange 2, 8 process 1 sulfide exchange 1,8,71 sulfide system 40, 94 system 80, 94 isotopic exchange of HC1 with natural 146 novel catalysts for isotopic exchange between hydrogen and liquid .. 93 processes, advantages of hydrogen 107 system, ice 7 tritium recovery from light 122 vapor and deuterium gas, catalytic exchange between heavy 164 vapor-hydrogen exchange 2 vapor and liquid water, deuterium exchange between the Ill Working conditions, determination of 74 2

V

Publication Date: June 1, 1978 | doi: 10.1021/bk-1978-0068.ix001

Vapor-hydrogen exchange, water Vibrational excitation, effectiveness of Vibrational quenching Vibrationally enhanced deuterium halide olefin addition reactions, deuterium isotope separation via

2

2 144 142

134

W

Water catalytic detritiation of circuit, deuterium concentration in the electrolysis cell crystallization deuterium exchange between hydrogen and liquid distillation component costs in heavy heavy

171 116 20 Ill 20 128 126

In Separation of Hydrogen Isotopes; Rae, H.; ACS Symposium Series; American Chemical Society: Washington, DC, 1978.