Industrial Gas Separations - American Chemical Society

1

Downloaded by INDIANA UNIV PURDUE UNIV AT IN on July 1, 2012 | http://pubs.acs.org Publication Date: June 16, 1983 | doi: 10.1021/bk-1983-0223.ch001

Helium Recovery Using Semipermeable Membranes F. E. MARTIN Westinghouse Oceanic Division, Annapolis, MD 21404 T. S. SNYDER and E. J. LAHODA Westinghouse Research & Development Center, Pittsburgh, PA 15235 A series of pure gas and gas mixture tests were performed, using a unique closed-circuit experimental loop. Based on data from continuous loop operations, a preliminary system design and economic evaluation were performed to recover helium from deep sea diving gas applications. This program was performed under Navy Contract N60921-79-C-A037 for the Naval Surface Weapons Center G-52. Membrane permeability was deter mined as a function of driving pressure and feed concentration for a single membrane element. Based on this data, a hypothetical design of a system to meet naval specifications was performed only as a con tractual requirement with the Navy and i s not intended as a specific Westinghouse system. Westinghouse at this time plans no such system for market. Projections based on the experimental data for the hypothetical system show that the least pure gas considered for the design, 58 mole % helium, could be enriched to better than 99.99% helium i n five permeator stages. This gas could be enriched, hypothetically, to a physiologically acceptable quality i n 3 stages. Carbon dioxide con centration i n the gas i s the design l i m i t i n g parameter. This i s a very conservative design estimate. The con servatism i s necessary due to the limited nature of the design data. The U . S . N a v y , i n p u r s u i t o f i t s many deep d i v i n g p r o g r a m s , must c u r r e n t l y d e a l w i t h e x p o n e n t i a l l y r i s i n g c o s t s and numerous supply d i f f i c u l t i e s concerning i t s prime d i l u e n t f o r b r e a t h i n g gas-helium. The l o g i s t i c s p r o b l e m s o f p r o v i d i n g l a r g e q u a n t i t i e s o f h i g h p r e s s u r e gas t o r e m o t e d i v i n g s i t e s o v e r e x t e n d e d d i v e i n t e r v a l s , r e g a r d l e s s of weather c o n d i t i o n s , a r e d i f f i c u l t to quantify. H o w e v e r , p r o v i s i o n f o r an i n d e f i n i t e s u p p l y o f d i l u e n t v i a an o n - b o a r d d e v i c e t h a t r e c y c l e s expended g a s , w i t h r e l a t i v e l y m i n o r p e n a l t y t o o p e r a t i o n a l / m a i n t e n a n c e c o s t s and d e c k s p a c e , 0097-6156/83/0223-0001$07.25/0 © 1983 American Chemical Society In Industrial Gas Separations; Whyte, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1983.


2

INDUSTRIAL

GAS

SEPARATIONS

would appear t o be d e s i r a b l e . The b e n e f i t b o t h t o p r o g r a m c o n t i n g e n c y p l a n n i n g and t o d i v e s a f e t y c o u l d be s u b s t a n t i a l , even i f t h e d e v i c e w e r e r e l e g a t e d t o a b a c k u p o r s u p p l e m e n t a l mode o f operation. M o r e amenable t o q u a n t i t a t i v e and o b j e c t i v e a n a l y s i s i s t h e economic i n c e n t i v e f o r d e v e l o p i n g a r e c y c l e system. I t was p r e d i c t e d i n 1974(1) t h a t , f o r h e l i u m r e c o v e r y a t t h e w e l l - h e a d , a c o s t growth average o f 17.9% p e r y e a r c o u l d be a n t i c i p a t e d f o r t h e d e c a d e s u c c e e d i n g t h a t r e p o r t . However, i t i s f u r t h e r p r e d i c t e d t h a t n a t u r a l gas f i e l d s b e a r i n g ^ 0 . 3 % h e l i u m w i l l be d e p l e t e d b y 1990-95, a t w h i c h t i m e f i e l d s b e a r i n g < 0.1% must b e used. This would produce a sharp p r i c e e s c a l a t i o n t o wholesale p r i c e s f i v e times then-current r a t e s . Thereafter, projections a r e e n t i r e l y d e p e n d e n t o n how, w h e t h e r , a n d when h e l i u m c o n s e r v a t i o n and r e s e r v e s t o r a g e p o l i c i e s a r e i m p l e m e n t e d , a n d o n whether f u t u r e a i r s e p a r a t i o n technology w i l l enable c o m p e t i t i v e e x t r a c t i o n o f h e l i u m from t h e atmosphere. The Navy, w h i c h , b y o u r c o n s e r v a t i v e e s t i m a t e , ( 2 ) i s a c u r r e n t u s e r o f some 2,800,000 s t d f t ^ o f h e l i u m p e r y e a r , w o u l d b e n e f i t s u b s t a n t i a l l y from a s h i p b o a r d system t h a t c o u l d c a p t u r e 9 0 - 9 5 % o f c u r r e n t l y w a s t e d h e l i u m and c o n d i t i o n i t t o a c c e p t a b l e p u r i t y f o rre-use. The d e f i n i t i o n o f a c c e p t a b l e p u r i t y i s a s shown i n T a b l e I , w h e r e i n t h e d e s i g n g o a l s and d e s i g n r e q u i r e m e n t s are s e t f o r t h . The d e s i g n g o a l r e f l e c t s h e l i u m p u r i t y a s f o u n d i n b o t t l e s u p p l i e s m e e t i n g t h e r e f e r e n c e d s p e c i f i c a t i o n , G r a d e A, whereas t h e d e s i g n requirement i s d e r i v e d from an assortment o f a n a l y s e s b a s e d on t h e p r a c t i c a l , o p e r a t i o n a l c o n s t r a i n t s on a d i v e r ' s d i l u e n t g a s . As p e r n o t e 2 o f T a b l e I , t h e d e s i g n r e q u i r e m e n t c a n a l l o w a s much a s 1% 02 and 1% N 2 , and c o n s e q u e n t d r o p o f He t o 9 7 . 8 % , w i t h o u t i m p a i r i n g o r j e o p a r d i z i n g t h e u s e r ; h o w e v e r , t h e d e s i g n was t o i n c l u d e s i z i n g t o t h e 99.995% d e s i g n g o a l l e v e l t o o b t a i n a n e s t i m a t e f o r maximum d e s i g n c a p a c i t y needed. E x p e r i m e n t a l System D e s c r i p t i o n Figure 1 i s a schematic of the experimental loop c o n s t r u c t e d by t h e W e s t i n g h o u s e O c e a n i c D i v i s i o n t o e v a l u a t e s e m i p e r m e a b l e g a s e o u s membranes f o r h e l i u m r e c o v e r y . The k e y s y s t e m components i n F i g u r e 1 a r e the permeator modules, compressor, a f t e r c o o l e r , h u m i d i f i e r and t h e o n l i n e g a s c h r o m a t o g r a p h f o r s a m p l e a n a l y s e s . T h i s t e s t s y s t e m was u n i q u e i n t h a t i t a l l o w e d c l o s e d c i r c u i t f l o w o f m u l t i c o m p o n e n t g a s m i x t u r e s t o t h e membrane f o r s e p a r a t i o n , f o l l o w e d b y i m m e d i a t e r e c o m b i n a t i o n o f t h e p e r m e a t e and r e s i d u a l streams f o r r e c y c l e t o t h e feed s i d e . T h i s arrangement p e r m i t t e d a c o n s t a n t v o l u m e t r i c f e e d r a t e t o t h e membrane f o r p r o l o n g e d p e r i o d s w i t h o u t r e q u i r i n g p r o h i b i t i v e and c o s t l y g a s i n v e n t o r y . F u r t h e r , the e x p e r i m e n t a l c o n f i g u r a t i o n p r o v i d e d complete m o n i t o r i n g and c o n t r o l c a p a b i l i t i e s o v e r s u c h p a r a m e t e r s a s b a c k - p r e s s u r e , s p l i t - s t r e a m f l o w r a t e s , g a s t e m p e r a t u r e , h u m i d i t y and c o m p o s i t i o n .

In Industrial Gas Separations; Whyte, T., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1983.

1.

MARTIN

ET

AL.

Helium


Table I .

3

Recovery

H e l i u m P u r i t y G o a l s and R e q u i r e m e n t s

Component

Design^ ) Goal

Helium (minimum %)

99.995

Water Vapor (ppm)

10

Design^ Requirement 99

8

(2)

200

Rationale for Requirements Federal Specification BB-H-11680, Type I , Grade Β 3 0 ° F dew point at 1000 ft

Oxygen (ppm)

2

1%

p 0 2 = 0.3 atm at 850 ft

Nitrogen (%)

0

1%

Results i n same p N 2 at 850 ft as initially pressurizing chamber to 14 ft with air

Carbon Dioxide (ppm)

0

100

Carbon Monoxide (ppm)

0

12

Gaseous Hydrocarbons measured as Methane (ppm)

1

1

Federal Specification BB-H-11686, Type I, Grade C

Oil (mg/liter)

0

0.001

O S H A exposure limit

A l l others (ppm)

NOTES:

(1) (2)

37

37

p C 0 2 = 0.003 atm at 850 ft O S H A exposure limit

Federal Specification BB-H-11680, Type I, Grade A

M a x i m u m values by volume, unless otherwise indicated May be further reduced by the amount of oxygen and nitrogen present


INDUSTRIAL

GAS

SEPARATIONS


4

ο •Η

ϊ Φ

ϋ

Ό) -Ρ 03

φ

-Ρ •Η

αϊ Η ϋ

Membrane

Feed

Residue

Circumferential Seal

Spacer

Between Element O.D. And Pressure Housing, I.D. (Actually Set Within

Two Asymmetric Membrane

Special Seal-Carrying

Sheets, Sandwiching A Porous

Fitting)

"Spacer", Are Adhesively Bonded At Edges And Spirally Wrapped About Permeate "Core", To Which "Spacer" Empties Through Penetrations. These Spiral Wraps Are Separated From One Another By An

Permeate Flow Entering Core Penetration

Open-Lattice Feed-Channelling Material, Concurrently

Permeator Housing

Wrapped With The Membrane "Sandwich". The Resultant Permeator Element Is Then Over-Wrapped With Fiberglass

Feed Channel (Thickness Exaggerated -

Lay-Up, And Provided Necessary

Actually < 1/32 Inch

Seals And Fittings.

Thickness Allowing Smooth Cylindrical Over-Wrap Sidewall)

Figure 2 .

Spiral-wound permeator

configuration.


8

INDUSTRIAL

GAS

SEPARATIONS


= p a r t i a l p r e s s u r e o f component i = p e r m e a b i l i t y c o n s t a n t f o r component i T a b l e I I I d e s c r i b e s t h e p e r m e a b i l i t y c o n s t a n t s as d e t e r m i n e d by t h i s s e t of experiments. As F i g u r e 3 shows, s t r i c t a p p l i c a t i o n o f E q u a t i o n 1 r e s u l t s i n 11 e q u a t i o n s i n 11 unknowns and an i t e r a t i v e s o l u t i o n f o r t h e d e s i g n s e q u e n c e . To c i r c u m v e n t t h i s cumbersome c a l c u l a t i o n , t h e s y s t e m p e r m s e l e c t i v i t y was u s e d t o e s t i m a t e t h e number o f s t a g e s r e q u i r e d i n t h e d e s i g n s e q u e n c e f o r t h e s e p a r a t i o n , and E q u a t i o n (1) was t h e n u s e d t o e s t i m a t e t h e a r e a r e q u i r e m e n t s k n o w i n g t h e s t a g e o u t l e t c o m p o s i t i o n s o f t h e p e r m e a t e and r e s i d u a l s t r e a m s . I n a d d i t i o n , s e p a r a t i o n f a c t o r s w e r e s e l e c t e d as t h e method of s c a l i n g the d a t a , r a t h e r than the p e r m e a b i l i t y c o e f f i c i e n t s , b e c a u s e t h i s method p r o v i d e s a more r e l i a b l e f i t o f t h e l i m i t e d data a v a i l a b l e . The d a t a was l i m i t e d b e c a u s e t h e 58% h e l i u m m i x t u r e i n T a b l e I I was n o t s t u d i e d e x p e r i m e n t a l l y due t o p l a s t i c i z a t i o n by w a t e r v a p o r o f t h e l a s t w o r k a b l e membrane m o d u l e . In a d d i t i o n t o b e i n g t h e most common h e l i u m m i x t u r e w h i c h t h e p r o t o type would encounter, t h i s m i x t u r e r e p r e s e n t s lower v a l u e s of the r a t i o 8 = [He]/[component i ] than s t u d i e d e x p e r i m e n t a l l y . U s i n g the s e p a r a t i o n f a c t o r s , the v a l u e s of 3feed/Bpermeate f o r the 58% h e l i u m m i x t u r e l i e b e t w e e n t h e o r i g i n ( 0 , 0 ) , a f i x e d b o u n d a r y , and t h e e x i s t i n g d a t a when p l o t t i n g 6 f e e d / B p e r m e a t e * Use o f p e r m e a b i l i t i e s w o u l d r e q u i r e e x t r a p o l a t i o n as o p p o s e d t o s e p a r a tion factor interpolation. T h e r e f o r e , t h e s e p a r a t i o n f a c t o r was selected for scaling. The p e r m s e l e c t i v i t i e s , o r s e p a r a t i o n f a c t o r s , d e f i n e d by E q u a t i o n (3) were u s e d t o s c a l e t h e e x p e r i m e n t a l d a t a f o r d e s i g n purposes. The s y s t e m p e r m s e l e c t i v i t y i s a n a l o g o u s t o t h e d i s t i l lation separation factor

rc [Sep.

( p

c + i factor]

H

e

He

}

= — x

v p

( P

feed

;

}

He , permeate / ~r~~r x'permeate

, . (3)

v p

x feed

d i s c u s s e d by McCabe & Smith(_3) and by T r e y b a l ( 5 ) , d e f i n e d by E q u a t i o n ( 4 ) , t h e r e l a t i v e v o l a t i l i t y cC i j , f o r a b i n a r y s y s t e m . a

i j

- PÎ'Pj -

(

P

/ P A

)

B vapor

/ ( p

a

/ p

)

B liquid

(4)

The p e r m s e l e c t i v i t y f o r membrane s e p a r a t i o n s can a l s o be c a l c u l a t e d by s u b s t i t u t i n g f u g a c i t i e s c a l c u l a t e d f r o m an e q u a t i o n o f s t a t e , here u s i n g the Beattie-Bridgeman e q u a t i o n , i n t o Equation (3) f o r t h e p a r t i a l p r e s s u r e v a l u e s ( 4 ) . The v a l u e s o f t h e perms e l e c t i v i t i e s i n T a b l e IV a r e r e l a t i v e l y c o n s t a n t a t a f i x e d f e e d c o m p o s i t i o n i n agreement w i t h the a p p r o x i m a t e l y l i n e a r b e h a v i o r n o t e d i n F i g u r e s 9-11.



©Dalton

2

A

7.43

6.31

183

184

185

5.75

201

28.9

36.7

37.6

38.4

181.8

186.8

190.7

(211.6)

31.3

77.3

2

Q f r o m ratio of Permeate Concentrations

Qj from Permeation Rates calculated by Dalton's Law

0.65 r«- 147.7

6.08 («'715.5 0.85 r«' 176.8

567.7

204

116.8

6.2

(μ

203

0.56

86.0

5.9

417.1

0.46

28.0

202

(«>

0.79 0" 35.3

7.2 Φ> 704.2

194

266.4

0.78

7.7 («> 529.7

0.72 r«' 20.7

193

(0.48)

K

130.6

Ν .

(w

Δ

0.59 r«' 31.4

Ν / *

0.44 & 20.4

Κ

164.8

He " 2%C02 I Q 200 psia

V2/|



CO*,

He

Composition (Vol. %)

Stage 1

2.92 71.03 25.20 0.85

Recovery

58.0 30.0 11.5 0.526

84.85

Row

(SLPM)

System Feed

Θ

Stream Name And Number

Format For All Streams

33.61

1st Stage Residual

©

99.32 0.21 0.36 0.12 96%

94.1 3.08 2.50 0.31

98%

1.23

3rd Stage Residual

©

99.994 99.98 0.006 0.01 0.01 92%

99.90 0.01 0.05 0.05 94%

90%

0.0061

44.47

5th Stage Permeate

© 45.39

4th Stage Permeate

Stage 5

99.15

0.92

5th Stage Residual

Qo;

46.36

3rd Stage Permeate

0.97

4th Stage Residual

©

Figure 1 2 . Helium reclaimer m a t e r i a l balance.

47.58

2nd Stage Permeate

51.24

1st Stage Permeate

3.65

2nd Stage Residual

Θ


0.0061

99.994

44.47

Storage

«··»»

to w

S'

S3

>

M H

3


24

INDUSTRIAL

GAS

SEPARATIONS

3. F o r a h y p o t h e t i c a l s y s t e m d e s i g n , b a s e d o n t h e e x i s t i n g d a t a , m u l t i s t a g e systems a r e r e q u i r e d t o r e c o v e r t h e h e l i u m from v e n t e d d i v i n g chamber g a s e s i n o r d e r t o meet t h e d e s i g n s p e c i f i cations o u t l i n e d i n Table I . 4. F i v e s t a g e s a r e r e q u i r e d t o a c h i e v e t h e h e l i u m p u r i t y g o a l and t h e c a r b o n d i o x i d e r e q u i r e m e n t i n T a b l e I . 5. C a r b o n d i o x i d e i s t h e l i m i t i n g g a s f o r t h e d e s i g n a s o x y g e n and n i t r o g e n r e q u i r e o n l y two s t a g e s t o meet t h e i r d e s i g n requirement l e v e l s . Use o f o t h e r membranes, h a v i n g d i f f e r e n t p r o p e r t i e s , w i l l , of course, r e s u l t i n a system d i f f e r e n t from t h a t i n d i c a t e d a b o v e . D e p e n d i n g o n t h e c h o i c e o f membrane m a t e r i a l , f e w e r o r more, s m a l l e r o r l a r g e r s t a g e s w o u l d b e r e q u i r e d f o r t h e s y s t e m . The e x p e c t e d c o s t o f r e c l a i m e d h e l i u m w o u l d b e c o r r e s p o n d i n g l y affected. Nomenclature J

k ρ Τ ρ L [i]^

p e r m e a b i l i t y c o e f f i c i e n t (STD f t / f t * h r 100 p s i ) p r e s s u r e (atm) t e m p e r a t u r e (°K e x c e p t a s n o t e d ) d e n s i t y (g/cc) some c h a r a c t e r i s t i c l e n g t h (cm) permeate c o n c e n t r a t i o n mole %

[i]^

r e s i d u a l c o n c e n t r a t i o n mole %

[i]^

feed c o n c e n t r a t i o n mole %

A F3 Fi F2 p?

area r e s i d u a l f l o w r a t e (SLPM) f e e d f l o w r a t e (SLPM) p e r m e a t e f l o w r a t e (SLPM) v a p o r p r e s s u r e o f component i

x.. iJ a..

i d e a l s e p a r a t i o n f o r d i s t i l l a t i o n = p!/p! i j separation factor or permselectivity

Literature Cited 1.

Howland, H. R.; Hulm, J . K. The Economics of Helium Conser vation, Final Report to Argonne National Laboratory, Contract No. 31-109-38-2820, December,1974. 2. Helium Reclaimer Study, Westinghouse Electric Corporation, Proposal No. Y7420, April.1978. 3. McCabe, W. G.; Smith, I.C. Unit Operations of Chemical Engineering, McGraw-Hill, 1967, Second Edition. 4. Balzhizer, R. W.; Samuels, M. R.; Eliassen, J. D. Chemical Engineering Thermodynamics, Prentice Hall, 1972. 5. Treybal, R.E. Mass Transfer Operations, McGraw-Hill, 1968.



1. MARTIN ET AL.

Helium Recovery

6.

Hwang, S. J.; Kemmermeyer, K. Membranes in Separation, Wiley & Sons, 1975.

7.

Bird, R. Β.; Stewart, W. E . ; Lightfoot, E.M. Transport Phenomena, Wiley & Sons, 1960.

8.

Schell, W. J. "Membrane Applications to Coal Conversion Processes," Envirogenics Systems Company, October, 1976, NTIS No. FE2000-4.

9. Li, Ν. N . , Ed.; Recent Developments in Separation Science, Vol. II, CRC Press, Cleveland, Ohio, 1972. RECEIVED January

18, 1983


Industrial Gas Separations - American Chemical Society

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