Sour Water Equilibria - ACS Symposium Series (ACS Publications)

9 Sour Water Equilibria Ammonia Volatility down to PPM Levels; pH vs. Composition; and Effect of Electrolytes on Ammonia Volatility GRANT M . WILSON, RICHARD S. OWENS, and MARSHALL W. ROE

Downloaded by UNIV LAVAL on May 26, 2014 | http://pubs.acs.org Publication Date: October 29, 1980 | doi: 10.1021/bk-1980-0133.ch009

Wilco Research Company, 488 South 500 West, Provo, Utah 84601

Undesirable sulfur, nitrogen, and oxygen compounds are often encountered in commercial gas production and gas treating f a c i l i ties relating either to natural sources or to synthetic processes. Water also occurs as condensate in these gas streams or water is brought in contact with gas streams in various processing steps. As a result aqueous waste streams are produced in which undesir able sulfur, nitrogen, and oxygen compounds are present. Their concentrations in the aqueous waste streams depend on their equi librium concentrations in gas streams from which the aqueous streams are derived. Present and future environmental control restrictions dictate that the concentrations of these undesirable compounds be maintained at very low levels before the streams can be released to the environment. Thus, methods must be developed for controlling these concentrations. One method used in refin eries for controlling the concentrations of undesirable compounds in aqueous waste streams is by means of a steam stripper called a sour water stripper where these trace compounds are steam dis t i l l e d and then condensed as a concentrated product in the con denser of the stripping column. The principal components in these strippers are hydrogen sulfide, carbon dioxide, and ammonia. This concentrated product stream is then further processed for removal of these undesirable compounds. Similar processes un doubtedly will be necessary in existing and new gas production or gas treating f a c i l i t i e s . The design of these processes requires data regarding the equilibrium concentrations of undesirable com pounds absorbed into various aqueous waste streams, and then equilibrium data are required relating to the removal of these compounds from aqueous waste streams. T h i s paper r e p o r t s on measurements made i n t h r e e a r e a s p e r t a i n i n g t o t h e p r o c e s s i n g o f aqueous w a s t e s t r e a m s as f o l l o w s . A. B. C.

V a p o r - l i q u i d e q u i l i b r i u m measurements on N H 3 - H 2 O m i x t u r e s a t 80 and 120°C pH o f NH3-H S-C0 -HoO m i x t u r e s a t 25 and 80°C E f f e c t - o f sodium h y d r o x i d e and sodium a c e t a t e on N H 3 v o l a t i l i t y a t 80°C 2

2

0-8412-0569-8/80/47-133-187$10.00/0 © 1980 American Chemical Society

In Thermodynamics of Aqueous Systems with Industrial Applications; Newman, S., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

188

THERMODYNAMICS


Measurement

OF

AQUEOUS

SYSTEMS

WITH

INDUSTRIAL

APPLICATIONS

Apparatus

A f l o w - t y p e v a p o r - l i q u i d e q u i l i b r i u m a p p a r a t u s shown s c h e m a t i c a l l y i n F i g u r e 1 was used f o r t h e v a p o r - l i q u i d e q u i l i b r i u m measurements on N H 3 - H 2 O . The method i n v o l v e s t h e a n a l y s i s o f an e q u i l i b r i u m n i t r o g e n s t r e a m f o r NHU a f t e r e q u i l i b r a t i o n w i t h a N H 3 - H 2 O m i x t u r e c o n t a i n e d i n c y l i n d e r s 1 and 2 o f F i g u r e 1 . The p a r t i a l p r e s s u r e o f N H 3 i s t h e n c a l c u l a t e d f r o m t h e v a p o r mole f r a c t i o n of N H 3 times the t o t a l pressure o f the system. Two c y l i n d e r s were used t o s a t u r a t e t h e n i t r o g e n s t r e a m i n o r d e r t o m i n i m i z e l i q u i d d e p l e t i o n e f f e c t s and t o i n s u r e e q u i l i b r i u m b e tween t h e gas and l i q u i d p h a s e s . Vapor phase a n a l y s e s were made by a b s o r b i n g t h e N H 3 i n t o an aqueous HCI s o l u t i o n w h i c h was s u b s e q u e n t l y t i t r a t e d and by m e a s u r i n g t h e amount o f n i t r o g e n i n t h e sample by use o f a c a l i b r a t e d wet t e s t m e t e r a c c u r a t e t o + 1 % . P r e s s u r e s were measured by means o f c a l i b r a t e d p r e s s u r e gauges a c c u r a t e t o + 0 . 1 % , and t e m p e r a t u r e s were measured by means o f c a l i b r a t e d thermocouples a c c u r a t e to + 0.05°C. The c o m p o s i t i o n o f b o t h t h e v a p o r and t h e l i q u i d s a m p l e s were d e t e r m i n e d by p o t e n t i o m e t r i c t i t r a t i o n by a d d i t i o n o f s t a n d a r d i z e d NaOH s o l u t i o n t o samples which i n i t i a l l y c o n t a i n e d a s l i g h t excess o f HCI. T h i s method worked v e r y w e l l even a t t h e ppm l e v e l s s t u d i e d i n some o f t h e r u n s . The same t i t r a t i n g s o l u t i o n was used f o r a n a l y z i n g b o t h t h e v a p o r and t h e l i q u i d s a m p l e s o f each r u n t h u s m i n i m i z i n g e r r o r s p r o d u c e d i n s t a n d a r d i z i n g t h e NaOH s o l u t i o n . F i g u r e 2 g i v e s a s c h e m a t i c o f t h e a p p a r a t u s used f o r pH measurements a t 25 and 8 0 ° C . It consisted o f a stoppered Erlenmeyer f l a s k submerged i n a t e m p e r a t u r e b a t h r e g u l a t e d a t e i t h e r 25 o r 8 0 ° C . The c o n t e n t s o f t h e f l a s k were s t i r r e d by means o f a m a g n e t i c s t i r r e r c o u p l e d t o a m o t o r b e n e a t h t h e b a t h . A pH p r o b e and t h e r m o m e t e r were i n s e r t e d t h r o u g h t h e s t o p p e r a t t h e t o p o f t h e f l a s k and a n o t h e r h o l e was s t o p p e r e d f o r use i n p i p e t i n g s o l u t i o n i n t o or out o f the f l a s k . Measurements were made by f i r s t c a l i b r a t i n g t h e pH p r o b e u s i n g two b u f f e r s o l u t i o n s a t p H ' s o f 7 and 10 s u p p l i e d by Van Labs o f Van W a t e r s and Rogers Equipment Company . These s o l u t i o n s have been c e r t i f i e d by t h e N a t i o n a l B u r e a u o f S t a n d a r d s t o be a c c u r a t e t o + 0.01 pH u n i t a t 2 5 ° C . T h i s pH c a l i b r a t i o n was made w i t h t h e p r o b e i n s e r t e d i n b u f f e r s o l u t i o n a t t h e same t e m p e r a t u r e as t h e pH measurements were made. A f t e r c a l i b r a t i o n t h e p r o b e was i n s e r t e d i n t o t h e f l a s k shown i n F i g u r e 2 . A concentrated s o l u t i o n of NH3-H2S-CO0-H2O o f measured d e n s i t y was t h e n p i p e t e d i n t o t h e f l a s k and a f t e r t e m p e r a t u r e and pH e q u i l i b r a t i o n t h e pH was r e a d . This normally took a period of f i v e minutes f o r the e q u i l i b r a t i o n process. A f t e r r e a d i n g t h e p H , t h e s o l u t i o n was d i l u t e d w i t h w a t e r by f i r s t r e m o v i n g by p i p e t a p o r t i o n o f t h e s o l u t i o n i n t h e f l a s k and by s u b s e q u e n t a d d i t i o n o f w a t e r t o r e p l a c e t h e s o l u t i o n



Figure L

3

2

Schematicflowapparatus used for NH -H 0 rium measurements

(and electrolyte) vapor-liquid equilib-


oo VO


Figure 2. Schematic of apparatus used for pH (or NH

3

probe) measurements


9.

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Sour Water Equilibria

AL.

191

removed. B o i l e d d i s t i l l e d w a t e r was used f o r b o t h t h e s o l u t i o n p r e p a r a t i o n and d i l u t i o n s t a g e s o f t h e e x p e r i m e n t . A f t e r each d i l u t i o n , t h e pH was a g a i n r e a d . The c o n c e n t r a t e d s o l u t i o n s were p r e p a r e d by b u b b l i n g a c i d gas i n t o a s o l u t i o n o f ammonia and w a t e r . No gas was a l l o w e d t o e s c a p e so t h a t t h e i n c r e a s e i n t h e w e i g h t o f t h e s o l u t i o n r e p r e s e n t e d t h e amount o f HoS o r C 0 a d d e d . No p r o b l e m s were e n c o u n t e r e d when a d d i n g H^S by t h i s m e t h o d , but C 0 i s a b s o r b e d v e r y s l o w l y and l o n g p e r i o d s o f a g i t a t i o n o f t h e s o l u t i o n i n c o n t a c t w i t h gaseous C 0 were n e c e s s a r y t o a c h i e v e t h e d e s i r e d l e v e l s . A t t h e h i g h e r l o a d i n g s o f a c i d gas t o ammonia, p r o b l e m s were e n c o u n t e r e d when t h e s e s o l u t i o n s were h e a t e d t o 80°C b e c a u s e t h e a b s o r b e d gases t e n d e d t o be d r i v e n o f f . T h i s p r o b l e m was s o l v e d by c o n n e c t i n g t h e a b s o r p t i o n t r a i n composed o f d i g l y c o l a m i n e (DGA) on sand shown i n F i g u r e 2 . By t h i s m e t h o d , any components d i s c h a r g e d from t h e c e l l were a b s o r b e d i n t h e s e s c r u b b e r t u b e s . The t u b e s were t h e n weighed and a c o r r e c t i o n was made i n t h e c o m p o s i t i o n o f the s o l u t i o n i n the Erlenmeyer f l a s k . Some p r o b l e m s were e n c o u n t e r e d w i t h t h e pH p r o b e s used i n t h e pH measurements because t h e r e f e r e n c e e l e c t r o d e i s s a t u r a t e d with AgCl. Hydrogen s u l f i d e can r e a c t w i t h t h e AgCl i n s o l u t i o n , t h u s p r e c i p i t a t i n g AgS a t t h e KCl j u n c t i o n between t h e r e f e r e n c e e l e c t r o d e and t h e s o l u t i o n . In t h i s r e g a r d i t was f o u n d t h a t c e r t a i n p r o b e s work b e t t e r t h a n o t h e r s . Our o b s e r v a t i o n s a r e as follows. 2

2


2

1.

Some r e f e r e n c e e l e c t r o d e s have an e x p o s e d f i l l i n g h o l e f o r a d d i n g A g C l - s a t u r a t e d K C l . The h o l e i s l o c a t e d on t h e s i d e o f t h e probe where H S can r e a d i l y e n t e r and contaminate the s o l u t i o n . These e l e c t r o d e s p r o v e d entirely unsatisfactory. Some e l e c t r o d e s have t h e KCl s o l u t i o n i n a g e l f o r m . These e l e c t r o d e s work f a i r l y w e l l but e v e n t u a l l y t h e g e l becomes c o n t a m i n a t e d w i t h s i l v e r s u l f i d e and t h e p r o b e must be r e p l a c e d . T h i s t y p e o f p r o b e was used f o r t h e measurements g i v e n i n t h i s r e p o r t . Two p r o b e s were a c t u a l l y used f o r t h e e n t i r e s e t o f m e a s u r e m e n t s . T h e r e a r e a l s o e l e c t r o d e s a v a i l a b l e w h i c h have a g r o u n d g l a s s j u n c t i o n between t h e r e f e r e n c e e l e c t r o d e and t h e s o l u t i o n b e i n g m e a s u r e d . These p r o b e s w o u l d p r o b a b l y be most s u i t a b l e b e c a u s e t h e y can be d i s m a n t l e d and cleaned. A probe a r r i v e d as o u r measurements were b e i n g c o m p l e t e d so t h i s t y p e o f p r o b e has not y e t been t e s t e d i n our l a b o r a t o r y . 2

2.

3.

The e f f e c t s o f sodium a c e t a t e and sodium h y d r o x i d e on NH3 v o l a t i l i t y a t 80°C were s t u d i e d by two m e t h o d s . Data on t h e e f f e c t o f sodium a c e t a t e were measured i n t h e same a p p a r a t u s used t o measure t h e NH3-H0O d a t a shown i n F i g u r e 1. In t h i s c a s e , sodium a c e t a t e was a l s o added t o t h e l i q u i d phase w i t h s u b s e q u e n t


192

THERMODYNAMICS

OF

AQUEOUS

SYSTEMS

WITH

INDUSTRIAL

APPLICATIONS

N H 3 p a r t i a l p r e s s u r e measurements made i n t h e same manner used f o r the N H 3 - H 2 O measurements. Data on t h e e f f e c t o f sodium h y d r o x i d e were measured by means o f an N H 3 probe s u p p l i e d by O r i o n R e s e a r c h Company w h i c h o p e r a t e s i n a manner a n a l o g o u s t o a pH p r o b e e x c e p t t h a t a mem b r a n e i s used t h r o u g h w h i c h o n l y t h e N H 3 p e r m e a t e s . Thus t h e response o f the probe i s p r o p o r t i o n a l t o t h e a c t i v i t y (or p a r t i a l p r e s s u r e ) o f ammonia. E . m . f . d a t a on t h e e f f e c t o f sodium h y d r o x i d e were c o n v e r t e d t o ammonia p a r t i a l p r e s s u r e d a t a u s i n g t h e f o l l o w i n g e q u a t i o n . mv - m v


% 3

=

where f

f

NH 3

f

ref

m v

r

5

=

f

u

9

a

c

i

t

y

·

1

(

= f u g a c i t y o f NH

N H 3

N H 3 *

F

1 0

r e f

°f

N

H

3

1

)

3

Ί

'

η

a

reference solution of

NH^-H 0 2

e . m . f . o u t p u t o f NFL e l e c t r o d e i n m i l l i v o l t s mv ^ u . .4-t p » .u.4-t o ~ -Γ ef.= o f NM Hi 3l e_ 1l e c tX.r .o—d eI « i *_ n tΛ-h Ue ~ r e f e-C~w.~ r e n c e ~ s o l"Iu. t i o n βΤ = m i l l i v o l t s p e r d e c a d e , a t 80°C Τ = 70.1 mv/decade

A t l o w p r e s s u r e s t h e f u g a c i t y o f a component can be r e p l a c e d by i t s p a r t i a l p r e s s u r e so t h a t E q u a t i o n 1 can be a p p r o x i m a t e d as follows. mv - mv

ref.

N H - NH3f* (2) One p r o b l e m e n c o u n t e r e d w i t h t h e N H p r o b e was t h a t i t s c a l i b r a t i o n d r i f t e d w i t h t i m e , thus r e q u i r i n g frequent r e c a l i b r a t i o n of the probe. For t h i s r e a s o n t h e p r o b e was abandoned when t h e measurements w i t h sodium a c e t a t e were made. P

3

P

1 0

T

3

Measurement

Results

Vapor-Liquid E q u i l i b r i u m Data. Vapor-liquid equilibrium measurements on N H - H 0 m i x t u r e s a t 80 and 120°C a r e summarized i n T a b l e s 1 and 2 , r e s p e c t i v e l y . A t each c o n d i t i o n , s e v e r a l v a p o r and l i q u i d s a m p l e s were removed f o r a n a l y s i s b e f o r e p r o ceeding to the next c o n d i t i o n . These t a b l e s summarize t h e a n a l y s e s o f t h e s e s a m p l e s a t each c o n d i t i o n and t h e n g i v e an a v e r a g e v a l u e f o r each r u n c o n d i t i o n . The c h a r g e a n a l y s e s a r e based on a n a l y s e s o f t h e s o l u t i o n c h a r g e d t o t h e measurement a p p a r a t u s a t t h e b e g i n n i n g o f each run and l i q u i d a n a l y s e s a r e based on sam p l e s removed from t h e a p p a r a t u s d u r i n g t h e r u n . A c o m p a r i s o n o f t h e s e a n a l y s e s shows t h a t t h e l i q u i d a n a l y s e s a r e a l l s l i g h t l y l o w e r t h a n t h e c h a r g e a n a l y s i s and t h a t t h e l i q u i d a n a l y s e s d e c r e a s e s l i g h t l y w i t h each s a m p l e . T h i s e f f e c t i s due t o l o s s o f ammonia t o t h e v a p o r phase i n s a m p l i n g t h e v a p o r and t h u s 3

2


WILSON

ET

TABLE 1.

Ammonia-Water Vapor-Liquid E q u i l i b r i u m Measurements a t 80°C by Flow C e l l Method

wt % NH, in in liquid charge

1.39 1.40 1.37 1.39

1.24 1.25 1.22 1.24

1.240 1.250 1.247 1.246

6.80 6.80 6.80 6.80

8.04 8.05 8.05 8.05

1.25 1.28 1.31 1.28

1.23 1.26 1.29 1.26

.122 .119 .119 .120

6.86 6.86 6.86 6.86

6.98 6.98 6.98 6.98

1.23 1.21 1.23 1.23

1.25 1.23 1.25 1.25

99.2 ppm 97.7 96.0 94.3 96.8

.0111 .0113 .0112 .0110 .0112

6.87 6.87 6.87 6.87 6.87

6.88 6.88 6.88 6.88 6.88

1.12 1.16 1.17 1.17 1.16

1.18 1.22 1.23 1.23 1.22

10.08 ppm 10.04 9.93 10.02

.00108 .00108 .00107 .00108

6.87 6.87 6.87 6.87

6.87 6.87 6.87 6.87

1.07 1.08 1.08 1.08

1.26 1.27 1.27 1.27

average

.0991 .0983 .0965 .0980

.0993

average

10.09 ppm

average

3

b

—3

13.39 13.37 13.16 13.31

.994 .974 .950 .973

average

Total V o l a t i l i t y Ratio Pressure, PNH /wt % . Uncorr. Corr. > psi a

6.51 6.51 6.51 6.51

1.000

100.0 ppm

Partial Pressure, psia

6.88 6.86 6.65 6.80

4.94 4.90 4.86 4.90

4.97


193


AL.

^Actual measurements were made under nitrogen pressure according to conditions summarized i n Table 4. The p a r t i a l pressure o f water as given here i s based on Raoult's Law which applies a t the low NHo concentrations given here. By t h i s method the p a r t i a l pressure of water i s given as f o l l o w s . P

P

X

H 0 " H 0 H 0' 2

2

P° Q = vapor pressure of pure water

2

x

u

n

= water mole f r a c t i o n

in liquid

The vapor pressure o f water was taken from the CRC Handbook, 52nd Ed., page D-147. b)See t e x t f o r c o r r e c t i o n s applied.


194

THERMODYNAMICS


TABLE 2.

OF

AQUEOUS

3

average

average 9.83 ppm

Partial Pressure, p s i a % \ -

Total V o l a t i l i t y Ratio Pressure, ^NHo/wt % psia Uncorr. Corr. 4..00 4..02 4..09 4,.04

3.81 3.83 3.89 3.85

28.52 28.53 28.54 28.53

32.1 32.1 32.1 32.1

3,.99 4,.03 4,.09 4..04

3.97 4.01 4.07 4.02

.342 .341 .329 .315 .332

28.77 28.77 28.77 28.77 28.77

29.1 29.1 29.1 29.1 29.1

3,.64 3..73 3,.75 3..75 3..72

3.69 3.78 3.80 3.80 3.77

92.2 ppm 90.0 87.8 84.8 88.7

.0332 .0332 .0326 .0317 .0327

28.79 28.79 28.79 28.79 28.79

28.8 28.8 28.8 28.8 28.8

3.,60 3..69 3.,71 3..74 3..69

3.77 3.86 3.88 3.91 3.86

9.72 ppm 9.44 9.12 . 9.43

.00358 .00368 .00367 .00364

28.80 28.80 28.80 28.80

28.8 28.8 28.8 28.8

3.,68 3. 90 4.,02 3.,86

4.24) 4.49(appear 4.63( high 4.45)

.0940 .0914 .0878 .0840 .0893

93.4 ppm

APPLICATIONS

46.4 45.9 45.6 46.0

.0955

average

INDUSTRIAL

27.35 27.39 27.44 27.39

.900 .880 .850 .877

.0898 .0856

average .

4.75 4.60 4.45 4.60

.905 .889 .867 average ,

WITH

Ammonia-Water Vapor-Liquid E q u i l i b r i u m Measurements a t 120°C by Flow Cell Method

wt % NH in in charge liquid 4.83 4.68

SYSTEMS

19.0 18.5 18.2 18.6 3.59 3.55 3.48 3.54

See footnote'a" at the bottom of Table 2. See t e x t f o r c o r r e c t i o n s applied.



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AL.

195

r e p r e s e n t s s l i g h t d e p l e t i o n o f t h e l i q u i d w i t h each v a p o r s a m p l e . The l i q u i d a n a l y s e s i n t h e s e t a b l e s a r e a v e r a g e s o f a n a l y s e s made b e f o r e and a f t e r s a m p l i n g t h e v a p o r so t h e c o n c e n t r a t i o n s g i v e n r e p r e s e n t t h e a v e r a g e l i q u i d c o m p o s i t i o n d u r i n g t h e v a p o r sam pling process. The ammonia p a r t i a l p r e s s u r e s g i v e n i n T a b l e s 1 and 2 a r e based on t h e c o n c e n t r a t i o n o f ammonia f o u n d i n t h e v a p o r s t r e a m times the t o t a l pressure. The a c t u a l p r e s s u r e s a p p l i e d a t each run c o n d i t i o n a r e summarized i n T a b l e 3 where t h e p r e s s u r e s v a r i e d f r o m 15 p s i a a t 80°C t o 90 p s i a a t 120°C. B e c a u s e n i t r o gen was used as a p r e s s u r i z i n g f l u i d , t h e p a r t i a l p r e s s u r e o f w a t e r and t h e t o t a l p r e s s u r e e x c l u d i n g n i t r o g e n have been compu t e d i n T a b l e s 1 and 2 based on R a o u l f s l a w f o r w a t e r as n o t e d a t t h e b o t t o m o f T a b l e 1. R a o u l t ' s law a p p l i e s f o r the p a r t i a l p r e s s u r e o f w a t e r because t h e a c t i v i t y c o e f f i c i e n t o f w a t e r i s v i r t u a l l y u n i t y a t t h e l o w l e v e l s o f ammonia used i n t h e l i q u i d phase. M i n o r e f f e c t s due t o v a p o r non- i d e a l i t y have n o t been applied. The l a s t two columns o f T a b l e s 1 and 2 g i v e e q u i l i b r i u m v o l a t i l i t y r a t i o s o f ammonia p a r t i a l p r e s s u r e d i v i d e d by t h e w e i g h t p e r c e n t o f ammonia i n t h e l i q u i d p h a s e . The column l a beled " U n c o r r . " gives the v o l a t i l i t y r a t i o computed s i m p l y as t h e p a r t i a l p r e s s u r e o f ammonia d i v i d e d by t h e t o t a l w e i g h t p e r c e n t o f ammonia i n s o l u t i o n . The s e c o n d column g i v e s a c o r r e c t e d v o l a t i l i t y r a t i o based on t h e d i s s o c i a t i o n o f ammonia a t l o w c o n c e n t r a t i o n s and e x t r a p o l a t i o n t o z e r o c o n c e n t r a t i o n o f ammonia. The d i s s o c i a t i o n c o r r e c t i o n was a p p l i e d by d i v i d i n g t h e u n c o r r e c t e d v o l a t i l i t y r a t i o by t h e computed r a t i o o f f r e e ammonia o v e r t o t a l ammonia i n s o l u t i o n . The r a t i o o f f r e e ammonia o v e r t o t a l ammonia was computed from t h e d i s s o c i a t i o n c o n s t a n t o f ammonia g i v e n by Edwards and P r a u s n i t z (]_) as f o l l o w s . NH 0H-^NH 4

Temperature

4

+

+ OFT

°C

Dissociation

25 80 120

Constant

1.78 χ 1 0 ~ 1 .66 χ Ι Ο " 1 .19 χ 1 0 " 5

5

5

W i t h no o t h e r i o n s p r e s e n t t h e c o n c e n t r a t i o n o f f r e e ammonia o v e r t o t a l ammonia p r e s e n t i s g i v e n by t h e f o l l o w i n g e q u a t i o n : (NH*)-

0 1

( 3)total where k = d i s s o c i a t i o n c o n s t a n t o f NFL C = t o t a l c o n c e n t r a t i o n o f NHg m o l e s / K g w a t e r N H

4 C

In a d d i t i o n t o t h i s c o r r e c t i o n t h e v o l a t i l i t y r a t i o o f ammonia


196

THERMODYNAMICS


TABLE 3.

Temp. °C

80

OF

AQUEOUS

WITH

INDUSTRIAL

APPLICATIONS

Measurement Pressures f o r Ammonia-Water Vapor-Liquid E q u i l i b r i u m Runs

NH wt j

NaAc wt %

q

5

0

1

Measurement Pressure with Ν 2 psia

30

0

20

.1

0

15

100 ppm

0

15

10 ppm

0

15

25

20

1

15

20

1

5

20

5

0

90

1

0

60

.1

0

60

100 ppm

0

60

10 ppm

0

60

1 wt

120

SYSTEMS

%


9.

197


WILSON E T A L .

v a r i e s due t o t h e s o l v e n t e f f e c t o f f r e e ammonia a c c o r d i n g t o t h e f o l l o w i n g equation given in Table 1 of reference 2. 1n(H

N H 3

)

- ln(H^

H 3

)

+

fiC

N

H

(4)

3

where H ° = v o l a t i l i t y r a t i o a t z e r o c o n c e n t r a t i o n o f f r e e ammonia CJS^HO e f f e c t o f f r e e ammonia on t h e v o l a t i l i t y 3 = t e m p e r a t u r e d e p e n d e n t c o n s t a n t ; β = 131.4/T°R - .1682 =

CNH3

=

c

o

n

c

e

n

t

r

a

t

Solving for ln(HNH ) 3

1Π(ΗΝΗ )


R

NH

H

=

3

H

o

NH

3

E

X

P

°^

n

f

r

e

e

a m m o n l

" »

moles/Kg water

a

gives the f o l l o w i n g equation.

= ln(H

3

O

l

N H 3

)

- 3 C

N

H

(5)

3

(^ NH ) C

(

3

E q u a t i o n s 2 and 5 can be combined t o g i v e a t o t a l follows. /

6

)

c o r r e c t i o n as

P u \° (P /wt % N F L ) exp(-BC ) 3 j = H Uncorr. 3 (7) Iwt % N H I . p^jr JTlNfT Π ' free total Thus t h e l a s t column i n T a b l e s 1 and 2 c o r r e s p o n d s t o t h e v o l a t i l i t y r a t i o o f ammonia based on f r e e ammonia and e x t r a p o l a t e d t o z e r o c o n c e n t r a t i o n o f f r e e ammonia. T h i s number s h o u l d be i n d e pendent o f t h e c o n c e n t r a t i o n s s t u d i e d a t a g i v e n t e m p e r a t u r e , and any v a r i a t i o n r e p r e s e n t s e r r o r s i n e i t h e r t h e measured d a t a o r i n t h e a p p l i e d c o r r e c t i o n s . The f o l l o w i n g i s a c o m p a r i s o n o f t h e a v e r a g e s f r o m each r u n . M U

N

N H

N

3

C

o

r

M U

3

3

N H

r

J

NH Concentration 3

5 wt % 1 wt % .1 wt % 100 ppm 10 ppm A v e r a g e ( E x c l u d i n g 10 ppm p o i n t a t 120°C)

(P u N

m

3 80°C

3

/wt % ) ° Corr. 120°C

1.24 1 .26 1.25 1 .22 1.27

3.85 4.02 3.77 3.86 4.45

1 .25 + 2%

3 . 8 8 + 4%

(appears

high)

T h i s agreement i s c o n s i d e r e d t o be q u i t e good when a l l o w a n c e i s made f o r t h e f a c t t h a t t h e s e a r e i n d e p e n d e n t l y measured r u n s a t c o n c e n t r a t i o n s v a r y i n g by a r a t i o o f 5000 t o 1! The 10 ppm r u n a t 120°C i s p r o b a b l y i n e r r o r due t o a t r a c e c o n t a m i n a n t i n t h e vapor samples observed i n t h e p o t e n t i o m e t r i c t i t r a t i o n c u r v e . T h i s p r o b l e m was n o t o b s e r v e d a t 8 0 ° C . The f a v o r a b l e c o m p a r i s o n g i v e n above shows t h a t t h e ammonia


198

THERMODYNAMICS

O F AQUEOUS

SYSTEMS

WITH

INDUSTRIAL

APPLICATIONS

v o l a t i l i t y r a t i o can be r e l i a b l y e x t r a p o l a t e d t o l o w c o n c e n t r a tions without loss o f accuracy. T h i s i s i m p o r t a n t because t h e b u l k o f p u b l i s h e d l i t e r a t u r e d a t a on t h e v o l a t i l i t y o f ammonia a r e a t c o n c e n t r a t i o n s o f λ% NhL o r h i g h e r . A c o m p a r i s o n o f t h i s new v o l a t i l i t y r a t i o w i t h measured l i t e r a t u r e d a t a i s g i v e n i n F i g u r e 3 where d e v i a t i o n r a t i o s o f N H 3 ( m e a s ) / 3 ( c a l c ) a r e p l o t t e d v e r s u s t e m p e r a t u r e where com p a r i s o n i s made w i t h t h e SWEQ c a l c u l a t i o n model o f r e f e r e n c e 2 . T h i s p l o t shows t h a t t h e s e new d a t a a r e i n f a i r agreement w i t h t h e c a l c u l a t e d v a l u e s w i t h r a t i o s o f a b o u t 1.05 a t b o t h 80 and 120°C. F o r t u n a t e l y f o r the authors these data a l s o agree q u i t e w e l l w i t h p r e v i o u s l y measured d a t a r e p o r t e d by M i l e s and W i l s o n P

PNH


(3). In summary t h e f o l l o w i n g can be c o n c l u d e d from t h e g i v e n i n T a b l e s 1 and 2 . 1.

2.

data

The v o l a t i l i t y o f ammonia a t ppm l e v e l s can be c a l c u l a t e d from t h e i o n i z a t i o n c o n s t a n t o f ammonia combined w i t h v o l a t i l i t y d a t a measured a t h i g h e r c o n c e n t r a t i o n s o f ammonia. The v o l a t i l i t y o f ammonia a t 80 and 1 2 0 ° C i s a b o u t 5% h i g h e r t h a n i s now p r e d i c t e d by t h e SWEQ m o d e l . This means t h a t t h e SWEQ model w i l l p r e d i c t s l i g h t l y more steam f o r a g i v e n s e p a r a t i o n , a l l o t h e r e f f e c t s b e i n g e q u a l , t h a n w i l l a c t u a l l y be r e q u i r e d .

pH o f NH3-H2S-CO2-H2O M i x t u r e s . pH measurements on NHo- H SCO2-H0O m i x t u r e s have been made a t 2 5 ° C and 8 0 ° C a s o u t l i n e d i n P a r t Β o f t h e Measurement P r o g r a m . The r e s u l t s o f t h e s e m e a s u r e ments a r e g i v e n i n T a b l e s 4 t o 2 2 . Each t a b l e g i v e s t h e c o m p o s i t i o n o f each s o l u t i o n a t v a r i o u s d i l u t i o n s and measured and c o r r e l a t e d pH d a t a a t each c o m p o s i t i o n . The SWEQ c o m p u t e r program ( 2 j does n o t a c c u r a t e l y p r e d i c t t h e s e pH d a t a , so an e m p i r i c a l c o r r e l a t i o n o f t h e d a t a was made i n o r d e r t o g i v e c o m p a r i s o n s between t h e d a t a and a s m o o t h i n g f u n c t i o n . T h i s s m o o t h i n g f u n c t i o n i s based on t h e f o l l o w i n g e q u i l i b r i u m w h i c h i s assumed t o be a f u n c t i o n o f t h e c o n c e n t r a t i o n o f t h e components i n s o l u t i o n . 2

NH3 + H ~ > N H +

4

(8)

+

(9) In E q u a t i o n 9, t h e hydrogen i o n c o n c e n t r a t i o n i s g i v e n by t h e pH m e a s u r e m e n t s ; and t h e r a t i o o f N r ^ / N H ^ can be a p p r o x i m a t e d from t h e m o l e s o f a c i d gas per mole o f NH3 a s s u m i n g a l l o f t h e a c i d gas r e a c t s a s f o l l o w s . NH

3

+ HA — > N H

4

+

+A"

,

A ' = HCO3

o

r H S

~


(10)


9.

WILSON

ET AL.

20

30

199


40

50

70

80

Ί00 110 120 130 140 150

Temperature, °C Figure 3. Ammonia mean ratio of measured over calculated partial pressures based on SWEQ correlation (®) new data; see Figure 2 of Réf. 1 for the following: (O) Miles & Wilson; Ο Clifford; (A) Van Krevelen NH -C0 ; (V) Cardon & Wilson; Badger & Silver; ( 0 ) Breitenback & Perman) 3

2


200

THERMODYNAMICS

OF


TABLE 4.

AQUEOUS

SYSTEMS

WITH

INDUSTRIAL

APPLICATIONS

Measured and Correlated pH of Water-Ammonia Mixtures with no Acid Gas Present, 25°C

Ratio 3

Ammonia ^ wt %

NH3/NH4

(SWEQ)

Meas.

PH Correl.

Diff.

2.82

9.491

9.606

-.115

.00308

5.19

9.807

9.875

-.068

.00925

9.34

10.123

10.137

-.014

.00103

.0277

16.5

10.369

10.397

-.028

.111

33.4

10.726

10.733

-.007

.335

58.6

11.014

11.021

-.007

1.01

102

11.283

11.337

-.054

3.05

177

11.597

11.709

-.112

6.17

254

11.883

11.997

-.114

8.30

293

12.066

12.130

-.064

11.21

339

12.272

12.276

-.004

15.20

391

12.588

12.436

.152

Balance i s water


9.

WILSON

ET AL.

201


TABLE 5. Measured and Correlated pH o f Water-Ammonia Mixtures with 0.253 Mole of H S/Mole o f NhU 25°C 9


ù

0

Ammonia ^ wt %

HS> wt %

Ratio NH /NH (SWEQ)

Meas.

PH Correl.

Diff.

.00135

.00068

1.69

9.303

9.385

-.082

.00404

.00205

2.26

9.414

9.517

-.103

.0121

.00612

2.66

9.495

9.604

-.109

.0364

.0184

2.85

9.567

9.643

-.076

.109

.0552

2.91

9.669

9.680

-.011

.328

.166

2.94

9.772

9.732

.040

.985

.499

2.95

9.896

9.818

.078

3

a

2

+

3

4

2.96

1.50

2.95

9.996

9.963

.033

5.97

3.02

2.96

10.083

10.108

-.025

8.90

4.50

2.96

10.155

10.216

-.061

10.50

5.31

2.96

10.196

10.267

-.071

14.11

7.14

2.96

10.230

10.370

-.140

Balance i s water


202

THERMODYNAMICS

OF

TABLE 6.

AQUEOUS

SYSTEMS

WITH

INDUSTRIAL

APPLICATIONS

Measured and Correlated pH of Water-Ammonia Mixtures with 0.491 Mole of H-S/Mole of NH 25°C


?

Ratio 3

Ammonia ^ wt %

H S wt %

a )

2

Meas.

PH Correl.

Diff.

9.040

9.143

-.103

NH3/NH4

(SWEQ)

.00407

.00400

.0122

.0120

1.01

9.080

9.178

-.098

.0366

.0359

1.03

9.174

9.204

-.030

.110

.108

1.04

9.290

9.239

.051

.330

.324

1.04

9.405

9.292

.113

.952

1.04

9.497

9.383

.114

2.97

2.91

1.05

9.599

9.546

.053

5.94

5.83

1.04

9.649

9.697

-.048

9.92

9.73

1.04

9.758

9.852

-.094

13.23

12.98

1.04

9.734

9.958

-.224

.990

.971

Balance i s water


9.

WILSON

ET

AL.

203


TABLE 7.

Measured and Correlated pH of WaterAmmonia Mixtures with 0.251 Mole of C0 / Mole o f NH , 25°C ?


3

aï Ammonia wt %

a) C0 wt %

.00180

Ratio (SWEQ)

Meas.

PH Correl.

Diff.

.00117

1.66

9.343

9.379

-.036

.00457

.00296

1.93

9.438

9.461

-.023

.0116

.00750

2.18

9.463

9.512

-.049

.0295

.0191

2.27

9.509

9.543

-.034

.0748

.0485

2.29

9.573

9.569

.004

.190

.123

2.29

9.606

9.605

.001

.481

.312

2.25

9.644

9.653

-.009

.791

a;

1.22

a ;

2

NH3/NH4

2.19

9.735

9.731

.004

1.75

1.13

2.17

9.768

9.775

-.007

5.72

3.71

2.07

10.005

9.988

.017

7.60

4.92

2.06

10.095

10.065

.030

10.1

6.53

2.04

10.210

10.153

.057

13.4

8.65

2.03

10.379

10.256

.123

Balance i s water


204

THERMODYNAMICS

OF

TABLE 8.

AQUEOUS

SYSTEMS

WITH

INDUSTRIAL

APPLICATIONS


3

3


Ammonia ^ wt %

a )

C0 wt % 2

Ratio NH /NH (SWEQ) 3

+

Meas.

PH Correl.

Diff.

4

.000297

.000400

.452

8.579

8.810

-.231

.000754

.00102

.592

8.789

8.929

-.140

.00191

8.951

9.003

-.052

.00257

.695

.00486

.00654

.746

9.028

9.040

-.012

.0123

.0166

.761

9.074

9.060

.014

.0313

.0421

.768

9.096

9.080

.016

.0794

.107

.748

9.105

9.096

.009

.201

.271

.704

9.127

9.112

.015

.661

.890

.597

9.138

9.133

.005

.507

9.162

9.146

.016

1.31

1.77

1.74

2.35

.466

9.163

9.154

.009

2.31

3.11

.428

9.176

9.168

.008

3.06

4.12

.388

9.189

9.184

.005

4.04

5.44

.349

9.210

9.204

.006

5.32

7.16

.314

9.240

9.233

.007

6.97

9.38

.280

9.277

9.268

.009

9.10

12.25

.248

9.329

9.311

.018

11.81

15.89

.220

9.430

9.366

.064

Balance i s water


9.

WILSON

ET

AL.

205


TABLE 9.

Measured and Correlated pH of WaterAmmonia Mixtures with .755 Mole of C0«/ Mole o f NH , 25°C


3

a) Ammonia* wt %

*) C0 wt %

Ratio ΝΗο/ΝΗλ (SWEQ)

Meas.

PH Correl.

Diff.

.00238

.00463

.278

8.629

8.608

.021

.00579

.0113

.283

8.679

8.623

.056

.0141

.0274

.289

8.709

8.644

.065

.0342

.0664

.285

8.716

8.657

.059

.0828

.161

.271

8.725

8.664

.061

.201

.391

.244

8.718

8.664

.054

.486

;

;

2

.201

8.698

8.650

.048

1..17

2..27

.145

8.641

8.616

.025

2..31

4..49

.0990

8.577

8.574

.003

4..50

8..74

.0632

8.500

8.549

-.049

5..90

11..46

.0513

8.472

8.545

-.073

.944

Balance i s water


206

THERMODYNAMICS

OF AQUEOUS

TABLE 10.

SYSTEMS

WITH

INDUSTRIAL

APPLICATIONS



3

3

Ammonia ^ wt %

a )

C0 wt % 2

Ratio NH /NH (SWEQ) 3

Meas.

PH Correl.

Diff.

+

4

.000902

.00207

.110

8.265

8.200

.065

.00219

.00501

.119

8.345

8.239

.106

.00532

.0122

.119

8.393

8.247

.146

.0129

.0295

.122

8.400

8.270

.130

.0314

.0719

.118

8.391

8.274

.117

.0761

.174

.113

8.400

8.285

.115

.185

.423

.0996

8.382

8.276

.106

1.02

.0789

8.335

8.245

.090

1.07

2.46

.0521

8.233

8.174

.059

2.11

4.83

.0346

8.131

8.120

.011

2.78

6.37

.0281

8.084

8.093

-.009

.446

Balance i s water


9.

WILSON

ET

207


AL.

TABLE 11. Measured and Correlated pH of WaterAmmonia Mixtures with .124 Mole of C0 and .124 Mole o f H S per Mole of NhL, 25°C

2

?


ά

Ratio Ammonia ^ wt %

co wt %

H S wt %

0.00298

0..000954

0.000737

0.00724

0,.00232

0.00179

0.0176

0.,00563

0.0427

3

2

a )

a )

2

N H

3

/ N H /

PH

Meas.

Correl.

Diff.

2.003

9,.248

9.463

-0.215

2.311

9,.435

9.531

-0.096

0.0435

2.494

9,.489

9.574

-0.085

0.,0137

0.0106

2.568

9..476

9.601

-0.125

0.104

0.,0332

0.0256

2.623

9.,546

9.634

-0.088

0.252

0.,0806

0.0623

2.622

9.,631

9.670

-0.039

0.612

0.,196

0.151

2.613

9.,733

9.724

0.009

1.49

0.476

0.367

2.603

9.,845

9.811

0.034

3.61

1. 16

0.893

2.562

9. 975

9.941

0.034

7.24

2.32

1.79

2.556

10. 116

10.100

0.016

9.67

3.09

2.39

2.560

10. 194

10.185

0.009

4. 13

3.19

2.554

10. 298

10.281

0.017

12.91

(SWEQ)

Balance i s water


208

THERMODYNAMICS

OF

TABLE 12.

AQUEOUS

SYSTEMS

WITH

INDUSTRIAL

Measured and Correlated pH o f WaterAmmonia Mixtures with .277 Mole of CO. and .277 Mole o f H S per Mole of NH ' 25°C ?


APPLICATIONS

V

Ratio Ammonia ^ wt %

co wt %

H S wt %

0.00136

0.000964

3

2

a )

a )

2

NH3/NH4

pH

(SWEQ)

Meas.

Correl.

Diff.

0.000753

0..635

8..576

8. 961

-0. 385

8.,745

9.,011

-0.,266

0.00363

0.00257

0.00201

0..704

0.00967

0.00686

0.00535

0..732

8.,877

9.,036

-0.,159

0.0258

0.0183

0.0143

0.,740

8.,934

9.,055

-0.,121

0.0687

0.0488

0.0382

0.,730

9.,002

9.,072

-0. 070

0.183

0.130

0.102

0. 706

9.,085

9.,095

-0.,010

0.408

0.346

0.271

0.,682

9.,150

9. 127

-0. 023

1.296

0.919

0.720

0.,587

9.,209

9. 177

0.,032

3.422

2.428

1.900

0.,499

9.,293

9. 273

0. 020

6.443

4.571

3.577

0.,447

9. 376

9.388

-0. 012

8.380

6.013

4.653

0.,417

9.,416

9. 443

-0.,027

7.800

6.035

0.,399

9. 479

9. 519

-0. 040

10.87

Balance i s water


9.

WILSON

ET

209


AL.

TABLE 13 .

Measured and Correlated pH of WaterAmmonia Mixtures with 0.375 Mole of H S and 0.372 Mole o f CO? per Mole of NhL, 25°C ?


0

Ratio 3

Ammonia ^ wt %

C0o wt %

a)

H S wt %

a )

2

(SWEQ)

Meas.

PH Correl.

Diff.

NH3/NH4

0.00280

0.,00269

0.00210

0.3074

8.542

8.650

-0.108

0.00680

0..00653

0.00509

0.3176

8.598

8.671

-0.073

0.0165

0.,0159

0.0124

0.3155

8.643

8.679

-0.036

0.0401

0.,0385

0.0300

0.3183

8.686

8.700

-0.014

0.0973

0..0934

0.0729

0.3091

8.732

8.714

0.018

0.0236

0..227

0.177

0.2886

8.768

8.647

0.121

0.0572

0..549

0.428

0.2573

8.774

8.617

0.157

1.38

1..33

1.034

0.2055

8.764

8.746

0.018

3.30

3..17

2.47

0.1514

8.740

8.772

-0.032

5.92

5,.69

4.44

0.1145

8.719

8.805

-0.086

7.56

7,.27

5.67

0.1003

8.715

8.827

-0.112

Balance i s water


210

THERMODYNAMICS

OF


TABLE 14.

AQUEOUS

SYSTEMS

WITH

INDUSTRIAL

APPLICATIONS

Measured and Correlated pH of WaterAmmonia Mixtures with No Acid-Gas Present, 80°C

Ratio 3

Ammonia ^ wt % 0.00202

Meas.

PH Correl.

Diff.

8.077

8.138

-.061

NH3/NH4

(SWE0)

4.4484

0.0121

11.565

8.432

8.636

-.204

0.0273

17.572

8.636

8.881

-.245

0.0614

26.638

8.826

9.143

-.317

0.221

51.020

9.156

9.597

-.441

10.127

-.601

0.887

102.43

9.526

1.79

145.48

9.717

10.396

-.679

3.61

208.46

9.865

10.662

-.797

b)

Balance i s water These differences i n d i c a t e that the NH /NH r a t i o from the SWEQ computer program are too high. 3

+ 4



9.

WILSON

ET

AL.


211

TABLE 15. Measured and Correlated pH o f WaterAmmonia Mixtures with 0.258 Mole o f H?S/ Mole o f N H 80°C V

Ratio 3

Ammonia ^ wt %

H S wt %

a )

2

(SWEQ)

Meas.

PH Correl.

Diff.

NH3/NH4

0.00292

0.00151

2.150

7.805

7.840

-.035

0.00709

0.00366

2.504

7.966

7.950

.016

0.0172

0.00889

2.709

8.057

8.045

.012

0.0418

0.0216

2.818

8.208

8.147

.061

0.102

0.0524

2.869

8.323

8.265

.058

0.246

0.127

2.891

8.470

8.400

.070

0.600

0.309

2.898

8.575

8.550

.025

1.46

0.756

2.894

8.675

8.699

-.024

3.58

1.85

2.891

8.777

8.836

-.059

Balance i s water


212

THERMODYNAMICS

OF

TABLE 16 .

AQUEOUS

SYSTEMS

WITH

INDUSTRIAL

APPLICATIONS

Measured and Correlated pH of WaterAmmonia Mixtures with 0.480 Mole of H S/ Mole o f N H , 80°C


?

3

Ratio 3

Ammonia ^ wt %

H S wt %

a )

(SWEQ)

Meas.

PH Correl.

Diff.

0.00178

.948

7.511

7.472

.039

0.00468

0.00451

1.041

7.618

7.553

.065

0.0119

0.0114

1.085

7.724

7.631

.093

0.0302

0.0291

1.105

7.863

7.722

.141

0.0767

0.0738

1.113

7.952

7.836

.116

0.195

0.187

1.115

8.062

7.975

.087

0.494

0.477

1.111

8.152

8.128

.024

1.26

1.22

1.107

8.235

8.283

-.048

3.21

3.12

1.096

8.324

8.422

-.098

0.00185

N H

2

3

/ N H /

Balance i s water



9.

WILSON

ET

AL.

213


TABLE 17.

Measured and Correlated pH of WaterAmmonia Mixtures with .555 Mole of H S/ Mole of NH , 80°C 2

3

a) Ammonia wt %

d;

a) H S wt %

Ratio

Eb

a ;

2

NH0/NH4

(SWEQ)

Meas.

Correl.

Diff.

.0935

.104

0.8439

7.809

7.750

.059

.187

.208

0.8453

7.853

7.855

-.002

.375

.416

0.8453

7.874

7.970

-.096

0.8453

7.916

8.088

-.172

.752

.834

1.55

1.70

0.8628

7.985

8.215

-.230

3.07

3.89

0.6293

8.094

8.187

-.093

Balance i s water


214

THERMODYNAMICS

OF


TABLE 18.

AQUEOUS

SYSTEMS

WITH

INDUSTRIAL

APPLICATIONS

Measured and Correlated pH of WaterAmmonia Mixtures with .315 Mole of CO?/ Mole o f NH , 80°C 3

Ratio 3

Ammonia ^ wt %

C0 wt %

3 )

2

(SWEQ)

Meas.

PH Correl.

Diff.

NH3/NH4

0.00175

0.,00142

1,.572

7.,830

7.687

.143

0.00425

0.,00346

1,.845

7.,927

7.792

.135

0.0103

0..00840

2..011

8..048

7.880

.168

0.0878

0,,0714

2..108

8.,272

8.118

.154

0.213

0..173

2,.075

8.,405

8.242

.163

0.515

0..420

1,.989

8..496

8.371

.125

1.25

1..02

1,.853

8.,591

8.491

.100

3.01

2..46

1..665

8..692

8.584

.108

5.98

4..95

1,.487

8..830

8.630

.200

Balance i s water



9.

WILSON

ET

AL.


215

TABLE 19. Measured and Correlated pH of WaterAmmonia Mixture with .429 Mole of CO?/ Mole of N H 80°C V

Ratio 3

Ammonia ^ wt %

co wt % 2

a )

(SWEQ?

Meas.

PH Correl.

Diff.

NH0/NH4

0.00244

0.00269

1.164

7.557

7.571

-.013

0.00548

0.00605

1.260

7.601

7.643

-.042 -.058

0.0123

0.0136

1.309

7.654

7.712

0.0278

0.0306

1.327

7.742

7.789

-.047

0.166

0.183

1.297

7.950

8.011

-.061

0.373

0.412

1.243

8.039

8.125

-.086

1.33

1.46

1.079

8.141

8.282

-.141

2.63

2.96

.908

8.210

8.316

-.106

5.13

6.08

.690

8.308

8.293

.015

Balance i s water


216

THERMODYNAMICS

OF AQUEOUS

TABLE 20.

SYSTEMS

WITH

INDUSTRIAL

APPLICATIONS

Measured and Correlated pH of WaterAmmonia Mixtures with .121 Mole of H S and .126 Mole of C0 per Mole of NFU, 80°C


?

?

ù

0

Ratio NH3/NH4 (SWEQ)

Meas.

E±L Correl.

Diff.

0.000430

1.962

7.737

7.783

-.046

0.,00131

0.000968

2.051

7.794

7.834

-.041

0.00902

0.,00294

0.00218

2.675

7.816

7.992

-.176

0.0542

0. 0176

0.0131

2.954

8.124

8.196

-.072

0.122

0. 0397

0.0295

2.977

8.264

8.306

-.042

0.275

0.,0895

0.0664

2.967

8.416

8.429

-.013

0.765

0.,252

0.185

2.889

8.609

8.589

.020

2.78

0. 925

0.670

2.740

8.787

8.777

.010

5.70

1.,90

1.39

2.622

8.901

8.858

.043

3

Ammonia ^ wt %

a )

C0 wt %

H S wt %

0.00178

0.000581

0.00401

2

a )

2

Balance i s water



9.

WILSON

ET

111


AL.

TABLE 21 . Measured and Correlated pH of WaterAmmonia Mixtures with .188 Mole of H S and .225 Mole o f CO? per Mole of NH,7 80°C ?

ά

Ratio.

co wt %

HS> wt %

0.00439

0.00236

0.00988

3

Ammonia ^ wt %

6

a

(SWEQ)

Meas.

PH Correl.

Diff.

0.00165

1.481

7.579

7.700

-.120

0.00530

0.00372

1.573

7.607

7.773

-.166

0.0593

0.0318

0.0223

1.635

7.833

7.962

-.129

0.133

0.0716

0.0502

1.643

8.020

8.074

-.054

0.300

0.161

0.113

1.608

8.158

8.193

-.035

1.08

0.581

0.406

1.522

8.336

8.387

-.051

2.16

1.26

0.813

1.214

8.408

8.406

.002

4.33

2.56

1.65

1.097

8.465

8.463

.002

8.68

5.28

3.50

0.933

8.596

8.480

.116

2

a )

2

NH3/NH4

Balance i s water



218

THERMODYNAMICS

OF AQUEOUS

SYSTEMS

WITH

INDUSTRIAL

APPLICATIONS

TABLE 22 . Measured and Correlated pH o f WaterAmmonia Mixtures with .363 Mole o f H S and .328 Mole of C 0 per Mole of N H L , 80°C ?

o

Ratio co wt %

wt %

(SWEQ)

Meas.

0.988

0.838

0.717

.4244

7.903

7.851

.052

1.97

1.71

1.45

.3584

7.926

7.889

.037

3.92

3.45

2.93

.2903

7.970

7.897

.073

3

Ammonia ^ wt %

2

a )

H

2

S

A

)

N H O / N H /

PH Correl.

Diff

Balance i s water


9.

WILSON

ET

free N H 3

"

n

NHt = 4 free

NH

NH NH

4

=

NH

n

NH

3

N

R

(11 )

±™1

α

«

+

- α

3

α

+

= τ .

3

NH

4

3

219


AL.

= m o l e s a c i d gas p e r m o l e N H 3

' P

R

N

NH

NH3 (12)

3

T h i s e s t i m a t e d r a t i o can be i m p r o v e d by u s i n g t h e SWEQ c o m p u t e r program w h i c h t a k e s t h e i o n i z a t i o n o f N H i n t o a c c o u n t a t l o w c o n centrations. For example i n T a b l e 5 , E q u a t i o n 12 g i v e s a N H 3 / N H J ratio of 2.95. T h i s a g r e e s w i t h t h e SWEQ program a t h i g h c o n c e n t r a t i o n s , b u t a t l o w c o n c e n t r a t i o n s t h e r a t i o d e c r e a s e s due t o t h e i o n i z a t i o n o f ammonia. In o r d e r t o t a k e t h i s i o n i z a t i o n e f f e c t i n t o a c c o u n t , t h e SWEQ c o m p u t e r program has been used t o c a l c u l a t e t h e N h L / N H ^ r a t i o s i n each t a b l e f o r use i n t h e s m o o t h i n g f u n c t i o n . These c a l c u l a t e d r a t i o s a r e t h e r e f o r e g i v e n i n e a c h t a b l e , and t h e s m o o t h i n g f u n c t i o n now i n v o l v e s a c o r r e l a t i o n o f t h e e q u i l i b r i u m c o n s t a n t g i v e n by E q u a t i o n 9 as a f u n c t i o n o f t h e c o n c e n t r a t i o n s o f t h e c o m p o n e n t s . The r e s u l t i n g equations are the f o l l o w i n g .


3

B\/(1 log

1 0

(k)

where A , B,

= A +

C

+

D>

/(1

+ R)(

wt % N H ) 3

+ R)(wt

% NH )

U

3

3

C, and D = c o n s t a n t s

ΝΤΓ+ + NH P °9 4 3 R = moles a c i d gas/mole NH wt % N H = t o t a l w e i g h t p e r c e n t o f ammonia i n V a l u e s o f t h e p a r a m e t e r s were f o u n d t o be as f o l l o w s . R

=

Η

F

R

O

M

S

W

E

Q

R

R A M

3

3

Temp.

soin.

Parameter

°C

A

25 80

Β

9.15 7.42

C

.178 1.36

1

D 0 1

.9

The f i r s t p a r a m e t e r , A , i s t h e p K o f N H w h i c h c a n be compared w i t h l i t e r a t u r e d a t a ; t h e c o m p a r i s o n i s as f o l l o w s . a

Temp.

3

pJC

°C

Meas.

LU.(2,4)

25 80

9.15 7.42

9.25 7.84

Difference -.10 -.42


)

220

THERMODYNAMICS

SYSTEMS

WITH

INDUSTRIAL

APPLICATIONS

From t h i s c o m p a r i s o n t h e agreement i s q u i t e good a t 2 5 ° C . A t 80°C t h e agreement i s n o t a s g o o d , but t h e l a r g e r d i f f e r e n c e i s n o t s u r p r i s i n g because b o t h t h e measurements r e p o r t e d h e r e and measurements i n t h e l i t e r a t u r e s u f f e r from measurement p r o b l e m s at higher temperatures. However, i t would be s u r p r i s i n g i f t h e d a t a r e p o r t e d h e r e a r e o f f by 0 . 4 u n i t because NBS recommended b u f f e r s o l u t i o n s a c c u r a t e t o + 0.01 pH u n i t o v e r t h e t e m p e r a t u r e r a n g e t o 80°C were u s e d . I f the data given here are r i g h t , i t p r o b a b l y means t h a t t h e d i s s o c i a t i o n c o n s t a n t o f ammonia a t 80°C i s a b o u t 0 . 6 5 χ 1 0 ~ r a t h e r t h a n 1.66 χ 1 0 " computed from t h e e q u a t i o n o f Edwards and P r a u s n i t z (1_). D i f f e r e n c e s between measured and c o r r e l a t e d pH d a t a a r e g i v e n i n each o f T a b l e s 4 t o 2 2 . No a t t e m p t was made t o do a l e a s t - s q u a r e f i t o f t h e d a t a so i n some c a s e s d e v i a t i o n s between t h e c o r r e l a t i o n and t h e d a t a can be r a t h e r l a r g e w i t h o u t any s i g n i f i c a n t e r r o r i n t h e measured d a t a . N e v e r t h e l e s s , most o f t h e d e v i a t i o n s a r e l e s s t h a n + 0.1 pH u n i t . One e x c e p t i o n i s d a t a i n T a b l e 14 on t h e pH o f NH3-H0O a t 80°C w i t h no a c i d gas p r e s e n t ; i n t h i s c a s e t h e c a l c u l a t e d pH d a t a depend h e a v i l y on t h e NH3/NH4" r a t i o g i v e n by t h e SWEQ m o d e l . D i f f e r e n c e s up t o 0 . 7 9 7 pH u n i t i n d i c a t e t h e m a g n i t u d e o f e r r o r i n t h e SWEQ model a t 8 0 ° C . S i m i l a r d a t a a t 25°C i n T a b l e 3 a r e b e t t e r p r e d i c t e d . The d a t a i n T a b l e s 4 t o 13 a t 25°C p l o t n e a r l y as v e r t i c a l l i n e s i n d e p e n d e n t o f t h e wt % NH3 i n s o l u t i o n e x c e p t f o r pure ammonia. A t low c o n c e n t r a t i o n s t h e curves tend t o d e v i a t e b e c a u s e o f t h e i o n i z a t i o n o f NH3 and w a t e r . I f t h e amount o f am monia i n s o l u t i o n i s a p p r o x i m a t e l y known, t h e s e c u r v e s can be used t o e s t i m a t e t h e m o l e s o f a c i d gas p e r mole o f NH3 w i t h f a i r l y good a c c u r a c y . A t 80°C t h e c u r v e s t e n d t o s l a n t more so t h e amount o f ammonia i n s o l u t i o n w o u l d have t o be known more a c c u r a t e l y b e f o r e an e s t i m a t e o f t h e r a t i o o f a c i d gas t o ammonia c o u l d be made. A l s o we do n o t recommend t h e use o f a pH probe a t 80°C a s a c o n t r o l i n d i c a t o r because t h e r e s p o n s e o f t h e p r o b e i s more e r r a t i c , and p r e c i s e d a t a a r e d i f f i c u l t t o o b t a i n . The use o f an i n d i c a t o r p r o b e a t 25°C seems more l o g i c a l because t h e o u t put i s more s t a b l e . One o b s e r v a t i o n t h a t can be made from t h e pH d a t a i n T a b l e s 4 t o 22 i s t h a t t h e pH a p p e a r s t o be a f f e c t e d a b o u t e q u a l l y by e i t h e r H2S o r CO2. T h i s r e s u l t c a n be seen f r o m an e x a m i n a t i o n o f t h e p l o t s g i v e n i n F i g u r e s 4 and 5. I n t h e s e f i g u r e s t h e pH i s p l o t t e d v e r s u s t h e m o l e s o f a c i d gas per mole o f NH3 a t a f i x e d c o n c e n t r a t i o n o f 1.0 wt % NH3. The c u r v e s i n F i g u r e 4 c o r r e s p o n d t o r e s u l t s a t 2 5 ° C , and t h e p l o t i n F i g u r e 5 c o r r e s ponds t o r e s u l t s a t 8 0 ° C . The p o i n t s p l o t t e d i n t h e s e two f i g u r e s r e p r e s e n t smoothed v a l u e s o b t a i n e d from T a b l e s 4 t o 2 2 . Data a t 25°C i n F i g u r e 4 c l e a r l y s e p a r a t e i n t o t h r e e d i s t i n c t curves although the curves a r e c l o s e t o g e t h e r . T h i s shows t h a t t h e r e i s some d i f f e r e n c e between t h e a c i d g a s e s , b u t n o t a l a r g e difference. The p o i n t s i n F i g u r e 5 a t 80°C do n o t r e s o l v e i n t o s e p a r a t e c u r v e s because t h e r e i s some s c a t t e r i n t h e p o i n t s . 5


O F AQUEOUS

5

4


WILSON


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ET AL.

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101

7

1

I

.

1

1

ι

ι

1

j

ι

1

1

1

.

.

.5

0

1

ι

r

ι

I

1.0

moles a c i d gas/mole Ν Η ,

Figure 5.

The pH of LO wt % H S-C0 -NH^-H 0 mixtures vs. acid gas loading at 80°C ((A) 100% CO,; Ο 100% H S; (0)50:50 H S/C0 ) 2

2

2

2

2

2


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W i t h i n t h i s s c a t t e r , t h e t h r e e t y p e s o f d a t a a p p e a r t o be c o r r e l a t e d by a s i n g l e c u r v e ; t h u s s h o w i n g t h a t t h e r e i s n o t a g r e a t d i f f e r e n c e i n t h e e f f e c t o f the a c i d gases a t 80°C. In summary t h e f o l l o w i n g c a n be c o n c l u d e d r e g a r d i n g t h e pH data i n Tables 4 to 2 2 . 1. 2.


3.

4.

5.

The d a t a can be c o r r e l a t e d u s i n g an e q u i l i b r i u m c o n s t a n t a p p r o a c h w i t h most d e v i a t i o n s b e i n g l e s s t h a n + 0.1 pH unit. The p K o f ammonia d e r i v e d f r o m t h e s e d a t a a g r e e s w i t h l i t e r a t u r e d a t a w i t h i n 0.1 pH u n i t a t 25°C and 0 . 4 2 pH u n i t at 80°C. The m o l a r r a t i o s o f H S / N r L o r C 0 / N H have a b o u t e q u a l e f f e c t s on t h e p H . A t 2 5 ° C , CO^ a p p e a r s t o have a s l i g h t l y greater e f f e c t . A s i m i l a r c o n c l u s i o n a t 80°C can be made e x c e p t t h a t no d i s t i n c t i o n between t h e a c i d g a s e s i s v i s i b l e b e c a u s e o f some s c a t t e r i n t h e d a t a . The pH p r o b e i s more s t a b l e a t 25°C t h a n a t 8 0 ° C . For t h i s r e a s o n i t i s recommended t h a t i f a pH p r o b e i s used as a c o n t r o l s e n s o r i n a p r o c e s s t h a t i t be used a t 25°C so t h a t t h e r e s p o n s e w i l l t e n d t o be more a c c u r a t e . pH d a t a a t 25°C i n T a b l e s 4 t o 13 can be used t o e s t i mate t h e m o l e s o f a c i d gas p e r m o l e s o f N H i n s o l u t i o n w i t h o n l y an a p p r o x i m a t e knowledge o f t h e t o t a l amount o f NH i n s o l u t i o n . a

2

2

3

3

3

Sodium H y d r o x i d e and Sodium A c e t a t e E f f e c t on NHg V o l a t i l i t y . Ammonia v o l a t i l i t y measurements a t v a r i o u s c o n c e n t r a t i o n s o f s o dium h y d r o x i d e and s o d i u m a c e t a t e a t 80°C a r e g i v e n i n T a b l e s 23 and 24 r e s p e c t i v e l y . Data on t h e e f f e c t o f sodium h y d r o x i d e were measured u s i n g an ammonia p r o b e f r o m O r i o n R e s e a r c h Company. These measurements were r e d u c e d t o NHo p a r t i a l p r e s s u r e m e a s u r e ments u s i n g E q u a t i o n 2 g i v e n a b o v e . In t h i s c a s e , t h e r e f e r e n c e s o l u t i o n i s the composition reached at zero s a l t c o n c e n t r a t i o n at t h e bottom o f T a b l e 2 3 . The ammonia p a r t i a l p r e s s u r e above t h i s s o l u t i o n can be i n f e r r e d f r o m T a b l e 1 where P N H 3 / w t % N H 3 a t 0.1 wt % N H 3 has a v a l u e o f 1 . 2 3 . This i n f o r m a t i o n gives the f o l l o w i n g v a l u e s f o r PjJ[jf- and m v r e f

Pj^fmv

ref.

= 0 . 1 0 0 5 χ 1.23 = 0 . 1 2 4

psia

_ = - 5 7 . 3 mv

These v a l u e s and t h e p r o b e o u t p u t d a t a i n T a b l e 23 were s u b s t i t u ted i n t o Equation 1 to give the p a r t i a l pressure data given i n Table 23. The d a t a i n T a b l e 24 on t h e e f f e c t o f sodium a c e t a t e were measured i n t h e same manner as d a t a i n T a b l e s 1 and 2 , so no a s s u m p t i o n s a b o u t t h e ammonia probe b e h a v i o r were n e c e s s a r y . This was done b e c a u s e r e a d i n g s f r o m t h e N H p r o b e became e r r a t i c a f t e r 3


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TABLE 23. E f f e c t o f Sodium Hydroxide E l e c t r o l y t e on Ammonia V o l a t i l i t y a t 80°C from Ammonia Probe Data )


3

NH Probe Output mv

NH psia

NH /wt psia

3

wt % i n L i q u i d NH NaOH 3

p P

3

3

0800

22.5

-57.1

.123

1.54

0891

12.7

-57.5

.125

1.40

0944

6.82

-57.3

.124

1.31

0974

3.60

-57.2

.124

1.27

.124

1.25

0995

1.27

1005

0

a

-57.3 ref

b

mv =-57.3 )

1.23

^ 0 r i o n Research Company ^This value of -57.3 mv was not d i r e c t l y measured, but i s a value obtained by e x t r a p o l a t i n g mv vs wt % NaOH to zero wt NaOH.

r) 'This p a r t i a l pressure f o r NFU was obtained from the NH p a r t i a l pressure data i n Table 2 a t 0.1 wt % ίΙΗ . The same r a t i o o f P N H 3 / ^ % NH , uncorr. was used at .1005 wt % NH to give P j ^ as follows. 3

3

w

3

3

P

N H

= 1.23 χ .1005 = .124 psia


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TABLE 24. E f f e c t of Sodium Acetate E l e c t r o l y t e on Ammonia V o l a t i l i t y a t 80°C from Flow C e l l Data

N H

charge, wt % NH NaAc 3

.802

25

average

.931

15

average .931

5

averaqe

1.00

0

i n

3 Liquid wt %

η *\ NH psia

.781 .734 .684 .644 .711

1.838 1.778 1.712 1.620 1.737

2.35 2.42 2.50 2.51 2.45

.992 .975 .959 .942 .967

1.812 1.817 1.796 1.756 1.795

1.83 1.86 1.87 1.86 1.86

.995 .985 .974 .964 .980

1.381 1.411 1.405 1.380 1.394

1.39 1.43 1.44 1.43 1.42

.973

1.246

1.28 average from Table 2

p

a ;

3

F

NH?M %

^Sampled a t 20 psia


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225

t h e measurements a t 80°C on t h e e f f e c t o f sodium h y d r o x i d e . These d a t a were measured a t a b o u t 1 wt % N H i n t h e l i q u i d phase i n s t e a d o f 0.1 wt % N H used f o r t h e NaOH m e a s u r e m e n t s . For t h i s r e a s o n t h e y do n o t e x t r a p o l a t e t o t h e same v o l a t i l i t y r a t i o a t zero concentration of e l e c t r o l y t e . When c o r r e c t i o n i s made f o r i o n i z a t i o n and s o l v e n t e f f e c t s o f ammonia, t h e n t h e two i n t e r cepts agree. From t h e d a t a i n T a b l e s 23 and 2 4 , t h e f o l l o w i n g can be c o n cluded. 3

3


1.

2.

The v o l a t i l i t y o f ammonia can be s i g n i f i c a n t e l y a f f e c t e d by h i g h c o n c e n t r a t i o n s o f d i s s o l v e d i o n s i n t h e l i q u i d phase. In sodium a c e t a t e t h e v o l a t i l i t y i n c r e a s e s by a f a c t o r o f 1.9 a t 25 wt % o f s a l t . In sodium h y d r o x i d e t h e v o l a t i l i t y i s enhanced t o a l e s s e r d e g r e e w i t h an i n c r e a s e o f 1.25 a t 2 2 . 5 wt % NaOH. Both e l e c t r o l y t e s p r o d u c e i o n s w i t h o n l y one e l e c t r o n i c c h a r g e , but t h e i r e f f e c t s on t h e v o l a t i l i t y o f ammonia a r e s i g n i f i c a n t l y different. Thus t h e e f f e c t s o f v a r i o u s i o n i c components must be s t u d i e d i n d i v i d u a l l y i n o r d e r t o d e t e r m i n e t h e i r e f f e c t on t h e v o l a t i l i t y o f N H 3 . At the low i o n i c c o n c e n t r a t i o n s encountered i n sour wat e r s t r i p p e r s , the e f f e c t of d i s s o l v e d ions i s probably small. Thus a t a 1% c o n c e n t r a t i o n o f sodium a c e t a t e t h e v o l a t i l i t y o f ammonia o n l y i n c r e a s e s a b o u t 2 . 5 % due t o the s a l t . This i s w i t h i n the p r e d i c t i o n accuracy o f the ammonia v o l a t i l i t y d a t a and no c o r r e c t i o n i s t h e r e f o r e required. However s i g n i f i c a n t i o n i c e f f e c t s c o u l d e x i s t i n t h e c o n d e n s e r where h i g h c o n c e n t r a t i o n s o f t h e i o n i c components c o u l d e x i s t .

Summary and

Conclusions

Ammonia p a r t i a l p r e s s u r e d a t a have been d e t e r m i n e d a t c o n c e n t r a t i o n s from 10 ppm up t o 5 wt % i n w a t e r a t t e m p e r a t u r e s o f 80 and 120°C. The pH o f N H o - H S - C 0 - H 0 m i x t u r e s have a l s o been measured a t 25 and 8 0 ° C . A l s o t h e e f f e c t s o f sodium h y d r o x i d e and sodium a c e t a t e on ammonia v o l a t i l i t y d a t a have been measured a t 80°C. V a r i o u s c o n c l u s i o n s made from t h e d a t a a r e as f o l l o w s . 2

1.

2. 3.

2

2

The v o l a t i l i t y o f N H 3 a t ppm l e v e l s can be c a l c u l a t e d from t h e i o n i z a t i o n c o n s t a n t o f ammonia combined w i t h v o l a t i l i t y d a t a measured a t h i g h e r c o n c e n t r a t i o n s o f ammonia. The v o l a t i l i t y o f ammonia a t 80 and 120°C i s a b o u t 5% h i g h e r t h a n i s now p r e d i c t e d by t h e SWEQ m o d e l . The v o l a t i l i t y o f ammonia can be s i g n i f i c a n t l y a f f e c t e d by h i g h c o n c e n t r a t i o n s o f d i s s o l v e d i o n s i n t h e l i q u i d phase. U n f o r t u n a t e l y t h e e f f e c t v a r i e s d e p e n d i n g on t h e t y p e s o f i o n s i n s o l u t i o n . Sodium a c e t a t e p r o d u c e s a


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much l a r g e r enhancement i n t h e v o l a t i l i t y t h a n i s p r o duced by sodium h y d r o x i d e . A t t h e low i o n i c c o n c e n t r a t i o n s encountered i n sour w a t e r s t r i p p e r s , the e f f e c t o f d i s s o l v e d ions i s probably small. A 1% c o n c e n t r a t i o n o f sodium a c e t a t e o n l y e n hances t h e v o l a t i l i t y o f ammonia by a b o u t 2 . 5 % . High i o n i c c o n c e n t r a t i o n s i n t h e c o n d e n s e r may p r o d u c e b i g g e r effects. M e a s u r e d pH d a t a on NH3-H2S-CO2- H 0 m i x t u r e s can be c o r r e l a t e d u s i n g an e q u i l i b r i u m c o n s t a n t a p p r o a c h w i t h most d e v i a t i o n s b e i n g l e s s t h a n + 0.1 ρ H u n i t . The p K o f ammonia d e r i v e d f r o m t h e pH d a t a a g r e e s w i t h l i t e r a t u r e d a t a w i t h i n 0.1 pH u n i t a t 2 5 ° C . A t 80°C t h e agreement i s n o t as good w i t h a d i f f e r e n c e o f 0 . 4 2 pH unit. HoS and CO? have a b o u t e q u a l e f f e c t s on t h e pH o f H SCOo-NHo-H^O m i x t u r e s w i t h C 0 s h o w i n g a s l i g h t l y g r e a t e r e f f e c t a t 25°C. pH measurements a t 25°C t e n d t o be more r e l i a b l e t h a n d a t a a t h i g h e r t e m p e r a t u r e s b e c a u s e t h e o u t p u t from t h e p r o b e i s more s t a b l e a t 2 5 ° C . For t h i s reason i t i s recommended t h a t i f a pH p r o b e i s used as a c o n t r o l s e n s o r i n a p r o c e s s t h a t i t be used a t 2 5 ° C . Measured pH d a t a on H0S-CO0-NH3- H 0 m i x t u r e s a t 25°C c a n be used t o e s t i m a t e t h e m o l e s o f a c i d gas per mole o f ammonia i n s o l u t i o n w i t h o n l y an a p p r o x i m a t e knowledge o f t h e t o t a l amount o f ammonia i n s o l u t i o n . C e r t a i n t y p e s o f r e f e r e n c e e l e c t r o d e s a r e f o u n d t o be more s u i t a b l e t h a n o t h e r s when d e t e r m i n i n g t h e pH o f s o l u t i o n s c o n t a i n i n g H2S. Recommendations r e g a r d i n g various electrodes a r e given i n t h e t e x t o f the paper. 2

a

2

2

8.

9.

10.

2

Acknowledgment T h i s work was s u p p o r t e d by t h e Gas P r o c e s s o r s A s s o c i a t i o n a n d the American Petroleum I n s t i t u t e . The c o n s c i e n t i o u s work o f K e n t C . W i l s o n i n d o i n g many o f t h e p o t e n t i o m e t r i c t i t r a t i o n s and K a t i e Toepke f o r t y p i n g t h i s r e p o r t is appreciated.

Literature Cited

1. Edwards, T. J. and Prausnitz, J. M. A.I.Ch.E. Journal, 1975, 21, (2), 248-259. 2. Wilson, G. M. "A New Correlation of NH , CO , and HS Volatil ity Data from Aqueous Sour Water Systems", American Petroleum Institute, February 1978. 3. Miles, D. H. and Wilson, G. M. "Vapor-Liquid Equilibrium Data for Design of Sour Water Strippers", Annual Report to the American Petroleum Institute for 1974, October 1975 (Data in this report are also summarized in reference 2). 4. CRC Handbook, 51st Edition, page D-122 (1970-1971). 3

2

2

RECEIVED February 27, 1980. In Thermodynamics of Aqueous Systems with Industrial Applications; Newman, S., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

Sour Water Equilibria - ACS Symposium Series (ACS Publications)

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