Sea Water Demineralization by Ammonium Salts Ion Exchange

Sea Water Demineralization by Ammonium Salts Ion Exchange

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on September 5, 2015 | http://pubs.acs.org Publication Date: January 1, 1960 | doi: 10.1021/ba-1960-0027.ch018

PAUL B. STEWART Department of Mechanical Engineering and Sea Water Conversion Laboratories, University of California, Berkeley, Calif.

Experimental data on mixed-bed ion exchange show that ammonium bicarbonate-sea water salts ion exchange is a possible route to saline water demineralization. Material balances for two processing schemes are presented: a four-stage ion exchange demineralizing plant using a regenerant solution of ammonium bicarbonate in fresh water, and a seven-stage plant, the first five stages of which use a regenerant solution made by dissolving ammonium bicarbonate in filtered sea water followed by two stages of sodium chloride-free regenerant. The distillation requirements for removing the ammonium salts between ion exchange stages and from all effluent streams are examined, and compared to the distillation load on multiple effect and multistage flash plants. On the basis of distillation requirements alone, the ammonium salts ion exchange method is not competitive with direct distillation.

Ion exchange, s t a r t i n g w i t h n a t u r a l zeolites u s e d f o r w a t e r s o f t e n i n g f o r a p p r o x i m a t e l y a h a l f - c e n t u r y , has d e v e l o p e d t h r o u g h t h e y e a r s t o m a n y o t h e r fields o f a p p l i c a t i o n , i n c l u d i n g b o i l e r feed w a t e r t r e a t m e n t , m e t a l s r e c o v e r y f r o m aqueous s o l u t i o n , t h e r e m o v a l of i o n i z e d m a t e r i a l s f r o m s u g a r s o l u t i o n s , a n d t h e p r o d u c t i o n o f h i g h p u r i t y w a t e r f o r s p e c i a l uses. T h i s e x p a n s i o n o f t h e uses of i o n exchange t e c h n o l o g y has i n l a r g e m e a s u r e b e e n m a d e possible b y i m p r o v e d i o n exchange m e d i a : s y n t h e t i c zeolites, t h e s o - c a l l e d c a r b o n a c e o u s zeolites, a n d m o s t r e c e n t l y t h e v a r i o u s classes o f s y n t h e t i c r e s i n i o n exchange m a t e r i a l s . S i n c e t h e a d v e n t o f t h e resins c a p a b l e o f b e i n g r e g e n e r a t e d w i t h acids a n d a l k a l i e s , r e s p e c t i v e l y , e x c h a n g i n g c a t i o n s f o r t h e h y d r o g e n ions a n d a n i o n s f o r t h e h y d r o x y l i o n , i t h a s b e e n r e a l i z e d t h a t i o n exchange p r o c e s s i n g is a possible r o u t e t o w a t e r d e m i n e r a l i z a t i o n . T h e cost of t h e régénérant c h e m i c a l , a c i d a n d base, has p r e v e n t e d t h e use o f the process e x c e p t i n c e r t a i n " c l e a n - u p " a p p l i c a t i o n s w h e r e t h e q u a n t i t y o f i o n i c m a t e r i a l s t o be r e m o v e d is e x t r e m e l y s m a l l . G i l l i l a n d (6) suggested t h e p o s s i b i l i t y o f a n i o n exchange process u s i n g régénérant chemicals t h a t could b e recovered b y distillation. H i s patent o n this subject ( 7 ) a p p e a r e d i n 1957. 178

In SALINE WATER CONVERSION; Advances in Chemistry; American Chemical Society: Washington, DC, 1960.

179

STEWART—DEMINERALIZATION BY AMMONIUM SALTS ION EXCHANGE

Basically, the relative volatility of the components in sea water or saline waters is reversed by this type of ion exchange. Thus, the 3.5% of ordinarily nonvolatile salts present in sea water are made volatile by substituting for them a volatile salt such as one of the ammonium carbonates. This substitution puts distillation in an entirely different light : The minor component is now to be distilled away from the major com ponent, water, which should reduce the amount of distillation to be done per unit quantity of water produced by many fold compared to distillation (or evaporation) processes in which all of the recovered water must be distilled.


Prior Work In the course of this work, particularly in its initial stages, extensive use was made of the pertinent technical literature. U n i t e d States Patents. Gilliland's patent ( 7 ) covers mixed-bed ion exchange of nonvolatile salts for "thermolytic salts"—those which decompose on heating or reduction of pressure into gaseous compounds, or into gases and insoluble solids—followed by recovery of the thermolytic salt and its re-use for regeneration of the ion exchange bed. Ammonium bicarbonate is specifically claimed as one of the possible thermolytic salts. The example cited in the patent used a mixed bed of Amberlite I R A 400 and Dowex 50 resins, and on an ammonium carbonate-sodium chloride exchange cycle reported a reduction of the sodium chloride content of the brine from 0.6iV to 02N in one stage (0.67V is approximately the value of total dissolved salts in sea water). I o n E x c h a n g e L i t e r a t u r e . The technical literature on ion exchange is rather voluminous, but not much of it is pertinent to the subject at hand. As might be expected, far more information is available on the laboratory use of ion exchange than on its processing applications. Two of the best books, general references, are by Kunin (17) and Nachod and Schubert (19). The annual reviews published by Industrial and Engineering Chemistry are excellent summaries of the literature appearing in the pre ceding year. Among the few quantitative data on ion exchange performance in the technical literature are those reported by Myers (IS) of the Rohm and Haas Co. He reports experimental results using Amberlite IR-1 in the hydrogen cycle with a sodium chloride feed solution, giving both feed and effluent concentrations. More typical of most of the journal articles are those by Bonner, Argersinger, and Davidson (2) Gregor, Belle, and Marcus (8), and Bonner and Payne (3). In the first of these papers the authors report on studies in dilute solutions of ion exchange reac tions of the type }

A

+

+ Β Res = A Res + Β

An equilibrium constant formulated as Ν A Res

NB

Res

where m = molality in solution and Ν = mole fraction on resin, gives good correlation of the experimental results. There is an extensive literature on applications of ion exchange in analytical chemistry. Trade literature published by the manufacturers of ion exchange resins is a valuable source of information. These manufacturers include the Chemical Process Co., Red wood City, Calif.; Dow Chemical Co., Midland, Mich.; and Rohm and Haas, Phila delphia, Pa. E q u i l i b r i u m D a t a . Liquid and Solid Phases, N H - C 0 - H 0 System. Equilib rium in condensed systems in the 20° to 40° C. temperature range and from 1- to 4.5atm. absolute pressure are reported by Neumann and Domke (21). Similar data are reported by Terres and Weiser (26) and Guyer and Piechowicz (9) but over a wider temperature range and for less complex systems. The latter authors also report that 3

2

2


ADVANCES IN CHEMISTRY SERIES

180

a m m o n i u m bicarbonate i n water solution evolves carbon dioxide, b u t m a k e n o m e n t i o n of a m m o n i a i n t h e c a r b o n d i o x i d e . G a s a n d L i q u i d Phases. E q u i l i b r i u m d a t a (P-V-T) and thermodynamic prop erties f o r t h e s i n g l e - c o m p o n e n t s y s t e m s w a t e r ( s t e a m ) a n d a m m o n i a a r e c o m p l e t e a n d a p p a r e n t l y o f t h e best a c c u r a c y because of t h e e x t e n s i v e use o f these substances i n c y c l i c


systems (14,20). S i m i l a r d a t a f o r t h e t w o - c o m p o n e n t s y s t e m w a t e r - a m m o n i a a r e also a v a i l a b l e a n d c o m p l e t e , because o f t h e use o f t h i s s y s t e m i n a b s o r p t i o n r e f r i g e r a t i o n . T h e d a t a o f S c a t c h a r d a n d c o w o r k e r s are t h e m o s t recent (24), a n d a r e u n i q u e a m o n g s u c h c o m p i l a t i o n s i n t h a t t h e a v a i l a b i l i t y f u n c t i o n i s t a b u l a t e d as w e l l as t h e u s u a l e n t h a l p y , e n t r o p y , a n d G i b b s free e n e r g y . T h e s e d a t a h a v e b e e n c o n v e r t e d t o g r a p h i c a l f o r m ( c h a r t s ) b y K o h l o s s a n d S c o t t (16) a n d B u l k l e y a n d S w a r t z (4). O l d e r d a t a , b u t m o r e c o m p l e t e i n t h e l o w c o n c e n t r a t i o n r a n g e , are those o f J e n n i n g s a n d S h a n n o n (11). D a t a f o r t h e t h r e e - c o m p o n e n t s y s t e m a m m o n i a - w a t e r - c a r b o n d i o x i d e a r e i n a less s a t i s f a c t o r y s t a t e . P e x t o n a n d B a d g e r (22) r e p o r t d a t a a t 2 0 ° , 3 0 ° , a n d 4 0 ° C . B a d g e r a n d W i l s o n (1) e x t e n d t h e d a t a t o t h e h i g h e r t e m p e r a t u r e r a n g e o f 9 0 ° t o 100° C , b u t t h i s w a s d o n e w i t h s o l u t i o n s n o t a t t h e b o i l . E g a l o n , V a n h i l l e , a n d W i l l e m y n s (δ) m e a s u r e d t h e p a r t i a l pressures o f a m m o n i a a n d c a r b o n d i o x i d e o v e r s o l u t i o n s of a m m o n i u m c a r b o n a t e s i n t h e 2 0 ° t o 5 0 ° C . r a n g e .

Ion Exchange Experimental Work T h e e x p e r i m e n t a l w o r k c a n b e d i v i d e d i n t o t w o g e n e r a l classes: (1) e x p l o r a t o r y e x p e r i m e n t s t o f i n d i o n exchange resins s u i t a b l e f o r t h e p r o p o s e d a p p l i c a t i o n , a n d ( 2 ) o b t a i n i n g q u a n t i t a t i v e d a t a o n one r e s i n p a i r selected. I o n E x c h a n g e R e s i n s . I o n exchange r e s i n s , r e g u l a r c o m m e r c i a l p r o d u c t s , w e r e obtained f r o m the C h e m i c a l Process C o . , R e d w o o d C i t y , C a l i f . D u o l i t e C - 2 0 is a polystyrene cation resin w i t h sulfonic acid functional groups. I t has a r a t e d c a p a c i t y o f 0.8 e q u i v a l e n t p e r l i t e r f o r c a t i o n e x c h a n g e , e x c e p t i n t h e h y d r o gen c y c l e , f o r w h i c h i t s c a p a c i t y i s 1.5 e q u i v a l e n t s p e r l i t e r . S u l f o n i c a c i d g r o u p s a r e c h a r a c t e r i z e d as s t r o n g a c i d g r o u p s . D u o l i t e A - 1 0 2 , a n a n i o n exchange r e s i n , h a s s t r o n g q u a t e r n a r y a m m o n i u m f u n c t i o n a l g r o u p s , w i t h a c a p a c i t y o f 0.8 e q u i v a l e n t p e r l i t e r . Q u a n t i t a t i v e D a t a . A series o f 18 e x p e r i m e n t a l r u n s w a s m a d e t o d e t e r m i n e q u a n t i t a t i v e l y t h e p e r f o r m a n c e o f a m i x e d - b e d i o n exchange c o l u m n u s i n g C h e m i c a l P r o c e s s C o . resins C - 2 0 a n d A - 1 0 2 . L a b o r a t o r y d a t a are s u m m a r i z e d i n T a b l e I . T h e c o l u m n s u s e d were f a b r i c a t e d f r o m a c r y l i c p l a s t i c ( P l e x i g l a s ) t u b i n g , 6 i n c h e s i n outside diameter, 5 / inches i n inside diameter, a n d 4 8 inches long. Flanges were cemented t o t h e t u b i n g b o t h t o p a n d b o t t o m , a n d cover plates w i t h nozzles were bolted to t h e flanges. T h e c a p a c i t y o f these c o l u m n s w a s c a l c u l a t e d t o b e 0.721 c u b i c f o o t (5.4 U . S . g a l l o n s ) . A s o l u t i o n feed t a n k o f 4 0 - U . S . g a l l o n c a p a c i t y w a s m o u n t e d o n a w a l l b r a c k e t a n d a b o v e t h e t o p o f t h e i o n exchange c o l u m n s t o p r o v i d e g r a v i t y feed. C o n n e c t i o n s ( p i p i n g ) w e r e o f glass t u b i n g / i n c h i n outside diameter w i t h joints m a d e w i t h r u b b e r t u b i n g . L a b o r a t o r y screw c l a m p s w e r e u s e d as flow c o n t r o l devices. A n i o n e x c h a n g e r e s i n b e d 3 2 inches d e e p m a d e u p o f e q u a l v o l u m e s o f C - 2 0 a n d A - 1 0 2 resins w a s u s e d i n e a c h of t h e t w o c o l u m n s . T h e b e d w a s s u p p o r t e d b y s e v e r a l i n c h e s o f g r a v e l c o v e r e d w i t h 2 t o 3 inches of coarse s a n d . I n o n e r u n ( N o . 7—1) t h e t w o c o l u m n s w e r e u s e d i n series t o a p p r o x i m a t e a deeper b e d (64 i n c h e s ) . T h e " s e a w a t e r " u s e d i n these e x p e r i m e n t s w a s S a n F r a n c i s c o B a y w a t e r c o l l e c t e d at t h e laboratory's salt water s u p p l y i n t a k e o n t h e pier a t t h e R i c h m o n d F i e l d S t a t i o n . B e c a u s e of t h e d i l u t i n g a n d p o l l u t i n g effect o f t h e S a c r a m e n t o R i v e r as w e l l as o t h e r effluents d u m p e d i n t o t h e b a y , t h e s a l i n i t y o f b a y w a t e r a t R i c h m o n d v a r i e s w i d e l y d u r i n g t h e t i d e c y c l e . I n o r d e r t o o b t a i n w a t e r of m a x i m u m s a l i n i t y , the^ i n t a k e p u m p is c o n t r o l l e d b y float s w i t c h e s a n d p e r m i t s t h e p u m p t o o p e r a t e o n l y a t o r n e a r h i g h tide f o r a p p r o x i m a t e l y 3 hours i n 24. E v e n w i t h this l i m i t e d p u m p i n g schedule t h e 3

4

1

7

3

2



0 2.56 2.56 2.56 2.52 2.61 2.82 2.42 0.92 0.98 0.31 0.31 1.75 2.45

2, .87 0..91 0. .21 0. .05 2 .87 2.,87 1..83 1..14 0..94 0 .61 0 .29 0 .29 1..00 0..33 1..00 2. .00 2,.87

15 18 18 15 15 30 21 21 21 21 21 21 21 21 21 21 42

Vol., liters

0 .625 0 .360 0 .083 0 .0815 0..715 1. 333 0.,700 0 .584 0 .467 0 .318 0 .167 0 .140 0..412 0,,140 0 .368 0 .700 0 .933

2. ,39 2. 62 4..24 2. .82 3.,74 7. 53 4. 75 5..59 5 .71 6 .25 5 .52 4 .70 5.,76 5. 17 4. 36 5 .58 6 .56

3,,54 3,.83 2, .24 1 .485 3..53 3 .23 3,.60 2 .26 3 .28 2 .99 2 .65 1 .97 2, .16 2, ,26 1 .95 2 .47 3 .10

NaCl

%

Av.

Table I.

6 9 12 6 6 6 9 9 12 9 15 15 6 12 9 6 9

Vol., liters 10.25 9.93 5.39 10.17 10.75 9.60 9.20 10.35 8.68 9.27 6.01 6.44 8.90 7.06 10.46 10.0 12.21

Av. % NH4HCO3

Rinse

2.52 1.91 0.863 1.99 2.92 2.54 2.54 2.45 2.09 2.27 1.556 0.892 1.20 0.823 1.05 2.20 2.51

NaCl

%

Av.

21 27 30 21 21 36 30 30 33 30 36 36 27 33 30 27 51 0.875 0.540 0.139 0.114 1.00 1.67 1.00 0.833 0.733 0.455 0.286 0.240 0.530 0.220 0.527 0.900 1.133

4.68 5.08 4.71 4.98 5.70 7.89 6.09 7.03 6.79 7.15 5.72 5.32 6.73 5.85 6.22 6.58 7.57

3.24 3.14 1.69 1.63 3.30 3.11 3.28 2.32 2.54 2.78 2.17 1.52 1.83 1.74 1.66 2.41 2.99

Régénérant + R i n s e Vol./ Av. vol. Av. % Vol., % liters p r o d . NH4HCO3 N a C l 24 50 216 384 21 18 30 36 45 66 126 150 51 150 57 30 45

4.59 1.47 0.334 0.111 2.87 2.71 1.48 1.22 0.960 0.703 0.305 0.362 1.29 0.447 1.46 2.10 2.61

4

Av. % Vol., liters N H H C 0

3

Product

%

0.804 0.190 0.0442 0.0454 1.93 1.80 1.14 0.511 0.506 0.312 0.144 0.0867 0.356 0.0650 0.222 1.091 1.90

NaCl

Av.

M i x e d bed of C - 2 0 a n d A - 1 0 2 resins ( C h e m i c a l Process C o . ) 32 inches i n d e p t h R u n

0.25 0.180 0.055 0.033 0.285 0.333 0.300 0.250 0.267 0.136 0.119 0.100 0.118 0.080 1.58 0.200 0.200

Vol./ vol. prod.

Summary of Ion Exchange Laboratory Data

R u n s 1 t h r o u g h 6-1 made a t a v . flow rate of 1 g a l . / m i n . / s q . f t . 6-1 u p flow. A l l others d o w n flow.

0

4 2-1 2-1A 2-2 2-3 2-3A 2-4 2-5 3-1 3-2 4-1 4-2 5-1 6-1

3

0 0

1 2

Run

NaCl, % Régénérant F e e d

Régénérant Vol./ vol. Av. % p r o d . NH4HCO3


182


d i l u t i o n b y m i x i n g w i t h less s a l i n e w a t e r i s a p p a r e n t . T a b l e I I gives some a n a l y s e s of b a y w a t e r m a d e a t v a r i o u s t i m e s , a n d shows t h a t , j u d g e d o n t h e c h l o r i d e i o n c o n t e n t , t h e b a y w a t e r a t R i c h m o n d i s a p p r o x i m a t e l y h a l f sea w a t e r a n d a p p r o x i m a t e l y h a l f water of low chloride content. T h e ratios of c a l c i u m i o n to chloride i o n , a n d of sulfate i o n t o c h l o r i d e i o n are b o t h h i g h e r i n b a y w a t e r t h a n i n n o r m a l sea w a t e r .


Table II.

Analysis of San Francisco Bay Water at Richmond

Hardness as C a C 0 , P.P.M. 3

Date

Ca , P.P.M.

Mg , P.P.M.

ciP.P.M.

S0 - , P.P.M. 2000 1830 1420 1960 1610 2000

+ 2

+ 2

4

2

Alkalinity as C a C 0 , P.P.M. 3

Na^

12-13-57 12-17-57 1-27-58 1-28-58 1-29-58 1-30-58 1 - 31-58 2 - 1-58

4560 3440 3050 3100 3300 3340 3280 3260

440 297 186 226 232 232 220 220

840 656 627 618 660 671 660 670

14,400 8,570 8,930 9,840 9,760 10,000 9,660 9,530

1570

840 290 190 120 135 140 120

Av.

3416

257

675

10,080

1770

262

7500

A v . sea water

6464

420

1318

19,324

2696

124

10,722

A v . b a y water A v . sea water

0.339 0.335

0.0255 0.0217

0.1755 0.1395

0.026 0.006

0.745 0.554

7500

Rain in Preceding 2 Days, Inches 0 1.37 1.01 0.01 0.01 0.42 0.43 0.02

R a t i o to Chloride 0.0670 0.0680

T o o b t a i n t h e m o r e c o n c e n t r a t e d " s e a w a t e r " u s e d i n these e x p e r i m e n t s , t h e c o n c e n t r a t e d effluent f r o m s o l a r s t i l l s w a s u s e d . T h i s was s e t t l e d , d e c a n t e d , a n d f i l t e r e d t o o b t a i n a c l e a r p r o d u c t , a n d t h e n a d j u s t e d t o t h e desired c h l o r i n i t y b y d i l u t i o n w i t h t a p water. T h e a m m o n i u m bicarbonate used was a technical grade product m a n u f a c t u r e d i n the U n i t e d K i n g d o m b y the I m p e r i a l C h e m i c a l Industries, L t d . T i t r a t i o n of this p r o d u c t f o r a m m o n i a w i t h s u l f u r i c a c i d t o t h e m e t h y l orange e n d p o i n t i n d i c a t e d a p u r i t y o f approximately 100%. T h e e x p e r i m e n t a l p r o c e d u r e w a s k e p t as s i m p l e as p o s s i b l e . F i r s t t h e régénérant s o l u t i o n w a s f e d t o the i o n exchange c o l u m n , f o l l o w e d b y t h e " s e a w a t e r " o r d i l u t e d " s e a w a t e r . " A l t h o u g h t h e flow r a t e v a r i e d s o m e w h a t , i t w a s h e l d as close t o 1 g a l l o n p e r m i n u t e p e r s q u a r e foot o f b e d cross s e c t i o n as c o n d i t i o n s p e r m i t t e d . T h e effluent f r o m the c o l u m n w a s c o l l e c t e d i n 3 - l i t e r p o r t i o n s , a s a m p l e f r o m w h i c h w a s r e s e r v e d i n a g l a s s - s t o p p e r e d b o t t l e f o r c h e m i c a l a n a l y s i s . T h u s t h e a n a l y s e s a r e those f o r 3 - l i t e r p o r t i o n s o f effluent, t h e c o m p o s i t i o n o f w h i c h w a s c h a n g i n g c o n s t a n t l y , a n d r e p r e s e n t ( i n h e a t t r a n s f e r t e r m i n o l o g y ) a m i x e d - m e a n a v e r a g e a n a l y s i s . T h e c h e m i c a l analyses used were M o h r t i t r a t i o n f o r chloride i o n , a n d acid t i t r a t i o n f o r a m m o n i a , the results of w h i c h were calculated t o sodium chloride a n d a m m o n i u m bicarbonate. I n t h e course of t h i s w o r k t w o p h e n o m e n a were n o t e d f o r w h i c h n o e x p l a n a t i o n w a s s o u g h t . W h e n a m m o n i u m b i c a r b o n a t e w a s a d d e d t o sea w a t e r t o p r e p a r e a régénérant solution, a white precipitate was formed w h i c h was settled o u t a n d discarded w i t h n o a t t e m p t m a d e a t c h e m i c a l a n a l y s i s . T o w a r d t h e e n d o f some o f t h e r e g e n e r a t i o n cycles a n d a t t h e s t a r t o f some of the feed cycles, gas w a s e v o l v e d i n t h e i o n exchange c o l u m n s , w h i c h e v e n t u a l l y d i s a p p e a r e d . T h i s gas, w h i c h w a s n o t i d e n t i f i e d , caused serious flow impedance. I n w o r k i n g u p t h e d a t a p r e s e n t e d i n T a b l e I , t h e t o t a l effluent f r o m t h e i o n exchange c o l u m n ( s ) i s d i v i d e d i n t o t h r e e p o r t i o n s : t h e régénérant, t h e r i n s e , a n d t h e p r o d u c t . F o r a c o m p l e t e c y c l e , t h e first p o r t i o n , e q u a l i n v o l u m e t o t h e régénérant s o l u t i o n i n t r o -


183


I I I II I I I I

I

IFRESH! WATER M I IREGENERATION I II I BEST

STRAIGHT BEST

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SEAWATER REGENERATION ( BEST STRAIGHT LINE )

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RELATION BETWEEN EFFLUENT AND FEED CONCENTRATIONS IN AMMONIUM BICARBONATE — SODIUM CHLORIDE ION EXCHANGE

O.OE

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Figure I.

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Relation between effluent and feed concentrations in ammo nium bicarbonate-sodium chloride ion exchange

ο ο or

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lu

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Figure 2. Effluent volumes (based on stage product volumes) as a function of feed composition ion exchange In SALINE WATER CONVERSION; Advances in Chemistry; American Chemical Society: Washington, DC, 1960.

184


RELATION

BETWEEN

BICARBONATE


EFFLUENT

0.04 0.06 PER

0.1

AND

FEED

0.2

CENT

AMMONIUM

C O N C E N T R A T I O N IN

0.4

SODIUM

COMPOSITION

0.6

CHLORIDE

IN

FEED

Figure 3. Relation between ammonium bicarbonate concentration in effluent and feed composition

5.0

I

1 I 1 I1 M

1

1 1 1 1 1

OPERATING EFFLUENT CONCENTRATIONS AS A FUNCTION ION

4.0

OF FEED

COMPOSITION

EXCHANGE REGENERANI

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1.0

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α 0 4

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0.20 CENT

SODIUM

0.40 CHLORIDE

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1.00

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FEED

Figure 4. Operating effluent concentrations as a function of feed composition ion exchange In SALINE WATER CONVERSION; Advances in Chemistry; American Chemical Society: Washington, DC, 1960.



Figure 6.

Densities of ammonium bicarbonate-normal sea water solutions at 20° C.


185


186


d u c e d , i s d e s i g n a t e d as t h e régénérant o r régénérant p r o d u c t . C h a r a c t e r i s t i c a l l y , t h i s f r a c t i o n increases i n a m m o n i u m i o n c o n t e n t ( c a l c u l a t e d as a m m o n i u m b i c a r b o n a t e ) w i t h t h r o u g h p u t . T h e c h l o r i d e i o n c o n t e n t ( c a l c u l a t e d as s o d i u m c h l o r i d e ) s t a r t s o u t a t a v a l u e d e t e r m i n e d l a r g e l y b y t h e c h l o r i d e c o n t e n t of t h e l i q u i d i n i t i a l l y i n t h e c o l u m n f r o m t h e p r e c e d i n g c y c l e , rises t o a m a x i m u m , a n d t h e n decreases. T h e p r o d u c t p o r t i o n o f t h e t o t a l effluent i s t h a t f r a c t i o n c o n t a i n i n g less c h l o r i d e t h a n t h e feed. I n g e n e r a l , t h e c h l o r i d e c o n t e n t s t a r t s a t a v a l u e s l i g h t l y less t h a n i n t h e feed, decreases t o a m i n i m u m , a n d t h e n m o r e s l o w l y rises t o t h e feed v a l u e as t h e i o n exchange process slows d o w n . T h e a m m o n i u m c o n c e n t r a t i o n decreases w i t h v o l u m e through i n this fraction. T h e i n t e r m e d i a t e p o r t i o n , c a l l e d t h e r i n s e , shows a m a x i m u m i n a m m o n i u m i o n concentration a n d a steadily decreasing chloride i o n concentration. F i g u r e s 1 t h r o u g h 4 are p l o t s o f c e r t a i n d a t a g i v e n i n T a b l e I , p r e p a r e d t o f a c i l i t a t e interpolation required i n w o r k i n g u p m a t e r i a l balances. T h e densities o f sea w a t e r , n o r m a l , d i l u t e d , a n d c o n c e n t r a t e d , a n d o f aqueous s o l u t i o n s o f a m m o n i u m b i c a r b o n a t e a r e g i v e n as a f u n c t i o n o f c o n c e n t r a t i o n i n F i g u r e 5. F i g u r e 6 gives t h e densities o f s o l u t i o n s o f a m m o n i u m b i c a r b o n a t e m a d e u p i n sea w a t e r of v a r y i n g s a l i n i t y . A l l of these d e n s i t y m e a s u r e m e n t s w e r e m a d e a t 2 0 ° C . b y m e a n s of a p y c n o m e t e r .

Discussion of Laboratory Data T h e first p a r t o f t h i s w o r k c o m p r i s e d a n i n i t i a l e c o n o m i c s t u d y o f a process s u c h as t h a t proposed b y G i l l i l a n d . O n using the few data available, extrapolations, estimates, a n d e v e n p u r e guesses, the r e s u l t s o f t h i s i n i t i a l w o r k i n d i c a t e d t h a t f u r t h e r w o r k w a s i n o r d e r . T w o questions w e r e left v e r y m u c h u n a n s w e r e d : W o u l d t h e i o n exchange process w o r k , a n d i f so, h o w w e l l ; a n d w h a t a b o u t r e c o v e r y o f c h e m i c a l s ? T h e s e d a t a p r o v i d e some a n s w e r s t o t h e first q u e s t i o n , a n d o n l y t o t h a t q u e s t i o n . B e c a u s e t h e first stage i n a n y e c o n o m i c e v a l u a t i o n o f a p r o p o s e d process i n v o l v e s a t e n t a t i v e flow sheet f o r t h e process, f o l l o w e d b y m a t e r i a l s a n d e n e r g y b a l a n c e s , t h e d a t a f o r s u c h c a l c u l a t i o n s w e r e c o n s i d e r e d t o b e of p a r a m o u n t i m p o r t a n c e . These aspects h a d t o b e e n c o u r a g i n g , because t h e y c o u l d m a k e o r b r e a k t h e e n t i r e c o n c e p t . T h e d a t a herein presented were gathered w i t h that purpose i n m i n d , a n d answer t h e o b j e c t i v e , a t least i n p a r t . T h e i n f l u e n t a n d effluent s t r e a m v o l u m e s , specific g r a v i ties, a n d c o n c e n t r a t i o n s enable t h e p r e p a r a t i o n o f m a t e r i a l s b a l a n c e s a r o u n d t h e i o n exchange u n i t s . H o w e v e r , s u c h m a t e r i a l b a l a n c e s are n o b e t t e r t h a n t h e d a t a o n w h i c h t h e y are b a s e d . T h e r e f o r e , i t i s a d v i s a b l e t o c o n s i d e r t h e assets a n d l i a b i l i t i e s o f t h e data. A m o n g t h e assets i s t h a t o f f a i r l y l a r g e size o p e r a t i o n ; t h e c o l u m n s w e r e 6 i n c h e s i n diameter instead of smaller units frequently used. T h e m e t h o d of operation w a s designed t o s i m u l a t e as f a r as possible t h e v i s u a l i z e d o p e r a t i o n o f a p r o d u c t i o n u n i t — a s s i m p l e a n d f o o l p r o o f as possible. T h e c h e m i c a l a n a l y s e s used were k e p t t o a m i n i m u m , a n d a s s i m p l e a s p o s s i b l e . M o r e d a t a c o u l d h a v e been g a i n e d b y c o m p l i c a t i n g t h i s f a c t o r ; a n d i n r e t r o s p e c t , i t w o u l d be comforting to have such data. T h e aliquots f r o m 3-liter samples certainly m a s k e d o u t c o m p l e t e l y a n y s h o r t - t e r m t r a n s i e n t s . A l s o , t h e fate o f t h e i o n s o t h e r t h a n c h l o r i d e a n d a m m o n i u m is n o t k n o w n . T h e a p p r o x i m a t e 1 foot of c l e a r l i q u i d a b o v e t h e r e s i n b e d i s a n o t h e r t r o u b l e s o m e factor. M i x i n g m u s t occur i n this volume when the composition of the influent solution is c h a n g e d . A s t h e r e w a s n o v i s u a l evidence o f gross t u r b u l e n c e i n t h i s v o l u m e , t h i s effect w a s n o t i n v e s t i g a t e d . O n t h i s basis these d a t a a r e c o n s e r v a t i v e ; p e r h a p s t o o m u c h so. T h i s l i s t o f w h a t w a s n o t d o n e c o u l d c o n t i n u e f o r some l e n g t h . Suffice i t t o s a y t h a t t h e d e s c r i p t i o n o f w h a t w a s d o n e a n d h o w i s t h o u g h t t o b e s u f f i c i e n t l y c o m p l e t e so that, t h i s is tint, nec.pssarv.


187


Material Balances for Sea Water Processing B y using the laboratory data described a n d presented above, p a r t i c u l a r l y t h e g r a p h i c a l c o r r e l a t i o n s , a n d m a k i n g some e n g i n e e r i n g a s s u m p t i o n s , m a t e r i a l b a l a n c e s f o r a sea w a t e r c o n v e r s i o n p l a n t u s i n g t h e a m m o n i u m b i c a r b o n a t e i o n exchange process were then developed.


A s t h e r e i s p r a c t i c a l l y n o difference i n t h e l a b o r a t o r y d a t a w i t h b e d d e p t h s o f 3 2 inches a n d 64 i n c h e s , a n d i o n exchange o p e r a t i o n s are r e v e r s i b l e , i t a p p e a r s n e c e s s a r y t o s t r i p t h e p r o d u c t f r o m o n e i o n exchange stage o f i t s a m m o n i u m b i c a r b o n a t e b e f o r e s e n d i n g i t o n t o the n e x t stage. A l s o , t h e l i m i t e d s o l u b i l i t y of a m m o n i u m b i c a r b o n a t e i n w a t e r , a p p r o x i m a t e l y 1 3 % at r o o m temperature, indicates t h a t i f one were t o a t t e m p t t o produce a distillate of g r e a t e r c o n c e n t r a t i o n t h e r e w o u l d b e d a n g e r o f d e p o s i t i o n o f solids w i t h a t t e n d a n t p o s sible p l u g g i n g i n p a r t s o f t h e r e c t i f i c a t i o n o r s t r i p p i n g u n i t s . O n t h i s b a s i s , i t w a s d e c i d e d t o fix a r b i t r a r i l y , a t least as a f i r s t a p p r o x i m a t i o n , t h e d i s t i l l a t e c o m p o s i t i o n f r o m the stills a t 1 3 % a m m o n i u m bicarbonate. T h i s decision then led t o another: T h e saturated a m m o n i u m bicarbonate solution o b t a i n e d f r o m t h e v a r i o u s s t i l l s i s a r e g e n e r a t i n g s o l u t i o n f o r t h e i o n exchange u n i t s — t h e s o - c a l l e d f r e s h w a t e r régénérant o f t h e l a b o r a t o r y w o r k . N o d i s t i l l a t i o n c a l c u l a t i o n s o f a n y k i n d were c a r r i e d o u t , o t h e r t h a n t h e s i m p l e m a t e r i a l balance type. I t was assumed t h a t a l l of the a m m o n i u m bicarbonate f e d t o a s t i l l w o u l d go t o t h e d i s t i l l a t e p r o d u c t , p l u s sufficient w a t e r t o f o r m a 1 3 % a m m o n i u m bicarbonate solution, a n d t h a t all of the sodium chloride plus the r e m a i n i n g water w o u l d be t h e s t i l l b o t t o m s p r o d u c t . D i s t i l l a t i o n of A m m o n i u m B i c a r b o n a t e S o l u t i o n s . Vapor-liquid equilibrium d a t a f o r a m m o n i u m b i c a r b o n a t e s o l u t i o n s a t t h e b o i l are a p p a r e n t l y n o t a v a i l a b l e i n t h e literature. T h e data i n the literature, however, do indicate that when the temperature of s u c h a s o l u t i o n i s i n c r e a s e d , o r t h e p r e s s u r e o n i t decreased, t h e gas t h a t i s e v o l v e d i s predominantly carbon dioxide. T h u s , i t appears that such a distillation would be t w o c o n s e c u t i v e processes: first, a s t e a m s t r i p p i n g o f t h e c a r b o n d i o x i d e i n t h e s o l u t i o n , followed b y a distillation of a m m o n i a f r o m a n a m m o n i a - w a t e r m i x t u r e containing p e r h a p s some c a r b o n d i o x i d e . P o s s i b l y t h e a m m o n i a , c a r b o n d i o x i d e , a n d w a t e r i n t h e d i s t i l l a t e p r o d u c t w o u l d r e c o m b i n e c o m p l e t e l y i n t h e condenser t o f o r m a n a m m o n i u m b i c a r b o n a t e s o l u t i o n . P e r h a p s a n a b s o r p t i o n t o w e r w o u l d b e necessary t o effect t h e recombination. E v e n t h o u g h m a n y questions c o n c e r n i n g t h e d i s t i l l a t i o n , o r s t r i p p i n g , of t h e a m m o n i u m b i c a r b o n a t e s o l u t i o n s r e m a i n u n a n s w e r e d , t h e r e seems t o b e n o reason t o assume t h a t t h i s o p e r a t i o n c a n n o t b e c a r r i e d o u t , a n d t h i s a s s u m p t i o n is m a d e i n t h i s w o r k . T h e first s y s t e m f o r w h i c h a m a t e r i a l b a l a n c e w a s c o m p u t e d w a s m a d e u p o f f o u r u n i t s i n series, each c o n s i s t i n g o f a n i o n e x c h a n g e stage a n d a d i s t i l l a t i o n a s s e m b l y t o r e m o v e t h e a m m o n i u m b i c a r b o n a t e f r o m t h e i o n exchange p r o d u c t effluent ( F i g u r e 7 and Table I I I ) .

Table III.

Summary of Main Process Streams

( 1 3 % N H 4 H C O 3 solution distillates) Lb. NaCl/ Vol100 Stream Δ Lb. ume, Gal. AV, % % No. Designation G a l . NaCl NaCl Feed Gal. Loss X - l feed 3.21 1 27.4 100 X - l prod. 4 73.2 0.94 21.57 26.8 26.8 5.87 X-2feed 7 46.7 +0.14» 1.525 6.01 26.5 36.2 X 2 p r o d . 10 9.2 10.7 1.145 4.865 37.5 0.36 X - 3 feed 11 31.6 0.434 0 15.7 1.145 5.9 X 3 p r o d . 14 0.202 0.943 2.7 28.9 0.084 8.5 X-4feed 15 2 7 . 2 0.0887 0.202 0 2.7 9.3 X - 4 prod. 18 0.155 2 6 . 0 0.0220 4.4 0.475 1.2 19 F r e s h water 2 5 . 7 0.0222 1.2 0 0.3 0.475 Increase because of recycle f r o m X - 4 .

%

Total % NaCl Removed

Entering NaCl Removed

78.6 +0.51° 17.8 0 3.44 0 0.566 0

78.6

α


81.0 82.2 76.9



Figure 7. Flow diagram of sea water demineralization by ammonium bicarbonate ion exchange A n o t h e r p o s s i b i l i t y i n t h e a m m o n i u m b i c a r b o n a t e d i s t i l l a t i o n is t o assume t h a t a d i s t i l l a t e o f a n h y d r o u s a m m o n i u m b i c a r b o n a t e c a n b e r e c o v e r e d f r o m a l l of t h e s t r i p p i n g u n i t s o r r e c t i f i c a t i o n assemblies. T h i s a s s u m p t i o n w o u l d seem t o b e t h e l o w e r l i m i t o n t h e q u a n t i t y o f m a t e r i a l t o be d i s t i l l e d . O n t h i s a s s u m p t i o n , a n d t h e f u r t h e r one t h a t t h e a n h y d r o u s a m m o n i u m s a l t i s d i s s o l v e d i n filtered sea w a t e r t o f o r m t h e régénérant s o l u t i o n , a n o t h e r m a t e r i a l b a l a n c e was m a d e . S e v e n i o n exchange stages are r e q u i r e d ; t h e first five use sea w a t e r r é g é n érant, a n d t h e l a s t t w o , f r e s h w a t e r régénérant. ( I f t h e p r o d u c t w a t e r f r o m s u c h a p l a n t a n d t h e a n h y d r o u s a m m o n i u m b i c a r b o n a t e d i s t i l l a t e are u s e d t o m a k e u p a l l f r e s h w a t e r régénérant, insufficient w a t e r i s p r o d u c e d f o r t h e i n - p l a n t r e q u i r e m e n t s o f r e g e n eration make-up.) T a b l e I V is a s u m m a r y of the m a t e r i a l balance thus developed.

Table IV.

Summary of Ion Exchange Stream

(Anhydrous N H H C 0 4

Stage

Total

1 2 3 4 5 6 7

11,570 8,855 7,202 5,960 5,059 4,380 4,089

1

7,578 3,502 4,497 2,246 2,661 1,608 1,514 1,092 823

F e e d Weights NaCl NH4HCO3 371 190 99 50 23 10.4 2

0 0 0 0 0 0 0

2 3 4 5 0

476 318 276 201 162 133 87 89 41 1783

distillates)

H 0 2

NaCl

P r o d u c t Weights Total N a C l NH4HCO3

11,199 8,665 7,103 5,910 5,036 4,370 4,087

3.21 2.14 1.37 0.84 0.455 0.238 0.049

8550 6908 5809 4995 4402 4120 3965

N o n r e c y c l e d Effluent Streams 302 98 166 55 89 36 47 27 23

3

6,800 3,086 4,055 1,990 2,410 1,440 1,380 975 759

%

Stage 5 6 7

179 93 48 23 10.4 2 0.57

256 145 81 37 22 18* 4* 563

NaCl

8115 6670 5680 4935 4370 4100 3960

2.09 1.34 0.825 0.46 0.236 0.048 0.0144

2

R e c y c l e d Effluent Streams 733 439 301 119 130

13.3 6 2.4 1.1 0.4

%

H 0

53.7 15.2 29.0 9.5 2.9 109.3

Recovered as 1 3 % solutions.


666 418 270 109 127

189


Discussion and Conclusions


T h e o b j e c t i v e of a n y sea w a t e r c o n v e r s i o n process is t w o f o l d : t o p r o d u c e a d e m i n e r a l i z e d w a t e r whose q u a l i t y is a d e q u a t e f o r t h e p r o p o s e d use, a n d t o p r o d u c e t h i s w a t e r a t as l o w a cost as possible. I n c o n s i d e r i n g a n y n e w c o n v e r s i o n process, a f t e r t h e e s t a b l i s h i n g o f t h e scientific a n d t e c h n o l o g i c soundness o f t h e m e t h o d , t h e q u e s t i o n t o b e a n s w e r e d i s t h e p r o b a b l e r e l a t i v e e c o n o m i c s o f t h e p r o p o s e d process as c o m p a r e d t o o t h e r processes, e i t h e r a c t u a l ( p r e f e r a b l e ) o r p r o p o s e d . One method of m a k i n g this c o m p a r i s o n i s t o p r e p a r e cost e s t i m a t e s . H o w e v e r , i n some cases, s u c h as t h i s o n e , o t h e r indexes c a n be u s e d . M u l t i p l e - e f f e c t e v a p o r a t i o n , o r m u l t i s t a g e flash e v a p o r a t i o n o f s e a w a t e r , i s as s i m p l e a d i s t i l l a t i o n process as c a n b e v i s u a l i z e d , because i t i n v o l v e s o n l y t h e s e p a r a t i o n of a s o l v e n t f r o m a n o n v o l a t i l e s o l u t e . R e c t i f i c a t i o n i s n o t i n v o l v e d i n t h i s o p e r a t i o n . T h e s e d i s t i l l a t i o n processes are those m o s t a d v a n c e d t e c h n o l o g i c a l l y a t t h e p r e s e n t t i m e , a n d t h e r e f o r e are a l o g i c a l s t a n d a r d f o r c o m p a r i s o n . I n a d d i t i o n t o these reasons, t h e a m m o n i u m b i c a r b o n a t e i o n exchange process e m p l o y s r e c t i f i c a t i o n , n o t m e r e l y s i m p l e d i s t i l l a t i o n , t o effect t h e i o n exchange régénérant r e c o v e r y . T h e r e f o r e , a c o m p a r i s o n o f t h e d i s t i l l a t i o n r e q u i r e m e n t s o f t h e t w o processes c o u l d b e i n t e r e s t i n g . T h e d i s t i l l a t i o n r e q u i r e m e n t s , o n t h e basis u s e d i n m a k i n g the. first m a t e r i a l b a l a n c e , f o r t h e a m m o n i u m b i c a r b o n a t e i o n exchange process are s u m m a r i z e d i n T a b l e V .

Table V.

Summary of Distillation Requirements

( A m m o n i u m bicarbonate i o n exchange process, 1 3 % N H H C 0 4

N o . of Stages

N o . of Stills

1 2 3 4

2 3 4 5

Feed, % NaCl 0.0887 0.434 1.525 3.21

3

solution distillate)

L b . H Q Distilled L b . Product

Total L b . Distilled L b . Product

0.0459 0.227 0.90 3.29

0.0527 0.274 1.035 3.78

2

I n a n y p l a n t d i s t i l l i n g sea w a t e r d i r e c t l y t o o b t a i n a d e m i n e r a l i z e d w a t e r , t h e r a t i o s of p o u n d s o f w a t e r d i s t i l l e d p e r p o u n d o f p r o d u c t , a n d p o u n d s o f t o t a l m a t e r i a l d i s t i l l e d p e r p o u n d of p r o d u c t , are i d e n t i c a l a n d are e q u a l t o u n i t y . T h e r e f o r e , i f a c o m p e t i n g process h a s a d i s t i l l a t i o n r a t i o g r e a t e r t h a n u n i t y , i t i s c l e a r l y u n e c o n o m i c a l w h e n c o m p a r e d t o d i r e c t d i s t i l l a t i o n . T a b l e V shows e i t h e r a t h r e e - s t a g e o r f o u r - s t a g e p l a n t t o f a l l i n t h i s c a t e g o r y ; t h e i o n exchange process, as v i s u a l i z e d , i n v o l v e s m o r e d i s t i l l a t i o n t h a n does d i r e c t d i s t i l l a t i o n . A n o t h e r f a c t o r i n c r e a s i n g t h e cost o f d i s t i l l a t i o n i n i o n exchange régénérant r e c o v e r y i s t h e need f o r s u p p l y i n g r e f l u x t o t h e r e c t i f y i n g c o l u m n s . T h e b o i l - u p f o r t h e r e b o i l e r s is t h e d i s t i l l a t e p r o d u c t p l u s t h e reflux, w h e r e i n d i r e c t d i s t i l l a t i o n t h e r e b o i l e r has t o v a p o r i z e o n l y t h e p r o d u c t . I f i o n exchange régénérant r e c o v e r y as a 1 3 % a m m o n i u m b i c a r b o n a t e s o l u t i o n i n v o l v e s t o o m u c h d i s t i l l a t i o n f o r t h e process t o b e a t t r a c t i v e , m i g h t n o t some o t h e r distillation conditions appear more favorable? T o a n s w e r t h i s q u e s t i o n t h e second m a t e r i a l balance was made w h i c h assumed a still overhead p r o d u c t of a 1 : 1 : 1 mole r a t i o o f N H : C 0 : H 0 , t h e s a m e r a t i o i n w h i c h these c o m p o u n d s u n i t e t o f o r m a n h y d r o u s a m m o n i u m b i c a r b o n a t e . T h i s i s t h e c o m p o s i t i o n o f t h e d i s t i l l a t e w h i c h gives a m i n i m u m a m o u n t o f d i s t i l l a t e p r o d u c t , a n d s t i l l a process w h i c h m i g h t b e feasible. S u m m i n g u p t h e a m m o n i u m b i c a r b o n a t e t o b e d i s t i l l e d , i n T a b l e I V , gives a t o t a l of 2455 p o u n d s t o p r o d u c e 3965 p o u n d s o f w a t e r . O n m e n t a l l y a d d i n g o n t h e e x t r a r e b o i l e r l o a d t o p r o d u c e t h e r e f l u x , p r o b a b l y s e v e r a l t i m e s t h e d i s t i l l a t i o n p r o d u c t as a m i n i m u m , t h e c o m p a r i s o n o f t h i s process t o m u l t i p l e - e f f e c t e v a p o r a t i o n does n o t a p p e a r promising. A n o t h e r q u e s t i o n comes t o m i n d a t t h i s s t a g e : I f t h e i o n exchange process u s i n g a m m o n i u m b i c a r b o n a t e does n o t a p p e a r t o b e p r o m i s i n g , m i g h t n o t some o t h e r s a l t perform more satisfactorily? 3

2

2



190


C r i t e r i a f o r C h o i c e o f S a l t . G i l l i l a n d has chosen t o c a l l these c h e m i c a l c o m p o u n d s " t h e r m o l y t i c s a l t s . " H e defines t h e m as m a t e r i a l s w h i c h , u p o n increase i n t e m p e r a t u r e , r e d u c t i o n i n p r e s s u r e , o r b o t h , d e c o m p o s e i n t o gases, o r i n t o gases a n d i n s o l u b l e solids. T h e idea b e h i n d this is t o have a n i o n exchange m a t e r i a l t h a t can be recovered w i t h o u t h a v i n g t o boil a w a y a l l of the solvent, water. A l s o i m p l i c i t i n this idea is the w i s h t h a t the i o n exchange m a t e r i a l , after its decomposition, be easily separable f r o m water. I t is o n t h i s l a s t f a c t o r t h a t a m m o n i u m b i c a r b o n a t e does n o t m e e t t h e d e s i d e r a t a . I n a w a t e r d e s a l t i n g o p e r a t i o n , t h e r e a p p e a r s t o b e n o m e a n s of a v o i d i n g d e a l i n g w i t h w a t e r . H o w e v e r , a t first glance i t seems possible t o s u b s t i t u t e some o t h e r b a s e f o r m i n g gas f o r a m m o n i a . T h e o n l y s u c h gases k n o w n t o t h e w r i t e r are t h e s u b s t i t u t e d a m m o n i a s , o r t h e a m i n e s . A n d a l l o f the a m i n e s c o n s i d e r e d seem t o b e less d e s i r a b l e t h a n t h e p a r e n t c o m p o u n d , a m m o n i a , f o r reasons s u c h as b o i l i n g p o i n t , cost, c h e m i c a l stability, and even odor. Other nonmetal hydrides similar to a m m o n i a t h a t might be c o n s i d e r e d , s u c h as p h o s p h i n e a n d a r s i n e , c a n b e r u l e d o u t because of t o x i c i t y , w i t h o u t considering any other properties. A n o t h e r s u b s t i t u t i o n t h a t c a n b e c o n s i d e r e d i s t h a t o f u s i n g some a c i d i c gas o t h e r t h a n c a r b o n d i o x i d e . T h e h y d r o g e n h a l i d e s d o n o t a p p e a r t o f i l l t h i s n e e d , because t h e c h l o r i d e i o n , d e r i v e d f r o m one o f t h e m , i s t h e p r i n c i p a l a n i o n p r e s e n t i n s e a w a t e r . H y d r o g e n c y a n i d e a n d h y d r o g e n sulfide c a n b o t h b e e l i m i n a t e d f r o m c o n s i d e r a t i o n because o f t o x i c i t y , a n d so o n d o w n t h e l i s t u n t i l w e c o m e t o s u l f u r d i o x i d e . S u l f u r d i o x i d e , f o r m i n g t w o series of s a l t s , t h e sulfites a n d t h e b i s u l f i t e s , seems t o m e r i t a s e c o n d l o o k . T h e s o l u b i l i t y o f t h e a m m o n i u m sulfites i n w a t e r — 3 2 t o 6 0 g r a m s of a n h y d r o u s salt f o r t h e n o r m a l sulfite p e r 100 g r a m s o f s a t u r a t e d s o l u t i o n i n t h e t e m p e r a t u r e r a n g e o f 0 ° t o 100° C , a n d 71 t o 8 6 g r a m s o f s a l t f o r t h e b i s u l f i t e , p e r 100 g r a m s o f s a t u r a t e d s o l u t i o n i n t h e 0 ° t o 6 0 ° C . r a n g e , as r e p o r t e d b y S e i d e l l (25)—is several times t h a t of a m m o n i u m bicarbonate. T h e v a p o r - l i q u i d , o r gas-liquid, equilibria a p p e a r t o b e less f a v o r a b l e t h a n f o r a m m o n i u m b i c a r b o n a t e . T h e s y s t e m N H - H 0 S 0 has b e e n s t u d i e d m o d e r a t e l y e x t e n s i v e l y as a possible m e a n s o f r e c o v e r i n g o r r e m o v i n g s u l f u r d i o x i d e f r o m s t a c k gases (12, 13, 15, 23). T h i s s y s t e m i s also o f i n t e r e s t t o t h e sulfite p u l p i n d u s t r y , as a m e a n s οΓ b o t h i n c r e a s i n g q u a l i t y o f p r o d u c t a n d d e c r e a s i n g w a t e r p o l l u t i o n p r o b l e m s , as i s a t t e s t e d b y a series o f p u b l i c a t i o n s (10, 27). A p p a r e n t l y t h e a m m o n i u m sulfites are m o r e s t a b l e c h e m i c a l l y t h a n t h e b i c a r b o n a t e , a n d m o r e difficult t o r e c o v e r f r o m a q u e o u s s o l u t i o n . C e r t a i n l y these s o l u t i o n s a r e m o r e c o r r o s i v e t o m e t a l s . T h e r e f o r e , t h e a m m o n i u m sulfites a p p e a r t o b e less w e l l s u i t e d t o t h i s i o n exchange c y c l e t h a n t h e b i c a r b o n a t e . 3

2

2

Summary O f t h e possible t h e r m o l y t i c a m m o n i u m s a l t i o n exchange processes f o r s e a w a t e r d e m i n e r a l i z a t i o n , t h e a m m o n i u m b i c a r b o n a t e process a p p e a r s t o b e t h e best. B u t i t a p p e a r s i n f e r i o r t o m u l t i p l e - e f f e c t e v a p o r a t i o n processes o n t h e sole basis o f t h e a m o u n t of d i s t i l l a t i o n r e q u i r e d f o r t h e régénérant r e c o v e r y .

Acknowledgment J a m e s W e l d y , a s s i s t a n t r e s e a r c h c h e m i s t , c a r r i e d o u t t h e i o n exchange r e s i n e v a l u ation. M r . W e l d y , and E n n e t h F r o h m a n , M y r o n D u n n , and Bruce W h i p p e r m a n , engin e e r i n g aides, p e r f o r m e d t h e q u a n t i t a t i v e i o n exchange e x p e r i m e n t s . C a l c u l a t i o n s w o r k w a s , i n p a r t , c a r r i e d o u t b y e n g i n e e r i n g aides E u g e n e B a r r i n g t o n , B r u c e W h i p p e r m a n , and Gerd Behrsing.

Literature Cited (1) B a d g e r , E. J. M., W i l s o n , D. S., J. Soc. Chem. Ind. 66, 84-6 ( M a r c h 1947). (2) B o n n e r , O . D., Argersinger, W . J., Jr., D a v i d s o n , A. W . ,J.Am. Chem. Soc. 74, 1044-7 (1952). (3) B o n n e r , O . D., P a y n e , W . H., J. Phys. Chem. 58, 183-5 (1954). (4) B u l k l e y , W . L., S w a r t z , R . , Refrig. Eng. 59, 660-2 (1951).


STEWART—DEMORALIZATION BY AMMONIUM SALTS ION EXCHANGE (5) (6) (7) (8) (9) (10)


(11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23) (24) (25) (26) (27)

191

E g a l o n , R . , V a n h i l l e , R . , W i l l e m y n s , M., Ind. chim. 1954, 293-8. G i l l i l a n d , E. R . , Ind. Eng. Chem. 47, 2410 (1955). G i l l i l a n d , E. R. (to Ionics, Inc.), U. S. P a t e n t 2,776,258 ( J a n . 1, 1957). Gregor, H. P., B e l l e , J a c k , M a r c u s , R. Α., J. Am. Chem. Soc. 76, 1984-7 (1954). G u y e r , Α., P i e c h o w i c z , T . , Helv. Chim. Acta 27, 858-67 (1944). H a y d e n , D. T., "Vapor-Liquid Equilibria in the S y s t e m A m m o n i a - S u l f u r Dioxide -Water," Ph.D. thesis, U n i v e r s i t y of W a s h i n g t o n , 1955: Dissertation Abstracts 15, 1935 (1955). Jennings, Β . H., S h a n n o n , F. P . , Refrig. Eng. 35, 333 (May 1938). Johnstone, H. F., Ind. Eng. Chem. 27, 587 (1935). Johnstone, H. F., K e y e s , D. B . , Ibid., 27, 659 (1935). K e e n a n , J. H., K e y e s , F. G., " T h e r m o d y n a m i c P r o p e r t i e s of S t e a m , " W i l e y , N e w Y o r k , 1936. K e l l e y , Κ. K., A n d e r s o n , C . T . , U. S. B u r . M i n e s , Bull. 384, 30 (1935). K o h l o s s , F. H., J r . , Scott, E. L., Refrig. Eng. 58, 970 (1950). K u n i n , R . , "Ion E x c h a n g e R e s i n s , " 2nd ed., W i l e y , N e w Y o r k , 1958. M y e r s , R. J., Ind. Eng. Chem. 35, 859 (1943). N a c h o d , F. C., Schubert, J., eds., " I o n E x c h a n g e T e c h n o l o g y , " A c a d e m i c Press, N e w Y o r k , 1956. N a t l . B u r . Standards, " T a b l e s of T h e r m o d y n a m i c Properties of A m m o n i a , " C i r c . 142 (1923). N e u m a n n , B e r n h a r d , D o m k e , R i c h a r d , Z. Elektrochem. 34, 136 (1938). P e x t o n , S., Badger, Ε. Η . Μ., J. Soc. Chem. Ind. 57, 106-13 (1938). S t . C l a i r , H. W . ,U.S. B u r . M i n e s , R e p t . Invest. 3339 (1937). Scatchard, George, E p s t e i n , L. F., W a r b u r t o n , James, J r . , C o d y , P. J., Refrig. Eng. 53, 413 (May 1947). S e i d e l l , A t h e r t o n , ed., " S o l u b i l i t i e s of Inorganic a n d M e t a l Organic C o m p o u n d s , " 3rd ed., Vol. 1, p . 1120, Van N o s t r a n d , N e w Y o r k , 1940; S u p p l . t o 3rd ed., p . 405, 1952. Terres, E r n s t , Weiser, H a n s , Z. Elektrochem. 27, 177 (1921). T h o d e , E. F., L e e ,V.H.,Tappi 33, 257-60 (1950).

RECEIVED for review N o v e m b e r 23, 1959.

A c c e p t e d J u n e 24, 1960.


Sea Water Demineralization by Ammonium Salts Ion Exchange

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