researc h corporation

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MSAR 60-67 . . . ---- TECHNICAL REPORT 73 on Contract NObs-77023 Index No. NS-200-023 and 200-027 Bureau of Ships Washington 25, D.C. THE REACTION RATE OF SODIUM SULFITE WITH DISSOLVED OXYGEN S,J. Rodgers 16 May 1960 Researc h Corporation Subsidiary of Mine Safety Appliances Company Callery, Pennsylvania Job NO. XA-720161, Exp No. 118

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M S A R 60-67

. . . ---- T E C H N I C A L R E P O R T 73

on C o n t r a c t NObs-77023

I n d e x N o . NS-200-023 a n d 200-027

Bureau of Ships Washington 2 5 , D . C .

T H E R E A C T I O N R A T E OF S O D I U M S U L F I T E W I T H D I S S O L V E D O X Y G E N

S,J. R o d g e r s

16 May 1960

Researc h Corporation

Subsidiary of M i n e Safety Appliances Company

Callery, Pennsylvania

J o b NO. XA-720161, E x p No. 118

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.

MSAR 6 0 - 6 7

T E C H N I C A L REPORT 73 o n

C o n t r a c t NObs-77023 I n d e x No. NS-200-023 a n d 200-027

B u r e a u o f S h i p s W a s h i n g t o n 2 5 , D O C ,

J o b N O . XA-720164 E x p e r i m e n t No. 118

T H E R E A C T I O N R A T E OF SODIUM SULFITE W I T H DISSOLVED O X Y G E N

S . J . R o d g e r s

1 6 May 1960

A p p r o v e d :

tor of R e s e a r c h of R e s e a r c h

MSA R e s e a r c h C o r p o r a t i o n G a l l e r y , P e n n s y l v a n i a

TABLE OF CONTENTS

J ABSTRACT

I H T R ODUC T I O N

EXPERIMENTAL PHILOSOPHY

EXPERIMENTAL EQUIPMENT A N D OPERATION TECHNIQUES

D A T A A N D RESULTS

I n t r o du c: t i o n R e a c t i o n T i m e a s a F u n c t i o n of Oxygen C o n c e n t r a t i o n E f f e c t of Na2S03/0 , R a t i o E f f e c t of T e m p e r a t u r e E f f e c t of C a t a l y s t E f f e c t of pH E f f e c t of S u r f a c e t o Volume R a t i o E f f e c t of S i m u l a t e d F e e d Water R e a c t i o n of H y d r a z i n e w i t h Oxygen

DISCUSSION

CONCLUSIONS

B I B L I OGRAPHY

P a g e No.

1

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3

6

6 7 7 11 11 11 1 5 1 5 17

18

19

21

J ABSTRACT f

The r e a c t i o n r a t e of s o d i u m s u l f i t e was s t u d i e d a s a f u n c t i o n of o x y g e n c o n c e n t r a t i o n , Na,SO3/0, r a t i o , t e m p e r a t u r e , c a t a l y s t , pH a n d s u r f a c e / v o l u m e r a t i o . The r e a c t i o n r a t e of h y d r a z i n e w i t h d i s s o l v e d o x y g e n was a l s o s t u d i e d . The r e a c t i o n s were s t u d i e d i n a dynamic s t a i n l e s s s t e e l sys tem. Oxygen c o n c e n t r a t i o n s were m e a s u r e d w i t h a m o d i f i e d B e t t i s d i s s o l v e d oxygen a n a l y s e r .

Oxygen r e m o v a l i s i n c o m p l e ' t e when t h e s u l f i t e t o o x y g e n r a t i o i s l e s s t h a n t h e s t o i c h i o m e t r i c q u a n t i t y , W i t h t h e s t o i c h i o m e t r i c q u a n t i t i e s of o x y g e n a n d s o d i u m s u l f i t e p r e s e n t , r e m o v a l i s i n c o m p l e t e a t 1 0 0 ° F i n 1 m i n 9 a t 200°F , a b o u t 95% of t h e o x y g e n i s r e m o v e d i n 1 0 s e e a n d a t 300°F o x y g e n r e m o v a l i s e s s e n t i a l l y c o m p l e t e i n 1 0 s e c .

W i t h a n e x c e s s of s u l f i t e p r e s e n t (10 Na,S03/1 O,, m o l a r ) , 95% of t h e o x y g e n i s r emoved a t lOOOF i n 1 0 s e c . A t 200 a n d 300°F, o x y g e n r e m o v a l i s e s s e n t i a l l y c o m p l e t e i n 1 0 s e c .

The r a t e of oxygen r e m o v a l i s d e p e n d e n t t o s o m e e x t e n t on t h e c o n t a i n e r m a t e r i a l . The s u l f i t e o x y g e n r e a c t i o n p r o g r e s s e s a t a h i g h e r r a t e i n b o i l e r w a t e r t h a n i n f e e d - wa te r

The r e a c t i o n r a t e of h y d r a z i n e w i t h o x y g e n i s l o w com- p a r e d wi t , h t h e r e a c t i o n r a t e of s u l f i t e a n d d i s s o l v e d o x y g e n , No r e d u c t i o n o f oxygen was n o t e d o v e r a one m i n u t e p e r i o d w i t h a n e x c e s s o f h y d r a z i n e .

> -

l o

THE R E A C T I O N RATE OF SODIUM SULFITE W I T H DISSOLVED O X Y G E N

S . J . R o d g e r s

I N T R I ODU C T I ON

The n e c e s s i t y of m a i n t a i n i n g d i s s o l v e d o x y g e n a t a l o w l e v e l i n power p l a n t b o i l e r s h a s l o n g b e e n r e c o g n i z e d . The c o r r o s i v e e f f e c t s of d i s s o l v e d o x y g e n on m e t a l l i c c o m p o n e n t s h a s b e e n t h e s u b j e c t of many s t u d i e s i n t h e p a s t a n d more r e c e n t l y , t h e c o n - t r i b u t i o n o f o x y g e n on c h l o r i d e s t r e s s c o r r o s i o n o f s t a i n l e s s s t e e l b o i l e r c o m p o n e n t s h a s b e e n i n v e s t i g a t e d . I t h a s b e e n shown t h a t c h l o r i d e s t r e s s c o r r o s i o n i s , f o r a l l p r a c t i c a l p u r p o s e s , e l i m i n - a t e d when t h e o x y g e n l e v e l i s m a i n t a i n e d b e l o w 0 .05 ppm. I t h a s a l s o b e e n d e m o n s t r a t e d t h a t c h l o r i d e c o n c e n t r a t i o n s u p t o 800 ppm c a n b e t o l e r a t e d i f t h e o x y g e n l e v e l i s l i m i t e d t o l e s s t h a n 0.1 ppm’.

Two m e t h o d s a r e u s e d t o r e m o v e d i s s o l v e d o x y g e n - t h e m e c h a n i - c a l m e t h o d a n d t h e c h e m i c a l m e t h o d . M e c h a n i c a l d e a e r a t i o n , w h i c h r e q u i r e s h e a t i n g , i s t h e m e t h o d m o s t w i d e l y u s e d f o r t h e r e m o v a l o f b u l k o x y g e n . The c h e m i c a l m e t h o d , w h i c h n o r m a l l y e n t a i l s t h e u s e o f s o d i u m s u l f i t e o r h y d r a z i n e , i s t h e m o s t e f f i c i e n t m e t h o d of r e m o v i n g t r a c e q u a n t i t i e s of o x y g e n .

B o t h c h e m i c a l s a r e c o m p a t i b l e w i t h b o i l e r c o m p o n e n t s a t t h e l e v e l s n e c e s s a r y t o m a i n t a i n minimum o x y g e n l e v e l s . Sodium s u l f i t e i s i n e x p e n s i v e , w a t e r s o l u b l e a n d f o r m s a w a t e r s o l u b l e r e a c t i o n p r o d u c t w i t h o x y g e n . The o v e r a l l r e a c t i o n of s o d i u m s u l f i t e w i t h o x y g e n i s :

2Na2S03 + 02-2Na2S04

w i t h t h e s t o i c h i o m e t r i c w e i g h t r a t i o b e i n g 7.88 N a 2 S 0 3 / 1 0 , a n d t h e s t o i c h i o m e t r i c m o l a r r a t i o b e i n g 2Na2S03 /1 0,. The r e a c t i o n of h y d r a z i n e w i t h o x y g e n i s :

N H 2 N H 2 + 0 2 4 2 H 2 O + N 2

w i t h b o t h t h e s t o i c h i o m e t r i c a n d m o l a r r a t i o s b e i n g 1 N H 2 N H 2 / 1 0 2 . Numbered among t h e d i s a d v a n t a g e s of h y d r a z i n e a r e t h e f o r m a t i o n of ammonia w i t h a l a r g e e x c e s s of h y d r a z i n e a n d t h e p o t e n t i a l ex- p l o s i o n a n d p o i s o n h q a a r d of t h e c h e n i c a l .

1

1 3

I

1 1 I

T h i s r e p o r t d e s c r i b e s a s y s t e m a t i c s t u d y of t h e r e a c t i o n r a t e o f s o d i u m s u l f i t e w i t h d i s s o l v e d oxygen a n d a l e s s e n c o m p a s s i n g s t u d y o f t h e r e a c t i o n r a t e o f h y d r a z i n e w i t h d i s s o l v e d o x y g e n -

EXPERIMENTAL PHILOSOPHY

S t u d y of t h e r e a c t i o n r a t e o f o x y g e n - c o n t r o l l i n g c h e m i c a l s w i t h d i s s o l v e d oxygen m u s t b e made u n d e r c o n d i t i o n s n o r m a l l y e n - c o u n t e r e d i n b o i l e r sys tems. T h e s e c o n d i t i o n s s h o u l d b e t y p i c a l of b o t h f e e d - w a t e r a n d b o i l e r w a t e r s i n c e o x y g e n w i l l b e c o n t r o l l e d i n b o t h s y s t e m s . It i s o b v i o u s t h a t t h e c o n d i t i o n s u n d e r c o n s i d e r - a t i o n may v a r y w i d e l y f r o m power p l a n t t o power p l a n t b u t some l i m i t i n g c o n d i t i o n s c a n b e s e t f o r n a v a l n u c l e a r power p l a n t s . An e v a l u a t i o n of t h e r e a c t i o n r a t e s w i t h i n t h e s e l i m i t s s h o u l d p r o v i d e r e a c t i o n r a t e d a t a s u i t a b l e f o r u s e b y power p l a n t o p e r a t i n g p e r s o n - n e l a

The e f f e c t of t e m p e r a t u r e i s of m a j o r c o n s i d e r a t i o n i n a n y r e a c t i o n r a t e s t u d y . The t e m p e r a t u r e s w h i c h w i l l n o r m a l l y b e e n - c o u n t e r e d i n a N a v a l p l a n t a r e i n t h e r a n g e o f 100-600'F w i t h t h e 1 0 0 ° F l e v e l t y p i c a l of t h e f e e d w a t e r p l a n t a n d 600'F t y p i c a l of t h e b o i l e r . T e m p e r a t u r e l e v e l s o f 10O0F9 200'F a n d 300°F were c h o s e n f o r t h i s s t u d y . The m a x i m u m of 300°F was c h o s e n t o a v o i d c o n s t r u c t i o n of a h i g h p r e s s u r e sys t em, w i t h t h e u n d e r s t a n d i n g t h a t i f t h e d a t a w a r r a n t e d , a sys tem would b e c o n s t r u c t e d f o r e v a l u a t i o n a t h i g h e r t e m p e r a t u r e l e v e l s .

The o x y g e n l e v e l of a i r - s a t u r a t e d wa te r a t room t e m p e r a t u r e i s of t h e o r d e r of 1-5 ppm. T y p i c a l o x y g e n l e v e l o f m e c h a n i c a l l y d e a e r a t e d wa te r i s i n t h e r a n g e of 0 .01 ppm a n d t r a c e o x y g e n l e v e l s c a n b e c o n s i d e r e d t o b e of t h e o r d e r of 0 .005 ppm. S i n c e i t i s p o s s i b l e t h a t a l l of t h e s e l e v e l s may b e e n c o u n t e r e d d u r i n g n o r m a l power p l a n t o p e r a t i o n , o x y g e n c o n c e n t r a t i o n s of 0 .01 , 0.10 a n d 1 . 0 were c h o s e n f o r s t u d y .

S p e c i f i c a t i o n s f o r s u l f i t e l e v e l s v a r y f r o m p l a n t t o p l a n t a n d d e p e n d u p o n t h e o x y g e n c o n c e n t r a t i o n a t a n y g i v e n t i m e . L e v e l s o f 2 5 , 100 a n d 300 ppm Na,S03 were o r i g i n a l l y c h o s e n b u t r e s u l t s a s t h e t e s t p r o g r e s s e d i n d i c a t e d t h a t i t was i m p r a c t i c a l t o r u n ex- t r e m e l y l o w 0, l e v e l s . I t was d e c i d e d t h a t t h e t e s t s w o u l d b e r u n w i t h v a r i o u s Na2S03 /0 , m o l a r r a t i o s s p e c i f i c a l l y 0 .5 Na,S03/1 O,, 2Na2S03 /1 0, a n d 10Na,S03/1 0, .

The pH l e v e l n o r m a l l y m a i n t a i n e d i s i n t h e r a n g e of 7-11. L e v e l s of 7 , 8 . 5 a n d 11 were c h o s e n f o r t h i s s t u d y .

3

d

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A l t h o u g h c a t a l y s t s a r e n o t n o r m a l l y e m p l o y e d , i t h a s b e e n r e p o r t e d t h a t c a t i o n s of h e a v i e r m e t a l s w i l l c a t a l y s e t h e s u l f i t e - o x y g e n r e a c t i o n 2 . The m e t a l s i n c l u d e c o p p e r p i r o n , c o b a l t , n i c k e l a n d m a n g a n e s e w i t h c o p p e r s h o w i n g t h e m o s t m a r k e d e f f e c t s . I t was a l s o r e p o r t e d t h a t a n i o n s a n d c a t i o n s of t h e a l k a l i a n d a l k a l i n e e a r t h m e t a l s a p p a r e n t l y e x e r t no c a t a l y t i c e f f e c t . F u r t h e r m o r e , s u b s t a n c e s w h i c h f o r m c p m p l e x e s w i t h t h e i o n s m i n i m i z e t h e c a t a l y t i c e f f e c t . A n o t h e r r e f e r q n c e i n d i c a t e s t h a t c o b a l t i s m o r e e f f e c t i v e t h a n c o p p e r . An i n i t i a l 0, c o n c e n t r a t i o n oi 8-10 ppm was r e d u c e d t o 0 ppm i n 30 s e c o n d s w i t h 0,Ol ppm c o b a l t a n d t o 0 ppm i n 4 m i n u t e s w i t h 1 . 0 ppm c o p p e r 3 . C o p p e r was c h o s e n as t h e c a t a l y s t f o r t h i s i n v e s t i g a t i o n a n d e v a l u a t e d a t t h e l e v e l s o f 0, 0 . 0 1 a n d 1-0 ppm. I€ w i l l b e shown l a t e r t h a n t h e r e a p p a r e n t l y is a l s o a s u r f a c e c a t a l y t i c e f f e c t of t h e s t a i n l e s s s t e e l c o n t a i n e r w a l l s w h i c h i s m o r e p r e d o m i n a n t t h a n t h a t o f t h e h e a v y m e t a l i o n s i n s o l u t i o n .

O t h e r f a c t o r s w h i c h , a l t h o u g h t h e y d o n o t n e c e s s a r i l y v a r y f r o m b o i l e r t o b o i l e r , must b e t a k e n i n t o c o n s i d e r a t i o n i n c l u d e p h o s p h a t e l e v e l ( 1 5 0 ppm) , c h l o r i d e s ( < 1 ppm) a n d s o l i d s (800-1000 p p m ) - These. f a c t o r s were m a i n t a i n e d a s n e a r t o z e r o as p o s s i b l e f o r e v a l u a t i o n of r e a c t i o n r a t e s i n f e e d w a t e r .

EXPERIMENTAL EQUIPMENT AND O P E R A T I O N TECHNIQUES

The e x p e r i m e n t a l e q u i p m e n t i s shown i n F i g 1 a n d was c o n s t r u c t e d o f Type 304 s t a i n l e s s s t e e l - Two r e s e r v o i r s e a c h c o n t a i n e d 1 0 0 g a l - o f w a t e r , o n e a d j u s t e d t o t h e s p e c i f i e d o x y g e n l e v e l a n d t h e o t h e r a d j u s t e d t o t h e s p e c i f i e d s u l f i t e l e v e l . C a t a l y s t , pH a n d p h o s p h a t e were a d j u s t e d t o t h e d e s i r e d l e v e l i n e a c h r e s e r v o i r p r i o r t o e a c h r u n . Oxygen l e v e l was r e d u c e d i n t h e o x y g e n r e s e r v o i r e i t h e r b y h e a t i n g t h e w a t e r o r a d d i n g s u f f i c i e n t s u l f i t e t o r e a c t w i t h t h e oxyg'en p r e s e n t . When n e c e s s a r y , t h e o x y g e n l e v e l was i n c r e a s e d b y b u b b l i n g a i r t h r o u g h t h e w a t e r i n t h e r e s e r v o i r . S u l f i t e w a s ad- j u s t e d b y a d d i n g a c o n c e n t r a t e d Na,S03 s o l u t i o n i n t h e a p p r o p r i a t e q u a n t i t y t o t h e s u l f i t e r e s e r v o i r .

Water was c i r c u l a t e d t h r o u g h t h e t e s t s e c t i o n w i t h a g e a r pump. M i x i n g i n t h e r e s e r v o i r was a t t a i n e d b y c i r c u l a t i n g t h r o u g h t h e pump a n d t h o u g h a b y - p a s s r e t u r n t o t h e r e s e r v o i r . F l o w r a t e was m e a s u r e d w i t h f l o w m e t e r s c a l i b r a t e d f o r 100% f l o w e q u i v a l e n t t o 0 . 2 4 gpm. I n i t i a l h e a t i n g of e a c h of t h e w a t e r s u p p l i e s was e f f e c t e d i n s e p a r a t e t a n k s w i t h i m m e r s i o n h e a t e r s .

T h r o t t l i n g v a l v e s p r o v i d e d a m e a n s of p r o p o r t i o n i n g t h e f l o w f r o m e a c h of t h e sys tems, w i t h t h e t o t a l v o l u m e t r i c f l o w r a t e t h r o u g h t h e t e s t s e c t i o n s b e i n g 0 .24 gpm (1.3 f p s ) . T h i s f l o w r a t e r e s u l t e d i n a R e y n o l d s number of 10 ,000 i n t h e t e s t s e c t i o n s a t lOOOF a s s u r i n g t u r b u l e n t f l o w . S i n c e t h e s t u d y was on r e a c t i o n r a t e s a n d n o t m i x i n g , t h a t t u r b u l e n t f l o w was d e s i r a b l e t o m i n i m i z e a n o m a l i e s d u e

. 1

1 1

I

d F i g . I - Flow D i a ~ r a n ~ - D i s s o l v e d O x y o e n - S u l f i t e R e a c t i o n R a t e A p p a r a t u s I "

- 5-

t o m i x i n g . A m i x i n g c h a m b e r was a l s o i n s t a l l e d a t t h e j u n c t i o n of t h e s u l f i t e a n d o x y g e n l i n e s a n d was composed of a 1 - 1 / 2 i n . l e n g t h of b a f f l e d 1 / 2 i n . p i p e . I t was f e l t t h a t t h e c o m b i n a t i o n of t h e m i x i n g c h a m b e r a n d t u r b u l e n t f l o w w o u l d p r o v i d e s u f f i c i e n t m i x i n g s o t h a t t h e r a t e s w h i c h were m e a s u r e d were t r u e r e a c t i o n r a t e s . A s t h e t e s t p r o g r e s s e d a h i g h i n i t i a l r e a c t i o n r a t e was o b s e r v e d . S i n c e r e s i d e n c e t i m e ( 0 . 2 s e c o n d s ) , s u r f a c e t o volume r a t i o a n d m i x i n g was g r e a t e r i n t h e m i x i n g c h a m b e r t h a n i n t h e s y s t e m p r o p e r , i t was f e l t t h a t t h e m e a s u r e d r e a c t i o n r a t e s may h a v e b e e n i n f l u e n c e d b y t h e m i x i n g c h a m b e r . The c h a m b e r w a s r e p l a c e d w i t h a t e e b u t no d i f f e r e n c e was n o t e d i n m e a s u r e d r e a c t i o n r a t e s .

V a r i o u s c o n t a c t t i m e s were a t t a i n a b l e w i t h a p p r o p r i a t e l e n g t h s o f 3/8 i n . O D t u b i n g . C o n t a c t t i m e s of 2 , 3 . 5 , 5 9 1 0 , 30 a n d 60 s e c o n d s were p o s s i b l e w i t h t h i s s y s t e m . W i t h t h e e x c e p t i o n of t h e t u b e c o r r e s p o n d i n g t o t h e 2 s e c o n d c o n t a c t t i m e w h e r e h e a t l o s s e s were n e g l i g i b l e , t h e t e s t s e c t i o n s were m a i n t a i n e d a t t h e d e s i r e d t e m p e r a t u r e b y a n o i l b a t h .

S a m p l e s were t a k e n f r o m t h e r e s e r v o i r s a n d a n a l y s e d f o r t h e v a r i o u s a d d i t i v e s . P h o s p h a t e c o n c e n t r a t i o n s were d e t e r m i n e d c o l o r i - m e t r i c a l l y u s i n g a T a y l o r S l i d e C o m p a r a t o r * The r a n g e of t h e m e t h o d w a s 10 -90 ppm w i t h c o n c e n t r a t i o n s a b o v e t h i s r a n g e a n a l y s e d a f t e r d i l u t i o n of t h e s a m p l e . Sod ium s u l f i t e c o n c e n t r a t i o n was d e t e r m i n e d v o l u m e t r i c a l l y b y t i t r a t i n g w i t h i o d i d e - i o d a t e s o l u t i o n . The pH l e v e l s were d e t e r m i n e d w i t h a Beckman pH me te r s t a n d a r d i z e d w i t h s t a n d a r d b u f f e r s o l u t i o n s . C h l o r i d e c o n c e n t r a t i o n was d e t e r m i n e d c o l o r i m e t r i c a l l y u s i n g t h e m e r c u r i c t h i o c y a n a t e m e t h o d e S o l i d s were m e a s u r e d b y e v a p o r a t i n g a 100 c c s a m p l e of t h e wa te r a n d w e i g h i n g . C o p p e r was d e t e r m i n e d b y t h e d i e t h y l d i t h i o c a r b a m a t e m e t h o d w i t h a l o w e r l i m i t of d e t e c t i o n of 1 x ppm.

H y d r a z i n e c o n c e n t r a t i o n was d e t e r m i n e d b y t w o m e t h o d s recom- mended b y H a l l L a b o r a t o r i e s 4 . c o n c e n t r a t i o n s w a s t h e c o l o r i m e t r i c m e t h o d e m p l o y i n g p - d i m e t h y l a m i n o - b e n z a l d e h y d e i n a c i d medium, H y d r a z i n e c o n c e n t r a t i o n s g r e a t e r t h a n 1 ppm were a n a l y s e d b y t i t r a t i n g w i t h i o d i n e i n a s a m p l e b u f f e r e d w i t h s o d i u m c a r b o n a t e .

The m e t h o d u s e d f o r l o w h y d r a z i n e

I t was r e c o g n i z e d t h a t a n i n s t a n t a n e o u s m e t h o d of a n a l y s i s f o r o x y g e n w a s n e c e s s a r y t o m e a s u r e t h e . q u a n t i t y of o x y g e n p r e s e n t a f t e r s h o r t c o n t a c t t i m e s c o n s i d e r e d i n t h i s s t u d y . The B e t t i s d i s s o l v e d o x y g e n a n a l y s e r s e e m e d m o s t p r o m i s i n g s i n c e i t s o p e r a t i o n i s b a s e d on c o n t i n u o u s f l o w of a s a m p l e t h r o u g h t h e a p p a r a t u s . T h u s , a s a m p l e f l o w i n g f r o m t h e 2 s e c o n d t u b e i n t o t h e a n a l y s e r r e p r e s e n t s t h e o x y g e n r e m a i n i n g a f t e r 2 s e c o n d s .

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A s c h e m a t i c d i a g r a m of t h e a n a l y s e r i s s h o w n . ( S e e F i g l e ) I t c o n - s i s t s of a n u p s t r e a m i o n e x c h a n g e c o l u m n , u p s t r e a m c o n d u c t i v i t y c e l l , t h a l l i u m c o l u m n , d o w n s t r e a m c o n d u c t i v i t y c e l l a n d a d o w n s t r e a m i o n e x c h a n g e c o l u m n i f t h e wa te r i s t o b e r e t u r n e d t o t h e s y s t e m . Water i s p a s s e d t h r o u g h t h e a n a l y s e r a t a f l o w r a t e of 1 5 0 c c / m i n a n d , f o r t h i s s t u d y , a c o n s t a n t t e m p e r a t u r e o f 90OF. I o n i c m a t e r i a l , b u t n o t o x y g e n , i s r emoved f r o m t h e w a t e r p a s s i n g t h r o u g h a n u p s t r e a m i o n e x c h a n g e c o l u m n . C o n d u c t i v i t y of t h e d e i o n i z e d w a t e r , w h i c h s t i l l c o n t a i n s t h e d i s s o l v e d o x y g e n , i s m e a s u r e d i n t h e u p s t r e a m c o n d u c t i v i t y c e l l .

C o n d u c t i v i t y of t h e w a t e r i n t h e d o w n s t r e a m c o n d u c t i v i t y c e l l i s a f u n c t i o n of t h e q u a n t i t y of o x y g e n i n t h e w a t e r , Oxygen con- c e n t r a t i o n of t h e w a t e r i s c a l c u l a t e d 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

w h e r e K, a n d K O a r e t h e e x p e r i m e n t a l l y d e t e r m i n e d c e l l c o n s t a n t s f o r t h e u p s t r e a m a n d d o w n s t r e a m c e l l s , r e s p e c t i v e l y . The r e s i s t a n c e s , R , a n d R o 9 a r e m e a s u r e d w i t h a c o n d u c t i v i t y b r i d g e .

A c c u r a c y of t h e m e t h o d was d e t e r m i n e d b y c o m p a r i s o n w i t h s a m p l e s a n a l y s e d b y t h e W i n k l e r Method f o r h i g h o x y g e n c o n c e n t r a t i o n s a n d t h e I n d i g o C a r m i n e Method f o r l o w o x y g e n c o n c e n t r a t i o n s . The r e s u l t s i n d i c a t e d t h a t t h e oxygen c o n c e n t r a t i o n d e t e r m i n e d w i t h t h e a n a l y s e r was r e p r e s e n t a t i v e of t h e t r u e o x y g e n c o n c e n t r a t i o n .

Some d i f f i c u l t y was e x p e r i e n c e d when t h e s y s t e m was f i r s t p u t i n t o o p e r a t i o n . I t was o b s e r v e d t h a t a f t e r t h e a n a l y s e r h a d r u n f o r a p e r i o d of t i m e , t h e o x y g e n c o n c e n t r a t i o n a p p a r e n t l y d r o p p e d . T h i s was f o u n d t o b e c a u s e d b y r e a c t i o n of o x y g e n , w h i c h n o r m a l l y w o u l d p a s s t h r o u g h t h e i o n e x c h a n g e c o l u m n , w i t h s u l f i t e w h i c h h a d S e e n r emoved b y t h e c o l u m n . T h i s d i f f i c u l t y was e l i m i n a t e d b y c o n - v e r t i n g t h e f i r s t 25-30;& of t h e r e s i n t o t h e i o d a t e form. T h u s , s u l f i t e i s c o n v e r t e d t o s u l d a t e i n t h e c o l u m n , p r e v e n t i n g a d d i t i o n a l o x y g e n r e m o v a l . R e l i a b l e r e s u l t s were = t h e n a t t a i n a b l e u n t i l t h e r e s i n b e d became s a t u r a t e d w i t h t h e n o r m a l i o n i c m a t e r i a l f o u n d i n t h e w a t e r .

J D A T A A N D RESULTS

I n t r oduc t i o n

Runs were made b y f i l l i n g t h e t a n k s w i t h d e m i n e r a l i z e d w a t e r . A s a m p l e o f .water f r o m e a c h t a n k was p a s s e d t h r o u g h t h e a n a l y s e r t o d e t e r m i n e t h e o x y g e n c o n c e n t r a t i o n a n d a p p r o p r i a t e a d d i t i o n s o r r e m o v a l of p h o s p h a t e , L i O H , s u l f i t e , c o p p e r a n d o x y g e n were made. T e m p e r a t u r e a d j u s t m e n t s were made a n d t h e r u n was i n i t i a t e d by

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p r o p o r t i o n i n g t h e f l o w f r o m t h e t a n k s t o g i v e t h e d e s i r e d N a 2 S 0 3 / 0 2 r a t i o . Water was p a s s e d t h r o u g h e a c h t e s t s e c t i o n f o r 10 m i n u t e s t o a s s u r e t h a t t h e sys tem was f l u s h e d . An a d d i t t o n a l 5 m i n u t e f l u s h was p a s s e d t h r o u g h t h e a n a l y z e r t o a s s u r e t h a t t h e s y s t e m was e q u i - l i b r a t e d . The f o l l o w i n g p r e s e n t a t l o n i s , u n l e s s o t h e r w i s e n o t e d s t y p i c a l of t h e r e a c t i o n i n b o i l e r wa te r in Type ?G4 s t a i n l e s s s t e e l .

R e a c t i o n T i m e a s a F u n c t i o n o f Oxygen C o n c e n t r a t i o n

Oxygen c ; o n c e n t r a t i o n s of l9 0 . 1 a n d 0 .01 ppm were c o n s i d e r e d i n t h i s s t u d y . T h e s e l e v e l s were s t u d i e d w i t h s o d i u m s u l f i t e t o o x y g e n m o l a r r a t i o s o f 0.5/1, 2/1 a n d 10/1 (2/1 m o l a r r a t i o r e p r e - s e n t s s t o i c h i o m e t r i c q u a n t i t i e s )

R e s u l t s shown i n F i g 2 i n d i c a t e t h a t t h e m a j o r f r a c t i o n of o x y g e n r e m o v a l o c c u r r e d d u r i n g t h e f i r s t 1 0 s e c o n d s . The i n i t i a l o x y g e n c o n c e n t r a t i o n s e e m e d t o h a v e no e f f e c t on t h e c h a r a c t e r i s t i c r e m o v a l d u r i n g t h e f i r s t 1 0 s e c o n d s . I t was n o t e d t h a t a t t h e oxygen l e v e l s o f G e l a n d 0 .01 ppm w i t h a 0 . 5 Na,S03/1 0, r a t i o t h e r e a c t i o n was c o m p l e t e , i . e . , 25% of t h e o x y g e n was removed w i t h i n 1 0 s e c o n d s . H o w e v e r g a t t h e 1.0 ppm o x y g e n l e v e l w i t h a 0 - 5 Na,S03/1 0, r a t i o , g r e a t e r t h a n 25% of t h e o x y g e n was removed ( F i g 3 ) 0 I t i s b e l i e v e d t h a t t h i s i s d u e t o t h e r e a c t i o n o f o x y g e n w i t h t h e t u b i n g wal ls i n a d d i t i o n t o t h e r e a c t i o n w i t h Na,S03,

E f f e c t of NazSO 3 / 0 R a t i o

The m o l a r s u l f i t e t o o x y g e n r a t i o s o f 0.5/1, 2/1 ( s t o i c h i o m e t r i c r a t i o ) a n d 10/1 were s t u d i e d a t t h e o x y g e n l e v e l s of 0 .01, C o l a n d 1 ppmo Oxygen c o n c e n t r a t i o n v e r s u s r e a c t i o n t i m e i s p l o t t e d a s a f u n c t i o n o f Na2S03 /02 i n F i g 4 0

W i t h a 0 , 5 Na,S03/1 0, r a t f o , r e m o v a l of o x y g e n f r o m t h e sys tem 1s i n c o m p l e t e . T h i s w o u l d b e e x p e c t e d s i n c e t h i s r a t i o c o r r e s p o n d s to 2 5 % removal of oxygen. An interesting f a c t w h i c h w a s noted, how- e v e r , was t h a t a s h i g h as 50% o f t h e o x y g e n was r emoved u s i n g t h i s r a t i o when t h e i n i t i a l oxygen c o n c e n t r a t i o n was 1 ppm o r h i g h e r D A s i n d i c a t e d b e f o r e , t h i s i s a t t r i b u t e d t o r e a c t i o n o f o x y g e c w i t h t h e e q u i p m e n t w a l l s .

5 S t r a u b h a s r e p o r t e d t h a t d i s s o l v e d o x y g e n w i l l r e a c t w i t h b o t h

s u l f i t e a n d s t e e l e v e n i n t h e p r e s e n c e of e x c e s s s u l f i t e . He h a s a l s o r e p o r t e d t h a t s u l f i t e w i l l r e d u c e ferr ic , o x i d e a t t e m p e r a t u r e s a b v o e 45OoF. I f oxygen i s r e m o v e d b y t h e s t a i n l e s s s t e e l s u r f a c e , o n e wou ld e x p e c t a f e r r i c o x i d e t o b e d e p o s i t e d on t h e s u r f a c e w h i c h w o u l d e v e n t u a l l y a c t a s a p r o t e c t i v e b a r r i e r t o a d d i t i o n a l r e m o v a l b y t h e v e s s e l w a l l s . H o w e v e r , i f t h e f e r r i c o x i d e i s r e d u c e d b y s u l f i t e a dynamic e q u i l i b r i u m w o u l d b e p r o d u c e d w h e r e i n s u l f i t e w o u l d b e consumed b y b o t h t h e o x y g e n a n d f e r r i c o x i d e a n d o x y g e n w o u l d b e c o n s u n e d b y b o t h t h e s u l f i t e a n d s t e e l wa l l s . R e s u l t s i n d i - c a t e t h a t t h i s i s p r o b a b l y t r u e .

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F i o . 2 - O x y o e n C o n c e n t r a t i o n v s R e a c t i o n Time 8 s a F u n c t i o n o f I n i t i a l 02 C o n c e n t r a t i o n

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F i Q . 3 - Oxygen C o n c e n t r a t i o n v s R e a c t i o n Time as a F u n c t i o n o f I n i t i a l 02 C o n c e n t r a t i o n

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-11-

W i t h a 2Na2SO3/1 0, r a t i o , o x y g e n r e m o v a l i s i n c o m p l e t e i n 60 s e c o n d s a t l Q O ° F w i t h a b o u t 50% removed i n 2 s e c o n d s , 58% removed i n 5 s e c o n d s a n d 6 0 % r emoved i n iC: sscaazds; l i t t l e a d d i t i o n a l remoira l o c c u r s a f t e r 1 0 s e c o n d s o T n c r e a s f n g t h e t e m p e r a t u r e t o 200 r e s u l t s i n o x y g e n r e m o v a l of 90% i n 2 s e c o n d s j 97% i n 5 s e c o n d s ar_d 98% i n 1 0 s e c o n d s ; a f t e r 60 s e c o n d s 99% o f t h e oxygen h a s b e e n r e m o v e d Y

W i t h a 1.0 N a 2 S 0 3 / l 0 , r a t i o ( 5 t imes s t o i c h i o m s t r i c r a t i o ) , 90% i s r e m o v e d i n 2 secoP .ds , 94% i s yemoved ia 5 s e c o n d s a n d 55% i s r e m o v e d i n 19 s e c o n d s a t l Q O ° F o A t 2 0 0 , S’i% o f t h e 0, i s r e m o v e d in 2 s e c o n d s c A t 3GO°F, 98% o f t h e o x y g e n i s r emoved i n t h e f i r s t 2 s e c o n d s ; at, 10 s e c o ~ d s 99% o f t h e oxygen i s r e m o v e d ,

E f f e c t of T e m p e r a t u r e

T e m p e p a t u r e L e a e l s o f l Q O ° F , 2Q0°F a n d 30G°F were s t u d i e d f o r t h e t h r e e Na,S03/0, r a t i o s . T e m p e r a t u r e l e v e l s of 6T°F a n d 15C°F were a l s o s t u d i e d f o r t h e 2Na,S03/1 0, r a t i o , e f f e c t of t e m , p e r % t u r e was qulPte p r o n o u n c e d 9 p a r t i c u l a r l y u p t o 2 0 0 ° F o P l o t s o f oxygen c o n c e n t r a t i o n v e r s u s r e a c t i o n t i m e f o r t h e v a r i o u s t e m p e r a t u r e s a t 2/l a n d 10/1 N a , S O 3 , , / O 2 r a t i o s a r e shown i n F i g s 5 a n d 6 .

I t was f o u n d t h a t t h e

E f f e c t o f C a t a l y s t

The e f i e c t o f a c a t a l y s t was s t u d i e d a t c o p p e r c o n c e n t r a t i o n s o f O, OoG1 a n d 1 ppm w i t h c o p p e r a d d e d a s CuSO,, I t was s u r p r i s i n g t o f i n d f n l i g h t of o t h e r work t h a t t h e a d d i t i o n of c a t a l y s t p r o d u c e d n o n o t f c e a b l e e f f e c t o n t h e r e a c t i o n r a t e . S i n c e e a r l i e r w o r k ( H i t c h e n s ) h a d b s e n p e r f o r m e d i n g l a s s , i t was d e c i d e d t h a t t h e r e - a c t i o n t i m e w o u l d b e s t u d i e d I n a n o n - m e t a l l i c sys t em.

The s t a i n l e s s s t e e l sys tem was m o d i f i e d by i n c o r p o r a t i n g a g l a s s s y s t e m , a Tygon sys tem a n d l a t e r a c o p p e r s y s t e m t h r o u g h w h i c h a sample w a s p a s s e d f o r a 1 m i n u t e y e s i d e n e e t i m e o R e s u l t s ape l i s t e d i n T a b l e 1 a n d p l o t t e d i n F i g 7 , I t c a n be s e e n t h a t c o p p e r d o e s c a t a l y s e t h e r e a c t f o n , d o u b l i n g t h e o x y g e n r e m o v a l r a t e when a d d e d a t a c o n c e n t r a t i o n O S 1 ppmo No c h a n g e i s n o t e d when c o p p e r i s a d d e d t o a s t a i n l e s s s t e e l sys tem, f n d l c a t i n g t h a t i n h e r e n t c a t a l y t i c e f f e c t s of t h e s t e e l s y s t e m o v e r s h a d o w s a n y c a t a l y t i c e f f e c t of c o p p e r . R e a c t i o n r a t e i n c o p p e r t u b i n g i s much h i g h e r t h a n i n a n o n - m e t a l l i c s y s t e m b u t l e s s t h a n i n s t a i n l e s s s t e e l .

E f f e c t of pH

The pH l e v e l s w h i c h were s t u d i e d were 7 , 8 , 5 a n d 11, No d i f f e r - e n c e was d e t e c t e d when t h e r e a c t i o n r a t e was s t u d i e d fn s t a i n l e s s s t e e l b u t t h e r e a c t i o n p r o c e e d e d a l i t t l e more r a p i d l y i n g l a s s a t a pH of 8 , 5 t h a n . a t e i t h e r 7 o r llo

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E f f e c t of S u r f a c e t o Volume R a t i o

The t e s t s e c t i o n s i n w h i c h t h e r e a c t i o n r a t e s s t u d i e s were p e r - f o r m e d h a d a s u r f a c e t o vo lume r a t i o o f 1 0 in-’, The t u b i n g was r e p l a c e d w i t h a v e s s e l w h i c h h a d a s u r f a c e t o vo lume r a t i o o f 2 i n c * ’ . L i t t l e d i f f e r e n c e was n o t e d i n t h e o v e r a l l r e m o v a l of o x y g e n i n 1 m’inute , b u t t h e r a t e of r e m o v a l d u r i n g t h e f i r s t 1 0 s e c o n d s was less p r o n o u n c e d . T y p i c a l v a l u e s shown i n T a b l e 2 f o r a 2Na,S03/1 0, . r a t i o a t 65OF show t h e e f f e c t of s u r f a c e t o v o l u m e r a t i o s on o x y g e n r e m o v a l r a t e s .

I f a s u r f a c e c a t a l y t i c e f f e c t d o e s e x i s t , t h e d e g r e e of m i x i n g i s p r o b a b l y a s i m p o r t a n t as s u r f a c e t o v o l u m e r a t i o s . I n b o t h c a s e s , g o o d m i x i n g o c c u r r e d b u t t h e m i x i n g r a t e was h i g h e r i n t h e t u b i n g t h a n i n t h e t a n k t y p e v e s s e l o The d i f f e r e n c e i n m i x i n g r a t e s c o u l d a c c o u n t f o r t h e d i f f e r e n c e i n t h e i n i t i a l r e a c t i o n r a t e .

E f f e c t of S i m u l a t e d F e e d Water

The r e s u l t s d e s c r i b e d t h u s f a r were i n s i m u l a t e d b o i l e r w a t e r w h i c h c o n t a i n e d 1 2 5 - 1 5 0 ppm p h o s p h a t e , 800-1000 ppm s o l i d s a n d was a d j u s t e d t o t h e d e s i r e d pM w i t h L i O H . F o r t h e s i m u l a t e d f e e d w a t e r s t u d y , t h e o n l y a d j u s t m e n t s made were i n i t i a l . o x y g e n c o n c e n t r a t i o n a n d Na,S03/0, r a t i o . R e d u c t i o n of o x y g e n i n 1 m i n u t e was l e s s i n f e e d w a t e r t h a n i n b o i l e r water a n d t h e d e g r e e of r e m o v a l d u r i n g t h e f i r s t 1 0 s e c o n d s i s l e s s p r o n o u n c e d . C o m p a r i s o n of r e a c t i o n r a t e i n f e e d w a t e r a n d b o i l e r w a t e r i s shown i n F i g 8 ,

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R e a c t i o n of H y d r a z i n e w i t h Oxygen

The r e a c t i o n of h y d r a z i n e w i t h d i s s o l v e d o x y g e n was s t u d i e d l e s s e x t e n s i v e l y t h a n t h e s u l f i t e - o x y g e n r e a c t i o n . The r e a c t i o n was s t u d i e d i n s i m u l a t e d f e e d w a t e r i n t h e same s y s t e m u s e d f o r t h e s u l - f i t e s t u d y u n d e r t h e c o n d i t i o n s l i s t e d b e l o w :

o x y g e n c o n c e n t r a t i o n (ppm) - 0 . 1 a n d 1 . 0

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c o p p e r c o n c e n t r a t i o m (ppm) - 0 a n d 1

t e m p e r a t u r e ( O F ) - 1 0 0 a n d 300

No r e a c t i o n was o b s e r v e d o v e r a 1 m i n u t e p e r i o d u n d e r c o n d i t i o n s m o s t c o n d u c i v e t o r e a c t i o n , i o e D , 1 ppm O,, S N H , N H , / l O,, 1 ppm c o p p e r a n d 300'F. Data i n t h e l i t e r a t u r e i n d i c a t e s t h a t t h e r e - a c t i o n i s v e r y slow, w i t h some s o u r c e s r e p o r t i n g r e a c t i o n t i m e s i n h o u r s f o r t h o s e c o n d i t i o n s ( S t r a u b )

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T h i s s t u d y was u n d e r t a k e n t o p r o v i d e i n f o r m a t i o n on t h e r e - a c t i o n of s o d i u m s u l f i t e w i t h o x y g e n u n d e r s i m u l a t e d power p l a n t s y s t e m s . I t i s b e l i e v e d t h a t t h i s s t u d y h a s p r o v i d e d p r a c t i c a l d a t a f r o m a n o p e r a t i o n a l s t a n d p o i n t . The r e m o v a l of oxygen f r o m a b o i l e r s y s t e m c a n now b e e v a l u a t e d i n t e r m s o f o x y g e n c o n c e n - t r a t i o n , s u l f i t e c o n c e n t r a t i o n a n d c o n t a c t t i m e .

One of t h e s u r p r i s i n g f e a t u r e s b r o u g h t o u t b y t h i s s t u d y was t h a t n e a r l y a l l of t h e r e a c t i o n o c c u r s d u r i n g t h e f i r s t 1 0 s e c o n d s . The work i n r e f e r e n c e 5 a l s o i n d i c a t e d a h i g h i n i t i a l r e a c t i o n r a t e . I t was f e l t t h a t t h i s may b e a f u n c t i o n of s y s t e m d e s i g n p a r t i c u l a r l y w i t h r e s p e c t t o t h e m i x i n g c h a m b e r , r a t h e r t h a n a c h a r a c t e r i s t i c of t h e Na,SO3/0, r e a c t i o n . c h a m b e r a n d r e p l a c i n g i t w i t h a t e e . Oxygen r e m o v a l was c h e c k e d a t 6 5 , 1 5 0 a n d 200'F i n s i m u l a t e d b o i l e r water a t 2 , 5 , lo, 30 a n d 60 s e c o n d s . R e s u l t s show t h e r e a c t i o n r a t e was t h e same w i t h b o t h t h e m i x i n g c h a m b e r a n d t h e t e e . Some m i x i n g o b v i o u s l y o c c u r s i n t h e t e e a n d t h e f l o w r a t e was h i g h e n o u g h t o a s s u r e t u r b u l e n t f l o w s o t h e o v e r - a l l m i x i n g e f f i c i e n c y i n t h e t w o m e t h o d s may n o t h a v e b e e n p a r t i c u l a r l y d i f f e r e n t . The s u r f a c e / v o l u m e s t u d y may h a v e i n d i c a t e d a n e f f e c t of m i x i n g i n a d d i t i o n t o a n e f f e c t of s u r f a c e t o v o l u m e .

T h i s w a s c h e c k e d b y r e m o v i n g t h e m i x i n g

The i n i t i a l oxygen c o n c e n t r a t i o n h a d l i t t l e e f f e c t on t h e r e - a c t i o n r a t e when t h e s u l f i t e t o o x y g e n r a t i o was h e l d c o n s t a n t . A t t h e h i g h e s t o x y g e n c o n c e n t r a t i o n (1 ppm)9 h o w e v e r p t h e r e was a p - p a r e n t l y a r e a c t i o n of o x y g e n w i t h t h e m e t a l w a l l s . S t r a u b r e p o r t s s i m i l a r o b s e r v a t i o n s i n h i s s t u d i e s o n s o d i u m s u l f i t e a n d h y d r a z i n e . He r e p o r t e d t h a t o x y g e n r e a c t s w i t h b o t h s u l f i t e a n d s t e e l e v e n i n t h e p r e s e n c e of e x c e s s s u l f i t e . He a l s o r e p o r t e d t h a t a b o v e 45OoF s u l f i t e w i l l r e d u c e f e r r i c o x i d e .

I t w a s f o u n d t h a t a t 1 0 0 ° F a large excess o f s u l f i t e d o e s n o t a s s u r e c o m p l e t e r e m o v a l of o x y g e n . A t 200 a n d 300°F, b e t t e r t h a n 95% of t h e o x y g e n i s r e m o v e d i n 1 0 s e c o n d s w i t h a 2Na2S03/1 0, r a t i o . W i t h a 1 0 Na2S03 /1 0, r a t i o a t 200 a n d 30O0F, 99 t o 100% of t h e o x y g e n i s r emoved i n 1 0 s e c o n d s . T h e s e s t a t e m e n t s a r e t r u e f o r r e a c t i o n s i n a s t a i n l e s s s t e e l sys t em a n d may r e p r e s e n t r e a c t i o n of o x y g e n w i t h t h e m e t a l wa l l s a n d q u i t e l i k e l y a c a t a l y t i c e f f e c t of t h e m e t a l w a l l s .

The e f f e c t of pH i s p r a c t i c a l l y n o n - e x i s t a n t i n a m e t a l sys tem. O t h e r i n v e s t i g a t o r s , who h a v e o b s e r v e d s i g n i f i c a n t c h a n g e s i n r e - a c t i o n r a t e s w i t h c h a n g e s i n pH l e v e l , a t t r i b u t e t h e e f f e c t t o a com- p l e x i n g o r p r e c i p i t a t i o n e f f e c t on t h e c a t a l y s t s i n s o l u t i o n . I n a m e t a l sys tem, t h e c a t a l y t i c e f f e c t seems t o b e a r e s u l t of s u r f a c e e f f e c t s r a t h e r t h a n of i o n s i n s o l u t i o n . T h u s , pH l e v e l w o u l d n o t b e e x p e c t e d t o c h a n g e t h e c a t a l y s t c o n c e n t r a t i o n a n d t h e r e f o r e h a v e n o e f f e c t on r e a c t i o n r a t e s .

1 - 19-

io 1 I

The p r e l i m i n a r y s t u d y of t h e r e a c t i o n r a t e of h y d r a z i n e w i t h o x y g e n i n d i c a t e d t h a t s u l f i t e i s f a r s u p e r i o r t o h y d r a z i n e o Com- p l e t e r e m o v a l o f o x y g e n c a n b e a t t a i n e d w i t h a n e x c e s s of s u l f i t e w i t h i n 1 m i n u t e a t 300°F w h i l e e x c e s s h y d r a z i n e r e s u l t s i n l i t t l e , 4f a n y , r e d u c t i o n i n o x y g e n i n 1 m i n u t e .

A p r a c t i c a l p r e s e n t a t i o n o f t h e d a t a f r o m a n o p e r a t i o n a l s t a n d - p o i n t i s shown i n F i g 9 w h e r e t h e q u a n t i t y of o x y g e n r e m a i n i n g a f t e r 2 s e c o n d s , 5 s e c o n d s a n d 1 0 s e c o n d s i s p l o t t e d f o r t h e t h r e e s u l f i t e - o x y g e n r a t i o s as a f u n c t i o n of t e m p e r a t u r e . The p l o t shows t h a t w i t h Na2SOa/0, r a t i o s e q u i v a l e n t t o o r g r e a t e r t h a n t h e s t o i c h i o - m e t r i c r a t i o b e t t e r t h a n 95% of t h e o x y g e n i s r emoved i n 1 0 s e c o n d s a t 200'F a n d a t 300°F e s s e n t i a l l y 100% r e m o v a l i s a t t a i n e d i n 10 s e c o n d s

C ONCLU S I O N S

The f o l l - o w i n g c o n c l u s i o n s h a v e b e e n d rawn f r o m t h e d a t a g e n e r - a t e d d u r i n g t h i s s t u d y :

1. W i t h l e s s t h a n t h e s t o i c h i o m e t r i c q u a n t i t y o f Na2S03 p r e s e n t , r e m o v a l of o x y g e n i s i n c o m p l e t e . However , t h e oxygen may be r e d u c e d t o a l e v e l l e s s t h a n t h a t p r e d i . c t e d on t h e b a s i s of t h e s u l f i t e a v a i l a b l e b y r e a c t i o n w i t h t h e sys tem w a l l s .

( 0 . 5 Na2S03 /1 O , , m o l a r ) ,

2. W i t h t h e s t o i c h i o m e t r i c q u a n t i t y of N a 2 S 0 3 a v a i l a b l e (2Na2S03 /1 O , , m o l a r ) , c o m p l e t e r e - mova l o f oxygen i s n o t a t t a i n e d a t l o w e r t e m p e r - a t u r e s . A t 2@0°F, b e t t e r t h a n 95% of t h e o x y g e n c a n b e r emoved i n 1 0 s e c o n d s a n d a t 300'F o x y g e n r e m o v a l i s e s s e n t i a l l y c o m p l e t e i n 1 0 s e c o n d s .

3. W i t h a n e x c e s s of s u l f i t e p r e s e n t (10 Na,SO3/1 O , , m o l a r ) , a 1 0 s e c o n d c o n t a c t t i m e r e s u l t s i n r e - m o v a l of 95% of t h e o x y g e n a t 100°F, 99% of t h e oxygen a t 200°F a n d 100% a t 300'F.

1 1

The s u l f i t e - o x y g e n r e a c t i o n p r o g r e s s e s a t a s l i g h t l y s l o w e r r a t e i n f e e d w a t e r a s c o m p a r e d t o b o i l e r water .

5 . The r e d u c t i o n of o x y g e n l e v e l w i t h h y d r a z i n e o v e r a 1 m i n u t e p e r i o d is s o s m a l l t h a t t h e c h a n g e c o u l d n o t b e d e t e c t e d .

1

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c1 < I ppm I N I T I A L 02 1 ppm

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TEMPERATURE ( O F )

F i g . 0 - P e r Cent Oxygen Remaintng vs Temperature

1 7

- 21- I

1

I

B I B L I O G R A P H Y

1. S t o e h l e , R . W . , Beck , F.H, a n d F o n t a n a , M . G , , Mechanism of S t r e s s C o r r o s i o n o f A u s t e n i t i c S t a i n l e s s S t e e l s i n C h l o r i d e Waters , C o r r o s i o n QB 373t (1959)

2 . H i t c h e n s , R . M , a n d L o u n e , R O W o , The R a t e o f R e a c t i o n o f Sod ium S u l f i t e w i t h Oxygen D i s s o l v e d i n Water , ASTM P r o c e e d i n g s 36, p 687 (1936),

3. P y e , D o J o 9 Chem. ica1 F i x a t i o n o f Oxygen, J. AWWA as, ( 1 9 4 7 ) .

4 * H a l l L a b o r a t o r i e s , D i v i s i o n o f Hagan C h e m i c a l s a n d C o n ' t r o l s , I n c P i t t s b u r g h , P e n n s y l v a n i a .

5 . S t r a u b , F.G. , C o m p a r i s o n of t h e R e d u c i n g Power of Sodium S u l f i t e a n d H y d r a z i n e i n t h e S t e a m - W a t e r C y c l e o f S t e a m Power P l a n t s , C o m b u s t i o n 28, ( 1 9 5 7 )