8/10/2019 Materials of Construction for Plate Heat Exchangers in Soda Ash Production - Babkina 1976

1/2

M A T E R I A L S O F C O N S T R U C T I O N F O R P L A T E

H E A T E X C H A N G E R S I N S O D A A S H P R O D U C T I O N

V . Y u . B a b k i n a , I . K . V a s i l ' e v a ,

O . V . G a p u n i n a , a n d E . G . C h u b

UDC [66 045:661 321 3]:669 018 8

S t u d ie s h a v e b e e n c a r r i e d o u t a t t h e S c i e n t i f i c - R e s e a r c h I n s t i t u t e o f B a s i c C h e m i s t r y ( N IO K h IM ) t o

s e l e c t m a t e r i a l s o f c o n s t r u c t io n f o r f a b r i ca t i n g p l a te h e a t e x c h a n g e r s t o c o o l a m m o n i a t e d b r i n e .

C o m p o s i t i o n o f a m m o n i a t e d b r i n e i s 1 0 8 g / l i t e r N a + , 1 6 6 g / l i t e r C 1 - , 5 0 g / l i t e r N H 3, 3 0 g / I i t e r

C O 3 2- , a n d 0 . 4 - 0 . 8 g / l i t e r N a2 S. I t i s q u it e c o r r o s i v e , c a u s i n g p it t in g an d c r e v i c e c o r r o s i o n o f p a s s i v a t e d

m e t a l s a n d r a p i d c o r r o s i o n o f c a r b o n s t e e l .

T h e s t u d i e s w e r e c a r r i e d o u t u n d e r i n d u s t r i a l c o n d i ti o n s u s in g a m m o n i a t e d b r i n e . T h e fo l lo w i n g

m a t e r i a l s o f c o n s t r u c t i o n w e r e s t u d i e d : 1 2 K h 1 8 N 1 0 T , 1 0 K h 1 7 N 1 3 M 2 T , 0 8 K h l 8 N 1 0 T , a n d 0 6 K h N 28 M D T

s t a i n l e s s s t e e l s w i th v a r i o u s s u r f a c e fi n i s h e s ; V T 1 - 0 t i t a n i u m ; A D 1 a l u m i n u m a ll o y ; a n d t e s t p i e c e s

f a b r i c a t e d o f c o r r u g a t e d p l a t e s c o n t a c t i n g e a c h o t h e r .

T h e r e s u l t s s h o w e d th a t a l l t y p e s o f s t a i n l e s s s t e e l s i n v e s t i g a t e d a r e s u b j e c t to p it t in g a n d c r e v i c e

c o r r o s i o n . L o w e r c a r b o n co n t e n t a n d s u r f a c e f i n is h ( e l im i n a t i n g f l aw s c a u s e d b y r o l l i n g : p o l i s h in g ,

p i c k li n g ) i n c r e a s e s t h e r e s i s t a n t o f s t e e l s t o p i t ti n g b u t d o e s n o t e l i m i n a t e i t . I n c r e a s e d l o c a l c o r r o s i o n

w a s o b s e r v e d a t t h e c o r r u g a t i o n p e a k s w h e n t h e c o r r u g a t i o n s w e r e i n c o n t a c t . P i t ti n g o f s t a i n l e s s s t e e l

i n co o l i ng w a t e r i s m i n o r . T i t a n i u m V T 1 - 0 a n d a l u m i n u m a l l o y A D 1 e x h ib i te d g o od c o r r o s i o n r e s i s t a n c e

i n a m m o n t a t e d b r i n e : n o c o r r o s i o n w a s o b s e r v e d a t t h e c o r r u g a t i o n p e a k s w h e n t h e y w e r e i n c o n t ac t e v e n

u n d e r s e v e r e c o n d i t i o n s. A n o d e p o l a r i z a t i o n c u r v e s w e r e a l s o r e g i s t e r e d f r o m p o l is h e d e l e c t r o d e s a t a

2 V / h p o t e n t i a l a p p l i c a t i o n r a t e a f t e r k e e p i n g t h e e l e c t r o d e i n t h e 6 0~ s o l u t io n f o r 10 m i n . E l e c t r o d e

s u r f a c e w a s c l e a n e d i m m e d i a t e l y b e f o r e i ts i m m e r s i o n i n t h e so l u t i o n . A s a t u r a t e d m e r c u r o u s c h l o ri d e

e l e c t r o d e s e r v e d a s t h e r e f e r e n c e .

E l e c t r o c h e m i c a l m e a s u r e m e n t s s h o w e d t h a t c o r r o s i o n p r o c e s s e s t a k e p la c e m o r e s l o w l y (0 .0 1 re_A /

c m 2) o n t i t a n i u m t h a n o n s t a i n l e s s s t e e l s ( 0.8 m A / c m 2) i n a n a m m o n i a t e d b r i n e c o n t a in i n g 0 .4 g / l i t e r N a2 S.

S t e e l is s u b j e c t e d t o p it t in g c o r r o s i o n a t a b o u t + 0. 5 V p o t e n t i a l w h i le t i t a n i u m e x h i b i ts s t a b l e p a s s i v a t i o n

a t e v e n h i g h e r p o s i t i v e p o t e n t i a ls . T h e b r e a k d o w n p o t e n t i a l o f s t a i n l e s s s t e e l s a n d t i t a n i u m i s s h i f t ed b y

~ + 0 . 3 V an d th e p a s s i v a t i o n z o n e is w i d e n e d .

T e s t p l a te s o f V T 1 - 0 t i ta n i u m w e r e f a b r ic a t e d fo r c o m m e r c i a l te s t i n g w i th h e r r i n g b o n e c o r r u g a -

t i o n l a y o u t . P l a t e s u r f a c e w a s p u r p o s e l y n o t m a c h i n e d .

T w o m e t h o d s o f p l a t e i n s t a l l a t i o n w e r e u s e d : 1 ) w i t h ou t a g a p s o t h a t th e p l a t e c o r r u g a t i o n s w e r e i n

c o n ta c t d u ri n g o p e r a t io n a n d 2) w i th a 5 - m m g a p c r e a t e d b y r u b b e r g a s k e t s .

S o l id s d e p o s i t i o n o c c u r s d u r i n g p l a t e o p e r a t i o n , b o t h f r o m t h e s o l u t i o n a n d t h e c o o l i n g - w a t e r s i d e .

T h i s r e d u c e s t h e h e a t - t r a n s f e r c o e f f i c ie n t a n d i n c r e a s e s l o c a l c o r r o s i o n . I t w a s o b s e r v e d th a t t h e fo u li n g

r a t e f o r p l a t e s w i t h a f i x e d g a p i s m u c h l o w e r . I t h a s b e e n e s t a b l i s h e d [1 , 2 ] t h a t c l e a n s t a i n l e s s - s t e e l

s u r f a c e s a r e l e s s p r o n e t o p i t t in g th a n fo u le d s u r f a c e s . T h e p l a t e s m u s t t h e r e f o r e b e p e r io d i c a l l y c l e an e d ,

e i t h e r m e c h a n i c a l l y o r c h e m i c a l l y ( w a s h i n g i n a n o x i d i z in g fl u id ) [ 3, 4 ] . T h e c h e m i c a l c l e a n i n g m e t h o d is

p r e f e r r e d s i n ce i t p r o v id e s c o m p l e t e a n d fa s t c l ea n i ng o f p l a te s u r f a c e s a n d do e s n o t r e q u i r e d i s a s s e m b l y

o f t h e e x c h a n g e r . T e s t s s h o w e d t h a t 5 - 10 % HN O ~ s o l u t io n is m o s t e f f e c t i v e . I t d o e s n o t c a u s e c o r r o s i o n

o f t h e m e t a l s i n v e s t i g a t e d , a s s i s t s i n r e s t o r i n g t h e p r o t e c t i v e f i l m o n t h e m e t a l , a n d g e n e r a t e s a n e a s i l y

s o l u b l e p r e c i p i t a t e . C l e a n i n g t i m e d o e s n o t e x c e e d 2 h . T h e h e a t e x c h a n g e r i s c o n n e c t e d t o a c i rc u l a t i n g

T r a n s l a t e d f r o m K h i m i c h e s k o e i N e f t y a n o e M a s h i n o s t r o e n i e , N o . 2 , p . 2 3 , F e b r u a r y , 1 9 76 .

9 P len u m Pu b l i s h in g C o r p o r a t io n , 2 2 7 W es t 1 7 th S t r ee t , N e w Y o r k , h r. Y . 1 0 0 1 1 . N o p a r t o f t h is p u b l i ca t io n m a y b e r ep r o d u ced ,

s to r ed in a r e tr i eva l s y s t em , o r t r a n s m i t t ed , i n a n y fo r m o r b y a n y m ea n s, e l ec t r o n ic , m ech an ica l , p h o to c o p y in g , m icr o f i lm in g ,

r eco r d in g o r o th erw is e , w i t h o u t w r i t t en p er m is s io n o f t h e p u b l i s h er . A co p y o f t h i s a r t i c le is a vai la b le f r o m th e p u b l i s h er fo r $ 1 5 . 0 0 .

48

8/10/2019 Materials of Construction for Plate Heat Exchangers in Soda Ash Production - Babkina 1976

2/2

l o o p c o n s i s t i n g o f a t a n k p u m p a n d p i p i n g . A l l p a r t s o f t h e l o o p m u s t b e f a b r i c a t e d o f s t a i n l e s s s t e e l o r

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

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 . T h e l o o p m u s t h a v e a v e n t v a l v e f o r g a s e s f o r m e d d u r i n g d i s s o l u t i o n o f t h e

precipitate.

The titanium plates retained their original shape after 1.5 months of testing. No traces of local

failure were observed.

Titanium VT1-0 can, therefore, be recommended as a promising material of construction for

ammoniated brine plate heat exchangers of soda ash production.

Heat exchangers constructed of chromium-- nickel or Chromium-- nickel-- molybdenum steel with

electropolarized plates have a limited service life.

2 .

3 .

4 .

L I T E R A T U R E C I T E D

L. M. Kolomb'e, Certain aspects of stainless-steel corrosion in water, in: Metal Corrosion

(edited by A. P. Zefarova) [in Russian], Metallurgizdat, Moscow (1964).

I. B. Ulanovskii and Yu. M. Korovin, The effect of oxygen concentration on failure initiation in

narrow gaps, Zh. Prik. Khim., No. 8, 1753 (1962).

P. A. Akol'zin and V. V. Gerasimov, Corrosion of Materials of Construction in Nuclear and Ther-

mal Power Plants [in Russian], Vysshaya Shkola (1963).

L. M. Kolomb'e, Stainless and Heat-Resistant Steels (edited by M. L. Bernshtein) [in Russian],

Moscow (1958).

149