Coupling phenomena in the transfer of elements between a gas phase and iron melts
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TUCHIYA,
MASANORI
TOKUDA,
AND
MASAYASU
OHTANI
T h e s i m u l t a n e o u s t r a n s f e r of Si and C f r o m a gas phase containing SiO and CO to liquid F e - C a l l o y s has been i n v e s t i g a t e d . It was found that, although the s i l i c o n content of the m e l t i n c r e a s e d with t i m e as e x p e c t e d , the c a r b o n content i n i t i a l l y d e c r e a s e d , in s p i t e of the fact that the carbon p o t e n t i a l of the gas p h ase was above that of the liquid a l l o y . T h e s e p h e n o m e n a a r e i n t e r p r e t e d in t e r m s of i r r e v e r s i b l e t h e r m o d y n a m i c s which shows that the o v e r a l l t r a n s f e r r e a c t i o n s a r e c o m p r i s e d of coupled r e a c t i o n s : SiO(g) + CO(g) ~ Si + CO2(g) and C + CO~(g) ~ 2CO(g). It is a l s o shown that the s i m u l t a n e o u s t r a n s f e r of c a r bon and oxygen f r o m gas m i x t u r e s of CO and CO2 to liquid i r o n o c c u r s v i a the coupled r e a c t i o n s CO2(g) ~ O + CO(g) and 2CO(g) ~ C + CO2. In e a c h c a s e t h e r e is a p r e d o m i n a n t , or d r i v i n g r e a c t i o n Which p r o m o t e s the o t h e r .
D E T E R M I N A T I O N of the m e c h a n i s m s of c a r b o n and s i l i c o n t r a n s f e r b e t w e e n g a s e o u s p h a s e s and liquid m e t a l s is p a r t i c u l a r l y r e l e v a n t to s t u d i e s of i r o n and s t e e l m a k i n g p r o c e s s e s . In an a t t e m p t to identify the m e c h a n i s m of c a r b o n and s i l i c o n t r a n s f e r in an i r o n b l a s t f u r n a c e , t h e i r t r a n s f e r f r o m SiO and CO conta ini n g gas to liquid i r o n was p r e v i o u s l y i n v e s t i g a t e d by the p r e s e n t a u t h o r s . l - s It was o b s e r v e d in t h e s e s t u d i e s that the r a t e of s i l i c o n t r a n s f e r f r o m gas to liquid F e - C a l l o y s was c o n s i d e r a b l y g r e a t e r than that of c a r b o n and that, c o n t r a r y to e x p e c t a t i o n , the c a r b o n content in the m e l t d e c r e a s e d in the i n i t i a l s t a g e of the run. The p h e n o m e n o n of u p - h i l l m a s s t r a n s f e r a g a i n s t a c h e m i c a l p o t e n t i a l g r a d i e n t has often b e e n o b s e r v e d d u r i n g i n i t i a l s t a g e s of s l a g - m e t a l r e a c t i o n s 4-~ as w e l l as in m u l t i c o m p o n e n t diffusion s y s t e m s . 7 F o r e x a m p l e , R a m a c h a n d r a n , King and G r a n t o b s e r v e d that when c a r b o n s a t u r a t e d i r o n containing s u l f u r and s i l i c o n o r a l u m i n u m , was p l a c e d in contact with a s l a g , the s u l f u r content of the i r o n d e c r e a s e d r a p i d l y . At the s a m e t i m e the i r o n and s i l i c o n , o r the i r o n and a l u m i n u m , t r a n s f e r r e d in a d i r e c t i o n opposite to that c o r r e s p o n d i n g to t h e i r f i n al e q u i l i b r i u m d i s t r i b u t i o n . T h i s would be in v i o l a t i o
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