The kinetics of gas-liquid metal reactions involving levitated drops. Carburization and decarburization of molten iron i

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EL-KADDAH

AND

D. G.C.

ROBERTSON

T h e k i n e t i c s of d e c a r b u r i z a t i o n and c a r b u r i z a t i o n of l e v i t a t e d m o l t e n i r o n - c a r b o n a l l o y d r o p s at 1650~ in CO-CO2 gas m i x t u r e s w e r e s t u d i e d at a p r e s s u r e of 40 a i m . T h e r e s u l t s showed that, u n d e r the e x p e r i m e n t a l c o n d i t i o n s used, the r a t e s w e r e c o n t r o l l e d by t r a n s p o r t in the gas p h a s e ( d e c a r b u r i z a t i o n ) o r by m i x e d t r a n s p o r t c o n t r o l ( c a r b u r i z a tion). T h e l e v i t a t e d d r o p s b e h a v e d as s t a t i c s p h e r i c a l p a r t i c l e s as f a r as t r a n s p o r t in the liquid p h a s e was c o n c e r n e d s i n c e the e f f e c t i v e d i f f u s i v i t y of c a r b o n in the liquid was c l o s e to the a t o m i c d i f f u s i v i t y . T h e t r a n s p o r t m o d e l d e v e l o p e d in the p a p e r was a p p l i e d to e x p l a i n the data f r o m s o m e e a r l i e r i n v e s t i g a t i o n s .

D E C A R B U R I Z A T I O N of b i n a r y i r o n - c a r b o n a l l o y s in s l a g - f r e e m e l t s has b e e n the s u b j e c t of n u m e r o u s i n v e s t i g a t i o n s . T h e e x p e r i m e n t a l t e c h n i q u e s used have i n v o l v e d a) blowing the oxidant gas onto m o l t e n m e t a l in a c r u c i b l e , b) flowing the gas p a s t a l e v i t a t e d drop and c) r e a c t i n g d r o p s in f r e e f a l l. T h e l e v i t a t i o n t e c h n i q u e was used in this study to avoid s i d e r e a c tions b e t w e e n the m e l t and the c r u c i b l e and b e c a u s e the s i m p l e g e o m e t r y a l l o w e d a c c u r a t e c a l c u l a t i o n of the r a t e of t r a n s p o r t in the gas p h a s e . 1,2 At high c a r bon l e v e l s in the m e t a l (>1 wt pct C) the r a t e is f r e quently d e t e r m i n e d by this p r o c e s s . l - 4 Sain and B e l ton s w e r e able to m e a s u r e the c h e m i c a l r a t e constant f o r the r e a c t i o n CO2 +_C = 2CO.

[I]

T h e y u s e d e x t r e m e l y high f l o w r a t e s of CO2 so that the r a t e of t r a n s p o r t in the gas p h a s e was p o t e n t i a l l y f a s t e r than the c h e m i c a l r a t e at the i n t e r f a c e . At l o w e r c a r b o n c o n c e n t r a t i o n s (

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