Rates and mechanisms of FeO reduction from slags
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The r a t e of FeO r e d u c t i o n f r o m CaO-SiO2 s l a g s has b e e n d e t e r m i n e d in a s t a t i o n a r y m a g n e s i a c r u c i b l e with a g r a p h i t e rod as the r e d u c t a n t . At 1650 ~ • 35~ with a slag b a s i c i t y CaO/SiO z = 1.2 + 0.3, and in the total i r o n c o n c e n t r a t i o n , C, r a n g e of 10 p c t < C < 40 pct, the s p e c i f i c r a t e , QE, of r e d u c t i o n in g - m o l e s p e r rain p e r sq c m was found to be
QE = 8.25
• 10 -e C 1.7~
According to this and p r e v i o u s l i t e r a t u r e r e s u l t s , the r e d u c t i o n r a t e s s p a n t h r e e p o s s i b l e s t a g e s . The o r d e r of r e a c t i o n in r e g a r d to c o n c e n t r a t i o n v a r i e s f r o m f i r s t o r d e r in the low c o n c e n t r a tions (0.1 pct < C < 1.5 pct) to s e c o n d o r d e r in the i n t e r m e d i a t e c o n c e n t r a t i o n s (1.5 pct < C < 15 pct) and f i n a l l y to 1.77th o r d e r in the high c o n c e n t r a t i o n s (15 pct < C < 40 pct). The r e d u c tion r e a c t i o n can b e s t be i n t e r p r e t e d by c o n v e c t i v e m e c h a n i s m s b e c a u s e the o b s e r v e d r a t e s fall b e t w e e n the r a t e s of the c h e m i c a l l y l i m i t e d g r a p h i t e g a s i f i c a t i o n and the r a t e s p r e d i c t e d f r o m m o l e c u l a r diffusion.
T H E r e d u c t i o n of i r o n oxide is of f u n d a m e n t a l i m p o r t a n c e to the f e r r o - m e t a l l u r g y i n d u s t r y . The need for p r e d i c t i n g and c o n t r o l l i n g the r e d u c t i o n for p r o d u c t i v e p u r p o s e s has s p u r r e d t r e m e n d o u s a m o u n t s of r e s e a r c h in this a r e a . As a c o n s e q u e n c e , a g r e a t deal has b e e n l e a r n e d about the r e d u c t i o n of solid oxide in v a r i o u s f o r m s and u n d e r v a r i o u s c o n d i t i o n s . However, the h i g h t e m p e r a t u r e m o l t e n - s t a t e r e d u c t i o n of i r o n oxide, p a r t i c u l a r l y f r o m complex s l a g s , has so far r e c e i v e d l i t t l e attention. T h e r e a r e v e r y few e x p e r i m e n t a l r e s u l t s in the l i t e r a t u r e for m o l t e n iron oxide r e d u c t i o n . Some of the r e s u l t s w e r e obtained for the r e d u c t i o n f r o m p u r e m o l t e n i r o n oxides 1-7 by graphite. O t h e r s were obtained f r o m s l a g s c o n t a i n i n g only a s m a l l p e r c e n t a g e of i r o n oxide. s-a The few i n v e s t i g a t o r s of this r e a c t i o n have p r o p o s e d d i f f e r e n t m e c h a n i s m s . Some c l a i m that the r e action is c o n t r o l l e d by the r a t e of graphite g a s i f i c a tion. 8'9 Others c l a i m that the r e a c t i o n is l i m i t e d by diffusion. 3 The r a t e of r e d u c t i o n is s o m e t i m e s d e s c r i b e d as f i r s t o r d e r , l-e and s o m e t i m e s as second o r d e r 5'e in r e g a r d to the i r o n oxide c o n c e n t r a t i o n . A c o m p l e
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