Gaseous reduction of iron oxides: Part IV. mathematical analysis of partial internal reduction-diffusion control
- PDF / 866,522 Bytes
- 10 Pages / 612 x 792 pts (letter) Page_size
- 8 Downloads / 207 Views
S U B S T A N T I A T E D by e x p e r i m e n t a l o b s e r v a t i o n s , T u r k d o g a n and V i n t e r s pointed out in e a r l i e r p a r t s of this s e r i e s of p a p e r s I-~ that t h e r e a r e t h r e e b a s i c l i m iting r a t e p r o c e s s e s : I) u n i f o r m i n t e r n a l r e d u c t i o n , II) l i m i t i n g m i x e d c o n t r o l , and III) gas diffusion in r e duced i r o n l a y e r . The r a t e p r o c e s s l i m i t e d by gas diffusion in the i r o n l a y e r was p r e v i o u s l y d i s c u s s e d in detail on the b a s i s of e x p e r i m e n t a l r e s u l t s for H 2 - r e d u c t i o n ~ and the p o r e c h a r a c t e r i s t i c s of the i r o n f o r m e d . 2 Based on e x p e r i m e n t a l o b s e r v a t i o n s u n d e r the c o n d i t i o n s of e s s e n t i a l l y u n i f o r m i n t e r n a l r e d u c t i o n , the k i n e t i c s of the H2 and C O - r e d u c t i o n on the p o r e w a l l s of w u s t i t e was a l s o d i s c u s s e d p r e v i o u s l y . 3 That i s , f r o m the p r e v i o u s i n v e s t i g a t i o n s the following r a t e p a r a m e t e r s have b e e n e v a l uated for the g a s e o u s r e d u c t i o n of i r o n oxides: i) s p e cific r a t e c o n s t a n t for r e a c t i o n on the p o r e w a l l s of w u s t i t e , ii) p o r e s u r f a c e a r e a of i r o n and w u s t i t e f o r m e d by r e d u c t i o n of h e m a t i t e , and iii) effective gas diffusivity in the p o r o u s i r o n l a y e r f o r m e d d u r i n g r e duction of h e m a t i t e . On the b a s i s of t h e s e p r e v i o u s findings, we have now c a r r i e d out a m a t h e m a t i c a l a n a l y s i s of the r e d u c t i o n of i r o n oxides affected c o l l e c t i v e l y by the r e a c t i o n on the p o r e w a l l s of w u s t i t e ( p a r t i a l i n t e r n a l r e d u c t i o n ) and gas diffusion in p o r o u s i r o n and w u s t i t e l a y e r s . It should be pointed out that m a n y b a s i c a s p e c t s of the p r e s e n t m a t h e m a t i c a l a n a l y s i s differ f r o m those p u b l i s h e d e a r l i e r by Seth and R o s s 4 and by Spitzer e t al. 5 These i n v e s t i g a t o r s a s s u m e d a sharp interface b e t w e e n the i r o n and w u s t i t c l a y e r s . Our findings ~-3 do not s u p p o r t such a n a s s u m p t i o n . Whether the h e m a tite that is r e d u c e d i s d e n s e or p o r o u s , the w u s t i t e R. H. TIEN and E. T. TURKDOGANare Senior Scientist and Manager, respectively, Chemical Metallurgy, U. S. Steel Corporation Research Laboratory, Monroeville,Pa. Manuscript submitted February 14, 1972. METALLUt~G1CALTRANSACTIONS
f o r m e d i s always, p o r o u s , c o n s e q u e n t l y , the i r o n / w u s tite " i n t e r f a c e " i s diffuse b e c a u s e of the p a r t i a l i n t e r n a l r e d u c t i o n of the w u s t i t e .
MATHEMATICAL FORMULATION B e c a u s e of the m a t h e m a t i c a l c o m p l i c a t i o n s involved, the m a g n e t i t e l
Data Loading...
