A physico-chemical investigation on the selective reduction of iron oxides in chromite
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c h r o m i t e o r e is the raw m a t e r i a l for m a n u f a c t u r e CraO3, v a r i a b l e a m o u n t s of other s p i n e l s such as of f e r r o c h r o m e and, for t h i s p u r p o s e , the C r : F e r a t i o F e O - Feg33 (magnetite), MgO. Cr20~, MgO .A1203, F e O . of the ore should be high. Many ore deposits throughout A12Oa and MgO 9Fe2Oa in solid s o l u t i o n with FeO oCr2Oa.9 the world do not meet this r e q u i r e m e n t , 1 and may be T h e r e f o r e FeK)a in c o m b i n a t i o n with FeO or MgO is the t e r m e d m e t a l l u r g i c a l l y as ' l o w - g r a d e ' d e p o s i t s . India one that d i l u t e s the s p i n e l with i r o n . The p r e s e n t i n has s i m i l a r l o w - g r a d e o r e s z P a s t i n v e s t i g a t i o n s have v e s t i g a t i o n is r e s t r i c t e d to the s p i n e l solid s o l u t i o n c o n shown that it is p o s s i b l e to r e m o v e i r o n f r o m t h e s e o r e s s i s t i n g of F e O . CrzO3 and F e O . FezO3, which may, i n by s e l e c t i v e r e d u c t i o n or c h l o r i n a t i o n of i r o n oxides in g e n e r a l , be r e p r e s e n t e d as Fe Fe~_xCrxO4 w h e r e x is a the solid state at high t e m p e r a t u r e followed by e i t h e r p a r a m e t e r v a r i a b l e between 0 to 2.0. X - r a y diffraction magnetic s e p a r a t i o n or l e a c h i n g . Selective r e d u c t i o n s t u d i e s of Y e a r i a n e t a l . '~ i n d i c a t e d that FeFe2-xCrxO4 has been t r i e d with a l l t y p e s of r e d u c t a n t , v i z . coal, i s a n o r m a l s p i n e l in the r a n g e : 1.28 < x -< 2.0. A coke, CO, H2 etc. at t e m p e r a t u r e s below 1,350~ a'6 g r a d u a l i n v e r s i o n s t a r t e d at x < 1.28, and the i n v e r s i o n Selective c h l o r i n a t i o n of i r o n oxides have also been was c o m p l e t e at x = 0.3. A n u m b e r of i n v e s t i g a t o r s found to be f e a s i b l e by a m i x t u r e of r e d u c i n g agent with t r i e d to identify the v a r i o u s p h a s e s and phase r e l a t i o n c h l o r i n e or h y d r o c h l o r i c acid. 7'8 ships i n C r - F e - O s y s t e m . A m o n g s t these, the study A s e a r c h of l i t e r a t u r e r e v e a l e d the d e s i r a b i l i t y of of K a t s u r a and Muan11 was the most c o m p r e h e n s i v e one. s o m e f u n d a m e n t a l p h y s i c o c h e m i c a l i n v e s t i g a t i o n s in It was found that the solid s o l u t i o n F e O . Cr203 - FeO 9 this s y s t e m . The p r e s e n t study c o n s i s t s of both t h e r m o - Fe2Os, when coexisting with m e t a l l i c i r o n has negligible d y n a m i c and k i n e t i c a s p e c t s of the s e l e c t i v e r e d u c t i o n n o n s t o i c h i o m e t r y . This c o n c l u s i o n is supported by the of i r o n oxides i n c h r o m i t e , and is r e s t r i c t e d to p u r e e x p e r i m e n t s of Y e a r i a n e t al~~~ as well. Dahl and Van synthetic m a t e r i a l o Vlack 12 found that the m e t a l l i c i r o n , c
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