On reduction roasting of taconite
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On Reduction Roasting of Taconite R. E. CECH AND T. D. TIEMANN T H E T a c o n i t e s of M i c h i g a n , M i n n e s o t a , and W i s c o n sin r e p r e s e n t the l a r g e s t p o t e n t i a l i r o n o r e s o u r c e within the c o n t i n e n t a l U. S. Mining a c t i v i t i e s a r e , at p r e s e n t , f o c u s e d on m a g n e t i c v a r i e t i e s b e c a u s e of the m o r e efficient b e n e f i c i a t i o n s c h e m e s for t h e s e o r e s . H o w e v e r , a s t h e s e o r e s b e c o m e d e p l e t e d it w i l l b e c o m e n e c e s s a r y to b e n e f i c i a t e n o n m a g n e t i c t a c o n i t e s u s i n g techniques yet to be p e r f e c t e d . Nonmagnetic i r o n m i n e r a l s can be c o n v e r t e d to a m a g n e t i c f o r m using e i t h e r an oxidizing r o a s t to f o r m y Fe203,1 o r a r e d u c i n g r o a s t to f o r m FeaO4 o r m e t a l l i c i r o n . 2-5 Both of t h e s e a p p r o a c h e s a r e c o s t l y b e c a u s e the high r o a s t i n g t e m p e r a t u r e s (~900~ f o r the o x i d i z i n g r o a s t and 650~ for the r e d u c i n g r o a s t ) r e q u i r e high c a p i t a l c o s t f u r n a c i n g equipment in a d d i t i o n to l a r g e fuel e n e r g y r e q u i r e m e n t s . This report summarizes preliminary experiments showing p r o m i s i n g i n d i c a t i o n s that r e d u c t i o n r o a s t i n g m a y be conducted at 400~ by m e a n s of a r e d u c i n g g a s p a r t i a l l y a c t i v a t e d with a c o r o n a d i s c h a r g e . The 40 pct lowering of r o a s t i n g t e m p e r a t u r e m a d e p o s s i b l e by the a d d i t i o n of c o r o n a d i s c h a r g e could m a r k e d l y d e c r e a s e the r o a s t i n g c o s t in a c o m m e r c i a l p l a n t both f r o m the standpoint of c a p i t a l equipment and s e n s i b l e heat r e q u i r e m e n t s . It should be k e p t in m i n d that r e d u c t i o n r o a s t i n g to render ore suitable for magnetic concentration need not r e m o v e m u c h of the oxygen in the o r e p a r t i c l e s . Existing magnetic concentrators will operate satisf a c t o r i l y on o r e s that contain a s l i t t l e a s 10 pct f e r r o m a g n e t i c p h a s e p e r p a r t i c l e . 1 T h u s , a p r o c e s s that f o r m s a thin s u r f a c e l a y e r of m a g n e t i t e on e a c h p a r t i c l e would be e n t i r e l y a d e q u a t e for u s e with m a g n e t i c concentrators. R. E. CECH, Scotia, N.Y., is unaffiliated. T. D. TIEMANN is Professor and Assoc. Chairman, Department of Minerals and Metals Engineering, University of Wisconsin, Madison, Wis. Manuscript submitted August 20, 1971. 5 9 0 - V O L U M E 3, F E B R U A R Y 1972
than the f i n e - g r a i n e d s a m p l e s . T h e r e was no c o r r e l a tion b e t w e e n the n u m b e r of m i c r o c r a c k s and the g r a i n s i z e . The t o t a l length of m i c r o c r a c k s p e r unit a r e a in the c o a r s e - g r a i n e d s a m p l e s was c o n s i d e r e d l o n g e
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