Process for enrichment of a ferronickel alloy to 90 Pct Ni
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T h e n i c k e l of m o s t l a t e r i t i c o r e s i s e x t r a c t e d a s a F e N i a l l o y c o n t a i n i n g a c e r t a i n a m o u n t of c o b a l t . T h e u t i l i z a t i o n of t h i s f e r r o a l l o y i s e f f e c t i v e l y l i m i t e d to the f a b r i c a tion of s t a i n l e s s s t e e l s , which a b s o r b s about 40 p c t of the t o t a l n i c k e l c o n s u m p t i o n . T h e p r o d u c t i o n of e l e c t r o l y t i c n i c k e l f r o m f e r r o n i c k e l i s f e a s i b l e , but it r e q u i r e s a n o d e s m a d e of a l l o y e n r i c h e d to at l e a s t 80 pct Ni. Such e n r i c h m e n t i s c o m p l i c a t e d by the s i m u l t a n e o u s o x i d a t i o n of n i c k e l d u r i n g the s l a g g i n g of i r o n , w h i c h a c c e l e r a t e s a s the i r o n i s d e p l e t e d and b e c o m e s p r o h i b i t i v e f o r an a l l o y with m o r e than 60 p c t Ni. A s i m p l e and e c o n o m i c a l u p g r a d i n g of f e r r o n i c k e l up to 90 p c t Ni is p r o p o s e d by a t w o - s t a g e c o n v e r t i n g with oxygen, u n d e r s i m u l t a n e o u s a d d i t i o n of n i c k e l i f e r o u s l a t e r i t e . N i c k e l l o s s e s a r e e f f e c t i v e l y r e s t r i c t e d by the t w o - s t a g e o p e r a t i o n . T h e r i c h s l a g s of the s e c o n d s t a g e , p r o d u c e d in c o n t a c t with an a l l o y of m o r e than 60 p c t Ni, a r e r e c y c l e d in liquid s t a t e into the e m p t y f i r s t s t a g e c o n v e r t e r . The s u b s e q u e n t a d d i t i o n of the low g r a d e liquid m e t a l into the f i r s t s t a g e c o n v e r t e r " w a s h e s " the r i c h s l a g s and r e d u c e s t h e i r n i c k e l content. T h e s l a g s of the f i r s t s t a g e , p r o d u c e d in c o n t a c t with low g r a d e a l l o y s , c o n t a i n l i t t l e n i c k e l and a r e d i s c a r d e d . T h e o v e r a l l n i c k e l l o s s i s c o n s i d e r a b l y r e d u c e d by b l o w i n g in s h o r t b l o w s with i n t e r m e d i a t e s l a g s k i m m i n g s . T h e a d d i t i o n of t h e l a t e r i t i c o r e , d u r i n g c o n v e r t i n g , a c h i e v e s a v e r y s a t i s f a c t o r y and i n e x p e n s i v e t e m p e r a t u r e c o n t r o l , s u b s t i t u t e s a s a flux, and i n t r o d u c e s n i c k e l and oxygen to the p r o c e s s at a v e r y m i n i m a l c o s t . T h e h e a t e v o l v e d d u r i n g the o x i d a t i o n of the i r o n in t h e m o l t e n a l l o y i s e f f e c t i v e l y u t i l i z e d f o r t h e s m e l t i n g of the l a t e r i t e added.
C O N S I D E R A B L E e f f o r t s led to the d e v e l o p m e n t of a n u m b e r of r e l a t i v e l y s i m p l e p y r o m e t a l l u r g i c a l p r o c e s s e s f o r the e x t r a c t i o n of n i c k e l f r o m l a t e r i t i c o r e s . T h e E l k e m , P e r r i n , L . M . , and F a l c o n b r i d g e p r o c e s s e s , a c t u a l l y in c o m m e
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