Selective recovery of copper from copper-nickel sulfide concentrates by applying segregation technology
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THE
s e g r e g a t i o n p r o c e s s for r e c o v e r i n g copper f r o m oxide o r e s has been used for a n u m b e r of y e a r s and plants have been constructed to t r e a t such oxide o r e s using e i t h e r r o t a r y kilns or moving bed r e a c t o r s . The TORCO p r o c e s s , 1 as operated at Rhokana in Z a m b i a on a r e f r a c t o r y oxide o r e containing about 3 pct Cu, is an example of this technology applied on a production s c a l e . In addition, numerous investigations have been r e p o r t e d of a t t e m p t s to s e g r e g a t e nickel f r o m oxidic o r e s . 2~ However, no c o m m e r c i a l i n s t a l l a t i o n s a r e known where this p r o c e s s is being p r a c t i c e d at the present time.
s e p a r a t i n g the copper while leaving the nickel in a product f r o m which it can be r e c o v e r e d by a n u m b e r of p r o c e s s e s . 8 Although numerous c o p p e r - n i c k e l sulfide concent r a t e s and m a t t e s have been t r e a t e d in the l a b o r a t o r y , only two g e n e r a l compositions a r e dealt with h e r e . The f i r s t is a low g r a d e c o p p e r - n i c k e l concentrate f r o m Botswana. The other is a c o m p a r a t i v e l y high grade concentrate t y p i c a l of those obtainable f r o m Minnesota o r e . C o m p a r a t i v e a n a l y s e s a r e shown in Table I. EXPERIMENTAL PROCEDURE
SEGREGATION OF COPPER-IRON SULFIDES
Dead Roasting
The application of s e g r e g a t i o n technology to c o p p e r sulfide o r e s has been studied at AMAX over the l a s t decade. ~ It was found that if a c h a l c o p y r i t e concent r a t e is r o a s t e d at a high enough t e m p e r a t u r e (850 to 900~ to r e m o v e most of the sulfur and convert the copper and iron to a stable f e r r i t e , in which the iron is e s s e n t i a l l y a l l t r i v a l e n t , the s e g r e g a t i o n r e a c t i o n can be c a r r i e d out efficiently at 700 to 800~ on the r e s u l t i n g calcine to s e l e c t i v e l y s e p a r a t e the copper. This p r o c e s s is d e s c r i b e d in U.S. Patent No. 3,799,764, i s s u e d in 1974. M a r c u s o n and Kellogg6'7 have made fundamental studies of the m e c h a n i s m s involved in copper s e g r e gation r e a c t i o n s as applied to c h a l c o p y r i t e calcine and have noted the potentially a t t r a c t i v e e n e r g y a s p e c t s of the p r o c e s s .
The l a b o r a t o r y - s c a l e r o a s t i n g p r a c t i c e was to heat 1000 g b a t c h e s of the concentrate in a fused quartz t r a y inside a Globar heated muffle furnace. A flow of a i r into the furnace of about 14 l / r a i n was maintained and the charge was r a b b l e d e v e r y 10 rain. The r o a s t was a c c o m p l i s h e d in two s t a g e s . In the f i r s t stage, the charge was heated for two h at 750~ and then for one h at 800~ To e n s u r e c o m p l e t e n e s s of the r o a s t , the calcine was r e m o v e d f r o m the furnace a f t e r the f i r s t stage and cooled. It was t
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