Improved leaching technologies in the electrolytic zinc industry
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A N D R. W. PICKERING
The d e v e l o p m e n t of the J a r o s i t e and Goethite P r o c e s s e s has m a d e it p o s s i b l e to r e m o v e high c o n c e n t r a t i o n s of i r o n f r o m m e t a l s u l f a t e s o l u t i o n s in r e a d i l y s e p a r a t e d c r y s t a l l i n e f o r m s . This h a s a l l o w e d the e c o n o m i c a l r e c o v e r y of zinc f r o m r a w m a t e r i a l s c o n t a i n i n g i r o n , and e s p e c i a l l y f r o m zinc f e r r i t e c o m m o n l y f o r m e d in the r o a s t i n g of zinc c o n c e n t r a t e s . The p r o c e s s e s have p r o v e d to b e r e a d i l y a d a p t a b l e to m e e t the p a r t i c u l a r n e e d s of the v a r i o u s l e a c h i n g p r o c e d u r e s that w e r e in use in p r e v i o u s l y e x i s t i n g zinc p l a n t s . The p r o c e s s e s have a l s o m a d e it p o s s i b l e to d e s i g n new zinc p l a n t s that give enhanced e c o n o m i c r e t u r n f r o m e l e g a n t l y s i m p l e p r o c e s s d e s i g n s . The p r o c e s s d e s i g n s that have b e e n a d o p t e d f o r v a r i o u s e l e c t r o l y t i c zinc p l a n t s a r e d e s c r i b e d , and i n d i c a t e the v e r s a t i l i t y of t h e s e new processes. A L M O S T without e x c e p t i o n , zinc p l a n t s that have b e e n c o m m i s s i o n e d r e c e n t l y , and p l a n t s that a r e in the p l a n ning s t a g e s , have adopted the e l e c t r o l y t i c p r o c e s s . There are several important reasons for this choice. One of the m a i n ones is t h a t the e l e c t r o l y t i c p r o c e s s can p r o d u c e e c o n o m i c a l l y a l l of the g r a d e s of z i n c t h a t a r e r e q u i r e d in the m a r k e t p l a c e . T h e r e is no n e e d f o r any a d d i t i o n a l p r o c e s s f o r r e f i n i n g of the m e t a l . At l e a s t e q u a l l y i m p o r t a n t h a s b e e n the advent of e l e g a n t l y s i m p l e p r o c e d u r e s f o r the l e a c h i n g of c a l c i n e that have m a d e it p o s s i b l e to r e c o v e r the zinc and o t h e r m e t a l s that w e r e p r e v i o u s l y l o s t in the zinc f e r r i t e r e s i d u e s . The two m a i n p r o c e d u r e s for a c h i e v i n g t h e s e o b j e c t i v e s a r e the J a r o s i t e P r o c e s s and the Goethite P r o cess.
One o r o t h e r of t h e s e p r o c e s s e s has now b e e n a d o p t e d in m o s t p r e v i o u s l y e x i s t i n g e l e c t r o l y t i c zinc p l a n t s . The p a r t i c u l a r v e r s i o n s of the p r o c e s s that have b e e n u s e d have d i f f e r e d s o m e w h a t , a c c o r d i n g to the l e a c h i n g p r o c e d u r e that was p r e v i o u s l y in use. In n e w e r e l e c t r o l y t i c z i n c p l a n t s that have b e e n b u i l t d u r i n g the l a s t y e a r o r so, and in p l a n t s t h a t a r e at p r e s e n t b e i n g c o n s t r u c t e d o r d e s i g n e d , it h a s b e e n p o s s i b l e to i n t e g r a t e the s
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