Three Component raoultian behavior in relation to metal refining by crystallization and reflux
- PDF / 819,370 Bytes
- 8 Pages / 603.28 x 783.28 pts Page_size
- 70 Downloads / 136 Views
THEp y r o m e t a l l u r g i c a l
r e f i n i n g of c o m m o n m e t a l s
(e.g. i r o n , a l u m i n u m , zinc, lead, t i n and c o p p e r ) a f t e r s m e l t i n g to p r o d u c e c r u d e m e t a l is g e n e r a l l y conc e r n e d with t h e r e m o v a l of i m p u r i t i e s f r o m d i l u t e s o l u t i o n s . A c c o r d i n g l y , it was d e c i d e d to u n d e r t a k e a t h e o r e t i c a l study which w a s to be i n i t i a l l y c o n c e r n e d with the b e h a v i o r of s o l i d and l i q u i d p h a s e s of b i n a r y s y s t e m s n e a r the m e l t i n g point of the s o l v e n t m e t a l . T h e f i r s t o b s e r v a t i o n , f r o m t h e p h a s e d i a g r a m s of H a n s e n and A n d e r k o / w a s that m a n y i m p u r i t i e s which a r e d i f f i c u l t to r e m o v e in p r a c t i c e (e.g. A g and Bi f r o m lead, Bi and P b f r o m tin, F e and Si f r o m a l u m i n u m , P b and Cd f r o m zinc, and S and P f r o m iron) p o s s e s s e d f a v o r a b l e d i s t r i b u t i o n r a t i o s b e t w e e n t h e r e s p e c t i v e liquid and s o l i d p h a s e s , i.e. t h e f o r m a t i o n of a s l u r r y of c r y s t a l s would be a c c o m p a n i e d by the c o n c e n t r a t i o n of i m p u r i t i e s into the liquid p h a s e in e q u i l i b r i u m with c r y s t a l s of substantially higher purity. It w a s found a l s o t h a t t h e p o o r p e r f o r m a n c e of the P a t t i n s o n b a t c h - w i s e c r y s t a l l i z a t i o n p r o c e s s f o r the r e m o v a l of s i l v e r and b i s m u t h f r o m l e a d (used b e f o r e 1910) w a s due to a high p r o p o r t i o n of liquid a d h e r i n g to, o r e n t r a i n e d by, the c r y s t a l s . T h u s , a c c o r d i n g to C o l l i n s 2 when d e s c r i b i n g the P a t t i n s o n p r o c e s s , if a l e a d b u l l i o n containing s i l v e r i s c o o l e d f r o m a m e l t and t w o - t h i r d s of t h i s i s r e m o v e d a s c r y s t a l s (containing e n t r a i n e d liquid) by a p e r f o r a t e d spoon, l e a v i n g o n e - t h i r d of the o r i g i n a l f e e d a s liquid, the c r y s t a l p r o d u c t w i l l c o n t a i n about o n e - h a l f of the f e e d c o n c e n t r a t i o n of s i l v e r , and the r e m a i n i n g liquid w i l l have about t w i c e the s i l v e r content of the f e e d . F r o m t h i s s t a t e m e n t i t i s a p p a r e n t t h a t the d i s t r i b u t i o n r a t i o of s i l v e r in the liquid to t h a t in the c r y s t a l s p l u s e n t r a i n e d liquid is a r o u n d 4, w h e r e a s J. D. ESDAILE is Principal Research Scientist, Division of Chemical Engineering, CSIRO, Clayton, Victoria, Australia. Manuscript submitted December 23, 1975. METALLURGICAL TRANSACTIONS B
t h e d i s t r i b u t i o n r a t i o of s i l v e r in l i q u i d to t h a t in the s o l i d c o n t a i n i n g no e n t r a i n e d liquid i s a r o u n d 25 at t h e e u t e c t i c point, a c c o r d i n g to
Data Loading...
