The effect of particle size distribution on the performance of a phosphate flotation process
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T H E difficulties associated with t h e formulation o f a mathematical description of the flotation p r o c e s s are w e l l - k n o w n , a n d a r e c a u s e d by i) t h e h e t e r o g e n e i t y o f the s o l i d m a t e r i a l w h i c h i s t o be f l o a t e d ; ii) t h e b u b b l e s u r f a c e a n d s t r u c t u r e particularly w i t h r e s p e c t t o t h e w e i g h t o f s o l i d s w h i c h c a n be l i f t e d by a n i n d i v i d u a l b u b b l e ; iii) bubble-particle i n t e r a c t i o n s w h i c h include i n t e r ception, impaction, and disengagement effects. Pogerely' and Imaizuni and Inoue2 c o n s i d e r e d t h e f l o t a t i o n p r o c e s s t o be f i r s t o r d e r i n t h e s o l i d s c o n centration and o v e r c a m e the inability of a d e t e r m i n i s t i c f i r s t - o r d e r p r o c e s s to d e s c r i b e o b s e r v a b l e p e r f o r m a n c e by p o s t u l a t i n g a o n e - d i m e n s i o n a l s p e c t r u m of rate constants throughout the s o l i d m a t e r i a l . Woodburn a n d L o v e d a y 3 d e s c r i b e d t h e s p e c t r u m in t e r m s o f a r f u n c t i o n a n d s h o w e d that f o r s i m p l e f l o t a t i o n i n a b a t c h cell o f a pyrite-silica m i x t u r e t h e stochastic m o d e l was able t o predict f l o t a t i o n c h a r a c t e r i s t i c s o f c o n c e n t r a t e a n d tailings s t r e a m s w h i c h r e n d e r e d it p o t e n t i a l l y suitable f o r use in a n e t w o r k . It h a s a l w a y s b e e n c l e a r that a o n e - d i m e n s i o n a l s p e c t r u m i s a s i m p l i s t i c v i e w of t h e c o m p l e x i n t e r actions and recently Zaidenberg, Lisovskii and Burovoi 4 have proposed a three-dimensional s p e c t r u m w h i c h is c e r t a i n l y t h e o r e t i c a l l y s u p e r i o r to a n y t h u s f a r s u g g e s t e d but h a s s e r i o u s c o m p u t a t i o n a l a n d e x p e r i m e n t a l p r o b l e m s a s s o c i a t e d with i t s use. It w a s c o n s e q u e n t l y c o n s i d e r e d u s e f u l t o e s t a b l i s h t h e p r a c t i c a l l i m i t a t i o n of a o n e - d i m e n s i o n a l t r e a t m e n t in a s i m u l a t e d n e t w o r k a n d t o e x t e n d w h e r e n e c e s s a r y t h e o n e - d i m e n s i o n a l t r e a t m e n t to a l l o w i n d e p e n d e n t l y f o r t h e m o s t o b v i o u s v a r i a t i o n in t h e s o l i d s t r u c t u r e , viz. p a r t i c l e - s i z e d i s t r i b u t i o n . EXPERIMENTAL The investigations were performed on a 25 cuft Denver cell. The cell was operated continuously with no tailings or concentrate recycle. Limitation of storage of feed made it necessary to restrict the inE. T , WOODBURN and R. P . KING are Professor of Chemical Engineering and Rsearch G r o u p Leader, National Institute for Metallurgy, respectively, University of Natal, Durban, South Africa. R.P. COLBORN is with the South African Atomic Energy Board, Pelindaba, Republic of South Africa. Manuscript submitted Augu
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