Dechlorination of ferric chloride with oxygen
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HENDERSON,
T. T. CAMPBELL,
AND
F. E. BLOCK
B e c a u s e of i n c r e a s i n g e c o l o g i c a l c o n c e r n , the B u r e a u of Mines is i n v e s t i g a t i n g the use of c h l o r i n a t i o n technology in e x t r a c t i v e m e t a l l u r g y . A key p r o b l e m is the fact that f e r r i c chloride i s c o m m o n l y g e n e r a t e d d u r i n g p r o c e s s i n g of a wide v a r i e t y of o r e s and m i n e r a l s . T h i s p a p e r d e s c r i b e s s m a l l l a b o r a t o r y - s c a l e s t u d i e s d e s i g n e d to effect d e c h l o r i n a t i o n of f e r r i c chloride by oxygen in a fluidized bed r e a c t o r to p r o d u c e a v i a b l e , n o n p o l l u t i n g i r o n oxide p r o d u c t and c h l o r i n e gas, which could be r e c y c l e d in a c h l o r i n a t i o n p r o c e s s . T h e s e s t u d i e s d e m o n s t r a t e d that c l o s e to 100 pct c o n v e r s i o n s of f e r r i c c h l o r i d e to f e r r i c oxide and c h l o r i n e can be effected by r e a c t i o n with oxygen at t e m p e r a t u r e s r a n g i n g f r o m 500 ~ to 650~ The off-gas f r o m the s i n g l e - s t a g e r e a c t o r contained up to 95 pct c h l o r i n e . The study a l s o d e m o n s t r a t e d that the p r e s e n c e of a s m a l l a m o u n t of NaC1 in the r e a c t o r c a t a lyzed the r e a c t i o n between f e r r i c c h l o r i d e and oxygen and p e r m i t t e d high c o n v e r s i o n s at t e m p e r a t u r e s a s low as 500~
BECAUSEof pending w o r l d - w i d e
s h o r t a g e s of r u t i l e , t h e r e has been i n t e n s i f i e d i n t e r e s t in m e t h o d s of u t i l i z i n g i l m e n i t e as a s o u r c e of t i t a n i a e i t h e r for p i g m e n t or for m e t a l p r o d u c t i o n . Although i l m e n i t e can be t r e a t e d by s u l f u r i c acid attack, u n d e s i r a b l e q u a n t i t i e s of f e r r o u s sulfate a r e g e n e r a t e d that c o n s t i t u t e a w a t e r pollution p r o b l e m . Other a p p r o a c h e s being studied i n clude p y r o m e t a l l u r g i c a l p r a c t i c e s to p r o d u c e hight i t a n i a s l a g s , synthetic r u t i l e , or t i t a n i u m c a r b i d e . 1 T h e s e u p g r a d e d m a t e r i a l s can be c h l o r i n a t e d to p r o duce t i t a n i u m t e t r a c h l o r i d e and a s m a l l a m o u n t of i r o n c h l o r i d e , which i s r e a d i l y r e m o v e d by f r a c t i o n a l cond e n s a t i o n and d i s t i l l a t i o n . After final p u r i f i c a t i o n the r e s u l t i n g t i t a n i u m t e t r a c h l o r i d e can be u s e d for m e t a l p r o d u e t i o n or c o n v e r t e d to p i g m e n t - g r a d e TiO2. An a l t e r n a t e a p p r o a c h for r e e o v e r i n g t i t a n i a f r o m i l m e n i t e i n v o l v e s d i r e c t c h l o r i n a t i o n ; however, in this e a s e , e x c e s s i v e q u a n t i t i e s of f e r r o u s or f e r r i c c h l o r i d e a r e g e n e r a t e d which constitute a l
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