Flow regimes in submerged gas injection
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AND
J. K. BRIMACOMBE
The b e h a v i o r of gas d i s c h a r g i n g into a liquid has been i n v e s t i g a t e d in the l a b o r a t o r y and i n p l a n t . The l a b o r a t o r y work has involved the i n j e c t i o n of d i f f e r e n t g a s e s f r o m a s u b m e r g e d , h o r i z o n t a l t u y e r e into w a t e r , z i n c - c h l o r i d e solution, and a m e r c u r y bath. High speed c i n e m a t o g r a p h y and p r e s s u r e m e a s u r e m e n t s ha the t u y e r e have been c a r r i e d out to c h a r a c t e r i z e the flow r e g i m e s . In the case of the m e r c u r y bath, a n o v e l " h a l f - t u y e r e " has b e e n developed to p e r m i t v i s u a l o b s e r v a t i o n of the g a s . In this way, two r e g i m e s of flow, b u b b l i n g and steady j e t t i n g , have been d e l i n e a t e d as a function of the modified F r o u d e n u m b e r and the r a t i o of gas to liquid d e n s i t i e s . P r e s s u r e m e a s u r e m e n t s at the t u y e r e tip have b e e n c o r r e l a t e d to the d i f f e r e n t s t a g e s of bubble growth in the b u b b l i n g r e g i m e , and can be used to d i s t i n g u i s h one flow r e g i m e f r o m the o t h e r . The m e a s u r e d b u b b l e f r e q u e n c y and v o l u m e c o r r e s p o n d r e a s o n a b l y well to p r e d i c t i o n s of a s i m p l e model of bubble growth u n d e r c o n d i t i o n s of c o n s t a n t flow. The f o r w a r d p e n e t r a t i o n of the jet c e n t e r l i n e f r o m the t u y e r e tip has b e e n m e a s u r e d and found to depend both on NFr' and pz/pl. In the i n d u s t r i a l t e s t s , p r e s s u r e taps have b e e n i n s t a l l e d in the t u y e r e s of a n i c k e l c o n v e r t e r to m o n i t o r the p r e s s u r e wave of the j e t s u n d e r n o r m a l , low p r e s s u r e blowing o p e r a t i o n s . The m e a s u r e m e n t s show that the c o n v e r t e r j e t s o p e r a t e in the b u b b l i n g mode with a bubble f r e q u e n c y of 10 to 12 s -1, s i m i l a r to a gas jet in m e r c u r y . T e s t s involving higher p r e s s u r e i n j e c t i o n i n d i c a t e that the steady j e t t i n g , or u n d e r e x p a n d e d , r e g i m e obt a i n s at p r e s s u r e s of about 340 k P a (50 psi). Based on e q u i v a l e n t e x p e r i m e n t s in the l a b o r a t o r y , it is c l e a r that low p r e s s u r e blowing has the d i s a d v a n t a g e of poor p e n e t r a t i o n of a i r into the bath so that the jets r i s e c l o s e to the b a c k wall and l o c a l l y a c c e l e r a t e r e f r a c t o r y w e a r . M o r e o v e r b e t w e e n the f o r m a t i o n of s u c c e s s i v e b u b b l e s , the bath w a s h e s a g a i n s t the t u y e r e mouth and c o n t r i b u t e s to a c c r e t i o n f o r m a t i o n . T h i s n e c e s s i t a t e s p e r i o d i c punching of the t u y e r e s which also c o n t r i b u t e s to r e f r a c t o r y w e a r at the t u y e r e l i n e . The u
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