Characterization of gas bubbles injected into molten metals under laminar flow conditions
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G A S bubble-liquid metal interactions are important in n u m e r o u s r e f i n i n g p r o c e s s e s such as the deoxidation of copper, d e g a s s i n g of a l u m i n u m , and d e c a r b u r i zation of high alloy and s t a i n l e s s s t e e l s . S u b m e r g e d lets which p r o d u c e l a r g e d i s p e r s i o n s of s m a l l b u b b l e s a r e used in the deoxidation of copper and s t e e l dec a r b u r i z a t i o n . The b a s i c action of the s u b m e r g e d jet in which l a r g e b u b b l e s m o v i n g away f r o m the o r i f i c e " e x p l o d e " into m a n y s m a l l e r b u b b l e s a f t e r t r a v e l i n g a s h o r t d i s t a n c e has b e e n q u a l i t a t i v e l y a p p r e c i a t e d for quite s o m e t i m e , and the high s p e c i f i c i n t e r r a c i a l a r e a of the g a s - l i q u i d d i s p e r s i o n is r e c o g n i z e d as b e i n g r e s p o n s i b l e for the r e l a t i v e l y high e f f i c i e n c i e s of t h e s e p r o c e s s e s . Much l e s s v i o l e n t c o n d i t i o n s a r e m a i n rained in a l u m i n u m d e g a s s i n g o p e r a t i o n s w h e r e n i t r o gen or n i t r o g e n - c h l o r i n e m i x t u r e s a r e i n t r o d u c e d v i r t u a l l y as s i n g l e b u b b l e s . In both types of s y s t e m s m a n y of the b a s i c p a r a m e t e r s have not yet b e e n well defined. In s i n g l e bubble p r o c e s s e s these p a r a m e t e r s i n c l u d e bubble s i z e and r e s i d e n c e t i m e in the m e l t . With r e s p e c t to jet phen o m e n a , the r e s i d e n c e t i m e of the gas and the s p e c i fic i n t e r r a c i a l a r e a of the d i s p e r s i o n a r e v e r y i m p o r t a n t i n d e t e r m i n i n g the e f f i c i e n c y of gas u t i l i z a t i o n , the extent of s p l a s h i n g , and the r a t e of r e f r a c t o r y erosion. B u b b l e s g e n e r a t e d i s t i n c t n o i s e s as they b r e a k f r o m a s u b m e r g e d o r i f i c e and b u r s t the s u r f a c e of the liquid. The b r e a k at the o r i f i c e c o n s i s t s of r e l a t i v e l y low f r e q u e n c y n o i s e c o m p o n e n t s while the sound gene r a t e d by b u r s t i n g through the s u r f a c e is r e l a t i v e l y high f r e q u e n c y . B e c a u s e of this d i f f e r e n c e , a n a c o u s tic t e c h n i q u e has b e e n developed which e n a b l e s data on gas bubble f o r m a t i o n f r e q u e n c y at a s u b m e r g e d o r i f i c e
t o g e t h e r with v e l o c i t y m e a s u r e m e n t s to be r e a l i z e d i n molten metals. P a r a m e t e r s which i n f l u e n c e the s i z e of b u b b l e s gene r a t e d at o r i f i c e s and bubble v e l o c i t i e s u n d e r d y n a m i c c o n d i t i o n s (where the b u b b l e s a r e f o r m e d c o n t i n u o u s l y at an o r i f i c e ) w e r e d e t e r m i n e d . The a c o u s t i c a l t e c h nique d e v e l o p e d p r o v i d e d a m e a n s for m a k i n g c o m p a r i s o n s
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