A mathematical approach for the mass transfer between liquid steel and an ascending bubble
- PDF / 802,989 Bytes
- 10 Pages / 612 x 792 pts (letter) Page_size
- 60 Downloads / 174 Views
K L A U S W. L A N G E , K A Z U O O K O H I R A ,
A m a t h e m a t i c a l m o d e l w h i c h is a d a p t a b l e to p r a c t i c a l c o n d i t i o n s h a s b e e n put f o r w a r d t o des c r i b e adequately t h e p u r g i n g o f l i q u i d s t e e l with a n i n e r t gas. T h e mass t r a n s f e r between l i q u i d s t e e l with varying C , O, H, N, and S contents and an a s c e n d i n g a r g o n b u b b l e has been i n v e s t i g a t e d . T h e s i m u l t a n e o u s m a s s t r a n s f e r o f all p o s s i b l e g a s e o u s c o m p o u n d s is c o n s i d e r e d a s a f u n c t i o n of t h e i n i t i a l b u b b l e m a s s , h e i g h t o f t h e s t e e l b a t h , t h e bulk c o n c e n t r a t i o n s i n t h e m e l t , a n d t h e e x t e r n a l p r e s s u r e . T h e m o d e l t a k e s into a c c o u n t t h e c h a n g e i n s i z e a n d f o r m of t h e b u b b l e r e s u l t i n g f r o m i t s r i s e a n d t h e m a s s t r a n s f e r b e t w e e n t h e b u b b l e a n d t h e m e l t , a n d also t h e influence o f s u r f a c e a c t i v e a g e n t s such a s s u l f u r a n d o x y g e n . T h e followi n g g e n e r a l c o n c l u s i o n s c a n be d r a w n : 1) T h e g a s e s f l u s h e d (out o f t h e m e l t ) by t h e b u b b l e c a n b e r e l a t e d t o t h e a m o u n t of a r g o n i n j e c t e d into t h e b a t h . 2) I n c r e a s e i n t h e i n i t i a l b u b b l e s i z e a n d t h e c o n t e n t o f t h e g a s i n t h e b a t h t o be p u r g e d , a n d d e c r e a s e i n t h e e x t e r n a l p r e s s u r e r e s u l t i n m o r e p r o n o u n c e d d e v i a t i o n s f r o m e q u i l i b r i u m s a t u r a t i o n w i t h i n t h e b u b b l e . 3) L o w e r e x t e r n a l p r e s s u r e , i n c r e a s i n g supersaturation o f CO, a n d g r e a t e r a m o u n t s o f p u r g i n g gas at h i g h e r dispersion are the chief factors responsible for increasing p u r g i n g efficiency for H, N 2 , C O i n s t e e l m e l t s . 4) S u r f a c e - a c t i v e a g e n t s d e c r e a s e t h e p u r g i n g r a t i o f o r n i t r o g e n i n a c a r b o n - f r e e m e l t , b u t , in c a r b o n - c o n t a i n i n g m e l t s , i n c r e a s i n g a m o u n t s o f o x y g e n a l o n e l e a d t o a c o n s i d e r a b l e i n c r e a s e i n t h e p u r g i n g r a t i o s f o r n i t r o g e n due t o t h e h i g h m a s s t r a n s f e r of C O t o t h e b u b b l e . I n t h e l a t t e r c a s e , t h e e f f e c t o f i n c r e a s i n g s u l f u r c o n t e n t o n t h e p u r g i n g r a t i o s i s o f no s i g n i f i c a n c e .
IN
this p a p e r a mathematical m o d e l has been d e v e l o p e d to i n v e s t i g a t e t h e m a s s t r a n s f e r b e t w e e n l i q u i d s t e e l a n d a n ascending i n e r t gas b u b b l e , thus p r o v i d i n g the b a s i s for simulating the d e g a s s i n g p r o c e s s . T h e l i q u i d s t e e l contains varying percentages of C, O, H, N, a n d S
Data Loading...
