Stirring and its effects on aluminum deoxidation in the ASEA-SKF furnace: Part II. Mathematical representation of the tu
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A N D K. N A K A N I S H I
A mathematical formulation is presented describing fluid flow and tracer dispersion in an A S E A - S K F f u r n a c e . T h e s t a t e m e n t of t h e p r o b l e m r e q u i r e d t h e s i m u l t a n e o u s s o l u t i o n of t h e t u r b u l e n t N a v i e r - S t o k e s e q u a t i o n s t o g e t h e r w i t h a s i m p l i f i e d f o r m of M a x w e l l ' s e q u a tions. The resultant partial differential equations were solved numerically using a digital computer. Computed results are presented describing the streamline pattern, the velocity f i e l d , t h e s p a t i a l d i s t r i b u t i o n of t u r b u l e n t e n e r g y w i t h i n t h e s y s t e m , t o g e t h e r w i t h t h e r a t e a t w h i c h a t r a c e r i s d i s p e r s e d . F o r a 50 t o n f u r n a c e , w i t h a c o i l c u r r e n t of 1300 A t h e c o m p u t e d l i n e a r v e l o c i t i e s r a n g e d up to 150 c m / s a n d t h e m e a n v a l u e s of t h e e d d y d i f f u s i v i t y w e r e of t h e o r d e r of 300 to 500 c m 2 / s . T h e c o m p u t e d r e s u l t s w e r e f o u n d to b e i n r e a s o n able agreement with previously reported tracer dispersion measurements. However, there is a disparity between the predicted circulation rates and those deduced from the measurem e n t s i n a n e a r l i e r p a p e r u s i n g a s i m p l e o n e d i m e n s i o n a l m o d e l f o r t h e i n t e r p r e t a t i o n of the r e s u l t s .
IN
recent years the ASEA-SKF furnace has provided an attractive means for stainless steel processing.~-s In t h i s s y s t e m m o l t e n s t e e l i s h e a t e d a n d a r e d u c i n g s l a g i s m e l t e d in a r e f i n i n g l a d l e b y m e a n s of a n e l e c tric arc while agitation is being provided by an electromagnetic force field. Subsequently the system is evacu a t e d and a l l o y i n g a d d i t i o n s a r e m a d e ; t h e c o m b i n e d e f f e c t of v a c u u m t r e a t m e n t a n d e l e c t r o m a g n e t i c s t i r r i n g a r e t h o u g h t to p r o m o t e b o t h e f f i c i e n t d e o x i d a t i o n a n d desulfurization. T h e w o r k to b e d e s c r i b e d in t h i s p a p e r i s p a r t of a continuing effort, aimed at providing a better unders t a n d i n g of m i x i n g p h e n o m e n a a n d d e o x i d a t i o n k i n e t i c s i n t h e A S E A - S K F p r o c e s s . In a p r e v i o u s p a p e r 2 r a d i o active tracer dispersion measurements were reported, w h i c h w e r e t a k e n in a 50 t o n A S E A - S K F f u r n a c e ; t h e s e r e s u l t s w e r e i n t e r p r e t e d in t e r m s of a r a t h e r s i m p l i f i e d o n e d i m e n s i o n a l d i s p e r s i o n m o d e l . A s a r e s u l t of t h i s interpretation it was possible to deduce eddy diffusivit i e s , * w h i c h w e r e f o u n d to r a n g e f r o m a b o u t 100 c m 2 / s *Some comment should be made here on the nature of eddy diffusivities.Eddy diffusivitieshave been used frequently for r
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