Determination of sulfide capacities of CaO-SiO 2 slags containing CaF 2 and B 2 O 3 by an encapsulation method
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BRONSON
AND
GEORGE
R. ST. PIERRE
T h e sulfide c a p a c i t i e s of CaO-SiO2 m e l t s containing CaF2 and B203 have b e e n m e a s u r e d by s i m u l t a n e o u s e q u i l i b r a t i o n of s a m p l e s within q u a r t z c a p s u l e s at 1503~ In t h i s method, the c o m p o s i t i o n s of both the c o n d e n s e d p h a s e s and the s t a t i c gas e n v i r o n m e n t a d j u s t to e s t a b l i s h a m u t u a l e q u i l i b r i u m . A l t h o u g h the s u l f u r i z i n g p o t e n t i a l , PsJP02, is n e i t h e r p r e s e t n o r d i r e c t l y m e a s u r e d , the s u l f i d e c a p a c i t i e s , CS, of a l l s a m p l e s within the c a p s u l e a r e r e l a t e d by the following equation: (p ct S)j CS(j) = (pct S)------i. " Cs(i). H e n c e , the sulfide c a p a c i t i e s of a l l s a m p l e s m a y be c a l c u l a t e d f r o m the m e a s u r e m e n t of the f i n a l s u l f u r content of e a c h s a m p l e and the i n c l u s i o n of a "reference" s l a g s a m p l e f o r which CS is known f r o m p r e v i o u s m e a s u r e m e n t s . In the p r e s e n t study, q u a r t z c a p s u l e s containing a s m a n y a s fifty s l a g s a m p l e s i n c l u d i n g s e v e r a l r e f e r e n c e s a m p l e s have b e e n e q u i l i b r a t e d . With c o n s i d e r a b l e d i f f i c u l t y the e n c a p s u l a t i o n - e q u i l i b r a t i o n method at 1503~ h a s b e e n d e v e l o p e d into an a c c e p t a b l e p r o c e d u r e . T h e i n f l u e n c e s of CaF2 and B203 on the s u l f i d e c a p a c i t i e s of s e v e r a l CaO-SiO2 m e l t s have been m e a s u r e d . T h e r e s u l t s m a y b e s u m m a r i z e d a s f o l l o w s : 1) f o r m e l t s of fixed CaO/SiO2 r a t i o , the a d d i t i o n of CaF2 inc r e a s e s sulfide c a p a c i t y and the a d d i t i o n of B203 d e c r e a s e s s u l f i d e c a p a c i t y , 2) the s u b s t i t u t i o n of CaFz for CaO d o e s not a l t e r sulfide c a p a c i t y s i g n i f i c a n t l y , and 3) the s u b s t i tution of B203 f o r SiO2 i n c r e a s e s s u l f i d e c a p a c i t y s l i g h t l y . T h e s e r e s u l t s have b e e n obt a i n e d f o r m e l t s with CaO/SiO2 m a s s r a t i o s r a n g i n g f r o m 1.00 to 1.28 and with flux a d d i t i o n s up to 10 wt pet.
T H E m e a s u r e m e n t of sulfide c a p a c i t y r e q u i r e s the e q u i l i b r a t i o n of s a m p l e s in an e n v i r o n m e n t with c l e a r l y defined v a l u e s of the c h e m i c a l p o t e n t i a l s of s u l f u r and oxygen. 1-1~ The sulfide c a p a c i t y a s d e f i n e d by F i n c h a m and R i c h a r d s o n ~ m a y be r e l a t e d to s l a g b a s i c i t y ~~ b y c o n s i d e r a t i o n of Eq. [1]: O2-(slag) + 1 S2(g) = S2-(slag) + ~ O 2 ( g ) .
[1]
T h e e q u i l i b r i u m constant of Eq. [1] m a y be r e a r r a n g e d to y i e l d Eq. [2]: [SZ-] . ( p O S P s 2 )1/2 = K1 a 02- -= c s .
containing CO(H2), COz(H20), and SO2(H2S) e s t a b l
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