Metal loss to slag: Part I. Sulfidic and oxidic dissolution of copper in fayalite slag from low grade matte
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SiO2. For a r e v e r b e r a t o r y furnace condition of three coexisting phases (matte, slag, gas), the number of degrees of freedom (F) of the system is given by F = 5 + 2 - 3 = 4. These may, for example, be specified as temperature, pct Cu in matte, pct SiO2 in slag and magnetite activity. This means that meaningful comparison of copper loss among various smelters can be effected only when the above four p a r a m e t e r s are well defined, in addition to the prerequisite that all the other c o m m e r c i a l l y common slag constituents, such as lime and alumina, be identical for each case under consideration. These rather strict requirements are t h e r m o dynamical, and therefore if the system is not under the equilibrium condition additional p a r a m e t e r s must be specified to define the system. This suggests extremely difficult comparisons among different smelters, accounting for contradictions and e r r a t i c arguments to date. Experimentally, it is difficult to control the pct SiO2 and magnetite activity, so that the initial approach can be made by fixing these under conditions of SiOa-saturation and Fe-saturation. Under these conditions the number of degrees of freedom becomes only 2, and therefore for a constant temperature and a given matte grade there is only one corresponding value of any v a r i able. SO2 gas continuously escaping from the system may tend to vary the composition of the slag and matte, but the partial p r e s s u r e of SO~ is so low that the equilibrium between four condensed phases can still be e s tablished under a neutral atmosphere. The present study was initiated to measure the solubility of matte in slag as a function of matte grade under the presence of excess oxygen, which approximates the case of r e v e r b e r a t o r y smelting in which an abundance of oxygen is charged as recycled converter slag, iron oxide in r o a s t e r calcine, and excess air in the gas phase. EXPERIMENTAL Materials
M. NAGAMORI, formerly with Noranda Research Centre, Pointc Claire, Quebec, is presently with Centre de Recherche industrielle du Quebec, Complexe Scientifique, Ste-Foy, Quebec, Canada. Manuscript submitted April 16, 1973. METALLURGICAL TRANSACTIONS
To prepare FeS (or Cu~S), reagent grade elemental sulfur powder was mixed well with electrolytic iron (or copper) powder and melted at 1200~ in a graphite VOLUME 5, MARCH 1974-531
c r u c i b l e with a g r a p h i t e c o v e r . F e O was p r e p a r e d by h e a t i n g a s t o i c h i o m e t r i c m i x t u r e of F e and Fe~O a p o w d e r s in an i r o n c r u c i b l e . The i r o n c r u c i b l e s (15 m m OD, 13 m m ID, 40 m m long) u s e d in the t e s t s w e r e m a d e b y d r i l l i n g a hole in an A r m c o i r o n r o d .
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Procedure During the m e l t i n g of m a t t e o r a m i x t u r e of Cu2S, F e S and i r o n o x i d e s , the s o l i d c o m p o n e n t s tend to r e a c t with the evolution of SO~. As a r e s u l t , w h e n e v e r s o l i d m a t t e and s l a g a r e m e l
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