The thermodynamic properties of the slag, matte,and liquid copper phases in the Cu-Ca-Fe-Si-O-S system havebeen critically assessed and optimized over the ranges ofcompositions of importance to copper smelting/converting basedon thermodynamic and phase equilibria information available inthe literature and using the modified quasichemical model. Athermodynamic database has been developed, which can be usedfor the calculation of matte-slag-copper-gas phase equilibria ofinterest for the production of copper. The model reproduceswithin experimental error limits all available experimental dataon phase diagrams, matte-alloy miscibility gap and tie-lines,enthalpies of mixing, and activities of Cu and S in the matte andliquid alloy. The calculated solubilities of Cu in both S-free slagand slag equilibrated with matte are also in good agreement withexperiment under all studied conditions, such as at SiO2saturation, in equilibrium with Fe, Cu, or Cu-Au alloys, at fixedoxygen or SO2 partial pressures and at different contents of CaOin the slag. Sulfide contents (sulfide capacities) of the slags arepredicted within experimental error limits from the modifiedReddy-Blander model, with no adjustable parameters. As anexample of the application of the database, the stability field ofmatte/slag equilibrium is calculated, and the matte and slagcompositions are plotted vs iron to silica ratio in the slag atvarious S02 pressures over this field. The matte-slag two-phasefield is limited by the calculated lines corresponding toprecipitation of copper, silica, and magnetite.
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