PHASE-EQUILIBRIUM BETWEEN CALCIUM FERRITE SLAG AND COPPER MATTE AT 1523 K UNDER HIGH PARTIAL PRESSURES OF SO2

As a fundamental study for the oxygen-blowing copper smelting, the pha se equilibrium between ferrite slag and copper matte was investigated at 1523 K under the partial pressures of SO2 controlled at 10.1, 50.7 and 101.3 kPa, using a sulfur reservoir for controlling the partial pr essure of S-2. An oxygen-sulfur potential diagram was constructed in r elation to matte grade, and it was clarified that the ratio of (p(o2)/ p(s2)) was constant against p(so2) when the matte grade was specified. The solubilities of copper and sulfur in the slag and calcium in the matte as well as (%Fe3+/%Fe2+) in the slag were also determined in rel ation to matte grade. The solubilities of copper and sulfur were found to be independent of p(so2) when the matte grade was specified and it was considered that this behavior was ascribable to the constancy of (p(o2)/p(s2)) against p(so2). The solubility of sulfur decreased gradu ally with increasing matte grade. On the other hand, the solubility of copper represented the minimum al matte grade with about 72.5 mass%Cu , which was analyzed thermodynamically based on a concept of oxidic an d sulfidic dissolutions of copper component in the slag.