Phase equilibrium and minor elements distribution between iron-silicate base slag and nickel-copper-iron matte at 1573 K under high partial pressuresof SO2

As a contribution to the understanding of oxygen-blowing smelting of the ni ckel-copper-iron matte, the phase equilibrium and the distribution of minor elements between the iron-silicate base slag saturated with silica and the Ni3S2-Cu2S-FeS matte with a Ni:Cu molar ratio of 1 was investigated in a m agnesia crucible under controlled partial pressures of SO2 at 10.1, 50.7 an d 101.3 kPa and 1573 K. At a given matte grade, the solubility of copper in the slag is found to be independent of p(SO2) while the solubility of nick el is dependent on p(SO2) and these behaviors are analyzed thermodynamicall y based on a concept of oxidic and sulfidic dissolutions of the components in the slag. The distribution ratio of X, L-X(s/m) is defined as (mass%X in slag)/{mass%X in matte}. At a fixed p(SO2), the distribution ratios of As and Sb decrease remarkably with increasing matte grade, and in the case of Bi, L-Bi(s/m) decreases with increasing matte grade up to about 55 mass%Ni and then increases slightly in the higher range. When the matte grade is sp ecified, the distribution ratios of As, Sb and Bi increase with increasing p(SO2). The results for the present Ni3S2-Cu2S-FeS matte system were compar ed with those for the Cu2S-FeS and Ni3S2-FeS matte systems.