Phase Equilibrium between Iron-Silicate Base Slag and Nickel-Iron Matte at 1573 K under High Partial Pressures of SO<SUB>2</SUB>

Abstract

As a fundamental study for the oxygen-blowing nickel smelting, the phase equilibrium between iron-silicate base slag saturated with silica and Ni3S2–FeS matte in a magnesia crucible was investigated at 1573 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 pressure of S2. An oxygen-sulfur potential diagram was constructed in relation to matte grade, and it was found that the ratio of (pO2⁄pS2) was constant against pSO2 when the matte grade was specified. The solubility of sulfur in the slag and that of oxygen in the matte decreased with increasing matte grade and the SO2 partial pressure gave no significant effect on these solubilities within the investigated pSO2 range. On the other hand, the solubility of nickel in the slag increased with increasing pSO2 at a given matte grade and this behavior was analyzed thermodynamically based on a concept of oxidic and sulfidic dissolution of components in the slag.