Phase equilibrium and distribution of minor elements between Ni-S melt and Al2O3-CaO-MgO Slag at 1873 K

Abstract

Distribution of nickel and minor elements such as Au, Ag, Fe, Co, Cu, As, and Sb between the Ni-S alloy and the CaO-Al2O3 based slag phases in a magnesia crucible was studied at 1873 K. Partial pressure of SO2 was controlled at 10.1 kPa, while partial pressures of O2 and S2 ranged between the point of NiO precipitation (po2 of 10.1 Pa) and the point at which Ni3S2 is formed (ps2 of 4.0 kPa). The nickel content in the slag and the sulfur and oxygen contents in the metal at a given po2 or pso2 decrease when the temperature is increased from 1773 to 1873 K. The distribution ratios of iron, cobalt, and copper, defined by (wt pct X in slag)/{wt pct X in alloy}, where X is the minor element in the slag, have larger values than that of nickel, while the values of Au, Ag, Sb, and As are lower than that of nickel. The distribution behavior of nickel and minor elements is discussed based on the concept of oxidic and sulfidic dissolution.