Tiiermodynamic Study of Oxygen-Smelting of Copper or Nickel Matte

"As a contribution to understand the smelting of copper or nickel matte by blowing oxygen or oxygen-enriched air, the phase equilibrium and the distribution of minor elements between the iron-silicate based slag and the Cu2S-FeS or Ni3S2-FeS matte at 1573K were investigated in a magnesia crucible under controlled partial pressures of SO2 at 0.1, 0.5 and 1.atm. At a given matte grade, the solubility of copper in the slag was found to be independent of p5O2 while that of nickel was dependent on pSO2 and these behaviors were analysed thermodynainically based on a concept of oxidic and sulfidic dissolution of the components in the slag. When the matte grade was specified, the distribution ratios of X, defined as (wt pct X in slag)/(wt pct X in matte}, for As, Sb and Bi increased with increasing p5O2 while that for Ag was constant against p5O2.IntroductionA combination of intensive reactors with the use of oxygen or oxygen-.enriched air as the blowing gas has provided a number of improved copper and nickel smelting processes such as INCO-Flash, Outokumpu-Flash, Mitsubishi-Continuous and IBRC (top blown rotary converter) processes. Phase equilibrium and thermodynamic studies for the slag and the copper matte or the nickel matte under high partial pressure of SO2 are of practical importance for evaluating the behaviours of the related components in the oxygen-smelting.A series of experimental studies have been already conducted in a limited range of conditions for Pso2 around 0.1 atm, which corresponds to the smelting with air-Stowing [1-5]. However, there remain very few data on the phase equilibrium in the matteslag systems under higher partial pressures of SO2. Tavera and Davenport studied the phase equilibrium between the copper matte and fayalite slag phases under the partial pressure of SO2 controlled at 0.1 - 1 atrn but without controlling the partial pressures of sulfur and oxygen [6]. A potential diagram for the Cu-Fe-S-O-SiO2 system at 1523 - 1573K suggests that the partial pressure of S2 equilibrated with the matte and the fayalite slag with saturated SiO2 under the high SO2 pressure is considerably high at 10-4 - 10-2 atrn [7]. This condition must require controlling of p52 as well as Pso2, in the equilibrium experiments, otherwise, the equilibrium condition may be hardly attained due to the continuous flushing of sulfur from the system."