Simulation of the removal of arsenic during the roasting of copper concentrate

To simulate the behavior of arsenic during the practical roasting of copper concentrate, a modified free-energy minimization method was developed. The calcine was assumed to be a pseudosolid solution in which the nonequilibrium arsenic species are contained as solutes, with a high activity (adjustment) coefficient. The validity of the method of calculation was checked by comparison to the results of conventional calculations. The validated procedure was then used to evaluate the effects of operating variables and to establish optimum roasting conditions. The change of the predominant gas and solid species during the course of oxidation and the effect on the volatility of arsenic are discussed. Arsenic removal from the concentrates was generally good, but it was affected by the extent of oxidation and the initial concentration in the concentrate. The extent of sulfur oxidation for optimum arsenic removal is around 70 pct. With the appropriate choice of an adjustment coefficient, the results simulated those obtained in practice.