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 nonequilibri um arsenic species are contained as solutes, with a high activity (adjustme nt) coefficient. The validity of the method of calculation was checked by c omparison to the results of conventional calculations. The validated proced ure was then used to evaluate the effects of operating variables and to est ablish optimum roasting conditions. The change of the predominant gas and s olid species during the course of oxidation and the effect on the volatilit y of arsenic are discussed. Arsenic removal from the concentrates was gener ally good, but it was affected by the extent of oxidation and the initial c oncentration in the concentrate. The extent of sulfur oxidation for optimum arsenic removal is around 70 pct. With the appropriate choice of an adjust ment coefficient, the results simulated those obtained in practice.