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.