A modified thermodynamic calculation procedure was used to simulate the beh
avior of a number of minor components in sulfation roasting. To account for
uncertain mineralogy and probable non-equilibrium situations it was assume
d that the calcine formed pseudo solid solutions and that the minor compone
nts had large values of activity coefficient, which were referred to as 'ad
justment coefficients.' The calculation method was a combination of the fre
e energy minimization procedure coupled with the introduction of the imagin
ary phases involving non-equilibrium forms of the minor constituents. The a
ppropriate choice of adjustment coefficients allowed the calculated behavio
r of the non-equilibrium minor components to reflect the results observed i
n practice and could be used to explore the relative effects of variables s
uch as temperature, pressure and concentration. The existence of narrow reg
ions of optimum temperature and gas compositions was confirmed for the sele
ctive sulfation-roasting of copper-nickel sulfide concentrate. Application
of the procedure to the sulfation roasting of a zinc plant residue was also
discussed. The proposed simulation method is useful for the complex system
including non-equilibrium components like waste treatment and recycling.