Kinetics of carbothermic reduction of zinc sulfide in the presence of calcium carbonate

The kinetics of the carbothermic reduction of zinc sulfide in the presence of calcium carbonate was investigated by an atomic absorption spectrometer (AAS) and a thermogravimetric analysis system (TGA). Experimental results indicate that TGA data accompanying with the equation derived from two-stage mechanism can be used to calculate the zinc yield properly. The results of TGA revealed that the rate of reduction in the presence of calcium carbonate was close to that in the presence of calcium oxide. The reduction rate was found to increase with increasing the reaction temperature, the initial molar ratio of C/ZnS, or the initial molar ratio of CaCO₃/ZnS and with decreasing the argon flow rate, the sample height, the size of carbon aggregate, the size of calcium carbonate aggregate or the initial bulk density. An empirical rate expression of zinc yield has been regressed based on the experimental data obtained.