The selective oxidation of mixed metal sulfides with lime in the presence of steam without emitting sulfur-containing pollutants

Abstract

The selective oxidation of mixed metal sulfides with lime in the presence of steam was studied as a function of the mixing ratio of the constituents, temperature, and steam concentration. Two combinations of samples were used in this study: ZnS/PbS/CaO and ZnS/FeS/CaO. The steam oxidizes one or both of the metal sulfides, and the hydrogen sulfide produced reacts with lime to form calcium sulfide and regenerate steam. There is no net consumption or generation of gaseous species; therefore, this process can be carried out in a closed system. The free energy of the reaction is negative only for certain metal sulfides, and thus selective oxidation for mixed sulfides can be achieved. An overall rate equation developed in this work satisfactorily predicted the experimental data obtained in the temperature range 823 to 1113 K. The potential implications of the results of this work in the treatment of complex sulfide ores are discussed.