China Nonferrous Metallurgy

Systemic thermodynamic study and experimental basis study have been carried out on the thermal decomposition behavior of gypsum. The results show that in the solid-solid carbon thermal decomposition of gypsum, when the Ca:S ratio is 3, the conversion rate of gypsum to CaS reaches the maximum (81.33%), and the CaS content in the reaction product is 71.19%; In the gas-solid thermal decomposition of gypsum, when the CO/（CO+CO₂）concentration in the gas is 50%, the conversion rate of gypsum to CaS is 91.80%, and the CaS content in the reaction product is 93.51%. When the CaS is used as sulfurizing agent for matte smelting, the utilization rate of the sulfurizing agent can reach above 74%. Based on the results, the process of using gypsum for selective reduction, sulfurization and enrichment of valuable metals before matte smelting is proposed, and it’s identified that the key control factor of the gypsum sulfurization reaction is CaS conversion rate. The test conclusions can provide theoretical basis for the application of gypsum in matte smelting in the non-ferrous metallurgy field.