Recovery of CaO from CaSO4 via CO reduction decomposition under different atmospheres

CaSO 4 reduction decomposition for CaO preparation provides a theoretical basis for the utilization of the industrial byproduct, gypsum. In this study, the effects of temperature (950 °C–1150 °C), CO 2 /CO partial-pressure ratio (1–15), CO concentration (1%–5%), and O 2 concentration (1%–7%) on the preparation of CaO from CaSO 4 by CO reduction decomposition under different reaction atmospheres were investigated. The physical properties of CaO prepared by the decomposition of CaSO 4 and CaCO 3 were analyzed and compared. Finally, the reaction mechanism of the reduction decomposition of CaSO 4 to CaO by CO was studied. The findings reveal that CaSO 4 can be completely decomposed into CaO when the reaction temperature exceeds 1000 °C, CO% ≥ 2%, and P(CO 2 )/P(CO) ≥ 8. Furthermore, the addition of an appropriate amount of O 2 can improve the yield of CaO in the products. In an O 2 –CO–N 2 atmosphere, where O 2 % = 7% and CO% = 16%, CaSO 4 can be completely decomposed into CaO without the addition of CO 2 . The physical properties of CaO prepared by the reduction and decomposition of CaSO 4 are better than those prepared by the calcination of CaCO 3 . An analysis of the reaction mechanism of the reduction decomposition of CaSO 4 by CO reveals that CaSO 4 generates CaO and CaS simultaneously. In addition, CaS can react with unreacted CaSO 4 to form CaO. Furthermore, it can react with CO 2 to produce CaO if an appropriate amount of CO 2 is added to the reaction atmosphere. The secondary interactions of CaS with CaSO 4 and CO 2 can significantly improve the yield of CaO in the product.