A novel approach of using SiC for the reductive decomposition of industrial by‐product gypsum

Abstract In this study, thermodynamic calculations indicate that using silicon carbide (SiC) as an additive for the reductive decomposition of industrial by‐product (IBP) gypsum is a feasible method to lower decomposition temperature and avoid the generation of liquid phase. Experimental results show that the decomposition rate of IBP gypsum exceeded 90% at 950°C for 2 h, while avoiding the generation of liquid phase. In addition, it was found that an intermediate product, 2Ca 2 SiO 4 ·CaSO 4 , was generated during the decomposition process. Through the reaction mechanism and kinetics analysis of IBP gypsum and SiC, the decomposition process can be divided into two steps. The first step was the conversion of CaSO 4 to 2Ca 2 SiO 4 ·CaSO 4 (decomposition rate <60%), and the chemical reaction was the controlling step. The second stage was the conversion of 2Ca 2 SiO 4 ·CaSO 4 to Ca 2 SiO 4 (decomposition rate >60%), and three‐dimensional diffusion was the controlling step. This novel method not only successfully lowered the decomposition temperature of IBP gypsum, but also avoided liquid phase generation.