Decomposition and solid reactions of calcium sulfate doped with SiO 2 , Fe 2 O 3 and Al 2 O 3

•The initial decomposition temperature of CaSO4 is reduced by silicate mineral.•The formation of 4CaO·2SiO2·CaSO4 inhibits CaSO4 decomposition.•Fe2O3 exhibits catalyzing desulfurization before 1273K.•Fe2O3 enhances the decomposition of CaSO4 after 1273K.•The decomposition of CaSO4 can be accelerated by the formation of CaAl2O4 while prevented by the formation of Ca4Al6SO16.