Combustion experiments of Datong coal and its Ca-added samples were performed in a fixed-bed reactor at different heating rates and different O2 concentrations. From the peak-fitting of SO2 curve according to Gaussian function

the SO2 formation temperatures of all kinds of sulfur forms were obtained. It was concluded that: (1) the combustion temperature of different sulfur forms was influenced by O2 concentration and heating rate. They could evolve as SO2 at lower temperature with increasing O2 concentration or decreasing heating rate. (2) The added CaO and Ca(OH)2 had better sulfur retention effect for the high reactivity. However CaCO3 could increase SO2 emission at a low temperature for its bad reactivity and its catalyzing effect on SO2 formation. (3) The impregnation with stirring and ultrasonic treatment had much better sulfur retention effect than mechanical mixing for the high dispersion. (4) While oxidizing CaSO3 to CaSO4

a small amount of SO2 was evolved.