Mineral characteristics of ash when combusting pulverized coal and calcium-based compound additives was studied with a lab-scale furnace used for combustion test. The mineralogical composition of the collected ash was determined by X-ray diffraction (XRD). The effects of temperature

residence time and content of additives on the mineral characteristics of ash were analyzed. The results revealed that the minerals in ash were principally free oxides and a small amount of gehlenite and dicalcium silicate at 1000℃; as the firing temperature increased above 1200℃

the major minerals in the ash were gehlenite and dicalcium silicate. Moreover

It was found that anhydrous calcium aluminosulfate formed at a high temperature，which plays the role of desulfurization.