The slag discharge method of fluidized bed gasifier is slag tapping. coal ash with high melting point can not satisfy the requirements of slag discharge. The slagging problem of coal ash is closely related to the fusibility of coal ash. In order to study effect of CaO in coal on the ash fusibility

different proportions of CaO were added to coal ash and fusion temperatures（AFTs） were measured. The element composition and micro-morphology of the sample were analyzed by scanning electron microscopy and X-ray powder diffractometer. The minerals’ composition of coal ash samples were investigated by X-ray diffraction. The results show that the AFTs drop first and rise later with the increase of CaO content. When the ratio of CaO increase from 0 to 30%

The anorthite with high melting point reduced in ash

and a large quantity of andradite with low melting point was generated in ash at high temperature

the AFTs decrease gradually. When the ratio of CaO was increased

the ratio of rankinite increased

the AFTs was increased gradually. When the ratio of CaO reached to 30%

the ash fusion temperatures could be reduced the most.