The melting temperature of Z coal ash was reduced by adding calcium-magnesium compound flux (

W

CaO

/

W

MgO

=1). In the process of simulated coal gasification

the coal ash and slag were prepared. The transformation of minerals in coal ash and slag upon the change of temperature was studied by using X-ray diffraction (XRD). With the increase of temperatures

forsterite in the ash disappears

while the diffraction peak strength of magnesium spinel increases

and the content of the calcium feldspar increases

then the content of the amorphous phase in the ash increases obviously. The species and evolution process of oxygen

silicon

aluminum

calcium

magnesium at different temperatures were analyzed by X-ray photoelectron spectroscopy (XPS). The decrease of the ash melting point mainly affects the structural changes of silicon

aluminum and oxygen. The coordination of aluminum and oxygen in the aluminum element structure

e.g

.

tetracoordinated aluminum oxide

was changed. Tetrahedral[AlO

4

]

and hexacoordinated aluminoxy octahedral[AlO

6

]

change with the temperature changing. The addition of Ca

2+

and Mg

2+

destroys silica chain

making bridge oxide silicon change into non-bridge oxysilicon; and bridge oxygen bond was broken and non-bridge oxygen bond was produced in the oxygen element structure. The addition of calcium and magnesium compound flux reacts with aluminum oxide tetrahedron

aluminum oxide octahedron and silicon tetrahedron to promote the breakage of the bridge oxygen bond. Ca

2+

and Mg

2+

are easily combined with silicon oxide and aluminum oxide tetrahedron and aluminum. Oxygen octahedrons combine with non-oxygen bonds to generate low-melting temperature feldspars and magnesite minerals

thereby reducing the coal ash melting temperatures. The structure of kaolinite and mullite was simulated by quantum chemistry calculation

and kaolinite molecule has a stable structure.