The serious slagging and fouling problems caused by high alkali content in Zhundong coal has drawn wide attentions. At present

most of the power plants add kaolin in Zhundong coal to remit the slagging problems.However

the economy of this method reduces due to the high price of kaolin. On the other hand

large quantities of fly ash in Zhundong coal are unavailable for treatment. So the fly ash is proposed to use as slagging inhibitor for coals with high alkali metal content. This study evaluates the fusion characteristics of the slagging inhibitor

and analyzes the fly ash treated by different ways via X-ray fluorescence spectrum analysis(XRF) and X-ray diffraction analysis(XRD). The reason of fusion points variation was determined. The results indicated that

the fusion points of the raw fly ash with different sizes were basically identical. The fusion points of the fly ash(37～100 μm) increased by only 30 ℃ after water-washing

while that of the other fly ashes(37 μm and 100 μm)almost unchanged. After the fly ash was washed by acid

the fusion points of large particles(100 μm) increased by over 100 ℃

while the fusion temperatures variation of the small particles was inconspicuous. The largeparticles(100 μm) in fly ash mainly came from the foreign minerals and the Kaolin additives. After the fly ash was washed by acid

the alkali and alkaline metal adhered on the surface of the particles was removed into the acid solution

causing significant increase in SiO_2 proportion in the ash

so the fusion points increased.