In order to further understand the deposition characteristics of high-carbon fly ash of Zhundong blended coal

differential scanning calorimeter(DSC) and X-ray diffractometer(XRD) were used to study the phase thermal transformation characteristics of one high-carbon fly ash of Zhundong blended coal and two other fly ashes. The results show that

the residual carbon in the Zhundong blended-coal fly ash burned out basically after a heat treatment at 500 ℃

it had little effect on the phase thermal transformation of fly ash at higher temperatures. In the low-temperature stage of DSC measurement

the heat release fluxes of the three fly ashes with different ash melting points had similar change trend. At temperatures above 880 ℃

the DSC heat release flux of the Zhundong blendedcoal fly ash increased more and more rapidly with the temperature

and reached its peak value at 1 080 ℃. This is due to the combination of calcium-containing and sodium-containing substances in fly ash with aluminosilicate substances to produce a large amount of sodium-containing anorthite

in which gehlenite and calcium silicate are the intermediate products. When depositing on the boiler heating surface where the flue gas temperature was not lower than 1 080 ℃

this kind of fly ash can solidify itself and cause fouling or slagging.