Study On Phase Trasition And Mechanism Of Coal Ash

For a long time,melting and slagging characteristics of coal ash are the main factors that do harm to the function of boilers, which endanger security, economical operation and equipment reliabilityof boiler. The coal ash fusibility has been studied in many different ways by many researchers, such as changing the kind of coals, admixture of different coals and affiliating minerals in the ash of coal. Because there are so many kinds of coal in our country and every one kind of coal contains a great deal of minerals which bring out many interferences factors to the mechanism of slagging, research on this field is not very easy.In this paper, three kinds of coal ash and three kinds of fluxes FeS2,Na2O,CaO were selected, then the fluxes were separately added into the ash. The paper studied the fusibility, and furtherly the fusion mechanism of six coal ash with thermal analysis, X-ray diffraction and Scanning electron microscope.The results of this paper were as following:1. To begin with,Studied the fusibility of six coal ash with differential scanning calorimetry and thermogravimetry and analyzed the causes of formation of characteristic peaks on the DSC,DDSC curves. Endothermic and weightlessness bring by resolution of carbonate and sulphate of coal ash lead to changes of TG-DSCcurves,while the temperature range where phase transitions happen can be judged by observation of DDSC curves. The ash melt point of the three ash can be judged through TG-DSC curves is on the basis of distince content of Kaolinic in different coal ash. The other three coal ash added three fluxes which reacted with minerals in ash produced melt-together-matter,which changed the melting and slagging characteristics of coal ash.2. Studied the mineral behaviour of six ash which has been heated at four characteristic temperature with X-ray diffraction qualitative analysis. The heat-behavior during heating of major mineral in ash was studied by changing curves according different temeratures of X-ray diffraction intensity of every kind of minerals. The effect of ash melting and slagging characteristics lead to the minerals produced by adding three fluxes into different coal ash was analysised.3. Scanned the coal ash sample that made at four characteristic temperature according to DSC curves , studied the reasons which caused differences of ash appearance characteristics the appearance characteristics of different ash under different temperatures combining X-ray diffraction. Furtherly,the conclusion that melt-together-matter produced by fluxes during the heating process reacted easily with minerals in coal ash to lower ash melt point was judged.4. It was feasible that utilizing the DDSC curves of TG-DSC method to judge the temperature range where the phase trasition happens in the coal ash in the basis of XRD,FESEM records.