Experimental study of ash formation under O2/CO2 combustion

AbstractOxy‐fuel combustion technology has been recognized as the most promising technology for controlling CO2 emission in coal‐fired boilers. The slagging characteristics of oxy‐fuel combustion (O2/CO2) are very different from those of air combustion (O2/N2). In this paper, an ash sample collection of Shenhua coal with high Ca and Fe content was carried out in a muffle furnace and a tubular furnace under different conditions. The ash melting point, X‐ray diffraction (XRD) and scanning electron microscopy (SEM) were used for characterization. The characteristics of Shenhua coal ash slagging in different atmospheres were studied, and the mineral transformation trend was obtained. It was concluded that the melting point of the ash samples under oxy‐fuel combustion was lower than that under an air atmosphere, and the slagging tendency was enhanced under conditions of high oxygen combustion. Under oxy‐fuel combustion, CaCO3 was found. This did not occur under an air atmosphere. The atmosphere has no obvious effect on the crystal minerals of Fe. The decrease in high melting point oxide, the formation of carbonate, and the increase in glass state and sulfate under an oxy‐fuel atmosphere all make the ash melting point lower than under an air atmosphere. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.