Experimental research on the characteristics of ash in oxy-fuel combustion

•A certain amount CaCO3 exists under oxy-fuel combustion.•Fe is more likely to react with Si, Ca, Al.•Slagging tendency of Shenhua coal is predicted by different indexes.•Slagging tendency under oxy-fuel combustion is obviously higher. CO2 capture and storage technology plays an important role in global carbon emission reduction, and oxy-fuel combustion is one of the key future technologies. The slagging and deposition characteristics of ash under oxy-fuel combustion restrict the competitiveness and development of this technology. In this study, an ash sample of Shenhua coal was obtained in a flat flame-assisted entrained flow reactor under different conditions, and an X-ray diffraction, X-ray fluorescence probe, and scanning electron microscope–energy dispersive spectrometer were used. The slagging tendency under oxy-fuel combustion was thoroughly analyzed. Results showed that the characteristics of the ash samples obtained under oxy-fuel and air combustion varied. Obvious differences existed in the mineral characteristics and relative content, and these may have affected the slagging characteristics. The presence of Ca in ash was mainly in the form of CaO, and Fe was likely to react with Si, Ca, Al, and other minerals. Compounds with low melting points were generated under oxy-fuel combustion, indicating that the slagging tendency was aggravated. Moreover, the slagging tendency of Shenhua coal in different atmospheres was predicted with common and viscosity slagging indexes, and the result was consistent with the experimental ones. The sphericity of the ash samples obtained under oxy-fuel combustion was better than that of the samples under air combustion.