Ash fusion behaviors and physicochemical characteristics of high-alkali coals under oxy-fuel condition

Oxy-fuel combustion is highly potential for extensive CO2 capture in utility power plants. However, little attention has been devoted to the influences of O2/CO2 atmosphere on fusion behaviors and microscopic physicochemical characteristics of high-alkali coal ash. The present study specifically focused on ash fusion behaviors and mineral transformation of Zhundong high alkali coals under oxy-fuel condition using various experimental approaches including the TG-DSC analysis, scanning electron microscopy (SEM), and X-ray diffraction techniques. The experimental results showed that the change among air, CO2, and O2/CO2 atmospheres had a slight impact on ash fusion points, while the physicochemical properties of the softening ash were affected. Oxy-fuel condition affected the volatility of high-alkali ash and the certain elements distributions on the softening ash surfaces, while the O2 content was the primary influential factor on micro-morphology of softening ash. The distributions of crystalline minerals in softening ash varied with atmospheres.