Effect of Cooling Process on the Generation and Growth of Crystals in Coal Slag

Slag tapping in the entrained-flow gasifier is of importance to the successful and stable operation. The aim of the paper was to study the effect of cooling process on the generation of,crystals in coal slag. A high temperature resistance furnace was applied to control the cooling process of the slag combined with the FactSage prediction. Crystal type and peak intensity were detected and analyzed by X-ray diffraction (XRD). Results of diffraction intensity and peaks indicated that low cooling rates and long residence times at fixed temperatures benefited the nucleation and growth of crystals. The relaxation and diffusion theory of crystals and glasses was applied to describe the promotion of crystal growth with longer residence time. Secondary electron images and backscattered electron images by scanning electron microscope (SEM) also proved the promoted growth of the crystals with amorphous phase, crystal number, size, and shape of regularity.