Morphological Evolution of a Single Char Particle with a Low Ash Fusion Temperature during the Whole Gasification Process

Abstract

Morphological evolution of single char particle with low ash fusion temperature (Tf ) was investigated during the whole gasification process using high temperature stage microscope. The experimental results showed that the shrinkage ratio of char particles above the Tf (1300 °C) was higher than that below the deformation temperature (1000 °C) finally. The TEM and SEM analysis results showed that the ash was a dispersed distribution in coal char. Dispersed molten slag aggregated to molten slag layer during the gasification process at the temperature above Tf, which evidently hindered the diffusion of gasifying agent. Therefore, there was a critical shrinkage ratio during the gasification process when the temperature above the Tf, and the critical shrinkage ratio of XLT char particles was 0.7-0.8. The SEM-EDS analysis results indicated that the critical points in the shrinkage rate curve were related to the molten slag on char surface. And the reaction mechanism was analyzed, the calculating critical thickn...