Modeling of Morphology of Char during Coal Gasification

Abstract

The entrained flow coal gasifiers, which are adapted for almost all IGCC technologies, are operated under the high-temperature and pressurized condition. It is necessary to clarify the coal behavior in such a condition for the design of the gasifier and the estimation of the gasifier's performance. In this work, the changes of char morphology, such as particle size distributions and bulk density, in the coal pyrolysis or the char gasification reaction were examined using a pressurized drop tube furnace facility (PDTF). Though a lot of pulverized coal particles have swelled by the rapid pyrolysis, the tendency was shown that the initial pyrolysis reaction of a coal with a high fuel ratio was controlled by pressure and the swelling was also suppressed. In the char gasification process, the change of the char particle diameter was few in the early stage of the gasification, because the surface was eroded by the reaction and the pore grew in the surface of char particles. The structure of char particles became fragile and the particles fragmented into smaller parts in the middle and latter stages of the gasification. The numerical model of particle size distributions and particle density of gasified char was proposed to explain the shrinkage and the fragmentation of char particles during gasification, and the validity of the model was shown.