Modeling the Vaporization of Inorganic Matter from a Single Coal Char Particle Burning in an O_2/CO_2 Atmosphere

摘要

The present work aims to model ash vaporization from a burning char particle during pulverized coal combustion in an oxygen-enriched O-2/CO2 atmosphere. The modeling development was to apply the classic ash vaporization model of Quann and Sarofim to cover oxy-coal combustion over a wide range of O-2 concentrations by coupling it with the double-film char burning submodel to properly describe the burning process of a single char particle. The model was extensively validated with literature data on the vaporization of SiO2, MgO, and CaO in both O-2/N-2 and O-2/CO2 atmospheres. The model was proved to be able to predict the vaporization behavior of SiO2 during char conversion stages in both atmospheres, covering the effects of coal type, particle size, and O-2 concentration. The model predicts the vaporization of MgO and CaO during char combustion of bituminous coal, but improvement is required to describe the vaporization of MgO and CaO during char combustion of lower-rank coals by considering the occurrence of Mg and Ca in the coals and their interactions with other included minerals at high temperatures. The model validations demonstrated the importance of considering CO homogeneous oxidation in the boundary layer to reasonably predict the char particle burning process and ash vaporization in both O-2-enriched O-2/N-2 and O-2/CO2 atmospheres.