The combustion reactivity of coal chars in oxyfuel atmosphere: Comparison of different random pore models

Recently the oxyfuel combustion of coal chars having a significant impact on reducing greenhouse emissions is gradually paid extensive attention by many researchers, but only a limited number of studies have focused on its reaction mechanism. Therefore, it is important to investigate the combustion mechanism of coal chars in oxyfuel atmosphere, while random pore model (RPM) is usually recommended as a model for the comprehensive simulation of coal chars reaction. In this context, the values of structure parameter ψ in RPM were calculated based on pore structural character at various carbon conversions, and show interesting evolution phenomena keeping constant at the preceding reaction stage before increasing remarkably at the end of stage. Consequently, a new model, two-stage random pore model (TRPM), was applied to the coal chars combustion in oxyfuel atmosphere. Compared to other models such as RPM, the Struis model (Model I), the Liu model (Model II), and fractal random pore model (FRPM), it shows that two-stage random pore model was more accurate to describe coal chars combustion under oxyfuel conditions, especially at higher carbon conversions. In addition, the oxyfuel combustion process of coal chars at 1323 K and 1373 K were analyzed.