Effect of High Temperature on CO2 Gasification Kinetics of Sub-Bituminous Coal Fly Ash

Abstract

Gasification is an eco-friendly thermochemical conversion process that can use various raw materials to generate high value-added products. Coal fly ash residue from coal-based thermal power plants must be effectively managed and utilized. Therefore, this study investigates the effects of high temperatures (1100–1300 °C) on the gasification kinetics of two types of coal fly ash (KPU and LG) under isothermal CO2 balance using a thermo-balance reactor. Three models were applied to study the reactivity of the coal fly ashes: the shrinking core model (SCM), the volume reaction model (VRM), and the random pore model (RPM). The results showed that among the three models, the SCM-based simulation was the most similar to the experimental data. We determined that low activation energy and a high pre-exponential factor achieve high gasification reactivity. With the SCM, the activation energy values for the CO2 gasification of the KPU and LG coal fly ashes were 52.7 and 59.6 kJ/mol, respectively, and their pre-exponential factors were 1.90 × 102 and 6.51 × 102, respectively. Moreover, the high reactivity of the two fly ashes was attributed to the high reaction temperature and presence of moisture and volatile matter.