A kinetic study of CO₂ gasification of a Chinese coal char during combined coal gasification and CH₄ reforming

The kinetics of CO₂ gasification of a Chinese coal char during combined coal gasification and methane reforming have been studied using a thermo-gravimetric analyzer. The effect of methane on CO₂ gasification of the char from 1173K to 1273K was examined. The results show that the coal char conversion rate increases with increasing temperature but decreases with increasing CH₄ concentration. Carbon deposition, due to CH₄ cracking, is reduced as temperature and carbon dioxide concentration increase. Two standard gas-solid reaction kinetic models, viz. the constant particle size (or progressiveconversion) model and the shrinking-core model, were applied to describe the overall carbon conversion of the char. It is found that the constant particle size model fits the experimental data better than the shrinking-core model. Accordingly the activation energy, reaction orders in CH₄ and CO₂ based on the constant particle size model are determined to be 312.4kJ/mol, -0.13 and 0.3, respectively. The presence of methane slows down the gasification rate of coal char.