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 1173 K to 1273 K 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 312.4 kJ/mol, -0.13 and 0.3, respectively. The presence of methane slows down the gasification rate of coal char.