Reaction kinetics of coal char gasification with CO₂ and the effect of internal diffusion on the gasification

The effects of temperature (850-1 150℃) and particle size (<60, 505, 950, 1 515 and 2 000 μm) on the gasification of Shenmu coal char with CO₂ were investigated by using thermogravimetric apparatus (TGA) under atmospheric pressure. Three kinetic models of volumetric, shrinking core and random pore were applied to validate the experimental results, which illustrates that the random pore model can accurately predict the conversion rate for coal char gasification. Thiele modulus and effectiveness factor were determined on the basis of the intrinsic kinetic rate at 850-1 000℃; a comparison between calculated and experimental effective factors suggests that the calculated effective factor can give a quantitative estimation of the effect of internal diffusion on the initial stage of gasification, but cannot describe the whole gasification process.