The gasification of two kinds of sub-bituminous char-coal in pure CO2 atmosphere has been performed in a thermogravimetric analyzer. The effect of gasification temperature (800-1100 degrees C) and particle size (0.125-1.4 mm) has been investigated. Different classical models (homogeneous model, shrinking-core model) have been adopted in order to determine the kinetic constants and the corresponding activation energies. We observed the necessity of including the effect of diffusion through the ash layer and of the non-uniform distribution of solid reactant in order to have a complete description of the conversion vs time curves. (C) 2014 Elsevier Ltd. All rights reserved.