Kinetic parameters of coal activation with oxidizing gases are depended of coal characters. In this work, activation of Iranian coal char with steam and CO2 is studied to find kinetic parameters of the reactions. These parameters are determined by unification of thermogravi metric analysis (TGA) data. Mathematical modeling of the reaction with random pore model also is investigated in this study to predict carbon conversion. Formulation of this model in the mixed controlling regime gives coupled partial differential equations, which has no analytical solution. In this work, a new and simple analytical-numerical solution method is presented to solve these complex equations with a good accuracy. The results show good agreement of this solution with the experimental data. (c) 2007 Elsevier B.V. All rights reserved.