The effect of particle size, porosity and reactor temperature/reaction rate constant on the progress of a char particle conversion has been investigated numerically by solving the transport equation inside a reacting char particle. Numerical simulations have been conducted for three cases that include two extreme cases and one general case. The two extreme cases correspond to a very large Damkohler number (3.2607 x 10(3)) and a very small Damkohler number (0.0042). The third case corresponds to an intermediate value of Damkohler number. For the very large Damkohler number case, concentration profiles of the gasifying agent showed a steep gradient across the particle and the reaction occurred mostly in outer layer of the particle. This behavior corresponds to a diffusion controlled process. For the very small Darnkohler number case, gasifying agent concentration was a straight line parallel to the x-axis, with a y-axis value of the surrounding concentration. The reaction occurred homogeneously across the particle and the degree of conversion was only a function in time. This behavior corresponds to a chemically controlled process. The total conversion of the char particle as a function of time has also been calculated for different particle sizes, initial porosity and reaction rate constant. Variation in conversion profiles as a function of time due to variation in initial porosity and reaction rate constant were limited to a certain extent. Very high initial porosity values tend to shift the process towards a chemically controlled one; any further increase in porosity does not have a positive effect on the conversion-time relationship. Very high reaction rate constants tend to shift the process towards diffusion controlled process. Kinetic parameters have been determined experimentally using a chemically controlled process. The obtained parameters have been used in the model to determine the progress of char particle conversion at an increased reactor temperature of 1000 degrees C. The model has been compared to experimental results at the same temperature (1000 degrees C). The results showed very good agreement. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.