Mathematical modelling of pyrolysis of large coal particles - estimation of kinetic parameters for methane evolution

This paper reports a study of mathematical modelling of pyrolysis of large coal particles using the distributed activation energy model. By comparing with the literature experimental data, it is shown that the model is effective in predicting the temperature response and the residual volatile matter content of large particles undergoing pyrolysis in both fluidised-bed and convective heating conditions. The model is further used to investigate the proposed kinetic parameters for methane evolution and suggests that incorrect assumptions in previous modelling attempts resulted in the selection of inappropriate kinetic parameters. Alternative kinetic parameters are suggested which give significantly better predictions for the evolution of methane under fluidised-bed conditions for both large and pulverised coal particles. The model predictions are shown to be more sensitive to the kinetics than the heat transfer coefficient, which suggests that the pyrolysis of the large coal particles under conditions discussed in this paper is primarily kinetically controlled, The proposed kinetics are shown to be accurate to +/- 6% given the relative accuracy of the heat transfer parameters, (C) 1999 Elsevier Science Ltd, All rights reserved.