Kinetics of coal char combustion with random pore model under O_2/CO_2 atmosphere

The combustion of Jiaozuo anthracite and Yunfu bituminous coal chars under O2/CO2 atmosphere was studied by isothermal thermogravimetric analysis.The characteristics of coal char combustion at different temperatures were examined in O2/CO2 environment.The relationship between reaction rate and carbon conversion of two coal chars was analyzed by the random pore model (RPM),and compared with the simulations from the unreacted shrinking core reaction model (Model Ⅰ) and the integrated model (Model Ⅱ).The results show that the random pore model is the best to fit the experimental data under different reaction conditions,and the correlation coefficient is 0.986.Comparison for the results from RPM,Model Ⅰ and Model Ⅱ shows that activation energy of isothermal combustion of Jiaozuo anthracite under O2/CO2 atmosphere is much higher than that of Yunfu bituminous,and the rate constant is larger when the combustion temperature of coal chars is higher.The random pore model is more accurate to describe the characteristics of coal char combustion under O2/CO2 atmosphere because the influence of variation of pore structure on coal char combustion can be well reflected by parameter ψ used in RPM.