Thermal degradation of bituminous coal with both model-free and model fitting methods

A series of thermogravimetric experiments was conducted to study the thermal degradation of bituminous coal at various heating rates in both nitrogen and air atmosphere. Both model-free and model-fitting methods were applied simultaneously to explore the reaction kinetic parameters. The activation energies were estimated in the range of 194.7-348.0 kJ/mol at different conversions by two typical model-free methods (Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose methods). Shuffled Complex Evolution method (SCE), as the representative of model-fitting method, was firstly used in the coal pyrolysis process. By comparison, the predicted activation energy (199.2 kJ/mol) by model-fitting method was just within the range of values obtained by the model-free methods, validating the applicability of this model-fitting method. Furthermore, the effect of char oxidation and its kinetic parameters are analyzed by SCE based on the difference of nitrogen and air atmosphere. These optimized parameters can be coupled with the pyrolysis model and applied in the following energy conversion processes.