Kinetic Analysis of Wheat Straw Oxidative Pyrolysis Using Thermogravimetric Analysis: Statistical Description and Isoconversional Kinetic Analysis

The oxidative pyrolysis kinetics of wheat straw was studied by thermogravimetric analysis (TGA) under oxygen dynamic atmosphere. Nonisothermal TGA data at three heating rates of 5, 10, and 20 K min(-1) were analyzed. The kinetic conversion data calculated from the TGA data were fitted by the Weibull and logistic mixture models, and the corresponding statistical analyses were performed. The statistical results showed that the Weibull mixture model fitted the experimental data better than the logistic mixture model and can accurately reproduce the kinetic conversion data. Making use of the data predicted by the Weibull mixture model, some data required in the isoconversional kinetic analysis, such as alpha vs T-alpha, can be easily obtained. An iterative linear integral isoconversional method was developed and applied to evaluate the activation energy of the oxidative pyrolysis process of wheat straw. The Vyazovkin-Dollimore nonlinear integral isoconversional method was also used to calculate the activation energy. The results have shown that two isoconversional methods are equivalent for the estimation of the activation energy and the obtained activation energy is significantly dependent upon conversion for the oxidative pyrolysis process of wheat straw.