Application limitations of single scanning rate method in pyrolysis kinetics of Zhundong coal

To improve the application effectiveness of single scanning rate method in the coal pyrolysis field, the weight loss data of temperature programmed pyrolysis of Zhundong coal at three heating rates were investigated and the kinetic parameters were calculated using single scanning rate methods. Several problems such as the impacts of segmentation viewpoint and weight loss in the dehydration and degassing stage on the kinetics calculation results, the possibility of obtaining an accurate and unique kinetic triplet and the theoretical significance of kinetic triplet were analyzed. The results show that the selected segmentation viewpoint affects the well-fitted model functions and Arrhenius parameters, the apparent activation energy (E) values based on sequential conversion viewpoint are obviously lower than those based on independent conversion viewpoint. When the sequential conversion viewpoint is used, excluding the weight loss in dehydration and degassing stage affects the intervals of the other stages and reduces the E values. The comprehensive application of the integral and differential methods as well as the three heating rates can not provide an accurate and unique kinetic triplet, so the theoretical significance of kinetic triplet is limited. Clarifying the pretreatment method of weight loss data and model function chosen are quite necessary for the evaluation and communication of kinetic parameters, and the explanations of pyrolysis mechanism using kinetic triplets should be made with extreme care.