Co-Pyrolysis Characteristics and Kinetic Analysis of High-Sulfur Coking Coal and Polypropylene

With the increasing shortage of high-quality coking coal resources, the efficient and clean utilization of high-sulfur coking coal has become an important research direction in the field of coal chemical industry. At the same time, the environmental problems caused by traditional plastic treatment methods (such as landfill and incineration) have become increasingly prominent. Therefore, in this study, hydrogen-rich plastic polypropylene (PP) was proposed as a hydrogen donor to co-pyrolysis with high-sulfur coking coal. The effects of coal characteristics and mixing ratio on pyrolysis weight loss characteristics and kinetic parameters were systematically studied by thermogravimetric experiment. The results show that the main pyrolysis weight loss temperature ranges of coal and polypropylene overlap significantly, which provides favorable conditions for the interaction between the two. Moreover, there is a significant deviation between the actual weight loss and the theoretical calculation value in the co-pyrolysis process. This phenomenon indicates that the hydrogen-rich components and active free radicals produced by PP during pyrolysis can interact with coal, and there is a significant synergistic effect between the two. Through kinetic analysis, the kinetic mechanism functions of single coal and mixture at different pyrolysis stages were determined. The addition of polypropylene made the temperature range of the second pyrolysis zone significantly narrower and the activation energy increased, but the activation energy of the third pyrolysis zone decreased. This finding not only verifies the synergistic effect again, but also provides an important basis for further understanding the co-pyrolysis mechanism of coal and plastic.