Kinetic Modeling of Coal Thermal Decomposition under Air Atmosphere

摘要

The paper aims at establishing kinetic model to predict the thermal decomposition of coal in air. Three different rank coals, meager lean coal, fat coal, and gas coal, are investigated using thermogravimetry (TG) and differential scanning calorimetry (DSC). By analyzing the experimental TG curves with a model-fitting method, a two separate stages model is presented to describe the mass variation with temperature and the reaction mechanism. The two stages are found to abide by the first-order mechanism and the contracting-sphere mechanism, respectively. The two separate stages model is validated by comparing experimental and simulated conversion curves and TG curves. By analyzing experimental DSC results with an isoconversional method, a two-step consecutive reactions model is developed. Kinetic parameters of each step are ascertained with a multivariate nonlinear regression method. The two-step consecutive reaction model is validated by comparison of experimental and simulated DSC curves. The two separate stages model and two-step consecutive reaction model are compared in terms of obtained kinetic parameters. The results indicate that the kinetic parameters obtained from the two kinetic models are very close. The kinetic models are useful for understanding the mechanistic pathway of coal thermal decomposition and effective for predicting key features of the overall decomposition process.