Kinetics of microwave radiation pulverized coal combustion based on non-isothermal thermogravimetric analysis

Abstract

ABSTRACT The combustion characteristics of Yangquan (YQ) and Yungang (YG) coal samples before and after exposure to microwave radiation were studied using the non-isothermal thermogravimetric method, and the combustion rules of pulverized coal before and after microwave exposure to radiation were investigated. The results show that after microwave modification the ignition temperature (T i), burnout temperature (T j) and the temperature of maximum combustion rate (T k) of coal sample were all reduced about 10-20°C and the burnout time was shortened by 1–2 min, indicating that the provided treatment effectively improved the combustion performance of the pulverized coal. The characteristic indices C and S of the modified coal samples increased at a high heating rate (20°C/min), which suggests that the microwave modification has a stronger effect on the combustion performance of coal samples at high heating rates. As per the FT-IR spectrum curve, the absorption peak intensity of the higher activity group in the coal sample increased significantly after microwave modification. A comprehensive VR model was employed to model the kinetics of the coal combustion process. The resultant model had a correlation coefficient (R 2) of above 0.999 and root means square error (RMSE) of less than 0.018%, which indicating that the combustion behavior of the pulverized coal can be well described using the VR model. The activation energies E 1 and E 2 of M-YQ and M-YG modified via microwave treatment were decreased by 3.12 kJ·mol−1, 1.02 kJ·mol−1, 4.55 kJ·mol−1, and 8.14 kJ·mol−1 respectively, which further demonstrates that the microwave radiation can effectively accelerate reaction rate of the coal combustion per unit time.