Thermal decomposition of selected coal gangue

Abstract

The thermal behavior of two mineral-type coal gangues under different temperature conditions was investigated by heating treatment of kaolinite-type coal gangue and illite-type coal gangue based on thermal analysis, X-ray diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). Thermogravimetric, differential thermogravimetric and differential scanning calorimetry results show the thermal decomposition process of kaolinite-type coal gangue and illite-type coal gangue can be divided into three stages, thermal decomposition of kaolinite and illite clay minerals occurred in the first stage and the third stage, and thermal decomposition of carbon material in coal gangue samples occurred in the second stage. Compared with illite-type coal gangue, the volatile of kaolinite-type coal gangue is released more intensely and pyrolysis performance of kaolinite-type coal gangue was better; initial temperature of heat decomposition was lower. The XRD, IR and SEM results showed the mineral phase transformation of kaolinite-type coal gangue occurred at 500 °C, the microscopic kaolinite changed obviously and its flake and layered structure started to break, and the phase of kaolinite transformed into amorphous glassy state, which was metakaolinite. In contrast, the mineral phase transformation of illite-type coal gangue occurred at 900 °C. According to the results of various research methods, it is considered that the thermal stability of kaolinite-type coal gangue is lower than that of illite-type coal gangue. This study has some theoretical significance for the rational use of coal gangue to produce highly activity powder materials.