Abstract:

In order to prevent and control the spontaneous combustion of residual coal in alkaline coal mines, the effect of coal particle size on coal oxidation self-ignition in an alkaline environment had been explored. Through water quality tests and Fourier-transform infrared spectroscopy (FTIR) tests, the microstructural changes of coal with different particle sizes soaked in alkaline solution were analyzed and judged. The oxidation kinetics of coals with varying particle sizes soaked in alkaline solutions had been investigated through programmed heating experiments and calculations of apparent activation energy. The results show that during the process of soaking coal particles of varying sizes in an alkaline solution, the redox potential (ORP) and total dissolved solids (TDS) exhibit significant changes as soaking time increases, the content of active functional groups in the coal increases, the coal samples with a particle size of 0-1 mm exhibit significantly higher levels of active functional groups compared to the other test groups. After soaking in an alkaline solution, coal samples with smaller particle sizes exhibit lower apparent activation energy. As particle size decreases, the amount of oxygen consumed during oxidation increases, enhancing the oxidation capacity. Consequently, the quantities of CH₄, and C₂H₆ gases released in the later stages of oxidation also progressively rise. In an alkaline environment, smaller coal particle sizes experience more severe erosion. The lower the energy barrier that must be overcome for oxidation, the more intense the coal-oxygen composite reaction becomes.

Key words: alkaline environment, different particle sizes, bituminous coal, spontaneous combustion characteristics, microscopic features