The effect of soaking in increasingly alkaline aqueous solutions on the spontaneous combustion characteristics of bituminous coal.

Summary: The spontaneous combustion characteristics of residual air‐dried coal change after soaking, which can pose a threat to coal mining safety. To study the effects of increasing alkalinity, pH values (7–11), on the spontaneous combustion characteristics of coal, we conducted a number of experiments using thermogravimetry (TG) and Fourier‐transform infrared spectroscopy (FTIR). TG was used to investigate parameters including the ignition index Di, combustion characteristic index (S), combustion intensity index (Hf), and activation energy (E) to show any variations in oxidative exothermic characteristics of coal. The results showed that the values of Di and S of the coal samples after alkaline treatment, increased with the increasing pH values. However, the values of Hf and E followed the opposite trend. To further explain the reason behind these variations, we investigated functional groups of coal using FTIR. These results indicated that the active functional groups, including oxygen‐containing functional groups, methyl and methylene groups, of the coal, increased after alkaline treatment, which showed microscopically that the coal was more active after soaking. These parameter variations together illustrate that the oxidation activity of the coal was enhanced after the alkaline treatment, and that it is more prone to spontaneous combustion. [ABSTRACT FROM AUTHOR]