Evaluation of the spontaneous combustion of soaked coal based on a temperature-programmed test system and in-situ FTIR

To explore the influence of long-term water immersion on the spontaneous combustion characteristics of coal, temperature-programmed test system and In-situ Fourier transform infrared spectroscopy (In-situ FTIR) were used. Differences in gas production of soaked coal and raw coal showed that the process of long-term water immersion played a different role before and after critical temperature. In the stage of surface oxidation, moisture could inhibit the spontaneous combustion of coal, when the critical temperature point was exceeded, it played a promoting role instead. As an explanation in support of the above arguments, the relative contents of active functional groups in raw and soaked coal were compared, which indicated that the process of water immersion could affect relative contents of hydroxyl, aromatic hydrocarbon, aliphatic hydrocarbon and oxygencontaining functional groups, giving rise to an acceleration in the reaction process of coal oxygen and exhibiting higher tendencies toward spontaneous combustion. A practical consequence of this finding is the soaking mechanism should not be neglected in any precautionary or preventive measures to avoid potential spontaneous combustion in overlying goaf of shallowly buried and close distance coal seams.

Automated summary

The study found that long-term water immersion can affect the spontaneous combustion characteristics of coal. Moisture plays a role in either inhibiting or promoting spontaneous combustion at different stages, depending on whether the critical temperature point is exceeded. Additionally, the water immersion process has an impact on the relative contents of active functional groups in coal, accelerating the coal oxygen reaction process and increasing the likelihood of spontaneous combustion.