Role of moisture content in coal oxidation during the spontaneous combustion latency

Abstract

The role of moisture content in coal oxidation during the spontaneous combustion latency was studied by an isothermal flow reactor. The physical and chemical changes during the drying and oxidation process were investigated using low-pressure nitrogen gas adsorption (LP-N2GA) experiments, Electron spin resonance (ESR) experiments and X-ray photoelectron spectroscopy (XPS) experiments. Experimental results reveal that moisture acts either as a promoting or an inhibiting agent under different contents. The differences in total temperature rise (TTR) of varying coal samples are the result of a complex set of competing factors. The LP-N2GA experiments reveal no pore collapse until the moisture reaches 3.05 %. Collapse clearly occurs with the micropore and mesoporous size range. When the moisture content is higher 3.05 %, the specific surface and pore volume increases with the removal of moisture. In addition, the evaporation of water also re-exposes the previously covered active sites and increases the concentration of free radicals. However, the removal of moisture makes the generation of peroxides more difficult due to moisture acts as a catalyst in the formation of such peroxide species.