Spontaneous combustion and oxidation kinetic characteristics of alkaline-water-immersed coal

Abstract

Most scholars used distilled-water-immersed coal to study the reasons why water-immersed coal was prone to self-ignition, while mine water in field was mostly alkaline. Thus, the influence of the alkalinity of mine water on the self-ignition properties of water-immersed coal was explored. Experimental results showed that during the low-temperature oxidation process, the CO productions of DL, ZX, XT alkaline-water-immersed coals were higher than that of raw coals when the temperature was increased to 392, 382, 370 K respectively. Compared with raw coals, the average apparent-activation-energies (Ea) of the distilled-water-immersed DL, ZX, XT coals decreased by 6.89%, 5.94%, 7.75%, respectively. Moreover, that of the alkaline-water-immersed coals decreased by 15.83%, 11.76%, 16.64%, respectively. The reduction in the average apparent Ea of the alkaline-water-immersed coal was approximately twice that of the distilled-water-immersed coal. Further investigation revealed that the content of oxygen-containing functional groups in alkaline-water-immersed coals were obviously more than those of the distilled-water-immersed coal. Therefore, the self-ignition ability of the alkaline-water-immersed coal was greater than distilled-water-immersed coal. Compared with the single soaking effect of pure water on coal, many physicochemical variations produced by the reactions of alkali ions with coal may be the main reason for the self-ignition of water-immersed coal.