Characteristics of mass, heat and gaseous products during coal spontaneous combustion using TG/DSC–FTIR technologyThe impacts of oxygen concentrations and heating rates

Spontaneous combustion, if not eradicated immediately, may lead to coal ignition and even a full-blown fire. An understanding of the characteristics of coal oxidation under various environmental conditions is conducive to the reveal of the mechanism and the prevention of coal spontaneous combustion. TG/DSC–FTIR coupling technology was employed to investigate the evolutions of coal mass, heat and gaseous products during coal spontaneous combustion. The experiments conclude that the mass loss rate in Combustion Stage was much higher than other stages and the major of coal mass (over 80%) was consumed at this stage. As the oxygen concentration decreased, the combustion of coal was evidently postponed and the exothermic region shifted to a higher temperature. Correspondingly, the temperatures at which productions of CO and CO2 reached to the maximum were deferred as well. Experimental results also indicated that heating rates behaved differently before and after the ignition temperature. The mass loss rates of coal were independent of heating rates before ignition temperatures but obviously expanded and moved to higher temperatures after exceeding the ignition temperature. Additionally, with the increase of the heating rates, the exothermic region shifted to higher temperatures and the release of CO and CO2 were delayed and reached to the maximum in a longer time.