Kinetics of oxidation and spontaneous combustion of major super-thick coal seam in Eastern Junggar Coalfield, Xinjiang, China

Abstract

In this study, the kinetics of a major coal seam oxidation which was collected from the Eastern Junggar coalfield of China, were investigated by programmed heating experiments and the thermo-gravimetric analysis (TGA) as well as the chemical thermodynamic tool FACTSage. Results show that the change of O2 consumption rate, CO and CO2 generation rate in process of coal oxidation are coincident with the content changes of fixed carbon, volatile, and sulfur but differ from those of ash and moisture contents. From results of TGA, the characteristic temperatures, i.e., the dehydration-oxygen-adsorption temperature T1, the pyrolysis temperature T2, the ignition temperature T3, the maximum combustion-rate temperature T4, and the burnout temperature T5, were calculated. The T3, T4, and T5 exhibit a similar variation tendency. It was found that the pyrolysis temperature T2 was easier reached by the coal sample collected from Xiheishan Mining area compared to those from other two mining areas. It also shows that the effect of particle size on characteristic temperatures are lightly different: T1 remained almost unchanged, T2 and T3 decreased, while T4 and T5 demonstrated an initial growth followed by a drop and a further rise. At the T2-T4 stage, the sample size is positively correlates with its reaction activation energy. Meanwhile, results also show the CO2 and CO are the major gaseous products in coal oxidation process, and some trace elements compounds are also produced at different stages of temperature. Therefore, these compounds prosed the possibility to indicate consequent stage of coal oxidation stages.