Study on the Re-ignition Characteristics of High-Temperature Oxidization & Water Immersion Long-Flame Coal at Different Heating Rates

Abstract

ABSTRACT The water immersion residual coal tend to happen spontaneous combustion accidents after mining the coal seam. For exploring the oxidative re-ignition properties of high-temperature oxidized water-impregnated long-flame coal, the thermal evolution law toward each pre-oxidized coal soaked in water under varying heating rates (Rh) (5, 10, 15°C/min) has been analyzed by thermogravimetric differential scanning calorimetry (TG-DSC). The findings are as follows: the DTG at the critical temperature (T1) and maximum weight loss temperature (T5) increases, the activation energy (E) decreases, and the heat output increases (maximum 6391J/g) with the rising Rh. The violent oxidated reaction process of coal samples has been delayed as the Rh was 10°C/min. The water-immersed coal sample (I200) contains more free water on the surface, and the maximum (0.45 mW/mg) and total (178.8 J/g) heat absorption of are higher. Oxidation at 200°C and soaking in water (O200I200) reduced the ignition point temperature (minimum 399°C) and E (minimum 18.5 kJ/mol), and increased the total heat release (maximum 323 J/g) making it easier to oxidize and re-ignite. Under the same Rh, the oxidation and combustion traits of each pre-oxidized water-immersed coal (PWIC) remained unchanged. Reducing the Rh can effectively prevent spontaneous combustion of high-temperature oxidized water-soaked coal in shallow-buried and short-distance coal seams in northwest of China.