Experimental investigation of methane content on the oxidation characteristics and spontaneous combustion limit parameters of coal

Abstract

ABSTRACT The methane contained in a coal seam is closely related to the oxidative properties of the coal and serves as an important basis for accurately evaluating the coal spontaneous combustion (CSC) behavior. In this paper, programmed temperature rise experiments were conducted on three coal samples with different methane contents. The sensitivity of oxidation products, olefin products, and their production rates to methane content were investigated. Also, the contribution made by methane content to the characteristic temperature point and CSC limit parameters were qualitatively assessed. When the methane content is 2.7 cm3/g, 4.5 cm3/g, and 6.8 cm3/g, the critical temperatures (CT) are 70°C, 80°C, and 100°C, respectively, and the dry cracking temperatures (DCT) are 100°C, 110°C, and 130°C, respectively. The higher the methane content, the greater the CT and DCT points during coal oxidation, which is because high concentration of methane will inhibit coal oxygen chemical reaction. The methane content is positively correlated with the minimum floating coal thickness (h min) and the lower limit oxygen concentration (C min), while the upper limit air leakage intensity (Q max) decreases with the increasing methane content. Coal samples with high methane content can withstand higher safe float thicknesses and oxygen concentrations and require less air leakage to carry away the heat accumulated by the residual coal in the mining area, making the CSC risk lower.