Coal spontaneous combustion (CSC) derives from the exothermic coal-oxygen reaction occurring at coal's surface. However, methane's influence on this process is still unclear in gob environments. To this end, non-isothermal experiments were performed to elucidate methane's impact on the exothermic effect, pore structure evolvement, and surface composite variation in CSC. Our findings indicated that methane inhibited the exothermic effect; however, low methane (<42.9 %) did not significantly reduce the danger of CSC, but increased methane explosion risk. Methane's influence on pore structure can be elevated by a higher temperature, leading to larger pores, greater surface area, and higher pore volumes. X-ray photoelectron spectroscopic analysis revealed an increase in C1s, C-C and C-H bonds with rising methane and a decrease in O1s and oxygen-containing groups. C-O groups were the main structures affected by methane. O1s and oxygen-containing groups remained stable at low (<20 %) and high (>50 %) methane concentrations, because coal lay in oxygen-rich and fuel-rich oxidation states, respectively. Methane's influence on exothermic reaction originates from competitive adsorption. Methane competes with oxygen and other gases for adsorption sites. This changes the surface properties and affects the competitive adsorption between methane and other gases. This study can provide valuable insights for mitigating CSC risk.

中文翻译：

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采空区煤自燃过程中煤与氧气受甲烷影响的表面放热反应的发展


煤自燃（CSC）源自煤表面发生的放热煤-氧反应。然而，在采空区环境中，甲烷对这一过程的影响仍不清楚。为此，进行了非等温实验来阐明甲烷对 CSC 放热效应、孔隙结构演变和表面复合变化的影响。我们的研究结果表明，甲烷抑制了放热效应；然而，低甲烷含量（<42.9%）并没有显着降低CSC的危险性，反而增加了甲烷爆炸的风险。较高的温度会增强甲烷对孔隙结构的影响，从而导致更大的孔隙、更大的表面积和更高的孔隙体积。 X射线光电子能谱分析显示，随着甲烷含量的增加，C1、CC和CH键增加，而O1和含氧基团减少。 CO基团是受甲烷影响的主要结构。 O1 和含氧基团在低 (<20 %) 和高 (>50 %) 甲烷浓度下保持稳定，因为煤分别处于富氧和富燃料氧化态。甲烷对放热反应的影响源于竞争吸附。甲烷与氧气和其他气体竞争吸附位点。这会改变表面特性并影响甲烷和其他气体之间的竞争吸附。这项研究可以为降低 CSC 风险提供有价值的见解。