The low-temperature oxidation of coal during coalbed methane extraction is inevitable. To study the evolution of the CH₄ adsorption and desorption characteristics in coal masses during the low-temperature oxidation of coal, starting from the evolution of physical and chemical adsorption of CH₄ in coal masses during the low-temperature oxidation of coal and combining it with the evolution of free radicals, we constructed a physical model of CH₄ adsorption and desorption in the coalbed methane extraction process. This model provides the theoretical basis for improving the efficiency and quantity of coalbed methane extraction. Our results indicate that during coalbed methane extraction, the mesopores, macropores, and overall porosity increase with the rise in oxidation temperature. However, the number of micropores first increases and then decreases during the process, leading to the CH₄ physical adsorption capacity showing a trend of first increasing and then decreasing with increasing oxidation temperature; however, the number of −COOH groups shows the opposite trend to that of the number of micropores, resulting in the CH₄ chemical adsorption capacity first decreasing and then increasing with the increase of the oxidation temperature; meanwhile, the free radical content increases gradually with the increasing oxidation temperature, leading to the continuous consumption of O₂ adsorbed on the coal surface and the reinforcement of the CH₄ adsorption capacity. To maximize coalbed methane extraction efficiency, it is necessary to take measures to avoid the low-temperature oxidation of coal at the initial stage.

中文翻译：

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煤层气萃取过程中煤质中CH ₄吸附解吸特性的演化规律

煤层气萃取过程中煤的低温氧化是不可避免的。为了研究煤低温氧化过程中煤团中CH _4的吸附和解吸特征的演变，从煤低温氧化过程中煤团中CH ₄的物理和化学吸附的演变开始，并结合随着自由基的进化，我们建立了CH ₄的物理模型煤层气提取过程中的吸附和解吸。该模型为提高煤层气提取效率和数量提供了理论依据。我们的结果表明，在煤层气提取过程中，中孔，大孔和总孔隙度随氧化温度的升高而增加。然而，在此过程中，微孔的数量先增加然后减少，导致CH ₄物理吸附能力呈现出随氧化温度升高先升高后降低的趋势。然而，-COOH基团的数量与微孔数量的变化趋势相反，导致CH ₄化学吸附量随氧化温度的升高先降低后升高。同时，随着氧化温度的升高，自由基含量逐渐增加，导致煤表面吸附的O ₂不断消耗，CH ₄吸附能力增强。为了使煤层气的提取效率最大化，有必要采取措施避免在初始阶段煤的低温氧化。