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构造煤质量占比对CH4吸附热力学特征参数演化规律的影响研究

Evolution mechanism of thermodynamic characteristic parameters of CH4 adsorption influenced by structural coal quality ratio

  • 摘要: 随着我国煤层开采深度不断增加,煤与瓦斯突出事故后果日趋严重,对矿井安全生产威胁巨大。构造煤是易发生突出的主要煤样类型之一,突出规律及现象随构造煤质量比有明显变化。为探究不同质量比构造煤瓦斯吸附过程中的热力学机理,采用PCT-C80吸附量热联用仪开展基于混合煤样的瓦斯等温吸附及量热测试试验,从热力学角度建立吸附焓、Gibbs自由能、瓦斯吸附熵计算模型。结合试验与计算结果,分别讨论不同质量比构造煤吸附量与吸附热、瓦斯吸附常数与构造煤占比的关系,分析不同质量比构造煤瓦斯吸附焓、表面自由能与吸附熵的变化规律。结果表明:不同质量比构造煤的瓦斯吸附热随着吸附量的不断增大而增大;吸附热与吸附常数a均随着构造煤质量比的增加呈现先增大后减小的趋势,吸附常数b呈现相反的变化规律;随着构造煤质量比的增加,瓦斯吸附热、吸附焓、吸附熵均呈现先增大后减小的趋势,且均在构造煤质量比为50%时达到最大值,而Gibbs自由能呈现相反的变化规律;根据试验结果与拟合公式,归纳出混合煤体吸附瓦斯吸附热力学参数与瓦斯涌出量的数学关系。通过研究得到构造煤质量比影响下的瓦斯吸附热力学特征参数变化规律,揭示混合煤样的热力学作用机制,为明晰开采扰动构造煤体致诱煤与瓦斯突出机制提供了参考。

     

    Abstract: With the increasing depth of coal seam mining in China, the consequences of coal and gas outburst accidents are becoming more and more serious, which poses a great threat to mine safety production. Tectonic coal is one of the main coal sample types prone to outburst, and the outburst law and phenomenon change obviously with the proportion of tectonic coal quality. In order to explore the thermodynamic mechanism of gas adsorption in structured coal with different mass ratios, PCT-C80 adsorption calorimeter was used to carry out gas isothermal adsorption and calorimetric test based on mixed coal samples, and the calculation models of adsorption enthalpy, Gibbs free energy and gas adsorption entropy were established from the thermodynamic point of view. Based on the test and calculation results, the relationships between adsorption capacity and adsorption heat, gas adsorption constant and the proportion of structural coal with different mass ratios are discussed respectively, and the variation laws of gas adsorption enthalpy, surface free energy and adsorption entropy of structural coal with different mass ratios are analyzed. The results show thatthe gas adsorption heat of structural coals with different mass ratios increases with the increase of adsorption capacity; The adsorption heat and adsorption constant A both increase first and then decrease with the increase of structural coal mass ratio, and the adsorption constant B shows the opposite change law. With the increase of the ratio of structural coal, the gas adsorption heat, adsorption enthalpy and adsorption entropy all increase at first and then decrease, and all reaching the maximum when the proportion of structural coal is 50%, while Gibbs free energy shows the opposite change law; According to the test results and fitting formula, the mathematical relationship between the thermodynamic parameters of gas adsorption and gas emission in mixed coal is summarized. Through the above research, the variation law of thermodynamic characteristic parameters of gas adsorption under the influence of structural coal ratio is obtained, and the thermodynamic action mechanism of mixed coal samples is revealed, which provides a certain theoretical basis for clarifying the mechanism of coal induction and gas outburst caused by mining disturbed structural coal.

     

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