气体吸附过程中煤比表面Gibbs函数变化规律

煤体瓦斯吸附为放热过程，解吸为吸热过程，其温度能量变化的幅度与煤的变质程度、瓦斯吸附平衡压力等有关。以往的研究都采用等温吸附实验得出气体相关吸附数据，并通过其孔隙结构、相互作用力等来分析煤吸附气体的影响因素，但是鲜有学者从比表面Gibbs函数变化角度来探讨煤吸附气体机理。为此，研究了气体吸附过程中煤比表面Gibbs函数变化的相关特征参数计算公式，利用凤凰山矿和裴沟矿两种煤样进行等温吸附实验，得到了在4个不同温度(20，30，40，50 ℃)以及6个压力(0.2，1.2，1.5，2.5，3.0，4.0 MPa)下的等温吸附实验数据，利用单层吸附和多层吸附模型分别计算出不同煤样吸附气体过程中的比表面Gibbs函数变化。研究表明:采用两种不同方式计算煤样吸附甲烷的比表面Gibbs函数，随着温度的升高比表面Gibbs函数变化量减少，随着压力的升高比表面Gibbs函数变化增加。而应用单层吸附和多层吸附计算的能量相差较大，对这种现象分析了原因;计算了气体吸附解吸过程的热量，对比分析可知采用多层BET吸附模型得出的比表面Gibbs函数变化更接近实际;探讨了气体吸附能量变化的机理，表明气体吸附能量变化影响着吸附量的变化，而能量变化又同样受到煤样微观结构以及内部化学结构的影响。因此，煤样吸附解吸是一个复杂多变的过程，可以从改变能量的角度去探讨如何影响瓦斯解吸，达到提高瓦斯抽采效果的目的。

Variation law of coal specific surface Gibbs function in gas adsorption process

The gas adsorption process of coal is an exothermic process and the desorption process is an endothermic process.The extent of temperature and energy changes is related to the degree of coal metamorphism,and the equilibrium pressure of gas adsorption,etc.The data of gas adsorption were obtained by using isothermal adsorption experiments,and the influencing factors of coal adsorption gas was analyzed through its pore structure and interaction force.However,few scholars have explored the mechanism of coal adsorbing gas from the perspective of the change of surface Gibbs function.Therefore,the calculation formulas of relevant characteristic parameters of the change of Gibbs function of coal specific surface in gas adsorption process were studied.Isothermal adsorption experiments were carried out using two coal samples from Fenghuangshan Mine and Qigou Mine in China.The data of isothermal adsorption experiment at four different temperatures (20,30,40 and 50 ℃) and six different pressures (0.2,1.2,1.5,2.5,3 and 4 MPa) were obtained.The specific surface Gibbs functions during the gas adsorption of different coal samples were calculated by using single layer adsorption and multi layer adsorption models.Studies showed that the specific surface Gibbs function of methane adsorbed on coal samples was calculated in two different ways,the change of Gibbs function of specific surface decreases with the increase of temperature and increases with the increase of pressure.The results of single layer adsorption and multi layer adsorption were quite different and this phenomenon was analyzed.The heat of the gas adsorption and desorption process was calculated.It can be seen from the calculation of heat that the specific surface Gibbs function obtained by using the multi layer BET adsorption model is closer to the actual situation.The mechanism of energy change in gas adsorption was discussed.The results show that the change of gas adsorption energy affects the change of adsorption capacity,and the change of energy is also affected by the microstructure and internal chemical structure of coal samples.Therefore,the adsorption and desorption of coal samples is a complex and changeable process.To explore how to influence gas desorption can improve the gas extraction effect from the perspective of changing energy.