基于分子模拟方法的温度对软硬无烟煤吸附甲烷特性的影响研究

Influence of temperature on methane adsorption characteristics of soft and hard anthracite based on molecular simulation method

以软、硬无烟煤为研究对象,基于分子模拟技术建立了煤大分子结构模型,模拟了293.15~333.15 K条件下4组煤样的甲烷吸附情况,据此分析了温度对无烟煤吸附参数的影响差异,计算了4组煤样的吸附热,进一步分析了温度效应下煤层瓦斯含量计算方程。结果表明:随着温度的升高,软、硬无烟煤的Langmuir体积不断降低而Langmuir压力呈上升趋势,其中4组煤样的Langmuir体积在30~40℃条件下变化最敏感,软煤的Langmuir压力受温度影响更显著;4组煤样的吸附热均在15 kJ/mol左右,研究发现煤大分子超晶胞结构模型研究软、硬无烟煤的甲烷吸附特性是可行的,并且软煤的吸附热高于硬煤;软、硬无烟煤的温度影响系数与温度均可用指数方程表征,其中温度影响程度系数n与甲烷压力的关系满足幂函数形式,同时软媒的温度影响系数小于硬煤,温度对软煤的瓦斯吸附量影响更突出。

As coal mining extends to the deep,the influence of stratum temperature on coal gas adsorption performance cannot be ignored.In this paper,soft and hard anthracite are taken as the research object,and the macromolecular structure model of coal is established based on molecular simulation technology.The methane adsorption of four groups of coal samples at 293.15-333.15 K is simulated.Based on this,the influence difference of temperature on the adsorption parameters of anthracite is analyzed,and the adsorption heat of four groups of coal samples is calculated.The calculation equation of coal seam gas content under temperature effect is further analyzed.The results show that with the increase of temperature,the Langmuir volume of soft and hard anthracite decreases continuously while the Langmuir pressure increases.The Langmuir volume of the four groups of coal samples changes most sensitively at 30-40℃,and the Langmuir pressure of soft coal is more significantly affected by temperature.The adsorption heat of the four groups of coal samples is about 15 kJ/mol.It is found that it is feasible to study the methane adsorption characteristics of soft and hard anthracite by using the super crystal cell structure model of coal macromolecules,and the adsorption heat of soft coal is higher than that of hard coal.Both the temperature influence coefficient and temperature of soft and hard anthracite can be characterized by exponential equation,in which the relationship between the temperature influence degree coefficient n and methane pressure satisfies the form of power function.Meanwhile,if the temperature influence coefficient of soft medium is smaller than that of hard coal,the influence of temperature on the gas adsorption capacity of soft coal is more prominent.