煤表面非均匀势阱吸附甲烷特性数值模拟
Numerical simulation on the methane adsorption characteristics of coal with non-uniform potential well
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摘要: 利用蒙特卡洛方法建立了煤与甲烷吸附动力学的数值模型,并对两种非均匀势阱煤样模型的吸附甲烷过程进行计算,分析其在不同温度与吸附压力下吸附甲烷特性以及吸附热的变化规律。研究表明:非均匀势阱煤样模型等温吸附过程与理想朗格缪尔曲线有明显不同,等压吸附过程可利用负指数规律精确描述。煤样模型势阱深度分布的非均匀特征对煤与甲烷吸附热,以及吸附量对于温度和压力的敏感性均有一定影响。通过对不同吸附压力下吸附速率参数b的拟合计算,推导出非均匀势阱等温吸附方程,物理实验验证表明该方程对真实煤样吸附解吸甲烷过程的描述比理想朗格缪尔方程更加精确。Abstract: The kinetics numerical model of methane adsorption in coal was established based on Monte Carlo method, the methane adsorption processes of two kinds of coal models with non-uniform adsorption potential well were calculat- ed,and the methane adsorption characteristics and the variation of adsorption heat under different temperatures and ad- sorption pressures were analyzed. Results show that the isothermal adsorption processes of coal sample models with non-uniform potential well are different from ideal Langmuir curves,and the isobaric adsorption processes can be accu- rately described by negative exponential decay law. The non-uniform distribution characteristics of potential well of coal sample models have effect on the variation of adsorption heat and the sensitivity of adsorption capacity to temperature and adsorption pressure. By curve fitting on adsorption pressure rate b under different adsorption pressures,the iso- therm adsorption equation of non-uniform well is derived. From the physical experiment,it is verified that the isotherm adsorption equation of non-uniform well can provide more accurate description on the processes of methane adsorption in coal than the ideal Langmuir equation.