不同温度和含水率条件下CH_(4)和CO_(2)吸附热力学特性的分子模拟

Molecular simulation of adsorption thermodynamic properties of CH_(4) and CO_(2) at different temperature and moisture content conditions

为了进一步明确CH_(4)和CO_(2)在煤中的吸附热力学特性,采用巨正则系综蒙特卡洛方法模拟CH_(4)和CO_(2)在不同温度、不同含水率煤中的吸附行为。结果表明:煤分子中CH_(4)/CO_(2)的吸附量随温度的升高和含水率的增加而降低,通过双组分吸附量的对比,发现高温和水分子的存在均不利于CO_(2)驱替CH_(4);CH_(4)的平均吸附热和温度、含水率呈负相关关系,CO_(2)的平均吸附热和温度呈负相关关系,和含水率呈正相关关系,水分子更倾向于和CO_(2)进行反应;CH_(4)/CO_(2)的吸附势整体和温度、含水率呈负相关关系,当压力较低时,随着温度的升高,CO_(2)的吸附势有微弱的增加;CH_(4)/CO_(2)的吸附熵随温度的升高而增加,随含水率的增加而降低,水对CO_(2)的影响要强于CH_(4),双组分注入时,水分子的存在使得整个系统更加稳定,不利于CH_(4)的产出。

In order to further clarify the adsorption thermodynamic characteristics of CH_(4)and CO_(2)in coal,the giant canonical ensemble Monte Carlo method was used to simulate the adsorption behavior of CH_(4)and CO_(2)in coal at different temperatures and different moisture content.The results show that the adsorption capacity of CH_(4)and CO_(2)in coal molecules decreases with the increasing temperature and moisture content.By comparing the adsorption amounts of the two components,it is found that both high temperature and the presence of water molecules are not conducive to displace CH_(4)by CO_(2);the average adsorption heat of CH_(4)is negatively correlated with temperature and water content,and average adsorption heat of CO_(2)has a negative correlation with temperature and a positive correlation with water content.Water molecules are more inclined to react with CO_(2);the overall adsorption potential of CH_(4)and CO_(2)is negatively correlated with temperature and moisture content.When the pressure is low,the adsorption potential of CO_(2)increases slightly with the increasing of temperature;the adsorption entropy of CH_(4)and CO_(2)increases with the increasing of temperature and decreases with the increasing of moisture content.The influence of water on CO_(2)is stronger than CH_(4).When two components are injected,the existence of water molecules makes the whole system more stable,which is not conducive to CH_(4)output.