基于蒙特卡洛方法的无烟煤中甲烷分子吸附量模拟研究

Molecular simulation of methane adsorption amount in anthracite coal based on Monte Carlo method

瓦斯压力、温度和含水率对煤中瓦斯吸附量具有重要影响,从微观角度进行无烟煤中甲烷分子吸附量研究对准确测定煤层原始瓦斯含量、防治瓦斯灾害、保障煤矿安全生产以及开发利用煤层气能源具有重要意义.本文以山西红旗一坑无烟煤为研究对象,构建了无烟煤大分子结构模型,采用巨正则系综蒙特卡洛方法(GCMC),通过288~308 K下对甲烷分子吸附热计算,验证了模型有效性,据此分析了瓦斯压力、温度和含水率对无烟煤中甲烷分子吸附量影响规律.研究结果表明:(1)温度和含水率一定时,随瓦斯压力增加,无烟煤中甲烷分子吸附量与Langmuir吸附模型一致;(2)含水率和瓦斯压力不变条件下,无烟煤中甲烷分子吸附量随温度升高线性减少,瓦斯压力在0.01~8 MPa范围内,随着瓦斯压力增加,温度对无烟煤中甲烷分子吸附量影响程度先减小后增大;(3)含水率在0~6.494%范围内,无烟煤中甲烷分子吸附量随含水率增加线性减少.

In view of the significant effect of gas pressure,temperature and moisture content on gas adsorption amount in coal,the research on the methane adsorption amount of anthracite coal from micro aspect is of great importance for accurate determination of primitive gas content of coal seam,prevention and control of gas disaster,safety production of coalmines and development and utilization of coal bed methane energy.In this paper,taken the anthracite coal samples produced from Hongqi-one pit in Shanxi Province as research systems,the macromolecular structure model of anthracite coal was constructed,the adsorption heat of methane molecules at 288~308 K was calculated using the grand canonical Monte Carlo（GCMC） method,and the effectiveness of models was verified.Based on the above studies,the effect of gas pressure,temperature and moisture content on gas adsorption amount in anthracite was analyzed,and the detailed conclusions are as follows.（1） Under the condition of constant temperature and water content,the adsorption of the methane molecule in anthracite is satisfied with the Langmuir adsorption model with the increase of gas pressure;（2） Under the condition of constant water content and gas pressure,the adsorption amount of methane molecule decreases linearly with the increase of temperature.The influence rank of temperature on the adsorption amount of methane in anthracite is firstly decreased and then increased with the increase of gas pressure in the range of 0.01~8 MPa;（3） when the moisture content is within the range of 0~6.494%,the adsorption amount of coal methane decreases linearly with the increase of water content.