含液态水情况下碳纳米管吸附煤层气的分子动力学研究

本文采用分子动力学方法模拟研究液态水对甲烷、氮气、二氧化碳等煤层气中不同组分在煤层表面吸附性质的影响。结果表明:不含液态水时,煤层组分在碳纳米管表面的吸附能从大到小依次为CO2>CH4>N2;当含液态水时,煤层组分的吸附能大小顺序变为N2>CH4>CO2>H2O。模拟中还发现,液态水存在时,碳纳米管表面首先吸附很薄一层甲烷分子,再吸附一层聚成水膜或水滴的水分子团,为剩余气体提供大量吸附位。加入氮气比加入二氧化碳更易导致碳纳米管对甲烷的吸附能降低;注入氮气和二氧化碳的混合气时,置换甲烷效果更好。

Study on Molecular Dynamics of Adsorption of CBM by Liquid Water Using Carbon Nano Tube

Using molecular dynamic method the authors make a simulation test to study the influence of liquid water on surface adsorption properties of different constituent gases,such as methane,nitrogen,carbon dioxide of CBM in the coal seam.The results showed that when there was not liquid water,the adsorption capacity of CBM gases on the surface of carbon nano-tubes,in the order of magnitude,was CO2>CH4>N2,and when there existed liquid water,the order of the adsorption capacity of gases changed into the order of N2>CH4>CO2>H2O.The simulation test also found that when there existed liquid water,the surface of nano-tubes may first absorb a very thin layer of methane molecules,and then a layer of water group,forming a layer of water film or water drops,providing large quantity of adsorption potential for the residual gases.It was easier to reduce adsorption capacity of carbon nanotubes for methane by adding nitrogen than carbon dioxide.When the mixed gas of nitrogen and carbon dioxide was injected,the result of substituring methane was even better.