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Outline
To study the adsorption and diffusion laws of CH4 and CO2 in the coal molecular structure model, the adsorption and diffusion processes of CH4 and CO2 in the coal molecular structure model under different temperatures, pressures and moisture contents were analyzed using the grand canonical ensemble Monte Carlo method and molecular dynamics simulation method. The results show that with increasing temperature or moisture content, the adsorption capacity of CH4 and CO2 decreases to a certain extent, while the adsorption and diffusion capacity of CO2 is better than that of CH4. With increasing pressure, the adsorption capacity of the two gases increases, but it tends to saturate, exhibiting typical saturated adsorption characteristics. The Langmuir fitting results show that the increase of temperature or moisture content leads to the decrease of adsorption parameters a and b, and the parameter value of CO2 is always higher than that of CH4, indicating that CO2 and coal show higher adsorption affinity. The increase of temperature can significantly enhance the kinetic energy of the two gas molecules and reduce their local enrichment in the coal molecular structure model, thus improving the diffusion performance. The mean square displacement of CO2 at each temperature is greater than that of CH4, indicating that the diffusion ability of CO2 is stronger and the spatial distribution is more uniform. With increasing moisture content, the average mass density of the two gases in the coal molecular structure model decreases. Although the presence of water molecules does not change the overall trend of the gas adsorption curve, the adsorption saturation point of the gas is significantly reduced. The high moisture content condition (6.55%) will significantly inhibit the gas diffusion behavior. Water molecules fill the pores and interact with coal molecules, resulting in restricted gas diffusion paths, weakening the degree of gas migration, and limiting the gas diffusion rate. The diffusion coefficients of CH4 and CO2 decrease to 0.063×10-8 m2/s and 1.33×10-8 m2/s, respectively. The research results provide a theoretical basis for improving coalbed methane recovery rate and optimizing CO2 sequestration strategy.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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