Molecular simulation of the preferential adsorption of CH4 and CO2 in middle-rank coal |
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Authors: | Kui Dong Jiancheng Jia Chen Chen Zewen Gong |
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Institution: | 1. China Coal Research Institute, Beijing, People's Republic of China;2. Xi’an Research Institute of China Coal Technology &3. Engineering Group Corp, Xi'an, People’s Republic of China;4. College of Mining Engineering, Taiyuan University of Technology, Taiyuan, People’s Republic of China;5. Shanxi Key Laboratory of Coal and Coal Measure Gas Geology, Taiyuan, People’s Republic of China |
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Abstract: | The adsorption of the CO2/CH4 mixture in coal affects the CO2-enhanced coalbed methane recovery project. To gain a better understanding of CH4 and CO2 interaction with middle-rank coal, we developed a molecular concept with support for the sorption of CH4 and CO2 on Ximing-8 coal (XM-8) (1.8% vitrinite reflectance). A XM-8 coal model was built by using molecular dynamic (MD) simulations. The molecular simulations were established by the Grand Canonical Monte Carlo and MD methods to study the effects of the temperature, pressure, and species bulk mole fraction on the pure component adsorption isotherms, isosteric heat and adsorption selectivity. It turns out that the CO2 selectivity decreases as the pressure and its own bulk mole fraction increases, but it increases as temperature increases, and the selectivity values are not always greater than 1. The interactions between the small molecules and XM-8 were determined by using density functional theory. It was found that the interactions between the CO2 and XM-8 surface is greater, particularly for the heteroatoms than CH4. The adsorption selectivity and interaction were simultaneously used to reveal that the advantageously substituted range is high temperature, low pressure and a high content of heteroatoms. |
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Keywords: | Methane carbon dioxide XM-8 model binary mixtures DFT |
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