title: Selective Adsorption and Selective Transport Diffusion of CO2-CH4 Binary Mixture in Coal Ultramicropores.
abstract: The adsorption and diffusion of the CO2-CH4 mixture in coal and the underlying mechanisms significantly affect the design and operation of any CO2-enhanced coal-bed methane recovery (CO2-ECBM) project. In this study, bituminous coal was fabricated based on the Wiser molecular model and its ultramicroporous parameters were evaluated; molecular simulations were established through Grand Canonical Monte Carlo (GCMC) and Molecular Dynamic (MD) methods to study the effects of temperature, pressure, and species bulk mole fraction on the adsorption isotherms, adsorption selectivity, three distinct diffusion coefficients, and diffusivity selectivity of the binary mixture in the coal ultramicropores. It turns out that the absolute adsorption amount of each species in the mixture decreases as temperature increases, but increases as its own bulk mole fraction increases. The self-, corrected, and transport diffusion coefficients of pure CO2 and pure CH4 all increase as temperature or/and their own bulk mole fractions increase. Compared to CH4, the adsorption and diffusion of CO2 are preferential in the coal ultramicropores. Adsorption selectivity and diffusivity selectivity were simultaneously employed to reveal that the optimal injection depth for CO2-ECBM is 800-1000 m at 308-323 K temperature and 8.0-10.0 MPa.
authors: School of Energy and Environmental Engineering, University of Science and Technology Beijing , Beijing 100083, China.|State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University , Xi'an 710049, China.
authors: Yongliang
authors: Y
authors: Zhao
authors: School of Energy and Environmental Engineering, University of Science and Technology Beijing , Beijing 100083, China.|Beijing Key Laboratory of Energy Saving and Emission Reduction for Metallurgical Industry, University of Science and Technology Beijing , Beijing 100083, China.
authors: Yanhui
authors: Y
authors: Feng
authors: School of Energy and Environmental Engineering, University of Science and Technology Beijing , Beijing 100083, China.|Beijing Key Laboratory of Energy Saving and Emission Reduction for Metallurgical Industry, University of Science and Technology Beijing , Beijing 100083, China.
authors: Xinxin
authors: X
authors: Zhang
mesh_terms: D000327:Adsorption; D002245:Carbon Dioxide; D003031:Coal; D004058:Diffusion; D008697:Methane
chemical_list: D003031:Coal; D002245:Carbon Dioxide; D008697:Methane