TY - JOUR
T1 - Comparisons of Methane Adsorption/Desorption, Diffusion Behaviors on Intact Coals and Deformed Coals
T2 - Based on Experimental Analysis and Isosteric Heat of Adsorption
AU - Zhang, Kun
AU - Meng, Zhaoping
AU - Liu, Shimin
N1 - Funding Information:
This work was financially supported by the Shanxi Province Science and Technology Major Project (grant nos. 20201102001, 20191102001, and 20181101013), the National Science and Technology Major Project of the Ministry of Science and Technology of China during “13th Five-Year Plan” (grant 2016ZX05067001-006), The authors thank the reviewers and the editor for their constructive comments.
Publisher Copyright:
© 2021 American Chemical Society.
PY - 2021/4/1
Y1 - 2021/4/1
N2 - Isosteric heat of adsorption is a key parameter to assess the thermodynamic properties in coals for gas adsorption and migration applications. To explore the relationships between isosteric heat of adsorption and gas storage and migration in intact and deformed coals, this paper carried out the isotherms experiments of CH4, low-temperature N2, and low-pressure CO2 on four coal samples with different deformation intensities. The results show that Langmuir VL in coal was dependent on temperature and coal structures. From 25 to 45 °C, Langmuir VL in coals decreased with the increased temperatures. Adsorption heat in intact coals was higher than deformed coals, illustrating that interaction actions between gas molecules and coal atoms were more intense in intact coal, which led to the hard desorption of gas molecules from intact coal surfaces. The specific area and pore volume of ultramicropore (<2 nm) and larger pores (>2 nm) positively increased with coal deformation intensities. The diffusion coefficients of four coal structures decreased as the depressurization processes, and the diffusion coefficient of tectonic coals was higher than intact coal in the whole diffusion stages. At a pressure zone of higher than 5 MPa, 1.5-5 MPa, and lower than 1.5 MPa, gas diffusion mainly occurred in macropores, mesopres, and micropores, respectively, corresponding to Fick's, transitional, and Knudsen diffusion. Additionally, it is found that the isosteric heat of adsorption can be effectively used to predict adsorption isotherms in coals, and the high initial diffusion coefficient in deformed coals is related to the low isosteric heat of adsorption.
AB - Isosteric heat of adsorption is a key parameter to assess the thermodynamic properties in coals for gas adsorption and migration applications. To explore the relationships between isosteric heat of adsorption and gas storage and migration in intact and deformed coals, this paper carried out the isotherms experiments of CH4, low-temperature N2, and low-pressure CO2 on four coal samples with different deformation intensities. The results show that Langmuir VL in coal was dependent on temperature and coal structures. From 25 to 45 °C, Langmuir VL in coals decreased with the increased temperatures. Adsorption heat in intact coals was higher than deformed coals, illustrating that interaction actions between gas molecules and coal atoms were more intense in intact coal, which led to the hard desorption of gas molecules from intact coal surfaces. The specific area and pore volume of ultramicropore (<2 nm) and larger pores (>2 nm) positively increased with coal deformation intensities. The diffusion coefficients of four coal structures decreased as the depressurization processes, and the diffusion coefficient of tectonic coals was higher than intact coal in the whole diffusion stages. At a pressure zone of higher than 5 MPa, 1.5-5 MPa, and lower than 1.5 MPa, gas diffusion mainly occurred in macropores, mesopres, and micropores, respectively, corresponding to Fick's, transitional, and Knudsen diffusion. Additionally, it is found that the isosteric heat of adsorption can be effectively used to predict adsorption isotherms in coals, and the high initial diffusion coefficient in deformed coals is related to the low isosteric heat of adsorption.
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U2 - 10.1021/acs.energyfuels.1c00325
DO - 10.1021/acs.energyfuels.1c00325
M3 - Article
AN - SCOPUS:85103448594
SN - 0887-0624
VL - 35
SP - 5975
EP - 5987
JO - Energy and Fuels
JF - Energy and Fuels
IS - 7
ER -