Effects of nano-pore system characteristics on CH4 adsorption capacity in anthracite

This study aims to determine the effects of nanoscale pores system characteristics on CH4 adsorption capacity in anthracite. A total of 24 coal samples from the southern Sichuan Basin, China, were examined systemically using coal maceral analysis, vitrinite reflectance tests, proximate analysis, ult...

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Bibliographic Details
Published in:Frontiers of earth science 2019-03, Vol.13 (1), p.75-91
Main Authors: Shan, Chang’an, Zhang, Tingshan, Liang, Xing, Shu, Dongchu, Zhang, Zhao, Wei, Xiangfeng, Zhang, Kun, Feng, Xuliang, Zhu, Haihua, Wang, Shengtao, Chen, Yue
Format: Article
Language:English
Subjects:
Adsorption
Analysis
Anthracite
Bound water
Capacity
Coal
Earth and Environmental Science
Earth Sciences
Low temperature
Magnetic permeability
Magnetic resonance
Methane
NMR
Nuclear magnetic resonance
Permeability
Pore size
Pores
Porosity
Reflectance
Research Article
Saturation
Seepage
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Summary:This study aims to determine the effects of nanoscale pores system characteristics on CH4 adsorption capacity in anthracite. A total of 24 coal samples from the southern Sichuan Basin, China, were examined systemically using coal maceral analysis, vitrinite reflectance tests, proximate analysis, ultimate analysis, low-temperature N 2 adsorption–desorption experiments, nuclear magnetic resonance (NMR) analysis, and CH 4 isotherm adsorption experiments. Results show that nano-pores are divided into four types on the basis of pore size ranges: super micropores (< 4 nm), micropores (4–10 nm), mesopores (10–100 nm), and macropores (> 100 nm). Super micropores, micropores, and mesopores make up the bulk of coal porosity, providing extremely large adsorption space with large internal surface area. This leads us to the conclusion that the threshold of pore diameter between adsorption pores and seepage pores is 100 nm. The “ink bottle” pores have the largest CH4 adsorption capacity, followed by semi-opened pores, whereas opened pores have the smallest CH 4 adsorption capacity which indicates that anthracite pores with more irregular shapes possess higher CH 4 adsorption capacity. CH 4 adsorption capacity increased with the increase in NMR porosity and the bound water saturation. Moreover, CH 4 adsorption capacity is positively correlated with NMR permeability when NMR permeability is less than 8 × 10 –3 md. By contrast, the two factors are negatively correlated when NMR permeability is greater than 8 × 10 –3 md.
ISSN:2095-0195
2095-0209
DOI:10.1007/s11707-018-0712-1