Characteristics of microscopic pore structure and fractal dimension of bituminous coal by cyclic gas adsorption/desorption: An experimental study

Wang, Zhenyang; Wang, Chenghao; Zhang, Kaizhong; Chen, Hao; Wang, Liang; Li, Wenyuan; Hu, Biao

doi:10.1016/j.fuel.2018.06.004

Cited by 84 publications

(45 citation statements)

References 37 publications

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“…The micro-, meso-, and macropore PV and SSA values increase after the methane adsorption (Figures 10 and 11), especially those for mesopores. The increase of PV may be relative to a transformation of the closed pores in the coal under the repetitively increased test pressure (Wang et al., 2018).…”

Section: Resultsmentioning

confidence: 99%

Isothermal characteristics of methane adsorption and changes in the pore structure before and after methane adsorption with high-rank coal

Wang

2020

Energy Exploration & Exploitation

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The pore structure is an essential factor that influences the isothermal characteristics of methane adsorption of coal, and the pore structure is altered after methane adsorption. In this study, a high-rank coal sample was investigated via methane adsorption isothermal measurement, and changes in the pore structure were studied using low-pressure N2 adsorption and low-pressure CO2 adsorption before and after the methane adsorption. The excess adsorption capacity exhibits a rapid increase at low pressure, reaching a maximum when the test pressure is approximately 8 MPa. Following that, the excess adsorption capacity of the high-rank coal tends to decrease. After the methane adsorption, the pore volume and specific surface area of the micro-, meso-, and macropores increase as compared to those before the methane adsorption, especially for micropores with apertures greater than 0.8 nm and mesopores with apertures below 10 nm. This is mainly caused by high pressure in the methane adsorption, indicating a pressure effect on the pore structure after the methane adsorption. After the methane adsorption, the ratio of pores with various sizes in the high-rank coal is enhanced, but the connectivity for meso- and macropores presents a slight decrease.

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Section: Resultsmentioning

confidence: 99%

Isothermal characteristics of methane adsorption and changes in the pore structure before and after methane adsorption with high-rank coal

Wang

2020

Energy Exploration & Exploitation

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“…To further characterize the high nonlinearity and disorder of these microfractures, fractal theory is introduced to calculate the structural parameters in this study. In previous studies, different fractal dimensions were calculated based on N 2 /CO 2 adsorption curve, mercury intrusion porosimetry as above mentioned, NMR and 2D or 3D pore‐fracture network data to characterize surface roughness, size distribution, and transport and adsorption capabilities (Z. Wang et al., 2018; Yao et al., 2008; Zheng et al., 2018; H. W. Zhou et al., 2018; S. Zhou et al., 2017). Yu and Cheng (2002) believed that TS images of both rocks and soils provide the actual morphology and interaction of flow channels.…”

Section: Materials and Methodologymentioning

confidence: 99%

Microstructure Analysis on the Fracture Network in High‐Rank Coals

Lyu

Chen

Li³

et al. 2021

Earth and Space Science

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Microfractures in the coal matrix have complex spatial structure because of the joint effects of coalification and tectonism. The accurate modeling and characterization of microfractures directly affect mechanism analysis of coal rock fracturing and mining. In this study, taking the high-rank coal in the north of Qinshui Basin, structural characteristics of microfracture in intact and tectonic coals were analyzed systematically using 2D thin section, 3D micro-CT modeling and mercury intrusion based on digital image analysis and fractal theory. Result indicates that response sensitivity of fractal parameters obtained from different methods to microfractures from two types of coal structures is different greatly. Single fractal dimension (Df) in tectonic coal is higher than that of intact coal. Specially, for 2D thin sections, the indicative effect on the Df of manually-corrected images is better than that of automaticallyextracted and linear ones. Df has a positive correlation with the pixel-based microfracture porosity, as well as generalized fractal parameters. Moreover, microfracture permeability based on the Cubic-Law increases with the increase of Df. For 3D micro-CT modeling, the classical Watershed algorithm cannot segment the spatial microfracture network, which however can be segmented and characterized by the self-developed FracSC3D program. Spatial microstructural parameters including volume, surface and length at three-axis directions meet bi-fractal characteristics.Specially, for 2D micro-CT slices, with the increase of porosity, the multifractal spectrum width Δα also increased.

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“…Gaseous CO 2 continues to infiltrate under pressure and a difference in concentration. Numerous studies have shown that 80%-90% of gas is in an adsorbed state under identical conditions [31] and that the adsorption capacity of CO 2 in a coal matrix is higher than that of CH 4 , leading to competitive adsorption between them [32]. Subsequently, the partial pressure of CO 2 entering the adsorption site of the coal matrix increases from the transport force, and with the transformation stress of liquid CO 2 , thereby lowering the partial pressure of the CH 4 , the adsorption-desorption equilibrium of the gas components inside the coal matrix is destroyed.…”

Section: Displacement Effect Of Liquid Comentioning

confidence: 99%

Gas Displacement Engineering Test by Combination of Low and Medium Pressure Injection with Liquid CO2 in High Gas and Low Permeability Coal Seam

et al. 2020

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Mining high-gas coal seams in China has the characteristics mining of deep, high storage and low permeability, and low drainage efficiency, which seriously restrict the efficient prevention and control of mine gas disasters. Based on the characteristics of low viscosity and permeability, phase change pressurization, and strong adsorption potential energy of liquid CO2, the technology system of liquid CO2 displacement for high-gas and low-permeability coal seam was developed, and field industrial of low-pressure (0.5~2.5 MPa) and medium-pressure (2.5~15.0 MPa) combined injection test was carried out. In this test, the mode of injection followed by drainage was adopted, and the gas drainage effect was investigated for 30 days. The test results show that the effective influence radius of CO2 in this test is 20 m, and the liquid seepage radius is 5 to 7 m. After the injection of liquid CO2 into coal seam, the average gas drainage concentration and drainage purity of all drainage holes were increased by 3.2 and 3.4 times, respectively, and the gas promotion effect was significant. Taking the liquid CO2 low-medium-pressure displacement gas test area as the calculation unit, from the comprehensive benefit analysis, compared with the original drainage mode, the liquid CO2-combined pressure injection process can save 34.7% of the engineering cost and shorten the gas drainage standard time by 45.9%. Therefore, the application of this technology has important technical support and reference significance for the efficient management of gas in the same type of mine.

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Characteristics of microscopic pore structure and fractal dimension of bituminous coal by cyclic gas adsorption/desorption: An experimental study

Cited by 84 publications

References 37 publications

Isothermal characteristics of methane adsorption and changes in the pore structure before and after methane adsorption with high-rank coal

Isothermal characteristics of methane adsorption and changes in the pore structure before and after methane adsorption with high-rank coal

Microstructure Analysis on the Fracture Network in High‐Rank Coals

Gas Displacement Engineering Test by Combination of Low and Medium Pressure Injection with Liquid CO2 in High Gas and Low Permeability Coal Seam

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