Thermodynamic characteristics of methane adsorption about coking coal molecular with different sulfur components: Considering the influence of moisture contents

Zhu, Hongqing; Zhang, Yilong; Qu, Baolin; Liao, Qi; Wang, Haoran; Gao, Rongxiang

doi:10.1016/j.jngse.2021.104053

Cited by 22 publications

(13 citation statements)

References 43 publications

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“…Coal is an extremely complex porous medium with many pores, and the PSD ranges from the millimeter to the nanometer scale. Pores with different sizes affect the gas adsorption and desorption, gas diffusion, and gas seepage behavior, thereby affecting the permeability of the coal seam. − Numerous researchers investigated the pore structure for coal using image observations and fluid injection. Image observation methods include using image slices to obtain quantitative statistics on holes and fractures in a small field of view using electron microscope imaging techniques such as SEM, atomic force microscopy (AFM), and transmission electron microscopy (TEM). − It is worth noting that measuring accuracy is substantially affected by the mode of handling, field of view, and device resolution.…”

Section: Experiments Sectionmentioning

confidence: 99%

Experimental Study of the Influence of Moisture Content on the Pore Structure and Permeability of Anthracite Treated by Liquid Nitrogen Freeze–Thaw

Nie

Feng

et al. 2022

ACS Omega

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The liquid nitrogen freeze–thaw (LN2-FT) method has been widely used to improve the coal permeability in the coalbed methane (CBM) production. However, the influence of moisture content on the permeability of coal treated by LN2-FT remains unclear, limiting the broad application of this technique. A novel seepage system was proposed to analyze the permeability evolution of anthracite coal samples treated by LN2-FT. Moreover, variations of the pore structure were analyzed using scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), and low-field NMR. The results showed that pores and fractures appeared on the coal surface after the LN2-FT treatment. As the moisture content of the coal increased, more pores and fractures tended to be formed during the LN2-FT treatment. The total pore volume, porosity, and average pore diameter of the anthracite coal after the treatment were 1.77, 2.44, and 5.58 times higher, respectively, than that of the raw coal. The change in the specific surface area exhibited three trends as the moisture content of the coal samples increased: a slow descent, a steady increase, and a rapid descent. Moreover, it was found that the LN2-FT treatment increased the connections between pores and fractures, improving gas migration in the coal. Furthermore, the LN2-FT treatment significantly increased the permeability of the anthracite coal samples. The higher the coal moisture, the higher the permeability of the coal samples after the LN2-FT treatment. Hence, the LN2-FT technique can substantially improve the permeability of coal reservoirs, providing essential information for the efficient utilization of CBM.

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Section: Experiments Sectionmentioning

confidence: 99%

Experimental Study of the Influence of Moisture Content on the Pore Structure and Permeability of Anthracite Treated by Liquid Nitrogen Freeze–Thaw

Nie

Feng

et al. 2022

ACS Omega

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“…Coal is a complex porous medium that contains pores, fractures, and coal skeletons. The pores and fractures are unevenly distributed. − At present, experimental methods used to study the structure of pores and fractures in coal are quite diverse. The methods fall mainly into fluid injection methods and image observation methods. − To investigate the structural changes of coal samples resulting from an HVEP, the structural parameters of coal samples were analyzed by means of SEM and LN 2 -A.…”

Section: Experimental Workmentioning

confidence: 99%

Experimental Study of the Structural Damage to Coal Treated by a High-Voltage Electric Pulse Discharge in Water

Nie

Zhang

et al. 2022

Energy Fuels

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High-voltage electric pulse (HVEP) technology has been gradually adopted as an effective method in the drainage and utilization of coalbed methane (CBM) in low-permeability coal reservoirs. An experimental device was established to study the structural variation characteristics of bituminous coal samples treated by an HVEP. The structure parameters of coal samples before and after the HVEP treatment were measured using a scanning electron microscope and low-temperature nitrogen adsorption. Additionally, the current waveforms in the process of HVEP discharge were analyzed by a digital oscilloscope. The results showed that the pressure of the shockwave produced by an HVEP increased with an increase in discharge energy, which intensifies the damage effect on the coal body. Some newly generated pores and cracks appeared in the bituminous coal samples after the HVEP treatment. As the discharge energy increased, the number of pores and fractures increased, and the diameters of the pores and the widths of the fractures also gradually increased. The average pore diameter, specific surface area, and most probable pore diameter of bituminous coal samples treated by an HVEP were greater than those of the untreated coal. Furthermore, after the HVEP treatment, the fractal dimension D 1 was larger than that of raw coal, while the fractal dimension D 2 was smaller than that of raw coal. This indicates that although the pore structure in coal became more complex after an HVEP, the surfaces of the pores became smoother. These changes were unfavorable to the adsorption of gas in the coal but conducive to the diffusion and flow of gas. The combined action of the shockwave cracking effect, the cavitation vibration effect, and the effect of thermal expansion promoted the expansion and connection of micro-and macropores and fractures in the coal, improving the permeability of coal seams. The research results demonstrate that the HVEP technology can significantly alter the structural characteristics of coal deposits in a way favorable for the development of CBM.

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“… 8 Zhu et al established the adsorption isotherm of methane under different water contents, and the results showed that the presence of water led to a sharp decrease in methane adsorption. 9 Guo et al studied the influence of moisture on the adsorption characteristics of low-rank coal and found that moisture obviously inhibited the gas adsorption capacity of low-rank coal and that the inhibition degree increased with increasing moisture content. 10 Although scholars have performed much research on the effect of moisture on gas adsorption in coal, most of them focus on high metamorphic coal with serious disasters, but there are few studies on low metamorphic coal, especially long-flame coal.…”

Section: Introductionmentioning

confidence: 99%

“…Yang et al investigated hydraulic cutting styles in boreholes and the optimal equivalent borehole diameter after discharging pulverized coal particles . Zhu et al established the adsorption isotherm of methane under different water contents, and the results showed that the presence of water led to a sharp decrease in methane adsorption . Guo et al studied the influence of moisture on the adsorption characteristics of low-rank coal and found that moisture obviously inhibited the gas adsorption capacity of low-rank coal and that the inhibition degree increased with increasing moisture content .…”

Section: Introductionmentioning

confidence: 99%

Effect of Moisture on Methane Adsorption Characteristics of Long-Flame Coal

et al. 2022

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Long-flame coal is a bituminous coal with the lowest metamorphic degree, accounting for 16.1% of China’s coal reserves. With increases in mining depths and intensities, mine gas disasters related to the mining of long-flame coal are becoming increasingly serious. Therefore, the exploration of the effect of moisture on the adsorption of methane in coal can provide support for popularizing the application of hydraulic measures in long-flame coal mining areas. In this paper, a molecular structure model of long-flame coal was established by molecular dynamics and the Monte Carlo method. The adsorption characteristics of methane in long-flame coal structures under different pressures were simulated, and the effects of different amounts of water on the methane adsorption and adsorption heat were explored. The results show that, under the same adsorption equilibrium pressure, the methane adsorption rate decreases with increasing water content, and with increasing adsorption equilibrium pressure, the adsorption capacity of methane increases gradually; this increasing trend is in agreement with the Langmuir equation. The water adsorption of coal is greater than the methane adsorption of coal. With the increase in the number of water molecules, when coal-based molecules adsorb methane and then adsorb water molecules, the adsorption heat of methane is reduced, and the desorption of methane molecules is promoted.

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Thermodynamic characteristics of methane adsorption about coking coal molecular with different sulfur components: Considering the influence of moisture contents

Cited by 22 publications

References 43 publications

Experimental Study of the Influence of Moisture Content on the Pore Structure and Permeability of Anthracite Treated by Liquid Nitrogen Freeze–Thaw

Experimental Study of the Influence of Moisture Content on the Pore Structure and Permeability of Anthracite Treated by Liquid Nitrogen Freeze–Thaw

Experimental Study of the Structural Damage to Coal Treated by a High-Voltage Electric Pulse Discharge in Water

Effect of Moisture on Methane Adsorption Characteristics of Long-Flame Coal

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