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

Chen, Xiangjun; Wang, Xiaodan; Zhao, San; Kang, Ningning; Feng, Shuailong

doi:10.1021/acsomega.2c01144

Cited by 7 publications

(8 citation statements)

References 27 publications

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“…With the increase of pressure, methane adsorption capacity also increases. When the pore surface that can pass through the gas molecules is gradually covered by methane molecules, the adsorption capacity will not increase and the adsorption will reach equilibrium. , It shows that increasing the adsorption equilibrium pressure is beneficial to the methane adsorption. Compared with dry anthracite, the excess adsorption of methane by water-injected anthracite is significantly lower, and the excess adsorption of methane decreases as the moisture content increases.…”

Section: Resultsmentioning

confidence: 99%

Effect of Different Placement Sequences of Water on the Methane Adsorption Properties of Coal

et al. 2023

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After the coal seam is injected with water, the moisture content in the coal body increases, which affects the output capacity of coalbed methane (CBM). In order to improve the effect of CBM mining, the classical anthracite molecular model has been selected. To analyze the influence of different placement orders of water and methane on the characteristics of coal-adsorbing methane from the micro point of view, a molecular simulation method is used for comprehensive consideration in the study. The results show that H2O does not change the mechanism of CH4 adsorption by anthracite, but it inhibits the adsorption of methane by anthracite. When water enters the system afterward, there arises an equilibrium pressure point where water plays the most significant role in inhibiting methane adsorption by anthracite coals, which increases with increasing moisture content. When water enters the system first, no equilibrium pressure point occurs. The excess adsorption of methane by anthracite when water enters second is higher. The reason is that H2O can replace CH4 at the higher energy adsorption sites of the anthracite structure, while CH4 can only be adsorbed at the lower energy sites, and some of CH4 is not adsorbed. For the coal samples with a low-moisture content system, the equivalent heat of adsorption of CH4 increases first rapidly and then slowly with the increase of pressure. However, it decreases with pressure in the high-moisture content system. The variation of the equivalent heat of adsorption further explains the variation of the magnitude of methane adsorption under different conditions.

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Section: Resultsmentioning

confidence: 99%

Effect of Different Placement Sequences of Water on the Methane Adsorption Properties of Coal

et al. 2023

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“…The result shows that the difference in K H values between the raw and dry conditions for all coal seams is significant where the drying process increases K H values by 80–100%. The higher K H value in dry coal increases the affinity between coal molecules and CO 2 due to a significant decrease in moisture during the drying process. , Coal seam C had the highest K H values under raw conditions compared to those of the other coal seams. As seam C has the lowest moisture content and high levels of huminite and liptinite, it has more potential for adsorbing CO 2 .…”

Section: Results and Discussionmentioning

confidence: 99%

Examination of the Factors Inhibiting CO₂ Adsorption on Coal: A Case Study from Shallow-Depth Low-Rank Coal Seams

Tambaria,

Sugai,

Anggara

2023

ACS Omega

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Understanding the inhibitory factors affecting the adsorption of CO 2 on low-rank coal from shallow-depth coal seams is essential to identify potential coal seams for CO 2 sequestration. The CO 2 adsorption capacity of shallow-depth coals was measured at a low pressure on raw and dry coals. The samples were also prepared for organic analyses, scanning electron microscopy analyses, and low-temperature nitrogen adsorption analyses to evaluate the CO 2 adsorption and identify the inhibitory factors. An investigation was conducted to determine how CO 2 adsorption occurs on coal by fitting experimental data to adsorption isotherm models, followed by analyzing the results based on the statistical analysis. In addition, this study used Henry's law, surface potential, and Gibbs free energy to identify the adsorption inhibitor between CO 2 and coal. The CO 2 adsorption experiment was conducted on raw coal with a moisture content of 15.18−20.11% and dry coal with no moisture. The experimental data showed that the CO 2 adsorption capacity in dry coal was 1.6−1.8 times greater than that in raw coal. A fitting graph between the adsorption data and the isotherm model indicated that CO 2 adsorption on coal occurred on monolayers and multilayers under raw and dry conditions. Statistical evaluation of the adsorption isotherm models showed that the Langmuir and Freundlich models aligned more closely to the experimental data. According to this result, low-pressure adsorption of CO 2 on coal occurred in monolayers and multilayers under raw and dry conditions. Coal containing a high huminite content had a higher potential for CO 2 adsorption, and the drying increased the positive relationship. On the other hand, coal containing high inertinite content inhibited CO 2 adsorption onto the coal, but the drying process did not adversely affect CO 2 adsorption. Furthermore, coal with high moisture and inertinite content inhibited the affinity, accommodation, and spontaneous CO 2 adsorption onto the coal. CO 2 adsorption could lead to swelling, but moisture loss opened more sites and micropores, resulting in the swelling effect not closing all micropores in dry coal. Based on these results, coal seams with low moisture and inertinite content are the most promising for CO 2 adsorption. Altogether, this study provides an understanding of the percentage of inhibitor factors that affects CO 2 adsorption on low-rank coal from shallow depths, which may lead to different CO 2 adsorption capacities.

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“…Some hydroxyl groups with polar sites on the surface of the coal matrix are more easily occupied by water, which reduces the adsorption capacity of the coal matrix for CH 4 and CO 2 . Therefore, the adsorption capacity of wet coal or low-rank coal is significantly lower than that of dry coal or high-rank coal. ,, …”

Section: Resultsmentioning

confidence: 99%

“…Therefore, the adsorption capacity of wet coal or low-rank coal is significantly lower than that of dry coal or high-rank coal. 45 , 49 , 58 …”

Section: Resultsmentioning

confidence: 99%

“…Therefore, the adsorption capacity of wet coal or low-rank coal is significantly lower than that of dry coal or high-rank coal. 45,49,58 With the increase of R o , the moisture in heat-affected coal decreases (Figure 7a). A negative linear correlation between the moisture content and R o was represented.…”

Section: Influence Of Igneous Intrusion On Adsorption/ Desorptionmentioning

confidence: 99%

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Evolution of Composition and Methane Occurrence of Bituminous Coal after Igneous Intrusion: A Case Study of Daxing Coal Mine, Tiefa Basin, China

et al. 2022

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Since 1987, there have been 10 coal and gas outbursts in Daxing Coal Mine, Tiefa Basin. It was reported that these outbursts were related to igneous intrusion. To study the influence of igneous intrusion into bituminous on coal bed methane (CBM) occurrence, eight coal samples were collected at different distances (0.2−10 m) from an intrusion in Daxing Coal Mine. The petrographic and chemical data, pore characteristics, and adsorption properties of unaltered and heat-affected coals were tested and compared. Approaching the dike, vitrinite reflectance (R o ) increases from 0.56 to 1.14%, while moisture decreases from 6.4 to 3.1%. According to R o , with the thermal evolution of igneous rocks, the temperature of heat-affected coal seams generally increases from ∼78 to ∼169 °C. The bituminous coal contained high moisture content before the intrusion, and after the igneous intrusion, partial heat may be used for moisture gasification; the other heat was used to improve coal metamorphism, resulting in little increase in the coal metamorphism as expected. The synergistic effect of igneous thermal evolution and moisture content change improves the adsorption capacity of coal. Affected by the igneous intrusion, the gas content of the heat-affected coal seams No. 4 (above the sill) and No. 7 (below the sill) is higher than that of the unaltered No. 12 coal seam, and the gas content of No. 7 coal seam (beneath the sill) is higher than that of No. 4 coal seam. The low permeability sill has a sealing effect on the gas in No. 7 coal seam. Therefore, the evolution process of CBM occurrence in the Daxing Coal Mine can be speculated, that is, after magma intrusion, the temperature increased, the metamorphic degree of coal increased, and water gasification occurred at the same time. The original adsorption site occupied by moisture was vacated, which improved the methane adsorption capacity of the coal and provided favorable conditions for CBM occurrence.

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

Cited by 7 publications

References 27 publications

Effect of Different Placement Sequences of Water on the Methane Adsorption Properties of Coal

Effect of Different Placement Sequences of Water on the Methane Adsorption Properties of Coal

Examination of the Factors Inhibiting CO₂ Adsorption on Coal: A Case Study from Shallow-Depth Low-Rank Coal Seams

Evolution of Composition and Methane Occurrence of Bituminous Coal after Igneous Intrusion: A Case Study of Daxing Coal Mine, Tiefa Basin, China

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

Cited by 7 publications

References 27 publications

Effect of Different Placement Sequences of Water on the Methane Adsorption Properties of Coal

Effect of Different Placement Sequences of Water on the Methane Adsorption Properties of Coal

Examination of the Factors Inhibiting CO2 Adsorption on Coal: A Case Study from Shallow-Depth Low-Rank Coal Seams

Evolution of Composition and Methane Occurrence of Bituminous Coal after Igneous Intrusion: A Case Study of Daxing Coal Mine, Tiefa Basin, China

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Examination of the Factors Inhibiting CO₂ Adsorption on Coal: A Case Study from Shallow-Depth Low-Rank Coal Seams