Molecular insights on influence of CO2 on CH4 adsorption and diffusion behaviour in coal under ultrasonic excitation

Yang, Wei; Wang, Liang; Yang, Kang; Fu, Shenguang; Tian, Chenhao; Pan, Rongkun

doi:10.1016/j.fuel.2023.129519

Cited by 8 publications

(2 citation statements)

References 75 publications

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“…when it comes to pressure's effect on diffusion coefficients, international scientists have conducted numerical and molecular simulations to determine its impact. However, consensus remains elusive regarding whether the effective diffusion coefficient increases or decreases with rising pressure [23]. Even utilising similar models, some authors concluded that diffusion coefficients increase with pressure [24][25][26], while others proposed that pressure-dependent changes in diffusion coefficients are model-dependent [27].…”

Section: Introductionmentioning

confidence: 99%

Influence of Grain Size and Gas Pressure on Diffusion Kinetics and CH4 Sorption Isotherm on Coal

Kozieł,

Gajda,

Skiba

et al. 2024

Archives of Mining Sciences

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The paper presents research on the influence of grain size of selected coals and their structural parameters on the diffusion coefficient and methane sorption isotherms. Two coals from Polish hard coal mines, differing in the coal rank, were tested. Sorption isotherms for methane were determined. An unconventional sequence of pressures 0→0.1→0→0.5→0→1.5 MPa was employed to assess the speed of achieving sorption equilibrium at different pressures. The studies of CH4 accumulation kinetics were performed on various grain classes of the tested coals. Both the sorption capacity of coal and the diffusion coefficient proved to be highly sensitive to the experimental methodology. Critical measurement parameters in terms of determining the diffusion coefficient concerning the assumptions of the Crank model were indicated. The influence of the equivalent radius of coal grain on the process kinetics was demonstrated. The stepwise pressure increase factor was examined in the context of minimising the impact of sorption isotherm non-linearity on the results. The importance of the width of the grain class of coals was determined to reduce their maceral inhomogeneities. These factors are the most common reason that makes it difficult to quantitatively compare diffusion coefficient values.

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Section: Introductionmentioning

confidence: 99%

Influence of Grain Size and Gas Pressure on Diffusion Kinetics and CH4 Sorption Isotherm on Coal

Kozieł,

Gajda,

Skiba

et al. 2024

Archives of Mining Sciences

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show abstract

“…Currently, methods such as Molecular Dynamics (MD), Grand Canonical Monte Carlo (GCMC), and Density Functional Theory (DFT) are widely employed to investigate the adsorption and diffusion characteristics of CO2 in coal, as well as the structural changes of coal pores and fractures after CO2 injection [25][26][27][28]. The results shown that, after CO2 adsorption, not only does the non-covalent bond energy decrease, but changes also occur in bond angle energy, torsion energy, etc., leading to alterations in the macromolecular structure of coal, thereby inducing changes in pore structure [29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%

Research on the Interaction Mechanisms between ScCO2 and Low-Rank / High-Rank Coal with ReaxFF-MD Force Field

Dong,

Kong,

Niu

et al. 2024

Preprint

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CO2 geological sequestration in coal seams can achieve the dual objectives of CO2 emission reduction and enhanced coalbed methane production, making it a highly promising carbon capture and storage technology. However, the injection of CO2 into coal reservoirs in the form of supercritical fluid (ScCO2) leads to complex physicochemical reactions with the coal seam, altering the properties of the coal reservoir and impacting the effectiveness of CO2 sequestration and methane production enhancement.In this paper, theoretical calculations based on ReaxFF-MD were conducted to study the interaction mechanism between ScCO2 and the macromolecular structure of both low-rank and high-rank coal, to address the limitations of experimental methods. The reaction of ScCO2 with low-rank coal and high-rank coal exhibits significant differences. At swelling stage, the low-rank coal experiences a decrease in aromatic structure and aliphatic structure, high-rank coal shows an increase in aromatic structure and a decrease in aliphatic structure, while swelling phenomenon is more pronounced in high-rank coal. At dissolution stage, low-rank coal is initially decomposed into two secondary molecular fragments, and then recombine to form new molecular structure, the aromatic structure increased and the aliphatic structure decreased. In contrast, high-rank coal occurs stretches-breakage-movement-reconnection, a reduction in aromatic structure and an increase in aliphatic structure.The primary reasons for these variations lie in distinct molecular structure compositions and the properties of ScCO2, leading to different reaction pathways of functional group and aromatic structure. The reaction pathways of functional groups and aromatic structures in coal can be summarized as follows: the breakage of the O-H bond in hydroxyl groups, the breakage of the C-OH bond in carboxyl groups, transformation of aliphatic structures into smaller hydrocarbon compounds or formation of long-chain alkenes, and various pathways involving broken, rearrangement, recombination of aromatic structures. In low-rank coal, there is a higher abundance of oxygen-containing functional groups and aliphatic structures. The breakage of O-H and C-OH chemical bonds results in the formation of free radical ions, while some aliphatic structures detach to produce hydrocarbons. Additionally, some of these aliphatic structures combine with carbonyl groups and free radical ions to generate new aromatic structures. Conversely, in high-rank coal, the lower content of oxygen-containing functional groups and aliphatic structures, along with stronger intramolecular forces, results in fewer chemical bond breakages and makes it less conducive to the formation of new aromatic structures.These results elucidate the specific deformations of different chemical groups, offering a molecular-level understanding of the interaction between CO2 and coal.

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Ultrasonic-Induced Changes in Nanopores: Molecular Insights into Effects on CH4/CO2 Adsorption in Coal

Wang,

Yang,

Yang

et al. 2024

Nat Resour Res

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Molecular insights on influence of CO2 on CH4 adsorption and diffusion behaviour in coal under ultrasonic excitation

Cited by 8 publications

References 75 publications

Influence of Grain Size and Gas Pressure on Diffusion Kinetics and CH4 Sorption Isotherm on Coal

Influence of Grain Size and Gas Pressure on Diffusion Kinetics and CH4 Sorption Isotherm on Coal

Research on the Interaction Mechanisms between ScCO2 and Low-Rank / High-Rank Coal with ReaxFF-MD Force Field

Ultrasonic-Induced Changes in Nanopores: Molecular Insights into Effects on CH4/CO2 Adsorption in Coal

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