Investigation of the Coal Oxidation Effect on Competitive Adsorption Characteristics of CO<sub>2</sub>/CH<sub>4</sub>

Hu, Yu; Wang, Shuai; He, Yurong

doi:10.1021/acs.energyfuels.0c02497

Cited by 16 publications

(9 citation statements)

References 36 publications

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“…In the previous literature, Hu et al 11 compared the CO 2 /CH 4 competitive adsorption behaviors on oxidized coal and nonoxidized coal based on the density functional theory, finding that the oxidation effect of coal can reduce the adsorption energies of CO 2 and CH 4 on the functional groups. Zhang et al 12 researched the adsorption properties of CH 4 , CO 2 , and their mixtures in the three carbon structure models using the grand canonical Monte Carlo method, showing that increasing pressure and decreasing temperature can improve the absolute adsorption quantity.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic Analysis of CH₄/CO₂/N₂ Adsorption on Anthracite Coal: Investigated by Molecular Simulation

et al. 2021

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The interpretation of gas adsorption behavior on a coal surface is an important theoretical basis for gas injection to enhance the recovery of coalbed methane. In order to further explore the adsorption properties of different gases (CH 4 /CO 2 /N 2 ) on the coal surface, the thermodynamic parameters of adsorption were revealed using a molecular simulation method. The results show that the Langmuir−Freundlich model is more accurate to represent gas adsorption on anthracite coal than the Langmuir model and Freundlich model, which reveal that the gas adsorption on the coal surface is heterogeneous. Also, thermodynamic parameters indicate that gas adsorption on anthracite coal is a thermodynamically spontaneous (ΔG < 0) and exothermic physisorption (0 < ΔH < 10 kcal/mol) process, and the gas molecules tend to be in an ordered state (ΔS > 0). According to adsorption affinity and thermodynamic parameters, the adsorption capacity of these three gases on a coal surface follows the sequence of CO 2 > CH 4 > N 2 . This research can provide foundational knowledge for further interpretation of gas adsorption behavior on a coal surface.

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Section: Introductionmentioning

confidence: 99%

Thermodynamic Analysis of CH₄/CO₂/N₂ Adsorption on Anthracite Coal: Investigated by Molecular Simulation

et al. 2021

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“…In the case of oxygen-containing functional groups, the oxygen atom is more electronegative than the carbon and hydrogen atoms; thus, it easily attracts electrons. Studies have reported that the shared electron pairs in the oxygen-containing group tend to favor the oxygen atom, leading to stronger polarity. − This results in an overall contribution to the SP value of coal.…”

Section: Discussion Of the Adsorption Behavior Mechanismmentioning

confidence: 99%

“…Studies have reported that the shared electron pairs in the oxygen-containing group tend to favor the oxygen atom, leading to stronger polarity. 34 − 37 This results in an overall contribution to the SP value of coal.…”

Section: Discussion Of the Adsorption Behavior Mechanismmentioning

confidence: 99%

Study on the Electrical Control Mechanism of Gas Occurrence in a Microscale Coal Matrix

et al. 2022

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The study of the gas occurrence mechanism in a microscale coal matrix is the basis of coalbed methane (CBM) reservoir formation mechanism analysis and its exploration and development scheme design, which has important scientific and engineering significance. Currently, many researchers are focusing on a specific coal type to explore the macroscopic adsorption characteristics of gas occurrence. However, the research on the microscale gas–solid coupling mechanism is relatively rare and the electrical control mechanism of gas occurrence is not reported in detail. This study focuses on the electrical mechanism of microscale gas occurrence using physical simulation experiments and molecular dynamics analysis. This study clarifies the “gas adsorption–electrical properties–functional group” linkage mechanism and explores the macroscopic performance of the microscale gas occurrence mechanism using electrical properties. The study reveals the following: (1) the coal reservoirs exhibit a weak negative potential at the nanoscale, and the trends of surface potential (SP) and surface electrical charging density (SECD) are fluctuated with the degree of coal rank increases; (2) there is a good correlation between the SP, SECD values, and the relative content of functional groups; and (3) the charge density on the coal’s microscopic surface influences their gas molecule attraction capacity, affecting the gas adsorption capacity of coal reservoirs at the macroscale. This study presents a theoretical foundation for establishing the molecular force field superposition mechanism of gas occurrence in microscale coal matrix and has broad application prospects in the macroscale numerical simulation of CBM development.

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“…The in situ stress and temperature underground will increase with the buried depth of the coal bed, and the phase of CO 2 will transfer to a supercritical state when the pressure and temperature reaches 7.38 MPa and 31.1 °C, respectively. SCCO 2 has salient properties like high density and strong diffusion, which are amenable to the flooding of the CO 2 over the coal bed and facilitate the exchange of CO 2 with CH 4 adsorbed on the pores and fissures surface in a coal mass. − With the injection pressure of CO 2 increasing in coal beds underground, the effect of fracturing is different from that of ordinary hydraulic fracturing . More fractures in different scales will be generated by SCCO 2 fracturing, and the formed fracture network has a more complex pattern, which reduces the effective stress of the coal body by permitting CO 2 to enter smaller pore fracture spaces. , The experimental results demonstrate that the break down pressure of SCCO 2 fracturing is lower than that of hydraulic fracturing while it takes a longer time. − However, the fractured volume is larger than that of traditional hydraulic fracturing.…”

Section: Stimulation Technologies With Energy Injectionmentioning

confidence: 99%

Review on Coal Bed Methane Recovery Theory and Technology: Recent Progress and Perspectives

Liang¹,

Yan

Zhang

et al. 2021

Energy Fuels

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Coal bed methane (CBM) is a primary clean energy source found in coal seams. The recovery ratio of CBM is very low, especially with ground extraction, due to the strong adsorption of CH 4 on the pores and fissures of coal and low permeability of the coal bed. On the basis of the theory of energy balance, a theory of enhanced CBM (ECBM) recovery by energy stimulation is proposed in this review. The desorption and transportation of CH 4 in coal beds are analyzed from the perspective of energy consumption. Two pacesetting stimulation technologies are proposed to increase the permeability of coal beds: supercritical CO 2 (SCCO 2 ) fracturing and thermal fracturing through steam injection. The experimental study and the related results of SCCO 2 -enhanced CBM recovery are presented and analyzed. The results demonstrate that the permeability of SCCO 2 in the tested four ranked coal specimens decreases in the form of a negative exponent function with the increase of effective stress. The transportation capacity of SCCO 2 in high ranked coal beds deep underground is inferior to that in low ranked coal beds at shallow depth. The experiment of the total permeability of CO 2 with CH 4 in coking coal shows that the permeability decreases in the form of a logarithmic function as the content of CO 2 increases. SCCO 2 has higher transportation capacity than gaseous CO 2 in coal beds, and the total permeability decreases with its content increasing in the synthetical system with CH 4 . The SCCO 2 -enhanced CBM recovery experiment demonstrates that the economic production time is different for the four ranked coal specimens given 50% of each content in production gas being defined as a threshold for economic production. The economic production for gas coal and anthracite takes a longer time than that in weakly caking coal of a lower ranked coal. The study demonstrates that different ranked coals have different inner structures and transportation properties. However, the original structures of different ranked coals can be modified by SCCO 2 by changing the void volume or the structure of the pores and fissures. The challenges and perspectives for the CBM recovery theory and technology are also presented. The study is of importance with the novel dual efficient approach for clean energy CBM recovery ratio improvement and greenhouse gas sequestration underground in deep coal beds.

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Investigation of the Coal Oxidation Effect on Competitive Adsorption Characteristics of CO₂/CH₄

Cited by 16 publications

References 36 publications

Thermodynamic Analysis of CH₄/CO₂/N₂ Adsorption on Anthracite Coal: Investigated by Molecular Simulation

Thermodynamic Analysis of CH₄/CO₂/N₂ Adsorption on Anthracite Coal: Investigated by Molecular Simulation

Study on the Electrical Control Mechanism of Gas Occurrence in a Microscale Coal Matrix

Review on Coal Bed Methane Recovery Theory and Technology: Recent Progress and Perspectives

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Investigation of the Coal Oxidation Effect on Competitive Adsorption Characteristics of CO2/CH4

Cited by 16 publications

References 36 publications

Thermodynamic Analysis of CH4/CO2/N2 Adsorption on Anthracite Coal: Investigated by Molecular Simulation

Thermodynamic Analysis of CH4/CO2/N2 Adsorption on Anthracite Coal: Investigated by Molecular Simulation

Study on the Electrical Control Mechanism of Gas Occurrence in a Microscale Coal Matrix

Review on Coal Bed Methane Recovery Theory and Technology: Recent Progress and Perspectives

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Investigation of the Coal Oxidation Effect on Competitive Adsorption Characteristics of CO₂/CH₄

Thermodynamic Analysis of CH₄/CO₂/N₂ Adsorption on Anthracite Coal: Investigated by Molecular Simulation

Thermodynamic Analysis of CH₄/CO₂/N₂ Adsorption on Anthracite Coal: Investigated by Molecular Simulation