Super-critical carbon dioxide flow behaviour in low rank coal: A meso-scale experimental study

Ranathunga, A.S.; Perera, M.S.A.; Ranjith, P.G.; Zhang, Xiaogang; Wu, Bailin

doi:10.1016/j.jcou.2017.04.010

Cited by 51 publications

(30 citation statements)

References 51 publications

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“…Compared with CH 4 , coal seams can adsorb CO 2 more easily. Injecting CO 2 and N 2 into the coal seams can promote CH 4 to escape from the coal seams [4][5][6][7][8]. Therefore, the unmineable coal seams have the potential to store CO 2 and enhanced coalbed methane recovery.…”

Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulation of Diffusion Behavior of CH4, CO2, and N2 in Mid-Rank Coal Vitrinite

Liu

Wang

2019

Energies

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The diffusion characteristics of CH4, CO2, and N2 in coal are important for the study of CO2-enhanced coalbed methane (CO2-ECBM) recovery, which has become the most potential method for carbon sequestration and natural gas recovery. However, quantitative research on the diffusion characteristics of CH4 and the invasive gases (CO2 and N2) in coal, especially those in micropores, still faces enormous challenges. In this paper, the self-, Maxwell’s, and transport diffusions of CO2, CH4, and N2 in mid-rank coal vitrinite (MRCV) macromolecules were simulated based on the molecular dynamics method. The effects of the gas concentration, temperature, and pressure on the diffusion coefficients were examined via the comparison of various ranks. The results indicated that the diffusion coefficients have the order of D(N2) > D(CO2) > D(CH4) in their saturated adsorption states. However, when MRCV adsorbed the same amounts of CH4, CO2, and N2, the self- and transport diffusion coefficients followed the order of DS(N2) > DS(CO2) > DS(CH4) and Dt(CO2) > Dt(N2) > Dt(CH4), respectively. Independent of the gas species, all these diffusion coefficients decreased with increasing gas concentration and increased with increasing temperature. In the saturated adsorption state, the diffusion activation energies of CH4, CO2, and N2 were ordered as CH4 (27.388 kJ/mol) > CO2 (11.832 kJ/mol) > N2 (10.396 kJ/mol), indicating that the diffusion processes of CO2 and N2 occur more easily than CH4. The increase of temperature was more conducive to the swelling equilibrium of coal. For the pressure dependence, the diffusion coefficients first increased until the peak pressure (3 MPa) and then decreased with increasing pressure. In contrast, the diffusion activation energy first decreased and then increased with increasing pressure, in which the peak pressure was also 3 MPa. The swelling rate changed more obviously in high-pressure conditions.

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Section: Introductionmentioning

confidence: 99%

Molecular Dynamics Simulation of Diffusion Behavior of CH4, CO2, and N2 in Mid-Rank Coal Vitrinite

Liu

Wang

2019

Energies

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“…According to the extensive present measurements, functional groups and pore structure of each pore phase vary hugely in different coal ranks before and after Sc-CO 2 treatment [8][9][10][11][12]. However, the coal permeability decreases mostly after Sc-CO 2 injection due to the dominant role of sorption-induced swelling [13,14]. Sc-CO 2 helps to develop seepage-flow pores (mesopores and macropores).…”

Section: Introductionmentioning

confidence: 99%

Time-Dependence of Mechanical Property Alterations on Anthracite Coals Treated by Supercritical Carbon Dioxide

Pang

et al. 2019

Geofluids

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The injection of supercritical carbon dioxide (Sc-CO2) into coal seams remarkably changes the physical-chemical structures of coal mass and thereby improves coal mechanical properties. In this study, a series of unconfined and triaxial compressive strength tests were performed on anthracite coal samples under the pressure of 8 MPa at the temperature of 35°C for 24 h and 48 h, respectively. Besides, experiments with longer Sc-CO2 treatment time were carried out on coal mass without stress constraint to observe the damage mode of coal. The results show that Sc-CO2 treatment obviously alters time-dependent mechanical properties of anthracite coal. The coal samples treated with Sc-CO2 for 240 h and 960 h show different damage modes from limited fractures to a complicated fracture network. The time-dependence of the mechanical weakening model on Sc-CO2-treated coal was proposed to explain the link between CO2 flow and mechanical weakening effect by means of physical-chemical effects on time scales.

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“…The process of gas displacement through the injection of liquid CO 2 into highly gassy coal seams is illustrated in Figure 1 [27]. Liquid CO 2 is injected into a borehole and diffused along the cracks of the coal seam around the borehole [28]. Under the effect of cryogenic damage from CO 2 and the thermal stress generated from the heat exchange between the CO 2 and the coal seam, a swelling of the coal matrix occurs [29].…”

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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Super-critical carbon dioxide flow behaviour in low rank coal: A meso-scale experimental study

Cited by 51 publications

References 51 publications

Molecular Dynamics Simulation of Diffusion Behavior of CH4, CO2, and N2 in Mid-Rank Coal Vitrinite

Molecular Dynamics Simulation of Diffusion Behavior of CH4, CO2, and N2 in Mid-Rank Coal Vitrinite

Time-Dependence of Mechanical Property Alterations on Anthracite Coals Treated by Supercritical Carbon Dioxide

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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