A fully coupled electromagnetic, heat transfer and multiphase porous media model for microwave heating of coal

Li, He; Shi, Shiliang; Lin, Baiquan; Lu, Jiexin; Lü, Yi; Ye, Qing; Hong, Youshi; Zhu, Xiangnan

doi:10.1016/j.fuproc.2019.03.002

Cited by 153 publications

(45 citation statements)

References 66 publications

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“…The boundary condition for the waveguide was set as the impedance boundary condition. This condition can be mathematically described as follows: (13) where E s is the electric field source that is used to specify a surface current source at the boundary; n is the normal vector of the boundary; µ 0 and µ r are the permeability of the vacuum and relative permeability, respectively.…”

Section: Boundary Conditionsmentioning

confidence: 99%

“…A fully coupled electromagneticthermal-mechanical model was developed to investigate the influence of coal compaction, thermal expansion, thermally induced gas desorption, and sorption-induced coal deformation on the coalbed methane extraction [12]. Microwave absorption by coal redistributes the electromagnetic field in the cavity, which leads to high-and low-energy regions [13]. Owing to water evaporation and thermal convection, the temperature increase in the coal sample during microwave drying exhibits a ''fast-slow-fast'' trend, and water evaporation is the key factor in the thermal distribution [14].…”

Section: Introductionmentioning

confidence: 99%

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Numerical Simulation of the Temperature Field of Coal Subjected to Microwave Directional Heating

Zhang

Yang

et al. 2020

IEEE Access

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Microwave directional heating can rapidly increase the temperature of coal and promote the desorption of coalbed methane. The temperature field of coal subjected to microwave directional heating was simulated by using COMSOL software. By coupling the energy conservation equation for an electromagnetic field with the heat conduction equation for solids, a heat conduction equation for the microwave directional heating of coal was established. The effects of the microwave heating time, power, frequency, incident distance and cross-sectional area of the waveguide on the temperature field of coal were studied via simulation. The results revealed that the increasing rate of temperature was high in the early stages of microwave heating. Moreover, higher microwave power corresponded to a higher coal sample temperature, a larger temperature gradient for the coal sample, and less energy being required to achieve the desired coal sample temperature. Additionally, it was found that there is an optimal microwave frequency that maximises the temperature of the coal sample. A larger microwave incident distance resulted in a lower average coal sample temperature. The waveguide was also found to have an optimal cross-sectional area that maximises the maximum temperature of the coal sample. INDEX TERMS Microwave, coal, directional heating, temperature field, numerical simulation.

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Section: Boundary Conditionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of the Temperature Field of Coal Subjected to Microwave Directional Heating

Zhang

Yang

et al. 2020

IEEE Access

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“…Due to the complexity of the HM model, the following assumptions are adopted: (a) coal seam is assumed as a dual‐porosity (fractures and matrix pores) single‐permeability elastic medium; (b) the free gases conform to the ideal gas law, and they exist and migrate in the space of fractures and pores; (c) the adsorbed gas exists on the surface of pores, and water only migrates in fractures; (d) for the transport of methane, it first desorbs from the surface of matrix pores—Langmuir equation, then diffuses from the pores to the fractures—Fick's law, and finally seepages from fractures to drainage borehole—Darcy's law; while for the injected flue gas, the transport direction is opposite—gas mixture first seepages from the injection borehole to the fractures, then diffuses from the fractures to the matrix, followed by the competitive adsorption with CH 4 on pore surfaces. The mass transport of gas and water mixture in the process of flue gas enhanced drainage is shown in Figure .…”

Section: Mathematical Model For Flue Gas Enhanced Coal Seam Gas Drainagementioning

confidence: 99%

Numerical investigation of flue gas injection enhanced underground coal seam gas drainage

Huo

Jing

Fan

et al. 2019

Energy Science & Engineering

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Coal seam with low permeability is widely distributed in China. Injection of flue gas (N2:CO2 = 0.85:0.15) is an effective approach to improve coal seam gas drainage efficiency. This process relates complex responses among ternary gases (CH4, CO2, and N2) competitive sorption on coals, gas diffusion, gas‐water migration by means of two‐phase flow, and coal deformation. In this paper, an improved hydraulic‐mechanical model coupling above interactions is established for flue gas injection enhanced gas drainage. This model is used to simulate flue gas enhanced drainage by finite element method. The sensitivity analyses of key factors are made to recovery a better understanding on the processes controlling flue gas enhanced drainage. Results show that the flue gas enhanced drainage can indeed improve the efficiency of gas extraction and reduce the gas pressure to the required value in a shorter duration. Due to the competitive adsorption and gas sweeping effect of injected flue gas, CH4 is driven toward drainage borehole, and CH4 pressure and content near the injection borehole decrease faster than that near the drainage borehole. The peak CH4 pressure laterally moves from the injection borehole to the drainage borehole. Higher injection pressure, initial permeability, and smaller sorption affinity ratios may lead to greater CH4 production rate at early drainage stage, but smaller CH4 production rate at late stage. The factors controlling the behavior of flue gas enhanced drainage are initial permeability, injection pressure, and sorption affinity ratios in order. This work offers useful framework to investigate important technical challenges associated with enhanced mine gas drainage, as well as unconventional gas development.

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“…Due to a change in effective stress, the corresponding fracture dilation can be obtained as follows [41,42] Δb…”

Section: Coal Deformationmentioning

confidence: 99%

Hydraulic‐Mechanical Coupling Model with Dual‐Porosity Dual‐Permeability for Anisotropy Coal Seams and Its Application in Mine Gas Extraction

Huo

Jing

et al. 2019

Advances in Civil Engineering

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The parameters of pore-fracture structure and permeability have a controlling effect on the behaviors of gas adsorption/desorption and transportation in coal reservoir. A mathematic model for coal seams is of great significance to evaluate the mass migration within the coal fracture-matrix system. In this paper, the hydraulic-mechanical coupling model considering both dual-porosity dual-permeability and anisotropy characteristics is first established by using the methods of theoretical analysis, nuclear magnetic resonance (NMR) test, and numerical simulation. Then, this model is applied to simulate the gas migration characteristics of No. 3 coal seam in Changping Mine, China. Results show that the pore structure of No. 3 coal seam is characterized by small radius of pores and pore throats, which is determined by the NMR test, verifying the dual-permeability dual-porosity of coal seams. Both matrix permeability and fracture permeability increase approximately linearly with the process of mine gas extraction. The increased magnitude of the matrix permeability is greater than that of the fracture permeability. The permeability is inversely proportional to the anisotropy coefficient. The pressure gradient within the coal matrix and fracture increases first and then decreases with the extraction time. This pressure gradient is proportional to the anisotropy coefficient at the early stage of extraction and is inversely proportional to the anisotropy coefficient at the later stage. The seepage and diffusion flux are proportional to the anisotropy coefficient. The proportion of matrix-to-fracture seepage flux to the total flux increases first and then decreases to a certain value. The proposed model provides a guide for accurate designation of gas extraction from coal seams.

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A fully coupled electromagnetic, heat transfer and multiphase porous media model for microwave heating of coal

Cited by 153 publications

References 66 publications

Numerical Simulation of the Temperature Field of Coal Subjected to Microwave Directional Heating

Numerical Simulation of the Temperature Field of Coal Subjected to Microwave Directional Heating

Numerical investigation of flue gas injection enhanced underground coal seam gas drainage

Hydraulic‐Mechanical Coupling Model with Dual‐Porosity Dual‐Permeability for Anisotropy Coal Seams and Its Application in Mine Gas Extraction

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