Modeling and experiment for effective diffusion coefficient of gas in water-saturated coal

Si, Leilei; Zhang, Hongtu; Wei, Jianping; Li, Bo; Han, Hongkai

doi:10.1016/j.fuel.2020.118887

Cited by 106 publications

(33 citation statements)

References 32 publications

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“…Coal is a typical heterogeneous porous medium whose pore structure is one of the key parameters for evaluating it [4]. Pore structure not only determines the physical and mechanical properties of coal, but also controls the process of gas adsorption, desorption, diffusion, and seepage in a coal seam [5][6][7]. In particular, the adsorption capacity of coalbed methane (CBM) is closely related to the pore development degree and pore structure characteristics.…”

Section: Introductionmentioning

confidence: 99%

Pore Structure Characteristics and Evolution Law of Different-Rank Coal Samples

et al. 2021

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In this study, the full-size pore structure characteristics of six different-rank coal samples were investigated and analyzed from three perspectives, namely, pore shape, pore volume, and pore specific surface area, by performing a high-pressure mercury injection experiment and a low-temperature nitrogen adsorption experiment. Next, the full-size pore volumes and pore specific surface areas of the six coal samples were accurately characterized through a combination of the two experiments. Furthermore, the relationships between volatile matter content and pore volume and between volatile matter content and pore specific surface area were fitted and analyzed. Finally, the influences of metamorphic degree on pore structure were discussed. The following conclusions were obtained. The pore shapes of different-rank coal samples differ significantly. With the increase of metamorphic degree, the full-size pore volume and pore specific surface area both decrease first and then increase. Among the pores with various sizes, micropores are the largest contributor to the full-size pore volume and pore specific surface area. The fitting curves between volatile matter content and pore volume and between volatile matter content and pore specific surface area can well reflect the influence and control of metamorphic degree on pore volume and pore specific surface area, respectively. With the increase of volatile matter content, the pore volume and the pore specific surface area both vary in a trend resembling a reverse parabola.

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Section: Introductionmentioning

confidence: 99%

Pore Structure Characteristics and Evolution Law of Different-Rank Coal Samples

et al. 2021

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“…Currents in coal samples reach peaks and then become stable after the "in ection points". (4) In an applied DC eld, the highest temperature on anthracite coal surface experiences three stages, namely, slowly warming stage, rapid warming stage and slow cooling to stabilize stage. Besides, the temperature rise effect on coal sample surface lags behind changes of currents that run through coal samples.…”

Section: Discussionmentioning

confidence: 99%

“…Many experts and scholars have proposed technologies to strengthen gas extraction from coal seams. Mechanical technologies mainly include high-pressure hydraulic measures, explosion-induced cracking, gas injection displacement of coal seams, etc [3][4][5][6] .…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Variation Laws of Electrical Parameters and Surface Temperature Rise Effect of Coal Samples in An Applied Direct Current Field

Yang¹,

Wen²,

Si³

et al. 2020

Preprint

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Joule heats which are generated by coals in an applied electric field are directly correlated with variation laws of electrical parameters of coals. Moreover, the joule heating effect is closely related with microstructural changes and relevant products of coal surface. In the present study, a self-developed applied direct current (DC) field was applied onto an experimental system of coals to investigate variation laws of electrical parameters of highly, moderately and lowly metamorphic coal samples. Moreover, breakdown voltages and breakdown field intensities of above three coal samples with different metamorphic grades were tested and calculated. Variation laws of electrical parameters of these three coal samples in 2kV and 4kV DC fields were analyzed. Results show that internal current of all coal samples increases continuously and tends to be stable gradually after reaching the “inflection point” at peak. The relationship between temperature rise effect on anthracite coal surface in an applied DC field and electrical parameters was discussed. The temperature rise process on anthracite coal surface is composed of three stages, namely, slowly warming, rapid warming and slow cooling to stabilize. The temperature rise effect on anthracite coal surface lags behind changes of currents which run through coal samples. There’s uneven temperature distribution on anthracite coal surface, which is attributed to the heterogeneity of coal samples. In the experiment, the highest temperature on anthracite coal surface 65.8℃ is far belower than the lowest temperature for pyrolysis-induced gas production of coals 200℃. This study lays foundations to study microstructural changes and relevant products on coal surface in an applied DC field.

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“…Two types of gas flow in coal seams have been identified including the diffusion flow and the laminar flow targeting different types of coal seams [3][4][5]. Generally speaking, in the coal seam with a microporous structure or low permeability, the diffusion flow plays a critical role while in the coal seam with microporous structure or high permeability, the laminar flow dominates [6][7][8]. In this study, the gas flow in the process of drainage is treated as laminar flow, following Darcy's law.…”

Section: Gas Solid Coupling Analysis Of Coal Seammentioning

confidence: 99%

A Case Study on the Gas Drainage Optimization Based on the Effective Borehole Spacing in Sima Coal Mine

Sun

2021

Geofluids

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Based on the dynamic expressions of permeability and porosity of the coal seam derived in the paper, a multiphysical field coupling numerical model of gas migration under the interaction of stress field and seepage field was established. The gas drainage project #3 Coal Seam operated by Sima Coal Industry Co., Ltd., was selected as the study object. Taking different drainage time periods in various positions of drainage holes into consideration, combined with the advance situation of the 1207 working face in the Sima Coal Mine, a mixed layout gas drainage scheme featured with the effective borehole spacing was obtained through the COMSOL multiphysics simulation. In addition, a series of field industrial tests were performed to validate the research result, revealing that comprehensively considering the extraction time of coal and optimizing the layout of extraction boreholes can effectively improve the engineering economic benefits.

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Modeling and experiment for effective diffusion coefficient of gas in water-saturated coal

Cited by 106 publications

References 32 publications

Pore Structure Characteristics and Evolution Law of Different-Rank Coal Samples

Pore Structure Characteristics and Evolution Law of Different-Rank Coal Samples

Experimental Study on Variation Laws of Electrical Parameters and Surface Temperature Rise Effect of Coal Samples in An Applied Direct Current Field

A Case Study on the Gas Drainage Optimization Based on the Effective Borehole Spacing in Sima Coal Mine

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