Study on the method of testing the adsorption and diffusion capacities of coal matrix and its influencing factors using the sliced coal samples

Ma, Pinghua; Li, Feng; Dickens, Oyaka; Li, Mingfeng; Liu, Zeheng; Zhang, Baocong; Shao, Xin

doi:10.1080/15567036.2020.1841850

Cited by 2 publications

(1 citation statement)

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“…The effective diffusion coefficient was proposed to characterize the diffusion process of the gas due to the difficulty in obtaining the exact diffusion distance during the calculation of the diffusion coefficient . As the difference between the two parameters depends only on whether the effective diffusion path is calculated or not, these two parameters have been widely used by scholars to characterize the gas diffusion behavior. − The porosity of coal samples with different degrees of metamorphism was found to be positively correlated with the diffusion coefficient in previous studies, while studies on samples with different particle sizes demonstrated that the pore development was higher as the sample size decreased. , However, there were studies that demonstrated that the effective diffusion coefficient was negatively correlated with the particle size as the sample size decreased. , Based on the previous studies, it is inferred that the effective diffusion coefficient may not be suitable for characterizing gas diffusion when the sample size is different. Therefore, in this paper, we further analyze the diffusion coefficients of different samples and the differences between the effective diffusion coefficients as well as the conditions for using the effective diffusion coefficients in depth.…”

Section: Introductionmentioning

confidence: 99%

Gas Diffusion Characteristics and Size Effect in Coal Particles with Different Degrees of Metamorphism

Zhai

Song

et al. 2023

Energy Fuels

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Coalbed methane (CBM) is a green unconventional energy source where the gas diffusion efficiency in coal directly limits the production capacity. Therefore, different gas adsorption experiments were used to determine the diffusion characteristics of coal samples with varying degrees of metamorphism. The influence law based on the gas type, pore structure, and coal sample size on the gas diffusion coefficient was analyzed, and the synergistic control effect of various factors on diffusion was discussed. The results show that when the particle size is the same, the diffusion coefficient of different gases shows the change rule of CO2 > N2 > CH4, and the diffusion coefficient of different samples is positively correlated with the degree of pore development. When the particle size is different, the diffusion coefficient is negatively correlated with the pore development degree and positively correlated with the sample particle size. The effective diffusion coefficient is consistent with the diffusion coefficient when the particle size of the sample is the same, and the effective diffusion coefficient is opposite to the diffusion coefficient when the particle size decreases. The analysis reveals that the diffusion coefficients of different gas are limited by the diameter of gas molecular dynamics, and the diffusion coefficient is reduced with the decrease in the diameter of the gas molecular dynamics. The change of diffusion coefficient caused by particle size change is positively correlated with the change of diffusion cross section caused by size effect. The difference between the effective diffusion coefficient and the diffusion coefficient mainly comes from whether the effective diffusion path is calculated. Therefore, when the particle size is constant, the effective diffusion coefficient can replace the diffusion coefficient to characterize the diffusion behavior. When the particle size is different, it is more appropriate to use the diffusion coefficient to characterize the gas diffusion behavior. The significance of the research findings in revealing gas transport in the coal matrix and coalbed methane formation is substantial.

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