Orthogonal Experimental Study on Multifactor Conditions for Gas Desorption in Coal

Wang, Fakai; Li, Xuelong; Li, Lei; Li, Jianggong; Chen, Yulong

doi:10.1155/2019/3028721

Cited by 10 publications

(8 citation statements)

References 41 publications

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“…Each recoverable coal seam is judged to be in danger of coal and gas outbursts according to the critical thresholds of four indicators for the identification of outburst-prone coal seams (as shown in Table 1) 24 . After fixed-size sampling of the coal seam, the coal sample is processed and industrially analyzed according to the Proximate Analysis Method of Coal (GB/T212-2008) 25 . The industrial analysis results are shown in Table 2.…”

Section: Methodsmentioning

confidence: 99%

Study on the gas desorption law and indicator influencing factors of fixed-size coal samples

Sun

Wang

et al. 2019

Sci Rep

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The prediction of dangerous hazards in working faces is an important link to prevent coal and gas outbursts. Improving the accuracy of predictive indicators is of great significance for reducing the phenomenon of being prominently below the critical value and ensuring safe production. The fixed-size desorption index K1 is one of the important indicators for coal face and gas outburst prediction. Based on the diffusion theory and the physical meaning of fixed-size coal samples, the mathematical expression of K1 is established by the self-developed high/low temperature pressure swing adsorption-desorption experimental system. According to the equation, the effects of gas pressure, loss time, coal particle size and diffusion coefficient on K1 are studied. The results show that the K1 index is logarithmically related to the gas pressure. Under the same conditions, the longer the loss time is, the smaller the measured K1 is, and the smaller the particle sizes of the drill cuttings are, the more notable the performance is; the diffusion coefficient represents the ability of gas to bypass micropores and the coal matrix. The greater the ability to bypass the matrix is, the larger the diffusion coefficient under the same conditions is, and the larger K1 is; the coal particle size has a greater influence on K1, and the smaller the size is, the more likely it is that the phenomenon of being prominently below the critical value occurs. Therefore, the particle size composition of coal during on-site measurements is crucial for obtaining the true K1 and the exact critical values.

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Section: Methodsmentioning

confidence: 99%

Study on the gas desorption law and indicator influencing factors of fixed-size coal samples

Sun

Wang

et al. 2019

Sci Rep

Self Cite

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“…Each coal sample is not less than 1 kg. According to the China Coal Industry Standard [19] to prepare the coal sample for proximate analysis and gas adsorption experiment, the humidification process for coal samples is shown in Figure 3. e data of proximate analysis of coal samples, coal hardiness coefficient, and initial gas diffusion velocity of coal are shown in Table 1.…”

Section: Sample Preparationsmentioning

confidence: 99%

Study on the Effect of Soft and Hard Coal Pore Structure on Gas Adsorption Characteristics

Zhao

Feng

Wang

et al. 2021

Advances in Civil Engineering

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In order to grasp the effect of soft and hard coal pore structure on gas adsorption characteristics, based on fractal geometry theory, low-temperature nitrogen adsorption and constant temperature adsorption test methods are used to test the pore structure characteristics of soft coal and its influence on gas adsorption characteristics. We used box dimension algorithm to measure the fractal dimension and distribution of coal sample microstructure. The research results show that the initial nitrogen adsorption capacity of soft coal is greater than that of hard coal, and the adsorption hysteresis loop of soft coal is more obvious than that of hard coal. And the adsorption curve rises faster in the high relative pressure section. The specific surface area and pore volume of soft coal are larger than those of hard coal. The number of pores is much larger than that of hard coal. In particular, the superposition of the adsorption force field in the micropores and the diffusion in the mesopores enhance the adsorption potential of soft coal. Introducing the concept of adsorption residence time, it is concluded that more adsorption sites on the surface of soft coal make the adsorption and residence time of gas on the surface of soft coal longer. Fractal characteristics of the soft coal surface are more obvious. The saturated adsorption capacity of soft coal and the rate of reaching saturation adsorption are both greater than those of hard coal. The research results of this manuscript will provide a theoretical basis for in-depth analysis of the adsorption/desorption mechanism of coalbed methane in soft coal seams and the formulation of practical coalbed methane control measures.

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“…Gas desorption of granular coal is the gas transfer process in porous media, and this process is affected by particle size, pressure, temperature, and other factors [12,13]. Wang et al [14] showed that the sensitivity of gas desorption law to particle size, temperature, pressure, moisture content, and forming pressure was pressure > temperature > particle size > moisture content > forming pressure. Qin et al [15] proved that the desorption process of granular coal was inhibited when the desorption environment pressure was higher than the atmospheric pressure.…”

Section: Introductionmentioning

confidence: 99%

Study on Change Rules of Factors Affecting Gas Loss during Coalbed Air Reverse Circulation Sampling

Chen

Long

et al. 2021

Advances in Civil Engineering

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The gas loss in sampling is the root of coalbed gas content measurement error. The pressure and particle size have a significant impact on the gas loss. Using the self-developed coal particle pneumatic pipeline transportation experimental system, this study investigated the pressure and particle size changes in the sampling pipeline. It is found that the sampling process can be divided into four stages: no flow field stage, sample outburst stage, stable conveying stage, and tail purging stage. The extreme pressure in the sampling pipeline appears at the sample outburst stage; and the pressure in the pipeline has levelled off after sharp decrease in the stable conveying stage. It is also found that the extreme pressure increases first and then decreases with the increase of particle size. The duration of outburst stage is negatively correlated with particle size, and that of stable conveying stage is positively correlated with particle size. In addition, the results show that the loss rate of 1–3 mm particles is the smallest after the test but that particles less than 1 mm increase by about two times and particles greater than 3 mm decrease by more than three times. The study also shows that the particle size distribution of coal samples is a single peak with left skew distribution, and the gas reverse circulation sampling test does not change the location of the peak but makes it higher and sharper. The single size coal sample is more likely to collide than the mixture. This study can help to advance the understanding of impact factors on gas loss during reverse circulation sampling.

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Orthogonal Experimental Study on Multifactor Conditions for Gas Desorption in Coal

Cited by 10 publications

References 41 publications

Study on the gas desorption law and indicator influencing factors of fixed-size coal samples

Study on the gas desorption law and indicator influencing factors of fixed-size coal samples

Study on the Effect of Soft and Hard Coal Pore Structure on Gas Adsorption Characteristics

Study on Change Rules of Factors Affecting Gas Loss during Coalbed Air Reverse Circulation Sampling

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