The Validation Process of the Method of Balancing Gas Contained in the Pore Space of Rocks via Rock Comminution

Kudasik, Mateusz; Pajdak, Anna; Skoczylas, Norbert

doi:10.20944/preprints201803.0023.v1

Cited by 7 publications

(6 citation statements)

References 27 publications

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“…At the Strata Mechanics Institute of the Polish Academy of Sciences, innovative measurement instruments for investigating the rock-gas system have been constructed [41][42][43][44][45][46][47][48][49]. The permeability of coal under stress conditions was investigated using a novel measurement stand, whose schematic representation is provided by Figure 3, and a photograph in Figure 4.…”

Section: Measurement Stand For Studies Into Permeability Of Coal Undementioning

confidence: 99%

Investigating Permeability of Coal Samples of Various Porosities under Stress Conditions

Kudasik

2019

Energies

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Among the numerous factors that have an impact on coal permeability, coal porosity is one of the main parameters. A change in the mechanical stress applied to coal results in a change of porosity. The main objective of the conducted research was to answer the following question: is a decline in coal permeability a direct effect of a decrease in coal porosity, and does mechanical stress result solely in a porosity change? A study of coal porosity under mechanical stress conditions was conducted using a uniquely constructed measurement stand. The coal samples used were briquettes prepared from a granular coal material (middle-rank coal of type B—meta bituminous, upper carboniferous formation) from the “Zofiówka” coal mine, in Poland. In order to describe coal permeability, the Klinkenberg equation was used, as it takes into consideration the slippage effect, typical of porous media characterized by low permeability. On the basis of the obtained results, it was established that the values of the Klinkenberg permeability coefficient decrease as the mechanical stress and the corresponding reduction in porosity become greater. As the briquette porosity increased, the Klinkenberg slippage effect: (i) disappeared in the case of nitrogen, (ii) and was minor for methane. The briquettes used were characterized by various porosities and showed that mechanical stress results mainly in a change in coal porosity, which, in turn, reduces coal permeability.

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Section: Measurement Stand For Studies Into Permeability Of Coal Undementioning

confidence: 99%

Investigating Permeability of Coal Samples of Various Porosities under Stress Conditions

Kudasik

2019

Energies

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“…The results of these studies prompted the comparison of methane emission through the shafts of hard coal mines with observations made with the use of aerial measurement techniques. There are also known research works on methane emission [20], and the results of their research allow for the forecasting of methane emissions.…”

Section: Discussionmentioning

confidence: 99%

The Impact of Cutting with a Shearer on the Conditions of Longwall Ventilation

Dziurzyński¹,

Krach²,

Pałka³

et al. 2021

Energies

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In coal mines that are exploiting methane-saturated seams, high-level emission of methane is often the basic limitation for modern and high-efficiency longwall complexes. This paper presents selected observations and tests carried out in the Cw-4 longwall in seam 364/2 of the Budryk mine, which belongs to JSW SA. To observe the methane levels in the Cw-4 longwall, additional sensors were installed at the end section of the longwall from the side of the gobs, and the air velocity and methane concentration were registered in a multi-point system that were built in the selected longwall cross-section. The air parameters were recorded in the monitoring system. The use of multi-point simultaneous measurements of the local velocities and concentrations of methane in the longwall cross-section allowed for the precise determination of the air and methane volume flow using the velocity field method. This allowed us to perform a comparative analysis of the obtained records of the air parameters using special software to determine the distribution of the parameters in the cross-section of the excavation. An important element of the study was the simultaneous registration of the methane concentration in the longwall, information on the operating times, the direction of shearer operation, and the type of work being done (i.e., mining/cleaning).

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“…Comparing the two processes, there a significant difference is seen between the values of energy obtained for the same parameters. For example, taking typical values for the porosity of dolomites (ε = 5%) [ 27 , 28 , 29 ] and for the pressure of gas in the porous structure ( p = 6.5 MPa) [ 30 , 31 , 32 ], the value of the energy obtained for an isothermal process is approximately 1.33 MJ/m 3 , while for an adiabatic transformation it is approximately 0.56 MJ/m 3 . For the same gas pressure, assuming a higher porosity of 20%, the energy value is almost 3 MJ/m 3 higher for isothermal than for adiabatic transformation.…”

Section: Energy Of the Gasmentioning

confidence: 99%

The Intensity of Heat Exchange between Rock and Flowing Gas in Terms of Gas-Geodynamic Phenomena

Koziel

Topolnicki

Skoczylas

2021

Entropy

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Gas-induced geodynamic phenomena can occur during underground mining operations if the porous structure of the rock is filled with gas at high pressure. In such cases, the original compact rock structure disintegrates into grains of small dimensions, which are then transported along the mine working space. Such geodynamic events, particularly outbursts of gas and rock, pose a danger both to the life of miners and to the functioning of the mine infrastructure. These incidents are rare in copper ore mining, but they have recently begun to occur, and have not yet been fully investigated. To ensure the safety of mining operations, it is necessary to determine parameters of the rock–gas system for which the energy of the gas will be smaller than the work required to disintegrate and transport the rock. Such a comparison is referred to as an energy balance and serves as a starting point for all engineering analyses. During mining operations, the equilibrium of the rock–gas system is disturbed, and the rapid destruction of the rock is initiated together with sudden decompression of the gas contained in its porous structure. The disintegrated rock is then transported along the mine working space in a stream of released gas. Estimation of the energy of the gas requires investigation of the type of thermodynamic transformation involved in the process. In this case, adiabatic transformation would mean that the gas, cooled in the course of decompression, remains at a temperature significantly lower than that of the surrounding rocks throughout the process. However, if we assume that the transformation is isothermal, then the cooled gas will heat up to the original temperature of the rock in a very short time (<1 s). Because the quantity of energy in the case of isothermal transformation is almost three times as high as in the adiabatic case, obtaining the correct energy balance for gas-induced geodynamic phenomena requires detailed analysis of this question. For this purpose, a unique experimental study was carried out to determine the time required for heat exchange in conditions of very rapid flows of gas around rock grains of different sizes. Numerical simulations reproducing the experiments were also designed. The results of the experiment and the simulation were in good agreement, indicating a very fast rate of heat exchange. Taking account of the parameters of the experiment, the thermodynamic transformation may be considered to be close to isothermal.

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The Validation Process of the Method of Balancing Gas Contained in the Pore Space of Rocks via Rock Comminution

Cited by 7 publications

References 27 publications

Investigating Permeability of Coal Samples of Various Porosities under Stress Conditions

Investigating Permeability of Coal Samples of Various Porosities under Stress Conditions

The Impact of Cutting with a Shearer on the Conditions of Longwall Ventilation

The Intensity of Heat Exchange between Rock and Flowing Gas in Terms of Gas-Geodynamic Phenomena

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