Dispersion of methane in tailgate of a retreating longwall mine: a computational fluid dynamics study

Mishra, Devi Prasad; Kumar, Poninder; Panigrahi, Durga Charan

doi:10.1007/s12665-016-5319-9

Cited by 32 publications

(23 citation statements)

References 11 publications

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“…In order to examine the air flow through the caving goaves of longwalls, it was also necessary to determine the vertical extent of this flow. Generally, it is assumed that the zone of air flow through the goaves with caving is equal to three to four times the thickness of the exploited seam (layer) [36].…”

Section: Problem Statement and Boundary Conditionsmentioning

confidence: 99%

“…The attempts to measure the ventilation parameters in the goaves made to date have been unsuccessful in the majority of cases. For this reason, this zone was demarcated using model-based tests, which are successfully used for variant analyses of the processes related to ventilation of underground mine headings, as well as for analyses of emergency states occurring in these headings [36][37][38].…”

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confidence: 99%

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The Impact of the Strength of Roof Rocks on the Extent of the Zone with a High Risk of Spontaneous Coal Combustion for Fully Powered Longwalls Ventilated with the Y-Type System—A Case Study

Tutak

Brodny

2019

Applied Sciences

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During the ventilation of longwalls in hard coal mines, part of the air stream migrates to the goaves with caving. These goaves constitute a space (void) filled with rocks following coal extraction. In the case where these goaves contain coal susceptible to spontaneous combustion, the flow of such an air stream through the goaves may lead to the formation of favourable conditions for coal oxidation, self-heating and spontaneous combustion. Such an area is referred to as the zone with a particularly high risk of spontaneous coal combustion (endogenous fires). The location and extent of this zone depend on many factors, with one of the most important being the permeability of the goaves which determines the tensile strength of the roof rocks forming the caving. This strength determines the propensity of these rocks to transform into the state of caving and the degree of tightness of the cave-in rubble (treated as a porous medium). The purpose of the present paper is to determine how the tensile strength of roof rocks influences the extent of the zone with a particularly high risk of spontaneous coal combustion (endogenous fires) in caving goaves of the longwalls ventilated with the Y-type system. To achieve this goal, model-based tests were conducted for a region of the longwall mined with caving and ventilated with the Y-type system. Critical air speed and oxygen concentration values in the caving goaves of this longwall were determined for the actual conditions of exploitation. These parameters define the risk zone of spontaneous coal combustion. The tests also helped to determine the extent of this zone, depending on the strength of the rocks forming the caving. The results obtained unequivocally indicate that the type of rocks forming the caving affects its permeability and the extent of the risk zone for spontaneous coal combustion. At the same time, the distribution of this zone is substantially different than in the case of other ventilation systems. The results obtained are of real practical significance for preventive measures to reduce fire risks. The effectiveness of these measures significantly improves the safety of mining exploitation.

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Section: Problem Statement and Boundary Conditionsmentioning

confidence: 99%

mentioning

confidence: 99%

The Impact of the Strength of Roof Rocks on the Extent of the Zone with a High Risk of Spontaneous Coal Combustion for Fully Powered Longwalls Ventilated with the Y-Type System—A Case Study

Tutak

Brodny

2019

Applied Sciences

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“…When the gas-solid two-phase inhibitors are injected into the explosion space, two aspects of inhibition effects work simultaneously. The inert gases dilute the concentration of CH 4 and O 2 and the powders react with free radicals to interrupt the explosion Energies 2019, 12, 398 8 of 10 chain's development. Both the inert gases and chemical powders play a critical role in the whole explosion process.…”

Section: Suppression Mechanism Of Gas-solid Two-phase Inhibitorsmentioning

confidence: 99%

“…It is also an important industrial raw material. However, it is easily ignited and causes explosion accidents, such as gas explosions in mines [3,4]. Explosion accidents caused by methane have caused great environmental damage and economic losses.…”

Section: Introductionmentioning

confidence: 99%

The Inhibition Effect of Gas–Solid Two-Phase Inhibitors on Methane Explosion

Wang

Meng

et al. 2019

Energies

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In order to study the inhibition effect of gas-solid two-phase inhibitors on a methane explosion, the influence of these parameters was investigated and compared with that of single-phase inhibitors. The results show that the inhibition effect of gas-solid two-phase inhibitors on a methane explosion is better than the added effect of two single-phase inhibitors, indicating that a synergistic effect can be obtained by gas-solid two-phase inhibitors. The two-phase inhibitors which are composed of NaHCO 3 (BC) powders and inert gas have a better suppressing property than those composed of NH 4 H 2 PO 4 (ABC) powders and inert gas. The two-phase inhibitors composed of CO 2 and powders have a better suppressing property than those composed of N 2 and powders. The 9.5% premixed methane-air mixture can be completely inhibited by 0.10 g/L BC powders mixed with 8% CO 2 . The suppression mechanisms of the gas-solid two-phase inhibitors on the methane explosion were discussed.Energies 2019, 12, 398 2 of 10 Chemical powders, such as carbonate, phosphate, halide etc., have widely been used as extinguishing agents on methane explosions and dust explosions, due to their physical and chemical inhibition effects. The inhibition effects of various chemical powders (such as SiO 2 , CaCO 3 , ABC, BC, zeolite, red mud, Al(OH) 3 , composite powders, etc.) on methane explosions have been studied [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. The experimental results presented that different powders showed different suppression performances on methane explosions.Recently, more attentions have been paid to gas-solid two-phase inhibitors [27][28][29]. Deng [30] studied the influence of a two-phase inhibitor Mg(OH) 2 /CO 2 on methane explosion, and observed that the actual superposition effect was inferior to the theoretical superposition effect. The research by Luo [31] showed that the ABC/CO 2 two-phase inhibitor had a cooperative synergism, which gave a good suppression performance on methane explosion. Jiang [32] researched the suppression effect of ultrafine ABC powders and N 2 mixture on methane explosions. The results showed that the maximum decreasing amplitudes of the overpressure and the flame speed were 76.8% and 100%, respectively. According to the research, it is clear that the suppression effect of gas-solid two-phase inhibitors was better than the single-phase gases or powders. However, there are few studies comparing the actual suppression effect of gas-solid two-phase inhibitors with the theoretical addition effect suppressed by single-phase gas and powders, respectively. It is not clear whether there is a cooperative effect between inert gas and powders.In this paper, the influence of ABC powders (NH 4 H 2 PO 4 ), BC powders (NaHCO 3 ), N 2 , CO 2 and gas-solid two-phase inhibitors on the 9.5% premixed methane-air explosion parameters, including the max-pressure, the time to max-pressure and the maximum rate of pressure rise, was experimentally researched using a 20 L spherical vessel. The actual suppre...

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“…Forecasts for methane release usually include mining excavations in terms of exploitation safety. This type of forecast can be exemplified by the dynamic prediction of absolute methane content of bearing capacity of longwalls [18], the prediction of methane concentration distribution in mining excavations using the Computational Fluid Dynamics (CFD) methods [21,22], or the prediction of methane concentration using artificial neural networks [23,24]. This approach is justified when considering safety of the exploitation process.…”

Section: Introductionmentioning

confidence: 99%

Forecasting Methane Emissions from Hard Coal Mines Including the Methane Drainage Process

Tutak

Brodny

2019

Energies

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With regard to underground mining, methane is a gas that, on the one hand, poses a threat to the exploitation process and, on the other hand, creates an opportunity for economic development. As a result of coal exploitation, large amounts of coal enter the natural environment mainly through ventilation systems. Since methane is a greenhouse gas, its emission has a significant impact on global warming. Nevertheless, methane is also a high-energy gas that can be utilized as a very valuable energy resource. These different properties of methane prompted an analysis of both the current and the future states of methane emissions from coal seams, taking into account the possibilities of its use. For this reason, the following article presents the results of the study of methane emissions from Polish hard coal mines between 1993–2018 and their forecast until 2025. In order to predict methane emissions, research methodology was developed based on artificial neural networks and selected statistical methods. The multi-layer perceptron (MLP) network was used to make a prognostic model. The aim of the study was to develop a method to predict methane emissions and determine trends in terms of the amount of methane that may enter the natural environment in the coming years and the amount that can be used as a result of the methane drainage process. The methodology developed with the use of neural networks, the conducted research, and the findings constitute a new approach in the scope of both analysis and prediction of methane emissions from hard coal mines. The results obtained confirm that this methodology works well in mining practice and can also be successfully used in other industries to forecast greenhouse gas and other substance emissions.

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Dispersion of methane in tailgate of a retreating longwall mine: a computational fluid dynamics study

Cited by 32 publications

References 11 publications

The Impact of the Strength of Roof Rocks on the Extent of the Zone with a High Risk of Spontaneous Coal Combustion for Fully Powered Longwalls Ventilated with the Y-Type System—A Case Study

The Impact of the Strength of Roof Rocks on the Extent of the Zone with a High Risk of Spontaneous Coal Combustion for Fully Powered Longwalls Ventilated with the Y-Type System—A Case Study

The Inhibition Effect of Gas–Solid Two-Phase Inhibitors on Methane Explosion

Forecasting Methane Emissions from Hard Coal Mines Including the Methane Drainage Process

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