Mine fire gas indices and their application to Indian underground coal mine fires

Singh, Ashok K.; Singh, Rajendra; Singh, Mahendra; Chandra, Hem; Shukla, Niraj Kumar

doi:10.1016/j.coal.2006.04.004

Cited by 149 publications

(54 citation statements)

References 2 publications

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“…This is why various fire prevention activities are undertaken in mining industry to mitigate these risks [1][2][3]. An example of such activities is a complex control of coal's self-heating process based on the monitoring of mine air composition, which enables early detection of self-heating centers and their elimination.…”

Section: Introductionmentioning

confidence: 99%

Effect of Coal Grain Size on Sorption Capacity with Respect to Propylene and Acetylene

2017

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Propylene and acetylene are released to mine air with the increase in the temperature of self-heating coal. Concentrations of these gases in mine air are applied as indicators of the progress of the self-heating process. Hydrocarbons emitted from the self-ignition center are sorbed on coal, while migrating through the mine workings. Coal crushed during the mining process is characterized by a high sorption capacity, which facilitates the sorption phenomena. This results in the decrease in hydrocarbons content in mine air, and in the subsequent incorrect assessment of the development of the self-heating process. The results of the experimental study on propylene and acetylene sorption on Polish coals acquired from operating coal mines are presented in this paper. Bituminous coal is characterized by a high sorption capacity with respect to unsaturated hydrocarbons, like propylene and acetylene. The sorbed volumes depend on the grade of metamorphism, porosity, and chemical characteristics of coal. Low level of metamorphism, increased porosity, and oxygen content result in higher sorption capacity of coals. The reduction in grain size of coals also results in the increased sorption capacity with respect to hydrocarbons. The most significant increase in the volumes of sorbed propylene and acetylene with the decrease in grain class was observed for coals of low porosity, high grade of metamorphism, and low to medium sorption capacities. The 10-fold decrease in coal grain size resulted in the 3 to 6-fold increase in the volume of sorbed propylene, and 2-fold increase for acetylene. The decrease in grain size results in higher accessibility of pore structure, increased pore volume and area, and higher number of active centers interacting with hydrocarbons of dipole characteristics. For coals with low grade metamorphism, high porosity, and high sorption capacity the volumes of sorbed propylene and acetylene increased only slightly with the decrease in coal grain size.

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Section: Introductionmentioning

confidence: 99%

Effect of Coal Grain Size on Sorption Capacity with Respect to Propylene and Acetylene

2017

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“…This phenomenon is a consequence of coal self-heating caused by the accumulation of heat released from the contact of hard coal with oxygen from the surrounding air. A number of techniques based on optical microscopy and thermal studies have been investigated to determine the susceptibility of coal to spontaneous combustion [1][2][3]; however, in order to evaluate the state of spontaneous combustion, mine operators apply fire indices [4][5][6]. The concept behind this method is based on the following: 1) the monitoring of mine air composition in selected places underground, 2) the assumption that the profile of the emission of gaseous oxidation products is characteristic of the temperature of the coal, and 3) determining the fire indices as calculated on the basis of the concentrations of gases in mine air.…”

Section: Introductionmentioning

confidence: 99%

Sorption characteristic of coal as regards of gas mixtures emitted in the process of the self-heating of coal

Wojtacha‐Rychter

Smoliński

2017

E3S Web Conf.

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Abstract. One of the most challenging tasks in the coal mining sector is the detection of endogenous fire risks. Under field conditions, the distance between the points where samples for the analyses are collected and the actual place where coal self-heating takes place may be quite remote. Coal is a natural sorbent with a diverse character of pore structures which are surrounded by fractures and cleavage planes constituting ideal spaces for the flow and adsorption of gases. The gases (methane, ethane, ethylene, propane, propylene, acetylene, carbon dioxide, carbon monoxide, hydrogen) released from the source of fire migrate through the seam and may be subject to adsorption, or they may cause the desorption of gases accumulated in coal. Therefore, the values of reference sample concentrations may be overstated or understated, respectively. The objective of this experimental study was to investigate the adsorption phenomena accompanying the flow of a multi-component gas mixture through a coal bed which may occur in situ. The research was conducted by means of a method based on a series of calorimetric/chromatographic measurements taken to determine the amount of gases released during coal heating at various temperatures under laboratory conditions. Based on the results obtained in the course of the experiments, it was concluded that the amount of gas adsorbed in the seam depends on the type of coal and the gas. Within the multi-component gas mixture, hydrocarbons demonstrated the largest sorption capacity, especially as concerns propylene.

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“…To prevent and control the spontaneous combustion of coal, the technologies of grouting (Xu et al 2012), nitrogen (Singh et al 2007), gel , foam (Tripathi 2014;Qin et al 2014) and inhibitor (Wang et al 2004;Yang et al 2014) have been adopted since the 1950s. They play an active role in the process of prevention of spontaneous combustion of coal in goaf; however, some shortages still exist: such as grouting, slurry only flows along the low-lying areas, and it cannot uniformly cover the coal in higher places; injecting nitrogen, the gas can easily diffuse along the air leakage and the ability of extinguishing and cooling is weak; pouring gel, it accompanies the shortages of high cost, small flow, and diffusion limitation in goaf; foam injection, the stability of foam is poor, and it generally bursts during 8-12 h, without having the persistent effective ability to prevent the spontaneous combustion of coal; spraying inhibitor, it is difficult to be uniformly dispersed in coal and easy to corrode the coal face mechanical equipment.…”

Section: Introductionmentioning

confidence: 99%

The fire extinguishing performances of foamed gel in coal mine

et al. 2016

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Experiments have been made to investigate how mass concentrations of thickener and crosslinker blends and foaming multiple affect temperature resistance of foamed gel. The results show that, at 100°C, the time for temperature tolerance of common foam is only 196 s, while the time of foamed gel formed by thickener and crosslinker with the mass fractions of both 0.3, 0.4 and 0.5 % is 570, 604 and 780 s, respectively. When the foaming multiple is 5, the time for temperature resistance is 620 s. But the time reduces to 360 s as the foaming multiple increases to 30. Furthermore, researches are also conducted on the extinguishing effect of foamed gel. It can be known from the results that, when putting out the coal fire with similar size, the volume of foamed gel used is only one-ninth of that of common foam and the extinguishing time is less than half of common foam. With increasing in the mass concentration of thickener and crosslinker blends, the extinguishing time first shortens and then prolongs. When the mass fraction of complex solution mixed by thickener and crosslinker is 0.6 %, the extinguishing efficiency is the highest. If the foaming multiple is 5, the extinguishing time is the shortest. However, the time remains constant when the foaming multiple is over 20.

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Mine fire gas indices and their application to Indian underground coal mine fires

Cited by 149 publications

References 2 publications

Effect of Coal Grain Size on Sorption Capacity with Respect to Propylene and Acetylene

Effect of Coal Grain Size on Sorption Capacity with Respect to Propylene and Acetylene

Sorption characteristic of coal as regards of gas mixtures emitted in the process of the self-heating of coal

The fire extinguishing performances of foamed gel in coal mine

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