Spontaneous Combustion In Coal Mines Research Articles

Study on Multi-Indicator Quantitative Risk Evaluation Methods for Different Periods of Coal Spontaneous Combustion in Coal Mines

ABSTRACT For the current coal spontaneous combustion fire risk evaluation method has the problems of single evaluation dimension, incomplete evaluation index and unreliable evaluation results. However, the coal spontaneous combustion fire risk evaluation can effectively guide coal mine fire prevention and control. Therefore, a multi-indicator quantitative risk evaluation method combining analytic hierarchy process (AHP) and linear interpolation for different periods of coal spontaneous combustion is proposed as a way to improve the rationality of coal spontaneous combustion fire risk evaluation. The continuous segmental evaluation model was established based on the factors that influence the three periods of coal spontaneous combustion (Latent Period, Self-heating Period and Combustion Period). The latent period evaluation model was established based on the fire-prone nature of coal, coal seam occurrence, mining technology, and fire prevention measures. The self-heating period evaluation model was established based on the degree of self-heating of coal, absolute CO generation, and Graham index. The combustion period, there was already a spontaneous combustion fire, directly set the fire risk score to 0. The score could fully reflect the level of coal spontaneous combustion fire risk. The higher the score, the relatively smaller the risk of coal spontaneous combustion, and vice versa, the relatively larger. According to this risk evaluation model, the risk of coal spontaneous combustion in the 2−2 coal seam of a coal mine in Shaanxi Province was evaluated. The result shows that the level of coal spontaneous combustion risk of 2−2 coal seam in this coal mine is in a safer state, and this result is consistent with the actual situation. The multi-indicator quantitative evaluation of different periods of coal spontaneous combustion effectively improves the accuracy of fire risk evaluation. Therefore, the evaluation model has certain theoretical guidance for the control of coal spontaneous combustion risk in coal mines.

Review of an Improved Longwall Panel Layout for Ground Control in Longwall Mining

Conventional longwall layout (CLL) for mining coal, trona, etc. is still fraught with problems including low resource recovery, wavy ground surface subsidence, bumps or rockbursts, gateroad support and maintenance, poisonous air hazard, spontaneous combustion in coal mines, instability of equipment at inclined, or steeply inclined working face, etc. In order to improve longwall mining, a novel alternate longwall panel layout that has been employed for over 20 years in China, Australia, and Russia, etc. is proposed termed “split-level longwall layout” (SLL). Gateroads on either end of the same SLL panel are split level, i.e., placed in different levels. This paper provides a review of existing research literature and insights on the problems encountered in CLL and the improvement of the new approach. Theoretical, numerical analysis, and field observation results of the new strategy demonstrate that the problems mentioned above in CLL are mitigated, and the development entries using the improved longwall system have a better stress environment with associated reduction in large roadway convergence, coal bumps or outbursts, and many other issues on ground control. Based on the current development of SLL and the future requirement of mining industry, the prospects as well as its applications, limitations, and concerns for SLL are presented.

A novel biomass thermoresponsive konjac glucomannan composite gel developed to control the coal spontaneous combustion: Fire prevention and extinguishing properties

Spontaneous combustion in coal mines continues to pose a significant risk. A novel biomass composite thermoresponsive gel produced by mixing konjac glucomannan (KGM) with fly ash (FA) was prepared to prevent coal spontaneous combustion. The composite gel had a controllable gelation time, a good seepage capacity, a high water retention capacity, a good combustion inhibition effect and an excellent fire extinguishing effect. Scanning electron microscopy indicated that the FA strongly interfacially adhered to the three-dimensional KGM framework and the gel wrapped around the coal surfaces well. Energy dispersive X-ray spectroscopy element mapping indicated that the FA was mixed uniformly with the KGM gel. The KGM@FA gel oxidation characteristics were analyzed by thermogravimetry infrared analysis and low-temperature coal oxidation system. The KGM@FA gel was found to effectively inhibit coal temperature increases, heat accumulation and CO generation during the process of oxidation and combustion, which would decrease the likelihood of coal spontaneous combustion. Fire-extinguishing experiments indicated that the gel covered the surfaces of burning coal well and markedly decreased the fire temperature and CO emissions and therefore stably extinguished the fire without combustion restarting. The KGM@FA gel is therefore an effective fire prevention and extinction material.

Monitoring and early warning technology of coal spontaneous combustion in coal mines: research status and intelligent development trends

Monitoring and early warning technology of coal spontaneous combustion in coal mines: research status and intelligent development trends

The graded warning method of coal spontaneous combustion in Tangjiahui Mine

The accurate prediction of the degree of coal spontaneous combustion is critical for the prevention and control of spontaneous combustion in coal mines. However, the qualitative three-stage classification method is difficult to meet the demand for accurate early warning of coal spontaneous combustion. Therefore, with long-flame coal in the Tangjiahui Mine as the study object, this paper conducted the temperature-programed coal spontaneous combustion experiment and the coal spontaneous combustion experiment. The parameters that were measured were O2 concentration and gas generation volume during the process of coal spontaneous combustion under different oxygen supply conditions. Furthermore, this study analyzed the characteristics of gas and gas ratio variation with coal temperature, screened out the characteristic gas indexes of coal spontaneous combustion in Tangjiahui Mine, and defined six characteristic temperatures and their threshold values. Accordingly, the coal spontaneous combustion process was divided into seven stages, including the latent stage, recombination stage, self-heating stage, activation stage, thermal decomposition stage, fission stage, and combustion stage. We provide the early warning criteria and the threshold values of characteristic gas parameters at each stage and define the names of graded warnings, such as gray, blue, yellow, orange, red, and black. With this warning method, we successfully forecasted the degree of coal spontaneous combustion in the gob of the 61,102 working face, guaranteeing the successful withdrawal of this working face.

Fire prevention and control using gel-stabilization foam to inhibit spontaneous combustion of coal: Characteristics and engineering applications

In order to address the issue of spontaneous combustion in coal mines during the mining process, we have proposed gel-stabilized foam (GSF) that can prevent and control fires in coal mines. In this work, GSF was successfully prepared by forming silica gel structure in the bubble film using compound foaming agent (CFA), modified polyethoxylated silicone (MPS), water glass (WG) and coagulant (NaHCO3). The effect of different concentrations of components on the properties of GSF was analyzed by studying the gelation time, foamability, and stability of the GSF. The foamability and foam stability indicated that the viscosity of foaming solution increases with the increase in the concentrations of NaHCO3 and WG. Furthermore, a higher viscosity of the foaming solution results in a poorer foaming performance, while it prolongs the foam stability. The extent of oxidation of hydroxyls and methylene on the coal sample surface treated with GSF was low. The fire-extinguishing experiments showed that the GSF could nicely cover the surface of burning coal, significantly reduce the fire source temperature, thermal radiation and emission of CO, and realize stable fire extinguishing without re-burning. The results of the on-site application of GSF in the withdrawal of 1301 working face of Shandong Longyun Coal Industry Co., Ltd., China suggest that the GSF effectively inhibited the oxidation of crushed coal body, significantly reduced the temperature of the coal body, and ensured a safe withdrawal of the rack on the working face.

A novel fire prevention and control plastogel to inhibit spontaneous combustion of coal: Its characteristics and engineering applications

In order to address the issue of spontaneous combustion in coal mines during the mining process, we have proposed a novel plastogel which can prevent and control fires in coal mines. The novel plastogel was prepared by introducing a polymer plasticizer into the conventional water glass gel (water glass/coagulant/bentonite system). The effect of different concentrations of components on the properties of plastogel was analyzed by testing the gelation time and water retention of the plastogel. The Infrared spectroscopy results indicate that plastogel can effectively inhibit the oxidation of methylene in the coal body. The SEM results illustrated that the surface morphology of the plastogel and conventional water glass gels were significantly different. The compactness and smoothness of the plastogel were significantly enhanced after the addition of plasticizer. The results of the on-site application of plastogel in the withdrawal of 1308 working face of Shandong Longyun Coal Industry Co., Ltd. suggest that the plastogel effectively inhibited the oxidation of the crushed coal body, significantly reduced the temperature of coal body, and ensured a safe withdrawal of rack on the working face. The formulated plastogel had distinct practical advantages and is proposed as an ideal fire prevention and control material.

Online fire protection technology based on fiber optic gas sensor

In recent years, the production safety has been paid by a lot of attention. Although the total number of accidents in production safety has shown a downward trend, the serious accidents occur frequently and seriously. The prediction and early warning of spontaneous combustion in coal mines mainly adopts the method of gas index analysis and prediction. The traditional trace gas detection equipment used in spontaneous combustion is mainly chromatographic analysis system, which has some problems such as complicated equipment, complicated operation, slow analysis speed and inability to realize on-line monitoring. The main purpose of this study is to develop a fire risk distribution determination system based on multi-sensor information fusion technology, which is aimed at assisting fire monitoring, fire emergency management, and fire rescue. After using the information from different sensors, the system can give an effective alarm to the fire and can provide the danger degree distribution information of different areas in the building. Based on the development status of fire safety, especially the demand of fire safety for gas detection technology, the tunable laser spectroscopy technology is proposed to solve the demand problem of gas sensing products urgently needed for major fire disasters.

Application of foam–gel technology for suppressing coal spontaneous combustion in coal mines

Coal spontaneous combustion in coal mines is an extremely destructive disaster that threatens the safety of workers in the mining process. To overcome the shortcomings of existing technologies and improve the efficiency of mine fire control, a foam–gel technique was developed. The foam–gel can capture more than 90 % of water while also covering dangerous areas in all directions in goaf based on the diffusion and stacking behavior of foam. In this paper, the details of this technique are introduced, including the foam–gel formation mechanism and production process as well as the features of foam–gel technology. This technique has been applied in many coal mines, and its application at the 72,205 underground working face at San Hejian Coal Mine belonging to Xuzhou Mining Group in Jiangsu Province, China, is presented as an example. The application process is described in detail. The application results show that this new technique has a remarkable ability to suppress coal spontaneous combustion in underground coal mines.

Study on the Hydrogen Generation Rules of Coal Oxidation at Low Temperature

Based on a hydrogen desorption experiment and a comparative experiment of low-temperature coal oxidation performed prior to and after hydrogen desorption, this paper demonstrates the occurrence of hydrogen adsorption in coal at room temperature and reveals that the hydrogen generated in the process of coal oxidation originates from coal oxidation and desorption. The results show that the hydrogen accumulation generated only by coal oxidation and the hydrogen accumulation generated solely by desorption both exhibit a LangmuirEXT1 function equation relationship with temperature. The result of the present research can provide a theoretical basis for the accurate prediction of spontaneous coal combustion and is of great significance to the prevention and control of coal spontaneous combustion in coal mines, industrial coal storage and transportation.

A comparison of three methods for the quantification of greenhouse gas emissions from spontaneous combustion in open-cut coal mines

Greenhouse gas emissions from spontaneous combustion in coal mines are currently excluded from national inventories by the United Nations Framework Convention on Climate Change because there are no robust methods available to quantify the emissions. This article reports on investigations of three approaches being pursued with the aim of developing methods which are sufficiently robust to enable these emissions to be included in inventories. The first method was based on the use of airborne thermal infrared photography coupled with chamber measurements of emissions from hot mine spoil pile surfaces. In the second method, crosswind traverses of the plume using an instrumented vehicle were used to estimate the emission fluxes. The third method was based on inverse atmospheric modelling using stationary CO2 monitors. All three methods showed considerable scatter in their estimates but also showed appreciable overlap. While the three methods used in this study have shown convergence, there is still considerabl...

Fuzzy c-means clustering approach for classification of Indian coal seams with respect to their spontaneous combustion susceptibility

Mine fire due to spontaneous combustion in coal mines is a global concern. This leads to serious environmental and safety hazards and considerable economic losses. Therefore, it is essential to assess and classify the coal seams with respect to their proneness to spontaneous combustion to plan the production, storage and transportation capabilities in mines. This paper presents a fuzzy c-mean approach for classification of coal seams based on their proneness to spontaneous combustion. This produces sets of non-exclusive clusters that allow coal samples to have memberships in multiple clusters, rather than only in exclusive partitiobns, as generated by hierarchical and k means clustering. In this research work, fifty one coal samples of varying ranks belonging to both high and low susceptibility to spontaneous combustion have been collected from all the major coalfields of India. Using moisture, volatile matter, ash content and crossing point temperature of the coal samples as the parameters, the proposed algorithm has been applied to classify the coal seams into three different categories. This classification will be useful for the planners and field engineers for taking ameliorative measures in advance for preventing the occurrence of mine fires.

An investigation of the factors associated with interpretation of mine atmosphere for spontaneous combustion in coal mines

The risk of spontaneous combustion of coal is highly serious especially in gaseous underground coal mines. In many cases such a spontaneous combustion is a source of initiation of methane-explosive mixture with tragic consequences. Early indication of spontaneous combustion and determination of its seat temperature is in a given environment a key part of safety of underground coal mines. A commonly used method for the detection of spontaneous combustion is an interpretation of coal oxidation gas products whose historical roots go back to the first halve of the 20th century as Graham's ratio. In the second half of this century a wide research on application of desorbed higher hydrocarbons C1–C4 and hydrogen for the given purpose took place. Until now, the interpretations in question encounter significant inaccuracies. The paper describes the research on factors affecting the accuracy of the determination of coal spontaneous combustion temperature on conditions of underground coal mines. The research was focused on the accuracy of interpretation of mine gases in connection with the use of laboratory verified gas characteristics of thermal oxidation of coal. Three chromatograph laboratories had been involved to test thermal oxidation of coal to determine a deviation of spontaneous combustion gases. The variability among the laboratories and used techniques were insignificant. Besides the laboratory methods, it may not reflect processes in coal mines and one of the results was that coal itself had been a source of substantial variability of desorption of spontaneous combustion gases. The spontaneous combustion data still requires human interpretation. Simple criteria for providing warning by a computer do not exist just yet.

A discrete particle swarm optimization approach for classification of Indian coal seams with respect to their spontaneous combustion susceptibility

Mine fires due to spontaneous combustion in coal mines is a global concern. This leads to serious environmental and safety hazards and considerable economic losses. Therefore it is essential to assess and classify the coal seams with respect to their proneness to spontaneous combustion to plan the production, storage and transportation capabilities in mines. This paper presents the formulation of clustering problem into a linear assignment model and the application of a discrete particle swarm optimization approach for the classification of coal seams based on their proneness to spontaneous combustion. In this research work, twenty nine coal samples of varying ranks belonging to both high and low susceptibilities to spontaneous combustion have been collected from all the major coalfields of India. Using moisture, volatile matter, and ash content and crossing point temperature of the coal samples as the parameters, the proposed algorithm has been applied to classify the coal seams into three different categories. This classification will be useful for the planners and field engineers for taking ameliorative measures in advance for preventing the occurrence of mine fires.

Spontaneous Combustion Prediction of Coal by C80 and ARC Techniques

Many coal fires were caused by spontaneous combustion in coal mines or coal storehouses, which resulted in a great loss and energy wastage. To identify and evaluate the hazardous degree of coal stockpile, a C80 microcalorimeter and accelerating rate calorimeter (ARC) were employed in this work. The coal samples undergo an exothermal process start at 80 °C with heat generation of −75.1 J g−1(mean value) detected by C80 experiment. The activation energies of the first exothermal process were calculated for the three experiments, and the mean value is 80.76 kJ mol−1, which is lower than that of obtained from the ARC result, 127.0 kJ mol−1. For a 300 tons coal stockpile, the self-heating oxidation temperatures (SHOT) were calculated as 164, 60, 90, and 68 °C based on the ARC experiment and three C80 experiments, respectively. Further research on the mass effect on SHOT shows that if the coal mass is less than 12 tons, the danger of thermal spontaneous combustion is less. However, if the mass amount is more th...

Mechanised Spraying Device—A Novel Technology for Spraying Fire Protective Coating Material in the Benches of Opencast Coal Mines for Preventing Spontaneous Combustion

Spontaneous combustion in coal mines play a vital role in occurrences of fire. Fire in coal, particularly in opencast mines not only causes irreparable loss of national wealth but damages the surface structure and pollutes the environment. The problem of spontaneous combustion/fire in opencast coal benches is acute. Presently over 75% of the total production of coal in Indian mines is being carried out by opencast mining. Accordingly a mechanised spraying device has been developed for spraying the fire protective coating material for preventing spontaneous combustion in coal benches of opencast mines jointly by Central Mining Research Institute, Dhanbad and M/s Signum Fire Protection (India) Pvt. Ltd., Nagpur under Science & Technology (S&T) project funded by Ministry of Coal, Govt. of India. The objective of this paper is to describe in detail about the mechanised spraying device and its application for spraying fire protective coating material in the benches of opencast coal mines for preventing spontaneous combustion/fire.

Algorithms for the Detection of Spontaneous Combustion in Coal Mines

Very effective detection of spontaneous combustion or open fires in coal mines can be provided from calculations based on measurements of a few parts per million of carbon monoxide (CO) in the ventilating air, even in the presence of CO from shotfiring, diesels and other sources. A project to develop automatic alarms is described.

Algorithms for the Detection of Spontaneous Combustion in Coal Mines

Algorithms for the Detection of Spontaneous Combustion in Coal Mines

石炭の表面反応 (第1報)

The researche of coal-surface oxidation at a low temperature is an important problem for the basic study on the spontaneous combustion in coal mines. Neverthless few detailed procedures of this reaction have been known.In this work, the authors essaied a systematic study on the surface reaction of coal with O2, and pursueing the sorption phenomena of O2.It is very important for us to get samples cleaned of the surface as possible, and so the authors used a vacuum-cleaning method for the purpose.The coal samples were mined in the Shin-Horonai Cosl-Mine and experimented after crushing to the size-rates of 4-8 mesh, 28-48mesh, 100-150mesh and 150-200mesh.The sorption tests at a vacuum pressure of about 10-6mmμHg were resulted as follows:1. The sorption is taken place at a room temperature and the gas capacity isotherms at 25°C are in characteristics similar to the one of Freundlich type.2. The sorption consists of two stages, namely a rapid stage (former stage) and a slow stage (latter stage) and these are different in a rate of sorption as formulated:dQ/dt=K/t...former stagedQ/dt=dktd-1...latter stage3. The velocity of sorption is generally expressed by a function of the diffusion coefficient of O2 through the pores of coal, and so always under the influence of physical condition-the external surface area and the presence of coal dust upon the surface specially in a former stage.

Mining Research at Birmingham

WE have received from the University of Birmingham the report on the work of the Mining Research Laboratory during the fifteen months to March 1935. The introduction explains how it is that the report ends with work done in March. The report especially discusses silicosis, pneumonoconiosis, etc., to which six pages out of twenty are devoted. Attention may be directed to the excellent article by Bax in Gliickauf, page 1241, upon the methods used in combating silicosis in the Ruhr district. The report before us shows, like Mr. Bax's paper, that nothing definite is yet known as to the causes of silicosis, etc. The suggestion is made that the incidence of silicosis may in large measure be due to the riding of men on ‘spakes’. The essential thing is that up to the end of December 1934 there have been a great many deaths in the country from silicosis, of which more than 50 per cent have occurred in the anthracite area of South Wales. Other subjects treated in the report before us are underground illumination, utilisation of coal by converting coke oven gas into gas with high calorific value, the quantity of firedamp in coal seams as worked, the pressure not having been investigated, spontaneous combustion in coal mines, control of atmospheric conditions in hot and deep mines, whilst investigations connected with the Gresford disaster apparently have occupied a great deal of the time and energies of the Research Laboratory, of which the late Prof. J. S. Haldane was director.