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Methane explosions often occur during the closure process of mine fire zones, during which the concentration of combustible gases such as monoxide and ethylene produced by coal combustion dynamically changes, which changes the risk of methane explosion. Therefore, studying the gas concentration distribution and methane explosion limits during the process of mine closure is of great significance for disaster prevention and control. In this paper, a three-dimensional physical model of gob was built, and the distribution of monoxide and ethylene in the process of fire zone closure was investigated. Further, the explosion limits of methane enriched with CO and C2H4 in the closed fire zone of gob were analyzed. The results indicate that CO and C2H4 would form a small-scale accumulation phenomenon near the fire zone after the closure of the fire zone, and when the fire zone is closed for more than 15 min, the mixed combustible gases in the environment lose their explosiveness. [ABSTRACT FROM AUTHOR]

• The coordination effect of Na+ and Mg2+ greatly improves the water absorption of coal; • Ion inhibition has no effect on the type of adsorption between CO 2 and coal molecules; • Ion inhibition approximately doubles the adsorption energy between CO 2 and coal molecules. In view of the limitations of single means of inhibiting coal spontaneous combustion and the lack of research on the joint mechanism of different inhibition means, this paper constructed a joint oxygen shielding structure based on the bionic principle that gastric mucosa and gastric mucus cooperate with each other to resist gastric acid and prevent gastric acid from eroding the gastric wall, and studied the microscopic mechanism of joint inhibition of coal spontaneous combustion by using Na+, Mg2+ blocking and CO 2 inerting at the same time. In this paper, the change of CO 2 adsorption strength before and after ionic inhibition is used to demonstrate that the two have a synergistic effect of inhibiting coal spontaneous combustion, and the micro-mechanism of the combination of these two means is not seen in related studies. In addition, this paper also made detailed quantum chemistry simulation calculations on the water absorption of ions, the existence of coordination bonds, and the chemical stability of coal molecules after inhibition, which is a refinement and supplement to the theory of coordination inhibition. The results showed that the coal molecules themselves were attractive to water, with an adsorption energy of -12.43 kJ/mol; the adsorption strength of coal molecules to water after Na+ inhibition was more than four times of that before the inhibition, at -53. 65 kJ/mol, and the effect of Mg2+ was even better, with the adsorption energy to water increasing to -180.98 kJ/mol, and from the point of view of adsorption of water, the ions exhibited a positive coal spontaneous combustion inhibition effect. The inhibitory effect of Na+ on aldehyde group is stronger than that of Mg2+; the initial adsorption energy between CO 2 and coal molecules was -12.34 kJ/mol, and the adsorption energy between the coal molecular structure and CO 2 after ionic inhibition was -18.12 kJ/mol ∼ -28.62 kJ/mol, which was significantly enhanced compared with that before the inhibition, suggesting that the combination of the two means can synergistically inhibit spontaneous combustion of coal, and the synergistic effect of Mg2+ with inert gases is stronger than that of Na+. [Display omitted] [ABSTRACT FROM AUTHOR]

• Release of CO and CO 2 at constant temperature with time follows two different rules. • C–H in side chains is oxidized into precursors of carbon oxides, C = O and –COO. • CO and CO 2 can be produced by stepwise decomposition at ambient temperature. • Production of CO and CO 2 by direct decomposition occurs only at high temperatures. Precursors of carbon oxides in coals are considered to be related to aldehyde group(–CHO) and carboxyl group (–COOH), but the way of decomposition of precursors to produce carbon oxides is not clear. Through theoretical analysis, experimental research and quantum chemical calculation at molecular scale, this paper explores the decomposition mode and products of carbon oxide precursors during coal spontaneous combustion (CSC). A programmed heating device was used to investigate the change rule of gas product concentration during the constant temperature oxidation of coals, and the microstructure of the coals was characterized by low-temperature nitrogen adsorption experiments (BET), X-ray Diffraction (XRD) and X-ray photoelectron spectrometer (XPS). The results of the study show that during coal oxidation, the inhomogeneous energy exchange between the coals and the external heat source results in the change of gas product concentration with time following two rules. BET experiments reveal that oxidation leads to the evolution of fine mesopores to macropores and an increase in the number of pores with diameters larger than 20 nm in the coals, which facilitates the transport of oxygen molecules through the pore structure. Within 200 °C, the microcrystalline structure of coals is basically unchanged, and the active structure C–C/C–H on the side chain is converted to –CHO and –COOH and then decomposed to produce carbon oxides. Quantum chemical calculation shows that the reaction energy barrier of carbonyl group and carboxyl group decomposed step by step to form carbon oxides is much smaller than that of direct decomposition, and carbon oxides and alkyl radicals can be produced even at room temperature by step decomposition. The research results provide theoretical guidance for the formation mechanism of carbon oxides during low temperature oxidation of coals. [ABSTRACT FROM AUTHOR]

• The pronounced retardation in the low-temperature oxidation process of methane-bearing coal samples was elucidated. • The inhibitory mechanism of coal oxidation by adsorbed gas molecules was elucidated. • The impact of microstructure on the gas desorption and oxidation at various stages for methane-bearing coals was elucidated. The coupling of coal spontaneous combustion and high methane is ubiquitously observed in coal mining and poses a significant jeopardy to production safety. The extant studies are largely focused on altering external methane conditions and fail to investigate the spontaneous combustion properties of methane-laden coal samples. This study conducted an evaluation of the microstructure of typical coal samples, followed by a fractal analysis. It discovered that the surface structure of the specimen is relatively homogeneous, and the mesopores (2–4 nm) exhibit a significant influence on the specific surface distribution. The overall pore structure is characterized by a multiplicity of peaks, which renders the coal sample markedly segmented during methane desorption, oxygen consumption, and gas products generation. The low-temperature oxidation tests under various working conditions reveal that methane desorption is a crucial factor in determining the spontaneous combustion pattern of the coal sample. The degree of methane desorption bears a close association with the oxygen concentration, and at an oxygen concentration of approximately 2 %, there is a turning point for gas generation and oxygen consumption. The present investigation provides a qualitative and quantitative exposition of the relevant laws, offering guidance for fire prevention and suppression in pertinent mines. [ABSTRACT FROM AUTHOR]

In order to study the law of spontaneous combustion in goaf under the condition of gas extraction, the method of beam tube monitoring and numerical analysis is adopted to obtain three dimensional distribution of oxygen concentration and contour map under the condition of different negative pressure. Based on the way of regression analysis, reasonable negative pressure are determined. The results show that with the increase of negative pressure, the spontaneous combustion "three-zone" in goaf: the heat dissipation zone and the spontaneous combustion zone become wider and the suffocation zone narrows. At the same time, the trend of spontaneous combustion zone presents to the deep part of the goaf; the amount of gas extraction increases first and then decreases with the increase of negative pressure. Combined with the trend of spontaneous combustion zone and the amount of gas extraction in goaf, and the reasonable negative pressure value is 32kpa and verified. [ABSTRACT FROM AUTHOR]

• A multi-physical coupling transient model during mining-stopped period was developed. • Initial condition should use the temperature distribution at the end of coal mining. • Effects of critical parameters on spontaneous combustion in stoppage are evaluated. Mining-stopped period is a high-risk stage owing to spontaneous combustion of coal in longwall gobs, but there have been few studies in this regard. To address this issue, a multi-physical coupling transient model was developed to characterize the evolution of coal self-ignition in longwall gobs during mining-stopped period. The initial condition of the model had used the temperature distribution of the gob at the moment when coal mining ends. The boundary of the solid temperature field, which was exchanging heat with airflow across working face, was set as the convective heat transfer condition. These improvements ensured that the calculative model was more realistic. The hazards due to spontaneous heating during stoppage period that were associated with some extrinsic mining parameters had been clearly evaluated. The results show that the high-temperature zones in the stoppage period are still located on the windward side of the gob, and the calculated spontaneous combustion period of the gob is consistent with the scenario on-site. Furthermore, the mining parameters can be optimized to effectively increase the time required for spontaneous combustion in the stoppage state by increasing the longwall advance rate or reducing the thickness of crushed coal in the coal mining process, and by further reducing the ventilation flux during the stoppage period. This work can provide suggestions on how to extend the spontaneous combustion period for safely dismantling and moving machines and equipment away from the working face. [ABSTRACT FROM AUTHOR]

Due to a gradual increase in mining depths in northern China, the water inrush problem there has become increasingly complex. In the present study, a physical model was developed of a syncline-axis structural fractured zone above confined water, using measured parameters from the Baizhuang coal mine. Using the similarity theory, water inrush from a fractured floor was simulated with different water heads and different structural zones. The mechanism of a delayed water inrush from the floor under the combined action of confined water and a fractured zone was also studied. The results demonstrated that: (1) Water inflow under different pressures; (2) Sand inrush discharges gradually increased under various pressurized water pressures and then decreased; and (3) Based on water and sand inrush discharges, the changes in the Reynolds number and porosity were analyzed, and a "void flow-fissured flow-pipeline flow" transition was proposed. This research provides a basis for developing methods to prevent floor water inrush during deep mining. [ABSTRACT FROM AUTHOR]

Coal mine fires continuously attract the attention of researchers recently. Firefighting is the most important activities for protecting the mining safety and coal resources at the same time. Among them, liquid nitrogen is usually employed as emergency treatment for sudden fire accidents. However, it as a normalized fire prevention technology is still in the blank. Subsequently, a new system called ground fixed liquid nitrogen station has been developed for normalizing fire prevention. It took 5 months to build such total flooding fire extinguishing systems in JF colliery, with a maximum flow rate: 5000 Nm3/h, pressure: 1.0 ± 0.05 MPa, high purity: ≥ 99.99%, and outlet temperature of CGN is 10°C lower than the atmospheric temperature. Field observations showed that it only took 3 days for the concentration of CO to decrease by 95.36%. The main fire extinguishing mechanism of the system is the nitrogen inertization, and the cooling effect is supplemented. By using the presented technique, there was no waste left behind. Thus, it is concluded that the newly developed firefighting system can be put into practice, especially its broad application prospects in large capacity collieries. [ABSTRACT FROM AUTHOR]

The purpose of this study is to accurately calculate the escape velocity of miners under different roadway conditions during mine fire periods. The experiment to examine escape velocity was carried out in the roadway of the Mu Chengjian Coal Mine. In the experiment, the relationships between the miner escape velocity and the inclination of the roadway, the area of the accessible section of the roadway, and the average wind velocity of the roadway were obtained through single factor analysis, and two multiple regression equations of the escape velocity were developed through multivariable linear regression analysis. The escape velocities of the miners were then predicted, and the error was analyzed with multiple regression equations. The experimental results show that the miner escape velocity decreases with an increase in the absolute value of the inclination of the roadway and increases with an increase of the accessible section area of the roadway and the average wind velocity of the roadway. In addition, the multiple regression equations have the strongest significance if the independent variables are the inclination of the roadway, the accessible section area of the roadway, and the type of roadway, and the contribution rate of the inclination of the roadway to the escape velocity is the highest. The predicted results calculated by the multiple regression equations are close to the experimental data, and the prediction errors are less than 10%. Consequently, we conclude that the multiple regression equations can be used to predict the miner escape velocity during periods of mine fires. [ABSTRACT FROM AUTHOR]

Existing research that relevant to thermodynamic disaster is artificially divided into gas disaster,fire disaster and coal dust disaster.The drawback of the division is that it fails to systematically construct a theoretical system,which makes the systematical and synthetical prevention and control of this kind of disaster unavailable.In this paper,a large number of serious and extraordinary coal mine accidents happened in China and other countries are collected and analyzed,based on which the concept of thermodynamic disaster is proposed.The theoretical system of thermodynamic disasters is also constructed.Several hot issues about thermodynamic disasters are analyzed and discussed,which are the compound disaster involving coal mine gas and coal fire,the safety of low gas coal mine,the role of gas drainage played in the prevention of gas accidents,the relationship between accident and management,the efficiency of inert medium in preventing and extinguishing coal fires,the effect of mine explosion-proof facilities,self-escape after thermodynamic disaster.Seven misconceptions are pointed out. [ABSTRACT FROM AUTHOR]

Mine fire is one of the major hazards in underground coal mines. Continuous monitoring of underground coal mines for early detection of fires is very much important from the mines safety point of view. In recent years, wireless sensor network (WSN) has gained enormous attention for monitoring of underground coal mines. In this technique, the sensor nodes are deployed in coal mines for collecting various environmental data, such as temperature, relative humidity, concentrations of different gases, etc. and send these data to a base station (sink) directly connected to the ground monitoring centre. Since the monitoring data are uncertain and imprecise in nature, it is important to interpret and analyze the data for taking measures for preventing fire hazard. In this paper, we propose a WSN-based fire monitoring system for underground coal mines using fuzzy logic approach for enhancing the reliability in decision-making process to alleviate the mine fire hazard. Mamdani fuzzy inference system is used as fuzzy model for taking real-time decisions on monitoring data. The system is extensively simulated using Fuzzy Logic Toolbox in MATLAB. The simulation results revealed that the proposed system is more reliable and responsive to fire hazard as compared to the offline monitoring system used in underground coal mines. [ABSTRACT FROM AUTHOR]

Coal spontaneous combustion makes coal suffer a high-temperature heating process (similar to a low-temperature pyrolysis). Additionally, low rank coal is considered to be friendly utilized through two steps, i.e. low-temperature pyrolysis of low rank coal to gain gas/liquid components and then coal char forwarded to the burning or other chemical applications. Therefore, it is necessary to investigate the effect of low-temperature pyrolysis on the surface properties of low rank coal and its role in the floatability of coal particles because coal already suffering spontaneous combustion should be upgraded before usage. In this investigation, SEM, XPS, attachment time and flotation tests were employed to reveal the changes of surface properties and floatability of sub-bituminous coal before and after the pyrolysis. After the pyrolysis, a significant mass loss was observed and many pores/cracks were newly created as well as the content of hydrophobic functional groups on coal surface was increased whereas the content of hydrophilic oxygen-containing functional groups was reduced. The attachment time of coal-bubble was significantly decreased after the pyrolysis, which directly made an increase in the hydrophobicity and floatability of sub-bituminous coal. The findings of this paper may be useful for a better use of sub-bituminous coal resources because sub-bituminous coal is well known as difficult to float and sub-bituminous coal fines are usually wasted in coal preparation plants. This paper proposes that coal char from sub-bituminous coal may be forwarded to a further upgrading process (i.e. flotation) because the floatability of sub-bituminous coal is significantly improved by the pyrolysis. [ABSTRACT FROM AUTHOR]

To study the effect of erosion on coal microstructure and its oxidation characteristics, eroded coals were prepared by eroding coal samples in an acidic aqueous solution for 30 days, 90 days and 180 days, respectively. The microcrystalline structure, pore structure and active groups distribution of coal samples were studied using X-ray diffractometer, low-temperature N 2 adsorption and infrared spectra. Temperature-programmed experiment was used to analyze the oxidation characteristics of raw coal and eroded coals. The results reflected that the number of aromatic layers and coalification degree of eroded coal are reduced compared with raw coal. The average pore diameter increases, which promotes oxygen transportation in coal pores. Under the erosion effects, the content of active groups such as hydroxyl (–OH), methylene (–CH 2), and methyl (–CH 3) in coal increases. Eroded coals, especially the coal eroded for 180-day demonstrate more oxygen consumption and CO production than raw coal during the oxidation process, and their apparent activation energies decrease. Besides, the enhancement mechanism of eroded coal's oxidation activity is expounded from the aspects of the increase of active sites and the improvement of pore structure. In brief, erosion effect increases the spontaneous combustion tendency of coal. • The effect of weak acid erosion with different durations on coal oxidation behavior was studied. • Changes of coal physicochemical structure after erosion effect were studied. • The apparent activation energy of eroded coal decreases during low-temperature oxidation. • Mechanism for easier oxidation of dried eroded coal was expounded. [ABSTRACT FROM AUTHOR]

Michael Colliery in east Fife was the largest National Coal Board (NCB) unit in Scotland when it closed in 1967, following a disastrous fire which killed nine miners. The NCB, operating within the constraints of the Labour government's policy framework, decided not to invest in Michael's recovery, although this would have secured profitable production within five years and access to thirtyplus years of coal reserves. This outcome, which had major local economic implications, demonstrates that deindustrialization is a willed and highly politicized process. The Labour government ignored workforce entreaties to override the NCB's decision and invest to bring the pit back into production, but made significant localized adjustments to regional policy that within a year attracted a major employer to the area, the Distillers Company Limited. The article relates the closure to moral economy arguments about deindustrialization. It shows that coal closures in the 1960s, while actually more extensive than those of the 1980s, were managed very differently, with attention to the interests of the workers and communities affected, and an emphasis on cultivating alternative industrial employment. [ABSTRACT FROM AUTHOR]

This paper examines how the availability or scarcity of water influenced the survival related decisions of households during the October 2013 State Mine Fire in the Blue Mountains, New South Wales, Australia. Narrative analysis of semi-structured interviews with 18 households impacted by the bushfire revealed that drought conditions in the months preceding the bushfire left many households dependent on non-reticulated water supplies vulnerable at the time the fire threat became apparent. Despite considerable preparations for water storage and usage during the fire, “weak links” in planning (e.g., top-ups, failure of pumps, generators and hoses) meant water was not accessible when needed most. This paper discusses a gap in bushfire safety scholarship on water usage and everyday trade-offs amongst residents in areas independent of reticulated (mains) water supplies. Findings suggest a need for more detailed and consistent information in official bushfire safety advice on storing water prior to a bushfire and effective water distribution systems for household defence and fire fighting. [ABSTRACT FROM AUTHOR]

Understanding the evolution of coal self-heating in longwall mining gob areas is important for the mitigation of underground mine fires. The coal self-heating involves a chain of complex interactions between compositional gas and solid coal. These interactions are normally regulated by the dynamic gob configuration due to the extraction of coal. In this study, a fully coupled transient model of compositional gas flow and transport, and the heat transfer between solid coal and gas is developed to quantify the evolution of coal self-heating processes under the in-situ gob configuration. The modelled results were matched reasonably well with the field measurements of air temperatures and oxygen concentrations for a Chinese coal mine. The verified model was applied to conduct sensitivity studies of (1) ventilation flux; (2) ventilation resistance; and (3) advance rate of face. The main results of the sensitivity study reveal that (i) the high temperature zones are mainly distributed near the intake airway of gob; (ii) the higher ventilation flux or ventilation resistance leads to the higher self-heating temperature and the larger oxidation self-heating zone. Moreover, the self-heating zone migrates towards the much deeper gob area. Whereas, the higher advance rate of face results in the lower self-heating temperature and smaller self-heating zone. The simulated results can provide some suggestions for the prevention of coal spontaneous combustion in gobs. [ABSTRACT FROM AUTHOR]

Subsurface fires are a common threat for coal mining, since spontaneous coal combustion can easily result in gas combustion and explosion. In this paper, aiming to solve problems of the low efficiency, the line clogging, and some other related field issues in liquid nitrogen perfusion, a fire extinguishing application by using immediate liquid nitrogen infusion was presented. The presented technique is efficient in absorbing heat, and consequently, displacing oxygen and combustible gases. Field tests justified the efficiency of the technique. Only 12 days were taken to unseal the coal mine, which provides a quick and efficient management of the fire zone. Furthermore, by using the presented technique, there was no waste left behind which may impede the subsequent production. The presented technique is of great benefit from the social, economic, and environmental aspects, which indicates its broad application in fire prevention for large-scale coal mines. [ABSTRACT FROM AUTHOR]

Out of the thermal balance method, a method of presenting mine fire data is proposed in this work. By grouping fuels into a pseudo fuel, grouping nitrogen and oxygen into a pseudo air, and using carbon dioxide as the diluent, a diluted flammability diagram is reconstructed for this oxygen-modified environment. The flammability envelop is controlled by oxygen availability, while the operation point is controlled by fuel/diluent availability. The relative position between the envelop and the operation point shows the flammable state of this mixture. Coward's explosive triangle is also applied using the limiting oxygen concentration derived from the diagram. Both are most useful in guiding the suppression operation for an underground coal mine fire. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article “Theoretical Flammability Diagram for Analyzing Mine Gas" by Tingguang Ma and Michael D. Larrañaga published in the August 08, 2013 issue.

The article offers information on a study on temperature distribution and its effect on ventilation system during open fire in a mine gallery. Topics discussed include carrying out experiments in the fire gallery under simulated fire conditions with varied air velocities, design parameters for experimentation for temperature distribution inside gallery, and the effect of fire on the ventilation system of the mine.

The Hazelwood mine fire was one of the largest incidents for air quality effects in Victoria's history. Communities throughout the Latrobe Valley were affected by smoke, especially the township of Morwell which was just a few hundred meters from the blazing coal faces. The Environment Protection Authority Victoria mounted a large scale response that involved monitoring and assessment of the effects of smoke from the fire, over a period of 45 days in February and March 2014. Concentrations of contaminants in the smoke, especially PM2.5, were very high, reaching 32 times the Reporting Standard. Elevated levels of carbon monoxide also severely impacted the local community. Along with the Victorian Department of Health, and in collaboration with the fire agencies and emergency response agencies, the EPA engaged in a large scale program of public information, forecasts and warnings of smoke effects. A recovery program is currently underway that will run until mid-2015 with continued monitoring, further community communications and a Citizen Science program. [ABSTRACT FROM AUTHOR]

This work deals with the preparation and characterization of fly ash (FA) supported aqueous three-phase foams containing N 2 for coal spontaneous combustion prevention and control. Uniform and dense three-phase foams featuring FA contents between 20 wt.% and 33 wt.% are prepared in batch mode using a home-made foam generating column with an internal Venturi tube. The effect of FA on the foamability, static and dynamic stability of the three-phase foams is discussed. Compared with two phase foams, the FA supported three-phase foams manifest higher static and dynamic stability, which increases with the FA content. Base on the excellent static and dynamic stability, a structure model to attach FA particles at the N 2 –water interfaces of the three-phase foams was proposed to elucidate the observed behaviors. The as prepared FA supported three-phase foams, exhibiting excellent coal fire extinguishing characteristic, can be used as a promising fire extinguishing material, especially for preventing the large coal area spontaneous combustion or extinguishing fire in high and unknown locations in goaf. [ABSTRACT FROM AUTHOR]

Aiming at the problem of the computation of ventilation heat resistance in a roadway during mine fire, to the ventilation roadways with airflow temperature and density variation, a normative computing formula was deduced. It was pointed out that according to generalized ventilation principle, the ventilation resistance during mine fire includes frictional resistance and local resistance, as well as an additional resistance caused by the external ventilation source, namely fire smoke. In the new formula, the computation of ventilation resistance is expressed from two media, namely fluid and roadway, and the conception of roadway geometry air resistance were introduced. Geometry air resistance is the resistance characteristic of roadway itself, and it has nothing to do with fluid. Geometry air resistance includes frictional resistance and local resistance too. Conceptually, the new formula has a clear discrimination to the essence of heat resistance, so the mistakes easily appear during computation and analysis will be avoided. The conclusion that the ventilation resistance of high temperature smoke flow is in direct proportion to fire temperature was drawn. To verify the heat flow resistance effect, an experimental pipeline facility was designed to determine the variation of heat resistance with temperature. The experimental results are identical to the conclusion drawn from theoretical derivation. The additional resistance of exogenous smoke flow was extracted successfully by using the experimental facility. Experimental results show that exogenous resistance is the physical image of combustion process. A practical method for computing the heat resistance with the participation of exogenous gas is provided. [ABSTRACT FROM AUTHOR]

Highlights: [•] Thermophile has been demonstrated to be an effective bacteria for desulphurization. [•] The weight gain rate due to oxidation is reduced by a factor of four after desulphurization. [•] The spontaneous combustion point has been increased from 140.7°C to 368.7°C after desulphurization. [•] The spontaneous combustion tendency level is downgraded from level I to level III after the bacterial treatment. [•] The likelihood of spontaneous combustions is greatly reduced by desulphurization. [ABSTRACT FROM AUTHOR]

Taking into consideration the differences of disaster prevention in gas and spontaneous combustion of coal seam and goaf cross-scale fracture fields, the cross-scale fractures field of coal and rock mass were defined in this study. In addition, this paper studied the symbiotic disaster prevention and control mechanism, and technical change in cross-scale fractures field flow distribution, through the rational elimination of gas and coal spontaneous combustion symbiotic disaster, that is, the symbiotic region was equal to 0. The authors also proposed two new control technologies, which are: to change coal- rock fractures leakscale through solid-phase media transport, and to change the goaf temperature field and the gas concentration field through low-temperature liquid inert gas seepage. A network graph theoretical model of a particle transport of fine solid phases to change coal-rock fractures scale had been developed in this study, which reveals that solid phase media can be embedded.in the pneumatic transport blocking air leakage in the coal-rock fractureds field, to reduce air leakage fractures scale and the effective fissure numbers, and change the scale of coal-rock fractures leak field, as well as to increase air leakage resistance to ensure the safety of coal spontaneous combustion for high gas extraction. Also, the authors built an experimental simulation platform for investigating liquid nitrogen extinguishing characteristics, and the results show that the liquid nitrogen injected into the fire area can quickly cause heat expansion, resulting in a large number of low-temperature nitrogen pockets in the goaf, forming a three-dimensional buffer zone to reduce the external air leakage into the goaf or fire zone, to isolate the goaf or fire area. At the same time, the low-temperature nitrogen gas carries water vapor condensation into the goaf, exchanging heat with hidden heat source ( fire source), which can reduce the temperature of the heat (fire source) to below the temperature of flammable point and actively engulf the heat source (fire source). [ABSTRACT FROM AUTHOR]

Discussion of 3D simulation modeling techniques of fire fume spread process is very necessary to effectively guide the formulation and implementation of underground mine fire rescue and evacuation plan. Therefore,3D simulation modeling techniques of fire fume spread were proposed, with 3 D structure model of underground mine roadways as the carrier,3D network model of ventilation system as the guarantee, and fume spread parameters model as the core. The volume rendering technology in time sequence was used to develop the 3D simulation model of fire fume spread process, which primarily simulated the fume dynamic spread process in 3D roadways and showed time and spatial change of fume temperature and concentration. Finally, the model was applied to a domestic mine and the simulation results indicated the model's effectiveness. [ABSTRACT FROM AUTHOR]

To investigate the characteristics of adiabatic oxidation phase and build the prediction model of coal spontaneous combustion critical point, the adiabatic oxidation experiment data of eight coal samples are given in this paper, based on the adiabatic oxidation experiment, element analysis experiment and industrial analysis experiment. The phase heating rates of adiabatic oxidation of these samples are also calculated. Then using the thermodynamic parameter calculation method, Tr0.05 and TΔmax are defined and obtained. Furthermore, based on the Levenberg-Marquardt method, the relationship between the coal element content, volatility, the phase heating rate of adiabatic oxidation and Tr0.05 are established. The results show that the content of N or S correlates positively with Tr0.05 Osand that O, C, or H content correlates negatively with Tr0.05. However, the link between these elements and stage-heating rate is the opposite. The law also suggests that stage-heating rate will be much faster and coal spontaneous combustion will be easier when Tr0.05 becomes much lower. The more volatile coal is, the lower Tr0.05, and the more likely it is to spontaneously combust. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

This section offers news briefs on the mining sector in South Africa as of October 2012. The Queensland Mining Industry Health and Safety Conference was held in Townsville, Queensland. A gas explosion at a coal mine in China registered a death toll of 41. Some 195 miners escaped a fire that broke out at a coal mine in Ukraine.

Pressurisation of a mine intake entry can be achieved through the use of check curtains, inflatable stoppings, and parachute stoppings. These devices, when correctly placed in an intake entry can increase the pressure out-bye and prevent air leakage from adjacent entries. The use of these devices minimises contamination of the intake escapeway in the event of a fire in an adjacent belt entry. The study was inspired by the recommendation of research on escapeway safety as stated in The Final Report of the Technical Study Panel on the Utilisation of Belt Air and the Composition and Fire Retardant Properties of Belt Materials in Underground Coal Mining. The debate on the safety and usefulness of the devices is ongoing. Also, emergency stoppings have not been compared side by side to evaluate their effectiveness, ease of use, and cost. This paper evaluates feasibility of the emergency stoppings and provides guidelines for their effective operation. A comparative evaluation of a parachute stopping, an inflatable stopping, a roof-mounted check curtain and a perimeter-mounted check curtain was performed to document the pressurising effects, the leakage prevention capabilities between an intake escapeway and an adjacent neutral entry, the ease of use, and cost. The perimetermounted check curtain outperformed the other emergency stoppings with its ease of use and good pressurisation characteristics that created a 200 Pa pressure differential across the device. The parachute stopping had few installation requirements and a strong overall performance. The inflatable stopping should be improved to better meet the requirements relevant to an emergency. The roofmounted check curtain was found to be unsuitable for emergency use. [ABSTRACT FROM AUTHOR]

Abstract: Serious mine fire disasters have occurred in Northwest China where there are abundant coal resources. For the shortage of water and loess, a large cost of conventional grouting slurry is needed. However, plenty of sand and fly ash resources have been found there. In order to improve the quality of sand injection and reduce the wastage of water during grouting, a kind of new compound material of sand-suspended colloid, which is composed of mineral inorganic gel and organic polymer, was developed in this paper. And the inhibition performance experiments of the sand-suspended colloid were carried out. The results show that the sand-suspended colloid efficaciously affected the oxidation characteristics above the critical temperature during the acceleration oxidation of the lignite and fat-gas coal samples and restrained the oxidation course by increasing the activation energy, so that it reduced the contents of CO and C2H4 and depressed the oxidation rate during the coal spontaneous combustion, and finally inhibited the coal spontaneous combustion. [Copyright &y& Elsevier]

Abstract: Fire in mine laneway leads to disordered ventilation system airflow, and smoke will result in staff poisoning. In such situation, it necessitates to install a rescue capsule in the common staff area. In this paper, the software Fluent was used to simulate the airflow conditions dynamically in No. 5 belt roadway of Kongzhuang Coal Mine when fire broke out. The migration law of CO front was determined. By underground escape experiments, personnel escape velocity model in pathway was established. Based on the numerical simulation and results of field experiments, the escape capsule installation location in the passageway of No. 5 belt roadway was ascertained. [Copyright &y& Elsevier]

Abstract: Thermal infrared imagery (TIR) is being used to identify the location and intensity of heat released from mine fire vents in Centralia, PA. Recent TIR images collected from 2007, 2009, and 2010 have been combined with previously collected TIR airborne images and other data from 1971, 1980, 1981, 1982, 1983, and 2002–2003 to produce a map that reveals the thermal history of the region. Additionally, borehole data, direct observations, false color imagery and aerial photographs were used to locate fire location. The compilation of these images into one map provides a history of the progressive coal fire movement since it''s ignition in 1962. The fire, which is thought to be located in the Buck Mountain coal bed (No. 5), at the base of the Llewellyn Formation (Middle Pennsylvanian), can be traced along the limbs of the eastwardly plunging Locust Mountain Anticline. It is moving west at a rate of less than 2m/yr, which is down from estimates made in previous decades of nearly 20–23m/yr. Along one of the main fire fronts, TIR images reveal circular to semicircular patterns that represent zones of subsidence as the fire advances. Temperature readings from the TIR imagery and ground measurements suggest a variable thermal history with a declining overall temperature. Today, temperatures at gas vents generally do not exceed 65°C. Given the changes in the fire over the years, it is suggested that the fire is decreasing in intensity and rate of movement as it moves deeper into the subsurface. Additionally, it may be encountering subsurface chambers where the anthracite coal has been removed. Preliminary CO/CO2 ratio measurements at gas vents are inconclusive but suggest oxygen is present in the subsurface. A decrease in coal, perhaps due to the shape of the coal bed or its absence due to mining, is the primary limiting factor affecting the rate of movement and temperature of the fire. This limited resource may cause the fire to smolder before naturally extinguishing. Early estimates predicted the fire would burn for a century or longer. This study suggests that the fire may extinguish earlier than previously thought. [Copyright &y& Elsevier]

Abstract: Coal mine fire is a major problem in Jharia Coal Field (JCF). The surface and subsurface mine fire areas can be detected with different type of techniques like borehole temperature measurement, geophysical methods, thermo-compositional analysis, thermo-graphic measurement, airborne remote sensing and space-borne remote sensing techniques. Of these the remote sensing technique is used to detect the coal fires covering a large area using multi-spectral and/or multi-temporal data. In this paper Landsat-7 Enhance Thematic Mapper Plus (ETM+) band 6 thermal data is used for detection of surface and subsurface coal fires. Thermal survey was carried out in the field using thermal imaging camera. The temperatures detected through ETM+ satellite image are validated against those observed field temperature of the study area. This technique is considered as a cost effective for the detection of surface and subsurface temperature profile in comparison to other techniques. [Copyright &y& Elsevier]

Abstract: 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. [ABSTRACT FROM AUTHOR]

Abstract: Uncontrolled coal fires can result in massive surface displacements due to the change in volume of burning coal and thermal effects in the adjacent rock mass; simultaneously, the resultant surface breakings provide greater access to air and water that in turn can aggravate the problem of underground coal seam burning. In this case study, we have investigated the feasibility and potential of detecting the land subsidence accompanying coal fires by means of satellite InSAR observations. Three groups of small-baseline InSAR approaches (PSI, stacking and 2-passDInSAR) were applied to the Wuda coalfield (Northern China) to reveal the spatial and temporal signals of the land subsidence in the areas affected by the coal fires. The interferometric results agree well with GPS observations and coal fire data obtained by field investigation, which demonstrates that the small-baseline InSAR techniques have remarkable potential to detect this land subsidence of interest. In particular, our results show that the development of coal fires can lead to new subsiding areas and also accelerate the ongoing surface subsidence, typically within the areas of mature coal fires, through a comparison of the interferometric observations and the multi-temporal coal fire maps. This timely and reliable information on land subsidence will be useful for the detection and mapping of the coal fire affected regions and thereby assist in fighting and controlling coal seam burning. [ABSTRACT FROM AUTHOR]

Coal from its excavation, processing, and utilization creates environmental problems and health hazards. In these processes, the mobilization of potential organic and heavy metal contaminants affects the quality of soil and health of the inhabitants. Soil samples were collected from the nearby areas of an opencast coal mine (OCM) and a coal fire affected area (CFA) located in Jharia coalfield of Dhanbad, India. The control site was an abandoned land approximately 15 km away from the sources of contamination. These samples were analyzed for trace elements including Cr, V, Co, Ni, Cu, Zn, Ga, Rb, Zr, Ba, Th, and U. The soils of OCM were enriched with Cr and Ni and this is attributed to the mining activities in view of the absence of other sources of pollutants. In case of CFA, the soils were enriched with Cr, V, Ni, and Zn. However, the concentrations of Cr, Ni, and Zn in both the soils were well below the USEPA soil screening levels for human health risk assessment. The levels of Co and V exceeded the soil screening limits. Human exposure risks were evaluated for Co and V. The total intake of V concentration exceeded the EPA's reference dose, which may pose adverse health risks. [ABSTRACT FROM AUTHOR]

Spontaneous combustion of coals has been pointed out as one of the most critical problems encountered in coal mining for years. This event occurring in underground and open pits as well as in the coal-hole of the apartments can cause severe fatalities together with loss of reserves and equipment. Spontaneous combustion phenomenon can be reduced to a minimum degree by taking necessary precautions in time. In order to carry out this important task, at first the susceptibility of coals to spontaneous combustion should be determined and then colliery working conditions should be arranged according to these findings. In this work, the spontaneous combustion liability of the coals taken from Western, Seyitome, and Degirmisaz Lignite Corporations have been identified. The spontaneous combustion profiles of the coals from Kutahya Region have been ascertained in general. Through out the present work, the crossing point method has been utilized. A total of 33 laboratory tests have been carried out. According to test results, the coal samples taken from Seyitomer have “medium to high” risk for spontaneous combustion while the coals from Western Lignite Corporation have shown “high” risk and the coals from Degirmisaz Corporation have “medium” risk. [ABSTRACT FROM AUTHOR]

Abstract: Mine fires due to spontaneous heating are an inherent but serious problem in the coal mines across the globe. Past research studies have proposed many classification schemes for categorization of coal seams with respect to their spontaneous heating susceptibility. This paper presents application of an empirical approach for classification of coal seams based on their proneness to spontaneous heating. In this research work, twenty nine coal samples of varying ranks belonging to both high and low susceptibility to spontaneous heating have been collected from all the major coalfields of India. Using moisture, volatile matter, ash and crossing point temperature of the coal samples as the parameters, principal component analysis 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. [Copyright &y& Elsevier]

Abstract: The Tiptop underground coal-mine fire in the Skyline coalbed of the Middle Pennsylvanian Breathitt Formation was investigated in rural northern Breathitt County, Kentucky, in May 2008 and January 2009, for the purpose of determining the concentrations of carbon dioxide (CO2), carbon monoxide (CO), and mercury (Hg) in the vent and for measuring gas-vent temperatures. At the time of our visits, concentrations of CO2 peaked at 2.0% and >6.0% (v/v) and CO at 600ppm and >700ppm during field analysis in May 2008 and January 2009, respectively. For comparison, these concentrations exceed the U.S. Occupational Safety & Health Administration (OSHA) eight-hour safe exposure limits (0.5% CO2 and 50ppm CO), although the site is not currently mined. Mercury, as Hg0, in excess of 500 and 2100μg/m3, in May and January, respectively, in the field, also exceeded the OSHA eight-hour exposure limit (50μg/m3). Carbonyl sulfide, dimethyl sulfide, carbon disulfide, and a suite of organic compounds were determined at two vents for the first sampling event. All gases are diluted by air as they exit and migrate away from a gas vent, but temperature inversions and other meteorological conditions could lead to unhealthy concentrations in the nearby towns. Variation in gas temperatures, nearly 300°C during the January visit to the fire versus <50°C in May, demonstrates the large temporal variability in fire intensity at the Tiptop mine. These preliminary results suggest that emissions from coal fires may be important, but additional data are required that address the reasons for significant variations in the composition, flow, and temperature of vent gases. [Copyright &y& Elsevier]

Abstract: Laboratory experiments were conducted to determine the responses of a prototype smoke detector and a commercially available photoelectric smoke detector to smoke particles generated from various combustion sources. The prototype smoke detector combines optical scattering measurements with ionization chamber measurements in order to reduce/eliminate nuisance alarms due to the presence of airborne dusts or diesel exhaust particles. The commercially available smoke detector is designed for use in harsh environments where airborne dust represents a major problem due to both nuisance alarms and detector contamination. In the experiments, the responses of the two detectors were measured when exposed to smoke particles from the exhaust of a diesel engine and from a variety of fire sources, including wood, coal, styrene butadiene rubber, and No. 2 diesel fuel. For the solid fuels, data were obtained for both smoldering and flaming combustions. This report describes the experiments, their results, and the use of these results as they apply to early-warning fire sensors capable of the rapid and reliable detection of fires in atmospheres that may or may not be contaminated by either airborne dust or the products produced from diesel engines. [Copyright &y& Elsevier]

Abstract: Over the time-scale, earth''s atmospheric CO2 concentration has varied and that is mostly determined by balance among the geochemical processes including burial of organic carbon in sediments, silicate rock weathering and volcanic activity. The best recorded atmospheric CO2 variability is derived from Vostok ice core that records last four glacial/interglacial cycles. The present CO2 concentration of earth''s atmosphere has exceeded far that it was predicted from the ice core data. Other than rapid industrialization and urbanization since last century, geo-natural hazards such as volcanic activity, leakage from hydrocarbon reservoirs and spontaneous combustion of coal contribute a considerable amount of CO2 to the atmosphere. Spontaneous combustion of coal is common occurrence in most coal producing countries and sometimes it could be in an enormous scale. Remote sensing has already proved to be a significant tool in coalfire identification and monitoring studies. However, coalfire related CO2 quantification from remote sensing data has not endeavoured yet by scientific communities because of low spectral resolution of commercially available remote sensing data and relatively sparse CO2 plume than other geological hazards like volcanic activity. The present research has attempted two methods to identify the CO2 flux emitted from coalfires in a coalmining region in north China. Firstly, a band rationing method was used for column atmospheric retrieval of CO2 and secondly atmospheric models were simulated in fast atmospheric signature code (FASCOD) to understand the local radiation transport and then the model was implemented with the inputs from hyperspectral remote sensing data. It was observed that retrieval of columnar abundance of CO2 with the band rationing method is faster as less simulation required in FASCOD. Alternatively, the inversion model could retrieve CO2 concentration from a (certain) source because it excludes the uncertainties in the higher altitude. [Copyright &y& Elsevier]

Abstract: A computational fluid dynamics (CFD) study was conducted to model effects of coal properties on the potential for spontaneous heating in longwall gob (mined-out) areas. A two longwall panel district using a bleeder ventilation system was simulated. The permeability and porosity profiles for the longwall gob were generated from a geotechnical model and were used as inputs for the three-dimensional CFD modeling. The spontaneous heating is modeled as the low-temperature oxidation of coal in the gob using kinetic data obtained from previous laboratory-scale spontaneous combustion studies. Heat generated from coal oxidation is dissipated by convection and conduction, while oxygen and oxidation products are transported by convection and diffusion. Unsteady state simulations were conducted for three different US coals and simulation results were compared with some available test results. The effects of coal surface area and heat of reaction on the spontaneous heating process were also examined. [Copyright &y& Elsevier]

Abstract: Many cotton fires were caused by spontaneous combustion, to identify the possible cause of such fires, a C80 microcalorimeter was employed in this paper. The cotton samples, dry or wetted, were sealed and heated from ambient temperature to 300°C at a 0.2°Cmin−1 heating rate. The result indicated that the dry cotton may not be the self-heating materials, but once it is wetted, its thermal stability is decreased with lower onset temperature and with larger heat generation, which can result to spontaneous combustion. It is speculated that microbiological degradation of cotton fibers has the potential to evolve methane and/or oxygen that in vapor phase could lead to spontaneous combustion. And therefore, it is confirmed that C80 can be used as an effective instrument to identify the cause of cotton spontaneous combustion fire. [Copyright &y& Elsevier]

The inhibitory effects of compound antioxidants (l -ascorbic acid (VC) and tea polyphenols (TP)) on coal oxidation were studied. The characteristics of coal oxidation was investigated by temperature-programmed experiments. The changes of active groups in coal were confirmed by Fourier-transform infrared spectroscopy. Quantum chemical theory was used to explore the reaction mechanism. Experimental results showed that compound antioxidants exhibit significant synergistic inhibition effect on coal oxidation. The apparent activation energy of coal oxidation increases by 16.23 kJ/mol for the addition of 6 wt% compound antioxidants (TP:VC = 2:1). The content of aliphatic hydrocarbons, –OH, C O and COOH in the antioxidant-treated coal decreases, while that of ether bond and aromatic bond increases. H15 of VC or H48 of epigallocatechin gallate (the main component of TP) can readily scavenge oxygen-containing radicals and inhibit the production of active groups in coal. Water-soluble antioxidants can be evenly dispersed on the coal surface, which provides an environment-friendly and efficient approach to preventing coal spontaneous combustion. • The mixture of VC and TP has a synergistic inhibitory effect on coal oxidation. • The content of active functional groups in coal treated with antioxidants is reduced. • The inhibitory mechanism of antioxidants on active radicals in coal is explored by quantum chemical theory. • Inhibitory effect is realized by eliminating oxygen-containing radicals and interrupting the generation of active groups. [ABSTRACT FROM AUTHOR]