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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 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]

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]

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]

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]

This article from the book "Labour/Le Travail" explores the fire occurred in the Malartic Gold Mine in northwestern Quebec in 1947. It discusses the claim that the fire was caused by a discarded cigarette in the lunch room in the Number 4 shaft. It notes the death of several miners during the fire and the survival of others, and explains the failure to rescue some miners. In addition, the article discusses the inquest over the accident and addresses the responsibility of the mining operator and the government over the occurrence of the fire.