Coal Mine Gas Explosion Research Articles

Chemical kinetic characteristics of methane/air mixture explosion and its affecting factors

Gas explosion in coal mines caused a large number of deaths, injuries and property losses. Gas explosion still happens occasionally in recent years. It is known that most people died from CO poisoning in gas explosion. But the details of toxic gases produced and their impacts on people need further investigation. In order to study the products and species in gas explosion, an analysis of chemical kinetic characteristics was conducted using CHEMKIN III with detailed mechanism (GRI-Mech3.0) package. A closed homogeneous 0-D reactor was adopted to investigate the kinetic behavior of gas explosion. The initial conditions were set, similar to those in the real tunnel environment. The profiles of four reactants, toxic gases and free radicals were obtained. The threshold values of people exposed to different poisonous gases were analyzed to study their impacts on people. Sensitivity analysis of key elementary reaction to free radical was performed to find possible reactions which can suppress gas explosion. The results show that the ignition delay time is the longest at fuel-rich condition. The O2 concentration decreases from 19% to 2% at stoichiometric ratio, which could not support normal respiration after explosion. It is found that the concentration of CO ranks the highest among the four toxic gases. Toxicity analysis indicates that those exposed to such condition will soon die of asphyxia. This is consistent with the accident investigation findings that the majority of fatalities result from inhalation of CO. The concentration of CO at fuel-rich condition is higher than that at fuel-lean condition. The relationship between the final free radical concentration and initial CH4 concentration exhibits a reverse U shape. Sensitivity analysis reveals that free radicals are mostly sensitive to the intermediate reaction R156 (forward direction) and R158 (reverse direction). It provides a possible direction to research the corresponding chemicals for gas explosion suppression. This work would provide theoretical support for gas explosion suppression technology and decision-making of personal protection in rescuing trapped coal miners. It is of great importance for developing suppression chemicals of gas explosion.

Experiments and Mechanisms of Gas Explosion Suppression with Foam Ceramics

ABSTRACTFoam ceramics as a porous medium have demonstrated huge utilization potentiality to suppress multiple and continuous gas explosions in coal mines. Explosion suppression ability and thermal conductivity of different foam ceramics was analyzed. Explosion energy that combines propagating velocity and overpressure was introduced to evaluate suppressing effect. It was indicated that the overpressure was significantly attenuated by foam ceramics. Besides, for two types of foam ceramics, Al2O3 foam ceramic showed a better suppressing performance on explosion energy than SiC. Foam ceramic of bigger pores exhibited a better inhibition effect on explosion energy. It was found that, as foam ceramic become thicker, thickness was becoming the dominant influential factor suppressing gas explosion. The results suggest foam ceramics with larger pores present a higher thermal conductivity, which account for why larger pores foam ceramic exhibits a better suppressing ability. It is a wall effect that prevents chemical chain reactions, the heat of flame would be transferred to the skeleton, and free radicals are reduced.

Fatal gas explosion accidents on Chinese coal mines and the characteristics of unsafe behaviors: 2000–2014

Although the total death toll due to various accidents in China’s coal mining industry has decreased in recent years, coal mine gas explosion is still occupied the main proportion of major accident and threatening miners’ lives. The repeated occurrence of gas explosions, often in a similar manner and triggered by unsafe behavior, indicates that we failed to learn from the past and make inadequate changes in response. In an effort to further reduce these rates, the human factors associated with accident need to be addressed. The exact direct causation and sub-standard performance at operator level have been quantitatively identified and classified within the sample of 201 significant gas explosions in China across 2000–2014. An analysis of the data revealed that unsafe behavior existed in and had precipitated influence to all of gas explosion accidents in sample, and all unsafe behaviors can be analyzed from 3 dimensions: accident site, working craft and equipment and installation. By illuminating the unsafe behaviors and its distribution characteristics in a systematic fashion, this study has provided mine safety professionals the information necessary to reduce gas explosion further.

Influences of fuel concentration, fuel volume, initial temperature, and initial pressure on flame propagation and flameproof distance of methane-air deflagrations

Purpose – The purpose of this paper is to understand a flameproof distance necessary to avoid the flame harms to underground personnel which may have great significance to the safety of underground personnel and the disaster relief of gas explosions in coal mines. Design/methodology/approach – Through a roadway with a length of 100 m and a cross-section area of 80 mm×80 mm, the flame propagation of premixed methane-air deflagrations were simulated by using AutoReaGas software for various fuel concentrations (7, 8, 9.5, 11, and 14 percent), fuel volumes (0.0128, 0.0384, 0.064, and 0.0896 m3), initial temperatures (248, 268, 288, 308, and 328 K), and initial pressures (20, 60, 101.3, 150, and 200 kPa). Findings – The maximum combustion rate for each point follows a changing trend of increasing and decreasing with the distance increasing from the ignition source, and it increases with the fuel volume increasing or the initial pressure increasing, and decreases with the initial temperature increasing. However, increasing the initial temperature increases the flame arrival time for each point. The flameproof distance follows a changing trend of increasing and decreasing with the fuel concentration increasing, and it linearly increases with the fuel volume increasing or the initial temperature increasing. However, the flameproof distances are all 17 m for various initial pressures. Originality/value – Increasing initial temperature increases flame arrival time for each test point. Flameproof distance increases and then decreases with fuel concentration increasing. Increasing fuel volume or initial temperature linearly increases flameproof distance. Initial pressure has little impact on the flameproof distance.

Spontaneous combustion in six types of coal by using the simultaneous thermal analysis-Fourier transform infrared spectroscopy technique

Using simultaneous thermal analysis-Fourier transform infrared spectroscopy, we analyzed the oxidation and exothermic behaviors of six types of coal based on various factors, such as characteristic temperature, heat release, and gas release, to establish a foundation for prevention and control of spontaneous combustion in six types of coal in China. According to the experimental results, a decrease in the metamorphic grade of coal causes an increase in the amount of volatile matter, the heat release rate, and the total heat released. The apparent exothermic onset temperature and initial temperature for the release of H2O, CO2, CO, and CH4 during the nonisothermal oxidation process of coal took place earlier, indicating that the oxidation reaction occurred more easily in lower-grade coal, increasing the hazards of spontaneous combustion. Moreover, when decomposing, coal releases large amounts of CH4, which may cause gas explosions in coal mines. Therefore, technology facilitating the detection of CH4 and prevention of explosions should be developed for use in the coal industry.

Трудноуправляемые факторы в статистике причин аварийных пылегазовых взрывов в угольных шахтах России

Трудноуправляемые факторы в статистике причин аварийных пылегазовых взрывов в угольных шахтах России

Suppressive Effects of Silicon Dioxide and Diatomite Powder Aerosols on Coal Mine Gas Explosions in Highlands

ABSTRACT A gas explosion is the severest threat to the safety of coal mines, particularly in highlands. For effectively preventing gas explosions in coal mines, a quartz tube–based gas explosion test system with an open end and a nearly spherically confined gas explosion testing device were devised, fabricated, and tested. The suppressive effects of aerosols, here silicone dioxide (SiO2) and diatomite powder aerosols, of various sizes on mine gas explosions were studied. Scanning electron microscopy, low temperature nitrogen adsorption, and thermogravimetry analysis conducted on diatomite showed the porosity, effective specific surface area, adsorbability, and excellent thermal stabilities of the aerosols. Explosion suppression experiments confirmed that a test system of SiO2 and diatomite powder aerosols remarkably prolonged the gas explosion induction period and the time of peak explosion pressure and reduced the flame propagation rate. In addition, the test system reduced the maximum explosion pressure and maximum and average explosion overpressure rising rates. The suppressive effects were clearly affected by the aerosol type and size. Microscale diatomite powder aerosol exhibited a stronger suppressive effect than microscale SiO2 powder aerosol did. The porous structure and thermal characteristics of diatomite powder was vital in the suppression efficacy because they restrained the growth rate and activity of free radicals obtained through explosion reactions and eventually eliminated them. The adsorption of formaldehyde, a major intermediary of gas explosion, by diatomite powder decreased the quantity of free radicals, eventually suppressing explosions.

Abnormality of the corpus callosum in coalmine gas explosion-related posttraumatic stress disorder.

Abnormal corpus callosum (CC) has been reported in childhood trauma-related posttraumatic stress disorder (PTSD); however, the nature of white matter (WM) integrity alterations in the CC of young adult-onset PTSD patients is unknown. In this study, 14 victims of a coal mine gas explosion with PTSD and 23 matched coal miners without experiencing the coal mine explosion were enrolled. The differences in fractional anisotropy (FA) within 7 sub-regions of the CC were compared between the two groups. Compared to the controls, PTSD coal miners exhibited significantly reduced FA values in the anterior sub-regions of the CC (P < 0.05, Bonferroni-corrected), which mainly interconnect the bilateral frontal cortices. Our findings indicated that the anterior part of the CC was more severely impaired than the posterior part in young adult-onset PTSD, which suggested the patterns of CC impairment may depend on the developmental stage of the structure when the PTSD occurs.

Application of Fault Tree Analysis Method in Gas Explosion Accident

According to the gas explosion theory and the investigation of occurred gas explosion, the basic events that lead to coal mine gas explosion are summarized and the fault tree is worked out. Besides, the fault tree analysis is used for qualitative analysis. The minimal cuts sets, minimal path sets and structure importance are solved. Accordingly, the reasons of gas explosion are obtained, which can provide references for the prevention of coal mine gas explosion. The study showed that: the minimal cut sets of gas explosion is much(165) and the minimal path sets is small(4), and it is the major dangerous and harmful factors in coal mine. It that gas concentration must be strictly controlled and all sources of ignition should be eliminated is the basic and fundamental way to prevent mine gas explosion.

Some electrostatic factors may cause gas explosion in coal mines

The human body capacitances vary greatly when miners leave a narrow tunnel. The human body electrostatic discharge energy is increased at the outlet of narrow tunnels. Thereby the possibility of detonating gas is greatly increased. Human body electrostatic half-life changes according to the dress of miner. Intense movements of human body will increase the static electricity produced in unit time. This can also increase the human body static electricity and cause gas explosion.

Research on simulation of human body electrostatic discharge on detonating gas in coal mines

Static electricity is one of the reasons for gas explosions in coal mines. When miners leave the narrow tunnel exit of a coal mine, the body voltage may increase by more than ten times with the body capacitance decreasing quickly to 1/10 of its original value, and the body electrostatic discharge (ESD) energy can increase greatly to become a dangerous gas ignition source. In this work, simulation research of human body ESD detonating the gas in a coal mine was conducted. Based on the analysis of the human body electrostatic leakage rules, it is found that electrostatic half-life is mainly relative to the medium resistivity. Therefore it is important to establish a standard for anti-static attire. A series of gas explosion experiments were also conducted by the simulation system, and the results showed that the gas in coal mines might be detonated when the human body capacitance was in the range of 100-1800 pF and the discharge gap between 0.3-1.2 mm. Moreover, gas concentration at approximately 8.5% was most likely to induce an explosion.

Premixed methane-air deflagrations in a completely adiabatic pipe and the effect of the condition of the pipe wall

A completely adiabatic pipe that is similar to a coal-mine coal or rock roadway was simulated using the computational software AutoReaGas. A partially adiabatic pipe was established using an experimental steel pipe with heat-insulating material installed in the inner wall, and a non-adiabatic pipe was also established using the experimental steel pipe without the heat-insulating material. Premixed methane/air deflagrations were studied in the three types of pipe to reveal the influence of the condition of the pipe wall on gas explosions. The results showed that in the completely adiabatic pipe, the maximum explosion overpressure was dynamic and decreased and increased with increasing distance; however, the flame-propagation speed increased gradually. In the partially adiabatic pipe and the non-adiabatic pipe, the maximum explosion overpressure and flame-propagation speed increased initially and then gradually decreased with increasing distance. The majority of explosion overpressure and flame-propagation speed values at each gauge in the completely adiabatic pipe were larger than those of the partially adiabatic pipe. Both measurements at each gauge in the partially adiabatic pipe were much greater than those of the non-adiabatic pipe. The condition of the pipe wall has a large influence on the maximum explosion overpressure and the flame-propagation speed. In future explosion experiments, heat insulating materials should be installed in the inner wall of steel pipes to obtain data for application to the prevention and control of gas explosions in underground coal mines.

Investigation on the Interactions of Gas Explosion Flame and Reflected Pressure Waves in Closed Pipes

In the present research work, the basic concepts of the coupling interaction mechanisms of gas explosion–reflected over pressure and flame were outlined by experiments and theory analysis. During the test processes, high speed cameras were employed for shooting the flame images, and pressure and flame sensors were set along the pipes for the signals detection. The research results show that the reflected reverse pressure wave has a significant influence on the transmission properties of gas explosion flame in the closed pipes. Under the effects of reversed pressure waves, gas explosion flames also present several discontinuous characteristics, such as flame ruptures or extinguishing. Generally, it can be inferred that the main effects of reflected explosion pressure on the flame propagations in the closed pipes are inhibitions. The present research results of these studies are shown to allow for a significant improvement in our ability to address practical problems of coal mine gas explosion mitigations.

Numerical Simulation on the Influences of Initial Temperature and Initial Pressure on Attenuation Characteristics and Safety Distance of Gas Explosion

Understanding a safety distance necessary to avoid the harms of a shock wave to underground personnel may have great significance to the safety of underground personnel, disaster relief efforts, and the treatment of the gas explosion in coal mines. Through a roadway model with a cross-section area of 80 × 80 mm2 and a length of 100 m, the explosive attenuation characteristics of a methane/air mixture with a fuel concentration of 9.5% and a filling ratio of 10% were simulated by using AutoReaGas software for various initial temperatures (248–328 K) and initial pressures (20–200 KPa). The results show that the safety distance increases with the increase of the initial temperature and follows the changing trend of decreasing, increasing, and decreasing again with the increase of the initial pressure. The time of flame arrival to each point away from initiation and the maximum distance of flame propagation both increase with the increase of the initial temperature, but they are almost the same for various initial pressures. Before the attenuation of the shock wave occurs, increasing the initial temperature increases the maximum temperature, but decreases the peak overpressure, the maximum density, the maximum combustion rate, and the maximum gas velocity. However, increasing the initial pressure increases the peak overpressure, the maximum density, and the maximum combustion rate. The influences of the initial temperature and the initial pressure on these parameters at the longer distance points from the ignition source are greater than those at the shorter distance points.

Research and Application of Safety Assessment Method of Gas Explosion Accident in Coal Mine based on GRA-ANP-FCE

According to the complexity and nonlinear interaction between influencing factors of gas explosion in coal mine, this paper analyzed the main influencing factors of coal mine gas explosion accident with Grey Relational Analysis, and built the risk assessment index system of coal mine gas explosion based on four factors of “man-machine-environment- management”. This paper built the multi-criterion and multi-level network calculation model for the index system and got the weight sets by using Analytic Network Process. Multi-level fuzzy comprehensive evaluation determined the risk of gas explosion level. A coal mine in the South, for example, its gas explosion risk assessment, results showed that the method could find the main key risk factors and deal effectively the complex influence relationship among them, and provide an important reference to coal mine gas accident risk control and management.

Analysis and Methods of the Blasters’ Unsafe Behavior Taking Gas Explosion Accident as an Example

Abstract According to the research of Heinrich, American DunPont and National Safety Council in the United States, etc, more than 80% accidents are caused by the human unsafe behavior. In order to reduce or eliminate the unsafe behavior of the blasters, and then to effectively prevent coal mine gas explosion, we discussed and analyzed the unsafe behavior of the blasters. The analysis results show that the unsafe behavior of incompletely filled lute and the unsafe behavior of unused the water stemming in the hole sealing are the key of the research in the charging process, accounts for 71% of the unsafe behavior in the charging process. The method of virtual reality experimental platform was used for training the blasters’ operation behavior repeatedly, and we took one operation motion in the process of the hole sealing operation as an example to design a training method for the blasters’ unsafe behavior.

Numerical Analysis of Effect of the Number of Nozzles on Water Mist Flow Field for Gas Explosion Suppression

Explosion suppression by water mist is a new technology for the control of coal mine gas explosion with the three elements in the gas explosion at the same time. By building the physical model of the horizontal laneway in mine, and using the method of theoretical research and numerical simulation, this paper studies the relationship between the number of nozzles and H2O percentage and the distance for stable percentage of H2O, and provides a reliable for the design of water mist system for gas explosion suppression in the horizontal laneway in mine.

The roles of foam ceramics in suppression of gas explosion overpressure and quenching of flame propagation

In order to substantially suppress the shock waves resulting from gas explosions in coal mines as well as to reveal the mechanism of explosion flame quenching by foam ceramics, a rectangular explosion test pipe was designed, which has a 200 mm × 200 mm cross-section and is similar in shape to the roadways in coal mines. Explosion flame propagation characteristics in empty pipe and in the presence of Al 2O 3 and SiC foam ceramics were experimentally investigated. To obtain direct observations, the flame propagation was photographed by a high-speed camera. Furthermore, the mechanism of foam ceramics affecting gas explosion propagation was analyzed. The results demonstrate that the foam ceramics attenuate drastically the maximal explosion overpressure by up to fifty percent; the interconnected micro-network structure of the foam ceramics contribute to quenching gas explosion flame and suppressing shock wave overpressure. These important findings hint that, if properly designed and deployed, this material is expected to be developed into a new suppression and isolation technique against multiple and continuous gas explosions that are presently a grave threat to production safety of coal mines across China and the rest of the world.

Numerical Simulation of Shock Wave Structure in Gas Explosion

Abstract In order to study the characteristics of gas explosion in coal mine, on the basis of theoretical analysis and experimental research, the ignition and propagation characteristics of gas explosion is simulated by the introduction of elementary chemical reaction .This essay is also on the research of the transmission and simulation characteristics of exploration flame in an barrier tube. Especially the 17- component, 58-step chemical reaction modeling is introduced. The results of simulation match with theoretical analysis and experimental research. In order to provide effective argument for the investigation of gas explosion, field exploration and the reconstruction of the accident.

Study on the Development of the Medium-Scale Gas Explosion Integrated Testing System

Abstract Based on the characteristics of gas explosion in coal mines, the medium-scale gas explosion integrated testing system is developed. The integrated testing system is comprised of shock tube, testing section, explosion venting capsule, measuring instruments system, and other auxiliary equipments. The measuring instruments system can detect parameters of explosions and flow fields by the study of coupling relation between explosion and flow field. The synchronous control mechanism is employed to ensure parameters being simultaneously detected. The testing section can be adjusted to matching different testing requirements. Results of testing are useful to the prevention of gas explosion, emergency response and accident investigation.