Mine Gas Explosion Research Articles

Study on microstructure characteristics of material evidence in coal dust explosion and its significance in accident investigation

The weakness of material evidence analysis brings challenges and problems to the investigation of mine gas and coal dust explosion accidents. As an important material evidence, post-explosion coal dusts contain rich information about explosion process and reaction mechanisms and can play an important role in explosion accident investigation. The study uses image processing technology and fractal theory to make qualitative and quantitative characterization of microstructure of post-explosion coal dusts and discuss its significance in mine explosion accidents investigation. Regular spherical residues particles were unique for post-explosion coal dusts and various explosion residue particles could be broadly classified into four types. Quantitative analysis suggests that the particle size distribution of post-explosion coal dusts exhibits fractal property and has smaller fractal dimensions due to the increase of fine particles and coarse particles. The roundness of explosion residues is larger than that of original coal dusts and has a negative correlation with particle size. It is also found that the isothermal adsorption–desorption curves of post-explosion coal dusts could be classified into Type II and are characterised by hysteresis loops of Type H3. The change laws of D1 and D2, two fractal dimensions obtained by using FHH method, indicate that post-explosion coal dusts have more irregular pore surface and more homogeneous pore structure. In addition, the present research work demonstrates that post-explosion coal dusts have application value in justifying the participation of coal dusts in mine explosion accident and deducing the explosion source.

Comprehensive consultation model for explosion risk in mine atmosphere-CCMER

Mine gas explosion is one of the most feared hazards in the coal industry worldwide. More often one gas explosion related accident can cause the death of multiple coal miners. Examination of recent mine explosion disasters that have occurred in the worldwide reveals that most explosions originated from or around the sealed areas. Therefore, a good understanding of the atmospheric status in a sealed coal mine area is crucial in preventing and reducing accidents associated with mine combustible gases and also for planning and implementing a mine rescue strategy. In this paper, a PC based computer gas explosion consultation software model developed by the authors is introduced. This model is called CCMER (Comprehensive Consultation Model for Explosion Risk in Mine Atmosphere). The computer model is a comprehensive, reliable and user-friendly one. The nature of “comprehensive” means the model can be used to consult the explosibility of a gas sample taken from underground atmosphere, can assist engineers to know how explosion dangerous the situation is or what the risk degree is for a not-explosive atmosphere, and also can perform quantified analyses on the changing time span between not-explosive state and explosive state to guide the recuse works. All of those works are very important to mine operators understanding the mine atmosphere and then taking proper measures to control the potential risk. In addition to that, usages of developed computer program are also very easy. Users can operate the program without possessing an in-depth knowledge on computer and mathematical theory. Until today, CCMER has been successfully employed in numerous cases of designing and assessing various mine atmospheres during the past decades. The reliability of mathematical models used in CCMER has also been proven by such applications.

Experimental studies and modeling on flame velocity in turbulent deflagration in an open tube

Studies on flame propagation during turbulent deflagration in a partly opened tube are important in developing explosion protection scheme and suppression technology for industrial process with explosion risk. Gas explosions in coal mines, deflagration in gas transmission tubes and dust explosions in confined working spaces can be simplified by a partly opened tube in studying deflagrations. An experimental rig with a 16m long open tube of 0.488m diameter was constructed for studying the flame propagation characteristics of premixed liquefied petroleum gas (LPG) under different mixing ratios with air. The transient flame propagation distance, flame velocity, pressure and temperature were analyzed. A flame velocity model for an explosion in an open tube was proposed and verified by the experimental data. This model was also used to calculate the flame velocity of experiments reported in literature. It is demonstrated that the developed flame velocity model is appropriate for premixed gas deflagrations up to an equivalence ratio of 1 at the initial stage of flame propagation, i.e., with a flame velocity less than 100m/s.

Risk Assessment of Miners' Unsafe Behaviors: A Case Study of Gas Explosion Accidents in Coal Mine, China.

China’s coal mine production situation is grim and various types of accidents occur frequently, and gas explosion accidents are the highest incidence of coal mine accidents. The authors selected 200 gas explosion accidents of coal mine enterprises in recent years, and extracted a large number of workers’ unsafe behaviors. Meanwhile, four working types related to gas explosion accidents were obtained, namely ventilation, gas prevention and fire extinguishing, blasting, and electrician. This article listed some influencing factors of unsafe behaviors and corrected the probability of unsafe behaviors. In addition, a probabilistic risk assessment model was established, and the Monte Carlo method was used to analyze the risks caused by unsafe behaviors of various working types. The results show that the risk of unsafe behaviors caused by the ventilation working type is the highest, followed by gas prevention and fire extinguishing, and finally blasting and electrician. This paper studies the influencing factors of miners’ unsafe behaviors from the perspective of behavior, guarantees effectively the safety management of coal mine enterprises, and lays a foundation for studying unsafe behaviors related to coal mine gas explosions.

Application of trend surface analysis in early warning model of coal mine gas explosion

Aiming at the catastrophic problem of common coal mine gas explosion, this paper combines the trend surface analysis method to establish a gas explosion warning model, and validates the model through actual data, and the model has good robustness. Through the data fusion of the comprehensive information of gas explosion, the gas and oxygen concentration are selected as the key indicators of the early warning model, and the trend surface analysis of the finite discrete data is established. The trend surface warning model of gas and oxygen concentration is established, and the distribution of key indicators is obtained. Features that enable predictions and warnings of potential gas hazards.

The Accident Path of Coal Mine Gas Explosion Based on 24Model: A Case Study of the Ruizhiyuan Gas Explosion Accident

In order to effectively prevent coal mine accidents, we selected the most serious type of accident in coal mines—gas explosions—as the research object. Based on the accident causation model (24Model), we propose an action path and analysis steps of accidents caused by different employees in the organization. A gas explosion coal mine accident was analyzed using the 24Model and the proposed action path, and 12 unsafe actions, 3 unsafe states, 4 habitual behaviors, 10 safety management systems, and 10 safety cultures were obtained. Case analysis results show that by using the 24Model and path analysis the proposed effect can help employees to clearly identify the cause of the accident, to better understand the logical relationship with the causes of the accident, improve the effectiveness of training, and effectively prevent similar accidents. The 24Model and the proposed path can be used to comprehensively analyze the reasons for and help to effectively prevent coal mine gas explosion accidents.

Study on noise-vibration coupling characteristics of premixed methane-air flame propagation in a tube with an acoustic absorption material.

To study the influence of an acoustic absorbing material (AAM) on the noise and vibration of a methane–air deflagration flame in a square plexiglass tube, a high-speed video camera, pressure sensors, and a noise and vibration tester were used to test the deflagration flame propagation velocity, deflagration pressure, noise and wall vibration characteristics in the tube. The tube length is 540 mm with a cross section of 80 × 80 mm2, and its wall thickness is 12 mm. The experimental results indicate that under the conditions of 8.96% CH4 by volume and fixed repeating obstacles, the built-in AAM of polyester fiber cotton can reduce the peak velocity of the deflagration flame propagation by 11.3%. In addition, the average maximum sound pressure level of the deflagration flame noise is decreased by 17.6%, and the peak vertical vibration velocity of the tube outer wall is decreased by 85.6%. Therefore, using AAM can effectively attenuate the flame propagation and its harmful effects. For the case with an AAM, the flame propagation velocity and deflagration pressure reached the maximum values at 33 ms after ignition, and the values were 62.50 m s−1 and 27.74 kPa, respectively. Similarly, the time history curves of the noise and the tube wall vibration caused by deflagration presented certain correlations. The experimental results and analysis in this paper provide reference values for controlling the hazards of gas explosions in underground mines and other combustible gases in industrial pipelines.

Characteristic Analysis of Unsafe Behavior by Coal Miners: Multi-Dimensional Description of the Pan-Scene Data.

As a high-risk occupation, coal mining has many accidents, primarily due to the unsafe behavior of coal miners. Based on the research of analysis of unsafe behavior and pan-scenario data of miners, a theoretical framework for the analysis of unsafe behavior characteristics was proposed in this paper. The collected data were divided into realistic scenes and abstract scenes according to different manifestations; the pan-scene data were described from the eight dimensions of time, behavioral trace, location, behavioral property, behavioral individual, degree, unsafe action, and specialty using a quantitative method for the structure conversion; and the rules were discovered through cluster analysis and association analysis. A total of 225 coal mine gas explosion accidents were used for analysis, and the pan-scene data description and structure conversion of unsafe behavior that caused these accidents were realized. In a certain cluster, the distribution rules of dimensions and the interaction between different dimensions of unsafe behavior were explored after analysis. The results show that the proposed eight dimensions can fully explain the basic characteristics and attributes of the unsafe behavior of coal miners. The structure conversion can reduce the workload of managers and effectively improve the safety data processing capabilities, and the result of data analysis can provide data support and a management basis for safety management. A new method and thought for the data analysis of miners’ unsafe behavior is provided.

Minimum explosive concentration of coal dust cloud in the coexistence of gas and coal dust

The present work was carried for the prevention of increasingly ever prevalent gas explosion accidents that had occurred in the coexistence of gas and coal dust in recent years. Using a 20 L explosion test system, we studied experimentally the explosive characteristics of the coexisting gas and coal dust and obtained the lower limit of gas explosion under different ignition energies, static and turbulent conditions and the lower limit concentration of coal dust explosion under different conditions. The results show that with the increase of gas concentration, the minimum explosive concentration of coal dust cloud decreases exponentially and that there is a critical gas concentration, in higher than which gas plays a leading role in the process of explosion, shown as the so-called strong gas. Otherwise, coal dust plays the leading role, which is characterized by the strong coal dust. The conclusions can serve as an important theoretical basis for preventing the coal mine gas and coal dust explosion.

Application of Bayesian approach to the assessment of mine gas explosion

Frequent mine gas explosion accidents in recent years have caused catastrophic casualties and economic loss in China. In this paper, based on expert knowledge with treatment by the Delphi method to determine conditional probabilities, a Bayesian network (BN) has been developed to investigate the factors influencing mine gas explosion accidents. Based on case analysis of typical mine gas explosion accidents and further evaluation by experts, twenty BN nodes are proposed to represent mine gas explosion process from occurrence causes to explosion impacts, and final consequences. The results of case studies and Sensitivity Analysis (SA) with the proposed Bayesian model indicate that the integration of Bayesian network and Delphi method is an effective framework for dynamically assessing mine gas explosion accident, which could provide a more realistic assessment for emergency decision-making on mine gas explosion disaster response and loss prevention.

Investigation on propagation mechanism of large scale mine gas explosions

This work presented an investigation into the gas explosions that occur in coal mines. The propagation of the explosion waves was studied by using large eddy simulation (LES) coupled with weighted essentially non-oscillatory (WENO) finite difference scheme. The results showed that the destructive effects of gas explosions were mainly caused by the high-speed airflow, and the high pressure of the shockwave. The comparison between the numerical and experimental results confirmed that the overpressure and airflow velocity initially increased, and then decreased slightly after the explosion has occurred in the coal mine, and their maximum values increased with the increase of the gas accumulation zone. The flame length was found to be far greater than the length of the original gas accumulation area, and the ratio of them is 5–7 which is related to the gas accumulation area.

Analysis of Risk Management for the Coal Mine Operations

More than half of the energy sources in China are provided by combustion of coal from thermal power stations. By lowering the risk of excavating coal mines, we can decrease the price of the energy. This paper stresses the danger of coal mine gas explosions and constructs a gas explosion risk prediction system based on standard Hypo-Variance by using Brain Storms Optimization implemented with MATLAB simulation software. Hypo-Variance is the new concept built on the basis of Gauss Variance and can be used to make more precise risk assessments. By analyzing the multiple connections among gas density, temperature, humidity, pressure, air velocity, we can predict the trend of the gas event and propose the most safely timed schedule: operating three shifts in a day starting from a particular hour right after the gas peaking is over.

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.

ASSESSMENT OF MINE VENTILATION SYSTEM RELIABILITY USING RANDOM SIMULATION METHOD

A mine ventilation system provides a fresh air flow to the underground workings in a coal mine. Such sufficient air volume can dilute and remove noxious gases (typically NOx, SO2, CH4, CO2 and CO) and maintain a suitable working environment for coal miners. On the other hand, a poor ventilation system often leads to serious consequences such as mine gas explosions, production loss or higher operational costs. Hence, the functions of mine ventilation system are very important for an underground mining system. This paper presents a reliability assessment approach for evaluating the mine ventilation system based on a random simulation method, Monte-Carlo Simulation (MCS). In detail, the first step of this method is to finish probabilistic descriptions of the mine ventilation network. Then, the criteria of successful conditions are defined. Finally, the Monte-Carlo Simulation (MCS) method is used for performing the reliability assessment. By using this assessment approach, the random characteristics in the system can be well considered. Hence, the results are more accurate and reliable. In addition, the risk evaluation for the mine main fan is also approached by the Monte-Carlo Simulation (MCS) method. Two important problems, the yearly percentage of loss time due to fan repairing and yearly breakdown times, are answered. Through the paper, a case study has been shown and investigated to demonstrate the assessment procedure for a mine ventilation system with using the MCS method.

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.