Explosions In Coal Mines Research Articles

Variation Law of Hybrid Explosion Characteristic Parameters of Gas and Coal Dust Coupled with Multiple Factors.

This study aims at extensively investigating the explosion characteristics of a hybrid mixture of gas and coal dust. Accordingly, the standard 20 L spherical explosion system was applied to measure parameters such as the lower explosion limit, maximum explosion pressure, and index of the hybrid mixture of different concentrations of gas and coal dust. Moreover, different coal dust particle sizes and components were measured. With regard to coal dust with different particle sizes and components, the obtained results revealed that, while the addition of gas significantly reduced the lower explosion limit, the maximum explosion pressure and index were increased; that is to say, the presence of gas will increase the explosion risk of coal dust. However, under conditions in which the particle size of the coal dust was large or the volatile content was low, the addition of gas was found to lead to a higher decrease of the lower explosion limit; this is, while the maximum explosion pressure and explosion index were increased. Consequently, gas can be argued to have a greater influence on the explosion risk of coal dust with a large particle size or low volatile content. Furthermore, regardless of the particle size or the volatile content of coal dust, the maximum explosion pressure and explosion index of the hybrid mixture were observed to be higher than that of the pure coal dust but lower than that of the pure gas. That is to say, the explosion intensity of the gas/coal dust composite system is higher than that of pure coal dust but less than that of pure gas. The research results can provide theoretical basis for coal mine explosion disaster prevention and control and have important significance.

Fuzzy multi-criteria decision-making framework for controlling methane explosions in coal mines

The structure of underground coal mines is vulnerable to many mishaps because of the challenging conditions of production and the unique features of the earth. These incidents could cause significant financial and production losses for the mines in addition to worker injury, disability, or death. In coal mines, methane explosions are a frequent threat. Establishing a safe work environment requires managing these problems with an accident control method. The current study used the fuzzy TOPSIS and fuzzy AHP techniques for this aim. The framework was used to tackle the four-alternative problem of underground coal mine explosion control method selection. To identify potential risks of a methane explosion, a data gathering survey was conducted as part of the suggested hybrid methodology. The fuzzy AHP was used to compute the fuzzy weights of the hazards. “Improper ventilation system” is ranked highest out of the 34 sub-risk factors. The fuzzy TOPSIS was then utilized to rank the explosion control methods using the weights. To assess the viability of the study’s conclusions, a sensitivity analysis was carried out. The findings indicate that “improving safety technology” and “financial investments” are the best ways to reduce such events. The results additionally indicate that the fuzzy TOPSIS approach in combination with the fuzzy AHP provides a helpful framework for dynamically assessing mine methane explosion accidents.

Experimental Study on the Isolation Effect of an Active Flame-Proof Device on a Gas Explosion in an Underground Coal Mine

Passive explosion-isolation facilities in underground coal mines, such as explosion-proof water troughs and bags, face challenges aligned with current trends in intelligent and unmanned technologies, due to restricted applicability and structural features. Grounded in the propagation laws and disaster mechanisms of gas explosions, the device in this paper enables accurate identification of explosion flames and pressure information. Utilizing a high-speed processor for rapid logical processing enables judgments within 1 ms. Graded activation of the operating mechanism is enabled by the device. The tunnel flame-proof device’s flame-extinguishing agent has a continuous action time of 6075 ms. Experiments on the active flame-proof effect of a 100 m3 gas explosion were conducted using a cross-sectional 7.2 m2 large-tunnel test system. With a dosage of 5.6 kg/m2, the powder flame-extinguishing agent completely extinguished the explosion flame within a 20 m range behind the explosion isolator. Numerical calculations unveiled the gas-phase chemical suppression mechanism of the powder flame-extinguishing agent NH4H2PO4 in suppressing methane explosions. Building upon these findings, application technology for active flame-proofing was developed, offering technical support for intelligent prevention and control of gas explosions in underground coal mines.

Numerical Simulation of Gas Explosion with Non-uniform Concentration Distribution by Using OpenFOAM.

Gas explosions in coal mines have occurred occasionally, which may cause casualties and economic losses. In the actual mine roadway, the gas concentration distribution is uneven because the gas density is lower than that of air. Gas explosion characteristics of uneven gas distribution with the concentration gradient in mine roadways were analyzed by using the open-source computational fluid dynamic code OpenFOAM. The flame and pressure characteristics were calculated, and the flame and shock wave propagation laws of the non-uniform gas-air mixture explosion with different concentration gradients were analyzed and compared with the uniform gas-air mixture gas. The results show that when the overall gas concentration is the same, the flame velocity and the pressure growth rate of the uniform gas explosion are lower than those of the non-uniform, but the pressure peaks of both are similar. At the same time, when the initial volume concentration is 10%, the non-uniform gas explosion has the highest flame propagation velocity and peak value. The peak explosion pressure of different concentration gradients is proportional to the initial concentration. The above studies clarified the characteristics of gas-air mixture explosions with concentration gradients and provided theoretical support for the prevention and control of gas explosion disasters.

Risk Assessment of Coal Dust Explosions in Coal Mines Using a Combined Fuzzy Risk Matrix and Pareto Analysis Approach

Risk Assessment of Coal Dust Explosions in Coal Mines Using a Combined Fuzzy Risk Matrix and Pareto Analysis Approach

Near-infrared wide-range dual-gas sensor system for simultaneous detection of methane and carbon monoxide in coal mine environment

To effectively monitor gas explosion and coal spontaneous combustion in coal mine, an intrinsically safe and explosion-proof dual-gas sensor system was developed for methane (CH4) and carbon monoxide (CO) measurement. A distributed feedback (DFB) laser was used to scan two adjacent absorption lines (CH4: 4284.51 cm−1, CO: 4285.01 cm−1). Two measurement ranges of 0–500 parts per million by volume (ppmv) and 0–300,000 ppmv for CH4 and 0–100 ppmv and 0–4000 ppmv for CO were realized using a ∼25 cm single-pass gas cell (SPGC) and a ∼25 m multi-pass gas cell (MPGC), respectively. A gas pre-treatment module was used to remove moisture and aerosols from gas samples. A temperature compensation algorithm was adopted to deal with ambient temperature change. Based on the Allan deviation analysis, the limit of detection (LoD) of CH4 is 0.19 ppmv and the LoD of CO is 0.12 ppmv, respectively, at an averaging time of 0.5 s. A continuous two-day CH4 measurement was performed to demonstrate the long-term stability and environmental monitoring capability. The sensor system was successfully deployed in coal mine gas analysis at Longjiapu, Changchun City, China.

Enhancement mechanism of In-situ self-growing calcium sulfate on fly ash-based sealing coatings

Explosion accidents sometimes occurred in the process of coal mining, resulting in many casualties and serious environmental pollution problems. Gas leakage was one of the causes of coal mine explosion. At the same time, gas was a serious greenhouse gas, so it was necessary to take certain protective measures in the process of coal mining. Spraying sealing coating on roadway was a green and safe method. But the fly ash-based sealing coating that was sprayed on the wall of the roadway is likely to break or peel due to vibration of the wall brought on by blasting and drilling during the construction process beneath the mine. In this paper, the comprehensive performance of the coating was enhanced by adding in-situ self-growing calcium sulfate. The results showed that at 3% in-situ self-growing calcium sulfate was added, the porosity of the coating was reduced by 79.14%. The yield point was increased by 48.69%. The bending resistance and bonding strength of the coating were the best. The experimental results were verified by simulation calculation. When the in-situ self-growing calcium sulfate content was 3.3%, the system performance was the best. It was consistent with the experimental results. In summary, it was confirmed that doping with in-situ self-growing calcium sulfate could enhance the performance of fly ash-based sealing coatings.

Study on the Multiphase Flow Mechanism of Coupling Gas-dust Coupling Explosion in Open and Closed Vessels

In order to study the flame propagation characteristics and influencing factors of gas-coal dust mixed explosion in containers, this paper quantitatively explores the effect mechanism of two-phase concentration ratio and closed section restraint mode on gas-coal dust coupling explosion by numerical simulation, comprehensively considering the coal pyrolysis model and the two-phase mass and heat transfer model. The current research results show that: in closed pipeline, with the increase of pulverized coal concentration, the gas explosion intensity of lean fuel shows a trend of first increase and then decrease. Under the methane concentration of 7%, the optimal concentration of pulverized coal is 100 g/cm3; a similar trend also occurs in the open pipe. Secondly, the two-phase flame propagation speed in the closed pipe is faster than that in the open pipe. The research results of this paper can provide scientific guidance for the prevention and control of coal mine explosion accidents.

Coal mine explosions in India: Management failure, safety lapses and mitigative measures

This paper critically analyzes data on major explosions that have occurred at Indian coal mines over the past 120 years (1900-2020). An estimated 71.79% of mine explosions and 90.68% of associated casualties in India have occurred in Jharkhand and West Bengal states. However, the number of mine-related accidents and casualties attributable to explosions have significantly reduced overall in the last few decades, most noticeably since nationalization of the coal industry. Approximately 92.31% of explosions at Indian coal mines during this period were triggered by methane gas. The use of defective safety lamps and naked lights are identified as the most prominent sources of ignition accounting for 28.21% of total explosions and 53.09% of casualties. Recommendations for improved mine safety are presented which, if adopted, could go a long way toward minimizing even further the possibility for explosions at coal mines in India.

Preventing dust explosions in coal mines: Methods and current trends

Preventing dust explosions in coal mines: Methods and current trends

Комплексный подход к обеспечению снижения риска взрывов голубого топлива на угольных шахтах с одновременной добычей угольного метана

Methane explosions in coal mines are the most dangerous type of accident, they often lead to serious destruction and casualties among workers. The main means of ensuring safety is the timely degassing of mines and coal seams, which requires special equipment, financial and time costs. The discharged gas-air mixture is released into the atmosphere or burned, but the most appropriate way of disposal is to use it as fuel for boilers, turbines and other devices. About 7% of mine methane is usefully used in Russia. The article discusses the problems of implementing such projects, analyzes foreign experience and tools for achieving return on investment in coal methane projects.

ОБОСНОВАНИЕ ТЕОРЕТИЧЕСКОЙ МОДЕЛИ МЕТАНООПАСНОЙ ШАХТЫ ДЛЯ РЕШЕНИЯ ПРОГНОЗНЫХ ЗАДАЧ НА ПРИМЕРЕ ШАХТ КУЗБАССА

Statistical analysis of accidents in coalmines by the aerogasdynamic factor shows that the effectiveness of existing methods for predicting the risk of explosions of methane-air mixture in the mine workings of coalmines is unsatisfactory. So it is necessary to improve the physical model and mathematical description of the threat of explosive gas situations in the mine workings of a model mine. In general, a systematic approach to reducing the risk and localizing the consequences of methane explosions in coalmines comes down to solving the following problems. Substantiation of algorithms and development of a software package for modeling air distribution in coalmine workings under normal and emergency operation modes. Improving the technology for examining mine ventilation systems and preparing initial data for models. Substantiation of algorithms and development of a software package for modeling coal-degassing systems. Substantiation of models of methane emission dynamics from various sources. Substantiation of models of dynamics of methane concentration in mine workings of coal mines.

A Scoring-Based Risk Assessment Method Proposal for Methane Explosions in Underground Coal Mines

Mining is one of the sectors with the highest number of fatal occupational accidents. According to statistics, the majority of these fatal accidents are caused by methane explosions. In order for the explosion to occur, methane needs to form a certain concentration, sufficient oxygen and igniting elements are required. One of the most important factors that can affect methane formation is the carbon content of coal. As the carbon content increases, the probability of formation of flammable hydrocarbon-derived gas increases. The porous structure is a factor that causes methane to accumulate and create instantaneous concentration. It is known that the formation of the ignition element is directly proportional to the quartz content of the wall rocks. In this study, a new risk assessment method is proposed by assigning scores to the linguistic expressions of all these side parameters. This proposed method enables a proactive approach regardless of exact measurements and forced ventilation principles. It is foreseen that unexpected results can be prevented with the measures to be taken in this direction.

Автоматизированная система управления флегматизацией взрывов пылеметановоздушной смеси в шахтной атмосфере

Introduction. The work presents a general and principal diagram of the control system, provides recommendations for the choice of a set of technical means of practical implementation of the system and justification of the application and parameters of various sensors, power supplies, controller, communications, signal converters and actuators, which use different methods and methods of processing signals of different nature, which ensures completeness and prevents distortion of signals and parameters that affect the quality of the automated system of phlegm The aim of the work is to develop and implement the technical support of an automated control system of phlegmatization explosions of dustmethane-air mixture in the mine atmosphere. Materials and methods of research. To achieve the goal of controlling phlegmatization of dust-methane-air mixture explosions in the mine atmosphere, the search and analysis of materials on this topic is carried out, an automated control system is developed and observation of its work in real conditions is made. Research results. The dependences of the upper and lower thresholds of explosiveness of dust-methane-air mixture, as well as the achievements in the study of the molecular structure of water and methane can assess the effectiveness of measures to prevent methane and dust explosions in coal mines and propose a patentable method of phlegmatization of methane explosions in coal mines. Discussion. At a choice of CTS the basic attention is given to reliability of functioning of measuring techniques, standardization of interfaces, software of controllers and processors, on the basis of which it is supposed to develop software and realization of algorithmic and mathematical maintenance of the automated control system and its debugging in industrial conditions. Conclusion. The studies have shown that the sequence of installation of nozzles along the length of the face, should not exceed 1/5-1/7 of the length of the mini-drops falling (if a weighted mini-drop falls for 6-8 seconds, at a speed of 2.5 m/s, it flies 15-20 m, and, therefore, nozzles should be set every 12-15 m). Resume. At successful approbation and positive results of the automated control system of phlegmatization of explosions of dust-methane-air mixture in a mine atmosphere it can be successfully included in the existing systems of gas protection, extending their functions and increasing the level of industrial safety of mines. Also, studies have shown that for the implementation of a phlegmatization control system of explosions of dust-methane-air mixture in a mine atmosphere to increase the accuracy it is necessary to increase humidity, which in turn leads to the need to choose the location of installation of nozzles. Suggestions. In real conditions the level of absolute moisture of 16 g/m3 is possible at a temperature not lower than 22 °C and relative humidity of not less than 90 %, therefore, the task of the automated control system of phlegmatization of dust-methane-air mixture explosions (ACS FVPS) in the mine atmosphere is to maintain the maximum absolute humidity at the existing humidity and temperature in the clearing or preparatory face, taking into account the methane and dust concentration in the mine atmosphere.

Superposition risk assessment of the working position of gas explosions in chinese coal mines

The prevention of gas explosion accidents is a key factor in enhancing the safety of production of coal mines. The effective management and control of the working position risks is of great significance for the prevention of such accidents. By analyzing data from 201 typical gas explosion accidents, 21 working positions related to the accidents were identified along with the main causing factors. By employing data statistical methods, the structural importance analysis method of fault tree analysis, and the summation method, the risk associated with each working position was evaluated. Then, this work built a risk assessment matrix to categorize risk levels associated with various working positions related to gas explosions in coal mines. Also, based on the kernel density analysis, a superposition risk assessment model was established. In addition, the ArcGIS software was used to simulate and calculate the superimposed risks and draw a risk distribution map. The results show that the number of working positions of Level I is mainly affecting the fully mechanized mining team, the fully mechanized excavation team, and the ventilation team. The risk distribution map intuitively shows that the high-risk working positions involving gas explosion accidents in Chinese coal mines mainly exist in the working face and the tunneling face. It is highlighted that the working position risk and grade distribution have a significant hierarchy after risk superposition.

Dynamic Response of the Steel Plate Under the Impact of High-Speed Coal Projectile

The coal-rock projectiles induced by gas explosions in coal mines have a strong destructive effect on mine facilities and equipment, which are mostly made of steel. The LS-DYNA is used to simulate the process of coal projectile striking the steel plate. The results show that during the failure process, the morphological change of the projectile consists of three stages including plastic deformation, partial crushing, and complete crushing, and the steel plate pits at the impact point. The duration of the stress peak value of the steel plate increases as the impact velocity increases. The farther away from the center point, the smaller the stress peak value is, and the shorter the duration is. When the impact velocity is 100 m/s and 300 m/s, the axial velocity curve at the impact point of the projectile is pulsating. When the impact velocity reaches 500 m/s, the axial velocity of the projectile rapidly increases and then tends to be stable. As the impact velocity increases, the energy absorbed by the steel plate increases, and the rate of increase also increases. However, the proportion between the absorbed energy of the steel plate and the initial kinetic energy of the projectile decreases. The projectile conversion energy of the 1 mm steel plate is slightly larger than that of 1.5 mm and 2 mm steel plates, and the energy absorbed by the steel plate decreases with the increase in thickness of the steel plate. When the thickness of the steel plate is more than 2 mm, the thickness of the steel plate has little effect. The results of the study have a direct sense for the antiknock design of coal mine facilities and equipment.

Experimental Study on Two-Phase Explosion Suppression of Gas/Pulverized Coal by Explosion Suppressant.

Pulverized coal is widely distributed in coal mine roadways, which can enhance the power of a gas explosion. Explosion suppression technology can effectively reduce the explosion power. At present, rock powder shed, a water bag, and ABC powder are widely used in most coal mine explosion suppression technologies. In order to verify the explosion suppression effect of rock powder, water, and ABC powder in the pulverized coal environment, a series of experiments on a suppressing gas/pulverized coal two-phase explosion were carried out with a self-built large-scale gas explosion experimental system. The experimental study in this paper can provide some reference for the improvement of explosion suppression technology in coal mines. In this paper, through the suppression of a secondary explosion, flame, and impact of pulverized coal, the explosion suppression effects of three kinds of explosion suppressants are comprehensively analyzed. The results show that rock powder has a good inhibitory effect on a secondary explosion and flame of pulverized coal, and water has a good inhibitory effect on the shock wave. ABC powder has the best explosion suppression effect; the inhibition of a secondary explosion of pulverized coal is 4.17 times that of rock powder, the inhibition of flame is 4.28 times that of rock powder, and the inhibition of shock wave is 2.24 times that of water.

Review of preventive and constructive measures for coal mine explosions: An Indian perspective

Firedamp and coal dust explosion constitute a lion’s share in mine accidents in a global mining scenario. This paper reports a list of mine explosion disasters since last two decades, a critical review of the different prevention and constructive measures, and its recent development to avoid firedamp and coal dust explosion. Preventive legislation in core coal-producing countries, viz. China, USA, Australia, South Africa, and India related to firedamp and coal dust explosion are critically analysed. Accidents occurred due to explosion after Nationalisation of Coal Mines (1973) in India are listed. Prevention and constructive measures adopted in India are critically analysed with respect to the global mining scenario. Measures like methane credit concept, classification of mines/seams with respect to explosion risk zone, deflagration index; installation of automatic fire warning devices, canopy air curtain technology, explosion-prevention measures, such as fire-retardant materials, inhibitors, extinguishing agent, dust suppressor, and active explosion barrier are discussed in detail to avoid explosion and thereby adhering to zero accident policy due to coal mine explosion.

Instantaneous discharge characteristics and its methane ignition mechanism of coal mine rock damage.

The goaf is the main site of gas explosions in coal mines. A large number of accidents indicate that the occurrence of gas explosion in the goaf is related to the deformation and fracture of the goaf roof. An experimental system was constructed to study the instantaneous discharge characteristics and its ignition mechanism caused by rock damage. The research results reveal that different rocks produce avalanche-like dust clouds ejected outward during the fracture process, and the generation process takes an extremely short time. This dust cloud is not caused by rock fragments heated to incandescence because of friction. The electric sparks produced in the process of rock rupture and the appearance of instantaneous discharge are related not only to the quartz content of the rock, but also to the compressive strength of the rock. The piezoelectric effect of the rock becomes the key factor for the strength or the generation of an electric spark. The instantaneous discharge leaded to the collision of high-energy electrons released during the fracture process with air molecules, ionising, and breaking down the air. When the surrounding medium is gas air within the explosion limit, ionisation is formed and causes gas explosions.

Experimental investigation on the effect of obstacle position on the explosion behaviors of the non-uniform methane/air mixture

Gas explosions in the underground coal mines where the obstacles exist can cause significant damage. A current knowledge gap in methane safety research concerns the effect of obstacle position on the explosion process of non-uniform mixtures. In this work, the effect of obstacle position on the explosion behavior of non-uniform methane/air mixture is investigated experimentally. The results show that the triple flame structure appears during the combustion of the non-uniform mixture, which appears delayed with increasing obstacle position. Then, broken flocculent turbulent flames occur when the obstacle is set at 400 and 600 mm, with the strongest turbulent disturbance response at 400 mm case. Moreover, the results show that the maximum flame front velocities and the maximum values of overpressures are obtained at the obstacle position of 400 mm in both diffusion times. Additionally, two obvious pressure peaks are found, which appear at increasing intervals as the distance between the obstacle and the ignition source increases. Meanwhile, the maximum overpressure values ranks as Pmax(400 mm) > Pmax(200 mm) > Pmax(600 mm). The study of gas explosion flame characteristics that meet the actual working conditions of coal mines plays an important role in the prevention of explosion accidents.