Mine Fire Research Articles

Mathematical Model and Numerical Simulation Study of the Mining Area with Multiple Air Leakage Paths

The natural fire in the mining area is the main source of mine fires, and the distribution of spontaneous combustion “three zones” is a key issue in mine fire prevention and suppression. In order to study the change law of spontaneous combustion “three zones” in the mining area with multiple air leakage paths, a segmented numerical simulation method is proposed. In order to consider the common influence of various factors, we firstly establish the coupled model of oxygen consumption rate of coal relics, the regional fluidity model of the porous medium and the three-dimensional distribution model of void rate in the mining area. Then, based on this, the corresponding conditions of air leakage speed, air leakage location and oxygen concentration are set in each stage of numerical simulation. The mathematical model shows that: the oxygen consumption rate of coal shows an approximate exponential growth trend with the increase in temperature, which is proportional to the original oxygen concentration; the void rate of the mining area shows a logarithmic distribution with a tendency of “double hump” proportional coupling. The numerical simulation results show that: the width of the “oxidation zone” decreases gradually along the tendency when there is only air leakage from the working face; the smaller airflow and lower oxygen concentration in the overlying mining area will increase the width of the “oxidation zone” in the coverage area; air leakage from the shelf road will form an “oxidation zone” near the entrance of the shelf road. The leakage of air from the shelf road will form an “oxidized zone” near the entrance of the shelf road; the leakage of air from the adjacent mining area will increase the width of the overall “dispersal zone” and “oxidized zone” due to the larger air flow and higher oxygen concentration. The comparison with the monitoring data of the downhole bundle tube verifies the rationality of the mathematical model and the accuracy of the numerical simulation results.

Accurate Concentration Measurement Model of Multicomponent Mixed Gases during a Mine Disaster Period.

A variety of gaseous products are formed when mine fires and coal and gas outbursts occur in mines. On the one hand, these gas products affect the normal production of mines and the occupational health of miners; on the other hand, the gaseous products can also provide much important information to prevent mine disasters. Thus, the rapid and accurate determination of the component content of multicomponent mixed gases is of great significance. However, the distortion of gas chromatography measurement results, which deviate from the true values, has a serious impact on gas composition determination in mines. To reduce the influence of distortion, an Agilent 490 portable gas chromatograph is used to measure the component content of 11 groups of standard multicomponent mixed gases. It is found that the error rate of the measured result is highly related to the concentration of the selected reference component and the component to be measured. Besides, the key point of each gas concentration is determined according to the scatter diagram of the error rate. Each gas is divided into a high and a low concentration group by the key points, and each gas is selected as the reference component to measure the corresponding component concentration in other gases with multiple-point external standards. Researchers have used the least-squares method to fit univariate linear regression analysis between the measured values and true values of mixed gases. Then, the optimal analysis function and the optimal reference component concentration of each gas can be determined by comparing the regression analysis parameters. Finally, it is found that the error rate of measured values corrected by the optimal analysis function is significantly reduced. It is proved that this method can effectively alleviate the measurement results’ distortion, which solves the problem of gas composition determination in underground areas.

A visual knowledge map analysis of mine fire research based on CiteSpace.

Mine fire has always been a serious disaster in coal industry; many academic achievements have poured out in the past two decades for solving this problem. In this study, visual analysis was conducted to grasp the hotspots and development trend of mine fire research. Papers that published in 1999-2020 were retrieved as the data basis from Web of Science, and CiteSpace was used to carry out knowledge map analysis. The results shown that number of papers has increased steadily since 2005 and achieved explosive growth since 2014. Deng J is the first published author among many scholars. China, the USA, and Australia are active areas in mine fire research and China University of Mining and Technology ranks first in this field. The highest co-occurrence frequency keyword is "spontaneous combustion." International Journal of Coal Geology and Fuel provide guidance for mine fire research. Fire prevention technology, low carbon, ecology, and sustainable development are the hot research in recent years. The prevention and control of mine fire from combustion mechanism should be further strengthened.

Prediction of coal spontaneous combustion temperature based on improved grey wolf optimizer algorithm and support vector regression

The effective prediction of coal spontaneous combustion temperature is of great importance to the monitoring and prevention of coal mine fires. Aiming at the problem of insufficient prediction accuracy of traditional coal spontaneous combustion temperature prediction model, and considering the characteristics of prediction data samples and the timeliness of applicable models, an improved grey wolf optimized support vector regression coal spontaneous combustion temperature prediction model based on nonlinear parameter control, dynamic inertia weights and grey wolf social hierarchy is proposed, and the effectiveness of the improved grey wolf optimizer algorithm is verified by numerical experiments. The O2 concentration, CO concentration, C2H4 concentration, CO/ΔO2, and C2H4/C2H6 selected from the coal spontaneous combustion procedure warming experiment were used as the input indexes of the prediction model, and the coal body temperature was used as the output index, and the prediction model was compared and analyzed with the particle swarm optimization support vector regression and grey wolf optimized support vector regression models through the experimental data. The results show that the improved grey wolf algorithm has stronger global search ability, faster convergence speed and better stability, and the proposed prediction model has strong advantages in accuracy and stability, which can provide better decision reference for coal spontaneous combustion fire prediction and warning in coal mines.

Hot Surface Ignition of Liquid Fuels Under Ventilation.

Mine equipment fires remain as one of the most concerning safety issues in the mining industry, and most equipment fires were caused by hot surface ignitions. Detailed experimental investigations were conducted at the NIOSH Pittsburgh Mining Research Division on hot surface ignition of liquid fuels under ventilation in a mining environment. Three types of metal surface materials (stainless steel, cast iron, carbon steel), three types of liquids (diesel fuel, hydraulic fluid, engine oil), four air ventilation speeds (0, 0.5, 1.5, 3 m/s) were used to study the hot surface ignition probability under these conditions. Visual observation and thermocouples attached on the metal surface were used to indicate the hot surface ignition from the measured temperatures. Results show that the type of metal has a noticeable effect on the hot surface ignition, while ventilation speed has a mixed influence on ignition. Different types of liquid fuels also show different ranges of ignition temperatures. Results from this work can be used to help understand equipment mine fires and develop mitigation strategies.

An Environmentally Friendly Antioxidant Foamed Gel for Inhibiting Spontaneous Combustion of Coal

ABSTRACT Coal spontaneous combustion can cause serious coal mine fire and gas explosion. In order to overcome the problem that the effect of existing materials to inhibit coal spontaneous combustion is reduced at high temperature and some environmental protection problems of materials, this study developed an effective, green and environmental protection antioxidant foamed gel (AFG). Modified sodium polyacrylate, konjac glucomannan, sodium dodecyl sulfate, sodium alpha-olefin sulfonate, modified silicone polyether microemulsion, montmorillonite, and tert-butyl hydroquinone were selected as raw materials. A single factor experiment was conducted to determine the appropriate adding proportions for each component. Then, the optimal proportion for the five components were fitted and verified by response surface analysis. The structures of the samples were characterized, and their properties were compared and tested. The fluidity, water loss, and thermogravimetry experiments demonstrated that the effect of AFG was excellent. In the experiment of in situ diffuse reflectance Fourier transform infrared spectroscopy, the AFG inhibition reaction was verified. Finally, combined with the structural characteristics of the AFG, the following inhibiting mechanisms were confirmed: AFG adhered to the coal surface and blocked the coal–oxygen contact; the antioxidant component slowed down chemisorption and the chemical reactions; AFG interrupted the free radical chain reaction.

An exploration of the trajectory of psychological distress associated with exposure to smoke during the 2014 Hazelwood coal mine fire.

Due to climate change, catastrophic events such as landscape fires are increasing in frequency and severity. However, relatively little is known about the longer-term mental health outcomes of such events. Follow-up was conducted of 709 adults exposed to smoke from the 2014 Hazelwood mine fire in Morwell, Victoria, Australia. Participants completed two surveys evaluating posttraumatic distress, measured using the Impact of Events Scale-Revised (IES-R), three and six years after the mine fire. Mixed-effects regression models were used to evaluate longitudinal changes in distress. IES-R total scores increased on average by 2.6 points (95%CI: 1.2 to 3.9 points) between the two survey rounds, with increases across all three posttraumatic distress symptom clusters, particularly intrusive symptoms. This increase in distress was evident across all levels of fine particulate matter (PM2.5) exposure to the mine fire smoke. Age was an effect modifier between mine fire PM2.5 exposure and posttraumatic distress, with younger adults impacted more by exposure to the mine fire. Greater exposure to PM2.5 from the mine fire was still associated with increased psychological distress some six years later, with the overall level of distress increasing between the two survey rounds. The follow-up survey coincided with the Black Summer bushfire season in south-eastern Australia and exposure to this new smoke event may have triggered distress sensitivities stemming from exposure to the earlier mine fire. Public health responses to disaster events should take into consideration prior exposures and vulnerable groups, particularly younger adults.

Vascular Responses Among Adults Four Years Post Exposure to 6 Weeks of Smoke from the Hazelwood Coal Mine Fire.

Background and AimsMega-wild fires are exposing large communities to weeks or months of high concentration smoke-related fine particulate air pollution (PM). However, little research has examined the long-term vascular responses from exposure to PM of this concentration and duration. We investigated whether level of exposure to 6 weeks of PM from the 2014 Hazelwood coal mine fire was associated with abnormal vascular responses approximately four years later.MethodsA cross-sectional analysis was undertaken of 387 participants (225 exposed, 162 unexposed) aged 55–89 years, 3.5–4 years after the mine fire. The primary outcome was flow-mediated dilatation (FMD), with time to reach peak diameter as the secondary outcome. Other secondary markers included high-sensitivity C-reactive protein (hsCRP) and ischaemic Electrocardiogram (ECG) changes.ResultsThere was no evidence of a difference in FMD between participants with high, medium, low or no mine-fire related PM2.5 exposure (4.09% vs 4.06% vs 4.02% vs 3.98%, respectively, p=0.99). Likewise, there was no difference in hsCRP or ischaemic ECG changes. In contrast, there was evidence of a difference in time to peak diameter (p=0.002) with more unexposed participants reaching peak diameter within 30 seconds (36%) compared to those who had high, medium, or low exposure (23%, 22%, 13%, respectively). Multivariate ordinal logistic regression analysis suggested that township, Morwell (exposed) vs Sale (unexposed), but not level of PM2.5 exposure, was associated with delayed time to peak diameter (OR 2.71; 95% CI 1.56, 4.69). Smokers also had delayed time to peak diameter.ConclusionThere was no association between level of exposure to PM2.5 from the 6-week Hazelwood coal mine fire smoke event and reduced FMD, elevated hsCRP or ischaemic ECG four years later. Evidence of delayed time to peak diameter observed in adults from the exposed town, compared to an unexposed town, requires further investigation.

Practical Application of Oxygen Augmentation Observation in the Process of Unsealing Fire Zone: Case study of Yu Wu coal mine in China

It is very important to unseal the closed coal mine fire zone safely. Although the fire source disappears in the closed fire zone, it is uncertain whether there are still have high-temperature ignition points, and there is a risk of fire or even explosion again after unsealing. To ensure that the closed fire zone can be unsealed successfully at one time, the study puts forward the method of oxygen augmentation observation to understand the combustion state of the closed fire zone in underground coal mine from the perspective of gas analysis technology. When the mine fire is detected to be extinguished, the method is to inject 8–12% oxygen into the fire area, and the fire area shall be monitored for 2 weeks to determine whether the fire area is completely extinguished. The accuracy and practicality of the method of oxygen augmentation observation are verified by comparing and analyzing the difference results generated by two oxygen augmentation observations in closed zone of Yuwu Coal Mine. In this paper, the use conditions of unsealing in fire zone, detailed methods and steps in the whole process of unsealing and emergency rescue plan are given. The research results can provide valuable reference for one-time safe unsealing of fire zone during the process of disaster relief.

Characteristics and main factors of foam flow in broken rock mass in coal mine goaf.

To protect the environment and reduce the occurrence of coal mine fire, foam injection in goafs is an effective measure for preventing and extinguishing mine fires. The flow characteristics of foams injected into goafs have a significant impact on the prevention and extinguishment of such fires. To study the flow characteristics of foam injected into a goaf, we first independently constructed a set of experimental platforms for the visualization of goafs. Next, we performed physical experiments on foam injection using similarity theory. Flow characteristics were simulated under different foam concentrations, flow rates, and goaf porosities. The exponential function was found to provide a good fit to the trajectory of the foam's stacking edge in the goaf. According to the foam injection volume, the trend of the fitting equation parameter a could be divided into two stages. The first stage was the rapidly decreasing stage, and the second stage was the stable stage. It was inferred that the stacking height and diffusion radius of the foam under different conditions were related to the speed of liquid film drainage. The results of this study can provide a valuable reference for the use of fire prevention and extinguishment technology in the goaf.

Effect of Water Evaporation on the Inhibition of Spontaneous Coal Combustion.

Spontaneous coal combustion is the primary cause of coal mine fires. During the production process, spontaneous coal combustion in the goaf is often affected by air leakage, which weakens or annuls the effect of inhibitors and leads to secondary oxidation. However, the action mechanism of inhibitors on secondary oxidation spontaneous coal combustion remains unclear. Thus, this study analyzes the influence of moisture evaporation on the performance of a high-water-content physical inhibitor (HWPI) using the Carbolite temperature-programmed experiment, differential scanning calorimetry, scanning electron microscopy, and a MINI MR test. The results demonstrate that as the moisture content of the inhibitor decreased, after being treated with the HWPI and drying for 24 h, the concentrations of O2, CO, and CO2 were found to be lower than the gas concentration of raw coal, which showed that although the moisture content is reduced, the treated coal sample still has a lower spontaneous combustion tendency than the raw coal. The apparent activation energy was reduced, and the heat absorption per unit time decreased, which eventually weakened or annulled the effect of the HWPI. Future research should further improve existing inhibitor types to reduce the impact of secondary oxidation on spontaneous coal combustion caused by water evaporation.

Coal Seam Fires Burn Beneath Communities in Zimbabwe

Underground fires threaten the health of people and livestock living near mines supporting the country’s growing coal industry.

Decision Support System for the Prediction of Mine Fire Levels in Underground Coal Mining Using Machine Learning Approaches

Decision Support System for the Prediction of Mine Fire Levels in Underground Coal Mining Using Machine Learning Approaches

Выбор средства пожаротушения угольных шахт на основе автокорреляционного анализа аварий

Purpose. The article describes of facility operation with the production of non-renewable energy resources in the Russian Federation. Based on the issues of ensuring technosphere and fire safety at such facilities the article has analyzed statistical indicators of сoal mines accidents in the country. The results of the analysis were processed by the method of mathematical regression. The presence of autocorrelation in the researched series of dynamics of accidents is defined, that allows establishing true connections of the corresponding series, namely the correlation of series "accident - casualties". The main cause of death in coal mines is not the accident itself, but endogenous fires and emergencies occurring after it. This allows speaking of the need to develop modern means and methods of extinguishing endogenous fires in coal mines. Extinguishing medium to suppress endogenous fires in coal mines is proposed. Methods. The authors have analyzed statistical data on the types of accidents in mines and the number of people who died and suffered as a result of these accidents. To determine the presence of autocorrelation in the studied series of dynamics of accidents in coal mines, methods of regression analysis were used. Findings. It has been established that the main cause of death in coal mines accidents is not collapses and explosions, but endogenous fires. The lack of means to combat this type of fires requires further research in this area. Conclusions on the causes of death in accidents have been drawn and dependence of the number of casualties on the accidents nature has been established. Research application field. The results obtained can be used in the development of new means and methods for extinguishing endogenous fires in coal mines. Conclusions. During a fire in a coal mine, combustion leads to a significant dynamics of oxygen reduction. Based on this fact we can conclude that the high death rate of miners in accidents is due, first of all, to insufficiently effective measures to prevent and extinguish endogenous fires.

Real Time Mine Fire Classification to Support Firefighter Decision Making

Real Time Mine Fire Classification to Support Firefighter Decision Making

Fire-Prevention Characteristics of an Active Colloid Prepared from Stimulated Fly Ash Component

In this paper, an active colloid (AC) with a three-dimensional network framework, prepared from stimulated fly ash (FA) component by an acid–base compound chemical method, was proposed for prevention of coal mine fire. During the stimulation process, the active substance in fly ash can be released and transformed into effective components for fire prevention. Research results show that Al3+, Fe3+, and Ti4+ from FA can serve as metal cross-linking agents to graft-copolymerize with sodium carboxymethyl cellulose. Mg2+ and Ca2+ can be formed into halogenated salts that are encapsulated by composite colloids and cooperate with them to participate in fire prevention. The remaining fly ash solid particles served as an inert component can be fixed in the framework to encapsulate more water, improving the colloid’s strength and water retention. The content of the active component was measured by inductively coupled plasma (ICP) emission spectroscopy to evaluate the stimulation effect of fly ash. The gel time, viscosity, water retention, and other performance parameters were determined for evaluation of physical characteristics. The fire-prevention performances of AC were also determined by the inhibition performance test, thermogravimetric analysis, and infrared spectroscopy. Moreover, the fire-prevention mechanism of AC was also explored. These results showed that the AC prepared from the stimulated fly ash component can greatly inhibit the spontaneous combustion of coal and can be chosen as a potential material for prevention of coal mine fire caused by spontaneous combustion of coal.

A Review on Mine Fire Disasters and Assessment of Fire Detection Using a Dual-Cab Suppression System

The health and productivity of mining operations are negatively impacted by coal mine fires, making them dangerous. It happened everywhere, in both working and abandoned coal mines. This study seeks to review and provide technical analytics of potential mine fires and fire detection in a Dual-Cab suppression system. Analysis was done on potential mine fires like spontaneous combustion, flammable gas explosions, and cab vehicle fires. Additionally, a review of the NIOSH experiment was conducted to assess the performance of smoke and flame detectors in a dual-cab suppression system. This study guides both open-pit and underground mining operations. Additionally, a few ideas and suggestions are presented to assist with on-the-job safety analysis, ensuing creative alterations, and technology advancement for the mining industry’s overall safety.

ДЕЯКІ ПИТАННЯ ВИЯВЛЕННЯ СТАДІЙ РОЗВИТКУ ШАХТНИХ ПОЖЕЖ

Purpose. Consideration and analysis of the methodology for detecting fires occurring in coal mines in order to establish the main issues of temperature assessment and the stages of an extinguished fire. Methodology. The research methodology consists of analysing the methodology for detecting the stages of development and attenuation of endogenous and exogenous mine fires, as well as assessing their similarities and differences. Using the data obtained as a result of research, we consider the possible temperature in the source of a mine fire, its change in the process of burning and attenuation of the fire. A new approach to assessing the state of a fire is proposed in the form of a temperature-heat-conducting method for assessing its state and other solutions. Results. The main features of underground fire detection are the large length, branching of underground workings and the complexity of the ventilation system. Also, such physical parameters of the air jet are taken into account that are associated with heat and mass transfer (flow velocity, the magnitude of the temperature field, gas concentrations and the general composition of the gaseous medium) and not associated with heat and mass transfer (spectral characteristics, air density (or transparency), electromagnetic characteristics). Physical features are of the greatest interest from the point of view of detecting an underground fire. The most effective additional emergency criteria for early detection of an underground fire are the rate of increase in air temperature and the rate of increase in the concentration of carbon monoxide. The paper substantiates a method for assessing the state of a fire in a mine based on the dynamics of temperature increase in its source. After the write-off of the fire, reconnaissance of mine workings in an insulating fire area, control observations of the gas composition of the air and the absence of signs of spontaneous combustion of coal, the jumpers are dismantled and installation and restoration work is carried out according to a specially developed project. Scientific novelty. It has been established that the main stage of development of a mine fire can be most correctly established by the dynamics of temperature changes, the method of such an assessment is substantiated. Practical significance. The research results will be necessary to develop a method for establishing the main stage of development and attenuation of a mine fire.

Supplemental Material for The Impact of a Mine Fire and Smoke Event on Academic Outcomes for Primary and Secondary School Students

Supplemental Material for The Impact of a Mine Fire and Smoke Event on Academic Outcomes for Primary and Secondary School Students

Effect of gas atmosphere change on radical reaction and indicator gas release during coal oxidation

Coal spontaneous combustion (CSC) caused by coal oxidation is the leading cause of mine fires. The essence of most CSC preventive measures is to change an oxygen-containing atmosphere into a nitrogen-rich atmosphere for suppressing continuous coal oxidation. This study investigates the effect of gas atmosphere change on the micro-group reaction and gas product release during coal oxidation. To achieve this aim, the radical parameters and CO were measured with the aid of an electron spin resonance (ESR) spectrometer and a gas chromatograph. The following conclusions show that, after converting the gas atmosphere from dry air to nitrogen, the linewidth of the ESR spectrum drops suddenly and ultimately stabilizes at around 0.46. Besides, a lower conversion temperature corresponds to a higher turning point temperature and a smaller maximum value of the g factor, especially when the temperature is below 90℃. After the gas atmosphere is converted, the radical concentration drops suddenly and rises again. The second increase of radical concentration is significant when the conversion temperature exceeds 130℃. While the atmosphere changes, CO release falls abruptly, and then it continuously increases. Finally, the mechanism of the effect of gas atmosphere conversion on the radical reaction of coal was analyzed. The results could enrich the coal oxidation research and be applied in CSC management and control.