Belt Fire Research Articles

Investigation of a conveyor belt fire in an underground coal mine: Experimental studies and CFD analysis

Coal produced in underground mines is transported to the surface by means of conveyor belts throughout long roadways. The combustion of belts puts a large number of employees at great risk. Underground collieries differ from other underground mines -due to the combustible nature of the product. The most prevalent cause of belt fires in underground coal mine is spontaneous combustion due to oxidation of the coal, which also enables the conveyor belt to burn over time. In 2014, a belt fire in an underground coal mine in Manisa-Soma, Turkey caused 301 fatalities. A study has been conducted on this accident for approximately 3 years, consisting of combustion tests in a purpose-built research gallery, comparison of the test results with mine records of the accident, and CFD modelling of the mine environment. The intensity of the fire was sufficient to redirect the air flow underground, causin large amounts of toxic gases to fill almost the entire mine in approximately 15 minutes. It is recommended that CFD analysis be used in planning emergency action strategies in underground mines.

Study on the characteristics of gas phase products in coal mine conveyor belt fire

This study aimed to use the thermogravimetric infrared coupling (TG-FTIR) and cone calorimeter coupling techniques to analyse the Pyrolysis characteristics and fire hazard of conveyor belt during heating process based on different stages of the combustion process. The results demonstrate that the conveyor belt is melted and volatilized by heat in the first stage (200∼350 °C), and a cross-linking polymerization process ensues, with the primary gas-phase products being chlorine-containing compounds, aromatic acid esters, and HCl. In the second stage (350∼600 °C), the conveyor belt started to burn fiercely, redox reactions occurred, the primary gas-phase products added to hydrocarbons, Benzoic acids, aldehydes, amides, and a significant number of CO2, CO, H2O(g). The third stage (600∼700 °C) corresponds to the recession phase of combustion, when the concentration of most gas phase products decreases and the production of amides and ketones increases. As the intensity of thermal radiation increases, the mass loss, heat release rate, fire hazard, CO/CO2 generation rate and smoke also increase.

Characteristics of the spatial and temporal evolution of the environmental parameters for belt fire in underground coal mine roadway

The high temperature and toxic gases produced by burning belt in mine are a serious threat to the miners’ safety. A full-scale fire experiment was conducted in an exercise roadway, as a basis for which a physical model was established. The spatial and temporal evolution of the environmental parameters was obtained in the U-shaped working face, and the effect of wind speed on the fire parameters was studied. It was found that the smoke concentration and temperature from large to small are the downwind side of the transport roadway, working face and return airway. The structure of smoke layer near the working face is disorganized, which is related to the local turning structure of the roadway. The smoke reverse occurs later than the spread of smoke downstream of the fire area. The thickness and maximum temperature of counterflow layer decreases linearly with the increase of ventilation speed. Increasing the critical ventilation speed can control the smoke reserve and increase the risk downstream of the fire area. The harmfulness of wind speed to smoke reserve and spread in single roadway and complex network is then discussed. In addition, the influencing factors of fire evolution in confined space are put forward.

Study on Mechanism of Influence of Microstructure on Combustion Characteristics of Mine Conveyor Belt

ABSTRACT The disaster regularity of conveyor belt fire has always been the focus of mine fire prevention and control. In order to study the pyrolysis and combustion characteristics of different types of conveyor belts, the BET model was used to calculate the specific surface area and pore size distribution of conveyor belts. Various chemical bonds or functional groups contained in different types of conveyor belts were tested by infrared spectrum, and the structural parameters of infrared spectrum were calculated by split-peak fitting, so as to quantitatively analyze the change rule of the content of each active functional group. The microscopic morphology and element information of different types of conveyor belts were systematically studied by means of scanning electron microscope and energy spectrum analysis, which laid the foundation for the pyrolysis and combustion experiments of conveyor belts. The experimental results show that the order of specific surface area and average pore size is NFR>SC>PVC>PVG; The degree of hydroxyl oxidation of NFR and lignite samples is higher, and the degree of fat branching of NFR and PVG samples is higher, indicating that the samples have less soluble organic matter and loose structure; SC and NFR powder have similar internal space structure, but NFR conveyor belt has more hole structure than SC conveyor belt; The biggest difference between conveyor belt and lignite is the existence of Cl element. The derivative of Cl element can be considered as an early warning indicator of conveyor belt combustion.

Simulation of Large-Scale Tunnel Belt Fire and Smoke Characteristics under a Water Curtain System Based on CFD.

Transport belt fires pose a serious threat to the lives of miners. The smoke spread characteristics of transport belt fires are important for the effective construction of underground safety works. In this paper, a water curtain system is added to ventilation to investigate the effectiveness of water spray in blocking fire-induced smoke and heat. Using computational fluid dynamics (CFD) simulations obtained with FDS 6.0.1, full-scale underground belt transport tunnel fire tests are conducted with mechanical ventilation and a water curtain system to obtain smoke spread characteristics, temperature distribution, visibility profiles, and CO distribution. The results show that the addition of a water curtain system can effectively limit temperature and smoke, but high mechanical ventilation velocities are not conducive to the water curtain system, limiting underground tunnel fires. This study found that the mechanical ventilation velocity should be controlled at approximately 0.8 m/s when the water curtain system is on a 100 m beltway. Smoke across the water curtain system area, smoke stratification in the lower layer of the water curtain area is lost, the water curtain system in the lower layer of the tunnel will affect the flow field and temperature field flowing to the fire source, and the blockage effect is the most obvious in the upper layer of the tunnel. The water curtain system reduces the distribution of temperature and CO concentration in the tunnel and rapidly restores visibility. With the addition of the water curtain system, the environment in the restricted area is suitable for occupant evacuation and firefighting, and the system can be considered a viable strategy for tunnel smoke control.

Mine conveyor belt fire classification

This article presents a conveyor belt fire classification model that allows for the determination of the most effective firefighting strategy. In addition, the effect of belt design parameters on the fire classification was determined. A methodology that involves the use of numerical simulations and artificial neural networks was implemented. An approach previously proposed for modeling fires over conveyor belts was used. With the objective of obtaining some required modeling input parameter and verifying the capacity of this approach to get realistic results, computational fluid dynamics model calibration and validation were carried out using experimental test results available in the literature. Results indicated that scenarios with belt positions closer to the mine roof and greater tunnel heights require a higher longitudinal air velocity to be attacked directly. Furthermore, the belt fire classification model provided by the artificial neural network had an accuracy around 95% when test scenarios were classified.

Methodology in early detection of conveyor belt fire in coal transportation

ABSTRACT Thermal power units are a major source of power generation in India. Belt conveyor is the leading transportation system in a thermal power plant. Belt conveyor fire in a thermal power plant breaks the chain of the transportation system, stops the feeding to the boiler, and often leads to closure of the plant, and thereby impacts the production for several months incurring huge losses. The main aim of this study is to design a model for early detection of belt conveyor fire and its automatic fire suppression system. The proposed model incorporates safety devices and sensors which shall be activated whenever it is necessary. Based on coal characteristics, threshold limit values (TLV) of sensors are defined. Proximate analysis, critical oxidation temperature, fire ladder, and differential scanning calorimetry (DSC) studies were conducted to characterize the five coal samples used in this study collected from Talwandi Sabo Power Ltd. (TSPL), Mansa, Punjab, India. For the coal samples used in this study (with an average moisture content of 7.59 wt %), the average critical oxidation temperature was observed to be 81.3 ⁰C. Further, the fire ladder study indicates that gas sensors like CO and H2 should be installed in the belt conveyor route. Based on laboratory and field investigations an automated model for early detection of fire was proposed which incorporates safety devices, temperature, and gas sensors, and fire suppression mechanisms.

The Field Model Construction and Analysis of Complex Mine Belt Fire Based on Personnel Evacuation Theory

In order to realize the visualization of the catastrophic law of mine belt fire on personnel evacuation theory, the complex roadway model is constructed by using the fire dynamic simulation software. The change of monitoring data such as temperature, smoke concentration and visibility is simulated in near-fire source of tape fire roadway. It is found that the main factors affecting the escape of personnel are smoke temperature, CO concentration and visibility in the mine tape fire. The first 100 s is a critical period for the smooth escape of the people on the wind side of the fire source after the tape fire. The high smoke temperature, high CO concentration and low visibility of the roadway seriously affect the escape of personnel after 150 s. At this time, the fire has developed into the flash-over stage. The parameters reach the critical value at 40 s with the 20% smoke concentration as the critical value in the roadway. It provides a reference for mine emergency rescue and fire escape.

Controlling Fire of Belt Conveyor and Ventilation Network Calculation in Underground Coal mines

Belt conveyor has played an essential role in underground coal transportation. However, due to long-distance transport, it facilely confused ventilation system. Furthermore, once belt fires occurred, the accident would be spread to other areas rapidly. Numerous toxic and harmful flue gases would flow along the roadway, which posed a significant threat to the safety of underground miners. In this research, the ventilation system in Wangjialing coal mine, Hejin City, Shanxi Province, China which was taken as the object to investigate how to control the spread of flue gases by the disaster-relief dampers, when the fire happened in belt conveying roadway. The air-quantity could be achieved before and after the adjustment of local ventilation system by the ventilation network calculation. Furthermore, airflow velocities markedly impacted on the belt fire in the roadway in the 20102 face, conducted by the FDS software. The results indicated that an effective method to control the spread of flue gases was install11 disaster-relief dampers in the underground connecting roadways which located among belt-conveying roadway, main return airway, and auxiliary-transport roadway. When the wind speed was about 2.5 m/s, the effect of exhaust smoke was better in the roadway of 20102 working face. The direction of flue gases changed observably after adjusting local ventilation as the disaster relief dampers. Most flue gases went into the main return airway, the quantity of flue gases significantly decreased flowing to the working areas. Therefore, the short circuit and the open circuit for air flow achieved by governing ventilation system as disaster relief dampers was significant for the control of areas flue gases spreading.

Numerical and experimental investigation of carbon monoxide spread in underground mine fires.

The primary danger with underground mine fires is carbon monoxide poisoning. A good knowledge of smoke and carbon monoxide movement in an underground mine during a fire is of importance for the design of ventilation systems, emergency response, and miners' escape and rescue. Mine fire simulation software packages have been widely used to predict carbon monoxide concentration and its spread in a mine for effective mine fire emergency planning. However, they are not highly recommended to be used to forecast the actual carbon monoxide concentration due to lack of validation studies. In this article, MFIRE, a mine fire simulation software based on ventilation networks, was evaluated for its carbon monoxide spread prediction capabilities using experimental results from large-scale diesel fuel and conveyor belt fire tests conducted in the Safety Research Coal Mine at The National Institute for Occupational Safety and Health. The comparison between the simulation and test results of carbon monoxide concentration shows good agreement and indicates that MFIRE is able to predict the carbon monoxide spread in underground mine fires with confidence.

Numerical simulation and application study on a remote emergency rescue system during a belt fire in coal mines

Once initiated, coal mine belt fires can develop rapidly, and if improperly controlled, these fires could easily lead to the airflow disorders that undermine the function of the ventilation system, and the smoke plume could lead to heavy casualties. However, belt fires can be effectively prevented by establishing a fire smoke plume control system. According to the characteristics of fire smoke plume control in the ventilation network, models of ventilation systems are analyzed, and different methods of fire emergency rescue systems are designed. A mathematical model for fire smoke flow was developed based on the west-wing mining area in Long-Dong coal mine. The distributions of the smoke parameters and airflow temperature on the roadway before and after performing the smoke flow control measures were simulated by Fluent software. The results indicate that 37 min after the fire began, the smoke plume had invaded all of the roadways in the west-wing mining area. The average temperature of the roadway in the west mining area is 332 K, the O2 concentration is 14.8 %, the CO2 concentration is 5.1 % and the highest concentration of CO is 0.98 %. In this environment, miners in distress are unable to survive. A function to adjust the opening degree of the air-doors was designed, and the air volume control of the key branches was realized during a fire emergency rescue. A permanent refuge chamber was situated in the mining area to provide a safe shelter for miners when a disaster occurs. Many field exercises have verified the combined function of the emergency rescue system and refuge chamber to ensure the security of the miners in the underground coal mine.

Information fusion of plume control and personnel escape during the emergency rescue of external-caused fire in a coal mine

After a fire occurred in a coal mine, compared with putting out the fire, organizing the miners’ safe escape was especially important. We established a local ventilation system model using TEPS (Thunderhead Engineering PyroSim) and set up control measures for fire smoke. The change rule of fire parameters, such as temperature, concentration of smoke, and visibility, was analyzed based on the results of FDS (Fire Dynamics Simulator). Without the control measures for fire smoke, the coal face and the intake airflow roadway were all polluted by smoke at 541 s after the fire broke out; at this time, personnel escape would be almost impossible in the coal face. Thus, the personnel escape conditions and routes are determined by the parameters of fire smoke flow. Evac was used to simulate the escape behavior of a miner who encounters an accident in a coal mine. After taking the fire smoke control measures into account, we performed simulation calculation to determine the best and fastest way for miners’ escape. We exploited the hardware and software, and the belt fire emergency rescue system of the No. 1 plate in the Da Liu-ta coal mine was established. The emergency rescue system successfully fused fire plume control and personnel escape information into one platform. Through simulating a fire drill three times, the air quantity of the key branches changed to within reasonable limits while the air-door's opening area was 2m2, field tests proved the reliability and feasibility of the system.

New improvements to MFIRE to enhance fire-modeling capabilities

NIOSH's mine fire simulation program, MFIRE, is widely accepted as a standard for assessing and predicting the impact of a fire on the mine ventilation system and the spread of fire contaminants in coal and metal/nonmetal mines, which has been used by U.S. and international companies to simulate fires for planning and response purposes. MFIRE is a dynamic, transient-state, mine ventilation network simulation program that performs normal planning calculations. It can also be used to analyze ventilation networks under thermal and mechanical influence such as changes in ventilation parameters, external influences such as changes in temperature, and internal influences such as a fire. The program output can be used to analyze the effects of these influences on the ventilation system. Since its original development by Michigan Technological University for the Bureau of Mines in the 1970s, several updates have been released over the years. In 2012, NIOSH completed a major redesign and restructuring of the program with the release of MFIRE 3.0. MFIRE's outdated FORTRAN programming language was replaced with an object-oriented C++ language and packaged into a dynamic link library (DLL). However, the MFIRE 3.0 release made no attempt to change or improve the fire modeling algorithms inherited from its previous version, MFIRE 2.20. This paper reports on improvements that have been made to the fire modeling capabilities of MFIRE 3.0 since its release. These improvements include the addition of fire source models of the t-squared fire and heat release rate curve data file, the addition of a moving fire source for conveyor belt fire simulations, improvement of the fire location algorithm, and the identification and prediction of smoke rollback phenomena. All the improvements discussed in this paper will be termed as MFIRE 3.1 and released by NIOSH in the near future.

Human evacuation affected by smoke movement in mine fires

The objective of this work is to investigate the influence of smoke movement during mine fires on miner evacuation behaviors. A three-dimensional computational fluid dynamics method was conducted to reconstruct the laneway conveyor belt fire scenes under two ventilating conditions. The parameters, including temperature–time histories, soot density, carbon monoxide and heat release rate, were simulated to characterize the mine fires at various ventilating speeds. A miner evacuation model affected by fire smoke movement was advanced to describe the miner evacuation behaviors, which can be divided into three stages. Based on the evacuation model coupled with the mine fire smoke movement, the available safety evacuation time for miners involved in coal mine fire located in different sites was estimated. Two evacuation patterns were advanced according to the ventilating speeds combined with the model of miner evacuation behaviors. The results show that the miners located between the inlet-air end and the air door in lane 1 should be evacuated to the inlet-air end and other miners involved in coal mine fire could choose the air door as the escaping destination, when the ventilation speed is greater than 3 m/s. Accordingly, the research can be used as references for the mine safety administration authorities to design the safety evacuation.

Numerical Simulating Long-Distance Emergency Rescue System for Belt Fire in Coal Mine

Numerical Simulating Long-Distance Emergency Rescue System for Belt Fire in Coal Mine

Numerical simulation and disaster prevention for catastrophic fire airflow of main air-intake belt roadway in coal mine—A case study

Coal mine belt fire develops very rapidly and is difficult to control. If not suppressed quickly, a belt fire could easily lead to airflow disorder and undermine the ventilation system. However, belt fire can be prevented effectively by establishing fire airflow control system. In this work, the 5th belt roadway of Kongzhuang coal mine was taken as the object of investigation, where geometrical models of this roadway were established firstly. Then, based on mathematical model of fire smoke flow, the CO volume fraction, smoke density distribution, air temperature and pollutant velocity vector in the roadway before and after taking airflow control measures were simulated by using Fluent software. It can be known from the simulation that with the normal ventilation status in 5th belt roadway, the countercurrent of smoke does not happen when a fire occurs; the roadway’s section is almost filled with CO at 10 m downstream from the fire source, and with air velocity getting stable gradually, the CO concentration reaches about 15 %. After taking airflow control measures, the effect range of temperature field which are harmful to the miners decreases from 69 m to 30 m; and the distance of the roadway fully filled with CO is 5 m farther than that before taking measures. Finally, according to the numerical simulation results and the actual condition of the belt roadway, the warning and automatic remote airflow control system with short-circuit method for the 5th belt roadway was designed to guarantee the safety production.

Numerical modeling of water spray suppression of conveyor belt fires in a large-scale tunnel

Conveyor belt fires in an underground mine pose a serious life threat to miners. Water sprinkler systems are usually used to extinguish underground conveyor belt fires, but because of the complex interaction between conveyor belt fires and mine ventilation airflow, more effective engineering designs are needed for the installation of water sprinkler systems. A computational fluid dynamics (CFD) model was developed to simulate the interaction between the ventilation airflow, the belt flame spread, and the water spray system in a mine entry. The CFD model was calibrated using test results from a large-scale conveyor belt fire suppression experiment. Simulations were conducted using the calibrated CFD model to investigate the effects of sprinkler location, water flow rate, and sprinkler activation temperature on the suppression of conveyor belt fires. The sprinkler location and the activation temperature were found to have a major effect on the suppression of the belt fire, while the water flow rate had a minor effect.

Numerical and experimental study on flame spread over conveyor belts in a large-scale tunnel

Conveyor belt fires in an underground mine pose a serious life threat to the miners. This paper presents numerical and experimental results characterizing a conveyor belt fire in a large-scale tunnel. A computational fluid dynamics (CFD) model was developed to simulate the flame spread over the conveyor belt in a mine entry. Thermogravimetric analysis (TGA) tests were conducted for the conveyor belt and results were used to estimate the kinetic properties for modeling the pyrolysis process of the conveyor belt burning. The CFD model was calibrated using results from the large-scale conveyor belt fire experiments. The comparison between simulation and test results shows that the CFD model is able to capture the major features of the flame spread over the conveyor belt. The predicted maximum heat release rate, and maximum smoke temperature are in good agreement with the large-scale tunnel fire test results. The calibrated CFD model can be used to predict the flame spread over a conveyor belt in a mine entry under different physical conditions and ventilation parameters to aid in the design of improved fire detection and suppression systems, mine rescue, and mine emergency planning.

A new feature of MFIRE: the moving fire simulation

MFIRE, a mine fire simulation program, is a very useful tool for fire prevention planning, fire control, and training in underground mines. However, all of its fire source models are stationary, which are incapable of simulating a moving fire such as a conveyor belt fire. In this paper, a moving fire source model which can be used to represent a conveyor belt fire is defined and incorporated into the MFIRE program for the first time. An illustrative case study has demonstrated that the upgraded MFIRE is capable of simulating a moving fire.

Heat release rate in evaluation of conveyor belts in full-scale fire tests

The theoretical bases for calculation of heat release rate during burning of conveyor belts in the fire-testing gallery has been presented. Taking as an example the results of measurements of oxygen, carbon dioxide and monoxide content in the products of combustion of conveyor belts during the testing of their flammability in the full-scale fire gallery, the possibility has been demonstrated for using the calculations of heat release rate in an assessment of conveyor belt flammability. The total quantity of heat released during the belt fire in the experimental gallery can provide the basis to develop a new method of testing as well as the criteria for assessment of fire resistance of the conveyor belts using oxygen consumption calorimetry. © 1997 John Wiley & Sons, Ltd.