Coal-fired Research Articles

Investigation into Dynamic Behaviors of High-Temperature Sandstone under Cyclic Impact Loading Using DIC Technology

Coal resources are rich in Ningxia. Long-term mining creates mine goaf, which causes coal to burn spontaneously for a very long time. Unavoidably, the rocks around the coal fire area are affected by high temperatures, which can alter the characteristics of rocks and lead to safety accidents. To explore the temperature influence of sandstone in coal fire areas under cyclic impact loading, the sandstone treated under different temperatures is tested by a split Hopkinson pressure bar (SHPB). The mechanical properties of rocks treated at different temperatures are obtained. The composition of rock is determined, and the energy dissipation is calculated. Meantime, the digital image correlation (DIC) method is applied to study the mechanical behaviors of sandstone. The results show that at the first impact, the peak stress of sandstone decreases as the temperature increases. However, there is no obvious trend in the peak strain. Under the SHPB cyclic impact, the sandstone specimen is completely destroyed after two to three times of impact at different temperatures. At 25~1000 °C, the dynamic peak stress of sandstone decreases with the increase in impact times, and brittle failure occurs. When the impact pressure is 0.6 MPa, the incident energy increases with the impact velocity; the dynamic peak stress increases with the transmitted energy. Using the DIC method, it is found that when the temperature is below 800 °C, the dynamic characteristics of rock specimen have a close correlation with the crack initiation point and extreme point. When the temperature exceeds 800 °C, the rock specimen is seriously damaged, the overall strain is small, and the stress transfer efficiency is low. These findings show that temperature significantly affects the mechanical properties and initial damage of the sandstone, and the performance and damage are abrupt at 800 °C. Meanwhile, the DIC technology can effectively characterize the strain evolution of rock materials and explain the formation and propagation process of cracks, which provides a valid means for studying the damage and crack evolution of materials.

Investigating the environmental impacts of coal mining using remote sensing and in situ measurements in Ruqigou Coalfield, China.

China is the largest producer and consumer of coal in the world. The extraction of coal is increasing intensively to meet the needs of the ever-increasing population and industries. However, coal mining has resulted in environmental changes, including deforestation, air, water, soil, and landform deterioration. This study investigates the impact of mining on the environment in Ruqigou coalfield by utilising in situ and remote sensing data. Field data collected include temperature, gas compositions, and water samples. Multi-temporal Landsat data of 1991, 2003, and 2019 were used in monitoring the impact of mining on different land covers, especially vegetation. A supervised classification was performed to assess the changes in land cover. In order to track the changes in vegetation, normalised difference vegetation index (NDVI) was employed. To study the changes in coal fire areas, thermal anomalies were extracted from the thermal infrared data using a dynamic thresholding technique. The results of in situ analyses show that water quality is unfit for domestic, industrial, and agricultural use. All the gas sampling sites emit noxious gases such as CO2, CO, NO2 and degrade the local air quality. The classified maps and vegetation indices show a significant decrease in vegetation. The thermal anomalies show an increase in fire areas over the years. Thus, it could be concluded that the conjunctive use of field-based measurements and remote sensing data can be a powerful tool for gaining a comprehensive understanding of the environmental impacts associated with large-scale mining.

Assessment of Mechanical Properties for High-Temperature Sandstone in Coal Fire Area Based on Different Cooling Methods

The rocks in coal fire areas are often in high-temperature environments. The mechanical properties of rocks play an important role in mining and engineering disturbance, so we aim to study the static and dynamic properties of high-temperature sandstone in the coal fire zone under different cooling methods, and to evaluate the degree of thermal damage at different high temperatures. The mechanical properties and failure modes of two cooling methods (natural cooling and watering cooling) were analyzed. In addition, the influence of the longitudinal wave velocity (Vp) on the mechanical properties of the high-temperature sandstone was analyzed, and the composition of the high-temperature sandstone was tested by XRD method. Under two cooling conditions, the static and dynamic peak strength of sandstone increases continuously with the increase of longitudinal wave velocity (Vp), and reduces with the increase of heat-treated temperature, but the damage degree increases with the increase of the heat treatment temperature. In the Split Hopkinson Pressure Bar (SHPB) test, the dynamic compressive strength of naturally cooled sandstone is higher than that of water-cooled sandstone. The failure of natural cooling high-temperature sandstone mainly occurs “X-shape”, transverse splitting failure or breaks into pieces, but the watering cooling high-temperature sandstone presents transverse or longitudinal splitting failure.

Study on Multi-Indicator Quantitative Risk Evaluation Methods for Different Periods of Coal Spontaneous Combustion in Coal Mines

ABSTRACT For the current coal spontaneous combustion fire risk evaluation method has the problems of single evaluation dimension, incomplete evaluation index and unreliable evaluation results. However, the coal spontaneous combustion fire risk evaluation can effectively guide coal mine fire prevention and control. Therefore, a multi-indicator quantitative risk evaluation method combining analytic hierarchy process (AHP) and linear interpolation for different periods of coal spontaneous combustion is proposed as a way to improve the rationality of coal spontaneous combustion fire risk evaluation. The continuous segmental evaluation model was established based on the factors that influence the three periods of coal spontaneous combustion (Latent Period, Self-heating Period and Combustion Period). The latent period evaluation model was established based on the fire-prone nature of coal, coal seam occurrence, mining technology, and fire prevention measures. The self-heating period evaluation model was established based on the degree of self-heating of coal, absolute CO generation, and Graham index. The combustion period, there was already a spontaneous combustion fire, directly set the fire risk score to 0. The score could fully reflect the level of coal spontaneous combustion fire risk. The higher the score, the relatively smaller the risk of coal spontaneous combustion, and vice versa, the relatively larger. According to this risk evaluation model, the risk of coal spontaneous combustion in the 2−2 coal seam of a coal mine in Shaanxi Province was evaluated. The result shows that the level of coal spontaneous combustion risk of 2−2 coal seam in this coal mine is in a safer state, and this result is consistent with the actual situation. The multi-indicator quantitative evaluation of different periods of coal spontaneous combustion effectively improves the accuracy of fire risk evaluation. Therefore, the evaluation model has certain theoretical guidance for the control of coal spontaneous combustion risk in coal mines.

An experimental study on smouldering coal particles: Effects of air leakage and burning position in underground coal fires

The dominant combustion mode in underground coal fires (UCFs) is smouldering. A packed coal bed reactor with natural convection as the driving force was designed to represent the spatial features of three typical UCFs. Effects of air leakage through the left-hand wall and the burning position were investigated with three experimental cases. The ignition test showed that coarser particles (0.5–1 mm) failed to be ignited, while self-sustained smouldering was successfully initiated for finer particles (<0.5 mm). The repeatability test yielded reproducible results at a macroscopic level (maximum difference of 6.4%), with main uncertainties coming from the ignition stage when the formation of cracks introduces randomness. It was observed that air leakage through the left-hand wall enhanced the smouldering temperature near the wall boundary, and the enhancement became more prominent with the increasing depth. When ignition was initiated at the middle part of the reactor, the top region of the coal bed burned nearly twice faster. The quantitative results are dependent on specific conditions in the present study, while the relative differences among three cases could shed some light on smouldering propagation in actual UCFs from the perspective of fire safety.

Laboratory investigation of pollutant emissions and PM2.5 toxicity of underground coal fires.

Widespread underground coal fires (UCFs) release large amounts of pollutants, thus leading to air pollution and health impacts. However, this topic has not been widely investigated, especially regarding the potential health hazards. We quantified the pollutant emissions and analyzed the physicochemical properties of UCF PM2.5 in a laboratory study of coal smoldering under a simulated UCF background. The emission factors of CO2, CO, and PM2.5 were 2489 ± 35, 122 ± 9, 12.90 ± 1.79 g/kg, respectively. UCF PM2.5 are carbonaceous particles with varied morphology and complex composition, including heavy metals, silica and polycyclic aromatic hydrocarbons (PAHs). The main PAHs components were those with 2-4 rings. Benzoapyrene (BaP) and indeno[1,2, 3-cd]pyrene (IcdP) were important contributors to the carcinogenesis of these PAHs. We quantitatively evaluate the toxicity of inhaled UCF PM2.5 using a nasal inhalation exposure system. The target organs of UCF PM2.5 are lungs, liver, and kidneys. UCF PM2.5 presented an enriched chemical composition and induced inflammation and oxidative stress, which together mediated multiple organ injury. Long-term PM2.5 metabolism is the main cause of persistent toxicity, which might lead to long-term chronic diseases. Therefore, local authorities should recognize the importance and effects of UCF emissions, especially PM2.5, to establish control and mitigation measures.

Study on Thermodynamic Characteristics and Heat Transfer Method of Uncontrolled Fire in Coal Mine Gangue Mountain Spontaneous Combustion Based on System Dynamics.

Coal fire disaster caused by the spontaneous combustion of coal has always been one of the serious problems that threaten the safety of coal mining. In our study, we first solved the dynamic parameters and mechanical functions of coal gangue using the Achar differential method and Coats-Redfern integral method. Then, based on the flow and heat transfer mechanism of hot rod vapor-liquid two-phase flow, combined with coal spontaneous ignition conditions, influencing factors, coal pile spontaneous combustion temperature field structure distribution, etc., the heat transfer process of the hot rod in the coal pile (coal gangue mountain) was analyzed. Results show the average activation energies of the second stage of different types of coal mine gangue. Upon comparing the characteristic parameters of coal gangue in different regions and ages, it is found that 8# coal gangue has better combustion and burn-out characteristics, and its comprehensive combustion characteristics are second only to those of the coal gangue in Datong and higher than those in Panzhihua, Pingdingshan, and Hancheng. The higher the content of volatile matter and fixed carbon in coal gangue, the lower the ash content, and the better the comprehensive combustion performance of the coal gangue. Under the condition of sufficient oxygen supply combustion, the larger the fuel ratio, the better the burnout performance of the coal gangue. The test of the influence of the hot rod on the temperature field distribution inside the coal pile shows that the maximum cooling rate of a single hot rod to the coal pile during the test period is 33.4°C, and the maximum cooling rate reaches 39.6%. The calculated heat dissipation of the 80 h hot rod is 1.0865, 2.1680, and 3.3649 MJ, respectively.

Semi-enclosed experimental system for coal spontaneous combustion for determining regional distribution of high-temperature zone of coal fire

Temperature variation and gas generation at different depths and positions in the coal combustion process were studied to determine the propagation and evolution of high temperature regions in the process of coal spontaneous combustion. This study selected coal samples from Mengcun, Shaanxi Province, People’s Republic of China, and developed a semi-enclosed experimental system (furnace) for simulating coal combustion. The thermal mass loss of coal samples under various heating rates (5, 10, and 15 °C/min) was analyzed through thermogravimetric analysis, and the dynamic characteristics of the coal samples were analyzed; the reliability of the semi-enclosed experimental system was verified through the equal proportional method of fuzzy response. The results reveal that the high-temperature zone is distributed nonlinearly from the middle to the front end of the furnace, and the temperatures of points in this zone decreased gradually as the layer depth increased. The apparent activation energy of the coal samples during combustion first increased and then decreased as the conversion degree increased. Furthermore, the proportion of mass loss and the mass loss rate in the coal samples observed in the thermogravimetric experiment is consistent with that observed in the first and second stages of the experiment conducted using the semi-enclosed system. The research findings can provide a theoretical basis for the prevention and control of high-temperature zones in coal combustion.

Insight into the low-temperature oxidation behavior of coal undergone heating treatment in N2

Heat treatment of coal under nitrogen is an effective technology to reduce water content and upgrade lignite, but the subsequent oxidation behavior and spontaneous combustion characteristic of dried coal are unclear, possibly posing a threat to lignite transportation and storage. In this study, raw coal and dried coal at different temperatures were selected and oxidation parameters were first analyzed by temperature-programmed experiment. The carbon oxides emissions and oxygen consumption of dried coals are obviously higher than that of raw coal, and increase with rising dehydration temperature, indicating coal after drying is more prone to oxidation and spontaneous combustion. Then, the physical structure, chemical groups and free radicals of coal were determined by nitrogen adsorption, FTIR and ESR technology. During drying process, gas release and water evaporation increase pore diameter and pore volume of coal, thus improving O2 transport capacity and oxidation rate. The hydroxyl content in coal decreases, but the CO content increases due to the polycondensation and dehydration reaction of hydroxyl groups after high-temperature drying. Meanwhile, carbonyl compounds and carboxyl groups undergo thermal decomposition and generate free radical active sites on the coal surface. The subsequent oxidation of accumulated free radicals not just release large amounts of carbon oxides, but also contribute to the formation of oxygen-containing groups inside coal with the rise of temperature, accelerating coal-oxygen reaction. Therefore, it is proposed that heat treatment expands physical channels, increases the content of CO groups, and enhances the content of active sites, which leads to vigorous oxidation of dried coal and even uncontrolled coal fires.

Evaluation of oxygen concentration on low-temperature oxidation kinetics of long-flame coal

Oxygen concentration is the vital environmental factor affecting the evolution of coal spontaneous combustion. Long-flame coal was heated from 30 to 800 °C at different oxygen concentrations (3, 5, 9, 13, 17, and 21 mass%) and heating rates (2.0, 5.0, 10.0, and 15.0 °C/min). The thermal reaction process was explored and analyzed. The effects of oxygen concentration on characteristic temperature and related parameters were assessed. The effects of heating rate and oxygen concentration on characteristic temperature and related parameters were evaluated. Under the condition of oxygen deficiency, the oxidation rate of coal was low, it took more time to consume the active groups in a given quality coal, and the increase of oxygen concentration had a strong positive effect on early and late combustion. The apparent activation energy (Ea) increased and decreased the conversion degree of oxygen absorption (mass gain) and high-temperature combustion stage, respectively. With the decrease of oxygen concentration, Ea in each stage decreased. These results contribute to the understanding of the evolution of coal fires in oxygen-lean environments.

Assessment of coal spontaneous combustion index gas under different oxygen concentration environment: an experimental study.

Oxygen plays a crucial role in coal spontaneous combustion (CSC), and the magnitude of oxygen concentration determines the oxidation reaction intensity of CSC. This work is aiming to investigate the contribution of oxygen concentration to CSC and to predict the spontaneous combustion stage of coal at different oxygen concentrations. Firstly, experiments on the spontaneous combustion of coal samples at six oxygen concentrations (6%, 9%, 12%, 15%, 18%, and 21%) were carried out combined with a temperature-programmed system. Then, the gas products at different temperature stages were extracted to provide detailed classification and assessment of the indicator gasses for coal spontaneous combustion at different oxygen concentrations. The results show that the oxygen concentration and the crossing point temperature (CPT) are inversely proportional. The higher the oxygen concentration, the more intense the coal-oxygen complex reaction and the greater the gas product concentration. The critical temperature of some stages in high oxygen concentration environment is lower than that in low oxygen concentration environment. The oxidation process can be slowed down by reducing the oxygen concentration as much as possible. Indicator gasses are different for different oxygen concentration environments and should be selected reasonably and optimally to match the specific environment for judging natural coal fires in order to effectively prevent coal spontaneous combustion fire disasters.

Assessment of Water Quality Parameters of The Kohelia River at Cox’s Bazar of Bangladesh

The study was conducted to explore the physicochemical parameters of surface water from the construction work involving the bridge over the river Kohelia and road along the bank of Kohelia for the construction of access road for Matarbari Coal Fired Power Plant is under construction area of Bangladesh starting from September 2020 to September 2021. The surface water samples were collected from three sampling stations in the Kohelia for the construction of access road for Matarbari. The result of the study showed that pH, Temperature (T), Dissolved Oxygen (DO), Total Suspended Solids (TSS), Turbidity, Electric Conductivity (EC), Total Dissolved Solids (TDS), Total Coliform (TC) and Fecal Coliform (FC) were ranged from 6.6 to 8.2, 24.8 to 31.6ºC, 4.3 to 6.1 mg/L, 4.0 to 15.0 mg/L, 7.4 to 117.0 NTU, 24.3 to 725.0 μS/cm, 200.0 to 2721.0 mg/L, 23.6 to 644.0 N/100 ML and 11.0 to 312.0 N/100 ML respectively. Some parameters showed no significant change with the time period. This might happen due to periodic changes per day or month due to tidal effects as the study area of Kohelia River is very close estuary of the Bay of Bengal. Except pH and Temperature (T), all others physicochemical parameters were across the acceptable range of standard limits. The Comparative study showed Total and Fecal coliform is higher than the Standard might be happen due to piling slurry, concrete debris, wastewater, unhygienic sanitary waste, soil &amp; silt dumping, surface runoff, oil and grease littering, solid waste created by workers, encroachment etc.&#x0D; Environ. Sci. &amp; Natural Resources, 13(1&amp;2): 76-81, 2020

Study on the pore structure and radon release characteristics of coal in northern China

Identifying the release characteristics of radon (Rn-222) in coal mines is critical preventing cancer risks for coal miners and coal fires. The present investigates the pore structure characteristics of coal samples from eleven coal mines in northern China, using low-temperature nitrogen adsorption (LTNA) test, combined with the radon exhalation rate in coal. The findings of the study reveal that the N2 adsorption isotherms of all the coal samples fall under the inverse S type, with micropores dominating in low-rank coals and mesopores dominating in the medium and high-rank coals, due to the separation of organic matter and quartz by shrinkage of micro-components and the orderly arrangement of aromatic rings as a result of ring condensation and thermal cleavage. The pore diameters of coal samples show similar distribution characteristics for sizes >2 nm, represented by a single peak near the pore diameter of 3 nm. Ash yield controls the mesopore and micropore volumes of medium and high-rank coal samples. The radon emission rate displays positive linear correlation (r2 = 0.87) with micropore volumes of analyzed coal samples due to the infillings of free radon in micropores. The radon element is derived by uranium decay, which causes a greater radon exhalation rate of coal mines in areas near the uranium mines. The results of the present study could be helpful to understand the influence mechanism of radon emission processes in coal, which provides an important basis for reducing cancer risks for coal miners and predicting coal fires.

Detection of coal fire by deep learning using ground penetrating radar

Coal fire seriously endangers coal resources. Accurate detection of its combustion range is the basis of disaster control. In this paper, a deep learning-based method of recognizing coal fire using ground-penetrating radar (GPR) is proposed, which improves the accuracy and speed of delineating coal fire areas. The self-built coal fire physical model is scanned by the GPR, and the radar images are obtained. The test results are compared with GPR images to summarize the spatial evolution law of coal fire areas and interpret the signal characteristics of the coal fire in radar images. The signal characteristics include combustion cavity, combustion surface, and underground combustion collapse surface. Comparing different algorithms, the results show that the YOLOv5l has the highest detection accuracy, which meets the need for detection of the coal fire. The proposed method lays the foundation for the detection of the combustion range in the coal fire areas.

Preparation and characterization of PVA-H18 gel foam for preventing spontaneous combustion of coal based on interfacial self-assembly

In order to improve the stability time and foaming ratio of gel foam, and change the traditional preparation method of gel foam. In this paper, using super-hydrophobic nanoparticles, PVA, sodium tetraborate and sodium bicarbonate as the main raw materials, based on the self-assembly effect of super-hydrophobic nanoparticles and hydrophilic macromolecules, a high-foaming gel foam (PGF) without foaming agent was prepared. Through the test, the foaming volume of the 100 ml PGF can reach 329 ml without adding foaming agent, which is 1.4 times of the traditional gel foam (TGF) and 1.2 times of the viscous foam (VF). Even without foaming agent, the PGF has a half-life of more than 13 days and can retain water for more than 15 h at 100 °C. Response surface analysis showed that the foaming performance of the PGF was affected by nanoparticles, sodium tetraborate and sodium bicarbonate, among which the content of nanoparticles was the main factor. At the same time, sodium tetraborate and sodium bicarbonate also significantly affect the water retention performance of PGF. Fire prevention experiments show that the gel foam prepared by this method also has excellent fire prevention ability, which can effectively inhibit the consumption of hydroxyl group and the generation of methyl and methylene group in the process of coal oxidation. Moreover, it can still play an inhibiting ability at a high temperature of 400 °C, and can effectively prevent the recurrence of coal fire after extinguishing. The development of PGF provides a new method for the preparation of gel foam in the future. At the same time, the application of foaming agent is avoided, which reduces the pollution of surfactant to the environment.

Inhibitory effect of green antioxidants acting on surface groups and structure on lignite

To contain coal fires, three green antioxidants of plant extract which cover resveratrol (Res), tea polyphenols (TP), and β-carotene (β-car) are investigated in this paper, and their inhibitory effects on surface groups and structure are revealed. X-ray diffraction test tells that antioxidants exert a slight augment of d100 and Lc and are able to destroy the unstable side chains to some extent. Though coal samples are affected by antioxidants, minimal differences of aromatic structure have been proved. Fourier-transform infrared spectroscopy technique is employed and a new concept of influence sensitivity value is introduced. The results indicate that antioxidants and addition amounts have an impact on various groups, and the majority of groups tend to be inhibited within 3 wt% addition. Further, the optimal inhibitory concentration of Res, TP, and β-car is 1 wt%, 3 wt%, and 1 wt%, respectively. Combined with gaseous indexes, CO2 emissions of Res and TP exhibit a wave variation under 100 °C, and exponential growths of others occurred twice is acquired. Antioxidants can bring out the decline of apparent activation energy (Ea), and TP worked most brilliantly and it increases Ea by 7.503 kJ/mol. In summary, the order of inhibitory effect is TP > Res >β-car.

Coal fire identification and state assessment by integrating multitemporal thermal infrared and InSAR remote sensing data: A case study of Midong District, Urumqi, China

Coal fire disasters generally occur in major coal-producing countries. They destroyed many coal resources and triggered various environmental problems. The identification and state assessment of coal fire areas are paramount to coal fire management. In this paper, a method for identifying coal fires by integrating land surface temperatures (LSTs) from multitemporal thermal infrared remote sensing and subsidence information from multitemporal interferometric synthetic aperture radar (MT-InSAR) is proposed. The method primarily consists of estimating the LSTs and subsidence values, normalizing and equidistantly partitioning the LSTs, estimating the thermal anomaly frequency (TAF), extracting high-subsidence areas, determining the thermal anomaly frequency threshold (TAFT), and identifying coal fire areas according to the TAFT. The coal fire ratio index (CRI) was developed to quantitatively evaluate the severity of coal fires and its variations. Midong District, Urumqi, Xinjiang, China, was selected as the study area. Forty-five Landsat 8 images and sixty-one Sentinel-1 SAR images were used to retrieve LST and subsidence time series, respectively. The proposed method and CRI were applied to identify and evaluate coal fires in the study area. The results demonstrate the satisfactory reliability of these methods compared with field surveys. The maximum CRI was 6.145 × 10-4 (July 28, 2019), and the minimum CRI was 2.685 × 10-5 (January 13, 2020). Coal fires in summer were more severe than those in winter. The CRI profile presented seasonal and annual periodicities and was affected by the local climate. The soil cohesion and humidity are higher in winter due to possible snowmelt, which weakens the interaction between oxygen and coal seams and the subsequent combustion of coal. The LST, thermal anomaly, and deformation information were combined in a time series overlay analysis to reveal the differences in the LSTs and subsidence values among mining areas, coal fire areas, and areas with both mining and coal fires. The results verify the applicability and reliability of the proposed method.

Overview of mine rescue approaches for underground coal fires: A South African perspective

Coal is mined by both surface and underground methods and its extraction is normally characterized by numerous hazards that can lead to catastrophic accidents, which result in devastating effects such as injuries or fatalities, damage to mining assets, and destruction of mineral resources. These hazards exist due to the ability of coal to support combustion and its association with toxic, flammable, and explosive gases. Underground coal mining entails higher safety risks than opencast coal mining, chiefly because of issues relating to mine ventilation and mine collapse. Furthermore, coal mine collapses mostly occur due to crumbling of mining supports, especially in room and pillar mining systems. To avoid such adverse occurrences, safety management systems need to be in place. This study reviews the various technological safety systems and principles that are used for safe-rescue and self-escape of miners in underground coal fires, particularly in South Africa, using data obtained from Mines Rescue Services in Carltonville, South Africa. The outcome of the review shows that practising safety culture has been given priority across many South African underground coal mines through setting up safety management systems and encouraging workers to stay committed to safety principles.

A spatio-temporal temperature-based thresholding algorithm for underground coal fire detection with satellite thermal infrared and radar remote sensing

Coal fire is a global catastrophe that causes resource waste, economic loss, and environmental pollution. Accurate detection of surface abnormalities induced by coal fires (such as thermal anomalies and land deformation) is critical for coal fire monitoring and extinguishment. However, the conventional thermal anomaly detection methods do not consider the temporal variation of land surface temperature (LST). Moreover, previous studies have not applied the polarimetric persistent scatterer interferometry(PolPSI) technique for coal-fire-related ground deformation monitoring, which is supposed to have better performance than conventional persistent scatterer interferometry (PSI) approaches. To this end, in this study, a spatio-temporal temperature-based thresholding (STTBT) algorithm is proposed to detect thermal anomalies, firstly. Then, the ground deformation obtained by the PolPSI method is combined with the detected thermal anomalies for the coal fire detection. Besides, a two-stage bandpass filter is employed to assist in detecting the suspected coal fire. The results in the Fukang coal fire area, China, demonstrate that, compared with the conventional methods, the proposed STTBT mothed achieves higher accuracy of thermal anomalies detection, thereby can able to detect coal fire areas more effectively. In addition, PolPSI has better performance than PSI in ground deformation monitoring over coal fire areas. The proposed STTBT combined with PolPSI can serve as a powerful tool for detecting and monitoring underground coal fires.

Application of a novel detection approach based on non-dispersive infrared theory to the in-situ analysis on indicator gases from underground coal fire

Application of a novel detection approach based on non-dispersive infrared theory to the in-situ analysis on indicator gases from underground coal fire