No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Coal fires burning out of control around the world: Thermodynamic recipe for environmental catastrophe
Abstract
Coal fires burning around the world are an environmental catastrophe characterized by the emission of noxious gases, particulate matter, and condensation by-products. Underground mine fires and burning culm banks ignited by natural causes or human error are responsible for atmospheric pollution, acid rain, perilous land subsidence, the destruction of floral and faunal habitats, human fatalities, and increased coronary and respiratory diseases. Some of the oldest and largest coal fires in the world occur in China, the United States, and India. Techniques used to fight coal fires include slurry and ash injection, surface and tunnel sealing, aqueous foam technology, remote sensing, and computer software. Elusive, unpredictable, or cost prohibitive coal fires may burn indefinitely, choking the life out of a community and its environs while consuming a valuable natural resource.
... 51 CSH gel can bind bentonite particles together and promote the formation of bentonite gel, so CaO/Na 2 SiO 3 was first selected as the gelatinizing agent for the preparation of hybrid gel. In addition, aluminum hydroxide [Al(OH) 3 ] is widely used in medicine, which can be dispersed in water to form a suspended gel. 52 Therefore, Al(OH) 3 is also selected as a possible gelling agent in this study. ...
... Two types of bentonite-based hybrid gels were synthesized by mixing bentonite (8 g), PAAs (0.3 g), and XG (0.1 g) and lignocellulose (2 g), CaO (0.5 g)/Na 2 SiO 3 (0.35 g), and Al(OH) 3 (0.5 g) were added to the reaction system as gelatinizing agents, respectively, and the effects of CaO/ Na 2 SiO 3 and Al(OH) 3 on the stability of the hybrid gel were then investigated. To our surprise, although the two hybrid gels were obtained successfully, a lot of water seeped out of the hybrid gel that used CaO/Na 2 SiO 3 as a gelling agent after it was left in room temperature for 3 days. ...
... The diffraction peak at 2θ = 7.45°corresponding to the layered structure has shifted to 7.21°after the interaction of organic compounds, and the intensity of the diffraction peak also increased, indicating that the d-value has been expanded from 1.18 to 1.23 nm after the addition of organic polymers, further indicating successful intercalation of organic compounds to the interlayer of bentonite, which is consistent with the result of SEM. At the same time, there is a diffraction peak of 18.27°detected in the hybrid gel, which is the peak of gelatinizing agent Al(OH) 3 . These results indicated that the organic polymer can enter the interlayer of bentonite and increase the d-space; thus, the crosslinking polymer matrix has been achieved successfully. ...
This paper presents an investigation of the feasibility of intercalating lignocellulose/xanthan gum (XG) and organic polymers into bentonite to obtain an efficient fire extinguishing gel material. The bentonite-based hybrid gel was prepared by adding polyacrylates, Al(OH)3, lignocellulose, and XG into a bentonite suspension, and the resulting gel was characterized. The results showed that no cracking and powdering were found on the surface of the hybrid gel due to the formation of the cross-linked network in the bentonite, and a wide mesopore size distribution and good thermal stability were observed. The hybrid gel also exhibits a wide range of water adsorption ratios, excellent water retention, adjustable gelation times, shear thinning characteristics, and improved compressive strength (the yield stress reaches up to 13 MPa). Based on these characterizations, the mechanism of hybrid gel formation is proposed. The inhibition performance of the hybrid gel on coal spontaneous combustion indicates that the addition of the gel slows down the oxygen chemisorption and thus increases the ignition temperature. Due to the presence of the hybrid gel in the coal, the crossing point temperatures were increased and the lowest CO concentration was produced.
... Coal fires are responsible for the destruction of a valuable energy resource, cause air, and water pollution, and may expose humans and wildlife to potentially toxic gases and particulate matter (PM) (Dhar et al., 2018). In addition, coal fires often produce land subsidence due to the loss in rock volume that occurs when coal burns underground (Kumar et al., 2020;Pone et al., 2007;Stracher & Taylor, 2004;Stracher et al., 2015). Fires can occur in coal deposits, within active or abandoned coal mines, and in waste piles produced from coal mining such as the coal deposits in the city of La Coruña, Spain. ...
... Coal fires occur in many regions such as Australia, Brazil, China, Colombia, India, Indonesia, USA, South Africa, Venezuela, and Europe ( Fig. 1) (Civeira et al., 2016;Hower et al., 2013;Liang et al., 2014;Pone et al., 2007;Quintero et al., 2009;Ribeiro et al., 2010;Silva et al., 2020a;Stracher & Taylor, 2004;Syed et al., 2018). Following the industrial revolution, the number of coal fires dramatically increased (Kuenzer et al., 2012) and occurred in all countries that had coal mining or exposed coal deposits ( Fig. 1 (Silva et al., 2021a)). ...
... In addition of collecting NPs on the mouth of coal fire vents, NPs should be sampled directly in the gaseous phase as NPs in the gas phase truly represent airborne NPs. Coal fire gases contain commonly the pollutants Hg, As, Cd, F, PAHs and benzene as well as the species CO, CO 2 , SO X , H 2 S, NO X , CH 4 , C 2 H 2 , C 2 H 6 , C 3 H 6 , C 3 H 8 , C 4 H 10 , CH 2 O, CH 2 O 2 , C 2 H 2 O 2 , C 2 H 4 O 2 (Engle et al., 2012;Li, Sun, et al., 2020;Liang et al., 2014;O'Keefe et al., 2010;Stracher & Taylor, 2004). These gases are collected, and their fluxes are recorded at the mouth of coal fire vents and on the top of the overlying soils (diffuse soil gas). ...
This review summarizes our current knowledge on the health and environmental impact as well as the mineralogical and geochemical composition of nanoparticles (NPs) associated with coal fires. It will furthermore recommend new sampling and characterization protocols to gain a better understanding of the various types of NPs that are either formed through high‐Temperature (T) nucleation and alteration processes or via low‐T dissolution‐reprecipitation and weathering processes. Coal fires impact the immediate environments of coal‐producing areas and produce positive and negative feedback to climate change through the emission of carbon‐ and sulfate‐bearing gasses and aerosols, respectively. Nanoparticles form during and after coal fires. They are composed of mainly soot and tar particles as well as amorphous phases, minerals, and complex mixtures of amorphous phases and minerals. It is recommended that NPs for mineralogical studies should be collected via impactors, a new generation of collectors for particulate matter such as the TPS100 nanoparticle sampler or borosilicate filters at the opening of pipes and chambers used to measure and collect gases emitted by coal fires. Furthermore, assemblages of NPs occurring at the mount of coal fire vents should be examined using a combination of the focussed ion beam (FIB) technology and transmission electron microscopy (TEM) and those containing ion‐ or electron‐beam sensitive phases with the corresponding cryo‐techniques such as cryo‐FIB, cryo‐ion mill, and cryo‐TEM. The mineralogical and chemical composition of NP‐bearing bulk samples should be examined with spectroscopy techniques such as X‐ray photoelectron spectroscopy, 13C nuclear magnetic resonance spectroscopy or time‐of‐flight secondary ion mass spectroscopy. This article is protected by copyright. All rights reserved
... Worldwide, coal fires with a large area, a high temperature, and a long duration occur frequently in exposed or underground coal seams [1]. In many countries, such as China [2,3], South Africa [4], India [5], USA [6] and Australia [7], coal fires cause major disaster during opencast working. Domestic and international research on coal fires primarily include the following aspects: the distribution and development of coal fires, the detection and monitoring of coal fires [8][9][10], the modelling of underground coal fires [11][12][13], assessments of the impact on the environment and human health [14] and fire-fighting engineering [15,16]. ...
... The excitation setting (5) was positioned directly abutting the quenching channel (3) and the second charge (10) to receive and transmit the blasting initiation signal. The explosion-proof structure (6) functioned to transmit the shock wave signal from the quenching channel (3) to the detonating cord of End B. Similar to the function of a It is significant that an explosive logic network was applied to field blasting to improve the safety of the blasting network. First proposed by D. A. Silvia [20,21] in the 1960s, an explosive logic network is composed of an explosive logic element and an initiating device. ...
... As shown in Figure 2, the unidirectional explosive element (named explosive diode) is composed of a metal shell (2), sealing elements (1 and 8) at both ends of the element, the input end of the detonation signal (14, End A), a hollow rubber structure (13), sealing wax paper (4), an excitation setting (5), an explosion-proof structure (6), and the output end of the detonation signal (7, End B). The relevant parameters of the initiating equipment (End A and End B) used in the experiment mentioned in this paper are listed in Table 1. ...
Considering the unsafety of the present blasting network used in the blasting mining of coalfield fires, a unidirectional explosive element (named explosive diode) is proposed according to explosive logic element principles. Through theoretical and experimental analysis, the internal structure and mechanism of the unidirectional transmission of the detonation signal were studied. For an explosive diode, the length of the quenching channel was defined to be the key parameter. The explosive diode was implemented in the traditional blasting network, obtaining an explosive logic network. To evaluate the safety and reliability of the explosive diode and explosive logic network, detonation propagation and explosion-proof experiments were conducted in the lab. The optimum length of the quenching channel to obtain unidirectional detonation transmission was established. The results showed that the explosive diode could reliably control the propagation direction of the detonation signal when the length of the quenching channel was between 15 mm and 25 mm. The explosive logic network achieved a reliable detonation propagation and was explosion-proof. In comparison with traditional networks, the explosive logic network showed increased safety and reliability as the number of subnets increased. This is a significant improvement to mining safety and demonstrates great promise for engineering applications.
... Hundreds of natural, accidental, or deliberately initiated coal-seam fires are burning today around the world [138]. Due to coal mining, their number has increased over time in the world, resulting in an ecological catastrophe because of the huge quantities of gases and particles, land subsidence, products polluting water and soil, displacement of communities, human disease and death, and the destruction of natural habitats [139]. It is estimated that 75% of coal fires were spontaneous [140] and occurred in deposits during the recent geological past [125]. ...
... An Australian underground coal seam named "Burning Mountain" is estimated to have been burning for the at last 6000 years, according to some researchers [142], or even 500,000 years according to others [143]. Fires are mostly extinguishable by human interventions, but due to the costs, risks, scale of the fire and its underground position, and unpredictable nature, it is very hard and sometimes even impossible to accomplish it, and the fires can burn for an indefinite period of time [139]. ...
During the MoDeCo2000 scientific and research project on mortars used in the territory of the Roman Danube Limes in Serbia, the biggest challenge was the quest for the provenance of raw materials. The area where Viminacium, the largest city in the province of Moesia Superior developed, with millennial continuity of land use and settlement, was selected as research case study and is presented in this research. People throughout history have always used what they had at hand, and the building remains were not only reused but also recycled for new constructions. Thus, the building material of Roman Viminacium has survived in the landscape through the in situ preserved remains of Roman buildings, as well as in the structures from the later periods, up to today. To the best of our knowledge, the use of natural sediments baked during the self-combustion or combustion of underneath layers (coal in our case) for the purpose of construction was extremely rare in the Roman Empire. In this study, we follow the presence of this type of material precisely in Viminacium construction, naming it natural brick, while focusing on its potential use in lime mortars whose production was perfected in the Roman period and has never been surpassed afterward. Archaeological contexts in which this material was found have been studied, along with simultaneous work in the laboratory and in the field during the research and experimental use of the natural brick in lime mortars. We sought to determine whether this material could have been recognised by Romans in Viminacium as a potential valuable pozzolanic component of mortar, along with or instead of fired brick, being locally available and recyclable. The final confirmation of its pozzolanic features and later discussion open completely new directions for the future research of Viminacium lime mortars.
... Several authors have attempted to use remote sensing data to delineate fires in Indian Prakash & Gupta, 1999;Chatterjee, 2006;Lahiri-Dutt & Gangopadhyay, 2007;Pandey et al., 2017;Roy et al., 2015;Chatterjee et al., 2017;Saini et al. 2018a;Mishra et al., 2020;Mujawdiya et al., 2020) and Chinese (Kuenzer et al., 2004(Kuenzer et al., , 2008(Kuenzer et al., , 2012Prakash et al., 2001;Rosema et al., 1999;Stracher & Taylor, 2004;Zhang & Kuenzer, 2007;Zhang et al., 2004a, b;Zhou et al., 2013) coal mines. Discussing each study would be out of the scope of this paper, but a few have been discussed here. ...
... Later, Prakash et al. (2001) used optical, thermal, and microwave data in conjunction with field data to identify areas affected by coal fires and land subsidence in the same coalfield. Stracher and Taylor (2004) studied major coal fires in China, the USA, and India and summarised the environmental degradation caused by them. Kuenzer et al. (2007a) attempted two complementary algorithms for detecting unknown coal fires using remote sensing data of Landsat 7 ETM + . ...
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 infra-red 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.
... During the CBM extraction process, the temperature of the coal seam changes dramatically due to geological disturbances and heat exchange of drilling fluids [1]. The change in temperature field will cause changes in the seepage and stress fields of the coal seam, resulting in changes in the rock mechanics of the coal seam rock, which will cause the collapse of the coal bed methane well wall [2]. ...
... Where G n , Gm are the coefficients of lamé of clay minerals and rock masses, MPa; is the Poisson's ratio; G is the effective stress, MPa; 1 , 2 , 3 are the maximum principal stress, intermediate stress and minimum principal stress, MPa. The deformation of the coal seam rock is affected by all three of these factors, so by superimposing equations (1) and (2), we can obtain the equation for controlling the deformation of the coal rock around the well. ...
To analyze the mechanical properties of coal and rock under variable temperature, the mechanical model of coal and rock around the well under variable temperature is studied based on elastic-plastic mechanics and thermodynamic theory. The control equations of coal and rock deformation, seepage field, and temperature field around the well considering temperature and clay mineral content are derived. On this basis, the finite element numerical simulation is carried out by using the relevant parameters obtained from coal and rock mechanics experiments. The numerical simulation results show that the coal rock strength, peak stress, and peak strain show a decreasing trend when the temperature increases and the simulation results of the coal samples are consistent with the experimental results, which verifies the reasonableness of the mechanical model.
... This process will generate heat, accelerating the oxidation reaction, and finally ignite coal, leading to selfignition [2,76]. Self-ignition of coal not only causes loss of valuable resources, but also emits hazardous particles and toxic gases such as carbon dioxide (CO 2 ), methane (CH 4 ), CO, H 2 S, Hg, and PAHs [3,4], which will pollute environment and threaten people's health [5]. Therefore, understanding coal self-ignition is critical to handling, storing and processing coal resources [6]. ...
... In addition, higher ash content reduces the concentration of combustible components and decreases the rate of oxidation reactions to coal self-ignition [25]. 5 Carbon content Mukherjee and Sarkar [26] proposed an empirical relationship between elemental analysis of coal and CPT (CPT = 2(C-H-O)). And it was found that the variation of petrographic composition, moisture and ash level of coal samples had a strong influence on this relationship. ...
Self-ignition of coal emits hazardous particles and toxic gases, polluting environment and threatening people’s health. Prediction of self-ignition tendency of coal is of great significance to prevent hazards of coal self-ignition. However, it is very challenging to forecast the self-ignition tendacy of coal, because of complex physicochemical processes and highly nonlinear correlation between factors and self ignition tendency. In this work, machine learning methods (Multilayer Perceptron (MLP) and Random Forest (RF)) are used to represent the complex physicochemical processes and effects of external factors. The regression prediction models with regarding to crossing point temperature (CPT) and 13 input features are established. The dependence of input features is examined using the feature engineering. Two hundreds and four CPT samples are collected, in which 142 (70%) samples and 62 (30%) samples are divided as training data and testing data, respectively. Results show that the accuracy of both MLP and RF predicted CPTs in the testing data reaches 90%, which proves good predictability of machine-learning based models with several hundreds of samples. This work improves prediction of the self-ignition tendency of coal impacted by complex physicochemical properties and a variety of external factors. It may help to predict other fuels susceptible to self-ignition e.g., oil shale and biomass fuels.
... Increased temperatures of sulfur-containing minerals through oxidation lead to spontaneous and even violent combustion of coal, causing underground coal fissures, coal seam outcrops, and coal gangue pile fires, resulting in coal fire disasters (Heffern & Coates, 2004;Stracher, 2004). Coal fires have been reported in China (Kuenzer & Stracher, 2012;Li et al., 2018), the USA (Stracher, 2004;Strachera & Taylor, 2004), India (Agarwal et al., 2006;Gangopadhyay et al., 2006), South Africa (Bell et al., 2001;Pone et al., 2007), Australia (Glasspool, 2000), and Russia (Sharygin et al., 2009;Stracher, 2004). Coal fires are widely distributed in northern China, resulting in a total loss of more than 200 million tons of coal annually (Kuenzer & Stracher, 2012). ...
The Wuda coalfield in Inner Mongolia is a vital coal base in China, and it is the hardest-hit area for coal fires (spontaneous combustion of coal seams and coal gangue). Using gas chromatography–mass spectrometry, this work tested the concentration and analyzed the characteristics, distribution, sources, and health risks of polycyclic aromatic compounds (PACs) in the surface soil of the Wuda District, including the coal mine, coal fire, agricultural, and background areas. The soil of coal mine and coal fire area were heavily polluted with PACs, with mean concentrations of 9107 and 3163 µg kg−1, respectively, considerably higher than those in the agricultural (1232 µg kg−1) and background areas (710 µg kg−1). Alkyl polycyclic aromatic hydrocarbons (APAHs) were the dominant pollutants among these PACs, accounting for 60–81%. Alkyl naphthalenes and alkyl phenanthrenes are the primary pollutants in APAHs, accounting for 80–90% of the total amounts. Additionally, using the positive matrix factorization method, it can be concluded that the primary PAC sources are petrogenic sources, coal and biomass combustion, coal fires, and vehicle emissions. Finally, according to the cancer risk values of 16 PAHs, only the coal mine area showed a potential cancer risk. However, this result lacks a risk assessment of APAHs and underestimates the actual risk. The results of this study improved the understanding of PAC pollution in coal fire and surrounding areas and provided a reference for environmental and health risk investigations.
... Fire incidents are common in coal mines [69] and, all too often, mining project impact assessments adopt a narrow range of health and wellbeing domains that omit consideration of epidemiological evidence and potential social consequences [70,71]. Accordingly, the impacts that events such as the Hazelwood mine fire can have on academic outcomes among schoolaged young people warrant consideration within mine project planning and impact assessment, more generally, within disaster risk reduction planning and education department policies. ...
Background:
Environmental disasters such as wildfires, floods and droughts can introduce significant interruptions and trauma to impacted communities. Children and young people can be disproportionately affected with additional educational disruptions. However, evaluating the impact of disasters is challenging due to difficulties in establishing studies and recruitment post-disasters.
Objectives:
We aimed to (1) develop a Bayesian model using aggregated school-level data to evaluate the impact of environmental disasters on academic achievement and (2) evaluate the impact of the 2014 Hazelwood mine fire (a six-week fire event in Australia).
Methods:
Bayesian hierarchical meta-regression was developed to evaluate the impact of the mine fire using easily accessible aggregated school-level data from the standardised National Assessment Program-Literacy and Numeracy (NAPLAN) test. NAPLAN results and school characteristics (2008-2018) from 69 primary/secondary schools with different levels of mine fire-related smoke exposure were used to estimate the impact of the event. Using an interrupted time series design, the model estimated immediate effects and post-interruption trend differences with full Bayesian statistical inference.
Results:
Major academic interruptions across NAPLAN domains were evident in high exposure schools in the year post-mine fire (greatest interruption in Writing: 11.09 [95%CI: 3.16-18.93], lowest interruption in Reading: 8.34 [95%CI: 1.07-15.51]). The interruption was comparable to a four to a five-month delay in educational attainment and had not fully recovered after several years.
Conclusion:
Considerable academic delays were found as a result of a mine fire, highlighting the need to provide educational and community-based supports in response to future events. Importantly, this work provides a statistical method using readily available aggregated data to assess the educational impacts in response to other environmental disasters.
... BC aerosol affects the rainfall pattern by influencing the cloud formation and precipitation process [28]. India is the worlds second largest producer of coal in the world and various mining activities performed in the coal mining regions are leading to the spontaneous emission of black carbon along with various other harmful gases in these regions [35]. ...
Time series analysis has been widely used by the researchers in the field of mathematical forecasting; it has been mainly used to obtain the forecast of time series dealing with pollutants, groundwater level, and stock exchange so as to study their future behavior of such time series. The present research work deals with the black carbon concentrations in three major coal mines of India namely, Bokaro, Jharia and Raniganj. In this study, a time series data last 38 years (from 1980 to 2018) obtained from a reliable source (NASA) have been considered by statistical analysis tools like mean, median, mode, standard deviation, skewness, kurtosis, coefficient of variation and time series (ARIMA (Autoregressive Integrated Moving Average)) model at 95% confidence limits have been applied. The validation of the model is tested using R-square, stationary R-square, root mean square error (RMSE), normalized Bayesian information criterion (BIC). It is observed that the model fitted very well, based on these past observations, ARIMA model is applied to obtain the prediction of the amount of black carbon emission for next 7 years 5 months (from Jun 2018 to Oct 2025). These results will help to develop new policies and preventive measures in future by the government agencies, NGOs in these areas and take a note of the seriousness and impact of such huge concentration of black carbon emission in these areas.
... LRC accounts for over 55% of China's coal reserves and is widely used in the power and chemical industries (Rong et al. 2020;Xing et al. 2017). However, owing to the complex physical and chemical properties of LRC, coal spontaneous combustion (CSC) remains one of the main problems hindering its efficient utilization (Nyashina et al. 2018;Stracher and Taylor 2004). A study reported that 56% of China's mines are at risk of CSC Wang et al. 2018). ...
Studying the evolution of the pore structure of coal during spontaneous combustion is of great value in further understanding the mechanism of coal spontaneous combustion (CSC) and its prevention. In this study, we selected three low-rank coals and used nuclear magnetic resonance (NMR) to visualize the macroscopic evolution of the pore structure of coal after heat treatment and to analyze the effect of temperature (25–500 °C) on the pore structure of coal, including porosity, permeability, and fractal dimensions. The obtained results show that the overall NMR signal in coal increases with increasing temperature, indicating that heat treatment can induce the enlargement, opening, and interconnection of pores and fractures in coal. The equivalent average pore radius (rm) of coal shows a positive correlation with temperature, with a substantial increase in rm, especially after temperatures above 200 °C. During heating, the porosity and permeability of all three coals tended to increase with temperature. At temperatures above 300 °C, the permeability of coal dramatically increases, predicting a higher fluid transport capacity. Furthermore, NMR multifractal theory was proposed for quantitative pore space dimensional characterization. The obtained results show that the fractal dimensions of the adsorption space of coal pores increase and then decrease with temperature during heating, while the fractal dimensions of percolation space are negatively correlated with temperature. In addition, the dimensions of adsorption space vary more strongly than those of percolation space, meaning that the adsorption capacity of low-rank coals is more significantly influenced by temperature.
... Coal fires pose great threats to valuable energy resources [1], the environment [2], and human health and safety [3]. They occur in numerous countries in the world. ...
The object of this study is coals of different stages of metamorphism. Currently, a situation has arisen when indicators developed to establish the consumer qualities of coal are used to predict the manifestation of hazardous properties of mine seams during mining operations. The need to consider the fuel for its working condition is due to different end goals between the establishment of consumer qualities of coal and the manifestation of the hazardous properties of mine seams. The condition and quality of coal after its preparation for use is significantly different from the condition in the mining area. Appropriate sample preparation changes the physical and chemical properties of coals, which determine the manifestation of the hazardous properties of mine layers during mining. To eliminate such a discrepancy, the quality indicators of coals were recalculated for their working condition, taking into account the yield of ash and moisture content for the mined mine seams, followed by an analysis of changes in the correlations be-tween the indicators. The indicators of the manifestation of the hazardous proper-ties of mine layers are borrowed from the characteristics of the quality of the fuel, reduced to a dry, ash-free state. Using these indicators, additional errors are introduced in advance into the accuracy of the prediction of the manifestation of hazardous properties during mining operations. The values of the indicators of the organic (combustible) part of the fuel serve as general reliable characteristics of its quality for the entire set of mine seams, but they cannot be used to predict the hazardous properties of a particular mine seam due to a decrease in the accuracy of their determination due to the unpredictable content of mineral impurities and moisture. The initial experimental data, which have been accumulated over several decades based on the experience of using coal for industrial purposes, are analyzed. On the basis of the conducted researches the peculiarities of the choice of indicators of metamorphic transformations of coal, which are used in parallel respectively to establish the quality of fuel and forecast the dangerous properties of coal seams, have been established. The discrepancies between the indicators of the degree of metamorphism used in the current regulatory framework for the safe conduct of mining operations, the state of fuel during mining operations in underground conditions.
... Pollutants released from coal re can also be a hazard to human health. In India, A large number of people were forced to evacuate their homes because of the potential heath risk associated with coal re (Stracher et al., 2004). In China, dental uorosis was spread among population due to the burning coal briquettes enriched uorine (Finkelman et al., 1999). ...
The emission of pollutants from the continuous spontaneous combustion of coal seams and coal gangue may leads to serious destruction of the global environment and ecology in the 21st century. The persistent coal fire in the Wuda coalfield in Inner Mongolia, China is a typical coal fire in north China, and it attracts global attention. In this paper, Coal fire sponge (CFS) samples were collected from the Wuda coalfield and tested in the laboratory. The results show extremely low pH value (0.30 ~ 0.96, n = 33) and extremely high sulfate concentration (125 ~ 427mg/g, n = 33). It is confirmed that 90% of the sulfate exists in the form of sulfuric acid according to further analysis. This fact reveals that the emission of sulfur from spontaneous combustion of coal and coal gangue is mainly in the form of sulfuric acid (H 2 SO 4 ·nH 2 O), which comes from conversion of sulfur in coal and coal gangue, and the accompanying emission of sulfur dioxide is secondary. Glauber's salt condensate, which is common in exposed rock cracks and voids in the Wuda coalfield, further indicates that at least in this coalfield, the spontaneous combustion of underground coal seams and coal gangue will inevitably emit sulfuric acid into the atmosphere. The strong water absorption of sulfuric acid droplets and the resulting condensation and nucleation in the atmosphere are the key factors leading to regional haze events and global climate radiation suppression. Anyway, this work reveals an important and unknown source of sulfuric acid emissions, and it is likely to be another way for coal fires to affect and endanger the global environment and ecology.
... However, the comprehensive utilisation rate of CG is only about 60% 5 . CG accumulation not only appropriates land but also leads to contamination of soil, water, and air, causing serious health risks to surrounding residents 6,7 . The temperature and heat content of CG piles tend to increase owing to oxidation, which can trigger spontaneous combustion of CG, forming hypergolic coal gangue (HCG) minerals 8 . ...
100% hypergolic coal gangue‐based geopolymer foams were produced by a novel saponification‐microwave foaming combined route. Microwave foaming with and without expired vegetable oil was first used to produce coal gangue‐based geopolymer foams. Macropores were mainly generated by microwave foaming, and mesopores were mainly obtained by the addition of expired soybean oil that underwent a saponification reaction. The effects of the oil content on the density, porosity, pore morphology, compression strength, and methylene blue adsorption properties were studied. High total porosity (85.9–89.0 vol%) and acceptable compression strength (0.46–1.1 MPa) hypergolic coal gangue‐based geopolymer foams were produced. Foams with 12.59 wt% oil exhibited the best adsorption properties, with an adsorption capacity up to 9.4 mg/g and high removal efficiency of about 95.3%. These solid‐waste‐based porous components are promising monolithic adsorbents for wastewater treatment. This article is protected by copyright. All rights reserved
... With the progress of coal mining activities, coal gangue accumulates in large quantities; it has become one of the largest industrial residues [5,6]. The accumulation of coal gangue not only occupies large land resources but also causes serious environmental problems, such as soil pollution, soil degradation, geological disasters, and air pollution [7][8][9][10][11][12][13][14][15][16]. Therefore, it is an urgent international task to improve the comprehensive utilization efficiency of coal gangue and eliminate its negative impact on the ecological environment [17]. ...
The chemical reaction between calcium ions (Ca2+) and phosphate in the soil is the main way to maintain the availability of soil phosphorus. Thus, we believe stimulating coal gangue with Ca2+ solution would be an effective way to improve its adsorption and desorption capacity toward phosphate. In order to explore the effects of different pH of Ca2+ solution on the modified effect of coal gangue, we conducted mechanical grinding (<1 mm), high temperature calcination (800 °C), and the stimulation of Ca2+ solution with different pH (2, 7, 13), to prepare acidic calcium-modified coal gangue (Ac-CG) (Ac-CG, acidic calcium-modified coal gangue; Ne-CG, neutral calcium-modified coal gangue; Al-CG, alkali calcium-modified coal gangue; RCG, raw coal gangue), neutral calcium-modified coal gangue (Ne-CG), and alkali calcium-modified coal gangue (Al-CG); raw coal gangue (RCG) was regarded as the control. The results indicated that Al-CG had better phosphate adsorption (3.599 mg g−1); this favorable adsorption performance of Al-CG was related to the formation of hydrated calcium silicate gel and ettringite, which provided more Ca2+, Al3+, and hydroxyl groups, and a larger specific surface area (9.497 m2 g−1). Moreover, Al-CG not only held more phosphate but also maintained its availability longer for plants. It is suggested that stimulating coal gangue with Ca2+ solution under alkaline conditions is a perfect way to enhance its adsorption and desorption capacity toward phosphate; the Al-CG we prepared could be used as filling material and soil conditioner in the reclamation area.
... e emissions from these coal fires pollute the atmosphere, destroy the ozone layer, cause the greenhouse effect and global warming, and seriously threaten ecological security. erefore, controlling the coal fires caused by the spontaneous combustion of coal has become a huge issue facing the world today [4]. e spontaneous combustion of coal gangue is a relatively special combustion system, which has the characteristics of large heat storage and easy reignition. ...
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.
... Additionally, the heat generated by the oxidation combustion of coal diffuses to the surface, resulting in surface water loss, reduced fertility, vegetation destruction, and soil erosion (Zhao et al. 2019a, b;Xu et al. 2020). Some metallic and non-metallic minerals burn at high temperatures to form acid-base compounds, a process that affects the formation of underground voids in the coal layer, causing geological disasters, such as surface subsidence, depressions, and landslides (Hao et al. 2020;Song et al. 2019;Stracher and Taylor 2004;Sun et al. 2020;Xiao et al. 2016;Xu et al. 2020). Because of the development of surface fissures, severe air leakage, and oxygen supply, shallow coal bodies oxidise and heat up, causing spontaneous combustion of coal (Song et al. 2021;Zhao et al. 2019a, b). ...
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.
... China, India, the United States, Indonesia, Australia, and Russia are the major countries of coal production and consumption. The spontaneous combustion of coal gangue releases a lot of harmful gas, which affects the air quality around mining areas [7][8][9]. When the combustion exothermic reaction speed is greater than the heat dissipation speed, heat accumulation occurs, and the generated heat and gas rapidly gather in the relatively sealed gangue dump, resulting in the explosion phenomenon, directly endangering the nearby construction facilities and personal safety [10,11].The prevention annual production design capacity and washing capacity has reached 2.4 million tons, and the output of gangue is about 400,000 tons/year. ...
Coal gangue spontaneous combustion is a serious catastrophe associated with mining activities. Generally, the areas of coal gangue spontaneous combustion are regions of tremendous heat accumulation. Mastering the regularity of deep temperature distribution and eliminating internal heat is an effective method to control spontaneous combustion. In this study, using self-developed heat pipe (HP) and intelligent cloud monitoring software, three sets of single pipe experiments were conducted in different temperature areas of the coal gangue dump in Yinying Coal Mine. A fitted model between shallow and deep temperatures was established using the least squares method to perform goodness-of-fit tests and significance analysis, and to analyze the internal temperature variation under the action of an HP. The results show that the quadratic model fits better and the regression is significant, and can be used as an empirical regression formula for the shallow temperature estimation of the deep temperature. The temperature was clearly suppressed by the HP, and the average cooling range reaches 21.44% within 700 h. However, the temperature of the control group without an HP continued to rise by 8%. In the three experimental groups, the effective control radius of the single HP was 3 m. The best cooling was achieved when the gangue depth was 1 to 4 m and the temperature was between 90 °C and 450 °C. The study shows that the HP has a great effect on thermal removal and inhibits spontaneous combustion of the gangue. In addition, this paper also provides a theoretical basis for the technology of HP treatment of spontaneous combustion gangue dumps.
... Several authors (Stracher 2004;Stracher and Taylor 2004;Kuenzer et al. 2007;Zeng et al. 2018;Deng et al. 2021) have reported the effects of coal mining and fires on the environment in Chinese coal mines. The studies include both fieldbased and remote sensing methods. ...
Coal is the major fossil fuel used for power generation. Coal mining activities lead to environmental changes to a large extent, such as degradation in the quality of air, water, and soil, changes in landform, land use/land cover, and vegetation distribution. Evaluating the environmental quality is therefore essential to study the nature and impact of mining activities on the environment. The present study attempts to use the analytic hierarchy process (AHP) to assess the environmental quality of Rujigou coalfield that lacked previous such analysis. The criteria used for evaluation were selected through a literature review and extensive field survey. A photo tour of the study area shows the current ground conditions. Weights were assigned to these criteria based on expert opinions, recommendations from published literature, and field investigation. The results indicate that mining activities in the study region most significantly impact the air quality, followed by soil, water, landform, and vegetation. The knowledge of environmental quality can forewarn policymakers and mine managers about impending environmental problems and improve their ability to manage and resolve them. Moreover, the systematic methodological process described in this research can be applied to any study area with similar features to the one investigated in this paper.
... Many scholars at home and abroad ha ried out multi-dimensional research on filling materials, mainly focusing on the se of filling materials and optimization of the ratio [6][7][8][9], the influence of mechanica erties [10][11][12], backfill mechanics constitutive models [13,14] and failure mech China started late, and the comprehensive utilization path is relatively simple, and la scale industrial utilization has not yet been achieved. At this stage, the method of l occupation and stacking is mostly adopted, occupying a large number of land resour and the heavy metals contained in it will pollute the environment, and the added valu deep-processing products is generally low, which will increase the production cost of terprises [4,5]. Taking desulfurized gypsum as an example, it is mainly used as a cem retarder, paper gypsum board, gypsum block, and other new wall materials. ...
To explore the strength development characteristics and engineering performance of different coal-based solid waste filling materials cemented into filling body, coal gangue was used as coarse material, fly ash, desulfurization gypsum, gasification slag, and furnace bottom slag as fine material, and cement as a gelling agent. The uniaxial compressive strength (UCS) and bleeding rate of coal-based solid waste cemented backfill (CBSWCB) were tested by an orthogonal experiment, and the influencing factors of mechanical properties and strength development were analyzed. The multiple generalized linear model of strength and bleeding rate was established, and the optimal filling material ratio was determined. The engineering performance index of CBSWCB with the optimal ratio was tested. The results show the following points: (1) the concentration and content of desulfurization gypsum had a great influence on the early compressive strength of CBSWCB, while fly ash, gasification slag, and furnace bottom slag had little influence on the early compressive strength. (2) High concentration, high content of fly ash and furnace bottom slag, low content of desulfurization gypsum, and gasification slag can significantly improve the early strength. High concentration and high content of fly ash, low content of gasification slag, furnace bottom slag, and desulfurization gypsum are beneficial to the later strength increase. (3) Under the optimal ratio scheme, the bleeding rate of CBSWCB was 1.6%, the slump was 16.6 cm, the cohesion was general, the segregation resistance was good, the initial setting time was 5.42 h, the final setting time was 7 h, and the early strength after curing for 8 h reached 0.24 MPa.
... Many studies reveal that coal-gangue-based zeolites have the potential of becoming cheap adsorbent by proper synthesis approach (Qian and Li 2015), which cannot only be compared favorably with reagent grade zeolites, but also solve the pollution and waste of coal gangue (Stracher and Taylor 2004), achieving high value-added utilization (Li and Wang 2019;Soliman and Moustafa 2020). However, most of these adsorbents are synthesized from coal gangue using traditional hydrothermal and alkaline-fusion methods (Lu and chen 2018;Bu et al. 2020;Jin et al. 2021); the shortcomings are the long reaction period and consuming more energy. ...
Heavy metal contamination of water has brought about serious harm to the ecological environment and also threatens human health to a certain extent. In this study, a composite structure comprised of analcime-activated carbon (ANA-AC) was synthesized in situ via a microwave-assisted hydrothermal method using coal gangue (CG) for the potential treatment of Pb²⁺ from aqueous solution. The products were systematically characterized using XRD, SEM, BET, FTIR, and XPS. The results showed that activated carbon was successfully integrated with the structure of the analcime and the BET surface area of the ANA-AC (20.82 m²/g) was much greater than that of the CG (9.33 m²/g) and ANA (10.04 m²/g) independently. The relationship between Pb²⁺ adsorption capacity and the initial solution concentration, adsorbent dosages, contact time, pH, and temperature was studied. Under optimal conditions (Pb²⁺ = 100 mg/L, dosage = 0.1 g, contact time = 6 h, pH = 5.4–6, temperature = 298 K), the maximum adsorption capacity of ANA-AC can reach 100%, which was higher than that of CG and ANA. The Langmuir isotherm model was in good agreement with the data obtained for Pb²⁺ adsorption, and the pseudo-second-order kinetic model was more suitable for describing the experimental data, showing that chemical adsorption was the controlling step during the adsorption process. In summary, analcime-activated carbon composite prepared from coal gangue could be used as an appropriate adsorbent for Pb²⁺ adsorption from an aqueous solution.
... As indicated previously, underground coal mines are characterized by numerous life-threatening hazards such as fires, explosions, toxic gases, dust, and mine collapse, but the major problem, which has the most devastating effects, is coal mine fires (Azam and Mishra, 2019;Stracher and Taylor, 2004;Wang, Yang, and Li, 2018). When such emergencies occur, it is required that miners evacuate the mine premises immediately and in a safe manner. ...
Synopsis 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.
... The unsustainable overexploitation of mines has led to coal fire (Pal et al., 2021) and huge areas which cannot be used for any other purposes in future. Since these lands have not been reclaimed properly (Paul, 2010;Stracher & Taylor, 2004;Tripathi et al., 2016) so it would be difficult to use those land for any other economy generation purpose in future due to coal fires and other such effects. This also has become a major reason for a lot of people to lose their jobs indicating the fact that coal mining does not assure long term employment. ...
Environmental sustainability of coal industry is a major concern considering the trends of its exponential effect on the region and towards climate change. The study examines the land use/land cover changes using spatio temporal datasets of the years 2000 and 2020 in Dhanbad district which comes under the major coal-belt of India. The study shows the impact of expanding industries on the environment depicting a remarkable decrease in vegetation (18.89%), increase in built-up land (14.32%) and coalfields (0.9%) exhibiting massive deforestation activities. The study focuses on the increase in emissions from coal mining activities including GHGs, SOx, PMs, etc. over the years and their harmful impacts on the region. The sustainability evaluation of the coalfields of the study area is done through 15 predetermined indicators, suggesting the urgency and need of actions for sustainable functioning of coal mining industry in order to limit global warming to below 2 °C as suggested in the Paris Agreement-2016. The study also lays stress on the changing economic pattern of the region as an effect of increasing industrialization and changes in the land use.
Closed coal bunkers emerged as a novel form of coal storage for coal-fired power stations. Nevertheless, heat builds continually in the storage process because of the constant oxidation of coal and combined with the impact of a confined coal bunker environment, it is difficult for heat to dissipate, resulting in frequent coal bunker fires. Consequently, research on coal pile combustion characteristics is crucial to the design of coal bunker safety. The experimental platform was set up in this study to conduct combustion tests of various specifications, and the burning rate, flame height, flame temperature, and heat radiation flux were analyzed to identify the critical parameters impacting coal bunker safety. First, the maximum burning rate of coal heaps during steady burning was calculated, improving coal pile combustion theory and providing guidance for coal bunker design. Second, the maximum flame height was determined, which can provide an important design guide for coal bunker height designs. In addition, it was discovered that high temperatures in flames, smoke, and smoldering coal might cause coal bunker buildings to collapse, so future designs should strengthen coal bunker fire resistance and keep the coal pile away from the load-bearing structures to prevent collapse from excessive temperatures. Moreover, the diameter of coal piles has an influence on the heat flow. For this reason, a coal bunker’s design must consider the coal pile’s fire separation distance from the coal bunker and avoid large coal piles. Consequently, the study gives recommendations and support for planning coal bunker safety and enriches experimental data for coal pile fires.
Emissions from underground coal fires extend the already well‐known adverse health impacts of coal extraction and combustion. The extraction, storage, transportation, and utilization of coal that produces fugitive dust pose a significant risk to human and animal health, and the environment. Emissions from coal‐fired power plants, and residential coal use, may expose individuals to hazardous air pollutants including mercury, sulfur dioxide, nitrogen oxides (NO x ), toxic heavy metals (e.g. As, Pb), radioactive elements (e.g. uranium, radium, and thorium), and volatile organic compounds. One aspect of coal combustion has been largely neglected, that is the threat of uncontrolled coal fires. The thousands of naturally occurring or anthropogenic‐induced uncontrolled coal fires worldwide are a major environmental insult to the air, soil, and water and a major threat to the health of those unfortunate enough to work or live in the vicinity. Some have persisted for decades or even centuries, constantly spewing hazardous material into the environment. Medical geology, the study of the impacts of natural materials on human health, can help by identifying and analyzing the toxic emissions as well as the health effects from collaboration with biomedical and public health researchers.
Coal mining has caused groundwater pollution and loss. Using a mined area as a water storage space for storing and purifying mine water is a low-cost environmentally friendly mining method. In this study, static and dynamic adsorption experiments on the ions in mine water were carried out using the roof rocks from the Lingxin coal mine. The sample analysis results show that the main chemical composition of the roof is mainly SiO2 and Al2O3. The water chemistry type of the mine water is SO4-HCO3-Cl-Na type, with an average mineralization of about 4000 mg/L. The experimental results show that gangue can stabilize the pH value of mine water with different pH values between 7.5 and 8.5. In the acidic and alkaline environment, the degree of void space increases the adsorption capacity of the gangue, in which the adsorption rate of gangue is between 3% and 5%. The calcium ion reduction rate reaches 75% in static leaching and 70% in dynamic leaching conditions. Medium-grained coarse sandstone has a stronger adsorption capacity than muddy siltstone. The results from this study can support further research on using gangue for water purification purposes in mines, simultaneously reducing the harmful accumulation of gangue and promoting the recycling of highly mineralized water.
The effects of water soaking on the microstructure and spontaneous combustion characteristics of coal samples were investigated by scanning electronic microscopy (SEM), Fourier transform infrared (FTIR) spectrometer, and temperature programmed testing system (TPTS). The SEM results showed that the pore structures on the surface of water−soaked coal were more developed than raw coal, the pores increased and enlarged, and the phenomenon of water absorption swelling occurred. At the same time, water soaking had a certain influence on the functional groups in coal. The results of FTIR clearly illustrated that the surface functional groups of water−soaked coal were more active, and the contents of functional groups such as hydroxyl, methylene, aliphatic ether and aromatic ether all increased to varying degrees. During the low−temperature oxidation process, the analysis results of TPTS indicated that the oxygen consumption rate and the production of CO, C2H4, and other gases of water−soaked coal were higher. Based on the analysis method of CO, CO/CO2 and C2H4 gas growth rate, the three peaks of the curve obtained correspond to the characteristic temperatures of each oxidation stage of the coal samples. The critical temperature, dry cracking temperature and fission temperature of water−soaked coal were 60 ± 10 ℃, 90 ± 10 ℃ and 120 ± 10 ℃, respectively, which was 10 ℃ lower than raw coal. The apparent activation energy (Ea) of coal was calculated by the CO model and fitted in sections. It can be seen that the Ea of water−soaked coal at different stages of low−temperature oxidation was lower, and the maximum difference was 2.1 kJ/mol. Therefore, from the above results, it inferred that the activity of bituminous coal became stronger after soaking in water, which may be due to the effect of soaking on the surface structure and active groups of coal, thus showing a higher risk of spontaneous combustion.
The present study explores a holistic approach toward better assimilation of the contextual relationship between coal fire-induced land subsidence in the Jharia Coalfield (JCF), India. For the process, 31 consecutive Sentinel-1A and Landsat 8 scenes of 2018 were processed to estimate mean Line-of-Sight displacement and Land Surface Temperature (LST) in JCF, respectively. The results indicated that the displacement rate in JCF significantly varies at active mine benches and overburden dump, and high degree of displacement owing to the additive compression inducted along with the volume reduction at the subsurface. The estimated displacement accounts were then spatially correlated with the thermally anomalous pixels to determine the categories of subsidence. Further, the contextual relationship between the displacements estimates (dependent variable) with a set of explanatory variables, i.e., pixel integrated LST was tested using Binary Logistic Regression. The performance of the model was cross-validated using statistical parameters derived from the confusion matrix.
The cavities formed by the combustion of underground coal fires and the overlying rock damage caused by the combustion will cause the surface to subside or even collapse, forming crisscrossing surface cracks. On the basis of studying the fracture, subsidence and caving characteristics of overlying strata in the coal seam mining-combustion composite open space, the temporal and spatial development of the coal seam mining-combustion composite open space and the three-dimensional movement law of the induced overlying rock are studied in order to build three-dimensional dynamic theoretical distribution model of porosity in coal seam mining and combustion disturbance zone. Based on the porosity evolution model, the fire zone isotope radon method is used to detect the temperature anomalous area in the goaf. According to the location of the abnormal high-temperature area, a comprehensive treatment method is carried out, which is mainly based on the combined grouting of the upper and lower the mine, and supplemented by nitrogen injection and three-phase foam injection, thereby to solve the problem of difficult quantitative characterization of the multi-void medium in the mining-influenced underground coal fire area and targeted treatment for coal fire prevention and control in the mining-combustion disturbance area.
The state of iron in coal gangue minerals is an important factor in determining the potential for value-added utilization of this solid waste; this is especially true for the coal gangue coming from the Pingshuo open-pit mine in China. The objective of the present study was to characterize the petrological, mineralogical, and chemical states of Fe in the coal gangue from the Carboniferous Taiyuan Formation. Methods used included polarizing microscopy, X-ray diffraction (XRD), scanning electron microscopy–energy-dispersive spectroscopy (SEM–EDS), X-ray fluorescence, micro-Fourier-transform infrared (micro-FTIR) spectroscopy, and Mössbauer spectroscopy. The coal gangues are mudstones, silty mudstones, and pelitic siltstones, which are composed primarily of kaolinite, quartz, feldspar, pyrite, illite, and magnesite. In coal gangue, the Fe was found to occur in ferruginous minerals, in crystal-lattice substitutions, or in a colloidal state. The ferruginous minerals in the coal gangue are pyrite and marcasite, and the pyrite morphologies are framboidal, euhedral octahedral crystals, subhedral granular crystals, and irregular crystals. The results of SEM–EDS and micro-FTIR confirmed that the lattice substitution of Fe in the coal gangue minerals occurred mainly in kaolinite, resulting in two types of kaolinite: iron-containing and iron-free kaolinite. The former may be transformed from volcanic biotite and the latter from volcanic feldspar. The Mössbauer spectra of kaolinite showed intense doublets with isomer shift and quadrupole splitting values consistent with tetrahedrally coordinated Fe3+ and ocahedrally coordinated Fe2+, suggesting the presence of two types of substitution sites: (1) Fe2+ replacing Al3+ in the octahedral sheet; and (2) Fe3+ replacing Si4+ in the tetrahedral sheet. This study has important theoretical significance for the high-value utilization of coal gangue.
The article concerns the effect of the additive on the inhibition of the coal spontaneous combustion process (CSC) by the Olpiński method. The influence of inhibitors on CSC in this method has not been studied so far. Coal samples used in the experiment were taken from Polish coal mines, from which four samples with the symbols S1, S2, S3, and S4 were created, respectively. For each coal sample, a spontaneous combustion index was tested following the Olpiński's method. In addition, analogous tests were performed for coal samples treated with an aqueous CaCl2 solution. A 20% CaCl2 solution has proved to be the most advantageous. Based on the Olpiński method, a fire incubation period is determined in natural conditions on a mine site. Based on the results of CaCl2 inhibition, the extension of that period for examined coals was determined. The results obtained can provide valuable references for developing technology in CaCl2 usage to prevent spontaneous fires in coal mines.
A B S T R A C T
A key index for assessing the risk of coal spontaneous combustion (CSC) is the incubation period of spontaneous combustion (IPSC). Long-flame coal samples were obtained from the Liushicun coal mine in Shaanxi, China. On the basis of the Kalenkin model and the thermal effect, thermophysical properties, and characterization parameters of CSC, an IPSC calculation model was established. The model assumes that surface oxidation and adsorption heat are combined to produce a heat effect, evaporate the water contained in coal, and desorb adsorbed gas. The time required for the temperature of coal to increase from room to ignition temperature can be calculated to obtain the IPSC of long-flame coal. In this study, the IPSC of long-flame coal was calculated to be approximately 45 days. This finding can provide a basis on which coal mines can formulate effective fire-fighting measures.
There is a critical situation that a huge amount of greenhouse gases is emitted into the atmosphere from natural coal fires in underground coal seams and spontaneous combustions in coal piles in the world. To reduce the emissions of combustion gases, such as CO2, CH4, etc., some technical challenges and researches are required related to CO2 flux measurements, developing an effective chemical water-solution extinguishes coal fires and inhibits spontaneous combustion, constructing a numerical simulation model to treat the aging effect in coal heating rate. In this article, firstly, the previous studies were reviewed to explain measurement results of CO2 emission from coal fire/spontaneous combustion fields and the aging model used to simulate coal heating rate. Secondary, a trial development of some chemical solutions has been introduced to inhibit microscopic and macroscopic coal oxidations by forming a gel. Especially, sodium meta silicate solution showed a relatively good performance shifting the critical self-ignition temperature (CSIT) of a low rank coal to be 4 to 5℃ higher than that of water by forming gel with CO2 gases in the air and combustion gases emitted from coals. The brooking effect in macro scale by forming gel is also expected to extinguish coal seam fires by reducing aperture width in fractures connecting to the atmosphere. A numerical simulation using ANSI FLUENT has showed an extinguishing fire process of an underground coal seam including a horizontal fracture that is connected inlet and outlet fractures being air paths for air and combustion gas, respectively. Finally, the the research challenges required for technical developments have been proposed to carry a project extinguishing the coal seam fires and spontaneous combustions of coal piles with reducing CO2 emissions.
Proanthocyanidin antioxidant was first selected for study, and the inhibitory effect of proanthocyanidin and the optimal mass ratio of 6 mass% were obtained through temperature-programmed experiments. To compensate for the inhibitory effect and action time of a single antioxidant, a composite inhibitor with a physical and chemical synergistic effect was obtained through compounding with sodium polyacrylate, a superabsorbent resin, which improved the inhibitory effect on the spontaneous combustion of long-flame coal. In addition to the temperature-programmed experiments, the spontaneous combustion of long-flame coal was researched through a thermogravimetric (TG)–differential scanning calorimetric (DSC) experiment, and the optimal compound ratio of proanthocyanidins/sodium polyacrylate was determined to be 1:4. Under this ratio, the inhibition rate was close to 88% when the coal temperature ranged from 40 to 130 °C. The TG–derivative TG curve moved to the high-temperature region, and the composite inhibitors improved the characteristic temperature of raw coal and reduced its mass loss. The temperature corresponding to the peak value of the DSC curve increased, and the maximum heat release power was reduced. Fourier-transform infrared spectroscopy experiments revealed that the intensity of the hydroxyl peaks was reduced with the addition of composite inhibitors, and the peak intensity of methyl and methylene was lower than that of the raw coal. The inhibition characteristics of the composite inhibitor were thus obtained through a study of the change pattern of functional groups of coal samples during the heating process.
Coal mining is a significant activity on the Mpumalanga Highveld. One of the major air pollution issues associated with coal mining, is the spontaneous combustion of coal. There are no abatement technologies in place for such emissions, and typically long- and shortlived greenhouse gases, other gaseous pollutants and particulate matter are emitted by such events. For ambient air quality models to accurately capture the contribution of spontaneously combusted coal, it is necessary to determine the locations and durations of these burning events. Such information will also assist in explaining experimentally determined ambient air quality data. In this article, satellite fire radiative power (FRP) data from the Moderate Resolution Imaging Spectro-Radiometer (MODIS) was used to determine the locations and durations of spontaneously combusted coal within the Mpumalanga Highveld for January 2001 to December 2019. From the results it was concluded that five mining sites were prone to spontaneous combustion. These sites were all opencast mines situated on old bord and pillar mines. Two of these areas were actively burning for most of the 19-year study period. A relatively well-defined seasonal pattern was also observed, with combustion events being more prevalent during the winter months. Considering the active burning periods of the areas where spontaneous combustion were recorded, it is obvious that this is a major source of atmospheric pollutants on the Mpumalanga Highveld.
Spontaneous combustion disasters occur in coal seams worldwide. Under high-temperature baking by a coal fire, surrounding rocks are metamorphosed to form combustion metamorphic (CM) rocks. To study the characteristics of erosion and deterioration of CM rocks water on CM rocks, a dry–wet cycling experiment was conducted. A Na2SO4 solution was used to wet CM rock samples obtained from several strata above the site of a coal seam fire, which were then oven-dried, and the process repeated for 50 cycles. Low-field nuclear magnetic resonance analysis found that the pore structures changed greatly. Porosity increased and then decreased with cycling, while the pore size distribution increased. The proportion of micropores decreased first and then increased, while that of macropores increased and then decreased. After 50 dry–wet cycles, the sample quality, hardness, and surface gloss decreased, while the surface roughness increased. Five weathering erosion types were identified: spherical, central, powdery, and interface types I and II. The rock pore structure and degree of combustion metamorphosis influence erosion, with the latter improving the erosion resistance.
Using coal gangue (CG) as a building material does not only reduce the disposal of industrial waste and promote the resource utilization of solid waste, but also solves the excessive consumption of sand and stone in construction. This study experimentally investigated calcining ceramisites from CG raw materials and the mechanical properties of CG ceramsite concrete were studied. Additionally, the physical, chemical and composition changes of CG before and after calcination were observed using scanning electron microscopy and X-ray diffraction analysis (XRD). The experimental results reveal that calcination can reduce the density, increase the strength, increase the porosity of CG, and change the microstructure and mineral composition of CG. Finally, there are great differences between coal gangue ceramsite concrete and ordinary concrete in the variation of compressive strength with time and the relationship between elastic modulus and compressive strength. In this paper, the existing formula is modified according to the experimental data.
In this paper, a new kind of environmental friendly double‐network gel material was prepared. The first network structure was formed by the graft copolymerization of sodium lignosulfonate (LS) and acrylic acid (AA), and the second network structure was formed by the chelation reaction of sodium alginate (SA) and carbide slag clarified solution (Ca2+). Through an orthogonal experiment, the effects of raw material addition on the compressive strength and apparent viscosity of the gel were analyzed. According to the analysis results, the optimal experimental ratio was obtained, i.e., 2 wt% of LS, 0.25 wt% of SA, 15 wt% of AA, 0.1 wt% of MBA and 0.3 wt% of APS. Furthermore, the structure of the gel are characterized by FTIR, XRD, SEM, XPS, and TG‐DTG, and the results prove that the gel successfully polymerized and a stable three‐dimensional network structure is formed. The results of water absorption experiment disclose that the gel is sensitive to ions and pH, and the water absorption rate reaches 121.25 times. In addition, the results of the air leakage experiment and fire extinguishing experiment show that the gel can effectively cover the surface of crushed coal and densely fill the gaps, demonstrating a good plugging capability and fire extinguishing capability.
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.
Residual coal is prone to spontaneous combustion under the influence of high ground temperature, and the risk increases with mining depth. This results in gradual increases in smoke and dust emissions, which seriously affect the ecological and geological environment of the mining area. To avoid spontaneous combustion of the residual coal, protect the resources and ecology of mining areas, and investigate the influence of the deep thermal environment on the microstructure and oxidation properties of coal, the pore evolution characteristics and functional group migration of coal in a thermal environment were studied by N2 adsorption and infrared spectroscopy. A temperature-programmed test system was used to simulate the low-temperature oxidation process occurring in deep coal seams, and the heat release characteristics and oxidation kinetic parameters of the index gas were calculated. The experimental results revealed that the pore oxygen storage capacities and coal oxygen contact areas of residual coal in deep mines are larger than those of coal in shallow seams. As the preheating temperature is increased, the rates of CO and CO2 production and the amount of oxygen consumed in oxidation of heat-treated coal increase. The crossing point temperature (CPT) of heat-treated coal decreases. The deep thermal environment accelerates the rate of condensation decomposition of the aliphatic hydrocarbon groups in coal and fracture of side chain hydrogen bonds connecting strong electron-absorbing groups, which increases the exothermic intensity of the oxidation process. The reaction trigger temperatures for aliphatic hydrocarbon groups, peroxyl radicals, associative hydrogen bonds and other active groups in coal are different. With increasing ambient temperature, the types of active groups in coal increase, and the contents accumulate. With an increase in the deep geothermal temperature, the oxidation activity of coal is enhanced, and the coal is more prone to spontaneous combustion. These research results provide a theoretical reference for deep coal clean mining and prevention of spontaneous combustion disasters and have a potential guiding role in environmental protection and ecological improvement of deep mining areas.
The effect of cellulose on pyrolysis characteristics of coal gangue was studied based on TG-FTIR experiment. Cellulose with different mass ratios is added to coal gangue. Synergistic effect between cellulose and coal gangue on mass loss was observed in this study. CG1CEL1 and CG1CEL3 samples have mutual promotion effect between CG and CEL. Conversely, the inhibitory effect of CG3CEL1 between CG and CEL was evident at high temperature. The reaction mechanism of coal gangue and cellulose co-pyrolysis based on lumped reaction model was determined. Furthermore, the comprehensive influencing factors of coal gangue and cellulose co-pyrolysis were analyzed by principal component analysis. There is little research on the influence mechanism of cellulose, the main component of biomass, on the pyrolysis of coal gangue. This paper is of great significance to clarify the mechanism of co-pyrolysis of biomass and coal gangue. This study provides a basis for revealing the influence mechanism of cellulose on coal gangue pyrolysis, which accelerates the process of carbon neutralization. This can promote resource disposal of coal gangue by reduction, so as to reduce environmental pollution and improve the utilization rate of fossil energy.
To reduce mine fire risk and ensure efficient resource utilization, an in-depth research must be conducted on the secondary oxidation of coal. Accordingly, the macroscopic oxidation characteristics and microscopic composition of newly-mined coal, artificially oxidized coal (the newly-mined coal oxidized at 70 °C and 180 °C) and repeated-mined coal (oxidized naturally over 10 years) were evaluated in this study. And these coal samples were labeled N, N-70, N-180, and R, respectively. The parameters indicating the oxidation characteristics of coal were analyzed by simultaneous thermal analysis-Fourier transform infrared spectroscopy (STA-FTIR) and Shimazu Fourier transform infrared spectrometry (FTIR-8400) from the perspective of coal thermal reaction and functional groups. The experimental results suggest that the temperature T2 required by N-70, N-180, and R to reach the oxidation stage was lower than that of N. In addition, CO and CO2 gases were released earlier from these coals than from N. The same release was earlier for N-180 and N-70 compared to that for R. Compared with N, the content of hydroxyl and aliphatic hydrocarbons in N-70, N-180 and R after the initial oxidation decreases, and the decrease of N-70, N-180 was greater than that of R. The content of oxygen-containing functional groups (-COOH, C=O, -COO-) increased significantly, and the increase for N-70, N-180 was greater than that of R. These results indicate that coal was more prone to secondary oxidization after primary oxidation. This is because the coal absorbed heat released during the primary oxidation and subsequently had a higher activity. The artificially-oxidized coal in the laboratory absorbed more heat and generated more oxygen-containing functional groups (-COOH, C=O, -COO-) than the chronic naturally-oxidized coal in the mine face, resulting in a higher risk of spontaneous combustion during secondary oxidation.
Coal spontaneous combustion (CSC) is a complex physical and chemical process. Numerical simulation is an efficient method for visualizing and quantifying CSC. However, in previous models, the property parameters of coal are frequently assumed to be constant and hence cannot be used to predict accurately the thermodynamic behaviors during CSC. In this study, a fully coupled porous media model considering water migration, heat transfer, and thermal deformation was developed to investigate the thermal kinetics of CSC. The porosity and thermal strain during CSC in the model were consistent with the experimental results. Moreover, a method based on nuclear magnetic resonance (NMR) was used to calculate the residual saturation of fluids in porous media during heat treatment. The results showed that porosity increased with temperature during CSC, and the NMR transverse relaxation cutoff values of coal depended nonlinearly on temperature. In the initial stage of CSC, moisture was the dominant factor affecting CSC. As time progresses, moisture and temperature exhibited a synergistic effect. Temperature was the leading factor contributing to CSC in the final stage. The temperature increase during CSC exhibited a ‘slow and then fast’ trend. In addition, the deformation of coal during CSC caused thermal shrinkage, and its magnitude depended on the temperature increase rate. The results can be used to identify the thermodynamic behaviors during CSC and contribute to a better understanding of the mechanism of CSC.
Coal mining is an industry that is associated with hard physical labor and harsh mental conditions. Modern artistic projects involving portraits of miners evolve as artists' responses to political and economic changes in the mining industry, which is currently in decline, and place a major focus on miner communities, rather than individual miners. This article presents an overview of relevant selected artistic projects, and supplements them with a small mini-gallery sketched by the author. The mini-gallery viewers have been invited to test their perception of miners based on a series of charcoal portraits representing men and women dressed in mining workwear and everyday clothes. Who in this mini-gallery is a miner, what serves as the basis for the respondents' guesswork, and, overall, how different is today’s perception of miners from those of the past centuries? Three main factors are outlined as potentially relevant for identifying miners: mining workwear, gender, and facial expression. The readers can compare their intuitive reactions with the results from an online experiment, which was presented in Norwegian, Russian, and English and collected 136 responses. Although the presence of mining workwear and male gender still carry a strong association with miners, the results reveal certain differences across Norway, Russia, and the United States. The article is interdisciplinary and combines aspects of art history, social studies and psychology with an artistic project.
Two samples (“O” and “C”) of aluminium-based powders were calorimetrically investigated with respect to the self-heating risk to water and aerial oxidation. Powder “C” was rich in aluminium (ca 85%); however, its particles were coarse, proving nominal size of ca 190 μm. On the other hand, sample “O” contained only 23% aluminium, but it was evidently fine-grained (nominal size about 3 μm). The fine character of the sample proved to be crucial for appearance of hydrolysis reaction with water. During the hydrolysis, about 36% of the aluminium of sample “O” was converted to aluminium hydroxide, while only about 0.15% it was for sample “C”. Studying aerial oxidation, unexpectedly high increase in self-heating risk was found for the pre-wetted samples. Both samples, regardless of the difference in their grain size, represent quite comparable self-heating risk. A probable explanation of the finding is suggested.
Coal fires have led to severe ecological disasters worldwide and threatened the health and safety of nearby residents to a certain extent. It is critical to detect the scope and extent of coal fires in order to control and extinguish them. In this article, the unmanned aerial vehicle (UAV), thermal infrared imaging, and oblique photogrammetry technologies were integrated to create a 3-D land surface temperature model of the Chunjingwa Coal Fire in Shanxi Province, China. Hundreds of visible and thermal infrared images were collected from five flight survey lines. The thermal infrared images were preprocessed in batches to meet the requirements of 3-D modeling. The construction of the thermal infrared 3-D model of the fires was achieved successfully, allowing for the visualization of the surface temperature field in true 3-D. Four high-temperature zones were delineated according to the 3-D land surface temperature model. Furthermore, the features of ground objects were clearly depicted by the visible 3-D model constructed by visible images, and the digital elevation model (DEM) was established based on the spatial coordinate contained in the visible 3-D model. The research results provide technical support for the subsequent firefighting plan and a reference for the high-precision detection of other coal fires around the world.
Coupled thermodynamic disasters in goaf, such as coal fires and gas explosions have long been one of the most serious disasters in major accidents of coal mines worldwide. In the case of deep mining becoming the new normal of future mine mining, there is still a lack of targeted technical methods for the prevention and treatment of major thermodynamic disasters, especially coal spontaneous combustion and gas coupling disaster. Rapid dangerous region identification and effective prevention of such disasters in goaf is extremely important for mine safety production. Based on the analysis of the coupling relationship between coal spontaneous combustion and gas disaster in fully mechanized caving goaf and the mechanism of collaborative control technology, coal spontaneous combustion and gas disaster formation characteristics, occurrence process and prevention and control methods were fully utilized. By injecting isolation material through the interval between the hydraulic support frames to form a row of discontinuous isolation blocking zones, a dynamic pressure injectionisolation technology for collaborative control of coupling thermodynamic disaster in goaf in special mining period was proposed and the isolation parameters of the field goaf were designed. The field measurement was carried out to obtain data and the distribution characteristics of spontaneous combustion-prone. The gas drainage and collaborative control efficiency befor an after isolation were verified. Our approach offers a new concept and method to identify and collaboratively control of coal spontaneous combustion and gas coupling disasters in goaf, which provides theoretical and technical ideas for the prevention and control of such disasters and guarantees the safe and efficient mining of deep mines.
Every day we eat, drink and breathe minerals and trace elements, never giving a thought to what moves from the environment and into our bodies. For most of us this interaction with natural materials is harmless, perhaps even beneficial, supplying us with essential nutrients. However, for some, the interaction with minerals and trace elements can have devastating, even fatal effects. These interactions are the realm of medical geology, a fast-growing field that not only involves geoscientists but also medical, public health, veterinary, agricultural, environmental and biological scientists. Medical geology is the study of the effects of geologic materials and processes on human, animal and plant health, with both good and possibly hazardous results. In its broadest sense, medical geology studies exposure to or deficiency of trace elements and minerals; inhalation of ambient and anthropogenic mineral dusts and volcanic emissions; transportation, modification and concentration of organic compounds; and exposure to radionuclides, microbes and pathogens. The name of the discipline may be new, but the impacts of geologic materials on human health have been recognized for thousands of years. Mercury, cadmium and selenium levels were measured from preserved, 7,000-year-old human hair in the Karluk Archaeological Site in Kodiak, Alaska; although the health implications of these data are difficult to determine due to the possibility of addition or degradation over time. Inhaled soot particles were detected in preserved lung tissue from the Tyrolean Iceman, which is at least 5,000 years old.
Coal will be a dominant energy source in both developed and developing countries for at least the first half of the 21st century. Environmental problems associated with coal, before mining, during mining, in storage, during combustion, and postcombustion waste products are well known and are being addressed by ongoing research. The connection between potential environmental problems with human health is a fairly new field and requires the cooperation of both the geoscience and medical disciplines. Three research programs that illustrate this collaboration are described and used to present a range of human health problems that are potentially caused by coal. Domestic combustion of coal in China has, in some cases, severely affected human health. Both on a local and regional scale, human health has been adversely affected by coals containing arsenic, fluorine, selenium, and possibly, mercury. Balkan endemic nephropathy (BEN), an irreversible kidney disease of unknown origin, has been related to the proximity of Pliocene lignite deposits. The working hypothesis is that groundwater is leaching toxic organic compounds as it passes through the lignites and that these organics are then ingested by the local population contributing to this health problem. Human disease associated with coal mining mainly results from inhalation of particulate matter during the mining process. The disease is Coal Worker's Pneumoconiosis characterized by coal dust-induced lesions in the gas exchange regions of the lung; the coal worker's “black lung disease”.
Domestic coal combustion has had profound adverse effects on the health of millions of people worldwide. In China alone several hundred million people commonly burn raw coal in unvented stoves that permeate their homes with high levels of toxic metals and organic compounds. At least 3,000 people in Guizhou Province in southwest China are suffering from severe arsenic poisoning. The primary source of the arsenic appears to be consumption of chili peppers dried over fires fueled with high-arsenic coal. Coal samples in the region were found to contain up to 35,000 ppm arsenic. Chili peppers dried over high-arsenic coal fires adsorb 500 ppm arsenic on average. More than 10 million people in Guizhou Province and surrounding areas suffer from dental and skeletal fluorosis. The excess fluorine is caused by eating corn dried over burning briquettes made from high-fluorine coals and high-fluorine clay binders. Polycyclic aromatic hydrocarbons formed during coal combustion are believed to cause or contribute to the high incidence of esophageal and lung cancers in parts of China. Domestic coal combustion also has caused selenium poisoning and possibly mercury poisoning. Better knowledge of coal quality parameters may help to reduce some of these health problems. For example, information on concentrations and distributions of potentially toxic elements in coal may help delineate areas of a coal deposit to be avoided. Information on the modes of occurrence of these elements and the textural relations of the minerals and macerals in coal may help predict the behavior of the potentially toxic components during coal combustion.
For several years the Extended Service Laboratories of NCB Scientific Control have been carrying out experimental work on the oxidation of coal, with specific reference to the early detection of spontaneous heating, using a nnon-isothermal dynamic method. The first results of this work covering the oxidation of samples representing all British rank coals at ambient temperatures (20-200 degree C) were published (see p 505, abs. No. 13131, Ei 1972). This dealt with the common detector gases and concluded that all the available evidence indicated that carbon monoxide would be the most useful gas and give the earliest warning of an incipient heating; this has formed the basis of installations for continuous monitoring at a number ofpits. In continuation of present work other aspects were investigatd such as the use of oxidation inhibitors, the relative liability to oxidation of lithotype and maceral constituents of coal, further work on the products of oxidation, some experiments on the mechanism of the reaction, some comments on the oxidation characteristics of manufactured fuels, and the probable part played in the phenomenon by ″active centers″ .
Landsat TM data were used to detect surface and subsurface fires in the Jharia coalfield (JCF). TM-6 was useful for mapping subsurface fires and TM-5 and TM-7 were useful for mapping surface fires. The distribution pattern of fires was studied and their temperature and areal extents were estimated. A comparison of the distribution of surface and subsurface coal fires indicated that at some sites fires occur only on the surface or only in the subsurface, while at other sites both surface and subsurface fires occur.
Dry and barren higher temperature areas can be easily identified on satellite sensor images and these may serve as indicators of subsurface fires. This is illustrated with a set of processed Landsat Thematic Mapper images from the Jharia coalfield. The images show thermal anomalies due to subsurface fires and the associated reflectance aureoles. High DN-values in both the red and the near-infrared bands observed over the subsurface fire areas indicate ground conditions of dry soil, bare of vegetation. It is interpreted that heating due to subsurface fires has caused the drying of the soil, increasing its reflectance and rendering the soil locally unfit for vegetation. Thus, the thermally anomalous regions are barren.
The present study aims at developing a quick method for estimating the temperature of the ground surface directly above subsurface coal fires. Utility of TM6 and TM7-band data for temperature estimation is briefly reviewed. It is argued that temperature calculations of surface anomalies related to subsurface fires can only be done on the basis of 8-14 μm band data, due to the low temperatures involved. In the Jharia coalfield, it is noted that subsurface fires in various coal-mines are associated with surface thermal anomalies, as has also been confirmed by ground checks. It is inferred that the depth of subsurface coal fire ranges between 45-55 m, in most cases, which is in general agreement with the field data. Limitations of the method are indicated. -from Authors
Surface fires occur at a number of places in the Jharia coalfield and are high-temperature phenomena of relatively local extent. The use of Landsat Thematic Mapper (TM) shortwave infrared (SWIR) bands in estimating temperatures of high-temperature objects is briefly reviewed. Study of data of TM7 and TM5 bands indicate the existence of surface fires in the Jharia coalfield at 59 pixels and this was supported by limited field checks. Pixel-integrated temperatures of surface fire areas are estimated to be in the range of 217 C to 410 C. However, as these fires often do not occupy the whole pixel area, the pixelintegrated temperatures are less than the actual fire temperatures. The relation between spectral radiance and temperature is nonlinear. Therefore, radiant temperature in TM5 and TM7 can be used to estimate the subpixel area and temperature of surface fires (provided there is no band saturation). In the Jharia coalfield, the subpixel area of some of the surface fires has been found to range between 0.2 of a pixel (180m2) to 0.003 of a pixel (27m2). The subpixel temperature corresponding to these instances has been found to range 342 C to 731 C. The limitations and operational aspects of these techniques are indicated.
Results of investigations of the causes, behavior, and control of anthracite mine fires are applied to the problem of fires in refuse banks and ways of decreasing the possibility of such fires are suggested.
. In an area like the Jharia coalfield (JCF), where extensive and rapid underground and opencast mining is going on continuously, land-use studies are of paramount importance. This paper discusses the remote sensing-GIS techniques used for identification of various land-use classes on satellite imagery and enhanced products and identification of time-sequential changes in land-use patterns. The various land-use classes, recognised from satellite image data and field surveys, are dense vegetation, sparse vegetation, fire, opencast mining (coal), overburden dump, subsidence and barren wasteland, settlement, transport network, river and water pond. A number of image processing operations have been carried out on remote sensing data for enhancing land-use patterns. It has been found that Landsat TM false colour composites (FCC) of bands 4, 3 and 2; FCC of bands 7, 5 and 3; FCC of bands 5, 4 and 2 and ratio images provide very useful information for land-use mapping. The normalised difference vegetation index (NDVI) images have been used for vegetation studies. Image characters of various land-use classes on black-and-white and enhanced colour products have been tabulated. Land-use maps of selected windows have been prepared and examples given. Time-sequential surface changes that have occurred in the JCF since 1975 and particularly between November 1990 to November 1994 have been investigated. For change detection analysis, data manipulation in several steps involving preprocessing, processing and colour display have been carried out. Land-use changes have been detected by (a) image differencing, (b) image ratioing, and (c) differencing of NDVI images. It is inferred from the remote sensing images that extensive mining, establishment of communication networks, expansion of settlements, decrease in the vegetation cover etc., have remodelled the face of the JCF.
Sulfur content in coal is converted into sulfur oxides during combustion which, among other effects, causes acid rain. To reduce this environmental impact, precombustion coal desulfurization by means of nitric leaching has been researched. Two Spanish high-rank thermal coals have been treated at laboratory scale using nitric acid concentra tions of 20 and 30 wt %, at 90 °C, and with residence times ranging from 5 min to 2 h. The tests have been carried out at atmospheric pressure. The evolution of total sulfur, pyritic, sulfate, and organic forms of sulfur and also the modification of ashes, nitrogen, and calorific value have been determined by applying European and ASTM standard methods. Results demonstrate that pyritic and sulfate sulfur are practically eliminated but organic sulfur is affected very little by the treatment. Ash is reduced, mainly by dissolving cabonates and sulfides, while the nitrification produced is moderate whenever the times of treatment are controlled. The calorific value expressed per unit of organic carbon practically does not vary. The coal energy recovery has been calculated using the experimental data for mass recovery and calorific value and demonstrated that, in this precombustion desulfurization process, very small losses of the total coal energy are produced.
Coal-mine fires are causing loss of valuable assets in India. Fires in the Jharia coalfield in particular, have caused loss of scarce prime coking coal resources. Coal-mine fires endanger safety and stability and cause environmental hazards. Prior to nationalization, fire control measures were constrained because of a lack of resources. In the post-nationalization period, several effective steps have been taken to contain, control, and liquidate coal-mine fires. The government is keen on speedy implementation of fire control projects. Research and development for innovative methods has been a part of this endeavor.
Coal seams and culm banks associated with mine fires in the anthracite region of eastern Pennsylvania have been burning for decades. Many of the fires may have ignited by spontaneous combustion or by the burning of trash. Minerals associated with the combustion of anthracite form by the condensation of gas exhaled through surficial gas vents or anthracite smokers. A Pressure-Temperature (P-T) stability diagram is constructed for the condensation of orthorhombic sulfur from anthracite gas using Thermodynamic Loop Analysis (TL analysis). This method of analyzing chemical systems incorporates Kirchhoff's Law into a four step procedure structured around a closed thermodynamic cycle or thermodynamic loop. The four steps, referred to us The Four S S of Thermodynamic Loop Analysis, include: (1) Set Up—graphical characterization of the problem. (2) Sum—the application of thermodynamic principles. (3) Substitute—the use of materials data available from the literature, and (4) Solve—computation of one or more variables. The example presented demonstrates that thermodynamic loops can incorporate any number of polymorphic phase transformations. In addition, thermodynamic loop analysis is applicable to any geologic process involving the condensation of minerals from a gas. The stability diagram derived by TL analysis may have applicability in monitoring the release of sulfur gas into the atmosphere.
In 11 yr of sampling at 14 volcanoes in Guatemala, El Salvador, Nicaragua and Costa Rica, we have identified 47 minerals in incrustations depositing at approximately 100 different high temperature fumaroles. Most of these minerals are sulfates. The most abundant and most frequently found minerals are: sulfur, hematite, halite, sylvite, gypsum, ralstonite, anhydrite, thenardite and langbeinite. Incrustation suites deposit around fumaroles to produce a zonal pattern which is a response to the rapidly changing temperature and oxygen pressure at the mouth of the vent. The observed zoning pattern can be explained by the reaction of a volcanic gas composed of H2O, SO2, CO2, HC1 and HF, along with trace amounts of volatile cations, which interacts with the atmosphere and the fumarole wallrock. This interaction is aided at lower temperatures by the formation of sulfuric acid. The mineralogies and descriptions of incrustations at fumaroles at a large number of other volcanoes from every part of the world are similar to what we have found in Central America. Thus we believe our conclusions have general applicability.
Coal mining areas all over the world are often threatened by serious environmental hazards such as the occurrence of coal fires, land subsidence, etc. Coal fires burn away the natural non-renewable coal resources, locally raise the temperature of the area, emit polluting gases such as oxides of carbon, sulphur and nitrogen, and when present underground are even the cause of land subsidence. Mining-induced subsidences, on the other hand, cause horizontal and vertical movements in the land surface, and open cracks and fissures that serve as inlets for oxygen, which in turn aggravate the problem of coal fires. These inter-related phenomena often render the mining areas unfit for human inhabitation and the commercial exploitation of coal nearly impossible in some parts. In this study, satellite data acquired in three regions of the electromagnetic spectrum, namely optical, thermal and microwave, along with field data, are used to identify the areas affected by coal fires and land subsidence in a coalfield in north-west China. Data fusion techniques are used for an integrated analysis of this complex problem.
Pleistocene coal fires in north-western China, Energy for early man One Million Years of Anthropogenic Global Environmental Change
- S B Kroonenberg
- X Zhang
Kroonenberg, S.B., Zhang, X., 1997. Pleistocene coal fires in north-western China, Energy for early man. In: van Hinte, J.E. (Ed.), One Million Years of Anthropogenic Global Environmental Change. Proceedings of the ARA Symposium at the Royal Netherlands Academy of Art and Sciences (KNAW), Amster-dam, pp. 39 – 44.
Mineralogy of Arizona Brief History of BCCL
- J W Anthony
- S A Williams
- R A Bideaux
Anthony, J.W., Williams, S.A., Bideaux, R.A., 1977. Mineralogy of Arizona. University of Arizona Press, Tucson. Bharat Coking Coal Limited, 2003. Brief History of BCCL. Coal India, Koyla Bhavan, Dhanbad, pp. 1 – 3. http://bccl.nic.in/ About-us.htm, November. Cassells, C.J.S., van Genderen, J.L., 1995. Thermal modeling of underground coal fires in northern China: Remote Sensing in Action. Proceedings of the 21st Annual Conference of the Remote Sensing Society. University of Southampton, England, pp. 544 – 551.
China battles coal fires
- R Wingfield-Hayes
Wingfield-Hayes, R., 2000. China battles coal fires (August 3). BBC News Online and BBC News on FireNet (Electronic Pages for the British Fire Service), http://news.bbc.co.uk and http:// www.fire.org.uk (August 2001).
Centralia mine fire control failure Case Histories of Mine Reclamation and Regulation
- M Magnuson
Magnuson, M., 2003. Centralia mine fire control failure. In: Shannon, S. (Ed.), Case Histories of Mine Reclamation and Regulation, Environmental Technology for Mining. Robertson GeoConsul-tants, Reno, NV, pp. 1 – 2. http://technology.infomine.com/ enviromine/case _ hist/centralia/fire.html (November 2003).
Titanic Disaster” Senate report No. 806, pursuant to S. Res. 283, 62nd Congress, 2d session
- U S Senate
U.S. Senate, 1912. ''Titanic Disaster'' Senate report No. 806, pursuant to S. Res. 283, 62nd Congress, 2d session. U.S. Government Printing Office, Washington, D.C. http://www. titanicinquiry.org (August 2001).
Mineralogy Associated with Burning Anthracite Depos-its of Eastern Pennsylvania A propos de la formation de miné lors de la combustion des Charbons
- D M Lapham
- J H Barnes
- Downey Jr
- W F Finkelman
Lapham, D.M., Barnes, J.H., Downey Jr., W.F., Finkelman, R.B., 1980. Mineralogy Associated with Burning Anthracite Depos-its of Eastern Pennsylvania. Mineral Resource Report, vol. 78. Pennsylvania Geological Survey, Harrisburg. Limacher, D., 1963. A propos de la formation de miné lors de la combustion des Charbons. Societe Geologique du Nord. Annales 83 (Part 4), 287 – 288.
Underground Mine Fires Spark Residents' Fears
- L Glover
Glover, L., 1998. Underground Mine Fires Spark Residents' Fears. Tribune-Review, Greensburg, PA (May 3), A-1, A-10.
As Centralia's Fires Smolder, Residents Hang On. The Philadelphia Inquirer, Philadelphia, p. 1. March 18. Sierra Club, 2003. International People's Organizations Demand Global Fossil Fuel Phaseout
- M Schogol
Schogol, M., 2001. As Centralia's Fires Smolder, Residents Hang On. The Philadelphia Inquirer, Philadelphia, p. 1. March 18. Sierra Club, 2003. International People's Organizations Demand Global Fossil Fuel Phaseout, http://www.sierraclub.ca/national/ media/fossil-fuel-india-01-02-03.html, 1-2, (November 2003).
Managing underground mine fires: the case of Centralia, Pennsylvania. The Pennsylvania Geographer
- J Geissinger
Geissinger, J., 1990. Managing underground mine fires: the case of Centralia, Pennsylvania. The Pennsylvania Geographer 28 (2), 22 – 26.
Pollution in India may effect climate Topic: Mining. Allegheny County Health Department – Risk Information System, Pitts-burgh, Pennsylvania
- S Perkins
- D J Piposzar
- M Jones
Perkins, S., 2001. Pollution in India may effect climate. Science News 159 (1), 15. Piposzar, D.J., Jones, M., 2000. Topic: Mining. Allegheny County Health Department – Risk Information System, Pitts-burgh, Pennsylvania, pp. 1 – 2. http://achd@trfn.clpgh.org/ Environment/pollution.html (September 2001).
Environmental monitoring of coal fires in north China
- A Rosema
- J L Genderen
- Van
- H J W G Schalke
Rosema, A., Genderen, J.L. van, Schalke, H.J.W.G., 1993. Envi-ronmental monitoring of coal fires in north China. Project Iden-tification Mission Report, BCRS 93-29, ISBN 90 5411 1054.
Pleistocene coal fires in Xin-jiang, northwest China. Abstracts of the 30th International Geo-logic Congress
- X Zhang
- S B G B Kroonenberg
- T P Stracher
- Taylor
Zhang, X., Kroonenberg, S.B., 1996. Pleistocene coal fires in Xin-jiang, northwest China. Abstracts of the 30th International Geo-logic Congress, Beijing, China (August 4 – 14) 1, 457. G.B. Stracher, T.P. Taylor / International Journal of Coal Geology 59 (2004) 7–17
Na-tional Abandoned Land Inventory System (NALIS), Open-File Coal Fires Database Bureau of Abandoned Mines and Reclamation, Harrisburg. Pennsylvania Department of Environmental Protection, 2001d. DEP Geologist helps fight mine fires in India. Division of Mines
- G B Stracher
- T P Taylor
G.B. Stracher, T.P. Taylor / International Journal of Coal Geology 59 (2004) 7–17 Pennsylvania Department of Environmental Protection, 2001c. Na-tional Abandoned Land Inventory System (NALIS), Open-File Coal Fires Database (September 25). Bureau of Abandoned Mines and Reclamation, Harrisburg. Pennsylvania Department of Environmental Protection, 2001d. DEP Geologist helps fight mine fires in India. Division of Mines, Harrisburg, PA, p. 1. http://www.dep.state.pa.us (November 2001).
Ningxia photo gallery
- Z Vekerdy
Vekerdy, Z., 1999. Ningxia photo gallery, p. 1. http://www.itc.nl/ personal/vekerdy/NingPhoto _ e.htm (November 2003).
Human-induced climate change: Improved knowledge and continuing uncertainties
- Collins
Collins, W., 2000. Human-induced climate change: Improved knowledge and continuing uncertainties. American Geophysical Union Fall 2000 Meeting, AGU Press Conference Release No. 00-29A, December 17, San Francisco.
Coal Fire Web Page, Geophysical Institute, Uni-versity of Alaska-Fairbank
- A Prakash
Prakash, A., 2003. Coal Fire Web Page, Geophysical Institute, Uni-versity of Alaska-Fairbank. http://www.gi.alaska.edu/~prakash (November 2003).
Unseen Danger. University of Pennsylvania Press, Philadelphia; iUniverse
- D Dekok
DeKok, D., 1986. Unseen Danger. University of Pennsylvania Press, Philadelphia; iUniverse.com, New York.
Coal fire in an exposed seam (left) in the Jharia coalfield Excavated material (right) is backfilled to seal goafs (openings) left after mining. Smoke is high in particulate matter as well as oxides and dioxides of nitrogen, carbon, and sulfur Courtesy of Anupma Prakash
- Stracher
Fig. 4. Coal fire in an exposed seam (left) in the Jharia coalfield, India. Excavated material (right) is backfilled to seal goafs (openings) left after mining. Smoke is high in particulate matter as well as oxides and dioxides of nitrogen, carbon, and sulfur (Stracher et al., 2002). Courtesy of Anupma Prakash, Geophysical Institute, University of Alaska, Fairbanks. G.B. Stracher, T.P. Taylor / International Journal of Coal Geology 59 (2004) 7–17 1997
Handbook of the Coal Fire Monitoring and Management System (CoalMan), software manual. International Institute for Geo-Information Science and Earth Observation, the Netherlands
- Z Vekerdy
- A M Ten Katen
- H Veld
Vekerdy, Z., ten Katen, A.M., Veld, H., 2000. Handbook of the Coal Fire Monitoring and Management System (CoalMan), soft-ware manual. International Institute for Geo-Information Sci-ence and Earth Observation, the Netherlands. http:// www.itc.nl/personal/coalfire/index.html and references therein (November 2003).
Coal fires: A syn-opsis of their origin, remote sensing detection, and thermody-namics of sublimation
- G B Stracher
- T P Taylor
- A Prakash
Stracher, G.B., Taylor, T.P., Prakash, A., 2002. Coal fires: A syn-opsis of their origin, remote sensing detection, and thermody-namics of sublimation. In: Shannon, S. (Ed.), Case Histories of Mine Reclamation and Regulation, Environmental Technology for Mining. Robertson GeoConsultants, Reno, NV; Vancouver, B.C, pp. 1 – 7. http://technology.infomine.0com/enviromine/ case _ hist/coal%20fires/Stracher _ et _ al.html (January 2002).
Fugitive emissions from coal mining. The Australian Academy of Technological Sciences and Engineer-ing
- D J Williams
Williams, D.J., 1999. Fugitive emissions from coal mining. The Australian Academy of Technological Sciences and Engineer-ing, pp. 1 – 8. http://www.atse.org.au (December 2000).
Coal Bed Methane and Tertiary Geology of the Powder River Basin. Wyoming Geological Association 50th annual Field Conference Guidebook
- R Miller
Miller, R. (Ed.), Coal Bed Methane and Tertiary Geology of the Powder River Basin. Wyoming Geological Association 50th annual Field Conference Guidebook, Casper, WY., 211 – 229.
The minerals formed on burning heaps in the coal basin of Kladno
- Rost
Rost, R., 1937. The minerals formed on burning heaps in the coal basin of Kladno. Academy of Sciences Bohema, 47 – 53.
An occurrence of cryptohalite (ammonium fluosilicate)
- Christie
Managing underground mine fires: the case of Centralia, Pennsylvania
- Geissinger
Mineralogy Associated with Burning Anthracite Deposits of Eastern Pennsylvania
- Lapham