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The occurrence of surface strata movement in underground coal mining leads to the generation of numerous ground fissures, which not only damage the ecological environment but also disrupt building facilities, lead to airflow and easily trigger coal spontaneous combustion, induce geological disasters, posing a serious threat to people's lives, property, and mining production. Therefore, it is particularly important to quickly and accurately obtain the information of ground fissures and then study their distribution patterns and the law of spatial-temporal evolution. The traditional field investigation methods for identifying fissures have low efficiency. The rapid development of UAVs has brought an opportunity to address this issue. However, it also poses new questions, such as how to interpret numerous fissures and the distribution law of fissures with underground mining. Taking a mine in the Shenfu coalfield on the semi-desert aeolian sand surface as the research area, this paper studies the fissure recognition from UAV images by deep learning, fissure development law, as well as the mutual feed of surface condition corresponding to the under-ground mining progress. The results show that the DRs-UNet deep learning method can identify more than 85% of the fissures; however, due to the influence of seasonal vegetation changes and different fissure development stages, the continuity and integrity of fissure recognition methods need to be improved. Four fissure distribution patterns were found. In open-cut areas, arc-shaped fissures are frequently observed, displaying significant dimensions in terms of depth, length, and width. Within subsidence basins, central collapse areas exhibit fissures that form perpendicular to the direction of the working face. Along roadways, parallel or oblique fissures tend to develop at specific angles. In regions characterized by weak roof strata and depressed basins, abnormal reverse-"C"-shaped fissures emerge along the mining direction. The research results comprehensively demonstrate the process of automatically identifying ground fissures from UAV images as well as the spatial distribution patterns of fissures, which can provide technical support for the prediction of ground fissures, monitoring of geological hazards in mining areas, control of land environmental damage, and land ecological restoration. In the future, it is suggested that this method be applied to different mining areas and geotechnical contexts to enhance its applicability and effectiveness. [ABSTRACT FROM AUTHOR]

This paper summarizes the results of determination of the washability characteristics of anthracite coal from Vrska Cuka coal mine, Serbia. The effect of different coal size fractions has been studied through washability studies. In this study, float-sink experiments were carried out with the anthracite coal samples on (−19 + 9.5) mm, (−9.5 + 4.75) mm, (−4.75 + 2.36) mm, and (−2.36 + 0.6) mm size fractions. Two washability parameters, Index of Washability (IW) and Near Gravity Material Index (NGMI), were calculated and the results were compared. The IW and NGMI values indicated that the washability of different size fractions of anthracite coal was easy to relatively difficult to wash. The obtained values of IW showed that the order of coal washing ability by size fractions was as follows: (−9.5 + 4.75) mm, (−4.75 + 2.36) mm, (−2.36 + 0.6) mm, and (−19 + 9.5) mm. The NGMI values decreased with increasing specific gravity and decreasing particle size fractions. The minimum values of NGMI were achieved at density of 1650 kg/m3 and these values were 0.1322, 0.0695, 0.0677, and 0.0240, respectively. The results presented in this study indicate that washability of the anthracite coal is relatively easy and should be washed at a specific density of 1650 kg/m3. [ABSTRACT FROM AUTHOR]

High-temperature coal oxidation generates a substantial amount of CO and CO2, especially CO, rapidly, which is a primary factor leading to casualties. The oxygen concentration is the predominant factor affecting the high-temperature oxidation of coal, particularly in the generation of CO and CO2. Understanding the generation patterns and relationship characteristics of CO and CO2 under various oxygen concentrations is important for predicting high-temperature coal oxidation and ensuring personnel safety. The paper used TG–MS and FTIR to study the formation characteristics of isothermal oxidation of CO and CO2 in long-flame coal under different oxygen concentrations. The results indicate that there exists an optimal threshold for CO production when the oxygen concentration is about 9% during the isothermal temperature oxidation process at 200.00–350.00 °C. When the oxygen concentration is less than 13%, the influence of oxygen on CO2 production is weakened. As the temperature increases, the pattern of CO + CO2 production and CO/CO2 is reversed, with CO + CO2 increasing and CO/CO2 decreasing. The relationship between the total production of CO and CO2 and the loss of coal mass follows the function y = a + bx at the isothermal temperatures of 300.00 °C and 350.00 °C. An increase in oxygen concentration does not alter the linear relationship. In the isothermal oxidation process of coal, carbonyl and carboxyl groups are the key groups for CO and CO2 production. At 200.00 °C and 250.00 °C, carbonyl and carboxyl groups increase, and other groups are being converted to carbonyl and carboxyl groups while decomposing into CO and CO2. At 300.00 °C and 350.00 °C, the relative content of carboxyl groups decreases. The research findings play a fundamental role in coal mine disaster prevention and control. [ABSTRACT FROM AUTHOR]

Long-term accumulation of coal gangue hill has a high risk of spontaneous combustion, and the toxic and harmful gases emitted by spontaneous combustion seriously pollute the atmosphere. The key to managing the spontaneous combustion fire of coal gangue hill lies in the accurate measurement of fire source location. However, measuring the fire source location of surface coal gangue hill lacks experimental and empirical research. In this paper, an oxidation warming experiment was conducted on the coal gangue samples, and the law of radon gas exhalation from coal gangue under different temperatures was analyzed. At the same time, surface thermometry and isotope radon measurement were applied to measure the high-temperature areas inside the gangue hill, and the measurement results were compared. The experimental results show that as the temperature of gangue increases, the amount of radon gas exhalation in gangue shows a changing trend of rising first and then decreasing. The radon exhalation from coal gangue can be divided into three stages. In the I stage (30 ~ 100°C), the evaporation of pore water in coal gangue leads to the exhalation of radon in water, causing the increase of radon concentration; in the II stage (100 ~ 350°C), the coal gangue is pyrolyzed at high temperature, and a large amount of radon is exhalated from the closed pores; in the III stage (350 ~ 450°C), after the first two stages of radon release, the number of radon atoms in this stage decreases, leading to a rapid decrease of radon concentration. The field measurement results show that compared with the surface thermometry method, the isotope radon measurement method is less disturbed by external conditions, and the circled fire area is more accurate, which has essential theoretical significance and practical application value for the accurate measurement of fire source location in coal gangue hill. [ABSTRACT FROM AUTHOR]

As coal mining continues to progress to deeper levels, the temperature of the coal and rock continues to rise, causing coal spontaneous combustion disasters to become increasingly prominent. This paper studies the spontaneous combustion characteristics of coal in a high temperature environment before and after coal seam mining. The results were as follows: 1) Before mining, under the action of a constant ground temperature, the deep coal seam continuously and slowly released heat, and the higher the ground temperature was, the more heat was released. 2) During mining, after air entered, the coal samples initially maintained the continuous slow heat release. With the continuous entry of air, the coal samples were in an endothermic state. Higher ground temperature provides favorable conditions for coal sample heat absorption and coal spontaneous combustion. 3) When the local temperature rises, the associated hydroxyl groups in the coal sample are gradually activated and become free hydroxyl groups that are more prone to chemical reactions; the methyl groups are destroyed to generate more methylene groups; the aromatic hydrocarbons change significantly after oxygen supply. The long-term high ground temperature environment could lead to an increase in the chemical activity of coal. [ABSTRACT FROM AUTHOR]

Coal spontaneous combustion is a common problem faced by many coal mines. Spontaneous combustion in goaf releases a large amount of harmful gases, polluting the environment while causing a large amount of wasted resources, and even endangering the lives of workers. Due to the collapse of the interior of the mining area, it is impossible to measure the internal gas composition directly. In order to more accurately predict the spontaneous combustion state inside the mining airspace, this paper obtains the CO generation law and the main source of the working face through the combination of laboratory experiments and on-site monitoring. The CO concentration prediction model of the return corner is established with CO as the index gas. Finally, the safe concentration and warning concentration of the working face are calculated according to the example, which provides theoretical basis for the prediction of spontaneous combustion of coal. [ABSTRACT FROM AUTHOR]

The productivity of coal mines is seriously threatened by the combined disasters of gas and coal spontaneous combustion, which have become a common disaster mode. It is unclear how the gas and coal spontaneously combusted in the roof cutting along gob working face. The goal of this study is to identify the distinctive features of combined disasters in gob from two different types of roof cutting along working faces. In these two different types of roof cutting along gob working faces, the paper constructs the permeability model of the gob. The findings demonstrate that the data from the field experiment and the simulation results agree, which validates the simulation's reliability. In contrast to single sided roof cutting along gob working faces, double sided roof cutting along gob working faces clearly has a thinner oxidation zone. Moreover, the oxidation zone of the double side roof cutting along gob working faces is closer to the working face, which is located in the shallow area of the gob 50 m behind the working face. The gas explosion area and the coal spontaneous combustion area are divided by the double side roof cutting along gob working face, which reduces the risk of compound disasters. Important theoretical direction for the prevention and control of gob disasters in the roof cutting along gob working face is provided by the simulation results. [ABSTRACT FROM AUTHOR]

To accomplish various and efficient inhibitions of coal spontaneous combustion (CSC) and solve the safety hazards of CSC encountered in the production and operation of coal mining enterprises, inhibitors play an important role in the prevention and management of CSC. Herein, we report quercetin, which is selection as an antioxidant to prepare a composite solid lipid inhibitor. The concentration of the composite solid lipid inhibitor with the best inhibition effect on the active groups is selected by Fourier pressure infrared experiments, the change pattern of gas content and characteristic temperature released from coal samples during an oxidation process warming process was tested by using a programmed warming test system and simultaneous thermal analysis experiments, and finally, the inhibitory rate and combustion characteristic index were calculated. The results of the research showed that 10 mass% of quercetin had the most impact on the various groups, the highest inhibitor rate of the composite solid lipid inhibitor is 80.67% in the coal low-temperature oxidation process, compared to the raw coal, the heat release of coal treated with the composite solid lipid inhibitor was decreased by 507.65 J g−1, the maximum amount of heat emitted was lowered by 60%, and the flammability index was reduced by 56.4. A composite solid lipid inhibitor containing quercetin developed in this paper indicated high effectiveness in inhibiting CSC, which is vital for coping with the safety management of coal mine production. [ABSTRACT FROM AUTHOR]

Mine fires have always been one of the disasters that restrict coal mining in China and endanger the life safety of underground workers. The research and development of new fire prevention materials are undoubtedly important to ensure the safe and efficient production of modern mines. At present, the main inhibiting materials used are grout material, inert gas, retarding agent, foam, gel, and so on. In order to explore the current situation of coal spontaneous combustion (CSC) fire prevention, the existing fire prevention materials were reviewed and prospected from three aspects: physical, chemical, and physicochemical inhibition. The results show that, at present, most of the methods of physicochemical inhibition are used to inhibit CSC. Antioxidants have become popular chemical inhibitors in recent years. In terms of physical inhibition, emerging biomass-based green materials, including foams, gels, and gel foams, are used to inhibit CSC. In addition, CSC fire-fighting materials also have shortcomings, including incomplete research on the mechanism of material action, poor stability of inhibitory properties, low efficiency, and economic and environmental protection to be improved. The future research direction of fire-fighting materials will be based on theoretical experiments and numerical simulation to study the mechanism and characteristics of CSC and develop new directional suppression materials with physicochemical synergies. These findings have extremely important implications for improving materials designed to prevent CSC. [ABSTRACT FROM AUTHOR]

Atmospheric dustfall is solid air pollutant, has a major impact on the environment and human health. The objective of this study was to investigate the microscopic characteristics and sources of atmospheric dustfall in open-pit mining coal resource-based city in the arid desert area of Northwest China. The characteristics of size and shape factors, variation of shape factors with size distribution, types of individual particles, and sources of atmospheric dustfall, which were collected in the open-pit mining area and surrounding areas, were analyzed by X-ray diffraction (XRD) and scanning electron microscopy coupled with an energy dispersive spectrometer (SEM–EDS) combined with graphical method and shape factors. The results showed that the atmospheric dustfall in all functional areas was dominated by coarse-grained particles. The shape of the atmospheric dustfall deviated from spherical shape, and with decreasing particle size, the difference in shape factors increased in each functional area. The EDS and XRD analyses indicated the presence of 13 types of particles. The sources were mainly local and included soil dust from each functional area; industrial dust, construction dust, biogenic impurities, fossil fuel combustion, wear products of motor vehicle parts, motor vehicle exhaust emissions, and emission and excreta from biological activities in each functional area except the desert area; emissions from a steel plant in the industrial area; coal-associated ore, coal dust, coal gangue emissions, and emissions from the spontaneous combustion of coal gangue in the open-pit mining area; secondary chemical crystallization products in the industrial area and the open-pit mining area; dust generated by vehicles abrading the surface of the off-mine coal road and in the open-pit mining area. [ABSTRACT FROM AUTHOR]

Coal production and usage have been declining in the past decade due to the transition to renewable energies, environmental regulations to reduce environmental pollution due to direct coal combustion from coal-fired power stations, and administrative policies. This downturn has created tremendous challenges for the coal industry, and many states rely on revenue from coal mining. Developing new valorization routes with high coal demand is essential and using coal-derived materials to make engineered products does offer an eco-friendly, attractive, and value-added use. This paper presents a brief introduction to the extraction process to derive coal deposits, extracts, and residuals (CDERs) and a comprehensive characterization analysis to determine the suitability of CDERs as binders to produce an innovative construction material named the carbon-based structural unit (CSU). CDERs are used to prepare the CSU with or without using mesophase pitch (MP) as binders and selected CDERs are heat-treated and pressure-heat-treated to improve their binding capabilities. The performances of the CSU specimens are evaluated based on compressive strength, density, and thermal conductivity. The CSU specimens mixed with distilled residue (DR) to pyrolysis char (PC) ratio of 1:2 achieve a compressive strength of 54.85 MPa, which is higher than the compressive strength of 30 MPa of normal concrete. The CSU specimens with deposit (De) and tetralin insoluble (TI) require the addition of MP to obtain compressive strengths greater than 30 MPa. These CSU specimens possess a relatively low density of about 1 g/cm3 and low thermal conductivity of less than 0.25 W/m.K. • A combination of CDERs and commercial mesophase pitch (MP) can be used to produce the CSU. • CDERs can effectively replace 50% to 100% of MP to produce CSU with a compressive strength over 30 MPa. • All CSU specimens have thermal conductivity less than 0.25 W/m.K. • The CSU specimens possess a relatively low density of about 1 g/cm3. [ABSTRACT FROM AUTHOR]