Coal Development Research Articles

Research on the activity of dry-discharge coal-fired slag of different particle sizes and their performance as precursors of alkali-activated backfilling cementitious materials.

Coal-fired slag (CFS) is one of the significant solid wastes generated in the process of coal development and utilization. There are obvious differences in the properties of CFS with different particle sizes after high-temperature melting, which affects its quality and limits its high-value application, exacerbating the contradiction between development and the environment. This study investigates the activity differences among various graded CFS and establishes a relationship between CFS particle size and its performance. Utilizing CFS as precursor, we explored the relationship between the macroscopic properties of modified magnesium slag-activated CFS cementitious material (CFS·C) and CFS activity. Physicochemical and activity assessments reveal that the pozzolanic activity (K and API values) of CFS across different particle sizes initially increases before decreasing with size increment, correlating positively and negatively with the contents of Si, Al, and Fe oxides and loss on ignition (LOI), respectively. Specifically, CFS with particle sizes <0.15 mm (S1) exhibited the lowest activity, impacting the overall activity of CFS, whereas sizes between 0.3 ∼ 1.18 mm (S3) demonstrated the highest activity. The hydration heat, mechanical properties and microstructural analyses of CFS·C correspond with these activity trends. CFS·C of S1 displayed the worst mechanical properties (3.61 MPa), minimal cumulative exothermic and thermogravimetric total mass loss (13.42 J/g and 2.81%), and a loose and porous structure. Conversely, CFS·C of S3 presented the highest 28 d strength (7.21 MPa), maximal cumulative exothermic and thermogravimetric total mass loss (17.2 J/g and 6.45%), and a dense microstructure. Correlation analyses confirm that Si, Al, and Fe oxides content, LOI, pozzolanic activity, cumulative heat release and thermogravimetric total mass loss effectively predict 28 d strength trends. In conclusion, enhancing the proportion of CFS particles above 0.15 mm in the discharge process could significantly improve the overall cementitious performance of CFS and promote its high-value utilization, thereby mitigating associated emission pollution issues.

SKL-YOLOv8s: an object detection method for coal gangue flow

ABSTRACT Coal gangue sorting is a critical process in the clean production of coal. To address the issues of high computational complexity and deployment challenges in coal gangue object detection tasks, this paper proposes the SML-Neck structure, which incorporates the KernelWarehouse, LSK module, and MPDIoU to enhance YOLOv8s, resulting in the lightweight SKL-YOLOv8s model. Experiments were conducted using a self-constructed dataset comprising 14,790 images of coal gangue. The experimental results demonstrate that the proposed method surpasses YOLOv5s, YOLOv5×, YOLOv7, YOLOv7×, SSD, Faster-RCNN, RT-DETR-l, RT-DETR-x, and YOLOv8s in both accuracy and speed. Compared to the original model, it achieves a 60.9% reduction in computational cost, a 49.5% improvement in inference speed, and a decrease in information transmission loss from 2.6 to 0.6. The GradGAM visualization algorithm reveals that the improved model concentrates its attention more effectively on the entire target, enhancing the network’s ability to distinguish between objects and background. This method contributes to advancing clean coal development and provides a significant reference for coal gangue sorting based on object detection.

The improvement in the quality of 6–0 mm low-grade high-sulfur lignite via a compound dry separation bed

ABSTRACT The drastic decline in high-quality coal leads to the extensive development and utilization of low-rank coal in China. This study employs a compound dry separation bed to desulfurize and reduce the ash content of lignite. It focuses on the influence of multistage separation trough angles (θ), vibration frequency (f) and vibration amplitude (A) on the spatial distribution of the sulfur content and systematically analyses the particles migration behavior. The results indicate considerable differences in the sulfur content spatial distribution when θ = 45°, f = 26 hz, and A = 3.2 mm, and the degree of sulfur desorption reaches its maximum value (S sulfur = 1.18–1.21) meanwhile. Separation and quality enhancement tests conducted under optimal parameters achieved a clean coal yield of 70.29%, a sulfur content of 0.74%, an ash content of 7.29% and a probable error (E p ) of 0.08 g/cm3, demonstrating high-precision dry desulfurization and quality enhancement of lignite.

New Insights for Improving Low-Rank Coal Flotation Performance via Tetrahydrofurfuryl Ester Collectors

With the advancement of large-scale coal development and utilization, low-rank coal (LRC) is increasingly gaining prominence in the energy sector. Upgrading and ash reduction are key to the clean utilization of LRC. Flotation technology based on gas/liquid/solid interfacial interactions remains an effective way to recover combustible materials and realize the clean utilization of coal. The traditional collector, kerosene, has demonstrated its inefficiency and environmental toxicity in the flotation of LRC. In this study, four eco-friendly tetrahydrofuran ester compounds (THF-series) were investigated as novel collectors to improve the flotation performance of LRC. The flotation results showed that THF-series collectors were more effective than kerosene in enhancing the LRC flotation. Among these, tetrahydrofurfuryl butyrate (THFB) exhibited the best performance, with combustible material recovery and flotation perfection factors 79.79% and 15.05% higher than those of kerosene, respectively, at a dosage of 1.2 kg/t. Characterization results indicated that THF-series collectors rapidly adsorbed onto the LRC surface via hydrogen bonding, resulting in stronger hydrophobicity and higher electronegativity. High-speed camera and particle image velocimeter (PIV) observation further demonstrated that THFB dispersed more evenly in the flotation system, reducing the lateral movement of bubbles during their ascent, lowering the impact of bubble wakes on coal particles, and promoting the stable adhesion of bubbles to the LRC surface within a shorter time (16.65 ms), thereby preventing entrainment effects. This study provides new insights and options for the green and efficient flotation of LRC.

Novel approach to achieving net-zero carbon emissions for development and utilization of coal: Principle, methods, and cost estimation.

China's energy mix is coal-dominated; therefore, it is unrealistic for the country to achieve carbon neutrality through complete decarbonization. As the world's largest carbon emitter, achieving global carbon reduction targets necessitates that China develops low-carbon, clean, safe, and efficient coal development and utilization technologies. This study proposes a new low-carbon coal development and utilization method that integrates in-situ conversion mining and mineral carbonation (ICMMC) to realize coal mining and separation, in-situ backfilling, in-situ conversion, energy storage, and carbon sequestration. This method addresses the technical bottleneck of slow mineral carbonation (MC) reaction rates that hinder the application of low-cost carbon sequestration engineering by utilizing in-situ backfilling strips to construct an in-situ carbonation repository, alongside a complementary in-situ layered carbonation process to enhance carbon sequestration efficiency. Life cycle assessment and levelized cost of electricity (LCOE) are employed to analyze the competitiveness and necessity of this new method compared to coal-fired power with carbon capture and sequestration (CPCCS) and onshore wind power with energy storage (OWPES) technologies. The results indicate that the carbon emissions of the ICMMC (0.091kg/kWh) are much lower than those of traditional coal-fired power, and its LCOE of 0.463 CNY/kWh has a cost advantage compared to both CPCCS and OWPES over the next seven years. The findings suggest that the ICMMC system can partially replace CPCCS and OWPES, helping to reduce global carbon reduction pressure; it can serve as a transition technology that supports the decarbonization of energy systems in countries where coal is the primary energy source.

Research on the Correlation Between Overburden Rock Fracture Development and High-Energy Events During Deep Mining in Extremely Thick and Weakly Consolidated Strata for Regional Coal Mining Safety

The environmental damage and mining accidents caused by water inrush accidents and rock burst are two major problems faced in the safe and sustainable deep mining of extremely thick weakly cemented overlying strata. Mastering the fracture development law of the overlying strata, the evolution characteristics of high-energy events, and their correlative relationships in the deep mining of extremely thick weakly cemented overlying strata is the key to solving the above two problems, which is directly related to the sustainable development of regional coal and the protection of underground water resources in mining areas. By integrating the geological characteristics of extremely thick and weakly cemented overburdens in the Shaanxi–Inner Mongolia mining region of China, this study adopts methods such as field measurements, numerical simulations, and theoretical analyses to investigate the energy evolution characteristics of regional mining-induced tremors, as well as the correlation and mutual influence mechanisms between overburden fracture development and high-energy events. The results indicate a positive correlation between high-energy events and the development height of overburden fractures, suggesting that the occurrence of high-energy events can increase the height of overburden fracture development. Furthermore, high-energy events occurring before and after the “parallel joining” of two working faces have a relatively minor impact on the development height of overburden fractures, with an increase in the fracture-to-mining ratio (FMR) ranging from 1.56 to 2.78. In contrast, high-energy events occurring during the “parallel joining” of two working faces significantly affect the development height of overburden fractures, resulting in an FMR increase of 10.33 to 13.44, approximately one-third of the FMR measured through boreholes. The research results can provide a scientific basis for the safe and sustainable coal mining and the protection of underground water resources in similar mining areas with extremely thick weakly cemented overlying strata.

Characteristics of coal crack development and gas desorption in the stress affected zone of rock pillar

Coal (Rock) pillar retaining in the mining of protective layer would cause gas dynamic disaster in the protected layer. Based on the gas geological conditions of the two-layer coal seam in Jinhe Coal Mine of Yaojie Mining District, the stress evolution law of coal seam in the rock pillar affected area was studied by theoretical analysis and numerical simulation, and the crack development law of coal seam in different loading stages under conventional triaxial loading was studied by CT scanning technology. With the analysis of the stress evolution and crack development of coal in rock pillar affected area, the gas extraction effect under different stress states and the gas desorption law after pressure relief antireflection were studied on site. The results showed that the stress of coal in the rock pillar affected area is in the approximate elastic stage of the conventional triaxial stress-strain curve, and the cracks of coal are mainly closed at this stage. Meanwhile, the increase of stress leaded to the decrease of coal permeability and the poor gas extraction effect. CT scanning tests under conventional triaxial loading were carried out in the laboratory, and three-dimensional visual models of coal sample cracks were constructed at different loading stages. When loading to the linear elastic stage, the crack volume and surface area were reduced by 74% and 71% compared with the ones in initial state. At the same time, the expression between stress σ and crack density T was further established. After comprehensive control measures such as intensive drilling discharge, presplitting blasting and coal water injection were taken to the coal in rock pillar affected area, the crack density T could reach the crack development level of the conventional triaxial loading softening stage, realizing the crack development of the coal under low stress. The enclosed gas in front of the coal could desorption flow during the roadway driving. And the predict index value K1 also decreased from 0.57 mL/(g·min1/2) to 0.17 mL/(g·min1/2) continuously. The safety of coal roadway in rock pillar affected area was realized, and the accuracy of numerical simulation and laboratory test results was verified, which had certain reference significance for coal roadway excavation under this similar conditions.

Improving microstructure and frictional wear behavior of plasma cladding FeCoCrNiMo high-entropy alloy layers by annealing treatment

The application of high-strength, wear-resistant materials for the restoration of large-scale coal development equipment is pivotal in ensuring efficient production and energy conservation within the industry. In this study, FeCoCrNiMo high-entropy alloy (HEA) cladding layers were fabricated on Q235 steel using plasma cladding techniques and subsequently subjected to annealing at 700°C, 800°C, 900°C, and 1000°C, respectively. The microstructural evolution, hardness, and wear resistance of the annealed cladding layers were thoroughly investigated. The results indicated that the microstructure of FeCoCrNiMo HEAs predominantly consisted of alternating eutectic formations of FCC, σ, and μ phases. The content of σ phase initially increased and then decreased with the increase of the annealing temperature. As the σ phase increased, both the microhardness and wear resistance were enhanced. Compared to HEA layers annealed at other temperatures, the HEA layer annealed at 900°C exhibited the highest hardness (700 HV). The wear mechanisms of the cladding layers were predominantly characterized by oxidative wear and adhesive wear. Notably, a stable oxide film was observed on the surface of the cladding layer treated at 900°C, with a wear rate as low as 1.27×10−7 mm3N−1mm−1. This study provided a technological basis and theoretical support for the repair of coal equipment.

Study on low-rank coal flotation collector screening and performance based on molecular polarity index.

Extensive studies using a trial-and-error approach have been conducted on low-rank coal flotation collectors. However, screening efficient collectors remains a considerable challenge due to the lack of suitable screening principles. It has proven that polar compounds such as carboxylic acids and esters are effective collectors for low-rank coal flotation. In this work, the effects of carboxylic acid, alcohol, and methyl ester on the floatability of low-rank coal were compared, the flotation performance of the polar collector was evaluated with theoretical calculations, a suitable evaluation parameter was determined and a screening principle based on this parameter was determined. The results show that the enhancement effects of polar collectors on low-rank coal floatability follow the order of methyl decanoate > methyl laurate > methyl octanoate > sec-octanol > methyl oleate (or methyl oleate > sec-octanol) > n-octanoic acid. Compared with the molecular polarity index, the hydrophobicity indices log P and dipole moment cannot be used to accurately evaluate different types of collectors and the same type of collectors, respectively. At room temperature, liquid polar compounds with molecular polarity indices in the range of 6.0 ~ 8.0kcal/mol effectively enhance the floatability of low-rank coal. The molecular polarity index of the collector is used for the first time to screen effective collectors of low-rank coal in this work. This parameter is anticipated to be highly important for the development and research of low-rank coal and other mineral collectors. To obtain reasonable and accurate molecular structure, geometry optimization and frequency calculations of the studied collectors were conducted via the Gaussian 09 software package based on density functional theory at the B3LYP/6-311 + G (d, p) level. The integral equation formalism for the polarizable continuum model (IEF-PCM) was utilized with water as the solvent (dielectric constant = 78.36, T = 298K) for all the calculations. Then, the atomic charge distributions (MPA and NPA) and electrostatic potential maps, the dipole moment and molecular polarity index, and the log P and water solubilities of studied collectors were shown or calculated by Gauss View 5.0, Mutiwfn program and website ( https://www.molsoft.com/mprop/mprop.cgi ), respectively.

Hydrogeochemical evolution patterns of diverse water bodies in mining area driven by large-scale open-pit combined underground mining-taking Pingshuo Mining Area as an example

Large-scale open-pit combined underground mining activities (OUM) not only reshape the original topography, geomorphology, and hydrogeochemical environment of the mining area, but also alter the regional water cycle conditions. However, due to the complexity arising from the coexistence of two coal mining technologies (open-pit and underground mining), the hydrological environmental effects remain unclear. Here, we selected the Pingshuo Mining Area in China, one of the most modernized open-pit combined underground mining regions, as the focus of our research. We comprehensively employed mathematical statistics, Piper diagram, Gibbs model, ion combination ratio, principal component analysis and other methods to compare the hydrochemistry and isotope data of different water bodies before (2006) and after (2021) large-scale mining. The changing patterns of hydrochemical characteristics of different water bodies and their main controlling factors in mining area driven by OUM were analyzed and identified, revealing the water circulation mechanism under the background of long-term coal mining. The results showed that: (1) The chemical composition of water has changed greatly due to large-scale coal mining. The hydrochemical types of Quaternary and Permian-Carboniferous aquifers shifted from predominantly HCO3-Ca·Mg before intensive mining to primarily HCO3·SO4-Ca·Mg, HCO3-Na, HCO3·SO4-Na·Mg, and HCO3·SO4-Ca·Mg, HCO3-Ca·Na, HCO3·SO4-Mg·Ca post-mining. Variations in the hydrochemical types of surface water were found to be complex and diverse. (2) Coal mining activities promote the dissolution of silicate rock and sodium-bearing evaporites, enhancing the strength and scale of positive alternating adsorption of cations. The oxidation of pyrite, dissolution of silicate weathering, and the leaching of coal gangue were identified as the main reasons for the significant increase of SO42−, while decarbonation in confined aquifers led to a decrease in HCO3−. (3) Results from the principal component analysis and stable isotopes demonstrated the hydraulic connection among surface water, Quaternary aquifers, and Permian-Carboniferous aquifers induced by long-term OUM. The research findings provide a reference basis for the coordinated development of coal and water in the Pingshuo Mining Area and other open-pit combined underground mining areas.

Experimental investigation of combustion characteristics of ammonia with sub-bituminous coal in a pilot circulating fluidized bed combustor

Recent research on power plant technology has focused on employing ammonia as a supplementary fuel with coal to reduce carbon dioxide emissions from coal-fired power plants. However, most of this research has concentrated on pulverized coal systems, with fewer studies on circulating fluidized bed (CFB) combustion systems. Additionally, no research has analyzed combustion and environmental impacts under varying operational conditions with a fixed ammonia co-firing ratio. This study advances the development of coal–ammonia co-firing technology for use in CFB power plants by conducting experiments on a 50 kWth CFB combustion test rig. The co-firing characteristics were evaluated by progressively increasing the ammonia co-combustion rate to 20%, calculated on a high calorific value basis relative to sole coal combustion. Furthermore, this research explored the variations in operational conditions during 20% ammonia co-firing to assess their effects on the temperature distribution within the combustor and the composition of the exhaust gases. The findings elucidate the combustion efficiency, thermal behavior, and emission profiles associated with coal–ammonia co-firing, thereby guiding the optimization of operational strategies to minimize the carbon footprint of CFB power plants.

Evolution of macromolecular structure during coal oxidation via FTIR, XRD and Raman

The analysis of the macromolecular structure and morphology in coal during oxidation is the basis to explore the mechanism of spontaneous combustion. To explore the evolutionary rules of coal macromolecular structure during oxidation, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Raman Spectroscopy (Raman) were employed to analyze the coal samples with different oxidation degrees. The results revealed that the oxidation action led to the decrease of the aliphatic structures and aromatic hydroxyl groups in coal, while promoting the formation of oxygen-containing functional groups and aromatic structures. It also led to a relative increase of free hydroxyl groups linked to hydrogen bonds. The aromatic layer spacing (d002) decreased with increasing oxidation degree, while the microcrystal stacking height (Lc), the aromatic layer diameter (La), the average number of crystal stacking layers (n) generally increased. It indicated that small aromatic ring molecules in coal could undergo continuous polymerization during oxidation to form a single aromatic layer structure. The variation of Raman spectrum parameters exhibited a consistent decreasing trend in WD/WG, ID/IG, AD/AG, and A(GR+SL)/AG value, indicating an increase in the vibration of sp2 hybridization carbon atoms within the lattice structure of coal. Conversely, PG-D, AS/AD and A(GR+VL+VR)/AD value increased overall, suggesting that small aromatic rings decreased in content during oxidation while polymerizing into larger aromatic rings. The coal structure underwent a brief stage of disordered evolution during oxidation, followed by removal of impurity structures and condensation of aromatic structures due to increasing oxidation temperatures, ultimately leading to a highly ordered crystalline state. The oxidation process significantly influenced the development of coal's aromatic structure, particularly in less metamorphic coal. The research findings provide a theoretical basis for analyzing the underlying mechanism behind spontaneous combustion induced by coal oxidation.

Dynamics of carbon sequestration in vegetation affected by large-scale surface coal mining and subsequent restoration

Surface coal development activities include mining and ecological restoration, which significantly impact regional carbon sinks. Quantifying the dynamic impacts on carbon sequestration in vegetation (VCS) during coal development activities has been challenging. Here, we provided a novel approach to assess the dynamics of VCS affected by large-scale surface coal mining and subsequent restoration. This approach effectively overcomes the limitations imposed by the lack of finer scale and long-time series data through scale transformation. We found that mining activities directly decreased VCS by 384.63 Gg CO2, while restoration activities directly increased 192.51 Gg CO2 between 2001 and 2022. As of 2022, the deficit in VCS at the mining areas still had 1966.7 Gg CO2. The study highlights that complete restoration requires compensating not only for the loss in the year of destruction but also for the ongoing accumulation of losses throughout the mining lifecycle. The findings deepen insights into the intricate relationship between coal resource development and ecological environmental protection.

Ecological disturbance effects of surface vegetation during coal mining in arid regions of Western China.

Coal mining in arid western regions is damaging the fragile ecology, causing problems such as surface damage, vegetation destruction, and soil erosion. These issues are obstacles to the development of green coal, as mining activities can disrupt the distribution of surface vegetation, leading to its spread outside the mining area and affecting surrounding areas. Based on Landsat data, the binary pixel model was used to calculate the vegetation coverage (FVC) in mining area from 2005 to 2021. Through vegetation coverage classification and regression trend analysis, the temporal and spatial changes and evolution trends of vegetation disturbance caused by coal mining and climate were analyzed. Correlation analysis revealed the range of ecological disturbance caused by coal mining at the coal mine scale and mining area scale. The results show that the vegetation coverage of the mining area showed a decreasing trend from 2005 to 2021. Winter and spring precipitation was the primary factor affecting vegetation growth in the area, while coal mining had indirect and secondary effects on vegetation. Human activities played a significant role in improving vegetation, and between 2015 and 2018, the area of vegetation improvement increased by 133.41% compared to that of 2009-2014. Compared to the reference area, the impact range of vegetation disturbance in the mining area is 2.5-5 km, while the impact range of vegetation disturbance in the coal mine is less than 500 m. Therefore, this study provides a theoretical basis for studying the impact of mining activities on vegetation and boundary identification.

A Water Resource Consumption Control Method for Energy Development Bases Based on IoT Technology and Energy–Water Correlation Law

Abstract To achieve the rational development and utilization of water resources in energy development bases and sustainable economic and social development, research is conducted on the control method of water resource consumption in energy development bases based on the law of energy–water correlation. Using Internet of Things technology to collect water resource consumption data from energy development bases, based on the results of data collection, taking Shanxi Coal Development Base as the research area, based on the objective relationship between energy and water, a multiregion input–output model and linear programming model are established, with objective functions and constraints set to achieve water resource consumption control in energy development bases. Under the dual constraint scenario of energy con-servation and water conservation, the optimization effect of the industrial structure of the water resource carrying capacity level in the research area is explored. The outcomes show that the water resource in the research area can bear 1,949.58 billion Yuan for 22.0336 million people. The water resources holding capacity is at the general level. Based on the limitations of energy consumption, raising the share of the mining sector and decreasing the share of the industrial and commercial service sectors can minimize the overall consumption of energy and water resources while ensuring the growth of the local economy. Reducing the extent of agricultural expansion supports both water conservation and regional economic growth because water resource consumption is constrained. A clear difference in the production and utilization effect of energy resource per unit will result from the direction difference in structural adjustment of the mining industry, which is based on the dual restrictions of energy–water resource.

Numerical simulation study on the evolution law of mechanical properties of different metamorphic coals after heat treatment.

In order to study the effect of temperature on the structure and mechanical properties of coal with different metamorphic degree. Three coal samples with varying degrees of metamorphism were chosen for analysis. The discrete element software PFC2D is used to simulate the heat treatment and compression of coal. The findings indicate that during the heating process, low-order coal exhibits noticeable thermal cracks at an early stage, while thermal crack development in middle-order coal is concentrated in the later stages. In contrast, high-order coal demonstrates a more stable macroscopic structure. The strength and stiffness of low rank coal show the lowest value and decrease significantly within 135°C. However, the strength and stiffness of medium rank coal decrease significantly after 135°C. The changes of mechanical properties and damage modes of coal caused by thermal damage are often ignored, which may lead to the deviation of design and research results from the actual situation. Therefore, this study is of great significance to the prevention and control of coal mine disasters.

New insights into dynamic disaster monitoring through asynchronous deformation induced coal-gas outburst mechanism of tectonic and raw coal seams

The coalbed methane energy resources waste, environmental pollution and miner's health remain challenging problems in worldwide mining operations accompanied by coal-gas outbursts; thus, the safe and efficient yield of these resources plays a vital role in the world's energy market. The tectonic coal development is a significant geological feature of coal and gas outburst sites, and the study of coal and gas outburst mechanism should be based on more precise geological occurrence characteristics. In this paper, the geological characteristics of coal and gas outburst sites were analyzed. The failure law of coal body under the stratified occurrence of tectonic coal and raw coal seam with different thickness was studied. The mechanical equilibrium equation of non-synchronous deformation of tectonic coal and raw coal was constructed, the initiation criterion of coal and gas outburst was established based on the support body model, and a case study was carried out. The results show that with the thickness increase of the tectonic coal seam, the peak displacement of the driving face increases. The outburst start-up and development of coal and gas outburst, coal and gas extrusion outburst and coal and gas collapse outburst were deeply analyzed, as well as the internal reasons of the occurrence of coal-gas outburst portent are explained, based on the support body model. The development process from the start to the end of coal and gas outburst is revealed, and a new perspective is proposed for the prevention and control of coal and gas outburst: improving the strength of support body is also of great significance for the prevention and control of coal and gas outburst.

Study on precursor features of coal and rock loading failure based on difference network

In order to reveal the spatio-temporal precursor features of coal and rock loading failure, and accurately identify the critical state of coal and rock failure, the development of coal and rock loading failure is regarded as the spatio-temporal evolution dynamical process of the complex network system, the spatio-temporal evolution dynamical characteristics of coal and rock dynamic disasters are analyzed. The precursor features indicators I(t) and Ia(t) of the coal and rock failure based on the difference network are proposed, Brazilian splitting experiments of different types of coal and rock are carried out. Combined with the damage theory, the load model of coal and rock damage characterization based Ia(t) is established. The results show that when the coal-rock system is in the warning critical period, the damage is accelerated, with high potential energy, low rebound and weak robustness, which is reflected in the acoustic emission (AE) and electromagnetic radiation (EMR) data at different spatial monitoring points. When the coal-rock system is in the stable stage, the structure of the correlation network at adjacent moment is similar, and the number of edges in the difference network is small. While when coal or rock is about to fracture, the correlation network at adjacent moment has great structure differences, and there are many edges in the difference network. I(t) and Ia(t) synthesize the signal characteristics of different spatial monitoring points, and reflect the spatio-temporal evolution process and damage state of coal and rock. The damage characterization load based on Ia(t) is in good agreement with the measured load, and the correlation coefficients between the measured load and the calculated load based on Ia(t) of most rock samples are more than 0.80. The research results can be used as the precursor features of coal and rock failure, and have certain significance for the early warning of coal and rock dynamic disasters.

Coal Gasification Technology to Support the Energy Transition: Opportunities and Challenges

Indonesia is a country that has quite abundant coal reserves. Coal reserves are most widely spread in Kalimantan and Sumatra and several other areas. When the production of other fossil energy such as petroleum decreases, the use of coal energy sources actually increases. However, coal is also known as a dirty fossil fuel because its use has a negative impact on the environment. This needs to be paid attention to in order to develop innovations in using coal that are more environmentally friendly, so that they can also support the energy transition to achieve the Net Zero Emission (NZE) target. The energy transition is a process that must be carried out by countries in the world to reduce carbon emissions which can cause climate change and global warming. The agreement on the energy transition aims to increase the use of clean energy. The energy transition does not have to eliminate coal. However, coal requires innovation for more environmentally friendly use. One of the environmentally friendly coal utilization technologies is coal gasification. In the road map for the development and utilization of coal by applying environmentally friendly technology through coal gasification, one of which is the coal development program to produce methanol and DME.

Potential impacts of coal mining activities on nitrate sources and transport in a karst river basin in southwest China.

Typical sources of nitrate pollution in the fragile ecological environment of karst areas, such as agricultural production activities and domestic sewage, have long attracted serious concern. However, coal development can play an equally significant role in releasing the nitrogen fixed in coal into surface watersheds in the form of nitrate, nitrite, or ammonia, consequently threatening the water quality of surface water systems in mining areas. In this study, a typical karst surface watershed system affected by coal mining activities was selected for an in-depth investigation with the aim of realistically assessing the potential contribution of coal mining to nitrogen pollution. The results reveal increasingly concerning nitrate pollution from August 2020 to November 2021 in the Huatan River watershed under the influence of anthropogenic activities, especially mining development and agricultural production. Given that the nitrogen and oxygen isotope compositions of nitrate do not support the presence of denitrification, the variation in the NO3-/Cl- ratio and the relatively stable Cl- concentration may be a reflection of nitrification. Although the leaching of atmospheric precipitation on the strata in the basin promoted the release of nitrogen associated with coal mining, the higher rate of nitrogen cycling in the oligotrophic mine water environment limited the contribution of coal mining to nitrogen pollution in the surface watershed. Specifically, the contribution of coal mining activities to nitrogen pollution in surface karst river is mainly NH4+-N, which contributes 10% or less to the nitrate input to the waters of the Huatan River. The findings thus highlight the necessity of further uncovering the geochemical cycling process of nitrogen during the transport of mine water in the coal mining environment.