Development Of Coal Resources Research Articles

Geochemistry Characteristics and Coal-Forming Environments of Carboniferous–Permian Coal: An Example from the Zhaokai Mine, Ningwu Coalfield, Northern China

In order to study the geochemical characteristics of coal in the Ningwu Coalfield of Shanxi Province and the coal-forming environments reflected by it, a detailed geochemical study was carried out on the No. 5 coal of the Zhaokai Mine. The results show that the content of major-element oxides SiO2 and Al2O3 is high. The trace elements Ni, Nb, Mo, Cd, Sn, Hf, Ta, W, Th, and U are slightly enriched, while the elements Li and Zr are enriched, indicating an overall LREY enrichment type in the samples. Elemental parameters suggest that the sedimentary environment in the study area is continental sedimentary, and the whole environment is reductive. The macerals in the coal samples are mainly vitrinite, with an average vitrinite reflectance (Ro) of 0.744%. The distribution range of n-alkanes in the coal samples is from n-C14~n-C32, with the main peak carbons being n-C24 and n-C25, showing the post-single-peak type distribution pattern. The average odd–even predominance index (OEP) is 0.40, the average of the light and heavy hydrocarbons ratio (∑C21−/∑C22+) is 0.42, and the average of Pr/n-C17 and Ph/n-C18 are 1.08 and 0.23, respectively. The coal samples also contain various aromatic hydrocarbons, mainly from the naphthalene- and phenanthrene-series compounds. Biomarker parameters indicate that the parent material of the coal samples in the study area is mainly continental higher plants. The maturity is low, and the coal-forming environment is a reduction environment. This study of the No. 5 coal’s geochemical characteristics has laid a foundation for the efficient, green, and comprehensive exploitation of coal resources in this region, and has also provided an important basis for the sustainable development of coal resources.

Mechanical properties and piecewise constitutive model of fine sandstone in mining area of western China

Owing to the differences in sedimentary environments in the mining areas of western China, the mechanical properties of rocks in this region are significantly different from those in the central and eastern regions. Therefore, uniaxial cyclic loading-unloading tests were conducted on fine sandstone found in many roof rocks to study the evolution laws of mechanical properties, deformation characteristics, acoustic emission (AE) parameters, and energy under cyclic loading and unloading conditions. The accumulated residual strain, dissipative energy, acoustic emission cumulative ringing counts, and cumulative energy were introduced to characterize the degree of rock damage. Based on this, a piecewise constitutive model was established for fine sandstone. The results indicate that (1) the cumulative ringing counts and cumulative energy of the AE increase in a stepwise manner with an increase in the cyclic loading and unloading times. Still, there is a sudden increase in the plastic failure and post-peak failure stages. (2) The fine sandstone specimens’ input energy, elastic energy, and dissipative energy density increased nonlinearly during the cyclic loading tests. Owing to the closure of the primary pores in the microfracture compaction stage, dominant matrix deformation in the elastic deformation stage, and development and expansion of cracks in the plastic failure stage, with an increase in the cyclic loading and unloading times, the dissipative energy ratio first decreased and then increased. (3) Based on the tangential modulus, residual strain, and Felicity ratio, fine sandstone’s cyclic loading and unloading stress-strain curves were divided into microfracture compaction, elastic deformation, and plastic failure stages. The piecewise constitutive model of fine sandstone constructed with accumulated AE energy was the closest to the real stress-strain curve of the rock, and the deviations of the peak stress and peak strain from the actual situation were 0.52% and 0.84%, respectively. The research results can provide theoretical support for identifying the degree of rock damage in western mining areas and ensure the safe and efficient development of coal resources.

Study on the safety distance determination model for natural gas wells in Ordos Basin subsidence areas of coal mining

To optimize the safe distance between coal mining faces and natural gas wells, with the Ordos Basin as the engineering background for the intersectional development of natural gas and coal resources, a Gaussian function equation for subsidence curves under complete mining was proposed based on the probability integral method, and a model was constructed to determine the coordinated mining safety distance between coal mining faces and natural gas wells. Based on the distributed optical fiber monitoring principle of the BOTDR technology, on-site monitoring of the simulated monitoring well GX1 within the safety distance was carried out. The results indicated that the maximum strain change values of the outer casing and inner production casing of the simulated monitoring well GX1 were 836 με and 766 με, respectively, far less than the maximum ultimate tensile strain value of the overlying rock at the same depth position. Furthermore, the casing structure possessed ample resistance capability, ensuring no noticeable deformation occurred. Through comparison, it was found that the discriminant model reduced the reserved safety distance between the coal mining working face and the natural gas well by 58% compared with the currently used avoidance method of the surface subsidence boundary, liberated coal resources, and achieved a "win–win" situation of the coordinated mining of natural gas resources and coal resources. It can reasonably adjust the coordinated mining problem without a natural gas-coal co-mining mechanism, provide a new method for the layout of natural gas wells in gas-coal overlapping areas, and provide new ideas for the coordinated mining of coal-related associated resources.

Characterization of the Porosity and Permeability of Gasified Coal in UCG Process: An Experimental and Simulation Study.

Under the environment of energy transformation in the world, underground coal gasification (UCG) is an important means to realize the green and clean development and utilization of deep coal resources. Due to a series of complex chemical reactions, the porosity and permeability of coal have changed significantly. Accurately characterizing the porosity and permeability of gasified coal is of great significance to the field screening, production control, and numerical simulation of the UCG project. In this study, the porosity and permeability of coal samples are studied by means of experiment and numerical simulation, respectively. Subsequently, a predictive model for porosity-permeability relationships is established with its feasibility verified by comparison to previous experimental results. In the experimental phase, a nitrogen atmosphere simulates pyrolysis conditions, while an air atmosphere replicates gasification environments. Scanning electron microscopy (SEM) is employed to characterize the porosity and permeability changes in heat-treated coal samples. For the numerical simulation component, through the analysis of UCG physical and chemical processes, the UCG three-dimensional numerical simulation model at the field scale is established by using CMG-STARS simulation software, and the changes in porosity and permeability during coal gasification are analyzed. The result shows that following heat treatment experiments, the average equivalent pore diameter of the coal sample increases to 0.748 μm, an increase of 493.65%, with general expansion observed across pore diameters. Additionally, the average shape factor decreases from 3.20 to 2.584, suggesting enhanced roundness in the porosity characteristics. Post-heat treatment observations reveal an increase in pore quantity alongside expanded diameters, thus indicating significant alterations in pore structure. Through 3D UCG numerical simulation, the evolution of coal porosity and permeability is categorized into three distinct stages: 25-320, 320-750, and 750-1000 °C. This categorization reflects the evolutionary model of the pore structure during coal gasification. In the predictive model, the permeability of coal during pyrolysis and gasification is represented as an exponential function of the porosity. As the porosity increases, the growth rate of permeability initially rises slowly before gradually accelerating. Furthermore, it is observed that in the gasification process, the increase in coal permeability with respect to porosity is less pronounced than that observed during pyrolysis. The findings presented in this paper hold significant implications for field screening, process design, and optimization of UCG applications.

Response surface optimization design of coal-derived activated carbon with high capacitance performance using decreased amount of KOH activated agent

ABSTRACT Coal-derived activated carbon (CAC) is considered as an important direction for high-economic utilization and sustainable development of coal resources. However, this process is limited due to the overall promotion of environmental protection. In this paper, CAC was prepared by H2O activation combined with KOH solution impregnation re-activation of Taixi anthracite. The addition of a small amount of KOH (less than 60 wt% of CACI) significantly promoted the pore formation of CAC, and in addition, a high CAC yield (about 56%) was also obtained. The effects of impregnation conditions of KOH on the specific capacitance of CACII were analyzed by response surface optimization, and the optimal preparation parameters (12.5 mol/L, 82°C and 8.3 h) were obtained. The specific capacitance of CACII prepared under this optimal condition is 334.2 F/g because it has a large specific surface area of 1909.92 m2/g and a defect degree greater than 1. KOH activation improves the wettability of CACII by introducing hydroxy groups. The assembled CACII//CACII symmetrical device also has a higher specific capacitance (224.3 F/g at 0.5 A/g) than the commercial YP-50F. At the same time, it also has a high energy density of 31.15 Wh/kg at 500 W/kg. The physical-chemical multi-stage activation method can significantly reduce the consumption of corrosive chemical reagents in the preparation of CAC, which greatly relieves the pressure of equipment and environment, and lays the foundation for the industrial production of CAC.

Numerical Simulation and Engineering Application of Temporary Stress Field in Coal Mine Roadway

The imbalance between excavation and mining is significant as it restricts the efficient development of coal resources. Slow tunneling speed is primarily due to the inability to concurrently conduct excavation and permanent support operations, and temporary support is considered a key solution to this problem. However, the mechanism by which temporary support affects the surrounding rock in unsupported are as remains unclear, hindering the assurance of stability in these areas and the determination of a reasonable unsupported span. To address this issue, this work proposed a stress distribution model as temporary support, elucidating the distribution law of support forces within the surrounding rock. By analyzing the stress differences between areas with and without temporary support, the stress field distribution characteristics of temporary support were determined. Subsequently, the evolution of stress and strain in the surrounding rock within unsupported areas was analyzed concerning changes in temporary support length, support force, and unsupported distance. The results indicated that, although temporary support does not directly act on unsupported areas, it still generates a supportive stress field within them. The maximum unsupported distance should not exceed 3 m, and there is a strong linear relationship between the optimal temporary support force and the unsupported span. Furthermore, the length of temporary support should not exceed 17 m from the tunnel face. The successful application of the shield tunneling robot system verifies that temporary support can ensure the stability of the surrounding rock in unsupported areas, confirming the validity of the temporary support stress distribution model. This research can be used to design and optimize cutting parameters and temporary support parameters, arrange equipment, and design and optimize tunnel excavation processes to achieve safe and efficient tunneling.

Effect of Froth on the Interaction Between Coal Particles and Cake Structures in the Dewatering Process of Clean Coal

Effective coal slurry water solid–liquid separation is indispensable for the recycling and sustainable development of coal resources. The interaction between bubble and coal particles plays a critical role in the process of dewatering for clean coal. In this study, we firstly conducted a comprehensive investigation of the impact of froth on the interactions between coal particles by rheological measurement and particle aggregation behavior. Furthermore, the macroscopic dewatering performance of coal slurry in the presence of froth and its microscopic cake structure were investigated using the filtration test and X-ray microtomography (CT). It was found that the interaction between coal particles in the presence of froth was enhanced as a result of the dynamic shear value, combined with the large floc size and compact structure, which led to a higher cake moisture and higher filtration velocity. The CT results indicated that the enhanced interaction of particles in the presence of froth also led to a dense microstructure of the filter cake. The porosity of the filter cake decreased to 2.05% when the aeration time increased from 0 s to 90 s, the throat radius in the filter cake was reduced to 1.32 μm, and the number of throat passages was reduced to one third. Multiple blind pores and low coordination numbers led to a poor connectivity of the pore network and high moisture content.

Experimental Study on the Strength Characteristics of Cast-In-Situ Mortar Specimens in a Slurry Environment

As coal resource development progresses deeper underground, the increasing depth of mine shafts poses significant challenges to the safety and stability of traditional shaft construction methods, further compounding operational difficulties. In this context, cast-in-situ concrete shaft walls in a slurry environment have emerged as an effective solution. The strength of these shaft walls is a crucial parameter for assessing their safety. To explore this, experiments were conducted on slurry preparation and mortar casting (used here as a substitute for concrete) under three different conditions: slurry environment, pure water environment, and dry environment. The cast specimens underwent compressive, tensile, shear, and microscopic observation tests to analyze the strength development patterns of the mortar specimens in these varied casting environments. The study yielded several key findings: As the casting environment becomes more complex, the strength of the mortar specimens gradually decreases. Specifically, specimens cast in a slurry environment exhibit strengths approximately 15% to 20% lower than those cast in a dry environment, although both environments show similar trends in strength development over time. Across all casting environments, the initial strength loss of the specimens is significant, while the rate of strength loss decreases in the later stages; the strength loss is minimal in specimens cast in a pure water environment and reaches its maximum in those cast in a slurry environment. Additionally, in specimens cast in a slurry environment, air void diameter tends to polarize, and the distribution of air void is denser compared to the other two environments. In conclusion, cast-in-situ mortar in a slurry environment exhibits the lowest strength and the greatest strength loss compared to specimens cast in dry and pure water environments. Nonetheless, the strength development trends over time remain similar across all conditions, providing theoretical and technical support for the construction of shaft walls in slurry environments.

Environmental life cycle assessment of large-scale coal mining with annual output of more than one million tonnes.

Coal occupies an absolute advantage in the primary energy structure of China. However, the production of coal poses a serious threat to the ecological environment and human health. In order to quantify the environmental impact of coal mining, this study used the life cycle assessment (LCA) method to analyse the life cycle of coal mining from the cradle-to-gate. Midpoint results based on ReCiPe 2016 indicated that coal mining had a remarkable impact on human carcinogenic toxicity, marine ecotoxicity, freshwater ecotoxicity, fossil resource scarcity, and human non-carcinogenic toxicity. The contribution analysis revealed that material production was identified as the main cause of environmental impacts, followed by energy consumption and process emissions. Steel consumption, electricity production, and wastewater discharge were identified as key environmental pollution processes. In addition, specific environmental pollution substances and their contributions were recognized from the source, and a sensitivity analysis between key processes and key impact categories was carried out. At the endpoint level, coal mining led to the most damage to human health, followed by ecosystems and resources. This study is of reference significance in guiding the construction of green mines and achieving sustainable development of coal resources.

Spatial-Temporal Changes in Ecosystem Service Value and Its Overlap with Coal Mining Intensity in the Yellow River Basin, China, During 2000–2030

Understanding the ecosystem services and their interaction with coal resource development is crucial for formulating sustainable development policies. In this study, we focused on the Yellow River Basin, characterized by both rich coal resources and ecological fragility. The key findings are that (1) the ecosystem service value (ESV) in the Yellow River Basin exhibited significant spatial heterogeneity during 2000–2030, decreasing from the southeast to northwest, and decreasing the most notably in the southern part of the upper reaches of the river basin; (2) the high-high clustering area of the ESV shifted from the upper-middle reaches in 2000 to the middle-lower reaches in 2020, while the low-low clustering area remained within Inner Mongolia. By 2030, the high-high clustering area is expected to stabilize in southern Shaanxi Province, and the low-low area will potentially spread eastward; (3) the overall ESV is low, and it experienced a significant decline from 2000 to 2020, with water supply emerging as a major limiting factor, although some policy-supported counties had better ecological service values and trends. (4) From 2000 to 2020, the coal mining intensity (CMI) was concentrated in the upper and middle reaches, particularly at the junctions of Shanxi, Shaanxi, and Inner Mongolia, and the pattern remained stable, but local areas experienced increased mining intensity; (5) the overlap of the CMI and ESV primarily exhibited a low-high clustering pattern in the middle and upper reaches of the Yellow River Basin and eastern Ordos City, and a high-high clustering pattern in the middle reaches of the basin in Shanxi Province, which remained stable and slightly expanded from 2000 to 2030; (6) the trade-off between the ecosystem services in the overlap area intensified, especially between the provisioning and support services, and was significantly impacted by the coal mining activities. The findings indicate that the area that overlaps with the coal mining area in the Yellow River Basin has expanded and has had an increasing negative impact on the ESV. It is also essential to address the trade-offs between the provisioning and support services and to implement ecological restoration measures to mitigate the risk of ESV loss. Future efforts should focus on the regions where the CMI and ESV overlap and have poor coordination and the adverse effects of resource extraction on ecosystem services are becoming more pronounced. The results of this study demonstrate that spatial overlap analysis is effective in identifying the hotspots and provides a foundation for developing sustainable and high-quality policies for ecologically fragile basins.

Evaluating the impact of coal seam roof groundwater using variable weights theory: A special emphasis on skylight-type water inrush pattern

Study regionThis study is based in the rapidly developing large-scale coal base located in Northwest China. Study focusThis study focuses on addressing a critical yet overlooked aspect of large-scale coal resource development in arid regions: the impact on coal seam roof groundwater. Recognizing the paramount importance of safeguarding groundwater resources for sustainable mining practices, the research introduces a novel concept of “skylight-type secondary water inrush pattern” and develops a comprehensive evaluation methodology to quantify its extent. New hydrological insights for the regionThe study presents groundbreaking hydrological insights into the behavior of groundwater systems impacted by coal mining in arid regions. It reveals that secondary water inrush pattern, a phenomenon driven by hydrodynamics, extends beyond the immediate mechanical footprint of mining, posing significant challenges for groundwater resource management. This research underscores the importance of considering not just the structural alterations to aquifers but also the broader hydrological consequences of mining activities. By integrating multivariate geological information with a variable weights theory, the developed evaluation method provides a nuanced understanding of how mining alters groundwater abundance and flow patterns. These new insights challenge traditional approaches and offer a scientific basis for designing effective strategies to mitigate water damage, manage mine groundwater, and promote sustainable mining practices in arid environments.

Deformation, Seepage, and Energy Characteristics of Gas-Containing Coal Rocks under Complex Stress Paths

The exploitation and utilization of coal resources are closely related to sustainable social and economic development. To uncover the deformation and seepage patterns of coal on the mining process, this study devised a new stress program with simultaneous changes in axial and confining pressures, then performed coal seepage experiments at various gas pressures. The results show that the residual deformation exhibited a stepwise change, the relative residual deformation at the same level decreased gradually, and the increase in gas pressure led to a reduction in residual deformation. In each stress grade, the absolute permeability damage rate increased gradually, while the relative permeability damage rate decreased with the number of cycles, and the growth of gas pressure could decrease the permeability damage rate. The higher gas pressure led to a lower average energy dissipation ratio at each stress level and increased the rate of growth of elastic energy before destruction of the specimens. A higher gas pressure led to a quicker rate of change in damage variables at high stress levels. The findings have implications for the effective mining and sustainable development of coal resources.

Prediction of airflow temperature in coal mining face under the influence of multiple heat sources coupling: Numerical simulation and verification

With the development of coal resources to the deep, the mine heat damage has become increasingly serious. In this work, we proposed a comprehensive airflow temperature prediction model considering the coupling effect of multiple heat sources in coal mining face. The model was then discretized and a coupled solution simulator was developed independently. Finally, we conducted field test to verify the simulation results, and carried out a multi-factor sensitivity analysis affecting the thermal environment of coal mining face. The results show that:(i) The maximum relative error of prediction results is less than 4 %, which verifies the reliability of the prediction model. (ii) Heat dissipation from electrical equipment, surrounding rock and hot airflow leakage of gob area account for 43.8 %, 28.8 % and 17.4 % of the total heat load, which are the main causes of heat damage. (iii) The maximum airflow temperature in coal mining face increases in a parabolic trend with average advance speed. (iv) As the original rock temperature increases, the thermal environment of coal mining face deteriorates rapidly. (v) Cooling the inlet airflow or increasing the airflow volume can alleviate the high temperature problem. This research can provide guidance for the treatment of deep mine heat damage.

Investigating the potential of in-situ fluidized mining of previously inaccessible coal seams through the utilization of super hot rock geothermic technology

This study aims to explore a cutting-edge model that combines geothermal energy and coal resource development. Specifically, it focuses on the development model of ultra-deep super-hot rock (SHR) resources and unmineable coal seams through in-situ thermal decomposition technology using supercritical water steam. Through extensive investigation and assessment of technical challenges, we have extensively explored the potential of using supercritical water steam for thermal decomposition of coal seams. We examined the potential benefits in terms of energy conversion efficiency and environmental impact. Despite the significant theoretical prospects of this method, practical application has encountered multiple challenges such as high costs, drilling technology difficulties, and the complexity of reservoir modification technology. The significant investment costs primarily arise from the expenses associated with drilling operations and acquiring equipment. Simultaneously, there are challenges in the realm of technology that require the adaptation of drilling techniques to withstand extreme temperatures and pressures. Additionally, there is a need to explore novel methods for modifying reservoirs in order to sustain fracture openings. In the face of these challenges, this study proposes three main directions for future research and technology development: developing new efficient and environmentally friendly reservoir reconstruction technologies, exploring technologies suitable for low-temperature catalytic reactions in deep coal seams, and improving the accuracy and practicability of microseismic monitoring technologies. With the help of these technological advancements, the aim is to address the existing challenges and drive the integrated progress ultra-deep super hot rock and coal measures towards a more sustainable and economically viable direction. The research results will offer fresh insights and solutions for the realm of deep energy development, playing a crucial role in advancing the progress of sustainable energy technology.

The Impact of Meteorological Drought at Different Time Scales from 1986 to 2020 on Vegetation Changes in the Shendong Mining Area

The Shendong Mining Area, being the largest coal base in the world, has significant challenges in the intensive development and utilization of coal resources, as well as the impact of a dry climate, which can have serious negative effects on the growth of flora in the region. Investigating the spatial and temporal patterns of how meteorological drought affects vegetation in the Shendong Mining Area at various time scales can offer a scientific foundation for promoting sustainable development and ecological restoration in the region. This study utilizes the Standardized Precipitation Evapotranspiration Index (SPEI) and Normalized Difference Vegetation Index (NDVI) data from 1986 to 2020 in the Shendong Mining Area. It employs Slope trend analysis, a Mann–Kendall test, a Geographic Detector, and other methods to examine the spatiotemporal distribution characteristics of meteorological drought at various time scales. Additionally, the study investigates the influence of these drought patterns on vegetation growth in the Shendong Mining Area. Across the mining area, there was a general decrease in the monthly average SPEI on an annual basis. However, on a seasonal, semi-annual, and annual basis, there was a gradual increase in the annual average SPEI, with a higher rate of increase in the southern region compared to the northern region. When considering the spatial variation trend in different seasons, both positive and negative trends were observed in winter and summer. The negative trend was mainly observed in the western part of the mining area, while the positive trend was observed in the eastern part. In spring, the mining area generally experienced drought, while in autumn, it generally experienced more precipitation. The mining area exhibits a prevailing distribution of vegetation, with a greater extent in the southeast and a lesser extent in the northwest. The vegetation coverage near the mine is insufficient, resulting in a low NDVI value, which makes the area prone to drought. Over the past few years, the mining area has experienced a significant increase in vegetation coverage, indicating successful ecological restoration efforts. Various forms of land use exhibit distinct responses to drought, with forests displaying the most positive correlation and barren land displaying the strongest negative correlation. Various types of landforms exhibit varying responses to drought. Loess ridge and hill landforms demonstrate the most pronounced positive association with monthly-scale SPEI values, whereas alluvial and floodplain landforms display the poorest positive correlation with yearly scale SPEI values. The general findings of this research can be summarized as follows: (1) The mining area exhibits a general pattern of increased humidity, with the pace of humidity increase having intensified in recent times. Seasonal variations exhibit consistent cyclic patterns. (2) There are distinct regional disparities in NDVI values, with a notable peak in the southeast and a decline in the northwest. The majority of the mining area exhibits a positive trend in vegetation recovery. (3) Regional meteorological drought is a significant element that influences changes in vegetation coverage in the Shendong Mining Area. Nevertheless, it displays complexity and is more obviously impacted by other factors at a small scale. (4) It should be noted that forests and barren land exert a more significant influence on SPEI values, despite their relatively lesser spatial coverage. The predominant land use type in most locations is grasslands; however, they have a relatively minor influence on SPEI. (5) A shorter time period, higher elevation, and steeper slope gradient all contribute to a larger correlation with drought.

Ethiopian Coal Deposits and Resource Development Prospects

ABSTRACTThe growing use of local coal in Ethiopia has created challenges for cement factories due to inconsistencies in grade and quality. This paper presents the main areas rich in coal resource and potential sites for their development. Field studies have been conducted extensively in some areas to explore coal and analyze its compostion for potential use as major energy source in addressing the high energy demands for cement production across the country. Ethiopian coal beds vary in thickness from a few centimeters to 6 m and encompass a range of ranks from lignite to bituminous coal. Quality also varies widely, with ash content being a significant parameter of concern, as some studies indicate elevated levels. However, because of insufficient data, it is challenging to generalize other quality parameters accurately. Ethiopia's coal exploration dates back to the 1940s, with rough estimated deposits totaling 600 million tons nationwide. Currently, small‐scale producers satisfy 66% of the cement industries coal demand, which is the major consumers. Efficient coal mining enables the country to substitute significant amounts of imported coal, reducing large expenditures in foreign currency. Local coal production offers cost savings, job creation, streamlined transport, and reduced import reliance, thereby preserving hard‐earned foreign currency and granting the country a competitive edge.

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.

Application of an Automated Top Coal Caving Control System: The Case of Wangjialing Coal Mine

China has made notable advancements in the intelligent construction of coal mines. However, for longwall top coal caving (LTCC) mining faces, a key obstacle impeding the intelligent transition of the coal-cutting process is automated control. This paper focuses on the aforementioned issue and comprehensively considers the pre-, intra-, and post-coal-caving stages. In this work, diverse detection and monitoring technologies are integrated at various stages through a computer platform, facilitating the construction of an automated coal caving control system with self-perception, self-learning, self-decision-making, and self-execution capabilities. Key technologies include ground-penetrating radar-based top coal thickness detection, inertial navigation-based shearer positioning, tail beam vibration-based identification of coal and gangue, and magnetostrictive sensor-based monitoring of the tail beam and insert plate attitude. In this study, the 12309 working face of the Wangjialing Coal Mine was experimentally validated, and the efficacy of the aforementioned key technologies was assessed. The results demonstrated that the control requirements for automated coal caving are satisfied by the maximum errors. Automatic regulation of coal caving was realized through the implementation of this system, thereby facilitating initiation and cessation and yielding promising experimental outcomes. Overall, this system offers practical insights for intelligent construction in current LTCC mining faces and the sustainable development of coal resources.

Can digital transformation affect coal utilization efficiency in China? Evidence from spatial econometric analyses

The swift development of digital technology in China, coupled with the escalating significance of coal resource utilization in the industrial sector, necessitates an investigation into the role of digital transformation in fostering the sustainable development of coal resources. We utilize the Spatial Dubin Model (SDM) to analyze data from 30 Chinese provinces between 2011 and 2019, exploring the relationship between digital transformation and coal utilization efficiency. Additionally, the research investigates spatial spillover effects and the moderating effect mechanism at play. Key findings reveal that: Firstly, a noteworthy positive correlation exists between digital transformation and coal utilization efficiency. Secondly, digital transformation yields significant positive impacts on proximate cities. Lastly, analysis of moderating effects indicates that digital development policies can enhance the positive association between digital transformation and coal utilization efficiency. These findings furnish novel insights and avenues for regions seeking to propel sustainable development in coal resource utilization.

Environmental impact assessment of acidic coal gangue leaching solution on groundwater: a coal gangue pile in Shanxi, China.

With the continual advancement of coal resource development, the comprehensive utilization of coal gangue as a by-product encounters certain constraints. A substantial amount of untreated coal gangue is openly stored, particularly acidic gangue exposed to rainfall. The leaching effect of acidic solutions, containing heavy metal ions and other pollutants, results in environmental challenges such as local soil or groundwater pollution, presenting a significant concern in the current ecological landscape of mining areas. Investigating the migration patterns of pollutants in the soil-groundwater system and elucidating the characteristics of polluted solute migration are imperative. To understand the migration dynamics of pollutants and unveil the features of solute migration, this study focuses on a coal gangue dump in a mining area in Shanxi. Utilizing indoor leaching experiments and soil column migration experiments, a two-dimensional soil-groundwater model is established using the finite element method of COMSOL. This model quantitatively delineates the migration patterns of key pollutant components leached from coal gangue into the groundwater. The findings reveal that sulfate ions can migrate and infiltrate groundwater within a mere 7years in the vadose zone of aeration. Moreover, the average concentration of iron ions in groundwater can reach approximately 58.3mg/L. Convection, hydrodynamic dispersion, and adsorption emerge as the primary factors influencing pollution transport. Understanding the leaching patterns and environmental impacts of major pollutants in acidic coal gangue is crucial for predicting soil-groundwater pollution and implementing effective protective measures.