Search

• Ecological restoration is not just an environmental issue and it is a societal problem. This paper analyzes ecological restoration and its impact on society in coal resource-based areas, focusing on the Ruhr region in Germany and Liulin County in China. Through the analysis and comparison, the study not only reveals the unique ecology-social system and explain the reasons for dependence on coal, but the finding shows that industrial transformation is a key factor in determining ecological restoration of coal resource-based regions. • The industries abandoned by the Ruhr area were taken over by China. Shanxi Province is very similar to the Ruhr area in terms of ecological destruction and social development at that time. The Ruhr region has become one of the most polluted areas in the world due to its coal and steel industry. After nearly 40 years of arduous practice, ecological governance and economic transformation in the Ruhr area achieved initial success. • Shanxi Province in China is a hub for energy and heavy chemical industries, and it ranks first in coal production nationally.. The Liulin county is located in the west of Shanxi Province, it is a typical coal mining subsidence and is scattered with numerous villages affected by subsidence due to coal mining. Shanxi Province and the Liulin county is undergoing difficult industrial transformation. • The author of this work visited the Duisburg-Essen University for a year, located in the Ruhr area of Germany, and learned about the ER and transformation in the Ruhr. When the author returned to China, she conducted field research for a two-month survey in Liulin County. Therefore, the author collected a large amount of literature ,data sources and gained practical experiences in these two areas. The coal resource-based areas rely on coal resources and primary processing as their pillar industries, such as the old industrial areas in China and Germany. Long-term, large-scale coal mining has significantly damaged the ecological environment of mining areas. Environmental restoration refers to repairing, rehabilitating, or revitalizing ecosystems that have been degraded, damaged, or destroyed by human activities or natural disasters. In fact, ecological restoration is not just an environmental issue and it is a societal problem. Ecological restoration is closely linked to natural resources, the environment, the economy, society, and politics. These factors form a social ecological system and it is the basis for local stability and sustainable development in the coal resource-based areas. In this process, the relationship between government, enterprise, and local people is constantly being reshaped and defined, then it causes changes in the local social ecology and political ecology. The paper researches the Ruhr area in Germany and the Liulin County in China, the former is a world-famous old industrial and the latter is a typical coal mining subsidence district. By analyzing and comparing the ecological restoration and significant social changes in the Ruhr area and the Liulin County at different periods, the findings show the unique ecology— social system of the coal resource-based area, then enhances the effective measures for ecological restoration and sustainable development of the coal resource-based areas. [ABSTRACT FROM AUTHOR]

• The applicabilities of three typical coal slags as storage materials are evaluated. • Thermophysical properties of three slags and other storage materials are compared. • Effects of coal types and slag morphology on the storage performances are analyzed. Refractory materials are considered as the most suitable high-temperature sensible heat storage materials due to their excellent thermo-mechanical resistance and superior thermophysical properties. Unfortunately, refractories are usually too expensive. To reduce the cost of energy storage materials, the recycling of refractory industrial solid wastes into storage materials is becoming increasingly prevalent. The paper innovatively proposes to use the slags from a liquid slagging furnace of a coal-fired power plant in China as packed bed sensible heat energy storage materials. This paper characterizes the chemical compositions and thermophysical properties of three typical coal slags (Fukang coal slag, Fukang coal granulated slag, Hongshaquan coal granulated slag) and evaluates their potentials as storage materials. The results show that the three kinds of coal slags have good thermophysical properties. At 380 °C, the energy storage densities per unit volume of the three materials are 1037 MJ/m3, 986 MJ/m3 and 920 MJ/m3, respectively. Fukang coal slag has good thermal stability and durability and can be directly used for ultra-high temperature energy storage at 1000 °C. Due to the low crystallization degree, the two granulated slags have poor thermal durabilities and need to be processed at high temperatures before using them for energy storage applications. [ABSTRACT FROM AUTHOR]

This paper analyzes the impact of COVID-19 on China's coal import trade. First , this paper makes a qualitative analysis of the status quo of China's coal import scale before and after COVID-19. Second, the impact of the pandemic on China's coal import was estimated by panel VAR model based on the confirmed global COVID-19 data and China's coal import data with Johns Hopkins University Center for Systems Science and Engineering database and Wind database from January 2019 to June 2021. The result shows that the pandemic has a significant impact on both the supply and demand of China's coal industry in short term. There is a rebound in coal demand due to manufacturing industries having resumed work and production under the successful pandemic control in China. Finally, this paper analyzes the measures of China's coal import process during the COVID-19 and suggests how to deal with the global public crisis in the future. [ABSTRACT FROM AUTHOR]

Co-combustion of semi-coke and coal is a prospective technique for large-scale disposal or utilization of the solid waste. In this paper, the co-combustion behaviors and kinetics of semi-coke and coal were studied by thermogravimetric analysis with a focus on the influence of blending method and synergy. The results indicated that the semi-coke combustion was improved by blending with coal, and the interaction between fuels tended to promote the co-combustion. The ignition and burnout temperatures were positively correlated with the carbon content of the mixture, while the comprehensive combustion index and stability index were negatively correlated with it. The layer blending and partition blending method seemed to show stronger promotion than uniform blending method, and the layer blending method with coal in the upper layer was recommended due to the better combustion behavior. The promotion of coal on semi-coke combustion was less affected in devolatilization stage but weakened by the decrease of O 2 concentration in char burnout stage. The apparent activation energy (E a) of the mixture decreased with the increasing faction of coal. The layer blending method with coal in the upper layer had the lowest E a in devolatilization stage and relatively high E a in char burnout stage. The work can give some new insights into waste co-disposal strategy and carbon emission reduction in China. [Display omitted] [ABSTRACT FROM AUTHOR]

Increasing expansion of China's coal mine production leads to the increased storage pressure in current coal silos. Most of these coals are stored in open-air coal pile. Therefore, those coal piles have caused a series of environmental pollution problems, which includes endangering workers' health and aggravating air pollution in the surrounding natural environment. Therefore, it is urgent to study and prevent the dust flying problem of coal pile. This paper, based on a single chemical dust suppressant, optimizes a new type of composite binder. This composite binder has advantages of dust suppression effect, relatively simple preparation process and the environmentally friendly agent. This paper is mainly divided into two parts: the study on the influencing factors of dust wetting and the development and application of related spraying systems. Through the energy spectrum analysis of scanning electron microscope and reverse osmosis method, it explores the dust wetting and suppression characteristics of the composite binder with different physical and chemical properties. The optimal application range of the composite binder are obtained. Finally, an automatic spraying system for dust suppression is designed. The composite binder developed in this paper is applied in the open-air coal yard and the results show that the composite binder studied in this paper has a good effect of dust suppression. [ABSTRACT FROM AUTHOR]

To achieve carbon neutrality, China must grasp the intricate factors driving coal market, as it addresses coal consumption and reduces the carbon footprint. While previous studies have identified certain factors, they have largely overlooked the impact of the overall industry sector on the coal market. In this paper, a hybrid causal machine learning model was proposed that combine with least absolute shrinkage and selection operator (LASSO), multiple linear regression (MLR), peter and clark momentary conditional independence (PCMCI) and interpretable machine learning. The approach employed a complex network perspective to identify 10 key factors in China's coal market from three dimensions: industrial sector, foreign trade and energy market. The hierarchical pattern of these factors is classified into two levels: direct factors, primarily encompassing crude oil futures, exchange rates and architectural decoration, and intermediary factors, mainly including the chemical industry and building material. Interestingly, this paper reaffirms the roles of crude oil futures and exchange rates in the coal market, as identified in prior studies. Additionally, it uncovers new influential factors primarily driven by the chemical industry and architectural decoration, previously unexplored. Furthermore, this paper found a significant contemporaneous relationship between crude oil futures and coal price index (0.151) as well as coal consumption (0.102), and the strong relationship between coal consumption and the Indonesian Rupiah to Chinese Yuan exchange rate (0.063) was also confirmed. Among the emerging dominant factors, the coal price index and the chemical industry (0.145), along with coal consumption and building materials (0.250), also exhibit a strong contemporaneous relationship. These findings highlight the importance of considering the entire industry sector while analyzing the coal market and promoting a cleaner transformation of the industry in China, and the paradigm presented not only applicable to the coal market, but can be extended to other industries. [Display omitted] • Better grasping key factors in China's coal market critical to carbon neutrality. • A comprehensive study encompassing industrial sector, foreign trade and energy market. • A novel hybrid machine learning models and industry-wide features are introduced. • Identification and categorization of direct and intermediary factors. • Findings offer a new paradigm for decision-making, driving cleaner production reforms. [ABSTRACT FROM AUTHOR]

In order to accurately analyze the safety management efficiency of China's coal enterprises, based on the panel data of 14 coal listed enterprises in 2012–2018, this paper analyzes the overall technical efficiency (TE), pure technical efficiency (PTE) and scale efficiency (SE) of safety management of sample enterprises by the Data Envelopment Analysis (DEA) model, and builds Tobit model of random panel effect to evaluate the impact of business management and safety investment on safety management efficiency. The results show that: in 2012–2018, the average values of TE, PTE and SE of sample enterprises are respectively 0.674, 0.777 and 0.864; all have great room for improvement. The development of PTE and SE in most sample enterprises is unbalanced; TE of sample enterprises does not significantly improve, and shows a trend of rising-decreasing-rising; safety investment, enterprise scale and labor productivity are significantly positively related to safety management technical efficiency, while safety training person time and employees quality are negatively correlated. This paper identified the positive and negative effects of various influencing factors on the safety management efficiency of coal enterprises, and analyzed the main reasons that hinder the improvement of safety efficiency, and puts forward corresponding countermeasures and suggestions, which are helpful for coal enterprises to effectively improve their safety management efficiency and economic efficiency. [ABSTRACT FROM AUTHOR]

This paper examines the coal reliance of all 31 provinces in China and assesses the potential for a just energy transition towards cleaner energy sources. The authors calculate a coal reliance index (CRI) for each province based on China statistical data. The CRI takes into account factors such as coal production, consumption, and import/export, as well as GDP, population, and gender differences in mining employment. The authors highlight the importance of considering the varying degrees of coal reliance among provinces in developing effective policies for a just energy transition. The findings suggest the provincial CRI has generally been decreasing across most provinces over the past 16 years. When looking at regional CRI rankings, the northwest region has the highest average CRI compared to other regions, while the northeast region has the lowest CRI, followed by the north, east, south central, and southwest regions. The gender CRI indicates that women in China are not benefiting as much as men from economic growth and development. The paper provides insights for policymakers seeking to achieve a more sustainable and just energy system in China. • Coal reliance is critical to developing effective policies for a just energy transition. • The authors calculate a coal reliance index (CRI) for 31 provinces in China. • The research provides insights for policymakers to achieve a just energy system. [ABSTRACT FROM AUTHOR]

Using fracturing fluids to modify coal seams to boost their permeability is an essential way to address the technical challenges of the resourceful and efficient extraction of coalbed methane from coal reservoirs in China. However, some current fracturing fluids are toxic or corrosive and pollute groundwater resources, which becomes one of the obstacles to the development of fracturing and penetration technology. Five new types of composite clean fracturing fluids were developed in this paper with Yunnan anthracite coal in China as the research object. The changing rules of functional groups and pore structures, which have a vital influence on gas adsorption and permeability of the treated coal samples, were systematically explored through infrared spectroscopy and low-temperature nitrogen adsorption experiments, and the highly efficient, environmentally friendly, and safe fracturing fluids that are suitable for the experimental coal seams were preferred. The new fracturing fluid effectively reduces the structure of aliphatic hydrocarbon and the structure of oxygen-containing functional groups, improves aromaticity, and lowers the adsorption capacity of coal for methane. Meanwhile, it simplifies the pore structure of coal and improves the average pore diameter. The research results are essential to the clean production and efficient exploitation of coalbed methane resources and safe coal production. • Five new clean fracturing fluids was prepared. • Analyze the effect of different clean fracturing fluids on coal microstructure. • Explored the mechanism of action of clean fracking fluids on coal. • Determined the optimal ratio of clean fracturing fluid. [ABSTRACT FROM AUTHOR]

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

• A joint berth allocation and ship loader scheduling problem in coal export terminals. • Deballasting restrictions and symmetrical berth layout-based rotary loading mode are considered. • A mixed-integer programming model is developed to minimize ship tardiness. • A logic-based Benders decomposition algorithm and effective acceleration strategies are proposed. • Compared to practical scheduling, the proposed methods achieve a reduction of 51.9% on tardiness. Due to nonmatching between the efficiency of ship deballasting and terminal loading, operations in modern coal export terminals (CETs) are frequently interrupted and significantly restricted by ship deballasting delays. This paper addresses a novel integrated problem of berth allocation and ship loader scheduling arising in CETs with new features, including the symmetrical berth layout-based rotary loading mode (SBLRLM) and deballasting restrictions. A mixed-integer programming (MIP) model is proposed to make joint decisions to minimize the total tardiness of all ships. By exploring the problem's decomposable structure, an exact method that relies on logic-based Benders decomposition (LBBD) is proposed to obtain optimal solutions. According to the problem features, the monolithic MIP formulation is decomposed into a new MIP (master problem) and a constraint programming (subproblem). Combinatorial valid inequalities are developed to enhance the master problem model and obtain a tighter lower bound. A Benders cut strengthening heuristic is developed to generate feasibility and optimality cuts to ensure efficient algorithm convergence. To evaluate the proposed method, computational experiments are conducted on a set of test instances generated based on real data collected from a major CET in northern China. The results indicate that the LBBD algorithm can optimally solve large-scale problem instances within a reasonable amount of time. The plan generated by the LBBD algorithm achieves a 51.9% reduction in ship tardiness, on average, compared to that of practical scheduling methods. By using the proposed method, the superiority of the SBLRLM in reducing deballasting delays becomes more significant as the problem scale increases. In addition, considering different working intensities, the results could also help port operators make decisions about the number of berths in the SBLRLM. [ABSTRACT FROM AUTHOR]

With the increasing depth of mining, the disasters of water inrush above confined aquifers tends to increase annually, which seriously threatens the safe mining of coal seam, especially the extra-thick coal seam floor in deep mining. This research is to study the characteristics of deformation and failure of extra-thick coal seam floor in deep mining, the field measurement is carried out by the distributed fiber optic sensing technology (BOTDR) and the 3D resistivity method of studying coal field in China. The axial strain curves and resistivity distribution characteristics of the mining face at different depth under the coal seam floor are obtained by extending the working face. Through the comprehensive comparison and analysis of monitoring data in the monitoring boreholes, the characteristics of deformation and failure of extra-thick coal seam floor in deep mining can be ascertained. The results indicate that the comprehensive monitoring technology can effectively distinguish the characteristics of stress excess, distortion and failure of rock during the process of the working face mining. The influence range of mining advance stress is about 36 m, the failure depth of coal seam floor is about 12 m and the depth of mining disturbance deformation is about 26 m. The formation of the deformation and failure of the coal seam floor have obvious stratification, which are mainly influenced by the formation structure and the lithology of the rock strata. The comprehensive monitoring technology can effectively capture the fine features of the deformation and failure of the coal seam floor, which is valuable for extra-thick coal seam floor in deep mining. • In this paper, the distributed fiber optic sensing technology is used for the first time to monitor the deformation and failure of the coal seam floor. • The coal seam studied in the paper is an extra-thick coal seam and the buried depth of the coal seam is large, belonging to the extra-thick coal seam in deep mining. • The high frequency of data acquisition and the long duration of acquisition, so as to realize the dynamic monitoring research on the deformation and failure of extra-thick coal seam floor in deep mining. [ABSTRACT FROM AUTHOR]

Substituting renewable energy for coal power under the carbon neutrality goal is an inevitable path for power system transformation, while the high share of renewable energy leads to a rapid rise in system flexibility demand. Currently, coal-fired power is still one of the most economical and reliable large-scale flexible resources in China. Therefore, the issue of how to mitigate the conflict between cleanliness and flexibility for coal-fired power is urgent to be solved. Accordingly, this paper established an optimization framework for the retirement and technology adoption of coal-fired power units with high spatial-temporal resolution, and the regional carbon emission budget is estimated from a top-down perspective. Secondly, a dynamic carbon quota allocation method considering technological innovation and adoption is proposed. The carbon trading cost of the units is evaluated from a bottom-up perspective, to realize the interaction between the obligatory policy constraints of the top-level target and the flexible incentives of the market mechanism. Finally, the empirical analysis was conducted in the Beijing-Tianjin-Hebei region of China. The optimal solution achieved by proposed method results in a substantial 27% reduction in total costs while keeping the increase in carbon emissions below 3%. By analyzing the dynamic evolution path of coal and the scale of diffusion of multi-type technologies, the differences in the roles coal power assuming at various stages of decarbonization are discussed. The robustness of the model and the validity of the proposed method were verified by comparing the dynamic/static carbon quota allocation. Overall, this study provides an effective optimization model for investigating the low-carbon technology adoption timing for coal power in Beijing-Tianjin-Hebei region, and offers valuable insights for other coal-dominated emerging economies seeking for power system transformation roadmap in the forthcoming net-zero carbon age. • A decision-making optimization model of CCPs low-carbon technology is proposed. • A dynamic CET system with upper-lower layer interaction is introduced. • The proposed dynamic CET system results in 27% reduction in total costs. • The high-resolution data of coal power in Beijing-Tianjin-Hebei region are used. • The strategy to solve the conflict between cleanliness and flexibility is given. [ABSTRACT FROM AUTHOR]

In 2013, “haze-fog” became an annual buzzword in China; this “haze-fog” is primarily attributed to coal combustion. If coal continues to be used as it has been previously, China will suffer as a result of air pollution. Different from coal, electricity is a highly efficient energy source with no pollution emissions. Electric power substitution (EPS) for coal can reduce air pollution and transmit electricity to a load intensive area by an ultra-high voltage transmission project that can promote renewable energy accommodations in remote areas. However, EPS was proposed in 2013 and is still in the initial stage. The present paper studies the relationship between coal and haze-fog, proposes an EPS action mechanism, and summarizes the EPS market and policies. A SWOT model has proved to be an efficient tool to analyze the internal and external competitiveness of a system. Therefore, to fully study the current development status of electric power substitution in China, this paper adopts a SWOT model to analyze the strengths, weaknesses, opportunities and threats of EPS. The conclusion is drawn that EPS is a good substitution for coal, but increased interest and use of EPS in China still needs support, including energy price marketization, electricity price subsidy, UHV optimization, clean coal technology innovation, and so on. This research can promote optimization in the energy structure and provides policy makers with good references and a clear direction in EPS development. [ABSTRACT FROM AUTHOR]

China, India, and the USA are the world's biggest energy consumers and CO 2 emitters. Being the leading contributors to climate change, these economies are also at the core of environmental solutions. This paper investigates the causal relationship among solar and wind energy production, coal consumption, economic growth, and CO 2 emissions for these three countries. To do so, we use an advanced methodology in Machine Learning to verify the predictive causal linkages among variables. The Causal Direction from Dependency (D2C) algorithm set CO 2 emissions as the target variable. The obtained results were disaggregated and estimated in a supervised prediction model. The findings, confirmed by three different Machine Learning procedures, showed an interesting output. While a reduction in overall carbon emissions is predicted in China and the US (resulting from the intensive use of renewable sources of energy), India displays critical predictions of a rise in CO 2 emissions. This indicates that curbing CO 2 emissions cannot be achieved without conducting a comprehensive shift from fossil to renewable resources, although China and the U.S. present a more promising path to sustainability than India. Being an emerging renewable energy leader, India should further enhance the use of low-carbon sources in its power supply and limit its dependence on coal. • Renewable energies, coal consumption, economic growth, and CO 2 we examine. • We investigate the causal predicted relationship on China, India, and the USA. • An advanced methodology in Machine Learning is used. • India has a prediction of an increase in emissions of CO 2. • China and the U.S. present a more promising path to sustainability than India. [ABSTRACT FROM AUTHOR]

Australia is a long-term key partner of China in coal trading, which is famous for high-quality coal and its price advantage. However, affected by the evolution of international political and economic situation, China has issued a coal ban on Australian coal since the end of 2020. The potential environmental consequences of this coal ban remain unclear. So, this paper quantifies the ban's impact on air pollution, human health and climate change by simulating the emission difference between the port scenario (simulating the emissions due to Australian coal import under business as usual) and the mine scenario (simulating the emissions due to domestic coal mining that converted from import share of Australian coal), and monetizes the losses into economic costs for direct comparison. The results illustrate the emission of SO 2 , VOCs and GHG in mine scenario grows up to 102, 12 and 6 times the amount of that in port scenario, mainly deriving from coal mining process in the North China Plain and Yunnan-Guizhou Plateau. It shows that the potential alternative of replacing import with mining leads to PM 2.5 pollution exacerbation and O 3 pollution abatement, which causes 148 (95 % CI: 101–183) non-communicable diseases and respiratory disease-related deaths in total. As for GHG, the emission of BC in transportation process and fugitive methane in coal mining process contribute to an impressive effect on warming potential with few quantities, which is worth noting in control process. In total, the environmental deterioration resulted in an economic loss of approximately 934 million yuan. The undiminished demand for high-quality industrial coal as well as growing carbon tax could make the economic value of the coal ban's environmental consequences more considerable in the near future. This research emphasizes the contradiction between economic development and environmental improvement caused by excessive dependence on coal and addresses a critical knowledge gap in assessing the ban's environmental impact by economic value. The result directly demonstrates the environmental consequences of the potential mining-replacing-import alternative and helps better understand environmental influences on the Chinese government's decision. [ABSTRACT FROM AUTHOR]

In the second of two companion papers, we quantify the potential ultimate benefits for public health and radiative forcing from the phase-out of coal use in China. With the baseline year of 2015, we estimate that the premature deaths and disability-adjusted life years (DALYs) in China will be reduced by 375,000 persons and 8.90 × 106 years (GEMM model), which is 41.7% and 54.5% of the total number of premature deaths and DALYs caused by PM 2.5 from anthropogenic sources, effectively improving the health of the population. The provinces with the most significant decreases in fatalities and disabilities are concentrated in large coal-consuming provinces. Regarding age distribution, the phase-out of coal use will effectively extend the life expectancy of the elderly, especially in the age group of 65–89 years. Health benefits' growth rate upsurges notably once more than half of coal is phased out. Based on the Parallel Offline Radiative Transfer (PORT) model, the global annual average radiative forcing due to changes in short-lived climate pollutants (SLCPs), including sulfate, black carbon, organic carbon, and O 3 associated with the phase-out of coal use, is 0.34 W m−2, -0.048 W m−2, 0.00064 W m−2, and 0.00055 W m−2, respectively. The complete phase-out of coal use in China also reduces the emission of long-lived climate pollutants (LLCPs) and causes negative radiative forcing. Among them, the global annual average radiative forcing of CO 2 , CH 4 , and N 2 O is −0.0073 W m−2, -5.48 × 10−5 W m−2, -1.60 × 10−5 W m−2. If the lifetimes of pollutants are considered, the total global reduction in heat uptake is −2.29 × 107 J m−2 over 100 years, dominated by the decrease of CO 2 , which will slow the rate of global warming and thus may reduce the probability of extreme weather events. This report will incentivize relevant policymakers to remove coal significantly to achieve carbon neutrality. [Display omitted] • Coal phase-out in China avoids half of premature deaths and DALYs attributed to PM 2.5 emission from anthropogenic sources. • The health benefits experiences an upsurge when coal removal exceeds 50%, non-linearly related to the coal removal. • Sulfate and CO 2 dominate positive and negative radiative forcing. Considering the lifetime, a cooling effect will occur. [ABSTRACT FROM AUTHOR]

• Fatigue effect of the PHF is dependent on the time scale of pulsating loading. • Coal porosity increases with the increased pulsating pressure based on the LF-NMR. • A larger pulsating pressure leads to a lower cracking pressure. • The PHF creates more cracks and higher porosity than the HF according to CT images. Coalbed methane recovery can largely ease the crisis of annually increasing energy consumption of China. Low permeability and porosity of deep coal reservoirs mainly cause the low gas production rate. Pulsating hydraulic fracturing (PHF) is an alternative tool to improve the reservoir permeability and stimulate the gas productivity. However, little has been done to directly observe the fatigue damage in coal created by the pulsating loading. Because the fatigue damage is primarily governed by the time-length of PHF period. Therefore, the effect of long period pulsating loading of PHF on coal damage has been investigated in this work. Results show that long-period pulsating loading of PHF can cause significant damage in coal. The low-field NMR data indicates coal porosity increases with the increase of maximum pulsating pressure. Pulsating pressure also plays an important role in the cracking pressure. A larger pulsating pressure leads to a lower cracking pressure. Comparison of PHF and HF damaged coal investigated by the X-ray CT indicates the PHF creates more fractures and higher porosity than conventional hydraulic fracturing. The increase ratios of the coal porosity by HF and PHF are 40 %–60 % and 80 %–100 %, respectively. This paper provides a better understanding the mechanism of the coal damage by the PHF under long-period pulsating loading which is of great importance for optimizing PHF technique and generating connected fracture networks. [ABSTRACT FROM AUTHOR]

Coal structure is closely related to microscopic and macroscopic properties of coal, and its accurate identification is of great significance to coalbed methane (CBM) reservoir evaluation, hydraulic fracturing performance and production efficiency prediction. The identification of coal structure based on geophysical logging data has become a popular topic as well as a challenge. The emerging Machine Learning (ML) provides convenience for this issue. Under this background, in the case of the Shanxi Formation No. 3 coal seam and the Taiyuan Formation No. 15 coal seam in Mabidong Block, Qinshui Basin, China, this paper proposed a new coal structure identification method based on geophysical logging data using Wavelet Transform (WT) and Particle Swarm Optimization Support Vector Machine (PSO-SVM) algorithms. Our results showed that the vertical resolution of logging data can be effectively improved when sym5 wavelet basis and third level decomposition were selected in wavelet decomposition, and 4.5 was selected as the weighting coefficient in wavelet reconstruction. The coal structure prediction model based on the logging data processed by WT was established by PSO-SVM algorithm, where PSO was used for parameter optimization (optimal penalty factor C and width parameter σ) and SVM with Radial Basis Function (RBF) kernel was used for model establishment. The Hold-out Cross Validation (HO CV) method was used to test the generalization ability of the prediction model, and the accuracy (ACC) of coal structure prediction in the training set and testing set was 94.26% and 88.46%, respectively. The prediction model was applied to identify the coal structure of two coring wells and the predicted coal structure class was consistent with the true coal structure class, confirming the validity of the model. The coal structure prediction results in the whole study area showed that the tectonic conditions control the coal structure. This work provides new insights for coal structure identification. • A new coal structure identification method based on geophysical logging data was proposed. • The vertical resolution of logging data was improved based on Wavelet Transform (WT). • The coal structure prediction model was established based on Particle Swarm Optimization Support Vector Machine (PSO-SVM). [ABSTRACT FROM AUTHOR]

• 1 Stress distribution was recalculated by stress-softening and prominent dilatancy. • 2 Gas-bearing coal under impact loading was a compaction followed by ruin process. • 3 Measures principles were mainly aimed at fracture and stress-concentration areas. • 4 Preliminary goal-reaching parameter based on principles was proposed and applied. As the increasing demand for coal and the depletion of shallow coal resources, the tendency of coal mining in China is progressively shifting to deeper areas, which brings about a circumstance where the frequency and intensity of coal and gas outburst accidents have further deteriorated. Nowadays, there are many outburst prevention measures being applied on site, while this disaster still occurs from time to time. Therefore, to better improve the preventing outcome of them, this paper came forward with some principles, based on the mechanical theory of deep mining and damage evolution procedure concerning coal containing gas underneath the impact load. The primary conclusions were as follows: the stresses, strains, and associated widths in the three areas, namely fracture area, plastic area, and elastic area, in front of the working face were recalculated by considering stress-softening and dilatancy of coal mass. The damage evolution of gas-bearing coal mass under impact loading was displayed in the LS-DYNA numerical simulation as a process of compaction followed by destruction. The proposed principles could be split into two perspectives, one for the fracture area, specifically, to minimize the descending of the coal mass's strength in this area; another for the stress-concentration zone, namely, to abate the thrust due to extrusion and deformation, on the coal body which was located in the front area. According to those principles, a preliminary goal-reaching parameter was proposed and it was implemented for the evaluation of advanced drilling. The results will cooperate to rationalize the design and layout of local outburst prevention measures, thereby enhancing the efficiency of control and ameliorating the deteriorating scenario of outburst disasters. [ABSTRACT FROM AUTHOR]

Igneous intrusions into coal affect the safety, productivity, and economic viability of many coal mines. Also, the alterations in coal caused by igneous intrusions encompass a deterioration in coal quality, a decrease in permeability, an enhancement of coal rank, and geochemical and mineralogical compositions. Although there have been some studies related to the effects of igneous intrusions on the inorganic constituents in the coal, the mechanism of newly formed chemical and mineralogical associations caused by igneous intrusions has not been fully understood. This paper investigates the mineralogical and geochemical responses of coal to thermal alteration by igneous intrusion into an Early Permian coal seam in Hebei Province, North China. The Fengfeng coalfield is structurally complex, experiencing variable rates of burial and uplift, with abundant intrusions during the upper Jurassic and maximum burial in the Cretaceous resulting in an increase in rank to the north. In the search for critical minerals and elements, intrusions and hydrothermal alteration are often cited as the source for elevated concentrations. Towards the intrusion, the coal rank indicators increase from semi-anthracite to anthracite over a 500-cm distance, as does the mineral matter. The clay minerals present in coals include NH 4 -illite, kaolinite, paragonite, and chlorite (chamosite and cookeite), which were all resulted from igneous intrusions. The epigenetic minerals mainly include quartz, ankerite, calcite, pyrite, and apatite, which were derived from fluids permeating into the coal seam and chemically interacting with the original minerals or precipitating directly to form new minerals. Geochemical indicators in this coal indicate hydrothermal solutions derived from igneous intrusion. The enrichment of Li and Hg is linked to the igneous activity, potentially influencing the utilization of the coal adjacent to the intrusions. However, the concentrations of the remaining elements in the coal closest to the intrusion show no significant changes, thereby supporting the notion of a "non-universal effect" of igneous intrusions on the elemental composition and concentrations. • Towards the intrusion, the coal rank indicators increase, as does mineral matter. • Various clay minerals in coal are associated with hydrothermal fluids. • Epigenetic minerals show at least three stages of hydrothermal fluids. • Geochemical indicators are used to characterize hydrothermal fluids from intrusion. • The enrichment of Li and Hg in coal nearby intrusion is linked to igneous activity. [ABSTRACT FROM AUTHOR]

As the world's largest producer and consumer of coal, coal phaseout is critical for China to achieve carbon neutrality and contribute to global decarbonization. Here, utilizing the Global Change Assessment Model, this paper simulates China's coal phaseout pathways at the sectoral level between 2015 and 2060, considering the deployment of carbon capture and storage (CCS). The results show that China's coal consumption peaks at 96.4 Exajoules (EJ) in approximately 2020 and needs to decrease to 10.9 EJ by 2060 to achieve carbon neutrality. Specifically, the power sector bears the most significant proportion of responsibility, as its coal consumption must fall to 1.4 EJ by 2060, which is approximately 97.2% lower than the peak in 2020. The industrial sector is next and needs to decrease consumption to 9.2 EJ of coal in 2060, which is a reduction of 32.3 EJ below the 2020 level. Electricity will replace coal as the dominant energy source in the industrial sector after 2040. However, a portion of feed coal will remain in the industry for a long time. Among the industrial subsectors, the steel sector needs to put significant pressure on efforts to phase out coal, followed by the cement and nitrogen fertilizer sectors. In 2060, these three sectors will consume 5.7 EJ of coal, accounting for 64.1% of the total coal consumption in the industrial sector. The deployment of coal-CCS is one of the alternatives to achieve carbon neutrality and ensure smooth coal phaseout. Under the carbon neutrality scenario, the annual deployment of coal-CCS needs to exceed 0.13 EJ from 2025 to 2045, with a peak at 3.3 EJ in 2045. • China's coal phaseout pathway is assessed in the carbon neutrality scenario (CNS). • Coal consumption needs to drop to 10.9 EJ in 2060 to achieve carbon neutrality. • The power sector's coal will decrease to 97.2% below the peak by 2060 in the CNS. • The industry will pass the power sector as the top coal consumer by 2045 in the CNS. • The deployment of coal-CCS will peak at 3.3 EJ after 2045 in the CNS. [ABSTRACT FROM AUTHOR]

This paper examines the asymmetric effects of oil price shocks on coal and renewable energy consumption in China over long and short periods. The novelty of this study is to investigate whether the consumption of coal and renewable energy are asymmetrically affected by the oil price in a time–frequency framework by performing a Fourier nonlinear ARDL model which is robust to overcome the multiple smooth structural changes in data. The bounds test of the FNARDL specification provide strong evidence of cointegration among variables, including coal energy consumption, renewable energy consumption, oil price, and economic growth. Results reveal the following: First, the oil price-coal energy consumption and oil price-renewable energy consumption relationships are nonlinear. Second, oil price increases have significant short-run effects on coal energy consumption. However, oil price increases induce an increase in renewable energy consumption in China in both the short and the long term. Finally, the relationship between coal energy consumption and economic growth is U-shaped. Hence, increasing oil prices boost China's prospects for coal in the short term and its usage of renewable energy in the long run. • Effect of oil price on coal and renewable energy consumptions in China is tested. • Strong evidence of cointegration among variables is shown. • Oil price increases have significant short-run effects on coal energy consumption. • Oil price increases induce an increase in renewable energy consumption in China. • Relationship between coal energy consumption and economic growth follows U-shaped. [ABSTRACT FROM AUTHOR]

China has a coal addiction that has worsened over time. Its share of the world׳s total final coal consumption more than doubled over the past decade. This fast growth of coal consumption presents serious challenges to the country׳s carbon emission. In 2011, burning coal contributed 72% of China׳s CO 2 emission and 19% of global CO 2 . A better understanding of the trajectory and drivers of Chinese coal usage will help catalyse Chinese efforts to kick its heavy addiction to coal. We analyze China׳s coal consumption during 1955–2011 using time-series data energy consumption, population, gross domestic product, and industrial production. Based on the change of its total coal consumption and coal consumption intensity, China׳s coal use for 1955–2011 is divided into six phases. Next, this paper quantifys the driving forces in each phase and drivers of coal consumption intensity, using the Logarithmic Mean Divisia Index (LMDI) technique. The result shows there is a strong positive correlation between economic growth and coal consumption, the coal intensity and economic output of second industry is the leading contributor to change of coal consumption intensity. Three policy recommendations are offered for China kicking its coal habit. This paper argues that improving coal consumption efficiency is the more optimum policy. [ABSTRACT FROM AUTHOR]

Traditional olefins production mainly depends on oil. In view of the short supply of oil, feedstocks are expanded to coal, natural gas, coke-oven gas, and methanol in China. In this paper, a comparative study of alternative olefins production is conducted from aspects of techno-economic feasibility and environmental friendliness. Results show that coal-to-olefins has a significant cost advantage. However, it suffers from low energy efficiency and serious CO 2 emissions. To address these problems, this study proposes and analyses coal-to-olefins with CO 2 capture, coal and natural gas-to-olefins, and coal and coke-oven gas-to-olefins. The two co-feed systems ensure great reduction of CO 2 emissions and significant improving energy efficiency. They should be actively developed in regions with rich coal and gas. While in regions with rich coal and lean gas, coal-to-olefins with CO 2 capture should be developed in large scale. This paper also provides several suggestions on planning these olefins production routes in China. [ABSTRACT FROM AUTHOR]

Coal power plants are crucial in both the power sector and central heating sector and also emit large amount of carbon dioxide. Existing research on coal power plants transformation mainly focused on their role in the power sector, with insufficient attention paid to their heat and power cogeneration capabilities. To address this gap, this paper proposes a long-term expansion joint optimization model for power sector and central heating sector incorporating the competitive technologies in both sectors, which is used to obtain the optimal low-carbon transition pathway of power sector and central heating sector, and analyse the pathway of coal power plants. China is selected for a case study for its largest scale of existing coal power plants in the world and urgent need of decarbonization. Compared to the scenario only considering electricity generation function from coal power plants to power sector, another scenario also considering the heating production to central heating sectors brings less than 5% increase in their remaining capacity, whilst results in significant changes in their regional distribution. Proportion of heat and power cogeneration of coal power plants in the heat generation structure is expected to increase first to 80% in 2030 and decrease to 58% in 2055. • A long-term optimization model for sectors of power and central heating is built. • Impacts of considering heating sector on coal power plants paths are quantified. • Proportion of coal power plants in total heat production increases to 80% in 2030. • Electric heat pumps are developed rapidly for negative carbon emission constraint. [ABSTRACT FROM AUTHOR]

Recently, with the ongoing development of the express industry, the consumption of waste plastic express bags has been increasing year by year, which has brought considerable pressure on municipal waste management. At the same time, in China, where coal is the main energy resource, the upgrading of low-rank coal is a more reliable and prospective way. An effective method for waste treatment and resource upgrading by synergistic co-liquefaction of waste plastic express bags and low-rank coal in a supercritical water-ethanol system has been developed. The effects of different experimental factors (temperature, residence time, plastic-coal ratio, water-ethanol ratio) on the conversion ratio and synergistic effect of co-liquefaction were investigated. The results showed that elevated temperature, lower water-ethanol ratio as well as suitable residence time, and plastic-coal ratio of 1:1 were conducive to the conversion ratio. Temperature ≥375 °C and suitable plastic-coal ratio (1:1) had a significant positive synergistic effect on the conversion ratio, whereas the other conditions exhibited no or negative synergistic effect on the conversion ratio. The maximum conversion ratio and positive synergistic efficiency were 85.11% and 12.25% at 425 °C, 60 min, water-ethanol ratio of 1:1, and plastic-coal ratio of 1:1, respectively. It was observed after FT-IR and elemental analysis based on the solid residue that the oxygen-containing functional groups in the residue disappeared, the oxygen content decreased, the carbon content increased, and the higher heating value (HHV) increased significantly, and the residue could be further used (such as gasification or pyrolysis) without the need for landfill. The GC-MS results of the oil products suggested that the oil products contained high content of hydrocarbons and phenols, as well as esters, alcohols, and other compounds. The hydrocarbons and phenols mainly derived from the decomposition of long chains in plastics and the decomposition of aromatic structures in coal, and the hydrocarbon and phenolic contents produced at 400 °C were 27.74% and 32.62%, respectively. Thus, the oil product can be used further as a chemical raw material. It cannot be ignored that the ethanol medium after reaction can also be further recycled by rotary evaporation. The synergistic co-liquefaction of waste plastic express bags and low-rank coal based on supercritical water-ethanol system is a promising method for waste treatment and resource upgrading. [Display omitted] • A synergistic co-liquefaction for waste express bags and low-rank coal was developed. • Ethanol can improve the synergistic efficiency of co-liquefaction. • The maximum conversion ratio of co-liquefaction reached 85.11% at 425 °C, 60 min. • Oil products from co-liquefaction contained hydrocarbons and phenolic compounds. [ABSTRACT FROM AUTHOR]

Understanding the modes of occurrence of elements in coal is important, not only to help properly evaluate the impacts of potentially toxic elements on the environment and human health but also to provide technical guidance for recovering critical elements from coal ash. Statistical and multivariate data analysis methods have widely been used, together with physical and chemical methods, to determine the modes of occurrence of elements in coal. However, some of the statistical methods, e.g., average linkage hierarchical clustering algorithm have some disadvantages (e.g., statistical errors and poor visualization). A self-organizing map is an unsupervised artificial neural network, and it is known for its high data mining capability and excellent data visualization. In contrast to the average linkage hierarchical clustering algorithm that is commonly used for analyzing the modes of occurrence of elements in coal, the self-organizing map algorithm can provide a topological relationship among elements instead of merely providing the groups to which the elements belong. This paper focuses on the application of self-organizing map to coal elemental data for analyzing the modes of occurrence of elements in coal. Samples used in this study are from the Adaohai, Hailiushu, and Datanhao mines, all located in the Daqingshan Coalfield, Inner Mongolia, China. The results obtained from the self-organizing map algorithm are compared with those produced by average linkage hierarchical clustering algorithm. Based on the previous investigations (mainly direct methods) and further analysis, it can be concluded that the results from the self-organizing map algorithm in this investigation are more consistent with the geochemical nature and previous investigations by direct methods than those from average linkage hierarchical clustering algorithm. Consequently, the self-organizing map algorithm is a new reliable and intuitive method for analyzing the modes of occurrence of elements in coal. [ABSTRACT FROM AUTHOR]

[Display omitted] • Li mostly occurs as adsorption or ion exchange in clay minerals. • The depositional environment of the No. 2 coal alternates between a hydrostatic reducing condition and an anoxic reducing environment. • Multiple geological effects influence the dissolution and migration of element-enriched minerals, resulting in the enrichment of stable components. In order to study the enrichment mechanism and depositional environment of valuable elements, this paper reports new geochemistry and mineralogy data on the No. 2 and No. 5 coals of the Nangou Mine, Ningwu Coalfield. Clay minerals and calcite are the dominant minerals in both the No. 2 and No. 5 coals. Additionally, small amounts of pyrite, quartz, rutile, and zircon are observed under scanning electron microscopy in the No. 5 coal. The studied coals in Nangou Mine are enriched in Li (CC = 8.50 and 5.80, respectively in the No. 2 and No. 5 coal), Zr (CC = 21.87 and 5.53), Nb (CC = 16.97 and 2.54), Hf (CC = 14.00 and 4.19), Ga (CC = 2.56 and 2.41). Li mostly occurs as adsorption or ion exchange in clay minerals, Nb, Zr, Hf, and Ga have organic affinities, rare earth elements and Y are mostly found in residue and organic binding states. The sediment source of the Nangou Mine is characterized by a multi-source area, with the dissolution and migration of element-enriched minerals under the influence of multiple geological effects, leading to the enrichment of valuable elements (Li, Nb, Zr, Ga, and REY). [ABSTRACT FROM AUTHOR]

[Display omitted] • A HSPC for permeable pavements was prepared by two-stage utilization of coal gangue. • The prepared WSAC meeting Chinese standard for 52.5 N ordinary Portland cement. • The HSPC has both high strength and high-water permeability. • The HSPC prepared with WSAC and coal gangue is an environmentally friendly product. As the most discharged solid waste in China; coal gangue (CG) occupies a considerable amount of land and severely pollutes the environment. Large-scale production, low added value of products, and lack of innovative disposal methods have lead to the difficult situation of effective utilization of CG. Therefore, it is very important to develop new ways to utilize CG on a large scale and with high-valued. This paper proposes a new method for reducing the environmental burden and realizing a high-value utilization of CG. The study was based on a two-stage utilization approach. Raw CG was first used to prepare solid-waste-based sulfoaluminate cement (WSAC). Then the prepared WSAC combined with self-ignited coal gangue (SCG) was used to prepare a high-strength pervious concrete (HSPC). The mechanical properties, mineral composition, and microstructure of the prepared WSAC clinker were analyzed. The results show that mortar from the prepared WSAC clinker had a reasonable mineral composition, well-developed crystals, and a compressive strength of 55.2 MPa at three days, which meets the standard for 52.5 N ordinary Portland cement. Furthermore, the influence of the water-binder (W/B) ratio, a ggregate-binder (A/B) ratio, and different SCG content on the performance of HSPC was studied. It was observed that the optimal HSPC was prepared when the W/B ratio and the A/B ratio were 0.22 and 4.0, respectively. Compared with traditional pervious concrete, the prepared HSPC has both high strength and high water permeability, and the obtained compressive strength is 34.8 MPa, a connected porosity of 19.80%, a water permeability of 7.95 mm/s, and a hardening density of 1930.8 kg/m3. An SCG content of 10%–20% was considered to the best dosage range for the preparation of HSPC. Furthermore, the freeze–thaw cycle analysis and abrasion resistance test indicated that HSPC with 10% SCG content has acceptable durability. Finally, the environmental impact of HSPC was evaluated through heavy-metal leaching tests, revealing that HSPC has a good curing ability on heavy metals and the leaching index was lower than the limit specified by the regulations, which reflects the environmental friendliness. Thus, this paper presents a low-cost and promising method for the resourceful utilization of CG and production of a sustainable pavement material. In addition, further research is needed before the application of this material to explore its durability and practicality in a specific environment. [ABSTRACT FROM AUTHOR]

The energy conversion efficiency of coal utilization is a focal point in modern energy management practices and in academic literature. This paper explores life cycle energy efficiency of coal (LEEC), which encompasses six distinct stages from the design of coal mines to the comprehensive reuse of resources. First, the study analyzes improvements to the evaluation of efficiencies in energy systems. Secondly, it proposes a multi-stage energy efficiency analysis and constructs an innovative LEEC model for coal exploitation and utilization. Thirdly, the energy efficiency of coal exploitation and utilization was evaluated, and found that total efficiency in China increased from 33.11% in 2010 to 37.69% in 2014, saving 126 Mtce of energy. Finally, this study found that mine design is the most important stage in improving energy efficiency, followed by the coal processing stage. Moreover, we found that coal processing has an indirect contribution to other stages in the life cycle utilization of coal, such as reducing transportation capacity. The primary research contribution is the development of a comprehensive LEEC model for the entire life cycle of coal, rather than just single-stage evaluation. This lays the foundation for further studies on energy efficiency of industrial chains and across entire systems. • Exploration of energy efficiency across the entire coal life cycle. • The energy efficiency of coal exploitation and utilization increased annually. • Analysis shows the implicit contribution of coal processing to life cycle. • Mine design is a crucial stage for overall life cycle energy efficiency. [ABSTRACT FROM AUTHOR]

Rare earth elements and yttrium (REY) in coal, fly ash as well as coal preparation products have attracted much attention due to the increasing demand worldwide. In this paper, the distribution of REY in different size and density fractions, their mode of occurrence, and the insight they provide on the sediment source region of the Reshuihe coal in southern China are studied. The results show that the physical separation method caused light-REY (LREY) to be enriched in the low-density and large-sized coal particles, whereas medium-REY (MREY) and heavy-REY (HREY) are enriched in small-sized and high-density fractions. In addition, LREY are more closely associated with organic matter, while MREY and HREY occur more often in aluminosilicate minerals. Moreover, the sediment source of the Reshuihe coal was mainly derived from the felsic–intermediate rocks at the top of the Emeishan basalt sequence. Further, REY in the feed coal are generally not enriched, though REY are enriched in density fractions of 1.4 kg/L. The combustion products of coal with a density of 1.4 kg/L obtained by gravity separation have a potential economic value as promising raw materials for REY. • LREY (MREY and HREY) are enriched in the larger (smaller) size fractions with low (high) density grades. • LREY are more closely associated with organic matter, while MREY and HREY tend to occur in aluminosilicate minerals. • The combustion products of coals with a density of 1.4 kg/L have a potential economic value. [ABSTRACT FROM AUTHOR]

Abstract Chinese energy consumption structure has been dominated by coal for a long time, which makes China facing serious environmental problems. To achieve the target of CO2 emission reduction, a carbon emission trading (CET) market and promoting the development of new energy should be worthy choices. The issues of dynamic linkages and spillover effects between the CET market, the coal market and the stock market of new energy companies (NEC) are important topics for studies. The paper applies a VAR(1)-DCC-GARCH(1,1) model and a VAR(1)-BEKK-AGARCH(1,1) model to obtain the following conclusions: (1) There exists significant time-varying correlations and long-run persistence of shocks to the DCCs between Beijing CET market, the coal market and the stock market of NEC, and the coal market and the new energy stock market have higher volatility persistence; (2) There is a bi-directional spillover effects between the coal market and the stock market of NEC, which is consistent with the results of the Granger causality; (3) The optimal weight is 82.65% for new energy stock and 17.35% for coal. The optimal hedge ratio is 49.98% for coal, while the optimal hedge ratio is 17.34% for new energy stock. Highlights • There are significant time-varying correlations and long-run persistence of shocks to the DCCs between three markets. • There is a bi-directional volatility spillover between the coal market and the new energy stock market. • The optimal weight is 82.65% for new energy stock and 17.35% for coal. • The optimal hedge ratio is 17.34% for new energy stock and 49.98% for coal. [ABSTRACT FROM AUTHOR]

Abstract This paper uses coal-measure shales from Carboniferous-Permian in Yushe-Wuxiang Block as an example to study the physical properties of transitional coal measure shales, including geochemical properties (e.g. total organic carbon content (TOC), organic matter maturity and hydrocarbon generation potential); mineral composition determined by X-ray diffraction (XRD) and pore structure characteristics determined by gas adsorption methods. The results indicated that the transitional coal measure shales in Yushe-Wuxiang area mostly comprise type III kerogen and are mostly in the over-mature stage, with shales in the range of 1.86%–3.36% R o. The TOC of transitional shales varied significantly, ranging from 0.10% to 34.37%. Clay minerals and quartz are major minerals in transitional shales, while the predominant clay minerals are illite-smectite mixed clay (I/S) and kaolinite. The total pore volume (TPV) and pore specific surface area (SSA) of investigated mud shales varies from 0.0071 to 0.023 cm3/g and 8.4059–18.2888 m2/g, respectively. The transitional shales mostly provide mesopores and macropores, whereas the micropores provide the main SSA. The TOC content has a distinct effect on the porosity and micropores volume but contributes little to the TPV and volumes of macropores and mesopores. Clay minerals are positively correlated with porosity, TPV and volumes of each class of pores, while quartz has an opposite effect. In the over-maturity stage, the increase of organic matter maturity will inhibit the development level of pores in shale. For the coal measure shales, I/S and illite contribute most to the pore development. Highlights • TOC is positively correlated with porosity and micropore volume. • Clay minerals are positively correlated with pore volumes. • Quartz inhibits the development level of transitional coal measure shales. • The development and evolution of pores was mainly attributed to the presence of I/S and illite. [ABSTRACT FROM AUTHOR]

Since the project approval right was decentralized from the central government to the local governments in 2014 in China, a large quantity of coal power projects has been approved and built, resulting in low operation efficiency and calling for strict de-capacity policy. In this paper, we estimate coal power overcapacity with a cross-province power and energy balance model. We estimate the overcapacity situation in 2015 at 140–160 GW with a comprehensive dataset. The 2020 overcapacity scenario is estimated with detailed representation of official planning and new projects under construction. The results show that there is a general trend of growing overcapacity in most provinces by 2020 and the national excess scale will be around 210 GW under the basic scenario and may even reach 240–260 GW under a High scenario. Relevant policy suggestions are put forward to address the overcapacity issue. [ABSTRACT FROM AUTHOR]

Currently, resource integration in coal-burning facilities and clean energy reconstruction are being strongly pushed forward in China. As a clean fossil energy, unconventional natural gas, such as coalbed methane (CBM), exhibits promise as an energy development strategy. In China, there are abundant CBM resources in the considerable reserves of low-rank coal. Therefore, the study of low-rank coal is the key to realize the high-yield and high-efficiency development of CBM resources in China. In this paper, a new water injection device was designed to prepare coal samples with a variety of moisture contents, and a novel method to measure the gas desorption properties in coal containing water was introduced. On this basis, the gas desorption law in low-rank coal with different moisture contents was tested, and the effect of moisture on the gas diffusion properties in low-rank coal was analyzed. The results indicate that the initial gas desorption volume of low-rank coal is extremely large and that the gas desorption law in the moisture-containing low-rank coal can be described by Airey's empirical equation. It is also observed that the ultimate gas desorption volume, initial gas desorption rate and initial effective gas diffusion coefficient all shift toward the direction that is beneficial to CBM development. Therefore, reducing the moisture content in low-rank coals through certain techniques can dramatically enhance the gas migration behavior and achieve the purpose of high-yield CBM development. [ABSTRACT FROM AUTHOR]

Abandoned coal tunnels (ACTs) pose risks to coal mine safety by accumulating gas and water, causing surface subsidence, and endangering infrastructure. Accurate detection of ACTs is vital for advanced prediction and geotechnical hazard warnings. Seismic methods, particularly the surface-wave method, have demonstrated reliability in detecting shallow buried tunnels within complex geological environments, but improvements in accuracy and resolution are still needed. In this paper, we suggest utilizing the multiscale window analysis of surface waves (MWASW) method for ACT surveys. We conduct a synthetic test and a real-world case study to evaluate the feasibility and validity of this approach. The synthetic test on a 2D ACT model reveals that MWASW can reconstruct anomalous structures and identify the presence of an ACT, while also highlighting some limitations of the method. In a real-world scenario, we applied MWASW to a multi-survey line dataset from a coal mine in Shanxi Province, China. The resulting meter-scale resolution pseudo-3D S-wave velocity structure uncovers a primary ACT and two sub-ACTs buried at approximately 60 m, offering valuable insights into their morphology and orientation. To our knowledge, this is the first application of the MWASW method in such a case study, indicating its potential as an emerging alternative for characterizing complex near-surface media, such as abandoned coal tunnels or mined-out areas in coal fields. • Detect coal tunnels using spatial multiscale dispersion analysis method. • Directly reveal 2D S-wave velocity profiles with high resolution and accuracy. • Reconstruct a pseudo-3D structure model in field case. [ABSTRACT FROM AUTHOR]

A more efficient use of China's coal resources is key to rapidly promoting the growth of the country's industrializing economy. As such, it is essential that an effective approach for measuring and evaluating the current efficiency of coal resources is developed. This paper measures the efficiency of coal resources in 30 provinces in China from 2000 to 2015 using an improved DEA model of Bootstrap, and it uses Tobit regression to analyze the influencing factors on the efficiency of coal resources. The results illustrate that: 1) The proposed approach could significantly improve upon the accuracy of the measurement of the traditional DEA model. 2) The efficiency of coal resources shows an uptrend of fluctuation for the research period. With respect to the influential factors, total coal consumption has the least influence on the efficiency of coal resources. In contrast, local financial science and technology expenditures have greatest influence on the efficiency of coal resources. Among all the influential factors, local financial science and technology expenditures have the greatest negative impact on energy efficiency of coal resources and it is very critical that the government increases investment in scientific and technological investment in the mining industry. • This paper uses Bootstrap-DEA to calculate the ECR of 30 provinces in China. • The finding that FST has negative impact on ECR is the most serious, particularly for 14 provinces in China. • GDP, IPC and SEC have negative impacts on ECR in 8 provinces. • COC has negative impact on ECR in 6 provinces. • TER and RPY have negative impacts on ECR including in 11 provinces and 9 provinces respectively. [ABSTRACT FROM AUTHOR]

The bottlenecks in developing high-efficiency ultra-super critical (USC) coal power technology are analyzed within the context of the growing pressure on the coal power industry to reduce carbon dioxide (CO 2 ) emissions. To meet these demands, further improving the annual average operating efficiency of coal power is essential. A cross-compound double reheat unit design characterized by an elevated and conventional turbine layout is proposed in this paper. This new design can greatly shorten the length of expensive high-temperature piping required, significantly cut piping costs as well as reducing pressure drops and heat losses, resulting in a much higher efficiency and performance-price ratio than conventional double reheat design. The engineering study demonstrates the feasibility and advantages of this design. Now this new design is being implemented on Pingshan Phase II Project as a demonstration coal power unit in China. Despite the new turbine arrangement, Pingshan Phase II Project also adopts a series of energy saving, environmental protection, efficiency preservation and safety technologies, of which some have already gained success in Shanghai Waigaoqiao No. 3 Power Plant. Based on the new design and further optimization, the unit net efficiency of Pingshan Phase II is expected to achieve 49.8% under rated conditions on a lower heating value (LHV) basis. Combined with a series of innovative technologies that can keep the efficiency from decreasing under operational conditions, the annual average net efficiency can achieve 48.8% on LHV basis. This efficiency level is high enough to meet the strict CO 2 emission standard proposed by United States Environment Protection Agency (U.S. EPA) based on the Pittsburgh #8 bituminous coal, showing significant potential for reducing CO 2 emissions. A series of low-energy-consumption and even energy-saving pollutants removal technologies are also be applied on this project to harmonize high efficiency and low emissions. [ABSTRACT FROM AUTHOR]

The variations in stress-sensitive minerals and elements in tectonically deformed coals (TDCs) were revealed in this paper. Results show that the clay minerals, carbonates and sulfides in the Middle to Lower Permian TDCs of the no. 8 and no. 10 coal seams of the Zhuxianzhuang mine are dominated by kaolinite, iron dolomite and calcite, and pyrite, respectively. The contents of Th are significantly higher than U, indicating that the sedimentary paleo-environment was almost independent of seawater and was characterized by hypoxia during peat accumulation periods. The light rare earth elements (LREEs) are enriched, yielding (La/Lu) N values of 1.00–12.30 and slightly positive Ce anomalies in the no. 8 (0.95–1.44, δ Ce/ δ Eu = 1.30–2.62) and no. 10 coal seams (1.02–1.31, δ Ce/ δ Eu = 1.66–2.17). The cluster results show that stress-sensitive elements in TDCs can be classified as aggregation-type (Si, Al, Ti, K, Fe, Sc, Li, Rb, Nb, Ag, Cd, Ta, Tl, Bi, Th, U, W), dissipation-type (N, H, Cl, Mo, Ni, Y, Sr), and mutant-type (O, Na, Ca, Be, Mn, Co, Ga, Ge, Pb, Bi, As). The enrichment effects of ductile deformations for major elements are more significant than those of brittle deformations. The combinations of (Nb, U), (Th, Rb), and (Li, Sc, Ag, Ta) are good brittle-, ductile-, and brittle-ductile enrichment-type elements, respectively, which can be used as good indicators of the coal's tectonic deformation. Sr records higher loss rates in brittle TDCs than in wrinkle coals. The Mo content gradually decreases with increasing tectonic deformation intensity, which is related to the dynamic metamorphism caused by tectonic deformation. Nucleophilic clay mineral elements (Be, Ga, Pb, Ge) in the no. 8 and no. 10 coal seams record similar trends and are highest in scaly coals, indicating that strong shearing effects can promote the enrichment of these elements. The contents of LREE and heavy rare earth elements (HREEs) both increase with the increasing tectonic deformation intensity. For various TDCs, LREE record higher degrees of fractionation than the HREE. [ABSTRACT FROM AUTHOR]

In the present paper, life cycle analysis of coal-based synthetic natural gas (SNG) is performed for heat supply and electricity generation in China with a full consideration of energy efficiency, environmental pollutions and greenhouse gas emissions. Several different technical routes of SNG are studied in detail and the emissions of SO 2 , NO x , CO 2 and energy efficiency are all calculated. For comparisons, technical routes of ultra supercritical and coal-fired power generations are also analyzed together with a direct use of coal for heat supply. Our results show that the cogeneration of heat and electricity is a suitable technical route for SNG utilization. Comparing with ultra-supercritical and coal-fired power generations, technical routes based on SNG could significantly reduce the emissions of pollutants (especially for heat supply) with an acceptable level of the energy efficiency. After synthesis of SNG, our life cycle analysis suggests that SNG should be transported to the energy demand center for further power generation locally. [ABSTRACT FROM AUTHOR]

Modes of occurrence of elements in Ge-rich coals are important because they provide an understanding of Ge mineralization and insight into Ge behavior during coal combustion and the modes of occurrence for Ge in the resulting combustion products. Previous researchers showed that the leaching of granite by N 2 – CO 2 mixed hydrothermal solutions in the Lincang coal in southwest China led to the enrichment of Ge. Elevated Ge concentrations from leaching of granite by hydrothermal solutions have been established in the nearby Lincang Ge ore deposit; however, the influence of hydrothermal solutions, especially mixed hydrothermal solutions, on the modes of occurrence of elements in coal have not been quantitatively analyzed. In this paper, we focus on the quantitative analysis of the influence of mixed hydrothermal solutions on the modes of occurrence of elements in coal. Samples used in this study were collected from the Dazhai Mine, located in the Lincang Ge ore deposit, Yunnan Province, southwestern China. The correlation coefficients between pyrite, ash yield, Al 2 O 3 , and SiO 2 versus elemental concentrations in coal are processed with the correlation analysis algorithm. The results show that a distinct break in pyrite content of ∼16.8 wt% as a threshold for different elemental modes of occurrence of elements as a result of hydrothermal fluids. The modes of occurrence of As and Hg changes from an organic-inorganic mixed affinity to predominantly in pyrite by the influence of volcanic hydrothermal fluids when the content of pyrite is higher than 16.8 wt%. • A correlation analysis algorithm is used to analyze the modes of occurrence of elements in high-germanium coals. • Existence of the associations between element concentrations and pyrite-content-changes. • Many elements show a significant change in correlation around 16.8 wt% pyrite content. [ABSTRACT FROM AUTHOR]

In China, the lack of Li resources is in stark contrast to a large amount of coal gangue produced by coal mining. To determine the distribution patterns and existing status of lithium (Li) elements in the coal gangue, the mineralogical and geochemical analysis were formed on samples of the roof, floor, and parting of No. 02, 2, 8, and 9 coal seams, being mined in Malan mine, Xishan coalfield, Shanxi Province. The results show that the lithium content in this study area is relatively enriched, the highest content is 499 μg/g in sample 02-G, and the average content is 109.8 μg/g, which is two times that of the world average value of claystone (45 μg/g). XRD analysis shows that the mineral composition of parting samples is mainly clay mineral kaolinite, while the coal seam roof and floor samples also include quartz and some iron-bearing minerals, such as pyrite and siderite. Likewise, possible lithium-rich mineral phases and possible lithium-rich factors were investigated in this paper. A comprehensive clay separation experiment and correlation analysis between lithium and major elements indicate that lithium is likely to exist in the clay mineral kaolinite in the study area. It is also found that the content of Li adsorbed by cryptocrystalline kaolinite is generally higher than that of crystalline kaolinite. According to the mechanism of Li+ adsorption in clay minerals, the higher lithium content of cryptocrystalline kaolinite is due to its larger specific surface area, which can adsorb more lithium on the surface. [ABSTRACT FROM AUTHOR]

• A LapSVM-based semi-supervised method is proposed for coal structure identification to address limited labeled-data issue. • Experiments show the LapSVM is efficient in coal structure identification using few labeled logging data. • Comparison indicates the LapSVM outperforms traditional SVM with improved classification accuracy and generalization ability. Coal structure is a critical parameter in coalbed methane (CBM) development due to its significant impacts on methane enrichment, fluid flow and hydraulic fracturing. Traditional statistical analysis and data-driven machine learning methods for coal structure identification are highly dependent on the labeled logging data and have potential limitations when labeled logging data is limited. To address this issue, this paper proposed a semi-supervised learning method based on Laplacian support vector machine (LapSVM) to identify coal structure by using few labeled logging data. By mining the structure information from abundant unlabeled data, LapSVM can improve the model performance and alleviate the over-reliance on labeled data. To evaluate and verify the effectiveness and reliability of the proposed LapSVM method in coal structure identification, datasets collected from 32 CBM wells in the southern Qinshui Basin, China, are utilized in this study. The particle swarm optimization (PSO) is adopted for parameter optimization of LapSVM models. For the LapSVM model, the addition of unlabeled data is conducive to enhance model accuracy, and unavoidably increases the computational cost at the same time. The comparison of training, testing and blind-well test results between the LapSVM and standard support vector machine (SVM) models indicates that the LapSVM outperforms traditional SVM and possesses higher accuracy and generalization in coal structure identification. It has been demonstrated that the LapSVM can be a reliable tool for coal structure identification when limited labeled logging data is available. [ABSTRACT FROM AUTHOR]

[Display omitted] • The genetic stage of siderite nodules of Late Paleozoic coal measures in North China epicontinental Sea Basin was identified. • The material source of siderite nodules in the study area was identified. • The genetic mechanism of siderite nodules in the study area was clarified. • The genetic model of siderite nodules in epicontinental sea basin coal measures was established. Siderite is a mineral resource and a climate sensitive mineral. Siderite nodule layers are widely developed in coal measures within the marine-ontinental transitional facies of North China epicontinental sea basin, yet their formation environment and genetic mechanism are poorly understood. In this paper, taking the siderite nodule layers in the coal measures of the Late Paleozoic Taiyuan Formation in Zibo area of North China as an example, the formation environment and genetic mechanism of siderite nodules in the transitional facies of the epicontinental sea basin are studied through detailed petrological, sedimentological and geochemical analysis. It is found that the siderite nodules in the research area were formed in a tidal flat-lagoon environment. The siderite nodules are formed in the synsedimentary stage, the original information of chemical composition and characteristics of the nodules being largely retained. Most of the carbon in the siderite nodules originates from inorganic carbon from marine carbonate rocks, with the remainder originating from inorganic carbon formed by dissimilatory iron reducing bacteria (DIR) degrading organic matter. Meanwhile, most of the iron in the siderite nodules originates from hydrothermal fluids, and the remainder from terrigenous sediments. The content of iron input from hydrothermal fluids and terrestrial sediment represents a trade-off relationship. The two genetic mechanisms of the siderite nodules are as follows: 1) Chemical genetic mechanism: The siderite nodules are mainly formed by the combination of low-valence iron (Fe2+) and inorganic carbon in seawater through reduction with iron input from hydrothermal fluids as the main source. 2) Biochemical genetic mechanism: Some is formed by the combination of low-valence iron (Fe2+) and inorganic carbon with high-valence iron (Fe3+) as an oxidant to degrade the organic matter and convert organic carbon into inorganic carbon through DIR. On this basis, a genetic model of the Late Paleozoic coal measures siderite nodules in the epicontinental sea basin is established. [ABSTRACT FROM AUTHOR]

To understand more about damage, failure, and transformation of coal, this paper performed triaxial loading tests on coal samples obtained from a deep coal mine in China. Results showed that the brittle failure characteristics of the specimens were obvious under single-axis loading, and that the ductile failure characteristics of the specimens increased as confining pressure increased. The ultimate strength and residual strength of the samples exhibited a sound linear growth relationship with confining pressure. And according to the change trend of damage variable with axial strain, the damage process of coal body is divided into four stages: initial damage stage, stable damage stage, rapid damage stage and damage failure stage. The energy conversion characteristics of the samples were thoroughly analysed and it was found that with the increase of confining pressure, the proportion of elastic energy of coal samples increases, while the proportion of dissipated energy decreases, indicating that confining pressure can inhibit the expansion of fractures and strengthen the energy storage capacity of coal samples. It was also discovered that the greater the confining pressure, the greater the ultimate elastic energy of the samples. This study is of great significance for mastering high energy level disasters in deep mines. • Confining pressure promotes the transformation of coal body failure characteristics. • Energy storage and release is the essence of coal body deformation and failure. • The confining pressure promotes the storage of elastic energy of coal body. • The confining pressure inhibits the energy dissipation of coal body. [ABSTRACT FROM AUTHOR]

China's coal-fired power plants (CPPs) have higher economics due to ignoring the coal resources externalities. Levying coal resource tax on CPPs conduces to make up for the coal resources externalities, and promote China's energy transformation. The key issues are to determine the reasonable resource tax rate and to analyze its impact on the performance of CPPs. This paper calculates the coal depletion cost (CDC) in China employing user cost approach, and evaluates the economic and environmental performance of CPPs under different resource tax scenarios by a system dynamics (SD) model. The results reveal that the reasonable coal resource tax rate should be 2.04%–9.70%, and levying resource tax on CPPs will not make CPPs unprofitable and can help to reduce CO 2 and pollutants emissions. This paper holds that levying resource tax with low and medium rates (3%–6%) on CPPs can compensate for the CDC and reduce the economic gap between coal-fired power and renewable energy, so as to support the promotion of clean energy. • Coal depletion cost is sensitive to discount rate and remaining mining life. • China's coal depletion cost accounts for 2.04%–9.70% of total mining revenue. • Levying resource tax will not make coal-fired power plants unprofitable. • Levying resource tax is conductive to reduce CO 2 and pollutants emissions. • The resource tax rate levied on coal-fired power plants should be 3%–6%. [ABSTRACT FROM AUTHOR]

The origin and modes of occurrence of rare metals in coal (e.g., rare earth elements, U, Se, Re, Ge, Ga, and Nb) have attracted much attention in recent years because such investigations can provide fundamental information for assessment of their economic significance. This paper investigates the abundance, modes of occurrence, and origin of rare metals in three Lopingian coals (LL5-K3, CG3-K6, and CG1-K7 Coals) from the Yishan Coalfield, Guangxi Province, southern China. The coals of this coalfield are preserved within carbonate successions and are characterized by super-high-organic sulfur (SHOS) contents (mostly 6–9%) and an elemental assemblage enriched in U-Se-Mo-V-Re. Two different hydrothermal solutions were responsible for the geochemical anomalies in the Yishan coals. One was responsible for the U-Se-Mo-V-Re enrichment in the three coal seams while the other was a high-temperature solution responsible for the positive Eu anomalies and the elevated rank ( R o,ran = 2.05%) of the LL5-K3 coal. The U, Se, Mo, V, and Re in the CG3-K6 and CG1-K7 coals mainly have an organic association, but the same elements in the LL5-K3 coal have a mixed organic-inorganic affinity, attributed to high-temperature leaching in the early coalification stage. In addition to highly elevated concentrations of U-Se-Mo-V-Re, the average concentration of oxides of the rare earth elements and Y in the LL5-K3 coal (1387 ppm on average, ash basis) is higher than the cut-off grade for industrial deposits of these elements and thus the coals also have potential as raw materials for the recovery of rare earth elements. [ABSTRACT FROM AUTHOR]

The rapid growth of vehicle ownership in China has brought severe energy and environmental challenges. By referring to a wide range of existing studies and policy documents, this paper reviews the rationality, pathway choice, policy initiatives, barriers and opportunities of developing coal-derived alternative fuels in China, including methanol, Dimethyl Ether (DME) and Coal-to-Liquid (CTL). The review suggests that (a) the production of coal-derived alternative fuels faces the constraints of coal resource, water consumption and CO 2 emissions. China should develop coal-derived alternative fuels with full considerations of these constraints. (b) Coal can be utilized as vehicle fuel through multiple pathways, each pathway with significant trade-off among its energy, environmental and economical attributes. Some critical issues, such as the toxicity of methanol use, the life cycle Greenhouse Gas emissions from different pathways, are still not fully justified. Demonstration plays an essential role in justifying these issues and identifying the optimal technology pathway. (c) The demonstration of methanol use as vehicle fuel faces several major barriers. To further promote the demonstration progress, an essential step is to adjust the excise tax rate for fuel methanol. Besides, the government should consider to establish a number of fuel methanol closed-operation regions in the coal-rich provinces. (d) Driven by the fluctuations in oil prices and policy incentives, the established and planned CTL capacities have been growing very fast. To protect CTL plants from the impacts of oil price fluctuations or carbon tax, the government can consider to provide appropriate subsidies to CTL plants when necessary. (e) The DME fuel and vehicle technologies are more likely to be developed as technology reserves rather than mainstream technologies. Regional demonstration projects should be maintained to improve infrastructure and vehicle technology maturity. [ABSTRACT FROM AUTHOR]

This paper presents an integrated approach for theoretical analysis and numerical modeling to investigate the ground response mechanism of entries and control methods induced by hard roof in longwall top coal caving panel (LTCC). The test site is located in the city of Jinzhong, Shanxi Province, China. A roof mechanical model for the main roof's different breaking positions was created to study the ground response mechanism of gob-side entries. The theoretical analysis indicated that the closer the main roof fracture line is to the gob, the smaller the lateral cantilever length of the main roof above the gob, and the surrounding rock of the roadway are more stable. Therefore, an innovative approach is proposed t to reduce the lateral cantilever length of the main roof above the gob area and automatically retain entry. This approach involves applying the "directional roof split blasting technique for pressure relief and automatic retained entry" (DRSBPRRE) in the thick coal seam of the LTCC panel. Meanwhile, numerical modeling results verified the results of the theoretical analysis. The results of the numerical simulation and practical application suggest that the DRSBPRRE approach can eliminate the cantilever length of the main roof, significantly reduce the peak vertical stress in the solid coal rib by approximately 13.76 % and reduce the surrounding rock damage and deformation. Therefore, the DRSBPRRE approach is a safe and efficient mining method for pressure relief and entry retention. This research could provide an important reference for thick coal seam LTCC panel non-pillar coal mining technology. [ABSTRACT FROM AUTHOR]