Search Results (1,183)

The influence of coal and gas outbursts from a coal seam adjacent to the working face is crucial for determining its automatic gas discharge width, which is an important basis for the roadway position design of the adjacent working face. This study focuses on determining the automatic gas discharge width of the coal body in the neighboring goaf, especially examining the working face of the E₁₀-32040 air mining area and the E₁₀-32060 wind tunnel of the No. 1 Mine operated by Pingmei Company. Theoretical analysis, strain-softening simulation, and field testing were adopted to study the automatic gas discharge width under the current mining conditions, and the results are as follows: (1) Back mining at the working face has a greater impact on the coal body of the neighboring goaf than roadway excavation, and the compression deformation at 50 m from the goaf after back mining is 6.18 times that during roadway excavation. (2) The gas content of the coal body of the neighboring goaf is linearly distributed, and the coefficient of determination (R²) is 0.98024. (3) The extent of compression and deformation of the neighboring coal body follows an exponential distribution, and the coefficient of determination (R²) is 0.99482. (4) Under the current mining conditions, the risk of protrusion can be considered eliminated when the residual gas content is below 4.45 m³/t. The compression deformation is 0.96‰ when the automatic gas discharge width is 30.11 m. The research results can provide theoretical reference and data support for adjacent roadway location design and the selection of gas prevention and control measures in coal seams. Full article

The article presents a comprehensive analysis of long-term studies on hydrogen-hydrocarbon free gases (FGs) in the rocks of the Khibiny massif, systematically organized and generalized for the first time. Gasometric observations were predominantly conducted within underground mine workings, with occasional measurements taken during the drilling of exploration boreholes at the surface or in subsurface air within loose sediments. Methane is the primary component of these gases, followed in descending order by hydrogen, ethane, helium, other methane homologs, and alkenes. Nitrogen is also presumed to be present, although its proportions remain undefined. The carbon and hydrogen in FGs exhibit relatively heavy isotopic compositions, which progressively lighten from methane to ethane. The intensity of gas emissions is characterized by a gas flow rate from shot holes and boreholes, reaching up to 0.5 L/min but generally decreasing significantly within an hour of reservoir exposure. Gas-bearing areas, ranging in size from a few meters to tens of meters, are distributed irregularly and without discernible patterns. The FG content in rocks and ores varies from trace amounts to approximately 1 m³ of gas per cubic meter of undisturbed rock. These gases are primarily residual, preserved within microfractures and cavities following the isolation of fluid inclusions. Their distribution and composition may fluctuate due to the dynamic geomechanical conditions of the rock mass. The release of flammable and explosive FGs presents a significant hazard during ore deposit exploration and development, necessitating the implementation of rigorous safety measures for mining and drilling operations. Additionally, the environmental implications and potential applications of gas emissions warrant attention. Future comprehensive studies of the Khibiny gases using advanced methodologies and equipment are expected to address various scientific and practical challenges. Full article

This study addresses the abnormal emission of pressure-relieved methane under high-intensity mining conditions by integrating geostatistical inversion, FLAC^3D-COMSOL coupled numerical simulations, and stable carbon–hydrogen isotopic tracing. Focusing on the 12023 working face at Wangxingzhuang Coal Mine, we established a heterogeneous methane reservoir model to analyze the mechanical responses of surrounding rock, permeability evolution, and gas migration patterns under mining intensities of 2–6 m/d. Key findings include the following: (1) When the working face advanced 180 m, vertical stress in concentration zones increased significantly with mining intensity, peaking at 12.89% higher under 6 m/d compared to 2 m/d. (2) Higher mining intensities exacerbated plastic failure in floor strata, with a maximum depth of 47.9 m at 6 m/d, enhancing permeability to 223 times the original coal seam. (3) Isotopic fingerprinting and multi-method validation identified adjacent seams as the dominant gas source, contributing 77.88% of total emissions. (4) Implementing targeted long directional drainage boreholes in floor strata achieved pressure-relief gas extraction efficiencies of 34.80–40.95%, reducing ventilation air methane by ≥61.79% and maintaining return airflow methane concentration below 0.45%. This research provides theoretical and technical foundations for adaptive gas control in rapidly advancing faces through stress–permeability coupling optimization, enabling the efficient interception and resource utilization of pressure-relieved methane. The outcomes support safe, sustainable coal mining practices and advance China’s Carbon Peak and Neutrality goals. Full article

Coal mining and combustion have the potential to increase exposure to radon, a form of radioactive gas recognized as one of the major contributors to lung cancer incidents. In South Africa, coal is used as the primary energy source for producing electricity and for heating, predominantly in informal settlements and township communities. Most of the existing coal-fired power plants are found in the Mpumalanga province. This paper presents long-term radon (²²²Rn) measurements in dwellings surrounding coal mining centres in the Mpumalanga province and evaluates their contributions to indoor radon exposures. The indoor radon measurements were conducted using solid-state nuclear track detectors and were performed during warm and cold seasons. It was found that the overall indoor radon activity concentrations ranged between 21 Bq/m³ and 145 Bq/m³, with a mean value of 40 Bq/m³. In all the measured dwellings, the levels were below the WHO reference level of 100 Bq/m³ and 300 Bq/m³ reference level recommended by the IAEA and ICRP, with the exception of one dwelling that was poorly ventilated. The results reveal that individuals residing in the surveyed homes are not exposed to radon levels higher than the WHO, ICRP, and IAEA reference levels. The main source influencing indoor radon activity concentrations was found to be primarily the concentration of uranium found in the geological formations in the area, with ventilation being an additional contributing factor of radon levels in dwellings. To maintain good air quality in homes, it is recommended that household occupants should keep their dwellings well ventilated to keep indoor radon levels as low as possible. Full article

As intelligent mining develops, utilizing coal mine production monitoring data for early warnings has become a crucial means of ensuring safety in mining operations. Assisting decision-makers in making scientific choices through multi-source and massive data is a complex yet vital task. Based on multi-source information fusion, a model for the coal mine production environment is proposed in this paper. It is designed to provide early warnings regarding the safety status of coal production environments in order to assist management and control personnel in making scientific decisions. Firstly, data integration of multi-source heterogeneous datasets was conducted. Multi-source heterogeneous data collected by various types of monitoring sensors in coal mines were analyzed, including temperature, dust, wind speed, vibration energy, and gas. Based on this, the factors influencing coal mine production safety were identified. These factors were then screened through factor analysis to determine the index. An early warning index system for coal mine production environment safety was established. The index weight was established by the principal component analysis method, and the index system for coal mine production environment safety and early warning systems was established. Secondly, based on BP neural networks, a multi-input single-output feature-level fusion model and a multi-input multi-output feature-level fusion model were constructed. Based on the above model, the safety warning for coal mine production environments was implemented. The accuracy of model was 89.29%. Based on multi-source information fusion, the early warning system for coal mine production environments was constructed. The system exhibited good feasibility. It could assist management and control personnel in making scientific decisions. Full article

With the popularization of comprehensive mechanized mining methods and the increase in coal mining intensity, production has become more concentrated and efficient, which inevitably leads to Coal seam accumulates a large amount of gas The existence of huge goaf and mining overburden cracks that form behind the working face provides favorable conditions for the migration of gas to the goaf and its subsequent accumulation. The high concentration of gas that accumulates in the goaf gradually flows toward the working face under the action of pressure and concentration gradients, which can easily cause gas overrun accidents at the working face. Therefore, effective relief of the gas pressure in the goaf is important to guarantee safe and efficient mining at the coal mine working face. One of the most used gas drainage methods in such mines is high-level borehole gas drainage. This method can effectively reduce the gas content of coal seams, ensure the safe production of working faces, and reduce carbon emissions. In this study, the mining of a high-gas and low-permeability extra-thick coal seam in the Shanxi mining area is taken as the engineering background. In order to optimize the extraction design and improve the efficiency of gas extraction, according to the dual characteristics of coal seam pores and cracks, the permeability, and migration form of the gas in the coal body are analyzed, and a COMSOL coal seam gas migration model is established. By controlling different gas extraction horizons, pressure, and the number of boreholes and by optimizing the trajectory of the boreholes, the law of gas migration during high-level borehole gas extraction and the variation law with extraction time and pressure are studied. From this, the effective extraction calculation formula is fitted and statistical analyses are carried out. Through on-site extraction and simulation verification, the gas concentration was found to reach a maximum of 86% at a distance of 23 m from the floor. When using similar extraction times, 20 MPa gas extraction was found to have the best effect. The highest gas concentration in the upper corner was only 0.71%, and the extraction efficiency is higher when the high-level borehole trajectory angle is 30 degrees. The research results have important reference value for gas disaster control in the fully mechanized caving face of high-gas low-permeability and extra-thick coal seams. Full article

Emulsion explosives are extensively utilized in the global mining industry due to their superior water resistance, high safety standards, cost-efficiency, and robust performance. The basic component of these explosives is a water-in-oil emulsion matrix, which, in its initial state, lacks the capacity for detonation. The sensitization process, achieved through either physical or chemical means, is a critical step that enhances the emulsion’s sensitivity to detonation, thereby improving its operational efficiency in blasting applications. This review presents a comprehensive and systematic analysis of the current scientific literature and experimental investigations concerning the impact of key sensitizing methods and agents on the detonation characteristics of emulsion explosives. Particular emphasis is placed on the classification of sensitizers, their physicochemical properties, and their interactions with the emulsion matrix. By examining various sensitization mechanisms, this study provides insights into the role and efficacy of both established and emerging sensitizing agents. The findings of this review highlight the pivotal role of sensitizer selection in defining the detonation performance of emulsion explosives, with implications for enhancing safety standards and ensuring the protection of both industrial operations and public safety. The most optimal sensitization method is chemical, utilizing cost-effective components that generate gas bubbles within the matrix. A key advantage is the in situ production of emulsion explosives, which eliminates the need for their transport on public roads, thereby enhancing safety and reducing the risk of terrorist threats. Full article

Critical mineral recovery from wastewater is an enhancement of conventional mining that can help meet growing demand. This work investigates two energy wastewaters that have previously been shown to be enriched in critical minerals, oil and gas produced water in the Permian Basin and combustion residual leachate. Treatment of these two wastewaters using reverse osmosis or thermal-based methods concentrates critical minerals, which improves the economic viability of critical mineral recovery. Revenue from mineral recovery could also offset treatment costs for operators. This work evaluates the cost of treatment for each wastewater and evaluates the potential revenue from critical minerals concentrated in the brine. The levelized cost of water for combustion residual leachate ranges from USD 1.90 to USD 16.20 (USD 2023/m³ permeate) and for produced water ranges from USD 14.40 to USD 24.30 (USD 2023/m³ distillate). Recovery opportunities range from USD 0.11 to USD 1.13 (USD 2023/m³ permeate) for leachate and from USD 8.28 to USD 42.10 (USD 2023/m³ distillate) for produced water, dominated by the value of magnesium and lithium. Comparing the maximum value of critical minerals contained in produced water and the maximum treatment costs, the value of critical minerals exceeds the cost of treatment by USD 17.80/m³ distillate, which signals a potential revenue opportunity. Full article

Hydraulic measures are widely used to improve coal seam permeability, but not all hydraulic measures have a positive effect on coal permeability in soft coal seams, and the permeability-enhancing effect of hydraulic measures in soft coal seams is not clear. To further study the permeability-enhancing mechanism of hydraulic measures and compare the effect of hydraulic punching and reaming in soft coal seams, this study takes Changping Mine, China, as its case study. A comparative analysis was conducted on the influence range and gas extraction effect of hydraulic reaming and punching on coal seam permeability enhancement. The following conclusions were mainly drawn: A mathematical calculation model was established for the strength and impact velocity of high-pressure water jet damage to the coal body, and the critical theoretical pressure threshold and jet velocity were obtained. During the implementation of hydraulic measures at the Changping Mine, the effective radius of hydraulic reaming is around 4.5 m, and the influence radius of hydraulic reaming is approximately 7.5 m; the effective radius of hydraulic punching is about 6.5 m, and the influence radius of hydraulic punching is approximately 7–9 m. The gas data from field monitoring show that hydraulic measures have significantly improved the extraction gas concentration and purity, and hydraulic punching has a more significant effect on enhancing permeability in soft coal seams. Full article

Concrete is known for its high structural performance and workability, but its environmental impact is significant in terms of the utilization of virgin resources and greenhouse gas emissions. To mitigate the negative climate effects of concrete, it is essential to continuously develop and adopt eco-friendly practices in the construction sector. This paper provides an overview of current practices, opportunities, and challenges for developing and adopting eco-friendly concrete. Promising paths for eco-friendly concrete construction include using supplementary cementitious materials (SCMs) instead of energy-intensive traditional cement, incorporating locally available, waste-based materials rather than virgin resources, adopting recycling and reusing techniques, employing advanced technologies, such as performance-enhanced concrete and carbon capture and utilization techniques, etc. Among the studied materials, some waste materials such as rice husk ash, mine tailings, and municipal solid waste ash have found potential and demand further research. The adoption of new materials in concrete and attributing them in practices faces significant social, economic, and regulatory challenges. Addressing these obstacles requires interdisciplinary research and development, the establishment of clear standards and incentives, and educating skilled professionals and efforts to raise social awareness. Full article

Gas explosions are the most serious type of accident in coal mines in China. This study analyzed 125 gas explosion accidents that occurred between 2010 and 2020. The results showed that the number of gas explosion accidents and deaths in 2010–2020 was stable and decreasing. The number of larger gas explosion accidents in 2010–2020 is the largest, but the death toll from major accidents was much greater. Coal faces, headings, and roadways are the main locations where gas explosions are initiated. The coal mines in which gas explosions occur in coal faces and headings are mainly “township” enterprises and private mines, all of which engage in illegal operations. The main cause of gas accumulations in roadways is ventilation system failure; these failures can be reduced with improved ventilations system management. The number of gas explosion accidents and related deaths in the Sichuan, Guizhou, and Heilongjiang provinces are very high. The annual change in the frequency of gas explosion accidents, the quarterly distribution of gas explosion accidents, and time during a mining shift when gas explosion accidents occur are closely related to national policies and regulations, company annual production goals, and the mental status of miners, respectively. Full article

S-wave seismic data are unaffected by natural gas trapped in strata, making them a valuable tool to study evaporite facies comparing to P-wave data. S-wave seismic data were utilized to construct an isochronous framework and analyze evaporite facies by seismic sedimentology methods in the Quaternary biogenic gas-bearing Taidong area, Sanhu Depression, Qaidam Basin, NW China, with calibration from wireline logs, geochemical evidences, and modern analogs. Techniques of phase rotation, frequency decomposition, R (Red), G (Green), B (Blue) fusion, and stratal slices were integrated to reconstruct seismic geomorphological features. Linear and sub-circular morphologies, resembling those observed in modern saline pans such as Lake Chad, were identified. Observations from Upper Pleistocene outcrops of anhydrite and halite at Yanshan (east of the Taidong area), along with lithological and paleo-environmental records from boreholes SG-5, SG-1, and SG-1b (northwest of the Taidong area), support the seismic findings. The slices generated from the S-wave seismic data indicate a progressive increase in the occurrence of evaporite features from the K2 standard zone upwards. The vertical occurrence of evaporite facies in the Taidong area increases, which coincides with the contemporary regional and global arid paleo-environmental changes. The interpretation of Quaternary stratal slices reveals a transition from a freshwater lake to brackish, saline, and finally, a dry saline pan, overlaid by silt. This analysis provides valuable insights into locating evaporites as cap rocks for biogenic gas accumulation and also into mining the evaporite mineral resources in shallow layers of the Taidong area. Full article

The massive emission of low-concentration coal mine methane (CMM) has resulted in the ineffective utilization of a large amount of energy methane and caused environmental pollution. The gas mixture used in the study consisted of methane (CH₄) 12% and nitrogen (N₂) 88%. The adsorbent was coconut activated carbon. This paper uses the adsorption method to conduct enrichment research on 12% low-concentration CMM. Firstly, the variation in methane gas concentration under different desorption methods was studied by numerical simulation, and the desorption methods suitable for increasing methane concentration were analyzed. A three-bed VPSA CMM separation experimental device was built, and three enrichment processes of feed gas pressurization, exhaust gas pressurization, and vacuum exhaust (VE) were studied. The results show that using the three-bed vacuum pressure swing adsorption (VPSA) process can effectively enrich low-concentration CMM. Under the adsorption pressure of 110 kPa and the desorption pressure of 10 kPa, 12% of CMM can be enriched to more than 25%, with a recovery rate higher than 80%. The exhaust process can significantly increase the product gas concentration. The product gas concentration increased by 18.2%, with the product rising from 22.5% to 26.6% when the extraction step increased from 0 s to 8 s. This research may provide reliable fundamental data for industrial-scale low-concentration CMM enrichment. Full article

The fuel-cell (FC) power system, utilizing biohydrogen from biomass resources, is a promising alternative to fossil fuels. However, hydrogen sulfide (H₂S) in bio-syngas can severely degrade FC performance and increase environmental impact, necessitating impurity removal. This study investigates a multi-stage desulfurization process using neutralized sediment (NS) and a metal hydride (LaNi₅) as H₂S adsorbents. NS, a mining waste material, can potentially reduce environmental impact when repurposed as an adsorbent, with its performance influenced by pore configuration and Fe content. However, the purified gas does not fully meet FC fuel specifications. To address this, LaNi₅, which selectively absorbs and releases hydrogen, was incorporated to achieve higher purification levels. In our study, H₂S adsorption tests were conducted using two fixed-bed flow reactors heated to 250 °C, where a gas mixture containing 196 ppm of H₂S flowed through the system. The proposed multi-stage system achieved a breakthrough time of 182.5 h with purified gas remaining under 0.1 ppm and an adsorption capacity of 16.4 g/g-sorbent. These results demonstrate the high desulfurization performance achieved using NS and LaNi₅. Full article

As mining progresses, complexities arise, leading to potential coal-rock gas dynamic disasters triggered by mining disturbances. These dynamic phenomena are influenced by factors such as loading mode, coal properties, and the presence of gas. To gain a comprehensive understanding of the mechanical properties, deformation, and failure characteristics of gas-containing coal under cyclic loading, we conducted uniaxial compression tests. These tests varied in loading frequencies, amplitudes, and durations. By analyzing the peak stress variation of gas-containing coal and utilizing digital image correlation (DIC) technology, we captured the deformation characteristics of the loaded coal surface. Following the tests, we examined the fragmentation degree of gas-containing coal under different cyclic loading using fractal theory. This involved screening and crushing samples to assess the impact of varying loading on coal fragmentation. The results showed that peak stress is positively correlated with loading frequency and negatively correlated with loading amplitude and the number of cycles. Cyclic loading significantly affects the surface deformation morphology of gas-containing coal, and there is a correlation between the stress level of the coal sample and its surface deformation, with the formation and development of cracks corresponding to the stress level. Fractal theory can analyze the crushing characteristics of materials and quantitatively characterize their degree of crushing, and the fractal dimension is closely related to the mode of cyclic loading and comprehensively reflects various experimental factors. The results of our study aim to provide insights that can guide the prevention and control of coal mine dynamic disasters. Full article