Search Results (53)

To address the limitations of traditional hardened concrete road surfaces in coal mine tunnels, which are prone to damage and entail high maintenance costs, this study proposes using modular concrete blocks composed of fly ash and coal gangue as an alternative to conventional materials. These blocks offer advantages including ease of construction and rapid, straightforward maintenance, while also facilitating the reuse of substantial quantities of solid waste, thereby mitigating resource wastage and environmental pollution. Initially, the mineral composition of the raw materials was analyzed, confirming that although the physical and chemical properties of Liangshui Well coal gangue are slightly inferior to those of natural crushed stone, they still meet the criteria for use as concrete aggregate. For concrete blocks incorporating 20% fly ash, the steam curing process was optimized with a recommended static curing period of 16–24 h, a temperature ramp-up rate of 20 °C/h, and a constant temperature of 50 °C maintained for 24 h to ensure optimal performance. Orthogonal experimental analysis revealed that fly ash content exerted the greatest influence on the compressive strength of concrete, followed by the additional water content, whereas the aggregate particle size had a comparatively minor effect. The optimal mix proportion was identified as 20% fly ash content, a maximum aggregate size of 20 mm, and an additional water content of 70%. Performance testing indicated that the fabricated blocks exhibited a compressive strength of 32.1 MPa and a tensile strength of 2.93 MPa, with strong resistance to hydrolysis and sulfate attack, rendering them suitable for deployment in weakly alkaline underground environments. Considering the site-specific conditions of the Liangshuijing coal mine, ANSYS 2020 was employed to simulate and analyze the mechanical behavior of the blocks under varying loads, thicknesses, and dynamic conditions. The findings suggest that hexagonal coal gangue blocks with a side length of 20 cm and a thickness of 16 cm meet the structural requirements of most underground mine tunnels, offering a reference model for cost-effective paving and efficient roadway maintenance in coal mines. Full article

Coal bottom ash (CBA) is a waste produced by burning coal that presents possible hazards to human well-being and the environment. Rapid economic expansion has increased the utilisation of CBA, resulting in a crisis concerning the disposal of this waste. By employing waste as a replacement for natural materials, it is possible to achieve sustainable and environmentally friendly construction. This study assesses the effects of utilising CBA waste as a replacement for fine aggregate in stone mastic asphalt (SMA) pavement. Seven asphalt mixture proportions were designed, each of which employed a different percentage of CBA (0%, 10%, 20%, 30%, 50%, 70%, and 100%) as a fine aggregate replacement. The performance tests conducted in this research were the Cantabro durability test, resilient modulus test, dynamic creep test, and moisture susceptibility test. The findings showed an improvement in the durability and resistance to permanent deformation of the SMA mixtures with 30% and 50% CBA replacement, respectively. However, further increases in the CBA content caused a decrease in the durability and resistance to permanent deformation. Meanwhile, the stiffness and tensile strength ratio (TSR) value decrease with the use of CBA replacement at any percentage. However, the TSR value of the SMA mixtures with 50% or less CBA replacement was more than 80%, which meets the minimum requirement set by JKR. In conclusion, incorporating CBA into SMA mixture has a positive effect on certain mechanical properties, particularly its durability and resistance to permanent deformation at optimal replacement levels, highlighting its potential to be used as a sustainable material in asphalt pavement construction. Full article

To overcome the low extraction efficiency and environmental concerns associated with traditional vanadium extraction methods, this study proposes an innovative nitric acid oxygen pressure leaching approach integrated with nitrogen recycling. Through systematic single-factor experiments and response surface optimization, key parameters, including nitric acid concentration, leaching temperature, liquid-to-solid ratio, and total pressure, were carefully evaluated and optimized. Under optimal conditions, consisting of 1.5 mol/L nitric acid, a temperature of 127.43 °C, a liquid-to-solid ratio of 5 mL/g, and a total pressure of 2 MPa, the vanadium leaching efficiency reached 73.1%. Cyclic leaching experiments confirmed the feasibility of nitrogen recycling. Characterization analyses by SEM-EDS, XRD, BET, and FTIR revealed that nitric acid oxygen pressure leaching significantly disrupted the mineral lattice structure, altering the coordination environment of metal ions and increasing surface porosity, thereby facilitating efficient vanadium dissolution from stone coal. This study provides valuable insights and establishes a scientific foundation for developing efficient, environmentally friendly, and economically viable vanadium extraction techniques from low-grade stone coal resources, thereby contributing to sustainable mining practices and resource utilization. Full article

Coal resources still occupy a dominant position in the energy consumption structure, and the prevention and control of coal dust explosion has become an important measure to ensure the safe production of coal. To this end, a new type of environmentally friendly, economical, and efficient composite powder explosion suppressant has been developed. CMS@C₁₂H₂₂O₁₄Fe was prepared by an anti-solvent crystallization method using Chinese Maifan stone (CMS) as the carrier and ferrous gluconate (C₁₂H₂₂O₁₄Fe) as the active component. The physicochemical properties of the explosion suppressant were analyzed using characterization techniques such as SEM and FT-IR. At the same time, the Hartmann tube experimental device was utilized to study the inhibition effect of the detonation suppressor on the coal powder flame, and to determine the optimal loading amount of the active component and the addition amount of the detonation suppressor. The results show that the composite powder synthesized by the anti-solvent crystallization method has a uniform particle size and good structure. The flame was almost completely suppressed when the active component loading was 50 wt.% and the additive amount of the detonation suppressant was 30 wt.%. Finally, a physicochemical synergistic inhibition mechanism of CMS@C₁₂H₂₂O₁₄Fe for coal dust explosion is proposed. Full article

Acid mine drainage (AMD) generated during the exploitation and utilization of mineral resources poses a severe environmental problem globally within the mining industry. The Xiaomixi Stream in Ziyang County, Shaanxi Province, is a primary tributary of the Han River, which is surrounded by historically concentrated mining areas for stone coal and vanadium ores. Rainwater erosion of abandoned mine tunnels and waste rock piles has led to the leaching of acidic substances and heavy metals, which then enter the Haoping River and its tributaries through surface runoff. This results in acidic water, posing a significant threat to the water quality of the South-to-North Water Diversion Middle Route within the Han River basin. According to this study’s investigation, Xiaomixi’s acidic water exhibits yellow and white precipitates upstream and downstream of the river, respectively. These precipitates stem from the oxidation of iron-bearing minerals and aluminum-bearing minerals. The precipitation process is controlled by factors such as the pH and temperature, exhibiting seasonal variations. Taking the Xiaomixi Stream in Ziyang County, Shaanxi Province, as the study area, this paper conducts field investigations, systematic sampling of water bodies and river sediments, testing for iron and aluminum pollutants in water, and micro-area observations using field emission scanning electron microscopy (FESEM) on sediments, along with analyzing the iron and aluminum content. The deposition is analyzed using handheld X-ray fluorescence (XRF) analyzers, X-ray diffraction (XRD), and visible–near-infrared spectroscopy data, and a geochemical model is established using PHREEQC software. This paper summarizes the migration and transformation mechanisms of iron and aluminum pollutants in acidic water and proposes appropriate prevention and control measures. Full article

Coal mining in China has resulted in numerous subsided areas, exacerbating land scarcity issues. The Yellow River carries a high sediment load of nearly 1.6 billion tons annually. Cleaning up the accumulated silt is costly and takes up land. Reusing the sediment from the Yellow River to fill and reclaim the subsided areas caused by coal mining addresses both sedimentation and land reclamation issues, killing two birds with one stone. Nonetheless, technical challenges have emerged, such as machinery sinking into the soil, difficulty draining water, and poor soil quality improvement. To tackle these issues, understanding the physical and mechanical properties of Yellow River sediment is essential. Results show that the average particle size (D₅₀) is 0.08 mm, categorized as fine-grained sandy soil with a relatively uniform particle size distribution. The permeability coefficient is 2.91 × 10⁻³ cm·s⁻¹, similar to that of silty soil, indicating the feasibility for filling reclamation. However, the low permeability requires drainage improvement to accelerate construction timelines. The internal friction angle of the sediment ranges from 34.67° to 31.76°, with a cohesion from 20.79 to 23.92 kPa. To ensure safe and stable construction, machinery must not sink into the fill material. It is recommended to enhance drainage to about 13% for quicker drainage and stable construction. The sediment has a compression coefficient of 0.05 ${\mathrm{M}\mathrm{P}\mathrm{a}}^{-1}$, indicating low compressibility. Mechanical compression is not economically viable during the reclamation process. Design elevation (H) and fill elevation (h) should account for cumulative deformation settlement. Full article

In order to explore the size effect of the mechanical and damage characteristics of coal measure sand stones under dynamic load, uniaxial impact compression tests were carried out on coal-bearing sand stones with a diameter of 50 mm and a length–diameter ratio of L/R = 0.5, 0.8, 1, 1.2, 1.5, 1.8, and 2 by using the Hopkinson pressure bar test system. The size effect law of the mechanical properties and energy dissipation of coal-bearing sandstone under a high strain rate were investigated. Then, the mercury injection test was carried out on the fragments at different positions, and the electron microscope scanning test was carried out on the fragments near the end of the transmission rod. Based on the area damage definition method and normalization treatment, the integrity model of coal measure sandstone, considering the influence of the length–diameter ratio, was established. The results showed that the peak strength and dynamic elastic modulus of coal measure sandstone increased first and then decreased with the increase in length–diameter ratio under impact compression load, and they reached the maximum when the length–diameter ratio was 1.2. The dynamic peak strain increased gradually with the increase in length–diameter ratio. The energy of coal-bearing sandstone showed strong size effect, that is, the total absorbed energy, elastic energy, and dissipated energy increased with the increase in length–diameter ratio, and the size effect of total absorbed energy was the most obvious. Under the same impact pressure, the porosity of coal-bearing sand stones with seven kinds of length–diameter ratios near the incident end was roughly the same. But when the length–diameter ratio was greater than 0.5, the porosity decreased gradually with the increase in the distance from the incident end. And the larger the length–diameter ratio, the more obvious the decreasing trend. When the length–diameter ratio was smaller, the size of the holes and cracks and the cluster density were larger. The integrity model of coal measure sandstone, considering the influence of the length–diameter ratio, showed that the larger the length–diameter ratio, the better the relative integrity of coal-bearing sandstone. Full article

In the process of mining and transportation, the temporary non-hardened mine-road structure is mainly a mixture of soil and stone, which very easily produces dust hazards via crushing and wind transportation. Geopolymers can be used in the road’s soil and stone mixture so that the road reaches certain strength requirements in line with the short-term use of the mine. However, in alpine open-pit coal mines, which are subject to the influence of weather changes, freezing and thawing phenomena will affect the long-term use of the road and its normal and safe operation. An open-pit coal mine in Xinjiang, China, was chosen as the research object of alpine open-pit coal mines. Using the method of indoor testing, different freeze–thaw freezing temperatures, different numbers of cycles, changes in the mechanical properties of the mine-road materials, and microscopic changes were studied. From the experimental results, it was determined that with a reduction in the freeze–thaw freezing temperature, the specimen strength declines after stabilizing, and with an increase in the number of freeze–thaw cycles, the specimen strength exhibits a linear decline. The specimen’s internal structure gradually changed from dense to loose; the fracture mode changed from toughness fractures to crystal fractures after the removal of the maximum load reduction. The uniaxial compressive strength was reduced to 61%; the tensile strength was reduced to 49%. The fracture zone of the specimen was analyzed using energy spectra, and the main elements changed from O (57.19%), Si (17.07%), and Al (12.19%) without freezing and thawing to O (49.76%), Si (15.70%) and Ca (11.09%) after freezing and thawing. Full article

The quality of borehole sealing is a key factor affecting the efficiency of gas production. A new water-rich grouting material (RW) with composite coagulant and other additives was prepared in this study to overcome the disadvantages of long setting time and low stone rate of traditional cement materials. When the coagulants A is 4 g and coagulants B is 2 g, the setting time of RW material was reduced by 60.85% and 50.62%, which significantly shortened the setting time of the RW material, respectively. Based on the orthogonal method, 29 groups of comparative experiments were designed to investigate the interaction mechanism between different additives on the performance index of RW, including setting time, water secretion rate, and compressive strength. Quadratic regression equations were fitted using the response surface method. All the correlation coefficients R² of each response model were greater than 0.97, R² and R²_adj were less than 0.2 through variance analysis, indicating a high correlation between the actual and prediction results. The water–cement ratio had the most significant effect among all factors on setting time, water secretion rate, and compressive strength of the RW material. The scanning electron microscope (SEM) was used to compared the micromorphological characteristics of RW and conventional Portland cement material (PC). The results showed that the hydration products of RW were mostly smack ettringite, calcium silicate hydrate gel, and calcium hydroxide, which interweaved with each other to form a network structure that was denser than the PC material. Furthermore, the interface bonding degree between RW and injected coal was tighter than that of PC, without obvious cracks at the slurry–coal interface. The results indicate that the addition of composite coagulant can significantly accelerate the hydration process of RW material and also enhance the interface strength of injected coal, which is conducive to improving the grouting quality and sealing effect of the extraction borehole. Full article

Laser-induced breakdown spectroscopy (LIBS) technology has the characteristics of small sample demand, simple sample preparation, simultaneous measurement of multiple elements and safety, which has great potential application in the rapid detection of coal quality. In this paper, 59 kinds of coal commonly used in Chinese power plants were tested by a lab-designed field-portable laser-induced breakdown spectrometer. The data set division methods and the quantitative analysis algorithm of ash content, volatile matter and calorific value of coal samples were carried out. The accuracy and prediction accuracy of three kinds of dataset partitioning methods, random selection (RS), Kennard–Stone (KS) and sample partitioning based on joint X-Y distances (SPXY), coupled with three quantitative algorithms, partial least squares regression (PLS), support vector machine regression (SVR) and random forest (RF), were compared and analyzed in this paper. The results show that the model featuring SPXY combined with RF has the best prediction performance. The R2 of ash content by the RF and SPXY method is 0.9843, the RMSEP of ash content is 1.3303 and the mean relative error (MRE) is 7.47%. The R2 of volatile matter is 0.9801, RMSEP is 0.7843 and MRE is 2.19%. The R² of calorific value is 0.9844, RMSEP is 0.7324 and MRE is 2.27%. This study demonstrates that the field-portable LIBS device combining appropriate chemometrics algorithms has a wide application prospect in the rapid analysis of coal quality. Full article

The stacking of impermissible materials in the disposal of dry fly ash is unprecedented in the last 40 years of power plant management in China, and their effect on the stability of the whole facility is uncertain. Due to the lack of relevant treatment experience, a more comprehensive method such as numerical modeling must be adopted for the final design. This paper set up a borehole database from geological logging data to obtain the distribution of the coal gangue solid waste. Then, it established an accurate three-dimensional mesh model through Rhino. Based on elastic–plastic mechanics, the finite difference code Flac3D 6.0 was employed to study the risk of the coal gangue as a dam foundation. A comparative analysis of the influence of the displacement method and the composite foundation method on subdam deformation and differential subsidence was conducted. The simulation revealed that the composite foundation method showed the best reductions: 70.57% in shear failure, 97.83% in tension failure, and 22.63% in maximum subsidence. Ultimately, the optimum stone column diameter of 0.5 m and the spacing of 6 m were proposed due to the standard deviation. Full article

Mining of mineral resources exposes various minerals to oxidizing environments, especially sulfide minerals, which are decomposed by water after oxidation and make the water in the mine area acidic. Acid mine drainage (AMD) from mining can pollute surrounding rivers and lakes, causing serious ecological problems. Compared with traditional field surveys, unmanned aerial vehicle (UAV) technology has advantages in terms of real-time imagery, security, and image accuracy. UAV technology can compensate for the shortcomings of traditional technology in mine environmental surveys and effectively improve the implementat ion efficiency of the work. UAV technology has gradually become one of the important ways of mine environmental monitoring. In this study, a UAV aerial photography system equipped with a Red, Green, Blue (RGB) camera collected very-high-resolution images of the stone coal mining area in Ziyang County, northwest China, and classified the very-high-resolution images by support vector machine (SVM), random forest (RF), and U-Net methods, and detected the distribution of five types of land cover, including AMD, roof, water, vegetation, and bare land. Finally, the accuracy of the recognition results was evaluated based on the land-cover map using the confusion matrix. The recognition accuracy of AMD using the U-Net method is significantly better than that of SVM and RF traditional machine-learning methods. The results showed that a UAV aerial photography system equipped with an RGB camera and the depth neural network algorithm could be combined for the competent detection of mine environmental problems. Full article

This article discusses the prospects for using large-format ceramic stones in the construction of contemporary homes, as well as an overview of raw materials and technologies for production. The most promising technology is stiff extrusion with the ability to load the raw products on firing trolleys and accelerate the processes of firing and drying. Characteristics of Eastern Donbass waste heaps processing screenings are given, which are coal mining by-products and are considered to be main raw material for the production of large-sized ceramic stone. It is shown that as a result of introduction of waste heaps into the production of ceramic stones with the lowest prime cost, the density of the resulting products will be less than 800 kg/m³, the thermal conductivity will be less than 0.20 m·°C/W, and the strength grade will be M150 and higher. Thus, the use of ceramic stones in total volume of wall products for residential construction will reach the level of 80% and will increase the competitiveness of the material, especially when compared with gas silicate products, as used in Western Europe. High economic feasibility of the production of such materials based on by-products of waste heap processing is shown as well. Full article

Climate change concerns have goaded countries toward seeking renewable energy options (bio-energy being one of them) to replace/supplant the conventional fossil-fuel alternatives (coal, oil and natural gas) commonly used now. Fuel pellets—at the confluence of the forestry, agriculture, waste management and bio-energy sectors—when produced from biomass residues, serve the dual purpose of ensuring energy security and environmental sustainability. By valorizing more and more organic wastes to bio-energy products, one could, to use the old adage, ‘kill two birds with one stone’. Social LCA is a method used to analyze a very wide range of social issues associated with the stakeholders in a value chain—workers, local community dwellers, society, global consumers, banks, investors, governments, researchers, international organizations and NGOs. In this analysis, the authors commence with a highly focused, niche literature review on the social dimension of sustainability in the African energy/bio-energy sector. The streamlined social footprint analysis inspired by the relatively lesser number of such studies for this sector in Africa is not a novel addition per se to the S-LCA knowledge base. The purpose of the application is to shed light on something in Zambia that must be understood better so as to bring about much-needed alterations in the direction of sustainable development. While the questions addressed to four different groups of stakeholders encompass a clutch of sustainable development goals, gender equality (SDG 5) and the need for greater interest on the part of governments and investors (SDG 9) to look at sustainable alternatives to the status quo stand out as concerns that need to be tided over. This paper and the streamlined social footprint analysis carried out are all the more relevant and timely when one considers some key changes that have happened in Zambia over the last five years—the implementation of the National Energy Policy in 2019 and the creation of the Ministry of Green Economy in 2021. These are verily harbingers of positive change auguring well for future developments in the bio-energy (and bio-pellets) sector, not just in Zambia but, by way of emulating and learning, in other countries on the continent. Full article

The Cretaceous Zhidan group (K1zh) pore fissure-confined water aquifer in Yingpanhao Coal Mine, Ordos City, China, has loose stratum structure, high porosity, strong permeability and water conductivity. In order to explore the fluid–solid coupling similar material and its constitutive model suitable for the aquifer, a kind of fluid–solid coupling similar material with low strength, strong permeability and no disintegration in water was developed by using 5~20 mm stone as aggregate and P.O32.5 Portland cement as binder. The controllable range of uniaxial compressive strength is 0.394~0.528 MPa, and the controllable range of elastic modulus is 342.22~400.24 MPa. The stress–strain curve and elastic modulus of similar materials are analyzed. It is found that the elastic modulus of similar materials with different water–cement ratios conforms to the linear law, the elastic modulus of similar materials with the same water–cement ratio after soaking treatment and without soaking treatment also conforms to the linear law. Based on the material failure obeying the maximum principal stress criterion and Weibull distribution, combined with the elastic modulus fitting formula, a constitutive model suitable for the fluid–solid coupling similar material was established, and the parameters of the constitutive model were determined by differential method. By comparing the theoretical stress–strain curve with the experimental curve, it is found that the constitutive model can better describe and characterize the fluid–solid coupling similar materials with different water–cement ratios and before and after soaking. Full article