Search Results (25)

The modified asphalt with high softening point was prepared by air oxidation polymerization with coal liquefied asphalt as raw material. The quality control model regarding the coking value and softening point of the product were established based on the DFSS (Design for Six Sigma) and RSM (response surface method). By means of elemental analysis, infrared, XPS, XRD, nuclear magnetic, MALDI-TOF and other characterization methods, the composition and structure characteristics of the modified asphalt were analyzed. Using the target product as raw material, general base asphalt carbon fiber was prepared by spinning, pre-oxidation and carbonization. The results show that the fitting effect of the quality control model about the coking value and softening point of the product is good, and the operating window range of the polymerization process parameters corresponding to the preparation of target product is wide. It can be found that the oxidation time and oxidation temperature has the most significant effect on the coking value and softening point of products, respectively, and all of them show a positive correlation. The dealkylation reaction and oxidative crosslinking reaction were carried out at the same time, and the bridging products of methylene bridging products, ether–oxygen bonds, carbonyl bonds, anhydride bonds and other oxygen-containing groups were generated. The properties of carbon fiber prepared with the target product are better: the tensile strength is 775 MPa, the elastic modulus is 68.6 GPa and the elongation at break is 1.13%. Full article

Glycolic acid (GA) is a versatile two-carbon organic chemical with multiple applications in industry and daily life. Currently, GA production depends heavily on the coal chemical industry. In this context, the sustainable production of GA from renewable resources has garnered significant attention. With the design and development of various catalytic systems, the yield of GA from biomass-based feedstocks has been improved observably. Poly(glycolic acid) (PGA) is an aliphatic polyester that exhibits a unique crystalline structure, excellent gas barrier properties, high mechanical strength, superior biocompatibility, and biodegradability. It has a wide range of applications in various fields, such as medical devices, oil extraction, bottle materials, film materials, and textile materials. This article comprehensively elaborates on the methods for the biomass-based synthesis of glycolic acid, the precursor of polyglycolic acid (PGA), as well as the preparation process of PGA. It fills the research gap regarding the sources of biomass raw materials for polyglycolic acid. Additionally, it delves into various modification strategies for PGA and provides an overview of its current applications in multiple fields, including biomedicine, food packaging materials, oil and gas resource development, and agricultural cultivation. The purpose of this article is to provide comprehensive reference information on the synthesis techniques, modification methods, and practical applications of PGA. Furthermore, it offers guidance for research on biodegradable plastics and the biomass-based synthesis of glycolic acid. Full article

Strong mine pressure often emerges when the working face of the lower coal seam in a closely spaced coal seam system passes through the remaining coal pillar in the overlying goaf. This study investigates the law of overburden movement and the manifestation of mine pressure during mining under the remaining coal pillar. A physical model measuring 2.5 × 0.2 × 1.503 m is constructed. Fiber Bragg grating sensing technology (FBG) and Brillouin optical time domain analysis technology (BOTDA) are employed in the physical model experiment to monitor the internal strain of the overlying rock as the working face advances. This study determines the laws of overlying rock fracture and working face pressure while mining coal seams beneath the remaining coal pillar. It analyzes the relationship between the pressure at the working face and the strain characteristics of the horizontally distributed optical fiber. A fiber grating characterization method is established for the stress evolution law of overlying rock while passing the remaining coal pillar. The experimental results indicated that the fracture angle of overlying rock gradually decreases during the mining stage through and after the coal pillar. In the mining stage through the coal pillar, the cycle pressure step distance of the working face is reduced by 33.3% compared to the stage after mining through the coal pillar. Initially, the strain pattern of the horizontal optical fiber is unimodal when pressure is first applied to the working face, and it transitions from unimodal to bimodal during periodic pressure. The peak value of fiber Bragg grating compressive strain and the range of influence of advanced support pressure are 3.6 times and 4.8 times, respectively, before passing through the remaining coal pillar. Finally, the accuracy of the FBG characterization method is verified by comparing it to the monitoring curve of the coal seam floor pressure sensor. The research results contribute to applying fiber optic sensing technology in mining physical model experiments. Full article

This study aims to explore microbial activity evidence, composition of archaeal communities, and environmental constraints in coalbed-produced waters from the Hancheng Block, a representative region for coalbed methane development on the eastern margin of Ordos Basin, China. The investigation involves analyzing microbial community composition using 16S rRNA sequencing analysis as well as examining hydrogeochemical parameters. The results indicate that Euryarchaeota and Thaumarchaeota are predominant phyla within archaeal communities present in coalbed-produced water from the Hancheng Block. Among these communities, Methanobacterium is identified as the most abundant genus, followed by Methanothrix and Methanoregula. Moreover, a positive correlation is observed between the abundance of Methanobacterium and the levels of total dissolved solids as well as Mn; conversely, there is a negative correlation with dissolved organic carbon, Zn concentrations, and pH. The abundance of Co and Ni primarily influence Methanothrix while pH and Zn play significant roles in controlling Methanoregula. Additionally, No. 5 coal seam waters exhibit greater species diversity in the archaeal community compared to No. 11 counterparts. The higher abundance of archaea in the No. 5 coal seam promotes biogas generation due to the correlation between bicarbonate and dissolved inorganic carbon isotope. These research findings hold scientific significance in guiding the exploration and development of biogas within coal seams. Full article

The mining face under the close coal seam group is affected by the superposition of the concentrated stress of the overlying residual diagonally intersecting coal pillar and the mining stress, which can easily cause the instability and damage of the section coal pillars during the process of mining back to the downward face. Additionally, the traditional methods of monitoring such as numerical simulation, drilling peeping, and acoustic emission fail to realize the real-time and accurate deformation monitoring of the internal deformation of the section coal pillars. The introduction of the drill-hole-implanted fiber-optic grating monitoring method can realize real-time deformation monitoring for the whole area inside the coal pillar, which solves the short board problem of coal pillar deformation monitoring. However, fiber-optic monitoring is easily disturbed by the external environment, which is especially sensitive to the background noise of the complex underground mining environment. Therefore, taking the live chicken and rabbit well of Shaanxi Daliuta Coal Mine as the engineering background, the ensemble empirical modal decomposition (EEMD) is introduced for primary noise reduction and signal reconstruction by the threshold determination (DE) algorithm, and then the singular matrix decomposition (SVD) is introduced for secondary noise reduction. Finally, a machine learning algorithm is combined with the noise reduction algorithm for the prediction of the fiber grating strain signals of coal pillar in a zone, and DBO-LSTM-BP is constructed as the prediction model. The experimental results demonstrate that compared with the other two noise reduction prediction models, the SNR of the EEMD-DE-SVD-DBO-LSTM-BP model is improved by 0.8–2.3 dB on average, and the prediction accuracy is in the range of 88–99%, which realizes the over-advanced prediction of the deformation state of the coal column in the section. Full article

The objective of this study is to enhance the resilience of the coal-to-liquids (CTL) industrial chain and supply chain to withstand increasing shock pressures. There is an urgent need to improve the resilience of the industrial chain and supply chain. This paper identifies 21 resilience-influencing factors from 4 perspectives: absorption capacity, adaptability, recovery capacity, and self-learning capacity; it then constructs an evaluation indicator system. The Interval Type 2 Fuzzy-Decision-Making Trial and Evaluation Laboratory-Analytic Network Process (IT2F-DEMATEL-ANP) method is adopted to determine the weights of the indicator system, and a resilience evaluation is performed based on the Interval Type 2 Fuzzy-Prospect Theory-Technique for Order Preference by Similarity to an Ideal Solution (IT2F-PT-TOPSIS) method. Furthermore, in the case of the CTL industrial chain and supply chain of China Shenhua Energy Group Ningxia Coal Industry Co., Ltd. (CENC) (Ningxia, China), this study ranks the resilience level from 2018 to 2022 to identify the factors that have contributed to a reduction in resilience and to implement measures to enhance the resilience of the CTL industrial chain and supply chain. The results show that the level of the CTL industrial chain and supply chain resilience was lowest in 2020, while it was highest in 2021. Factors such as the degree of domestication of key technologies, the rationality of the CTL industry layout, and the stability of supply and demand chains are identified as significant determinants of resilience levels. This points the way to enhancing the resilience of the CTL industry and supply chain. Full article

In this paper, the coal pillar dam body of the underground reservoir in Daliuta coal mine, along with the residual coal and the mine water present in the goaf, were taken as research subjects, and a dynamic simulation experiment device was constructed to simulate the actual process of a coal mine underground reservoir (CMUR). The composition and structure of middling coal during the experiment were determined by X-ray diffraction analysis (XRD) and X-ray fluorescence spectrometry (XRF), while changes in ion content in the mine water were assessed through ion chromatography (IC) and inductively coupled plasma emission spectrometry (ICP-OES). Based on both the composition and structure of coal as well as variations in ion concentrations in water, the interaction mechanism between coal and mine water was explored. The results showed that the water–coal interaction primarily arose from the dissolution of minerals, such as rock salt and gypsum, within coal. Additionally, coal samples in mine water exhibited adsorption and precipitation of metal ions, along with cation exchange reaction. Na+ in mine water predominantly originated from the dissolution of rock salt (sodium chloride) in coal, while Ca²⁺ and ${\mathrm{SO}}_4^{2-}$ were released through the dissolution of gypsum and other minerals in coal. In the process of the water–coal interaction, Ca²⁺ in the water body was adsorbed and immobilized by the coal sample, leading to the formation and deposition of CaCO₃ on the surface of the coal, thereby increasing the calcite content. These processes collectively contributed to a decrease in the concentration of Ca²⁺ in the water body. Moreover, the cation exchange reaction occurred between Ca²⁺ and Mg²⁺ in mine water and Na⁺ in the coal sample. The presence of Ca²⁺ and Mg²⁺ resulted in their displacement of Na⁺ within the coal matrix, consequently elevating Na⁺ concentration in the mine water while reducing both the Ca²⁺ and Mg²⁺ concentrations. On this basis, combined with insights from the water–rock interaction, it can be inferred that the adsorption mechanisms involving rocks played a dominant role in the decrease of Ca²⁺ concentration during the water–rock interactions. Meanwhile, the dissolution processes of minerals both in the water–rock and water–coal interactions predominantly contributed to the increase of Na⁺ and Cl⁻ concentrations. Full article

A rising quantity of coal gasification slag (CGS) is produced annually. Land reclamation is a valuable method for efficiently utilizing coal gasification slag on a large scale. The ecological influence of CGS during land reclamation has not been widely investigated. This article covers the entire CGS use cycle for land reclamation, which includes generation, storage, and disposal. The environmental risk of using CGS for land reclamation was assessed by combining four environmental risk assessment methods. The results show no environmental risk for coal gasification coarse slag (CGCS) and coal gasification fine slag (CGFS) at the generation and storage stages. However, a concern remains regarding manganese leaching from CGCS during the storage stage. In the disposal phase, no environmental risk is present when up to 15% of CGCS and CGFS are applied to land reclamation projects. However, the environmental risk of disposing of 100% of CGS in a landfill cannot be disregarded. Conversely, the full-cycle use of CGS for land reclamation carries no environmental risk. Full article

In past years, lithium-ion batteries (LIBs) can be found in every aspect of life, and batteries, as energy storage systems (ESSs), need to offer electric vehicles (EVs) more competition to be accepted in markets for automobiles. Thick electrode design can reduce the use of non-active materials in batteries to improve the energy density of the batteries and reduce the cost of the batteries. However, thick electrodes are limited by their weak mechanical stability and poor electrochemical performance; these limitations could be classified as the critical cracking thickness (CCT) and the limited penetration depth (LPD). The understanding of the CCT and the LPD have been proposed and the recent works on breaking the CCT and improving the LPD are listed in this article. By comprising these attempts, some thick electrodes could not offer higher mass loading or higher accessible areal capacity that would defeat the purpose. Full article

SEM, particle size analysis, and contaminant content of coarse coal gasification slag (CCGS) produced by Shenhua Xinjiang Chemical Co., Ltd. were measured, respectively, and the physicochemical properties of the soil after improvement using gasification slag were investigated in this paper. The results showed that the slag was porous, the particle size was small and the pollutant content was extremely low. Its pollutants were closely related to the pollutants in the raw coal. The coarse slag had a limited effect on soil particle size and texture improvement; the soil water retention performance increased with the increase of proportion of the slag, while pH and conductivity decreased; the improvement effect on soil SOM and available potassium was remarkable; the larger the proportion of the slag, the stronger the effect on maintaining soil alkali-hydrolyzed nitrogen, ammonium nitrogen, and available phosphorus. However, the effect was small, and increased the ion content, especially the cation in soil, and the sum of the eight soil ions before and after evaporation decreased. The results demonstrated that the CCGS generated by the corporation is feasible for soil improvement, and the study has important reference value for the comprehensive utilization of coal gasification slag. Full article

Surface subsidence caused by underground coal mining has received wide attention due to its impact on the ecological environment. To obtain first-hand data on mining subsidence, we arranged line measurement stations in the mining area of the Weiqiang coalfield and implemented surface movement observation at its first mining working face and obtained the dynamic subsidence curve. The subsidence curves reflected the initial, active and declining stages of subsidence at each measurement point at a basic level, and were consistent with the general rule of surface subsidence. To accurately analyze the surface movement caused by coal mining, based on the probability integral method and considering the actual advancement progress of the working face, a new three-dimensional dynamic prediction model, namely the strip unit mining model, was proposed. The core assumption of this model was that the longwall mining is regarded as the result of superposition of many units of mining. Considering the influence of different mining times and periods after mining, the subsidence time function of two-time factors was introduced into the strip unit mining model, and the final formulation of the dynamic subsidence prediction of the three-dimensional surface is derived by considering the time factor. Based on the analysis of the measured data of the Weiqiang coalfield, the prediction parameters of surface movement were obtained, and the surface movement and deformation are predicted via the probability integral method. Finally, the measured surface subsidence was compared with the theoretically-predicted one. The good match showed that the parameters of the probability integral method, determined according to the measured data, meet the requirements of geological conditions and mining settings in the mining area, and the predicted subsidence curves agreed well with the field measurements, demonstrating the effectiveness of the newly-developed strip unit mining model. Full article

The soil water behavior of sandy soils was studied under semiarid conditions in the Shendong mining area (China). The soil water content (θ) was measured under different depths and topographies using an HH2 moisture meter. The infiltration process was studied using a Guelph soil permeameter. A set of hydrodynamic variables was calculated in the laboratory. The θ of the first 20 cm was the lowest and increased with depth. The content of soil water increased from the top slope to the bottom slope. The infiltration experiments showed that the steady state infiltration rate was >40 mm h⁻¹ in most cases. Owing to the higher contents of sand and soil macropores at the top of the slope and the top 0–20 cm of surface soil, the initial infiltration rate and steady infiltration rate were higher. The average available water capacity was 18.28%, which was consistent with the predominance of a sandy textural fraction. The results of a soil water retention curve and a rainfall simulation experiment showed that there was a low soil water retention capacity throughout the whole profile. This study contributes to the understanding of several aspects of the soil water behavior of sandy soils and provides key information for environmental management and land reclamation under semiarid conditions in the Shendong mining area. Full article

Membrane distillation (MD) has unique advantages in the treatment of high-salt wastewater because it can make full use of low-grade heat sources. The high salinity mine water in western mining areas of China is rich in Ca²⁺, Mg²⁺, SO₄²⁻ and HCO₃⁻. In the MD process, the inorganic substances in the feed will cause membrane fouling. At the same time, low surface tension organic substances which could be introduced in the mining process will cause irreversible membrane wetting. To improve the anti-fouling and anti-wetting properties of the membrane, the PVDF omniphobic membrane in this paper was prepared by electrospinning. The water contact angle (WCA) can reach 153°. Direct contact membrane distillation (DCMD) was then used for treating high-salinity mine water. The results show that, compared with the unmodified membranes, the flux reduction rate of the omniphobic membrane was reduced by 34% in 20 h, showing good anti-fouling property. More importantly, the omniphobic membrane cannot be wetted easily by the feed containing 0.3 mmol/L SDS. The extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory was used to analyze the free energy of the interface interaction between the membrane and pollutants, aiming to show that the omniphobic membrane was more difficult to pollute. The result was consistent with the flux variation in the DCMD process, providing an effective basis for explaining the mechanism of membrane fouling and membrane wetting. Full article

An understanding of the spatial variation and influence factors of soil nutrients in mining areas can provide a reference for land reclamation and ecological restoration. Daliuta was used as the study area. The spatial variability of soil nutrients was analyzed using traditional statistics and geostatistics. The effects of topography, mining history, and soil erosion were discussed. The results indicate that the soil pH of the Daliuta mining area is slightly acidic to slightly alkaline, and the soil organic matter, available nitrogen, available phosphorus, and available potassium belonged to the five levels (very low), six (extremely low), five (extremely low), and four (moderately low), respectively. The soil water and salt content indicated that the soil environment in the mining area is arid and has normal levels of salinity. The organic matter, available nitrogen, available phosphorus, available potassium, and soil salt varied moderately, and the pH did not change much, while the soil water varied strongly. The organic matter, pH, and soil salinity are moderately spatially autocorrelated, and the available nitrogen, available phosphorus, available potassium, and soil water are weakly spatially autocorrelated. Each nutrient index had a certain spatial trend effect. The slope, aspect, elevation, and topographic wetness index are the primary topographic factors that control the spatial distribution of soil nutrients. The organic matter, pH, and soil salinity are moderately spatially autocorrelated, and the available nitrogen, available phosphorus, available potassium, and soil water are weakly spatially autocorrelated. Each nutrient index had a certain spatial trend effect. The slope, aspect, elevation, and topographic wetness index are the primary topographic factors that control the spatial distribution of soil nutrients. Soil erosion and mining history are also important factors that lead to the spatial variation of soil nutrients. Full article

We conducted molecular dynamics (MD) simulations to investigate the structural evolution of molten slag composed of wheat straw (WS) and Shenhua (SH) coal. The content of wheat straw in the slag was varied from 0 to 100 wt%. The MD results indicated a slight reduction in the sharpness of the radial-distribution-function curve of each ion–oxygen pair and a decrease in bonding strength with increasing WS content. WS introduced many metal ions to the ash system, increasing its overall activity. The number of bridging and non-bridging oxygen atoms changed upon straw addition, which affected the stability of the system. There were relatively few highly coordinated Si ions. The number of low-coordination Si was highest for a WS content of 30%, at which the density reached a minimum value. The degree of ash polymerization was analyzed by counting the number (Q) of tetrahedra with the number (n) of the bridging oxygen atoms. With increasing WS content, Q⁴ (tetrahedral Si) decreased, whereas Q³, Q², Q¹, and Q⁰ increased. Q⁴ reached a minimum value for a WS content of 30%, at which point the degree of ion aggregation was the weakest and the degree of disorder was the strongest. Full article