Search Results (491)

Hydrogen energy is acknowledged as being the cleanest energy source. As hydrogen fuel cell technology advances, the development of low-cost, high-quality hydrogen purification technologies has grown increasingly critical. Targeting the separation of steam methane reforming gas mixture with a typical composition of H₂/CO₂/CH₄/CO = 76%/20%/3.5%/0.5%, a 6-bed-13-step pressure-swing adsorption process featuring four pressure-equalization steps was designed, in which a multi-layer adsorbent packing strategy was adopted to investigate the purification performance. The effects of feed flow rate, adsorbent packing combination, and purge-to-feed ratio on hydrogen purity and recovery, and on the impurity content level were analyzed. Furthermore, the gas-phase and solid-phase concentration distributions of each adsorbent layer under cyclic steady state were studied in detail, and the variation characteristics of their adsorption–desorption behaviors were systematically elaborated. Eventually, the optimal adsorbent combination and process condition configurations were determined. The results show that the proposed process can achieve a hydrogen purity of 99.99971%, with a concentration of CO of less than 0.2 ppm, which meets the fuel cell-grade hydrogen standard. Full article

As a perfluorinated compound with a high global warming potential, octafluoropropane (C₃F₈) needs to be efficiently separated from industrial waste gas, but separating it from nitrogen at low concentrations is highly challenging. To address the common drawback of using corrosive acids in conventional MIL-101(Cr) synthesis, this study developed a green, acid-free solvothermal method for preparing graphene oxide (GO)-modified MIL-101(Cr) composites (MIL-101/GO). By systematically varying the GO doping, the optimal composite (MIL-101/GO-0.1) exhibited breakthrough adsorption performance: its equilibrium adsorption capacity for C₃F₈ reached 210 mg/g in fixed-bed breakthrough experiments. The predicted C₃F₈ adsorption selectivity relative to N₂ reached 17,069, ranking among the highest values reported for adsorbents, indicating a significant performance enhancement over the pristine MIL-101(Cr). Mechanistic analysis reveals that graphene oxide not only increases specific surface area and micropore volume but also enhances dispersion forces, substantially boosting affinity for C₃F₈. Additionally, the composite exhibits outstanding cycling stability and thermal stability. This study provides a novel eco-friendly synthetic strategy for high-performance metal–organic frameworks and offers a highly promising candidate material for industrial-scale fluorocarbon recovery. Full article

l-menthol is one of the most popular flavors in the world. The separation of menthol enantiomers is crucial because of the unpleasant taste of d-menthol. This work presents the chiral separation of racemic menthol by simulated moving bed chromatography for the first time. Six preparative columns packed with amylose 3,5-dimethylphenylcarbamate coated on silica gel were used for separation, and a mixture of n-hexane/isopropanol was selected as the mobile phase. The hydrodynamic properties of the SMB columns were studied to minimize the packing asymmetry in the SMB experiment. The binary adsorption isotherm of menthol enantiomers was measured by the adsorption–desorption method. Fixed-bed batch chromatography was carried out to evaluate the adsorption kinetic behavior. Mathematical models, considering the mass transfer resistance and axial dispersion, were applied to describe the dynamics of the chromatographic separation process. The SMB process for chiral separation of racemic menthol was designed by evaluating the separation region using simulations. Reasonable agreements were achieved between the predicted results and the experimental results. Purities for both the extract and raffinate were above 99.0%, and a productivity of 0.267 g_racemate/(L_CSP∙min) and a solvent consumption of 0.431 L/g_racemate were achieved. Full article

The interaction of emergent vegetation and three-dimensional (3D) bedforms is essential for understanding turbulent flow dynamics in curved channels. A laboratory investigation can help to collect required data under controlled conditions. Experiments were conducted in a 9.5 m-long, 0.9 m-wide recirculating flume incorporating a 90° bend and a sculpted 3D pool bedform. Artificial rigid vegetation, designed to replicate the hydraulic behavior of natural emergent plants, was installed along both sidewalls. Instantaneous three-dimensional velocities were recorded using an acoustic Doppler velocimeter (ADV) across multiple cross-sections under both bare-bed and vegetated conditions. The results reveal that emergent vegetation markedly increases flow resistance, distorts mean velocity distributions, and suppresses the classical logarithmic velocity profile, particularly within the bend and pool regions. The combined presence of vegetation and the 3D pool bedform amplified turbulence intensity, elevated Reynolds shear stresses, and redistributed turbulent kinetic energy (TKE), which increased by up to sevenfold from the bend entrance to its exit. In vegetated pool sections, Reynolds stresses were approximately 12% greater than under bare-bed conditions, underscoring the synergistic effects of vegetation drag, secondary circulation, and flow separation in producing anisotropic turbulence. These findings highlight the importance of incorporating vegetation–bedform interactions in fluvial modeling frameworks, with significant implications for sediment transport prediction, channel stability evaluation, river restoration, and aquatic habitat design. Full article

Riverbed topography in natural rivers commonly features sand dunes, whose morphological variations can alter the turbulent flow structure near the bed and thereby affect processes of channel scour, deposition, and sediment transport. In this study, a series of flume experiments was conducted using an acoustic Doppler velocimeter (ADV) to simulate fixed bedforms of different dune scales (ratio of wavelength to flow depth, λ/h) in a laboratory flume. Velocity measurements were taken along the water depth at the dune crest and trough for each test case. The near-bed distributions of mean flow velocity, Reynolds stress, turbulent kinetic energy (TKE), and turbulence intensity were obtained at the crest and trough under three flow conditions, allowing analysis of the vertical decay of turbulence intensity at different locations on the dune. The results show that the dune steepness (Ψ, defined as dune height over wavelength) is a key parameter controlling the near-bed flow structure. As Ψ increases, the near-bed velocity gradient, Reynolds stress, TKE, and peak turbulence intensity all increase significantly, with the peak positions shifting closer to the bed. The trough region, due to flow separation and vortex shedding, exhibits substantially higher values of all turbulence-related parameters than the crest, making it the primary zone of energy dissipation and turbulence production. This study provides experimental evidence and theoretical reference for understanding the mechanism by which sand dune morphology influences flow structure, and it offers insight for predicting riverbed evolution. Full article

Chemical looping combustion (CLC) has been recognized as a promising CO₂ capture technology, in which oxygen carriers (OCs) transport lattice oxygen to the fuel instead of the air. This study aims to evaluate a newly developed perovskite OC for biomass CLC and to clarify the role of staged fuel conversion in improving gas–solid redox efficiency. This is the first application of perovskite OC CaMn_0.625Ti_0.125Fe_0.125Mg_0.125O₃ in biomass CLC using a dual-stage fluidized bed. The perovskite OC was synthesized via a solid-phase synthesis method, and its performance in a dual-stage fluidized bed reactor was evaluated using pine wood chips and furfural residues as model solid fuels. The in situ conversion of volatile compounds and gasification products derived from the two biomass types was comprehensively studied. The effects of operational parameters, including temperature, OC-to-biomass ratio, and gas flow rate, on the combustion efficiency and CO₂ yield were examined. Results showed that separated gasification–combustion enhanced the combustion efficiency and CO₂ yield. At 950 °C, an OC-to-pine chip ratio of 100:1, and a gas flow rate of 0.7 L/min, the maximum combustion efficiency and CO₂ yield of 79% and 82% were obtained, respectively. Moreover, under the optimal gasification conditions (gasification rate > 99%), increasing the fuel concentration resulted in an increase in the oxygen release from 0.21 g to 0.40 g. Concurrently, the corresponding total oxygen demand increased from 4.34% to 10.56%, indicating the suitability of CaMn_0.625Ti_0.125Fe_0.125Mg_0.125O₃ in the CLC of biomass. Full article

Traditional overburden bed-separation grouting technology often leads to issues of grout leakage and insufficient control of surface subsidence, primarily due to its poor adaptability to specific mining conditions such as isolated coal pillar recovery, the development of stratigraphic faults and fractures, or the absence of clearly identifiable key strata. To address these limitations, this study proposes an innovative multi-bed-separation precise grouting technology. The formation mechanism of multi-bed separations is analyzed, their development positions are determined, and an engineering solution for controlling surface subsidence after multi-bed-separation grouting is proposed. Key technical parameters, including grouting pressure, stability of grout-isolating layers, grouting space volume, and grout amount, are theoretically analyzed. A “three-step” precise grouting process—consisting of separation detection and verification, fracture curtain sealing, and precise grouting for subsidence reduction—was developed and applied in the 12030 isolated coal pillar panel of Xinyi Coal Mine. A total of 504,500 tons of fly ash (including cement) was grouted, of which 398,600 tons was used for precise grouting in multi-bed separations of overburden. This approach recovered 1,364,400 tons of coal resources beneath village buildings, with a grouting–extraction ratio (volume ratio) of 0.53. The technology demonstrates clear advantages: no grout leakage occurred during the process, the surface subsidence reduction rate reached approximately 75.81%, and building damage was controlled within Grade I. The results demonstrate that this technology has a significant effect on subsidence reduction and damage control, enabling safe and green mining of coal resources beneath villages under special geological and mining conditions. Full article

The operating conditions of engines in motor vehicles used in conditions of high air dustiness resulting from sandy ground and helicopters using temporary landing sites were analyzed. The impact of mineral dust on accelerated abrasive and erosive wear of components and assemblies of piston and turbine engines was presented. Attention was drawn to the formation of dust deposits on turbine engine components. Possibilities for minimizing abrasive wear through the use of two-stage intake air filtration systems in motor vehicle engines were presented. Three forms of protection for helicopter engines against the intake of dust-laden air and for extending their service life are presented: intake barrier filters (IBF), tube separators (VTS), and particulate separators (IPS) called Engine Air Particle Separation (EAPS). It has been shown that pleating the filter bed significantly increases the filtration area. It has been shown that increasing the suction flow from inertial filters increases separation efficiency and flow resistance. IPS are characterized by a compact design, low external resistance, and no need for periodic maintenance, but it has a lower separation efficiency (86–91%) than VTS and IBF systems (up to 99.3–99.9%). The tested “cyclone-partition filter” filtration system achieves a filtration efficiency of 99.9%, reaching the acceptable pressure drop value four times slower than if it were operating without a cyclone. Two-stage filtration systems ensure high friction durability at the lowest possible energy costs. Full article

This paper takes a fully caving face in a coal mine in western China as an example and analyzes several water-inrush cases in the roof-bed separation of the first mining face. Various causes and characteristics of water inrush in bed separation are also analyzed. The bed separation closure distance in the working face mining was calculated using the thin-slab theory. The results show that the roof-bed separation first closure distance was about 250–300 m, and the cycle closure distance was about 150–175 m. Moreover, a water-in-bed separation-disaster prevention method was proposed by conducting a ground straight-through diversion borehole, which is used for dewatering in bed separation. Furthermore, the groundwater level supplying the roof-bed separation was observed. The results show that the ground straight-through diversion borehole was good for dewatering the bed separation before the closure of the bed separation. This measure eliminated the danger of water inrush in roof-bed separation, which ensures the safe mining of the working face. This study, through the integration of theoretical analysis and engineering practice, proposes and validates a prevention and control technology for water hazards in roof-bed separation based on ground straight-through diversion boreholes, providing a reliable technical approach for safe mining under similar geological conditions. Full article

Under the dual pressures of global climate change and anthropogenic activities, enhancing the ecological functions of hydraulic structures has become a critical direction for sustainable watershed management. While traditional spur dike designs primarily focus on bank protection and flood control, current demands require additional consideration of river ecosystem restoration. Numerical simulations were performed using the RNG k-ε turbulence model to solve the three-dimensional Reynolds-averaged Navier–Stokes equations, a formulation that enhances prediction accuracy for complex flows in curved channels, including separation and reattachment. Following a grid independence study and the application of standard wall functions for near-wall treatment, a comparative analysis was conducted to examine the flow characteristics and ecological effects within a 180° channel bend under three configurations: no spur dikes, a single-side arrangement, and a staggered arrangement of non-submerged, flow-aligned, rectangular thin-walled spur dikes. The results demonstrate that staggered spur dikes significantly reduce the lateral water surface gradient by concentrating the main flow, thereby balancing water levels along the concave and convex banks and suppressing lateral channel migration. Their synergistic flow-contracting effect enhances the kinetic energy of the main flow and generates multi-scale turbulent vortices, which not only increase sediment transport capacity in the main channel but also create diverse habitat conditions. Specifically, the bed shear stress in the central channel region reached 2.3 times the natural level. Flow separation near the dike heads generated a high-velocity zone, elevating velocity and turbulent kinetic energy by factors of 2.3 and 6.8, respectively. This shift promoted bed sediment coarsening and consequently increased scour resistance. In contrast, the low-shear wake zones behind the dikes, with weakened hydrodynamic forces, facilitated fine-sediment deposition and the growth of point bars. Furthermore, this study identifies a critical interface (observed at approximately 60% of the water depth) that serves as a key interface for vertical energy conversion. Below this height, turbulence intensity intermittently increases, whereas above it, energy dissipates markedly. This critical elevation, controlled by both the spur dike configuration and flow conditions, embodies the transition mechanism of kinetic energy from the mean flow to turbulent motions. These findings provide a theoretical basis and engineering reference for optimizing eco-friendly spur dike designs in meandering rivers. Full article

The scour protection performance of the conical structure under different slope angles, α, was investigated through numerical simulations. By solving the Navier–Stokes (N–S) equations, using the Renormalization Group (RNG) k–ε turbulence model and the Meyer-Peter and Müller (MPM) sediment transport formula, the scour protection performance, undermining process, and the flow field around the devices were fully analyzed at different slope angles. The findings indicate that the conical scour protection provides effective protection against scour damage. As the slope angle increases, greater scour depth is observed around the structure. A critical slope angle was identified between 30° and 40°, slope angle effects are obvious below the threshold; otherwise, it minimized. Undermining is the main cause of failure of such stiff scour protection, mainly driven by flow contraction and sand sliding. Upstream undermining beneath the structure is more pronounced, while the downstream undermining is largely related to the near-bed flow separation point. The critical undermining point (CUP) is proposed based on the undermining curve to distinguish the undermining state, which is critical in scour protection and structural stability. Full article

Biomass gasification, as a thermochemical process, has attracted growing interest due to the increasing popularity of biofuel production based on syngas or pure hydrogen. Moreover, when integrated with CO₂ capture, this method of producing gaseous fuels can achieve negative CO₂ emissions, making it competitive with other production systems based on either fossil or renewable sources. This paper presents the results of a process and economic analysis of synthetic natural gas (SNG) production systems integrated with a commercial fluidized-bed gasification reactor based on Synthesis Energy Systems (SES) technology. The study examines the potential integration of the system with a water electrolyzer at two levels of coupling: one providing oxygen for the gasification process, and the other eliminating the need for CO₂ separation before the SNG synthesis stage. Using a single gasification unit with a raw biomass feed rate of 60 t/h, the system produces 188 t/d of SNG. Integration with a water electrolyzer increases SNG production to 259 and 621 t/d. For cases without electrolyzer integration and under the assumption of zero emissions from biomass processing, the application of CO₂ separation enables the achievement of negative CO₂ emissions. This creates an opportunity for additional revenue from the sale of CO₂ emission allowances, which can significantly reduce SNG production costs. In this analysis, the break-even CO₂ price, above which the SNG production cost becomes negative, is USD 251/t CO₂. In systems integrated with water electrolysis, the cost and carbon footprint of the electricity consumed in the electrochemical water-splitting process have a decisive impact on both the overall SNG production cost and its carbon intensity. Full article

This study investigated methane (CH₄) production in a bioelectrochemically enhanced anaerobic digester (BEAD) equipped with a pair of 3-dimensional flow-through electrodes made of conductive polypropylene biorings. The performance of the BEAD reactor was compared to that of a similarly sized Anaerobic Upflow Sludge Bed (UASB) reactor. The reactors were operated at a temperature of 22 ± 1 °C using food waste (FW) leachate fed at organic loading rates of 3–8 g (L_R d)⁻¹ or at a temperature of 35 ± 1 °C using the liquid fraction of FW separated using a screw press. With both tested feedstocks, the BEAD reactor demonstrated up to 30% higher CH₄ yield, reaching 0.35–0.38 L g⁻¹ (COD consumed), compared to the UASB reactor. Additionally, reactor stability under organic overload conditions improved, with the difference more pronounced at organic loads above 6 g (L_R d)⁻¹. Energy consumption for bioelectrochemical CH₄ production was estimated at 5.1–12.4 Wh L⁻¹ (of CH₄ produced), which is significantly below the energy consumption for electrochemical H₂-based methanation. Overall, BEAD increases methane production and improves process stability, offering a novel sustainable solution for waste management. Full article

Gas–solid separation fluidized bed is an efficient coal cleaning and separation technology, and this technology has been extensively used in coal separation. The separation of the feeding coal particles in the fluidized bed is generally carried out in the form of particle groups, hence, a systematic examination of stratification as well as diffusion of the feeding particle group in the gas–solid separation fluidized bed is required. Simulated particles are used in this study and the technique that combines both theoretical calculation and an experimental method is used to investigate the effect of the inherent properties of the feeding particle group, bed characteristics, and operating parameters on the variation in voidage and air drag force in the separation process. According to the correlation between the separation density of the single-component particle group and the voidage of the gas–solid separation fluidized bed, the ρ_G.drag (change in separation density brought about by the upward airflow drag force during particle group fluidized bed separation) prediction model of the single-component spherical feeding particle group in the gas–solid separation fluidized bed is developed with the correction of voidage. When the prediction error of the ρ_G.drag prediction model is 10%, the confidence degree is 90.00%. Based on the particle segregation model and the ρ_G.drag prediction model, the separation density prediction model for the single-component spherical feeding particle group in the gas–solid separation fluidized bed is proposed. On this basis, the separation density prediction model for the single-component non-spherical feeding particle group in the gas–solid separation fluidized bed is further introduced. The separation density prediction model provides critical guidance for optimizing the gas–solid fluidized bed separation process. Full article

Introduction: Paternal filicide is a rare and complex form of intrafamilial homicide, frequently associated with underlying psychopathology, interpersonal conflict, and psychosocial stressors. While maternal filicide has been more extensively studied, cases involving fathers—especially those employing multiple homicidal methods—remain significantly underrepresented in the forensic literature. This paper presents an unusual case of paternal filicide involving combined lethal methods, contextualized through a narrative review of comparable cases. Methods: A comprehensive forensic-pathological and psychiatric investigation was conducted following the homicide of an 8-year-old boy, killed by his father through a combination of asphyxiation and stabbing. A narrative literature review was performed using PubMed, Scopus, and Google Scholar, focusing on case reports and case series concerning paternal filicide. Particular attention was paid to homicidal methods, motivational dynamics, psychiatric comorbidities, and post-crime behavior. Results: The child’s body was found concealed in a building, in a bed storage drawer, with packing tape tightly wrapped around the mouth and nose and a kitchen knife embedded in the neck. No defensive wounds were observed, suggesting a sudden and unopposed assault, likely facilitated by the victim’s trust in the perpetrator. Autopsy findings revealed signs of asphyxiation and three stab wounds to the chin, neck, and thorax, involving vital structures such as the thyroid cartilage and heart. The father was found in a state of acute alcohol intoxication and subsequently convicted of intentional homicide. The motive appeared to be revenge-related, stemming from a highly conflictual marital separation. The literature review confirmed the predominance of retaliatory motives, frequent substance use, and post-crime suicidal behavior. However, the use of combined homicidal methods and the concealment of the body were found to be exceedingly rare. Conclusions: This case, combined with the literature review, highlights the need for deeper scientific exploration of paternal filicide. Comprehensive forensic and psychiatric assessments are essential to identify recurring situational patterns, motivational profiles, sociocultural contexts, and psychiatric vulnerabilities. These findings are critical not only for post-crime evaluations but also for the development of interdisciplinary prevention strategies targeting early warning signs and high-risk family dynamics. Full article