Particle separation of biomass-derived granular flows in bioenergy systems using high-load cyclone separators: effects of vortex finder geometry

Packing media regulate nitric oxide removal performance by driving community assembly and biofilm evolution in biotrickling filters.

Steam-air reflux condensation with realistic cooling channel boundary conditions: A parametric study using a fully coupled ALE-IT method

This study presents the design and optimization of a laboratory-scale bubble column bioreactor (BCB) for bioethanol fermentation. Python-based simulations in Google Colab were employed to analyze mass transfer dynamics, hydrodynamic behavior, and reactor scale-up strategies under varying aeration rates. Although ethanol production is an anaerobic process, oxygen transfer analysis was conducted to characterize reactor performance and establish oxygen-limited conditions suitable for Saccharomyces cerevisiae fermentation, incorporating mass transfer modeling, reaction kinetics, process control, and sparger design to enhance fermentation efficiency. To further enhance fermentation efficiency, Response Surface Methodology (RSM) was applied following a two-stage optimization approach. A working volume of 500 mL was defined using fermentation kinetics, including an oxygen uptake rate of 1.1 g O₂/g cells, biomass yield of 0.5 g/g glucose, and kLa of 50 h⁻¹. A perforated plate sparger with six 1.2 mm orifices achieved a gas velocity of 90.3 m/s and 2.68 mm bubble size. Aeration was dynamically controlled to maintain 0.002 g/L dissolved oxygen, while pH was regulated at 5.0–5.5 using NaOH dosing. These conditions yielded 44.3% ethanol. A full factorial design identified Time, Air Flow Rate, Cell Loading, and Bead Mass as significant factors. RSM with Central Composite Design confirmed a significant quadratic model (F = 14.14, p < 0.0001; R² = 0.9601, Adjusted R² = 0.9201). Cell Loading (F = 48.48) and Bead Mass (F = 26.53) had the strongest effects. Optimal conditions yielded 47.9% ethanol at 52.70 h, 1.55 L/min air, 1.51 g/L cells, and 47.20 g beads, with 0.84% prediction error. Copyright © 2026 by Authors, Published by Universitas Diponegoro and BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

High-pressure gas intrusion during drilling operations poses significant well control challenges, heightening blowout risks. To address this critical safety concern, this paper proposes a real-time monitoring framework by characterizing gas-liquid flow pattern transitions through ultrasonic Doppler detection and time-frequency analysis. The proposed methodology systematically integrates three innovative processes: (1) gas-phase channel enumeration for spatial quantification of gas distribution patterns, (2) Doppler frequency shift range analysis enabling dynamic flow characteristic resolution, and (3) flow pattern threshold calibration to establish robust classification criteria. The thresholds of various flow patterns are obtained by the number of gas-phase channels and Doppler frequency shift range to achieve the purpose of real-time monitoring of gas intrusion status. To validate the methodology, an experimental gas intrusion simulation system was developed, comprising a wellbore pipeline integrated with a drilling fluid circulation pool and an ultrasound Doppler detection array. This system replicates downhole flow pattern transitions by injecting controlled gas velocities (0.1-5m/s) at multiple axial positions, enabling spatial-temporal analysis of gas-liquid phase redistribution under simulated drilling conditions. The results show that, our method effectively explain the dynamic evolution of two-phase flow under different flow regimes and achieved early detection of phase transitions. This method provide a non-invasive ultrasound-based pipeline, offering a high-responsiveness solution for gas kick monitoring in high-risk drilling.

ABSTRACT Coal occupies a dominant position in China’s energy structure, with lignite representing a particularly abundant resource. Enhancing the quality and efficient utilization of low-rank lignite is therefore of substantial significance for alleviating energy shortages and promoting sustainable energy development. In this study, a gas – solid area autogenous-medium fluidized bed was employed to upgrade low-rank, high-sulfur lignite through density-based dry separation. The research primarily focused on elucidating the migration and spatial distribution characteristics of coal-powder medium particles with differentiated densities within the area-specific fluidized bed. The dominant density composition of the coal-powder medium and the optimal fluidization area were identified. Furthermore, the effects of operating parameters on the spatial uniformity and stability of bed density, as well as on the distribution patterns of sulfur content, were systematically analyzed, leading to the delineation of functional Areas within the bed. The study also examined the significance levels of various operating factors and their interactions on separation performance, from which the optimal parameter combination was determined. Additionally, the mass distribution of materials across different areas of the bed after separation was investigated. Experimental results indicate that the optimal single-density and mixed-density compositions of coal-powder media for forming a stable area fluidized bed are ρ = 1.45 g/cm3 and ρ = 1.45 g/cm3 +1.65 g/cm3, respectively. Under these conditions, the coal-powder medium particles exhibit uniform and stable distribution throughout the bed, with minimal fluctuations in the mean bed-density profile, yielding an optimal fluidized medium layer in Area I. Three functional spatial Areas within the bed were identified: Area I functions as a low-density separation medium layer enriched in low-sulfur materials; Area II serves as a medium- and high-density stratified area where medium-sulfur materials are interspersed; and Area III acts as a high-density extraction layer uniformly enriched with high-sulfur materials. Among the operational factors, the degree of significance in influencing separation performance follows the order frequency > amplitude > gas velocity. The optimal parameter combination was determined to be A = 3.0 mm, f = 30 Hz, and v = 0.65 m/s. Under these optimal conditions, the upgraded low-rank high-sulfur lignite achieved a clean-coal ash content of 8.67% with a yield of 66.56%, whereas the tailings exhibited an ash content of 43.20% with a yield of 33.44%. The probable error was E = 0.12 g/cm3, demonstrating that the process effectively accomplished clean dry upgrading of low-rank high-sulfur lignite in the 25–0 mm size range.

Investigation of particle accumulation under electrostatic effects in a circulating fluidized bed riser using CFD simulation and statistical experimental design and analysis

This study compares real-time magnetic resonance imaging (MRI) measurements with three-dimensional CFD-DEM simulations for fluidized beds of Geldart Group D particles under non-vibrated and vibrated conditions. Simulation data were analyzed both in a central 10 mm slice, mimicking the MRI measurement, and across the full three-dimensional domain to assess the representativeness of slice-based evaluation. Bed height, bubble diameter, bubble count, and bubble rise velocity were quantitatively compared. For non-vibrated cases, CFD-DEM agrees well with MRI across all metrics and reproduces established correlations for bubble diameter and rise velocity. For vibrated conditions at 10–30 Hz and 0.5 mm peak-to-peak amplitude (dimensionless acceleration Γ < 1) and superficial gas velocities of 2–4 Umf, no systematic changes in bed expansion or bubble-scale properties was observed. These findings indicate that, for Geldart D particles operating well above minimum fluidization, gas-driven bubbling dominates bed hydrodynamics and low-to-moderate vibration intensities do not substantially alter macroscopic behavior. Comparing slice-based and full-domain analyses revealed systematic offsets in absolute values, most notably in bed height and small-bubble statistics. Thus, central-slice measurements capture hydrodynamic trends reliably but can bias absolute quantities relative to full three-dimensional evaluation. These results define a regime of weak vibration influence for Geldart D particles and provide guidance for interpreting tomographic measurements of fluidized beds. • Comparison of MRI data to CFD-DEM of vibrated and non-vibrated fluidized beds. • CFD-DEM reproduces MRI trends in bubble and bed parameters. • CFD-DEM slightly overpredicts bubble size and bed height, underpredicts bubble count. • No systematic vibration effect observed for vibration acceleration Γ < 1 at 2–4 Umf. • Slice analysis captures trends but differs systematically from full 3D evaluation.

Two types or operating modes of gas-liquid-solod three-phase flow reactors, slurry bed and fluidized bed, are widely used in chemical industry. Early they were distinguished by the size and density of solid particles and the distribution of axial solid holdup. With the development of modern multiphase flow measurement technology and the requirement of chemical reaction to control multiphase flow more accurately, it is necessary to study the classification of multiphase flow reactors more carefully. In this paper, acceleration vibration signal detection and telecentric photography are used to study the classification criteria of reactor types. The acceleration vibration time series signals at different axial positions of the three-phase reactor are measured by high-precision acceleration sensors and their standard deviation and power spectral density (PSD) are analyzed. Combined the telecentric image visualization results, the operating modes and their transitions are identified and confirmed, and the fine classification criterion of the two operation modes is obtained. When the superficial liquid velocity is 0.01 m/s and no gas is input, the transition boundary between liquid-solid slurry-like bed and fluidized bed is particle size 150 mesh (100 μm); when the superficial liquid velocity is 0.01 m/s and the superficial gas velocity is 0.0033 m/s, the transition boundary between slurry bed and fluidized bed is particle size 80 mesh (180 μm). These findings provide useful guidance for the accurate control of three-phase flows and reactions.

Scaling biotechnology processes such as gas fermentation remains resource- and time-intensive, both experimentally and in modeling. To improve the efficiency of reactor geometry optimization, we evaluated the transferability of findings from pilot-scale (950 L) simulations to industrial-scale simulations (950 m3). At constant geometric ratios and aeration (vvm) across scales, highly similar flow patterns were observed, especially in airlift reactors. Reactor design enhancements at the pilot scale were transferable to the industrial scale, delivering improvements of up to 17% for kLa. Surprisingly, the commercial simulation resulted in an order-of-magnitude-higher gas holdup and kLa than the pilot, owing to a longer bubble residence time in the taller vessel. Thus, transferability can be further enhanced by enforcing constant superficial gas velocity between scales. This leads to more similar CO transfer rates and regime distributions inside the tank but will challenge reaching sufficient mass transfer for industrial applications.

Abstract Star formation occurs within dense regions of giant molecular clouds (GMCs); however, exactly how gas collects and evolves to form individual stars and what role dense cores play remains unclear. We use the Lagrangian cell information in the STARFORGE simulation suite to track star-forming gas in three GMCs with varying magnetic field strengths. We find that once a protostar forms, the lifetime of the unaccreted gas correlates with the final stellar mass, where low-mass stars ( M * &lt; 0.5 M ⊙ ) accrete for 0.5–0.6 Myr from a relatively local reservoir of gas and high-mass stars ( M * &gt; 2 M ⊙ ) accrete over 3.3–4.7 Myr from a much larger volume. Although the protostellar accretion time increases weakly with magnetic field strength, the accreting gas radii, velocity dispersions, virial parameters, and magnetic energy ratios are largely insensitive to the global cloud properties. At the time of protostar formation, the unaccreted gas exhibits linewidth-size and mass-size relations characteristic of turbulently regulated, isothermal dense cores, following σ v ∝ R 1.0−1.1 and M ∝ R 0.47−0.55 , respectively. Low- and intermediate-mass stars undergo relatively continuous accretion, and their accretion histories are well-fit by isothermal sphere, turbulent core, or competitive accretion models, where no one model fits all masses. However, many high-mass stars experience intermittent accretion, and their accretion histories are not well-fit by any of these models. While the distribution of accreting gas is more extended than typically defined dense cores, the physical properties and structure of the star-forming gas resemble those of observed cores and are largely regulated by turbulence and feedback.

Efficient sand transport in wellbores: Exploring optimal superficial liquid and gas velocity configurations through multiphase flow analysis

Multi-Objective Optimization of Fluidized Bed Hydrodynamics via Spatial Modulation of Inlet Gas Velocities

ABSTRACT This paper focuses on typical valve types in actual natural gas pipelines and conducts research on the pipe explosion characteristics of methane and hydrogen under the condition of actual valve obstacles, aiming to bridge the gap between existing studies on simplified obstacle structures and real-world scenarios, which have been inadequate in supporting engineering applications. In this study, a numerical simulation method is employed to systematically analyze the influence mechanisms of three typical valve structures (butterfly valve, ball valve, and gate valve) on the explosion characteristics of methane and hydrogen in enclosed pipelines. By adjusting the blockage ratio (BR = 0.4, 0.6, and 0.8), the influence mechanisms of valve geometric features on the peak explosion overpressure, flame morphology evolution, and turbulent flow are quantitatively evaluated. The research results indicate that different valve structures significantly affect flame propagation behavior and explosion characteristics by inducing distinct vortex structures and influencing flow pressure drops. Taking the ball valve as an example, its complex structure reduces the gas velocity from 578.63 m/s to 281.48 m/s, with a decrease of 51.35%. Under low blockage ratios, the damage effects before and after the obstacle are similar. However, under high blockage ratios, the overpressure value upstream of the obstacle significantly increases, enhancing the damage effect, while the shock wave overpressure downstream of the obstacle decreases. With a 30% hydrogen blending ratio, the flame acceleration effect is intensified, reaction rates and temperature levels are increased, the maximum speed increases by 18.4%, and these effects are further amplified under conditions of high blockage ratios and hydrogen blending ratios. The research findings provide theoretical support for the safety design of methane and hydrogen-blended natural gas pipelines and valve selection.

Polyvinylidene fluoride (PVDF) hollow fiber mixed matrix membranes (HFMMMs) were prepared by incorporating hydrophobic Zeolite Socony Mobil–5 (ZSM-5) particles into the spinning dope. These membranes were then applied for CO₂ stripping from a diethanolamine (DEA) solution. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) analyses were carried out to examine the membrane morphology and surface roughness. The cross-sectional SEM images showed that adding ZSM-5 changed the membrane structure from a sponge-like form to a finger-like configuration. AFM results indicated that surface roughness increased when ZSM-5 was introduced into the dope solution. In CO₂ stripping tests, both stripping flux and efficiency improved as the liquid-phase velocity increased, whereas changes in gas velocity had only a minor effect on the flux. For the HFMMM, the maximum CO₂ stripping flux reached 2.30 × 10⁻³ mol/m²·s, and the highest stripping efficiency was 83.3% at a liquid velocity of 0.7 m/s. When the liquid temperature was raised from 80 to 90 °C at the same velocity, the CO₂ flux further increased from 2.30 × 10⁻³ to 6.30 × 10⁻³ mol/m²·s. In long-term operation, the HFMMM exhibited better resistance to wetting and showed a smaller decline in flux. Over 120 h, the plain PVDF membrane experienced a flux reduction of 73.5%, while the HFMMM showed only a 24.2% decrease.

As an efficient dry separation technology, electrostatic separation exhibits significant potential for application in the sorting and recovery of carbon-rich resources from coal gasification fine slag (CGFS). The small particle size and high moisture content of CGFS particles are the main factors affecting the efficiency of separation. This study proposes a method integrating particle moisture reduction and charging promotion based on molecular sieves, with the aim of investigating its feasibility in improving the electrostatic separation efficiency of CGFS particles. The results indicate that molecular sieves can effectively adsorb moisture from the ambient humid air and the surface of particles, allowing for rapid drying of wet particles. The reduction in moisture content on the particle surfaces significantly promotes their charging capability, creating favorable conditions for electrostatic separation. After molecular-sieve-assisted charging enhancement, the carbon content in the ash-enriched positive plate product decreased by 4.96%, while the carbon content in the carbon-enriched negative plate product increased by 12.15%, indicating a significant improvement in carbon–ash separation efficiency. Correspondingly, the decarbonization efficiency of the positive plate and carbon recovery efficiency of the negative plate were increased by 21.30% and 52.17%, respectively. Furthermore, when the moisture content exceeds 10%, the phenomenon of inter-particle agglomeration can adversely affect the separation of carbon and ash particles. The most suitable operating conditions are a moisture content no higher than 10%, an electric field density of 30 kV/m, a filling molecular sieve of 400 g, and a gas velocity of 12 m/s (volumetric flow rate 84.78 m3/h). In practical industrial applications, it is advisable to consider pre-treating the particles for drying or employing secondary separation to enhance sorting accuracy.

Abstract We map the extraplanar gas, with ∼50-200 pc resolution, in nine star-forming galaxies using Multi-Unit Spectroscopic Explorer (MUSE) observations from the GECKOS VLT Large Program targeting edge-on galaxies with similar stellar mass as the Milky Way. The narrow range in stellar mass (±0.35 dex) of the GECKOS sample makes it ideal for studying trends with star formation rate (SFR). We find strong extraplanar emission reaching ∼2-8 kpc from the disk midplane in all targets with $\rm {SFR}\ge$1 M⊙ yr−1. Targets with SFR ≥ 5 M⊙ yr−1 have brighter, more extended Hα emission compared to lower SFR targets. In high-SFR systems, the gas velocity dispersion (σHα) shows a biconical morphology, consistent with the expectation of outflows. This agrees with previous works suggesting high velocity dispersion in a biconical shape is a good means to identify outflows. We find mixed results using line diagnostics ([OIII]5007/Hβ - [NII]/Hα and σHα - [SII]/Hα) to spatially resolve ionisation mechanisms across the extraplanar gas. The highest [NII]/Hα are found in the extraplanar gas of the highest SFR systems , yet main-sequence galaxies have the highest [OIII]/Hβ. While the morphology of [NII]/Hα may be useful to identify outflows, the absolute value of the line ratio alone may not distinguish strong outflows from extraplanar gas of main-sequence galaxies. The ubiquitous extraplanar emission can be interpreted as the result of feedback, in the form of large-scale winds for starbursts or smaller-scale galactic fountains for main-sequence galaxies. Moreover, shock-heating may ionise gas at the interface of the disk and the circumgalactic medium, independent of the source of the gas.

The article presents the results of numerical simulation of unsteady gas-dynamic and thermal processes occurring during combustion of a stoichiometric mixture of heptane vapors with air in a semi-closed cylindrical tube simulating the gas-generating cavity of a pulse-action fire extinguishing device. The relevance of the study is determined by the need to create a reliable physical and mathematical basis for describing the working process of gas generation, which is a prerequisite for designing fire extinguishing devices with enhanced characteristics. The simulation was performed in the ANSYS Fluent 2023 R1 software package using unsteady Navier-Stokes equations for a compressible reacting multicomponent gas, a k-ε realizable turbulence model and a Species Transport combustion model with oxidation kinetics according to the Arrhenius law.Based on the calculation results, the spatial and temporal distributions of temperature and pressure at five characteristic stages of the process are obtained. It is shown that the gas temperature in the reaction zone increases from 1 653 K at initiation to 4 884 K at the stage of advanced combustion at the closed end, and then stabilizes at the level of ~3 100K by the time the mixture is completely burned out.Gorenje. The maximum pressure at the closed end reaches 4,2 atm with an increase rate of ~5,1 atm/s. It is established that the acceleration of the flame front is realized by the Shelkin mechanism due to the interaction of expanding combustion products with an unburned mixture. The velocity of hot gases escaping from the open end in the initial phase of the ejection reaches sound values. The data obtained are verified based on analytical estimates of the adiabatic gorenje temperature and the normal velocity of the laminar front and form the basic boundary conditions for subsequent calculation stages.

U-bend geometries are commonly used flow restrictions in nuclear reactor systems. Two-phase flows through U-bends are quite different from those in straight pipes, yet systematic modeling of inverted U-bend effects is lacking. A separate-effects air-water two-phase flow test facility has been used to study the two-phase flow transport from vertical upward to vertical downward across a vertical U-bend (25.4-mm inner diameter; curvature-to-diameter ratio = 9). Detailed data, including void fraction, gas velocity, bubble diameter, and pressure loss, were obtained. Using the obtained experimental data, models and correlations were developed to characterize the U-bend effects, which include models and correlations for variance of void fraction σ 2, U-bend dissipation length, bubble velocity, and pressure loss. The U-bend strength can be represented by the variance of the void fraction, which dissipates exponentially in the U-bend dissipation region. The dissipation lengths of U-bend effects under different test conditions are determined by the dissipation rate β . The bubble velocity correlations are related to the development of σ 2. The Lockhart-Martinelli’two-phase flow frictional loss correlation can be used to predict the experimental two-phase pressure drop across the U-bend with some modifications. Experimental data also suggest a strong correlation between σ 2 and bubble interaction covariance terms (covariance of random collision, CO V RC ) in the U-bend and U-bend dissipation region. A modified Froude number, F r m , derived from the two-fluid model momentum equation is used as a fundamental parameter in developing the correlations for σ 2, β , U-bend dissipation length, bubble velocity, and CO V RC . To model the void fractions in the interfacial area transport equation across the U-bend, a continuity equation was used, while conventional drift-flux models were used in the straight pipe sections. Model coefficients of different bubble interaction terms were determined by evaluating each region (i.e. vertical upward, U-bend, U-bend dissipation, vertical downward) using experimental data individually. The one-group interfacial area transport from vertical upward to vertical downward two-phase flow across a vertical U-bend is then evaluated using all the above developed models and correlations. The evaluation shows that the models predict a i development effectively, with deviations generally within ±15%.

Characterizing instability in gas-liquid flows is difficult because flow dynamics interact across multiple scales. In this work, we develop an integrated framework that combines multi-resolution analysis with composite multiscale equiprobable symbolic sample entropy (MRA-CMESSE). This combination enables us to examine flow instability from a multistructural and multiscale perspective. A comprehensive evaluation across four distinct metrics shows that our method is more robust to changes in data length than multiscale sample entropy and composite multiscale sample entropy approaches. Furthermore, MRA-CMESSE is applied to analyze differential pressure time series from vertical air-water two-phase flow, providing a quantitative characterization of the instability of three flow patterns. Among these, bubble flow is the most unstable, with energy spread out and high complexity at small scales; slug flow is the most stable, with its energy focused at larger scales with low complexity, and churn flow falls in between. A central finding is that as superficial gas velocity increases, energy and complexity shift to the meso-scale and micro-scale. This quantitative analysis identifies increased agitation at the meso-scale and micro-scale as the primary driver of enhanced overall flow instability. This framework offers a new quantitative basis for analyzing gas-liquid two-phase flows and strengthens the physical foundation for the monitoring and control of related industrial systems.