Curved hydrocyclones are promising for multistage separation, but the coupled effects of structural sequence and split-ratio allocation remain unclear. A spline-curved-cone hydrocyclone (H1) and a Bezier-curved-cone hydrocyclone (H2) were arranged into four two-stage configurations. Response surface models for separation efficiency (η) and pressure drop (Pd) were developed using a Box-Behnken design and optimized using NSGA-II/TOPSIS. A simplified mechanistic framework based on mass balance, two-stage efficiency composition, and hydraulic energy dissipation was introduced to interpret sequence and split-ratio effects. Experiments used hollow glass microspheres (density: 0.80–0.84 g/cm³) dispersed in water (density: ∼1.0 g/cm³) at 250 mg/L, with inlet flow rates of 0.5–1.5 m³/h and stage-wise overflow split ratios (S1 and S2) of 5–15%. S1 exerted a stronger influence on η than S2. H1-H2 achieved higher η than H2-H1 but incurred a higher Pd, confirming a sequence effect. H1-H1 achieved the highest η, H2-H2 minimized Pd, and H1-H2 provided the best overall trade-off. Compared with baseline conditions, TOPSIS compromise solutions increased η by 2–19% while reducing Pd by 75–78%. Relative to Pareto extreme-efficiency solutions, they reduced Pd by 87–90% with a 24–28% reduction in η. These findings provide practical guidance for optimizing two-stage curved-hydrocyclone systems for relevant environmental separation and water-treatment applications.
Widespread presence of the caffeine derivatives in aquatic environment poses a high environmental and health risks due to its persistence and partial removal in conventional treatment processes. This study investigated the degradation of caffeine by electrooxidation in a novel Inclined Electrode Reactor (IER) under varying initial conditions of pH (3-9.5), caffeine concentration (4-20 mg/L), NaCl dosage (50-250 mg/L), and current density (1-5 mA/cm2). Optimal degradation efficiency up to 95.2 ±2.93% was achieved at pH 3, 150 mg/L NaCl, and 5 mA/cm² within 60 min in deionised water. Acidic conditions favoured the stability of reactive chlorine species (HOCl), while elevated pH levels reduced efficiency due to less effective oxidant speciation. A lower pollutant load improved degradation kinetics, whereas higher concentration led to oxidant competition. Initial electrolyte concentration of 150 mg/L NaCl balanced oxidants generated and side reactions. Increasing current density resulted in faster degradation but raised energy consumption, indicating a compromise between efficiency and cost. Further, application to sewage wastewater achieved >95% caffeine removal and a up to 85% in COD removal, demonstrating robustness against matrix interference. Specific energy consumption ranged from 1.42-12.49 kWh/m3, lowest under optimal conditions. The IER showed stable operation with minimal electrode fouling, confirming its potential for scalable, energy-efficient degradation of emerging contaminants in complex wastewater.
Electric dehydrators are conventional crude oil treatment equipment with inherent drawbacks, including narrow inlet water content adaptability and limited performance improvement potential. To address these issues, a compact electrostatic coalescer (CEC) is developed and be installed at its upstream to enhance the dehydration performance. The separation performance under series connection of a CEC and an electric dehydrator is experimentally studied. The water content at oil outlet of the separator is used as the evaluation indicator. Influence of different parameters such as temperature, inlet water content, demulsifier, electrical field parameters on the dehydration performance for crude oil emulsion are systematically investigated. Presence of CEC enables the electric dehydrator to overcome its limitation of only being able to treat crude oil with water content of less than 30%. The electric dehydrator could still operate normally and achieve good performance even when the inlet water content is 40%. Existence of CEC helps to reduce temperature in electric dehydrator by 10 °C, or the residence time by 10 minutes, as well as reducing the amount of demulsifier by 87.5%. The research results provide guidance and reference for improving the performance of electric dehydrator and the promotion and application of CEC in offshore platform.
To enhance the temperature uniformity and thermal-hydraulic performance of multi-cluster radial fractal microchannel heat sink (MCHS) radiating outward from the center of a disc, two new types of microchannel heat sinks with multiple loops structure are proposed, which are microchannel heat sink with two connected loops (MCHS-TCL) and microchannel heat sink with three discontinuous loops (MCHS-TDL). Results illustrated that the heat transfer enhancement effect of connected loop structure is significantly higher than that of discontinuous loop structure compared to the design without loop structure. The comprehensive performance (FOM) of MCHS-TCL and MCHS-TDL is 1.127 and 1.049 times than MCHS, respectively. However, there is a serious problem of uneven heat transfer flow in the secondary branch channels of MCHS-TCL. Therefore, rectangular fins are embedded in the MCHS-TCL to examine heat transfer performance. Results illustrated that the temperature uniformity of the secondary branch with symmetrical fins (MCHS-TCL-SMF) and staggered fins (MCHS-TCL-SGF) of MCHS-TCL increased by 24.74% and 22.37%, and FOM increased by 23.51% and 21.50% respectively, which enhanced the heat dissipation of the secondary branch flow path. MCHS-TCL-SMF demonstrates a good thermal and hydraulic performance can achieve the best cooling capacity.
Isopropyl palmitate (IPP) is an ester widely used in personal care formulations. This study investigated its catalyst-free synthesis from palmitoyl chloride and isopropanol using computational fluid dynamics (CFD) and experiments in a 3D-printed PLA microreactor containing periodically arranged static elements. The CFD model represented a section of the complete 2632μL device and was used to assess hydrodynamics, species redistribution, reaction progress, volumetric productivity, and hydraulic demand. Reactive simulations were performed at 65 °C using a literature-derived second-order rate constant. Hydrogen chloride was represented as a pseudo-dissolved numerical species to close the stoichiometric mass balance, whereas gas–liquid partitioning was not modeled. Experimentally, temperature and nominal space time were evaluated using a 2² factorial design with triplicate center points. The CFD results showed repeated stream redistribution around the static elements and progressive attenuation of palmitoyl chloride-rich regions along the modeled section. Increasing the prescribed CFD space time increased predicted conversion and reduced pressure drop and hydraulic power, whereas the associated decrease in flow rate reduced volumetric productivity. At 65 °C and a nominal experimental space time of 15 min, the microreactor achieved an apparent conversion of 76.3%, compared with 56.1 ± 3.2% in the batch system, corresponding to approximately 36% on a relative basis. Although the unreplicated microreactor condition and the hydrodynamic differences between the reduced CFD domain and the complete reactor prevented statistical inference and formal numerical–experimental validation, the combined results showed how static elements redistribute the reactant streams and identified the trade-off among conversion, productivity, and hydraulic demand. This integrated assessment provides a mechanistic basis for reaction-specific reactor optimization and supports continuous-flow processing with static elements as a promising catalyst-free route to IPP.
The global transition toward green energy is accelerating. Newly installed wind and solar power capacity is growing faster than conventional thermal power generation. However, the inherent variability and intermittency of renewable electricity pose increasing challenges to grid stability. At the same time, industrial electrolysis is under increasing decarbonization pressure because of its high electricity demand and associated emissions. Against this background, integrating fluctuating renewable electricity into industrial electrolysis provides a practical route to flexible electrolysis. By absorbing variable green electricity and converting it into stable, high-value products, electrolysis systems can serve as a form of “virtual energy storage”. This process also links renewable electricity utilization with industrial emission reduction. Based on recent literature, this review summarizes progress in three representative pathways: flexible hydrogen production, metal electrolysis, and electrochemical synthesis of chemicals. This review also discusses common challenges and possible solutions under flexible operating conditions. The analysis suggests that these pathways are complementary across different timescales. They can be integrated to provide flexible regulation capacity for the power system. This approach provides a feasible route for transforming energy-intensive industries from rigid electricity consumers into active participants in grid flexibility.
Biological methanation in ex situ biotrickling filter reactors (BTFRs) is a promising power-to-gas solution for converting renewable H₂ and CO₂-rich gas streams into biomethane under mild operating conditions. However, cross-study comparison remains difficult because reactor configurations, operating definitions, normalization bases, and performance metrics are reported inconsistently. This review critically synthesizes up-to-date evidence linking gas–liquid–biofilm mass transfer, hydrogenotrophic metabolism, reactor design, and operating conditions to CH₄ productivity, H₂ utilization, CO₂ conversion, product-gas quality, and long-term stability. Quantitative evidence reveals recurring process-intensification trade-offs: shorter gas residence time can increase productivity but reduce substrate utilization, while pressurization can improve conversion at the expense of compression and pressure-rated equipment. Packing architecture and liquid delivery enhance biofilm retention and effective contact but may also increase pressure drop, liquid hold-up, and diffusion resistance. Pilot and field-integrated studies demonstrate real-biogas utilization, recovery after H₂ interruptions, modular operation, and extended production of high-CH₄ gas. Although biological methanation has reached commercial application in other reactor configurations, publicly documented ex situ BTFR biomethanation remains predominantly at pilot scale. By consolidating the latest quantitative evidence and reporting needs, this review provides a knowledge base to guide scale-up and commercial development.
The trade-off between efficient mixing and low energy consumption remains a potential limitation of static mixers. This paper proposes a biomimetic symmetrical helical static mixer (HSSM) based on the internal spiral configuration of snails, aiming to synergistically enhance flow restructuring and efficient scalar transport. This structure induces periodic secondary flow and coherent vortex coupling through gradient curvature and spatially symmetric layout, achieving synergistic optimization of hydrodynamic intensification and pressure drop regulation. Three mixing unit arrangements (HSSM-A, B, C) were designed, and the reliability of the mathematical model was validated through a combination of experimental and CFD numerical simulations. Compared to Kenics mixers, HSSM reduces pressure drop and friction factor by 14.2%–37.8%, decreases G-value by 7.4%–21.1%, and increases mixing index by 15.3%–58.1%. Compared to LPD mixers, it lowers the CoV value by 53.2%–71.2% and achieves a maximum mixing degree of 99.48%. Through numerical simulation, the hydraulic resistance, shear generation characteristics, turbulence evolution, and concentration field development were systematically investigated. Mechanistic analysis indicates that the symmetric spiral structure induces stable counter-rotating vortex pairs and periodic secondary flows, thereby converting axial transport into coupled axial-radial convection. This ordered vortex coupling enhances scalar gradient stretching and interface renewal while suppressing large-scale flow separation, achieving efficient scalar homogenization and controllable energy dissipation. Among all configurations, HSSM-C exhibits the best overall transport performance under complete mixing constraints. The proposed design provides a structural strategy for low-energy, high-efficiency mixers.
This study investigates the influence of solvent physical properties on cavitating flow dynamics in micro-scale hydrodynamic cavitation (HC) reactors using green solvent systems (de-ionized water (DIW)–isopropyl alcohol (IPA) and DIW–ethanol mixtures). The primary focus of this work is to resolve cavity dynamics in the presence of graphite and relate them to process intensification of graphene exfoliation. Experiments were conducted in two reactor configurations—a long diaphragm and a micro-step design—using four micro-scale HC reactors under varying solvent conditions. High-speed visualization revealed that alcohol-based mixtures generate vapor structures with reduced thickness and coherence compared to DIW, with IPA forming a confined and stable vapor core, while ethanol produces broader and more oscillatory cavities. At 3.45 MPa in Reactor 4, the IPA-based solution led to an approximately 30% lower mean void fraction than the EtOH-based solution, with dominant frequencies of 1.0–1.5 kHz for IPA and approximately 2.0 and 4.5 kHz for EtOH. Compared to long diaphragm design, the micro-step configuration enhances cavitation localization and shear-layer development. Raman and UV–Vis analyses show that IPA-based systems yield more uniform graphene flakes with lower relative layer thickness, whereas ethanol leads to higher edge-related disorder. The IPA-based solution achieves ∼10% higher exfoliation yield, particularly in the micro-step reactors. These results indicate an association of the solvent-dependent cavitation dynamics with the exfoliation performance, while the possible contributions of the localized collapse and shear-layer effects are inferred from the combined hydrodynamic and material-characterization results. The findings establish HC-on-a-chip as an energy-efficient, scalable, and surfactant-free route for intensified graphene production.
