Gas Liquid Solid Three-phase Research Articles

Efficient photocatalytic degradation of potent greenhouse gas SF6 at liquid-solid interface

Sulfur hexafluoride (SF6), widely used in industries, poses a significant threat as the strongest greenhouse gas. Current methods for degrading SF6 are hindered by high energy consumption and costs, thus there is an urgent need for a low-cost, convenient, and efficient solution. In response, we established a gas-liquid-solid three-phase (GLS) system for efficient photocatalytic SF6 degradation by Bi2O2CO3, whose efficiency was approximately 20 times that of traditional gas-solid systems. Further, possible degradation mechanisms were demonstrated through the detection of material changes in three phases, respectively. Detailed studies revealed Bi2O2CO3 can in-situ form Bi2S3 heterojunction during the reaction, facilitating carrier separation. Besides, O2 can transform to ·O2− and accelerate the photodegradation process. This approach offered a novel toolbox for SF6 degradation. We predict this method will have a wider range of applications in the field of solar-powered catalytic degradation of extremely stable fluorinated pollutants at lower costs in the future.

Gas–Liquid–Solid Three-Phase Boundary in Scanning Electrochemical Cell Microscopy

Gas–Liquid–Solid Three-Phase Boundary in Scanning Electrochemical Cell Microscopy

VOF-DEM study of particle entrainment behaviors in the gas–solid-liquid system with multi-inlet configuration

Enhancing the entrainment capability of particles by bubbles is pivotal for facilitating particle elutriation and augmenting reaction efficiency in gas–liquid-solid systems. The current work utilizes the volume of fluid method in conjunction with discrete element method (VOF-DEM) to study particle entrainment in gas–liquid-solid three-phase reactors featuring different gas inlet layouts. Following model validation, this study delves into the multiphase flow characteristics and particle behaviors in detail. The results reveal that the merging of adjacent channels leads to the formation of larger combined bubbles, thereby increasing particle force, velocity and entrainment height. The average entrainment height during the merging of adjacent bubble channels is 42% higher compared to the four-channel configuration. However, this amalgamation diminishes the channel count and particle entrainment count. Specifically, the highest particle entrainment occurs in the two-channel configuration, which is 26% greater than that in the adjacent-channel merging configuration. Conversely, increasing the channel number decreases bubble size and overall particle entrainment capacity. With consistent bubble sizes, an increase in particle entrainment is associated with reduced entrainment height, indicative of diminished momentum transfer from bubble wakes to individual particles. Additionally, maintaining an optimal number of channels ensures high gas inlet velocity and bubble size, thereby enhancing particle entrainment efficiency. Lastly, appropriately reducing channel distance fosters interaction between adjacent channels, resulting in a meandering bubble path that further promotes particle entrainment and elution efficiency. The results obtained from this study serve as a useful reference for the design and optimization of similar systems.

Air-Lift Pumping System for Hybrid Mining of Rare-Earth Elements-Rich Mud and Polymetallic Nodules around Minamitorishima Island

REE-rich mud under the seabed at a 5500–5700 m water depth around Minamitorishima island and polymetallic nodules buried in the deep seabed are very promising and attractive to explore and develop. REEs are critical to develop due to the recent paradigm shift to renewable energies based on green technologies. Numerical analysis using a one-dimensional drift–flux model for gas–liquid–solid three-phase flow and gas–liquid two-phase flow was conducted to examine the characteristics of an air-lift pumping system for mining these mineral resources. Empirical equations of REE-rich mud and the physical properties of polymetallic nodules around Minamitorishima island were utilized in the analysis. As a result, the characteristics, i.e., the performance of the system, were clarified in three cases: REE-rich mud, polymetallic nodules, and both. The time transient, i.e., the unsteady characteristics of the system, was also shown, such as the start-up and feeding slurry with REE-rich mud and polymetallic nodules. The findings from the unsteady characteristics will be useful in considering the operation of a real project or a commercial system in the future.

Computational fluid dynamics study on first reaction chamber of internal circulation anaerobic reactor

This study aims to investigate the characteristics of gas–liquid-solid three-phase flow in an Internal Circulation (IC) anaerobic reactor during the treatment of wastewater. Through computational fluid dynamics (CFD) simulations of the gas–liquid-solid three-phase in the first reaction chamber and based on the anaerobic granule swarms drag coefficient model, the study investigates the effects of superficial liquid velocity and superficial gas velocity on granules distribution, uniformity index, gas holdup, flow velocities of each phase, and the dimensionless variance of residence time distribution. In addition, the relationship between the fully mixed superficial velocities of gas and liquid in the first reaction chamber is also determined.

Investigation on gas–liquid–solid three-phase flow model and flow characteristics in mining riser for deep-sea gas hydrate exploitation

In response to the problem of gas–liquid–solid three-phase flow in deep-sea hydrate extraction pipelines, a gas–liquid–solid three-phase flow model considering the dynamic decomposition of hydrates is established using continuity equations, momentum equations, and energy equations. The numerical solution of the theoretical model is achieved using the finite difference method. Comparing the theoretical model with the experimental results, the results showed that the average error of gas holdup, liquid holdup, solid phase content, gas phase velocity, liquid phase velocity, and solid phase velocity obtained from the theory and experiment are 8.24%, 0.41%, 1.88%, 5.80%, 2.81%, and 2.22%, respectively, which verified the correctness of the theoretical model. On this basis, the influences of hydrate abundance, liquid phase displacement, and wellhead backpressure on the gas–liquid–solid three-phase flow characteristics in the pipeline were investigated, and it was found that the gas holdup rate will increase with the increase in hydrate abundance, liquid phase displacement, and wellhead backpressure, with the influence of hydrate abundance being more sensitive. The liquid holdup rate increases with the increase in hydrate abundance and liquid phase displacement, but decreases first and then increases toward the wellhead position with the increase in wellhead backpressure. The solid phase content decreases with the increase in hydrate abundance, and first increases and then decreases toward the wellhead position as the liquid phase displacement and wellhead backpressure increase. The influence of gas phase velocity on the abundance of hydrates is relatively small, but it increases with the increase in liquid phase displacement. When the wellhead backpressure increases, the instantaneous increase then tends to flatten out. The influence of hydrate abundance on the liquid phase velocity is also relatively small, but it increases with the increase in liquid phase displacement and decreases with the increase in wellhead backpressure. The solid phase velocity will increase with the increase in hydrate abundance and liquid phase displacement, but it will not show significant changes with the change of wellhead backpressure. The research results can provide a theoretical basis for the safety of hydrate mining.

Simulation of Elbow Erosion of Gas–Liquid–Solid Three-Phase Shale Gas Gathering Pipeline Based on CFD-DEM

Shale gas gathering pipelines often contain liquid water and solid sand in the early stage of production, which leads to the failure of pipeline components easily under the action of gas–liquid–solid three phases. A computational fluid dynamics (CFD) model based on the fluid volume method (VOF) and discrete element method (DEM) was established to study the flow law of gas–liquid–solid three-phase flow in the elbow of shale gas gathering pipeline and the erosion law of the inner surface of the elbow was studied by coupling the Oka erosion prediction model. By comparing the experimental results of erosion damage of the elbow, it is found that the model established can well predict the erosion characteristics and erosion amount under the action of three phases. Combined with the field pipeline parameters and operating conditions, the paper further simulates the elbow erosion behavior under relevant working conditions. The results show that the particles rotate clockwise from the outer wall of the pipe through the bottom of the pipe when passing through the elbow under the action of gas and water phases. When the gas velocity increases, the particles at the elbow mainly gather at the bottom of the elbow and the wall of the outer arch. When the water content increases gradually, the particles gathered on the outer arch wall of the elbow move along the outer arch wall of the elbow and face the inner arch surface gradually, and the erosion area is mainly concentrated on the outer arch wall of the elbow and the outlet horizontal pipe. Under the condition of the liquid phase, the movement characteristics of the water phase and particles in the elbow of the gas gathering pipeline and the erosion characteristics of the pipeline surface are obviously different from those under the condition of the gas–solid two-phase. The model and simulation results established in this paper provide a reference for the erosion damage protection of shale gas gathering pipeline elbow.

MIL-101(Fe) supported Au-Cu nanoalloy for enhanced electrochemical nitrogen fixation in gas–liquid-solid three-phase reactor

Low-temperature electrocatalytic nitrogen fixation technology is a green artificial nitrogen fixation technology. Here, we designed and synthesized AuxCuy/MIL-101 series catalysts, i.e., using simple alloy engineering strategy, the synthesized AuCu nanoalloy particles were efficiently loaded onto MIL-101(Fe) by one-step co-reduction. Experiments and calculations show that (Ⅰ) MIL-101(Fe) as support not only enhances the N2 enrichment ability of catalysts, but also facilitates the high dispersion of AuCu nanoparticles. (II) In AuCu nanoalloy, the strong coupling between Au-Cu sites bridges its effective electron transfer, improves the charge structure of Au sites, thereby enhancing the Au 5d-N2 π* interaction, which not only facilitates the adsorption of N2 by catalysts, but also weakens the N≡N triple bond and reduces RDS (N2 → NNH*, 0.38 eV). (III) Au-Cu alloying increases the hydrogen adsorption free energy (0.76 eV), which weakens the competitive adsorption between H+ and N2 by catalysts, and optimizes the charge transfer efficiency of AuxCuy/MIL-101 catalysts. Therefore, the overall NH3 yield and FE of AuxCuy/MIL-101 catalysts are higher than those of MIL-101, Cu/MIL-101 and Au/MIL-101. After optimization, Au1Cu1/MIL-101 with the highest ECSA and suitable Rct has the highest NRR activity (NH3 yield: 161.07 μg h−1 mg-1cat., FE: 58.86 %), which exceeds most Au-based catalysts. Meanwhile, the in-situ FTIR test results further indicate that Au-Cu alloying can accelerate the cleavage of N≡N and the adsorption of N2 by catalysts. This study demonstrates that the gold-copper alloying strategy not only promotes Au 5d feedback to N≡N bond, reduces RDS but also increases ΔGH*, inhibits proton adsorption, ultimately promoting Au1Cu1/MIL-101 catalyst to perform highly efficient NRR performance.

Continuous synthesis of calcium hydrogen phosphate dihydrate (DCPD) in an annular rotating flow loop reactor

The synthesis of calcium hydrogen phosphate dihydrate (DCPD) involves a gas–liquid-solid three-phase slurry system that poses challenges for precise control using traditional batch reactors to produce crystals with controlled morphologies and particle sizes. In this study, an annular rotating flow loop reactor (ARLR) was developed to continuously synthesize DCPD. The unique internal loop and annular rotating flow field of the reactor delivered exceptional plug-flow characteristics, ensuring that the obtained DCPD exhibited a controlled morphology and particle size. The morphology of DCPD was adjusted to be bowknot-shaped (BS) agglomerate crystals, reaching a length of 120 μm and a D50 size of 70 μm. The ARLR can achieve long-term stable operation with high-solid holdup slurries, outputting up to 125 g/h by maintaining precise and controllable flow and mixing conditions. Notably, ARLR marked a significant advancement in processing high-solid-holdup slurries, offering the adaptability to adjust the geometric design for various slurry systems and forecasting promising prospects.

Experimental study of diphenylmethane gasification with supercritical CO2

Supercritical carbon dioxide (SCCO2) gasification reaction is one of the current popular research fields with wide application prospects in green chemical synthesis, environmental protection and energy conversion. This work aimed to investigate the effects of different conditions on the gas–liquid-solid three-phase products during the reaction of SCCO2 gasification of diphenylmethane. As a result, the carbon gasification efficiency (CE) and the hydrogen gasification efficiency (HE) were 25.99 % and 21.97 % respectively at 700 ℃ for 40 min, in which the CO reached the maximum of 15.64 ± 0.16 mol/kg. As the temperature and residence time increased, the apparent morphology of solid products became more homogeneous. In addition, based on the theories of cleavage of free radicals, secondary cleavage of free radicals and binding of free radicals, three pathways for the generation of fluorene, biphenyl and m-terphenyl were postulated. The experimental results provide fundamental data and theoretical support for an in-depth understanding of the reactions mechanism under the SCCO2 atmosphere, which is of great significance for deepening our knowledge of supercritical carbon dioxide reduction reactions and promoting green chemical synthesis research.

Investigation on gas–liquid–solid three-phase flow characteristics in aircraft wastewater pipes

The aircraft wastewater system is an important system for civil aircraft. The wastewater is transported through the pipeline under the pressure difference between the cabin and the vacuum wastewater tank, and its flow time and characteristics are crucial for the system design. In this paper, the gas–liquid–solid flow of aircraft wastewater is investigated using the Euler–Euler–Euler multiphase flow numerical simulation method. The influencing factors of wastewater flow are analyzed. Afterward, the impact of different factors on the flow time and characteristics is analyzed, such as pressure differences between the cabin and the tank, pipeline length, pipeline inner diameter, and the disturbance for a straight long pipeline. The results show that the wastewater flow time is reduced from 6.4 to 2.6 s with the increase in the pressure difference from 20 to 60 kPa and increased from 3.4 to 10.2 s with the increase in the pipeline length from 30 to 70 m. The results obtained provide a modern theoretical basis for the design of such systems of vacuum wastewater and have a wide range of applications not only in aviation but also in other modern kinds of transport (rail, shipping), contributing to reducing their negative impact on the environment.

Exploring the surface plasmon catalytic reactions mechanism by three-phase interface modification combining with in-situ EC-SERS methods

Local surface plasmon resonance (LSPR) is a novel catalytic technique that has emerged in recent years, especially in the catalysis of aromatic amine compounds. However, the response process and mechanism are still unclear in current study. In the current field of study, the response process and mechanism are still unclear. In this work, the gas–liquid-solid three-phase interface (GLSTI) was innovatively utilized in this study to validate the reaction mechanism by surface-enhanced Raman spectroscopy. P-Aminothiophenol (PATP) and P-Phenylenediamine (PDA) underwent a surface plasmon-catalyzed reaction by using a silver nano-dendrites substrate with strong SERS activity. The GLSTI significantly facilitates the occurrence of surface plasmon catalytic reactions, which can supply enough oxygen by providing three-phase points. In situ SERS and EC-SERS technologies were combined in this study for the explorations. Therefore, this work is dedicated to deepening the exploration and expanding into new directions in plasmon-induced catalytic reactions.

Study on the Characteristics of Gas–Liquid–Solid Three-Phase Unstable Flow in the Aeration Tank Driven by the Inverted Umbrella Aerator

Study on the Characteristics of Gas–Liquid–Solid Three-Phase Unstable Flow in the Aeration Tank Driven by the Inverted Umbrella Aerator

Interelectrode gas–liquid-solid three-phase flow analysis and simulation for drilling holes with high aspect ratio by micro-EDM

Interelectrode gas–liquid-solid three-phase flow analysis and simulation for drilling holes with high aspect ratio by micro-EDM

Polydopamine-engineered design of Nafion-free powder electrode with superhydrophilicity/superaerophobicity and superior adhesive structure for efficient overall water splitting

Absolute exploitation on the intrinsic catalytic property of powder electrocatalysts always faces the obstacles caused by the existing gas–liquid-solid three-phase interface problem and overwhelming dependence on Nafion usage. Herein, a general polydopamine (PDA)-engineering method is developed to construct Nafion-free powder electrode for efficient overall water splitting. The several nanometer scale PDA coating layers that are self-polymerized on catalyst surfaces, enable the superhydrophilicity/superaerophobicity for more exposed electroactive sites and smoother interfacial mass transfer, and meanwhile, render a superior structural stability inside working electrode with equivalent but more homogeneous adhesion compared with that of Nafion-used electrode. At 300 mA cm−2, the CoMoSxOy@PDA exhibits the low overpotential of 311 mV for OER and 343 mV for HER, and meanwhile demonstrates a cell voltage of only 1.89 V for over 200 h of stable operation and almost unaffected catalytic activity even under harsh ultrasonic working conditions. By theory calculations, the reduced reaction energy barrier for oxygen evolution and the optimized adsorption free energy for hydrogen evolution are revealed in depth.

Hydrophobic Hollow-Structured nanocatalyst for Aqueous-Phase selective hydrogenation of Furfural: “H2 storage and Supercharging” effect

Aqueous-phase hydrogenation of furfural (FFR) to furfuryl alcohol (FOL) has environmental advantages and industrial application potential. However, the diverse hydrogenation pathways and the extremely low solubility of H2 in water limit the hydrogenation performance. Herein, a hollow-structured SiO2-supported NiCu nanocatalyst was prepared and modified with organosilane. The NiCu alloy effectively improves the selectivity of FOL. The formation of microbubbles and “H2 storage and supercharging” inside the microbubbles and hollow structures as a result of the hydrophobic modification significantly increases the H2 pressure. This unique gas–liquid-solid three-phase interface makes H2 more fully contact the active sites, and thus improves the aqueous-phase hydrogenation activity. Besides, an excellent catalytic stability is shown due to the close contact between the metals and SiO2 derived from the same precursor. This work provides a direction for the manufacture of highly efficient metal nanocatalysts for gas–liquid-solid three-phase reactions, and has latent industrial application in the field of aqueous-phase catalytic conversion of biomass.

Interaction effects of inlet velocity and apex diameter on the separation performance of two-stage cone hydrocyclones

Hydrocyclones are widely employed in industrial fields to separate particles. The interaction between the apex diameter and inlet velocity is important for the regulation of the two-stage cone hydrocyclone, but it is not clear. In this study, a gas–liquid–solid three-phase turbulence simulation method, which combines the volume of fluid method, the Reynolds stress model and the discrete element method (VOF–RSM–DEM) via open source software, OpenFOAM, and our in-house developed software, DEMms, is developed. The reliability and validity of this method has been verified by the experiment results. Then it is conducted to investigate the interaction effects of inlet velocity and apex diameter on the separation performance of two-stage cone hydrocyclones. Results show that there are intense interaction effects between the apex diameter and inlet velocity and the variations of cut size and Ecart probable with apex diameter and inlet velocity are not always monotonic.

Correlation for calculating frictional pressure drops in vertical three-phase flows for subsea-resource production

Subsea minerals and methane hydrate are found in deep seas within the exclusive economic zone of Japan. However, they have not been commercialized owing to some technical issues.Gas-lift pumping is a promising technique for transporting subsea minerals and methane hydrate from the seafloor to the sea surface. Nevertheless, methods for calculating frictional pressure drops in three-phase flows need to be established because internal flows in pipes become three-phase flows in gas-lift pumping systems. To establish such methods, we reviewed existing correlations for calculating frictional pressure drops in two- and three-phase flows. Next, we conducted an experiment on gas–liquid two-phase and gas–liquid–solid three-phase flows through transparent polyvinyl chloride pipes using resin balls as solid particles. Subsequently, we compared the calculated results with the experimental data. We modified the correlations that showed good performance in the comparison for three-phase flows and proposed new correlations for calculating frictional pressure drops in vertical three-phase flows.Further, we compared the calculated results based on the modified and new correlations with the experimental data for a three-phase flow to evaluate the correlations.The new correlation could be used to calculate frictional drops in three-phase flows more accurately than the other correlations. In addition, the new correlation could be used to calculate a wider range of pressure drops than the other correlations because it contains no experimental constant. Thus, the proposed correlation is more accurate and effective for calculating frictional pressure drops in vertical two- and three-phase flows than other correlations.

Removal of the effect of the high solids holdup ring in the fluidized bed on electromagnetic tomography

Electromagnetic tomography (EMT) system based on tunneling magneto resistance (TMR) sensor, as a non-invasive multiphase flow measurement technique, can effectively detect the solid-phase distribution in the gas–liquid–solid three-phase fluidized bed with magnetic catalysts by reconstructing the permeability distribution image. The radial distribution of solid particles in the gas–liquid–solid three-phase fluidized bed with uneven fluidization is non-uniform, in which a high solids holdup ring exists near the wall of the riser. When the TMR-EMT system is used directly for image reconstruction, the high solids holdup ring will greatly reduce the image quality, further leading to the inability to detect phase information in the riser. To improve the reconstructed image by the TMR-EMT system, a removal method for the high solids holdup ring is proposed. The method firstly estimates the equivalent thickness of the high solids holdup ring based on the boundary measurement data. Then the influence of the high solids holdup ring on the boundary measurement data is subtracted. By the removal method, the internal phase distribution information is prominent. The simulation and experimental results demonstrate that the proposed method can realize the permeability distribution detection by the TMR-EMT system in the presence of the high solids holdup ring.

Review of bubble dynamics on charged liquid–gas flow

When a fluid is subject to an electric field, it usually processes unique features compared to the conventional fluid that arises from coupling between charged particles and fluid interface. Based on this commonality, we defined the concept of “charged multiphase flow” and constructed a generalized charged multiphase flow system using the “Tai Chi Diagram” to analyze the properties and features of different study objects, with an emphasis on the bubble dynamics on the charged liquid–gas flow object, covering the processes of bubble generation, motion, and interaction, as well as the important dynamic behaviors, involved such as bubble deformation, coalescence, and breakup. Furthermore, in light of the special plasma–liquid interface phenomenon formed by the ionization of the gas/vapor phase in the liquid phase in strong electric fields, the traditional gas–liquid–solid three-phase flow system is expanded into a broader range of multiphase flow systems involving plasma, which enriches the theoretical and frontier scientific problems of the multiphase flow. In addition, technical innovations, remaining work, and future trends in the development of the charged liquid–gas flow, and their potential applications are discussed.