Gas-liquid Separation Research Articles

Study on Flow Characteristics of Venturi Accelerated Vortex Drainage Tool in Horizontal Gas Well

Vortex drainage gas recovery has been used to carry liquid from gas wells. However, the traditional vortex tools in gas wells cannot produce long effective distance spiral flow at a low gas flow rate, and their operating mechanism has not been thoroughly analyzed. In this paper, the venturi acceleration vortex tool for a horizontal gas well is designed to improve drainage performance. The tube drainage, the vortex tool, and the venturi accelerated vortex tool were applied in a horizontal tube to investigate their drainage capacities by a horizontal well multiphase flow experimental device. The influence of different gas flow rates and liquid flow rates on the length of the spiral flow and pressure drop produced by the three tools was analyzed. The results show that the vortex tool can convert the gas–liquid mixing flow into the gas–liquid separation flow, that is, the liquid flows spirally along the wall and the gas flows in the center of the horizontal tube. Compared with the vortex tool, the venturi accelerated vortex tool can form a longer and more stable spiral flow. The laminar spiral flow reduces the total pressure drop in the tube. The length of the spiral flow increases with the increase in the gas flow rate. With the increase in the liquid flow rate, the spiral flow is not clear because of the turbulent flow. The length of the spiral flow and the pressure drop for the venturi accelerated vortex tool with different gas and liquid flow rates are analyzed to guide the application of the tool. This study provides a new means for the drainage of a horizontal gas well and further clarifies the working mechanism of the vortex drainage tool.

A New Multi-Objective Optimization Strategy for Improved C3MR Liquefaction Process

In the traditional C3MR process (T-C3MR), the boiling gas (BOG) output from the last stage of the gas–liquid separator is directly discharged, in which the excellent low-temperature capability is not utilized, and the system efficiency is decreased. In liquefied natural gas (LNG), single-objective optimization methods are commonly used to optimize system parameters, which may result in incomplete system analysis. To solve the above problems, this paper proposes a multi-objective optimization strategy for the improved C3MR process(I-C3MR) based on a new multi-objective optimization algorithm called EHR-GWO-GA. Firstly, the main work proposes an I-C3MR structure. Secondly, an optimization strategy of the I-C3MR with the maximization of liquefaction amount, minimization of unit energy consumption and minimization of exergy loss as objective functions are proposed. Based on the optimization results, the influence of decision variables on liquefaction amount, unit energy consumption and exergy loss are analyzed, and the results show that the decision variables have good adaptability. Finally, a detailed exergy analysis of the equipment used is made, and the results show that the main exergy losses come from the water coolers and compressors, accounting for 32% and 34%, respectively. Compared to the T-C3MR, the improved C3MR based on EHR-GWO-GA(E-C3MR) has an approximate 8% increase in liquefaction amount—a roughly 23% decrease in unit energy consumption and a decrease of nearly 24% in exergy loss.

Experiment of contact angle hysteresis of a droplet on hydrophobic fibrous membrane

Fibrous membranes are widely used in liquid-gas filtration and separation, porous structures formed by randomly cross-layered fibers have a significant influence on interfacial free energies, showing complex changes in contact angle. The present paper aims to measure the pore structures of a hydrophobic ((C2F4)n, PTFE) fibrous membrane by Confocal Laser Scanning Microscope (CLSM), and analyze the droplet contact angle hysteresis along its circumference. The capillary force of the solid-liquid interface is calculated by the surface integral of Laplace pressure on half droplet surface, and the solid-liquid and liquid-vapor interface area ratios are obtained according to the Cassie-Baxter model. The liquid penetration depth in pore structures is calculated by the quasi-equilibrium of the interface free energy. The experimental result shows that for the PTFE fibrous membrane, the liquid-vapor interface area ratio (f2The experimental result shows that for the PTFE fibrous membrane, the liquid-vapor interface area ratio (f2

Understanding the role of perforations on the local hydrodynamics of gas–liquid flows through structured packings

Structured packings are widely used to perform gas–liquid separation processes as they provide a large mass-transfer area and low-pressure drop. The overall performance of these packings is governed by the local liquid distribution/gas–liquid interfacial area. The local liquid distribution is substantially influenced by the arrangement and geometrical features of the structured packing. While the influence of arrangement and few geometrical features on the local liquid distribution has recently been investigated using the structure-resolved simulations, the perforations on the structured packings are usually ignored. In the present work, we have performed structure-resolved gas–liquid flow simulations, using the Volume-of-Fluid (VOF) method implemented in the open-source C++ library OpenFOAM, in a periodic domain of Mellapak.250 with and without resolving the perforations. We show that the presence of perforations results in flow separation as well as droplet formation leading to an increase in the liquid holdup, interfacial and wetted areas, irrespective of the fluid properties and wetting conditions (specified using static contact angle ‘θw’) considered in this work. We also show that at an inclination angle ‘β’ of 45° from horizontal, the location of the perforations governs the local liquid distribution and the resulting flow metrics. However, at a β of 90°, the number of perforations governs the local liquid distribution, irrespective of their location. Further, we also show that the predictions of structure-resolved VOF simulations, with perforations resolved, are in a relatively better agreement with the correlations in the literature at small values of θw in terms of liquid holdup and interfacial area.

Analysis of the Possibility of Modeling Gas Separators using Computational Fluid Dynamics

Abstract Today, gas-liquid separators are usually used for the purification of gas mixtures from droplet liquid, and there are many designs of which. However, in order to improve the efficiency of their work, increase throughput, reduce mass and dimensions, they are constantly being improved. Usually, developing a new or improving an existing separator design is a long-term and relatively expensive process. Today, computer programs that implement the finite element method make it possible to speed up and reduce the cost of designing both a gas separator and other equipment. FloEFD program is one of these programs. However, it is more convenient during design to use one computer program that allows you to build 3D models (CAD) and in the same program to use a module for simulating the movement of gas and liquid flows (CFD). Such a program is SolidWorks with the FlowSimulation application module. As for the physical processes that occur during the operation of gas separators, they are quite complex, since a multiphase gas flow with an existing liquid phase is simulated. In the article, simulation modeling of the C-2-1 separator was carried out and the values and distributions of velocities and pressures in its various cross-sections were determined. Special attention was paid to the following cross-sections of the separator: along the axis of its inlet pipe; in the middle is the spigot of the blade screw; on a block of blinds. The difference in pressure at the outlet and inlet of the separator was determined, which is 20267 Pa. Based on the simulation results obtained, recommendations are given for further research and optimization of the separator design. The main parameter that characterizes the degree of separation of liquid from gas in the separator is the efficiency factor, which depends on the design of the separator, thermobaric conditions, parameters of the technological scheme, composition and physical and chemical properties of the gas-liquid flow. As a result of simulated modeling of the separator, its efficiency coefficient was determined when it extracted droplet liquid from the gas-liquid mixture in its various fractions (from 0.01 to 0.1 mm). The efficiency factor is about 100%.

In situ membrane separation drives nitrous oxide enrichment from nitrate denitrification for energy recovery

Efficiently enriching nitrous oxide (N2O) can provide a foundation for energy recovery during wastewater treatment. In this study, gas-liquid separation membranes were placed in a sequencing batch reactor fed with acidic nitrate-containing wastewater to determine the feasibility of enriching N2O by in situ separation of dissolved gases. Gas separation across the membrane (GSM) had no obvious effect on chemical oxygen demand and nitrate removal, but N2O production efficiency (NPE) increased from 11.0 % to 82.6 %. Denitrifying bacteria with low N2O yield such as Thauera, Diaphorobacter, and Flavobacterium were eliminated, and Propioniclava (46.79 %) and Candidatus_Competibacter (22.53 %) became dominant. Metagenomic sequencing showed that the abundance of the nosZ gene encoding N2O reductase decreased from 17.3 % to 6.1 %. In conclusion, GSM prevented the further reduction of N2O, eliminating denitrifying bacteria carrying the nosZ gene, which the enriched Propioniclava likely lacked. This demonstrates that GSM is an alternative strategy for N2O enrichment through nitrate denitrification.

The study of dynamic characteristics on a novel air source heat pump coupled with liquid-storage gas-liquid separator under non frosting and refrigeration conditions

Air source heat pump is widely used for heating as it has high efficiency and environmentally friendly advantages, but there is frosting issue in low temperature and high humidity conditions. In order to improve the performance of air source heat pump (ASHP) when its evaporator is subject to frosting, a novel ASHP system coupled with liquid-storage gas-liquid separator was proposed in previous work, which was conducted at a constant temperature. However, the environment temperature is variable during the actual operation, the influence mechanism of the temperature change on the dynamic characteristics of the system and operation characteristics is still unclear. Therefore, experimental method is employed in this work, the aim is to investigate the dynamic performance of the novel ASHP in heating and refrigeration modes in actual environment, including suction/exhaust pressure, suction/exhaust temperature, inlet/outlet water temperature, the coefficient of performance (COP) etc. to improve the adaptability of the heat pump unit. The results indicate that the COP is 2.78–3.49 when the ambient temperature is 6.5–12.5 °C under the heating condition. Also, in refrigeration mode, the COP of the system is 3.28–3.04 under the ambient temperature of 22∼38 °C. This study shows that the novel ASHP has a good dynamic performance during heating/cooling operation in the actual environment. Also, some suggestions for improvement are put forward to solve the existing problems in this work.

A flow-batch lab-in-syringe foam microextraction platform for the simultaneous preconcentration and in situ membraneless gas-liquid separation of mercury prior to cold vapor atomic absorption spectrometry

Herein, the proof-of-concept of a novel lab-in-syringe (LIS) foam microextraction platform is presented as a front-end to cold vapor atomic absorption spectrometry (CVAAS) for the simultaneous preconcentration and membraneless gas-liquid separation (GLS) of inorganic mercury in biological samples. The proposed method is based on the on-line formation of the ammonium pyrrolidine dithiocarbamate complex with mercury that was retained in the pores of polyurethane foam immobilized on the piston of the LIS system. Metal complex elution and in situ mercury vapor generation are accomplished inside the microsyringe in a flow-batch format, while the separation of vapor species is achieved via the membraneless GLS found at the top of the syringe’s barrel. Under optimized operation conditions, for 90 s preconcentration time, the limit of detection was 0.02 μg L−1 and the repeatability (RSD) was 3.8% (at the 0.5 μg L−1 concentration level), within a working range extending up to 4.0 μg L−1. The practicality of the novel manifold was demonstrated using the Blue Applicability Grade Index, while the accuracy of the method was evaluated using certified reference materials and spiked samples.

The Analysis of Gas-liquid Separation Technology Research Progress

Gas-liquid separators are commonly utilized in the energy and chemical industries. This paper briefly introduces the separation principles and research progress of the primary gas-liquid separation equipment domestically and internationally. The paper briefly summarizes the working principles of gravity separation, filtration separation, and centrifugal separation equipment. Next, attention is focused on optimizing the separation performance of centrifugal separation equipment, which offers advantages of small size and high separation efficiency. Finally, a comparative analysis of these gas-liquid separators is provided.

Study on flow field characteristics of gas-liquid hydrocyclone separation under vibration conditions.

The complex vibration phenomenon occurs in the downhole environment of the gas-liquid hydrocyclone, which affects the flow field in the hydrocyclone. In order to study the influence of vibration on hydrocyclone separation, the characteristics of the flow field in the downhole gas-liquid hydrocyclone were analyzed and studied under the condition of vibration coupling. Based on Computational Fluid Dynamics (CFD), Computational Solid Mechanics Method (CSM) and fluid-solid coupling method, a fluid-solid coupling mechanical model of a gas-liquid cyclone is established. It is found that under the condition of vibration coupling, the velocity components in the three directions of the hydrocyclone flow field change obviously. The peak values of tangential velocity and axial velocity decrease, and the asymmetry of radial velocity increases. The distribution regularity of vorticity and turbulence intensity in the overflow pipe becomes worse. Among them, the vorticity intensity of the overflow pipe is obviously enhanced, and the higher turbulence intensity near the wall occupies more area distribution range. The gas-liquid separation efficiency of the hydrocyclone will decrease with the increase of the rotational speed of the screw pump, and the degree of reduction can reach more than 10%. However, this effect will decrease with the increase of the rotational speed of the screw pump, so the excitation effect caused by the rotational speed has a maximum limit on the flow field.

Recent advances in porous organic cages for energy applications.

In recent years, the energy and environmental crises have attracted more and more attention. It is very important to develop new materials and technologies for energy storage and conversion. In particular, it is crucial to develop carriers that store energy or promote mass and electron transport. Emerging porous organic cages (POCs) are very suitable for this purpose because they have inherent advantages including structural designability, porosity, multifunction and post-synthetic modification. POC-based materials, such as pristine POCs, POC composites and POC derivatives also exhibit excellent energy-related properties. This latest perspective provides an overview of the progress of POC-based materials in energy storage and conversion applications, including photocatalysis, electrocatalysis (CO2RR, NO3RR, ORR, HER and OER), separation (gas separation and liquid separation), batteries (lithium-sulfur, lithium-ion and perovskite solar batteries) and proton conductivity, highlighting the unique advantages of POC-based materials in various forms. Finally, we summarize the current advances, challenges and further perspectives of POC-based materials in energy applications. This perspective will promote the design and synthesis of next-generation POC-based materials for energy applications.

Fabrication and characterization of highly hydrophobic PVDF membrane by phase inversion method with high anti-wettability characteristics

Membrane gas-liquid separation technology has garnered significant attention in applications such as membrane desalination, distillation, and gas absorption due to its operational flexibility, compact design, and large specific interfacial area. However, the currently used membranes are prone to pore wetting under high operational pressures, transitioning from a non-wetted state to partially or fully wetted conditions. This undesired wetting increases mass transfer resistance for water vapor molecules, ultimately leading to reduced removal efficiency. To address this issue and enhance wetting resistance, membrane hydrophobicity needs to be improved. In this study, a highly hydrophobic polyvinylidene fluoride (PVDF) membrane was developed using the phase inversion method for membrane distillation applications. We mixed a 16wt% polymer concentration with N-Methylpyrrolidone (NMP) as a solvent at 50°C for 24 hours. Subsequently, the polymer solution was cast and exposed to different non-solvents, namely water and methanol, to investigate their impact. Surface morphology and hydrophobic properties of the synthesized membranes were analyzed using Scanning Electron Microscope (SEM) and a Goniometer. Our findings indicate that the PVDF membrane fabricated with methanol as the non-solvent exhibited a significantly higher water contact angle of 126°, compared to 70° when deionized water was used as the non-solvent. This change from water to methanol as the non-solvent resulted in a more symmetrical membrane structure, enhancing the water contact angle from 70° to 126°. It is interesting to note that increase in the water contact angle increases the hydrophobicity of the PVDF membrane.

Investigation of microgravity vortex phase separator for spacecraft liquid amine CO2 removal system

Spacecraft cabin atmosphere revitalization, more specifically CO2 removal, is a key technology to pursue long-duration, crewed space missions, such as the ones to the Moon and Mars. The ISS currently uses the Carbon Dioxide Removal Assembly (CDRA) as the primary system that employs solid sorbent (zeolite) to remove CO2 from cabin air. However, CDRA cannot meet high reliability and low maintenance requirements. Liquid sorbents may be used as an alternative to solid sorbents and are estimated to attain 65 % less power, weight, and volume than solid based CO2 scrubbers. Liquid amines (liquid sorbent) are currently being researched by NASA for CO2 capture, however their implementation for space applications depends on an effective gas-liquid separation method under microgravity conditions. The Vortex Phase Separator (VPS) offers a new approach for a liquid amine CO2 removal system, and initial investigation of the prototype VPS system demonstrated up to 90.3 % CO2 removal from a humid CO2 stream at 1.47 l/min flow rate. Tests were conducted to determine the CO2 removal efficiency considering several operating parameters, including the liquid amine flow rate, initial fill (charge) level, and temperature; CO2 flow rate; extended-time operation; and CO2-amine pre-mixing length. Results provided key insights on design, operation, and performance aspects of a subscale system, and demonstrated the feasibility of the microgravity VPS for liquid amine CO2 removal system as an alternative, novel spacecraft air revitalization approach.

CO2 Separation Using Electrochemical Hydrogen Pumping

IntroductionCarbon dioxide (CO2) separation and capture technologies are necessary for a decarbonized society. The chemical absorption method using an amine solvent has been demonstrated in steel and power industry. However, the separation process has some drawbacks such as material corrosion. In this study, we examined CO2 separation by electrochemical approach using hydrogen pumping.ExperimentalThe JARI fuel standard cell was employed and modified. It was divided in anode and cathode compartment by a cation exchange membrane. KHCO3 solution and KCl solution were circulated in the anode and cathode compartment, respectively. H2 gas was supplied to the anode at a constant flow rate by mass flow controller. Electrolysis was carried out at various cell voltages using a DC power supply unit. The gas from the anode was introduced into a quadrupole mass spectrometer (QMS). The volume rate of CO2 gas was measured by a mass flow meter.Results and discussionFigure 1 shows the current-voltage curve when H2 gas was supplied, and constant voltage electrolysis was carried out. The current was detected below the theoretical decomposition voltage of water (1.23 V). This supported that the reversible reaction of hydrogen pumping (H2 ⇆ 2H+ + 2e-) was occurred as expected. The Pt catalyst was contributed to the small overvoltage.During electrolysis, gas was generated in the anode solution. It was separated by a gas-liquid separator, and then introduced to QMS. Figure 2 shows the relationship between the ratio of CO2 gas and cell voltage. In our experiment, the CO2 purity was over 90% at all voltages. This suggested that water electrolysis with O2 evolution did not occur. That is, by controlling the cell voltage, the hydrogen pumping reaction take place preferentially, and H+ is effectively supplied to the anode compartment. This archive high CO2 gas separation. In poster session, results on energy consumption will also be presented. Figure 1

Reduced-Order Model for Predicting the Performance of Small-Scale Unidirectional Cyclone Aerosol Separators

This paper presents a reduced-order model for the design of miniaturized unidirectional air cyclones serving as gas–liquid separators for the removal of oil aerosols from a gas stream. Conservation equations for mass, momentum and energy form the basis for predicting the pressure loss within the model; a modified residence-time model is employed for the separation behavior of oil droplets on the cyclone wall. CFD analysis results for one of the investigated geometries are also presented, serving to validate the velocity field employed within the simplified model and providing predictions for particle trajectories and overall separation efficiency. The numerical model is based on the incompressible RANS equations using the k-ω-SST turbulence model and a Lagrangian description of the dispersed phase (Discrete Particle Method, DPM) with a random-walk model for turbulent dispersion. Numerical solutions have been obtained using the commercial FV (Finite-Volume) solver ANSYS Fluent version 2022R1. Both models are benchmarked against experimental data obtained for a large number of cyclone geometries. Good agreement between experimental results, numerical results and results from the reduced-order model is found. The derived reduced-order model is suitable for rapid design of uniflow cyclones in the investigated configuration space.

Experimental investigation on the separation characteristics of the novel combined separator

The cyclone separator is widely used as the efficient steam separation device for the nuclear reactor. In this study, a novel gas–liquid separator that can realize efficient and stable gas–liquid separation under a wide range of working conditions is designed. The separator is organically combined with an axial cyclone separator and a tangential cyclone separator. The axial cyclone separator performs the role of rectification and pre-separation, and the tangential cyclone separator ensures separation performance. The variation in the gas–liquid interface characteristics and separation characteristics of cyclone separation under different inlet flow rates are investigated. Compared with the single tangential cyclone separator, the separation deterioration range of the novel separator is significantly reduced. The addition of the pre-separator effectively broadens the operating conditions for efficient separation. The pressure drop of the novel separator is reduced by more than 50 %. Based on the separated flow model, the relationship between the separation pressure drop ratio and dimensionless number is established, and the prediction method for the pressure drop is put forward with the prediction accuracy within ±10 %, which provides reference for the practical application of the novel separator.

Numerical simulations of a compact inline gas-liquid separator: a comparison between RANS and a hybrid LES-RANS approach

Two computational fluid dynamics approaches are adopted to simulate the single-phase and the gas-liquid flow field generated by a compact inline separator based on the generation of a swirling flow. The results of a detached eddy simulation, DES, combining a large eddy approach with the realizable k-ε turbulence model were compared to RANS results and experimental data from the literature. The DES better replicates the experimentally observed velocity fluctuations, pressure drop, gas distribution and gas-liquid separation profiles, with respect to the RANS approach. A population balance equation was solved in the flow fields produced by the two simulation approaches, and important differences were found in the mean bubble characteristic diameter spatial distributions, possibly due to the different predictions of the local values of turbulent dissipation rates, which affect the bubble breakup and coalescence phenomena.

Performance analysis of a dual-ejector enhanced two-stage auto-cascade refrigeration cycle for ultra-low temperature refrigeration

Auto-cascade refrigeration cycle (ARC) is a cost-effective solution for ultra-low temperature refrigeration. This paper proposes a dual-ejector enhanced two-stage auto-cascade refrigeration cycle (ETARC). In ETARC, two ejectors replace the throttle valves at the liquid phase outlet of the two gas–liquid separators in the conventional two-stage auto-cascade refrigeration cycle (CTARC). They are connected in series to recover partial expansion work in the throttling process, aiming to lift the suction pressure of the compressor. The ternary mixture component is selected and R600a/R41/R1150 is supposed to be the working fluid due to the best performance. The mass fraction ratio of the refrigerant mixture components, the quality at the inlet of two separators and the expansion ratio of the throttle valve (EPR) of the two cycles are optimized using particle swarm optimization (PSO) with respect to the maximum COP. The performances of the two cycles at optimum operating conditions are compared using energetic and exergetic methods, and the effect of the evaporation temperature and the condensation temperature on cycle performances and operating characteristics are discussed in detail. The results show that applying the two ejectors effectively improves the performance of ETARC. Compared with the CTARC at the evaporation temperature of −85℃, and the condensation temperature of 45℃, the ETARC cycle exhibits 16.07% improvement in COP, 29.43% increase in the volumetric refrigeration capacity qv, 17.17% reduction in the total exergy destruction rate. ETARC shows significant performance improvement and has a remarkable energy-saving potential.

Investigation of Gas-liquid Separation Experiment of Electric Pump Drainage and Gas Extraction Unit in High Gas-liquid Ratio Gas Wells

Given the prominent problem of water in the Tarim basin of China with high formation temperature and large water production, a preferred scheme of electric pump drainage and gas extraction unit for gas fields with a high gas-liquid ratio is proposed by the mechanical principle and structural design method. Then, the corresponding electric pumps were developed, and the drainage and gas extraction scheme of a permanent magnet electric pump unit with gas-liquid separation in the way of an inverted deflector is designed. Through indoor experiments simulating the downhole gas-liquid ratio environment, the gas-liquid separation ability and adaptability of the design scheme under different good conditions are verified. The results obtained demonstrate that the cable connection process can meet the requirements of high-pressure resistance (≥25 MPa), and the gas-liquid separation effect is very good in vertical wells by adopting the inverted deflector scheme. The separation effect exceeded 90% under different working conditions (production from 30 to 150 m3/day and inhalation gas-liquid ratio from 50% to 95% and even higher) in the experiment with high gas content. The results will promote the gas recovery rate of high gas-liquid ratio gas fields and improve extraction efficiency.

HI decomposition over the HI-100 test apparatus at a hydrogen production rate over 100 L/h

Studies on the iodine-sulfur (IS) thermochemical cycle for hydrogen production has been carried out since about 2005 by the Institute of Nuclear and New Energy Technology, Tsinghua University, China. The HI decomposition occupies the important position of hydrogen generation in the IS cycle. In this paper, the HI-100 test apparatus with a H2 production rate of 100 L/h was constructed and the HI decomposition was tested. First, the process and components for HI decomposition were designed. Then, the key components, including the feed tank, evaporator, gas heater, adiabatic reactor, condenser, and gas-liquid separator were made of industrial materials. After building this apparatus, the sealing test, heating water test, and HI decomposition have been conducted. The stable hydrogen production operation of more than 100 L/h had been achieved for 5 h, the maximum hydrogen production reached approximately 130 L/h, and the hydroiodic acid decomposition rate maintained about 22 %. The test results provide the design and experimental guidance for further amplification of HI decomposition for hydrogen production by the IS cycle.