Gas-liquid Separation Research Articles

Membrane electrolysis distillation for volatile fatty acids extraction from pH-neutral fermented wastewater

Volatile fatty acids (VFAs) serve as building blocks for a wide range of chemicals, but it is difficult to extract VFAs from pH-neutral wastewater using evaporation methods because of the ionized form. This study presents a new membrane electrolysis distillation (MED) process that extracts VFAs from such fermentation solutions. MED uniquely integrates pH regulation and joule heating to facilitate the efficient evaporation of VFAs. This integration occurs alongside a hydrophobic membrane that ensures effective gas-liquid phase separation. Operating solely on electricity, MED achieved an acid flux rate of 12.03 g/m2/h at 6V. In contrast, the control results without the joule heating or pH swing only obtained a 0.23 g/m2/h and 0.32 g/m2/h flux, respectively. In addition, a physicochemical model was developed to assess the impacts of temperature on membrane surface pH. This system enhances resource recovery from waste streams and helps achieve a circular carbon economy.

Co2+ - assisted continuous flow UV-induced Hg vapor generation coupled with a modified MSIS gas–liquid separator and microwave plasma atomic emission spectrometry

Co2+ - assisted continuous flow UV-induced Hg vapor generation coupled with a modified MSIS gas–liquid separator and microwave plasma atomic emission spectrometry

Facile scalable one-flow synthesis of ionizable cationic lipid library as precursors of nanoparticle carriers

A variety of ionizable and cationic lipids have been synthesized as precursors for nanoparticle carriers. However, the laborious synthetic routes in batch reactors often involve the use of toxic and carcinogenic agents, as well as challenge of removing gaseous byproducts. In this study, we present facile one-flow micro-reaction process that enables the synthesis of 11 ionizable lipids as well as 7 cationic lipids, including the well-known DODAP and DOTAP. These lipids can be scaled up to produce approximately ∼10g/h by using a straightforward size-up approach. The development of the lipid library was involved generating highly moisture-sensitive acyl chloride at 25 °C for 1.5 min. The toxic byproducts such as HCl, CO2 and CO were subsequently removed using a liquid–gas separator. The esterification with dimethylamino-1,2-diol at 25 °C for 3 min, monitored in-line with FTIR, completed the process. Additionally, the synthesized ionizable lipids were converted to cationic lipids with methyl sulfate, chloride ions via dimethyl sulfate and Steglich esterification in a continuous flow system. Finally, the produced DODAP was transformed into a uniform-sized LNPs (64 nm, PDI 0.07) and liposomal nanoparticles (72 nm, PDI 0.05) while DOTAP was converted to liposomes (55 nm, PDI 0.08) using a custom micro-mixer. This efficient platform for lipid synthesis significantly contributes to the practical applications of lipid-based nanomedicines.

In Situ High-Precision Measurement of Deep-Sea Dissolved Methane by Quartz-Enhanced Photoacoustic and Light-Induced Thermoelastic Spectroscopy.

Rapid and accurate realization of in situ analysis of deep-sea dissolved gases imperative to the study of ecological geology, oil and gas resource exploration, and global climate change. Herein, we report for the first time the deep-sea dissolved methane (CH4) in situ sensor based on quartz-enhanced photoacoustic and light-induced thermoelastic spectroscopy. The developed sensor system has a volume of φ120 mm × 430 mm and a power consumption of 7.6 W. The sensor, in the manner of frequency division multiplexing, is able to simultaneously measure the photoacoustic signals and light-induced thermoelastic signals, which can accurately correct laser-intensity induced influence on concentration. The spectral response of CH4 concentration varying from 0.01 to 5% is calibrated in detail based on the pressure and temperature in the application environment. The trend of the photoacoustic signal of CH4 at different water molecule (H2O) concentrations is investigated. An Allan variance analysis of several hours demonstrates a minimum detection limit of 0.21 ppm for the CH4 spectrometer. The sensor combined with the gas-liquid separation and enrichment unit is integrated into a compact marine standalone system. Since the specifically designed photoacoustic cell has a volume of only 1.2 mL, the time response for dissolved CH4 detection is reduced to 4 min. Furthermore, the sensor is successfully deployed in the vicinity of the "HaiMa" cold seeps at 1380 m underwater in the South China Sea, completing three consecutive days of measurements of dissolved CH4.

Optimizing CO2 Purification in a Negative CO2 Emission Power Plant

AbstractIn the pursuit of mitigating CO2 emissions, this study investigates the optimization of CO2 purification within a negative CO2 emission power plant using a spray ejector condenser (SEC) coupled with a separator. The approach involves direct‐contact condensation of vapor, primarily composed of an inert gas (CO2), facilitated by a subcooled liquid spray. A comprehensive analysis is presented, employing a numerical model to simulate a cyclone separator under various SEC outlet conditions. Methodologically, the simulation, conducted in Fluent, encompasses three‐dimensional, transient, and turbulent characteristics using the Reynolds stress model turbulent model and mixture model to replicate the turbulent two‐phase flow within a gas–liquid separator. Structural considerations are delved into, evaluating the efficacy of single‐ and dual‐inlet separators to enhance CO2 purification efficiency. The study reveals significant insights into the optimization process, highlighting a notable enhancement in separation efficiency within the dual‐inlet cyclone, compared to its single inlet counterpart. Specifically, a 90.7 % separation efficiency is observed in the former, characterized by symmetrical flow patterns devoid of wavering CO2 cores, whereas the latter exhibits less desirable velocity vectors. Furthermore, the investigation explores the influence of key parameters, such as liquid volume fraction (LVF) and water droplet diameter, on separation efficiency. It is ascertained that a 10 % LVF with a water droplet diameter of 10 µm yields the highest separation efficiency at 90.7 %, whereas a 20 % LVF with a water droplet diameter of 1 µm results in a reduced efficiency of 50.79 %. Moreover, the impact of structural modifications, such as the addition of vanes, on separation efficiency and pressure drop is explored. Remarkably, the incorporation of vanes leads to a 9.2 % improvement in separation efficiency and a 16.8 % reduction in pressure drop at a 10 % LVF. The findings underscore the significance of structural considerations and parameter optimization in advancing CO2 capture technologies, with implications for sustainable energy production and environmental conservation.

The Mechanism of Air Blocking in the Impeller of Multiphase Pump

The exploitation and transportation of deep-sea and remote oil and gas fields have risen to become important components of national energy strategies. The gas–liquid separation and gas blocking caused by the large density difference between the gas and liquid phases are the primary influencing factors for the safe and reliable operation of gas–liquid mixed transportation pump systems. This paper takes the independently designed single-stage helical axial-flow mixed transportation pump compression unit as the research object. Through numerical simulation, the internal flow of the mixed transportation pump is numerically calculated to study the aggregation and conglomeration of small gas clusters in the flow passage hub caused by gas–liquid phase separation, influenced by the shear flow of phase separation, forming axial vortices at the outlet where gas clusters gather in the flow passage. The work performed by the impeller on the gas clusters is insufficient to overcome the adverse pressure gradient formed at the outlet of the flow passage due to the gathering of the liquid phase in adjacent flow passages, resulting in the phenomenon of gas blocking, with vortex gas clusters lingering near the hub wall of the flow passage.

Liquid carry-over control using three-phase horizontal smart separators in Khor Mor gas-condensate processing plant

Liquid carry-over phenomenon, where liquid droplets escape with gas, is a prevalent operational challenge in gas–liquid separators. Liquid carry-over leads to foaming issue and performance reduction within separator downstream absorption processes. In order to ascertain whether liquid carry-over is inducing foaming within the gas sweetening process’s absorption tower at Iraq’s Khor Mor gas-condensate processing plant, this study initiated an evaluation of the liquid droplet size distribution in the gas product and gas/liquid separation efficiency of upstream Alpha, Bravo #1, Bravo #2, and Charlee separators that feed into the aforementioned tower by using the Horizontal Vessel and ProSeparator correlations in Aspen HYSYS v.11 software. The study revealed that Alpha and Bravo #2 experienced liquid carry-over issues. In response to these challenges, an innovative smart separator design, referred to as an adjustable separator, was proposed, employing the Arnold-Stewart semi-empirical procedure. This design allows for easy adjustment to accommodate changes in feed composition and operational conditions, mitigating the liquid carry-over problem. The smart design demonstrated a significant increase in gas/liquid separation efficiency for Alpha separator, improving by 31.11% under current conditions and 77.65% under future conditions. Similarly, under both current and future conditions, the smart design of Bravo #2 separator yielded an enhancement of 21.31% and 28.23%, respectively. These results suggest that the smart design can be considered an optimal solution for controlling liquid carry-over. This innovation not only maintains high gas/liquid separation efficiency but also prevents foaming, offering a robust solution for ensuring sustained operational performance and productivity in gas–liquid separation processes.

Numerical simulation of structural optimization within a supersonic cyclone separator

Abstract Supersonic cyclone separation technology, as a new type of natural gas dewatering technology, utilizes the temperature drop generated by ultrahigh velocity fluid flow to condense the water vapor, thus accomplishing the goal of gas-liquid separation. At the input pressure of 8.48×104 Pa (G), the input temperature of 279.6 K, and the input water steam quality score of 5%, the flow fields and condensation characteristics were compared within the steeped, attached, five-curved three separator structures and the control group without the separator structure. The result shows that when the number of mahs of the ultrasonic spin separator of the ladder separator structure reached 1.51, the minimum pressure is −7.49×104 Pa, resulting in a temperature drop of approximately 100 K, and the flow field is most conducive to droplet condensation and growth; the maximum nucleation rate is 2.23×1023 kg−1·s−1, and the droplet diameter is 6.64×10−3μm.

Continuous alkylation of 1,3,5-trihydroxy-2,4,6-trinitrobenzene in microreactor: Process intensification and reaction kinetics

1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is an essential insensitive energetic material. The alkylation of 1,3,5-trihydroxy-2,4,6-trinitrobenzene (Trinitrophloroglucinol, TNPG), which yields 1,3,5-triethoxy-2,4,6-trinitrobenzene (TETNB), is a pivotal step for the synthesis of TATB. The conventional synthetic process has suffered from long reaction time (∼165 min), intricate procedures, and intensive evaporation of a large number of volatile by-products, which increases the risk of spill and eruption of the reaction system, and necessitates in situ continuous gas–liquid separation. A new process for continuous alkylation in microreactors was proposed in this study. Firstly, a parametric investigation in the batch reactor was performed to explore the effects of various process parameters on the yields, resulting in the optimal experimental conditions, i.e., no reflux condensation, triethyl orthoformate (TEOF) as alkylation reagent, molar ratio of 12, reaction temperature of 120 °C and reaction time of 40 min. Subsequent continuous synthesis in microreactors was conducted, which realized the convenient process operation and no need of gas–liquid separation, leading to substantial improvement in the reaction efficiency and safety. Remarkably, within a packed microreactor, under the reaction temperature of 130 °C and residence time of 3 min, 99.24 % in the yield of TETNB was achieved. Comparing with conventional batch reactors, the required reaction time was reduced to approximately 1/50. Taking the advantages of precise control of temperature and reaction time in the microreactors, the kinetics of alkylation reaction were determined. This innovative approach of continuous synthesis can provide an efficient and alternative route for the synthesis of TATB, as well as other energetic materials and similar processes.

Highly efficient hydrogenation of carbonate to methanol for boosting CO2 mitigation

The massive CO2 emissions from the energy-intensive industrial sectors can trace to the thermal decomposition of raw mineral carbonates during high-temperature manufactories. To mitigate CO2 emissions, we propose a novel strategy of carbonate-to-methanol through a highly efficient hydrogenation, where the carbon in mineral magnesite is used as a precious resource to unleash its tremendous value. More significantly, we break the trade-off between the excessive H2 for the complete magnesite conversion and the utilization efficiency of H2 by the recycle usage of H2 through the convenient gas–liquid separation of H2/CH3OH. Guided by the thermodynamic predictions, without any catalysts, the excessive H2 accelerates the direct hydrogenation of magnesite in a twin tower at a relatively low temperature of 550 °C, almost approaching thermodynamic limit of 67 % CO selectivity at a complete magnesite decomposition. The outlet syngas with an extremely high molar ratio of H2 to CO of 8 is further used for subsequent methanol production, achieving an outperformed 70 % CO conversion efficiency and over 99 % CH3OH selectivity. Comprehensive scale-up process simulations indicate that the proposed strategy could increase the H2 utilization efficiency by over 80 %, where the carbon footprint assessment illustrates when the green H2 from wind energy is supplied, the negative net CO2 emissions of −5.6 kgCO2/kgmethanol at a low energy consumption of 10 MJ/kgmethanol can be achieved, which highlights its promising industrialization prospects.

High ethane content enables efficient CO2 capture from natural gas by cryogenic distillation

Cryogenic CO2 capture technique is superior to other CO2 capture methods in terms of potential environmental protection, because it uses no chemical solvent or membrane materials that need regular replacement. However, the freezing problem of CO2 makes it difficult to achieve CO2 capture through simple gas–liquid separation, and the existing cryogenic CO2 capture techniques often require a specially designed separation equipment. In addition, cryogenic CO2 capture is generally considered a method with high energy consumption due to the need for refrigeration. This study proposes a cryogenic distillation-based CO2 capture method for natural gas with high ethane content, such as shale gas and oilfield associated gas. This method utilizes the azeotropic characteristics of CO2 and ethane to avoid CO2 freeze-out and the energy consumption for CO2 capture is minimized through process integration with natural gas liquefaction and ethane recovery. The proposed system uses the propane precooled mixed refrigerant process to provide the required refrigeration, and it is simulated in Aspen HYSYS and optimized by a combined method of a genetic algorithm and sequential optimization. The results show that the proposed process can remove up to 17 mol% of CO2 to less than 50 ppm. With extractive distillation, 99.50 % of the ethane in the feed gas is recovered with a purity of 99.50 mol%. The optimal results corresponding to the maximum allowable CO2 content to avoid its freeze-out (with a solubility margin of 500 ppm) show that when ethane content is 2–20 mol%, the specific power consumption of the system is about 0.43 kWh/Nm3(NG) with an exergy efficiency higher than 50 %. The proposed process achieves energy-saving and efficient CO2 capture method for natural gas with high ethane content.

Design and performance study of gas–liquid separation–mixing device for electric submersible pump in high-gas-content oil wells

In the process of oil production, wells containing gas can impact the efficiency of electric submersible pump (ESP), potentially causing gas lock. This issue can lead to the loss of lifting capacity in ESP, affecting the normal production of oil wells. To address this problem, the concept of gas separation before mixing transportation has been proposed, and a gas–liquid separation–mixing device has been designed. Experimental tests on the gas–liquid two-phase flow under various working conditions were conducted. A numerical model of the physical process was developed and validated with the experimental results. The results indicate that when the inlet flow rate exceeds 8.75 m3/h, the gas phase can be effectively accumulated in the center of the main pipeline after flowing through the guide vanes, thereby achieving efficient gas–liquid separation. Centrifugal number, which is defined as the ratio of axial flux of centrifugal force to axial flux of gravity, was proposed for evaluating the flow characteristics. When the centrifugal number exceeds 6.5, a high-quality gas core is formed in the pipe. At high inlet gas content, the volume fraction of gas in the main pipe initially decreases to 2% as the flow rate increases to 15 m3/h. However, at a flow rate of 30 m3/h, the volume fraction gradually rises to 30%, which results in a significant amount of gas being forced into the main pipe. The results are beneficial for expanding the use of ESP and improving the lifting efficiency in the development of oil field with high gas content.

The influence of the gap width of the blade on the performance of the mixing pump

Abstract The spiral axial flow gas-liquid mixed pump has some problems, such as unsteady flow and sharp decline in performance, when it runs in the biased condition with high gas content. Based on the principle of fluid flow and the design concept of slot drainage, a slit blade is proposed in this study to improve the degree of gas-liquid separation inside the mixing pump. The slit connects the pressure surface of the blade of the mixing pump with the suction surface. The pressure difference between the pressure surface and the suction surface leads to the generation of slit jet, which plays a “blowing” role in the adhesion of the gas phase on the suction surface inside the mixing pump. And make the stagnant air mass in the flow passage move again, so as to slow down the gas-liquid separation in the mixed transport pump. This study provides theoretical reference for the design and optimization of spiral axial flow gas-liquid mixed pump.

Analysis of the Bubble Diameter Effect on the Gas-liquid Flow Characteristics of a Multiphase Rotodynamic Pump

Abstract In order to study the effect of bubble diameter on the gas-liquid flow in the multiphase rotodynamic pump, steady simulations with different bubble diameters were conducted using ANSYS CFX17.0. When the inlet gas content IGVF is 10%, the pump head and efficiency decrease with the increased inlet bubble diameters, and there are different downward trends at different stages of bubble diameter increase. The pump head and efficiency with small bubble diameter (d≤0.3 mm) are much higher than those of large bubble diameter(d≥0.4 mm). A small amount of gas accumulates on both the blade suction and pressure surfaces near the hub under conditions of small bubble diameters. When the bubble diameter is large, A large amount of gas accumulates on the blade suction surface, and almost no gas accumulates on the blade pressure surface. Due to the density difference between gas and liquid phases, gas accumulates near the hub. The gas content rapidly decreases when away from the hub under small bubble diameter conditions, resulting in good gas-liquid fluidity and weak gas-liquid separation.

Flow characteristic and separation performance of co-current gas-liquid vortex separator

A co-current gas-liquid vortex separator (C-GLVS) with a built-in closure hood is proposed to improve the separation efficiency. The internal flow field and separation performance are investigated with respect to different operating conditions by cold modeling experiments. The C-GLVS is divided into three zones, i.e., the separating zone, the discharging zone, and the settling zone. The lowest static pressure and the highest tangential velocity are observed in the separating zone. Furthermore, A swirling gas stream (r/R = 0.75–1) around the bottom of the closure hood prevents the droplets entrainment flowing upward from the wall area, which is believed to be benefit to gas-liquid separation. Experimental results also show that the introduction of the closure hood enables the gas-liquid separation efficiency of C-GLVS to achieve 98.6%, which is about 22.76% higher than that of GLVS. The pressure drop of the gas discharging accounts for about 60% of the total pressure drop.

Design and simulation of an efficient gas-liquid separation device for component regulation of zeotropic mixtures

ABSTRACT Improving the overall energy efficiency of thermodynamic cycles relies heavily on the replacement of traditional pure fluids with zeotropic mixtures. The selection of the optimal components within the zeotropic mixture depends on the specific operating conditions of the thermodynamic cycle. Therefore, significant enhancements in performance can be achieved across varying operating conditions by effectively controlling the composition of zeotropic mixtures in the cycle. According to the gas-liquid equilibrium characteristics of the zeotropic mixtures, the adjustment of the medium components and the boundary conditions can be realized if the components can be adjusted through the gas-liquid separation. In this study, a novel device is proposed for automatically regulating the speed of gas-liquid separation in order to separate the components of the zeotropic mixtures. The CFD simulation was utilized to analyze the structural parameters and boundary conditions that impact the efficiency of gas-liquid separation. The results indicate that the adjustable mass flow range of the optimal structure is broadened by 5.5 times compared to conventional gas-liquid separation devices, ranging from 0 kg/s to 0.15 kg/s. Additionally, within this range, the gas-liquid separation efficiency exceeds 95%, representing a 10% improvement over traditional phase separators.

Impact of optimized gas-liquid separator on temperature and frost distribution in electric vehicle heat pump AC

In the context of low temperatures, the outdoor evaporator surface in an electric vehicle's heat pump air conditioning system tends to accumulate frost unevenly. This uneven frosting occurs due to the varying heat exchange capacity of the refrigerant's two phases within the evaporator. Any reduction in the heat exchanger's capacity would lead to a negative impact on system performance. To address these challenges, this study introduces a gas–liquid separator placed in front of the outdoor evaporator. The aim was to enhance both the outdoor evaporator's performance and the overall system efficiency while investigating frost formation and heat distribution in the outdoor evaporator within a heat pump air conditioning system. The research outcomes demonstrate that the gas–liquid separator can effectively enhance evaporating pressure by regulating the opening degree of the gas-phase bypass valve. Optimal performance is achieved with the gas-phase branch bypass valve set between 20% and 30%, ensuring a stable operational condition and higher evaporating pressure. Moreover, the incorporation of a gas–liquid separator could lead to significant improvements in system performance, with increases of 6.9% in heat capacity and 7.4% in COP observed. Additionally, this enhancement extends to the outlet air temperature, showing improvements ranging from 3.6% to 11.2%.

Experimental study of swirling flow pattern at the swirler outlet using a Wire-Mesh sensor

Entrained droplets and flow pattern change adversely affects separation performance of swirl-vane separators. Investigating gas–liquid distribution at swirler outlet, an experiment was conducted using a wire-mesh sensor positioned. Air and liquid superficial velocities ranged from 8.3 to 25.6 m/s and 0.1 to 1.4 m/s, respectively, covering swirling annular and swirling churn flow at swirler outlet. In swirling annular flow, liquid phase primarily exists as a stable thin film which facilitates efficient separation. In swirling churn flow, wall liquid film has unstable large amplitude disturbance waves. Disrupting liquid film leads to entrained droplets forming in gas center, increasing separation distance and hindering gas–liquid separation. The transition boundary from swirling churn to swirling annular is crucial. Increasing swirler angle shifts the transition boundary towards higher gas velocity at the same liquid velocity. A theoretical model based on interfacial shear stress and gas core blockage predicts the flow pattern transition at swirler outlet.

Numerical simulation of the effect of jet small orifice structure on cavitation characteristic and jet impact flow field

The jet impingement-negative pressure deamination reactor (JI-NPDR) is a continuous, non-clogging, and efficient deamination equipment characterized by its simple structure. Research has demonstrated that the fluid passing through the jet orifices in the jet impact section of the reactor leads to partial cavitation. This situation directly impacts the flow characteristics before jet impact and the gas-liquid separation behavior in the negative pressure separation section. Therefore, this work proposes to utilize the CFD numerical simulation method to analyze the fluid cavitation evolution rules under the aspect ratio l/d structure of different jet orifices and to investigate the influence of orifice structure on the jet impact flow field. The results indicate that an increase in the liquid flow rate and the small orifice aspect ratio l/d promotes the conversion of pressure energy to kinetic energy, leading to an increase in cavitation intensity in the jet orifice. Furthermore, the evolution behavior of the jet impact flow field can be effectively controlled based on the l/d structural parameter of the small orifice aspect ratio. The research results can provide fundamental data support for the structural optimization design and engineering application of the JI-NPDR.

Experimental evaluation of liquid circulation flow rate induced by an air-injection-type aerator

Despite previous research efforts, there is a lack of experimental data on liquid circulation flow rates, particularly in real-scale facilities. The study aims to fill this gap by proposing a momentum transfer model using a gas–liquid separation flow to estimate inner flow in a real-scale air-injection-type aerator. The liquid circulation flow rate was evaluated using velocity measurements. The air supply pressure and dissolved oxygen (DO) were determined. Experiments were performed at depths of 0.90, 1.30, and 1.75 m. The effect of the inner diffuser was investigated at each depth. The inner diffuser reduced the circulation flow rate but increased the vertical upward flow velocity. For the deepest condition (1.75 m), the inner diffuser reduced the air supply pressure and increased the overall oxygen transfer coefficient. Momentum analysis indicated a suppression effect of the air velocity at the aerator exit owing to the inner diffuser. This indicated that an increase in the gas holdup owing to the deceleration of the air velocity at the aerator exit reduced the air supply pressure owing to the reduction in downstream pressure. This study provides valuable insights into aeration system optimization, considering factors such as energy efficiency and oxygen transfer effectiveness.