Gas-Liquid Cyclone Research Articles

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.

Investigation on the formation mechanism and flow characteristics of liquid carry-over in gas–liquid cyclone separator

The liquid carry-over (LCO) phenomenon brings about the performance deterioration of gas–liquid cyclone separator and an increase in pressure drop. However, the formation mechanism of the LCO and its manifestation in the separator cylinder and the overflow pipe have not been fully understood. This work investigated the flow process of the LCO by visual observation and quantitative measurement of the overflow liquid flow rate and liquid holdup. The transient gas–liquid flow feature in the overflow pipe and spatiotemporal relationship between the separator inlet and outlet were characterized by time-frequency analysis and wavelet coherence of liquid holdup, respectively. The results showed that the size of air core determines two kinds of sources of the LCO, including the surrounding liquid direct entry into the overflow pipe and the film short-circuit flow beneath the top wall of the separator. When the air core can continuously wrap up the overflow inlet, the film short-circuit flow became the primary source of the LCO, which was embodied in the significant reduction of the overflow liquid flow rate. Three flow patterns, namely, slug flow, churn flow, and annular flow, were classified in the overflow pipe. The inlet intermittent flow of the separator led to the distribution of churn flow expanding toward higher gas velocity, which was interpreted by flow pattern transition theory. The time-averaged overflow liquid holdup was well predicted by drift-flux model. The results are beneficial to the proposal of inhibition methods of the LCO and structure design of the separator.

Working Performance and Structure Optimization of Spindle-Shaped Axial Gas–Liquid Cyclone Separator

Working Performance and Structure Optimization of Spindle-Shaped Axial Gas–Liquid Cyclone Separator

Research on the Gas-Liquid Two-Phase Distribution Behavior and Influencing Factors of Swirling Flow in Horizontal Pipe

Gas-liquid two-phase swirling flow is widely used for gas-liquid separation in the power, chemical, petroleum, and nuclear industries. However, the majority of current research on swirling flow focuses on identifying flow patterns and does not pay more attention to topics such as the boundary where swirling flow forms. The length and diameter of the central gas core are the main focus of the current studies as well as the distribution patterns of gas-liquid two-phase. Comparative studies on the gas-liquid distribution morphology, such as whether the gas phase is separated and the separation mode, are lacking. In this paper, a combination of visual experimental observations and numerical simulations of Computational Fluid Dynamics (CFD) is used to investigate the formation conditions of gas-liquid two-phase swirling flow in three types of cyclonic components. The results show that the minimum superficial liquid velocity for the formation of swirling flow in the horizontal tube is about 0.375~0.82 m/s when the superficial gas velocity is less than 10 m/s. The formation of swirling flow is almost independent of the geometric swirl number and superficial liquid velocity when the superficial gas velocity is greater than 10 m/s. At low inlet superficial velocities, the tangential velocity determines the transition from swirling flow to stratified flow. However, at higher inlet superficial velocities, the decay of the cyclonic field is mainly affected by the wave amplitude of the gas-liquid interface. In both co-current and counter-current horizontal inline gas-liquid cyclone separators, the flow split is related to the vortex core breakdown of the central gas core. In addition, the numerical simulation results show that the breakdown of the vortex core is related to the pressure distribution inside the separator. This work enriches the study of swirling flow and provides a basis for the performance improvement of inline gas-liquid cyclone separators.

Experimental investigation of oil film flow and droplets behavior in the annular channel of a cyclone separator

The separation of the gas and liquid in the gas-liquid cyclone separator is achieved through the swirling flow. The liquid film flow characteristics and the dynamics of droplets impacting the liquid film are very important for the separation performance, but these phenomena have not been well understood in the swirling flow. In this work, an experiment was conducted to investigate the liquid film flow and droplet impingement in the annular channel of the gas-liquid cyclone separator. Three regions of the annular channel could be divided based on the film flow patterns, which were the inlet region, the annular region, and the outlet region; and four typical droplet impact outcomes could be observed, which were splashing, coalescence, bouncing, and jet breakup. According to the characteristics of the liquid film and the outcome of droplet liquid film impingement, if the droplet splashing in the inlet region could be weakened and the length of the annular region was lengthened, it would be beneficial for gas-liquid separation. The impact outcomes were shown to undergo a transition from bouncing to coalescence as the droplet Weber number increased. Droplet coalescence was affected by the disturbance of gas flow and the evenness of the liquid film, so when the superficial velocity of the gas flow was fixed, the transition boundary was constant whatever the liquid volume fraction in the channel, and when the Reynolds number of the gas flow increased, the transition boundary of droplet Weber number increased first and then decreased. This work may provide a basis for a comprehensive understanding of the liquid film flow pattern and droplet behavior in the cyclone separator, and the results have the potential to be applied in other multiphase studies.

Numerical analysis of a novel cascading gas–liquid cyclone separator

Numerical analysis of a novel cascading gas–liquid cyclone separator

Optimum design of inline gas-liquid cyclone separator for wide range of inlet gas volume fractions

ABSTRACT The inline gas-liquid cyclone separator has been gradually used in oil & gas industry due to its high separation efficiency and less footprint. However, under the inlet flow conditions with large range of gas volume fractions, the research on structure design and separation performance are seriously insufficient. The preliminary structural design of the inline gas-liquid separator was carried out according to the particle separation theory, and the key structural parameters were optimized by using the Response Surface Method (RSM) together with Computational Fluid Dynamics (CFD). The structure optimization has improved the degassing efficiency by 17.44% and dehydration efficiency by 7.59%. With air and water as working medium, the separation performance of the inline gas-liquid cyclone separator was experimentally investigated in laboratory under a large range of gas volume fractions. The results show that the separation efficiency for both degassing and dehydration can exceed 80% with the inlet gas volume fraction ranges from 0.2 to 0.8. The optimum normalized flow split and liquid volume flow rate are 0.9 –1.2 and 8 m3/h, respectively.

Design and performance study of a two-stage inline gas-liquid cyclone separator with large range of inlet gas volume fraction

With the advantages of high separation efficiency and less footprint, the inline gas-liquid cyclone separator has gained wide attention in the fields of petroleum, chemical industry, nuclear energy and aerospace. However, single-stage gas-liquid cyclone separator usually cannot accommodate a large range of inlet gas volume fractions. For gas-liquid cyclone separator operating in series with the same structure, it is difficult to operate the second stage efficiently. Therefore, a new two-stage inline gas-liquid cyclone separator is designed in this study considering the bubble size and the variation of inlet gas volume fraction. It integrates the advantages of horizontal and vertical inline gas-liquid cyclone separator, so as to meet the separation requirement for both gas and liquid. The tangential velocity, gas volume fraction and pressure distribution inside the separator are studied by numerical simulation using Computational Fluid Dynamics. The experimental results show that the optimal standardized flow split is about 1.0. When the inlet gas volume fraction varies from 10% to 90%, the degassing efficiency gradually increased with a maximum value of 8.88%. Meanwhile, the dehydration efficiency gradually decreases, with a maximum value of 4.24%. In addition, the maximum pressure drop of the two-stage inline gas-liquid cyclone separator is only 140 kPa during the process of experimental test. This research can provide efficient solution to the working condition with wide range of inlet gas volume fraction and to meet the requirement of high compactness as well.

Optimization analysis and Field application of gas-liquid cyclone separator based on CFX

At present, large and cumbersome gravity sedimentation separators are generally used in the separation of liquid and gas in the wellbore during emergency blowout or circulating degassing in drilling, and innovation and improvement are urgently needed. In this paper, CFX commercial simulation software is used to analyze the cut-in cyclone separator, and the axial inlet type cyclone separator with different length ratios of cylinder-cone section in swirling flow section under different flow channel structures, and carried out indoor simulation and field test verification. The results show that the axial inlet type cyclone separator is more suitable for gas-liquid separation than the cut-in cyclone separator, and the separation can be well improved by increasing the length-diameter ratio of the cyclone section under the cut-in cyclone separator structure. Finally, the experimental separation efficiency reached 99%, and the field test separation efficiency reached more than 98%. This greatly improves the separation efficiency of liquid and gas during the drilling process, and also plays a certain role in promoting the separation of gas and liquid in the entire oil and gas industry.

Study on Separation Performance of Gas-Liquid Cyclone Separator with Pulsating Feeds

Background: In recent years, a kind of drilling method of solid-liquid separation combined with pulsating vacuum formed by vibrating screen and compressed air injection has emerged in oil drilling, which profoundly improves the gas, solid, and liquid separation ability of the drilling fluid vibration screen. Objective: Based on the above ideas, a kind of hydrocyclone used for gas-liquid separation with the pulsating feed boundary was proposed. The separation performance of gas-liquid hydrocyclone may change significantly due to the mixed pulsation of the gas-liquid fluid transported by the jet pump. Therefore, the flow characteristics of the pulsating feed hydrocyclone need to be analyzed and explored to provide basic data for further improvement of the structure. Methods: The development status of cyclone separators are summarized through related literature and patent investigation. The Computational Fluid Dynamics (CFD) software ANSYS Fluent 2019 R3 is used to analyze the flow field characteristics and optimize the parameters of the hydrocyclone with stable feed. Then, the programming by the User-Define-Function (UDF) of Fluent is used to simulate the flow field of the separator under the condition of pulsating feed. Meanwhile, the flow field analysis and parameter optimization are carried out accordingly. Results: The optimal parameters in a stable state and pulsed state are obtained from the analysis of the efficiency curve. The results show that the flow field can be stabilized in the pulsating feed state, and the sinusoidal pulsing with a frequency of 0.4 Hz is used to achieve the highest separation efficiency, i.e., 85.5%. Conclusion: The separators with pulsating feed and stable feed have similar flow field characteristics, and the optimal structural parameters under pulsating feed are obtained. Compared with the stable feed condition, the pulsating feed condition can connect multiple cyclone separators, which can separate more drilling fluid in unit time and improve the work efficiency. It has strong practicability, which provides a critical foundation for structure optimization in the future.

Design and Performance Study of a Two-Stage Inline Gas-Liquid Cyclone Separator with Large Range of Inlet Gas Volume Fraction

Design and Performance Study of a Two-Stage Inline Gas-Liquid Cyclone Separator with Large Range of Inlet Gas Volume Fraction

The Structure Design And The Flow Field Analysis Of The Gas-Liquid Separation Cyclone

This paper introduces the structural characteristics and working principle of the gas-liquid cyclone separation device, and explores the laws of changing of gas volume fraction distribution, velocity field and pressure drop with or without a thimble in the underflow port and under different thimble shapes. The separation efficiency of gas-liquid separator reaches 80% after adding a thimble. At the same time, indoor experiments fully verified that the pressure loss is greater and the speed increases after changing the shape of the thimble to a truncated cone shape. Truncated cone thimble helps the dense liquid move to the sidewall and the low density gas gathers toward the central axis. And the distribution of internal fluid makes the treatment effect of degassing more superior.

Analysis of Bubble Flow Mechanism and Characteristics in Gas–Liquid Cyclone Separator

The separation of bubbles in a gas–liquid cyclone is complicated. A combination of numerical simulation and visual experimentation was considered apt to reveal the microscopic mechanisms of bubble flow. First of all, cyclones with different structures were numerically simulated. The calculation results show that the larger the diameter of the exhaust port, the better the bubble flow effect. When the exhaust port diameter was 24 mm, the gas discharge efficiency was 8% higher than that with an exhaust port diameter of 16 mm. The sequence of the bubble flow effect of a four-structure cyclone was obtained, and the gas discharge efficiency of the cyclone with a rectangular inlet was 7% higher than that of the trapezoidal inlet. Finally, a visual experimental platform was built to compare the rectangular inlet cyclone and spiral inlet cyclone with the best bubble flow effect. In accordance with the simulation numerical calculations, the bubble flow effect of the rectangular inlet cyclone was better than that of the spiral and trapezoid inlet cyclones, and the rectangular inlet in the middle was better. This article provides a specific theory and experience to guide further research on the separation mechanism, flow field characteristics and structurally optimal design of gas–liquid cyclones.

Experimental research on the separation characteristics of a gas-liquid cyclone separator in WGS

Wet Gas Scrubbing (WGS) is one of the important steps in Fluid Catalytic Cracking (FCC) process, which removes SOX from the flue gas. The gas-liquid cyclone separator in the WGS system is adopted to separate the clean gas from alkaline solution. To improve the separation efficiency of the separator, the flow structure therein is to be investigated. In this paper, the pressure and velocity distributions of the gas flow were measured by pressure sensors and five-hole probe. The influence of operating parameters such as the inlet gas velocity and the inlet liquid concentration on the separation efficiency were analyzed. Experimental results showed that the total pressure drop was less than 30 Pa, while the Eu number remained 4.7 × 10−4 under the inlet gas velocity ranging from 3.7 to 9.8 m/s. The separation efficiency was increased from 82% to 93% with an increasing of inlet liquid concentration from 30 g/m3 to 60 g/m3 at a fixed gas velocity of 9.8 m/s. Based on experimental results, a model was formed to predict the pressure drop. Besides, an improved weighting method to calculate the droplet separation efficiency was also given. Furthermore, empirical correlations were proposed to predict the separation efficiency with an average deviation of 1.84%.

An Analysis of Inlet Inclination on the Performance of a Gas-Liquid Cylindrical Cyclonic Separator

Gas-Liquid cylindrical cyclonic separator plays a significant role with regards to gas-liquid separation in the oil fields. Its major operational challenges include liquid carryover and excessive pressure losses. The Inlet geometry of a gas-liquid cylindrical cyclone is one of its critical parts that affect the performance of the separator. The inlet geometry drives the performance of the separator in terms of liquid carryover and pressure drop. Traditionally, the 27° downward inclined inlet is usually used because of its advantage in terms of liquid carryover operating envelope. However, detail comparison in terms of pressure drop in the gas leg of the separator is yet to be reported. In this paper, the author presents experimental results on the effect of inlet inclination on the performance of a gas-liquid cyclonic separator in terms of separation efficiency (liquid carryover) and pressure drop. The results showed that under the same inlet conditions, the liquid carryover operating envelope of the 27° downward inclined inlet pipe cyclonic gas-liquid separator is slightly wider than the horizontal inlet of the same separator. However, the pressure drop across the gas leg of the 27° downward inclined inlet pipe cyclonic gas-liquid separator is far greater than the horizontal inlet of the same separator. The paper concludes that, where there is a strict requirement on pressure drop, the horizontal inlet cyclonic separator should be favoured against the 27° inclined inlet.

A Study of Flow Regimes in the Upper Part of a Compact Gas-liquid Separator

In the offshore oil and gas environment, there is usually the challenge with regards to available space offshore platforms for equipment installation; hence, compact separators are more attractive due to their small footprint. Also, in subsea oil and gas production, compact separators are attractive because of their light weight and ease of installation. A good understanding of the flow regimes in the upper part of the separator is essential for a robust design and operation. The performance of gas-liquid compact separator in terms of liquid carryover (LCO) and pressure drop depends on the type of flow regime in the upper part of the separator. However, there is a lack of experimental data on flow regimes in the upper part gas-liquid cyclone separators. In this research, data on flow regimes in the upper part of a 1.5-inch horizontal-inlet gas-liquid cylindrical cyclone separator was acquired using electrical resistance Tomography (ERT), wire mesh sensor (WMS), pressure transducer and visual observation. Based on flow imagining, observations and statistical analysis, the flow regimes were classified as swirling-annular, light-mist, heavy-mist and churn flow. A flow regime map for the separator was proposed based on a modified liquid and gas-Froude number. The work would be a useful guide to process engineers during the preliminary design and sizing of separators with similar geometry configuration.

Numerical analysis of a novel gas-liquid pre-separation cyclone

Abstract A novel gas-liquid cyclone characterized by the generation of swirl flow via guide vanes and a uniflow stream was designed for the pre-separation of a horizontal gravity based separator. The internal flow field and separation performance of the cyclone were investigated by numerical simulation. The Eulerian-Lagrangian approach with the Reynolds stress model (RSM) was used in the simulations. Contours of velocity and pressure within the cyclone are shown, and the trajectories of the droplets are also presented, demonstrating the separation mechanism of the cyclone. Then numerous simulations were conducted with different structural parameters to optimize the cyclone performance. The results show that broadening the width of the gap lw is good for large droplets separation; Decreasing the discharge angle α or increasing the torsion angle β of the guide vanes can increase the tangential velocity and improve the separation efficiency, but the pressure drop also increases fast; The increase of the diameter of the central body Dc will lead to an increase of tangential and axial velocity, and the pressure drop increases significantly as well.

Improving the efficiency of gas-liquid high-pressure cyclone separator

The research results focused on improving the efficiency of gas-liquid cyclone separator with high operating pressure value of 2.5 MPa and a high flow density in the separation chamber are presented. With increasing of the gas dynamic pressure value increases the probability of entrainment processes and ascending film flow on the chamber walls which leads to a decrease of the separation efficiency. The gas-liquid separator construction provided the gas dynamic pressure reduce in the areas with high concentration of the liquid phase and excluded the separated liquid removal to the output collector is performed. This collector formed by conical confuser and round tube with external finning is located in the center of the separator’s cylindrical chamber. A ribbed tubular flow conditioner is placed before collector’s inlet face. The detailed structure of the flow in the separator by using a computational fluid dynamics based on RANS equations solving with the anisotropic RSM turbulence model is obtained. CFD simulation results are used to evaluate the main separator characteristics and the probability of entrainment processes and ascending film flow.

Optimization and industrial application of recycled hydrogen desulfurization process in a hydrogenation unit

ABSTRACTA novel gas-liquid cyclone operated under high-pressure conditions (13.7 MPa) was developed. For optimizing recycled hydrogen desulfurization system, an array of this type of cyclone separators was set in the top of the high-pressure separator and desulfurizing tower. The industrial application results illustrated that the average separation efficiency of the cyclone deliquid device was 85.4%. By adopting the optimized system, a large amount of investment cost was saved and a series of significant improvements were achieved.

Modeling the Mean Residence Time of Liquid Phase in the Gas–Liquid Cyclone

Residence time is a key parameter for the cyclones with mass transfer or reaction process. A model for the cylinder-on-cone cyclone was presented to calculate the mean residence time of the liquid phase, based on a force balance on the wall film. This model was validated using an experiment, which measured the residence time of the liquid phase by the hold-up method. The results demonstrated that the predicted residence times are in good overall agreement with the measured values. Furthermore, the liquid residence time decreases obviously with increasing droplets loading, and decreases less with increasing inlet velocity. The liquid residence time increases with the cylinder diameter. The wall film velocity, however, decreases with increasing cylinder diameter, because the perimeter of liquid wall film is directly proportional to the cylinder diameter.