Hydrocyclone Flow Research Articles

High-efficiency microplastic removal in water treatment based on short flow control of hydrocyclone: Mechanism and performance

Microplastics have been identified as a potentially emerging threat to water environment and human health. Therefore, there is a pressing demand for effective strategies to remove microplastics from water. Hydrocyclone offers a rapid separation and low energy consumption alternative but require reduction of microparticle entrainment by short flow, which limits the effectiveness for small density differentials and ultralow concentrations separation. We proposed an enhanced mini-hydrocyclone with overflow microchannels (0.72 mm width) based on the active control of short flow in hydrocyclone for microplastic removal from water. The overflow microchannels effectively redirect the particles that would typically be entrained by the short flow, leading to higher separation efficiency. Simulation results show overflow microchannels effectively reduced short flow to 0.7 %, a reduction of up to 94 % compared to conventional hydrocyclones. The hydrocyclone with overflow microchannel demonstrated a removal efficiency exceeding 98 % for 8 μm plastic microbeads at ultralow concentrations (10 ppm), which is a 33.7 % improvement over conventional hydrocyclone. Compared with other methods (e.g., filtration, adsorption, coagulation) for microplastic removal, this work achieves rapid separation capability and long period operation, highlighting hydrocyclone as a promising approach for microplastic removal in industry-scale water treatment.

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.

Two-Fluid Large-Eddy Simulation of Two-Phase Flow in Air-Sparged Hydrocyclone

The two-fluid (Euler–Euler) model and large-eddy simulation are used to compute the turbulent two-phase flow of air and water in a cyclonic flotation device known as an Air-Sparged Hydrocyclone (ASH). In the operation of ASH, air is injected through a porous cylindrical wall. The study considers a 48 mm diameter hydrocyclone and uses a block-structured fine mesh of 10.5 million hexagonal elements. The air-to-water injection ratio is 4, and a uniform air bubble diameter of 0.5 mm is specified. The flow field in ASH was investigated for the inlet flow rate of water of 30.6 L/min at different values of underflow exit pressure. The current simulations quantify the effects of the underflow exit pressure on the split ratio and the overall flow physics in ASH, including the distribution of the air volume fraction, water axial velocity, tangential velocity, and swirling-layer thickness. The loci of zero-axial velocity surfaces were determined for different exit pressures. The water split ratio through the overflow opening varies with underflow exit pressure as 6%, 8%, 16%, and 26% for 3, 4, 5, and 6 kPa, respectively. These results indicate that regulating the pressure at the underflow exit can be used to optimize the ASH’s performance. Turbulent energy spectra in different regions of the hydrocyclone were analyzed. Small-scale turbulence spectra at near-wall points exhibit f−4 law, where f is frequency. Whereas for points at the air-column interface, the energy spectra show an inertial subrange f−5/3 followed by a dissipative range of f−7 law.

Influence of Feed Rate on the Performance of Hydrocyclone Flow Field

In order to clarify the influence of feed rate on a hydrocyclone flow field, numerical simulation was employed to model the influence of feed rate on the pressure field, velocity field, air column, turbulent kinetic energy, and split ratio. The results revealed that static pressure, tangential velocity, and radial velocity increased with an increase in the feed rate. When the feed rate at the inlet increases from 1 m/s to 5 m/s, the static pressure increases from 5.49 kPa to 182.78 kPa, tangential velocity increases from 1.97 m/s to 11.16 m/s, and radial velocity increases from 0.20 m/s to 1.16 m/s demonstrating that a high feed rate facilitated the strengthening separation of the flow field. Meanwhile, with the increase in the feed rate, the split ratio of the hydrocyclone decreased, indicating that the concentration effect of the hydrocyclone improved. Additionally, the formation time of the air column was reduced, and the flow field became more stable. Nevertheless, the axial velocity and the turbulent kinetic energy also increased with the increase in the feed rate, and the increase in the axial velocity reduced the residence time of the material in the hydrocyclone, which was not conducive to the improvement of separation accuracy. In addition, the increase in turbulent kinetic energy led to an increase in energy consumption, which was not conducive to the improvement of the comprehensive performance of the hydrocyclone. Therefore, choosing an appropriate feed rate is of great significance to the regulation of the flow field and the improvement of hydrocyclone separation performance.

The Modification of the Dynamic Behaviour of the Cyclonic Flow in a Hydrocyclone under Surging Conditions

The aim in this study was to determine how surging modifies the dynamic behaviour of the cyclonic flow in a hydrocyclone using computational fluid and granular dynamics models. The Volume-of-Fluid model was used to model the air-core formation. Fluid–particle, particle–particle, and particle–wall interactions were modelled using an unsteady two-way coupled Discrete Element Method. Turbulence was modelled using both the Reynold’s Stress Model and the Large Eddy Simulation. The model predictions indicate that the phenomenon of surging modifies the dynamics of the cyclonic flow in hydrocyclones and subsequently impacts separation. The results reveal that the primary cyclonic separation mechanisms break down during surging and result in air-core suppression. The flow and primary separation mechanism in the core of the hydrocyclone is driven by the pressure drop and the flow and primary separation mechanism near the wall is primarily driven by the gravitational and centrifugal force-induced momentum. However, surging causes a breakdown in this mechanism by swapping this primary flow and separation behaviour, where the pressure drop becomes the primary driver of the flow near the walls and gravitational and centrifugal force-induced momentum primarily drives the flow in the core of the hydrocyclone.

A CFD–DEM analysis of the de-cementation behavior of weakly cemented gas hydrate–bearing sediments in a hydrocyclone separator

The de-cementation mechanism and performance of weakly cemented gas hydrate–bearing sediment (GHBS) particles in downhole hydrocyclone play a key role in the commercial production of natural gas hydrate through solid fluidization. This study considers the effect of weak cementation between particles in the hydrate separation process and studies the stress state of weakly cemented hydrates in the hydrocyclone flow field. A mechanical model and a maximum load calculation model of weakly cemented hydrate bond were established, providing a basis to judge the effect of the separator to break the cementation bond. Furthermore, the computational fluid dynamics (CFD) software and discrete element method (DEM) software were used to analyze the kinematic characteristics and the de-cementation process of weakly cemented particles occurring in the internal flow field and evaluate the hydrocyclone effects. According to the analysis and evaluation results, the cementation breaking effect of hydrocyclones is directly proportional to the inlet velocity in the range of 6–14 m/s and particle size in the range of 0.2–1.0 μm. This study provides certain theoretical support for the structural design of downhole hydrocyclones, the improvement of hydrate de-cementation performance, and the future commercial exploitation of natural gas hydrates (NGHs) in solid fluidization mining.

Development of a methodology to assess the hydrocyclone process with account of the rheological properties of the mineral slurry

The paper studies the possibility of assessing the separation of mineral raw materials, taking into account the rheology of the mineral slurry. The ores of the Mayskoye deposit were chosen as the object of the study, characterized by a thin impregnation of the valuable component – gold in the host minerals, which determines the use of fine and ultrafine milling. This fact is essential because the presence of a fine grade seriously affects the rheology of the mineral slurry used in subsequent mineral processing stages. This predetermines the necessity to take into account rheological parameters. The research performed provides the development of a methodology for assessing the separation of minerals in the hydrocyclone based on the interpretation of numerical and mathematical modeling data. using the object-oriented programming language Python, a program for calculating empirical coefficients of the rheological equation, theoretically describing the dynamics of internal transformations of the mineral slurry, was developed. Taking into account the process parameters of the laboratory unit with hydrocyclone and ore properties, three concentrations of solids in the mineral slurry were selected, conditionally corresponding to the minimum, average and maximum values. Rheological equations successively composed for three concentrations, i.e., 400, 500, and 700 g/l, made it possible to calculate the critical shear rates corresponding to the maximum dispersion of the mineral slurry in the hydrocyclone flow. Subsequent numerical simulation using Ansys Fluent software, as well as statistical evaluation of the shear rates at different levels of solids content showed that the shear rate profile in the cross-section of the hydrocyclone corresponding to the maximum dispersion of the mineral slurry is obtained at the content of 400 g/l.

Hydrocyclone flow characteristics and measurements

The issue of water scarcity in many countries across the globe has become one of the most pressing challenges due to the limited availability of renewable water resources. After rainfall, the runoff water picks up the topsoil and sweeps them downstream towards a river, downstream dam, and groundwater storage. The deposition of sediment may reduce the storage capacity of dams, lowering the ability to utilize the groundwater that is now considered as unusable wastewater and causing for the silted up canals to become inoperable. A hydrocyclone is an effective separation device wherein water is mixed with sands. It can be used to classify or filter specific solid and liquid components in a feed stream. This study investigates the flow field characteristic within the hydrocyclone. The Laser Doppler Anemometry (LDA) has been deployed to measure the mean velocities in the hydrocyclone. Traditionally, a flat surface box or jacket is used to encase the hydrocyclone, filled with water or other materials, to minimize the refraction effects of laser beams, which are caused by the curved solid wall of the hydrocyclone and the refractive index of the test medium. In this study, a new method is applied that enables us to use the LDA directly in the hydrocyclone wall without recourse to such a flat surface box or jacket.

Optimization of geometry parameters with separation efficiency and flow split ratio for downhole oil-water hydrocyclone

High water cut of crude oil has already become a serious problem for earlier oil well, and downhole oil-water hydrocyclone is thought as one of the solutions to solve this problem. But high separation efficiency usually accompanies with big flow split ratio which still costs large efforts to treat it. In this work, research was carried out to detect the effects of geometry factors on separation efficiency and flow split ratio to optimize the geometry. The oil-water two-phase flow in two-cone hydrocyclone was seriously analyzed and a mathematic model was built to describe it. Results show that backflow generates in upper cone and lower cone, therefore the evaluation and optimization are focused on upper cone, lower cone and lower cylinder. First, cases were designed using orthogonal analysis to overcome the interaction of different factors with constant length of lower cone. The angle of lower cone should be bigger than 0.5° and smaller than 3.0° to obtained a high efficiency with suitable flow split ratio. The change of angle of lower cone alters the critical diameter and affects the velocity and backflow in upper cone. Then, simulations were carried out with constant critical diameter to eliminate this influence to further detect their effects on separation and optimize the geometry. The differences of separation efficiencies are all within 1% with same critical diameter, but effects on flow split ratio are much obvious. The optimization of geometry should be focused on flow split ratio, and the promotion of separation efficiency should be focused on determine the relationship between critical diameter and flow rate. The optimal values are recommended for angle of upper cone, angle of lower cone and length of lower cylinder with critical diameter 28 mm.

Short‐Circuit Flow in Hydrocyclones with Arc‐Shaped Vortex Finders

AbstractSeveral new arc‐shaped vortex finder structures were developed to restrain the circulation flow and reduce short‐circuit flow. These problems were investigated by conducting laboratory experiments and using a computational fluid dynamics numerical simulation method. To verify the accuracy of the numerical simulation, a type A vortex finder was employed to perform a particle image velocimetry test under identical working conditions. Then, these new structures were compared with a type O vortex finder to reveal the differences in pressure field, velocity field, and separation performance. The arc‐shaped vortex finder was able to restrain the circulation flow and reduce the maximum pressure drop at the outer wall of the vortex finder.

Modeling the Multiphase Flow in Hydrocyclones Using the Coarse-Grained Volume of Fluid—Discrete Element Method and Mixture-Discrete Element Method Approaches

Hydrocyclones are widely used in various industries to classify particles mainly by size. In this work, two numerical models are developed to model the multiphase flow in hydrocyclones: one is a combined approach of volume of fluid (VOF) model and discrete element method (DEM) with the concept of the coarse-grained (CG) particle (CG VOF-DEM); the other is a combined approach of the Mixture model and DEM model with the CG concept (CG Mixture-DEM). The simulation results show that the CG VOF-DEM model is quantitatively applicable to relatively dilute flows while only qualitatively applicable to dense flows. On the other hand, the CG Mixture-DEM model can be quantitatively applicable to both dilute and dense flows. The work suggests that the CG Mixture-DEM approach could be a useful tool to estimate the performance of hydrocyclones.

Hydrocyclone equivalent settling area factor at higher concentrations and developing a performance chart

Abstract The equivalent settling area factor allows for comparison amongst different centrifuge separators. For hydrocyclones, the so far developed factor does not consider the effect of concentration of solid particles c in the feed stream, because particle interactions at high concentrations cause hindered settling and reduce hydrocyclone performance. The focus of this paper is a modification of this factor to allow prediction of the influence of higher particle concentration in the feed stream. In particular, the equivalent area factor is modified at high particle concentration by applying different forms of hindered settling concentration functions and using data obtained from experiment or from existing empirical correlations. This results in a set of modified models that are evaluated using statistical techniques. Through statistical analysis, the function f ( c ) = c 0.0488 exp ( - 9.445 c ) is selected to modify the equivalent settling area for hydrocyclones. A performance chart is developed for hydrocyclones by undertaking the modified equivalent area model that can be used in hydrocyclone design applications. The developed performance chart is validated and is shown to be capable of predicting the hydrocyclone performance over a wide range of hydrocyclone flow rates and separation cut sizes. This chart is compared with a performance chart available in the literature and the chart in the literature is shown to over-predict the hydrocyclone performance.

Numerical simulation of industrial hydrocyclones performance: Role of turbulence modelling

Abstract Flow in industrial hydrocyclones is always turbulent, selection of suitable turbulence model is key for accurate predictions. This paper aims to find the appropriate turbulence model for the hydrodynamic predictions in industrial hydrocyclones. Two-phase and multiphase simulations are conducted in various size industrial hydrocyclones using volume of fluid and modified mixture models coupled with Reynolds Stress Model (RSM), Detached Eddy Simulation and Large Eddy Simulation (LES) turbulence models. Assessment of turbulence model effect on two phase flow field is made with respect to air-core, flow split, mean and turbulent velocities. The simulated flow field in 75 and 250 mm hydrocyclones is validated against literature based Laser Doppler Velocimetry, in-house high speed video and Electrical Resistance Tomography measurements. Mean density segregation contours and radial density profiles variation at different axial positions in a 350 mm dense medium cyclone is compared against Gamma Ray Tomography data. Turbulent intensity profiles are compared to display the turbulence levels. Further turbulence effect on the particles in various size hydrocyclones is analyzed by dispersion index formulation. Multiphase flow predictions in 75 and 250 mm hydrocyclones with RSM and LES models are compared against classical experimental classification performance in terms of cut size and sharpness of separation.

Eulerian–Lagrangian study of dense liquid–solid flow in an industrial-scale cylindrical hydrocyclone

Hydrocyclone has been widely used in particle separation processes. Extensive efforts have been devoted to studying the liquid–solid flow in conical hydrocyclone, however, studies on cylindrical hydrocyclone were much less, regardless of its industrial importance. To this end, an Eulerian–Lagrangian model, dense discrete phase model (DDPM), was used to simulate the complex liquid–solid flow in an industrial-scale cylindrical hydrocyclone, where Reynolds stress model (RSM) was used to model the turbulence of liquid phase due to its swirling nature, and then the numerical results were validated against the experimental data obtained from an industrial-scale cylindrical hydrocyclone. The validated model was then used to systematically study the effects of operating conditions as well as the geometry of cylindrical hydrocyclone on its separation efficiency. It was shown that (i) particle concentration at inlet had a remarkable influence on particle separation efficiency, but had a negligible effect upon processing capacity, expressed as the inlet volumetric flow rate of liquid–solid mixture; (ii) the increase of the length of vortex finder resulted in a slight decrease of separation efficiency and larger diameter of vortex finder led to increased mass flow rate through overflow and slightly decreased separation efficiency; (iii) increasing the height of cylindrical part resulted in a larger mass flow rate through underflow and better particle separation efficiency. Present studies indicated that DDPM method coupled with RSM was an effective tool for the design of liquid–solid hydrocyclone.

Numerical analysis of non-Newtonian rheology effect on hydrocyclone flow field

Abstract In view of the limitations of the existing Newton fluid effects on the vortex flow mechanism study, numerical analysis of non Newton fluid effects was presented. Using Reynolds stress turbulence model (RSM) and mixed multiphase flow model (Mixture) of FLUENT (fluid calculation software) and combined with the constitutive equation of apparent viscosity of non-Newtonian fluid, the typical non-Newtonian fluid (drilling fluid, polymer flooding sewage and crude oil as medium) and Newton flow field (water as medium) were compared by quantitative analysis. Based on the research results of water, the effects of non-Newtonian rheology on the key parameters including the combined vortex motion index n and tangential velocity were analyzed. The study shows that: non-Newtonian rheology has a great effect on tangential velocity and n value, and tangential velocity decreases with non-Newtonian increasing. The three kinds of n values (constant segment) are: 0.564(water), 0.769(polymer flooding sewage), 0.708(drilling fluid) and their variation amplitudes are larger than Newtonian fluid. The same time, non-Newtonian rheology will lead to the phenomenon of turbulent drag reduction in the vortex flow field. Compared with the existing formula calculation results shown, the calculation result of non-Newtonian rheology is most consistent with the simulation result, and the original theory has large deviations. The study provides reference for theory research of non-Newtonian cyclone separation flow field.

A Lagrangian study of liquid flow in a reverse-flow hydrocyclone using positron emission particle tracking

In this study, the liquid flow in a reverse-flow hydrocyclone is studied experimentally using the Lagrangian approach. Resin beads with densities that are close to the density of the liquid in which they move, i.e., neutral-density particles, are used to model a fluid element in the highly turbulent flow in a hydrocyclone separator and tracked using PEPT with a temporal resolution of up to 0.5 ms. A method of producing neutral-density particles for PEPT was developed. The data processing algorithm was improved for the extra challenging tracking conditions that were encountered. The components of velocity, which reveal the detailed velocity field of the fluid, were calculated from the positions of the tracers. Various noise-removal methods, again to cope with the challenging tracking conditions, were applied and discussed.

Computational and experimental study of the effect of inclination on hydrocyclone performance

In this paper, the effect of inclination on hydrocyclone performance is studied using both computational fluid dynamics (CFD) and experimental methods. Experiments with water medium and the corresponding water–air two-phase CFD simulations in a 75mm diameter cyclone are carried out at various inclined positions to the vertical plane. The two-phase CFD flow analysis shows that the water split to underflow decreases as the inclination increases, which is consistent with the experiments. The predicted flow velocity profiles were analyzed for different inclinations. An increase in the inclination results the air-core size reduction and reduced pressure drop profiles. Experimental classification also performed using the silica slurry. The experimental analysis shows the increased cut-size and the reduced water split with the inclination. Cross validation of inclined cyclone’s CFD data is attempted with Electrical Resistance Tomography (ERT) and High speed video imaging experiments. The inclination effect on hydrocyclone flow field is further analyzed in terms of turbulence parameters; turbulent intensities, and radial RMS velocities. Turbulent dispersion of the particles is calculated using the CFD data and plotted by using a dispersion index formulation. Fish hook phenomena and possible mechanism of particle classification under the influence of inclination is also explained. Experimentally measured cut size and water recovery to underflow for 10wt% silica slurry at various inclinations are compared with numerical predictions. Predicted efficiency curves are found in a close agreement with experiments for all the inclinations.

Hydrocyclone Numerical Simulation and Separation Efficiency Optimization

For the hydrocyclone’ separation efficiency affects by many factors, this paper combined Reynolds stress model and SIMPLEC algorithm of Fluent software with orthogonal test to simulate hydrocyclone’s operating process and analysis the flow field. Different overflow pipe wall thickness values (4mm, 8mm, 12mm), volume fraction values (1%, 5%, 10%) and inlet velocities (3m/s, 4m/s, 5m/s) was considered as the separation efficiency affective factors. Results show that the overflow pipe wall thickness has greatest influence on separation efficiency. The inlet velocity is the second and the volume fraction value is the last. The optimal combination is the overflow pipe wall thickness value 8mm, the volume fraction 5% and the inlet velocity 5m/s. The overflow pipe wall thickness value increasing can decrease the turbulent kinetic energy and increase the stability of hydrocyclone flow field.

Three-Dimensional Measurement of the Hydrocyclone Flow Field Using V3V

The three dimensional three component (3D3C) flow field inside hydrocyclone was investigated using Volumetric 3-component Velocimetry (V3V). To improve the spatial resolution of the measurement, a refractive index matching method is used in the experiment. The three components of the velocity in the hydrocyclonic flow is measured, and the measurement produced huge amount of data, which enabled detailed analysis of the hydrocyclonic flow field. The tangential and axial is quasi-symmetric while the radial velocity is non-axisymmetric. The radial velocity is one order smaller in value than the other two component. Results show V3V with index matching is a robust method to the measurement of hydrocyclone flow field.

Computational Study of the Multiphase Flow and Performance of Hydrocyclones: Effects of Cyclone Size and Spigot Diameter

This paper presents a numerical study of multiphase flow in hydrocyclones with different configurations of cyclone size and spigot diameter. This is done by a recently developed mixture multiphase flow model. In the model, the strong swirling flow of the cyclone is modeled using the Reynolds stress model. The interface between liquid and air core and the particle flow are both modeled using the so-called mixture model. The solid properties are described by the kinetic theory. The applicability of the proposed model has been verified by the good agreement between the measured and predicted results in a previous study. It is here used to study the effects of cyclone size and spigot diameter when feed solids concentration is up to 30% (by volume), which is well beyond the range reported before. The flow features predicted are examined in terms of the flow field, pressure drop, and amount of water split to underflow, separation efficiency and underflow discharge type. The simulation results show that the mult...