Conventional Hydrocyclone Research Articles

A study on the classification performance of water-injection hydrocyclone

Aiming at the problem of fine particles entrainment in the underflow of hydrocyclone during the metal grinding classification process, a water-injection hydrocyclone was proposed to improve the classification efficiency. Through external injection of water on the wall surface of the cone section, the particles settling in the region were loosely graded so that the fine particles settled in the wall surface returned to the inner swirl again, thus reducing their entry into the underflow. Numerical simulation was used to explore the differences in the internal flow field characteristics and separation performance of the hydrocyclone after adding the water-injection structure. Then the industrial tests were conducted on the classification performance of the water-injection hydrocyclone. Numerical results showed that compared with the conventional hydrocyclone, the static pressure, tangential and axial velocity of the fluid inside the water-injection hydrocyclone increased, while the turbulence intensity decreased. The experimental results showed that with the increase of water-injection flow rate, the content of -74 μm particles in the underflow of water-injection hydrocyclone first decreased and then increased, and the comprehensive classification efficiency increased and then decreased accordingly. Compared with the conventional hydrocyclone, the content of -74 μm particles in the underflow of the water-injection hydrocyclone was reduced from 26.34% to 23.95%, and the comprehensive classification efficiency was increased from 69.22% to 73.03%, which mitigated the phenomenon of fine particles entrainment in the underflow.

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 the separation performance of a three-product hydrocyclone with overflow reseparation

This manuscript proposes a three-product hydrocyclone with overflow reseparation to reduce the particle misplacement in overflow, which achieves secondary separation by utilizing the after-energy of internal swirling flow. Numerical simulations and physical tests were applied to investigate the separation performance. The simulation results revealed that the coarser particles entrapped were effectively recovered by sideflow, the recovery of 20 μm particles in the overflow decreased by 16.71 % ∼ 23.09 % with significant fineness improvement compared with conventional hydrocyclone. The intensity of the internal centrifugal field decreased with the overflow separation chamber expanded, which resulted in an increased probability of particle misplacement during overflow. The test results revealed that the particle content of more than 20 μm in overflow was reduced by 2.44 % compared with conventional hydrocyclone, reducing the overflow separation chamber increased the sideflow ratio and solid phase yield, increased the difference in fineness between sideflow and overflow, and improved the narrow-grain separation performance.

Hydrodynamic Evaluation of a Filtering Hydrocyclone for Solid Particle/Water Separation.

A conventional hydrocyclones is a versatile equipment with a high processing capacity and low maintenance cost. Currently, several studies aim to alter the typical structure of the conventional hydrocyclone in order to modify its performance and purpose. For this, filtering hydrocyclones have emerged, where a porous membrane replaces the conic or cylindrical wall. During the operation of this equipment, in addition to the traditionally observed streams (feed, underflow, and overflow), there is a liquid stream resulting from the filtration process, commonly referred to as filtrate. This work proposes to numerically investigate the solid particle/liquid water separation process in a filtering hydrocyclone using the commercial software Ansys CFX® 15.0. The proposed mathematical model for the study considers three-dimensional, steady state and turbulent flow, using the Eulerian-Eulerian approach and the Shear Stress Transport (SST) turbulence model. This study presents and analyzes the volume fraction, velocity, and pressure fields, along with flowlines and velocity profiles. The results indicate that the proposed model effectively captures the fluid dynamic behavior within the filtering hydrocyclone, highlighting higher pressures near the porous membrane and a higher concentration of solid particles in the conical region, with water being more concentrated in the cylindrical part of the hydrocyclone. Additionally, the findings show that the volumetric flow rate of the filtrate significantly influences the internal flow dynamics, with conventional hydrocyclones demonstrating higher pressure gradients compared to the proposed filtering hydrocyclone.

Study of hydrocyclone with flushing water device for sand washing of municipal sludge

Municipal sludge particles with size range between 0.045 and 0.2 mm were difficult to be precisely separated due to fine size distribution and high content of organic matter, resulting in low sand recycling efficiency. In view of the above problems, this paper proposed a flushing water device which was settled at the cone section of conventional hydrocyclone, aiming to utilize the supplementary water to strengthen the shear force field. Comparative test results showed that the organic matter content in the underflow product was significantly reduced after the addition of flushing water. Using the organic matter content and the sand recovery rate as the response index, the prediction models were established by using response surface optimization test. The influence order of different parameters on the response index was apex diameter, flushing device position and flow rate. Finally, an underflow product with organic matter content of 3.96 % and sand recovery rate of 48.03 % was obtained under the conditions of optimized parameter combinations. The research results can contribute to the development of a new method of residual sludge disposal that improves the sand washing efficiency and the cost-effectiveness of sludge treatment.

Strengthened oil-water separation by swirl vane hydrocyclone based on short-circuit flow regulation

Hydrocyclones make it possible to separate oil/water efficiently. Short-circuit flow (SCF), which is a local secondary vortex in hydrocyclones, significantly restricts efficient separation. This study proposes a novel swirl vane hydrocyclone to regulate the trajectory of the SCF to reduce the SCF rate. The separation process in the hydrocyclone field is calculated using computational fluid dynamics coupled with the population balance modeling. The strengthened separation mechanism by the swirl vane is revealed, and the response of structural parameters, such as the angle, numbers, and width of the swirl vane, to the SCF rate and separation efficiency is investigated using the response surface optimization method. The results show that the swirl vane structure prevents the direct generation of SCF, strengthens the outward migration of the heavy-phase droplets, and reduces the probability of droplet breakage. The optimal structural parameters of the swirl vane are a swirl vane angle of 31°, vane number of 6 pcs, and vane width of 2 mm, which has the lowest SCF rate of 1.62 %. The separation efficiency increases by 21.53 %, and the SCF rate decreases by 85.33 % compared with a conventional hydrocyclone. This study provides theoretical guidance and data support for SCF regulation and the development of oil-water separation hydrocyclone.

Study on the separation performance of honeycomb cone hydrocyclone

ABSTRACT The entrainment of fine particles in the underflow and coarse particles in the overflow are well-known problems during separation using conventional cylindrical-conical hydrocyclone. In order to enhance the separation accuracy, the paper proposed a new type of honeycomb cone hydrocyclone and investigated its separation performance. Numerical simulations were conducted to study the effects of different structural parameters on the internal flow field, including the concave ball diameter db, the distribution position of concave balls Pb and the area occupancy ratio of concave balls Nb. Compared with conventional hydrocyclone, the turbulence intensity inside the honeycomb cone hydrocyclone is reduced, and higher separation accuracy is obtained. Better separation effect is found when the structural parameter db is 6 mm, Nb is 40%, and the concave ball is distributed in the upper part of the cone. The classification efficiency of particles smaller than 45 μm is increased by 7.86%.

Numerical and experimental study on enhanced oil–water separation performance using hydrocyclone coupled with particles

Oil is one of the world's most crucial energy sources. In recent years, the separation of hydrocyclones coupled with multiphase or multifield has emerged as a leading trend in oilfield-produced fluid pre-separation technology. The study of complex dynamics among particles is crucial in multiphase-coupled separation systems. In this paper, we explore a novel separation approach: hydrocyclone separation coupled with particles to enhance oil–water separation, based on the composite force field. The computational fluid dynamics-discrete element method is utilized to analyze the dynamic behavior of particles and oil droplets within the coupling field, as well as the interactions among particles, oil droplets, and the flow field. Furthermore, the effects of operating parameters on the hydrocyclone coupled with particles (HCCP) and the conventional hydrocyclone (CHC) are compared through separation performance experiments. Results show that within a swirling flow field, the introduction of particles significantly exerts a pronounced influence on both the flow characteristics of the continuous-phase and the motion behavior of oil droplets. The coupling effect between particle movement and hydrocyclone separation is most pronounced when the density ratio of particles to oil ranges from 0.94 to 1. The separation performance experiments show that compared to CHC, HCCP can improve by 2.12–8.22 percentage points, and HCCP not only enhances separation efficiency but also exhibits wider applicability than CHC at lower inlet flow rates and split ratios. The numerical simulation results closely matched the experimental findings. This study may provide a reference for developing and applying hydrocyclones coupled with multiphase.

Effect of spiral vanes width on the separation performance of a hydrocyclone

Aiming at the problem of “entrainment fine particles in underflow” of hydrocyclone in grinding and classification process, a hydrocyclone with spiral vanes (the SV hydrocyclone) was proposed. The CFD techniques were used to study the pressure field, velocity field, turbulence field, particle field and classification efficiency of hydrocyclones with spiral vanes of different widths. The results show that the pressure drop, axial velocity, tangential velocity, turbulence intensity of SV hydrocyclone are reduced in different degrees compared with conventional hydrocyclone, and the reduction becomes more obvious with the increase of vane width. In the case of a vane width of 0.04D, the underflow recovery rate of 5μm and 10μm fine particles was reduced by 16.2% and 15.7%. The selection of spiral vanes with small widths is beneficial to improve the separation accuracy of fine particles and reduce the cut particle size.

Classification of Ultrafine Particles Using a Novel 3D-Printed Hydrocyclone with an Arc Inlet: Experiment and CFD Modeling.

Ultrafine particle classification can be realized using hydrocyclones with novel structures to overcome the limitations of conventional hydrocyclones with tangential inlets or cone structures. Herein, the hydrocyclones with different inlet structures and cone angles were investigated for classifying ultrafine particles. Computational fluid dynamics (CFD) simulations were performed using the Eulerian-Eulerian method, and ultrafine MnO2 powder was used as a case study. The simulation results show a fine particle (≤5 μm) removal efficiency of 0.89 and coarse particle (>5 μm) recovery efficiency of 0.99 for a hydrocyclone design combining an arc inlet and a 30° cone angle under a solid concentration of 2.5 wt %. Dynamic analysis indicated that the novel arc inlet provided a preclassification effect to reduce the misplacement of fine/coarse particles, which cannot be provided by conventional tangential or involute inlets. Furthermore, the proposed design afforded comprehensive improvement in the flow field by regulating the residence time and radial acceleration. Subsequently, a novel hydrocyclone with an arc inlet and 30° cone angle was manufactured using the three-dimensional (3D) printing technology. Experiments were conducted for classifying ultrafine MnO2 particles using the novel 3D-printed hydrocyclone and conventional hydrocyclone. The results demonstrate that the classification performance of the 3D-printed hydrocyclone was superior to that of the conventional one, in particular, the removal efficiency of fine particles from 0.719 to 0.930 using a 10 wt % feed slurry.

Ultra-clean separation of micro-particles in lubricant oil based on short-flow control of mini-hydrocyclone

Continuous online ultra-clean separation of micro-particle contaminants is vital for lubricant oil. Although hydrocyclone is widely used to separate fine particles, it often suffers from short-flow, which makes ultra-clean separation of trace micro-particle contaminants remain challenging. Here, mini-hydrocylones with overflow microchannel based on the active control of short-flow were proposed for ultra-clean separation of micro-particle contaminants in lubricating oil. Φ18 mm mini-hydrocyclones with different overflow microchannel widths (1.5,1.25, 1, 0.75 mm) were manufactured by 3D printing technology for online micro-particle number separation experiments under low flow rates. The CFD simulation results show that the overflow microchannels reduce the short-flow by up to 72.4%. When the overflow microchannel width to vortex finder diameter ratio is 0.21, the maximum number separation efficiency and mass separation efficiency can reach 99.98% for micro-particles larger than 9.8 μm. The concentration of particle larger than 9.8 μm at the outlet was 0.003 mg/L, which is 1/22 of that at the conventional hydrocyclone outlet; the number of particle was 1/ml, which is 1/30 of that at the conventional hydrocyclone outlet. The cleanliness of the purified oil reached the international standard (ISO 4406) of 17/13/7 grade, and it also showed excellent technical–economic performance.

Investigation of optimal design and separation performance of the hydrocyclone with a vorticose involute-line diversion feeding body

As an important transport channel for multi-phase flow, the feeding body imposes significant effects on the formation of granularity layer and pre-separation of particles. In a conventional feeding body, particles are generally under a turbulent state and intensively collide with the wall surface, thereby leading to the decline in particle separation precision. In this study, a novel hydrocyclone with a vorticose involute-line diversion feeding body was designed, and meanwhile the feeding body was optimized in structure. By means of numerical analysis, the inner flow field and particle separation performance were examined. It was found that using the novel structure of the feeding body can effectively reduce the inner turbulence in the hydrocyclone, accompanied with the enhancement of flow field stability and particle separation precision. Compared with the conventional hydrocyclone, the content of fine particles in the overflow can be enhanced by 32.68% while that in the underflow can be reduced by 43.17% using the novel feeding body. To be specific, the quality efficiency and quantity efficiency of the novel hydrocyclone were 15.66% and 14.87% higher than that of the conventional hydrocyclone, respectively, exhibiting remarkable improvement. Finally, the effect of inlet flow rate on the separation performance of the novel hydrocyclone was investigated. Results show that fine particles moved gradually outwards with the increasing inlet flow rate, accompanied with gradually increasing content of fine particles in the underflow and the decline in the mass of coarse particles. The cutting capability can also be enhanced with the increase of the inlet flow rate. At an inlet flow rate of 4.1055 L/min, the separation precision reached a peak. The present conclusion can offer insightful guidance for the further development of novel hydrocyclones.

Influence of taper angle on the inner field and separation performance of a hydrocyclone

ABSTRACT Taper angle is an important factor for characterizing a hyrocyclone’s separation performance. Appropriate setting of the taper angle can contribute to particle grading and separation performance of the hydrocyclone. Through numerical analysis, this study investigated the flow fields and separation performances of the hydrocyclones with different taper angles in depth. Moreover, the numerical simulation results were compared with experimental data of the conventional hydrocyclone for accuracy validation. The results showed that the tangential velocity, axial velocity, and the diameter of air core increased with the increasing taper angle. At a too large or a too small taper angle, the inner flow field would become unstable, thereby leading to the increasing number of dislocated particles and reducing the particle separation precision. For the hydrocyclone with a diameter of 75 mm, the separation precision of fine particles can be remarkably enhanced by setting the taper angle of 15°, accompanied with the improvement of product quality. The present data can provide the related enterprises with favorable guidance and a theoretical foundation for further designing the taper angle of novel hydrocyclones.

Iron ore slimes beneficiation using optimised hydrocyclone operation

With increasing steel production, an exponential increase in demand for steel is rapidly depleting the high-grade iron ore deposits. Hence, in search of an alternative source of iron ores, the steel industries are forced to use low-grade ores. The large amount of iron ore slimes accumulated in slime ponds at mine sites also poses a challenge for the environment. Iron ore slimes typically consist of iron, alumina, and silica at a wide range of sizes and densities. The marginally varying density components (iron oxide and alumina particles) of iron ore slimes can be separated by hydrocyclones based on size and density. Therefore, this work is aimed to experimentally study the iron ore slime beneficiation using a novel 100 mm hydrocyclone (with small cone angle, tapered vortex finder and optimum cylindrical length) design developed by computation fluid dynamics (CFD) simulation studies. As the design is developed using numerical studies, the initial experiments are conducted with mono density silica particles to test and validate the performance. Further, the experiments are continued with iron ore slimes. The novel hydrocyclone is able to provide desired cut size and sharpness of separation required to separate iron from alumina and silica. It also enhances the classification by reducing coarse and fine particle misplacement compared to the conventional hydrocyclone design. The product obtained from the underflow of the optimised hydrocyclone operation is suitable for direct pellet grade feed with iron and alumina as ∼61% and 2.77%.

Effects of a rough surface vortex breaker hydrocyclone on the separating capacity of heterogeneous fluid systems

This paper considers the issue of heterogeneous system separation efficiency under the action of centrifugal forces working in hydrocyclones. The main problem with these apparatuses is related to vortex forming. The paper describes the negative effects of vortexes on the heterogeneous medium separation process. A hydrocyclone design was developed and described, which improves the hydrocyclone separation capacity. This design introduces a vortex breaker. Furthermore, vortex formation can be eliminated or minimized by providing the vortex breaker with a rough surface. To determine the separation efficiency and the adequacy of the proposed solution, hydrodynamic computer simulation and experimental studies were conducted. Solidworks Flow Simulation software was used for hydrodynamic computer simulation. To check the medium separation degree, an experimental study was conducted showing improvement of the hydrocyclone separation capacity efficiency by 3% in the developed apparatus compared to conventional hydrocyclone designs. Keywords: hydrocyclone; separation; separating capacity; vortex breaker; heterogeneous system; oil preparation; hydrodynamics.

Separation Characteristics of an Axial Hydrocyclone Separator

An innovative axial hydrocyclone separator was designed in which a guide vane was installed to replace a conventional tangential inlet, potentially aggravating inlet turbulence. The characteristics of velocity distribution, concentration distribution, and pressure distribution inside the separator were obtained through the numerical simulation of the turbulent flow of oil and water. The results showed that the flow field presented good symmetry, which eliminated the eccentric turbulence phenomenon in the conventional hydrocyclone separators and was beneficial for the oil–water separation.

Numerical analysis on the effect of the length of arc-shaped vortex finder on the hydrocyclone’s flow field and separation performance

Because of the short-circuit flow, coarse particles may be carried in overflow when using a conventional hydrocyclone, which seriously affects the separation precision. Many scholars found that using arc-shaped vortex finder can effectively reduce short-circuit flow rate, however, the effect of arc segment length on the hydrocyclone’s separation performance has rarely been investigated. For this reason, this study employed computational fluid dynamics (CFD) for numerical simulation on the Φ50 mm hydrocyclones with different lengths of arc-shaped vortex finders. The pressure field, the velocity field, the turbulent intensity and the separation efficiency of each hydrocyclone were examined in depth. Then the simulation results were compared with classical experimental data by Hsieh for effectiveness validation. Results show that both tangential velocity and pressure drop first increased and then dropped with the increasing arc length, both of which reached the maximum at an arc length of 30 mm; greater pressure drop and tangential velocity promoted the separation of particles. The axial velocity in the hydrocyclone with arc-shaped vortex finder was lower than that in a conventional hydrocyclone, accordingly, particles stayed in the hydrocyclone with arc-shaped vortex finder for a longer time, resulting in more thorough separation. Additionally, as the arc length increased, both the split ratio and the short-circuit flow rate dropped, which lowered the number of misplaced particles. In the arc-shaped vortex finder, particles moved smoothly, accompanied with the decline in collision probability among particles. The turbulent intensity dropped with the increasing arc length so as to make the flow field more stable. Finally, as the arc length increased, the cutting dimension first dropped and then increased, while the steepness index first increased and then dropped. At an arc length of 30 mm, the cutting dimension dropped to the minimum and the separation precision was highest. Conclusively, the Φ50 mm hydrocyclone including the vortex finder with an arc length of 30 mm can manufacture fine and high-quality products.

Computational Modeling of Flow Characteristics in Three Products Hydrocyclone Screen

Three products hydrocyclone screen (TPHS) can be considered as the combination of a conventional hydrocyclone and a cylindrical screen. In this device, particles are separated based on size under the centrifugal classification coupling screening effect. The objective of this work is to explore the characteristics of fluid flow in TPHS using the computational fluid dynamics (CFD) simulation. The 2 million grid scheme, volume fraction model, and linear pressure–strain Reynolds stress model were utilized to generate the economical grid-independence solution. The pressure profile reveals that the distribution of static pressure was axisymmetric, and its value was reduced with the increasing axial depth. The maximum and minimum were located near the tangential inflection point of the feed inlet and the outlets, respectively. However, local asymmetry was created by the left tangential inlet and the right screen underflow outlet. Furthermore, at the same axial height, the static pressure gradually decreased along the wall to the center. Near the cylindrical screen, the pressure difference between the inside and the outside cylindrical screen dropped from positive to negative as the axial depth increased from −35 to −185 mm. Besides, TPHS shows similar distributions of turbulence intensity I, turbulence kinetic energy k, and turbulence dissipation rate ε; i.e., the values fell with the decrease in axial height. Meanwhile, from high to low, the pressure values are distributed in the feed chamber, the cylindrical screen, and conical vessel; the value inside the screen was higher than the outer value.

Numerical analysis of the effect of solid rod on the flow field and separation performance of thick-walled overflow pipe hydrocyclone

Hydrocyclone is one of the common equipment for solid-liquid separation. Although the hydrocyclone has a simple structure, it has many shortcomings. Among them, short-circuit flow and air core are two important factors that affect the separation performance. Many researchers have tried to weaken the short-circuit flow by changing the structure of the overflow pipe and the trajectory of the particles. This is certainly a feasible method to reduce the short-circuit flow. Is it possible to reduce the short-circuit flow by increasing the movement distance of the short-circuit flow and re-entering the short-circuit flow into the separation area without changing the structure of the overflow pipe? The answer is yes. In this paper, a thick-walled overflow pipe structure was proposed to increase the distance of the short-circuit flow into the bottom end of the overflow pipe.In the proposed structure, the particles in the short-circuit flow can be brought back into the separation area through the circulating flow at the bottom of the overflow pipe. During the working process, the hydrocyclone produces a unique phenomenon-air core. Although the air core does not participate in particle separation, it consumes energy and compresses the separation area. In order to further improve the separation performance of the thick-walled overflow pipe hydrocyclone, a central solid rod was traversed throughout the hydrocyclone to weaken the air core. In addition, FLUENT was used to numerically analyze the thick-walled overflow pipe hydrocyclone with an inserted solid rod in the center. Moreover, we investigated the effect of the solid rod with different diameters on the separation performance of the hydrocyclone. The numerical simulation was verified by comparing the simulation data with the classic data. The results showed that the pressure distribution of the thick-walled overflow pipe hydrocyclonewas more reasonable. The inserted solid rod significantly improved, the pressure distribution. Compared with the conventional hydrocyclone, the short-circuit flow rate of the thick-walled overflow pipe hydrocyclone was reduced by 8.09%. The cutting size of the particles can be adjusted by changing the diameter of the solid rod. When the diameter of the solid rod was 5–6 mm, the cutting size was in the range of 11.6–12.2 μm. When the diameter of the solid rod exceeded 6 mm, the cutting size gradually increased. The appropriate diameter of the solid rod can improve the separation accuracy of thick-walled overflow pipe hydrocyclone, resulting in thinner and higher quality products.

Mechanism of the Absent Air Column in Three Products Hydrocyclone Screen (TPHS): Experiment and Simulation

Three products hyrdrocyclone screen (TPHS) has been proposed for particle separation based on size. In TPHS, a cylindrical screen was embedded in a conventional hydrocyclone (CH) to combine the centrifugal classification and screening to particle separation based on size. The industrial application of TPHS indicates its better device performance than CH. Although, the earlier studies reveal some common understanding for TPHS, the information of the absent air column remains unknown. Hence, the combination of physical experiment and numerical simulation was considered involving a 75 mm TPHS for this knowledge gap. First, both the computational fluid dynamics (CFD) simulation with Reynolds stress mode and the physical experiment with a high-definition camera illustrate the development process details of a flow field in TPHS. That is, the water was imported along the tangential inlet into TPHS; then under the effects of the feed chamber wall and gravity, the liquid phase spiraled downward until the cylindrical screen passed through the sieve; as the liquid moved to the spigot, it could be discharged in time due to the small underflow port, thus the volume fraction of air rapidly reduced from 1 to 0; subsequently the water filled the TPHS and the absent air column could be observed. Furthermore, the distribution comparisons of air volume fraction and static pressure show that TPHS displayed the absent air core with the negative static pressure in the center region along the z-axis, while CH displayed the opposite features. In addition, despite the different inlet velocity, TPHS consistently presented the vanished air column which could be ascribed to the fact that the present cylindrical screen resulted in positive static pressure distribution inside TPHS.