Particle Separation Efficiency Research Articles

Numerical Simulation of an Oil Mist Particle Emission and Gas-Oil Separation Device of a Closed Machine Tool in the Post-Environmental Area.

Owing to the airflow field within airtight machines, oil mist particles escape with the airflow from the machine shell gaps and are emitted externally to the post-environmental area, causing air pollution and threatening workers' health. The existing local exhaust system is ineffective in capturing oil mist particles. This study proposes a gas-oil separation device that can "in-situ control" the oil mist particles in situ and weaken their outgoing emission and that uses numerical simulations to compare and analyse the emission characteristics of oil mist particles, before and after the addition of the separation device at different exhaust air volumes and particle emission speeds, and to design the structural parameters of the device to improve the separation efficiency of oil mist particles. The structural parameters of the proposed device are designed to improve the separation efficiency of oil mist particles. Studies have shown that for every 200 m3/h increase in exhaust air volume, the capture efficiency increases by around 3%, and the particle concentration at the gap in the machine loading door decreases from 9.4 × 10-7 kg/m3 to 7.7 × 10-7 kg/m3. The overall escape rate of oil mist particles is in the range of 10-13% after the addition of a pressure relief device. Numerical simulations are performed to analyse the effects of inlet airflow velocity, folding plate spacing, and folding plate angle on the separation efficiency of oil mist particles. Results show that an increase in the inlet velocity of the airflow increases the particle separation efficiency. The most suitable structural parameters for the separation device and the machine are as follows: 60° angle of the folding plate and 30 mm distance between plates, where the separation efficiency is above 80%, and the average separation efficiency is about 86%. The results of this study can be used as a reference for the study of the emission of oil mist particles from enclosed mechanical cutting machines.

Numerical simulation and optimization of coupled demister with directing and perforated plate in MSF plants

The coupled demister with directing and the perforated plate was proposed in this work, which was applied in the fine droplets removal process for the multistage flash (MSF) desalination process. The performance was evaluated with three criteria, overall particle removal efficiency, pressure drop, and impact factor. The results show that the main influencing factors of the performance of the directing plate mist eliminator are the directing plate length, the installation upper wall angle, and the installation position. The interaction effects occur while two individual directing plates are installed. For improving the fine droplets removal performance, perforated and directing plate coupled mist eliminator was designed, and the results show that the coupled mist eliminator has the best performance compared to the others. The particle separation efficiency is significantly improved, and the efficiency can reach >93.75 %, Euler number is only 5.54, compared to individual structural design, the pressure drop declined and particle removal efficiency increased significantly. Besides, the coupled mist eliminator has a simple structure and can be processed by integrated technology. All these advantages make the directing and perforated plate coupled mist eliminator a promising candidate for fine droplet removal in the MSF desalination process.

Numerical simulation and experimental study of gas cyclone–liquid jet separator for fine particle separation

To address the shortcomings of existing particulate matter trapping technology, especially the low separation efficiency of fine particles, herein, a novel gas cyclone–liquid jet separator was developed to research fine particle trapping. First, numerical simulation methods were used to investigate the flow field characteristics and dust removal efficiency of the separator under different working conditions, and to determined suitable experimental conditions for subsequent dust removal experiments. Afterward, the separation efficiency of the separator against five kinds of common particles, including g-C 3 N 4 , TiO 2 , SiC, talc, and SiO 2 , was experimentally studied. A maximum separation efficiency of 99.48% was achieved for particles larger than 13.1 μm, and 96.55% efficiency was achieved for particles larger than 2 μm. The best crushing atomization effect was achieved for the separator when u G was 10 m·s −1 and u L was 3 m·s −1 , while the best separation effect was achieved when u G was 10 m·s −1 and u L was 3.75 m·s −1 . Studies have shown that the gas cyclone–liquid jet separator has excellent applicability in the separation of fine particles.

Investigation of the effects of particle size on the performance of classical gravity concentration equipment

ABSTRACT The use of gravity concentrators involves several challenges, such as determination of the liberation sizes of the minerals, selection of appropriate particle sizes for the applied concentration method, and the severity of the beneficiation of fines.In this study, the effects of fully liberated (artificial mixtures of magnetite and quartz) and non-liberated particles (chromite ore collected from a chromite processing plant) on various gravity concentration equipment were investigated as a function of particle size considering recoveries, separation efficiencies, and grades of products. A series of tests were conducted on shaking tables, spiral concentrators, and a Falcon concentrator with different design features under various operating conditions. Finally, the separation efficiencies were correlated with the settling rates of the particles.The test results confirmed a certain trend in the separation efficiency as a function of particle size for each condition. The separation efficiency initially increased with increasing particle size, peaked, and eventually decreased with increasing particle size. The maximum separation efficiency attained was 90% for 141 µm particles in the shaking table and 54% for 245 µm particles in the Falcon concentrator, both of which were used to treat the artificial feed. In the spiral concentrator, which treated chromite ore as feed, the maximum separation efficiency attained was 82% for 178 µm particles.This experimental study provides data to identify the concentration behavior of particles by investigating possible separation mechanisms. Consequently, it provides an understanding of the relationships between particle size and separation efficiency in terms of settling rates, especially in spiral concentrators.

A magnetophoretic microdevice for multi-magnetic particles separation based on size: a numerical simulation study

Due to the outstanding properties, magnetic particles have been widely used as magnetic carriers and adsorbents in a diverse range of fields, such as biomedical diagnostics, food safety, and environmental monitoring, etc. Sorting different magnetic particles from each other based on size simultaneously can be very useful in multiple targets separation. To the best of our knowledge, this research firstly proposes the arc comb structure microfluidic (ACSM) chip for multi-magnetic particles separation based on size by magnetophoresis. And the parameters affecting particle trajectory and separation efficiencies, such as flow velocity, velocity ratio of the two inlets, the remanent flux density of the magnets, and dynamic viscosity of the buffer solution, were investigated by numerical simulations in this study. Particle magnetophoresis spectrum width and general separation ratio are put forward to characterize the particles separation efficiency. Under the recommended simulation condition, six kinds of magnetic beads were separated with a general separation ratio of 0.83 using the newly designed chip. And the separation ratio of the 0.5, 1.8, 2.5, 3, 3.5 and 4.5 µm magnetic particle is 100.00%, 98.18%, 66.36%, 97.25%, 97.27% and 96.36%, respectively. This numerical simulation study provides a theoretical basis for multiple magnetic particles’ separation before experimental trials and also facilitates the utilization and development of microfluidic chips in the future.

Effects of particle size on the separation efficiency in a rotary-drum eddy current separator

Eddy current separation is a technology for recovering non-ferrous metals. The influence of particle size on the separation is of significant importance due to the variety of materials. It was investigated by combining simulations and physical experiments. A strong correlation between the simulation and the experiment was found by Pearson correlation analysis. Then the interaction effects between the particle size and the material type, rotational speed, magnetic pole arrangement were investigated. It shows that an optimal particle size exists for a specific condition, and the separation efficiency of fine particles can be improved by increasing rotational speed, magnetic pole number, and the electrical conductivity/density of material, as well as utilizing torque of Lorentz force. The underlying mechanism of particle size affecting separation was discovered by analyzing eddy current distribution and field gradient. These results provide insight into the design and optimization of eddy current separation for particles of various sizes. • The correlation between simulation and physical experiment was established. • There is an optimal particle size for separation under a specific condition. • The rotation of the particles increases with the decrease of the particle size. • The magnitude and distribution of eddy current is related to the particle size. • Some optimization principles of the eddy current separator were proposed.

Numerical Investigation on the Effect of the Diversion Layer on the Flow Field of the α-Type Cyclone Separator

The flow field stability and separation performance of the cyclone separator decrease significantly as its size increases. An inner guider was added in α-type cyclone separator, and in this paper, a numerical investigation on the gas-solid two-phase flow in the α-type cyclone was conducted. The Reynolds stress model and the DPM model were used to simulate the gas flow and the motion of particles, respectively. The influence of the guider on the velocity field, pressure field, turbulent kinetic energy field, and particle separation efficiency of the cyclone separator was analyzed. The results showed that after adding an inner guider, the tangential velocity increases, the turbulent kinetic energy decreases, the downward area of the axial airflow increases, and the number of airflow-carrying particles downward increases.

Effect of process parameters on separation efficiency in a deterministic lateral displacement device

Deterministic lateral displacement (DLD) is a hydrodynamic method known for its high-resolution sorting of particles. It achieves this through a periodic array of obstacles and laminar flow that passively directs particles along in two different directions depending on the particles’ diameter. Many prior publications have been dedicated to the structural and geometrical development of DLD arrays to improve separation performance; however, a successful separation requires much more than a well-designed array. This paper shows how separation performance is affected by process parameters. For this purpose, the design and fabrication of a DLD device are described. Then three experiments show how process parameters affect the performance of the device. The first experiment uses dye solutions to visualize the formation of a hydrodynamically focused sample stream. The second experiment shows that the particle separation performance (of 7- & 15-µm particles) is affected by the way output fluids are collected. Finally, the third experiment looks at the particle separation efficiency as the input flow rates and the ratio of buffer to sample are changed. The results show that the proper range for buffer and sample flow rate in this device is 1–10 and 0.1–1 (µl/min), respectively. The buffer to sample flow rate ratio of 10 gives the highest separation efficiency, but at a lower sample throughput. The optimized values are specific for our device but demonstrate processes that we believe are universal for DLD separations.

Peculiarities of particle motion inside cyclone separator by using LES-DRW model

The short-circuit flow has a great influence on the separation performance in cyclone separator. Herein, we used the LES model and particle random trajectory model to simulate gas-solid two-phase flow, and analyzed the particle motion from two aspects of particle trajectory and residence time. The results showed that the separation efficiency of particles from 1 µm to 10 µm diameter presented an increasing first and then a gentle distribution. The separation efficiency began to decrease when the particle size was less than 10 µm. When the particle size was larger than 3 µm, the separation efficiency was above 80%, and the separation efficiency decreased sharply when the particle size was less than 3 µm. There was a phenomenon of top ash ring in the annular space, especially near the cyclone proof, where a lot of particles gathered. The particle aggregation was serious in 130–180 degrees. The top ash ring could be formed only when the force of particles was balanced, which was unevenly distributed and had a quasi-periodic shedding characteristic. In addition, part of the airflow blew obliquely to the incoming airflow after a rotation, resulting in compression phenomenon. These performances would not only cause the escape of particles and reduce the separation efficiency, but also cause abrasion of the wall.

Enhancement of selective fine particle flotation by microbubbles generated through hydrodynamic cavitation

The flotation of fine particles less than 50 μm is challenging for the mining industry. By using hydrodynamic cavitation, a significant improvement on the recovery of fine particles has been found. This study aims to investigate the effect of hydrodynamic cavitation on the selective flotation of fine particles from detailed mechanism. Our single-bubble flotation results indicated that the bubble-particle collection efficiencies of fine silica particles (D50 = 6 μm and D50 = 16 μm) improved after hydrodynamic cavitation, especially for hydrophobized silica particles. The improved flotation performance of fine particles was investigated from three perspectives: (1) By zeta potential distribution measurements, bubble-frosting on hydrophobic particles was demonstrated after hydrodynamic cavitation. (2) The formation of large aggregates of hydrophobic fine particles after cavitation was revealed by slurry turbidity and particle size measurements, potentially contributing to the improved collision efficiency of the fine particles due to the bridging effect provided by microbubbles. (3) The attachment efficiency between a solid surface and flotation bubbles was enhanced if the surface was covered with hydrodynamic cavitation-generated microbubbles. Compared to the hydrophilic particles, the hydrophobic particles benefited from the hydrodynamic cavitation from the perspectives of bubble frosting, particle-bubble collision efficiency and attachment efficiency. Based on this study, it is expected that the separation efficiency for fine hydrophilic and hydrophobic particles can be improved by hydrodynamic cavitation.

Intensification of coal slime separation in fluidized bed flotation column: change of turbulence

ABSTRACT Flotation cell and flotation column are widely used as the separation equipment for coal slime. In order to obtain better flotation results for different particle sizes, different turbulence intensity of flow field need to be created, but the turbulence intensity is not easy to adjust in conventional flotation equipment. In this paper, a new fluidized bed flotation column was designed to control turbulence intensity by the liquid velocity and static bed height. The effects of liquid velocities (0.198 m/s,0.226 m/s,0.254 m/s) and static bed heights (0.317 m,0.343 m,0.380 m) on coal slime flotation with different particle sizes were studied, which were evaluated by the combustible recovery, ash content, and the yield of clean coal. The research results showed that the flotation performance of coarse particles is better with low turbulence caused by low liquid velocity and great static bed height than that in high turbulence. Under the condition of high liquid velocity and low bed height, a high turbulence intensity environment is created, and the fine particle separation efficiency is better than that in low turbulence.

Purification of fluid catalytic cracking slurry oil at room temperature using ceramic membrane

The catalyst particles were removed from fluid catalytic cracking (FCC) slurry oil by two-step separation processing. FCC slurry oil was mixed with water and surfactant to make the lower viscosity emulsion. The catalyst particles were removed from the emulsion using the modified hydrophobic ceramic membrane (0.1 μm) and then the water was filtered out from oil/water emulsion using an unmodified hydrophilic ceramic membrane (0.05 μm) at room temperature. The separation efficiency of catalyst particles and emulsion reached 99.9% and the oil/water separation efficiency also reached 99.9%. FCC slurry oil was effectively purified at room temperature by a two-step treatment.

Purification and reuse of carbon black wastewater of acetylene production from natural gas by microchannel filtration

Carbon black wastewater is a by-product of partial oxidation of natural gas to acetylene and can cause serious pollution to the environment. In this study, the effect of deep bed filtration (microchannel filtration) in the synergistic separation of particulate pollutants and organic pollutants in carbon black wastewater were investigated. The results indicated that the separation efficiency of carbon black particles with a mean diameter of 6.88 µm was 95%− 98%, 95–97%, and 95%− 96% when the filter material was quartz sand + quartz sand, quartz sand + activated, and quartz sand + anthracite, respectively. The solid content of inlet was 300 mg/L and 145 NTU, respectively, and those of the purified effluent were below 15 mg/L and 14 NTU, which meet the first-class B standard of China sewage discharge. The total kinds of organics were reduced from 29 to 2. The separation efficiency of C6-C24 all higher than 97%. A 150 m3/h full-closed treatment process for carbon black wastewater was designed to replace the original open sedimentation tank. The carbon black wastewater could be efficiently purified by this method, the purified carbon black wastewater could be reused, and the carbon black was used to make a filter cake for recycling in rubber without discharge. Finally, the possibility of achieving zero discharge of carbon black wastewater is shown.

Numerical simulation and instability analysis of particles in liquid–solid concave‐wall jet using DPM‐RSM

AbstractThe liquid–solid concave‐wall jet existed in the vertical cylinder separator with tangential inlet; the instability near concave‐wall was the key factor for centrifugal separation. The effects of jet flowrate and wall curvature radius on the instability of solid‐particles were explored by experiment and numerical simulation. The results showed that the separation efficiency of particles decreased with the increase of centrifugal separation factor. The liquid–solid concave‐wall jet flow in separator was unstable in this study. The decay rate of jet maximum velocity on the concave‐wall was larger than that on plane‐wall jet. The ratio of half‐width value to wall curvature radius was about 0.08 at the circumferential direction 90°, which coincided with the critical value of centrifugal instability in strongly concave‐wall jet. The pressure, velocity, and vorticity fluctuated periodically along streamwise direction in separator. The fluctuation period was linearly related to the wall curvature, and the radial range of fluctuation was only half of jet width. The paired longitudinal vortices formed along the flow direction, and the longitudinal vortices merged at length 0.74 m from the inlet cross‐section along circumferential direction. After the position of vortices merged, the particle trajectory oscillated obviously.

Operational performance characteristics of an axial double baffles three channels classifier for coarse pulverized coal

In order to obtain the working principle of the axial direction classifier and raise its separation efficiency, the flow field and classification performance of the classifier was investigated by numerical simulation and experimental measurement. The particle size distribution at inlet, outlet and return pipe was measured by laser particle size analyzer and coupled with Rosin-Rammler model. The particle trajectory was analyzed using the discrete phase model. The tangential velocities played a dominant role in particles radial distribution mainly in the form of Rankine vortex. The axial velocities determine the vertical distribution of particles. The velocity distributions and turbulence influence the cutting particle size and separation efficiency mostly. The most suitable condition is baffles angle of 20° and inlet velocity of 19.3 m/s considering the load of the mill and the fineness of the pulverized coal at the inlet of the classifier.

Study on the performance of a vortex mist eliminator for improving the separation efficiency of fine particles

AbstractIn the process of natural gas purification, common baffle demister has the problem of low separation efficiency and incomplete separation of fine droplets with the particle size in the range of 5–25 μm. This situation not only affects the quality of natural gas, but also causes corrosion and damage to gas equipment, and even seriously affects normal production. In order to solve these problems, we have carried out an innovative design for its structure. Based on the single‐stage baffle, vortex blades are added at the first straight plate section from the inlet and the second straight plate section in the middle to enhance the turbulent vortex degree and complexity of the flow field in this area and improve the probability of collision of small particles with the wall, thus achieving the purpose of improving the demisting efficiency. In this paper, performance of the new mist eliminator is analyzed and evaluated by means of experimental study and computational fluid dynamics (CFD) numerical simulation. The results show that when the flow rate is 3.5–5.5 m/s, total separation efficiency of the new mist eliminator for fine particles with a particle size of 5–25 μm is about 51.72%–86.13%, which is about 38.57%–55.76% higher than ordinary baffled mist eliminator. The separation efficiency of particles with a diameter of 5 μm is about 31.79%, increased about 26.15%. The separation efficiency of particles with a diameter of 10 μm is about 52.09%, increased about 37.21%. In addition, when the flow rate is 3.5–5.5 m/s, the pressure drop is increased by about 41.68–135.97 Pa. It could be concluded that the new type of mist eliminator could effectively improve the demisting efficiency of fine droplets.

High-throughput particle focusing and separation in split-recombination channel

Inertial microfluidic has been widely applied to manipulate particles or bio-sample based on the inertial lift force and Dean Vortices. This technology provides significant advantages over conventional technologies, including simple structure, high throughput and freedom from an external field. Among many inertial microfluidic systems, the straight microchannel is commonly used to produce inertial focusing, which is a phenomenon that particles or cells are aligned and separated based on their size under the influence of inertial lift force. Besides the inertial lift force, flow drag forces induced by the geometrical structures of microchannel can also affect particle focusing. Herein, a split-recombination microchannel, consisting of curved and straight channels, is proposed to focus and separate particles at high flow rate. As compared with the straight channel, the particle focusing in the split-recombination channel is greatly improved, which results from the combined effects of the inertial lift force, the curvature-induced Dean drag force and the structure of split and recombination. Moreover, the distribution of different-sized particles in designed microchannel is investigated. The results indicate that the proposed microchannel not only enhances the particle focusing but also enables the separation of different-sized particles with high throughput. Finally, it is discovered that the larger length of straight channel and curvature radius of curved channel can result in a more efficient particle separation. Another important feature of designed split-recombination microchannel is that it can be arranged in parallel to handle large-volume samples, holding great potential in lab-on-a-chip applications.

Continuous size-based DEP separation of particles using a bi-gap electrode pair.

A novel microfluidic device containing a bi-gap electrode pair is presented in this paper, and it is capable of continuously separating three different populations of particles using dielectrophoresis. A mixture of 5, 10, and 20 μm polystyrene particles is focused by a sheath flow and then separated based on size after flowing over a bi-gap electrode pair. A new solver is developed in OpenFOAM to investigate the effects of various parameters such as the flow rate, gaps, and electrode pair angles to achieve an appropriate configuration of the bi-gap electrode pair for efficient particle separation. Based on the numerical simulation results, three different configurations of bi-gap electrode pairs are fabricated. The paths of three populations of polystyrene particles under various operating conditions are experimentally examined and compared with numerical results. Then, by examining the purity of the separated particles with three different electrode configurations at different flow rates, the performance of the device is experimentally investigated. The results showed that by employing the proposed electrode configuration, at a maximum flow rate of 100 μL h-1 (25 μL h-1 for the sample), particles are separated precisely (with more than 99% purity for all particles at desired outlets) using a 20 Vpp sinusoidal electric potential with a frequency of 100 kHz. This novel microfluidic device is thus a practical device for continuously separating three different populations of particles/cells according to size in a heterogeneous admixture.

Simulation and experimental study of effect of vortex finder structural parameters on cyclone separator performance

This study attempts to clarify the correlation between the structural parameters of vortex finders (diameter ratio and insertion depth) and the strong turbulent flow field and performance of cyclone separators. To elucidate the effects due to the overflow pipe diameter, insertion depth, and Reynolds number on the tangential velocity index (n) and separation efficiency, 0.3D, 0.4D, 0.5D, 0.6D, and 0.7D (where D is the diameter of the cyclone separator’s cylindrical section) were selected as the vortex finder diameter and insertion depth, which were studied using three methods: computational fluid dynamics (CFD) software Fluent, experiments, and artificial neural network simulations. With Fluent, the Reynolds stress model (RSM) of turbulence was adopted to describe transport equations, and the discrete phase model (DPM) for two-phase flow was used to calculate the efficiency and separate particles at different inlet velocities. Experiments were conducted to measure the operational pressure drop and separation efficiency of the system; subsequently, the results were used to validate the CFD calculation results. Finally, a 5–5-1 three-layer artificial neural network was established based on 336 sets of data for values of n obtained from numerical simulations. In addition, a backpropagation (BP) artificial neural network model was employed to predict the correlation between the structural and operational parameters of the cyclone separator and n values. The obtained results indicate that the BP artificial neural network can accurately predict the distribution of n values within the flow field of the cyclone. Increasing the diameter of the vortex finder with the same inlet velocity can reduce the total pressure drop due to the cyclone, thereby reducing the kinetic energy loss and improving the separation efficiency of fine particles. Increasing the insertion depth of the vortex finder leads to an increase in the values of n. Considering the stability of the flow field structure and energy dissipation, an S/D value between 0.5 and 0.6 is preferred.

Nonnegligible nano-confinement effect on solvent-mediated interactions between nanoparticles

Separating nanoparticles (NPs) by means of microfluidics represents a promising method. One of the associate challenges is how to regulate the interactions between NPs in confined solvents for avoiding particle aggregation. To tackle this challenge, herein we conduct a theoretical study to interpret the confinement effects on the potential of mean force between two NPs in nanochannels. By using the classical density functional theory, the effects of pore width, wall wettability, NP size, and solvent-NP interactions are unraveled. It is found that the nano-confinement can noticeably enhance the short-ranged attraction between NPs, and the attraction strength can be moderated by enlarging pore size, making wall solvophobic, shrinking NP size, and widening the range of solvent-NP interaction. This study provides a theoretical guidance towards the development of efficient particle separation method in nanochannel-based devices.