Wire-plate Electrostatic Precipitator Research Articles

Numerical study on the effect of staggered wire electrodes in an electrostatic precipitator

In this paper, a numerical model is developed to describe the wire-plate electrostatic precipitator used in industrial application for air cleaning. The complex interactions between fluid dynamics, electric fields and particle dynamics are considered. Therefore, the combined Eulerian and Lagrangian approach is used in this study. In order to describe corona phenomena around high voltage electrode, electric field and ion current density field in electrostatic precipitator are numerically calculated using the iterative method for corona discharge model suggested by Kim [1]. The charging model suggested by Lawless [2] is used for the charging phenomena of particles by corona discharge because it was designed to predict combination effect of diffusion charge and field charge. The numerical model in this study is implemented by UDF in commercial software FLUENT and validated with experimental and numerical results from literatures. The effects of wire arrangement on electrostatic precipitator characteristics are investigated. Both inline and staggered arrangements of wire electrode have been considered for fixed value of gas velocity equal to 2 m/s. Applied voltage on wire electrode is varied in the range of 6 to 13 kV and particle diameter is 4 µm. For low voltage condition, staggered arrangement of wire electrode caused the turbulent effect so that the collection efficiency increases more than inline arrangement. However, the collection efficiency decreases in high voltage condition because electric force applied on particles passing between the wire electrodes is canceled out by both side wire electrodes.

Study on performance of electrostatic precipitator under multi-physics coupling.

A wire-plate electrostatic precipitator (ESP) is developed to analyze the particle transport characteristics and the influence of various factors on the performance of ESP. Above all, an experimental device is built to measure the current density distribution of the plates and obtain good consistency with the numerical simulation results, taking the ESP model established by COMSOL/Multiphysics as the numerical simulating object. Firstly, the electric field is solved by finite element method(FEM) to obtain the potential and charge density distribution. Then, the influence of secondary flow on the main flow at different flow velocities is explored. Finally, multi-physics coupling calculations show the influence of dust particle properties, electrode configuration, and operating conditions on ESP performance. The study found that the particle diameter is positively correlated with its charge, force, and motion, and the relative permittivity of the particles affects the collecting efficiency by affecting its charge difficulty. The wire-to-wire spacing is not proportional to collecting efficiency, when the spacing is 80 mm, the efficiency and the corona current can be maximized. Average electric field strength, corona current density, and current density distribution standard deviation satisfy the cubic function relationship. In addition, the effect of airflow velocity on collecting efficiency and particle precipitation is revealed. It provides a valuable basis for design and performance optimization of ESP.

Numerical simulation of electrostatic field and flow field in an electro- static precipitator

Introduction: The computational fluid dynamics (CFD) simulation of three- dimensional wire-plate electrostatic precipitator is performed in the present study. Materials and methods: The momentum equation, the electric potential equation and current continuity equation are solved by using ANSYS Fluent. The ion charge density at the corona is calculated iteratively using the Peek formula. The SIMPLE algorithm is used to treat the pressure-velocity cou- pling. The RNG k-ε model is used to describe turbulence. Results: The airflow keeps stable away from the first corona electrode. The distribution of the electric potential is dependent on the wire-plate distance and the wire-wire distance. The potential and ion charge density increase with the increase of the wire-plate distance. With the increase of wire-wire dis- tance, the maximum electric field strength decreases whereas the maximum ionic charge density increases. The ion charge density near the second corona electrode is relatively small. A small wire-wire distance will make the electric field concentrated around the wires. Conclusion: According to this study, the wire-wire distance and the wire- plate distance have great effect on the distribution of ion charge density and electric field strength.

Numerical simulation of electrostatic precipitator considering the dust particle space charge

The coupled electric field, gas-particle flow and particle charging processes are simulated using Eulerian-Lagrangian method in Computational Fluid Dynamics (CFD), for a wire-plate electrostatic precipitator with four-wire electrodes configuration. The effects of particle charging on the electric field distribution, VI characteristics and particle collection efficiency are investigated, as the entry particle loading/concentration varies from 0 up to 50 g/Nm3 for a particle size of 0.25–5.0 μm under fixed gas velocity of 1.0 m/s.The results show that the electric field can be distorted significantly by the secondary electric field generated by the space charges on the floating particles, which mostly reduces particle collection efficiency, except at a very low loading. A maximum collection efficiency exists at a particle loading that depends on particle size. Under fixed voltage applied, the corona current decreases as particle loading/concentration increases. As particle loading increases to some point, the corona current from the downstream wires can be extinguished completely (corona quenching). At high particle loadings, corona ion charges may fail to reach the plate due to the absorption of passing particles. The electric streamlines in a small zone around the last wire reverse direction locally. A charged particle, once falls accidently within the zone, could be trapped and be attracted to the same wire. Thus this wire is subject to heavier dust deposition. The significance of ion transfer and space charge of fine dust particles is clarified systematically.

Efficiency of electrostatic precipitation of NiO nanoparticles dispersed by atomization

ABSTRACT The dispersion of metal oxide nanoparticles by pneumatic atomization of oxide suspensions has rarely been used in laboratory-scale research on electrostatic precipitation, due to the insolubility of the oxides under ambient conditions, the particle agglomeration and sedimentation in aqueous mixtures. Therefore, the aim of this work was to evaluate the performance of a wire-plate electrostatic precipitator in the collection of NiO nanoparticles produced by nebulization of suspensions pretreated with ultrasonic bath, which resulted in reproducible aerosol concentrations and particle size distributions. Increase of the voltage and decrease of the gas flow rate improved the charging and collection efficiencies.

Effect of low gas velocity on the nanoparticle collection performance of an electrostatic precipitator

ABSTRACTGas velocity is a critical operational variable in the electrostatic precipitation process. However, studies concerning the collection of nanoparticles have ignored the effect of low gas velocities. Therefore, the aim of this work was to use a wire-plate electrostatic precipitator to investigate the effects of atypical gas velocities under different electric fields on the efficiency. Increasing of both variables enhanced the efficiency, under the conditions used. Unusual behaviors of the grade efficiency curves were associated with diffusional effects. The experimental overall efficiency data were compared with the Deutsch model, and effective migration velocity curves with maximum points were obtained.

Influence of particle concentration and residence time on the efficiency of nanoparticulate collection by electrostatic precipitation

The influence of gas velocity on the efficiency of electrostatic precipitators has previously been discussed exclusively in terms of the gas residence time, even when there are changes in aerosol concentration. Therefore, the aim of this work was to separately evaluate the influences of residence time and concentration by performing sets of experimental tests with KCl nanoparticles in a wire-plate electrostatic precipitator. A proportional increase in the nanoparticles flow rate with increase of the gas stream mitigated dilution effects, allowing exclusive evaluation of the effect of residence time on efficiency.

Electrohydrodynamic flows in electrostatic precipitator of five shaped collecting electrodes

The electrohydrodynamic (EHD) flows in wire-plate electrostatic precipitators (ESP) of five shaped collecting electrodes are simulated by employing the CFD code FLUENT with the aid of a user defined function (UDF). The results show that the EHD flow patterns are different in the five configurations. Bending of the collecting plate can easily lead to the peak of the electric field intensity near the collecting surface. The space charge density near the W-type collecting surface is more uniform than those of the other four types. The flow induced by ionic wind in the C-type plate is strongest among the five channels.

The influence of design parameters on the occurrence of shielding in multi-electrode ESPs and its effect on performance

A numerical model in which OpenFOAM® is used to model the electrostatic field resulting from corona discharge in single-channel wire-plate electrostatic precipitators (ESPs) was applied to systematically study the shielding effect that can arise between adjacent discharge electrodes. It is shown that the OpenFOAM model is capable of accurately quantifying the extent of shielding, and that the degree of shielding is predicted to increase as the spacing between the cylindrical discharge electrodes is decreased. This increase in the degree of shielding consequently resulted in a reduction of the discharge current. The numerical model was also used to quantify the effect of various other ESP parameters on the degree of shielding by studying the space charge density and current density distributions, and the plate-to-plate spacing was found to be the most influential parameter. By incorporating the electrostatic field obtained from the OpenFOAM model in a CFD model based in Star-CCM+®, it is further shown that a decrease in particle collection efficiency is predicted to occur when the shielding intensity increases. Such a systematic study to quantify the extent of shielding and its effect on ESP performance in terms of particle collection efficiency has not received much attention in the literature to date. Predicting the incidence and extent of shielding as a function of geometric ESP parameters are also invaluable to avoid laboratory or pilot scale results that are biased because of the occurrence of shielding.

Numerical study on fine-particle charging and transport behaviour in electrostatic precipitators

In this work, a numerical study on the charging and transport of fine particles has been carried out based on wire-plate electrostatic precipitators (ESPs) with multiple wire electrodes. The effect of the applied wire voltage, inlet height, and wire spacing on particle charging and transport, and the influence of the precipitator structure on particle trapping are analysed in detail. Results indicate that a voltage increase in the high voltage range improves the particle-trapping efficiency. However, the Brownian diffusion causes the particle fluctuation, but it doesn't change the direction of main movement. Particles injected into the precipitator at the channel centre are influenced most intensively, whereas particles injected at approximately 5 mm from the centre of the precipitator exhibit the poorest particle-trapping ability. An increased wire spacing enhances particle trapping, within a certain range, and a larger particle size causes an even more obvious enhancement. Furthermore, changing the discharge-electrode arrangement shows a much greater effect on the charging and transport behaviour of particles in the model of M3, which has the highest trapping efficiency.

Numerical simulation of corona discharge and particle transport behavior with the particle space charge effect

The corona discharge characteristics of an electrostatic precipitator are an important factor that affects particle charging and collection. The electrical characteristics of a wire-plate electrostatic precipitator and the particle transport behavior were studied by considering the electrohydrodynamics (EHD) and the effect of particle space charge through numerical simulation. Simulation results showed that the effect of particle space charge intensifies in extremely small particles, such as submicron particles. This condition significantly influences electric field, ionic charge density, and current. The electric field intensity and ionic charge concentration significantly decreased. The reduction in the minimum field intensity between the electrodes decreased to 50%, and the lowest concentration of the ionic charge tended to 0 when the particle size varied from 5µm to 0.1µm. When the applied voltage increased from 13kV to 40kV, the space charge ratio of the particles larger than 2µm was reduced to almost 0 but remained at a high level for the particles less than 0.5µm whose corresponding current was lower by 20% than that without particle condition. The ionic wind in the electrostatic field also weakened because the movement of ions was restricted for corona suppression, leading to decreased corona current. Furthermore, the particle transport behavior was compared considering the effect of particle space charge. Results indicated that the difference between the two conditions increased from 1.3% to 47.4% with decreasing particle size from 5µm to 0.07µm. In addition, the particle migration velocity of the 0.1µm particles increased by 9.8%, from 0.2 to 0.1µm, even if the drag force was reduced when considering the particle space charge. A modified I–V equation was provided, with fitting coefficient of 0.996, and is thus worthy of reference in practical application.

Mechanism study of electrostatic precipitation in a compact hybrid particulate collector

Hybrid structure significantly affects the collection mechanism and performance of a hybrid particulate collector. The electrostatic precipitation of particles in the wire-perforated plate structure of a full-scale compact hybrid particulate collector is numerically simulated in this study. The distributions of electric and flow fields and the charging, motion, and precipitation of particles in this specific structure are studied. The results show that the distribution of electric field in the final stage is asymmetrical because of the baffle plate at the end of the channel. The field distributions of other stages are identical to that of wire-plate electrostatic precipitator. The openings increase the electric field strength in the region adjacent to the perforated plate. The electric field passes through the openings, which is then distributed to the back side of the perforated plate. The aerosol cross flow rate along the perforated plate varies periodically under the effect of electric body force. Whereas, the overall cross flow rate of each stage is the same, except the first stage. Two counter-rotating eddies are formed behind the perforated plate between every two openings. Particle charge exceeds 80% of the final charge when the particles move to the position of the first wire. The 10 μm particles finish their charging processes faster than 1 μm particles with a final charge of approximately 100 times that of 1 μm particles. The charge acquired by a particle under the wire-perforated plate structure is 3% higher than that under the wire-plate structure. Particle trajectory result shows three modes of electrostatic precipitation in a compact hybrid particulate collector, namely, collection on the front, flank, and back sides of the perforated plate. Particle transport by eddies on the back of the perforated plate plays an important role in particle deposition on the back side. Variation in the capture probability of particles released from different positions corresponds to the opening structure. High and low probability areas separate with each other. The collection efficiency of 10 μm particle is higher than that of the 1 μm particle. The results can explain hybrid mechanism and optimize hybrid structure.

Experimental Study on Electrostatic Precipitation of Low-Resistivity High-Carbon Fly Ash at High Temperature

A high-temperature electrostatic precipitator (ESP) is a good solution for hot gas cleaning to ensure the long-term stability of the production system in many energy-consuming industries. The high-carbon fly ash particles in the gasification of coal pyrolysis process are typical particles with low resistivity. In this paper, the characteristics of the coal pyrolysis furnace fly ash (ash A) were compared with coal-fired power plant fly ash (ash B). The effects of their characteristics on particle removal were compared in a wire-plate ESP. The particle collection efficiency was found to decrease with increasing temperature. From 363 to 523 K, the collection efficiencies of both ash samples were as high as above 95%. However, at 623 and 723 K, the collection efficiency of ash A was obviously lower than ash B. A method of enhancing particle removal was proposed by particle conditioning to reduce the occurrence of particle re-entrainment, and the fine calcium carbonate powders were used as the conditioning par...

Numerical simulation on the fine particle charging and transport behaviors in a wire-plate electrostatic precipitator

In this work, an integrated numerical model is presented and validated to investigate the particle charging and transport behaviors in a wire-plate electrostatic precipitator (ESP). Calculations of gas flow, electrostatics field and particle motions are coupled in the model, and the influences of electro-hydrodynamics (EHD) flows are also taken into account. The dynamic charging process of particles was treated with separate field and diffusion charging rates, and the trajectories of particles in the ESP were tracked with a Lagrangian-type method. Numerical results show that electric field strengths and charging ion densities varied largely in the computational domain, and inlet particles were initially charged primarily by diffusion charging mechanism. The particles were then charged to a near-saturation state in the discharging zone, while their transverse velocities showed considerable fluctuations along the trajectories. Numerical results indicate that particles with diameter between 0.2 and 1μm normally exhibited lowest average transverse velocities, and longer residential time could slightly improve the transverse velocities for all sizes of particles. Moreover, increasing voltages could greatly improve the acquired charges and collecting performances for particles larger than 1μm, while higher ion current value was more effective in achieving higher collection efficiencies for sub-micron particles.

Electrode geometry optimization in wire-plate electrostatic precipitator and its impact on collection efficiency

Wide Electrostatic Precipitator (having plate-to-plate spacing 400 mm or more) is one of a promising ways to improve existing ESPs, yet its large-scale application has been limited because of potential collection efficiency reduction. This article focus on study the electrohydrodynamic flow inside the ESP and the particle collection efficiency by using Particle Image Velocimetry and Electrical Low Pressure Impactor respectively when several different electrode geometries were applied, in order to increase wide ESP efficiency. Results showed that geometry with juxtaposed high voltage wires provided best performance of the wide ESP (both in collection efficiency and running cost) among our tests.

CFD simulation of high-temperature effect on EHD characteristics in a wire-plate electrostatic precipitator

A computational fluid dynamics (CFD) model is carried out to describe the wire-plate electrostatic precipitator (ESP) in high temperature conditions, aiming to study the effects of high temperature on the electro-hydrodynamic (EHD) characteristics. In the model, the complex interactions at high temperatures between the electric field, fluid dynamics and the particulate flow are taken into account. We apply different numerical methods for different fields, including an electric field model, Euler–Lagrange particle-laden flows model, and particle charging model. The effects of high temperature on ionic wind, EHD characteristics and collection efficiency are investigated. The numerical results show high temperature causes more significant effects of the ionic wind on the gas secondary flow. High viscosity of gas at high temperature makes particles follow the gas flow pattern more closely. High temperature reduces the surface electric strength, so that the mean electric strength weakens the space charging. On the contrary, there is an increase in the diffusion charging at high temperature compared with at low temperature. High temperature increases the ratio of mean drag force over mean electrostatic force acting on the particles which may contribute to a decline of collection efficiency.

Numerical simulation of temperature effect on particles behavior via electrostatic precipitators

A comprehensive numerical model is developed and applied to study the effect of temperature on the behavior of charged particles in a wire-plate electrostatic precipitator (ESP). In this model, the complex interactions in different temperature conditions between the electric field, fluid dynamics and the particulate flow are taken into account. The finite volume method is used to solve the electric field and Euler-Lagrange model is used to describe particle-laden flows. From the present simulation, the effect of temperature on electro-hydrodynamics (EHD) characteristics and particle charging and tracing are investigated. The numerical results show that high temperature thickens the boundary layer along the plate and strengthens turbulence. The corona onset electric field intensity and mean field intensity both decrease as temperature increases. Considering space charging and diffusion charging, high temperature weakens the particle charging. With the increase of temperature, the Coulomb, Saffman lift and Brownian forces go down while the drag force goes up. The Coulomb force and the drag force are the key forces acting on particles in the ESP for 10 μm particle. The variation of the two forces along with particles trajectories indicates that high temperature enhances the interaction between particles and fluid. Finally, it becomes more difficult to collect particles when temperature increases.

Numerical analysis of charged particle collection in wire-plate ESP

Abstract In this paper, the structure of single wire-plate unit in electrostatic precipitator (ESP) was optimized and dust removal process in an entire ESP was investigated using computational fluid dynamics (CFD). Collection efficiency is higher in the center of the ESP, but becomes lower near the edges. High applied voltage, low inlet velocity and large particle diameter are beneficial for dust collecting. As particle concentration increases, collection efficiency increases at the beginning, then decreases. When particle diameter is smaller, inlet velocity and particle concentration is higher, particle trajectories become less stable as turbulence is more severe.

Modeling particulate removal in plate-plate and wire-plate electrostatic precipitators

The present study is concerned with the modeling of electrically charged particles in a model plate-plate and a single wire-plate electrostatic precipitator (ESP). The particle concentration distributions for both a plate-plate and a wire-plate ESP are calculated using a modified drift flux model. Numerical investigations are performed using the modified drift flux model for particle number concentration, in addition to the RNG k - e model for the mean turbulent flow field and the Poisson equation for the electric field. The proposed model and the outlined methodology for coupling the flow field, electric field, charging kinetics and particle concentration is applied to two model precipitators that are truly representative of a wide class of commercialized ESPs. The present investigation is quite different from the earlier studies as it does not make assumptions like a homogeneous electric field or an infinite turbulent diffusivity. The electric field calculated is a strong function of position and controls the migration velocity of particles. Hence, the proposed model can be implemented in a flow solver to obtain a full-fledged solution for any kind of ESP with no limitations on the particle number concentration, as encountered in a Lagrangian approach. The effect of turbulent diffusivity on particle number concentration in a plate-plate ESP is investigated in detail and the results obtained are compared with available experimental data. Similarly, the effect of particle size/diameter and applied electric potential on the accumulative collection performance in the case of a wire-plate ESP is studied and the results obtained are compared with available numerical data. The numerical results obtained using the modified drift flux model for both the plate-plate and wire-plate ESP are in close agreement with available experimental and numerical data.

Experimental and Simulation Study of V–I Characteristics of Wire–Plate Electrostatic Precipitators Under Clean Air Conditions

In this paper, a laboratory-scale model for prediction of the voltage–current (V–I) characteristics of wire–plate electrostatic precipitators (ESPs) under clean air conditions is presented and experimentally validated. The model investigates the effect of electrode configurations, wire diameter, spacing between wire electrodes, number of discharge wires and distance between collecting plates that on V–I characteristic of wire–plate ESPs. Also, this paper presents a simulation model, based on the finite difference method, to simulate electric conditions of wire–plate ESPs under clean air conditions. The experimental results of some models are compared with those obtained from the simulation models.