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In the electrostatic precipitation of microparticles, it is common to evaluate the voltages between the corona onset voltage and the breakdown point. However, the charging of particles in the nanoscale size range mainly occurs by diffusion, suggesting the possibility of its occurrence, even at low values. This paper investigates the implications of a wide range of electric fields applied in the collection of nanoparticles (6.15–241.4 nm). Two electrostatic precipitators (P.I. and P.II.), both with plates 10 cm high and 30 cm long, but with different plate spacings (4 and 6.5 cm), were tested using three air velocities (1.9, 2.9, and 3.9 cm/s) and 36 electric fields (0.0 − 5.0 kV/cm). Under the highest electric fields, both precipitators showed efficiencies above 99.9%. Furthermore, nanoparticles were collected before the corona onset voltage, with efficiencies of around 28% (P.I.) and 35% (P.II.). Even though no current was detected by the high voltage source, charges on the particles were measured in electric fields lower than 3.0 kV/cm. The higher the applied voltage, the higher the residual charge of the particles at the precipitator outlet. It is expected that the findings of this work should contribute to the technological development of electrostatic processes for air treatment. [ABSTRACT FROM AUTHOR]

Dust emissions must be managed and reduced as much as possible to safeguard the environment and human health. Plate-type electrostatic precipitators have been used to decrease pollution in a number of sectors, particularly for applications needing massive volumes of gas to be dedusted at high dust concentrations and temperatures. This paper examines large-capacity plate-type electrostatic precipitators with three sections used in a coal-fired thermal power plant. Using simulations and experiments, the collection efficiency (in different ways of supplying sections, without and with sections rapping), the influence of dust resistivity and a dust layer on the surfaces of collection electrodes, the electrical parameters (voltage, current density, and space charge density) for the sections of the electrostatic precipitators, and the electrical parameters of the power sources (voltage, current, power, and power factor) are studied. A higher dust resistivity will cause a change in the shape of the voltage delivered to the sections, an increase in the average voltage from sections, and a decrease in collecting efficiency (by a few percent). A greater degree of intermittence alters the current-voltage characteristics of the sections, decreases the current across the sections, and improves collection efficiency. The density of space charges increases with the degree of intermittency and is highest at the input section. With increasing thickness of the dust layer on the collection electrodes, the collection efficiency increases. PM10 dust particles (which have a lower migration speed) are the hardest to collect with ESPs. When the sections are rapping, PM 20–30 dust particles are more difficult to collect because their migration speeds decrease significantly (compared to the situation when the sections are not rapping). The operation of the power sources of the ESP sections is dynamic, being controlled by the regulators, and the current (or current density), depending on the voltage characteristics, changes permanently (at intervals of a few seconds). The power sources of the sections are deforming consumers (the current is much different from the sinusoidal form). [ABSTRACT FROM AUTHOR]

Utilizing electrostatic precipitators (ESPs) is an efficient particle removal method that sees a wide usage in industrial environments. This is mainly because of the low drop of the pressure flow, while retaining high collection efficiency, alongside being cost-effective. This paper reviewed previous works concerning optimizing the performance of single- and multi-stage ESPs by changing several design parameters and evaluating the effects on different performance indices, such as the corona power ratio, current-voltage characteristics, and overall collection efficiency. The review then goes through several modelling methodologies, showcasing their shortcomings and developments, as well as the relationship between the electrohydrodynamic (EHD) flow and the precipitation performance. The performance effects of using different electrode configurations and designs in terms of the number of electrodes, relative dimensions, spacings, channel lengths, and overall design were also reviewed. [ABSTRACT FROM AUTHOR]

In this paper, a wire-plate electrostatic precipitator with expanded-contracted plates（ESP-ECP） was proposed. A numerical method was adopted to investigate the influences of different arrangements of ECP on the electric field intensity, airflow field, particle trajectory and collection efficiency under different voltages, inlet gas velocities and particle sizes. Furthermore, it was compared with the traditional ESP with parallel plates（ESP-PP）. The results indicated that the ECP expands the surface area of the collecting electrode, and effectively enhances the electric field intensity near the collecting electrode. With the increase of the ECP height, the electric field intensity and influence range increase. The low-velocity vortices generated by the ECP help to prolong the retention time of particles, which is conducive to particle removal. In general, the collection efficiency of the ESP-ECP is superior to the ESP-PP. [ABSTRACT FROM AUTHOR]

The filtration performance of bag filter for fly ash from power plants can be improved by unipolar charger. In this paper， hybrid electrostatic filter comprised of pre-charger and fibrous filter were designed and manufactured. Under different charge types， applied voltages and flow velocities， collection efficiency and pressure drop of PPS fibrous filter for unipolarly charged fly ash particles were investigated. The results indicated that with the increase of the applied voltage and the decrease of filtration velocity， the collection efficiency of bag filter is improved， and the growth rate of pressure increment is significantly reduced. The smaller the particle size， the more obvious the increase in the filtration effect， and the improvement effect of negatively charged particles is better than that of positively charged particles. [ABSTRACT FROM AUTHOR]

Utilizing electrostatic precipitators (ESPs) is an efficient particle removal method that sees a wide usage in industrial environments. This is mainly because of the low drop of the pressure flow, while retaining high collection efficiency, alongside being cost-effective. This paper reviewed previous works concerning optimizing the performance of single- and multi-stage ESPs by changing several design parameters and evaluating the effects on different performance indices, such as the corona power ratio, current-voltage characteristics, and overall collection efficiency. The review then goes through several modelling methodologies, showcasing their shortcomings and developments, as well as the relationship between the electrohydrodynamic (EHD) flow and the precipitation performance. The performance effects of using different electrode configurations and designs in terms of the number of electrodes, relative dimensions, spacings, channel lengths, and overall design were also reviewed.

Electrostatic precipitators (ESPs) can achieve high collection efficiencies. However, their application for nanoparticle removal has not been widely discussed, largely because the charging mechanism is affected by the small diameter of these particles. Therefore, this work evaluated the influence of the discharge electrode parameters such as number (1–4), diameter (0.3 and 0.4 mm) and spacing (6.5 and 12 cm) on the electric characteristics of a wire-plate ESP and the nanoparticle collection efficiency (5.94–224.7 nm). A greater number of wires and a smaller wire diameter improved particle collection almost three-fold but under some operating conditions was reduced by the shielding effect. On the other hand, the wire spacing had a small influence on the particle collection. The highest collection efficiency (99.99%) was achieved using 4 discharge wires and wire diameter of 0.4 mm, although similar collection efficiencies were achieved with the configuration of 2 wires and wire diameter of 0.3 mm. Image 1 • Evaluation of the discharge electrode parameters in the collection of nanoparticles. • Low air velocities favored nanoparticles collection. • Particle removal increased with decreasing diameter of discharge electrode wire. • Shielding effect impaired the collection efficiency for some experimental conditions. • Increased wire spacing reduced the shielding effect and improved particle removal. [ABSTRACT FROM AUTHOR]

In this article, an electrostatic precipitators (ESP) with high electric field, which does not use corona discharge, was investigated. The ESP had a parallel plate configuration composed of a high voltage application plate electrode and grounded plate electrode with a gap of 5 mm. The electrode length was between 150 and 450 mm. The air was flowed at the gas velocity between 0.5 and 5 m/s in the ESP by a fan. A voltage up to 12.5 kV was applied to the high voltage application electrode, whereby the electric field intensity of 25 kV/cm was generated between the electrodes. The particle concentration in the air for the particle size between 0.3 and 5 μm was measured to calculate the collection efficiency. The collection efficiency in a conventional two-stage type ESP was also measured, and compared to the result in the ESP with high electric field. As a result, the collection efficiency at the electrode length of 450 mm was 77.6% at 12.5 kV, when the ratio of the input power was lower than 0.33 W/(m3/s), in the ESP with high electric field. On the other hand, the collection efficiency in the conventional ESP was 65.6% or 82.0% at the input power of 14.2 W/(m3/s) or 24.8 W/(m3/s). Therefore, it is revealed that the ESP with high electric field is effective for energy saving. [ABSTRACT FROM AUTHOR]

Two-stage electrostatic precipitators are widely used in oil particle purification in industrial workshops, kitchens and ship cabins. As described in this paper, a two-stage electrostatic module was designed, and the effects of seven parameters on the efficiency of collecting oil mist particles with different particle sizes were studied experimentally. On the basis of these experimental results, a semi-empirical efficiency model was developed, and the measured efficiency and calculated efficiency of the present model and the Deutsch model were compared. The comparison results show that the proposed semi-empirical model can well predict the fractional efficiency of the two-stage ESP, whereas the Deutsch model is clearly not applicable in this case. In addition, the degree of influence of seven parameters on the two-stage ESP collection efficiency was studied by using the single-factor sensitivity analysis method with the experimental data. The results show that the degree of influence of various parameters on the particle collection efficiency of 0.31 μm, from high to low, is as follows: the voltage applied to the precharger, the heteropolar distance of the precharger, velocity, the heteropolar distance of the collector, the voltage applied to the collector, the length of the collector plate, and the length of the precharger grounding plate. Unlabelled Image • The grade efficiency the two-stage ESP were studied experimentally. • The influences of seven factors on the efficiency of the two-stage ESP were analyzed. • A new collection efficiency model of the two-stage ESP was developed. [ABSTRACT FROM AUTHOR]

The paper presents experimental studies on the effect of sodium bicarbonate and calcium hydroxide dry, low temperature sorbent injection on the concentration and size distributions of precipitated particles (fly ash and sorbent particles mixture), fractional collection efficiency, and particles morphology. The measurements were carried out on a lab-scale system comprising unipolar electrostatic agglomerator and electrostatic precipitator. In the experiments presented in this paper, the sorbent was injected upstream of electrostatic agglomerator. Results of SEM studies revealed the process of sorbent and fly ash particles agglomeration. The measurement of resistivity of fly ash and sorbent mixtures have shown that injected sorbent has a large effect on the particles resistivity, when the temperature of dust cake is increasing. In practical situations, too high resistivity can lead to back corona discharge generation, while too low causes the particles re-entrainment; both of these phenomena can reduce the dust collection efficiency of an electrostatic system. [Display omitted] • Agglomeration of PM2.5 particles with particles >5 μm improves PM2.5 removal. • Dry sorbent injected to fly ash in flow provides new agglomeration collectors for PM2.5. • Dry sorbent injection upstream of agglomerator increases PM2.5 collection efficiency. • Dry-injected sorbent to fly ash flow has a large effect on resistivity of dust cake. • Synergistic effect of electrostatic agglomeration and precipitation was obtained. [ABSTRACT FROM AUTHOR]

This study presents experimental results of the particle layer growth with the operation of a small-scale ESP as a flue gas cleaning method from domestic biomass combustion. The retention efficiency of the ESP is maintained above 90% for 40 h of operation, which is in agreement with its natural regeneration by partial collapses of the dust layer. The measurements of profile and thickness of the dust layer endorse the aforementioned collapses as discontinuous re-entrainment events that are also identified as abrupt peaks on the particle concentration at the outlet of the ESP and drops on the current values. • The thickness and profile of the accumulation of particles on the collection electrode of a small-scale ESP were measured. • The small-scale ESP efficiently reduces particle emissions, especially in the coarse fraction. • The re-entrainment of particles naturally regenerates the ESP, providing a constant retention efficiency. • Partial collapses of the dust layer are identified as increases of particle emissions and simultaneous current drops. [ABSTRACT FROM AUTHOR]

The monochromatic optical current-voltage characteristic performances of cadmium telluride solar cells with different structures were tested, and the collection efficiency at different wavelengths was calculated. The results show that high resistivity layer can greatly improve the collection efficiency of solar cell short-wave, and has a certain effect on the collection efficiency of long-wave. The back contact layer facilitates forming ohmic contact on the back of the solar cells. And the appropriate cadmium sulfide layer can improve the interface of window layer and improve the device performance of solar cells. The relationship between device structure and device performance is obtained by the measure method in order to provide theoretical and experimental basis for further optimization of battery structure and preparation technology and improvement of solar cell conversion efficiency. [ABSTRACT FROM AUTHOR]

Abstract Particle Image Velocimetry studies of velocity field of the EHD flow during the back corona discharge at atmospheric pressure in an electrode system comprising a needle discharge electrode at negative potential and a grounded plate collection electrode covered with fly ash layer are presented in this paper. It was found that the magnitude of velocity vector of the EHD flow starting from the crater formed in fly ash layer after the onset of back corona discharge is of the same order of magnitude as for the flow generated by the corona discharge from the needle electrode. The measurements have shown that both these flows do not mix, but deflect each other off the axis of the needle electrode. The conclusion from this research is that the EHD deflection of the trajectories of particles flowing towards the collection electrode by the particles erupted from the crater at the collection electrode probably prevents those particles from the precipitation on the collection electrode that can result in a decreased collection efficiency of electrostatic precipitator during back corona discharge. This new mechanism has been called the "dynamic" process of the collection efficiency reduction. Graphical abstract Unlabelled Image Highlights • The velocity field of the EHD flow during back corona discharge was investigated. • The properties of back corona discharge modes have been determined experimentally. • The dynamic mechanism of the reduction of particle collection efficiency due to back corona discharge has been proposed. [ABSTRACT FROM AUTHOR]

Abstract To improve the fine particle collection efficiency, a bipolar transverse plate electrostatic precipitation (ESP) technology was developed. In this ESP, there are not only the negative wire electrodes and ground plate electrodes, but also the ground wire electrodes and the negative plate electrodes. It has aroused a special interest about the corona discharging effect of the ground wire electrodes. Therefore, the corona currents of the negative wire-ground plate, the ground wire-negative plate, as well as the bipolar wire-plate electrodes have been investigated experimentally. In the experiments, the RS barbed wire and the C-plate are used as the electrodes for the purpose of the industrial application. The experimental results have shown that, when the wire-plate spacing is 200 mm, the corona current of the wire in the smooth side of the ground C-plate is 15% higher than that of curved side, however the corona current of the ground wire is about 30% less than that of the negative wires regardless of the wire is located at different sides of the industrial plate electrode. Moreover, the corona current of bipolar wire-plate electrodes is 30% less than that of the traditional wire-plate electrodes, and an important phenomenon had been discovered from this experimental work that, for the bipolar wire-plate electrodes, whenever the front side of the C-plate faces to the gas flow or not, the V I characteristics curve keeps almost no change at given wire-plate spacing. Last, an experimental setup was established for comparison of collection efficiency. When the negative polarity is applied to the bipolar transverse plate ESP, the collection efficiency increases sharply from 69.1% to 99.1%. Since both electrical forces and inertial forces play important roles in the bipolar transverse plate ESP, the penetration of the bipolar transverse plate ESP is 0.9%, which is substantially less than the penetration of 4.2% of the conventional ESP. The advantage of bipolar transverse plate ESP unit has been proved by successful operation in sintering flue control in China. Highlights • A bipolar transverse plate ESP experimental device was developed. • Ground plate and negative plate are used to enhance fine particle collection. • The corona current of ground wire is 30% less than that of negative wire. • The penetration of the bipolar transverse plate ESP is substantially reduced. [ABSTRACT FROM AUTHOR]

Abstract Electrostatic precipitators (ESPs) are considered as cost-effective technology for separating the charged particle from flue gas. In this paper, a modified ESP model was developed to investigate the effects of charged particle on the electric field, ion density, particle charging and migration regarding various particle concentrations. Coupled processes of corona discharge, flow field, particle charging and transport were considered. Results showed that the particle space charge presented trajectory-dependent effects on the distributions of electric field and ion density in the gas flow direction. With the particle concentration increasing from 0 to 200 mg/m3, the electric field strength on the electrode surface was inhibited from 1.32 × 106 to 1.24 × 106 V/m, while the electric field strength on the plate surface was raised from 7.1 × 105 to 8.3 × 105 V/m. By contrast, the ion density within the whole domain decreased when particle space charge considered, and it decreased by more than 40% when the particle concentration was 50 mg/m3. The particle charging rate decreased due to particle space charge effects and consequently the overall particle charge decreased by 45.7% as particle concentration increased to 200 mg/m3. The correlation between collection efficiency and corona current was discussed, and it showed that the two didn't vary synchronously with the increasing concentration. A criterion for efficiency deterioration, under corona suppression conditions, was first proposed for instructing ESP design and operation. Graphical abstracts Unlabelled Image Highlights • A modified ESP model was established to study the particle space charge effects. • Corona discharge, flow field, particle charging and transport were coupled. • Correlation between corona current and collection efficiency was analyzed. • A criterion for ESP performance deterioration was first proposed. [ABSTRACT FROM AUTHOR]

Electrostatic precipitator is the most efficient device used for the removal of fly ash particles from the flue gases produced by coal-fired boilers in power plants. However, the fractional collection efficiency of electrostatic precipitators steeply decreases for particles smaller than 1 μm, and particles in the size range of 200–500 nm are removed with lower collection efficiency than those outside this range. These particles are dangerous to humans and have detrimental environmental effects, so there is a need for novel more efficient technologies for their control. One of the answers to this challenge is the two-stage electrostatic precipitator, in which the electrostatic charging and precipitation processes have been separated. The PM2.5 particles (of a size < 2.5 μm) are electrically charged in a separate device (precharger) to a maximal possible electric charge, and then precipitated in a parallel plate collector, free of corona discharge. The electric field in the collection stage can be higher than in an electrostatic precipitator due to the lack of sharp discharge points. A higher electric field allows an increase of the collection efficiency for PM2.5 particles. Another solution is the agglomeration of submicron particles to form larger particles before their precipitation by a parallel-plate collector, conventional electrostatic precipitator or any other gas cleaning device. In some of the reviewed devices, both of these processes were combined in a single device that allowed further increases in the collection efficiency for submicron particles. Devices of this type have been tested in a lab- or semi-industrial scale for the removal of PM2.5 particles from flue gases or diesel engine exhausts. In this paper, various constructions of two-stage electrostatic precipitators, comprising a precharger and/or agglomerator in the first stage, and an electrostatic collector in the second stage, have been reviewed. Some of these devices were able to increase the mass collection efficiency above 95% for PM2.5 particles. [ABSTRACT FROM AUTHOR]

The structure of the hybrid electrostatic-fabric precipitator (HEFP) is a key factor affecting the overall performance. In this paper, we experimentally study the PM collection efficiency and power consumption of four model HEFPs. Types A and C (abbreviated as COHPAC and AHPC) are two typical structures. Type D incorporates a first-stage ESP with the AHPC. Type B is just used for comparison. We find that in all HEFPs, the penetration of the ultrafine fraction PM 0.2 may increase with the electric field intensity (to ∼0.4% for Type D). Then, it is verified that Type D retains the advantages of AHPC and overcomes the drawbacks. It can meet the strictest emission limit of 2–5 mg/m3 and has the minimum power consumption at optimal voltages. It is demonstrated that the superior performance of Type D exhibited in this work can be inherited by utility-scale HEFPs of the same design after system scaling up. [Display omitted] • Four types of hybrid electrostatic-fabric precipitators (HEFP) are investigated. • Type D has two-stage electric fields to reduce PM loading and particle charge loss. • Type D meets the ultra-low emission limit of 2–5 mg/m3 at the tiniest energy cost. • The advantage of Type D can be inherited by the practical industrial-scale version. [ABSTRACT FROM AUTHOR]

The collection efficiency of lab-scale, two-stage electrostatic precipitator comprising a dual-corona particle precharger and parallel-plate particle collector for the removal of PM 2.5 particles was investigated in this paper. In the precharger stage, particles conveyed by a gas were electrically charged by ionic current in corona discharge, and in the collection stage, the charged particles were removed from the gas by DC electric field between two parallel-plate electrodes. For the same electrode geometry, the precharger can operate as unipolar or bipolar precharger and/or agglomerator, depending on the mode of electrode supply. The collection efficiency of the system was determined for various modes of precharger electrodes supply with DC or AC voltage. The measurements have shown that number collection efficiency for PM 2.5 particles was higher than 80% for the system with dual-corona unipolar precharger supplied with AC voltage and >90% for supply with DC voltage of negative polarity. For the same system, mass collection efficiency was >90% and >96% for PM 2.5 particles when precharger was supplied with AC and DC voltages, respectively. [ABSTRACT FROM AUTHOR]

Lab-scale, two-stage electrostatic precipitation system comprising of precharging stage, in which PM2.5 particles are electrically charged, and collection stage, in which the charged particles are removed from the flowing gas by electric field, was investigated in this paper. Two types of electrostatic particle prechargers were compared with respect to the collection efficiency of the system: (1) co-flow precharger, in which ionic current was generated co-currently with the gas conveying the particles, and (2) counter-flow precharger, in which ionic current was generated oppositely to the flowing gas. In each case, the electrodes of precharger were supplied with DC or AC high-voltage in order to compare the effect of discharge mode on the collection efficiency of two-stage electrostatic precipitator. The collection stage was formed by two parallel-plate electrodes connected to DC high voltage source. Plate electrodes without discharge points (spikes) are corona-free electrodes, which prevent the collection stage from electrical discharges, and reduce the probability of back discharge ignition. The back discharge decreases collection efficiency of conventional electrostatic precipitators. It was concluded that the co-flow electrode configuration of the precharger, supplied with DC high voltage, has the highest total number collection efficiency for PM2.5 particles, higher than 95% and the mass collection efficiency larger than 99%. The counter-flow precharger provided only about 90% number collection efficiency of two-stage electrostatic precipitator. It was also shown that by AC electrode excitation, the collection efficiency of the system is lower than for DC supply. The two-stage electrostatic precipitators allowed obtaining higher fractional collection efficiency for PM2.5 particles than other conventional systems and can be recommended as highly effective devices for gas cleaning in power plants or cement industry. [ABSTRACT FROM AUTHOR]

Air pollution is a topic currently studied to address the well-known health problems that can arise from it. The use of an ESP (electrostatic precipitator) for treatment with submicron particles from sources such as small-scale combustion systems presents some advantages in comparison to other possible devices. In this study, a new ESP prototype geometry based on separating the discharge electrode support from the gas stream path was designed, constructed and tested. The gas stream from a small-size diesel internal combustion engine was used. Good ESP behavior over moderate time periods was verified by achieving average collection efficiencies of 97 ± 4%. TG (Thermogravimetric) and SEM-EDS (Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy) analyses were performed. The influence of the regulation power value and the discharge electrode effective length on the collection efficiency was evaluated. Higher removal efficiencies were linked to higher power values and higher discharge electrode effective lengths. A high impact of the operating time was observed. Different discharge electrode geometries were tested, indicating an increase in collection efficiency as the power increased for stainless steel electrodes and the opposite trend for M12 threaded rod electrodes. [ABSTRACT FROM AUTHOR]

This study analyzed the concentrations and size distributions of ultrafine particles, as well as their chemical components and morphologies, in the context of manufacturing processes, focusing on injection molding and tool repair. The concentrations of water-soluble gases such as sulfur dioxide (SO 2 ), which is an undesirable emission, were measured during the manufacturing process. To remove particles and gaseous pollutants from manufacturing sites simultaneously, we improved the recently introduced electrostatic precipitator (ESP) system, in which wet-porous electrodes (WPEs) are used. The modified novel ESP consisted of an ionization part, for particle charging, and a collection part, installed in the working chamber of a manufacturing facility along with the WPE array to maintain a high-humidity environment using a water bucket. The proposed ESP could be also be coupled with laminar flow modules that are typically mounted in manufacturing facilities and used to maintain a clean environment during working processes. To evaluate the performance of the proposed ESP, the removal efficiencies of airborne particles and SO 2 gas were investigated under operating conditions, with an applied electric field strength in the collection part of the ESP and flow velocities in the working chamber. The collection efficiency of the WPE-ESP was improved by increasing the electric field strength of the collection plates, and the maximum total collection efficiency of the system was ~99.5% for a 13.3 kV/cm collection environment under 0.4 m/s conditions. The proposed system also removed SO 2 at 88.5–92.5% under flow conditions of 0.4–2.0 m/s. Furthermore, this system shows potential for increasing energy efficiency in workplaces due to the extremely low pressure drop. [ABSTRACT FROM AUTHOR]

Electrostatic precipitator (ESP) with a wet membrane collecting electrodes plays an important role in the flue gas cleaning process. In this work, a lab scale ESP model, with a wet membrane collecting electrode, was constructed and investigated. The collection and charging characteristics of particles in the ESP model were studied. In addition, the discharge characteristics and electric power consumption of ESP were also presented. The mechanisms causing higher collection efficiency of this wet membrane-based ESP in the aspect of electrical characteristics were discussed in detail. Compared with the ESP with dry metal collecting electrode, results show that the discharge current of the ESP with wet membranes collecting electrode was higher for the same conditions. The wet membranes electrode had a better effect on the charging process of particles, especially for particles smaller than 1 μm in diameter. The collection efficiency of this ESP is by 3%–5% higher than the dry metal one at an equivalent discharge corona power consumption. [ABSTRACT FROM AUTHOR]

In this paper, a new electrostatic precipitator (ESP) with asymmetrical wire-to-cylinder configuration is investigated experimentally and numerically. The main objective is to evaluate the collection efficiency of high resistivity particles. The electrical measurements show that the corona discharge behavior is similar to that obtained in symmetrical wire-to-cylinder configuration. Results show that the collection efficiency can reach 95% in the case of negative corona discharge. In order to understand the particle trajectories inside the ESP, the experimental results are compared with numerical simulation by using a coupled model. Numerical results indicate that particles can be collected on the collecting electrode backside. [ABSTRACT FROM AUTHOR]

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 1 μm 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 1 μm, while higher ion current value was more effective in achieving higher collection efficiencies for sub-micron particles. [ABSTRACT FROM AUTHOR]

In this paper, the collection efficiency of a plane-to-plane dielectric barrier discharge electrostatic precipitator is investigated experimentally and theoretically using a new model. A parametric study is carried out to evaluate the effects of the applied voltage amplitude and frequency on submicron particles motion and collection within the size range from 0.18 to 0.7 μm. Results show that the amplitude of the particles oscillatory motion increases with the voltage and the particles diameter which increase their collection. The collection efficiency decreases at low frequencies because of the low charge of particles and at high frequencies because of particles fast oscillation. [ABSTRACT FROM AUTHOR]

Electrostatic precipitators (ESPs) with the wet membrane-based collecting electrode play an important role on the flue gas cleaning process. However, the mechanism researches on the excellent collection efficiency of the membrane-based ESPs are insufficient. This paper aims at characterizing the excellent collection efficiency of the ESPs in the aspect of the electrical characteristics. The discharge current density and distribution of the metal and wet membranes collecting electrode were measured using the boundary probe method under different conditions. The differences of the discharge current density and distribution between the wet membranes collecting electrode and the metal one were discussed in detail. In addition, the effects of applied voltage, distance between the electrodes and discharge electrode construction on the difference of the discharge current density between the wet membranes electrode and the metal one were also presented. The results show that the discharge current density is strongly increased by the wet membranes electrode, the increased discharge current density is the main reason for the excellent collection efficiency of the membrane-based WESPs. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this work, a computational model for the simulation of electrostatic precipitators' (ESPs) operation was developed. Special attention has been paid to several parameters that greatly influence the voltage–intensity curve, namely: ion mobility, ion diffusion coefficient and roughness of the electrode. Specifically, a reliable value for ion diffusion coefficient is given. The model proposed takes into account the coupling between gas, electric fields, and particle motion. The model is applied to a 3D geometry and validated against the experimental data reported in the literature. The comparison is made through the V–I characteristic, showing that the computed results reproduce quite faithfully those reported experimentally. Once the model is validated, the theoretical distributions of velocity, electric potential and ionic density are obtained; in addition, the theoretical collection efficiency is obtained as a function of particle diameter. The proposed methodology allows for the complete modeling of ESP and the estimation of their performance and may be a very helpful tool in the development of this type of equipment. [ABSTRACT FROM AUTHOR]

Particle emission (PM) is a large source of air pollution, so that research on this topic for minimizing the well-known health problems is currently developed. Various devices can be employed to remove these particles; however, electrostatic precipitators (ESPs) exhibit advantages when submicron particles must be treated. In this study, a lab-scale tubular type ESP is designed, constructed and tested with the main purpose of broadening the lack of experimental results with this kind of ESP. A series of experiments are performed using a small-size diesel internal combustion engine as the smoke and PM source. A smoke meter and a low-pressure impactor are used as measuring devices. A correlation between opacity and particle concentration is obtained and compared with the literature. The theoretical voltage-intensity (VI) curve of the ESP is compared with experimental values. In addition, the influence of some well-known operative parameters on the VI curves is evaluated (voltage polarity, discharge electrode diameter and humidity) to ascertain their influence. On the other hand, the effect of the discharge electrode temperature and fouling is included in this work. Short test durations and high collection efficiencies are obtained with negative voltages. Finally, an interesting design tip can be extracted; structures linking discharge and collection electrodes should be avoided in the flue gas to prevent unexpected electrical currents due to fouling. [ABSTRACT FROM AUTHOR]

In this study, a numerical model of an electrostatic precipitator (ESP) suitable for high-temperature flue gas was established using COMSOL Multiphysics, and the effects of temperature and H 2 O concentration on the high-temperature ESP performance were studied. The results showed that, at the same voltage, increasing the temperature increased the negative ion density, thereby improving the particle charge and collection efficiency. However, increasing the temperature led to a decrease in the maximum operating voltage of the ESP, which reduced the negative ion density and electric field intensity at the maximum operating voltage and weakened the diffusion and field charges of the particles, leading to a further decrease in the maximum collection efficiency. Increasing the H 2 O concentration in the flue gas increased the negative ion density and, thus, enhanced the diffusion charge of the particles, which helped improve the collection efficiency. [Display omitted] • A modified ESP model suitable for high temperature gas was established. • The plasma model was used to simulate corona discharges in the ESP. • The effect of temperature on ESP performance was studied numerically. • The effect of H 2 O concentration in flue gas on ESP performance was studied. [ABSTRACT FROM AUTHOR]

In this work, magnetic field was introduced to improve the PM2.5 collection efficiency in a wire-plate electrostatic precipitator (ESP). The mathematical model considering multifield coupling and diffusion charging was established, and the effects of magnetic field and diffusion charging on PM2.5 collection efficiency at different gas velocities and working voltages were simulated numerically. The results indicate that both diffusion charging and magnetic field can improve the collection efficiency of the ESP and that the effect of either diffusion charging or magnetic field becomes more obvious under the conditions of low-voltages and high-gas velocities. Furthermore, diffusion charging has a more significant impact on removal efficiency than magnetic field. The combined effect of diffusion charging and magnetic field is better than any individual one. The research results can provide theoretical and technical references for the design of novel ESPs aiming at economy and high efficiency. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 697-702, 2015 [ABSTRACT FROM AUTHOR]

A Computational Fluid Dynamics model is presented to calculate the particle collection efficiency in electrostatic precipitators in terms of the interactions among gas-particle flow, dust resistivity and electric field. Various material properties and operation parameters are included to extend the model capability for process optimization. The current paper focuses on the effect of gas temperature for a cold-side precipitator. It is found that, as temperature increases in the range 90–120 °C considered, the operation voltage drops significantly, due to increased dust resistivity. Behaviors of fine particles in the range from 0.05 to 25 μm in diameter are simulated in a circular wire-plate configuration. A minimum efficiency is predicted for particle size around 0.5 μm. Below this critical size, the increased collection efficiency results from relatively large surface charge density due to diffusion charging, and reduced inter-phase drag. For moist gas, temperature has significant non-linear effect on the fly ash resistivity. It is demonstrated that a same change in temperature from 120 °C to 90 °C is more effective than from 150 °C to 120 °C, as far as the collection efficiency is concerned. [ABSTRACT FROM AUTHOR]

A single-stage, single-wire vertical wet electrostatic precipitator was designed and operated in air–water droplets flow to investigate its performance. The efficiency was compared with a glass micro fiber filter and proposed semi-empirical efficiency model, which was in good accuracy while considering the vapor content. Effects of geometric parameters on efficiency under different charge conditions were discussed. Due to evaporation mechanism, the corona current decreases for high flow rates at the same applied voltage. Findings indicated while developing flow is created inside the ESP, there exists an optimum wire-to-flow inlet spacing that provides maximum droplet collection efficiency. [ABSTRACT FROM AUTHOR]

The PM10 collection efficiency of a wire-cylinder electrostatic precipitator (ESP) was studied by means of a developed mathematical model, including the multi-field coupling between the gas flow field, the particle dynamic field and the electric field, and applying the Deutsch–Anderson Equation. The diffusion charging mechanism was considered due to the diameter range of PM10. The investigated variables were the applied potential, the gas velocity and the particle distribution. Numerical results indicate that the diffusion charging has significant influence on PM10 removal performance and the effect is more obvious with the decreasing diameter, and that the PM10 collection efficiency increases with the increasing applied potential and the increment of collection efficiency is more significant at lower voltage. Moreover, as the gas velocity at inlet decreases, collection efficiency of PM10 will increase. Finally, the overall efficiency increases with increasing the mean diameter of particle distribution. The research results can provide theoretical and technical references for the design of novel ESP aiming at economy and environment protection. [ABSTRACT FROM AUTHOR]

Abstract: The effects of thermophoresis, vapor, and water film on the collection efficiency of wet electrostatic precipitators (wet ESPs) were experimentally investigated. The results showed that the fractional collection efficiency curve on the influence of thermophoresis, vapor, and water film was similar to that of traditional ESPs, which exhibited the minimum value at particle diameters of about 0.5μm. Thermophoresis was beneficial to the collection efficiency of ESPs but the promotion of collection efficiency was not obvious due to the suppression of the ion current caused by lower gas temperature. Vapor significantly improved the collection efficiency of small particles (with diameters smaller than 0.2μm). However, it had little effect on the removal of large particles (those with diameters over 2μm). When water was injected into the wet ESP, water film formed on the surface of the collection electrode greatly improved the collection efficiency of submicron particles and it also promoted the removal of large particles significantly. The effect of the water film on the collection efficiency of wet ESPs was a combined result of thermophoresis, vapor, and water flushing. [Copyright &y& Elsevier]

A compact electrostatic nanoparticle sampler has been developed to support the offline analysis of nanoparticles via electron microscopy. The basic operational principle of the sampler is to electrically charge particles by mixing nanoparticles and unipolar ions produced by DC corona discharge, and electrostatically collecting charged particles. A parametric study was first performed to identify the optimal operating condition of the sampler: a total flow rate (i.e., the sum of the particle and ion carrier flow rates) of 1.0 lpm, an aerosol/ion carrier flow rate ratio of 1.0, and a collection voltage of 4.5 kV. Under the above condition, the sampler achieved a collection efficiency of more than 90 % for particles ranging from 50 to 500 nm. The effect of particle material on the sampler's performance was also studied. The prototype had lower collection efficiencies for oleic acid particles than for sodium chloride particles in the size range from 50 to 150 nm, while achieving a comparable efficiency in the size range large than 150 nm. Effects of particle diameter, particle material, and total flow rate on the sampler's collection efficiency are explained by the particle charging data, i.e., charging efficiencies and average charges per particle. [ABSTRACT FROM AUTHOR]

Abstract: Recently, narrow electrostatic precipitators (ESPs) have become a subject of interest because of their possible application for the cleaning of the exhaust gases emitted by diesel engines. Diesel engines emit fine particles, which are harmful to human and animal health. There are several methods for decrease particulate emission from a diesel engines, but up to now, these methods are not enough effective or very expensive. Therefore, an electrostatic precipitation was proposed as an alternative method for control of a diesel particulate emission. In this work, results of electrohydrodynamic (EHD) secondary flow and particle collection efficiency measurements in a narrow wire-cylinder type ESP are presented. The ESP was a glass cylinder (300 mm × 29 mm) equipped with a wire discharge electrode and two collecting cylinder-electrodes. A 0.23 mm in diameter and 100 mm long stainless-steel discharge wire electrode was mounted in the center of the cylinder, parallel to the main flow direction. The collecting electrodes were made of stainless steel cylinders, each with a length of 100 mm and inner diameter of 25.5 mm. An air flow seeded with a cigarette smoke was blown along the ESP duct with an average velocity of 0.9 m/s. The EHD secondary flow was measured using 2-dimensional particle image velocimetry (PIV) method. The PIV measurements were carried out in the wire electrode mid-plane, perpendicularly to the wire and the collecting electrodes. The results show similarities and differences of the particle flow in the wire-cylinder type ESP for a negative and a positive DC voltage polarity. The collection efficiency was calculated from the fractional particle concentration. The fractional particle concentration was measured using the optical aerosol spectrometer. The results of the fractional collection efficiency confirmed the common view that the collection efficiency of fine particles in the ESP increases with increasing voltage and it is higher for negative voltage polarity and decreases when decreasing particle diameter. [Copyright &y& Elsevier]

Abstract: This paper presents comparative experimental studies of the morphology and elemental composition of fly ash particles from coal- and biomass-fired boilers, deposited in each stage of 3-stage electrostatic precipitators (ESPs). It was shown that fly ash morphology, its physical properties, and the percentage of elements in the fly ash taken from each stage of ESP depend on the kind of fuel. The biomass fly ash contains many irregular large particles, which are pieces of unburned wood. Bulk density of biomass fly ash is on average lower than that of coal fly ash, and drastically decreases in the second and third stages of ESP. The resistivity, measured at electric field of 4 kV/cm, of fly ash from biomass-fired boilers is much lower than that from coal, and can be below 102 Ω m, whereas from coal, except the first stage, varies in the range from 107 to 1010 Ω m. The low resistivity of coal fly ash in the first stage of ESP results from high carbon content, and of biomass is probably an effect of additional high percentage of potassium, calcium and sodium sulfates. The percentage of Si, Al, Na, Fe, and Ti in fly ash from coal-fired boilers is much higher than from biomass, and in the opposite, the percentage of Mg, K, Ca, Mn, Mo, S, Cl, and P in biomass ash exceeds that in coal fly ash. Potential detrimental effects of biomass combustion products (salts, acids, tar) leaving the boiler on the construction elements of the electrostatic precipitator, including electrodes and HV insulators have been discussed in this paper. It was concluded that the long-term effects of biomass co-firing on the electrostatic precipitator performance, including the collection efficiency, have not been sufficiently studied in the literature and these issues require further detailed investigations. [Copyright &y& Elsevier]

Abstract: Electrostatic precipitators (ESPs) have been widely used for air purification applications as they have no degradation issues and do not need to be replaced periodically. However, the generation of ozone by ESPs has been regarded as one of their most serious drawbacks. This paper presents the development of an ozone emission free ESP comprising a carbon brush ionizer and a polymeric arrayed collector (PAC). The collector consisted of sixty layers, where each layer had three stratums: polyethylene terephthalate (PET) film, conductive ink (CI), and PET film. The performance of the ESP was evaluated for three CI resistance levels: 107, 1010, and 1013 Ω/m2. The ESP was evaluated for particle filtration efficiency in a wind tunnel with a 0.3μm challenge aerosol for an applied voltage ranging from 3 to 9kV. The clean air delivery rate (CADR) was evaluated by coupling the ESP to a commercial air purifier to deliver purified air to a controlled 30-m 3 chamber in which particle concentration and ozone monitoring instruments were placed. Single pass ESP efficiency peaked at 89.5% for a high voltage (9kV), high resistance (1013 Ω/m2), and low face velocity (1m/s). The CADR for the ESP was 1.2 times higher than that for a standard high efficiency particulate air filter, with no ozone generation in a 24-h test. Thus, the proposed PAC-based ESP provides a viable solution for an ozone-free ESP, one that retains the benefits while eliminating the risk. [Copyright &y& Elsevier]

In this paper, a numerical simulation was carried out to analyze the effect of diffusion charging on collection efficiency of a wire-plate electrostatic precipitator (ESP). The gas flow field, the electric field, and the particle field with diffusion charging considered were included in the numerical model, which was implemented by using the commercial FLUENT software. Collection efficiency was calculated by using the Deutsch–Anderson equation, in which the parameters were provided from the numerical solutions. The simulated results indicate that the effect of diffusion charging on the wire-plate ESP particle collection increases with the decreasing particle diameter, as well as applied potential, particularly for PM10. Moreover, with the increasing applied potential, collection efficiency of PM10 is obviously improved, and the effect extent first increases and then decreases with particle size increasing, but also, the size range of particle, which is significantly affected by the diffusion charging, becomes smaller. As gas velocity becomes higher, the effect of diffusion charging on grade efficiency also becomes more obvious, and the affected range of particle size gets much larger, however, at the price of grade efficiency decreasing. Using collection efficiency as reference variable of judgment, instead of particle charge, may lead to a more accurate estimation of the aforementioned size range, which can provide a great help in the further analysis of fine particle collection. [ABSTRACT FROM PUBLISHER]

Abstract: In this paper, the technique of electrostatic precipitation was used to remove excess ions from a mixture with charged particles before collection on a filter in a Faraday cup electrometer of an electrical aerosol detector. The ion precipitator part of the detector was designed, constructed, and evaluated. An analytical model was developed to investigate ion and particle transports due to diffusion and space charge effects inside the ion precipitator. Experimental investigations were carried out for positive ions, the positively applied voltage at the wire electrode ranged from 10 to 150 V, ion flow rates ranged from 5 to 15 L/min, and the radial distance of the inlet was 0.15 and 14 mm at a fixed separation between the wire and outer electrodes. The calculation results showed that all charged particles of 10 nm in diameter could pass through the ion precipitator smoothly without precipitation at the outer electrode. For all ion flow rates, an increase in ion trap voltage produced an increase in ion collection efficiency of the precipitator. Experiments confirmed that the efficiency of the ion precipitator could increase to 99% at an ion trap voltage larger than 100 V for all ion flow rates. [Copyright &y& Elsevier]

This paper describes a strongly coupled calculation procedure for the particle dynamics in electrostatic precipitators (ESP) subjected to the applied magnetic field with the statistical particle size distribution taken into account. The turbulent gas flow and the particle motion under external forces are modeled by using the commercial computational fluid dynamics (CFD) code FLUENT. Numerical calculations for the gas flow are carried out by solving the Reynolds-averaged Navier-Stokes equations and turbulence is modeled using the k - ℇ turbulence model. An additional source term, which is obtained by solving a coupled system of the electromagnetic field and charge transport equations, is added to the gas flow equation to capture the effect of electromagnetic field. Discrete Phase Model (DPM) is employed to achieve the simulation of the particle phase. Different kinds of particles which follow Rosin-Rammler distribution were simulated under different conditions, and the influence of magnetic field density on the capture of fine particle was investigated. In order to show the dust removal effect, the collection efficiency and the escaped particle size distribution were discussed in case of different applied magnetic fields. The particles trajectories inside the ESP were also given under the effects of both aerodynamic and electromagnetic forces. Numerical results indicate that the collection efficiency increases with the increase of applied magnetic field, that the particles trajectory are more visible to the direction of dust collection plate, and that the collection efficiency varies smoothly when the applied magnetic field is up to a certain value. Furthermore, the average diameter of escaping particles decreases and the dispersion for dust particles in different size increases with applied magnetic field increasing, and particle sizes is linearly decreasing with magnetic field before the particle reaches a certain size. [ABSTRACT FROM AUTHOR]

We recently developed an electrostatic precipitator with superhydrophobic surface (EPSS), which collects particles into a 10- to 40-µl water droplet allowing achievement of very high concentration rates (defined as the ratio of particle concentration in the collection liquid vs. the airborne particle concentration per time unit) when sampling airborne bacteria. Here, we analyzed the performance of this sampler when collecting three commonly found fungal spores -- Cladosporium cladosporioides, Penicillium melinii, and Aspergillus versicolor -- under different operating conditions. We also adapted adenosine triphosphate (ATP)-based bioluminescence for the analysis of collection efficiency and the concentration rates. The collection efficiency ranged from 10 to 36% at a sampling flow rate of 10 l/min when the airborne fungal spore concentration was approximately 105--106 spores/m³ resulting in concentration rates in the range of 1 x 105--3 x 105/min for a 10-µl droplet. The collection efficiency was inversely proportional to the airborne spore concentration and it increased to above 60% for common ambient spore concentrations, e.g., 104-- 105 spores/m³. The spore concentrations determined by the ATP-based method were not statistically different from those determined by microscopy and allowed us to analyze spore concentrations that were too low to be reliably detected by microscopy. [ABSTRACT FROM AUTHOR]

In this paper, particle velocity fields inside three electrostatic precipitators (ESPs) are investigated experimentally using particle image velocimetry (PIV). The reference case is a typical wire-to-plane ESP under negative and positive dc high voltages. The two other ESPs use an ac high voltage to generate a dielectric barrier discharge (DBD) in wire-to-plane and plane-to-plane configurations. The main objective of this paper is to analyze the effect of the ionic wind on the particle collection efficiency in such systems. The high voltage magnitude and the frequency are the major parameters taken into account. With the wire-to-plane ESPs, PIV results show a strong interaction between the primary flow and the secondary flow (ionic wind). Near the wire electrode, the strong electric forces move the particles from the central part of the channel to the plate electrodes. Within the drift region, the velocity magnitude depends essentially on the balance between the electric and viscous forces. With this configuration, the particle trajectory is 3-D. In the case of the plane-to-plane ESP, a 2-D analysis of the time-averaged flow can be accepted. The time-averaged flow is only modified in the boundary layer, which becomes thinner. The time-averaged effect of the ionic wind on the primary flow in such a configuration is negligible. The correlation between the electrohydrodynamic flow and the collection efficiency shows that increasing the ionic wind magnitude did not improve necessarily the electrostatic precipitation effectiveness of submicrometer particles, particularly using DBD precipitators. [ABSTRACT FROM AUTHOR]

The goal of experimental investigations shown in this paper is to estimate the operating efficiency degree of the electrostatic precipitator on a real industrial plant (a the thermal power plant „Gacko“ with the electric power of 310 MW, Bosnia & Herzegovina) and to use the obtained results as a base of periodical engineering or continual measurement and compare them with the investigations of other investigators. The investigation of the electrostatic precipitator performance was done according to BAS ISO 9096:2003. In this paper, the electrostatic precipitator efficiency during the ash particle removal with a wide range of particle sizes from 1 to 250 μm is evaluated. The exploitational experience points out that electrostatic precipitators are efficient for the coals of different quality (coal particles with diameters bigger than 1 μm) and that they could be optimized during the exploitation itself and for some following processes (e.g., flue gas desulphurization). Within the measurement plane, the measurements were made on 20 points per section. It has been noticed that ash removal degrees obtained experimentally (3 investigations) have approximately equal value (95.93 to 97.78%). The best concordance with the results of experimental investigation shows the Deutsch equation, while theoretical models of Zhibin-Guoquan and Nobrega-Falaguasta-Coury do not correspond well to the results of experimental investigations. For the ash particles with the diameters less than 17.5 μm there is no good correlation between investigated theoretical models. The highest deviation of the model for ash particles with diameters less than 17.5 μm is notable in the case of using the Deutsch equation. [ABSTRACT FROM AUTHOR]

Abstract: Electrostatic precipitator (ESP) is a major dust collection device used in pulverized coal combustion boilers in Japan. Although the collection efficiency of ESP is over 99%, the performance of ESP is affected by dust properties, especially the electric resistivity of the dust. In Japan, many different kinds of coal are used in pulverized coal combustion boilers. The property of coal ash formed in pulverized coal combustion is different for different coals. It is very important to develop high performance ESPs for different kinds of coal ash. In general, the low temperature ESP operated at about 423K has been used for a long time, but the electric resistivity of some kinds of coal ash is higher than suitable for the ESP in this temperature range. A high temperature ESP operated at 623K was developed about 20years ago and an advanced low temperature ESP operated at 373K has been used recently for control of the electric resistivity of coal ash. In this paper, we report on the influence of operating temperature from 363K to 623K on performance of ESP for a pulverized coal combustion boiler. The influence of coal ash properties including electric resistivity, alkali metal concentration, and operating condition on collection efficiency of an ESP is estimated. [ABSTRACT FROM AUTHOR]

The influence of electrode thickness on ozone generation in an electrostatic precipitator (ESP) was experimentally investigated. The experimental ESP was a two-stage-type consisting of a precharger followed by the collecting section. The precharger consisted of high-voltage electrodes and grounded electrodes. The thickness of the high-voltage electrodes was selected as 0.1, 0.2, 0.5, and 0.8 mm and that of the grounded electrodes was 1.0 mm. The collecting electrode section had a parallel-plate configuration. The gases emitted from the diesel engine were diluted with air and introduced into the ESP in order to measure the particle counts. In the present study, the electric field distribution was calculated using the “Ansys” software. The relationship between ozone generation and collection efficiency was investigated. The ozone concentration was found to decrease with decreasing electrode thickness, while the same collection efficiency was maintained. This result was attributed to a decrease in the dissociation area of O2 in the vicinity of the electrodes. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(7): 24–31, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10291 [ABSTRACT FROM AUTHOR]

A novel wet electrostatic precipitator is designed for control of fine aerosol from humid effluent gases. It operates on the principle of unipolar particle charging in a dc corona discharge in a high-velocity (> 20 m/s) ionizing stage and aerosol precipitation in the low-velocity (< 3 m/s) collection stage under the field of the particle's own space charge. The high gas velocity in the ionizing section diminishes the corona suppression at high particle number concentrations of H2SO4 and HCl aerosol. [ABSTRACT FROM AUTHOR]

The aim of the present work has been to quantify the efficiency of Dielectric Barrier Discharges (DBDs) for the collection of submicron particles. The experiments were performed with incense smoke particles having a mean size of about 0.3 μm. An aerosol spectrometer was employed for characterizing the size distribution of these particles at the outlet of Wire-to-Cylinder (WC) and Plate-to-Plate (PP) DBD reactors. The collection efficiency was estimated for various applied voltages (6 - 26 kV, 1 - 2000 Hz), and airflow rates of 1.6 - 24 L/min. The discharge mode was diffuse, in the case of the axisymmetric configuration, and filamentary, in the case of the planar configuration. When flow rate increases, the discharge current and the electric power decrease in both cases. This effect is less pronounced with the planar configuration. Results obtained with the aerosol spectrometer show that the particle collection efficiency of both reactors is higher at high applied voltage and low flow rate; it decreases at high frequency because of particle oscillations, and at low frequency due to the intermittent nature of the discharge. The frequency range for which the collection efficiency is higher than 90% is wider in the case of WC reactor. [ABSTRACT FROM AUTHOR]

The electrostatic precipitator (ESP) technique is a promising method for enhancing the particulate matter (PM) emission reduction efficiency of diesel engines, and is much better than the diesel particulate filter (DPF) technique. However, the ESP''s low efficiency in collecting PM with diameters less than several tens of nanometers remains a problem because the particle charging efficiency decreases as the size of the nanoparticles decreases. To improve the collection efficiency of nanosized PM, we used a photoelectric charger to increase the charging efficiency of nanoparticles ahead of the ESP system. Carbon nanoparticles produced using a spark discharge generator were used to evaluate the collection efficiency of the combined photoelectric charger and ESP system. The particle sizes were measured using a scanning mobility particle sizer system at various experimental temperatures similar to the temperature of DPF systems commonly used in diesel engines. We succeeded in obtaining improved collection efficiencies at increased inner temperatures of the photoelectric charging chamber. As the temperature increased from 694 °C to 839 °C at the inlet of the photoelectric chamber, the efficiency of PM collection improved significantly to 28.5% for a particle diameter of 18.4 nm. [Copyright &y& Elsevier]