Study on Water Spraying System in Wet Electrostatic Precipitator

To prevent fouling in blast furnace gas top pressure recovery turbine units, the dust content of the gas must be reduced, necessitating its deep purification. A critical challenge to be addressed is the low collection efficiency of fine particulate matter. To improve the collection efficiency of the fine particulate dust in BFG by wet electrostatic precipitators (WESPs), this study implemented measures such as optimizing nozzle atomization performance and the spatial distribution of droplets, along with adding chemical agglomeration agents and surfactants. These approaches promoted the chemical agglomeration of fine dust and enhanced dust collection efficiency. In this study, five nozzle types, six chemical agglomerating agents, and three surfactants were tested. The results show that, under overlapping spray conditions, the 1/8 solid cone nozzle produced the smallest droplet size with the most uniform spatial distribution, exhibiting a d50 of 141.17 μm. When this nozzle was used in combination with guar gum (GG) as a chemical agglomerant, the d50 of BFG dust increased from 8.46 μm to 14.75 μm. The synergistic application of 5 mg/m3 sesbania gum (SBG) and 5 mg/m3 octylphenol ethoxylate (OP-10) further increased the dust d50 to 19.08 μm. Using the 1/8 solid cone nozzle and an XTG concentration of 5 mg/m3 resulted in the highest dust collection efficiency of 96.76%, while the synergistic use of SBG/OP-10 achieved an efficiency of 97.69%. This study elucidates the influence of nozzle atomization characteristics and spray liquid type on dust agglomeration and collection efficiency, achieving an improvement in dust-removal efficiency and the capture of fine-particulate dust, and providing both theoretical and practical foundations for the deep purification of blast furnace gas.

In this study, two different dust collectors, one based on an inertial separator and the other based on an electrostatic precipitator (ESP), were developed in order to reduce brake wear particulate matter (PM) emissions. Additionally, the collection efficiencies for brake wear particles (BWPs) of the inertial separator and the ESP were evaluated according to brake pad type. In the case of the inertial separator, the BWP collection efficiencies for the low-metallic (LM) and non-asbestos organic (NAO) pads were similar, and the cut-off size at 50% collection efficiency (D50) was 2.2 µm. The ESP was designed without an additional electrostatic charging device because naturally induced electrostatic charging occurred due to the friction between the brake disc and pad. The BWP collection efficiency of the ESP was higher for NAO pad than for LM pad because the BWPs generated from the NAO pad contained a relatively low iron (Fe) component compared to that of the LM pad, thereby generating more frictional electricity. The maximum ESP collection efficiencies of the BWPs generated from the LM and NAO pads were determined to be 60% and 75%, respectively, and the remaining BWPs that were not collected were presumed to be particles that were not frictionally charged.

The model of a traditional vortex apparatus in a program complex is constructed and constructive changes of such apparatuses are proposed. The adequacy of the constructed model in comparison with the existing traditional vortex apparatus is evaluated. The conclusion about the important influence of the design solution on the efficiency of dust collection is made. It is revealed that due to insignificant changes in the angle of inclination of the gas stream inlet, there is an increase in the fractional efficiency, approximately by 4–7 %.

The production of solid recovered fuel (SRF) from sewage sludge has been credited with facilitating Korea’s waste management shift toward a resource circular economy. In this study, a novel pilot-scale wet electrostatic precipitator (WESP) was developed and installed in a bio-drying-assisted solid recovered fuel (SRF) generation plant for the first time. To investigate the performance of the novel WESP, various sizes of particulate matter, i.e., total particle matter (PM), particle matter smaller than 10 μm (PM10), and particle matter smaller than 0.1 μm (PM0.1), collection efficiencies were evaluated and demonstrated promising performances. Under optimal operating conditions (flow rate of 5 m3/min and an applied voltage of 30 kV), 99.76% PM and 91% PM10 collection efficiencies were achieved, and the PM concentration was 0.16 mg/m3, which met the exhaust emission standard. However, a dramatic increase in PM0.1 was observed and could be explained by the break-up theory, binary homogenous nucleation, and ion-induced nucleation. The experimental findings could serve as useful information to understand the WESP system.

The fine particles are considered a significant environmental pollution problem. The wet electrostatic precipitators (ESPs) are now used most widely among the advanced fine particle removal technologies. The rigid glass fiber reinforced plastics (FRP) collectors modified with hole-slotted structures were used to enhance the water film distribution over their surfaces. This paper experimentally investigated the effects of the hole-slot patterns and the operating parameters on the particle removal performance in wet ESPs using the hole-slot-structured collector. The voltage-current characteristics and the energy consumption among the different pattern collectors were discussed. Besides, the effects of the water film on the particle number concentration classification and the effects of the applied voltage and the specific collecting electrode areas (SCA) on the relative collection efficiency (RCE) were investigated and discussed. The experiment results show that the corona current of three hole-slot structured FRP collectors was higher than that of the conventional rigid collectors (CRC) at the same voltage. Using the FRP collectors with circular holes and horizontal slots could decrease the energy consumption and using the FRP collectors with vertical slots increases the energy consumption compared with the CRC when the collection efficiency was lower than 92.5%. The water film could increase the collection efficiency of the fine particles and prevent the fine particles cross through the holes and the slots. The hole-slot-structured FRP collectors were appropriate for the working conditions of high SCA and long residence time. When the water film in the hole and slotted structures was incomplete, the fine particles could pass through the collector plate to form secondary back-mixing. Implications: The wet ESPs are used most widely among the advanced treatment technologies of the fine particles’ removal. The rigid glass fiber reinforced plastics (FRP) collectors modified with hole-slotted structures were used to enhance the water film distribution over their surfaces. The hole-slot-structured FRP collectors were appropriate for the working conditions of high SCA and long residence time. When the water film in the hole and slotted structures was incomplete, the fine particles could pass through the collector plate to form secondary back-mixing.

The collection of low resistive particles from diesel engine emission is difficult by the conventional electrostatic precipitators (ESPs). The low resistive diesel engine particles are detached from the collection plate, which causes the dust reentrainment, resulting in poor collection efficiency. The new electrohydrodynamically (EHD) assisted ESP (EHD ESP) was developed to minimize reentrainment. The EHD ESP utilizes the ionic wind, combined with electrostatic force to transport the charged particles into the pocket zone attached to the collection plate effectively. The pocket zones are designed as zero electrostatic field, i.e., no electrostatic repulsion force acting on particles, so that no reentrainment takes place. The electrode position was designed to achieve an optimum electrode location with respect to pocket position, which was determined by observing EHD streamlines and particle collection efficiency. The particle size dependent collection efficiency was obtained using scanning mobility particle sizer (SMPS).

Current trends observed in air pollution control technology are closely related to the development of new, more efficient hybrid systems, i.e., those, which simultaneously utilize two or more physical mechanisms for dust or gaseous contaminants removal. These systems can operate more economically than conventional devices, especially in the removal of PM2.5 particles. The electrostatic scrubber (electroscrubber), discussed in this paper, is one of such types of devices, which combines advantages of electrostatic precipitators and inertial wet scrubbers, and removes many shortcomings inherent to both of these systems operating independently. The electroscrubber is a device in which Coulomb attraction or repulsion forces between electrically charged scrubbing droplets (collector) and dust particles are utilized for the removal of particles from a gas. Unlike wet electrostatic precipitators in which particles are precipitated only on the collection electrode, in electroscrubbers, the collection of dust particles takes place in the entire precipitator chamber. Compared to inertial scrubbers, the electroscrubbers can operate at lower droplet velocities, but the collection efficiency for a single droplet can be larger than 1. The paper reviews the state-of-the-art of wet electrostatic scrubbing (electroscrubbing) technique used for gas cleaning from dust or smoke particles. Three groups of problems are discussed: (1) The fundamental problems concerning the charged dust particle deposition on a charged collector, usually a drop, with a focus on different models describing the process. (2) The experimental works of fundamental importance to our knowledge referring to the scrubbing process, which can be used for validating the theory. (3) The laboratory demonstrations and industrial tests of different constructions of electroscrubbers designed for effective gas cleaning. The electroscrubber is not designed to replace wet or dry electrostatic precipitators but can be used as a complementary device following the last stage of conventional electrostatic precipitator, which helps to remove submicron particles. It was shown in the paper that a higher collection efficiency of an electroscrubber could be obtained for higher values of Coulomb number (i.e., higher electric charges on the collector and particle), and for a Stokes number lower than5 (i.e., low particle-collector relative velocity).

The collection efficiency of many electrostatic precipitators (ESPs) must be improved in order to fulfill the particulate emission standard, which has become increasingly rigorous. According to classical collection theory, decreasing the gas velocity for an electric field is one of the most effective methods of enhancing the collection efficiency. Thus, we proposed a side-flow ESP, which, compared to its conventional counterpart, requires a far lower gas velocity for the electric field when the gas flow rate is constant. First, using aerodynamics, a theoretical expression of the collection efficiency and dust re-entrainment lift force was derived for a turbulent flow. The calculations indicated that a greater increase in efficiency was achieved by decreasing the gas velocity, which potentially reduces dust re-entrainment, than by lengthening the electric field. To confirm the advantages of the side-flow ESP, the collection efficiency and dust re-entrainment were measured in comparison experiments with a conventional ESP, in which talc powder with a medium diameter of 11.6 µm was used as the test dust. The dust concentration at the inlet averaged ~1400 mg m–3, and the strength of the electric field ranged approximately from 3 to 4 kV cm–1. The experimental results indicated that the emitted concentration and the dust re-entrainment were 45% and 42% lower, respectively, for the side-flow ESP than for the conventional ESP at the same gas flow rate.

This paper explores the collection efficiency of Electrostatic precipitator (ESP) of a laboratory scale model which is geometrically similar to the industrial ESP of a local coal based power station. The variable fly ash velocity is used to determine the collection efficiency of an ESP. The applied voltage and current are being kept constant during different field test. Moreover a test run will be conduct to see the collection efficiency without applying high voltage. The experimental result shows that ESP collection efficiency is higher at lower fly ash velocity and suddenly decreases after a range of velocity. To confirm the validity of collection efficiency a mathematical model has been built and verified with experimental data. In addition, a test run is conducted without the high voltage (HV) supply to see the ability of capturing fly ash particles by keeping all other parameter same. The peak efficiency of ESP found in this experiment is 99.87%.

Forward ultra-low emission for power plants via wet electrostatic precipitators and newly developed demisters: Filterable and condensable particulate matters

ABSTRACTThe fine particles are considered a significant pollution problem. The wet electrostatic precipitators (ESPs) have advantages of efficient collection of the fine particles with lower pressure drop and eliminating reentrainment. The wetting properties of the collector surfaces have significantly important effect on wet ESPs’ stable and secure operation. The modified rigid collector (MRC) was modified by coating specific vinyl ester resin composites and loose glass fiber cloth over the conventional carbon steel in a certain way. The rigid collector surfaces before and after modification had been characterized by scanning electron microscopy (SEM) and interface tensiometer. The effect of operating temperatures on the wetting properties of the rigid collector surfaces before and after modification was investigated. The temperature range was 40~90 °C, and the wetting properties contained liquid holdup, surface flow rate, film rate, average film thickness, and critical saturation time. The modified rigid collector surface exhibited excellent wetting properties at the operating temperatures. The fine particles collection performance compared among the MRC, the conventional rigid collector (CRC), and the flexible collector (FC) in the wet ESPs was investigated. The effects of the applied voltage, the water film, corona power, and the specific collecting area on the fine particles collection were evaluated. The modified rigid collector provided high fine particles collection effect with lower energy and water consumption.Implications: To improve the submicron particles collection efficiency and decrease energy and water consumption, the formation of uniform water film over the collector surfaces has been widely studied. The modified rigid collector was modified by coating specific vinyl ester resin composites and loose glass fiber cloth (ERGF) over the conventional carbon steel (CCS) in a certain way. The modified rigid collector surface exhibited excellent wetting properties. The wet ESPs by the modified rigid collector exhibited significantly higher particles collection efficiency than by the conventional rigid collector.

One of the electrostatic precipitator (ESP) applications is the cleaning in superhighway tunnels. In superhighway tunnels, contaminants in the air are carbon particles, NO/sub x/ etc. The ESP consists of the precharger and collecting section. The ESP can little remove NO/sub x/, when corona discharge is used as a precharger. The autors suggest a barrier discharge-type precharger instead of corona discharge. In this work, experiments were carried out using small two-stage type ESP with barrier discharge. As a result, it was shown that the particle collection efficiency and NO/sub x/ removal rate were high in barrier discharge type ESP.

Average iron content in industrial ores decreases from year to year. To use them in the processes of agglomeration and pelletizing, enrichment is necessary, accompanied by abundant emission of dust. A significant amount of iron is lost in tailings at existing magnetic enrichment technologies. Therefore, the development and implementation of new generation cyclone facilities to increase the efficiency of iron ore beneficiation and dust collection during its processing is an urgent scientific, practical and social task. The results of the of new generation cyclone facilities implementation for enrichment of iron ore and dust collection during its processing at the mining and processing factories of Kryvbas (Ukraine) are presented. It has been established that dry magnetic separation of finely crushed ore makes it possible to isolate a magnetic product with an iron content of 64-65%. The yield is up to 45%, the extraction of iron into the magnetic product is 73-75% in two-stage schemes. The degree of dust collection by the new generation cyclone facility is exponentially dependent on the speed of the cleaned flow, number and size of coaxial shells, as well as the diameter of dust particles) and is 1.23 times higher comparing with the previously used cyclone of the same size and capacity. The mobile magnetic field in the recommended cyclone allows to capture magnetic dust with an efficiency of up to 95%, and at the same time the dust is separated into a magnetic component (with an iron content of up to 65%) and a non-magnetic component (up to 12% of Fe) with an initial total iron content of up to 33%.

In order to reduce air pollution caused by fine dust, the emission standards for environmental pollutants generated from ships are being strengthened. The fine dust reduction device for ships needs a function that can be used in combination with SCR(Selective Catalytic Reduction) due to the limited space of the engine room. In this study, gas flow analysis was performed to predict the dust collection efficiency of the electrostatic precipitator to develop the electrostatic precipitator with low back pressure for 300 kW class of marine diesel engine. In order to analyze the dust collection efficiency according to the shape of the electrode and collecting plate, the gas flow was analyzed by modeling the three shapes, and the theoretical dust collecting efficiency was calculated for the three models. Based on the results of gas flow analysis, the dust collecting efficiency of the semicircular designed the electrode and collecting plate was found to be the highest. In the future, the gas flow analysis results of this study will be used to develop the semicircular electrode and collecting plate as well as to improve the dust collection efficiency of the electrostatic precipitator.

In this paper, a numerical model was developed to describe the wire-plate electrostatic precipitator, commonly called electronic air cleaners. Electrostatic precipitator have been widely used to control particulate pollutants, which adversely affect human health. In this model, the complex interactions between fluid dynamics, electric fields and particle dynamics are considered. Therefore different approach methods are used in this study for each field, Eulerian reference frame was used for the fluid flow field and the electric field, Lagrangian reference frame used for the particles trajectories. 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 (2010). The most important concept in electrostatic precipitator is the electric force applied to particles through the particle charging phenomena. The charge acquired by the particle in the corona region was obtained by combining the field charge, the diffusion charge and the time available for charging being the residence time of the particle in the corona region. In order to simulate more accurately, the charging model suggested by Lawless (1996) is used for the charging phenomena of particles by corona discharge because this model was designed to predict combination effect of diffusion charge and field charge. The diminution of particle concentration along the collection plate was derived from Deutsch’s theory, and migration velocity of the particle was developed from the condition that the magnitude of Coulomb force is equal to that of Stoke’s resistance force. This model is implemented by UDF in commercial software Fluent and validated with experimental and numerical results from literatures. CFD results had been compared with various experimental data obtained by Penney&Matick, Parasram and Kihm. Our results shows good agreement in terms of distributions of electric potential, current density, electrohydrodynamic flow pattern, and particle trajectories as well as corona current and collection efficiency. From this simulation, the effect of wire arrangement on electrostatic precipitator characteristics and particle charging are investigated. Both inline and staggered arrangements of wire electrode have been considered for fixed values of gas velocity equal to 2m/s. Applied voltage on wire electrode varies 6∼13kV and particle diameter is 4μm. For low voltage condition, staggered arrangement of wire electrode caused the turbulent effect so that collection efficiency increase more than inline arrangement. However, collection efficiency decrease in high voltage condition because electric force applied on particles passing between the wire electrodes is canceled out by both side wire electrodes.