Efficiency Of Electrostatic Precipitator Research Articles

Effect of selective catalytic reduction denitrification on fine particulate matter emission characteristics

Selective catalytic reduction (SCR) may affect the emission characteristics of fine particulate matter due to NH3 slip during denitrification. In this study, an experimental facility equipped with a coal-fired boiler, SCR unit, electrostatic precipitator (ESP), and wet flue gas desulfurization (WFGD) unit was adopted to investigate the effect of SCR on final fine particulate matter emission characteristics. The migration and transformation of the generated ammonium sulfates and NH3 slip in the downstream ESP and WFGD were also investigated. The results indicate that SCR can increase the final emissions of submicron particles due to the formation of (NH4)2SO4 and NH4HSO4 aerosols. In the ESP system, the generated ammonium sulfate particles can be effectively captured by the electric field force, which can also improve the capture efficiency of ESP on fine particles. Nonetheless, the operation of SCR with an NH3 injection still leads to an increase in fine particle emission levels at the ESP outlet. In the WFGD system, ammonium sulfates and ammonia can be partly removed by desulfurization through slurry scrubbing. However, the accumulated NH4+ in slurry will generate new ammonium species and ammonia through the entrainment and evaporation of the slurry. Finally, although both ESP and WFGD have a good removal effect on the generated fine particles, the SCR operation with the NH3 slip still results in an increase in the emission of fine particles and NH4+. As the formation and transformation mechanism of ammonia slip and ammonium sulfates generated by SCR is complex and affected by many factors, further research will be required.

Effects of coal blending in electrostatic precipitation efficiency—Inner Mongolia, China

Based on this study, the Al2O3 content of Jungar coal ash is over 45%, and the resistivity of high-Al2O3 ash in Jungar reaches up to 1012Ω​·cm. These results seriously influenced the electric characteristics of fly ash, and the collection efficiency of electrostatic precipitators (ESPs) evidently decreased. To facilitate the effective collection of fine particle in the flue gas generated before and after coal blending via ESP, the fly ash obtained from a power plant electrostatic precipitation was analyzed in terms of resistivity, size distribution, and cohesive force through a portable dust electrical resistivity test instrument, Bahco centrifuge, and a cohesive force test apparatus invented by the researchers. The mixed ratio of else coal is higher than 50%, the resistivity of the fly ash in the flue gas was lowered to approximately two orders of magnitude, and the size distribution showed an evident decrease in the PM2.5 and PM10 content in fly ash. In addition, the adhesive force and efficiency increase from 95.9 to 99.5% in the electrostatic precipitation. Therefore, the combustion of blending coal is an effective approach to improve the efficiency of ESP used to collect high-Al2O3 fly ash.

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.

Experimental and analytical study on the performance of novel design of efficient two‐stage electrostatic precipitator

This study presents a novel design of high-efficiency two-stage electrostatic precipitator (ESP). For its design, different electrode configurations were tested and the corresponding onset and breakdown voltages were measured and compared. Based on findings, an optimal arrangement was then defined and a novel design of a two-stage ESP prototype, using needle electrodes instead of long wires utilised in conventional ESPs, is realised. For comparison, a single-stage ESP was also built. The influence of various parameters on the performances of both two-stage and single-stage ESPs was evaluated numerically using 2D modelling and compared with the experimental ones for the same dimensions of laboratory-scale ESP. The numerical simulation was implemented using COMSOL Multiphysics package that uses finite element method (FEM) solver. The main investigated parameters are the electric potential, electric field distribution and collection efficiency under the loading conditions as a function of air flow velocity, magnitude and polarity of voltage, ESP geometry design (size, shape and number of discharge electrodes). It is shown that the collection efficiency of this novel ESP increases when decreasing air flow velocity; and its effectiveness is higher when using negative ionisation polarity. Also, the collection efficiency of this ESP could greatly improve the existing ESPs under the same applied physical conditions.

Investigating the impact of an Al-Si additive on the resistivity of biomass ashes

Ash resistivity is an important factor in the collection efficiency of electrostatic precipitators (ESPs). There is good experience in the industry regarding resistivity of coal fly ash and well-established models for its prediction based on coal ash composition. The same is not true for biomass ash and this paper reports much-needed data for three different biomass types. Coal pulverised fuel ash (PFA), can be used as an aluminosilicate additive to mitigate biomass ash deposition issues. The effects of PFA additive on the resistivity of biomass ashes is also reported here. Biomass ash resistivity is an order of magnitude lower than that of typical coal ashes, and thus re-entrainment of particles in ESPs may become an operational issue, exacerbated by the presence of moisture and sulphur. PFA additive can increase the resistivity, but also leads to higher ash loading. Regression analysis indicates that potassium in biomass ash impacts significantly upon resistivity, contrary to previous studies. Various existing resistivity models were tested for predicting biomass ash resistivity; they produced significant overestimates when compared to experimental results due to omission of potassium as a component of the ash. Modifications to existing models or new models are required to predict resistivity of biomass ashes, and the data reported here will be important for developing such a model.

Study on the Change Characteristics of Dust Specific Resistivity and Electrostatic Precipitation Efficiency

Specific resistance is an important factor affecting the performance of ESP. For the dust resistance than the impact of electrostatic dust removal mechanism, the relationship between dust specific resistance and electrostatic dust removal efficiency, high dust specific resistance and low dust specific resistance in the electrostatic dust produced by the adverse effects. The method of controlling the specific resistance of dust is proposed, which reduces the specific resistance of high specific resistance dust by adjusting the flue gas humidity, changing the flue gas temperature and flue gas quenching. The surface modification technology is used to improve the low specific resistance dust. By controlling the dust specific resistance to 104 to 1010 Ω · cm, the electrostatic precipitator is kept at a high dust removal efficiency.

Electrostatic Precipitation of Submicron Particles with an Enhanced Unipolar Pre-Charger

A two-stage electrostatic precipitator (ESP) has been developed using an enhanced unipolar pre-charger with dielectric coated ground electrodes. The electrical and particle collection performance was evaluated for particles in the submicron range. By varying the voltage applied to the pre-charger, the particle charging characteristics was compared with that calculated by the theoretical model. The experimental results show that with the adoption of the pre-charger, the charging of the particles at submicron range was enhanced. Further results indicate that the collection efficiency can be improved by about 12.1%–15.9%, compared with the results obtained without the pre-charger. Higher particle collection efficiency can be achieved by increasing the voltage applied to the pre-charger. The unipolar pre-charger studied in this paper proves to be a simple and useful device to improve the submicron particle collection efficiency of conventional ESPs.

Fly ash classification efficiency of electrostatic precipitators in fluidized bed combustion of peat, wood, and forest residues

The increasing use of biomasses in the production of electricity and heat results in an increased amount of burning residue, fly ash which disposal is becoming more and more restricted and expensive. Therefore, there is a great interest in utilizing fly ashes instead of just disposing of it. This study aimed to establish whether the utilization of fly ash from the fluidized bed combustion of peat, wood, and forest residues can be improved by electrostatic precipitator separation of sulfate, chloride, and some detrimental metals. Classification selectivity calculations of electrostatic precipitators for three different fuel mixtures from two different power plants were performed by using Nelson's and Karnis's selectivity indices. Results showed that all fly ashes behaved similarly in the electrostatic separation process SiO2 resulted in coarse fractions with Nelson's selectivity of 0.2 or more, while sulfate, chloride, and the studied detrimental metals (arsenic, cadmium, and lead) enriched into fine fractions with varying selectivity from 0.2 to 0.65. Overall, the results of this study suggest that it is possible to improve the utilization potential of fly ashes from fluidized bed combustion in concrete, fertilizer, and earth construction applications by using electrostatic precipitators for the fractionating of fly ashes in addition to their initial function of collecting fly ash particles from flue gases. The separation of the finer fractions (ESP 2 and 3) from ESP 1 field fly ash is recommended.

Experimental and DFT studies of PM2.5 removal by chemical agglomeration

Fine particles are significantly harmful to the human body and the atmospheric environment. However, the electrostatic precipitator (ESP) removal efficiency for PM2.5 is low, therefore chemical agglomeration technology, which uses various chemical agents to induce particle agglomeration, improving the efficiency of ESP seems to be a promising pretreatment technology. In the present contribution a combination of experimental and DFT calculations has been used to study this technique. We used water, pectin and sodium alginate solutions as agglomeration agents. Experimental results showed that sodium alginate solutions is most effective, the particle diameter increased from 0.1 μm to 1 μm and the ESP removal efficiency of number concentration increased above 20% with chemical agglomeration technology. In theoretical studies we simulated various molecular clusters consisting of water, pectin and sodium alginate in combination with simple model silica particles (TOS) by using DFT calculations to explore the internal interactions in ESP system at molecular level. In our results, water, pectin and sodium alginate interacted with TOS by hydrogen bond, with interaction energy of 4.0 kcal/mol, 6.7 kcal/mol and 7.4 kcal/mol, respectively. Finally, according to the experimental and theoretical results, the chemical agglomeration models were put forward.

SO3 Reduction in the Flue Gas by Adding a Chemical Agent

Chemical agglomeration is presented as a promising process to reduce the submicron particles and SO3 in coal-fired power plant, which uses chemical agent to induce particles and SO3 agglomerate and improves the removal efficiency of electrostatic precipitation (ESP). In this study, an experimental plant containing a chemical agglomeration chamber connected to an ESP unit has been built to investigate the particles and SO3 removal effect. The results showed that chemical agglomeration technology increased the average size of particles and the fine particle and SO3 concentration reduced at the ESP outlet, the improvement of collection efficiency was over 5%-20%. The removal mechanism was investigated by Density Functional Theory (DFT) calculations at molecular level, the reasonable calculation model with pectin as agglomeration agent was established, the interactions between SO3, H2SO4, SiO2 and pectin were explored. In the results, adsorption ability of pectin for H2SO4 is better than SiO2 and relative ener...

PM2.5 and SO3 collaborative removal in electrostatic precipitator

Coal-burning pollution caused harmfully to human and environment. However, the efficiency of electrostatic precipitator (ESP) for PM2.5 is low. Reducing the ESP inlet temperature is widely concerned. This technology could simultaneously control of PM2.5 and SO3. In this study, a lab-scale low temperature ESP performance was designed under controlled conditions, the operating effects were evaluated under different temperature and SO3 concentration, SO3 and particles coagulation mechanism was discussed. Experimental results show that the operating temperature was important for ESP, The ESP outlet particle size showed a increasing trend that the median diameter d50 increased to 0.08μm from 0.05μm, and the d90 increased to 0.23μm from 0.09μm with the inlet temperature reduced from 150°C to 90°C. Particle removal efficiency increased when ESP inlet temperature reduced, especially particles with diameters of around 0.1–1μm increased obviously. SO3 removal efficiency improved from about 20% to above 80%, when the ESP inlet temperature drops below the acid dew point. Furthermore, SO3 binary nucleation mechanism was discussed, the analysis results of the adsorption mechanism indicated that SO3 condensation on the fly ash was mainly controlled by internal diffusion.

Fine particle migration and collection in a wet electrostatic precipitator

ABSTRACTElectrostatic precipitation is considered as an effective technology for fine particle removal. A lab-scale wet electrostatic precipitator (ESP) with wire-to-plate configuration was developed to study particle migration and collection. The performance of the wet ESP was evaluated in terms of the corona discharge characteristics, total removal efficiency and fractional removal efficiency. The corona discharge characteristics and particle removal abilities of the wet ESP were investigated and compared with dry ESP. Particle removal efficiency was influenced by discharge electrode type, SO2 concentration, specific collection area (SCA) and particle/droplet interaction. Results showed that the particle removal efficiency of wet ESP was elevated to 97.86% from 93.75% of dry ESP. Three types of discharge electrodes were investigated. Higher particle removal efficiency and larger migration velocity could be obtained with fishbone electrode. Particle removal efficiency decreased by 2.87% when SO2 concentration increased from 0 ppm to 43 ppm as a result of the suppression of corona discharge and particle charging. The removal efficiency increased with higher SCA, but it changed by only 0.71% with the SCA increasing from 25.0 m2/(m3/s) to 32.5 m2/(m3/s). Meanwhile, the increasing of particle and droplet concentration was favorable to the particle aggregation and improved particle removal efficiency.Implications: This work tends to study the particle migration and collection under spraying condition. The performance of a wet electrostatic precipitator (ESP) is evaluated in terms of the corona discharge characteristics, total particle removal efficiency, and fractional particle removal efficiency. The effects of water droplets on particle removal, especially on removal of particles with different sizes, is investigated. The optimization work was done to determine appropriate water consumption, discharge electrode type, and specific collection area, which can provide a basis for wet ESP design and application.

微粉炭燃焼火力用低低温電気集じん装置の微粒子捕集性能

Electrostatic precipitator (ESP) is a major dust collection equipment in pulverized coal combustion boiler in Japan. As the environmental influence of fine particle such as PM2.5 in the atmosphere is focused recently, the improvement of the collection efficiency of fine particle on ESP is desired. An advanced low temperature ESP operated under 363 K has been used recently because of its availability for high electric resistivity coal ash. In this study, the separation characteristics of fine coal ash particle by the control of operation condition on advanced low temperature ESP in a pulverized coal combustion boiler is investigated. It is estimated that the fractional collection efficiency of advanced low temperature ESP shows a minimum value at the particle size in the range 0.5 to 1.0 μm. The collection efficiency of fine particle under 2.5 μm is improved by the increase of current density of ESP and the control of gas flow pattern in ESP is one of the effective method for the improvement of the collection efficiency of ESP.

Experimental Study on Dust Removal Efficiency of Electrostatic Precipitation for Biomass Flue Gas

In view of the problem of electrostatic dust removal of biomass flue gas, the performance of line type high voltage electrostatic precipitator is systematically studied. The effects of the form of the electrode line, the size of the operating voltage (V), the voltage polarity and the inlet flue gas concentration (ρ1) on the dust removal efficiency (η) were obtained. The results show that the dust removal efficiency of the T-shaped line is higher than that of the circular line. The efficiency of dust removal increases first and then tends to be constant with the increase of the voltage. Under the same conditions, the negative voltage efficiency is higher than the positive voltage’s. The efficiency of dust removal decreases with the increase of the inlet concentration.

Collection and charging characteristics of particles in an electrostatic precipitator with a wet membrane collecting electrode

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.

Predicting acid dew point with a semi-empirical model

Decreasing the temperature of exhaust flue gas in boilers is one of the most effective ways to further improve the thermal efficiency, electrostatic precipitator efficiency and to decrease the water consumption of desulfurization tower, while, when this temperature is below the acid dew point, the fouling and corrosion will occur on the heating surfaces in the second pass of boilers. So, the knowledge on accurately predicting the acid dew point is essential. By investigating the previous models on acid dew point prediction, an improved thermodynamic correlation formula between the acid dew point and its influencing factors is derived first. And then, a semi-empirical prediction model is proposed, which is validated with the data both in field test and experiment, and comparing with the previous models.

Electrode configurations inside an electrostatic precipitator and their impact on collection efficiency and flow pattern

Electrostatic precipitator (ESP) units have wide application in lots industries processes as gas filtration devices. Regarding their high efficiency, further improvement is still required. Wide ESP (plate-to-plate distance greater than 400 mm) is one of a promising way to improve existing ESP due to its ability to reduce equipment investment significantly. However, its large-scale application has been limited because it may potentially lead to collection efficiency reduction. This article focuses on the study of two major effects when several different electrode configurations are applied. The electrohydrodynamic (EHD) flow pattern inside ESP and particle collection efficiency were investigated by using particle image velocimetry (PIV) and electrical low pressure impactor (ELPI) respectively. Results suggested that the collection efficiency of wide ESP is rather complicated and highly related to inner gas flow pattern.

Field Measurements on the Emission and Removal of PM2.5 from Coal-Fired Power Stations: 3. Direct Comparison on the PM Removal Efficiency of Electrostatic Precipitators and Fabric Filters

This contribution reports direct comparison of the particulate matter (PM) removal efficiencies of electrostatic precipitators (ESPs) and fabric filters (FFs) installed in two 300 MW coal-fired power station units that are equipped with identical boilers and DeNOx units. Field PM measurements were carried out at the horizontal ducts at the inlets of the DeNOx units, as well as the inlets and outlets of the two dust collectors when the two boilers burned the same coal under identical combustion conditions. The PM and total fly ash were collected via a low-pressure impactor (LPI) and/or a smoke analyzer. The collected samples were then subjected to analysis for chemical composition and morphology using an X-ray fluorescence (XRF) probe and a field emission scanning microscope with an energy-dispersive X-ray analyzer (FESEM-EDX). The results show that both the ESPs and the FFs can effectively capture PM, with a PM2.5 collection efficiency of 99.63% and 99.95%, respectively. For the PM with similar properties, the collection efficiencies in the FFs are only marginally higher than those in the ESPs. The most notable discrepancies between the fractional PM removal efficiencies of ESPs and FFs are observed for PM in the size range 0.3–2 μm. The PM removal performance of both the ESPs and the FFs is related to particle size. At 0.3–2 μm, the performance of the ESPs is more sensitive to particle size than the FFs. The PM collection efficiency of the FFs is inversely related to particle size, and the capture of PM around 0.4 μm is slightly weak, most likely due to the transition of capture mechanisms from impaction to Brownian diffusion.

Prediction of Acid Dew Point in Flue Gas of Boilers Burning Fossil Fuels

The temperature of flue gas should be controlled to be higher than the acid dew point to avoid fouling and corrosion of heating surfaces in the second pass of boilers. Decreasing the temperature of flue gas in boilers is one of the most effective ways to improve thermal efficiency, enhance electrostatic precipitator efficiency, and decrease water consumption of the desulfurization tower. Accurate knowledge in predicting acid dew point is required. Thus, based on previous research achievements, a measuring device is designed based on the principle of conductive dew point meter, and the acid dew points under different flue gas conditions are measured in this work. An improved thermodynamic correlation formula between the acid dew point and its influencing factors is also derived based on previous research achievements. Then, a semiempirical prediction model that considers the functions of H2SO4 and H2O is proposed. The proposed prediction model is validated by field test data, experimental data, and predict...

Electrical characteristics of electrostatic precipitator with a wet membrane-based collecting electrode

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.