Search

Electrode configuration is a key parameter that affect the operation of ESPs. In this study, through a wire-plate ESP at wide temperatures, the dynamic and ultimate removal characteristics of coal-fired power plant and coal pyrolysis furnace fly ash (ash A and B) with different resistivity under four electrode configurations were investigated. For ash A, the sawtooth electrode DE3 exhibited the largest current density under identical applied voltage. Each discharge electrode configuration had its efficient operating temperature. DE3 had the best removal performance when the temperature was 363 K and DE1 performed excellently at 500 K. For ash B, the removal efficiency with rod electrode DE4 was only 91.2% at 700 K in the simulated inert atmosphere. Through the optimization of electrode configuration with DE1, particles were effectively removed with collection efficiency exceeding 95%, and the particle removal efficiency of each diameter distribution was remarkably higher than that of DE4. Unlabelled Image • Four different electrode configurations were conducted to enhance the performance of ESP at high temperature. • The dynamic and ultimate removal characteristics were investigated. • The barbed electrode performed relatively best to remove particles at high temperatures. • A discharge electrode optimization with temperature regulation method was proposed. [ABSTRACT FROM AUTHOR]

Aiming at enhanced particulate matter (PM) removal of electrostatic precipitators (ESPs) in coal-fired power plants, a pulse energization power supply that generates high-voltage pulses superimposed on a high-voltage dc was designed. The integrated theories of corona discharge, particle charging, and removal were presented, and the pulse energization strategy was studied through fractional particle removal simulation. The conclusion of simulation stated that pulse energization could significantly improve particle charge with a maximum enhancement at a particle diameter of $20~\mu \text{m}$ , while the fractional particle removal efficiency shows a different distribution that removal of particles less than $2.5~\mu \text{m}$ had the most significant enhancement. Based on the design and simulations, a full-scale comparative operation study testified the potential of dc + pulse energization to enhance particle removal with a limited power consumption increase. Pulse energization was applied to different industrial ESPs with various design and operation parameters and shown multicondition adaptability in PM removal enhancement, with the emission reduction ranging from 45.48% to 58.00% and outlet concentration from 8.60 to 47.48 mg/Nm3, proving it a convenient and economical method in the performance boost of industrial ESPs. [ABSTRACT FROM AUTHOR]

Abstract A hybrid modeling scheme for electrostatic precipitators (ESPs) integrating particulate matter (PM) removal mechanism and the data-driven compensation method is presented in this article. The structure of the training and coupling method for the mechanism model, which considers electrodynamics, including corona discharging, particle charging, and removal, and the data-driven method that was trained based on operation data to compensate for the distortion and flaw of the mechanism model was constructed. Design parameters and operation data of an ESP in a coal-fired power plant were collected for model training, and prediction performances were compared. Different combinations of correction factors, including exponential, proportional, and bias, were studied. The form with the highest prediction R2 of 0.889 on the training set and 0.867 on the validation set was chosen as the mechanism part of the model. Deep neural networks with the highest R2 of 0.885 on the training set and 0.857 on the validation set were also trained as a comparison group. The performance of the hybrid model achieved a R2 of 0.933 on the training set and 0.887 on the validation set and outperformed the mechanism and data-driven models, thereby indicating that the hybrid modeling method could enhance prediction performance while maintaining the generalization capability of the PM removal mechanism in ESP. Graphical abstract Unlabelled Image Highlights • Hybrid modeling scheme for electrostatic precipitators is proposed. • PM removal mechanism model with best combined of correction factors is derived. • Performance of deep neural networks is compared with mechanism models. • Data-driven model is coupled with mechanism model to enhance performance. • Hybrid model has better prediction performance compared with other models. [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]

Abstract Improving the removal efficiency of fine particle is significant for the elimination of particle emission from coal-fired power plants. This work reports a combined wet electrostatic precipitator (WESP) enhanced by a novel perforated pre-charger to efficiently remove fine particle from wet flue gas. Penetration and charging characteristics of fine particle through the WESP were evaluated as a function of particle size. The collection performance was investigated under controlled gas temperatures and varied electrical conditions. Results showed that there was a maximum penetration ratio around 0.1 μm and it decreased with the increasing applied voltage. A portion of the escaping fine particles were not charged through the WESP, and the size limit for partial charging can be reduced to 0.025 μm when the applied voltage increased to 32 kV. Reducing gas temperature leaded to an obvious improvement in collection efficiency for particles in the size range of 0.1–1.0 μm. The test results of different electrodes showed that both the corona current and maximum collection efficiency ranked in the order of pin > sawtooth > rod. With the assistance of pre-charger, the particle charging was significantly improved and the charge amount was more than doubled. Consequently, the effective migration velocity for PM 0.1 , PM 1.0 and PM 2.5 increased by 69.9%, 65.7% and 34.2%, respectively. Actual application results showed that the average PM emission level can be reduced to 0.43 mg/m3 by the combined WESP in a 1000 MW coal-fired power plant. Graphical abstract Unlabelled Image Highlights • A combined WESP was developed to help to realize ultra-low emission. • Particle penetration and charging were evaluated as a function of particle size. • The charge amount was more than doubled assisted with the pre-charger. • The average PM emission level can be reduced to 0.43 mg/m3 in an actual plant. [ABSTRACT FROM AUTHOR]

Wet electrostatic precipitators (WESP) have been proven to be a promising technology for the removal of sulfuric acid mist from flue gases. Recent studies indicate that WESPs, when mitigating sulfuric acid mist, can be less effective on systems that burn high sulfur content fuel. This paper reports on a pilot-scale WESP used to investigate SO 3 removal with high SO 3 concentration. Both mass concentration of SO 3 and number concentration of sulfuric acid mist were measured. Two key parameters, i.e., electrical characteristics and gas loading, were studied to evaluate their effects on SO 3 removal efficiency under severe corona suppression conditions. Results showed that the maximum corona current was reduced by 83.1% when the WESP inlet SO 3 concentration increased from 0 to 5 c 0 , and the corresponding SO 3 removal efficiency decreased from 74.5% to 54.2%. SO 3 removal efficiency can be improved by increasing corona power and reducing gas velocity. A comprehensive method was proposed to enhance SO 3 removal efficiency, with removal efficiencies greater than 90% using proper electrode configurations and lower velocity under a pilot plant condition. In addition, other challenges including new ultra-fine mist generation, material corrosion and insulator failure are summarized. [ABSTRACT FROM AUTHOR]

Resistivity is a key factor in the efficient and stable operation of electrostatic precipitators. Sixty types of typical industrial fly ashes were collected for this study. Subsequently, fly ash resistivity at the temperature range of 303–1073 K, and the chemical compositions, micrographs, and size distributions of the samples were measured. The joint influence of chemical composition and temperature on resistivity was also investigated. The main components of the fly ash samples were Fe (0.8–5.0%), K + Na + Li (0.3–5.1%), Ca + Mg (0.5–4.0%), and Al + Si (10–34%), respectively. Fe, K, and Na were highly sensitive to fly ash resistivity. Resistivity decreased with the increase in Fe, K, Na, and Li contents; by contrast, resistivity increased with Ca and Mg contents. The effects of Si and Al on fly ash resistivity were weak. Resistivity initially increased first and then decreased with the increase in temperature. Maximum resistivity was observed at 373–473 K. Based on the experimental data, a prediction model for fly ash resistivity over a wide range of temperature (303–1073 K) was established. The resistivity diagrams generated specifically for this study suggest that typical fly ash samples from different industries can be estimated using chemical composition and temperature data. [ABSTRACT FROM AUTHOR]

This study investigated the influence of electrode configuration on corona discharge and particle collection from 300 K to 900 K. Electrodes of different shapes (rod, saw, and screw), diameters (3, 5, and 8 mm), and intervals (55, 110, and 165 mm) were tested in an experimental-scale electrostatic precipitator (ESP). Results showed that a high current was generated with a saw electrode and increased the particle collection efficiency, particularly for fine particles (diameter smaller than 0.1 μm), with the best particle collection efficiency being 99.8% at 300 K. However, with an increase in temperature, the rod electrode obtained an applied voltage higher than those of other electrode types and, as a result, generated relatively high particle collection efficiencies at 700 K and 900 K. Increasing the electrode diameter from 3 mm to 5 mm improved the applied voltage, whereas increasing this diameter from 5 mm to 8 mm reduced the discharge current. Among electrodes with different diameters, the electrode with a diameter of 5 mm achieved the best particle collection efficiency (87.4%) at 900 K. The applied voltages of the electrodes with different intervals were almost similar, but the discharge currents varied significantly. The best particle collection efficiencies were achieved by the electrode with an interval of 55 mm at 300 K and 500 K, but at 700 K and 900 K, the electrode with an interval of 110 mm obtained the best result. The interval between electrodes should be expanded with an increase in temperature to avoid the offsetting of electric field between neighboring electrodes. [ABSTRACT FROM AUTHOR]

High-temperature electrostatic precipitators for removing dust from fuel or flue gases were proposed to improve energy efficiency or to avoid damaging downstream equipment. This paper attempts to provide a comprehensive understanding of negative DC corona discharges and find ways to increase corona stability at high temperatures. The characteristics of corona discharges were studied in a wire–plate discharge configuration under different discharge gaps and electrode geometries at temperatures ranging from 293 K to 1173 K. The V – I characteristics were analyzed, including corona onset/spark voltages, operating voltage ranges, and corona current compositions. The discharge current density increases as the temperature increases, and the electron-carried current becomes significant at high temperatures. For example, the electron-carried current makes up ∼40% of the total discharge current at 1073 K under an applied voltage of 10 kV. The applied voltage range decreases as the temperature increases. The corona discharges become unstable, and localized breakdowns occur frequently when the temperature exceeds 1073 K and the discharge gap is less than 50 mm, because the ionization coefficient and the number of electrons greatly increase. The operating voltage range increases from 8.2 kV to 13.6 kV at 1073 K when the discharge gap increases from 30 mm to 70 mm. Compared with the wire and spiral electrodes, the ribbon electrodes produce sparks more easily. The wire diameter has little influence on the spark voltage and corona stability at high temperatures. [ABSTRACT FROM AUTHOR]

Pollutant abatement systems are widely applied in the coal-fired power sector, and the energy consumption is considered an important part of the auxiliary power. An energy consumption analysis and assessment model of pollutant abatement systems in a power unit was developed based on the dynamic parameters and technology. The energy consumption of pollutant abatement systems in a 1000-MW coal-fired power unit that meets the ultra-low emission limits and the factors of operating parameters, including unit load and inlet concentration of pollutants, on the operating power were analyzed. The results show that the total power consumption of the pollutant abatement systems accounted for 1.27% of the gross power generation during the monitoring period. The wet flue gas desulfurization (WFGD) system consumed 67% of the rate, whereas the selective catalytic reduction (SCR) and electrostatic precipitator (ESP) systems consumed 8.9% and 24.1%, respectively. The power consumption rate of pollutant abatement systems decreased with the increase of unit load and increased with the increase of the inlet concentration of pollutants. The operation adjustment was also an effective method to increase the energy efficiency. For example, the operation adjustment of slurry circulation pumps could promote the energy-saving operation of the WFGD system. Implications: The application of pollutant abatement technologies increases the internal energy consumption of the power plant, which will lead to an increase of power generation costs. The real-time energy consumption of the different pollutant abatement systems in a typical power unit is analyzed based on the dynamic operating data. Further, the influence of different operating parameters on the operating power of the system and the possible energy-saving potential are analyzed. [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]

• A novel-designed current measurement system contained 171 probes was designed. • The evolution of electric characteristics under various conditions was analyzed. • The current density distribution along the airflow direction was presented. • Some suggestions for relieving corona suppression were proposed. The high emission of SO 3 or sulfuric acid aerosol became a new environmental issue and has attracted international concerns. The sulfuric acid aerosol could be removed through droplet charging and transportation in the electric field. However, the charged droplets also have a converse effect on the electrostatic field. In this study, a novel-designed current measurement system contained 171 probes was designed to automatically scan and record the current density distribution along the airflow direction. Results show that the average current density was reduced by 31.3 % when SO 3 concentration was increased from 0 to 53.6 mg/m3, and the current density of the first electrode was only accounted for 11.3 % of the original current. A higher corona onset voltage was required to ionize the flue gas because of a reverse electric field formed by the charged droplets. The current density was also decreased with the flue gas velocity under the SO 3 presence condition. When the flue gas velocity reached 4 m/s, the corona suppression was severe and the inflection point was no longer obvious. The region that the relative current density below 0.6 was comprised 70 %. The current density could be enhanced by increasing the spike length and decreasing the spike spacing. The larger the corona current of the discharge electrode, the less the effect of the particle space-charge. Meanwhile, some suggestions for relieving corona suppression by enhancing the corona discharge at the inlet and promoting the droplet growth were proposed. [ABSTRACT FROM AUTHOR]

• A modified wet ESP model was established to study the particle space-charge effect. • The role of ultrafine particles in collection performance was investigated. • A combined wet ESP was developed and compared with the common wet ESP. • The correlation between precharging and particle charging was analyzed. • The contribution of precharging to particle precipitation was quantified. The collection performance of wet electrostatic precipitators (ESPs) considerably deteriorates in the presence of ultrafine particles, which confer difficulties in realizing the ultra-low emission of particulate matter (PM). In this work, the use of a wet ESP combined with a perforated precharger was proposed to investigate its electrical and collection characteristics in flue gas containing ultrafine particles and compared these characteristics with those of the common wet ESP. Results indicated that the distributions of ion density and electric field were affected by ultrafine particle loadings. With increased PM 0.1 concentration from 0 mg/m3 to 100 mg/m3, the average ion density of the common wet ESP decreased by more than two orders of magnitude. Meanwhile, the particle charging and transport performance deteriorated, even for large particles (10 μm), and migration velocity sharply decreased by more than 85 %. The corona electrostatic field was significantly improved by installing the precharger. The combined wet ESP can be operated well even under problematic conditions. Additional electrons were generated by the corona discharge of the precharger, which contributed to subsequent particle capture. When the applied voltage of the precharger exceeded 15 kV, the electrostatic precipitation of 1 μm particles only slightly weakened with increased PM 0.1 concentration to 40 mg/m3, and the capture of >5 μm-diameter particles was nearly unaffected by ultrafine particles. [ABSTRACT FROM AUTHOR]

The life cycle environmental impacts of widely used flue-gas cleaning processes, including limestone-gypsum wet flue-gas desulfurization (FGD), selective catalytic reduction denitration (SCR) and electrostatic precipitators (ESP), are compared. The abbreviations FGD, SCR and ESP in this article refer in particular to the above listed processes. Energy consumption, resource consumption and emission inventories of each life cycle phase are established. The potentials of five environmental impact categories, namely, global warming, acidification, nutrient enrichment, photochemical ozone formation, soot and ashes are finally obtained. The current paper reveals that the total energy consumption and resource consumption are dominated by the process operation. The three processes are compared and it is found that to achieve equal environmental burden reductions, the SCR process consumes more energy and approximately the same amount of air and inert rock as the FGD. But the water consumption of the FGD is much higher than the SCR. The ESP process consumes both the least energy and the least resource in general. The economic assessment indicates that the performance of the ESP process tends to be the best and the FGD follows when equally invested. [ABSTRACT FROM AUTHOR]

[Display omitted] • Se and As were mainly distributed in PM 1.0 and PM 1-2.5 with a relatively dispersed distribution, while Cu and Pb were densely distributed on particles. • When the temperature difference of HT-ESP narrowed to 23 K, the enrichment ratio in the gas phase ( ER G) of As and Se increased by 2.7 % and 18.5 %. • During the PM removal process of HT-ESP, 8.8% of copper, 7.9% of lead, 8.3% of arsenic and 45% of selenium migrated from the gas phase into the hopper particles. Recently, large amounts of particulate matter (PM) and heavy metals (HMs) have been generated in the processes of non-ferrous metal smelting (NFMS). High-temperature electrostatic precipitator (HT-ESP) was the key method to capturing PM while extensive HMs enriched. In this work, the PM collection and migration of HMs in the HT-ESP process of copper smelting were investigated through an established pilot-scale platform. The excellent performance of the pilot-scale HT-ESP could achieve a particle collection efficiency of 99.5 %. The distribution patterns of HMs in various particle sizes revealed that the volatile heavy metals, arsenic (As) and selenium (Se) were predominantly distributed in PM 1.0 and PM 1-2.5 with a moderately dispersed distribution, whereas copper (Cu) and lead (Pb) were densely concentrated on particles. When the temperature difference between the inlet and the outlet of the HT-ESP narrowed to 23 K, the original As and Se enriched in hopper particles partially volatilized and migrated into the gas phase and adhered to tiny size particles. The enrichment ratio in the gas phase ( ER G) of As and Se increased by 2.7 % and 18.5 %, respectively. The results were beneficial to reducing the enrichment of volatile HMs in copper smelting ash and provided guidance for resource utilization of the copper smelting industry. [ABSTRACT FROM AUTHOR]

Ionic wind propulsion plays a vital role in charged particle transport during flue gas purification, which is closely related to high-efficiency particulate removal. Here, we establish a comprehensive model to investigate the effect of ionic wind on the transport and deposition of charged particles. The high-speed ionic wind disturbs the space flow field in a meaningful way, which also causes the formation of 'U'-shaped high-speed zones within the near-plate region. After the dusty flue gas enters the electrostatic field, due to the disturbance of high-speed ionic wind, apart from the electric force, particle transportation is acted by ionic wind propulsion. Charged particles can be significantly accelerated with ionic wind propulsion, while it also introduces an uneven distribution of deposited particles. Based on these findings, a novel electrostatic precipitator is proposed to optimize the space flow field, and the collection efficiency and dust layer shape are both significantly improved. [Display omitted] • A comprehensive particle removal model considered ionic wind is developed. • The flow field is visualized through different presentations to indicate ionic wind performance. • The roles of ionic wind in particle transport and deposition are quantified. • A novel electrostatic precipitator is proposed to improve removal performance. [ABSTRACT FROM AUTHOR]

The high-temperature electrostatic precipitator (ESP) is a potentially efficient method for hot-gas cleaning in advanced technologies, e.g., the coal-staged conversion poly-generation system and IGCC. This paper investigates the characteristics of the ash layer on the internal surface of the anode pipe of a wire–cylinder ESP at temperatures ranging from 350 °C to 700 °C, including ash deposition forms, growth of ash layer and the effect of ash layer on back corona discharge. There are four typical ash deposition forms: the belt form, the slope with ribs form, the slope form and the slope with a thick bottom edge form. Ash layer thickness generally decreases with increasing height. When T ⩽ 500 °C, ash belts form under low port voltages, and with increasing port voltage, they will overlap each other to form ash ribs. When T ⩾ 500 °C, particles are deposited in the smooth slope form if the port voltage is great enough. When T ⩾ 700 °C, a thick bottom ash edge occurs. Ash deposition forms can vary under different operating conditions. As the operating time increases, the thickness growth rate at a given point decreases, and the ash layer height increases because of the repulsive electrical force between the ash layer and the particles. Back corona discharge always occurs on the thickest portion of the ash layer first. The back corona discharge onset voltage decreases nearly linearly with increasing ash layer thickness, from 19,787 V to 17,197 V as the maximum thickness of the ash layer increases from 0.34 to 2.02 mm when T = 500 °C, U p = 17,200 V and m in = 650 mg/N m 3 . [ABSTRACT FROM AUTHOR]

[Display omitted] • A modified charging model and an experimental system were further developed to study the charging of particle-SO 3 system. • Particle charging characteristics with the presence of different concentration of SO 3 was studied. • Charging of sulfuric acid aerosol was investigated under various conditions. • The method of discharge electrode optimization was developed to enhance particle charging. • Theoretical guidance to enhance particle charging under different conditions was proposed. Particle and SO 3 emitting from the processes of fuel combustion considerably deteriorate environment. Charging of particle in electric field was widely used for achieving effective removal of particle from SO 3 -containing flue gas in various industries. This study provided an insight into particle charging in electric field with presence of SO 3 in terms of particle charging simulation and experiments under various conditions. Results illustrated that once temperature was below acid dew point, particle charge increased and then declined with the increasing concentration of SO 3. Besides, sulfuric acid aerosol transformed from gaseous SO 3 was enhanced by higher electric field strength and temperature, but this increase seemed to be limited when reached maximum. Meanwhile, electrode optimization could enhance charging by improving ion density, which charge of particle with 0.04 μm and 1.22 μm was increased by 3.53 and 1.16. Moreover, improving dielectric constant and electric field strength mainly acted on charging of larger particle, whereas improving ion density determined small particle charging. As for medium-sized particle, simultaneously combining electric field strength and ion density adjustment to enhance particle charging was effective. Find suggested that different parameter adjustment methods should be selected according to particle diameter to enhance particle charging and reduce particle emission of SO 3 -containing flue gas. [ABSTRACT FROM AUTHOR]