Wire-cylinder Electrostatic Precipitator Research Articles

Convective heat transfer enhancement by corona discharge in a wire–cylinder electrostatic precipitator with the water-cooling system

Aiming at the current wet plume problem, we present a novel technique to integrate electrostatic precipitator (ESP) and heat exchanger in order to simultaneously increase heat exchange efficiency, collect water and control particle emission from flue gases. Unlike the conventional ESP, a lab-scale wire–cylinder type ESP with the collection electrode cooling by water is used for investigations in this paper. Our research indicates that the heat transfer coefficient of the ESP rises with reducing gaseous velocity, increasing applied voltage, corona current or gas temperature. The maximum improvement of the total heat transfer coefficient of 271% was achieved at 0.15 m/s, 80 °C and 16 kV of the negative discharge. Moreover, the presence of Particle matters can enhance the heat transfer coefficient by 9%–16%. The ionic wind, which is quantitatively expressed by electro-hydrodynamic number, plays a key role in modifying the gas flow patterns and consequently improving the heat exchange coefficient. For lowering the overall energy consumption, it is suggested that the ESP should be operated at a specific mode of low voltage and high current.

Study of PM2.5 capture performance in a new wire-cylinder ESP with applied magnetic field

ABSTRACTTo enhance PM2.5 capture performance of a wire-cylinder electrostatic precipitator (ESP), magnetic field was introduced into ESP, and a mathematical model with multi-field coupling effect between gas flow field, electromagnetic field, and particle dynamical field was built. PM2.5 collection efficiency in ESP was simulated using computational fluid dynamics and Fluent software. Under the consideration of diffusion charge, the influence of applied magnetic field on PM2.5 collection efficiency at different working voltages and flue gas velocities was discussed. The research results indicate that no matter what operating parameters, the introduction of magnetic field obviously improves the capture performance of wire-cylinder ESP. The PM2.5 capture performance in magnetic field environment is better in the condition of higher working voltage and/or lower flue gas velocity. Furthermore, the capture effect of applied magnetic field on PM2.5 increases with the increase of flue gas velocity or the decrease of working voltage. The related results can provide references for researchers aiming at equipment modification and technological innovation of traditional ESP.

Experimental investigation on the characteristics of ash layers in a high-temperature wire–cylinder electrostatic precipitator

Abstract 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 .

Development of back corona discharge in a wire-cylinder electrostatic precipitator at high temperatures

High-temperature electrostatic precipitation is a potential method for hot gas clean-up that is hindered by the issue of back corona discharge (BCD). This paper reports on the development of BCD at 350–700°C in a wire-cylinder electrostatic precipitator (ESP). As the output voltage of power supply increases, BCD begins at the surface of the ash layer, and then it extends toward the electrode gap space, forming consecutive discharge channels that bridge the two electrodes, ultimately leading to spark breakdown (SB). The discharge process that follows BCD can be classified into different stages: the NCD & BCD stages, the weak NCD, BCD & glow discharge stage, and the BCD & SB stages. At high temperatures (500°C or above), BCD is likely to convert to SB. In the NCD & BCD stages, the collection efficiency of the electrostatic precipitator is not affected, i.e., the collection efficiency is ~99.65%, regardless of whether BCD exists or not at a temperature of 350°C and a port voltage of ~17,200V. In the BCD & SB stages, the collection efficiency is greatly reduced, i.e., it is ~88.35% in the NCD-only stage at a temperature of 500°C and a port voltage of ~14,000V, whereas it is only ~67.42% in the BCD & SB stages. It should be noted that BCD results in an increase in the power consumption of the ESP for all stages. A physical model is proposed to explain the processes that initiate, maintain, and develop BCD.

Use of Pulse-Energized Electrostatic Precipitator to Remove Submicron Particulate Matter in Exhaust Gas

An electrostatic precipitator (ESP) with negative pulse corona discharge for removal of submicron particles in the exhaust gas of thermal equipment such as boilers, burners or internal combustion engines is presented. A wire-cylinder ESP was designed and constructed for experimental testing at laboratory scale. The collection efficiency of submicron particles in the exhaust gas of a diesel burner under various dust loadings and gas velocities was investigated. The results were compared with those obtained from the conventional DC ESP technique. It was found that the pulse peak voltage supply could be set much higher than the sparking limit of the DC energized unit. Thus, the electric field density could be increased, which resulted in a higher collection efficiency. The higher pulse frequency also increased the collection efficiency, especially for submicron particles.

Numerical study on PM10 collection efficiency in a wire-cylinder electrostatic precipitator under multi-field coupling

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.

Effect of the experimental parameters on the number of free electrons in the drift region of a wire-cylinder electrostatic precipitator

Abstract The aim of this paper is to highlight the number evolution of free electrons in the drift region of a wire-cylinder electrostatic precipitator in negative voltage depends on the experimental parameters, more particularly of gas composition. A numerical model of the negative DC corona discharge developed by Chen et al. was used and modified to investigate the negative discharge corona for different gases. A parametric study was conducted to examine the effect on the electron distribution of operating conditions. The results showed the electron concentration increases with temperature, decreases when the pressure increases, and is closely related to gas composition.

Optimisation of the intermittent operation of a wire-cylinder electrostatic precipitator

Intermittent operation mode is specific to electrostatic precipitators (ESP) used in workshops where the polluting product is produced in a discontinuous way. The present work aimed at validating a standard procedure for modelling and optimisation of such a wire -cylinder ESP, using an appropriate method of experimental design. The experiments were carried out with samples of micronized wood, using a laboratory cylindrical ESP built by one of the authors. The factors considered in the study were the applied high voltage U (κV), the air flow F (m3/h), the mass of pollutant at the input of the ESP mi (g) and the size of particles S (μm). Several ‘one-factor-at-a-time’ experiments followed by a factorial composite design were performed, in order to identify the domain of variation of each factor and determine the mathematical model of the process.

Modeling of the electrical parameters of a wire-cylinder electrostatic precipitator under pulse energization

Modeling of the electrical parameters of an electrostatic precipitator (ESP) with dust loading under pulse energization is difficult, and little progress has been made in the past. A method for modeling a wire-cylinder ESP under pulse energization based on the characteristics of Trichel pulses, and a means of dealing with the particle charging under such conditions are presented. The quantitative studies of the interactions between ion space charge and particle charging and their influence on the electric potential and field distributions have been numerically obtained under nanosecond pulse energization. The results show that the time-averaged current increased with applied peak voltage, pulsewidth, and pulse frequency and decreased with increased dust loading as expected. The space-charge density distribution was significantly influenced by the dust loading under pulse energization conditions. The proposed model is valid as long as the width of the applied voltage is less than 1 /spl mu/s.

A study of pulsed energized particle collection in a bench-scale cylindrical electrostatic precipitator

Careful laboratory measurements have been conducted on a 5-cm-diam wire-cylinder electrostatic precipitator (ESP) in order to examine and understand the salient electrical behavior, particle charging, and collection characteristics for pulse powering under clean plate conditions. The importance of electrical parameters has been examined experimentally to determine the variation in performance for medium width pulses up to 250 μs. Operation at reduced current levels is shown to be possible only when the dc pedestal voltage is below corona inception. A good fit of the experimental data to predictions given by a spatiotemporal model indicates that the physics can be effectively described for both dc-powered and pulsed systems. In particular, the impact and interplay of particle diffusivity and electron charging is investigated. For ESPs of small size, electron charging appears to be significant.

A Technique for Pressure Measurement in the Active Electrical Zone of a Wire-Cylinder Electrostatic Precipitator

Probe techniques are discussed which have proven useful in the measurement of the current induced pressure distribution in the active electrical zone of a wire-cylinder electrostatic precipitator. The cylindrical electrode configuration is somewhat unique in that the pressure distribution is exactly known in the case of negligible axial flow and thus provides a check on the experimental technique. The measurement strategy combines alignment of the probe on an equipotential surface, control of probe current drainage to a level consistent with the probe's size and location in the field, and use of a guard electrode near the probe insertion point. Pressure measurements made with probe electrical characteristics indicating a minimally perturbed electric field are in close agreement with analytical prediction, and the experimental techniques appear to be applicable to other types of flow measurement in cylinder and duct precipitators.