Zhengda Yang

Fine particle migration and collection in a wet electrostatic precipitator

ABSTRACT Electrostatic 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.

Highly efficient removal of sulfuric acid aerosol by a combined wet electrostatic precipitator

Eliminating sulfuric acid aerosol from flue gas is of vital importance to improve air quality. In this paper, a wet electrostatic precipitator (WESP) assisted with novel pre-charger was proposed to efficiently remove sulfuric acid aerosol. Parameters including residence time, gas temperature and SO3 concentration were studied to find the key factors influencing sulfuric acid aerosol removal. Results showed that the removal efficiency of sulfuric acid aerosol increased with the increasing residence time and the decreasing gas temperature. The maximum corona current was reduced from 0.79 to 0.28 mA when the SO3 concentration increased from 0 to 25 ppm, and the removal efficiency also decreased with the increasing SO3 concentration. A novel perforated pre-charger was designed to improve the WESP performance for sulfuric acid aerosol removal. With assistance of the pre-charger, the removal efficiency was improved from 90.3 to 95.8%, and the corresponding emission concentration was lower than 2 mg m−3. Moreover, the removal efficiency could be further improved to 97.8% with a heat exchanger, and the corresponding emission concentration could be lower than 1 mg m−3.

Current density distribution and optimization of the collection electrodes of a honeycomb wet electrostatic precipitator

Wet electrostatic precipitators (ESPs) demonstrate a robust adaptability for particulate matter control and have been confirmed to be a promising technology for removing particles and sulfuric acid aerosol from flue gas. Recent studies have shown that removing fine particles or sulfuric acid aerosol from wet ESPs requires further development. Among the components of wet ESPs, discharge electrode configurations are crucial for determining the performance of wet ESPs. This paper reports the corona discharge characteristics and removal performance of sulfuric acid aerosol using different discharge electrode configurations in a honeycomb wet ESP experimental system. Two key parameters, namely, V–I characteristics and current density distribution, with different discharge electrode geometries (e.g., electrode type, spike spacing, and spike length) and rotation angles, were investigated by using a novel electrical parameter measurement system to evaluate the effects of these parameters on corona discharge. The results showed that triple-spike and sawtooth electrodes exhibit the highest average current density. The average current density of the triple-spike electrode increased with the spike length from 10 mm to 20 mm, and the peak current density distribution on the collection electrode increased by 62.1%, but the current density decreased sharply away from the spike. Moreover, the average peak current density decreased by 30.1% when the spike spacing was 25 mm given the sharp point discharge suppression when spikes were significantly dense. The electrode configuration was optimized on the basis of the current density distribution. The highest removal efficiency of sulfuric acid aerosol was 99.2% at a specific collection area of 23.09 m2 (m3 s−1)−1.