10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Effect of a Two-Stage Type Electrostatic Precipitator on Collection Efficiency and Ozone Concentration
KOJI YASUMOTO, Hidetoshi Sawano, Kohei Ito, Akinori Zukeran, Kanagawa Institute of Technology
Abstract Number: 305 Working Group: Indoor Aerosols
Abstract Electrostatic Precipitators (ESPs) have been extensively used for the cleaning of industrial process flue gases, combustion flue gases and ventilation flue gases for road tunnels, etc. A home air cleaner is also one application of ESP. However, such air cleaners which utilize corona discharge must be improved the collection efficiency without increasing ozone concentration.
In this study, the collection efficiencies and the ozone concentrations were measured in a single-stage ESP and a two-stage type ESP.
The two-stage type ESP has a discharging section and an electrostatic section. The discharging section (single stage ESP) has a wire-and-plates configuration composed of a high-voltage application wire electrode (f: 0.45 mm, L: 70 mm, SUS304) placed between grounded plate electrodes (70×270 mm) with a gap of 10 mm. The electrostatic section has a parallel-plate electrode structure composed of a high-voltage application electrode (70×174 mm) sandwiched between grounded plate electrodes (70×174 mm) with a gap of 10 mm. All plate electrodes are made of stainless steel with a thickness of 0.8 mm. Room air was used, and the gas flow velocity was adjusted to 0.5 m/s by a fan located on the downstream side of the ESP. Maximum voltages of DC -12 kV and DC -9 kV were applied to the discharging and the electrostatic sections using high voltage generators. 1, and discharge current was measured. Ozone concentration was measured using an ozone monitor at the downstream side of the ESP. The number concentrations for the particle size between 0.3 and 5 mm at upstream and downstream sides of the ESP were measured using particle counters, and the collection efficiency was calculated by equation (1).
η = (1-NDd/NUd) ×100 % (1)
As a result, the collection efficiency increased as the particle diameter increased due to increasing the charge in the single stage ESP. The efficiency improved with increasing applied voltage, however ozone concentration also increased. This cause is that the reaction between O2 and O generated by dissociation increases with increasing discharge current.
In the two-stage type ESP, the applied voltage on the discharging section was 9.37 kV at any voltage applied to the electrostatic section. The collection efficiency improved with increasing applied voltage to the electrostatic section with increasing the migration velocities of charged particles in the electrostatic section. The discharge current was constant in the discharging section, whereby the ozone concentration at any voltage was approximately 1 ppm. Furthermore, the energy consumption did not increase, since current did not flow in the electrostatic section. Therefore, it was clear that the collection efficiency could be improved without increasing ozone concentration and energy consumption in the two-stage-type ESP.