Effect of Electrode Length and Gas Velocity on the Collection of Diesel Exhaust Particle in an Electrostatic Precipitator with a High Electric Field

Abstract

In this study, the effect of the electrode length and the gas velocity on the collection of diesel exhaust particle (DEP) in an electrostatic precipitator (ESP) with a high electric field, which does not use corona discharge, was investigated. The ESP was a double cylindrical configuration composed of a grounded cylindrical electrode and a high voltage application columnar electrode. The edges of the electrodes were chamfered round to relax the concentration of electric lines of force. The length of the electrodes was between 100 mm and 1,000 mm. The gas velocity in the ESP was between 1 m/s and 4.8 m/s. A negative DC high voltage was applied to the high voltage application electrode. Diesel exhaust gas was flowed into the ESP. The gas temperature was between 50 ℃ and 110 ℃. The particle concentrations at the downstream side of the ESP were measured using a low volume air sampler, and the collection efficiency was calculated. As a result, the collection efficiency increased with increasing the electrode length, and reached 51% at the length of 1,000 mm and the gas velocity of 4.0 m/s. The efficiency increased as the gas velocity decreased, and that was greater than 70% at the length of 470 mm and the velocity of 1 m/s. An observation using a scanning electron microscope showed that particles were collected on both positive and negative electrodes. Therefore, it was revealed that DEP contains both positively charged particles and negatively charged ones, whereby these can be collected.