Effect of the Applied Voltage Waveform at the Collecting Section on Re-entrainment Phenomena in Two-stage Type Electrostatic Precipitator

Abstract

Electrostatics precipitators (ESP) are used extensively for decontaminating industrial contaminated gas and for air cleaning of a highway tunnel. The collection efficiency in gas flow velocity 7m/s is usually over 80% as the performance of ESP for the tunnel. Recently, high performance ESP is used. Its gas flow velocity is 9m/s and the collection efficiency is higher than 90%. However, the collection efficiency for the size of an aggregating particle decreases due to particle re-entrainment. Suspended aggregating particles decrease a visibility index. When their particles deposit on cameras, lamp covers, walls, etc., it becomes difficult to distinguish sight at observation points of the tunnel. Therefore, it is very important to prevent particle re-entrainment. In this work, we focus on controlling re-entrainment phenomena and improving collection efficiency. The effect of the applied voltage waveform of the collecting section in the two-stage type ESP has been investigated experimentally. Consequently, when rectangular voltage is compared with DC voltage, the collection efficiency by rectangular voltage is about 10% higher than that by DC voltage. When rectangular voltage is applied, particles deposited on the downstream surface of the wall decrease and the wall contamination is improved.