Collection efficiency of ultrafine particles by an electrostatic precipitator under DC and pulse operating modes

High particle collection efficiency in terms of particle weight/volume mg/m³ is achieved by a conventional electrostatic precipitator (ESP). However, the collection efficiencies in terms of number density for the ultrafine (particle size between 0.01-0.1 μm) or submicrometer particles by a conventional ESP are still relatively low. Therefore, it is necessary to improve the collection efficiency for ultrafine particles. In this paper, attempts have been made to improve the ultrafine particle collection efficiency by controlling dust loading, as well as using the short pulse energizations. The present version of the ESP consists of three sets of wire-plate-type electrodes. For the ESP under DC operation modes, experimental results show that the collection efficiency for DC applied voltage decreases with increasing dust loading when particle density is larger than 2.5×10¹⁰ particles/m³ due to inefficient collections of ultrafine particles. However, under pulse operating modes without DC bias, high particle collection efficiency for ultrafine particles was obtained, which is thought to be due to the enhancement of particle charging by electrons