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/m (3) is well achieved by a conventional electrostatic precipitator (ESP). Ho wever, the collection efficiencies in terms of number density for the ultra fine (particle size between 0.01-0.1 mu m) or submicrometer particles by a conventional ESP are still relatively low. Therefore, it is necessary to im prove the collection efficiency for ultrafine particles. In this paper, att empts have been made to improve the ultrafine particle collection efficienc y by controlling dust loading, as well as using the short pulse energizatio ns. The present version of the ESP consists of three sets of wire-plate-typ e electrodes. For the ESP under de operation modes, experimental results sh ow that the collection efficiency for dc applied voltage decreases with inc reasing dust loading when particle density is larger than 2.5 x 10(10) part icles/m(3) due to inefficient collections of ultrafine particles. However, under pulse operating modes without de bias, high particle collection effic iency for ultrafine particles was obtained, which is thought to be due to t he enhancement of particle charging by electrons.