Electrostatic charging and precipitation of diesel soot

Exhaust treatment systems consisting of new catalyst technologies and particulate filters is indispensable to meet increasingly stringent global regulations limiting particulate matter (PM) and nitrogen oxide (NO_X) emissions from heavy duty and light duty diesel vehicles. Diesel particulate filter (DPF) has been established as a key technology in reducing diesel particulate emission. However, pressure drop, durability and insufficient collection efficiency for nano-particles call for technological improvements. Electrostatic Precipitation (ESP) is another leading technology used in exhaust treatment but it is currently limited to applications for stationary sources. In this paper we have proven that concurrent use of DPF and ESP show synergetic effects with very high collection efficiency and slower rise up of the pressure drop. The number density of particles observed downstream of the combined system was 98 % less compared with that of DPF only. In addition, it was confirmed that increase in the pressure drop of the DPF was slower. In this study, filter that exposed exhaust gas was observed by using SEM (Scanning Electron Microscope). In addition, the electrical impact with the electrification particle on the surface of the filter was considered with a sucking type Faraday cage. The influence that the diesel particulate exerted on DPF by such an experiment was able to be clarified. Moreover, as the accumulation of PM causes breakdown, it is necessary to remove the PM for stable operation. In this study surface discharge was also examined to remove accumulated PM. It has been demonstrated that the surface discharge could also oxidize not only the oxidation of PM but also NO.