Removal of ultrafine particles in a full-scale two-stage electrostatic precipitator employing a carbon-brush ionizer for residential use

Abstract

Despite recent advances in the area of industrial electrostatic precipitators (ESPs), their residential use remains uncertain owing to the concern about ozone emissions when the removal efficiency of fine and ultrafine particles is increased. In this study, we propose a comprehensive numerical simulation of a full-scale two-stage ESP equipped with a carbon-brush ionizer that is capable of efficiently removing ultrafine particles with minimal ozone emissions. We calculated the spatial distributions of the electric potential and ionic charge density, the turbulent gas flow field coupled with ionic currents, and charge states and behavior of ultrafine particles in the entire region of the ESP. However, we did not investigate the ozone emission from the ionizer. In addition, we built an identical system to measure the profile of the local ionic current at the bottom of the discharging zone as well as the particle-collection efficiency. We clarified the effects of the orientation of the carbon brush tip and gas flow on the behavior of the ions and explored the behavior of charged particles in the collection unit with the insertion of a dielectric separator, thereby preventing air breakdown and increasing collection efficiency. All the simulation results were found to be consistent with experiments. We determined that a single carbon-brush electrode was sufficient to remove ultrafine particles at an efficiency of approximately 100% at 225 m3/h.