Numerical simulation of simultaneous electrostatic precipitation and trace gas adsorption: Electrohydrodynamic effects

Abstract

Electrostatic precipitators (ESPs) are now being tasked with simultaneously removing particulate matter (PM) and trace gas-phase pollutants such as mercury released during coal combustion. This represents a significant expansion of their original operational mission, one which is not captured by decades old quasi-1-D analytical expressions developed from first principles for predicting PM removal alone. At the same time, technological advances in ESP power supplies have led to steady increases over the years in the applied voltage achievable in new or refurbished ESPs. In light of these industry trends, the present study extends our previous study to examine the multiphase flow phenomena that may occur during such ESP operations, specifically the effects of electrohydrodynamic (EHD) fluid flow phenomena that can emerge when electrical current densities are high and/or fluid velocities are low. The results show good agreement at low current densities between the present numerical simulation results and ESP performance predictions obtained from classical analytical expressions, with increasing divergence in predicted performance at higher current densities. Under the influence of EHD phenomena, the acceleration of the fluid by electric body forces effectively increases average fluid velocities through the ESP channel with a commiserate reduction in PM removal efficiency. The impact on trace gas-phase pollutant removal is mixed, with EHD phenomena found to variously promote or inhibit gas-phase pollutant removal.