Abstract View
Modeling of Heterogeneous Dustcake Effects by PAC Injection in a Cylindrical Electrostatic Precipitator for Mercury Emissions Control at Coal-Fired Power Plants
ERIC MONSU LEE, Herek Clack, Northern Illinois University
Abstract Number: 49
Working Group: Control and Mitigation Technology
Abstract
Injection of powdered activated carbon (PAC) upstream of an electrostatic precipitator (ESP) is the mature mercury emissions control technology at coal-fired power plants (CFPPs). Based on National Energy Technology Laboratory (NETL)-funded full-scale testing results with PAC injection, conducted by ADA-ES, increasing the rate of PAC injection can potentially promote penetration of submicrometer PAC particles through an ESP, indicated by darkened PM filters from sampling of stack emissions. PAC injection into utility ESPs leads to formation of a heterogeneous dustcake layer on the collection electrodes because of different particle deposition patterns between coal fly ash and PAC. The present study aims to model the effect of such a heterogeneous dustcake in a cylindrical ESP to characterize the induced vortex flows under conditions associated with high electrohydrodynamic (EHD) numbers and its effect on the formation of particle clusters and ESP collection efficiency. A multiscale ESP model is established in COMSOL Multiphysics based on a Euler-Lagrange numerical scheme by considering the effect of particle drag on the fluid flow (i.e. two-way coupling). The heterogeneous dustcake is modeled by imposing a boundary condition assuming spatially varied powder resistivity along the collection electrode surface. The results serve to optimize the process of PAC injection in terms of reducing the PM emissions from ESPs.