AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
On the Electrical Properties of Carbon Sorbents and Their Impact on Electro-Hydrodynamic Phenomena within Utility ESPs: Numerical Simulation and Field Data
HEREK CLACK, University of Michigan
Abstract Number: 342 Working Group: Control Technology
Abstract Powdered activated carbon (PAC) injection upstream of an electrostatic precipitator (ESP) has emerged as a leading technology capable of reaching the 90% target for reducing mercury emissions mandated in 2012 by the U.S. EPA’s Mercury and Air Toxics Standard. However, in previous studies we have measured and reconfirmed that the electrical resistivity of PAC falls well below the accepted range for optimal ESP removal efficiency, and the addition of PAC to fly ash significantly lowers the bulk electrical resistivity of the mixture. Further, our previous analyses estimated that the lower removal efficiency for PAC could increase particulate carbon emissions from ESPs by more than 100%. The present study offers fundamental details of the internal gas-particle dynamics of ESPs that govern particle collection, mercury adsorption, and undesirable particulate carbon emissions associated with PAC injection. Using a multi-physics computational software suite to solve the coupled set of fluid dynamic and charged particle transport equations that govern the electro-hydrodynamic (EHD) fluid-particle phenomena within ESPs, the computed solutions provide insight into how these EHD-driven phenomena vary as a result of the addition of PAC to the suspended fly ash and the resulting change in electrical properties of the bulk particulate matter. Performance trends that are extracted from these computed solutions are compared against particulate samples collected from the hoppers of a full-scale utility ESP during PAC injection that have been analyzed for both their mercury and carbon content. The comparison provides a full-scale validation of a computational model of combined fly ash and PAC EHD and adsorptive behavior within ESPs, contributing to improved ESP performance in the simultaneous control of both mercury and PM.