Numerical Simulation of Simultaneous Electrostatic Precipitation and Trace Gas Adsorption: Electrohydrodynamic Effects

Herek L Clack

doi:10.3389/fenrg.2017.00003

Abstract

Quasi-1-D analytical expressions for predicting the performance of electrostatic precipitators (ESPs) were developed from first principles decades ago and still find use in the present day, although significant simplifying assumptions are employed and manufacturers and operators still incorporate adjustable parameters to match field data. ESPs tasked with simultaneous particulate removal and trace gas-phase pollutant removal, however, represent a significant departure from their original operational mission. The present study extends our previous study of such ESP operations and uses the same computational platform to examine details of the multi-phase flow phenomena within ESPs as a function of the strength of the electro-hydrodynamic (EHD) fluid flow phenomena that can occur under high current density operating conditions or low fluid velocities. In particular, the results show good agreement between numerical simulation and classical ESP performance prediction equations at low current densities, and 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 the expected reduction in PM removal efficiency. The impact on trace pollutant is mixed, with both promotion and inhibition mechanisms associated with EHD phenomena identified.

Highlights

Over decades of use in controlling particulate emissions, electrostatic precipitators (ESPs) have been proven to be robust devices with electronic control systems that often operate virtually independently with minimal human intervention
Limestone, or trona to neutralize acid gases and powdered mercury sorbents such as powdered activated carbon (PAC) to adsorb toxic trace metals such as mercury has grown in the United States as new and more stringent regulations take effect
Comparisons to the classical D-A ESP performance prediction equation show that the high current densities required to induce EHD phenomena lead to higher electric fields and greater saturation charge on particles, both of which promote more rapid particle collection independent of the onset of EHD phenomena

Summary

Introduction

Over decades of use in controlling particulate emissions, electrostatic precipitators (ESPs) have been proven to be robust devices with electronic control systems that often operate virtually independently with minimal human intervention. When significant changes in particulate control performance have been needed, often due to changes in particle electrical properties, flue gas conditioning additives such as sulfur trioxide, and less commonly ammonia, have been. Electrostatic Precipitation and Gas Adsorption injected upstream of ESPs (Shanthakumar et al, 2008), altering particle electrical properties and improving the particulate matter (PM) removal performance of the device. The development of combustion systems capable of postcombustion carbon capture has driven studies of ESP operation during oxy-fueled combustion (Han et al, 2010; Kim et al, 2014). Limestone, or trona to neutralize acid gases and powdered mercury sorbents such as powdered activated carbon (PAC) to adsorb toxic trace metals such as mercury has grown in the United States as new and more stringent regulations take effect

Methods

Results

Conclusion