A computational model for the description of electrostatic precipitator performance

Abstract

A comprehensive computational model of an electrostatic precipitator was developed by incorporating the interacting phenomenon of fluid dynamics, particle dynamics and electrostatics using the commercial software STAR-CCM+® and the open source software package OpenFOAM®. The electrostatic equations were solved using OpenFOAM while particle charging and particle dynamics were solved using STAR-CCM+. The Euler-Lagrange approach was used to model the respective gas and particle flow, and turbulence were taken into account using the k-ε turbulence model. The developed computational model was intermittently validated with experimental results available in literature in terms of the electrostatics properties as well as particle collection efficiency. The results of a sensitivity analysis with respect to varying geometric and operating parameters are also reported. In this regard, the computational modelling results showed, in accordance with the literature, that the particle collection efficiency increases with increasing particle diameter, decreasing air velocity, decreasing wire-to-plate spacing and with an increasing number of discharge wires. It was further found that variation of relative permittivity also has significant influence on the particle collection efficiency which increases with increasing relative permittivity. The model was subsequently further refined and validated with experimental and computational results taken from the literature to study the shielding effect that can arise in the case of multi-electrode ESP systems. Shielding was shown to significantly influence the space charge and current density distributions that are obtained during corona discharge. More specifically, the computational modelling results showed that the current density and space charge density developed around the inner wire-electrodes were suppressed relative to the outermost wires. The intensity of shielding was quantified in terms of the peak current density and space charge density resulting from corona discharge from the outer wires relative to that of the inner wires. Consequently, the modeling results showed that the intensity of shielding was dependent on the wire-to-wire spacing, the plate-to-plate spacing, and the number of wire-electrodes, although the plate-to-plate spacing was found to be the most influential parameter. The developed computational model was finally validated with experimental results obtained using an in-house laboratory-scale ESP. The use of both wire-electrodes and spiked electrodes were studied, and the modeled and experimentally measured V-I relationships and particle collection efficiencies were compared under shielding and non-shielding conditions. Good agreement was achieved between the measured and modeled V-I relationships of the wire-electrodes, both under shielding and non-shielding conditions. Consequently, the shielding effects predicted with the computational model was confirmed in terms of the V-I characteristics and particle collection efficiencies that were achieved under varying geometric parameters. Additionally, the experimental results obtained with a spiked electrode also confirmed the validity of the computational model with respect to modeling ESP operation with irregularly shaped electrodes.