Study of Effective Particle Charging Regions in a Corona Discharge in an Electrostatic Precipitator

Every electrostatic precipitator uses a corona discharge to charge the material particles to be precipitated, and two particle charging processes occur in it: field charging and diffusion charging. The aim of this study is to evaluate the dependence of particle charging on the number density of negative ions and the electric field distribution. For this work, we replaced the space-charge with the number density of negative ions. We used a wire–plate-type electrode structure for the calculation model, applying negative DC high voltage to the wire electrode, and grounding the plate electrode. We previously calculated the distributions of the electric field and of the number density of negative ions using a two-dimensional finite-element method. In the present work, we calculate both the field charging and diffusion charging processes based on those results. However, we did not include the negative ions lost during particle charging in these calculations. Our results show that electric field charging tends to occur directly under the wire electrode, while diffusion charging is more widespread. For a constant-power discharge, we found that, although increasing only the voltage increases the electric field that accelerates the charges, it decreases the space-charge density. We also found that larger particles tend to be charged closer to the grounded plate electrode than in the vicinity of the wire electrode.