Maintaining the PM Removal Efficiency of a Two-Stage ESP With External Ion-Injection Discharge via a Water Film on the Collection Plate and Cleaning of the Ionizer

Abstract

A two-stage electrostatic precipitator (ESP) with a reduced footprint, external ion-injection discharge, and water film on the collection plate was developed for long-term operation. For optimal particulate matter (PM) removal efficiency, the ionizer of the external ion injection system was fixed at a distance of 5 mm from the bias plate. Under these operating conditions, the 0.3- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m PM (PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.3</sub> ) removal efficiency was reduced to approximately 70% due to low migration velocity. The application of an additional collection plate extended the residence time of the charged particles in the electric field, which resulted in a removal efficiency exceeding 95%. However, long-term operation (675 min) of the two-stage ESP with external ion-injected discharge resulted in spark generation due to contamination of the ionizer, and the PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.5</sub> and PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> removal efficiencies decreased linearly from 80.4% to 62.2% and 87.7% to 68.2%, respectively. Changing the ionizer to a pin shape with electrical specifications similar to those of carbon fibers resulted in water film formation on the collection plate. The PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.5</sub> and PM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> removal efficiencies remained at their initial levels for 120 min. The two-stage ESP with external ion-injected discharge operating with a water film is likely suitable for long-term operation in an industrial setting.