Particle Collection Efficiency of Polypropylene Nonwoven Filter Media Charged by Triode Corona Discharge

The aim of this paper is to evaluate the collection efficiency of submicron particles using electrically charged nonwoven filter media. A triode-type electrode arrangement consisting of a high-voltage wire-type ionizing electrode, a metallic grid, and grounded plate electrode is employed to control the distribution of electric charges deposited on the media. Surface electric potential measurement is carried out to study the evolution in time and the repartition in space of deposited charges. The collection efficiency is estimated by measuring the particle concentrations downstream and upstream of the charged filter media. The main results show good correlation between the surface potential level and the collection efficiency of submicron particles for several charging conditions. In particular, filtration performance increases with increasing the corona current through the media during the charging process. Increasing the electric field between the grid and the media during corona charging has also a positive effect on the collection efficiency. Results indicate that high collection performances could not be achieved using thin monolayer media.