Experimental investigation of the effect of collection length in a two-stage electrostatic precipitator for removal of PM2.5

In this work, a laboratory-scale charger, with a single wire electrode of one charging unit for effective ozone control, and collector with a 300 mm length and 5 mm plate-plate distance extremely short for high-efficient capture of noxious particles, was designed and assembled as a two-stage ESP to study the effect of collection length for removal of PM2.5, in particular to these sub-micron particles which had the highest penetration rate during the electrostatic capture process. The influence factors, including the current density of charger, the electric field strength of collector, and gas velocity, were investigated in detail. Multiple channels of the collector were chosen to thoroughly compare the performance difference by detecting the particle concentration in the electric field directly. Besides, the ozone concentration test was carried out in various parameters to explore the influence degree simultaneously. Experimental results showed that the collection efficiency based on the number concentration could reach up to be 92.9%, 96.7%, and 97.7% for 0.25 mu m, 0.35 mu m, and 0.45 mu m diameter particles at 4 m/s gas velocity, respectively, which benefited from the advantages of long collection plate and short migration distance. Compared with the influence factors of charger current density and gas velocity, electric field strength occupied the middle position in effecting the collection efficiency, whose most massive index factor was about 18 at a collection length of 30 cm. While the maximum index factor of current density was 3.7 at a collection length of 15 cm and of gas velocity was 27.5 at a collection length of 10 cm. The ozone concentration test suggested that charger current, gas velocity, collection length, and electric field strength could affect the ozone concentration from strong to weak in sequence.