Performance of Ultrafine Particle Collection of a Two-Stage ESP Using a Novel Mixing Type Carbon Brush Charger and Parallel Collection Plates

A novel two-stage electrostatic precipitator (ESP) for information technology manufacturing industries was developed. It uses a mixing type carbon brush charger located outside of the main gas flow duct to completely prevent contact of the polluted gases with the chargers, and applies an additional electric field between the upper and bottom plates of the charging stage to enhance collisions between ions and particles, thereby increasing the particle charges. The performance of the ESP was evaluated experimentally for ultrafine particles with a mean diameter of 100 nm based on number, and of 200 nm based on surface area by varying the voltages of the chargers and for generating the additional electric field, and by varying the number of the chargers. Finally, the collection efficiencies of the ESP were compared to those obtained from Deutch's collection theory using the average experimental particle charges. The total air flow rate used in the tests was approximately 110 L/min with a 10:1 ratio of the main and mixing flows in the ESP, and the applied voltages of the charger and additional electric field were -10 to -22 kV, and -5 to -10 kV, respectively. Collection efficiencies in the ESP were linearly proportional to the increase in the number of chargers and the increase in the applied voltage to the chargers, which in turn were inversely proportional to the increase in the applied voltage used to generate the additional electric field. A collection efficiency of the ESP of > 90% was obtained at a flow rate of 110 L/min, corresponding to flow speeds of approximately 0.19 m/s through the charging stage and 0.23 m/s through the collection cell based on the total particle number at an applied voltage to the triple chargers of -15 kV and an additional electric field between the upper and bottom plates in the charging stage of -6 kV/100 mm.