Fine particle removal performance of a two-stage wet electrostatic precipitator using a nonmetallic pre-charger

Abstract

A novel two-stage wet electrostatic precipitator (ESP) has been developed using a carbon brush pre-charger and collection plates with a thin water film. The electrical and particle collection performance was evaluated for submicrometer particles smaller than 0.01∼0.5 μm in diameter by varying thevoltages applied to the pre-charger and collection plates as well as the polarity of the voltage. The collection efficiency was compared with that calculated by the theoretical models. The long-term performances of the ESP with and without water films werealso compared in tests using Japanese Industrial Standards dust.The experimental results show that the carbon brush pre-charger of the two-stage wet ESP had approximately 10% particle capture, while producing ozone concentrations of less than 30 ppb. The produced amounts of ozone are significantly lower than the currentlimits set by international agencies. The ESP also achieved a high collection rate performance, averaging 90% for ultrafine particles, as based on the particle number concentration at an average velocity of 1 m/sec corresponding to a residence time of 0.17sec. Higher particle collection efficiency for the ESP can be achieved by increasing the voltages applied to the pre-charger andthe collection plates. The decreased collection efficiency that occurred during dust loading without water films was completely avoided by forming a thin water film on the collection plates ata water flow rate of 6.5 L/min/m2. © 2011 Air & Waste Management Association.