Development of back corona discharge in a wire-cylinder electrostatic precipitator at high temperatures

Abstract

High-temperature electrostatic precipitation is a potential method for hot gas clean-up that is hindered by the issue of back corona discharge (BCD). This paper reports on the development of BCD at 350–700°C in a wire-cylinder electrostatic precipitator (ESP). As the output voltage of power supply increases, BCD begins at the surface of the ash layer, and then it extends toward the electrode gap space, forming consecutive discharge channels that bridge the two electrodes, ultimately leading to spark breakdown (SB). The discharge process that follows BCD can be classified into different stages: the NCD & BCD stages, the weak NCD, BCD & glow discharge stage, and the BCD & SB stages. At high temperatures (500°C or above), BCD is likely to convert to SB. In the NCD & BCD stages, the collection efficiency of the electrostatic precipitator is not affected, i.e., the collection efficiency is ~99.65%, regardless of whether BCD exists or not at a temperature of 350°C and a port voltage of ~17,200V. In the BCD & SB stages, the collection efficiency is greatly reduced, i.e., it is ~88.35% in the NCD-only stage at a temperature of 500°C and a port voltage of ~14,000V, whereas it is only ~67.42% in the BCD & SB stages. It should be noted that BCD results in an increase in the power consumption of the ESP for all stages. A physical model is proposed to explain the processes that initiate, maintain, and develop BCD.