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

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 degrees C in a wirecylinder 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 degrees 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 degrees C and a port voltage of similar to 17,200 V. In the BCD & SB stages, the collection efficiency is greatly reduced, i.e., it is similar to 88.35% in the NCD-only stage at a temperature of 500 degrees C and a port voltage of similar to 14,000 V, whereas it is only similar to 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. (C) 2015 Elsevier B.V. All rights reserved.