Back corona

Unlike dry ESPs, resistivity of the collected material is generally not a major factor in performance. Because of the high humidity in a wet ESP, the resistivity of particles is lowered, eliminating the "back corona" condition. The frequent washing of the pipes also limits particle buildup on the collectors. 

Back corona is caused by the electrical breakdown of gas in the dust layer. This breakdown produces positive ions, which drift toward the negative discharge electrode. The presence of ions with opposite polarity causes a reduction in the particle-charge and -collection efficiency. To avoid this problem, several methods are used. These include... 

Back corona (back ionization) The discharge phenomenon that takes place from a particulate layer in an electrostatic precipitator. 

A second effect of high fly ash resistivity is observed when the difference in potential across the collected dust layer rises to too high a value. A back corona can form as the EMF differential breaks down due to sparking across the dust layer. High currents flow between the wire cathode and plate anode thereby destroying the ability of the ESP to charge particulates. 

Biris, A.S. Mazumder, M.K. Sims, R.A. Yurteri, C.U. Farmer, S. Snodgrass, J. The effect of ring electrodes attachment to a corona gun on control of free ion concentration and back corona for improving powder paint appearance. IEEE Trans. Ind. Appl. 2003, 39 (6), 1614-1621. 

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