Experimental Studies of Novel Constructions of Discharge Electrode in ESP for the Reduction of Fine Particles and Mercury Emission

A. Świerczok and M. Jędrusik

Wrocław University of Technology, Poland

Abstract- Flue gases from coal-fired power plants in Poland are mainly cleaned by electrostatic precipitators (ESPs). New restrictive legislation (Directive of IED) regarding the emission of particulate matter to the atmosphere will require novel solutions and/or modification of the existing electrostatic precipitators in order to increase the collection efficiency, particularly in PM2.5 range. Although the mass percentage of PM2.5 particles in total emission is small, the impact of these fractions on human health is relatively large, particularly due to high content of mercury. For these reasons, new constructions of emission electrode applied in ESPs have been investigated in this paper. The current-voltage characteristics and current density distribution over the collection electrode for different types of emission electrodes have been presented. It was shown that for particles from coal-combustion boilers, the collection efficiency of fine particles can be increased for certain constructions of the emission electrode. The size of particles precipitated on the collection electrode varies depending on the place of deposition, relative to the axis of emission point. It was also confirmed that the percentage of mercury is higher in small particles fractions than in the larger ones.
The results indicate that proper selection of emission electrode construction allows increasing total collection efficiency and decreasing of the emission of fine particles of high mercury content. It seems, therefore, that the selection of emission electrode is one of the prospective solutions, which will allow comply with new restrictive emission regulations.

Keywords-Electrostatic precipitator, discharge electrode, corona current, fly ash

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