(376b) Advanced Oxidation Processes with Tube-Type Wet Electrostatic Precipitators

The electrostatic precipitator (ESP) is commonly used for the removal of particulate matter in off- gas purification in process industries and other applications. During operation, the discharge electrode produces ozone.^{1, 2} which is considered as hazardous pollutant in off-gas treatment.

This project has a focus on the investigation of ozone generation under specific operational conditions of wet electrostatic precipitators for applications in wastewater treatment and off-gas purification. Focus of this project was to determine the degradation rate of different organic constituents like acetone, isopropanol, phenol and EDTA in the rinsing water flux of a tube-type wet ESP. Objective was optimisation of the current/voltage characteristic, air flow rate and water circulation rate for efficient degradation of constituents. The results reveal that degradation efficiency of constituents in aqueous effluents by corona discharge is enhanced due to ozone formation with increasing operation voltage for fixed air flow rate. When water circulation rate is optimised nearly complete absorption of generated ozone and degradation of constituents is observed. Complete degradation of acetone, iso-propanol as well as decomposition of phenol and EDTA in water was achieved. TOC depletion and pH variation are very comparable with the results obtained by UV irradiation of ozonated effluents.

The experimental results of investigating degradation of specified constituents confirm that with minor adjustments wet electrostatic precipitators work as very efficient oxidation reactors for advanced oxidation processes. Wet ESP can well be applied for gas purification (including precipitation of particulate as well as gaseous matter), or water purification as well as simultaneous gas and water purification.  

Figure 1 shows a comparison of acetone oxidation with corona discharge in the ESP and with UV-irradiation. Initial acetone concentration was 0.5 g/dm³.

UV-irradiation was carried out with a 15 W low pressure lamp.  Acetone oxidation with corona discharge was operated at U = 16 kV and I = 0.75 mA. The specific power was 7.5 W/dm³ in case of UV-irradiation and it was 1.2W/dm³ in case of corona discharge.

Figure 1: Comparison of acetone oxidation with corona discharge and UV irradiation at ambient

                 temperature and pressure

Literature

[1]   Jody. Ozone production in electrostatic air cleaner with contaminated electrode by. IEEE TRANSACTION ON INDUSTRY APPLICATION, 30(2):370?376, 1994.

[2]   Kimberly. Ozone generation by indoor, electrostatic air cleaners. Aerosol Science and Technology, 27(6):689?708,, 1997.