Performance of a pilot-scale wet electrostatic precipitator for the control of sulfuric acid mist.

Abstract

The use of a wet electrostatic precipitator (WESP) is often regarded as a viable option to reduce sulfuric acid mist emitted from the wet flue gas desulfurization (WFGD) tower in coal-fired power plants. In this study, a pilot-scale wet electrostatic precipitator equipped with a wall-cooled collection electrode is investigated for the control of sulfuric acid mist from a simulated WFGD system. The results show that due to partial charging effect, the removal efficiency of sulfuric acid aerosol decreases when the aerosol size decreases to several tens of nanometers. Moreover, due to the plasma-induced effect, a large number of ultrafine sulfuric acid aerosols below 50nm formed at a voltage higher than 24kV inside the WESP. The percentages of submicron-sized aerosols significantly increase together with the voltage. To minimize the adverse plasma-induced effect, a WESP should be operated at a high gas velocity with an optimum high voltage. Even at a high flue gas velocity of 2.3ms(-1), the mass concentration and the total number concentration of uncaptured sulfuric acid aerosols at the WESP outlet are as low as ca. 0.6mgm(-3) and ca. 10(4) 1cm(-3) at 28kV, respectively. The corresponding removal efficiencies were respectively higher than 99.4 and 99.9% and are very similar to that at 1.1 and 1.6ms(-1). Moreover, the condensation-induced aerosol growth enhances the removal of sulfuric acid mist inside a WESP and enables a low emission concentration of ca. 0.65mgm(-3) with a corresponding removal efficiency superior to 99.4% even at a low voltage of 21kV, and of ca. 0.35mgm(-3) with a corresponding removal efficiency superior to 99.6% at a higher voltage level of 26kV.