Enhanced Pulsed Corona Method for the Removal of SO2 and NOx from Combustion Gas in a Wet Electrostatic Precipitator
This research investigated the removal of sulfur dioxide (SO2, up to 3000 ppm) and nitrogen oxides (NOx, up to 1000 ppm) in a bench-scale pulsed corona enhanced wet electrostatic precipitator (wESP). High level of SO2 (up to 70%) was removed by using water and pulsed corona discharge (45 kV, 40 watt) without any additives. SO2 removal efficiency increased with gas residence time, water flow rate, inlet SO2 concentration, and applied corona power. Corona discharge forced the charged SO2 to reach equilibrium with the water. The primary removal mechanisms for SO2 are the selective charging of SO2 molecules and the wet wall absorption. A n-CSTR/mass transfer model was developed for this wESP system. The overall SO2 removal efficiency and the overall SO2 mass transfer coefficient of the wESP can be predicted from wESP system parameters and operational conditions. NOx removal efficiency increased with gas residence time, inlet NOx concentration, and applied corona power. Without any additives, the maximum De-NOx efficiency were 20% and 5% in an air stream and in a 3%-O2 simulated flue gas, respectively. The maximum NOx removal in this simulated flue gas was 40% due to the formation of NH4NO3 aerosols with the injection of O3 and NH3 (without ammonium sulfur aerosols). High NOx removals (~80%) were measured when the in-situ ammonium sulfur aerosols were formed in simulated flue gas that contained NH3, SO2, and ozone. It was determined that the in-situ ammonium sulfur aerosols served as a highly efficient adsorbent with tremendous surface area which enhanced the oxidation of NO, as well as the formation of NH4NO3. A batch reactor was also constructed to study the SO2 mass transfer and removal mechanisms. The results showed that a positive pulsed corona achieved the maximum pollutant removal rate as compared to any other types of coronas. The overall mass transfer was enhanced by 160% with a power density of 685 watt/m3. A thin film mass transfer model was developed by introducing both the gas and liquid side electrostatic enhancement factors. It is believed that both the gas side and the liquid side boundary layer thicknesses were reduced by the corona discharge.
School:University of Cincinnati
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:desulfurization denitrification plasma flue gas electron attachment
Date of Publication:01/01/2000