Enhanced pulsed corona method for the removal of sulfur dioxide and nitrogen oxides from combustion gas in a wet electrostatic precipitator .

摘要

This research investigated the removal of sulfur dioxide (SO₂, up to 3000 ppm) and nitrogen oxides (NO_x, 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 SO ₂ 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 nCSTR/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.; NO_x removal efficiency increased with gas residence time, inlet NO_x concentration, and applied corona power. Without any additives, the maximum De-NO_x efficiency were 20% and 5% in an air stream and in a 3%-O₂ simulated flue gas, respectively. The maximum NO_x removal in this simulated flue gas was 40% due to the formation of NH₄NO₃ aerosols with the injection of O ₃ and NH₃ (without ammonium sulfur aerosols). High NO _x 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 NH₄NO ₃.; 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.