Combined Effects of Pulsed Discharge Removal of NO,SO2, and NH3 from Flue Gas

Experiments have been performed using pulsed high-voltage discharges with the aim of removing NO and SO₂from flue gas obtained from a methane burner. It is found that the NO conversion is strongly increased by the addition of SO₂or NH₃. When both gases are added simultaneously the increase almost disappears. The synergetic effect can be maintained, as is shown, when NH₃is introduced much later than SO₂. The SO₂removal is already 70% upon stoichiometric addition of NH₃, but the electric discharge improves this to >95% and reduces the NH₃leak to a few ppm. This increase is probably related to aerosol production by the pulsed discharge which enhances the ammonium salt production. A so-called history effect is observed, i.e., the removal of NO and SO₂depends on the time that is taken to reach the required energization. It appears that the discharge has to create favorable conditions for the cleaning process. Using the synergetic and history effects the best cleaning result, at initial concentrations of 300 ppm, is 80% NO removal and 95% SO₂removal with 3 ppm NH₃leak. In this case the energy cost is 13 eV/NO (or a yield of 90 g NO and 200 g SO₂per kWh). Possibilities for further improvement are indicated.