ENERGY EFFICIENCY OF NO REMOVAL BY PULSED CORONA DISCHARGES

Pulsed positive corona discharges are used to remove NO from the flue gas of a methane burner. At low power input this leads to an increase in NO2, which shows that the process is oxidative. Removal efficiency is greatest when discharges are produced with high-voltage guises, whi ch are shorter in duration than the time required by the primary strea mers to cross the discharge gap, in combination with a dc bias. Other important parameters are input power density and residence time. Tire best result obtained so far is an energy consumption of 20 eV per NO m olecule removed, at 50% deNOx i.e., a removal of 150 ppm NOx, using a residence time of 15 s and an input power density of 3.5 Wh/Nm(3). [Wh /Nm(3) stands for watt-hour per normal cubic meter, i.e., at normal co nditions (273 K and 1 bar). This implies that 1 Nm(3) contains 2.505 1 0(25) molecules.] There appears to be room for improvement by the addi tion of gaseous and particulate chemicals or the use of multiple coron a treatment. It is argued from comparison between results from models and experiments that rite direct production of OH by the discharge is only the initiation of the cleaning process.