The work performed during the project is summarised. In the project we focused on removal of nitrogen oxides NOx (NO, NO2) and, in particular, on removal of nitrogen monoxide (NO) by injection of plasma-produced reactive agents. As reactive agents wetested ozone (O3), NH and NH2 radicals from ammonia (NH3) and nitrogen atoms (N) generated in dielectric barrier discharges (DBDs). Hydrazine (N2H4) as a reducing agent and direct plasma treatment of the entire exhaust gas was investigated as well. Weperformed laboratory experiments on synthetic exhaust gases, modelling of the mechanisms and a demonstration of the technique on a test engine, a 30 kW combustion engine fuelled with natural gas. We achieved the best results with ozone injection into theexhaust gas. This technique is based on oxidation of NO to N2O5 that is subsequently removed from the exhaust gas by a scrubber. In the laboratory experiments we obtained complete removal of NO by injection of an ozone/oxygen mixture from an oxygen (O2)DBD into synthetic exhaust gases with compositions close to those of real exhaust gases. Ozone injection was chosen for demonstration of NOx removal from the exhaust gas of the test engine. We achieved 95 % NOx removal with an oxygen DBD and 70 % NOxremoval with an air DBD. The running costs relating to the demonstration were estimated to be approximately 30 DKK per kg removed NOx for the oxygen DBD, and 25 DKK per kg removed NOx for the air DBD. For a commercially available ozone generator, thetotal costs of NOx removal from a 3 MW power plant were estimated to 27 DKK per kg removed NOx for oxygen as the feed gas, and 21 DKK per kg removed NOx for air as the feed gas.
Energiteknologier på vej; Risø-R-1545; Risø-R-1545(EN)