Berlin 2001 – scientific programme
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P: Plasmaphysik
P 2: Plasma Technology, Diagnostics I
P 2.5: Talk
Monday, April 2, 2001, 17:40–17:55, 2032
Pulsed atmospheric microwave discharges for removal of NOx from exhaust gases — •A. Pott1, M. Baeva1, H. Gier1, J. Uhlenbusch1, J. Höschele2, and J. Steinwandel2 — 1Institut für Laser– und Plasmaphysik, Heinrich–Heine–Universität Düsseldorf — 2DaimlerChrysler Aerospace / Dornier GmbH, Friedrichshafen
A pulsed microwave plasma at atmospheric pressure (microwave frequency 3.0 GHz, pulse length 3.5 µs, repetition rate 40 Hz, flowrate 6−60 slm) is operated in mixtures of N2, O2 and NO and studied with regard to the ability to reduce NOx. The breakdown fieldstrength required is obtained using resonant structures with a high quality factor. Coherent anti–Stokes Raman scattering (CARS) has been used to examine the temporal development of the rotational and vibrational temperature Trot and Tvib of N2 in the plasma. Tvib rises in pure N2 up to more than 3000 K, whereasw Trot remains below 500 K. Admixing of NO and/or O2 leads to a decrease of Tvib below 2000 K. In O2–free mixtures more than 90 % reduction of NOx could be observed by means of a FTIR spectrometer. After admixture of 2 % O2 there still remains a reduction of about 50 %. A plasma model is developed, which considers beside the electronical processes as well the vibrational kinetics of N2, O2 and NO as the plasmachemical processes. The calculated concentrations of the species and the temporal development of the vibrational temperature are in a good agreement with the measured values. The project has been partially supported by the german BMBF (FKZ 13N7197/4).