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Poster Session II

4:30 pm – 6:30 pm, Wednesday October 15 Session DW5 COEX, Lobby E
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Downstream oxygen quenching of microwave nitrogen plasma: A pathway to NOx production

Poster 61
Presenter: Omid Samadi (Maastricht University)
Authors: Stijn Helsloot (Maastricht University), Thomas Butterworth (Maastricht University), Niek den Harder (Maastricht University), Gerard van Rooij (Maastricht University)

Plasma-assisted nitrogen fixation can decarbonize and decentralize fertilizer production if its performance can be enhanced [1,2]. One innovative approach involves separating the plasma-induced nitrogen activation step from subsequent reactions with O2, allowing a higher degree of activated nitrogen to be transported downstream, thereby enhancing NOx production. This method offers a direct route from molecular nitrogen to nitric oxide, which bypasses the need for the conventional ammonia synthesis stage.

In this work, we investigate the process performance and temperature evolution during oxygen injection into the afterglow of a nitrogen plasma, using FTIR and Raman spectroscopies, respectively. Different quenching nozzles are employed to improve the mixing of N-radicals generated in the discharge with O2 quench gas. Systematic parameter-space measurements are conducted, including scans of plasma power, flow ratio and discharge pressure, to boost NOx production. The highest NOx yield is observed with O2 flow fractions exceeding 50% at atmospheric pressure. Temperature imaging indicates a range of 1400-2000 K for an O2 flow fraction of 23% and 1200-1400 K for a flow fraction of 50%. Overall, these findings indicate that higher O2 flow fractions result in better mixing and more rapid quenching, and suggest that N-radical transport likely plays a key role in downstream NOx production.

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