Experimental study on single-mode microwave-induced tungsten wire discharge for NO conversion in NO/N2 atmosphere

Single-mode microwave-induced tungsten wire discharge was conducted to investigate discharge phenomena in Ar, N 2 , NO, and their mixtures, as well as the effects of parameters, including diameter and number of tungsten wire, initial NO concentration, total gas flow rate, and microwave power, on NO conversion. The discharge phenomena verified that intense discharge could be observed in pure Ar or N 2 , but the discharge was considerably weakened in gas mixtures. The results of NO conversion showed that the increases of the tungsten wire diameter (0.1–0.12 mm), the tungsten wire number (1–3 wires), and microwave power (400–700 W), or the decreases of the total gas flow rate (2–0.5 L/min), and the initial NO concentration (800–200 ppm) could effectively lead to the increase of NO conversion. A maximum NO conversion of 91.5% can be achieved under the optimal conditions in the examined range. Besides, spectral analysis showed that W, O, and N ions were found in the discharge zone. After reactions, depositions were found on the inner surface of reaction tube, and the results of EDS (energy dispersive X-ray spectrometer) tests show that the depositions were composed of W, O, and N. Therefore, a portion of NO was inferred to be consumed by tungsten ions through the formation of tungsten oxides and tungsten nitrides.