Treatment of N2O in pulsed microwave torch discharge

Abstract

Results of using a moderate-power (several hundred Watts) pulsed microwave torch plasma (MTP) to the conversion of atmospheric-pressure nitrous oxide (N 2O) into nitrogen oxides (NO, NO2 and N2O4) are presented. The pulsed regime allowed to decrease the average power used, resulting in a higher value of energy efficiency by about 10 % (reaching several hundred g[N2O]/kWh) at the same efficiency of the decomposition of N 2O (70 ÷ 90 %) as at the continuous operation of MTP. The removal rate increased up to 200 g[N2O]/h. The obtained results suggest the pulsed MTP promising for efficient decomposition of various gaseous pollutants, e.g. fluorocarbons.

Destruction of Freon HFC-134a Using a Nozzleless Microwave Plasma Source

“…The energetic parameters of Freon destruction obtained in the present experiment are superior to those when other plasma methods (e.g. corona [22], barrier discharges [23,24], gliding [25] and arc [8,26,27] discharges, low-power [10][11][12] or moderated-power [13] microwave torch discharges) were employed for destruction of Freons. Among the other plasma methods, the best energetic parameters (mass yield rate and energetic mass yield) of HFC-134a destruction were achieved by Watanabe et al [26] and Ohno et al [27] using DC arc plasma torches.…”

“…In this paper we report results of testing a new waveguide-based nozzleless cylinder-type microwave plasma source (MPS) with high power (600-3000 W) and high gas flow rate for Freon destruction, using HFC-134a as an example. In contrast to our previous microwave plasma systems [10][11][12][13], Freon is the only gas being processed in the present MPS, without any additions. The MPS used for HFC-134a destruction has been originally designed and proved for hydrogen production via methane pyrolysis [14,15].…”

“…In our previous works [10][11][12][13] we described results of the destruction of highly concentrated Freons using low power (*100 W) and moderated-power (up to 400 W) microwave torch discharges (MTDs) operating at atmospheric-pressure air or nitrogen. The presented results showed that the destruction of Freons using the low-and moderate-power MTDs is highly efficient (decomposition efficiency of CFC-11, CFC-12, HCFC-22 and HFC-134a was almost 100% with energy efficiency and destruction rate up to 840 g kWh -1 and 335 g h -1 , respectively).…”

CFC-11 destruction by microwave torch generated atmospheric-pressure nitrogen discharge

“…However, one may expect that also the N 2 : CCl 3 F MTD plasma is in the nonthermodynamic equilibrium. Our attempt to measure the neutral gas temperature in an N 2 : CCl 3 F MTD flame by the spectroscopic method as in [21], unsuccessful due to opaque carbon deposits on the reactor walls, showed qualitatively that the neutral gas temperature in such a mixture seems to be lower than that in the nitrogen MTD flame. Assuming that the electron density and temperature in the N 2 : CCl 3 F MTD flame core cannot be much different than those in the nitrogen MTD (since they have to sustain the plasma), the non-thermodynamic equilibrium seems to be preserved in N 2 : CCl 3 F MTDs.…”

“…In the flame envelope, just above the flame core, the nitrogen temperature is higher (4000 K), while the electron temperature (17 000 K) and density (10 20 m −3 ) are lower than those in the core. Jasiński et al [21] measured that the nitrogen temperature in the flame envelope, just above the flame core, is 3700±500 K, regardless of the microwave power (100-400 W) and nitrogen flow rate (1-3 litre min −1 ). This is due to the almost linear increase of MTD flame volume with increasing microwave power, which causes that the microwave power delivered to the unit volume of the flame remains constant, resulting in the constant nitrogen temperature.…”