Formation of NO_x from air and N₂/O₂ mixtures using a nonthermal microwave plasma system

We present an experimental study of NO_x (NO and NO₂) formation from air and N₂/O₂/NO_x mixtures using a nonthermal microwave plasma device. The tests were performed considering the energy consumed to generate plasma gas and the flow rate of air. The results demonstrated that NO_x production was proportional to input power and the inverse of air flow rate. In the experiments that used N₂ and O₂ mixtures instead of air, the maximum NO_x concentration produced at equilibrium was 16.02 × 10¹⁶ molecules/J (0.66 × 10¹⁶ NO molecules/J and 15.36 × 10¹⁶ NO ₂ molecules/J). Under the condition of the source gases consisting of NO and NO₂ of 970 ppm in the N₂ and O₂ mixture with a ratio of 79/21, the concentrations of NO_x generated were 5,571 and 5,320 ppm.