Removal of High Concentration of Nitrous Oxide for Anesthetic Gas Using Nonthermal Plasma Combined with Adsorbent

Nitrous oxide (N2O), which has been used as an anesthetic gas in hospitals, is one of greenhouse gases and it should be removed. Nonthermal plasma is considered to be useful for low concentration gas treatment due to low electron density. N2O is extremely stable in the troposphere and it is difficult to decompose it. In this paper, the high concentration of N2O removal system was investigated using nonthermal plasma combined with adsorbent. N2O gas that simulates the waste gas from anesthetic equipment used for operation rooms was decomposed using the surface discharge plasma reactor. When N2O was decomposed, NO (=NO + NO2) was generated. The generated NO was adsorbed by adsorbent. As a result, 66% of N2O decomposition efficiency was achieved with 12.8% of N2O, the flow rate of 1.1 L/min, and the input power to the plasma reactor of 375 W. Furthermore, 0.4% of NO and 1.0% of NO2 were generated upon N2O decomposition; both of them were removed using adsorbent. The adsorbed NO was able to be decomposed with nitrogen plasma. It was demonstrated that high concentration of N2O removal system can be accomplished using nonthermal plasma combined with adsorbent process. As a practical process, much higher N2O removal without NO formation can be accomplished with a series of plasma reactors with recirculation, followed by N-2 plasma for NO reduction system.