Removal of high concentration of nitrous oxide for anesthetic gas using nonthermal plasma combined with adsorbent

Nitrous oxide (N
₂
O), 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. N
₂
O is extremely stable in the troposphere and it is difficult to decompose it. In this paper, the high concentration of N
₂
O removal system was investigated using nonthermal plasma combined with adsorbent. N
₂
O gas that simulates the waste gas from anesthetic equipment used for operation rooms was decomposed using the surface discharge plasma reactor. When N
₂
O was decomposed, NO
_x
(=NO + NO
₂
) was generated. The generated NOx was adsorbed by adsorbent. As a result, 66% of N
₂
O decomposition efficiency was achieved with 12.8% of N
₂
O, 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 NO
₂
were generated upon N
₂
O decomposition; both of them were removed using adsorbent. The adsorbed NO
_x
was able to be decomposed with nitrogen plasma. It was demonstrated that high concentration of N
₂
O removal system can be accomplished using nonthermal plasma combined with adsorbent process. As a practical process, much higher N
₂
O removal without NO
_x
formation can be accomplished with a series of plasma reactors with recirculation, followed by N
₂
plasma for NO
_x
reduction system.