Removal of High Concentrations of the Anesthetic Gas Nitrous Oxide Using Nonthermal Plasma Combined With an Adsorbent

Nitrous oxide (N 2 O) is commonly used as an anesthetic gas in hospitals. It is a greenhouse gas and should therefore be removed to limit pollution. As nonthermal plasma has low electron density, it has been considered effective for the treatment of low concentrations of gas. Moreover, N 2 O is extremely stable in the troposphere, and is therefore difficult to decompose. In this study, a system to remove high concentrations of N 2 O using nonthermal plasma along with an adsorbent was investigated. A surface discharge plasma reactor was employed to decompose N 2 O gas. This gas simulated the waste gas from the anesthetic equipment used in operating theatres. Because of its high concentration, the decomposition of N 2 O afforded the mononitrogen oxides, nitric oxide, and nitrogen dioxide (NO x = NO + NO 2 ), respectively. The generated NO x was adsorbed by the adsorbent. As a result, an N 2 O decomposition efficiency of 66% was achieved with air-based 12.8% N 2 O at a flow rate of 1.1 L/min and a plasma reactor input power of 375 W. Furthermore, 0.4% NO and 1.0% NO 2 were generated during N 2 O decomposition. Both gases were removed by the adsorbent. It was confirmed by the previous studies that the adsorbed NO x was decomposed by N 2 plasma. It was demonstrated that the removal of high concentration of N 2 O could be accomplished by using a system that combines nonthermal plasma with an adsorbent. In practice, much higher volumes of N 2 O can be removed, without NO x formation, in a setup that involves a series of plasma reactors with recirculation, followed by an NO x reduction system with N 2 plasma.