NO/sub X/ reduction using nitrogen nonthermal plasma desorption

In the flue emission from internal combustion system using diffusing combustion such as coal or oil fuel boiler, incinerator or diesel engine, around 10% oxygen is usually included. It is difficult to reduce the NO/sub X/ in the emission completely using catalysts or plasma alone because the part of NO/sub X/ is oxidized under O/sub 2/ rich environment. In order to overcome these difficulties, we proposed a new after treatment system of NO/sub X/ included in exhaust gas of combustion system using nonthermal plasma (NTP) desorption and reduction. In this system, exchangeable adsorbent columns are equipped. First, the exhaust gas including NO/sub X/ is adsorbed to a NO/sub X/ adsorbent for a period of /spl Delta/T/sub a/. After the period of /spl Delta/T/sub a/ the path of exhaust gas is changed with a pair of rotary valves and NO/sub X/ adsorbent is changed. The adsorbed NO/sub X/ is desorbed from the adsorbent and reduced by applying NTP for a period of /spl Delta/T/sub a/ using N/sub 2/ or low oxygen concentration gas. The exhaust gas is always kept clean by the exchange of adsorbent. Further, total electric energy can be reduced by taking /spl Delta/T/sub d///spl Delta/T/sub a/ smaller because NTP is not applied for /spl Delta/T/sub a/. This system can be operated at atmospheric temperature because no catalyst is used. As an initial step to realize such kind of after treatment system, the basic characteristics of the N/sub 2/ NTP desorption and NO/sub X/ reduction were examined experimentally using a pulse corona NTP reactor. After several adsorption/desorption processes, the amount of NO/sub X/ adsorbed becomes equal to that of NO/sub X/ desorbed, that is, all the NO/sub X/ was desorbed in a single desorption process. It is confirmed that the NO/sub X/ complete reduction using N/sub 2/ NTP desorption is possible not only for a simulated exhaust gas but for a real diesel engine gas. The effective or apparent SED can be decreased down to 29 Wh/m/sup 3/. Further improvement will be obtained by decreasing the ratio of /spl Delta/T/sub d///spl Delta/T/sub a/.