저온 플라즈마와 촉매 복합공정에서 질소산화물의 제거에 대한 연구가 수행되었다. 선택적 촉매 환원에 의한 질소산화물 제거는 플라즈마 반응기의 특성에 영향을 받으므로 먼저 플라즈마 반응기의 특성을 개별적으로 평가한 후 두 공정을 결합하였다. 플라즈마 반응기의 경우 상온에서는 NO를 NO2로 쉽게 시킬 수 있었으나 온도의 증가에 따라 산화반응속도가 크게 감소되어 반응속도 증가를 위한 반응첨가제가 필요한 것으로 나타났다. 본 연구에서 반응첨가제로 사용한 것은 에틸렌이었으며, 에틸렌 존재하에서는 100-200 ℃ 범위에서도 NO의 산화반응이 빠르게 일어났다. 촉매 반응기(V2O5/TiO2)의 경우 플라즈마 방전에 의한 NO2/NO 농도비 변화에 따라 질소산화물 제거효율 증가가 나타났다. 플라즈마 반응기에서 에틸렌으로부터 생성되는 포름알데히드는 후단의 촉매반응기에서 완전히 제거시킬 수 있었으나, 일산화탄소 및 미반응 암모니아의 배출이 관찰되었다. 이와 같은 플라즈마/촉매 복합공정에서는 선택적촉매환원법의 반응온도(300-350 ℃)보다 훨씬 낮은 100-200 ℃ 범위에서 80% 이상의 NOx를 제거할 수 있었다.

Removal of nitrogen oxides using a non-thermal plasma process combined with catalyst was investigated. In this system, selective catalytic reduction of nitrogen oxides is affected by the operating condition of the plasma process, and thus the characteristics of the plasma process were separately examined before combining two processes. The oxidation of NO to NO2 in the plasma reactor greatly decreased as the temperature increased, which implies that an additive to increase the oxidation rate is necessary. In the presence of ethylene used as an additive, the oxidation of NO to NO2 was largely enhanced at relatively high temperatures in the range of 100-200 ℃. The removal efficiency of NOx on the catalyst(V2O5/TiO2) was found to get higher as the ratio of NO2 to NO increased by the plasma discharge. The byproduct formaldehyde formed from ethylene in the plasma reactor could be completely removed in the catalytic reactor while significant amount of carbon monoxide and ammonia slip were observed. The plasma-catalyst system used in this study was able to remove 80% of NOx or more at temperature range of 100 to_x000D_ 200 ℃ that is much lower than typical temperature window of selective catalytic reduction(300-350 ℃).

Non-Thermal Plasma Selective Catalytic Reduction Combined Process Nitrogen Oxides

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