Applied Chemistry for Engineering (공업화학)

The Korean Society of Industrial and Engineering Chemistry (한국공업화학회)
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Effect of Intermittent Plasma Discharge on the Hydrocarbon Selective Catalytic Reduction of Nitrogen Oxides

간헐적 플라즈마 방전이 질소산화물의 탄화수소 선택적 촉매환원에 미치는 영향

  • Kyeong-Hwan Yoon (Department of Chemical Engineering, Jeju National University) ;
  • Y. S. Mok (Department of Chemical Engineering, Jeju National University)
  • 윤경환 (제주대학교 화학공학과) ;
  • 목영선 (제주대학교 화학공학과)
  • Received : 2023.07.14
  • Accepted : 2023.07.25
  • Published : 2023.10.10
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Abstract

The selective catalytic reduction (SCR) of nitrogen oxides (NOx) was investigated in a catalyst (Ag/γ-Al2O3) packed dielectric barrier discharge plasma reactor. The intermittent generation of plasma in the catalyst bed partially oxidized the hydrocarbon reductant for NOx removal to several aldehydes. Compared to using the catalyst alone, higher NOx conversion was observed with the intermittent generation of plasma due to the formation of highly reductive aldehydes. Under the same operating conditions (temperature: 250 ℃; C/N: 8), the NOx reduction efficiencies were 47.5%, 92%, and 96% for n-heptane, propionaldehyde, and butyraldehyde, respectively, demonstrating the high NOx reduction capability of aldehydes. To determine the optimal condition for intermittent plasma generation, the high voltage on/off cycle was adjusted from 0.5 to 3 min. The NOx reduction performance was compared between continuous and intermittent plasma generation on the same energy density basis. The highest NOx reduction efficiency was achieved at 2-min high voltage on/off intervals. The reason that the intermittent plasma discharge exhibited higher NOx reduction efficiency even at the same energy density, compared to the continuous plasma generation case, is that the intermediate products, such as aldehydes generated from hydrocarbon, were more efficiently utilized for the reduction of nitrogen oxides.

촉매(Ag/γ-Al2O3) 충진형 유전체 장벽 방전 플라즈마 반응기를 이용한 질소산화물(NOx)의 선택적 촉매 환원을 조사하였다. 촉매 상에서 간헐적으로 플라즈마를 발생시킬 때 NOx의 환원제인 탄화수소가 부분 산화되어 알데하이드류를 생성하였으며, 알데하이드류의 높은 환원력으로 인해 촉매를 단독으로 사용한 경우에 비해 높은 NOx 전환율을 보여주었다. 동일한 운전 조건(온도: 250 ℃; C/N: 8)에서 비교한 NOx 저감 효율은 탄화수소(n-헵테인), 프로피온알데하이드, 뷰티르알데하이드에 대해 각각 47.5%, 92%, 96%로 나타났으며, 알데하이드류의 높은 질소산화물 환원 성능이 확인되었다. 간헐적 플라즈마 발생시 적정 조건을 파악하기 위하여, 고전압 on/off 주기를 0.5~3 min으로 조절하였고, 연속적인 플라즈마 발생의 경우와 동일한 에너지밀도에서 NOx 저감 성능을 비교하였다. 고전압을 2 min 간격으로 on/off 하여 간헐적으로 플라즈마를 생성시켰을 때 연속적인 플라즈마 발생 대비 가장 높은 질소산화물 저감 효율이 얻어졌다. 동일한 에너지밀도에서도 간헐적 플라즈마 방전의 경우가 연속 플라즈마에 비해 높은 NOx 저감 효율을 보이는 것은, 탄화수소가 분해되어 생성되는 알데하이드류 등의 중간생성물들이 NOx 저감 반응에 보다 효율적으로 이용되었기 때문이다.

Keywords

Acknowledgement

이 논문은 2023학년도 제주대학교 교원성과지원사업에 의하여 연구되었음.

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