Korean Chemical Engineering Research

The Korean Institute of Chemical Engineers (한국화학공학회)
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A Study of Nitrous Oxide Decomposition using Calcium Oxide

Calcium Oxide를 이용한 N2O 분해에 관한 CO2의 영향 연구

  • 백진영 (대전대학교 공과대학 환경공학과) ;
  • 박영성 (대전대학교 공과대학 환경공학과) ;
  • 선도원 (한국에너지기술연구원 유동층기술연구센터) ;
  • 배달희 (한국에너지기술연구원 유동층기술연구센터)
  • Received : 2002.07.22
  • Accepted : 2002.09.26
  • Published : 2002.12.01
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Abstract

Fluidized bed combustion is a coal combustion technology that can reduce both SOx and NOx emission; SOx is removed by limestone that is fed into the combustion chamber and the NOx is reduced by low temperature combustion in a fluidized bed combustor and air stepping, but $N_2O$ generation is quite high. $N_2O$ is not only a greenhouse gas but also an agent of ozone destruction in the stratosphere. The calcium oxide(CaO) is known to be a catalyst of $N_2O$ decomposition. This study of $N_2O$ decomposition reaction in fixed bed reactor packed over CaO bed has been conducted. Effects of parameters such as concentration of inlet $N_2O$ gas, reaction temperature, CaO bed height and effect of $CO_2$, NO, $O_2$ gas on the decomposition reaction have been investigated. As a result of the experiment, it has been shown that $N_2O$ decomposition reaction increased with the increasing fixed bed temperature. While conversion of the reaction was decreased with increasing $CO_2$ concentration. Also, under the present of NO, the conversion of $N_2O$ decomposition is decreased. From the result of kinetic study gained the heterogeneous reaction rate on $N_2O$ decomposition. In the case of $N_2O$ decomposition over CaO, heterogeneous reaction rate is. $\frac{d[N_2O]}{dt}=\frac{3.86{\times}10^9{\exp}(-15841/R)K_{N_2O}[N_2O]}{(1+K_{N_2O}[N_2O]+K_{CO_2}[CO_2])}$. In this study, it is found that the calcium oxide is a good catalyst of $N_2O$ decomposition.

석탄 연소기술에서 타 연소로에 비해서 유동층 연소는 황산화물과 질소산화물 배출을 줄이는 기술이다. 석회석의 소성으로 생성되는 CaO에 의한 황산화물의 제거와 저온 연소와 공기 다단계 주입에 의한 NOx를 줄일 수 있다는 것이 유동층 연소로의 큰 장점이지만, 상대적으로 $N_2O$의 배출은 매우 높다. $N_2O$는 지구온난화 가스일 뿐만 아니라 성층권내의 오존층을 파괴하는 물질이기도 하다. CaO는 $N_2O$ 분해를 위한 촉매 물질로 알려져 있다. 본 연구는 CaO를 충진시킨 고정층 반응기에서 CaO에 의한 $N_2O$의 분해특성에 관하여 수행하였으며, 유동층 연소온도와 가스조성에서 온도변화에 대한 $N_2O$의 분해특성, CaO 충진량의 변화와 $CO_2$, NO, $O_2$ 농도변화에 따른 $N_2O$ 분해특성에 관하여 수행하였다. 또한 실험 결과로부터 CaO표면에서 $N_2O$분해반응에 대한 반응속도식을 나타낼 수 있었다. 결과로서 온도가 증가함에 따라 $N_2O$ 분해반응이 증가하였으며, $CO_2$의 농도를 변화시킬 경우 $CO_2$ 농도가 증가할수록 $N_2O$ 분해반응이 감소하였다. NO 존재시와 비교하였을 때 $N_2O$의 분해반응이 감소함을 알 수 있었다. 반응속도론적으로 해석한 결과 $CO_2$ 농도에 대한 $N_2O$ 분해반응의 반응속도식을 다음과 같이 나타내었다. 본 연구 결과 CaO는 $N_2O$분해 반응에서 좋은 촉매 기능을 지니고 있음을 알 수 있었다. $\frac{d[N_2O]}{dt}=\frac{3.86{\times}10^9{\exp}(-15841/R)K_{N_2O}[N_2O]}{(1+K_{N_2O}[N_2O]+K_{CO_2}[CO_2])}$

Keywords

References

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