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서충길(C. K. Seo),최병철(B. C. Choi) 한국동력기계공학회 2008 한국동력기계공학회 학술대회 논문집 Vol.2008 No.11
Urea-SCR system, the selective catalytic reduction using urea as reducing agent, is a powerful technique to reduce nitrogen oxides(NOx) emitted from diesel engines. However, a tank of urea(32.5%)-water solution can be frozen in low ambient temperature levels of below -11℃. The purpose of this study is to understand freezing and melting phenomena of the urea-water solution, and its will be applied to get the urea-water solution from frozen it within 5minutes after cold start. Factors considered are the type of heater and the urea tank. From the results, it was found that melting volume of cartridge heater B during 5 minutes of heating period got 83 ml when supplying electric power of 150W. Horizontal heater B, which put in the narrow bottom space of the tank T1, has fast melting characteristics.
서충길(C. K. Seo),김화남(H. N. kim),최병철(B. C. Choi),정종우(J. W. Jeong) 한국동력기계공학회 2009 한국동력기계공학회 학술대회 논문집 Vol.2009 No.6
Selective catalytic reduction using urea is a powerful technique to reduce nitrogen oxides(NOx) emitted from diesel engines. However, it has a problems where NOx conversion efficiency is low at low temperature region with non-precious metal catalyst as zeolite. The purpose of this study is to understand fundamental characteristics of LNT(Lean NOx Trap) and SCR(Selective Catalytic Reduction) catalysts to improve NOx conversion efficiency and wide window width using LNT+SCR combination system. It was found that LNT Catalyst had much NOx storage capacity at 350°C condition than that at 200°C. NOx conversion efficiency of SCR catalyst was decremented about 5% with H<sub>2</sub>O 5% condition below temperature of 450°C. Hydrogen as a reductant which was used at LNT contributed NOx reduction, and this process formed NH<sub>3</sub> that is useful reductant for the SCR system. LNT+SCR combination system without additional injection was improved NOx reduction about 10-30% at temperature region below 400°C.
디젤자동차용 SCR 촉매의 저온영역에서 NOx 정화율 개선
서충길(C.-K. Seo),김화남(H. N. Kim),최병철(B. C. Choi),이천환(C. H. Lee),오광철(G. C. Oh),이춘범(C. B. Lee) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5
The purpose of this paper is to perform the optimum contents of ZrO₂ with a promoter to improve NOx reduction activity of a Cu-ZSM-5 catalyst in low temperature below 300℃. NOx conversion of ZrO₂(2wt%) improved to 10∼20% in the temperature range from 200℃ to 300℃ compared to no ZrO₂ loaded SCR catalyst. It is because the NH₃ absorption was improved by acidity strengthening of acid sites of SCR catalyst as well as the improvement of thermal stability by a resonable ZrO₂ loading. The LOT(light-off temperature) 50 of Cu-ZSM-5/ZrO₂(2wt%) appeared at 180℃ that was decreased about 50℃ compared with Fe-Zeolite catalyst. The maximum NOx conversion of Cu-ZSM-5/ZrO₂(2wt%) was obtained 93% at 300℃, however that of Fe-zeolite catalyst was 88% at 350℃.