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Modeling of $NH_3$-SCR Diesel $NO_x$ Reduction and Effects of $NO_2/NO_x,\;NH_3$/NO Ratios on the De-$NO_x$ Efficiency  

Jung, Seung-Chai (Department of Mechanical Engineering, Yonsei University)
Yoon, Woong-Sup (Department of Mechanical Engineering, Yonsei University)
Publication Information
Transactions of the Korean Society of Automotive Engineers / v.16, no.3, 2008 , pp. 179-187 More about this Journal
Abstract
A mathematical modeling of $NO_x$ reduction in $NH_3$-SCR process is conducted. The present deterministic model solves one-dimensional conservation equations of mass and species concentrations for channel flows and the catalytic reaction. NO and NO_2$ reactions by the vanadium catalyst in the presence of $NH_3$ are calculated with the rate expressions of Langmuir-Hinshelwood scheme. The modeling was validated with extensive empirical data regarding $NO_x$ reduction efficiency. Analysis of De-$NO_x$ sensitivity conducted with regard to oxygen and water yielded highly accurate prediction over a wide range of $NO_2/NO_x$ ratios from 0 to 1 in a temperature range of $200^{\circ}C{\sim}550^{\circ}C$. The $NO_x$ reduction largely depends on $NO_2/NO_x$ ratio at temperatures lower than $300^{\circ}C$. NO reduction efficiency is significantly augmented with increasing in $NH_3$/NO ratio at higher temperatures, whereas rather insensitive to the $NH_3$/NO ratio at lower temperatures.
Keywords
$NH_3$-SCR; Urea-SCR$NO_x$;
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