Abstract ▼ AI-Helper

The selective catalytic reduction(SCR) system is potentially a highly-effective means of $NO_x$ reduction for diesel engine. Generally, SCR makes use of a reductant added to the exhaust gas that can be used for reacting NO and $NO_2$ to $N_2$. The reductant, ammonia(...

The selective catalytic reduction(SCR) system is potentially a highly-effective means of $NO_x$ reduction for diesel engine. Generally, SCR makes use of a reductant added to the exhaust gas that can be used for reacting NO and $NO_2$ to $N_2$. The reductant, ammonia($NH_3$) generated from a liquid urea-water solution. De-$NO_x$ process in the SCR, the ideal ratio of $NH_3$ molecules to $NO_x$ molecules is 1:1 for high efficiency of $NO_x$ reduction. The SCR system has good $NO_x$ reduction performance in the temperature window of about 250 to $400^{\circ}C$, low space velocity also leads an increase of $NO_x$ reduction efficiency, due to long residence time in the catalyst. This paper reviews a laboratory study to evaluate the effects of $NO_x-NH_3$ concentrations, gas temperature and space velocity on the $NO_x$ reduction efficiency of the SCR. The maximum reduction efficiency is indicated when the $NH_3$ to $NO_x$ ratio is 1.2 and the space velocity is $30,000\;h^{-1}$ in $300^{\circ}C$. However, under various exhaust conditions, NH3 injection amount need to be controlled for a high $NO_x$ conversion efficiency because of reducing unnecessary $NH_3$ consumption. Based on results of the rig-test, this study suggests the control strategy of $NH_3$ injection for optimizing $NO_x$ reduction efficiency.