Selective Catalytic Reduction with Urea – The Most Effective Nitrous Oxide Aftertreatment for Light-Duty Diesel Engines

Authors

Dipl.-Ing. C. Enderle, Dr.-Ing. H. Breitbach, Dipl.-Ing. M. Paule, Dr.-Ing. B. Keppeler, DaimlerChrysler AG, Stuttgart

Year

2005

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 595

Summary

This article briefly describes different nitrous oxide aftertreatment systems for light duty diesel engines. The key characteristics and the key requirements of Mercedes-Benz for a suitable aftertreatment system will be presented. The classical trade-off between particulate and nitrous oxide emissions has become much less important through the widespread use of particulate traps. Due to more stringent future nitrous oxide legislation, two new trade-offs become more important: the hydrocarbon vs. NOx trade-off and the fuel consumption vs. NOx trade-off. Both excellent driveability and low fuel consumption have been key for the market success of the diesel engine. Thus, the impact of the aftertreatment system on fuel consumption is extremely important for Mercedes-Benz. Additionally, the efficiency of the aftertreatment is another key factor, so that the engine related NOx reduction measures can be limited as much as possible to measures without fuel economy disadvantages. The system that best meets the requirements is the SCR Urea Aftertreatment. It is based on the selective catalytic reduction of the nitrous oxides with ammonia, which is generated by thermal decomposition of urea sprayed into the hot exhaust gases. The system has an excellent efficiency over a wide temperature range, shows good life time stability, and additionally good packaging. Compared to other systems, it does not have a negative impact on the hydrocarbon emissions...

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