High Performance SCR Catalyst System: Elements to Guarantee the Lowest Emission of NOx

Authors

Dr. E. Jacob, Dr. R. Müller, Dr. A. Scheeder, Emitec GmbH, Lohmar; Dipl.-Ing. T. Cartus, Dipl.-Ing. R. Dreisbach, AVL List GmbH, Graz; H.-P. Mai, Roth-Technik-Austria GmbH, Gaggenau; Dr. M. Paulus, Dr. J. Spengler, Süd-Chemie AG, Bruckmühl

Year

2006

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 622

Summary

The progressing NOx-Exhaust Emission regulation for commercial vehicles and the upcoming NO2 ambient air quality standard in the EU require significant reduction of NO and NO2 in the exhaust gas of diesel engines. Based on the present state of technologies it is expected that SCR techniques will become a major element of future engine concepts with lowest NOx-emissions. Cost pressure and limited space allocation require compact and highly efficient exhaust emission control systems. A forewardlooking concept for further investigation is a two-stage, advanced high-performance SCR-System with increased volume-specific catalytic activity, characterized by „turbulent” catalyst with internal flow exchange, enabling increased mass transfer and optimizing the homogeneity of the of the chemical reactants inside the catalyst, assistant catalysts: urea (“Harnstoff”)-decomposition catalyst (H-cat), with system configuration in a slip-stream (so-called 1/H-pre-reactor) or with parallel arranged H- and V-catalyst (V-catalyst, i.e. pre-oxidation catalyst), socalled V/H-pre-reactor, upstream of the SCR-catalyst The required SCR-catalyst volume in V/H-RO system configuration with assistant catalysts can be reduced by 40 % when applying the „turbulent“ LS/PE-structure with internal flow distribution instead of the traditional laminar-flow standard catalyst structures, while maintaining the same emission reduction performance level . These improvements are achieved with the described substrate and system technology and by applying a new-developed coating technology process from Süd-Chemie for Emitec’s “turbulent”-metal catalyst substrates with internal flow exchange.

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