Concepts for Integrated Regeneration of Diesel Particulate Traps and NOx-Storage Catalyst

Authors

Prof. Dr.-Ing. S. Pischinger, Dipl.-Chem. B. Sliwinski, RWTH Aachen; Dipl.-Chem. J. Schnitzler, Dr.-Ing. A. Wiartalla, FEV Motorentechnik GmbH, Aachen

Year

2006

Print Info

Fortschritt-Berichte VDI, Reihe 12, Nr. 622

Summary

Future emission limits will most probably impose further restrictions on particle and nitrogen oxide emissions. Apart from engine control measures exhaust gas treatment components, e.g. particulate traps and NOx adsorber catalysts, will have to be used increasingly for emission reduction. It has to be investigated in how far synergies between the operation of the different exhaust gas treatment systems can be achieved. In the course of the studies described here with a particulate trap with NOx adsorber catalyst coating we were able to identify the influencing factors causing a significant particle reduction during a typical DeNOx regeneration for NOx adsorber catalysts. Amongst these influencing parameters ranks the temperature profile during DeNOx operation which results from the conversion of the reductant generated during rich engine operation. The maximum temperatures, however, are significantly below those temperatures which are usually necessary for a fast thermal regeneration of a particulate trap, and are only reached during short time intervals. The catalytic coating can influence the activity with respect to the conversion of the reductants rather strongly. Analytical results show further that soot from lean and rich engine operation differs significantly regarding composition and morphology. It seems that the ease of ignition of soot can be improved through lean and rich engine operation control and therefore the overall combustion behaviour of the soot collected in the particulate trap can be regulated. The possibility of a particle reduction through increased temperature over short term intervals in a particulate trap caused by a change of the combustion process engine control can be used with respect to different concepts. E. g. the loading can be effectively kept at a very low level. This allows the use of highly porous filter materials with reduced stability and therefore limited soot loading quantity. Further, the reactive properties of soot from rich engine operation can be specifically used to realize conventional particulate trap regeneration in an expanded engine map area.

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