An Integrated SCR and Continuously Regenerating Trap System to Meet Future NOx and PM Legislation

The tightening NOx and particulate matter (PM) emission standards for heavy duty diesel powered vehicles are stimulating the development of aftertreatment systems to reduce NOx and PM emissions from such vehicles. Here we present data on a new system which combines NO₂-based continuously regenerative trap particulate removal technology with urea-based Selective Catalytic Reduction (SCR) NOx removal technology. There are a number of beneficial synergistic effects associated with combining these two technologies, including a significant improvement in the low temperature NOx removal performance of the SCR system. The development of this PM/NOx control system is described, and the main features of this novel strategy are outlined.

The PM/NOx control system has been evaluated on a number of different engines and over a number of different drive cycles. During testing we have shown that this technology enables simultaneous NOx conversions of 75-90% and PM conversions of 75-90% to be obtained on current engines using both US and European test procedures. These results are presented and discussed.