Development of an Integrated NOx and PM Reduction Aftertreatment System: SCRi™ for Advanced Diesel Engines

Diesel engine emission regulations throughout the world have progressed over the last 20 years. In the U.S. the most stringent medium/heavy duty standard will be implemented for on highway vehicles starting in 2010. Although changes to engine design will improve engine out emissions, in order to meet both PM and NO_x regulations, combination systems including PM and NO_x aftertreatment, are planned to be utilized. In order to achieve the required regulations, a new substrate technology has been developed using advanced “turbulent” flow characteristics, and it has been combined with a novel approach to reduce system complexity: the “SCRi™” or “SCR integrated” system. Such a system uses a continuously operating PM-Metalit with advanced “turbulent” SCR-catalysts in a unique configuration. The reduction of both PM and NO_x also has to be seen in context with its effect on CO₂ emissions. This paper will discuss the work carried out to understand and characterize the SCRi™ system performance and illustrate its advantage in complexity compared to other exhaust systems.