Intensification of Catalytic Aftertreatments Systems for Mobile Applications 2013-01-0530

Stricter emission limitations for NO_x and particulates in mobile applications will require the use of active aftertreatment methods like Diesel Particulate Filters (DPF), Selective Catalytic Reduction (SCR) with urea and Lean NO_x Trap (LNT) as combinations in the 2010's. Due to the significant total space and required investments, a lot of efforts have been focused recently on the optimization of the combinatory aftertreatment systems (ATS).

In this study the possibilities to intensify the catalytic ATS were analyzed and reviewed by the examples and studies with engines, laboratory reactors and simulations. The focus was on diesel applications, where the number of needed ATS units is the widest. The diesel engine modifications on SCR or EGR engines have to be also designed together with ATS. The intensification includes the principles of down-sizing and the integration of ATS units with control systems. The reaction engineering of catalytic reaction and regenerations (DPF, LNT) was also analyzed. The intensification covered the examples about the integration of DOC, LNT and SCR on DPF, high cell density substrates (metallic) and the integration of hydrolysis and ammonia slip catalysis on the SCR unit. The intensification cases were analyzed by the observed catalytic activities, pressure drop, the volume of systems and costs. The LNT coating on DPF gave a promising possibility to integrate PM, nitrate and sulfate regeneration methods and OBD. The integration of control units and their functions is also a modern way to keep emissions, complexity and costs low.

The use of natural gas as fuel results in low PM emissions and no DPF is needed in Euro 6. However, the intensification of ATS may result in a stoichiometric engine with a three-way catalyst instead of a lean combustion engine with oxidation and SCR catalysts in heavy-duty natural gas applications.