Rolling Regeneration Trap for Diesel Particulate Control

One way to achieve low temperature regeneration on diesel particulate traps is to employ NO₂ as the oxidant. However, the engine may not produce sufficient NO_x to achieve the required particulate regeneration. An RRT (rolling regeneration trap) was proposed as a way to enhance the effective concentration in diesel engine exhaust. The RRT uses catalyzed ceramic foam, which allows repeated use of existing NO_x in the exhaust stream. The ceramic foam is a filter itself: thus, it can reduce the particulate loading on the wall-flow filter, which is more prone to plugging by the particulate deposits. Furthermore, the presence of particulate matter in the catalyzed section circumvents the high temperature limit imposed by thermodynamic equilibrium of a simple NO+NO₂ +O₂ system. However, experimental results revealed that the regeneration efficiency on the wall-flow section was very low and NO₂ slip is an issue.