Method for determining the ammonia storage capacity of SCR catalytic converters in an exhaust aftertreatment system and an exhaust aftertreatment system

摘要

The invention relates to a method for determining the ammonia storage capacity of SCR catalytic converters (48, 50, 52) in an exhaust system (40) of an internal combustion engine (10). A first SCR catalyst (48) close to the engine and a second SCR catalyst (52) downstream of the first SCR catalyst (48, 50) are arranged in the exhaust system (40). Each of the SCR catalytic converters (48, 50, 52) is assigned a metering element (56, 58) with which a reducing agent (78) is metered into the exhaust gas duct (42) upstream of the respective SCR catalytic converter (48, 50, 52) can be. Furthermore, downstream of the SCR catalytic converters (48, 50, 52), there are respectively NOx sensors (64, 92) with which an ammonia breakthrough through the respective SCR catalytic converter (48, 50, 52) can be detected. that the ammonia store of the first SCR catalytic converter (48, 50) is completely emptied and this ammonia store is then filled in a controlled manner until the NOx sensor (64) enters downstream of the first SCR catalytic converter (48, 50) Ammonia breakthrough is detected. From this ammonia breakthrough, it is concluded that the ammonia reservoir has been completely filled.