METHOD FOR REGENERATING NITROGEN OXIDE STORAGE CATALYSTS

摘要

Nitrogen oxide storage catalysts are periodically regenerated in order to clean the exhaust gas of lean-mix engines by switching the engine from lean operation to rich operation. Following the regeneration, the engine is again switched to lean operation. At this point rich exhaust gas is still located in the exhaust pipe between the engine and the catalytic converter and is pushed out through the catalytic converter into the environment by the subsequent lean exhaust gas. This leads to brief peaks in the emission of rich exhaust gas constituents and weakens the exhaust emission control that can be achieved. In order to solve this problem it is proposed that air be blown in front of the storage catalyst in order to create oxidising conditions so that rich exhaust gas constituents still located in the exhaust pipe before the storage catalyst can be converted into innocuous products. The proposed method can lead to a significant improvement in exhaust emission control, in particular in catalysts which as a result of ageing have a reduced storage capacity and need to be regenerated much more frequently than newer catalysts. ® KIPO & WIPO 2008