Exhaust system for use in e.g. diesel engine, has nitrogen oxide removal unit arranged downstream from oxidizing catalyst, and another oxidizing catalyst placed upstream from unit, where catalysts are designed for different activities

摘要

The system (1) has an exhaust manifold (3), in which an exhaust gas after-treatment apparatus is arranged. A nitrogen oxide removal (DeNOx) unit is arranged downstream from an oxidizing catalyst (4), and another oxidizing catalyst (5) is placed upstream from the unit. The catalysts are designed for different activities and/or for different temperature ranges. The catalyst (5) has a noble metal mass larger than the catalyst (4). An independent claim is also included for a method for operating an exhaust gas after-treatment system for selective catalytic reduction (SCR) catalysts.