Patent attributes
Exhaust gas post treatment system for nitrogen oxide and particle reduction of an internal combustion engines operated with excess air. An oxidation catalytic converter is disposed in the exhaust gas stream of the engine for converting at least a portion of the nitric oxide of the exhaust gas into nitrogen dioxide. A metering device adds reduction agent to the exhaust gas stream downstream of the oxidation catalytic converter and/or to a partial exhaust gas stream branched off upstream of the oxidation catalytic converter and returned to the exhaust gas stream downstream thereof. The reduction agent is ammonia or a material that releases ammonia downstream of the supply location due to the hot exhaust gas. A particle separator or filter is disposed in the exhaust gas stream downstream of the oxidation catalytic converter and of the supply location, and converts carbon particles accumulated in the separator or filter into carbon monoxide, carbon dioxide, nitrogen and nitric oxide with the aid of nitrogen dioxide in the exhaust gas stream. An SCR catalytic converter is disposed downstream of the separator or filter for reducing nitrogen oxides in the exhaust gas stream into nitrogen and water vapor with the aid of ammonia or released ammonia by selective catalytic reduction.
