Patent ID: 7937933

Claim:
An exhaust gas post treatment system for nitrogen oxide and particle reduction of an internal combustion engine operated with excess air, comprising: an oxidation catalytic converter disposed in the exhaust gas stream of the internal combustion engine for converting at least a portion of the nitric oxide contained in the exhaust gas stream into nitrogen dioxide; a supply tank for a reduction agent; a metering device for receiving the reduction agent from the supply tank and for adding the reduction agent to at least one of the group consisting of the exhaust gas stream at a supply location downstream of said oxidation catalytic converter, and a partial exhaust gas stream that is branched off from the exhaust gas stream upstream of the oxidation catalytic converter, extends parallel to said oxidation catalytic converter and is returned to the exhaust gas stream downstream of said oxidation catalytic converter, wherein the reduction agent is ammonia or a material that is adapted to release ammonia downstream of said supply location for reduction agent as a result of the hot exhaust gas; a particle separator or particle filter disposed in the exhaust gas stream downstream of said oxidation catalytic converter and downstream of said supply location for reduction agent, wherein said particle separator or particle filter is adapted to convert carbon particles accumulated in said particle separator or particle filter into carbon monoxide, carbon dioxide, nitrogen and nitric oxide with the aid of nitrogen dioxide contained in the exhaust gas stream; and an SCR catalytic converter disposed downstream of said particle separator or particle filter for reducing nitrogen oxides contained in the exhaust gas stream to nitrogen and water vapor with the aid of ammonia or released ammonia by way of selective catalytic reduction.