Device and method for reduction of a gas component in an exhaust gas flow of a combustion engine

A device for reducing an amount of oxide of nitrogen (NOx compound) in an exhaust gas flow of a combustion engine which is adapted for operation by a lean air/fuel mixture, said device including:

• a separation unit operable to be fed an exhaust gas flow from the engine, said separation unit comprising a wall structure for separating the gas component from the exhaust gas flow, said gas component being constituted by an oxide of nitrogen (NOx compound) or water present in the exhaust gas flow, said wall structure comprising a porous material which provides a selective passage of the gas component through the wall structure before other gas components in the exhaust gas flow based on molecular size and molecular form;
• a conduit for returning the separated gas component to an inlet of the engine, said gas component including fresh air as a carrier gas for the gas component;
• and
• a detector for detecting an amount of the oxide of nitrogen (NOx compound) in the exhaust gas flow for controlling the amount of the oxide of nitrogen (NOx compound) present in the exhaust gas flow,
• wherein the combustion engine includes a turbo-aggregate comprising an exhaust gas operated turbine and a compressor for compressing air for feeding into the engine, characterized in that the conduit is connected upstream of the compressor, said device being operable to supply a reducing agent to an inlet of the separation unit for resulting in a catalytic reduction of the gas component in the wall structure by using the reducing agent.