Catalyst operation for selective nitrogen oxides reduction causes potential pollutants nitrogen oxides and ammonia to destroy each other when hot exhaust gases arise

摘要

A temperature rise is to be expected in the SCR catalyst (3). The reductant quantity which can be stored in the catalyst at the expected temperature is determined. Should there exist a reductant excess ( DELTA m) which cannot be stored as a result of the temperature rise, then the reductant excess ( DELTA m) is consumed. Preferred Features: Consumption of non-storable reductant excess, results from additional, intentionally-generated nitrogen oxides in the exhaust gases. The nitrogen oxides excess, is produced by engine control. It is produced by control of stoichiometry, setting an air/fuel ratio at the engine of lambda = 1.1 and/or by adjustment of ignition timing and/or by reducing exhaust gas recycle and/or by adjusting the start of injection and/or by adjusting the fuel injection pressure.