Patent ID: 7731925

Claim:
A method of reducing agent control in an exhaust gas aftertreatment system of a combustion engine with an exhaust gas pipe in which in the direction of flow of the exhaust gas there is an SCR catalyzer, whereby a reducing agent generating system has an NO x and CO/H 2 generating unit, an oxidation catalyzer, and a combined NO x storage/ammonia generating unit in a standard gas path of the reducing agent generating system, the method comprising: introducing ammonia as a reducing agent for a reduction of nitric oxides before the SCR catalyzer of the reducing agent generating system and directing, at least temporarily, precursor materials for generation of ammonia to the NO x and CO/H 2 generating unit through a fuel feed and an air feed, wherein a CO/H 2 reducing agent stream is temporally modulated during a rich phase with λ<1 serving as a reducing phase for the NO x storage/ammonia generating unit, whereby a CO/H 2 concentration is primarily held constant at a high level.