Patent ID: 7614220

Claim:
A method of controlling a reducing agent in an exhaust gas post-processing system of a combustion machine with an exhaust gas duct, in which an SCR catalytic converter is provided in the direction of flow of the exhaust, wherein a reducing agent generation system has an NO x and CO/H 2 generation unit, an oxidation catalytic converter and a combined NO x storage/ammonia generation unit in the standard gas route of the reducing agent generation system, the method comprising: adding ammonia as a reducing agent in front of the SCR catalytic converter by the reducing agent generation system in order to reduce nitrogen oxide and intermittently adding, at least source materials for the generation of ammonia to the NO x and CO/H 2 generation unit via a fuel supply line and via an air supply line, wherein a CO/H 2 reducing agent flow is temporally modulated with λ<1, during a temporally short, pulsed fat phase serving as a reduction phase for the NO x storage/ammonia generation unit, wherein, during the fat phase, the air/fuel composition before the oxidation catalytic converter is changed to the form of a lambda modulation for a lambda value, wherein the lambda value within the pulsed fat phase is held in a range or 0.33 through 0.45 and drops below this range for a short period of time at the beginning of the fat phase of the lambda value.