Patent ID: 6843052

Claim:
A method for desulfating a nitrogen oxide adsorber of an exhaust emission control system for a combustion device emitting an exhaust gas, the method comprising: operating the combustion device so as to vary a composition of the exhaust gas oscillatingly between a lean composition and a rich composition; accumulating oxygen in an oxygen accumulator downstream from the nitrogen oxide adsorber during a period when the exhaust gas has the lean composition; releasing at least a portion of the oxygen from the oxygen accumulator during a period when the exhaust gas has the rich composition so as to oxidize sulfur components of the nitrogen oxide adsorber; and sensing an exhaust gas air-fuel ratio of the exhaust gas composition downstream from the oxygen accumulator using a lambda probe, wherein the step of operating the combustion device so as to vary a composition of the exhaust gas is performed according to whether the sensed exhaust gas composition begins to fall or to rise from a stoichiometric value.