Patent ID: 6922988
Filing Date: 2005-08-02
Classification: B01D,F01N,F02B,F02D,Y02A

Abstract:
1. An exhaust emission control apparatus for an internal combustion engine comprising: an NOx catalyst adapted to occlude NOx when an oxygen concentration of an exhaust is higher than or equal to a predetermined value, and reduce said NOx occluded in said NOx catalyst in the existence of a reducing agent when the oxygen concentration of the exhaust is lower than said predetermined value; a reducing agent supplying section for supplying said reducing agent to said NOx catalyst; an SOx poisoning recovering section for recovering said NOx catalyst from its SOx poisoning by supplying said reducing agent through said reducing agent supplying section to vary the oxygen concentration of the exhaust passing through said NOx catalyst; a hydrogen sulfide concentration estimating section for estimating a concentration of hydrogen sulfide in an atmosphere into which said hydrogen sulfide is discharged; and an estimated concentration derived reducing agent supply amount control section for controlling an amount of reducing agent supplied from said reducing agent supplying section in such a manner that the amount of reducing agent to be supplied is decreased in accordance with the increasing concentration of hydrogen sulfide estimated by said hydrogen sulfide concentration estimating section while said NOx catalyst is recovered from the sulfur oxide poisoning.