SULFUR PURGE CONTROL METHOD AND EXHAUST EMISSION CONTROL SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a sulfur purge (desulfurization) control method and exhaust emission control system capable of efficiently purging sulfur accumulating in NOx occlusion reduction type catalyst while preventing emission of carbon monoxide to the air in an exhaust emission control system purifying NOx by the NOx occlusion reduction type catalyst. SOLUTION: An exhaust emission control system 1 purifying NOx in exhaust gas of an internal combustion engine E by the NOx occlusion reduction type catalyst. A sulfur purge control means C24 controls air fuel ratio of exhaust gas by setting a target air fuel ratio to a predetermined first air fuel ratio which is a rich air fuel ratio after start of sulfur purge, after that, air fuel ratio of the exhaust gas is controlled by changing the target air fuel ratio to a predetermined second air fuel ratio which is a stoichiometric air fuel ratio when oxygen concentration Od in a downstream of the NOx occlusion reduction type catalyst measured by an oxygen concentration detection means C12 gets lower than a predetermined criterion Od0. COPYRIGHT: (C)2005,JPO&NCIPI