Exhaust purification system and catalyst regeneration method

Abstract

Provided is an exhaust purification system including: an NOx occlusion reduction type catalyst that is provided in an exhaust system of an internal combustion engine, and occludes NOx when an exhaust gas is in a lean state, and reduces the NOx when the exhaust gas is in a rich state; a regeneration control unit that executes a regeneration process of bringing the exhaust gas into a rich state to reduce the NOx occluded in the NOx occlusion reduction type catalyst; a storing unit that stores an exhaust lambda prediction value in advance when the regeneration process is executed; a reduction amount estimating unit that estimates an NOx reduction amount when the regeneration process is executed; and a prohibition unit that prohibits the execution of the regeneration process by the regeneration control unit when the estimated NOx reduction amount is less than a predetermined lower limit threshold.