EXHAUST EMISSION CONTROL DEVICE

摘要

PROBLEM TO BE SOLVED: To provide a highly practical exhaust emission control device for well recovering a NOx storing and reducing catalyst while greatly improving fuel consumption with lean combustion. SOLUTION: The exhaust emission control device comprises the NOx storing and reducing catalyst 15 provided in an exhaust passage for reducing and cleaning NOx which is oxidized and temporarily stored in the state of nitrate when the concentration of oxygen in an exhaust gas 12 is high and which is decomposed and released via a reducer when the concentration of oxygen in the exhaust gas 12 is low. Cylinders for the engine 10 are grouped into two types, lean combustion cylinders 1-5 and a rich combustion cylinders 6, so that the exhaust gas from the lean combustion cylinders 1-5 is introduced into the NOx storing and reducing catalyst 15 for removing NOx and the exhaust gas 12 from the rich combustion cylinder 6 is intermittently introduced to the NOx storing and reducing catalyst 15 for recovering the NOx storing and reducing catalyst 15.