| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust emission control device capable of performing the composition process at a lean operation ratio as high as possible while effectively reducing the nitrogen oxide content contained in the combustion waste gas such as the exhaust of internal combustion engine for vehicle at a relatively low cost. SOLUTION: An exhaust emission control device for internal combustion engine has a first catalyst device 3 for generating ammonia NH3 from an exhaust gas component in the case of the thick exhaust gas composition and a second catalyst device 4 connected behind of a the first catalyst device 3. The second catalyst device 4 temporarily stores the ammonia generated by the first catalyst device 3 in the case of thick exhaust gas composition, and on the other hand, in the case of the lean exhaust gas composition, the ammonia temporarily stored in the nitrogen oxide NOx contained in the exhaust gas is used as a reducing agent so as to react for reduction. With this structure, a third catalyst device 2 connected ahead of the first catalyst device 3 temporarily stores the nitrogen oxide contained in the exhaust gas in the case of lean exhaust gas composition, and on the other hand, in the case of thick exhaust gas composition, the previously and temporarily stored nitrogen oxide is liberated again. |
