Exhaust gas purification system

Abstract

To provide an exhaust emission control device capable of purifying an ammonia component in exhaust gas by using a simple structure and control and suppressing outflow of the ammonia component to outside.SOLUTION: An exhaust emission control device includes: a tank that stores liquid in which an ammonia component can be dissolved; an exhaust gas treatment passage for causing exhaust gas discharged from a three-way catalyst to pass through the liquid and releasing the exhaust gas to outside; and an exhaust gas supply pump for supplying exhaust gas from an exhaust passage to the exhaust gas treatment passage. When an internal combustion engine is being operated in a first state where a temperature of the three-way catalyst is a predetermined temperature or higher and an air-fuel ratio of exhaust gas flowing into the three-way catalyst is on a rich side of a theoretical air fuel ratio and an ammonia component is generated in the three-way catalyst (Yes in Step S2), a control section operates the exhaust gas supply pump to send the exhaust gas to the tank and dissolves the ammonia component included in the exhaust gas in the liquid for recovery (Step S3).SELECTED DRAWING: Figure 2

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