An exhaust gas purification device for an engine

Abstract

Abstract The exhaust gas purification device according to the present invention utilizes two NO x absorbents (7a,7b) in order to remove NO x from the exhaust gas of an engine (1) operated at a lean air-fuel ratio. The NO x absorbents (7a,7b) are disposed, in series, in the exhaust passage (3) of the engine and a nozzle (12a) for supplying a reducing agent is disposed in the exhaust passage at a position between the two NO x absorbents. Further, the device includes switching valves (5) for changing the direction of the exhaust gas flow in the exhaust gas passage. When the switching valves are set to direct the exhaust gas flow to one direction, the exhaust gas first flows through one of the NO x absorbent (first NO x absorbent) (7a), and after passing through the first NO x absorbent, the reducing agent is supplied to the exhaust gas before it flows into the other NO x absorbent (second NO x absorbent) (7b). Thus, the first NO x absorbent (7a) absorbs NO x in the exhaust gas, and the NO x absorbed by the second NO x absorbent is released from the second NO x absorbent. When the switching valves (5) are switched, the exhaust gas flows in the opposite direction, and flows through the second NO x absorbent (7b) and the first NO x absorbent (7a) in this order. In this case, the second NO x absorbent (7b) absorbs NO x in the exhaust gas, and the NO x absorbed by the first NO x absorbent (7a) is released and reduced to N₂. Therefore, by reversing the direction of the exhaust gas periodically, the absorbing operation of NO x and releasing/reducing operation of NO x are performed by two NO x absorbents alternately. Thus, it becomes possible to remove NO x in the exhaust gas continuously while the NO x absorbents are prevented from being saturated by the absorbed NO x .

Inventors

• 👤 Yukio Kinugasa
• 👤 Toshifumi Takaoka
• 👤 Kouhei Igarashi
• 👤 Takaaki Itou

Bibliographic Details