| 摘要 |
PURPOSE:To discharge a sulfur oxide (SOx) efficiently as well as to prevent a nitrogen oxide (NOx) absorbent from being subject to SOx poisoning by making exhaust gas forward when the sulfur oxide in the exhaust gas is absorbed, while when it is dis charged, making the exhaust flow back and simultaneously maintaining an air-fuel ratio of the exhaust in the rich side. CONSTITUTION:When both sulfur and nitrogen oxides in the exhaust are absorbed each, two exhaust selector valves 4 and 5 are selected upwards each, and almost the whole quantity of exhaust gas is made to pass through both SOx and NOx absorbents 6b and 7b at the side of a branched passage 3b on one side. On the other hand, when the absorbed SOx is discharged, these valves 4 and 5 are selected downward each, while an exhaust inlet port 9b on one side is connected to a pump 13 via a three-way valve 12. In succession, the exhaust gas on the upstream side is absorbed and discharged out of an exhaust outlet port 14, while the exhaust gas on the downstream side is made to flow back to the upstream side. At this time, a reducer is fed out of a nozzle 8b on one side, and an air-fuel ratio of the exhaust gas flowing into the SOx absorbent 6b is maintained in the rich side. With this constitution, the SOx is discharged speedily and appropriately. |
