| 摘要 |
PROBLEM TO BE SOLVED: To remove NOx in exhaust gas by catching NOx by means of a NOx catching means connected bypass-likely when conversion catalyst has a conversion factor under a prescribed value, and providing a flow distribution valve between the bypass line and a main exhaust line so as to exhaust simultaneously with the conversion. SOLUTION: At least one trapping means (NOx absorbent) 4 is arranged on a main exhaust line 2, at least one bypass line 5 is provided thereon, and a valve 6 is provided on the intersection of the main exhaust line of the upper stream part and the bypass line 5. When the conversion factor of conversion catalyst 3 due to temperature of exhaust gas is under a prescribed value, and the NOx absorbent 4 is in the range to be activated, whole the exhaust gas is let flow in the bypass line 5. When the temperature of exhaust gas at the NOx absorbent 4 does not reach a level enough to surely remove NOx, it is heated by a heating means 7 to the level capable of removing NOx, and a flow passing through the bypass line 5 is controlled by the use of the valve 6. |
