| 摘要 |
<p>A plurality of lean NOx catalysts (8a,8b) are installed in parallel passages (6a,6b), respectively, of a dual passage portion (6) of an exhaust conduit (4) of an internal combustion engine (2). A space velocity changing means (10) including a valve is provided at a connecting portion of the passages (6a,6b) so that the amount of exhaust gas flowing through the lean NOx catalysts (8a,8b) is altered periodically. When a space velocity of exhaust gas at the lean NOx catalyst (8a,8b) changes from a low velocity to a high velocity, an NOx purification rate of the lean NOx catalyst (8a,8b) increases momentarily. By repeatedly generating the NOx purification rate increased conditions, the NOx purification rate of the NOx purification apparatus including the plurality of lean NOx catalysts is greatly increased. <IMAGE></p> |
