| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a simple and inexpensive exhaust gas treatment device having a selective reduction NOx catalyst device. <P>SOLUTION: A combustion burner 8, a particulate filter 4, a urea water adding device 5, a urea SCR catalyst device 6, and an ammonia oxidation catalyst device 7 are disposed in an exhaust passage 2 in this order. An HC trap catalyst device 10 is disposed between a filter 4 and the urea water adding device 5. The HC trap catalyst device 10 temporarily traps HC in the exhaust gas when an exhaust gas temperature is equal to or below a predetermined one. When the temperature exceeds the predetermined one, the catalyst device releases the trapped HC while oxidizing. When the filter 4 is regenerated by the combustion burner 8, therefore, the HC trap catalyst device 10 decreases the possibility that the urea SCR catalyst device 6 is poisoned by trapping unburned HC to suppress the lowering of an NOx reduction performance. The HC trap catalyst device 10 is a zeolite catalyst which is lower in price than an oxidation catalyst formed mainly of a precious metal such as platinum. <P>COPYRIGHT: (C)2009,JPO&INPIT |
