Exhaust emission control device

Abstract

The invention has its object to provide an exhaust emission control device with realized lessening of both particulates and NO x which can always ensure high NO x reduction ratio irrespective of operation conditions. The exhaust emission control device has a selective reduction catalyst 5 as NO x lessening catalyst incorporated in an exhaust pipe 4 and having a property of capable of selectively reacting NO x with ammonia even in the presence of oxygen, and a particulate filter 13 arranged upstream of the catalyst. A burner 14 for injection, ignition and combustion of a proper amount of fuel is arranged in front of the particulate filter 13 , and an oxidation catalyst 15 is interposed between the particulate filter 13 and the selective reduction catalyst 5 so as to conduct oxidation treatment of unburned HC in exhaust gas 3 and so as to facilitate oxidation reaction of NO in the exhaust gas 3 into NO 2 .

1 . An exhaust emission control device with an NO x  lessening catalyst incorporated in an exhaust pipe and a particulate filter arranged upstream of said NO x  lessening catalyst, comprising a burner in front of said particulate filter for injecting, igniting and burning a proper amount of fuel and an oxidation catalyst interposed between said particulate filter and said NO x  lessening catalyst so as to conduct oxidation treatment of unburned HC in exhaust gas and so as to facilitate oxidation reaction of NO in the exhaust gas into NO 2 . 
     
     
         2 . An exhaust emission control device as claimed in  claim 1 , wherein the NO x  lessening catalyst is selective reduction catalyst or NO x  absorption reduction catalyst.