Exhaust emission control device

Abstract

Even in a vehicle with travel pattern of continuing operational status with low exhaust temperature, a satisfactory NO x reduction effect can be attained even at exhaust temperature lower than that required conventionally therefor. In an exhaust emission control device with selective reduction catalyst 10 incorporated in an exhaust pipe 9, ammonia being added upstream of the catalyst 10 for reduction and purification of NO x , the device comprises an ammonia generator 12 with a vessel 15 for holding urea water 23 a and with an electrode 16 for generation of ammonia 13 a, 13 b through action of plasma on the urea water 23 a in the vessel, the ammonia 13 a, 13 b generated in the generator 12 being fed upstream of the catalyst 10.

1 . An exhaust emission control device with a selective reduction catalyst incorporated in an exhaust pipe, ammonia being added upstream of the catalyst so as to reduce and purify NO x , said exhaust emission control device comprising an ammonia generator with a vessel for holding urea water and with an electrode for generation of ammonia through action of plasma on the urea water in the vessel, the ammonia generated in the ammonia generator being fed upstream of the catalyst. 
   
   
       2 . An exhaust emission control device as claimed in  claim 1 , wherein dielectric pellets are charged in the urea water in the vessel. 
   
   
       3 . An exhaust emission control device as claimed in  claim 1 , wherein ammonia gas is taken out from the ammonia generator. 
   
   
       4 . An exhaust emission control device as claimed in  claim 2 , wherein ammonia gas is taken out from the ammonia generator. 
   
   
       5 . An exhaust emission control device as claimed in claim  1 , wherein ammonia water is taken out from the ammonia generator. 
   
   
       6 . An exhaust emission control device as claimed in  claim 2 , wherein ammonia water is taken out from the ammonia generator. 
   
   
       7 . An exhaust emission control device as claimed in any one of  claims 1 - 6  further comprising a pH meter for detecting concentration of ammonia taken out from the vessel and a controller for outputting a command on an amount of ammonia to be fed upstream of the catalyst on the basis of the detected value from the pH meter.