Patent ID: 6826906
Filing Date: 2004-12-07
Classification: B01D,F01N,Y02A,Y02C,Y02T

Abstract:
An emission purification system for treating exhaust gases produced by a vehicle powered by a diesel engine comprising:a) a catalyzed soot filter adjacent and in direct fluid communication with said engine without intervening catalysts therebetween, said soot filter of the wall-flow type having gas permeable walls formed into a plurality of axially extending channels, each channel having one end plugged with any pair of adjacent channels plugged at opposite ends thereof, said exhaust gases passing through said channel walls as said gases travel from an entrance to an exit of said soot filter; b) a valve downstream of said soot filter's exit in fluid communication with a nitrogen reductant and with said exhaust gases after exiting said soot filter; c) means for regulating said valve to control the quantity of said nitrogen reductant admitted to said exhaust gases; and, d) a nitrogen reductant SCR catalyst downstream of said valve and said soot filter in direct fluid communication with said soot filter, said SCR catalyst having a set temperature at which said SCR catalyst becomes catalytically active for a set space velocity if said exhaust gases pass through said SCR catalyst with a set quantity of reductant immediately upon exit from said engine that is higher than the temperature at which said SCR catalyst becomes catalytically active when said exhaust gases pass through said SCR catalyst at said set space velocity with said set quantity of reductant after passing through said soot filter.