| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an NOx emission control method and an NOx emission control system having an oxidation catalyst and a urea selective reduction catalyst in the exhaust passage of an internal combustion engine in this order from the upstream side which can increase the temperature range of exhaust gas with excellent NOx emission control efficiency to low temperature side. <P>SOLUTION: When the temperature Tg1 of the exhaust gas comes within a predetermined first temperature area F1, hydrocarbon is supplied from a first hydrocarbon supply device 7 on the upstream side of the oxidation catalyst 4 to raise the temperature of the exhaust gas by the oxidation catalyst 4 and eliminate the NOx adsorbed to the oxidation catalyst 4. When the temperature Tg1 of the exhaust gas comes within a second temperature area F2 higher in temperature than the first temperature area F1, urea water is supplied from a urea water supply device 5 to eliminate NOx by the urea selective reduction catalyst 5. <P>COPYRIGHT: (C)2009,JPO&INPIT |
