EXHAUST EMISSION CONTROL SYSTEM

摘要

PROBLEM TO BE SOLVED: To prevent excessive temperature rise of exhaust in supplying HC (unburned hydrocarbon) to an oxidation catalyst, and effectively suppress heat deterioration of an SCR catalyst.SOLUTION: An exhaust emission control system includes: a first oxidation catalyst 31 that is provided in an exhaust system of an internal combustion engine 10; a second oxidation catalyst 32 that is provided on the exhaust system on a downstream side with respect to the first oxidation catalyst 31; a selective reduction catalyst 41 that is provided on the downstream side with respect to the second oxidation catalyst 32 and reduces and purifies NOx in exhaust with NH3 generated from urea water as reductant; a third exhaust temperature sensor 53 detecting a temperature of exhaust inflowing to the selective reduction catalyst 41; a temperature rise control unit 62 periodically executing temperature rise control of supplying HC (unburned hydrocarbon) to the first oxidation catalyst 31 and increasing the exhaust temperature detected by the third exhaust temperature sensor 53 to a predetermined target temperature; and a target temperature correction unit 63 correcting a target temperature in temperature rise control executed next to the current temperature rise control, on the basis of the exhaust temperature detected by the third exhaust temperature sensor 53 during execution of temperature rise control and the target temperature.SELECTED DRAWING: Figure 4