EXHAUST EMISSION CONTROL DEVICE

摘要

PROBLEM TO BE SOLVED: To provide an exhaust emission control device capable of satisfactorily inhibiting accumulation of urea-derived deposits in an exhaust gas passage, and preventing ammonia slip accompanying elimination of urea-derived deposits.

SOLUTION: This device is provided with: an ammonia selective reduction type NOx catalyst 40 selectively reducing NOx contained in exhaust gas of an engine 1 by using ammonia as a reducer; a urea water injector 44 supplying urea water into exhaust gas upstream of the ammonia selective reduction type NOx catalyst 40; and an ECU 50 executing exhaust gas temperature raise control raising exhaust gas temperature to target temperature when quantity of the urea origin deposits formed out of urea water supplied from the urea water injector 44 and accumulating in an exhaust gas after-treatment device 28 achieves prescribed reference accumulation quantity Qr. The ECU 50 raises target temperature as quantity of the urea origin deposits reduces.

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