| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust emission control system capable of optimizing the balance between the improvement in a NOx purification rate and the suppression of ammonia slip.SOLUTION: An exhaust emission control system comprises: an SCR catalyst provided in an exhaust pipe in which exhaust gas discharged from an internal combustion engine flows; urea water supply means supplying urea water into the exhaust pipe on an upstream side of the SCR catalyst; first calculation means calculating a quantity of the urea water converted into ammonia and a quantity of the urea water that is not converted into ammonia out of the urea water supplied from the urea water supply means; second calculation means calculating a quantity of consumed ammonia and a quantity of unconsumed, discharged ammonia in the SCR catalyst; and control means controlling the supply of the urea water by the urea water supply means on the basis of the quantity of the urea water that is not converted into ammonia calculated by the first calculation means and the quantity of unconsumed, discharged ammonia calculated by the second calculation means. |
