| 摘要 |
PROBLEM TO BE SOLVED: To distinguish between a fall in the addition capacity of an addition valve and the accumulation of deposits as a cause of a fall in the NOx purification capacity in a urea selective reduction catalyst, and to perform the processing of burning out deposits on the basis of a determination that deposits are accumulated.SOLUTION: An exhaust emission control apparatus is equipped with an SCR catalyst 12 provided in an exhaust passage 11 of an internal combustion engine 10, and an addition valve 30 that adds a reducing agent to the SCR catalyst 12. The exhaust emission control apparatus performs the increasing processing of increasing an amount of the reducing agent added from the addition valve 30 when a NOx purification capacity of the SCR catalyst 12 is low. The exhaust emission control apparatus performs the processing of burning out deposits when the NOx purification capacity of the SCR catalyst 12 has fallen along with the performance of the increasing processing. |
