| 摘要 |
PROBLEM TO BE SOLVED: To control a mixture ratio of a mixed solution so that a NOx purification rate is maintained within a prescribed temperature range in which the NOx purification rate reaches a target value or higher over a long period of time, in an exhaust emission control device which injects a mixed solution in which a solution in which a reductant or a precursor of the reductant is dissolved, and a solvent of the solution are mixed into an exhaust gas which flows into an SCR catalyst.SOLUTION: When a floor temperature of an SCR catalyst is within a prescribed temperature range in which a NOx purification rate reaches a target value or higher, a mixture ratio of a mixed solution injected from an injection part is controlled within a prescribed range of the mixture ratio so that a ratio of a storage amount of a solution and a storage amount of a solution with respect to the sum of a storage amount of a solvent is brought into a prescribed range of the mixture ratio at which the floor temperature of the SCR catalyst is maintained within the prescribed temperature range. |
