EXHAUST EMISSION CONTROL SYSTEM

摘要

PROBLEM TO BE SOLVED: To improve accuracy in supply of a reducing agent added from an addition valve to a reduction catalyst in an exhaust emission control system in which the reduction catalyst is arranged in an exhaust passage of an internal combustion engine and a part of an upstream exhaust passage of the reduction catalyst serves as a swirl flow type passage.SOLUTION: In an exhaust passage 3 of a diesel engine 2 as an internal combustion engine, an SCRF 5 as a reduction catalyst and an oxidation catalyst 4 located upstream of the SCRF 5 are arranged. An exhaust passage 31 between the oxidation catalyst 4 and the SCRF 5 serves as a spiral mixer (swirl flow type passage) through which an exhaust gas passes with a swirl flow. An external cylinder 311 of the spiral mixer 31 is provided with an addition valve 6 for adding urea water as a reducing agent into the spiral mixer 31. In the addition valve 6, two injection holes are formed of which injection angels are different. At positions corresponding to the injection angles of the injection holes in the spiral mixer 31, two collision plates 314a and 314b are provided with which urea water added from the injection holes collides.