ENGINE EXHAUST GAS PURIFICATION APPARATUS

摘要

[PROBLEMS] To effectively remove NOx from exhaust gas even when the temperature of exhaust gas is relatively low. [MEANS FOR SOLVING PROBLEMS] The exhaust gas purification apparatus includes selective reduction type catalyst (21) disposed in exhaust pipe (16); liquid injection nozzle (23) disposed upstream thereof; liquid injection means (30) capable of injecting ureal liquid (32) through the liquid injection nozzle; controller (44) and mixer (26). The apparatus further includes ammonia purification catalyst (54) disposed downstream of the selective reduction type catalyst (21); particulate filter (51) disposed upstream of the nozzle (23); oxidation catalyst (53) disposed upstream of the same; and temperature sensor (43) for detecting the temperature of the selective reduction type catalyst (21). Further, there is provided a fuel injection device structured so as to inject fuel into a cylinder after an upper dead center of piston and furnished with a controller for controlling the fuel injection device so as to inject fuel into a cylinder after an upper dead center of piston when a temperature sensor detects that the temperature of the selective reduction type catalyst (21) is a given value or below.