ENGINE EXHAUST-GAS PURIFICATION DEVICE

There is provided an exhaust gas purifying apparatus for an engine 1 including a urea water injector 40 and a low-pressure exhaust gas recirculation passage 45. The urea water injector 40 supplies urea water to an upstream side of selective reduction catalyst 34 provided in an exhaust pipe 30 of the engine 1 and hydrolyzes the urea water in the exhaust pipe 30 to cause the generated ammonia to flow into the selective reduction catalyst 34 thereby tc reduce and purify nitrogen oxides in exhaust gas. The low-pressure exhaust gas recirculation passage 45 introduces the exhaust gas from the exhaust pipe 30 and recirculates the exhaust gas into an intake pipe 20 of the engine 1. A reduction in exhaust gas temperature inside the exhaust pipe 30 between the urea water injector 40 and the selective reduction catalyst 34 reduces a supply rate of the urea water and increases a recirculation rate of the exhaust gas.