PURPOSE: To maintain a high conversion ratio of NOx over a long period of time in an apparatus for treating engine exhaust gas by arranging a particle- removing filter in the upper part of an exhaust system, a unit for removing water in the exhaust gas in the middle part, and a zeolite catalyst in the lower part.
CONSTITUTION: In an apparatus for treating engine exhaust gas, a particle removing filter 2 is arranged in the upper part of an exhaust system, a unit 4 for removing water in the exhaust gas is arranged in the middle part, and a zeolite catalyst 6 is arranged in the lower part, respectively. A water vapor separation membrane is preferably used for the water removing unit 4. In this way, the water content in the exhaust gas discharged from the water removing unit 4 is low enough so that the zeolite catalyst is not deactivated by water. Since the amount of a reducing component necessary for removing NOx does not change even after passing through the water removing unit, NOx can be removed efficiently. Particles in the exhaust gas can be removed efficiently by using the filter 2 so that the conversion efficiency of NOx does not drop for a long time.
JIYOU KUNITAKA
OGATA TOMOHIKO
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