METHOD FOR REDUCING NITROGEN OXIDE IN INTERNAL COMBUSTION ENGINE AND DEVICE THEREFOR

Provided are a method for reducing a nitrogen oxide in an exhaust gas from an internal combustion engine, a membrane module, an apparatus for reducing a nitrogen oxide from an internal combustion engine using the membrane module, and an internal combustion engine apparatus. A method for reducing a nitrogen oxide in an exhaust gas from an internal combustion engine, the method comprising: a step of bringing pressurized air into contact with one surface of a steam permeable membrane (11), and allowing water to flow along the other surface of the steam permeable membrane (11) to moisturize the pressurized air; and a step of introducing the moisturized air into the internal combustion engine.