| 摘要 |
PURPOSE:To make it possible to effectively decompose NOx by supplying a part of fuel to a lower unsaturated hydrocarbon gas generator, and reacting the gas generated at the above generator with a cupper ion exchange type high silica zeolite or metal-silica catalyst. CONSTITUTION:A gas supply valve 3 is attached to an exhaust gas collecting unit 15 located in front of a catalyst layer 16 for injecting lower unsaturated hydrocarbon gas in a small amount corresponding to that of NOx in exhaust gas. Furthermore, there is provided a lower unsaturated hydrocarbon gas generator 8 adapted to reduce NOx on catalyst, to which a part of fuel in a fuel tank 11 is supplied. A gas supply valve is controlled to be opened by a gas supply controller 10 based on an output signal from a NOx sensor 17 disposed downstream from the catalyst layer 16, to supply lower unsaturated hydrocarbon gas in an amount enough to reduce NOx in exhaust gas. Then, the lower unsaturated hydrocarbon gas and NOx in high temperature exhaust gas are introduced into the catalyst layer 16, to decomposed the NOx into N2 and H2O.
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