PURPOSE: To effectively remove the NOx in the exhaust gas over the entire range of the actual exhaust gas temp. from an automobile by controlling the surface temp. of an exhaust gas purifying material in the optimum temp. range to NOx removal and adding hydrocarbons or oxygen-contg. org. compds. into the exhaust gas on the upstream side of the purifying material.
CONSTITUTION: An exhaust gas purifying material 3 is set midway in an exhaust gas duct 2, and a reducing agent such as hydrocarbons and oxygen-contg. org. compds. is added to the exhaust gas on the upstream side of the material 3 by an adding device 4. The surface temp. of the material 3 measured by a temp. measuring device 6 is controlled in the optimum temp. range to NOx by a temp. control means. The optimum temp. is controlled within about ±100°C, preferably about ±50°C, of the temp. exhibiting the maximum NOx removing rate by the material 3. The temp. control means consists of a double- structure exhaust gas duct 7 and a refrigerant circulating device 8, and the refrigerant is filled in the outer layer of the duct 7.
MAKINO SEIJI
MURAMATSU AKIRA
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