FLUE GAS-CLEANING DEVICE AND FLUE GAS-CLEANING METHOD THAT USE SELECTIVE CATALYTIC REDUCTION CATALYS

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An exhaust gas purification catalyst apparatus using a selective reduction-type catalystwhichiscapable ofeffectively purifying a nitrogen oxide even at low temperature, as well as suppressing leakage of ammonia, in technology for purifying a nitrogen oxide contained in exhaust gas discharged from a lean burn engine such as a diesel engine, with ammonia and the selective reduction catalyst, and a method for exhaust gas purification. An exhaust gas purification catalyst apparatus arranged with a spraying means of a reducing agent selected from ammonia or urea, and two selective reduction-type catalysts (SROC) in series, in a flow passage of exhaust gas of a lean burn engine, to oxidize nitrogen monoxide (NO) in exhaust gas, as well as to reduce a nitrogen oxide by the reducing agent which is sprayed in exhaust gas, to oxidize excess ammonia, characterized in that : the selective reduction-type catalyst (SROC) has a lower catalyst layer (A) and an upper catalyst layer (B) at the surface of an integral structure-type carrier (C), wherein the lower catalyst layer (A) contains the following components (i) a noble metal component, component (ii) alumina, titania, silica, zirconia, tungsten oxide, a transition metal oxide, a rare earth oxide, and a complex oxide thereof, and component (iii) zeolite; on the other hand, the upper catalyst layer (B) does not substantially contain the following component (i) and contains the following component (iii); the component (i) of the lower catalyst layer (A1) of the selective reduction-type catalyst (SROC1) at the forward stage contains a platinum component in an amount of 90% by weight or more in metal equivalent; and the component (i) of the lower catalyst layer (A2) of the selective reduction-type catalyst (SROC2) at the backward stage contains a palladium component in an amount of 40% by weight or more inmetal equivalent; or the like.