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

摘要

The disclosed flue gas-cleaning device and flue gas-cleaning method that use selective catalytic reduction catalysts are technologies for removing nitrogen oxides contained in flue gas that is exhausted from lean burn engines such as diesel engines using ammonia and selective catalytic reduction catalyst, and can remove nitrogen oxides effectively even at low temperatures while also being able to limit ammonia leakage. Concretely, the device and method are provided with a flue gas-cleaning catalytic device wherein two selective catalytic reduction catalysts are disposed in series and each selective catalytic reduction catalyst comprises a lower catalytic layer and upper catalytic layer. The lower catalytic layer contains (i) a precious metal component, (ii) alumina or the like, and (iii) zeolite. Meanwhile, the upper catalytic layer contains essentially no (i) and contains (iii). (i) in the lower catalytic layer of the first selective catalytic reduction catalyst contains 90 wt% or more in metal equivalents of platinum component in the total precious metal components. Component (i) of the lower catalytic layer of the second selective catalytic reduction catalyst contains 40 wt% or more in metal equivalents of palladium component in the total precious metal components.