| 摘要 |
PURPOSE:To prevent the deterioration with the noble metals of denitrifying catalysts and to maintain a high denitrification rate over a long period of time by providing a packed bed for capturing the noble metal components splashed from oxidizing catalysts within the waste gas passage after the oxidizing catalysts on the upstream of an ammonia injection device. CONSTITUTION:A waste gas is subjected to oxidation of the CO contained in the CO oxidizing catalysts 5a to CO2 and is then introduced through the packed bed 5b for trapping the noble metals to the denitrifying catalysts 5c where NOX is reduced by the ammonia injected from the ammonia injection device 6. The noble metal components, such as Pt, Pd and Rh are used for the CO oxidizing catalysts. The catalysts formed by using titanium oxide as an essential component and adding the oxides of tungsten, molybdenum, etc., thereto are used as the denitrifying catalysts. The oxides of the same compsn. as the compsn. of the denitrifying catalysts, i.e., molybdenum oxide, tungsten oxide, etc., are used as the packed bed 5b installed for the purpose of capturing the noble metal components splashed from the denitrifying catalysts. The packed bed is installed in the lowest possible temp. part on the rear flow side of the CO oxidizing catalysts and the front flow part of the NH3 injection device. |
