A METHOD OF PURIFYING GASES CONTAINING NITROGEN OXIDES AND AN APPARATUS FOR PURIFYING GASES IN A STEAM GENERATION BOILER

摘要

A method of reducing the nitrogen oxide level in the flue gases issuing fromcombustion units by introduction of reducing agents into contact with gasescontaining nitrogen oxides in first and second reducing stages, is provided.The first reducing stage is a non-catalytic stage (e.g. at temperatures over800 ~C), while the second stage is a catalytic stage (e.g. at temperatures ofabout 300-400 ~C). A steam generation boiler with improved nitrogen reductionfacilities is also provided. The amount of nitrogen oxides in the hot gases isreduced in the combination of the first and second reducing stages whileproducing steam in a steam generation boiler system, thus resulting in gasesessentially free from nitrogen oxides while eliminating the possibility of NH3(or other reducing agent) slip in the exhausted flue gases. Heat transfers ina convection section are used to establish stabilized temperature conditionsfor catalytic reduction.