Patent ID: 6080376
Filing Date: 2000-06-27
Classification: B01D,B01J

Abstract:
A method of denitrating an exhaust gas containing nitrogen oxides by means of catalytically removing said nitrogen oxides using ammonia as a reducing agent while introducing said exhaust gas into a reaction vessel packed with a catalyst, comprising:passing said exhaust gas catalyst through a) a first denitration catalyst layer in the upstream of the gas flow under conditions effective to reduce said nitrogen oxides, then b) through an ammonia decomposition catalyst layer containing an ammonia decomposition catalyst under conditions effective to decompose ammonia into nitrogen and nitrogen oxides and then c) through a second denitration catalyst layer downstream from the second layer,wherein ammonia is added in an amount not less than the stoichiometric equivalent of the nitrogen oxides in the exhaust gas at the inlet of the first denitration catalyst layer, andwherein the ammonia decomposition catalyst is a catalyst having a performance of 70% or higher as % nitrogen selection defined as follows:% nitrogen selection=[1-(NOx (ppm) at outlet of ammonia decomposition catalyst-NOx (ppm) at inlet of ammonia decomposition catalyst/NH.sub.3 (ppm) at inlet of ammonia decomposition catalyst-NH.sub.3 (ppm) at outlet of ammonia decomposition catalyst)].times.100.