CATALYST SYSTEM, USE THEREOF AND METHOD FOR OPERATING THE SAME

摘要

The invention relates to a catalyst system (1,21,41,61), the use thereof and a method for operating said catalyst system (1,21,41,61). A catalyst system (1,21,41,61) is used to decompose nitrogen oxides in an exhaust gas, by means of a reactant (11,55,57,69). Said catalyst system comprises a reaction zone (3,27,53) which is crossed by the exhaust gas, a catalyst device (5), and an addition device (7) which is associated with the catalyst device and by which means the reactant (11,55,57,69) can be introduced into the reaction zone (3,27,53). The inventive catalyst system is embodied in such a way that the reactant (11,55,57,69) can be added not in one step, but in two or three steps. The addition by high excess also stimulates the oxidation of the reactant (11,55,57,69), in such a way that the reactant (11,55,57,69) can be added in a favourable manner. This is especially significant when the exhaust gas is at a high temperature, e.g. above 450 DEG C, and/or when the nitrogen oxides have small inlet concentrations, e.g. below 200 ppm.