Method and device for catalytically removing a pollutant from the exhaust gas of an internal combustion system

A process for catalytic removal of a pollutant from a combustion installation exhaust gas includes calculating, from operationally relevant parameters of the installation, a pollutant concentration using a predetermined characteristic diagram. A predetermined quantity of a reagent is introduced into the exhaust per unit time as a function of the calculated pollutant concentration, the reagent reacting with the pollutant at a catalytic converter. Operating states of the installation with substantially constant pollutant emission levels are determined. The pollutant concentration during an operating state of the installation with a substantially constant pollutant emission level is determined with a sensor and only a pollutant concentration from the installation in a steady operating state is used to correct the diagram. The pollutant concentration from the installation is calculated with the diagram in a non-steady operating state. An apparatus for the catalytic removal of the pollutant from the exhaust gas is also provided.