METHOD FOR OPERATING AN EXHAUST GAS TREATMENT SYSTEM HAVING AN SCR CATALYTIC CONVERTER

摘要

The invention relates to a method for operating an exhaust gas treatment system, comprising an SCR catalytic converter (5) for cleaning an exhaust gas of a motor vehicle internal combustion engine (1), wherein a metering unit (27) controllable by a control unit adds an ammonia-containing reducing agent to the exhaust gas at an adjustable metering rate, and an exhaust enriched with ammonia according to the metered addition is fed to the SCR catalytic converter (5). A computer model calculates an ammonia filling level value (F) for a filling level of ammonia stored in the SCR catalytic converter (5) and a model metering rate (D) for the metered addition of the reducing agent into the exhaust gas, at which a target filling level of ammonia stored in the SCR catalytic converter (5) specified by the computer model and/or a target efficiency (?) specified by the computer model for a nitrogen oxide conversion (UNOx) with ammonia stored in the SCR catalytic converter (5) and/or fed to the SCR catalytic converter (5) must be at least approximately achieved. According to the invention, either a model-based filling level regulation for achieving the target filling level or a model-based efficiency control for achieving the target efficiency (?) is performed according to predetermined values for certain operating variables such as a temperature of the exhaust gas or of the SCR catalytic converter (5).