Method for operating an exhaust after-treatment system comprising an SCR-catalyst

An exhaust gas aftertreatment system, comprising:

• an SCR catalyst;
• a dosage unit;
• and
• a control unit comprising:
• a steady state recognition element;
• a characteristic map containing predetermined, fixed target values for a nitrogen oxide concentration downstream of the SCR catalyst;
• a closed-loop emission control element configured to actuate a dosage unit for dosage of a reducing agent based on a determining parameter from the characteristic map that affects a nitrogen oxide concentration downstream of the SCR catalyst;
• a breakthrough recognition element configured to conduct recognition of breakthrough for the SCR catalyst, and, when a breakthrough is recognized, to change the determining parameter toward higher nitrogen oxide concentration downstream of the SCR catalyst;
• a calculation element connected to receive inputs from the breakthrough recognition element and the steady-state recognition element;
• and,
• a change element connected to receive inputs from the calculation element and the characteristic map, and connected to output a change parameter to the control element,
• wherein the omission control element is configured to actuate the dosage unit for dosage of the reducing agent based on the changed determining parameter.