Patent ID: 8061122

Claim:
A device for removing nitrogen oxides from exhaust of an internal combustion engine operated predominantly with excess air, comprising: an exhaust line, a metering point, which is assigned to the exhaust line, for metering a reducing agent containing additive into exhaust gas, a nitrogen oxide reduction catalytic converter, which is arranged in the exhaust line downstream of the metering point, for reduction of nitrogen oxides contained in the exhaust gas with the reducing agent, having a first catalytic converter part and a second catalytic converter part arranged downstream of the first catalytic converter part, the nitrogen oxide reduction catalytic converter being designed to store the reducing agent, a dosing unit for setting a metering quantity for the additive metered to the exhaust gas via the metering point, and filling level determining means for determining a reducing agent filling level of reducing agent which is stored in at least one of the first catalytic converter part and the second catalytic converter part, wherein the metering quantity of the additive is set as a function of the reducing agent filling level, determined by the filling level determining means, of the at least one of the first catalytic converter part and the second catalytic converter part, and wherein the reducing agent filling level of a respective catalytic converter part is determined by summing and integration with respect to time of at least a conversion rate of reducing agent which is converted in the respective catalytic converter part, a desorption rate of reducing agent which is desorbed by the respective catalytic converter part, and a supply rate of reducing agent which is supplied to the respective catalytic converter part with the exhaust gas.