Method for adapting NH3 dosing and NH3 filling level distribution of SCR catalyst

Abstract

A method for adapting the NH 3 dosing and NH 3 fill level distribution of an SCR catalyst (22) for an SCR exhaust aftertreatment system (25) having at least one SCR catalyst (22).

Description

Background Art

[0001] DE 102019216520 A1 relates to a method for adapting the dosing of a reducing agent of an SCR catalytic converter, comprising: determining (110) an expected temperature profile in at least one axial section of the catalytic converter (70) within a predetermined time period (tSim); performing a first simulation (120) of a resulting reducing agent amount after the at least one section of the catalytic converter with a predetermined first dosing of the reducing agent according to the determined expected temperature profile; comparing the simulated first reducing agent amount with a limit value; selecting a predetermined second dosing according to a result of the comparison and performing a second simulation (130, 160) of the resulting reducing agent amount after the at least one section of the catalytic converter (70) with the second dosing; comparing the simulated second reducing agent amount with the limit value; and adapting (140, 150, 170, 180, 190, 195) the dosing of the reducing agent for injection into the catalytic converter based on the first comparison and / or the second comparison.

[0002] DE 102016201602 A1 relates to a method for determining the ammonia mass flow rate between two SCR catalytic converters arranged one after the other in an exhaust system in an SCR catalytic converter system, wherein the SCR catalytic converter system has only one reducing agent metering unit located upstream of the first SCR catalytic converter, characterized in that the determination is performed based on the signal of a NOx sensor arranged between the two SCR catalytic converters and the signal of a NOx sensor arranged downstream of the second SCR catalytic converter.

[0003] DE 102021213316 A1 relates to a method for estimating an ammonia concentration (xNH3est) downstream of at least one SCR catalytic converter (22) arranged in an exhaust system (11) of an internal combustion engine (10), the system having at least one reducing agent metering unit (21) upstream of a first SCR catalytic converter (22), wherein a first NOx sensor (31) is arranged upstream of the SCR catalytic converter (22), the first NOx sensor determining a first NOx signal (xsens, US), wherein a second NOx sensor is arranged downstream of the SCR catalytic converter (22). x sensor (32), wherein the second NOx sensor determines a second NOx signal (xsens, DS), wherein the method is permitted to release when an operating state of the internal combustion engine (10) is detected, and a starting time (t0) for estimating an ammonia concentration (xNH3est) is determined based on the permitted release, an estimate of the ammonia concentration (xNH3est) is determined based on the first and second NOx signals (xsens, US, xsens, DS) and an efficiency model (ηNOxmdl), and the SCR system (20) is adapted based on the estimated ammonia concentration (xNH3est). Summary of the invention

[0004] In a first aspect, the invention relates to a method for adapting the NH3 dosing and NH3 filling level distribution of an SCR catalytic converter for an SCR exhaust gas aftertreatment system having at least one SCR catalytic converter, wherein the at least one SCR catalytic converter is divided into at least two blocks, wherein a first NOx sensor signal is determined upstream of the SCR catalytic converter and downstream of the internal combustion engine by means of a first NOx sensor, wherein a second NOx sensor signal is determined downstream of the SCR catalytic converter by means of a second NOx sensor, wherein the first and second NOx sensors have a cross-sensitivity to ammonia, wherein a division of the second NOx sensor signal into a modeled NOx mass flow and a modeled NH3 mass flow is determined by means of a model stored in a control unit, wherein an evaluation window begins according to a first criterion and ends according to a second criterion, wherein a modeled cumulative NH3 mass flow is determined over the evaluation window, and a first cumulative NH3 mass flow is determined by means of an SCR model, wherein an overdosage model determined on the basis of the SCR model The overdosing model achieves a virtually increased NH3 dosing compared to the SCR model, wherein a second cumulative NH3 mass flow is determined with the aid of the overdosing model, wherein an underdosier model is determined based on the SCR model, wherein the underdosier model achieves a reduced NH3 dosing compared to the SCR model, wherein a third cumulative NH3 mass flow is determined with the aid of the underdosing model, wherein an adaptation value between the modeled NH3 mass flow and the first NH3 mass flow is determined with the aid of a predeterminable regulator, wherein an adaptation of the filling level distribution of the blocks of the SCR catalytic converter and / or an adaptation of the NH3 dosing is performed as a function of the modeled cumulative NH3 mass flow and the second cumulative NH3 mass flow and the third cumulative NH3 mass flow.

[0005] The method has the particular advantage that under defined operating conditions, the SCR state can be evaluated with the aid of the amount of stored ammonia (NH3 slip) from the SCR catalytic converter. The aim of the method is to correct deviations and / or dosing in a modeled filling level distribution of the SCR catalytic converter via adaptation factors. This should ensure that NOx and NH3 emissions remain below defined limits.

[0006] It is also advantageous that the method can be used to adjust to a maximum NOx conversion level. The SCR catalytic converter is thus placed on its NH3 slip side, so that the method is suitable for zero-NOx emission SCR control. System tolerances due to aging effects of installed components or components of the SCR system can be compensated, in particular on average. Furthermore, deviations from the NH3 model can be checked and adapted.

[0007] In a specific embodiment, oxygen concentration, exhaust gas mass flow, exhaust gas pressure, exhaust gas temperature and metering information downstream of the internal combustion engine and upstream of the SCR catalytic converter are determined as input variables for a management model, an overdosing model and an underdosing model.

[0008] In another embodiment, if the modeled cumulative NH3 mass flow exceeds the second cumulative NH3 mass flow, an adaptation of the NH3 dosing is performed based on the adaptation value, in particular a reduction of the NH3 dosing is performed. Thus, the adaptation can counteract the overdosing of ammonia and thus reduce the NH3 slip in the SCR catalyst.

[0009] In an advantageous embodiment, if the modeled cumulative NH3 mass flow does not exceed the third cumulative NH3 mass flow, an adaptation of the NH3 dosing is performed based on the adaptation value, in particular an increase in the NH3 dosing is performed. This has the advantage that the effects of ammonia underdosing can be offset, so that an optimal NOx conversion can be performed.

[0010] In an alternative embodiment, a first, a second and a third filling level are determined for at least two blocks of the SCR catalytic converter as a function of the SCR model, the overdosing model and the underdosing model, wherein an approximation function is determined as a function of the first, the second and the third filling level and the first, the second and the third cumulative NH3 mass flow for each block, wherein a target NH3 filling level is determined for each block by means of the approximation function and the modeled cumulative NH3 mass flow, and an adaptation of the filling level of the at least two blocks of the SCR catalytic converter is performed as a function of the target NH3 filling level, in particular for adapting the SCR model, the overdosing model and the underdosing model. The adaptation of the SCR model, in particular the management model, the overdosing model and the underdosing model, has the particular advantage that a correction of the modeled filling level distribution can be performed. As a result, a continuous improvement of the SCR model is achieved and the emissions can be compensated even better.

[0011] In a further embodiment, if the modeled cumulative NH3 mass flow exceeds the first cumulative NH3 mass flow, the filling level is adapted, in particular linearly, as a function of the first filling level and the second filling level, respectively. Thus, the NH3 filling level profile of the SCR catalytic converter is improved and a more precise prediction of the filling level is provided.

[0012] In a particular embodiment, if the modeled cumulative NH3 mass flow does not exceed the first cumulative NH3 mass flow, the adaptation is performed in particular linearly as a function of the first filling level and the third filling level, respectively. Thus, the NH3 filling level profile of the SCR catalyst is improved and a more accurate prediction of the filling level is provided.

[0013] In an alternative embodiment, the first criterion is satisfied if the modeled NH3 concentration exceeds a predeterminable first NH3 threshold value, and the second criterion is satisfied if the modeled NH3 concentration does not exceed the predeterminable first NH3 threshold value. This is advantageous because ammonia can neither be modeled continuously sufficiently well nor can it be reliably measured below a certain concentration amount.

[0014] In a specific embodiment, the first criterion is satisfied if the first NH3 mass flow exceeds a predeterminable first NH3 threshold value, and the second criterion is satisfied if the first NH3 mass flow does not exceed the predeterminable first NH3 threshold value. This is advantageous because ammonia can neither be modeled continuously sufficiently well nor can it be reliably measured below a certain concentration amount.

[0015] In an alternative design, the NH3 mass flow sensor value of the NH3 sensor is used instead of the modeled NH3 mass flow.

[0016] In a further aspect, the invention relates to an apparatus, in particular a control device and a computer program, which is arranged, in particular programmed, to perform one of the methods. In yet another aspect, the invention relates to a machine-readable storage medium having a computer program stored thereon. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention is explained in more detail below using the embodiments shown in the accompanying drawings. In which:

[0018] Figure 1 A schematic diagram showing an internal combustion engine having an exhaust gas aftertreatment arrangement according to the invention; and

[0019] Figure 2 is an exemplary measurement result of the proposed method,

[0020] Figure 3 A flow chart for graphically representing the flow of an embodiment of the method is shown. DETAILED DESCRIPTION

[0021] like Figure 1As shown, the internal combustion engine 10 has an SCR exhaust gas aftertreatment system 25 in its exhaust system 11, and the SCR exhaust gas aftertreatment system 25 has at least one SCR catalyst 22. The SCR exhaust gas aftertreatment system 25 has a reducing agent metering unit 21, through which a urea aqueous solution (AdBlue) can be injected into the exhaust system 11. Under high temperatures of the exhaust gas, ammonia is released from the urea aqueous solution. The first SCR catalyst 22 is arranged downstream of the reducing agent metering unit 21. Another SCR catalyst can be arranged downstream of the first SCR catalyst 22. The first NOx sensor 31 and the temperature sensor 12 are arranged upstream of the reducing agent metering unit 21 and downstream of the internal combustion engine 10 in the exhaust system 11. The first NOx sensor 31 measures a first NOx concentration sensor value NOx1, preferably as a NOx concentration or as a NOx mass flow. The second NOx sensor 32 is arranged downstream of the first SCR catalyst 22 and measures a second NOx concentration sensor value NOx2, preferably as a NOx concentration or as a NOx mass flow. This also applies in particular to the NH3 concentration or the NH3 mass flow.

[0022] In an optional design, the NH3 sensor 33 can also be installed downstream of the SCR catalyst 22. The NH3 sensor can determine the NH3 mass flow rate here. All NOx sensors 31, 32 transmit their signals to the electronic control device 100. Since in addition to nitrogen oxides, the NOx sensors 31, 32 also react sensitively to ammonia cross, their signals are summation signals of nitrogen oxides and ammonia. However, the first NOx sensor 31 is arranged upstream of the reductant metering unit 21, so that it reliably measures only the amount of nitrogen oxides in the exhaust gas. The reductant metering unit 21 also transmits the amount of ammonia metered into the exhaust system 11 to the control device 100.

[0023] A model N1 is also stored on the control device 100, which can determine the NOx concentration component (Konzentrationsanteil) and the NH3 concentration component of the sum signal for the second NOx sensor 32 based on the second NOx concentration sensor value NOx2. However, the model N1 does not provide continuous NOx and NH3 concentration components and is based on the second NOx concentration sensor value NOx2 downstream of the SCR catalyst 22. Optionally, the exhaust gas temperature of the temperature sensor 12 and / or the first NOx concentration sensor value NOx1 can be used for the determination. It is also possible to determine the NOx concentration component and the NH3 concentration component of the sum signal for the first NOx sensor 31 based on the first NOx concentration sensor value NOx1 with the help of the model N1.

[0024] Furthermore, an SCR model M1 is stored in control unit 100 for SCR catalytic converter 22 , in particular an NH 3 management model, which subdivides SCR catalytic converter 22 into n virtual blocks, wherein The SCR catalytic converter 22 is modeled here using a multi-chip model, wherein the current filling level variable F is determined for each virtual block n. M1i The filling level preferably corresponds to the NH3 filling level. In addition, the oxygen concentration, the exhaust gas mass flow rate downstream of the internal combustion engine 10 and upstream of the SCR catalyst 22 are determined. Exhaust pressure p exh , Exhaust temperature T exh In particular, according to the determined exhaust gas temperature T exh The block temperature T t is determined for each block n of SCR catalytic converter 22 using a temperature model stored in control device 100 . exh，n And it is used as an input variable for the SCR model M1.

[0025] Furthermore, an overdosage model M2 is determined based on the SCR model M1, which is assigned a virtually increased NH3 dosing as an input variable compared to the SCR model M1. In an advantageous embodiment, the overdosage model M2 is assigned a dosing information that is, for example, 10% higher than that of the SCR model M1 as an input variable. The overdosage model M2 is modeled with the aid of a multi-slice model, wherein the current filling level F is determined for each virtual block n. M2i .

[0026] Furthermore, based on the SCR model M1, an underdosing model M3 is determined, which is assigned as an input variable a virtually reduced NH3 dosing compared to the SCR model M1. In an advantageous embodiment, the underdosing model M3 is assigned as an input variable a dosing information that is reduced by 10% compared to the SCR model M1. In this case, the underdosing model M3 is modeled with the aid of a multi-slice model, wherein the current filling level F is determined for each virtual block. M3i .

[0027] A dosing strategy is also stored in the control device 100, which is based on, for example, the NOx concentration upstream and downstream of the SCR catalyst 22, the exhaust gas mass flow rate, and the The dosing is determined based on the temperature of the SCR catalyst 22 and the ammonia fill level of the SCR catalyst 22 .

[0028] Figure 2 An exemplary measurement result for the proposed method is shown in FIG. The NH3 mass m is plotted on the ordinate. NH2 , preferably in grams, and the time t is plotted on the abscissa. At a first time point Ex，start , showing the evaluation window E x At the beginning, and at the second time point E x，end , showing the evaluation window E x The end of NH3. A total of four NH3 mass flows 40; 41; 42; 43 are shown. The first NH3 mass 40 corresponds to the evaluation window E x The integral of the second NH3 mass flow NH3 M2 , which is determined by the overdosage model M2. The second NH3 mass 41 corresponds to the estimated window E x The integral of the modeled NH3 mass flow NH3 N1 , which is determined by the model N1 from the second NOx concentration sensor value NOx2. The third first NH3 mass 42 corresponds to the evaluation window E x The integral of the first NH3 mass flow rate NH3 M1 , which is determined by the SCR model M1. The fourth NH3 mass 43 corresponds to the value obtained via the evaluation window E x The integral of the third NH3 mass flow NH3 M3 , which is determined by the under-measurement model M3.

[0029] exist Figure 3 An exemplary sequence of a method for adapting the NH 3 dosing and the NH 3 filling level profile of an SCR catalyzer 22 of an SCR exhaust gas aftertreatment system having at least one SCR catalyzer 22 is shown in FIG.

[0030] In a first step 200, the first and second NOx sensor signals NOx1 and NOx2 are continuously received and stored by the control device 100. With the aid of the model N1 stored in the control device 100, the modeled NH3 mass flow NH3 is determined from the second NOx sensor signal NOx2. N1 and NOx mass flow rate NOx N1 The modeled NH 3 concentration component and the modeled NOx concentration component correspond to the NH 3 and NOx concentration signals downstream of the SCR catalyst 22 , in particular at the location of the second NOx sensor 32 .

[0031] Furthermore, an SCR model M1 for the SCR catalytic converter 22 is stored in the control unit 100 , which subdivides the SCR catalytic converter 22 into n virtual blocks, wherein In this case, the SCR catalytic converter 22 is modeled with the aid of a multi-chip model, wherein the current filling level variable F is determined for each virtual block n. M1iPreferably, the filling level corresponds to the NH3 filling level. In addition, the oxygen concentration, the exhaust gas mass flow rate, and the NH3 filling level downstream of the internal combustion engine 10 and upstream of the SCR catalyst 22 are determined. Exhaust pressure p exh , Exhaust temperature T exh In particular, according to the determined exhaust gas temperature T exh The block temperature T t is determined for each block n of SCR catalytic converter 22 using a temperature model stored in control device 100 . exh，n And it is used as an input variable for the SCR model M1.

[0032] Furthermore, an overdosing model M2 is determined based on the SCR model M1, which is assigned a virtually increased NH3 dosing as an input variable compared to the SCR model M1. In an advantageous embodiment, the overdosing model M2 is assigned dosing information that is, for example, 10% higher than that of the SCR model M1 as an input variable. The overdosing model M2 is modeled with the aid of a multi-slice model, wherein the current filling level F is determined for each virtual block n. M2i .

[0033] Furthermore, based on the SCR model M1, an underdosing model M3 is determined, which is assigned as an input variable a virtually reduced NH3 dosing compared to the SCR model M1. In an advantageous embodiment, the underdosing model M3 is assigned as an input variable a dosing information that is reduced by 10% compared to the SCR model M1. In this case, the underdosing model M3 is modeled with the aid of a multi-slice model, wherein the current filling level F is determined for each virtual block. M3i The method then continues in step 210 .

[0034] In step 210, the evaluation window E x The control device 100 monitors the NH3 concentration NH3 in this case. N1 .

[0035] If the modeled NH3 concentration is N1 Exceeding a predeterminable first threshold value S NH3 , then the evaluation window E is identified x At the beginning, and if the modeled NH3 concentration NH3 N1 does not exceed a predeterminable first threshold value S NH3 , then the evaluation window E x End again.

[0036] In an alternative embodiment, in this case the first NH 3 mass flow NH 3 is monitored by the control device 100 M1In this case, if the first NH3 mass flow rate NH3 M1 Exceeding a first predefinable NH3 threshold value S NH3 , then the evaluation window E is identified x at the beginning, and if the first NH3 mass flow NH3 M1 does not exceed a predeterminable first NH3 threshold value S NH3 , the end of the evaluation window is identified.

[0037] This method can be directly used to identify the evaluation window E x The process continues in step 220 or alternatively with the identification of the evaluation window E x The process continues in step 220 only after the completion of the process.

[0038] In step 220, in the evaluation window E x The modeled cumulative NH3 mass flow NH3 is determined by the control device 100 N1，Ex , the first accumulated NH3 mass flow NH3 M1，Ex 、The second accumulated NH3 mass flow NH3 M2，Ex and the third accumulated NH3 mass flow NH3 M2，Ex .

[0039] Here, the SCR model M1 stored in the control device 100 is used to calculate the oxygen concentration, the exhaust gas mass flow rate, and the exhaust gas mass flow rate downstream of the internal combustion engine 10 and upstream of the SCR catalyst 22. Exhaust pressure p exh , Exhaust temperature T exh Or block temperature T exh，n and the dosing information to determine the first accumulated NH3 mass flow rate NH3 M1，Ex The SCR model M1 is also related to the NH3 management model M1.

[0040] Furthermore, the modeled NH3 mass flow NH3 is determined by means of a predeterminable regulator, in particular an integral regulator or a virtual regulator. N1 With the first NH3 mass flow NH3 M1 The adaptation value between NH3 Adaption The method may then continue in step 230 .

[0041] In step 230 , it is checked whether the determined adaptation value NH3 Adaption Is it higher than the second accumulated NH3 mass flow rate NH3 M2 , E x , which is lower than the third accumulated NH3 mass flow rate NH3 M3 , E x, or the second and third accumulated NH3 mass flow NH3 M2 , E x NH3 M3 , E x between.

[0042] If the modeled cumulative NH3 mass flow rate NH3 N1 , E x Exceeding the second accumulated NH3 mass flow NH3 M2 , E x , then based on the adaptation value NH3 Adaption Instead, an adaptation of the NH3 dosing is performed. In particular, in this case, an overdosage of ammonia to the SCR system is detected and a reduction of the NH3 dosing of the dosing strategy is performed accordingly.

[0043] If the modeled cumulative NH3 mass flow rate NH3 N1 , E x No more than the third cumulative NH3 mass flow NH3 M3 , E x , then based on the adaptation value NH3 Adaption Instead, an adaptation of the NH3 dosing is performed. In particular, in this case, an underdosing of ammonia to the SCR system is detected and an increase in the NH3 dosing of the dosing strategy is performed accordingly.

[0044] If the modeled cumulative NH3 mass flow rate NH3 N1 , E x In the second accumulated NH3 mass flow NH3 M2 , E x and the third accumulated NH3 mass flow NH3 M3 , E x The first, second and third filling level variables F are determined for at least two blocks of the SCR catalytic converter 22 by means of the SCR model M1, the overdosing model M2 and the underdosing model M3. M1i , F M2i , F M3i Then, according to the first, second and third accumulated NH3 mass flow rates NH3 M1 , E x ; NH3 M2 , E x ; NH3 M3 , E x and the first, second and third filling level quantities F M1i , F M2i , F M3i An approximation function A is determined in each case for the at least two blocks. In particular, linear interpolation is used for this purpose.

[0045] For the modeled cumulative NH3 mass flow NH3 N1 , E x Exceeding the first accumulated NH3 mass flow NH3 M1 , E x According to the first filling level F M1i and the second filling level F M2i , in particular the fill level F is linearly enforced M1i , F M2i , F M3i For this purpose, the modeled cumulative NH3 mass flow NH3 N1 , E x Insert (einsetzen) into the approximate function A i and obtaining target NH3 filling levels for the at least two blocks of the SCR catalyst 22, respectively. The filling level F of the at least two blocks of the SCR catalyst 22 M1i , F M2i , F M3i Adaptation according to the target NH3 filling level The method can then be started and ended again in step 200 .

[0046] For the modeled cumulative NH3 mass flow NH3 N1 , E x No more than the first accumulated NH3 mass flow NH3 M1 , E x According to the first filling level F M1i and the third filling level F M3i , in particular the fill level F is linearly enforced M1i , F M2i , F M3i For this purpose, the modeled cumulative NH3 mass flow NH3 N1 , E x Insert into the approximate function A i and obtaining target NH3 filling levels for the at least two blocks of the SCR catalyst 22, respectively. The filling level F of the at least two blocks of the SCR catalyst 22 M1i , F M2i , F M3i Adaptation according to target NH3 filling level The method can then be started and ended again in step 200 .

Claims

1. A method for adapting the NH3 dosing and NH3 filling level distribution of an SCR catalyst (22) for an SCR exhaust gas aftertreatment system (25) having at least one SCR catalyst (22), wherein the at least one SCR catalyst (22) is divided into at least two blocks, wherein a first NOx sensor signal (NOx1) is determined upstream of the SCR catalyst (22) and downstream of an internal combustion engine (10) by means of a first NOx sensor (31), wherein a second NOx sensor signal (NOx2) is determined downstream of the SCR catalyst (22) by means of a second NOx sensor (32), wherein the first and second NOx sensors (31, 32) have a cross sensitivity to ammonia (NH3), wherein the second NOx sensor signal (NOx2) is determined to a modeled NOx mass flow (NOx) by means of a model (N1) stored in the control device (100). N1 ) and the modeled NH3 mass flow rate (NH3 N1 ) is divided into two parts, where the evaluation window (E x ) starts according to a first criterion and ends according to a second criterion, wherein the evaluation window (E x ) to determine the cumulative NH3 mass flow (NH3 N1 , E x ), and determine the first accumulated NH3 mass flow (NH3 M1 , E x ), An overdosing model (M2) is determined based on the SCR model (M1), which overdosing model achieves an increased NH3 dosing compared to the SCR model (M1), wherein: The second cumulative NH3 mass flow (NH3 M2 , E x ), wherein based on the SCR model (M1) a deficiency metering model (M3) is determined, which achieves a reduced NH3 dosing compared to the SCR model (M1), wherein a third accumulated NH3 mass flow (NH3 M3 , E x ), wherein the modeled NH3 mass flow (NH3 N1 ) and the first NH3 mass flow rate (NH3 M1 , E x ) between the adaptation values ​​(NH3 Adaption ), wherein according to the modeled cumulative NH3 mass flow (NH3 N1 , E x ) and the second and third accumulated NH3 mass flows (NH3 M2 , E x NH3 M3 , E x ) and performs an adaptation of the filling level distribution of the blocks of the SCR catalytic converter (22) and / or an adaptation of the NH3 dosing.

2. The method according to claim 1, characterized in that The oxygen concentration and the exhaust gas mass flow rate downstream of the internal combustion engine (10) and upstream of the SCR catalyst (22) are determined as input variables for a management model (M1), an overdosing model (M2) and an underdosing model (M3). Exhaust pressure (p exh ), exhaust temperature (T exh ) and dosage information.

3. The method according to claim 1, characterized in that If the modeled cumulative NH3 mass flow (NH3 N1 , E x ) exceeds the second accumulated NH3 mass flow rate (NH3 M2 , E x ), then based on the adaptation value (NH3 Adaption ) performs an adaptation of the NH3 dosing, in particular performs a reduction of the NH3 dosing.

4. The method according to claim 1, characterized in that: If the modeled cumulative NH3 mass flow (NH3 N1 , E x ) does not exceed the third accumulated NH3 mass flow rate (NH3 M3 , E x ), then based on the adaptation value (NH3 Adaption ) performs an adaptation of the NH3 dosing, in particular performs an increase of the NH3 dosing.

5. The method according to claim 1, characterized in that wherein a first, a second and a third filling level (F) are determined for at least two blocks of the SCR catalyst (22) based on the SCR model (M1), the overdosing model (M2) and the underdosing model (M3). M1i , F M12 , F M3i ), wherein the first, second and third filling level quantities (F M1i , F M2i , F M3i ) and the first, second and third accumulated NH3 mass flows (NH3 M1 , E x ; NH3 M2 , E x ; NH3 M3 , E x ) and determine the approximate function (A i ), where by means of the approximate function (A i ) and the modeled cumulative NH3 mass flow (NH3 N1 , E x ) Determine the target NH3 filling level for each block separately And according to the target NH3 filling level to perform a filling level (F) of at least two blocks of the SCR catalyst (22) M1i , F M2i , F M3i ), in particular for adapting the SCR model (M1), the overdosing model (M2) and the underdosing model (M3).

6. The method according to claim 5, characterized in that If the modeled cumulative NH3 mass flow (NH3 N1 , E x ) exceeds the first accumulated NH3 mass flow rate (NH3 M1 , E x ), then according to the first filling level (F M1i ) and the second filling level (F M2i： ) respectively, in particular linearly, executes the fill level (F M1i , F M12 , F M3i )’s adaptation.

7. The method according to claim 5, characterized in that If the modeled cumulative NH3 mass flow (NH3 N1 , E x ) does not exceed the first accumulated NH3 mass flow rate (NH3 M1 , E x ), then according to the first filling level (F M1i ) and the third filling level amount (F M3i ) respectively and in particular linearly (F M1i , F M2i , F M3i )’s adaptation.

8. The method according to claim 1, characterized in that If the modeled NH3 concentration (NH3 N1 ) exceeds a predeterminable first NH3 threshold value (S NH3 ), the first criterion is met, and if the modeled NH3 concentration (NH3 N1 ) does not exceed the first predeterminable NH3 threshold value (S NH3 ), then the second criterion is met.

9. The method according to claim 1, characterized in that: If the first NH3 mass flow rate (NH3 M1 ) exceeds a predeterminable first NH3 threshold value (S NH3 ), the first criterion is met, and if the first NH3 mass flow rate (NH3 M1 ) does not exceed the first predeterminable NH3 threshold value (S NH3 ), then the second criterion is met.

10. The method according to any one of the preceding claims, characterized in that Instead of the modeled NH3 mass flow rate (NH3 N1 ) and use the NH3 mass flow sensor value of the NH3 sensor (33). 11 . A computer program, which is configured to execute the method according to claim 1 .

12. An electronic storage medium having a computer program according to claim 11.

13. An apparatus, in particular a control device (100), which is configured to carry out the method according to any one of claims 1 to 10.

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