METHOD FOR REDUCING DEPOSITS RELATED TO A REDUCTION AGENT IN A PORTION OF AN EXHAUST AFTERTREATMENT SYSTEM

Abstract

A method for reducing deposits related to a reduction agent (RA) in a portion of an exhaust aftertreatment system (EAS) of an internal combustion engine (ICE) and comprising an injector for injecting the RA into said EAS, said portion located downstream of said injector, as seen in an intended direction of flow of exhaust gas in said EAS, said method comprising: identifying for said ICE, a future operating sequence (FOS) comprising a first temporal portion (t.sub.1) and a second temporal portion (t.sub.2) subsequent to t.sub.1, confirming that said FOS is suitable for reducing deposits and that said ICE operates in accordance with said FOS, in response to said confirming being affirmative, injecting a first dosage (d.sub.1) of RA into said EAS during at least a part of said t.sub.1 and injecting a second dosage (d.sub.2) of RA smaller than d.sub.1 into said EAS during at least a part of t.sub.2.

Claims

1. A method for reducing deposits related to a reduction agent in a portion of an exhaust aftertreatment system of an internal combustion engine, said exhaust aftertreatment system comprising an injector for injecting the reduction agent into said exhaust aftertreatment system, and said portion of said exhaust aftertreatment system being located downstream of said injector, as seen in an intended direction of flow of exhaust gas in said exhaust aftertreatment system, said method comprising the steps of: identifying a future operating sequence for said internal combustion engine, said future operating sequence comprising a first temporal portion (t.sub.1) and a second temporal portion (t.sub.2), said second temporal portion (t.sub.2) being subsequent to said first temporal portion (t.sub.1), performing a confirmation procedure comprising: confirming that said future operating sequence is suitable for reducing said deposits and confirming that said internal combustion engine operates in accordance with said precedingly identified future operating sequence, in response to said confirmation procedure being affirmative, executing a deposit removal dosage procedure comprising controlling said injector such that a first dosage (d.sub.1) of reduction agent is injected into said exhaust aftertreatment system during at least a part of said first temporal portion (t.sub.1) and that a second dosage (d.sub.2) of reduction agent is injected into said exhaust aftertreatment system during at least a part of said second temporal portion (t.sub.2) said second dosage (d.sub.2) being smaller than said first dosage (d.sub.1).

2. The method according to claim 1, wherein a ratio between said second dosage (d.sub.2) and a maximum dosage that can be injected by the injector is less than 0.05, and/or wherein a ratio between said second dosage (d.sub.2) and said first dosage (d.sub.1) is less than 0.05.

3. The method-according to claim 1, wherein said first dosage (d.sub.1) of said reduction agent is such that a ratio between an actual reductant buffer and a maximum reductant buffer at a current operating condition in a selective catalytic reduction catalyst located downstream said portion of said exhaust aftertreatment system is within the range of 0.2 to 0.6.

4. The method-according to claim 1, wherein said future operating sequence is determined to be suitable for reducing said deposits if a ratio between an estimated workload of said internal combustion engine in said first temporal portion (t.sub.1) and the estimated workload in the second temporal portion (t.sub.2) is at least 1.5, and wherein preferably a ratio between said estimated workload in the second temporal portion (t.sub.2) and said maximum workload of said internal combustion engine is less than 0.5.

5. The method according to claim 1, wherein said method further comprises a step of identifying a deposits parameter indicative of a level of deposits in said portion of said exhaust aftertreatment system and wherein said confirmation procedure further comprises: confirming that said level of deposits is equal to or exceeds a predeterminable threshold.

6. The method according to claim 1, wherein said method further comprises identifying a temperature parameter indicative of a temperature of said portion of said exhaust aftertreatment system and wherein said deposit removal dosage procedure is performed in dependence on said temperature parameter, preferably the initiation of said second dosage (d.sub.2) is dependent on said temperature parameter.

7. The method according to claim 6, wherein said second dosage (d.sub.2) is initiated in response to detecting that said temperature parameter has a temperature increase rate at or below a predetermined increase rate threshold.

8. The method according to claim 6, wherein said temperature of said portion of said exhaust aftertreatment system is a temperature of a wall portion of said portion of said exhaust aftertreatment system.

9. The method according to claim 1, wherein said future operating sequence further comprises a third temporal portion (t.sub.3), said third temporal portion (t.sub.3) being subsequent said second temporal portion (t.sub.2), and wherein said deposit removal dosage procedure further comprises controlling said injector such that a third dosage (d.sub.3) of reduction agent is injected into said exhaust aftertreatment system during at least a part of said third temporal portion (t.sub.3), said third dosage (d.sub.3) being such that a ratio between an actual reductant buffer and a maximum reductant buffer at a current operating condition in a selective catalytic reduction catalyst located downstream said portion of said exhaust aftertreatment system is within the range of 0.2 to 0.6

10. The method according to claim 1, wherein said internal combustion engine propels a vehicle and wherein said feature of confirming that said future operating sequence is suitable for reducing said deposits comprises confirming that said vehicle is predicted to be driven in at least one of the following driving conditions: uphill driving during at least a majority of said first temporal portion (t.sub.1) and level or downhill driving during at least a majority of said second temporal portion (t.sub.2), acceleration during at least a majority of said first temporal portion (t.sub.1) and driving at constant speed or deceleration during at least a majority of said second temporal portion (t.sub.2), entering a motorway during said first temporal portion (t.sub.1) and driving on said motorway during said second temporal portion (t.sub.2), overtaking another vehicle during said first temporal portion (t.sub.1) and driving at constant speed or deceleration during said second temporal portion (t.sub.2).

11. The method according to claim 10, wherein said vehicle comprises a route planning system comprising a GPS and/or a map database, and wherein said feature of confirming that said vehicle is predicted to be driven in at least one of said driving conditions comprises using said route planning system.

12. The method according to claim 1, wherein said reduction agent is a reduction agent for NOx emissions, preferably an aqueous urea solution.

13. A control unit adapted for reducing deposits related to a reduction agent in a portion of an exhaust aftertreatment system of an internal combustion engine, said exhaust aftertreatment system comprising an injector for injecting said reduction agent into said exhaust aftertreatment system, and said portion of said exhaust aftertreatment system being located downstream of said injector, as seen in an intended direction of flow of exhaust gas in said exhaust aftertreatment system, said control unit being adapted to: identify a future operating sequence for said internal combustion engine, said future operating sequence comprising a first temporal portion (t.sub.1) and a second temporal portion (t.sub.2), said second temporal portion (t.sub.2) being subsequent to said first temporal portion (t.sub.1), perform a confirmation procedure comprising: confirming that said future operating sequence is suitable for reducing said deposits and confirming that said internal combustion engine operates in accordance with said precedingly identified future operating sequence, in response to said confirmation procedure being affirmative, execute a deposit removal dosage procedure comprising controlling said injector such that a first dosage (d.sub.1) of reduction agent is injected into said exhaust aftertreatment system during at least a part of said first temporal portion (t.sub.1) and that a second dosage (d.sub.2) of reduction agent is injected into said exhaust aftertreatment system during at least a part of said second temporal portion (t.sub.2), said second dosage (d.sub.2) being smaller than said first dosage (d.sub.1).

14. An exhaust aftertreatment system for an internal combustion engine, said exhaust aftertreatment system comprising a source of reduction agent, said source being in fluid connection with an injector, said injector being adapted to inject said reduction agent into a portion of said exhaust aftertreatment system, said portion of said exhaust aftertreatment system being located downstream of said injector, as seen in an intended direction of flow of exhaust gas in said exhaust aftertreatment system, said exhaust aftertreatment system comprising a control unit according to claim 13, said control unit being adapted to issue a signal to said injector in order to control a dosage of reduction agent from said injector.

15. The control unit according to claim 13 where the control unit is part of a vehicle.

16. The exhaust aftertreatment system according to claim 14 wherein the exhaust aftertreatment system is part of a vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0071] With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

[0072] In the drawings:

[0073] FIG. 1 is a schematic drawing illustrating a vehicle;

[0074] FIG. 2 is a schematic drawing illustrating an exhaust aftertreatment system;

[0075] FIG. 3. is a schematic illustration of an implementation of the invention, and

[0076] FIG. 4 is a flowchart illustrating an embodiment of the method of the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0077] In the present detailed description, embodiments of the present invention are mainly described with reference to a vehicle in the form of a truck 100 comprising an internal combustion engine 102 such as the truck illustrated in FIG. 1. However, it should be noted that various embodiments of the described invention are equally applicable for a wide range of vehicles and vessels, as well as for stationary applications.

[0078] FIG. 1 shows a simplified side-view of a vehicle, in the form of a truck 100, which is equipped with an internal combustion engine 102. The internal combustion engine 102 may be the single prime mover for propelling the truck 100, or it may be comprised in a drive system comprising at least two engines and/or motors, such as electric motors. The internal combustion engine 102 runs on fuel, for instance diesel fuel, which is supplied to the internal combustion engine 102 by means of a fuel supply system (not shown).

[0079] Purely by way of example, the truck 100 may comprise a route planning system 104, which will be presented more in detail below.

[0080] The exhaust gas which is emitted as a result of the combustion of fuel in the internal combustion engine 102 flows into an exhaust aftertreatment system 200, where the exhaust gas is purified to at least a certain extent and/or rendered innocuous.

[0081] An example embodiment of an exhaust aftertreatment system is schematically shown in FIG. 2. As may be gleaned from FIG. 2, the exhaust aftertreatment system comprises an injector 202 for injecting a reduction agent 204 into the exhaust aftertreatment system 200. Preferably, the injector 202 injects the reduction agent 204 upstream an aftertreatment component 206. Upstream as used herein refers to upstream as seen in an intended direction of flow 208 of the exhaust gas in the exhaust aftertreatment system 200.

[0082] The injector 202 may be positioned to inject the reduction agent 204 in a direction substantially perpendicular to the intended direction of flow 208 of exhaust gas in the exhaust aftertreatment system 200, as schematically illustrated in FIG. 2. However, the injector 202 may alternatively be positioned to inject the reduction agent 204 at an angle to the intended direction of flow 208 of exhaust gas.

[0083] It is also conceivable that the exhaust aftertreatment system may comprise a plurality of injectors. For instance, the exhaust aftertreatment system may comprise a plurality of injectors injecting the reduction agent 204 upstream the aftertreatment component 206 and/or the exhaust aftertreatment system may comprise a plurality of aftertreatment components and a plurality of injectors each injecting a reduction agent upstream of a respective aftertreatment component.

[0084] Preferably, the reduction agent 204 may be a reduction agent for NO.sub.x, emissions, most preferably the reduction agent is an aqueous urea solution.

[0085] The reduction agent 204 comes from a source 210 of reduction agent 204, which source 210 is in fluid communication with the injector 202. Purely by way of example, the source 210 may be implemented as a tank adapted to contain the reduction agent 204. It should be noted that the setup in FIG. 2, showing that the source 210 may be located near the injector 202, is purely intended for illustrational purposes and should in no way be construed as limiting for the invention. Any other position of the source 210 is feasible, as long as it is in fluid communication with the injector 202.

[0086] The exhaust aftertreatment system further comprises a portion 212 located downstream of the injector 202. Downstream as used herein refers to downstream as seen in the intended direction of flow 208 of the exhaust gas in the exhaust aftertreatment system 200. Purely by way of example, the portion 212 may be a portion of a pipe designed for optimum spray propagation from the injector 202 and efficient decomposition of the reduction agent 204 before reaching the aftertreatment component 206. Although the pipe in FIG. 2 is exemplified as being straight, it is envisaged that the pipe may have other shapes, e.g. bent.

[0087] By way of example, the aftertreatment component 206, which may be, e.g., a selective catalytic reduction catalyst 206, may be located downstream the portion 212 of the exhaust aftertreatment system 200. Purely by way of example, the aftertreatment component 206 may utilize the reduction agent 204 when treating the exhaust gases.

[0088] Further, the exhaust aftertreatment system comprises a control unit 214. Even though the control unit 214 functionally is comprised in the exhaust aftertreatment system 200, it is not necessarily physically comprised therein. Instead, the control unit 214 may be located anywhere outside of the exhaust aftertreatment system 200, such as on the truck 100, as long as the control unit 214 is operationally connected to the exhaust aftertreatment system 200.

[0089] The control unit 214 is adapted to issue control signals to one or more components of the exhaust aftertreatment system to thereby reduce deposits related to the reduction agent 204 in the portion 212 of the exhaust aftertreatment system of the internal combustion engine (not shown in FIG. 2). More specifically, the control unit 214 is adapted to issue a signal to the injector 202 to control the dosage of the reduction agent 204 from the injector 202. It should be noted that features of the control unit 214 as presented hereinbelow are equally applicable to a method for reducing deposits related to the reduction agent 204 in the portion 212 of the exhaust aftertreatment system of the internal combustion engine 102.

[0090] Further, as a non-limiting example, the exhaust aftertreatment system may comprise a temperature sensor 216 configured to sense a temperature in the portion 212 of the exhaust aftertreatment system and provide signal input to the control unit 214. The temperature may be a temperature of a wall portion of the portion 212 of the exhaust aftertreatment system 200. Preferably, the temperature sensor 216 may be located at an inlet of the portion 212 of the exhaust aftertreatment system 200. More preferably, the temperature sensor 216 may be located upstream the injector 202. It is conceivable that the exhaust aftertreatment system may comprise a plurality of temperature sensors.

[0091] Purely by way of example, the exhaust aftertreatment system may comprise additional sensors, such as a first NO.sub.x sensor 218, providing a signal input to the control unit 214. Additionally, a second NO.sub.x sensor 220 may be positioned downstream the selective catalytic reduction catalyst 206, providing signal input to the control unit 214.

[0092] Further, as a non-limiting example, the exhaust aftertreatment system may comprise further aftertreatment components, such as a diesel particulate filter 222, which may be located upstream the portion 212 of the exhaust aftertreatment system 200.

[0093] The control unit 214 is further adapted to identify a future operating sequence 300 for the internal combustion engine 102. Depending on the application of the internal combustion engine 102, such an identification may be carried out in a plurality of different ways, such as, e.g., by assessing a future operating scheme for the internal combustion engine 102. As may be gleaned from FIG. 3, the future operating sequence comprises a first temporal portion t.sub.1 and a second temporal portion t.sub.2, the second temporal portion t.sub.2 being subsequent the first temporal portion t.sub.1. Optionally, the future operating sequence 300 may comprise also a third temporal portion t.sub.3, subsequent the second temporal portion t.sub.2.

[0094] Further, the control unit 214 is adapted to perform a confirmation procedure. The confirmation procedure comprises confirming that the future operating sequence 300 is suitable for reducing deposits and confirming that the internal combustion engine 102 operates in accordance with the precedingly identified future operating sequence 300.

[0095] Purely by way of example, the future operating sequence 300 may be determined to be suitable for reducing deposits if a ratio between an estimated workload of the internal combustion engine 102 in the first temporal portion t.sub.1 and the estimated workload in the second temporal portion t.sub.2 is at least 1.5, preferably at least 2. By way of example, the estimated workloads may be determined by calculating the average workload for each temporal portion t.sub.1, t.sub.2. Optionally, for the future operating sequence 300 to be determined as suitable for reducing deposits, it may also be required that a ratio between the estimated workload in the second temporal portion t.sub.2 and a maximum workload of the internal combustion engine 102 is less than 0.5.

[0096] According to one embodiment, when the internal combustion engine 102 is adapted to propel a vehicle such as the FIG. 1 truck 100, the feature of confirming that the future operating sequence 300 is suitable for reducing deposits may comprise confirming that the truck 100 is predicted to be driven in at least one of the following driving conditions: [0097] uphill driving during at least a majority of the first temporal portion t.sub.1 and level or downhill driving during at least a majority of the second temporal portion t.sub.2, [0098] acceleration during at least a majority of said first temporal portion t.sub.1 and driving at constant speed or deceleration during at least a majority of said second temporal portion t.sub.2, [0099] entering a motorway during said first temporal portion t.sub.1 and driving on said motorway during said second temporal portion t.sub.2, [0100] overtaking another vehicle during said first temporal portion t.sub.1 and driving at constant speed or deceleration during said second temporal portion t.sub.2.

[0101] Purely by way of example, the control unit 214 may be adapted to receive information from the route planning system 104. Preferably, the route planning system 104 may comprise a map database and/or a satellite-based radionavigation system, such as, e.g., GPS or GLONASS. The map database, if provided, may be provided in the truck 100, or may be provided externally, such as in a cloud-based service. The feature of confirming that the vehicle is predicted to be driven in at least one of the driving conditions above may comprise using the route planning system 104.

[0102] For a stationary application, the control unit 214 may be adapted to receive, e.g., information about a scheduled work cycle for the internal combustion engine 102. Purely by way of example, if the internal combustion engine is used in a stationary machinery such as a rock crusher, the control unit 214 may be adapted to receive information from working machines supplying rocks to the crusher about their estimated arrival times and their load.

[0103] The control unit 214 is further adapted to, in response to the confirmation procedure being affirmative, execute a deposit removal dosage procedure. The deposit removal procedure comprises controlling the injector 202, more specifically its dosage of reduction agent 204. Thus, the injector 202 is controlled such that a first dosage d.sub.1 of reduction agent 204 is injected into the exhaust aftertreatment system during at least a part of the first temporal portion t.sub.1 and such that a second dosage d.sub.2 of reduction agent 204 is injected into the exhaust aftertreatment system during at least a part of the second temporal portion t.sub.2, wherein the second dosage d.sub.2 is smaller than the first dosage d.sub.1.

[0104] Purely by way of example, a ratio between the second dosage d.sub.2 and a maximum dosage that can be injected by the injector 202 may be less than 0.05, preferably less than 0.03, more preferably less than 0.02, most preferably less than 0.01.

[0105] By way of example, a ratio between the second dosage d.sub.2 and the first dosage d.sub.1 may be less than 0.05, preferably less than 0.03, more preferably less than 0.02, most preferably less than 0.01.

[0106] By way of example, the control unit 214 may be adapted to adjust the first dosage d.sub.1 of reduction agent 204 such that a ratio between an actual reductant buffer in the selective catalytic reduction catalyst 206 and a maximum reductant buffer in the selective catalytic reduction catalyst 206 at a current operating temperature in the selective catalytic reduction catalyst 206 is within the range of 0.2 to 0.6, preferably 0.3 to 0.5, more preferably 0.4 to 0.5.

[0107] By way of example, the control unit 214 may further be adapted to adjust a third dosage d.sub.3 of reduction agent 204 as a part of the deposit removal dosage procedure. Preferably, the injector 202 may be controlled such that the third dosage d.sub.3 is injected into the exhaust aftertreatment system during at least a part of the third temporal portion t.sub.3, and the control unit 214 may be adapted to adjust the third dosage d.sub.3 such that ratio between an actual reductant buffer and a maximum reductant buffer at a current operating condition in the selective catalytic reduction catalyst 206 is within the range of 0.2 to 0.6, preferably 0.3 to 0.5, more preferably 0.4 to 0.5.

[0108] The maximum reductant buffer in the selective catalytic reduction catalyst 206 is dependent on the operating temperature of the catalyst 206, and may be known from, e.g., models of the exhaust aftertreatment system 200, look-up tables, and/or empirical data. Further, and purely by way of example, the actual reductant buffer may be estimated based on the precedingly identified future operating sequence 300, in conjunction with any other operating data from the internal combustion engine 102 and/or the exhaust aftertreatment system 200, as well as data from the above-mentioned models of the exhaust aftertreatment system 200, look-up tables, and/or empirical data.

[0109] Purely by way of example, the control unit 214 may be adapted to identify a deposits parameter indicative of a level of deposits in the portion 212 of the exhaust aftertreatment system 200. The deposits parameter may be indicative of a level of liquid and/or solid deposits. Purely by way of example, the confirmation procedure may comprise confirming that the level of deposits is equal to or exceeds a predeterminable threshold. The deposits parameter may be estimated based on future and/or historical operating data from the internal combustion engine 102 and/or the exhaust aftertreatment system 200, as well as on data from models of the exhaust aftertreatment system 200, look-up tables, and/or empirical data.

[0110] By way of example, the control unit 214 may be adapted to identify a temperature parameter indicative of a temperature of the portion 212 of the exhaust aftertreatment system 200. Preferably, the control unit may be adapted to receive information from the temperature sensor 216. According to one exemplary embodiment, the control unit 214 may be adapted to perform the deposit removal procedure in dependence on the temperature parameter. Preferably, the control unit 214 may be adapted to initiate the second dosage d.sub.2 in dependence on the temperature parameter, in particular to initiate the second dosage d.sub.2 in response to detecting that the temperature parameter has a temperature increase rate at or below a predetermined increase rate threshold.

[0111] The above operation of the control unit 214 and the method associated therewith are schematically exemplified in FIG. 4. As such, the method 400 comprises the steps of: [0112] 402: Identifying the future operating sequence 300. [0113] 404: Performing the confirmation procedure. [0114] 406: Checking if the confirmation procedure of step 404 is affirmative or not. [0115] 408: If the confirmation procedure of step 404 is affirmative, executing the deposit removal dosage procedure.

[0116] As non-limiting examples, embodiments of the invention may be defined in accordance with any one of the below points. [0117] 1. A method (400) for reducing deposits related to a reduction agent (204) in a portion (212) of an exhaust aftertreatment system (200) of an internal combustion engine (102), said exhaust aftertreatment system (200) comprising an injector (202) for injecting the reduction agent (204) into said exhaust aftertreatment system (200), and said portion (212) of said exhaust aftertreatment system (200) being located downstream of said injector (202), as seen in an intended direction of flow (208) of exhaust gas in said exhaust aftertreatment system (200), said method comprising the steps of: [0118] a) identifying a future operating sequence (300) for said internal combustion engine (102), said future operating sequence (300) comprising a first temporal portion (t.sub.1) and a second temporal portion (t.sub.2), said second temporal portion (t.sub.2) being subsequent to said first temporal portion (t.sub.1), [0119] b) performing a confirmation procedure comprising: [0120] confirming that said future operating sequence (300) is suitable for reducing said deposits and [0121] confirming that said internal combustion engine (102) operates in accordance with said precedingly identified future operating sequence (300), [0122] c) in response to said confirmation procedure being affirmative, executing a deposit removal dosage procedure comprising controlling said injector (202) such that a first dosage (d.sub.1) of reduction agent (204) is injected into said exhaust aftertreatment system (200) during at least a part of said first temporal portion (t.sub.1) and that a second dosage (d.sub.2) of reduction agent (204) is injected into said exhaust aftertreatment system (200) during at least a part of said second temporal portion (t.sub.2) said second dosage (d.sub.2) being smaller than said first dosage (d.sub.1). [0123] 2. The method (400) according to point 1, wherein a ratio between said second dosage (d.sub.2) and a maximum dosage that can be injected by the injector (202) is less than 0.05, preferably less than 0.03, more preferably less than 0.02, most preferably less than 0.01. [0124] 3. The method (400) according to point 1 or 2, wherein a ratio between said second dosage (d.sub.2) and said first dosage (d.sub.1) is less than 0.05, preferably less than 0.03, more preferably less than 0.02, most preferably less than 0.01. [0125] 4. The method (400) according to any one of the preceding points, wherein said first dosage (d.sub.1) of said reduction agent (204) is such that a ratio between an actual reductant buffer and a maximum reductant buffer at a current operating condition in a selective catalytic reduction catalyst (206) located downstream said portion (212) of said exhaust aftertreatment system (200) is within the range of 0.2 to 0.6, preferably 0.3 to 0.5, more preferably 0.4 to 0.5. [0126] 5. The method (400) according to any of the preceding points, wherein said future operating sequence (300) is determined to be suitable for reducing said deposits if a ratio between an estimated workload of said internal combustion engine in said first temporal portion (t.sub.1) and the estimated workload in the second temporal portion (t.sub.2) is at least 1.5, preferably at least 2. [0127] 6. The method (400) according to point 5, wherein a ratio between said estimated workload in the second temporal portion (t.sub.2) and said maximum workload of said internal combustion engine is less than 0.5. [0128] 7. The method (400) according to any of the preceding points, wherein said method further comprises a step of identifying a deposits parameter indicative of a level of deposits in said portion (212) of said exhaust aftertreatment system (200) and wherein said confirmation procedure further comprises: [0129] confirming that said level of deposits is equal to or exceeds a predeterminable threshold. [0130] 8. The method (400) according to any of the preceding points, wherein said method further comprises identifying a temperature parameter indicative of a temperature of said portion (212) of said exhaust aftertreatment system (200) and wherein said deposit removal dosage procedure is performed in dependence on said temperature parameter, preferably the initiation of said second dosage (d.sub.2) is dependent on said temperature parameter. [0131] 9. The method (400) according to point 8, wherein said second dosage (d.sub.2) is initiated in response to detecting that said temperature parameter has a temperature increase rate at or below a predetermined increase rate threshold. [0132] 10. The method (400) according to point 8 or 9, wherein said temperature of said portion (212) of said exhaust aftertreatment system (200) is a temperature of a wall portion of said portion (212) of said exhaust aftertreatment system (200). [0133] 11. The method (400) according to any of the preceding points, wherein said future operating sequence (300) further comprises a third temporal portion (t.sub.3), said third temporal portion (t.sub.3) being subsequent said second temporal portion (t.sub.2), and wherein said deposit removal dosage procedure further comprises controlling said injector (202) such that a third dosage (d.sub.3) of reduction agent (204) is injected into said exhaust aftertreatment system (200) during at least a part of said third temporal portion (t.sub.3), said third dosage (d.sub.3) being such that a ratio between an actual reductant buffer and a maximum reductant buffer at a current operating condition in a selective catalytic reduction catalyst (206) located downstream said portion (212) of said exhaust aftertreatment system (200) is within the range of 0.2 to 0.6, preferably 0.3 to 0.5, more preferably 0.4 to 0.5. [0134] 12. The method (400) according to any of the preceding points, wherein said internal combustion engine (102) propels a vehicle (100) and wherein said feature of confirming that said future operating sequence (300) is suitable for reducing said deposits comprises confirming that said vehicle (100) is predicted to be driven in at least one of the following driving conditions: [0135] uphill driving during at least a majority of said first temporal portion (t.sub.1) and level or downhill driving during at least a majority of said second temporal portion (t.sub.2), [0136] acceleration during at least a majority of said first temporal portion (t.sub.1) and driving at constant speed or deceleration during at least a majority of said second temporal portion (t.sub.2), [0137] entering a motorway during said first temporal portion (t.sub.1) and driving on said motorway during said second temporal portion (t.sub.2), [0138] overtaking another vehicle during said first temporal portion (t.sub.1) and driving at constant speed or deceleration during said second temporal portion (t.sub.2). [0139] 13. The method (400) according to point 12, wherein said vehicle (100) comprises a route planning system (104), preferably comprising a GPS and/or a map database, and wherein said feature of confirming that said vehicle (100) is predicted to be driven in at least one of said driving conditions comprises using said route planning system (104). [0140] 14. The method (400) according to any of the preceding points, wherein said reduction agent (204) is a reduction agent for NOx emissions, preferably an aqueous urea solution. [0141] 15. A control unit (214) adapted for reducing deposits related to a reduction agent (204) in a portion (212) of an exhaust aftertreatment system (200) of an internal combustion engine (102), said exhaust aftertreatment system (200) comprising an injector (202) for injecting said reduction agent (204) into said exhaust aftertreatment system (200), and said portion (212) of said exhaust aftertreatment system (200) being located downstream of said injector (202), as seen in an intended direction of flow (208) of exhaust gas in said exhaust aftertreatment system (200), said control unit (214) being adapted to: [0142] identify a future operating sequence (300) for said internal combustion engine (102), said future operating sequence (300) comprising a first temporal portion (t.sub.1) and a second temporal portion (t.sub.2), said second temporal portion (t.sub.2) being subsequent to said first temporal portion (t.sub.1), [0143] perform a confirmation procedure comprising: [0144] confirming that said future operating sequence (300) is suitable for reducing said deposits and [0145] confirming that said internal combustion engine (102) operates in accordance with said precedingly identified future operating sequence (300), [0146] in response to said confirmation procedure being affirmative, execute a deposit removal dosage procedure comprising controlling said injector (202) such that a first dosage (d.sub.1) of reduction agent (204) is injected into said exhaust aftertreatment system (200) during at least a part of said first temporal portion (t.sub.1) and that a second dosage (d.sub.2) of reduction agent (204) is injected into said exhaust aftertreatment system (200) during at least a part of said second temporal portion (t.sub.2), said second dosage (d.sub.2) being smaller than said first dosage (d.sub.1). [0147] 16. The control unit (214) according to point 15, wherein a ratio between said second dosage (d.sub.2) and a maximum dosage that can be injected by the injector (202) is less than 0.05, preferably less than 0.03, more preferably less than 0.02, most preferably less than 0.01. [0148] 17. The control unit (214) according to point 15 or 16, wherein a ratio between said second dosage (d.sub.2) and said first dosage (d.sub.1) is less than 0.05, preferably less than 0.03, more preferably less than 0.02, most preferably less than 0.01. [0149] 18. The control unit (214) according to any of points 15 to 17, wherein said control unit (214) is adapted to adjust said first dosage (d.sub.1) of reduction agent (204) such that a ratio between an actual reductant buffer in a selective catalytic reduction catalyst (206) located downstream said portion (212) of said exhaust aftertreatment system (200) and a maximum reductant buffer in said selective catalytic reduction catalyst (206) at a current operating temperature in said selective catalytic reduction catalyst (206) is within the range of 0.2 to 0.6, preferably 0.3 to 0.5, more preferably 0.4 to 0.5. [0150] 19. The control unit (214) according to any of the points 15 to 18, wherein said future operating sequence (300) is determined to be suitable for reducing said deposits if a ratio between an estimated workload of said internal combustion engine (102) in said first temporal portion (t.sub.1) and the estimated workload in the second temporal portion (t.sub.2) is at least 1.5, preferably at least 2. [0151] 20. The control unit (214) according to point 19, wherein a ratio between said estimated workload in the second temporal portion (t.sub.2) and said maximum workload of said internal combustion engine (102) is less than 0.5. [0152] 21. The control unit (214) according to any of points 15 to 20, wherein said control unit (214) further is adapted to identify a deposits parameter indicative of a level of deposits in said portion (212) of said exhaust aftertreatment system (200) and wherein said confirmation procedure further comprises: [0153] confirming that said level of deposits is equal to or exceeds a predeterminable threshold. [0154] 22. The control unit (214) according to any of points 15 to 21, wherein said control unit (214) further is adapted to identify a temperature parameter indicative of a temperature of said portion (212) of said exhaust aftertreatment system (200) and wherein said control unit (214) is adapted to perform said deposit removal dosage procedure in dependence on said temperature parameter, preferably said control unit (214) is adapted to initiate said second dosage (d.sub.2) in dependence on said temperature parameter. [0155] 23. The control unit (214) according to point 22, wherein said control unit (214) is adapted to initiate said second dosage (d.sub.2) in response to detecting that said temperature parameter has a temperature increase rate at or below a predetermined increase rate threshold. [0156] 24. The control unit (214) according to point 22 or 23, wherein said temperature of said portion (212) of said exhaust aftertreatment system (200) is a temperature of a wall portion of said portion (212) of said exhaust aftertreatment system (200). [0157] 25. The control unit (214) according to any of points 15 to 24, wherein said future operating sequence (300) further comprises a third temporal portion (t.sub.3), said third temporal portion (t.sub.3) being subsequent said second temporal portion (t.sub.2), and wherein said deposit removal dosage procedure further comprises controlling said injector (202) such that a third dosage (d.sub.3) of reduction agent (204) is injected into said exhaust aftertreatment system (200) during at least a part of said third temporal portion (t.sub.3), said control unit (214) being adapted to adjust said third dosage (d.sub.3) such a ratio between an actual reductant buffer and a maximum reductant buffer at a current operating condition in a selective catalytic reduction catalyst (206) located downstream said portion (212) of said exhaust aftertreatment system (200) is within the range of 0.2 to 0.6, preferably 0.3 to 0.5, more preferably 0.4 to 0.5. [0158] 26. The control unit (214) according to any of the preceding points, wherein said internal combustion engine (102) propels a vehicle (100) and wherein said feature of confirming that said future operating sequence (300) is suitable for reducing said deposits comprises confirming that said vehicle (100) is predicted to be driven in at least one of the following driving conditions: [0159] uphill driving during at least a majority of said first temporal portion (t.sub.1) and level or downhill driving during at least a majority of said second temporal portion (t.sub.2), [0160] acceleration during at least a majority of said first temporal portion (t.sub.1) and driving at constant speed or deceleration during at least a majority of said second temporal portion (t.sub.2), [0161] entering a motorway during said first temporal portion (t.sub.1) and driving on said motorway during said second temporal portion (t.sub.2), [0162] overtaking another vehicle during said first temporal portion (t.sub.1) and driving at constant speed or deceleration during said second temporal portion (t.sub.2). [0163] 27. The control unit (214) according to point 26, wherein said vehicle (100) comprises a route planning system (104), preferably comprising a GPS and/or a map database, and wherein said feature of confirming that said vehicle (100) is predicted to be driven in at least one of said driving conditions comprises using said route planning system (104), preferably said control unit (214) is adapted to receive information from said route planning system (104). [0164] 28. The control unit (214) according to any of points 15-27, wherein said reduction agent (204) is a reduction agent for NOx emissions, preferably an aqueous urea solution. [0165] 29. An exhaust aftertreatment system (200) for an internal combustion engine (102), said exhaust aftertreatment system (200) comprising a source (210) of reduction agent (204), said source (210) being in fluid connection with an injector (202), said injector (202) being adapted to inject said reduction agent (204) into a portion (212) of said exhaust aftertreatment system (200), said portion (212) of said exhaust aftertreatment system (200) being located downstream of said injector (202), as seen in an intended direction of flow (208) of exhaust gas in said exhaust aftertreatment system (200), said exhaust aftertreatment system (200) comprising a control unit (214) according to any one of points 15-28, said control unit (214) being adapted to issue a signal to said injector (202) in order to control a dosage of reduction agent (204) from said injector (202). [0166] 30. A vehicle (100) comprising a control unit (214) according to any one of points 15-28 and/or an exhaust aftertreatment system (200) according to point 29.

[0167] It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.