Exhaust gas treatment system, method of treating exhaust gas stream, and associated control system

Abstract

An exhaust gas treatment system (250, 350) is presented, the exhaust gas treatment system being arranged for treating an exhaust gas stream (203, 303) resulting from combustion in a combustion engine (201, 301). The exhaust gas treatment system comprises a reduction catalyst arrangement (220, 320) arranged downstream of the dosing arrangement (270, 372) and comprising a first selective catalytic reduction catalyst (221, 321) predominantly arranged for reducing nitrogen oxides NOx in a first temperature interval T1, and a second selective catalytic reduction catalyst (222, 321) predominantly arranged for reducing nitrogen oxides NOx in a second temperature interval T1, and a second selective catalytic reduction catalyst (222, 322) arranged downstream of the first selective catalytic reduction catalyst (221, 321) and predominantly arranged for reducing nitrogen oxides NOx in a second, at least partially higher temperature interval T2; wherein the first selective catalytic reduction catalyst (221, 321) has an opening such that particles in the exhaust gas flow (203, 303), which are produced by supplying an additive into the exhaust gas flow (203, 303) and / or by a transition of the additive when flowing through the exhaust gas treatment system (250, 350), are caused to interact with the first selective catalytic reduction catalyst (221, 321), whereby:-the particles are captured and removed at least partially by the first selective catalytic reduction catalyst (221, 321); and-the accumulation of soot and ash resulting from the combustion that would affect the interaction of the first selective catalytic reduction catalyst (221, 321) with the particles is at least partially avoided.

Description

Technical Field

[0001] The present invention relates to an exhaust gas treatment system, a method for treating an exhaust gas stream, and a control system for controlling the exhaust gas treatment system to perform the method.

[0002] The present invention also relates to a computer program and a computer program product for implementing the method according to the present invention. Background Art

[0003] The following background art description constitutes a description of the background art of the present invention and, therefore, does not necessarily have to constitute prior art.

[0004] Related to the increased attention of governments to pollution and air quality, mainly in urban areas, emission standards and regulations regarding emissions from combustion engines have been drafted in many jurisdictions.

[0005] Such emission standards typically consist of requirements that define acceptable limits for exhaust emissions from, for example, combustion engines in vehicles. For example, for most types of vehicles, the emission levels of nitrogen oxides NO x , hydrocarbons C x H y , carbon monoxide CO, and particulate matter PM are typically regulated by such standards. Vehicles equipped with combustion engines generally produce such emissions to varying degrees. In this document, the application of the present invention in vehicles, i.e., for internal combustion engines, will be mainly described. However, the present invention can be used in substantially all applications using combustion engines, such as in ships or aircraft / helicopters, for example, where regulations and standards for such applications limit the emissions of combustion engines.

[0006] To comply with these emission standards, the exhaust gas caused by the combustion of the combustion engine is treated (purified).

[0007] A common way to treat the exhaust gas from a combustion engine consists of a so-called catalytic purification process, which is why vehicles equipped with combustion engines generally include at least one catalyst. There are different types of catalysts, and different corresponding types can be suitable, depending on, for example, the combustion concept, combustion strategy, and / or fuel type used in the vehicle, and / or the type of compounds in the exhaust gas stream to be purified. Regarding at least nitrous gases (nitric oxide, nitrogen dioxide), hereinafter referred to as nitrogen oxides NO x , vehicles generally include a catalyst to which an additive is supplied to the exhaust gas stream generated by the combustion in the combustion engine in order to mainly reduce the nitrogen oxides NO x to nitrogen and water vapor. This will be described in more detail below.

[0008] SCR (Selective Catalytic Reduction) catalysts are a common type of catalyst used for this type of reduction, mainly for heavy-duty trucks. SCR catalysts typically use ammonia NH3 or a composition from which ammonia can be produced / formed as an additive to reduce nitrogen oxides NO in the exhaust gas. x The amount of the additive, such as urea, is injected into the exhaust gas stream generated by the combustion engine upstream of the catalyst. The additive added to the catalyst is adsorbed (stored) in the catalyst in the form of ammonia NH3, such that a redox reaction can occur between the nitrogen oxides NO x in the exhaust gas and the ammonia NH3 obtainable via the additive. SUMMARY OF THE INVENTION

[0009] When the additive is injected into the exhaust gas stream, i.e., when the additive is supplied to the exhaust gas treatment system, small particles may be generated upon injection of the additive. Additionally, when the injected additive travels through the components of the exhaust gas treatment system together with the exhaust gas stream, more small particles may be generated from the additive due to the treatment performed on the exhaust gas stream by the components of the exhaust gas treatment system. Thus, these small particles may be generated by the additive upon injection and / or by various transformations of the additive as it flows through the exhaust gas treatment system. Therefore, the particles may include urea and / or urea-based polymeric by-products, depending on where they are generated in the exhaust gas treatment system.

[0010] These small particles may, for example, have a diameter in the range of 10 to 23 nm and may flow through the entire exhaust gas treatment system together with the exhaust gas stream and be discharged at the exhaust pipe. Thus, at least a portion of these additive-based particles may pass through each component of the exhaust gas treatment system, also through the SCR catalyst, due to their small size, for example, and may be discharged into the environment as emissions. The additive-based particles may also include combustion-based particles, i.e., particles generated during combustion in the combustion engine. Thus, due to the interaction and / or mixing with the particles from combustion, the small-sized particles may subsequently include a mixture of additive-based particles and soot and / or ash. If these small particles are discharged, they may have health effects.

[0011] Additionally, in certain driving situations, the reduction efficiency of nitrogen oxides NO x in the exhaust gas stream of today's exhaust gas treatment systems may be insufficient.

[0012] An object of the present invention is to at least partially prevent the emission of these additive-based small particles into the environment and to improve the overall reduction of nitrogen oxides NO x .

[0013] The object is achieved by the above-mentioned exhaust gas treatment system, which is arranged to treat the exhaust gas stream generated by combustion in a combustion engine, the exhaust gas treatment system comprising:

[0014] - A particulate filter, which is arranged to capture soot and ash produced by combustion;

[0015] - A metering arrangement, which is arranged downstream of the particulate filter to supply an additive into the exhaust gas stream; and

[0016] - A reduction catalyst arrangement, which is arranged downstream of the metering arrangement for reducing nitrogen oxides NO in the exhaust gas stream by utilizing the supplied additive x , wherein the reduction catalyst arrangement comprises a first selective catalytic reduction catalyst mainly arranged to reduce nitrogen oxides NO in a first temperature range T1 x and a second selective catalytic reduction catalyst arranged downstream of the first selective catalytic reduction catalyst and mainly arranged to reduce nitrogen oxides NO in a second temperature range T2 x , wherein the first temperature range T1 is at least partially higher than the second temperature range T2;

[0017] wherein

[0018] - The first selective catalytic reduction catalyst has a certain opening degree such that particles in the exhaust gas stream caused by supplying the additive into the exhaust gas stream and / or by the transformation of the additive when flowing through the exhaust gas treatment system interact with the first selective catalytic reduction catalyst, whereby:

[0019] -- At least partially capture and remove particles by the first selective catalytic reduction catalyst; and

[0020] -- At least partially avoid the accumulation of soot and ash produced by combustion that would affect the interaction between the first selective catalytic reduction catalyst and the particles.

[0021] Therefore, before the exhaust gas stream is discharged from the exhaust pipe, at least partially remove the additive fine particles from the exhaust gas stream. Therefore, these fine particles, which may have diameters in the range of 10 to 23 nm, are dissolved by interaction with the first selective catalytic reduction catalyst and at least partially prevented from leaving the exhaust pipe.

[0022] In addition, effective reduction of nitrogen oxides NO x can be provided because the first selective catalytic reduction catalyst and the second selective catalytic reduction catalyst can be optimized here for their respective individual temperature ranges T1, T2. In addition to the improved nitrogen oxides NO xIn addition to the reduction, the optimization of the first selective catalytic reduction catalyst and the second selective catalytic reduction catalyst can minimize the production of nitrous oxide N2O ("laughing gas"). Therefore, the first selective catalytic reduction catalyst and the second selective catalytic reduction catalyst can be differently designed to match these different properties of the exhaust gas stream. Therefore, a more effective overall reduction of nitrogen oxides is provided.

[0023] In addition, when the exhaust gas stream reaches the first selective catalytic reduction catalyst, there are still available nitrogen oxides NO x and nitrogen dioxide NO2 in the exhaust gas stream. The nitrogen oxides NO x and nitrogen dioxide NO2 can thus be used to remove the soot and ash accumulated in the first selective catalytic reduction catalyst, which reduces the risk that the interaction between the particles and the first selective catalytic reduction catalyst will accumulate soot and ash in the first selective catalytic reduction catalyst. Therefore, a performance reduction pressure drop on the first selective catalytic reduction catalyst is avoided.

[0024] In addition, due to its position and design, the first selective catalytic reduction catalyst can provide an exhaust gas stream flow distribution.

[0025] Therefore, the exhaust gas treatment system according to the present invention provides an effective reduction of nitrogen oxides NO x and also removes small-sized urea-based particles from the exhaust gas stream, making it possible to meet the emission requirements in current and / or future emission standards.

[0026] It should be noted that the first selective catalytic reduction catalyst is specifically designed to No capture all the particles in the exhaust gas stream because it is designed not to accumulate excessive soot and ash. In other words, the first selective catalytic reduction catalyst is designed as a medium / poor filter in a traditional sense, i.e., it provides a relatively low filtration efficiency at least in terms of capturing soot and ash particles. Therefore, the first selective catalytic reduction catalyst thus defined will capture far fewer soot particles and ash particles than a traditional particulate filter will capture. However, tests have shown that although the first selective catalytic reduction catalyst is a poor filter in the traditional sense of capturing large soot and ash particles, surprisingly, it can effectively capture and remove small particles generated by supplying additives to the exhaust gas stream and / or through the transformation of additives.

[0027] According to an embodiment,

[0028] - The first selective catalytic reduction catalyst includes a first active catalytic material;

[0029] - The second selective catalytic reduction catalyst includes a second active catalytic material; and

[0030] - The first active catalytic material is different from the second active catalytic material.

[0031] Thus, each of the first selective catalytic reduction catalyst and the second selective catalytic reduction catalyst can be specifically designed and thus optimized for the specific properties of the exhaust gas stream reaching it, such specific properties being, for example, the temperature of the exhaust gas stream and / or the amount of reactants such as nitrogen oxides NO x and / or nitrogen dioxide NO2 in the exhaust gas stream.

[0032] According to an embodiment, the first active catalytic material comprises one or more of the following groups:

[0033] - Cu zeolite;

[0034] - Fe zeolite; and

[0035] - Vanadium.

[0036] Thus, the first selective catalytic reduction catalyst can provide an effective reduction of nitrogen oxides NO x .

[0037] According to an embodiment, the first active catalytic material is coated on the first selective catalytic reduction catalyst.

[0038] Coating of the material can improve the efficiency of the first selective catalytic reduction catalyst in capturing and dissolving particles. This can be used for catalytic synergy with nitrogen oxides NO x reduction and / or nitrous oxide (“laughing gas”) N2O limitation in the exhaust gas treatment system.

[0039] In addition, the coating enables the first selective catalytic reduction catalyst to be assembled within an existing exhaust gas treatment system / tank / muffler.

[0040] According to an embodiment, the first selective catalytic reduction catalyst comprises a filter structure.

[0041] Thus, the opening degree of the first selective catalytic reduction catalyst can be effectively implemented within the first selective catalytic reduction catalyst. For example, the first active catalytic material can be coated on the filter structure such that an overall reduction of nitrogen oxides NO x and the removal of small-sized particles are provided. Thus, within the same space where the reduction of nitrogen oxides NO x usually occurs in selective catalytic reduction, a coated filter structure having an opening degree defined herein is arranged, the coated filter structure being arranged for reducing nitrogen oxides NO x and for removing the particles described herein by the induced interaction.

[0042] In addition, it is possible to readily produce a first selective catalytic reduction catalyst applied to the filter structure, particularly because coating the filter structure with the active catalytic material of the selective catalytic reduction catalyst is straightforward and simple.

[0043] Furthermore, the first selective catalytic reduction catalyst requires limited space, which provides both the reduction of nitrogen oxides NO x and the capture and removal of small-sized particles. Thus, this component provides two functions within the same component, which saves valuable space in the exhaust gas treatment system.

[0044] According to an embodiment, the filter structure has open and / or closed filter channels respectively corresponding to the opening degree of the first selective catalytic reduction catalyst.

[0045] By opening and / or closing the filter channels, the selected opening degree provides the required interaction between the first selective catalytic reduction catalyst and the particles without causing an excessive pressure drop across the first selective catalytic reduction catalyst.

[0046] Therefore, the first selective catalytic reduction catalyst causes a low back pressure on the exhaust gas flow. Thus, the impact of the first selective catalytic reduction catalyst on other exhaust gas treatment processes in the exhaust gas treatment system is minimized, such that the overall exhaust gas treatment is substantially unaffected.

[0047] In addition, over time, the robustness of the component without service is improved.

[0048] According to an embodiment, the filter structure includes channels, each of which is closed at one or more of the following groups:

[0049] - at its upstream end;

[0050] - at its downstream end; and

[0051] - between its upstream end and downstream end.

[0052] Thereby, a closed filter structure is provided by closing the filter channels, which enables the effective removal of additive-based particles from the exhaust gas flow.

[0053] According to an embodiment, the opening degree of the first selective catalytic reduction catalyst is zero.

[0054] The closed filter structure enables the effective removal of additive-based particles from the exhaust gas flow.

[0055] According to an embodiment,

[0056] - the first selective catalytic reduction catalyst has a cross-sectional area A in square inches and a length L in inches; and

[0057] - The area-to-length ratio A / L of the first selective catalytic reduction catalyst in inches has a value of at least 17 inches and at most 50 inches; 17 ≤ A / L ≤ 50 inches.

[0058] Using this interval of the area-to-length ratio A / L provides a small-sized and effective first selective catalytic reduction catalyst arranged in a closed filter structure.

[0059] The first selective catalytic reduction catalyst has a cross-sectional area A in square inches and a length L in inches, resulting in an area-to-length ratio A / L having a value of at least 17 inches and at most 50 inches; 17 ≤ A / L ≤ 50 inches. This defines that the first selective catalytic reduction catalyst has a relatively short length L with respect to the area A, such that it has a higher area-to-length ratio A / L value compared to that of a conventional particulate filter. Therefore, the first selective catalytic reduction catalyst is specifically designed to No Capture all particles in the exhaust gas stream, because a shorter structure generally provides less effective filtration. In other words, the first selective catalytic reduction catalyst is designed as a poorer filter in a conventional filter, i.e., providing a lower filtration efficiency at least in capturing soot and ash particles. However, tests have shown that although the first selective catalytic reduction catalyst is a poorer filter in the conventional sense of capturing large soot and ash particles, surprisingly, it can effectively capture and remove the above-mentioned additive-based small particles.

[0060] In addition, when the area-to-length ratio A / L of the first selective catalytic reduction catalyst in inches has a value of at most 50, it is possible to coat the first selective catalytic reduction catalyst with a catalytically active material.

[0061] According to an embodiment, the filter structure includes one or more channels that open through the filter structure.

[0062] Therefore, the first selective catalytic reduction catalyst can be implemented in a non-closed filter structure, for example, in an open filter structure.

[0063] The open filter structure results in extremely low back pressure on the first selective catalytic reduction catalyst from the exhaust gas stream. Therefore, the impact of the first selective catalytic reduction catalyst on other exhaust gas treatment processes in the exhaust gas treatment system is minimized, such that the overall exhaust gas treatment is basically unaffected.

[0064] In addition, over time, the robustness of the non-service parts is improved.

[0065] According to an embodiment, the opening degree of the first selective catalytic reduction catalyst is in one of the intervals in the following group:

[0066] - 1% to 80%:

[0067] -10% to 80%;

[0068] -20% to 80%;

[0069] -10% to 60%;

[0070] -20% to 60%;

[0071] -10% to 50%;

[0072] -20% to 50%; and

[0073] -30% to 50%.

[0074] In the presented opening intervals, for various embodiments of the first selective catalytic reduction catalyst, effective removal of additive-based particles is provided without harmful accumulation of soot and ash.

[0075] According to an embodiment,

[0076] - the first selective catalytic reduction catalyst has a cross-sectional area A in square inches and a length L in inches; and

[0077] - the area-to-length ratio A / L of the first selective catalytic reduction catalyst in inches has a value of at least 17 inches and at most 100 inches; 17 ≤ A / L ≤ 100 inches.

[0078] Within this interval of the area-to-length ratio A / L, an efficient first selective catalytic reduction catalyst in an at least partially open filter structure is provided. The non-closed filter structure enables the first selective catalytic reduction catalyst to potentially have an even smaller size, i.e., a length L that is even smaller relative to the cross-sectional area A compared to a closed filter structure. Thus, the area-to-length ratio can have a higher value than in an open structure.

[0079] The first selective catalytic reduction catalyst has a cross-sectional area A in square inches and a length L in inches, resulting in an area-to-length ratio A / L having a value of at least 17 inches and at most 100 inches; 17 ≤ A / L ≤ 100 inches. This defines that the first selective catalytic reduction catalyst has a length L that is shorter relative to the area A compared to a conventional particulate filter. Thus, the first selective catalytic reduction catalyst is specifically designed to No capture all particles in the exhaust gas stream, i.e., is designed as a medium / poor filter in a conventional sense. However, surprisingly, the first selective catalytic reduction catalyst can effectively capture and remove the above-mentioned additive-based small particles.

[0080] According to an embodiment

[0081] - The filter structure includes at least one open channel and at least one closed channel passing through the filter structure;

[0082] - At least one open channel has an open channel cross-sectional area A oc ; and

[0083] - At least one closed channel has a closed channel cross-sectional area A cc , the closed channel cross-sectional area A of the closed channel cc is equal to the open channel cross-sectional area A oc ; A oc = A cc .

[0084] Thus, a symmetric filter structure design is provided with similar dimensions (i.e., cross-sectional area) for all channels in the filter.

[0085] According to an embodiment,

[0086] - The filter structure includes at least one open channel and at least one closed channel passing through the filter structure;

[0087] - At least one open channel has an open channel cross-sectional area A oc ; and

[0088] - At least one closed channel has a closed channel cross-sectional area A cc , the closed channel cross-sectional area A of the closed channel cc is different from the open channel cross-sectional area A oc .

[0089] Thus, an asymmetric filter structure design is provided with different, i.e., non-similar, dimensions (e.g., cross-sectional area) for the channels in the filter. According to some embodiments, the open channels have a smaller cross-sectional area than the closed channels.

[0090] According to an embodiment,

[0091] - The first selective catalytic reduction catalyst includes at least one section arranged to be heated to an interaction temperature T I by an exhaust gas flowing therethrough, the interaction temperature T I exceeds the particle temperature T at which particles thermally dissolve P ; T I > T P ; and

[0092] - The first selective catalytic reduction catalyst is arranged to interact with the particles such that the particles are at least partially in physical contact with the at least one heated section.

[0093] Thus, the particles are effectively dissolved by the first selective catalytic reduction catalyst which is at least partially heated by the exhaust gas stream.

[0094] According to an embodiment, the interaction temperature T I is at least 150 °C.

[0095] When the interaction temperature T I reaches and / or exceeds 150 °C, the particles are effectively dissolved and thus removed from the exhaust gas stream. Thus, if the interaction temperature T I is initially below 150 °C, some particles can first accumulate in the first selective catalytic reduction catalyst. Then, when the interaction temperature T I reaches 150 °C, these accumulated particles are dissolved.

[0096] According to an embodiment,

[0097] - the first selective catalytic reduction catalyst comprises a first active catalytic material carried by a first support;

[0098] - the second selective catalytic reduction catalyst comprises a second active catalytic material carried by a second support;

[0099] - the second active catalytic material is the same as the first active catalytic material; and

[0100] - the second support is different from the first support.

[0101] Thereby, separate temperature ranges T1, T2 of the first selective catalytic reduction catalyst and the second selective catalytic reduction catalyst can be provided by separate design of the first support and the second support. Then, the corresponding temperature ranges T1, T2 of the first selective catalytic reduction catalyst and the second selective catalytic reduction catalyst are optimized so that they match different properties of the exhaust gas stream when the exhaust gas stream reaches each of the first selective catalytic reduction catalyst and the second selective catalytic reduction catalyst. Thereby, a more effective overall reduction of nitrogen oxides is provided.

[0102] According to an embodiment, the additive comprises one or more of the following groups:

[0103] - ammonia, and

[0104] - a substance from which ammonia can be extracted and / or released.

[0105] Ammonia is used by one or more reduction catalyst arrangements in the exhaust gas treatment system for reducing nitrogen oxides NO in the exhaust gas stream x . Thereby, the nitrogen oxides NO in the exhaust gas stream can be effectively reduced x .

[0106] According to an embodiment, the particles include one or more of the following groups:

[0107] - urea; and

[0108] - urea-based polymerization by-products.

[0109] Therefore, the particles are unstable and can be dissolved by the first selective catalytic reduction catalyst. Alternatively, the particles are captured by the first selective catalytic reduction catalyst.

[0110] According to an embodiment, the exhaust gas treatment system further includes a slip catalyst arrangement disposed downstream of the reduction catalyst arrangement for oxidizing gas additive residues in the exhaust gas stream.

[0111] The slip catalyst arrangement removes any additive traces here, such as ammonia NH3.

[0112] According to an embodiment, the exhaust gas treatment system includes:

[0113] - an upstream metering device arranged to supply an additive into the exhaust gas stream;

[0114] - an upstream reduction catalyst device arranged downstream of the upstream metering device for reducing nitrogen oxides NO in the exhaust gas stream by utilizing the supplied additive x ;

[0115] - a particulate filter arranged downstream of the upstream reduction catalyst device for capturing soot and ash generated by combustion;

[0116] - a metering arrangement arranged as a downstream metering device downstream of the particulate filter for supplying an additive into the exhaust gas stream; and

[0117] - a reduction catalyst arrangement including a first selective catalytic reduction catalyst and a second selective catalytic reduction catalyst, the reduction catalyst arrangement being arranged as a downstream reduction catalyst device downstream of the downstream metering device for reducing nitrogen oxides NO in the exhaust gas stream by utilizing the supplied additive x 。

[0118] The upstream and downstream reduction catalyst devices can be optimized separately, and considering the function of the entire exhaust gas treatment system, this can achieve a very effective overall purification of the exhaust gas. This separate optimization can also be used to reduce one or several of the volumes occupied by the upstream and downstream reduction catalyst devices, so as to obtain a compact exhaust gas treatment system.

[0119] In addition, the two additive metering devices in the system make it possible to adjust separately the amounts of additives injected by the upstream and downstream metering devices. Thus, by actively controlling the upstream metering and the downstream metering separately, the amount of additives and / or the amount of additive-based particles at the downstream reduction catalyst arrangement can be controlled to be suitable for the effective reduction of nitrogen oxides NO x and / or to keep the additive-based particles at a reasonable level with respect to the permitted emission levels.

[0120] According to an embodiment, the upstream reduction catalyst device includes one or more of the following groups:

[0121] - an upstream selective catalytic reduction catalyst; and

[0122] - an upstream slip catalyst.

[0123] Thereby, a flexible exhaust gas treatment system is provided that effectively reduces nitrogen oxides NO in the exhaust gas stream x .

[0124] The above object is also achieved by the above method for treating an exhaust gas stream generated by combustion in a combustion engine. The method includes:

[0125] - capturing soot and ash generated by combustion by means of a particulate filter;

[0126] - controlling the supply of an additive to the exhaust gas stream by means of a metering arrangement arranged downstream of the particulate filter;

[0127] - reducing nitrogen oxides NO in the exhaust gas stream by means of the supplied additive and a reduction catalyst arrangement arranged downstream of the metering arrangement, x wherein the reduction includes a first reduction of nitrogen oxides NO mainly in a first temperature range T1 by a first selective catalytic reduction catalyst x and a second reduction of nitrogen oxides NO mainly in a second temperature range T2 by a second selective catalytic reduction catalyst arranged downstream of the first selective catalytic reduction catalyst, x wherein the first temperature range T1 is at least partially higher than the second temperature range T2; and

[0128] - the interaction of the first selective catalytic reduction catalyst with the particles in the exhaust gas stream generated by supplying the additive to the exhaust gas stream and / or by the transformation of the additive during its flow through the exhaust gas treatment system, the interaction being caused by the opening degree of the first selective catalytic reduction catalyst, the first selective catalytic reduction catalyst being arranged such that:

[0129] --Cause the particulate matter to interact with the first selective catalytic reduction catalyst, thereby at least partially capturing and removing the particulate matter through the first selective catalytic reduction catalyst; and

[0130] --At least partially avoid the accumulation of soot and ash generated by combustion that would affect the interaction between the first selective catalytic reduction catalyst and the particulate matter.

[0131] As stated above for the exhaust gas treatment system, the method has corresponding advantages.

[0132] The above object is also achieved by the control system arranged to treat the exhaust gas flow generated by combustion in a combustion engine. The treatment includes:

[0133] -Capture the soot and ash generated by combustion by using a particulate filter;

[0134] -Control the supply of an additive to the exhaust gas flow by using a metering arrangement disposed downstream of the particulate filter;

[0135] -Reduce nitrogen oxides NO in the exhaust gas flow by using the supplied additive and a reduction catalyst arrangement disposed downstream of the metering arrangement x wherein the reduction includes a first reduction of nitrogen oxides NO mainly by a first selective catalytic reduction catalyst in a first temperature range T1 x and a second reduction of nitrogen oxides NO mainly by a second selective catalytic reduction catalyst disposed downstream of the first selective catalytic reduction catalyst in a second temperature range T2 x where the first temperature range T1 is at least partially higher than the second temperature range T2; and

[0136] -The interaction between the first selective catalytic reduction catalyst and the particulate matter in the exhaust gas flow generated by supplying the additive to the exhaust gas flow and / or by the transformation of the additive during the flow through the exhaust gas treatment system, the interaction being caused by the opening degree of the first selective catalytic reduction catalyst, the first selective catalytic reduction catalyst being arranged such that:

[0137] --Cause the particulate matter to interact with the first selective catalytic reduction catalyst, thereby at least partially capturing and removing the particulate matter through the first selective catalytic reduction catalyst; and

[0138] --At least partially avoid the accumulation of soot and ash generated by combustion that would affect the interaction between the first selective catalytic reduction catalyst and the particulate matter.

[0139] The control system has advantages corresponding to the above advantages for the exhaust gas treatment system.

[0140] The above object is also achieved by the above computer program and computer program product.

[0141] The computer program and computer program product respectively have the corresponding advantages described above for the exhaust gas treatment system. BRIEF DESCRIPTION OF THE DRAWINGS

[0142] The present invention will be illustrated in more detail below with reference to the drawings, in which like reference numerals are used for like parts, and wherein:

[0143] Figure 1 An example vehicle showing an exhaust gas treatment system that may include various embodiments according to the present invention,

[0144] Figure 2a An example showing an exhaust gas treatment system in which aspects and embodiments of the present invention may be implemented,

[0145] Figure 2b Showing various embodiments of the implementation of the present invention in an exhaust gas treatment system,

[0146] Figure 3a An example showing an exhaust gas treatment system in which aspects and embodiments of the present invention may be implemented,

[0147] Figure 3b Showing various embodiments of the implementation of the present invention in an exhaust gas treatment system,

[0148] Figure 4 Showing a flowchart of a method for exhaust gas treatment according to the present invention,

[0149] Figure 5 Showing a control device according to the present invention, and

[0150] Figure 6a -b shows a non-limiting example of a filter structure. DETAILED DESCRIPTION

[0151] Figure 1 An example vehicle 100 including exhaust gas treatment systems 250, 350 is schematically shown. The exhaust gas treatment systems may be exhaust gas treatment systems 250, 350 according to an aspect or an embodiment of the present invention. The powertrain includes a combustion engine 101, which is connected to a transmission 103 in a conventional manner via an output shaft 102 of the combustion engine 101 via a clutch 106. The output shaft 107 from the transmission 103 can drive wheels 113, 114 via, for example, a final drive 108, such as a conventional differential, and drive shafts 104, 105 connected to the final drive 108.

[0152] A combustion engine 101, such as an internal combustion engine, can be controlled by the engine control system via a control device 115. Similarly, the clutch 106 and the transmission 103 can be controlled by the vehicle control system by means of one or more suitable control devices (not shown). Of course, the powertrain of the vehicle can also be of another type, such as a type with a conventional automatic transmission, or a type with a hybrid powertrain, etc.

[0153] The vehicle 100 also includes exhaust gas treatment / purification systems 250, 350 for treating / purifying the exhaust emissions generated by combustion in the combustion chamber of the combustion engine 101.

[0154] Figure 2a An exhaust gas treatment system 250 is shown, which may represent a so-called Euro VI system. The exhaust gas treatment system 250 is connected, for example, via an exhaust gas duct 202 to a combustion engine 201, where the exhaust gas generated during combustion, i.e., the exhaust gas stream 203, is indicated by an arrow. The exhaust gas stream 203 is directed to a coated diesel particulate filter (cDPF) 210, which is coated with a catalytic oxidation coating, for example including at least one noble metal. Alternatively, instead of a coated diesel particulate filter (cDPF), a diesel oxidation catalyst (DOC) followed downstream by an uncoated diesel particulate filter (DPF) or a coated diesel particulate filter (cDPF) can be arranged in the exhaust gas treatment system 250. Thus, either the coated diesel particulate filter (cDPF) 210 or the diesel oxidation catalyst (DOC) followed by a diesel particulate filter (DPF / cDPF) is arranged downstream of the combustion engine 201 in the exhaust gas treatment system 250.

[0155] During combustion in the combustion engine 201, soot and ash are generated, and the coated diesel particulate filter (cDPF) 210, or the diesel particulate filter (DPF), is used to capture the soot and ash. The exhaust gas stream 203 is hereby directed through the filter structure, where the soot and ash from the exhaust gas stream 203 are captured during passage and stored in the particulate filter 210.

[0156] The catalytic coating in the coated diesel particulate filter (cDPF) 210 or the oxidation catalyst (DOC) has several functions and is generally mainly used to oxidize the remaining hydrocarbons C x H y (also referred to as HC) and carbon monoxide CO in the exhaust gas stream 203 into carbon dioxide CO2 and water H2O. Additionally, most of the nitrogen oxides NO present in the exhaust gas stream can be oxidized to nitrogen dioxide NO2. The oxidation of nitric oxide NO to nitrogen dioxide NO2 is important for the NO2-based soot and ash oxidation in the filter and in the nitrogen oxides NO xIt is also advantageous for potential subsequent reduction.

[0157] In this regard, the exhaust gas treatment system 250 further includes a reduction catalyst arrangement 220 disposed downstream of the coated diesel particulate filter cDPF 210. The reduction catalyst arrangement 220 may include at least one selective catalytic reduction (SCR) catalyst and / or at least one slip catalyst. The reduction catalyst arrangement 220 uses ammonia NH3 or a composition capable of generating / forming ammonia therefrom, such as urea, as an additive for reducing nitrogen oxides NO in the exhaust gas stream 203. x After passing through the components of the exhaust gas treatment system, the exhaust gas stream is discharged into the environment at the exhaust pipe.

[0158] However, the reaction rate of this reduction is affected by the ratio between nitric oxide NO and nitrogen dioxide NO2 in the exhaust gas stream, such that the reduction reaction in the forward direction is affected by the previous oxidation of NO to NO2 in the coated diesel particulate filter (cDPF) or in the oxidation catalyst (DOC).

[0159] The reduction catalyst arrangement 220 requires an additive to reduce compounds such as nitrogen oxides NO x in the exhaust gas stream 203. Such an additive is injected into the exhaust gas stream downstream of the particulate filter 210 and upstream of the reduction catalyst arrangement 220, Figure 2a shown as the metering arrangement 270 in. Such additives are typically based on ammonia and / or urea, or consist of substances from which ammonia can be extracted or released, and may for example consist of AdBlue, which consists essentially of urea mixed with water. Urea forms ammonia upon heating (pyrolysis) and upon heterogeneous catalysis (hydrolysis) on an oxidation surface, which may for example consist of titanium dioxide TiO2 within the reduction catalyst arrangement 220. The exhaust gas treatment system may also include a separate hydrolysis catalyst. The additive can be provided from a container / tank 275, and the metering of the additive can be controlled by a control unit / system 290.

[0160] The exhaust gas treatment system 250 may also be equipped with a slip catalyst (SC) 240, which is arranged downstream of the reduction catalyst arrangement 220 to oxidize any excess ammonia that may remain after the reduction catalyst arrangement 220, and / or to assist the reduction catalyst arrangement 220 in further reducing NO x . Thus, the slip catalyst SC 240 can provide the potential to improve the overall conversion / reduction of the system to NO x .

[0161] According to an embodiment of the present invention, an evaporation arrangement (not shown), such as a hydrolysis catalyst, which may include substantially any suitable hydrolysis coating and / or mixture, may be arranged at the metering arrangement 270. The hydrolysis catalyst and / or mixture is then used to increase the rate of urea decomposition into ammonia, and / or to mix an additive with the emissions, and / or to evaporate the additive.

[0162] The exhaust gas treatment system 250 may also be equipped with one or more sensors, such as one or more NO x and / or temperature sensors, for determining nitrogen oxides and / or temperature in the exhaust gas treatment system.

[0163] Figure 3a Another exhaust gas treatment system 350 is schematically shown, which is connected to the combustion engine 301 via the exhaust pipe 302. The exhaust gas is generated by combustion in the engine 301, and the exhaust gas stream 303 (indicated by the arrow) is directed to the upstream dosing device 371 arranged to add an additive to the exhaust gas stream 303. The upstream reduction catalyst device 330 is arranged downstream of the upstream dosing device 371. The upstream reduction catalyst device 330 is arranged to reduce nitrogen oxides NO in the exhaust gas stream 303 by using the additive added to the exhaust gas stream by the upstream dosing device 371. x More specifically, the upstream reduction catalyst device 330 uses an additive such as ammonia NH3 or a substance capable of generating / forming / releasing ammonia to reduce nitrogen oxides NO in the exhaust gas stream 303. x This additive may for example consist of the above-mentioned AdBlue and may be provided by a container / tank 375. The injection of the additive may be controlled by a control unit / system 390.

[0164] According to various embodiments, the upstream reduction catalyst device 330 may include an upstream selective catalytic reduction (SCR) catalyst and / or an upstream slip catalyst. The upstream slip catalyst may be a conventional ammonia slip catalyst (ASC) or may be a multifunctional slip catalyst (SC), which is mainly arranged for reducing nitrogen oxides NO x and secondly arranged for oxidizing the additive in the exhaust gas stream 303.

[0165] The multifunctional slip catalyst (SC) contains a nitrogen oxides NO x reduction coating in direct contact with the exhaust gas stream 303. The multifunctional slip catalyst (SC) also contains one or more substances included in the platinum group metals and / or one or more other substances providing properties similar to those of the platinum group metals.

[0166] Thus, according to various embodiments, the upstream reduction catalyst device 330 may for example include one of the following:

[0167] - An upstream selective catalytic reduction catalyst SCR1, followed downstream by an integrated or separate upstream slip catalyst SC1, where the upstream slip catalyst SC1 is mainly arranged to reduce nitrogen oxides NO x , and secondly arranged to oxidize additive residues in the exhaust gas stream 303;

[0168] - An upstream slip catalyst SC1, followed downstream by an integrated or separate upstream selective catalytic reduction catalyst SCR1, where the upstream slip catalyst SC1 is mainly arranged to reduce nitrogen oxides NO x , and secondly arranged to oxidize additives in the exhaust gas stream 303;

[0169] - An upstream slip catalyst SC1, followed downstream by an integrated or separate upstream selective catalytic reduction catalyst SCR1, followed downstream by an integrated or separate additional upstream slip catalyst SC 1b , where the upstream slip catalyst SC1 and / or the additional upstream slip catalyst SC 1b is mainly arranged to reduce nitrogen oxides NO x , and secondly arranged to oxidize additives in the exhaust gas stream 303;

[0170] - An upstream slip catalyst SC1, which is mainly arranged to reduce nitrogen oxides NO x , and secondly arranged to oxidize additive residues in the exhaust gas stream 303.

[0171] Downstream of the upstream reduction catalyst device 330, the exhaust gas treatment system 350 further includes a coated diesel particulate filter (cDPF) 310, which is coated with a catalytic oxidation coating, for example including at least one noble metal for capturing and oxidizing soot and ash. Alternatively, instead of the coated diesel particulate filter (cDPF), a diesel oxidation catalyst (DOC) followed downstream by a diesel particulate filter (DPF / cDPF) can be arranged in the exhaust gas treatment system 350. Thus, the coated diesel particulate filter (cDPF) 310, or the diesel oxidation catalyst (DOC) followed by the diesel particulate filter (DPF / cDPF), is arranged downstream of the upstream reduction catalyst device 330 in the exhaust gas treatment system 350.

[0172] Downstream of the particulate filter 310, the exhaust gas treatment system 350 includes a downstream dosing device 372 arranged to supply an additive to the exhaust gas stream 303, where such a downstream additive includes ammonia NH3, or a substance that can generate / form / release ammonia, such as AdBlue, as described above. The downstream additive can here be the same additive as the above-mentioned additive injected by the upstream dosing device 371 and may also be from the same container / tank 375. Alternatively, the additives injected by the upstream dosing device 371 and the downstream dosing device 372 can also be of different types and can be from different tanks. The injection carried out by the downstream dosing device 372 can be controlled by the control unit / system 390.

[0173] According to an embodiment of the invention, an evaporation arrangement can be arranged at the upstream metering arrangement 371 and / or the downstream metering arrangement 372 respectively to increase the rate of decomposition of urea into ammonia, and / or to mix the additive with the emissions, and / or to evaporate the additive.

[0174] The exhaust gas treatment system 350 further includes a downstream reduction catalyst device 320 arranged downstream of the downstream dosing device 372. The downstream reduction catalyst device 320 is arranged to reduce nitrogen oxides NO in the exhaust gas stream 303 by using the additive injected by the downstream dosing device 372 and possibly also the remaining additive injected by the upstream dosing device 371 in the exhaust gas stream 303. x 。

[0175] The downstream reduction catalyst device 320 can include at least one selective catalytic reduction catalyst and / or at least one slip catalyst.

[0176] After passing through the components of the exhaust gas treatment system, the exhaust gas stream is discharged into the environment at the exhaust pipe of the exhaust gas treatment system.

[0177] The exhaust gas treatment system 350 can also be equipped with one or more sensors (not shown), such as one or more NO x sensors and / or one or more temperature sensors, which are arranged to respectively determine the NO x concentration and temperature in the exhaust gas treatment system 350.

[0178] By using Figure 3a the exhaust gas treatment system 350 shown in x , both the upstream reduction catalyst device 330 and the downstream reduction catalyst device 320 can be optimized respectively with respect to the selection of the catalyst characteristics for reducing nitrogen oxides NO

[0179] The particulate filter 310 can be used herein to increase efficiency by considering how its thermal mass, i.e., its thermal inertia, affects the temperature of the downstream reduction catalyst 320. By considering the thermal inertia of the particulate filter 310, the upstream reduction catalyst device 330 and the downstream reduction catalyst device 320 can be optimized relative to the specific temperature functions they will each experience.

[0180] The exhaust gas treatment system 350 reduces the amount of nitrogen oxides NO in the exhaust gas stream in substantially all drive modes, which drive modes particularly include cold start and throttle, i.e., an increased requested torque. x

[0181] According to various embodiments, the above-described slip catalyst SC can be a catalyst arranged to oxidize an additive in the exhaust gas stream 303 and / or a catalyst arranged such that it can reduce residual nitrogen oxides NO in the exhaust gas stream 303. x

[0182] More specifically, according to various embodiments, such a slip catalyst SC can be arranged, for example, primarily to reduce nitrogen oxides NO, x and secondarily to oxidize the additive. In other words, the slip catalyst SC can handle the escape residues of both the additive and nitrogen oxides NO. x This can also be described as the slip catalyst SC being an extended ammonia slip catalyst ASC, which is arranged to reduce nitrogen oxides NO in the exhaust gas stream 303, x such that a general / multi-functional slip catalyst SC capable of handling several types of escapes is obtained, which means it can handle the residues of both the additive and nitrogen oxides NO. x At least the following reactions can take place, for example, in the multi-functional slip catalyst SC, which multi-functional slip catalyst SC both reduces nitrogen oxides NO x and oxidizes the additive:

[0183] NH3 + O2 → N2; (Equation 1)

[0184] and

[0185] NO x + NH3 → N2 + H20. (Equation 2)

[0186] Here, the reaction according to Equation 1 causes the oxidation of the residues of the additive including ammonia. The reaction according to Equation 2 causes the reduction of nitrogen oxides NO. x

[0187] Thus, the additive can be oxidized herein, and the residues of ammonia NH3, isocyanic acid HNCO, urea, or the like can be oxidized. These residues of the additive, i.e., ammonia NH3, HNCO, urea, or the like, can also be used herein to oxidize nitrogen oxides NO. x ​

[0188] To obtain these properties, that is, to obtain a multifunctional escape catalyst, according to one embodiment, the escape catalyst may include one or several substances included in platinum group metals (PGM; platinum group metals), that is, one or several of iridium, osmium, palladium, platinum, rhodium, and ruthenium. The escape catalyst may also include one or several other substances that impart properties similar to those of platinum group metals to the escape catalyst. The escape catalyst may also include NO x reduction coating, where the coating may include, for example, Cu zeolite or Fe zeolite or vanadium. The zeolite can be activated here with active metals such as copper (Cu) or iron (Fe).

[0189] For each of the upstream reduction catalyst device 330 and the downstream reduction catalyst device 320, their catalytic properties can be selected based on the environment they are exposed to or will be exposed to. Additionally, the catalytic properties of the upstream reduction catalyst device 330 and the downstream reduction catalyst device 320 can be adapted such that the catalytic properties can allow them to function symbiotically with each other. The upstream reduction catalyst device 330 and the downstream reduction catalyst device 320 may also include one or several materials that provide the catalytic properties. For example, transition metals such as vanadium and / or tungsten can be used in catalysts such as V2O5 / WO3 / TiO2. Metals such as iron and / or copper can also be included in the upstream reduction catalyst device 330 and / or the downstream reduction catalyst device 320, for example, in zeolite-based catalysts.

[0190] As explained above, the reduction catalyst arrangements 220, 320, that is, the reduction catalyst arrangement 220 arranged downstream of the metering arrangement 270 shown in Figure 2a and the downstream reduction catalyst 320 arranged downstream of the downstream metering device 372 shown in Figure 3a are arranged to reduce nitrogen oxides NO in the exhaust gas streams 203, 303 by utilizing the supplied additives x .

[0191] According to the present invention, as shown in Figure 2b and 3b , the reduction catalyst arrangements 220, 320 include a first selective catalytic reduction catalyst 221, 321 mainly arranged to reduce nitrogen oxides NO in a first temperature range T1 x , and a second selective catalytic reduction catalyst 222, 322 arranged downstream of the first selective catalytic reduction catalyst 221, 321 and mainly arranged to reduce nitrogen oxides NO in a second temperature range T2 x .

[0192] Therefore, according to Figure 2bIn the embodiment shown, the reduction catalyst arrangement 220 includes a first selective catalytic reduction catalyst 221 mainly arranged to reduce nitrogen oxides NO in a first temperature range T1 x and a second selective catalytic reduction catalyst 222 mainly arranged to reduce nitrogen oxides NO in a second temperature range T2 x .

[0193] In addition, according to Figure 3b the embodiment shown, the downstream reduction catalyst 320 includes a first selective catalytic reduction catalyst 321 mainly arranged to reduce nitrogen oxides NO in a first temperature range T1 x and a second selective catalytic reduction catalyst 322 mainly arranged to reduce nitrogen oxides NO in a second temperature range T2 x .

[0194] The first temperature range T1 is at least partially higher than the second temperature range T2 here, that is, the first temperature range T1 includes at least one value higher than the second temperature range T2. As a non-limiting example, the first temperature range T1 can be 250 to 550 °C, and the second temperature range T2 can be 200 to 475 °C.

[0195] Furthermore Figure 2b and Figure 3b the first selective catalytic reduction catalysts 221, 321 shown respectively have an opening degree such that some small-sized particles in the exhaust gas streams 203, 303 interact with the first selective catalytic reduction catalysts 221, 321. As mentioned above, these particles may be generated by supplying an additive to the exhaust gas streams 203, 303 and / or by the transformation of the additive when the additive flows through the exhaust gas treatment systems 250, 350. The additive includes ammonia and / or a substance from which ammonia can be extracted and / or released. Therefore, the particles can include urea and / or urea-based polymerization by-products, which are quite unstable and easily soluble.

[0196] Due to the opening degree, the interaction of the particles with the first selective catalytic reduction catalysts 221, 321 causes the particles to be at least partially captured and removed from the exhaust gas streams 203, 303. The opening degree is also selected such that the accumulation of soot and ash generated by combustion is at least partially avoided, so that the interaction between the first selective catalytic reduction catalysts 221, 321 and the particles is not affected, and the accumulation of soot and ash is prevented from causing the clogging of the first selective reduction catalysts 221, 321.

[0197] The opening degree is a measure of the extent to which the first selective catalytic reduction catalysts 221, 321 block the waste gas flow along the length L of the first selective catalytic reduction catalysts 221, 321. Thus, the opening degree indicates to what extent one or more flow paths through the first selective catalytic reduction catalysts 221, 321 are blocked, i.e., to what range.

[0198] For example, for those embodiments in which the first selective catalytic reduction catalysts 221, 321 include a filter structure, one or more flow paths through the first selective catalytic reduction catalysts 221, 321 may include filter channels through the filter structure of the first selective catalytic reduction catalysts 221, 321. Then, if at least one of the one or more flow paths, i.e., if at least one of the one or more filter channels is blocked / obstructed at any position along its length L, this reduces the opening degree of the first selective catalytic reduction catalysts 221, 321.

[0199] It should be noted that the opening degree thus takes into account obstacles / plugs at any position along the entire length of the flow paths of the first selective catalytic reduction catalysts 221, 321, and thus provides a general measure / ratio of the degree of obstruction of the waste gas flow through the first selective catalytic reduction catalysts 221, 321. The opening degree can be defined as the cross-sectional area A o (i.e., the unobstructed flow path) to the total cross-sectional area A of the component tot ; A o / A tot .

[0200] It should be noted that the opening degree defined herein is different from the known open frontal area (OFA) ratio, which is defined as the ratio of the free cross-section of the catalyst or monolith in the front or opening of the catalyst or monolith to the total cross-section. Thus, the open frontal area ratio does not take into account obstacles in components located downstream of its front or opening.

[0201] On the other hand, as explained above, the opening degree (OD) defined herein is not limited to the front section of the component. Instead, the opening degree takes into account whether the flow path is blocked in the flow direction at any position along the length L of the component. The more flow paths that are blocked, the lower the opening degree value. Additionally, by reducing the opening degree, the interaction between the gas flow (and specifically its components, such as additive-based particles) and the component increases. Additionally, the pressure drop across the component generally increases as the opening degree decreases.

[0202] Accordingly, a lower value of the opening degree of the first selective catalytic reduction catalysts 221, 321 causes more interaction between the additive-based particles and the first selective catalytic reduction catalysts 221, 321 than a higher value does, and thus results in capturing and / or dissolving more additive-based particles.

[0203] For example, for embodiments in which the first selective catalytic reduction catalysts 221, 321 comprise a closed filter structure, the opening degree has a value of zero; OD = 0%, because then the entire exhaust gas flow is forced through one or more walls of the filter structure and interacts with one or more walls of the filter structure. This closed filter structure can also be represented as a wall-flow filter, and by this definition, the wall-flow filter has an opening degree of zero; OD = 0%.

[0204] In contrast, for embodiments in which the first selective catalytic reduction catalysts 221, 321 comprise an open structure, i.e., a so-called flow-through substrate / monolith, the opening degree can have a value of approximately 80%; OD = 80%, depending on its design, such as wall thickness and channel layout.

[0205] By the above design of the reduction catalyst arrangements 220, 320 such that they comprise first selective catalytic reduction catalysts 221, 321 that are mainly arranged to reduce nitrogen oxides NO x and are arranged to have an opening degree such that they interact with small-sized particles, and second selective catalytic reduction catalysts 222, 322 that are arranged downstream of the first selective catalytic reduction catalysts 221, 321 and are mainly arranged to reduce nitrogen oxides NO x many advantages are provided.

[0206] Effective reduction of nitrogen oxides NOx can be provided because the first selective catalytic reduction catalysts 221, 321 and the second selective catalytic reduction catalysts 222, 322 can be optimized here for their respective temperature ranges T1, T2. The exhaust gas flows 203, 303 will have a higher temperature at the first selective catalytic reduction catalysts 221, 321 than at the second selective catalytic reduction catalysts 222, 322, and this is utilized when designing the first selective catalytic reduction catalysts 221, 321 and the second selective catalytic reduction catalysts 222, 322. Accordingly, an overall more effective reduction of nitrogen oxides is provided.

[0207] Additionally, due to the lower opening degree at this position for the first selective catalytic reduction catalysts 221, 321, the interaction between the particles and the first selective catalytic reduction catalysts 221, 321 reduces the risk of soot and ash accumulation in the first selective catalytic reduction catalysts 221, 321 because at this position, nitrogen oxides NOx, especially nitrogen dioxide NO2, still exist in the exhaust gas streams 203, 303. Therefore, the nitrogen oxides NOx, especially nitrogen dioxide NO2, in the exhaust gas streams 203, 303 can be used to remove the accumulated soot and ash in the first selective catalytic reduction catalysts 221, 321.

[0208] Since soot and ash do not accumulate in the first selective catalytic reduction catalysts 221, 321, or will accumulate to at least a very small extent, the opening degree and thus the interaction between the additive-based particles and the first selective catalytic reduction catalysts 221, 321 do not cause an excessive backpressure increase in the first selective catalytic reduction catalysts 221, 321 that may affect the performance of the exhaust gas treatment systems 250, 350.

[0209] According to various embodiments, Figure 3b the downstream reduction catalyst device 320 shown in may include a first selective catalytic reduction catalyst 321 and a second selective catalytic reduction catalyst 322, and an escape catalyst SC integrated with or separate from it and arranged downstream of the second selective catalytic reduction catalyst 322. Then, this escape catalyst SC is arranged to oxidize the residues of the additive and / or assist the first selective catalytic reduction catalyst 321 and the second selective catalytic reduction catalyst 322 in additionally reducing nitrogen oxides NO in the exhaust gas stream 303 x .

[0210] According to an embodiment, the exhaust gas treatment systems 250, 350 further include escape catalyst arrangements 240, 340 arranged downstream of the reduction catalyst arrangements 220, 320 for oxidizing the additive residues in the exhaust gas streams 203, 303, as Figure 2b and 3b shown respectively. The escape catalyst arrangements 240, 340 remove additive residue particles larger than the above-mentioned small-sized additive-based particles.

[0211] According to an embodiment, the first selective catalytic reduction catalysts 221, 321 include a first active catalytic material, and the second selective catalytic reduction catalysts 222, 322 include a second active catalytic material. The first active catalytic material is different from the second active catalytic material. For example, the first active catalytic material is selected to provide effective reduction of nitrogen oxides NO x in a first temperature range T1, and the second active catalytic material is selected to provide nitrogen oxides NO xEffective reduction.

[0212] According to an embodiment, the first active catalytic material includes Cu zeolite, Fe zeolite, and / or vanadium. Additionally, the second active catalytic material may include Cu zeolite, Fe zeolite, and / or vanadium.

[0213] According to various embodiments, one of the following combinations of the first active catalytic material and the second active catalytic material is used:

[0214] - The first active catalytic material is Fe, and the second active catalytic material is Cu;

[0215] - The first active catalytic material is Fe, and the second active catalytic material is vanadium;

[0216] - The first active catalytic material is vanadium at a lower concentration, and the second active catalytic material is vanadium at a higher concentration;

[0217] - The first active catalytic material is a lower level of the carrier coating, i.e., a smaller amount of material per volume of the substrate, and the second active catalytic material is a higher level of the carrier coating, i.e., a larger amount of material per volume of the substrate; and

[0218] - The first active catalytic material has a lower NH3 storage capacity, and the second active catalytic material has a higher NH3 storage capacity.

[0219] According to an embodiment, the first selective catalytic reduction catalyst 221, 321 includes the first active catalytic material carried by the first carrier, and the second selective catalytic reduction catalyst 222, 322 includes the second active catalytic material carried by the second carrier. The first active catalytic material and the second active catalytic material are the same here, while the first carrier and the second carrier are different, i.e., different from each other. Thus, the same active catalytic material, such as the same carrier coating, can be used for both the first selective catalytic reduction catalyst 221, 321 and the second selective catalytic reduction catalyst 222, 322. However, the first selective catalytic reduction catalyst 221, 321 is arranged to provide effective reduction of nitrogen oxides NO x in the first temperature range T1 by selecting / designing the first carrier, and the second selective catalytic reduction catalyst 222, 322 is arranged to provide effective reduction of nitrogen oxides NO x in the second temperature range T2 by selecting / designing the second carrier, where the second carrier is different from the first carrier.

[0220] Then, the first carrier and the second carrier may have different structures, such as the first carrier having a wall flow filter structure and the second carrier having a flow-through structure, respectively providing the first temperature range T1 and the second temperature range T2 for effective nitrogen oxides NO xReduction, but the first active catalytic material and the second active catalytic material are the same. Alternatively or in combination with different structures, the first carrier and the second carrier may respectively have different first thermal mass / inertia / density and second thermal mass / inertia / density, thereby providing a first temperature range T1 and a second temperature range T2 for effective nitrogen oxides NO x Reduction, but the first active catalytic material and the second active catalytic material are the same.

[0221] The above embodiments are designed to support the above temperature optimization utilized according to various embodiments of the present invention.

[0222] According to various embodiments, the first selective catalytic reduction catalysts 221, 321 and the second selective catalytic reduction catalysts 222, 322 are respectively made of a first active catalytic material and a second active catalytic material. Alternatively, the first active catalytic material and the second active catalytic material are respectively coated on the first selective catalytic reduction catalysts 221, 321 and the second selective catalytic reduction catalysts 222, 322.

[0223] According to an embodiment, the first selective catalytic reduction catalysts 221, 321 include a filter structure. Then, the filter structures 223, 323 may respectively have open and / or closed filter channels corresponding to the opening degrees of the first selective catalytic reduction catalysts 221, 321. Therefore, the filter structures here cause the interaction between the particles and the first selective catalytic reduction catalysts 221, 321.

[0224] According to some embodiments, the filter structure may be a closed filter structure. Therefore, the filter structure may include channels passing through the filter, where each such channel is closed / plugged at one or more of its ends or between the ends. In other words, there are no open, i.e., unblocked, channels leading through the filter because each channel is closed / plugged at one or both of its ends or between the ends. For the closed filter structure embodiment, the opening degree of the first selective catalytic reduction catalysts 221, 321 is zero, i.e., 0%.

[0225] For the closed filter structure embodiment, the first selective catalytic reduction catalysts 221, 321 have a cross-sectional area A in square inches and a length L in inches, such that the area-to-length ratio A / L of the first selective catalytic reduction catalysts 221, 321 in inches has a value of at least 17 inches and at most 50 inches; 17 ≤ A / L ≤ 50 inches.

[0226] According to other embodiments, the filter structure includes one or more channels opening through the filter structure. This means that the filter is at least partially open, i.e., the filter is not completely closed.

[0227] For such an open filter structure embodiment, the opening degrees of the first selective catalytic reduction catalysts 221, 321 are in one of the intervals in the following groups:

[0228] -1% to 80%:

[0229] -10% to 80%;

[0230] -20% to 80%;

[0231] -10% to 60%;

[0232] -20% to 60%;

[0233] -10% to 50%;

[0234] -20% to 50%; and

[0235] -30% to 50%.

[0236] According to the embodiment, the first selective catalytic reduction catalysts 221, 321 are implemented as an open filter structure and have a cross-sectional area A in square inches and a length L in inches, such that the area-to-length ratio A / L of the first selective catalytic reduction catalysts 221, 321 has a value of at least 17 inches and at most 100 inches; 17 ≤ A / L ≤ 100 inches.

[0237] According to this embodiment, the ratio between the cross-sectional area A and the length L of the first selective catalytic reduction catalysts 221, 321 is important. The first selective catalytic reduction catalysts 221, 321 should have a length L that is shorter relative to the area A compared to, for example, the filter structure of a conventional particulate filter.

[0238] As described above, for some embodiments, if the area A is measured in square inches and the length L is measured in inches, the area-to-length ratio A / L can be in the interval of 17 ≤ A / L ≤ 100 inches. If the area A is measured in mm 2 and the length L is measured in mm, the above interval corresponds to an area-to-length ratio A / L interval of 432 ≤ A / L ≤ 2540 mm.

[0239] As Figure 6a shown in -b, the channels passing through the filter structure can be designed symmetrically ( Figure 6a ) or asymmetrically ( Figure 6b ) with respect to their cross-sectional area.

[0240] According to Figure 6aIn the embodiment shown, the filter structure includes at least one open channel and at least one closed channel passing through the filter structure. The open channel cross-sectional area A of the at least one open channel oc is here substantially equal to the closed channel cross-sectional area A of the at least one closed channel cc . Accordingly, the open channel cross-sectional area A oc and the closed channel cross-sectional area A cc have no intentional difference between them. This can be represented as a symmetric design of the filter structure.

[0241] According to Figure 6b another embodiment shown, the open channel cross-sectional area A of the at least one open channel oc is here alternatively different from the closed channel cross-sectional area A of the at least one closed channel cc . Accordingly, the open channel cross-sectional area A oc and the closed channel cross-sectional area A cc are designed to be different. For example, the open channel cross-sectional area A oc can be smaller than the closed channel cross-sectional area A cc . This can be represented as an asymmetric design of the filter structure.

[0242] It should be noted that Figure 6a the filter structure shown in Figure 6b has a higher opening degree than the filter shown in Figure 6a -b. It should also be noted that, according to the definition of the opening front area (OFA) ratio,

[0243] the filter structure shown in

[0244] will have the same opening front area ratio. By selecting the filter design, that is, by selecting a symmetric filter design or an asymmetric filter design, an opening degree matching a specific embodiment can be achieved, so as to provide effective removal of additive-based particles. cc According to an embodiment, the first selective catalytic reduction catalyst has an asymmetric ratio between the cross-sectional area A of at least one closed channel oc and the cross-sectional area A of at least one open channel, and its value is at least 1.3 respectively; A cc / A oc ≥1.3. By increasing the asymmetry with a ratio higher than 1, the opening degree decreases, and the interaction between the filter structure and the additive-based particles in the exhaust gas increases. Therefore, the filtration of these particles is increased, thereby increasing the capture and / or removal of particles.

[0245] The reducing catalyst arrangements 220, 320 and thus the first selective catalytic reduction catalysts 221, 321 contained therein can have many different shapes. According to various embodiments, the reducing catalyst arrangements 220, 320 have a circular cross-section, an oval cross-section, a rectangular cross-section or another suitable form. The cross-section of the reducing catalyst arrangements 220, 320 can have substantially any shape suitable for connecting the reducing catalyst arrangements 220, 320 to upstream and / or downstream components in the exhaust gas treatment systems 250, 350.

[0246] According to an embodiment, the first selective catalytic reduction catalysts 221, 321 include at least one section arranged to be heated to an interaction temperature T by the exhaust gas flow 203, 303 when the exhaust gas flow passes through the first selective catalytic reduction catalysts 221, 321. I . Here, the interaction temperature T I exceeds the particle temperature T at which particle thermal dissolution occurs; P T I >T P . Additionally, the first selective catalytic reduction catalysts 221, 321 are arranged according to their opening degree to interact with the exhaust gas flow 203, 303 and thus also with the additive-based particles, such that at least a portion of the particles physically contacts the at least one heated section. Thereby, the additive-based particles impinging on the at least one heated section are thermally dissolved and removed from the exhaust gas flow. According to an embodiment, the interaction temperature T I can be at least 150 °C.

[0247] During cold start, i.e., before the at least one section has been heated to the interaction temperature T I , then some particles may initially accumulate in the first selective catalytic reduction catalysts 221, 321. However, when the at least one section has been heated to the interaction temperature T I , the accumulated additive-based particles are thermally dissolved and removed.

[0248] According to one aspect of the present invention, there is provided a method for treating exhaust gas flows 203, 303 generated by combustion in combustion engines 201, 301.

[0249] In a first step 410, soot and ash generated by combustion are captured by using particulate filters 210, 310.

[0250] In a second step 420, the supply of additives to the exhaust gas flow is controlled by using a metering arrangement 270, 372 arranged downstream of the particulate filters 210, 310.

[0251] In a third step 430, nitrogen oxides NO in the exhaust gas streams 203, 303 are reduced by utilizing the supplied additives and the reduction catalyst arrangements 220, 320 disposed downstream of the metering arrangements 270, 372. x The reduction 430 includes a first reduction of nitrogen oxides NO mainly in the first temperature range T1 by the first selective catalytic reduction catalysts 221, 321. x and a second reduction of nitrogen oxides NO mainly in the second temperature range T2 by the second selective catalytic reduction catalysts 222, 322. x As described above, the second selective catalytic reduction catalysts 222, 322 of the reduction catalyst arrangements 220, 320 are disposed downstream of the first selective catalytic reduction catalysts 221, 321. The first temperature range T1 is at least partially higher than the second temperature range T2, i.e., the first selective catalytic reduction catalysts 221, 321 and the second selective catalytic reduction catalysts 222, 322 are respectively arranged to operate mainly in different temperature ranges (i.e., the first temperature range T1 and the second temperature range T2).

[0252] In a fourth step 440, the particles in the exhaust gas streams 203, 303 are made to interact with the first selective catalytic reduction catalysts 221, 321. As described above, these particles are produced by one or more of the supply of the additives to the exhaust gas streams 203, 303 and the transformation of the additives during the flow through the exhaust gas treatment systems 250, 350. The first selective catalytic reduction catalysts 221, 321 have an opening degree arranged such that:

[0253] -- causes the particles to interact with the first selective catalytic reduction catalysts 221, 321, whereby they are at least partially captured and removed by the first selective catalytic reduction catalysts 221, 321; and

[0254] -- at least partially avoids the accumulation of soot and ash produced by combustion that would affect the interaction between the first selective catalytic reduction catalysts 221, 321 and the particles.

[0255] Those skilled in the art should recognize that the method for treating an exhaust gas according to the present invention can also be implemented in a computer program, which, when executed on a computer, will cause the computer to execute the method. The computer program generally forms part of a computer program product 503, where the computer program product includes a suitable digital non-volatile / permanent / persistent / durable storage medium on which the computer program is stored. The non-volatile / permanent / persistent / durable computer-readable medium consists of a suitable memory, such as: ROM (Read Only Memory), PROM (Programmable Read Only Memory), EPROM (Erasable PROM), flash memory, EEPROM (Electrically Erasable PROM), hard disk devices, etc.

[0256] Figure 5 Schematically shows a control device 500. The control device 500 includes a computing unit 501, which can basically consist of a processor or microcomputer of a suitable type, such as a circuit for digital signal processing (Digital Signal Processor, DSP) or a circuit with a predetermined specific function (Application Specific Integrated Circuit, ASIC). The computing unit 501 is connected to a memory unit 502 installed in the control device 500, thereby providing, for example, stored program code and / or stored data to the computing device 501, which the computing device 501 needs for calculations. The computing unit 501 is also arranged to store the intermediate or final results of the calculations in the memory unit 502.

[0257] In addition, the control device 500 is equipped with devices 511, 512, 513, 514 for receiving and sending input and output signals respectively. These input and output signals can include waveforms, pulses or other attributes, which can be detected as information by the devices 511, 513 for receiving input signals, and can be converted into signals that can be processed by the computing unit 501. These signals are then provided to the computing unit 501. The devices 512, 514 for sending output signals are arranged to convert the calculation results from the computing unit 501 into output signals for transmission to other parts of the vehicle's control system and / or the components that the signals are intended for.

[0258] Each of the connections to the devices for receiving and sending input and output signals can consist of one or more of the following: a cable, a data bus such as a CAN (Controller Area Network) bus, a MOST (Media Oriented Systems Transport) bus, or any other bus configuration; or consist of a wireless connection.

[0259] Those skilled in the art will recognize that the above-mentioned computer can consist of the computing unit 501, and the above-mentioned memory can consist of the memory unit 502.

[0260] Typically, the control system in a modern vehicle consists of a communication bus system, which is composed of one or several communication buses to connect multiple electronic control units (ECUs) or controllers and different components located on the vehicle. Such a control system can include a large number of control devices, and the responsibility for a specific function can be distributed among more than one control device. Therefore, a vehicle of the type shown typically includes significantly more control devices than Figure 5 the control devices shown in

[0261] As will be recognized by those skilled in the art, Figure 5 the control device 500 in Figure 2a may respectively include one or several of the control devices 290 and 390 in

[0262] In the illustrated embodiment, the present invention is implemented in the control device 500. However, the present invention can also be implemented in whole or in part in one or several other control devices already existing in the vehicle, or in a control device dedicated to the present invention.

[0263] Those skilled in the art will also recognize that the above exhaust gas treatment system can be modified in accordance with different embodiments of the method according to the present invention. In addition, the present invention relates to a motor vehicle 100, such as a car, a truck or a bus, or another unit including at least one exhaust gas treatment system according to the present invention, such as a ship or a voltage / current generator.

[0264] The present invention is not limited to the embodiments of the present invention described above, but relates to and includes all embodiments within the scope of the appended independent claims.

Claims

1. An exhaust gas treatment system (250, 350) which is arranged to treat an exhaust gas stream (203, 303) generated by combustion in a combustion engine (201, 301), the exhaust gas treatment system comprising: - A particulate filter (210, 310) which is arranged to capture soot and ash generated by the combustion; - A metering arrangement (270, 372) which is arranged downstream of the particulate filter (210, 310) to supply an additive into the exhaust gas stream (203, 303); And - Reduction catalyst arrangement (220, 320), which is arranged downstream of the metering arrangement (270, 372) for reducing nitrogen oxides NO in the exhaust gas stream (203, 303) by utilizing the supplied additive x , the reduction catalyst arrangement (220, 320) includes a first selective catalytic reduction catalyst (221, 321) mainly arranged for reducing nitrogen oxides NO in a first temperature range T1 x , and a second selective catalytic reduction catalyst (222, 322) arranged downstream of the first selective catalytic reduction catalyst (221, 321) and mainly arranged for reducing nitrogen oxides NO in a second temperature range T2 x , wherein the first temperature range T1 is at least partially higher than the second temperature range T2; wherein - The first selective catalytic reduction catalyst (221, 321) has an opening such that particles in the exhaust gas stream (203, 303) caused by supplying the additive into the exhaust gas stream (203, 303) and / or by the transformation of the additive as it flows through the exhaust gas treatment system (250, 350) interact with the first selective catalytic reduction catalyst (221, 321), whereby: -- At least partially capture and remove the particles through the first selective catalytic reduction catalyst (221, 321); and -- At least partially avoid the accumulation of soot and ash generated by the combustion which would affect the interaction of the first selective catalytic reduction catalyst (221, 321) with the particles.

2. The exhaust gas treatment system (250, 350) according to claim 1, wherein - The first selective catalytic reduction catalyst (221, 321) comprises a first active catalytic material; - The second selective catalytic reduction catalyst (222, 322) comprises a second active catalytic material; and - The first active catalytic material is different from the second active catalytic material.

3. The exhaust gas treatment system (250, 350) according to claim 2, wherein the first active catalytic material comprises one or more of the following groups: - Cu zeolite; - Fe zeolite; and - Vanadium.

4. The exhaust gas treatment system (250, 350) according to any one of claims 2 to 3, wherein the active catalytic material is coated on the first selective catalytic reduction catalyst (221, 321).

5. The exhaust gas treatment system (250, 350) according to any one of claims 1 to 4, wherein the first selective catalytic reduction catalyst (221, 321) comprises a filter structure (223, 323).

6. The exhaust gas treatment system (250, 350) according to claim 5, wherein the filter structure (223, 323) has open and / or closed filter channels respectively corresponding to the opening of the first selective catalytic reduction catalyst (221, 321).

7. The exhaust gas treatment system (250, 350) according to any one of claims 5 to 6, wherein the filter structure comprises channels, each channel closing at one or more of the following: - At its upstream end; - At its downstream end; and - Between its upstream end and downstream end.

8. The exhaust gas treatment system (250, 350) according to claim 7, wherein the opening degree of the first selective catalytic reduction catalyst (221, 321) is zero (0%).

9. The exhaust gas treatment system (250, 350) according to any one of claims 7 to 8, wherein - the first selective catalytic reduction catalyst (221, 321) has a cross-sectional area A in square inches and a length L in inches; and - the area-to-length ratio A / L of the first selective catalytic reduction catalyst (221, 321) in inches has a value of at least 17 inches and at most 50 inches; 17 ≤ A / L ≤ 50 inches.

10. The exhaust gas treatment system (250, 350) according to claim 5, wherein the filter structure includes one or more channels opened through the filter structure.

11. The exhaust gas treatment system (250, 350) according to claim 10, wherein the opening degree of the first selective catalytic reduction catalyst (221, 321) is in one of the intervals in the following groups: - 1% to 80%: - 10% to 80%; - 20% to 80%; - 10% to 60%; - 20% to 60%; - 10% to 50%; - 20% to 50%; and - 30% to 50%.

12. The exhaust gas treatment system (250, 350) according to any one of claims 10 to 11, wherein - the first selective catalytic reduction catalyst (221, 321) has a cross-sectional area A in square inches and a length L in inches; and - the area-to-length ratio A / L of the first selective catalytic reduction catalyst (221, 321) in inches has a value of at least 17 inches and at most 100 inches; 17 ≤ A / L ≤ 100 inches.

13. The exhaust gas treatment system (250, 350) according to any one of claims 5 to 12, wherein - the filter structure includes at least one open channel and at least one closed channel passing through the filter structure; - The at least one open channel has an open channel cross-sectional area A oc ; and - The at least one closed channel has a closed channel cross-sectional area A cc , the closed channel cross-sectional area A of the closed channel cc is equal to the open channel cross-sectional area A oc ; A oc = A cc .

14. The exhaust gas treatment system (250, 350) according to any one of claims 5 to 12, wherein - the filter structure includes at least one open channel and at least one closed channel passing through the filter structure; - The at least one open channel has an open channel cross-sectional area A oc ; and - The at least one closed channel has a closed-channel cross-sectional area A cc , the closed-channel cross-sectional area A of the closed channel cc is different from the open-channel cross-sectional area A oc .

15. The exhaust gas treatment system (250, 350) according to any one of claims 1 to 14, wherein - The first selective catalytic reduction catalyst (221, 321) includes at least one section arranged to be heated by the exhaust gas flow (203, 303) flowing therethrough to an interaction temperature T I wherein the interaction temperature T I exceeds the particulate temperature T at which the particulates thermally dissolve P ; T I > T P ; and - the first selective catalytic reduction catalyst (221, 321) is arranged to interact with the particles such that the particles are at least partially in physical contact with the at least one heated section.

16. The exhaust gas treatment system (250, 350) according to claim 15, wherein the interaction temperature T I is at least 150 °C.

17. The exhaust gas treatment system (250, 350) according to any one of claims 1 to 16, wherein - the first selective catalytic reduction catalyst (221, 321) includes a first active catalytic material carried by a first carrier; - the second selective catalytic reduction catalyst (222, 322) includes a second active catalytic material carried by a second carrier; - The second active catalytic material is the same as the first active catalytic material; and - The second carrier is different from the first carrier.

18. The exhaust gas treatment system (250, 350) according to any one of claims 1 to 17, wherein the additive comprises one or more of the following groups: - Ammonia, and - Substances from which ammonia can be extracted and / or released.

19. The exhaust gas treatment system (250, 350) according to any one of claims 1 to 18, wherein the particles comprise one or more of the following groups: - Urea; and - Urea-based polymerization by-products.

20. The exhaust gas treatment system (250, 350) according to any one of claims 1 to 19, the exhaust gas treatment system comprising: - An upstream metering device (371) arranged to supply an additive into the exhaust gas stream (303); - An upstream reduction catalyst device (330), which is arranged downstream of the upstream metering device (371) for reducing nitrogen oxides NO in the exhaust gas stream (303) by using the supplied additive x ; - The particulate filter (310) arranged downstream of the upstream reduction catalyst device (330) to capture soot and ash produced by the combustion; - The metering arrangement arranged as a downstream metering device (372) downstream of the particulate filter (310) to supply an additive into the exhaust gas stream (303); And - The reducing catalyst arrangement, which includes the first selective catalytic reduction catalyst (321) and the second selective catalytic reduction catalyst (322), is arranged as a downstream reducing catalyst device (320) downstream of the downstream metering device (372) to reduce nitrogen oxides NO in the exhaust gas stream (303) by utilizing the supplied additive x .

21. The exhaust gas treatment system (250, 350) according to claim 20, wherein the upstream reduction catalyst device (330) comprises one or more of the following groups: - An upstream selective catalytic reduction catalyst; and - An upstream slip catalyst.

22. A method (400) for treating an exhaust gas stream (203, 303) produced by combustion in a combustion engine (201, 301), the method comprising: - Capturing (410) soot and ash produced by the combustion by means of a particulate filter (210, 310); - Controlling (420) the supply of an additive into the exhaust gas stream by means of a metering arrangement (270, 372) arranged downstream of the particulate filter (210, 310); - reducing (430) nitrogen oxides NO in the exhaust gas stream (203, 303) by utilizing the supplied additive and a reduction catalyst arrangement (220, 320) disposed downstream of the metering arrangement (270, 372) x , the reduction (430) comprising a first reduction of nitrogen oxides NO mainly by a first selective catalytic reduction catalyst (221, 321) in a first temperature range T1 x , and a second reduction of nitrogen oxides NO mainly by a second selective catalytic reduction catalyst (222, 322) disposed downstream of the first selective catalytic reduction catalyst (221, 321) in a second temperature range T2 x , wherein the first temperature range T1 is at least partially higher than the second temperature range T2; And - The interaction (440) of the first selective catalytic reduction catalyst (221, 321) with the particles in the exhaust gas stream (203, 303) produced by the supply of the additive into the exhaust gas stream (203, 303) and / or by the transformation of the additive during flow through the exhaust gas treatment system (250, 350), the interaction (440) being caused by the opening of the first selective catalytic reduction catalyst arranged such that: -- At least partially capturing and removing the particles by the first selective catalytic reduction catalyst (221, 321); and -- At least partially avoiding the accumulation of soot and ash produced by the combustion that would affect the interaction of the first selective catalytic reduction catalyst (221, 321) with the particles.

23. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to perform the method according to claim 22.

24. A computer-readable medium comprising instructions which, when the program is executed by a computer, cause the computer to perform the method according to claim 22.

25. A control system (500) arranged to control an exhaust gas treatment system (250, 350) for treating an exhaust gas flow (203, 303) generated by combustion in a combustion engine (201, 301), the treatment comprising: - capturing (410) soot and ash generated by the combustion by means of a particulate filter (210, 310); - controlling (420) the supply of an additive to the exhaust gas flow by means of a metering arrangement (270, 372) arranged downstream of the particulate filter (210, 310); - reducing (430) nitrogen oxides NO in the exhaust gas stream (203, 303) by utilizing the supplied additive and a reduction catalyst arrangement (220, 320) disposed downstream of the metering arrangement (270, 372) x , the reduction (430) including a first reduction of nitrogen oxides NO mainly by a first selective catalytic reduction catalyst (221, 321) in a first temperature range T1 x , and a second reduction of nitrogen oxides NO mainly by a second selective catalytic reduction catalyst (222, 322) disposed downstream of the first selective catalytic reduction catalyst (221, 321) in a second temperature range T2 x , wherein the first temperature range T1 is at least partially higher than the second temperature range T2; and - the interaction (440) of the first selective catalytic reduction catalyst (221, 321) with the particles in the exhaust gas flow (203, 303) generated by the supply of the additive to the exhaust gas flow (203, 303) and / or by the transformation of the additive as it flows through the exhaust gas treatment system (250, 350), the interaction (440) being caused by the opening of the first selective catalytic reduction catalyst (221, 321), the first selective catalytic reduction catalyst being arranged such that: -- at least partly capturing and removing the particles by means of the first selective catalytic reduction catalyst (221, 321); and -- at least partly avoiding the accumulation of soot and ash generated by the combustion which would affect the interaction of the first selective catalytic reduction catalyst (221, 321) with the particles.

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