Device for treating exhaust gas I

Abstract

Device (1) for directing and treating an exhaust gas stream with a) an outer casing (2), an inlet pipe (10) adjoining the outer casing (2) and an outlet pipe (11) adjoining the outer casing (2), b) a flow channel (K) arranged in the outer casing (2) and conducting the exhaust gas flow, having a channel wall and several channel sections, which connects the inlet pipe (10) to the outlet pipe (11), c) wherein the flow channel (K) has two channel sections (K1a, K1b) with a common front channel wall (KW1), wherein the two channel sections (K1a, K1b) are arranged side by side and one after the other in the flow direction (S) in this flow channel (K) perpendicular to a flow direction (S) and form a front pair (P1), characterized in that d) the flow channel (K) has two rear channel sections (K2a, K2b) with a common rear channel wall (KW2), wherein the two rear channel sections (K2a, K2b) are arranged side by side perpendicular to the flow direction (S) and one after the other in the flow direction (S) and form a rear pair (P2), wherein e) a first SCR catalyst unit (31) is arranged in the flow channel (K) downstream of the two front channel sections (K1a, K1b), and f) that a second SCR catalyst unit (32) is arranged in the flow channel (K) downstream of the two rear channel sections (K2a, K2b).

Description

[0001] The invention relates to a device for guiding and treating an exhaust gas stream, comprising an outer housing, an inlet pipe adjoining the outer housing, an outlet pipe adjoining the outer housing, and a flow channel arranged within the outer housing that guides the exhaust gas stream. The flow channel has a channel wall and several channel sections, connecting the inlet pipe to the outlet pipe. The flow channel comprises two channel sections with a common front channel wall, the two channel sections being arranged side by side and one after the other in the flow direction, perpendicular to the direction of flow. The two channel sections form a front pair. Such a geometry is referred to as a "duct-in-duct" and serves as a heat transfer zone for heat from a hot exhaust gas stream to a relatively cooler exhaust gas stream.This type of heat input into the relatively colder exhaust gas stream is described as passive heat input. In contrast, active heat input, as defined in this invention, is achieved using an additional device for generating thermal energy, such as a burner.

[0002] A flow channel within the meaning of the invention is a device that guides the exhaust gas flow and is formed by the channel walls that carry the exhaust gas and optionally also includes the wall of the outer housing. The outer housing in which the flow channel is arranged is designed as a box. The exhaust gas flows through the flow channel in one direction. All components, such as SCR catalyst units, are arranged within the flow channel. These channel walls are formed by the walls of pipes or the walls of housings and the outer housing, or by other components such as substrates, etc., which guide the exhaust gas flow with their inner and / or outer surfaces and which primarily define the flow channel perpendicular to the flow direction, but also fundamentally. The respective wall limits the flow channel inwards or outwards with respect to the respective central flow axis.In the specific case of a heat transfer zone, the same wall delimits one channel section of the flow channel inwards and another channel section outwards. Or at least, the same wall delimits one channel section of a heat transfer zone in a different direction than another channel section of the heat transfer zone. A channel section is understood to be a portion of the flow channel in the direction of flow. The direction of flow is understood to be the fundamental main flow direction within the flow channel. The direction of flow changes relative to the central axis of the outer casing. Other flow directions deviating from the main flow direction are only relevant for the definition of the relevant features if they are explicitly referenced. Individual points arranged successively in the direction of flow are referred to as being arranged downstream.Accordingly, points arranged against the flow direction are referred to as upstream. Individual components are thin or single-walled sheet metal parts, in particular the heat transfer zones.

[0003] In principle, the pipes and catalysts can have a round cross-section, an oval cross-section, or even a cross-section with several straight sides in the form of a polygon. Every component forming the flow channel is in direct contact with the exhaust gas flow.

[0004] Depending on the process within this device, the exhaust gas flow on one side of a component with flow around it from both sides has a different temperature than on the other side. The sheet metal construction allows heat transfer through the respective component from the hotter exhaust gas flow to the relatively cooler exhaust gas flow. This heat input is influenced not only by the temperature difference between the inside and outside and by the length of the respective section in the flow direction or the residence time of the exhaust gas flow, but also by the flow direction. If the inside and outside are traversed in the same direction, the temperature difference decreases in the flow direction. With opposite flow, the temperature difference remains more constant. Downstream and upstream refer to the flow channel and the flow direction within the flow channel.By definition, downstream and upstream also apply to an exhaust gas particle moving in a changing flow direction within the flow channel. For example, at time t1, the particle is located at a position in the axial direction on the inside of a pipe, and at time t2 greater than t1, it is located at a position in the axial direction on the outside of the pipe.

[0005] Interlocking channel sections are also referred to as "duct-in-duct." For the purposes of this invention, such a "duct-in-duct" construction is defined as two channel sections arranged downstream, one after the other and side by side, which share a common channel wall through which the heat is conducted. "Side by side" essentially means adjacent to each other in one direction perpendicular to the flow direction. Heat is transferred directly from a hotter exhaust gas in one of the two channel sections to a cooler exhaust gas in the other channel section via the common channel wall. Means for increasing the surface area of ​​the wall of the respective channel section are optionally included. The common channel wall is preferably single-walled, but it can also be double-walled or multi-walled.For the purposes of this invention, the feature “duct-in-duct” also includes an arrangement in which the exhaust gas flow is divided from one channel to several channels, as long as the feature of a common channel wall is fulfilled for all channels and for the entire exhaust gas flow at the same time t.

[0006] Devices for treating exhaust gas with these generic features of a "duct-in-duct" geometry are known from DE 10 2010 021 438 A1 or DE 10 2015 004 425 A1, in which a central tube with a coaxially circumferential outer casing is provided. DE 697 04 351 T2 describes a housing arrangement with two pairs of channel sections in which SCR catalysts or other catalysts are arranged.

[0007] The present invention is aimed at overcoming one or more of the problems or disadvantages associated with the prior art. In particular, the object of the invention is to maximize the hydrolysis reactions using the heat energy introduced into the outer casing by the exhaust gas stream, while simultaneously saving additional energy.

[0008] The object of the present invention is achieved by a device for guiding and treating an exhaust gas stream according to claim 1 and by a system according to claim 13. The dependent claims relate to preferred embodiments of the invention. The object is achieved according to the invention in particular by the fact that the flow channel has two rear channel sections with a common rear channel wall, wherein the two rear channel sections are arranged side by side and one after the other in the flow direction at right angles to a flow direction and form a rear pair.

[0009] According to the invention, the exhaust housing, in the form of a box, has two independently functioning "duct-in-duct" zones connected in series as a system. This series of two heat exchanges within the exhaust gas stream makes it possible to improve passive heat transfer in the flow channel and simultaneously achieve a relatively balanced temperature along the entire length of the flow channel, while also ensuring a sufficiently high temperature for the hydrolysis reaction. It was determined that a sufficiently high temperature in the second "duct-in-duct" zone can be guaranteed if the heat exchange in the first "duct-in-duct" zone is limited to the amount necessary for the reaction, rather than the maximum possible heat exchange. Sufficient heat also remains available for the second "duct-in-duct" zone due to the geometry of the box.The box-like geometry of the outer casing is essential because the box forms a thermally closed unit, which essentially retains heat and distributes it through the flow channel. Sufficiently high temperatures are reached within the box during critical operating conditions of the internal combustion engine to ensure that all introduced reagent undergoes a hydrolysis reaction and that the subsequent reaction with individual components of the exhaust gas occurs. Separating the two channel sections of the respective "duct-in-duct" zone with only one, preferably simple or single-walled, channel wall enables optimal heat exchange in the heat transfer zone, where thermal energy can be transferred quickly and with minimal losses through the channel wall.

[0010] It can be advantageous if the flow directions in the two front duct sections are opposite and in the same direction in the two rear duct sections, or vice versa. By choosing different relative flow directions, the temperature differences that develop along each duct section between the hot and cold exhaust gas streams can be influenced. This allows the amount of heat to be exchanged to be distributed evenly between both "duct-in-duct" zones or both pairs of duct sections.

[0011] Furthermore, for the utilization of the transferred heat, it is advantageous that a first SCR catalyst unit is arranged in the flow channel downstream of the two front channel sections. This allows the heat transferred in the front pair to be used for hydrolysis upstream of the first SCR catalyst unit.

[0012] In addition, it is advantageous that a second SCR catalyst unit is arranged in the flow channel downstream of the two rear channel sections. This allows the heat transferred in the rear pair to be used for hydrolysis upstream of the second SCR catalyst unit.

[0013] In cases of insufficient heat due to critical operating parameters in the system, it can be advantageous to include a device for active heat input into the flow channel. The device for generating thermal energy is located on the exhaust housing, which is in the form of a box, and is designed such that the thermal energy is introduced simultaneously before the first SCR unit and before the second SCR unit.

[0014] With regard to separately introduced active heat energy, it can be of particular importance for the present invention if the flow channel has two further upper channel sections with a common upper channel wall, wherein the two upper channel sections are arranged side by side perpendicular to a flow direction and one after the other in the flow direction, forming an upper pair. This makes it possible to utilize the separate active heat input twice: once in the channel into which it is introduced, and a second time on the indirectly heated outer surface of this channel wall. The exhaust gas flow inside the two upper channels can be heated firstly directly by the hot gas from a burner or by an electric heat source and subjected to a first hydrolysis reaction. The channel wall of the corresponding upper section of the flow channel into which the active heat is introduced is thereby also heated.The heat from these heated channel walls is conducted outwards from the inner flow channel to the outer side of the channel wall, leading to the outer flow channel. According to the invention, the heat is then extracted a second time by the exhaust gas flow further downstream, which is then fed into a second hydrolysis reaction.

[0015] In connection with the design and arrangement according to the invention, it can be advantageous if all channel sections are arranged sequentially in the direction of flow. The channel sections are arranged such that every theoretical flow particle of the exhaust gas stream in the flow channel K passes through all channel sections. It is not intended that the exhaust gas stream be divided into several channel sections.

[0016] Furthermore, it can be advantageous if the first channel section of the downstream pair is arranged upstream of the first SCR catalyst unit and the second channel section of the downstream pair is arranged downstream of the first SCR catalyst unit. This ensures that sufficient passive heat is still available downstream of the first SCR catalyst unit to support hydrolysis upstream of the second SCR catalyst unit, and not upstream of the first. This measure serves to better distribute the passive heat input within the flow channel.

[0017] Furthermore, it can be advantageous if the first channel section of the upper pair is located upstream of the first channel section of the front pair, and the second channel section of the upper pair is located downstream of the first SCR catalyst unit. This also ensures that sufficient passive heat is available downstream of the first SCR catalyst unit to support hydrolysis upstream of the second SCR catalyst unit, rather than upstream of the first. This measure also serves to better distribute the passive heat input within the flow channel.

[0018] It can be advantageous if the second channel section of the upper pair is positioned upstream of the second channel section of the rear pair. This, combined with a third measure, ensures that sufficient passive heat is available downstream of the first SCR catalyst unit to support hydrolysis upstream of the second SCR catalyst unit, rather than upstream of the first. This also improves the distribution of passive heat input within the flow channel.

[0019] Finally, it can be advantageous to have a first opening in the flow channel upstream of the first SCR catalyst unit for injecting additive into the flow channel, and / or a second opening in the flow channel downstream of the first SCR catalyst unit and upstream of the second SCR catalyst unit for injecting additive into the flow channel. Access to the respective SCR catalyst unit through the outer casing into the flow channel must be provided regardless of whether the outer casing forms part of the flow channel or whether the flow channel is limited in the area of ​​the opening, for example, by the mixing tube.

[0020] With regard to achieving the longest possible flow channel, it is advantageous if the upstream flow channel is designed such that it deflects or folds the exhaust gas flow four to eight times, preferably six times, by 180°. The folding or deflection occurs in the area of ​​or towards the end faces of the outer casing, so that the main flow direction runs essentially along the central axis in both directions, and the change in direction is achieved by the folding or deflection.

[0021] The terms "front," "back," and "top" serve solely to clearly differentiate the components. With regard to their function and the interaction according to the invention, the geometric position of the components is irrelevant.

[0022] Further advantageous features are listed below, which are also shown in the figures in a special embodiment, but are not limited to these embodiments: - a first opening in the flow channel provided upstream of the first SCR catalyst unit for injecting additive into the flow channel, wherein a second opening in the flow channel is provided downstream of the first SCR catalyst unit and upstream of the second SCR catalyst unit for injecting additive into the flow channel. - the additive is injected through the first opening in a direction opposite to the direction in which the additive is injected through the second opening; - the two openings are arranged opposite each other on the outer casing in relation to the central axis and / or offset in a radial direction on the outer casing; - the two openings are provided in the outer casing and the outer casing forms part of the flow channel in the area of ​​the respective opening; - at the respective opening, one or more injectors or a receptacle for one or more injectors or several openings in the area of ​​the respective injection point are provided; - Downstream of the opening and upstream of the SCR catalyst unit, a mixer is provided as a static mixing element; - the flow channel connects the central tube to the first outer tube and the first outer tube to the first SCR catalyst unit; - the flow channel connects the first SCR catalyst unit with the second jacket pipe; - the first jacket pipe is arranged upstream and the second jacket pipe downstream of the first SCR catalyst unit; - the second SCR catalyst unit is located downstream of the second outer tube; - the intermediate housing is coupled with a device for active heat supply; - between the central tube and the first opening, a filter unit with a filter body and a filter housing is provided in the flow channel, the filter housing forming part of the flow channel; - Between 8 and 12, preferably 9 channel sections are provided, which are arranged straight and parallel to each other and in the direction of flow, one after the other, and which are separated by a curved section that deflects the exhaust gas flow by at least 90°.

[0023] Further advantages and details of the invention are explained in the claims and the description and illustrated in the figures of a specific embodiment. These show: Fig. 1 a stylized sectional view of a device with an outer casing in the form of a box; Fig. 2 an enlarged representation of a central tube with two outer tubes and end collars; Fig. 3-5 sectional views AC according to Fig. 1; Fig. 6-8 Schematic diagrams of exhaust gas treatment; Fig. 9-10 illustrations of two inner housings each.

[0024] A device 1 for guiding and treating an exhaust gas stream has, as in Fig. Figure 1 shows an outer housing 2 in the form of a box. The exhaust gas flow is introduced into the outer housing 2 via an inlet pipe 10 and discharged via an outlet pipe 11. The inlet pipe 10 and the outlet pipe 11 each connect to the outer housing 2. A flow channel K is arranged in the outer housing 2, which guides the exhaust gas flow and connects the inlet pipe 10 to the outlet pipe 11. The flow channel K, or rather the channel wall of the flow channel K, is formed by various components, such as pipes, housings within the outer housing 2, and the outer housing 2 itself. According to Fig. 1. Starting from the end of the inlet pipe 10, the flow channel K is essentially formed by the following components arranged sequentially in the flow direction S: connecting pipe 29, channel segment 27 consisting of intermediate housing 28 and connecting pipe 29, central pipe 20, guide plate 23, filter unit 6, outer housing 2, first mixing pipe 25, inner housing 50, first jacket pipe 21, collar 203, first SCR catalyst unit 31, outer housing 2, second mixing pipe 26, inner housing 51, second jacket pipe 22, collar 204, second SCR catalyst unit 32, outer housing 2, and pipe 30. The outer housing 2, together with various unspecified parts of the housing wall, forms different sections of the flow channel K.

[0025] The device 1 is partially symmetrical about a central axis Z. The central tube 20, the two outer tubes 21, 22, the filter unit 6, and the intermediate housing 28 are arranged coaxially with the central axis Z, as is a separate fuel supply device 7, which is attached to the outer housing 2 from the outside. Each of the two SCR catalyst units 31, 32 comprises four catalysts 31a-d, 32a-d, which are arranged according to the sectional view AA. Fig. The three components are positioned symmetrically around the central axis Z, each offset by 90°. The outer housing 2 contains several intermediate shelves for storing the components. Intermediate shelves 241 and 242 are shown as examples.

[0026] The flow channel K contains a total of three heat transfer zones for transferring heat from a hot exhaust gas stream to a cooler exhaust gas stream relative to the hot exhaust gas stream. Specifically, the heat transfer zones are designed as a "duct-induct" configuration. Using the front heat transfer zone as an example, the "duct-induct" design comprises two channel sections K1a and K1b with a common front channel wall KW1. Channel section K1a is formed by a front portion of the central tube 20. Channel section K1b is bounded internally by the outer front portion of the central tube 20 and externally by the inner surface of the first casing tube 21. The two channel sections K1a and K1b are separated from each other by the central tube 20 and thus by a common channel wall KW1. The two channel sections K1a and K1b are arranged side by side at right angles to a flow direction S, in this case radially to the central axis Z.Furthermore, the two channel sections K1a and K1b are arranged sequentially in the flow direction S such that the exhaust gas flow, after passing through the first channel section K1a, first flows through further components of the flow channel K before flowing through the second channel section K1b. These two front channel sections K1a and K1b form a front pair P1 of channel sections.

[0027] A second and rear pair P2 of channel sections K2a and K2b, forming a rear heat transfer zone according to the "duct-in-duct" principle, comprises the rear part of the central tube 20 and the second outer casing 22. Here, too, the central tube 20 defines the outer boundary of channel section K2a and the inner boundary of channel section K2b. The second outer casing 22 defines the outer boundary of channel section K2b. This arrangement results in the adjacent geometry, oriented perpendicular to the flow direction S, with only one common channel wall KW2. Following channel section K2a, the flow in the rear pair also passes through further components of the flow channel K before entering the second channel section K2b.

[0028] The third heat transfer zone with a common channel wall KW3 is formed by the upper pair P3 of channel sections K3a and K3b. Channel section K3a is formed by channel segment 27, which includes connecting pipe 29 and intermediate housing 28, and which externally delimits channel section K3a and forms the common channel wall KW3. Channel section K3b is internally delimited by connecting pipe 29 and intermediate housing 28. Externally, the inner surface of the outer housing 2 essentially forms the boundary for channel section K3b.

[0029] In addition, two SCR catalyst units 31, 32 are provided and upstream of each SCR catalyst unit 31, 32 an injector 41a, 42a is arranged for injecting additive.

[0030] The type of heat transfer in the heat transfer zones to the relatively colder exhaust gas stream is described as passive heat input. In contrast, active heat input into the exhaust gas stream is achieved with the help of the additional device 7 arranged on the outer casing 2 for generating thermal energy.

[0031] For this purpose, a flame tube 70 is provided in the intermediate housing 28, which is surrounded and through which the exhaust gas flow passes. The hot exhaust gas flow passes directly and successively through the upper channel section K3a, the front channel section K1a, and the rear channel section K2a. The first passive heat exchange occurs in the front pair P1 in the front outer channel section K1b in the first jacket tube 21, after reducing agent has been added to the exhaust gas flow via an injector 41a and before it flows into the first SCR catalyst unit 31. Subsequently, the rear outer channel section K2b is provided to passively heat the exhaust gas flow again after the addition of reducing agent via an injector 42a, before it flows into the second SCR catalyst unit 32. The upper outer channel section K3b allows the exhaust gas flow to be additionally supplied with passive heat at the point where heat is actively supplied to the exhaust gas flow by means of the device 7.Active heat is supplied in the upper channel section K3a and passively transferred to the exhaust gas stream in the upper channel section K3b via the common channel wall KW3. The third pair also ensures that the exhaust gas stream is supplied with passive heat a second time before the second treatment with reducing agent and after a sufficiently long flow path. The first time occurs before the second injector 42a upstream of the mixing tube 26, and the second time after the second mixing tube 26 immediately upstream of the second SCR catalyst unit 32.

[0032] This architecture ensures that heat transfer in the three "duct-in-duct" heat transfer zones occurs sequentially. A theoretical flow particle is only introduced to the rear heat transfer zone once the front heat transfer is complete. Similarly, the upper heat transfer only takes place once the rear heat transfer is finished. Another crucial aspect of the architecture is that the exhaust gas flow is folded a total of six times, i.e., deflected by 180°. A key component for this is the one located at the end of the central tube 20 and in Fig. Figure 2 illustrates the collars 203, 204, which cause a folding of the exhaust gas flow exiting the respective outer casing 21, 22 and flowing into the catalysts 31a-d, 32a-d after folding. The outer surface 203a, 204 of the collars 203, 204 deflects the exhaust gas flow exiting the outer casing 21, 22 by 180°. The inner surface 203i of the collar 203 forms a funnel for the exhaust gas flowing into the central tube 20 at the inlet side 201, and the inner surface 204i of the collar 204 forms a diffuser for the exhaust gas flowing out of the central tube 20 at the outlet side 202.

[0033] The numerous flow paths are also found in the Fig. Figures 3-5 illustrate which show a section in a plane, as described in Fig. 1 is recognizable. The openings shown, insofar as they do not bear reference numbers, are unspecified openings in one of the intermediate floors. Fig. Section AA, a section through the rear heat transfer zone, reveals the four catalysts 32a-d, which are arranged around the central tube 20 and the second jacket tube 22. The first mixing tube 25 is shown in section in the upper section. In the lower section, the tube 30, which collects the exhaust gas flow in the outer housing 2 and directs it into the outlet tube 11, can be seen in alignment. Section BB is located in an intermediate floor 241 immediately upstream of the four catalysts 32a-d. In the upper section, the exhaust gas flows from the first mixing tube 25 into the inner housing 50. In the lower section, the exhaust gas flows from the inner housing 51 into the second jacket tube 22. Additionally, a further portion of the exhaust gas flow exits the catalysts 32a-d and finds its way downwards through several openings in the intermediate floor to the tube 30. After section CC, the exhaust gas flow moves according to... Fig. The exhaust gas flows from the connecting pipe 29 into the intermediate housing 28 and around the flame tube 70 located in the intermediate housing 28, which is arranged coaxially to the central tube 20. The exhaust gas flow exiting the catalysts 31a-d (not shown in this section) passes through openings in an intermediate floor (not specified) to the second mixing tube 26. A guide plate 23 is provided downstream of the central tube 20, through which the exhaust gas flow is distributed onto a filter body 60 of the filter unit 6, which is located further downstream and is mounted in a filter housing 61.

[0034] In the Fig. 6, Fig. 7 to Fig. Figure 8 presents various simplified models for passive and active heat input that can be implemented using the specific box geometry described above. For clarity, these models omit the outer casing, inlet pipe, outlet pipe, duct segment, intermediate casing, and other components. Fig. 6. The still relatively hot exhaust gas flows into the central tube 20 and, after injection with the first injector 41a containing a reducing agent in the front "duct-in-duct" arrangement, is passively heated for the first time in the first jacket tube 21 through the common front channel wall KW1 before flowing into the first SCR catalyst unit 31. The second injection with injector 42a then takes place in the second mixing tube 26, followed by a second passive heating in the rear "duct-in-duct" arrangement through the second common channel wall KW2, before it flows through the second SCR catalyst unit 32. In addition to the passive heating, according to Fig. 7. Active heat is supplied to the exhaust gas stream immediately after it enters the box via device 7. The further possibility of extracting passive heat from the actively heated exhaust gas stream via a "duct-in-duct" arrangement is described in Fig. Figure 8 shows that the exhaust gas flow absorbs passive heat through the common third channel wall KW3 before entering the second mixing tube 26.

[0035] The core of the box geometry, as seen in the Fig. 1, Fig. 2, Fig. 3, Fig. 4 to Fig. As shown in Figure 5, the two inner housings 50, 51, which are located in the Fig. 9 and Fig. Figure 10 shows the inner housings 50 and 51. Each inner housing connects the mixing tube 25 and 26 to the outer casing 21 and 22, downstream of which the catalysts 32a-32d are arranged. The design of the two inner housings 50 and 51, which encompasses the outer casing 21 and 22, allows the two housings to be arranged around the outer casing 21 and 22, while simultaneously guiding two exhaust gas flows independently of each other and in opposite directions along the central axis Z through the outer housing 2.

[0036] The respective inner housings 50, 51 are arranged around the central axis Z and enclose a volume that connects the mixing tube 25, 26 in its function as an inlet nozzle and the outer casing 21, 22 in its function as an outlet nozzle. The inner housing defines a separate or independent volume completely independent of the outer housing. The inlet nozzle 25, 26 is parallel and eccentric to the central axis Z, and the outlet nozzle 21, 22 is arranged relative to the inner housings 50, 51 and axially opposite the inlet nozzle 25, 26 and coaxial to the central axis Z. The inner housings 50, 51 are combined with the central tube 20 such that the central tube 20 completely passes through the inner housings 50, 51, with the inner housings 50, 51 being sealed against the central tube 20.Two identical inner housings 50, 51, positioned radially to the central axis Z, form a point-symmetrical overall housing G with two separate chambers. The overall housing G has a contour circumferential around the same central axis Z for mounting in an outer housing 2. The inner housings 51, 52 each have an identical outer contour at their edges, which, when assembled to form the overall housing G, result in an outer collar 52 circumferentially, elliptically, or continuously around the central axis Z. The outer housing 2 has an intermediate base 242 into which the inner housings 50, 51 are inserted. The inner housing 50, 51 has a semicircular, volume-limiting contour circumferential around the outlet nozzle 21, 22, which is concentric to the central axis Z. The geometry of a single intermediate housing 50 is shown in [reference missing]. Fig. 10 shown in more detail.

Claims

[1] Device (1) for directing and treating an exhaust gas stream with a) an outer casing (2), an inlet pipe (10) adjoining the outer casing (2) and an outlet pipe (11) adjoining the outer casing (2), b) a flow channel (K) arranged in the outer casing (2) and conducting the exhaust gas flow, having a channel wall and several channel sections, which connects the inlet pipe (10) to the outlet pipe (11), c) wherein the flow channel (K) has two channel sections (K1a, K1b) with a common front channel wall (KW1), wherein the two channel sections (K1a, K1b) are arranged side by side and one after the other in the flow direction (S) in this flow channel (K) perpendicular to a flow direction (S) and form a front pair (P1), characterized by , that d) the flow channel (K) has two rear channel sections (K2a, K2b) with a common rear channel wall (KW2), wherein the two rear channel sections (K2a, K2b) are arranged side by side perpendicular to the flow direction (S) and one after the other in the flow direction (S) and form a rear pair (P2), wherein e) a first SCR catalyst unit (31) is arranged in the flow channel (K) downstream of the two front channel sections (K1a, K1b), and f) that a second SCR catalyst unit (32) is arranged in the flow channel (K) downstream of the two rear channel sections (K2a, K2b). [2] The device (1) according to claim 1, characterized by , that the flow directions (S) in the two front channel sections (K1a, K1b) are opposite and in the two rear channel sections (K2a, K2b) are in the same direction. [3] The device (1) according to claim 1 or 2, characterized by, that a device (7) is provided for active heat input into the flow channel (K). [4] The device (1) according to any one of the preceding claims, characterized by , that the flow channel (K) has two further upper channel sections (K3a, K3b) with a common upper channel wall (KW3), wherein the two upper channel sections (K3a, K3b) are arranged next to each other perpendicular to a flow direction in one direction and one after the other in the flow direction (S) and form an upper pair (P3). [5] The device (1) according to any one of the preceding claims, characterized by that all channel sections (K1a-K3b) are arranged one after the other in the direction of flow (S). [6] The device (1) according to any one of the preceding claims, characterized by , that a) the first channel section (K2a) of the rear pair (P2) is located upstream of the first SCR catalyst unit (31) and that the second channel section (K2b) of the rear pair (P2) is located downstream of the first SCR catalyst unit (31) and / or b) the first channel section (K3a) of the upper pair (P3) is located upstream of the first channel section (K1a) of the front pair (P1) and that the second channel section (K3b) of the upper pair (P3) is located downstream of the first SCR catalyst unit (31) and / or c) the second channel section (K3b) of the upper pair (P3) is arranged upstream of the second channel section (K2b) of the rear pair (P2). [7] The device (1) according to any one of the preceding claims, characterized by, that upstream of the first SCR catalyst unit (31) a first opening (41) in the flow channel (K) is provided for injecting additive into the flow channel (K) and / or downstream of the first SCR catalyst unit (31) and upstream of the second SCR catalyst unit (32) a second opening (42) in the flow channel (K) is provided for injecting additive into the flow channel (K). [8] The device (1) according to any one of the preceding claims, characterized by , that in the direction of flow (S) the front pair (P1) is arranged between each pair of the following components and the rear pair (P2) is arranged between each pair of the following components: a first opening (41) a first mixing tube (25) a first SCR catalyst unit (31) a second opening (42) a second mixing tube (26) a second SCR catalyst unit (32). [9] The device (1) according to any one of the preceding claims, characterized by , that the flow channel (K) is constructed in such a way that the flow channel (K) deflects or folds the exhaust gas flow four to eight times, preferably six times, by 180°. [10] The device (1) according to any one of the preceding claims, characterized by , that the front pair (P1) is formed by a central tube (20) and a first outer tube (21) arranged around the central tube (20) or coaxially to the central tube (20), wherein a first part of the central tube (20) forms the common first channel wall (KW1), the central tube (20) is arranged coaxially to a central axis (Z), and the rear pair (P2) is formed by the central tube (20) and a second jacket tube (22) arranged around or coaxially to the central tube (20), and wherein a second part of the central tube (20) forms the common rear channel wall (KW2). [11] The device (1) according to one of the preceding claims comprising an inner housing (50, 51) for directing an exhaust gas flow and for arranging and fastening within an outer housing (2), wherein the inner housing (50, 51) is arranged around the central axis (Z) enclosing a volume and the inner housing (50, 51) has the mixing tube (25, 26) as an inlet nozzle and the outer casing (21, 22) as an outlet nozzle, wherein the mixing tube (25, 26) and the outer casing tube (21, 22) connect to the inner housing (50, 51) and are connected through the inner housing (50, 51), characterized by , that the mixing tube (25, 26) is arranged parallel and acentric to the central axis (Z) and the jacket tube (21, 22) is arranged relative to the inner housing (50, 51) and in the axial direction of the central axis (Z) opposite the mixing tube (25, 26) and coaxial to the central axis (Z). [12] The device (1) according to claim 11, characterized by, that the inner housing (50, 51) is combined with the central tube (20) and the central tube (20) is arranged coaxially to the central axis (Z) and in the outer tube (21, 22) such that the central tube (20) completely passes through the inner housing (50, 51) and / or the outer tube (21, 22). [13] System comprising the device for treating exhaust gas according to one of the preceding claims and an exhaust system for an internal combustion engine, wherein the exhaust system comprises a manifold system, a system with an oxidation catalyst, a pipe system and a silencer system as well as sensors.

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