JP2017194063A - Mixer for exhaust gas aftertreatment system of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a new type mixer for an exhaust gas aftertreatment system of an internal combustion engine.SOLUTION: A mixer (1) for an exhaust gas aftertreatment system of an internal combustion engine, namely for mixing a liquid, in particular ammonia or an ammonia precursor substance, with exhaust gas, comprises a pipe (2) in which the exhaust gas is guided. In the mixer, at least one device (3a; 3b) is positioned in the pipe (2), the device (3a; 3b) comprises plate-like elements (4a, 5a; 4b, 5b) mounted at a defined angle, and the exhaust gas in the region of one or more devices (3a; 3b) first collides with a connection region (7a; 7b) of the plate-like elements (4a, 5a; 4b, 5b) and then is guided via the plate-like elements (4a, 5a; 4b, 5b) diverging from the connecting region (7a; 7b) in the flow direction of the exhaust gas.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a mixing device for an exhaust gas aftertreatment system of an internal combustion engine.

For example, combustion processes of static internal combustion engines used in power plants and non-static internal combustion engines used in ships, for example, produce nitrogen oxides, which are generally fossil fuels, For example, produced during the combustion of charcoal, coal, lignite, mineral oil or heavy oil. For this reason, exhaust gas aftertreatment systems are arranged in such internal combustion engines, and these aftertreatment systems are particularly useful for the denitrification of exhaust gases leaving the internal combustion engines. In order to reduce the nitrogen oxides in the exhaust gas, firstly so-called SCR catalytic converters are used in exhaust gas aftertreatment systems known from practice. In the SCR catalytic converter, selective catalytic reduction of nitrogen oxides is performed, and in this selective catalytic reduction, ammonia (NH ₃ ) is required as a reducing agent for the reduction of nitrogen oxides. Ammonia or an ammonia precursor, such as urea, is introduced into the exhaust gas in liquid form for this purpose upstream of the SCR catalytic converter, and the ammonia or ammonia precursor is thoroughly mixed with the exhaust gas upstream of the SCR catalytic converter. It is very important to. For this reason, according to practice, a relatively long mixing loop is required between the introduction of ammonia or ammonia precursor and the SCR catalytic converter. Thus, a mixing device for an exhaust gas aftertreatment system, with which a liquid can be effectively introduced into the exhaust gas stream and mixed with the exhaust gas stream, ie a particularly short mixing There is a need for a mixing device that allows liquid to be effectively introduced into the exhaust gas stream and mixed with the exhaust gas stream even when only the loop is available.

  Starting here, the present invention is based on the task of creating a new type of mixing device for an exhaust gas aftertreatment system of an internal combustion engine. This problem is solved by a mixing device for an exhaust gas aftertreatment system of an internal combustion engine according to claim 1. According to the invention, at least one device comprising a plate-like element mounted at a defined angle is positioned in the pipe, and exhaust in the region of one or more devices is first made into the connection region of the plate-like element. It can be led through a plate-like element that collides and then branches off in the flow direction of the exhaust gas from the connection area. The invention makes it possible to mix the liquid with the exhaust gas stream particularly effectively. The exhaust gas stream impinges on the connecting area of the plate-like elements of each device, resulting in a turbulent exhaust gas stream and a liquid jet introduced into the exhaust gas stream effectively mixing with the exhaust gas. Can be done.

  According to an advantageous further development, each plate-like element in the region of one or more devices is fixed to or via a common support shaft, each device having a respective support shaft. Fixed to the wall of the pipe through which the support shaft is configured to help guide the liquid, on which the metering device is arranged, the liquid is placed downstream of the connection area of the plate-like element, It can be introduced into the exhaust gas via a metering device. Thereby, the liquid can be particularly effectively introduced into the exhaust gas stream and mixed with the exhaust gas stream.

  According to an advantageous further development, each plate-like element in the region of one or more devices is between 40 ° and 160 °, preferably between 60 ° and 120 °, most preferably between 70 ° and 110 °. With an angle between. This relative position of the plate-like elements of the respective devices makes it possible to mix the liquid with the exhaust gas stream particularly advantageously.

  According to a further advantageous further development, the mixing device comprises a plurality of devices, the plurality of devices being positioned side by side in the flow direction of the exhaust gas, the plurality of devices being mounted at a defined angle; And the support axes of the devices positioned side by side do not extend parallel to each other and are projected, in particular between 40 ° and 150 °, preferably between 70 ° and 120 °. Having an angle between 0 ° and most preferably between 80 ° and 100 °. In particular, in a mixing device, the liquid can be mixed particularly advantageously and effectively with the exhaust gas flow, if a plurality of devices comprising plate-like elements are positioned side by side when viewed in the flow direction.

  According to a further advantageous further development, the mixing device comprises a baffle plate positioned upstream of the one or more devices. In particular, if the mixing device comprises a selective baffle plate, mixing the exhaust gas stream and the liquid introduced into the exhaust gas stream can be further improved.

  Optionally, in the region of one or more devices, the plate-like element and / or baffle plate of the one or more devices has a catalytically active coating. This helps to improve the aftertreatment of the exhaust gas.

  Preferred further developments of the invention result from the dependent claims and the following description. Exemplary embodiments of the present invention are described in more detail using the drawings without being limited to the drawings.

1 is a schematic perspective view of a mixing device according to the invention for an exhaust gas aftertreatment system of an internal combustion engine.

  The present invention relates to a mixing device for an exhaust gas aftertreatment system of an internal combustion engine, for example for a static internal combustion engine in a power plant or for a non-static internal combustion engine used on ships. In particular, the mixing device is used in exhaust gas aftertreatment systems in marine diesel engines operated with heavy oil.

  The mixing device according to the invention serves to mix the liquid with the exhaust gas stream, and as a liquid, in particular ammonia or an ammonia precursor, for example urea, is mixed with the exhaust gas stream, so that the exhaust gas installed downstream of the mixing device. It makes it possible to effectively reduce the exhaust gas nitrogen oxides in the SCR catalytic converter of the aftertreatment system.

  A mixing device 1 according to the invention for mixing a liquid with an exhaust gas stream comprises a pipe 2 through which the exhaust gas or the exhaust gas stream is guided. In the exemplary embodiment of FIG. 1, the exhaust pipe 2 has a circular outer cross section. The exhaust pipe 2 that guides the exhaust gas flow can also have different contours.

  At least one device 3a, 3b is positioned in the pipe 2 for guiding the exhaust gas or the exhaust gas flow, the devices 3a, 3b comprising plate-like elements 4a, 5a and 4b, 5b mounted at a predetermined angle, respectively. Yes. In the exemplary embodiment shown, two such devices 3a, 3b are positioned side by side in the pipe 2 when viewed in the flow direction 6 of the exhaust gas or exhaust gas flow, so that each of these devices 3a and 3b is Plate-like elements 4a and 5a and 4b and 5b, respectively.

  The exhaust gas flowing through the pipe 2 in the flow direction 6 firstly in the region of the respective devices 3a and 3b, respectively, the connection regions 7a and 7b of the respective plate-like elements 4a, 5a and 4b, 5b of the respective devices 3a and 3b. And then led from the respective connection regions 7a and 7b through the plate-like elements 4a and 5a and 4b and 5b branched in the flow direction of the exhaust gas.

  In the preferred exemplary embodiment of the invention shown, each device 3a, 3b comprises two plate-like elements 4a, 5a and 4b, 5b, respectively, and the plate-like elements 4a, 5a and 4b, 5b are circular. The outer shape is in the form of a section and has straight edges 8a, 9a and 8b, 9b, respectively, and arc-shaped edges 10a, 11a and 10b, 11b, respectively. In each region of the devices 3a, 3b, the respective plate-like elements 4a, 5a and 4b, 5b receive each other in the region of the straight edges 8a, 9a and 8b, 9b in response to the formation of the respective connection regions 7a, 7b. Thus, the exhaust gas flow is firstly connected in the region of the respective device 3a, 3b to the interconnecting edges 8a, 9a and 8b of the respective plate-like elements 4a, 5a and 4b, 5b of the respective devices 3a, 3b. , 9b. In the region of the respective device 3a, 3b, the plate-like elements 4a, 5a and 4b, 5b are of different sizes and / or different profiles and / or have different mounting angles with respect to the longitudinal axis of the pipe 2. Can have. Furthermore, recesses can be introduced into the plate-like elements 4a, 5a and 4b, 5b of the respective devices 3a, 3b.

  As already explained, the plate-like elements 4a, 5a and 4b, 5b are connected to each other in the respective regions of the devices 3a, 3b in response to the formation of connection sections or connection regions 7a, 7b, and the respective plate-like elements 4a. , 5a and 4b, 5b diverge from this connection region 7a, 7b when viewed in the flow direction of the pipe 2, i.e. in the region of the respective device 3a, 3b, the respective plate-like elements 4a, 5a and 4b, 5b branches to have an angle between 40 ° and 60 °, preferably between 60 ° and 120 °, most preferably between 70 ° and 110 °, respectively.

  From FIG. 1, in each region of the devices 3a, 3b shown, the respective plate-like elements 4a, 5a and 4b, 5b are on a common support shaft 12a, 12b or via a common support shaft 12a, 12b. It is clear that each is connected or fixed to a common support shaft 12a, 12b and each device 3a, 3b is fixed to the wall of the pipe 2 via the respective support shaft 12a, 12b. is there. Here, each support shaft 12a, 12b extends perpendicularly across the longitudinal axis of the pipe 2 selectively.

  In the regions of the respective devices 3a, 3b, the edges 8a, 9a and 8b, 9b of the plate-like elements 4a, 5a and 4b, 5b, which are connected to each other, are respectively longitudinal central axes of the respective support shafts 12a, 12b. Rather, it extends rather upstream of each longitudinal central axis parallel to the longitudinal central axes of the support shafts 12a, 12b.

  According to an advantageous further development of the invention, it is provided that a metering device is arranged on at least one support shaft 12a, 12b of at least one device 3a, 3b shown in FIG. The In this case, each support shaft 12a, 12b is optionally realized as a pipe that serves to guide the liquid mixed with the exhaust gas stream, and a metering device is connected to each support shaft 12a, 12b. The liquid which is continuously arranged and mixed with the exhaust gas flow is introduced into the exhaust gas flow downstream of the connection regions 7a and 7b of the plate-like elements 4a, 5a and 4b, 5b via the respective support shafts 12a and 12b. And in particular sprayed. Thereby, the liquid mixed with the exhaust gas is particularly preferably introduced into the exhaust gas and mixed with the exhaust gas stream.

  As already explained, the two devices 3a, 3b comprising two plate-like elements 4a, 5a and 4b, 5b, respectively, in the exemplary embodiment shown in FIG. Are arranged side by side.

  It is pointed out that only one or more such devices may be arranged side by side in the pipe 2.

  In particular, as shown in FIG. 1, when a plurality of devices 3a, 3b having plate-like elements 4a, 5a and 4b, 5b, respectively, are arranged in the pipe 2 side by side when viewed in the exhaust gas flow direction 6, The support shafts 12a, 12b of the plurality of devices 3a, 3b do not extend parallel to each other, but rather, when projected in the flow direction 6, are between 40 ° and 60 °, preferably 70 ° -120. With an angle a between 0 ° and most preferably between 80 ° and 100 °.

  In the exemplary embodiment shown in FIG. 1, the two devices 3a, 3b, positioned side by side in the pipe 2 when viewed in the exhaust gas flow direction 6, are offset by 90 ° relative to each other and are therefore supported by the support shaft. 12a and 12b have an angle of 90 ° with respect to each other when projected.

Each plate-like element 4a, 5a and 4b, 5b of each device 3a, 3b has a different profile and / or different size and / or of the pipe 2 in order to optimize the flow guidance. It can have different mounting angles with respect to the longitudinal axis and / or have a recess, optionally with a catalytically active coating comprising in particular TiO ₂ .

Thereby, the catalysis of the feed urea to NH ₃ + CO ₂ can already be carried out with the exhaust gas already in the region of the respective devices 3a, 3b, as a result of which downstream of the mixing device 1 The exhaust gas aftertreatment in the components of the installed exhaust gas aftertreatment device, in particular in the SCR catalytic converter, is improved.

  As shown in FIG. 1, when a plurality of devices 3a and 3b are arranged side by side in the pipe 2 when viewed in the flow direction of the pipe 2, at least one support shaft 12a and 12b is introduced into the exhaust gas. And at least one of the devices is arranged with a corresponding metering device for introducing or injecting the liquid into the exhaust gas stream.

  In the exemplary embodiment of FIG. 1, this is the case for the region of device 3a or the region of device 3b, but in addition to both the devices 3a and 3b shown in FIG. 1, ie the support shafts of devices 3a and 3b. It is possible to arrange metering devices corresponding to 12a, 12b and the liquid introduced into the exhaust gas is injected into the exhaust gas stream in the region of both devices 3a, 3b.

Supplying the liquid can be effected via individual pipes, the discharge distance of the liquid from the support shaft 12 and / or from the connection areas 7a, 7b and / or from the center point of the baffle plate. The downstream arrangement is:
0.1 × cos (a / 2) × baffle plate length ≦ distance ≦ 3 × cos (a / 2) × baffle plate length.

  The mixing device 1 can optionally comprise a baffle plate not shown, which is positioned upstream of the one or more devices 3a, 3b. The baffle plate has a mounting angle between 20 ° and 60 °, preferably between 30 ° and 55 °, more preferably between 40 ° and 50 °, based on the longitudinal axis of the pipe 2.

The baffle plate can have a catalytically active coating that optionally comprises TiO ₂ .

  The mixing device according to the invention makes it possible to mix the liquid with the exhaust gas stream particularly advantageously. The mixing device 1 according to the invention comprises at least one device 3a and 3b respectively positioned in a pipe 2, the devices 3a and 3b comprising plate-like elements 4a, 5a and 4b, 5b, respectively, , 5a and 4b, 5b are connected to each other and are positioned like V in relation to each other when viewed in side view. Therefore, the devices 3a and 3b positioned in the exhaust gas pipe 2 can be described as V plate type mixing devices 3a and 3b.

  Each of these devices 3a, 3b optionally comprises two plate-like elements 4a, 5a and 4b, 5b, respectively, the two plate-like elements 4a, 5a and 4b, 5b being connected to the connection region 7a. 7b, the exhaust gas flows first collide with the connection regions 7a and 7b, and plate-like elements 4a, 5a and 4b branch off from the connection regions 7a and 7b in the exhaust gas flow direction 6. , 5b, respectively. When viewed in the flow direction of the exhaust gas, the liquid is injected into the exhaust gas selectively via the metering device, selectively downstream of the connection regions 7a, 7b of the respective devices 3a and 3b. , Arranged on the support shafts 12 and 12b of the respective V plate type mixing devices 3a and 3b.

  The mixing apparatus 1 has a simple configuration in which the V-plate type mixing devices 3a and 3b provide only a small-scale loss of pressure and provide a complicated flow field that quickly mixes the exhaust gas flow with the liquid. Have.

  One or more V-plate type mixing devices 3a, 3b provide a macroscopic transport of the liquid introduced into the exhaust gas into the outer edge of the pipe 2 which guides the exhaust gas flow. The one or more V-plate type mixing devices 3a, 3b generate a stable reflux region, and as a result, the residence time of the liquid ejected in the mixing loop is extended. In short, it is ensured that the liquid is well mixed with the exhaust gas stream, even though the mixing loop is realized relatively short.

1 Mixing device, 2 pipe, 3a device, 3b device, 4a plate-like element, 4b plate-like element, 5a plate-like element, 5b plate-like element, 6 flow direction, 7a connection area, 7b connection area, 8a edge, 8b Edge, 9a Edge, 9b Edge, 10a Edge, 10b Edge, 11a Edge, 11b Edge, 12a Support shaft, 12b Support shaft

Claims (18)

A mixing device (1) for an exhaust gas aftertreatment system of an internal combustion engine, ie for mixing a liquid, in particular ammonia or an ammonia precursor, with the exhaust gas,
In a mixing apparatus having a pipe (2) through which the exhaust gas is guided,
At least one device (3a; 3b) is positioned in the pipe (2), the device (3a; 3b) comprising plate-like elements (4a, 5a; 4b, 5b) mounted at a defined angle. The exhaust gas in the region of one or more of the devices (3a; 3b) first strikes the connection region (7a; 7b) of the plate-like element (4a, 5a; 4b, 5b) and then the Mixing device characterized in that it can be guided from the connection region (7a; 7b) via the plate-like elements (4a, 5a; 4b, 5b) branched in the flow direction of the exhaust gas.   In the region of one or more of the devices (3a; 3b), each said plate-like element (4a, 5a; 4b, 5b) is on a common support shaft (12a; 12b) or a common support shaft (12a; 12b), and the respective devices (3a; 3b) are fixed to the wall of the pipe (2) via the respective support shafts (12a; 12b). The mixing device according to claim 1. The support shaft (12a; 12b) is configured to help guide the liquid;
A metering device is arranged on the support shaft (12a; 12b) and the liquid is metered downstream of the connection area (7a; 7b) of the plate-like element (4a, 5a; 4b, 5b). The mixing apparatus according to claim 2, wherein the mixing apparatus can be introduced into the exhaust gas via a supply device.   In the region of one or more of the devices (3a; 3b), each said plate-like element (4a, 5a; 4b, 5b) is between 40 ° and 160 °, preferably between 60 ° and 120 °, 4. Mixing device according to any one of claims 1 to 3, characterized in that it has an angle (a) most preferably between 70 [deg.] And 110 [deg.].   In the region of one or more of the devices (3a; 3b), the plate-like elements (4a, 5a; 4b, 5b) have a straight edge (8a, 9a; 8b, 9b) and an arcuate edge (10a , 11a; 10b, 11b), and each plate-like element (4a, 5a; 4b, 5b) of the plate-like element (4a, 5a; 4b, 5b). 5. The mixing device according to claim 1, wherein the mixing devices are connected to each other in the region of the straight edges (8 a, 9 a; 8 b, 9 b).   6. The region of one or more of said devices (3a; 3b), wherein each said plate-like element (4a, 5a; 4b, 5b) is sized differently A mixing device according to claim 1.   In the region of one or more of the devices (3a; 3b), each said plate-like element (4a, 5a; 4b, 5b) has a different mounting angle with respect to the longitudinal axis of the pipe (2) 7. Mixing device according to any one of the preceding claims, characterized in that it is characterized in that   The mixing device includes a plurality of devices (3a, 3b) positioned side by side when viewed in the flow direction of the exhaust gas, and the plurality of devices (3a, 3b) are plate-like elements attached at a specified angle ( 4a, 5a; 4b, 5b) and a support shaft (12a, 12b), respectively, and the mixing device according to any one of claims 1 to 7,   The support shafts (12a; 12b) of the devices (3a: 3b) positioned side by side do not extend parallel to each other and when projected, in particular between 40 ° and 150 °, preferably between 70 ° and preferably 9. Mixing device according to claim 8, having an angle between 120 [deg.], Most preferably between 80 [deg.] And 100 [deg.].   10. Mixing device according to claim 8 or 9, characterized in that a metering device is arranged on at least one support shaft (12a; 12b) of the plurality of devices (3a; 3b). In the area of; (3b 3a), said plate-like element 1 or more of said devices; claim 1 (4a, 5a 4b, 5b), characterized in that it has a catalytically active coating comprising selectively TiO ₂ To 10. The mixing apparatus according to any one of 10 to 10.   12. Mixing device according to any one of the preceding claims, comprising a baffle plate positioned upstream of one or more of the devices (3a; 3b).   13. Mixing according to claim 12, characterized in that the mounting angle of the baffle plate is between 20 ° and 60 °, preferably between 30 ° and 55 °, most preferably between 40 ° and 50 °. apparatus. It said baffle plate, the mixing device according to claim 12 or 13, characterized in that it has a catalytically active coating comprising selectively TiO _2.   The mixing device according to any one of claims 1 to 14, wherein the pipe (2) through which the exhaust gas is guided has a rounded cross section.   15. Mixing device according to any one of the preceding claims, characterized in that a recess is present in the plate-like element (4a, 5a; 4b, 5b).   11. Mixing device according to any one of claims 2 to 10, characterized in that the support shaft (12a; 12b) intersects the axis of the pipe. When supplying the liquid into the discharge pipe, the discharge distance of the liquid from the support shaft (12) or from the connection region (7a, 7b) and / or downstream of the baffle plate from the center point of the baffle plate The arrangement of
According to any one of claims 1 to 17, characterized in that 0.1 x cos (a / 2) x baffle plate length ≤ distance ≤ 3 x cos (a / 2) x baffle plate length. The mixing device described.

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