Exhaust aftertreatment system

Abstract

The utility model discloses an exhaust aftertreatment system which comprises an exhaust pipe, the exhaust pipe comprises an exhaust main pipeline (1) and an exhaust by-pass pipeline (4), a throttle valve (2) is arranged on the exhaust main pipeline (1), an HC injection device (3) and a mixer (5) are sequentially arranged on the exhaust by-pass pipeline (4), and the HC injection device (3) is connected with the mixer (5). An exhaust outlet of the exhaust main pipeline (1) is sequentially connected with a diesel oxidation catalyst (8), a diesel particle catcher (9) and a selective catalytic reduction reactor (10); on one hand, the distribution uniformity of HC in tail gas is improved through the arranged mixer, on the other hand, the airflow uniformity of the tail gas at the DOC inlet is improved through the arranged baffle, the distribution uniformity of the HC on the cross section of the DOC inlet is improved through the two aspects, the problem of the distribution uniformity of the HC before DOC can be solved, and the service life of the DOC is prolonged. And the problems of DOC over-aging, incapability of ignition, large HC leakage and the like during regeneration are avoided.

Description

Technical Field

[0001] The utility model belongs to the technical field of waste gas treatment, and in particular relates to an exhaust gas post-treatment system. Background Art

[0002] The statements herein merely provide background art related to the present invention and do not necessarily constitute prior art.

[0003] The exhaust aftertreatment system processes the hot exhaust gas generated by the engine through various upstream exhaust components to reduce the emission of pollutants. The various upstream exhaust components may include one or more of the following components: pipes, filters, valves, catalysts, mufflers, etc. For example, the upstream exhaust components guide the exhaust gas to a diesel oxidation catalyst (DOC) having an inlet and an outlet. The carrier of the DOC is divided into ceramic and metal. Usually the ceramic is cordierite, and there are many types of metals, such as iron, copper, brass, etc. The coating on the carrier is mainly composed of precious metal components, such as platinum, iridium, palladium, etc., and the catalytic effect is mainly the precious metals on these coatings.

[0004] As the precious metal content of DOC decreases, the uniformity of DOC inlet airflow is improved by improving the structure of the DOC inlet air intake baffle, which puts higher requirements on the uniformity of HC distribution before DOC. In the prior art, the uniformity of DOC inlet airflow is usually improved by improving the structure of the DOC inlet air intake baffle. For example, Chinese utility model patent CN212716830U discloses a DOC pre-uniformity device, specifically a swirl mixing baffle, so as to make the airflow flowing to the air intake end of DOC more uniform. However, this method has the following problems: only improving the uniformity of DOC inlet airflow cannot solve the problem, and adding a mixer to the air intake cone will increase the back pressure of the post-treatment system, and the economy and power performance will deteriorate. Utility Model Content

[0005] The utility model aims to provide an exhaust gas aftertreatment system, which can solve the problem of HC distribution uniformity before DOC and avoid the problems of DOC over-aging, failure to ignite, large HC leakage, etc. during regeneration.

[0006] In order to achieve the above purpose, the utility model is implemented through the following technical solutions:

[0007] In a first aspect, an embodiment of the utility model provides an exhaust aftertreatment system, comprising an exhaust pipe, wherein the exhaust pipe comprises an exhaust main line and an exhaust bypass line, wherein a throttle valve is arranged on the exhaust main line, an HC injection device and a mixer are arranged in sequence on the exhaust bypass line, and an exhaust outlet of the exhaust main line is connected to a diesel oxidation catalyst, a diesel particulate trap and a selective catalytic reduction reactor in sequence.

[0008] As a further technical solution, the mixer includes a mixer body, the mixer body is in a cylindrical shape, a plurality of blades are arranged on the inner wall of the mixer body, and the plurality of blades are connected to the center position of the mixer body.

[0009] As a further technical solution, the blade is a rectangular sheet structure, and the blade is obliquely arranged on the inner wall surface of the mixer body along the axis of the mixer body.

[0010] As a further technical solution, the outer diameter of the mixer body is the same as the inner diameter of the exhaust bypass pipeline, and the outer wall surface of the mixer body is in close contact with the inner wall surface of the exhaust bypass pipeline.

[0011] As a further technical solution, eight blades are provided and evenly distributed in the circumferential direction to form a cross-shaped structure.

[0012] As a further technical solution, the main exhaust pipe is connected to the diesel oxidation catalyst through an intake cone, and a baffle is arranged inside the intake cone.

[0013] As a further technical solution, the HC injection device comprises an HC nozzle, which is installed on the exhaust bypass pipeline and is inclined toward the mixer.

[0014] As a further technical solution, the filter body of the diesel particulate trap is made of metal wire mesh or silicon carbide.

[0015] As a further technical solution, the diesel oxidation catalyst uses precious metals or ceramics as catalyst carriers.

[0016] As a further technical solution, the selective catalytic reduction reactor includes a catalyst, a urea tank, a urea supply unit and a urea nozzle.

[0017] The beneficial effects of the above-mentioned embodiments of the utility model are as follows:

[0018] The exhaust after-treatment system provided by the utility model, on the one hand, increases the uniformity of HC distribution in the exhaust gas by means of a provided mixer, and on the other hand, improves the airflow uniformity of the exhaust gas at the DOC inlet by means of a provided baffle. By improving the uniformity of HC distribution in the DOC inlet cross section through the above two aspects, the problem of HC distribution uniformity before the DOC can be solved, and the problems of DOC over-aging, inability to ignite, large HC leakage, etc. during regeneration can be avoided.

[0019] The exhaust after-treatment system provided by the utility model is provided with a main exhaust pipeline and a bypass exhaust pipeline. A throttle valve is provided on the main exhaust pipeline, and an HC injection device and a mixer are provided on the bypass exhaust pipeline. The throttle valve opening can be adjusted according to the engine mode to control the direction of the exhaust gas, thereby avoiding problems such as economy and power performance caused by high back pressure of the HC mixer. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention.

[0021] Figure 1 is a schematic diagram of an exhaust gas aftertreatment system of the utility model;

[0022] Figure 2 It is a structural schematic diagram of the mixer of the utility model;

[0023] Figure 3 This is a graph showing the uniformity test results for mixers with different numbers of blades.

[0024] The schematic diagram is for illustrative purposes only;

[0025] Among them, 1. exhaust main line; 2. throttle valve; 3. HC injection device; 4. exhaust bypass line; 5. mixer; 501. mixer body; 502. blades; 6. intake cone; 7. baffle; 8. diesel oxidation catalyst; 9. diesel particulate trap; 10. selective catalytic reduction reactor. DETAILED DESCRIPTION

[0026] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0027] Example 1

[0028] In a typical implementation of the present invention, Figure 1 As shown, an exhaust aftertreatment system is provided, including an exhaust pipe, wherein the exhaust pipe includes an exhaust main line 1 and an exhaust bypass line 4, wherein a throttle valve 2 is arranged on the exhaust main line 1, an HC injection device 3 and a mixer 5 are arranged in sequence on the exhaust bypass line 4, and an exhaust outlet of the exhaust main line 1 is connected to a diesel oxidation catalyst 8, a diesel particulate trap 9 and a selective catalytic reduction reactor 10 in sequence.

[0029] like Figure 2As shown, the mixer 5 includes a mixer body 501 , which is in a cylindrical shape. A plurality of blades 502 are arranged on the inner wall of the mixer body 501 , and the plurality of blades 502 are connected to the center of the mixer body 501 .

[0030] Furthermore, the blade 502 is a rectangular sheet structure, and the blade 502 is obliquely arranged on the inner wall surface of the mixer body 501 along the axis of the mixer body 501. The outer diameter of the mixer body 501 is the same as the inner diameter of the exhaust bypass pipe 4. The outer wall surface of the mixer body 501 is close to the inner wall surface of the exhaust bypass pipe 4, so that the mixer body 501 can be installed on the exhaust bypass pipe.

[0031] In this embodiment, the blades 502 are provided with eight blades, which are evenly distributed in the circumferential direction to form a cross-shaped structure. After bench testing of mixers with different numbers of blades, the results are as follows: Figure 3 As shown, the mixer adopts an eight-blade structure to ensure that HC is evenly distributed in the exhaust gas.

[0032] In this embodiment, the exhaust main line 1 is connected to the diesel oxidation catalyst 8 through the intake cone 6. A baffle 7 is provided in the intake cone 6. The baffle 7 can adopt an existing structure that allows the airflow to flow evenly to the intake end of the DOC.

[0033] In this embodiment, the HC injection device 3 includes an HC nozzle, which is installed on the exhaust bypass line and tilted toward the mixer. The HC injection device is used to inject diesel into the engine exhaust pipe. Hydrocarbons (HC) are oxidized in the DOC to increase the exhaust gas temperature.

[0034] In this embodiment, the filter body of the diesel particulate filter (DPF) is made of metal mesh or silicon carbide, and the DPF filters and reduces the particles in the exhaust gas.

[0035] In this embodiment, the diesel oxidation catalyst (DOC) uses precious metals or ceramics as catalyst carriers. The main function of the DOC is to oxidize CO and HC in the exhaust gas and convert them into non-toxic and harmless CO2 and H2O. It can also absorb soluble organic components and some carbon particles to reduce the emission of some PM.

[0036] In this embodiment, the selective catalytic reduction reactor (SCR) includes a catalyst, a urea tank, a urea supply unit and a urea nozzle. The working principle is: under the action of the catalyst, the reducing agent ammonia or urea is sprayed to reduce NOx in the exhaust gas into N2 and H2O.

[0037] The exhaust after-treatment system provided in this embodiment, when the engine is regenerated, the throttle valve is fully closed, the exhaust gas flows from the exhaust bypass line, the HC injection device injects diesel, enters the DOC with the exhaust gas, and is oxidized and burned inside the DOC. The mixer behind the HC injection device ensures that the HC is evenly mixed in the exhaust gas, and the baffle of the intake cone in front of the DOC ensures that the airflow is evenly distributed at the DOC inlet. Therefore, the HC is evenly distributed in the DOC inlet cross section, ensuring that the DOC performance is fully utilized and preventing the DOC from being overheated and damaged. When operating in other modes, the throttle valve is fully opened to avoid problems such as economy and power caused by high system back pressure.

[0038] The above description is only the preferred embodiment of the utility model, and is not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

Claims

1. An exhaust aftertreatment system, It is characterized in that The invention comprises an exhaust pipe, wherein the exhaust pipe comprises an exhaust main line (1) and an exhaust bypass line (4), wherein a throttle valve (2) is arranged on the exhaust main line (1), an HC injection device (3) and a mixer (5) are arranged in sequence on the exhaust bypass line (4), and an exhaust outlet of the exhaust main line (1) is connected in sequence to a diesel oxidation catalyst (8), a diesel particulate trap (9) and a selective catalytic reduction reactor (10).

2. The exhaust gas aftertreatment system according to claim 1, It is characterized in that The mixer (5) comprises a mixer body (501), the mixer body (501) is in a cylindrical shape, a plurality of blades (502) are arranged on the inner wall of the mixer body (501), and the plurality of blades (502) are connected to the center position of the mixer body (501).

3. The exhaust gas aftertreatment system according to claim 2, It is characterized in that The blade (502) is a rectangular sheet-like structure, and the blade (502) is arranged obliquely on the inner wall surface of the mixer body (501) along the axis of the mixer body (501).

4. The exhaust gas aftertreatment system according to claim 2, It is characterized in that The outer diameter of the mixer body (501) is the same as the inner diameter of the exhaust bypass pipe (4), and the outer wall surface of the mixer body (501) is in close contact with the inner wall surface of the exhaust bypass pipe (4).

5. The exhaust gas aftertreatment system according to claim 2, It is characterized in that The blades (502) are provided in eight numbers and are evenly distributed in the circumferential direction to form a cross-shaped structure.

6. The exhaust gas aftertreatment system according to claim 1, It is characterized in that The main exhaust pipe (1) is connected to a diesel oxidation catalyst (8) via an intake cone (6), and a baffle (7) is arranged inside the intake cone (6).

7. The exhaust gas aftertreatment system according to claim 1, It is characterized in that The HC injection device (3) comprises an HC nozzle which is mounted on the exhaust bypass line (4) and is arranged to be inclined toward the mixer (5).

8. The exhaust aftertreatment system according to claim 1, It is characterized in that The filtering body of the diesel particle trap (9) is made of metal wire mesh or silicon carbide.

9. The exhaust gas aftertreatment system according to claim 1, It is characterized in that The diesel oxidation catalyst (8) uses precious metals or ceramics as catalyst carriers.

10. The exhaust gas aftertreatment system according to claim 1, It is characterized in that The selective catalytic reduction reactor (10) comprises a catalyst, a urea tank, a urea supply unit and a urea nozzle.

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