CN108252771B

CN108252771B - Tail gas post-treatment box for heat preservation by using treated tail gas

Info

Publication number: CN108252771B
Application number: CN201611231615.0A
Authority: CN
Inventors: 丁宁宁; M·艾尔玛诺坦
Original assignee: Robert Bosch GmbH
Current assignee: Bosch Automotive System Wuxi Co Ltd
Priority date: 2016-12-28
Filing date: 2016-12-28
Publication date: 2021-11-30
Anticipated expiration: 2036-12-28
Also published as: CN108252771A

Abstract

An exhaust aftertreatment case comprising: a box body (1); an oxidation catalyst (2), a reducing agent mixer (3) and selective catalytic reducers (4, 5) which are sequentially flowed through by the tail gas, and are carried by the box body (1), the main body of the oxidation catalyst, the reducing agent mixer (3) and the selective catalytic reducers is positioned in the inner space of the box body (1), and outlet ends (42, 52) of the selective catalytic reducers (4, 5) are communicated with the inner space of the box body (1); a reductant injector (9) arranged to inject reductant into the reductant mixer (3); and a tail gas outlet (14) which is arranged on the box body (1) and is opened in the inner space of the box body (1), so that the treated tail gas discharged by the selective catalytic reduction device (4, 5) flows through the inner space of the box body (1) and then is discharged out of the tail gas post-treatment box through the tail gas outlet (14).

Description

Tail gas post-treatment box for heat preservation by using treated tail gas

Technical Field

The application relates to an integrated tail gas aftertreatment case for treating tail gas discharged by an engine.

Background

Engine exhaust gases contain harmful components. In order to reduce the emission of harmful components in the exhaust gas, various post-treatment techniques have been developed. A typical integrated exhaust aftertreatment tank for a diesel engine adapted to be mounted on both sides of a finished vehicle chassis includes a Diesel Oxidation Catalyst (DOC), a Selective Catalytic Reduction (SCR), and a diesel particulate trap (DPF).

DOC), SCR, and DPF do not perform their full effectiveness, or even may not work, at low temperatures. Therefore, it is necessary to maintain the necessary temperature in the exhaust gas aftertreatment tank. Therefore, according to the prior art, a thermal insulation material is provided in the exhaust gas aftertreatment box to prevent the temperature in the exhaust gas aftertreatment box from being too low due to heat loss to the outside environment. However, the addition of insulation clearly increases the overall cost of the exhaust aftertreatment tank. Furthermore, when the engine is operated under low power conditions, the temperature of the exhaust gas discharged is low, and even if there is an insulating material, it is sometimes difficult to maintain the temperature required for the catalyst in the exhaust gas treatment element to operate normally, which makes it difficult for the exhaust gas after-treatment tank to achieve an optimum operating state, the exhaust gas treatment capability is low, and the exhaust gas does not meet high-level exhaust gas emission requirements, such as the euro-six standard and the Real Driving Emissions (RDE) test requirements.

It is therefore desirable to be able to maintain the necessary temperature in the exhaust gas aftertreatment tank with better measures.

Disclosure of Invention

It is an object of the present application to provide an exhaust gas aftertreatment tank for engine exhaust gas that is capable of maintaining a necessary temperature in the exhaust gas aftertreatment tank at low cost and reliably.

To this end, the present application provides, in one of its aspects, an exhaust gas aftertreatment kit for treating engine exhaust gas, in particular diesel engine exhaust gas, comprising: a box body; the selective catalytic reduction device comprises an oxidation catalyst, a reducing agent mixer and a selective catalytic reduction device which are sequentially flowed by tail gas, wherein the oxidation catalyst, the reducing agent mixer and the selective catalytic reduction device are carried by a box body, a main body is positioned in the inner space of the box body, and an outlet end of the selective catalytic reduction device is communicated with the inner space of the box body, so that the treated tail gas discharged by the selective catalytic reduction device enters the inner space of the box body at a part surrounding the peripheries of the oxidation catalyst, the reducing agent mixer and the selective catalytic reduction device; a reductant injector arranged to inject reductant into the reductant mixer; and the tail gas outlet is arranged on the box body and is opened in the inner space of the box body, so that the treated tail gas entering the inner space of the box body is discharged out of the tail gas post-treatment box through the tail gas outlet.

According to one possible embodiment, the outlet end of the selective catalytic reducer is open to the inner space of the cover fixed to the outside of the case, and the portion of the case facing the cover is formed with an exhaust gas through hole establishing communication between the inner space of the cover and the inner space of the case.

According to one possible embodiment, the case includes first and second end walls and a peripheral wall extending along peripheries of the two end walls, the outlet end of the selective catalytic reducer opens into the inner space of the housing through a selective catalytic reducer support hole formed in the second end wall, and the portion of the second end wall facing the housing is formed with the exhaust gas passing hole.

According to one possible embodiment, the second end wall further has an oxidation catalyst support hole and a reducing agent mixer support hole formed therein, and the exhaust gas through hole is formed in a region between the selective catalytic reduction support hole and the oxidation catalyst support hole and the reducing agent mixer support hole.

According to a possible embodiment, the second end wall has a plurality of exhaust gas through holes formed therein.

According to one possible embodiment, the exhaust gas through-holes are a group of exhaust gas through-holes formed around the outer circumference of the selective catalytic reducer support hole.

According to one possible embodiment, the exhaust gas outlet is arranged on the housing close to the oxidation catalytic converter.

According to a possible embodiment, said exhaust gas outlet is provided on said peripheral wall.

According to one possible embodiment, the exhaust gas outlet is arranged on the circumferential wall in a region close to the oxidation catalytic converter.

According to one possible embodiment, the outlet end of the selective catalytic reduction device opens into the interior space of the housing.

According to one possible embodiment, the exhaust gas outlet is disposed at a position remote from the outlet end of the selective catalytic reducer in the axial direction.

According to one possible embodiment, the selective catalytic reducer includes a plurality of selective catalytic reducers connected in parallel with each other.

According to one possible embodiment, the oxidation catalyst, the reducing agent mixer and the selective catalytic reduction device are arranged substantially parallel to one another.

According to one possible embodiment, the oxidation catalytic converter has a particle trap integrated therein.

According to one possible embodiment, a swirl guide is arranged in the reducing agent mixer, which swirl guide is configured to generate a swirl of the mixture of reducing agent and exhaust gas in the reducing agent mixer.

According to the application, the tail gas treated by the tail gas post-treatment box is discharged from the tail gas post-treatment box after flowing through each tail gas treatment element in the tail gas post-treatment box, and the temperature of the treated tail gas is used for maintaining the temperature of each tail gas treatment element, so that each tail gas treatment element, especially a catalyst in the tail gas treatment element can work in an optimal state, and the high-grade tail gas emission requirement can be met more easily.

Drawings

The foregoing and other aspects of the present application will be more fully understood from the following detailed description, taken with reference to the accompanying drawings, in which:

FIGS. 1 and 2 are perspective views from the front and rear of an exhaust aftertreatment tank, respectively, according to one possible embodiment of the present application;

FIG. 3 is a perspective view of the exhaust gas aftertreatment tank taken from the front side thereof after the peripheral wall of the tank body has been removed;

FIG. 4 is a perspective view of the exhaust aftertreatment tank taken from the rear side thereof, with the third enclosure separated from the tank to show the flow of exhaust gases within the third enclosure;

FIG. 5 is a schematic cross-sectional view through an oxidation catalyst (integrated particulate trap) and reductant mixer in the exhaust aftertreatment tank;

FIG. 6 is a schematic cross-sectional view through a selective catalytic reducer in the exhaust aftertreatment box;

FIG. 7 is a schematic cross-sectional view showing the distribution of the treated tail gas in the tank;

FIG. 8 is a perspective view of one possible configuration of swirl guides in a reductant mixer;

figure 9 is a schematic view of one possible configuration of the second end wall of the tank.

Detailed Description

The present application generally relates to a tail gas aftertreatment case for treating engine tail gas, this tail gas aftertreatment case is suitable for installing in whole vehicle chassis both sides. The exhaust aftertreatment tank of the present application is typically suitable for treating exhaust gases of diesel engines; however, the exhaust aftertreatment tank may also be suitable for engines consuming other types of fuel (some components in the exhaust aftertreatment tank may need to be modified accordingly).

An integrated exhaust gas aftertreatment tank according to a possible embodiment of the present application will be described with reference to the accompanying drawings. It is to be noted that the terms "upstream" and "downstream" used in the following description to indicate relative positions are defined with respect to the flow direction of the exhaust gas.

The integrated exhaust gas aftertreatment tank shown in figures 1 to 6 comprises a tank 1 and various exhaust gas treatment elements carried by the tank 1. These exhaust gas treatment components mainly comprise: an oxidation catalyst 2, a reducing agent mixer 3, a pair of selective

catalytic reduction devices

4, 5 disposed in parallel with each other, which are arranged substantially in parallel with each other, and whose main portions are located in a casing 1 with both axial ends supported by the casing 1.

The tank 1 comprises a first (front) end wall 11 and a second (rear) end wall 12 opposite each other, and a peripheral wall 13 extending along the outer peripheries of the two end walls, the two end walls and the peripheral wall 13 defining a tank interior space.

In the illustrated example, the bodies of the first end wall 11 and the second end wall 12 are flat plates arranged substantially parallel to each other, and the peripheral edges of the bodies are formed with flanges for coupling with the peripheral wall 13; however, they may be designed to have any suitable shape and arrangement, as desired.

The oxidation catalyst 2 has a substantially cylindrical housing defining an inlet end 21 and an outlet end 22 of the oxidation catalyst 2 and a central axis of the oxidation catalyst 2, the inlet end 21 passing through the first end wall 11 to the outside of the first end wall 11 and being supported by the first end wall 11, the outlet end 22 passing through the second end wall 12 to the outside of the second end wall 12 and being supported by the second end wall 12. The inlet end 21 is provided with or integrally formed with a substantially conical exhaust gas inlet 23 located on the front side (the first end wall 11 side) of the tank 1.

The exhaust gas inlet 23 is configured to be connected to an upstream exhaust gas pipe section near the engine, for example, to the outlet end of a turbo in an Exhaust Gas Recirculation (EGR) system. The exhaust gas inlet 23 receives exhaust gas emitted from the engine. A particle trap may be integrated into the oxidation catalytic converter 2. In particular, an oxidation catalytic section 25 and a particle trap section 26 are arranged in the housing of the oxidation catalytic converter 2, the particle trap section 26 preferably being located downstream of the oxidation catalytic section 25. The exhaust gas entering the oxidation catalyst 2 flows through the oxidation catalyst section 25 and the particulate trap section 26 in this order, so that hydrocarbons and carbon monoxide in the exhaust gas undergo oxidation catalytic reaction to produce water and carbon dioxide, and particulate matter in the exhaust gas is trapped.

The exhaust gas inlet 23 is preferably offset and inclined with respect to the central axis of the oxidation catalyst 2. This arrangement enables the exhaust gas to more fully impinge on the oxidation catalyst in the oxidation catalyst 2, which enhances the catalytic reaction in the oxidation catalyst 2.

The reducing agent mixer 3 is arranged beside the oxidation catalyst 2, for example above it as shown in the figure, and defines a mixing chamber for the reducing agent with the exhaust gases. In the illustrated example, the reductant mixer 3 comprises two axially joined sections, an upstream conical section (e.g. conical section) 31 and a downstream cylindrical section (e.g. cylindrical section) 32, which may be made separately and combined together, or may be made integrally. The tapered section 31 has a cross-sectional dimension that gradually decreases in a direction from upstream to downstream. The upstream port of the conical section 31 constitutes an inlet end 33 of the reducing agent mixer 3, the downstream port of the conical section 31 is joined to the upstream port of the cylindrical section 32, and the downstream port of the cylindrical section 32 constitutes an outlet end 34 of the reducing agent mixer 3. The inlet end 33 passes through the second end wall 12 to the outside of the second end wall 12 and is supported by the second end wall 12, and the outlet end 34 passes through the first end wall 11 to the outside of the first end wall 11 and is supported by the first end wall 11. The conical section 31 is substantially coaxial with the cylindrical section 32. Swirl guides 35 are disposed in the cylindrical section 32, preferably near the upstream ports of the cylindrical section 32.

Selective

catalytic reducers

4, 5 are arranged beside the reducing agent mixer 3 and the oxidation catalyst 2, wherein the selective catalytic reducer 4 is arranged side by side with the reducing agent mixer 3 and the selective catalytic reducer 5 is arranged side by side with the oxidation catalyst 2. The selective

catalytic reducers

4, 5 have inlet ends 41, 51 and outlet ends 42, 52, respectively, the inlet ends 41, 51 passing through the first end wall 11 to the outside of the first end wall 11 and supported by the first end wall 11, and the outlet ends 42, 52 passing through the second end wall 12 to the outside of the second end wall 12 and supported by the second end wall 12.

The selective

catalytic reducers

4, 5 each have a substantially cylindrical housing, and since the radial space occupied by the reducing agent mixer 3 is smaller than that of the oxidation catalyst 2, the radial space left for the selective catalytic reducer 4 is large, and the diameter of the selective catalytic reducer 4 can be larger than that of the selective catalytic reducer 5. Of course, the selective

catalytic reducers

4, 5 may also have the same diameter.

It is to be noted here that in the illustrated example, the oxidation catalyst 2 and the selective

catalytic reduction devices

4, 5 each have a substantially cylindrical housing, however, they may be configured as housings having other shapes, such as an elliptical cylindrical or other form of cylindrical housing, according to the actual needs, for example, in order to more reasonably occupy the internal space of the casing 1.

On the rear side (second end wall 12 side) of the case 1, the outlet end 22 of the oxidation catalyst 2 and the inlet end 33 of the reducing agent mixer 3 communicate through the first closed cover 6. The first housing 6 may be attached to the outlet end 22 and inlet end 33, respectively, by fasteners such as clips 63. The first enclosure 6 defines a substantially vertically extending flat interior space into which the outlet end 22 and the inlet end 33 open and thus communicate with each other. Also, the first hood 6 comprises a first portion 61 facing said outlet end 22 and a second portion 62 facing said inlet end 33, respectively.

Meanwhile, the outlet ends 42, 52 of the selective

catalytic reducers

4, 5 are covered by the second cover body 7 at the rear side of the case 1. The second cover 7 has a wall and a flange extending from the periphery of the wall, which is sealingly fixed to the second end wall 12 and defines an inner space, into which the outlet ends 42, 52 open and thus communicate with each other.

On the front side of the case 1, the outlet end 34 of the reducing agent mixer 3 and the inlet ends 41, 51 of the selective

catalytic reducers

4, 5 are closed by the third cover 8. The third cover 8 has a wall and a flange projecting from the periphery of the wall, the flange being sealingly fixed to the first end wall 11 and defining an inner space into which the outlet end 34 and the inlet ends 41, 51 open and thus communicate with each other. And the third cover 8 comprises a first portion 81 facing said outlet end 34, a second portion 82 facing said inlet end 41 and a third portion 83 facing said inlet end 51, respectively.

The outlet end 34 of the reducing agent mixer 3 is exposed in the internal space portion defined by the first portion 81 of the third cover body 8, and the exposed portion of the outlet end 34 is a circular arc segment extending in the circumferential direction, instead of a complete circle, as shown in fig. 4. The circular arc segment is preferably located substantially on the side of the inlet end 41 with respect to the central axis of the reducing agent mixer 3. The exposed portion of the arcuate segment shape of the outlet end 34 may extend axially all the way into abutment with the wall of the first portion 8 of the third casing 8.

A reducing agent injector 9 is mounted on the first housing part 6 for injecting a reducing agent, for example an aqueous solution of urea, typically AdBlue, into the reducing agent mixer 3 in a metered manner. The reducing agent injector 9 is mounted on the second portion 62 of the first cover 6 with its injection port facing the inlet end 33 of the reducing agent mixer 3. Preferably, the central axis of the injection port of the reducing agent injector 9 is substantially collinear (coaxial) with the central axis of the reducing agent mixer 3. Further, in order to make the reducing agent injected by the reducing agent injector 9 uniformly enter the reducing agent mixer 3, a recess portion (see fig. 5) that is recessed in the axial direction toward the inlet end 33 of the reducing agent mixer 3, to which the reducing agent injector 9 is mounted, may be formed on the wall portion of the second portion 62 of the first cover body 6. Therefore, the tail gas is not easy to blow off the injected reducing agent, and simultaneously, the tail gas enters the reducing agent mixer 3 circularly and symmetrically.

The exhaust gas is mixed with the reducing agent injected from the reducing agent injector 9 while passing through the reducing agent mixer 3. In order to increase the degree of mixing of the reducing agent in the exhaust gas, the swirl guide 35 is configured to generate a swirl flow in the reducing agent mixer 3. The swirl guide 35 may be designed to have any configuration suitable for swirling the airflow passing through it. According to one possible embodiment, as shown in fig. 8, the swirl guide 35 comprises a cylindrical wall 351 and a plurality of evenly distributed

fins

352 and 353 extending radially inwardly from the axial front and rear edges of the cylindrical wall 351, respectively. The cylindrical wall 351 is sized to fit within the cylindrical section 32, such as by crimping. The surface of each of the

fins

352 and 353 is inclined with respect to the circumferential direction, and the inclination angle may be the same. Thus, the mixed flow of the reducing agent and the exhaust gas that impinges on each of the

vanes

352 and 353 is deflected by the vanes in the circumferential direction. Under the deflection of all of the

fins

352 and 353, a swirling flow is formed. It will be appreciated that the

fins

352 and 353 may be provided only on one axial side edge of the cylindrical wall 351 if sufficient swirling flow can be formed. The swirl guide 35 may be stamped from a single piece of sheet metal.

In addition, the exhaust gas aftertreatment tank comprises a substantially conical exhaust gas outlet 14 for discharging treated exhaust gas. The exhaust gas outlet 14 is provided in the peripheral wall 13 of the casing 1, preferably in a portion of the peripheral wall 13 close to the oxidation catalyst 2, as shown in fig. 1 and 2, and opens into the internal space of the casing 1. The benefit of this arrangement of the exhaust gas outlet 14 is that the heat of the treated exhaust gas can be used to provide thermal insulation for the various exhaust gas treatment components in the enclosure 1.

Further, in the axial direction, the exhaust gas outlet 14 is preferably provided at a position distant from the

outlet end

42, 52 of the selective

catalytic reducer

4, 5, i.e., at a position close to the first end wall 11. In this way, the treated exhaust gas more easily spreads over the outer periphery of all the exhaust gas treatment elements.

Since the outlet ends 42, 52 of the selective

catalytic reducers

4, 5 are spaced apart from the exhaust gas outlet 14 by the second end wall 12, in order to achieve communication between the outlet ends 42, 52 and the exhaust gas outlet 14, as shown in fig. 9, exhaust gas through holes 120 may be formed in a portion of the second end wall 12 surrounded by the second cover 7. The position at which the flange of the second cover 7 is fixed on the body of the second end wall 12 is shown in broken lines in fig. 9, and the portion inside the broken lines, i.e., the portion at which the second end wall 12 is surrounded by the second cover 7, is formed outside of which the oxidation catalyst support hole 22a and the reducing agent mixer support hole 33a through which the outlet end 22 of the oxidation catalyst 2 and the inlet end 33 of the reducing agent mixer 3 pass, respectively, are formed, and inside of which the selective

catalyst support holes

42a, 52a through which the outlet ends 42, 52 of the

selective catalyst reducers

4, 5 pass, respectively, are formed. These support holes take up a large part of the space of the second end wall 12, since the exhaust gas treatment elements are arranged as compactly as possible in the tank 1. The exhaust gas passing holes 120 are formed at a large area between the support holes as much as possible, and as three exhaust gas passing holes 120 are schematically shown in fig. 9, each exhaust gas passing hole 120 should be shaped and sized to fit in a position left for its usable area. It will be appreciated that other forms and numbers of exhaust gas pass-through holes may be formed in the second end wall 12, such as a set of circular, square, elongated exhaust gas pass-through holes evenly distributed around the outer periphery of the selective catalytic

reduction support holes

42a, 52a, respectively. The total flow area of the exhaust gas through holes should be large enough to minimize the pressure drop that occurs when the exhaust gas flows through them.

Through these exhaust gas through holes 120 in the second end wall 12, communication is established between the interior space of the second enclosure 7 and the space surrounding the exhaust gas treatment elements in the casing 1, and thus between the outlet ends 42, 52 of the selective

catalytic reducers

4, 5 and the exhaust gas outlet 14.

The exhaust gas aftertreatment box according to various embodiments of the present application forms an exhaust gas flow path, and exhaust gas enters from the exhaust gas inlet 23, flows through the oxidation catalyst 2, the reducing agent mixer 3, the selective

catalytic reduction devices

4 and 5, the space surrounding each exhaust gas treatment element in the box body 1 in sequence, and is finally discharged from the exhaust gas outlet 14.

The operation of the off-gas aftertreatment tank shown in figures 1 to 6 is described below. The flow of the exhaust gas is indicated by arrows in the figure.

First, the exhaust gas discharged from the engine flows into the oxidation catalyst 2 through the exhaust gas inlet 23, as indicated by an arrow F1 in fig. 1 and 5. Next, referring to fig. 5, the exhaust gas flows generally in a first axial direction in the oxidation catalyst 2, thereby being subjected to the treatment of the oxidation catalyst stage 25 and the particulate trap stage 26, respectively. The exhaust gases then enter the first portion 61 of the first hood 6 via the outlet end 22 of the oxidation catalyst 2 and flow towards the second portion 62 of the first hood 6. The exhaust gas then passes from the second portion 62 into the reductant mixer 3.

In the reducing agent mixer 3, it first enters the conical section 31 and flows in a converging manner in the conical section 31 in the direction of the cylindrical section 32. At the same time, the reducing agent injector 9 ejects the reducing agent toward the swirl guide 35. The reducing agent first enters the conical section 31 and mixes with the exhaust gas and moves axially toward the swirl guide 35. The reductant impinges on the

vanes

352, 353 of the swirl guide 35 and is deflected by each vane. The exhaust gas is also deflected and guided by the vanes. In this way, a swirling flow of the mixture of reductant and exhaust gas (which may also be referred to as exhaust gas mixed with reductant) is formed in the cylindrical section 32, i.e. the mixture of reductant and exhaust gas spins and moves towards the outlet end 34 of the reductant mixer 3. In general, the mixture of reductant and exhaust gas flows in the reductant mixer 3 in a second axial direction, opposite to the first axial direction.

When flowing through the reducing agent mixer 3, the reducing agent evaporates under the effect of the high temperature of the exhaust gas when it mixes in the exhaust gas. The reductant impinges on the

fins

352, 353 of the swirl guide 35 so that the reductant is further mixed in the exhaust gas and atomized and evaporated. The reductant is then thoroughly mixed into the exhaust gas and thoroughly vaporized as it flows through the cylindrical section 32 in a swirling flow.

The mixture of reducing agent and exhaust gas flows in a swirling flow through the outlet end 34 of the reducing agent mixer 3 into the first portion 81 of the third enclosure 8. As shown in fig. 4, due to the intercepting action of the circle segment shaped exposed portion of the outlet end 34, the mixture of the reducing agent and the exhaust gas does not immediately flow to the second portion 82 and the third portion 83 of the third enclosure 8, but continues to rotate in the first portion 81 and then flows around the circle segment shaped exposed portion of the outlet end 34 to the second portion 82 and the third portion 83. The mixture of reductant and exhaust gas then flows from the second and

third portions

82, 83 into the selective

catalytic reducers

4, 5 through the

inlet ports

41, 51. The swirling flow of the mixture of reductant and exhaust gas in the third enclosure 8 further promotes mixing of the reductant in the exhaust gas. Furthermore, optionally, the outer contour of the third hood part 8 is shaped such that the mixture of reducing agent and exhaust gas is guided into the selective

catalytic reduction devices

4, 5 in a homogeneously distributed manner while the reducing agent and exhaust gas are mixed further.

As shown in fig. 6, the mixture of reductant and exhaust gas flows in the selective

catalytic reducer

4, 5 in a first axial direction. In the selective

catalytic reducers

4, 5, the exhaust gas undergoes a selective catalytic reduction reaction with the reducing agent, and nitrogen oxides are converted into nitrogen and other non-toxic components (e.g., water). The treated exhaust gas flows from the

outlet end

42, 52 of the selective

catalytic reducer

4, 5 into the second housing 7.

The exhaust gases then flow through the exhaust gas through holes 120 in the second end wall 12 into the space surrounding the exhaust gas treatment elements in the housing 1, as indicated by the "x" in fig. 7, in order to maintain the performance of the exhaust gas treatment elements, in particular of the catalyst, by maintaining the outer periphery of these exhaust gas treatment elements at a higher temperature and at a temperature which is maintained with respect to the external environment, by virtue of the temperature of the treated exhaust gases. The treated tail gas is then discharged through the tail gas outlet 14 into a downstream tail gas duct section, as indicated by arrow F2 in fig. 2.

In the case where the exhaust gas outlet 14 is provided on the peripheral wall 13 at a portion close to the oxidation catalyst 2 as shown in the drawing, the exhaust gas flowing into the case 1 first flows axially along the outer peripheries of the selective

catalytic reducers

4, 5, then flows laterally toward the reducing agent mixer 3 and the oxidation catalyst 2, and flows toward the exhaust gas outlet 14 over the outer peripheries of the reducing agent mixer 3 and the oxidation catalyst 2. Therefore, the treated exhaust can surround each exhaust treatment element more uniformly, so that each exhaust treatment element can be insulated uniformly.

According to a possible embodiment of the present application, not shown, the outlet ends 42, 52 of the selective

catalytic reducers

4, 5 do not pass through the second end wall 12, but are supported in the inner space of the tank 1, for example by a support structure provided on the inner side of the second end wall 12, the outlet ends 42, 52 of the selective

catalytic reducers

4, 5 opening directly into the inner space of the tank 1. Thus, the second cover body 7 is not necessary, and the selective catalytic reduction device support holes and the exhaust gas through holes do not have to be formed in the second end wall 12. The treated exhaust gas discharged from the outlet ends 42, 52 of the selective

catalytic reducers

4, 5 flows directly around the respective exhaust gas treatment elements in the casing 1 and is discharged through the exhaust gas outlet 14 provided on the peripheral wall 13. The embodiment can also realize the function of insulating each tail gas treatment element by using the treated tail gas. Other aspects of this embodiment are the same as or similar to the embodiment shown in fig. 1-6, and will not be repeated here,

it will be appreciated by those skilled in the art that changes could be made to the embodiments described above in accordance with the basic principles of the application.

For example, in the previously described example, the housing is formed from first and second end walls and a peripheral wall, however, the housing could have a variety of other possible configurations so long as it is capable of supporting the exhaust gas treatment elements such that the subject matter of the exhaust gas treatment elements is located within the housing. The tail gas outlet can be arranged on any suitable part of the box body and is opened in the inner space of the box body.

In the example described above, two selective

catalytic reducers

4, 5 are provided, however, a single selective catalytic reducer may be provided or more than two selective catalytic reducers connected in parallel with each other may be provided as long as they are arranged substantially in parallel with the oxidation catalyst 2 and the reducing agent mixer 3, according to the actual need.

It is noted that a single selective catalytic reducer may be sufficient for an exhaust aftertreatment tank requiring less exhaust gas treatment capacity. For the exhaust gas after-treatment tank with larger required exhaust gas treatment capacity, it is more desirable to use a plurality of selective catalytic reducers connected in parallel with each other, which is advantageous to reduce the back pressure of the whole exhaust gas after-treatment tank. For the scheme of arranging a plurality of selective catalytic reducers, the shape and size (especially, the radial size) of each of them can be optimally designed according to the condition of the internal space of the box body.

Furthermore, in the previously described examples, the exhaust gas treatment elements are arranged parallel to each other, however, the concept of insulating the exhaust gas treatment elements with the treated exhaust gas of the present application is equally applicable to cases where some or even all of the exhaust gas treatment elements in the exhaust gas aftertreatment tank are not arranged parallel to each other.

Furthermore, in the examples described above, the particle trap is integrated in the oxidation catalyst, but alternatively or additionally, it is also possible to integrate the particle trap in each selective catalytic reduction device as required.

Modifications to other aspects of the exhaust aftertreatment tank of the present application are also contemplated.

According to the present application, the exhaust gas treated by the exhaust gas aftertreatment tank flows inside the exhaust gas aftertreatment tank so as to maintain the temperature of each exhaust gas treatment element in the exhaust gas aftertreatment tank, so that each exhaust gas treatment element, in particular, the catalyst, can be operated with as high a performance as possible, even when the engine is operated in a low power condition. Therefore, the exhaust after-treatment box can more efficiently convert harmful substances in the exhaust into harmless substances, and can more easily meet the requirement of high-grade exhaust emission.

In addition, because of the heat preservation function provided by the treated tail gas, the heat insulation material can be eliminated from the tail gas post-treatment box, and the consumption of the heat insulation material is at least reduced. Therefore, the cost of the exhaust gas aftertreatment tank can be reduced.

In addition, when the reducing agent mixer, the oxidation catalyst, and the selective catalytic reduction in the exhaust gas aftertreatment tank are arranged substantially parallel to each other, a compact exhaust gas aftertreatment tank can be produced, so that the entire exhaust gas aftertreatment tank has a small size, thereby being easily installed on both sides of the entire vehicle chassis. In addition, through the parallel layout and the action of the rotational flow guide piece in the reducing agent mixer, the reducing agent is fully mixed in the tail gas, the mixing uniformity of the reducing agent in the tail gas is improved, the conversion rate of nitrogen oxides is improved, and the exhaust gas easily meets the requirements of higher tail gas emission standards. Simultaneously, make the tail gas aftertreatment case of this application be particularly suitable for being arranged in with heavy-duty diesel vehicle.

Although the present application has been described herein with reference to particular embodiments, the scope of the present application is not intended to be limited to the details shown. Various modifications may be made to these details without departing from the underlying principles of the application.

Claims

1. An exhaust aftertreatment kit for treating engine exhaust, comprising:

a box body (1);

an oxidation catalyst (2), a reductant mixer (3) and a selective catalytic reducer (4, 5) through which the exhaust gas flows in sequence, each end of which is carried by a first end wall (11) and a second end wall (12) of the housing (1) respectively and the body of which is located in an interior space between the first end wall (11) and the second end wall (12), an outlet end (42, 52) of the selective catalytic reducer (4, 5) being arranged to communicate with the interior space of the housing (1) such that treated exhaust gas discharged from the selective catalytic reducer (4, 5) enters the interior space around the oxidation catalyst (2), the reductant mixer (3) and the outer periphery of the selective catalytic reducer (4, 5) so as to utilize heat of the treated exhaust gas in the interior space for the oxidation catalyst (2), the reductant mixer (3) and the selective catalytic reducer (4), 5) providing a heat preservation effect;

a reductant injector (9) arranged to inject reductant into the reductant mixer (3); and

and the tail gas outlet (14) is arranged on the box body (1) and is opened in the inner space of the box body (1), so that the treated tail gas entering the inner space of the box body (1) is discharged out of the tail gas post-treatment box through the tail gas outlet (14).

2. The exhaust gas aftertreatment box of claim 1, wherein the outlet ends (42, 52) of the selective catalytic reducers (4, 5) open into an inner space of the hood (7) fixed outside the box (1), and a portion of the box (1) facing the hood (7) is formed with exhaust gas through holes (120) establishing communication between the inner space of the hood (7) and the inner space of the box (1).

3. The exhaust gas aftertreatment tank of claim 2, wherein the tank body (1) further comprises a peripheral wall (13) extending along peripheries of the first end wall (11) and the second end wall (12), the outlet ends (42, 52) of the selective catalytic reducers (4, 5) are open to the inner space of the enclosure (7) through selective catalytic reducer support holes (42a, 52a) formed in the second end wall (12), and the exhaust gas through holes (120) are formed at a portion of the second end wall (12) facing the enclosure (7).

4. The exhaust gas aftertreatment tank according to claim 3, wherein the second end wall (12) further has an oxidation catalyst support hole (22a) and a reductant mixer support hole (33a) formed therein, the exhaust gas through hole (120) being formed in a region between the selective catalytic reduction support hole (42a, 52a) and the oxidation catalyst support hole (22a) and reductant mixer support hole (33 a).

5. The exhaust aftertreatment tank of claim 4, wherein a plurality of exhaust through holes (120) are formed.

6. The exhaust gas aftertreatment tank of claim 3, wherein the exhaust gas through holes (120) are a set of exhaust gas through holes (120) formed around the outer circumference of the selective catalytic reducer support holes (42a, 52 a).

7. The exhaust gas aftertreatment tank of any one of claims 1 to 6, wherein the exhaust gas outlet (14) is arranged on the tank body (1) in a region close to the oxidation catalyst (2).

8. The exhaust gas aftertreatment tank of any one of claims 3 to 6, wherein the exhaust gas outlet (14) is provided on the peripheral wall (13).

9. Exhaust gas aftertreatment tank according to claim 8, wherein the exhaust gas outlet (14) is arranged on the circumferential wall (13) at a location close to the oxidation catalyst (2).

10. The exhaust gas aftertreatment box of claim 1, wherein the outlet end (42, 52) of the selective catalytic reducer (4, 5) opens into the interior space of the box (1).

11. The exhaust aftertreatment tank of any one of claims 1 to 6, wherein the exhaust gas outlet (14) is disposed axially away from an outlet end (42, 52) of the selective catalytic reducer (4, 5).

12. The exhaust aftertreatment tank of any one of claims 1 to 6, wherein the selective catalytic reducer comprises a plurality of selective catalytic reducers in parallel with each other.

13. The exhaust aftertreatment tank of any of claims 1 to 6, wherein the oxidation catalyst (2), reductant mixer (3) and selective catalytic reducer (4, 5) are arranged substantially parallel to each other.

14. The exhaust aftertreatment tank of any of claims 1 to 6, wherein a particulate trap is integrated in the oxidation catalyst (2).

15. The exhaust aftertreatment tank of any one of claims 1 to 6, wherein a swirl guide (35) is arranged in the reductant mixer (3), the swirl guide being configured to generate a swirl of the mixture of reductant and exhaust gas in the reductant mixer.