JP2020023953A - Exhaust emission control device - Google Patents

Abstract

To provide an exhaust emission control device which can evenly mix a reductant into exhaust emission, and can suppress a pressure loss.SOLUTION: In this exhaust emission control device 1 having a selective catalyst reduction device SCR which is arranged in an exhaust flow passage S in which exhaust emission from an internal combustion engine ENG flows, and a nozzle N arranged at an upstream side rather than the selective catalyst reduction device SCR, and injecting a reductant to the exhaust flow passage S, the exhaust emission control device 1 comprises an evaporation plate 20 which is arranged so as to block an injection path D of the reductant as a whole, and the evaporation plate 20 is arranged so that a front side face 20t and a back side face 20b which are exposed to the exhaust flow passage S are flat, and the front side face 20t and the back side face 20b become parallel with a flow direction SS of exhaust emission which flows in the exhaust flow passage S.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exhaust gas purification device.

Conventionally, a urea SCR (Selective Catalytic Reduction) system has been known as an exhaust gas purification device in an internal combustion engine such as a diesel engine. The urea SCR system includes an injector that injects urea water serving as a reducing agent into an exhaust passage, and a reduction catalyst provided in the exhaust passage downstream of the injector.
In a conventional urea SCR system, when urea water is injected into exhaust gas by an injector, the injected urea water undergoes a reaction of thermal decomposition and hydrolysis to produce ammonia (NH3). Nitrogen oxides (NOx) in the exhaust gas are reduced to nitrogen (N2) and water (H2O) in the reduction catalyst by the generated ammonia. In this way, the conventional exhaust gas purification device purifies the exhaust gas by selectively reducing nitrogen oxides in the exhaust gas, thereby rendering the exhaust gas harmless.

  In addition, conventionally, there is an exhaust gas purification device provided with an injection device that injects a reducing agent in an exhaust passage upstream of a catalyst (for example, see Patent Document 1).

JP 2014-100628 A

However, for example, in an exhaust gas purification device as disclosed in Patent Document 1, a guide member that branches the flow of a reducing agent is disposed in an exhaust passage in order to suppress the uneven distribution of the reducing agent in the exhaust gas. Since the guide member serves as a resistance to the flow of exhaust gas, the pressure loss increases, which is not preferable.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust gas purification apparatus that can uniformly mix a reducing agent in exhaust gas and suppress pressure loss.

In order to achieve the above object, the following configuration is grasped.
(1) An exhaust gas purification apparatus of the present invention includes a selective catalytic reduction device disposed in an exhaust flow path through which exhaust gas from an internal combustion engine flows, and a reducing agent disposed upstream of the selective catalytic reduction device and flowing through the exhaust flow path. And a nozzle that ejects the exhaust gas, wherein the exhaust gas purification device includes an evaporator plate that is disposed so as to block all the ejection paths of the reducing agent, and the evaporator plate is exposed to the exhaust passage. The front side surface and the back side surface are flat, and the front side surface and the back side surface are arranged so as to be parallel to the flow direction of the exhaust gas flowing through the exhaust passage.
(2) In the configuration of (1), the evaporating plate is curved so as to be convex in a direction away from the nozzle.
(3) In the configuration of the above (1) or (2), the evaporating plate includes a first evaporating plate having a short distance to the nozzle, and a second evaporating plate having a distance to the nozzle longer than the first evaporating plate. , A third evaporating plate.
(4) In the configuration of (3), the upstream end of the second evaporator plate in the flow direction of the exhaust gas is downstream of the upstream end of the first evaporator plate in the flow direction of the exhaust gas. It is located in.
(5) In the configuration of (3) or (4), the first evaporating plate has a passage hole through which the ejected reducing agent passes.
(6) In the configuration of (5), the passage hole is a long hole along the flow direction.
(7) In any one of the constitutions (1) to (6), a control blade for diffusing the exhaust gas is provided between the evaporating plate and the selective catalytic reduction device.
(8) In the configuration of the above (7), the control blade includes a diffusion blade having a flat surface obliquely intersecting with the flow direction, a rectifying blade having a flat surface parallel to the flow direction, Having.
(9) In the configuration of the above (7) or (8), the control blade is constituted by a plurality of separate blade pieces, and is adjacent to the center of the exhaust passage when viewed in the flow direction. It is arranged in the exhaust passage so as to have an opening between the blade pieces.
(10) In the configuration of the above (9), the blade piece has an arc-shaped tip at the center side of the exhaust passage when viewed in the flow direction.
(11) In the configuration of the above (9) or (10), the number of the blade pieces is different from the number of the evaporating plates.

  Advantageous Effects of Invention According to the present invention, it is possible to provide an exhaust gas purification device that can uniformly mix a reducing agent in exhaust gas and suppress pressure loss.

It is a schematic diagram of an exhaust gas purification device according to an embodiment. FIG. 2 is a sectional view taken along the arrow A in FIG. 1. FIG. 2 is a sectional view taken along the arrow B in FIG. 1. It is the perspective view of the evaporating plate seen from the upper stream side. It is the perspective view of the control blade seen from the upper stream side. FIG. 2 is a sectional view taken along the arrow C in FIG. 1. FIG. 2 is a sectional view taken along the arrow D in FIG. 1.

(Embodiment)
Hereinafter, embodiments for implementing the present invention (hereinafter, embodiments) will be described in detail with reference to the drawings. Note that the same reference numerals are given to the same elements throughout the description of the embodiments. In the following, unless otherwise specified, the internal combustion engine side is referred to as upstream or upstream side, and the opposite side (outside air side) is referred to as downstream or downstream side based on the flow direction of exhaust gas.

  FIG. 1 is a schematic diagram of an exhaust gas purification device 1 according to the embodiment. FIG. 2 is a cross-sectional view taken along the arrow A in FIG. FIG. 3 is a cross-sectional view taken along the arrow B in FIG. In FIG. 1, the illustration of an upstream container that accommodates the oxidation catalyst DOC and the diesel particulate filter DPF and that forms the exhaust passage S inside is omitted. The white arrows in FIG. 1 indicate the flow direction of the exhaust gas.

  The exhaust gas purification device 1 according to the embodiment is a device that purifies exhaust gas discharged from an internal combustion engine ENG such as a diesel engine, and is provided between the internal combustion engine ENG and the outside air in the middle of the flow of exhaust gas. The exhaust gas purifying device 1 uses, for example, urea water (aqueous urea solution) as a reducing agent (a source that actually produces ammonia NH3 that performs a reducing action) to reduce nitrogen in exhaust gas discharged from the internal combustion engine ENG. This is a selective catalytic reduction (SCR) type purification device that selectively reduces oxide NOx.

  As shown in FIG. 1, the exhaust gas purification device 1 has an exhaust passage S formed inside an airtight tubular casing 60 and a container K. The cross section of the exhaust passage S is circular in order to suppress pressure loss as much as possible. The upstream side and the downstream side of the casing 60 are appropriately connected to a container K forming an exhaust passage S inside.

  Specifically, the exhaust purification device 1 includes an oxidation catalyst (Diesel Oxidation Catalyst) DOC (not shown) and diesel particulates in an exhaust passage S formed inside a container (not shown) upstream of the casing 60. And a collection filter (Diesel Particulate Filter) DPF (not shown), and a selective catalyst reduction in which a reduction catalyst is carried in an exhaust passage S formed inside a container K downstream of the casing 60. A device (Selective Catalytic Reduction) SCR is provided. The exhaust gas purification device 1 is appropriately disposed downstream of the selective catalyst reduction device SCR in the exhaust flow path S formed inside the container K on the downstream side to prevent ammonia NH3 from passing through and being released into the outside air. An ammonia slip catalyst ASC, which is an oxidation catalyst for the oxidation, is provided.

  The oxidation catalyst DOC is for oxidizing and purifying hydrocarbon HC and carbon monoxide CO, which are one of the harmful components in the exhaust gas, and forms the hydrocarbon HC and carbon monoxide CO on a ceramic honeycomb or a metal mesh. It supports a catalyst component such as platinum or palladium that promotes the oxidation reaction.

  The diesel particulate filter DPF is a filter that traps particulate matter in exhaust gas.

  The selective catalytic reduction device SCR is a device in which a zeolite-based, vanadium oxide-based, tungsten oxide-based, or other catalyst is supported on a porous ceramic substrate such as cordierite.

  The exhaust gas purification device 1 includes a mixer 100 that is arranged upstream of the selective catalyst reduction device SCR carrying a reduction catalyst and mixes a reducing agent into exhaust gas from the internal combustion engine ENG.

  Here, the mixer 100 includes an injector 10 for adding a reducing agent to an exhaust flow path S from the internal combustion engine ENG, an evaporator 20 disposed downstream of the injector 10, and a control blade disposed downstream of the evaporator 20. 30. A nozzle N for ejecting the supplied reducing agent is attached to the injector 10.

Then, in the exhaust gas purification device 1, when the reducing agent (urea water) is ejected from the nozzle N into the exhaust gas flowing through the exhaust passage S, the ejected reducing agent (urea water) reacts by thermal decomposition and hydrolysis. Thus, ammonia NH3 is generated. The ejection path of the reducing agent ejected from the nozzle N has a substantially conical shape with the tip of the nozzle N as an apex. Then, by the generated ammonia NH3, the nitrogen oxide NOx in the exhaust gas is reduced to nitrogen N2 and water H2O in the selective catalytic reduction device SCR. The reduced nitrogen N2 and water H2O are released into the outside air.
In this way, the exhaust gas purification device 1 purifies the exhaust gas by selectively reducing the nitrogen oxides NOx, thereby rendering the exhaust gas harmless.

Here, the exhaust gas purification device 1 includes an evaporating plate 20 that is arranged so as to block the entire ejection path D of the reducing agent. That is, since the evaporating plate 20 overlaps the substantially conical portion serving as the reducing agent ejection path D, most of the ejected reducing agent collides with the evaporating plate 20.
This allows the ejected reducing agent to reliably collide with the evaporating plate 20, so that the particle size of the reducing agent (aqueous urea) can be reduced by the collision, and the reduced reducing agent diffuses into the exhaust gas. Thus, the reducing agent can be prevented from directly adhering to the inner wall of the casing 60. Further, since the evaporating plate 20 is provided in the exhaust passage S and is easily heated by the heat of the exhaust gas and can maintain a high temperature, the reducing agent can be easily hydrolyzed and thermally decomposed to generate ammonia NH3.

Further, as shown in FIG. 3, the evaporating plate 20 has a flat front surface (upper surface) 20t and a rear surface (lower surface) 20b exposed to the exhaust flow path S, and a front surface 20t and a rear side surface 20b formed in the exhaust flow path S. It is arranged so as to be parallel to the flow direction (direction connecting the cross-sectional center of the exhaust passage S) SS of the exhaust gas flowing through S.
As described above, since the evaporating plate 20 is arranged parallel to the exhaust gas flow direction SS, the resistance is minimized, and the pressure loss can be suppressed.
Next, each unit constituting the mixer 100 will be described in order.

(Injector 10)
First, the injector 10 will be described with reference to FIGS.
As shown in FIGS. 1 to 3, the injector 10 has, at one end, a nozzle attachment portion 11 to which a nozzle N for ejecting a reducing agent is attached. At the periphery of the nozzle mounting portion 11, three mounting holes 13 are provided. In addition, the injector 10 has a guide hole 10a at a substantially center of the nozzle attachment portion 11 as a path for the reducing agent ejected from the nozzle N. Usually, the nozzle N is arranged such that the tip is located at the center of the guide hole 10a. The injector 10 has a casing connection portion 14 formed to match the shape of the opening 60a provided in the casing 60 so as to cover the space from the guide hole 10a to the opening 60a provided in the casing 60. are doing.
Since the injector 10 has such a structure, the injector 10 can be directly connected to the outer peripheral surface of the casing 60 as a module.

(Evaporation plate 20)
Next, the evaporating plate 20 will be described in detail with reference to FIGS.
FIG. 4 is a perspective view of the evaporating plate 20 viewed from the upper side on the upstream side.
As shown in FIG. 3, the evaporating plate 20 is arranged so as to completely block the ejection path D of the reducing agent. This allows the reducing agent ejected into the exhaust passage S to collide with the high temperature evaporating plate 20 without adhering to the inner wall of the casing 60 without leaking, thereby increasing the production amount of ammonia NH3. be able to.

  Further, as shown in FIGS. 2 and 3, the evaporating plate 20 has a flat front surface 20 t (upper surface) and a rear surface 20 b (lower surface) exposed to the exhaust passage S, and has a flat front surface 20 t and a rear surface 20 b. It is arranged so as to be parallel to the flow direction SS of the exhaust gas flowing through the exhaust passage S. Thereby, the projected area of the evaporating plate 20 viewed from the exhaust flow direction SS can be minimized only by the plate thickness, and the pressure loss can be suppressed. Note that the upstream end of the evaporating plate 20 may have a sharp edge. Thereby, the pressure loss in the exhaust passage S can be further suppressed, and heat can be easily transferred from the exhaust to the evaporating plate 20.

As shown in FIG. 3, the evaporating plate 20 includes a first evaporating plate 21 whose distance d1 to the nozzle N is short, a second evaporating plate 22 whose distance d2 to the nozzle N is longer than the distance d1, and a third evaporating plate 23. And Thus, a part of the ejected reducing agent is first blocked by the first evaporating plate 21, and a part of the reducing agent not blocked by the first evaporating plate 21 is blocked by the second evaporating plate 22, However, the remaining reducing agent not blocked by the second evaporation plate 22 can be blocked by the third evaporation plate 23. Further, the evaporating plate 20 includes a first evaporating plate 21 whose distance d1 to the nozzle N is short, a second evaporating plate 22 whose distance d2 to the nozzle N is longer than the distance d1, and a distance d3 to the nozzle N which is equal to the distance d1. And a third evaporating plate 23 longer than the distance d2. In FIG. 3, the third evaporating plate 23 is disposed at a position where the distance d3 to the nozzle N is longer than the distance d2. It may be arranged at a position shorter than the distance d2.
The upstream end of the second evaporator plate 22 in the exhaust flow direction SS is located downstream of the upstream end of the first evaporator plate 21 in the exhaust flow direction SS. Thus, a part of the ejected reducing agent is first blocked by the first evaporating plate 21, and a part of the reducing agent not blocked by the first evaporating plate 21 is blocked by the second evaporating plate 22, However, the remaining reducing agent not blocked by the second evaporation plate 22 can be blocked by the third evaporation plate 23. Therefore, the evaporating plate 20 can evenly block the ejection path D of the reducing agent by the first evaporating plate 21, the second evaporating plate 22, and the third evaporating plate 23. Therefore, ammonia NH3 can be efficiently generated from the reducing agent ejected from the nozzle N.

  The first evaporating plate 21 is arranged so as to block an upper region of the reducing agent ejected from the nozzle N and to impinge on approximately １ ／ of the amount of the reducing agent ejected from the nozzle N. Similarly, the second evaporating plate 22 blocks the middle area of the reducing agent ejected from the nozzle N, and is arranged so that approximately ３ of the amount of the reducing agent ejected from the nozzle N collides. . Similarly, the third evaporating plate 23 blocks the area of the lower layer of the reducing agent ejected from the nozzle N, and is arranged so that approximately ３ of the amount of the reducing agent ejected from the nozzle N collides. . Thus, the evaporating plate 20 allows the reducing agent ejected from the nozzle N to uniformly collide with the first evaporating plate 21, the second evaporating plate 22, and the third evaporating plate 23. Therefore, ammonia NH3 can be efficiently generated from the reducing agent ejected from the nozzle N.

  Since the three evaporating plates 20 are formed in this way, the area where the reducing agent is ejected is located above the first evaporating plate 21 and above the second evaporating plate 22 as compared with the case where one or two evaporating plates are used. And at least three above the third evaporation plate 23. Accordingly, since the evaporating plates 20 corresponding to the respective regions are allocated, the reducing agent ejected from the nozzle N can be blocked while the heat capacity of each evaporating plate 20 is reduced, and the evaporating plate 20 is heated by the exhaust gas. Can be maintained at a high temperature. Further, since the temperature of the evaporating plate 20 can be maintained at a high temperature, the reducing agent in each region can be made finer and evaporate at the same time, thereby promoting hydrolysis and thermal decomposition, and increasing the production amount of ammonia NH3. . Therefore, the efficiency of uniformly mixing ammonia NH3 in exhaust gas can be increased.

The first evaporator plate 21, the second evaporator plate 22, and the third evaporator plate 23 are formed of a flat material. Specifically, the first evaporating plate 21, the second evaporating plate 22, and the third evaporating plate 23 are bent at both ends when viewed in the exhaust gas flow direction SS, and the both ends are welded to the inner wall of the casing 60. Is a fixed portion V. Further, the first evaporating plate 21, the second evaporating plate 22, and the third evaporating plate 23 are formed by bending so as to be curved around the exhaust flow direction SS.
The first evaporating plate 21 and the second evaporating plate 22 may be integrated into a unit in a state where the fixing portions V of the first and second evaporating plates are fitted to each other. Thus, in a state where the arrangement relationship between the first evaporator plate 21 and the second evaporator plate 22 is maintained with high accuracy, the casing is maintained while maintaining the distance from the nozzle N of the first evaporator plate 21 and the second evaporator plate 22 with high accuracy. 60, and the assembly work can be made more efficient while maintaining high accuracy.

  In addition, since the first evaporating plate 21, the second evaporating plate 22, and the third evaporating plate 23 constituting the evaporating plate 20 are arranged in this order so as to be separated from the nozzle N, they are ejected from the nozzle N in a conical shape. The reduced agent can reliably collide without leakage.

  The dimension e3 of the third evaporator plate 23 in the exhaust flow direction SS is longer than the dimension e1 of the first evaporator plate 21 in the exhaust flow direction SS and the dimension e2 of the second evaporator plate 22 in the exhaust flow direction SS. . Further, in plan view (when viewed from above in FIGS. 2 and 3), the plane size of the third evaporator plate 23 may be larger than the plane size of the first evaporator plate 21 and the second evaporator plate 22. . This reliably blocks the ejected reducing agent in a region that is not blocked by the first evaporator plate 21 or the second evaporator plate 22, and is located above the third evaporator plate 23 (the second evaporator plate 22 and the third evaporator plate 23). And the reducing agent can flow downstream together with the exhaust gas without adhering the reducing agent to the inner wall of the casing 60 (particularly, the lower portion of the inner wall).

  Further, as shown in FIGS. 2 and 4, the evaporating plate 20 is curved so as to be convex in a direction away from the nozzle N. This makes it possible to increase the area in contact with the ejected reducing agent as compared with the evaporating plate 20 having a straight cross section as viewed in the exhaust gas flow direction SS. The chances of contact are increased, and ammonia NH3 can be efficiently generated from the reducing agent in a short time.

  As shown in FIG. 2, the first evaporating plate 21, the second evaporating plate 22, and the third evaporating plate 23 have a larger width b1, a width b2, and a width b3 in this order. Further, the first evaporator plate 21, the second evaporator plate 22, and the third evaporator plate 23 are arranged such that the vertical distance between them is substantially equal. The degree of curvature of each of the first evaporator plate 21, the second evaporator plate 22, and the third evaporator plate 23 (the degree of curvature of the arc when curved in an arc shape) is determined by the first evaporator plate 21. It is largest and becomes smaller in the order of the second evaporator plate 22 and the third evaporator plate 23.

  As shown in FIG. 4, the first evaporating plate 21 has a passage hole 21a through which the ejected reducing agent passes. The shape, size, number and combination of the passage holes 21a can be appropriately set according to the balance between the reducing agent colliding with the first evaporating plate 21 and the reducing agent colliding with the second evaporating plate 21. Since the area of the passage hole 21a is relatively large in contact with the exhaust gas, the temperature of the exhaust hole 21a tends to be high due to the heat of the exhaust gas. The passage hole 21 a allows a portion of the reducing agent ejected from the nozzle N in a region blocked by the first evaporating plate 21 to be partially evaporated without touching the upper surface of the first evaporating plate 21. The reducing agent adhered to the upper surface of the first evaporating plate 21 can reach the lower surface of the first evaporating plate 21 or the upper surface of the second evaporating plate 22 through the passage hole 21a while being able to directly reach the plate 22. Can be. Therefore, the reducing agent can be prevented from staying on the upper surface of the first evaporating plate 21 for a long time, and the reducing agent can be reliably hydrolyzed and thermally decomposed by the heat of the portion of the passage hole 21a.

Here, the passage hole 21a may be a long hole along the exhaust gas flow direction SS. Three passage holes 21a may be arranged at equal intervals and symmetrically in the left-right direction when viewed in the exhaust gas flow direction SS. Accordingly, while suppressing an increase in pressure loss due to the formation of the passage hole 21a, the reducing agent propagating on the upper surface of the first evaporating plate 21 is moved through the passage hole 21a while moving in the exhaust flow direction SS. Can be.
The first evaporating plate 21 may have the passage holes 21a concentrated at the upstream end in the exhaust gas flow direction SS. In particular, it is preferable that the first evaporating plate 21 has the passage hole 21a arranged at a position overlapping the ejection path D of the reducing agent. Thereby, the reducing agent colliding with the first evaporating plate 21 and the reducing agent colliding with the second evaporating plate 21 can be easily balanced, and hydrolysis and thermal decomposition of the reducing agent are performed by the heat of the passage hole 21a. Can be promoted more.

(Control blade 30)
Next, the control blade 30 will be described in detail with reference to FIGS. 1 to 3 and FIGS. 5 to 7.
FIG. 5 is a perspective view of the control blade 30 as viewed from above on the upstream side. FIG. 6 is a sectional view taken along the arrow C in FIG. FIG. 7 is a sectional view taken along the arrow D in FIG.
As shown in FIGS. 1 and 3, the control blade 30 is disposed in the exhaust passage S between the evaporating plate 20 and the selective catalytic reduction device SCR. The control blade 30 diffuses the exhaust gas and the reducing agent from the upstream toward the selective catalytic reduction device SCR located downstream while mixing them uniformly.

  The control blade 30 is attached to the inner wall of the casing 60 by appropriate means such as welding. The size of the outer shape of the control blade 30, that is, the diameter of the exhaust passage S inside the casing 60 at the portion where the control blade 30 is attached is smaller than the diameter of the selective catalyst reduction device SCR.

  As shown in FIGS. 5 to 7, the control blade 30 includes a diffusion blade 31 having a flat surface 31s obliquely intersecting the exhaust flow direction SS, and a flat surface 32s parallel to the exhaust flow direction SS. And a rectifying blade 32 having The term “flat surface” as used herein means a surface having no undulation such as resistance to the flow of exhaust gas. Since the surface of the control blade 30 that is in contact with the flow is a flat surface, the resistance to the flow can be reduced and the pressure loss can be suppressed.

  The flat surface 31s of the diffusion blade 31 may be a flat surface or may be a curved surface along a spiral shape. By having the curved surface conforming to the spiral shape, the flow of exhaust gas can be smoothly changed from a straight line to a spiral shape.

  Then, when the exhaust gas flowing from the upstream strikes the flat surface 31s of the diffusion blade 31, the exhaust gas changes its direction along the flat surface 31s and flows downstream in a spiral. As described above, since the flat surface 31s obliquely intersects the flow direction SS of the exhaust gas, the reducing agent and the exhaust gas that have hit the flat surface 31s are changed in direction by the flat surface 31s and diffuse in a spiral shape. And flow. In addition, since the reducing agent in the exhaust collides with the diffusion blade 31, the reducing agent that has collided with the evaporating plate 20 can be further miniaturized, and the reduction efficiency can be increased.

  The angle at which the flat surface 31s of the diffusion blade 31 intersects with the exhaust flow direction SS is determined by the size of the flow path cross section of the exhaust flow path S downstream of the control blade 30 (selective catalytic reduction disposed in the downstream exhaust flow path S). The size is set according to the distribution of the exhaust gas flow (direction, flow velocity or pressure) downstream of the evaporating plate 20.

  When a plurality of diffusion blades 31 are provided as in the present embodiment, the angle at which the flat surface 31s of each diffusion blade 31 intersects the exhaust flow direction SS may be different. Thereby, the gas can be uniformly diffused over a wider area with respect to the flow path cross section of the exhaust flow path S downstream of the control blade 30.

  The flat surface 32s of the rectifying blade 32 may be a flat surface or a curved surface parallel to the exhaust gas flow direction SS.

  The exhaust gas flowing from the upstream is aligned by the flat surface 32s of the rectifying blade 32, and flows in a direction parallel to the flat surface 32s, that is, in a direction of the exhaust gas flow direction SS. As a result, it is possible to suppress the occurrence of turbulence when the exhaust goes to the downstream side. Then, the exhaust gas and the reducing agent are combined with the flow of the exhaust gas and the reducing agent intersecting with the flow direction SS of the exhaust gas, the directions of which are changed by the diffusion blades 31, to form a cross section of the exhaust flow channel S downstream of the control blade 30. On the other hand, it can spread uniformly over a wider area.

  In addition, the control blade 30 includes a plurality of separate first blade pieces 30A, second blade pieces 30B, third blade pieces 30C, and fourth blade pieces 30D. The blade pieces 30A to 30D are arranged at equal intervals (90-degree intervals) in the circumferential direction around the center of the cross section of the exhaust passage S with respect to the casing 60. Each of the blade pieces 30A to 30D has both a diffusion blade 31 and a rectifying blade 32. In the present embodiment, the control blade 30 is configured by the four blade pieces 30A to 30D, but is not limited thereto, and may be, for example, two or three blades.

  Each of the blade pieces 30A to 30D can be formed, for example, as follows. Diffusion blades 31 are formed by using approximately half of the plate-shaped material, and a cut Q is made in the other half from the periphery of the plate-shaped material. Next, the portions divided by the cuts Q are bent in opposite directions to the front side and the back side of the material, respectively. Then, one of the portions divided by the cut Q is used as a welding allowance W so that it can be welded to the inner wall of the casing 60, the rectifying vane 32 is formed from the other tip, and the other remaining portion is the same as the above. Used as the welding allowance W.

  Further, as shown in FIG. 6, the control blade 30 has an opening H that does not hinder the exhaust flow between the center of the exhaust flow path S and the adjacent blade pieces when viewed in the exhaust flow direction SS. It is arranged in the exhaust flow path S so as to have. Since the control blade 30 is arranged in this manner with the opening H, a part of the exhaust flowing from the upstream hits the flat surface 31 s of the diffusion blade 31 and changes its direction, and the other part has the central part of the exhaust passage S and the other part. Since the gas can flow downstream through the opening H between the adjacent blade pieces, the exhaust gas flowing downstream can be uniformly diffused while suppressing the pressure loss as much as possible.

  As shown in FIG. 6, each of the blade pieces 30 </ b> A to 30 </ b> D has an arc-shaped tip at the center of the exhaust passage S when viewed in the exhaust flow direction SS. This makes it possible to uniformly diffuse the exhaust gas flowing downstream while suppressing the pressure loss as much as possible.

  By the way, the number of each of the blade pieces 30A to 30D constituting the control blade 30 is different from the number of the evaporating plates 20. More specifically, in the present embodiment, the number of the evaporating plates 20 is three, whereas the number of the control blades 30 is four. Accordingly, even if the flow path is divided by the evaporating plate 20, the flow is further divided into a different number of flow paths by the control blade 30, so that the exhaust gas is uniformly distributed downstream without uneven distribution of the reducing agent in the exhaust gas. Can spread.

As described above, by the cooperation of the rectifying blade 32 and the diffusion blade 31, the exhaust gas and the reducing agent downstream of the evaporating plate 20 are rectified by the flat surface 32 s of the rectifying blade 32 and flow straight, and the flat surface of the diffusion blade 31. Spiral diffusion and flow by 31s. Thereby, a spiral flow can be formed in the exhaust flow path S downstream of the control blade 30 while suppressing the pressure loss, and the exhaust gas and the reducing agent can be uniformly diffused while being efficiently mixed.
According to such a control blade 30, the added reducing agent is miniaturized, the thermal decomposition and hydrolysis of the reducing agent are promoted, and the spiral flow in which the flow of the micronized reducing agent and the flow of the exhaust gas are combined. Can be generated, and can be uniformly diffused and mixed in the exhaust gas passing through the exhaust passage S. Further, since the pressure loss is small and the flow velocity can be maintained high, it is possible to suppress the reducing agent and the generated ammonia NH3 from adhering to or remaining on the control blade 30 and the inner wall of the casing 60. Therefore, the ammonia NH3 can reach the selective catalytic reduction device SCR disposed downstream of the control blade 30 in a state of being uniformly distributed in the cross section of the exhaust passage S. Therefore, the nitrogen oxides NOx in the exhaust gas can be efficiently reduced in a short flow distance, that is, in a limited narrow space.

(Operation of Exhaust Purification Device 1 Using Mixer 100)
The operation until exhaust gas is purified by the exhaust gas purification device 1 using the mixer 100 described above will be described along the flow of exhaust gas.

  As shown in FIG. 1, the exhaust gas containing the nitrogen oxides NOx discharged from the internal combustion engine ENG is guided to the exhaust gas purification device 1.

  Subsequently, the exhaust gas guided to the exhaust gas purification device 1 passes through the oxidation catalyst DOC arranged in the exhaust passage S. At this time, hydrocarbon HC and carbon monoxide CO, which are one of the harmful components in the exhaust gas, are oxidized and purified by the oxidation catalyst DOC.

  The exhaust gas having passed through the oxidation catalyst DOC passes through a diesel particulate filter DPF disposed in the exhaust passage S. At this time, the particulate matter in the exhaust gas is collected by the diesel particulate filter DPF.

  The exhaust gas that has passed through the diesel particulate filter DPF is guided to the mixer 100.

  The exhaust gas guided to the mixer 100 is located above the first evaporating plate 21, between the first evaporating plate 21 and the second evaporating plate 22, between the second evaporating plate 22 and the third evaporating plate 23, Each passes below the plate 23 to reach the control blade 30.

While the exhaust gas is flowing in this manner, the reducing agent (urea water) sprayed from the nozzle N attached to the nozzle attachment portion 11 of the mixer 100 first becomes the closest to the nozzle N at a distance closest to the nozzle N. The particles collide with a certain first evaporating plate 21 and become finer in particle diameter, evaporate, and the high temperature held by the first evaporating plate 21 promotes the thermal decomposition and hydrolysis reactions to produce ammonia NH3. .
A part of the ejected reducing agent passes through the passage hole 21a provided in the first evaporating plate 21, reaches the second evaporating plate 22, and generates ammonia NH3 by a reaction of thermal decomposition and hydrolysis. I do.

  Next, the part of the reducing agent ejected from the nozzle N and atomized, which is not blocked by the first evaporating plate 21, is the second evaporating agent which is located at a short distance from the nozzle N next to the first evaporating plate 21. The particles collide with the plate 22 and become finer in particle size, evaporate, and the high temperature held by the second evaporating plate 22 promotes the thermal decomposition and hydrolysis reactions to produce ammonia NH3.

  Lastly, the part of the reducing agent ejected from the nozzle N and atomized, which is not blocked by the first evaporating plate 21 or the second evaporating plate 22, is the third agent located farthest from the nozzle N. The particles collide with the evaporating plate 23 and become finer in particle diameter, evaporate, and the high temperature held by the third evaporating plate 23 promotes the thermal decomposition and hydrolysis reactions to generate ammonia NH3.

  The ammonia NH3 generated above each of the first evaporator plate 21, the second evaporator plate 22, and the third evaporator plate 23 merges with the exhaust gas and reaches the control blade 30 while mixing with each other.

  The mixed gas of the exhaust gas and the ammonia NH 3 arriving at the control blade 30 is divided into a laminar flow and a spiral flow by the diffusion blade 31 and the rectifying blade 32 constituting the control blade 30. Then, the mixed gas is uniformly mixed without the flow velocity being excessively reduced, and thus without excessively increasing the pressure loss, and is discharged toward the downstream where the selective catalytic reduction device SCR is disposed. As S expands, it spreads.

  The exhaust gas and the ammonia NH3 mixed and diffused through the control blade 30 reach the selective catalytic reduction device SCR.

  The nitrogen oxides NOx and ammonia NH3 in the exhaust gas that have reached the selective catalytic reduction device SCR are decomposed and decomposed into nitrogen N2 and water H2O by the action of the catalyst carried on the selective catalytic reduction device SCR.

  After passing through the selective catalytic reduction device SCR, the ammonia NH3 remaining in the exhaust gas having passed through the selective catalytic reduction device SCR is captured by the ammonia slip catalyst ASC disposed downstream of the selective catalytic reduction device SCR in the exhaust passage S. You. Then, the nitrogen N2 and the water H2O are appropriately released into the outside air.

  In this way, the exhaust gas purification device 1 efficiently purifies the nitrogen oxides NOx in the exhaust gas and makes the exhaust gas harmless. Further, the exhaust gas purification device 1 can uniformly mix the reducing agent in the exhaust gas and can suppress the pressure loss. Therefore, it is possible to provide the exhaust gas purification device 1 with high reduction efficiency, and as a result, it is possible to make the entire exhaust gas purification device 1 compact.

  As described above, the preferred embodiment of the present invention has been described in detail. However, the exhaust emission control device 1 according to the present invention is not limited to the above-described embodiment, but may fall within the scope of the present invention described in the appended claims. In the above, various modifications and changes are possible.

  According to the present invention, the exhaust gas purification device 1 includes a selective catalytic reduction device SCR disposed in an exhaust flow passage S through which exhaust gas from the internal combustion engine ENG flows, and an exhaust flow passage S disposed upstream of the selective catalytic reduction device SCR. And a nozzle N that ejects a reducing agent to the exhaust gas purifying apparatus 1, the evaporating plate 20 is disposed so as to block all the ejecting paths D of the reducing agent, and the evaporating plate 20 is exposed to the exhaust passage S. The front side surface 20t and the back side surface 20b are flat, and the front side surface 20t and the back side surface 20b are arranged so as to be parallel to the flow direction SS of the exhaust gas flowing through the exhaust flow channel S. The reducing agent ejected onto the inner wall of the casing 60 can be made to collide with the high temperature evaporating plate 20 without leaking without adhering to the inner wall of the casing 60. Therefore, the generation time (distance) of ammonia NH3 can be shortened, the reducing agent can be uniformly mixed in the exhaust gas, and the flow resistance can be minimized to suppress the pressure loss. Therefore, it is possible to provide the exhaust gas purification device 1 that can uniformly mix the reducing agent in the exhaust gas and suppress the pressure loss.

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification device 10 Injector 10a Guide hole 11 Nozzle attachment part 13 Attachment hole 14 Casing connection part 20 Evaporation plate 20b Back side surface 20t Front side surface 21 First evaporation plate 21a Passage hole 22 Second evaporation plate 23 Third evaporation plate 30 Control blade 30A First blade piece 30B Second blade piece 30C Third blade piece 30D Fourth blade piece 31 Diffusion blade 31s Flat surface 32 Rectifying blade 32s Flat surface 60 Casing 60a Opening 100 Mixer b1 Width b2 Width b3 Width d1 Distance d2 Distance d3 Distance e1 Dimension e2 Dimension e3 Dimension S Exhaust flow path SS Exhaust flow direction K Container ENG Internal combustion engine DOC Oxidation catalyst DPF Diesel particulate collection filter ASC Ammonia slip catalyst SCR Selective catalyst reduction device N Nozzle D Spout path Q Break V Fixed section W Welding allowance H Opening CO Carbon monoxide H2O Water HC Hydrocarbon N2 nitrogen NH3 ammonia NOx nitrogen oxide

Claims (11)

An exhaust purification device comprising: a selective catalyst reduction device disposed in an exhaust passage through which exhaust gas flows from an internal combustion engine; and a nozzle disposed upstream of the selective catalyst reduction device and ejecting a reducing agent to the exhaust passage. At
The exhaust gas purification device includes an evaporating plate disposed so as to block all the ejection paths of the reducing agent,
The evaporating plate has flat front and back surfaces exposed to the exhaust passage,
An exhaust gas purification apparatus, wherein the front side surface and the back side surface are arranged so as to be parallel to a flow direction of exhaust gas flowing through the exhaust passage. The exhaust gas purifying apparatus according to claim 1, wherein the evaporating plate is curved so as to be convex in a direction away from the nozzle. The evaporating plate includes a first evaporating plate having a shorter distance from the nozzle, a second evaporating plate having a longer distance from the nozzle than the first evaporating plate, and a third evaporating plate. The exhaust purification device according to claim 1 or 2. The upstream end of the second evaporator plate in the exhaust flow direction is located downstream of the upstream end of the first evaporator plate in the exhaust flow direction. Item 4. An exhaust gas purification device according to Item 3. The exhaust gas purification apparatus according to claim 3, wherein the first evaporation plate has a passage hole through which the ejected reducing agent passes. The exhaust gas purifying apparatus according to claim 5, wherein the passage hole is a long hole along the flow direction. The exhaust purification device according to any one of claims 1 to 6, further comprising a control blade that diffuses the exhaust gas between the evaporating plate and the selective catalyst reduction device. The method according to claim 7, wherein the control blade includes a diffusion blade having a flat surface obliquely intersecting with the flow direction, and a rectifying blade having a flat surface parallel to the flow direction. The exhaust gas purifying device according to the above. The control blade is formed of a plurality of separate blade pieces, and, when viewed in the flow direction, has an opening between the center of the exhaust passage and between the adjacent blade pieces, The exhaust gas purifying apparatus according to claim 7, wherein the exhaust gas purifying apparatus is disposed in the exhaust passage. 10. The exhaust gas purification apparatus according to claim 9, wherein the blade piece has an arc-shaped tip at the center of the exhaust flow path when viewed in the flow direction. The exhaust gas purification device according to claim 9, wherein the number of the blade pieces is different from the number of the evaporating plates.

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