JP5020028B2 - Exhaust purification device - Google Patents

Description

  The present invention relates to an exhaust purification device that purifies engine exhaust, and more particularly, to an exhaust purification device that includes an ammonia selective reduction type NOx catalyst that selectively reduces NOx in exhaust using ammonia generated from urea water as a reducing agent.

Exhaust gas discharged from an engine such as a diesel engine contains NOx (nitrogen oxide), which is one of the pollutants. In order to reduce this NOx and purify the exhaust gas, 2. Description of the Related Art There is known an exhaust emission control device that includes an ammonia selective reduction type NOx catalyst.
When an ammonia selective reduction type NOx catalyst is used in an exhaust purification device, in order to supply ammonia as a reducing agent to the ammonia selective reduction type NOx catalyst, urea water that is easier to handle than ammonia is supplied into the exhaust gas. Generally, urea water is injected into the exhaust gas using a urea water injection nozzle or the like. The atomized urea water supplied into the exhaust gas from the urea water injection nozzle is hydrolyzed by the heat of the exhaust gas, and the resulting ammonia is supplied to the ammonia selective reduction type NOx catalyst. The supplied ammonia is once adsorbed by the ammonia selective reduction type NOx catalyst, and the NOx reduction reaction between this ammonia and NOx in the exhaust is promoted by the NOx catalyst, whereby the NOx is reduced and the exhaust gas is purified.

  The urea water used for supplying such ammonia may cause clogging by solid urea crystals being deposited on a urea water injection nozzle or the like when water as a solvent evaporates. Therefore, in order to prevent the occurrence of such clogging, an exhaust is provided between the urea water injection nozzle and the wall of the exhaust passage so that the temperature of the urea water injection nozzle does not rise excessively. A purifying device is proposed in Japanese Patent Application Laid-Open No. H10-228707.

Further, in the exhaust gas purification device of Patent Document 1, a portion that is not easily affected by exhaust heat, such as a pipe for supplying urea water to the urea water injection nozzle, is overheated with an electric heater as necessary. The urea water injection nozzle is prevented from being clogged by promoting the melting of urea.
JP 2005-127318 A

  There are two types of urea water injection: an airless type that injects only urea water into the exhaust, and an air assist type that injects urea water together with compressed air. In addition to the urea water injection nozzle being easily cooled, the injected urea water is easily vaporized by the compressed air, so that the tip portion of the urea water injection nozzle is further easily cooled. If the temperature of the urea water injection nozzle drops excessively, urea water tends to adhere to the urea water injection nozzle, and the urea of the attached urea water will crystallize, causing clogging of the urea water injection nozzle. There's a problem. In particular, in the case of Patent Document 1, since the heat of the exhaust gas is made difficult to be transmitted to the urea water injection nozzle, there is a problem that clogging due to such a temperature drop is likely to occur.

In order to prevent the deposition of urea crystals, urea water supply is generally prohibited when the exhaust temperature is low, but when urea crystals are likely to accumulate in this way, the exhaust prohibiting urea water supply is prohibited. The temperature range must be expanded, and accordingly, NOx in the exhaust gas cannot be reduced well, resulting in a problem that exhaust purification performance is lowered.
Further, in the exhaust gas purification device of Patent Document 1, it has also been proposed to prevent the temperature drop of the urea water injection nozzle by an electric heater. In this case, however, the engine is used to replenish the energy consumed by the electric heater. Since a part of the output is used, there arises a problem that the fuel consumption of the engine is deteriorated.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide an exhaust purification device capable of satisfactorily preventing the occurrence of clogging associated with a temperature drop of the urea water injection nozzle. Is to provide.

In order to achieve the above object, an exhaust emission control device of the present invention includes an ammonia selective reduction type NOx catalyst that selectively reduces NOx in the exhaust of an engine using ammonia as a reducing agent, and an exhaust gas upstream of the ammonia selective reduction type NOx catalyst. A urea water injection nozzle that injects urea water into the exhaust gas that is attached to the passage and flows in the exhaust passage toward the ammonia selective reduction type NOx catalyst, and a heat insulating material, and among the urea water injection nozzles, A heat insulating member that covers at least a part of a portion located outside the exhaust passage from the outside, and the urea water injection nozzle includes a nozzle main body that injects the urea water, and the nozzle main body outside the exhaust passage. consists of a flange portion for fixing to the exhaust passage, the exhaust passage is a tubular shape, the peripheral wall portion along its axial direction, the exhaust passage The exhaust gas is provided with an exhaust outlet that flows out toward the ammonia selective reduction type NOx catalyst, and extends from the exhaust outlet toward the peripheral wall of the exhaust passage facing the exhaust outlet. The rectifying body has a plurality of holes through which the exhaust can pass, the end portion of the rectifying body passes through the peripheral wall portion of the exhaust passage, and protrudes to the outside of the peripheral wall portion. The urea water injection nozzle is attached via a flange portion to a mounting seat fixed to the inner peripheral surface of the rectifying body by forming a recess on the end side of the rectifying body, and the heat insulating member is It is inserted into a recess to cover at least the flange portion of the urea water injection nozzle, and the end portion of the rectifier is closed by a lid (claim 1).

  According to the exhaust gas purification apparatus configured as described above, the urea water injected from the urea water injection nozzle is hydrolyzed by the heat of the exhaust to generate ammonia, and this ammonia flows into the ammonia selective reduction type NOx catalyst together with the exhaust. To do. In the ammonia selective reduction type NOx catalyst, the exhaust gas is purified by selectively reducing NOx in the exhaust gas using ammonia in the exhaust gas as a reducing agent.

The urea water injection nozzle is attached to the exhaust passage on the upstream side of the ammonia selective reduction type NOx catalyst, and at least a part of the urea water injection nozzle located outside the exhaust passage is formed by a heat insulating member made of a heat insulating material. It is covered from the outside. For this reason, the heat radiation from the part located outside the exhaust passage of the urea water injection nozzle is suppressed .

In addition, since the urea water injection nozzle is attached to the exhaust passage through the flange portion outside the exhaust passage, and this flange portion is covered with the heat insulating member, heat dissipation from the flange portion is suppressed by the heat insulating member.
More specifically, an exhaust outlet is provided in the peripheral wall portion along the axial direction of the cylindrical exhaust passage, and the exhaust in the exhaust passage is a cylindrical rectifier extending from the exhaust outlet. After passing through a plurality of holes formed in the side wall, the exhaust gas flows out from the exhaust outlet toward the ammonia selective reduction type NOx catalyst. The end of the rectifier passes through the peripheral wall of the exhaust passage and protrudes to the outside of the exhaust passage, and the mounting seat is fixed on the inner peripheral surface of the rectifier so as to form a recess on the end of the rectifier Has been. The urea water injection nozzle is attached to the exhaust passage through a flange portion on the mounting seat, and a heat insulating member is inserted into the recess to cover at least the flange portion of the urea water injection nozzle, and at the end of the rectifying body. The part is closed by the lid.
In the exhaust gas purification apparatus, the urea water injection nozzle injects the urea water together with compressed air (claim 2).

According to the exhaust gas purification apparatus configured as described above, the urea water injection nozzle injects urea water together with the compressed air .

  According to the exhaust gas purification apparatus of the present invention, at least a part of a portion of the urea water injection nozzle located outside the exhaust passage is covered from the outside with a heat insulating member made of a heat insulating material. The heat radiation from the part located outside the exhaust passage is suppressed. Therefore, it is possible to prevent urea crystals from being deposited due to cooling of the urea water injection nozzle. As a result, it is possible to prevent clogging due to urea crystal deposition and to expand the exhaust temperature range in which urea water can be supplied, thereby improving exhaust purification performance by reducing NOx. Can do.

Especially in this invention, the flange part for attaching a urea water injection nozzle to an exhaust passage is covered with the heat insulation member. Since the flange portion serves as a heat radiator and promotes heat dissipation from the urea water injection nozzle, covering the flange portion with the heat insulating member in this way has a large effect of suppressing heat dissipation from the urea water injection nozzle. Accordingly, it is possible to effectively suppress the temperature drop of the urea water injection nozzle and prevent clogging due to urea crystal deposition.
More specifically, a mounting seat fixed to the inner peripheral surface of the rectifying body is provided so as to form a recess on the end side of the rectifying body protruding outward from the exhaust passage, and a flange portion is provided on the mounting seat. Further, the urea water injection nozzle is attached, and a heat insulating member is inserted into the recess to cover at least the flange portion of the urea water injection nozzle, and the end of the rectifier is closed by the lid. Therefore, the portion of the urea water injection nozzle covered by the heat insulating member is located outside the exhaust passage, but is located inside the rectifying body, and after being covered with the heat insulating member, the end of the rectifying body is covered by the lid. Since it is obstruct | occluded, it becomes easy to receive the heat transfer from the exhaust_gas | exhaustion which flows through the inside of a rectifier, and heat dissipation is suppressed by the heat insulation member. As a result, the temperature drop of the urea water injection nozzle can be more effectively suppressed.

Further, according to the exhaust gas purification apparatus of claim 2 , the urea water injection nozzle injects urea water together with the compressed air. In such a case, the vaporization of urea water is promoted by the compressed air, and the urea water injection nozzle Since it is further cooled, suppressing heat dissipation from the urea water injection nozzle by the heat insulating member is particularly effective in preventing urea crystal accumulation due to cooling of the urea water injection nozzle.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows an overall configuration diagram of a four-cylinder diesel engine (hereinafter referred to as an engine) to which an exhaust emission control device according to an embodiment of the present invention is applied. Based on FIG. The structure of will be described.
The engine 1 includes a high-pressure accumulator chamber (hereinafter referred to as a common rail) 2 common to each cylinder, and high-pressure fuel supplied from a fuel injection pump (not shown) and stored in the common rail 2 is supplied to an injector 4 provided in each cylinder. Then, fuel is injected from each injector 4 into each cylinder.

  The intake passage 6 is equipped with a turbocharger 8. The intake air drawn from an air cleaner (not shown) flows into the compressor 8a of the turbocharger 8 from the intake passage 6, and the intake air supercharged by the compressor 8a is intercooler. 10 and the intake control valve 12 are introduced into the intake manifold 14. An intake air amount sensor 16 for detecting an intake air flow rate to the engine 1 is provided upstream of the compressor 8a in the intake passage 6.

On the other hand, an exhaust port (not shown) through which exhaust is discharged from each cylinder of the engine 1 is connected to an exhaust pipe 20 via an exhaust manifold 18. An EGR passage 24 that communicates the exhaust manifold 18 and the intake manifold 14 via the EGR valve 22 is provided between the exhaust manifold 18 and the intake manifold 14.
The exhaust pipe 20 passes through the turbine 8 b of the turbocharger 8 and is connected to an exhaust aftertreatment device 28 via an exhaust throttle valve 26. The rotating shaft of the turbine 8b is connected to the rotating shaft of the compressor 8a so that the turbine 8b receives the exhaust flowing in the exhaust pipe 20 and drives the compressor 8a.

  The exhaust aftertreatment device 28 includes an upstream casing 30 and a downstream casing 34 that is communicated with the downstream side of the upstream casing 30 through a communication passage 32. The upstream casing 30 is divided into three parts, a first casing 30a, a second casing 30b, and a third casing 30c. The upstream casing 30 is configured by being connected via bolts and nuts. In this embodiment, the upstream casing 30, the communication path 32, and the downstream casing 34 form an exhaust passage of the present invention.

The first casing 30a is connected to the exhaust pipe 20, and the pre-stage oxidation catalyst 36 is accommodated in the first casing 30a. And the particulate filter (henceforth a filter) 38 is accommodated in the 2nd casing 30b located in the downstream of the 1st casing 30a.
The filter 38 is made of a honeycomb-type ceramic body, and has a large number of passages communicating with the upstream side and the downstream side, and the upstream side opening and the downstream side opening of the passage are alternately closed. Particulates in the exhaust gas are collected by the exhaust gas of 1 flowing inside. On the other hand, the front-stage oxidation catalyst 36 oxidizes NO in the exhaust to produce NO _2. Thus, by arranging the front-stage oxidation catalyst 36 and the filter 38 in this way, the particulates collected and deposited in the filter 38 are collected. The curate reacts with NO ₂ supplied from the pre-stage oxidation catalyst 36 to be oxidized, and the filter 38 is continuously regenerated.

Further, a communication passage 34 is connected to the third casing 30c located on the downstream side of the second casing 30b, and flows out of the filter 38 to the communication passage 34 at a position facing the connection portion of the communication passage 34. A urea water injection nozzle 40 for injecting urea water into the exhaust gas flowing is attached.
The urea water supplied from the urea water tank (not shown) and the compressed air supplied from the air tank (not shown) are supplied to and mixed with the urea water injection device 42, and the urea water becomes mist-like. And is supplied to the urea water injection nozzle 40 via the urea water supply pipe 44. The amounts of urea water and compressed air supplied to the urea water injection nozzle 40 are adjusted by the urea water injection device 42, and the urea water supplied to the urea water injection nozzle 40 is injected into the exhaust together with the compressed air. The urea water injected into the exhaust is hydrolyzed by the heat of the exhaust and ammonia is generated.

On the other hand, in the downstream casing 34, ammonia in the exhaust produced as described above is adsorbed, and an ammonia selective reduction type NOx catalyst (hereinafter referred to as SCR) that selectively reduces NOx in the exhaust using the adsorbed ammonia as a reducing agent. 46) and a downstream oxidation catalyst 48 for removing ammonia flowing out from the SCR catalyst 46 are accommodated downstream of the SCR catalyst 46. The post-stage oxidation catalyst 48 also has a function of oxidizing CO generated when the particulates are incinerated by forced regeneration of the filter 38 and discharging it to the atmosphere as CO ₂ .

By configuring the exhaust aftertreatment device 28 in this manner, ammonia generated from the urea water injected from the urea water injection nozzle 40 is supplied to the SCR catalyst 46. SCR catalyst 46 adsorbs the supplied ammonia, by promoting the denitration reaction with NOx in the exhaust and the adsorbed ammonia, to purify the NOx to harmless N _2. At this time, when ammonia flows out of the SCR catalyst 46 without reacting with NOx, the ammonia is removed by the post-stage oxidation catalyst 48.

Next, the mounting structure of the urea water injection nozzle 40 will be described in detail with reference to FIG.
FIG. 2 is a cross-sectional view of a main part of the third casing 30c taken along line II-II in FIG. As shown in FIG. 2, the third casing 30 c employs a heat insulating structure in which a heat insulating material 54 is interposed between the outer shell 50 and the inner shell 52.
An exhaust outlet 58 through which the exhaust gas that has passed through the filter 38 flows out toward the communication path 32 is provided in the peripheral wall portion 56 along the axial direction of the third casing 30c. One end portion of the exhaust outlet 58 located outside the third casing 30 c is connected to the communication path 32, and the other end of the exhaust outlet 58 is provided continuously to the exhaust outlet 58. The cylindrical rectifying body 60 extends so as to cross the third casing 30 c to the peripheral wall portion 56 facing the exhaust outlet 58. The side wall of the rectifying body 60 is formed with a large number of holes that communicate the outside and the inside of the rectifying body 60, and the rectifying body 60 passes through the peripheral wall portion 56 and the end portion 60 a is outside the third casing 30 c. It protrudes.

  A mounting seat 62 is welded to the inner peripheral surface on the end 60 a side of the rectifying body 60 at a position substantially corresponding to the peripheral wall portion 56, and the nozzle body 40 a of the urea water injection nozzle 40 is located at the central portion of the mounting seat 62. The urea water injection nozzle 40 is mounted on the third casing 30c by being inserted into the formed mounting hole and fixing the flange portion 40b of the urea water injection nozzle 40 to the mounting seat 62 via the bolt 64 and the nut 66. It has come to be.

  By mounting the urea water injection nozzle 40 on the third casing 30 c in this way, the urea water injection nozzle 40 is disposed to face the exhaust outlet 58. The nozzle body 40a is partially exposed in the exhaust passage formed by the third casing 30c in a state where the injection hole (not shown) provided in the end of the nozzle body 40a is located in the rectifying body 60. The urea water is injected from the injection hole of the urea water injection nozzle 40 toward the exhaust outlet 58.

  As shown in FIG. 2, the end 60a of the rectifying body 60 protrudes from the third casing 30c and the mounting seat 62 is located at a position corresponding to the peripheral wall portion 56 of the third casing 30c. A recess is formed at the end of the rectifying body 60 by providing the mounting seat 62 in this manner. Then, after fixing the urea water injection nozzle 40 to the mounting seat 62, a heat insulating member 68 made of a ceramic heat insulating material is inserted into the recess, and the lid 74 is connected to the rectifying body 60 via the bolt 70 and the nut 72. It attaches to the end part 60a and closes the end part 60a of the rectifying body 60. By doing so, the flange portion 40b of the urea water injection nozzle 40 located outside the exhaust passage formed by the third casing 30c and a part of the nozzle body 40a are covered with the heat insulating member 68. . The heat insulating member 68 is provided with a recess corresponding to each bolt 64 to avoid interference with the bolt 64.

  Exhaust gas that has passed through the filter 38 flows to the third casing 30 c and flows into the rectifying body 60 through a large number of holes formed in the rectifying body 60, and then flows into the communication passage 32 through the exhaust outlet 58. Then, it flows into the downstream casing 34. Thus, when urea water is injected from the urea water injection nozzle 40 while the exhaust gas flows from the rectifier 60 into the communication passage 32, the injected urea water is hydrolyzed by the heat of the exhaust gas, and ammonia is generated. Is done. The produced ammonia is supplied to the SCR catalyst 40 in the downstream casing 34 and used as a reducing agent for the selective reduction of NOx by the SCR catalyst 40 as described above.

  At this time, in the urea water injection nozzle 40, the urea water flows inside and the urea water injected into the exhaust gas with the compressed air is vaporized and takes heat, so that the temperature of the nozzle body 40 a is lowered. However, since a part of the nozzle body 40a and the flange portion 40b located outside the exhaust passage formed by the third casing 30c are covered from the outside by the heat insulating member 68, heat radiation from the nozzle body 40a and the flange portion 40b is performed. Is suppressed. Therefore, it is possible to suppress the temperature drop of the urea water injection nozzle 40 due to heat radiation, and it is possible to prevent the deposition of urea crystals due to the temperature drop. In particular, since the flange portion 40b that can serve as a heat radiator and promote heat dissipation from the urea water injection nozzle 40 is covered by the heat insulating member 68, the temperature drop of the urea water injection nozzle 40 can be effectively suppressed. . Moreover, the portion covered by the heat insulating member 68 is outside the exhaust passage formed by the third casing 30 c, but is located inside the rectifying body 60, and is further covered with the heat insulating member 68 and then the lid 74. As a result, the end portion 60a of the rectifying body 60 is closed, so that heat transfer from the exhaust flowing in the rectifying body 60 is easily received and heat dissipation is suppressed by the heat insulating member 68. As a result, the temperature drop of the urea water injection nozzle 40 can be more effectively suppressed.

  In order to prevent the deposition of urea crystals when the temperature of the urea injection nozzle 40 is low, it is necessary to prohibit the supply of urea water when the temperature of the urea injection nozzle 40 is low. Therefore, it is possible to expand the exhaust temperature range in which urea water can be supplied from the urea injection nozzle 40, and to improve exhaust purification efficiency by reducing NOx in the SCR catalyst 46. Can be made.

Although the description of the exhaust emission control device according to one embodiment of the present invention is finished above, the present invention is not limited to the above embodiment.
For example, in the above embodiment, the flange portion 40b and a part of the nozzle body 40a are covered with the heat insulating member 68 in the portion of the urea water injection nozzle 40 located outside the third casing 30c. You may make it cover the whole part of the urea water injection nozzle 40 located in the outer side of the casing 30c with the heat insulation member 68. FIG.

  Furthermore, in the said embodiment, although the cover body 74 and the heat insulation member 68 were set as the different bodies, the heat insulation member 68 is previously fixed to the cover body 74, and the edge part 60a of the rectifying body 60 is obstruct | occluded with the cover body 74. At this time, the heat insulating member 68 may simultaneously cover the flange portion 40b and a part of the nozzle body 40a. Alternatively, the lid 74 may be formed of the same heat insulating material as the heat insulating member 68, and the lid 74 and the heat insulating member 68 may be configured integrally.

Moreover, in the said embodiment, although the urea water injection nozzle 40 was attached to the attachment seat 62 welded to the rectifier 60 via the flange part 40b provided in the urea water injection nozzle 40, the urea water injection nozzle 40 of FIG. The attachment method is not limited to this.
For example, the rectifying body 60 may not be extended to the peripheral wall portion 56, but a mounting seat may be provided in a hole formed in the peripheral wall portion 56, and the urea water injection nozzle 40 may be attached to the mounting seat. In this case, if the heat insulating member is attached so as to cover the flange portion 40b fixed to the mounting seat, the heat radiation from the flange portion 40b can be suppressed and the temperature drop of the urea water injection nozzle 40 can be suppressed.

Alternatively, the end portion 60a of the rectifying body 60 and the mounting portion of the mounting seat 62 are configured in the same manner as in the above embodiment, and the portion of the rectifying body 60 in which the hole through which exhaust passes is formed is omitted and passes through the filter 38 The exhausted gas may flow directly from the exhaust outlet 58.
Further, in the above embodiment, the urea water injection nozzle 40 is disposed in the third casing so as to face the exhaust outlet 58 so that the exhaust gas flows out from the side wall portion 56 of the third casing 30 c through the exhaust outlet 58. However, the configuration of the exhaust aftertreatment device 28 and the mounting position of the urea water injection nozzle 40 are not limited to this.

  For example, the upstream casing 30 and the downstream casing 34 may be linearly arranged and communicated with each other through the communication path 34, and the urea water injection nozzle 40 may be attached to the communication path 34. In this case, for example, a mounting seat similar to that of the above embodiment may be provided in a hole formed in the wall surface of the communication passage 34, and the urea water injection nozzle 40 may be mounted on this mounting seat. And if a heat insulation member is attached so that the flange part 40b of the urea water injection nozzle 40 fixed to the mounting seat may be covered, the heat radiation from the flange part 40b is suppressed and the temperature drop of the urea water injection nozzle 40 is suppressed. Can do.

  Alternatively, the downstream side casing 34 may be provided in parallel with the third casing 30c without using the communication passage 32 as in the above embodiment, and the exhaust outlet 58 may be directly communicated with the downstream side casing 34. The downstream casing 34 may be directly connected to the downstream side of the three casings 30c in a straight line. Even in these cases, it is possible to attach the urea water injection nozzle to the third casing 30c as in the above embodiment, and it is possible to obtain the same effect as in the above embodiment.

  In the above-described embodiment, the upstream oxidation catalyst 36 and the filter 38 are accommodated in the upstream casing 30, and the SCR catalyst 46 and the downstream oxidation catalyst 48 are accommodated in the downstream casing 34 to constitute the exhaust aftertreatment device 28. However, the configuration of the exhaust aftertreatment device 28 is not limited to this, and the present invention is applied to any exhaust aftertreatment device provided with the SCR catalyst 46 and the urea water injection nozzle 40. Is possible.

  Furthermore, in the above embodiment, the engine 1 is a four-cylinder diesel engine, but the number of cylinders and the type of the engine 1 are not limited thereto.

1 is an overall configuration diagram of an engine to which an exhaust emission control device according to an embodiment of the present invention is applied. It is principal part sectional drawing in alignment with the II-II line | wire in FIG.

Explanation of symbols

1 Engine 30 Upstream casing (exhaust passage)
30c 3rd casing (exhaust passage)
40 Urea water injection nozzle 40a Nozzle body 40b Flange 46 SCR catalyst (ammonia selective reduction type NOx catalyst)
68 Thermal insulation

Claims (2)

An ammonia selective reduction type NOx catalyst that selectively reduces NOx in engine exhaust using ammonia as a reducing agent;
A urea water injection nozzle that is attached to an exhaust passage on the upstream side of the ammonia selective reduction type NOx catalyst and injects urea water into the exhaust gas flowing toward the ammonia selective reduction type NOx catalyst in the exhaust passage;
A heat insulating member made of a heat insulating material and covering at least a part of a portion of the urea water injection nozzle located outside the exhaust passage from the outside;
The urea water injection nozzle includes a nozzle body for injecting the urea water and a flange portion for fixing the nozzle body to the exhaust passage outside the exhaust passage,
The exhaust passage has a cylindrical shape, and an exhaust outlet through which exhaust in the exhaust passage flows out toward the ammonia selective reduction type NOx catalyst is provided in a peripheral wall portion along the axial direction thereof,
A cylindrical rectifier extending from the exhaust outlet to the peripheral wall of the exhaust passage facing the exhaust outlet;
The rectifier is formed with a plurality of holes through which the exhaust can pass, and an end portion of the rectifier passes through the peripheral wall of the exhaust passage and protrudes to the outside of the peripheral wall.
The urea water injection nozzle is attached to a mounting seat fixed to the inner peripheral surface of the rectifying body by forming a recess on the end side of the rectifying body via the flange portion,
An exhaust emission control device, wherein the heat insulating member is inserted into the recess to cover at least the flange portion of the urea water injection nozzle, and the end portion of the rectifier is closed by a lid .   The exhaust purification apparatus according to claim 1, wherein the urea water injection nozzle injects the urea water together with compressed air.

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