JP2015110928A - Exhaust emission control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy in supply of a reducing agent added from an addition valve to a reduction catalyst in an exhaust emission control system in which the reduction catalyst and an oxidation catalyst at its upstream are arranged in an exhaust passage of an internal combustion engine and the exhaust passage between the reduction catalyst and the oxidation catalyst serves as a swirl flow type passage.SOLUTION: In an exhaust passage 3 of a diesel engine 2 as an internal combustion engine, an SCRF 5 as a reduction catalyst and an oxidation catalyst 4 located upstream of the SCRF 5 are arranged. An exhaust passage 31 between the oxidation catalyst 4 and the SCRF 5 serves as a spiral mixer (swirl flow type passage) through which an exhaust gas passes with a swirl flow. An addition valve 6 for adding urea water as a reducing agent is arranged upstream of the oxidation catalyst 4. In the oxidation catalyst 4, a through-hole 41 is formed through which urea water added from the addition valve 6 passes. At an end of a boss 312 of the spiral mixer 31, a diffuser 314 for radially diffusing the urea water passing through the through-hole 41 is arranged.

Description

  The present invention relates to an exhaust gas purification device, and more particularly to an exhaust gas purification device that reduces and purifies harmful components in exhaust gas using a reduction catalyst disposed in an exhaust passage of an internal combustion engine.

  A urea SCR system is known as one of exhaust gas purification systems for internal combustion engines. In the urea SCR system, a reduction catalyst (SCR catalyst, NOx selective reduction catalyst, SCRF) for selectively reducing and purifying NOx in the exhaust gas is provided in the exhaust passage. An addition valve for adding urea water as a reducing agent to the exhaust gas is provided upstream of the reduction catalyst. In the reduction catalyst, a reduction reaction is performed in which NOx is decomposed into nitrogen and water with ammonia generated from the urea water.

  In order to effectively reduce and purify NOx with the reduction catalyst, it is necessary to atomize the liquid reducing agent added from the addition valve and disperse it in a wide range in the exhaust gas. Therefore, conventionally, in order to efficiently disperse (atomize and evaporate) urea water, there is a proposal of a technique in which the exhaust passage upstream (upstream) of the reduction catalyst is a swirling flow passage (see Patent Document 1). In the technique of Patent Document 1, urea water is added to the swirling flow type passage, and the added urea water and the exhaust gas pass through the swirling flow type passage in a swirling flow, so that the urea water and the exhaust gas reach the reduction catalyst. It is possible to earn a distance until the end, that is, a dispersion distance of urea water.

US Patent Application Publication No. 2012/0216513

  By the way, in this type of exhaust purification system, an oxidation catalyst for oxidizing and purifying HC, CO, etc. in the exhaust gas may be provided in the exhaust passage upstream of the reduction catalyst. In this case, in order to prevent the reducing agent added by the addition valve from being oxidized by the oxidation catalyst, it is necessary to arrange the addition valve in the swirl flow path between the reduction catalyst and the oxidation catalyst. In this case, if the amount of the reducing agent added increases, the reducing agent does not evaporate and stays on the passage wall of the swirl type passage. When the reducing agent stays on the passage wall, the wall temperature decreases, and the evaporation of the reducing agent is further delayed. As a result, the accuracy of the amount of the reducing agent to be supplied according to the amount of emission reaching the reduction catalyst is greatly deteriorated by the amount of the reducing agent staying on the passage wall. In addition, the reducing agent staying on the passage wall may evaporate over time and reach the reduction catalyst. In this case, more reducing agent than the expected amount is supplied to the reduction catalyst, contributing to reduction purification. A phenomenon called slip is generated in which the reducing agent that is not released is released downstream from the reduction catalyst.

  The present invention has been made in view of the above problems. A reduction catalyst and an oxidation catalyst are disposed upstream of an exhaust passage of an internal combustion engine, and the exhaust passage between the reduction catalyst and the oxidation catalyst is a swirl flow passage. An object of the present invention is to provide an exhaust gas purification device that can improve the supply accuracy of a reducing agent added from an addition valve to a reduction catalyst.

In order to solve the above problems, an exhaust gas purification apparatus of the present invention includes a reduction catalyst disposed in an exhaust passage of an internal combustion engine,
An oxidation catalyst disposed in the exhaust passage upstream of the reduction catalyst;
A swirl flow path between the reduction catalyst and the oxidation catalyst, the swirl flow path configured to allow exhaust gas to pass in a swirl flow;
An addition valve for adding a reducing agent for causing a reduction reaction with the reduction catalyst to the exhaust passage;
The addition valve is disposed upstream of the oxidation catalyst;
The oxidation catalyst is formed with a through hole through which the reducing agent added from the addition valve passes to the swirl type passage.

  According to the present invention, the addition valve is disposed upstream of the oxidation catalyst, and the reducing agent added from the upstream passes through the through-hole formed in the oxidation catalyst and reaches the swirl flow passage. Therefore, the distance from the addition of the reducing agent to the reduction catalyst can be increased, and the reducing agent can be easily atomized, compared to the case where the addition valve is arranged in the swirling flow passage. Thereby, it is possible to prevent the reducing agent from staying in the passage wall of the swirling flow passage, and as a result, it is possible to improve the supply accuracy of the reducing agent to the reduction catalyst. Further, since the reducing agent passes through the through hole of the oxidation catalyst, it is possible to prevent the reducing agent from being oxidized by the oxidation catalyst.

It is the figure which showed the exhaust gas purification system. It is sectional drawing when an exhaust passage is cut along the II-II line of FIG. It is the figure which showed the exhaust gas purification system which concerns on the modification 1. FIG. It is the figure which showed the exhaust gas purification system which concerns on the modification 2. FIG. It is sectional drawing when an exhaust passage is cut | disconnected by the VV line | wire of FIG.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an exhaust purification system 1 mounted on a vehicle. First, the configuration of the exhaust purification system 1 will be described. The exhaust purification system 1 corresponds to the “exhaust gas purification device” of the present invention, and is a system that purifies exhaust gas discharged from a diesel engine 2 (hereinafter simply referred to as an engine) as an internal combustion engine. Specifically, the exhaust purification system 1 is configured to include a urea SCR system that purifies NOx in the exhaust gas. In the exhaust purification system 1, a cylindrical exhaust passage 3 is connected to the engine 2, and exhaust gas discharged from the engine 2 flows through the exhaust passage 3 and is discharged outside the vehicle.

  An oxidation catalyst 4 (DOC: Diesel Oxidation Catalyst) that oxidizes and purifies HC and CO, which are one of harmful components in the exhaust gas, is disposed in the exhaust passage 3. The oxidation catalyst 4 is arranged with no gap between the exhaust catalyst 3 and the passage wall of the exhaust passage 3. The oxidation catalyst 4 carries, for example, a catalyst component (for example, Pt (platinum) or Pd (palladium)) that promotes the oxidation reaction of HC and CO on a wall-through type ceramic honeycomb or metal mesh. It has a structure.

  The activity of the oxidation catalyst 4 is highly dependent on temperature, and has little oxidizing action at low temperatures. Therefore, in order to warm the oxidation catalyst 4 early after the engine 2 is started and promote the oxidation purification of HC and CO, the oxidation catalyst 4 is arranged upstream of the SCRF 5 described later (side closer to the engine 2). The oxidation catalyst 4 also has a role of raising the temperature of the exhaust gas by an oxidation reaction and burning and removing particulate matter (PM, soot) deposited on the SCRF 5 by the heated exhaust gas.

  Furthermore, the oxidation catalyst 4 has a through hole 41 (axis L2) penetrating between the upstream surface 4a and the downstream surface 4b. In the present embodiment, the through hole 41 is formed in the center of the oxidation catalyst 4, in other words, an axis L 1 of a boss 312 described later and an axis L 2 of the through hole 41 are coaxial. Yes. The diameter of the through hole 41 is set to a size that allows urea water 7 added from the addition valve 6 described later to pass through the through hole 41. In addition, since the oxidation purification by the oxidation catalyst 4 will be impaired when the diameter of the through-hole 41 is too large, it is preferable to make it the minimum necessary size. Further, in order to prevent oxidation of the urea water 7 passing through the through hole 41 (preventing ammonia from being generated from the urea water), the inner wall 411 of the through hole 41 is not coated (supported).

  Although not shown in FIG. 1, between the engine 2 and the oxidation catalyst 4, for example, a turbocharger turbine (variable nozzle turbo (VNT)) (not shown) that recovers energy from exhaust gas is disposed. ing.

  An SCRF (Selective Catalytic Reduction Filter) 5 that selectively reduces and purifies NOx in the exhaust gas is disposed in the exhaust passage 3 downstream of the oxidation catalyst 4. The SCRF 5 is arranged in a state where there is no gap with the passage wall of the exhaust passage 3. SCRF5 contains a catalyst component (SCR catalyst) that promotes SCR (selective catalytic reduction) of NOx, and also has a function of capturing particulate matter in exhaust gas. The SCRF 5 has a structure in which, for example, a catalyst component is supported on a wall-through type ceramic honeycomb. The exhaust gas flows downstream while passing through the porous partition walls of SCRF 5, and particulate matter in the exhaust gas is collected by SCRF 5 during that time.

The catalyst component contained in SCRF5 promotes the reduction reaction of, for example, the following formula 1, formula 2, and formula 3 as a reduction reaction between ammonia (NH3) generated from urea water and NOx, such as vanadium, Base metal oxides such as molybdenum and tungsten. Thus, while the exhaust gas passes through the SCRF 5, NOx is decomposed (purified) into water and nitrogen by, for example, the following formula 1, formula 2, and formula 3. Instead of SCRF5, a normal SCR catalyst, that is, a catalyst that does not have a particulate matter collecting function and performs only NOx reduction purification may be employed.
4NO + 4NH3 + O2 → 4N2 + 6H2O (Formula 1)
6NO2 + 8NH3 → 7N2 + 3H2O (Formula 2)
NO + NO2 + 2NH3 → 2N2 + 3H2O (Formula 3)

  In addition, SCRF5 cannot store ammonia inexhaustably, and the maximum amount of ammonia that can be stored in SCRF5 varies depending on the temperature (catalyst temperature) of SCRF5. When the catalyst temperature rapidly decreases or when ammonia (urea water) is excessively supplied to the SCRF 5, a phenomenon called ammonia slip in which ammonia is released from the SCRF 5 occurs. For this reason, an oxidation catalyst for purifying ammonia released from SCRF 5 may be provided in the exhaust passage downstream of SCRF 5.

  The exhaust passage 31 between the oxidation catalyst 4 and the SCRF 5 is configured as a swirling flow passage that allows the exhaust gas to pass in a swirling flow, that is, generates a swirling flow. Hereinafter, the swirl flow path is referred to as a spiral mixer. The length of the spiral mixer 31, that is, the length between the oxidation catalyst 4 and the SCRF 5, is about 50 mm to 100 mm, for example. The spiral mixer 31 is a passage for dispersing the added urea water in the exhaust gas to improve mixing of the urea water and the exhaust gas. The spiral mixer 31 is disposed on a cylindrical outer cylinder 311 constituting the outer peripheral wall of the spiral mixer 31, and a central axis L1 of the outer cylinder 311 (same as the axis of the boss 312). A rod-like boss 312 (shaft portion) extending in the direction, and a swirl flow plate 313 formed in a spiral shape (spiral shape) along the outer periphery of the boss 312 by being welded to the outer cylinder 311 and the boss 312. Yes.

  Further, the spiral mixer 31 includes a diffusion plate 314 that is fixed to the upstream end of the boss 312 by welding or the like. The diffusion plate 314 corresponds to the “diffusion part” of the present invention, and is a plate for diffusing the urea water 7 that has passed through the through hole 41 in the radial direction of the spiral mixer 31 (direction intersecting the central axis L1). . For example, the diffusion plate 314 is formed in a conical shape whose bottom surface is connected to the tip of the boss 312 and whose tip is directed toward the through hole 41. The angle of the tip of the diffusion plate 314 (conical angle) is, for example, 90 degrees, but other angles may be used. However, if the angle is too large or too small, it becomes difficult to diffuse urea water in the radial direction.

  Note that the diffuser plate 314 may have a shape other than a conical shape as long as it has a surface that faces obliquely toward the outer cylinder 311, for example, a semicircular shape, a spherical shape, or a convex lens shape. Further, instead of the diffusion plate 314, the tip of the boss 312 may be processed like the shape of the diffusion plate 314.

  An addition valve 6 that adds urea water to the exhaust passage 3 is disposed in the exhaust passage 3 upstream of the oxidation catalyst 4. Specifically, the addition valve 6 is disposed on the same axis as the through-hole 41, that is, on the axis L 2 of the through-hole 41 in FIG. 1 (also on the central axis L 1 of the outer cylinder 311) toward the through-hole 41. It arrange | positions so that the water 7 may be added (jetting). Therefore, the exhaust passage 3 upstream of the oxidation catalyst 4 is bent so as to have a passage wall 32 facing the through hole 41. An opening is formed in a portion of the passage wall 32 facing the through hole 41, and a cylindrical portion 62 for mounting the addition valve 6 is attached to the opening. The addition valve 6 is attached to the cylindrical portion 62.

  The addition valve 6 has the same structure as a fuel injection valve (injector) that injects fuel into a cylinder of a gasoline engine or into an intake port. That is, the addition valve 6 is an electromagnetic on-off valve provided with a drive unit composed of an electromagnetic solenoid or the like, and a valve main unit having a urea water passage for passing urea water and a needle for opening and closing a nozzle 61 (front end outlet). It is configured as. When the electromagnetic solenoid is energized, the needle moves in the valve opening direction along with the energization, and urea water is injected from the nozzle 61 as the needle moves.

  The exhaust purification system 1 includes a urea water tank (not shown) for storing urea water, a pipe (not shown) connecting the urea water tank and the addition valve 6, and pumping urea water from the urea water tank through the pipe. A pump (not shown) that discharges to the addition valve 6 side, a regulator (not shown) that adjusts the pressure of urea water in the pipe to a predetermined pressure, a control circuit (not shown) that controls the addition valve 6, Is provided. The control circuit intermittently drives the addition valve 6 and causes the addition valve 6 to inject a urea water amount corresponding to the operating state of the engine 2, in other words, a urea water amount corresponding to the NOx amount discharged from the engine 2.

  The above is the configuration of the exhaust purification system 1. Next, the operation of the exhaust purification system 1 will be described. When urea water spray 7 (hereinafter simply referred to as urea water) is added from the addition valve 6, most of the urea water 7 passes through the through hole 41 and reaches the spiral mixer 31. As described above, the urea water 7 is not oxidized when passing through the through hole 41 because the inner wall 411 of the through hole 41 is not covered with the catalyst component.

  The urea water 7 that has passed through the through hole 41 collides with the diffusion plate 314 disposed at a position facing the through hole 41. Since the diffusion plate 314 is formed in a conical shape, for example, the urea water 7 that has collided with the diffusion plate 314 diffuses in the radial direction of the spiral mixer 31. Here, FIG. 2 is a cross-sectional view of the exhaust passage 3 taken along the line II-II in FIG. 1 (a line orthogonal to the axis L1 in the inlet region of the spiral mixer 31). FIGS. 1 and 2 illustrate urea water 71 diffusing toward the outer cylinder 311 and urea water 72 diffusing toward the swirl flow plate 313 (obliquely behind the diffusion plate 314). In this way, the urea water 71 and 72 is evenly distributed over a wide area of the outer cylinder 311 and the swirling flow plate 313.

  The urea water and the exhaust gas scattered in a wide range pass through the spiral passage surrounded by the swirl flow plate 313 and reach the upstream surface of the SCRF 5 as a swirl flow. The urea water is converted into ammonia (NH 3) by hydrolysis inside the SCRF 5 or before reaching the SCRF 5. Then, at SCRF5, ammonia reacts with NOx, and NOx is reduced and purified.

  As described above, according to the present embodiment, the addition valve 6 is disposed upstream of the oxidation catalyst 4 and the urea water that has passed through the through hole 41 is diffused in the radial direction by the diffusion plate 314. The dispersion distance of urea water from the valve 6 (nozzle 61) to the SCRF 5 can be increased, and urea water can be prevented from staying in the passage wall (swirl flow plate 313, outer cylinder 311, etc.) of the spiral mixer 31. . Therefore, the supply accuracy of urea water (ammonia) to SCRF 5 can be improved, and as a result, ammonia slip due to excessive supply of urea water can also be prevented. Further, since the diffusion plate 314 is disposed at the tip of the boss 312, the diffusion plate 314 can be easily installed in the spiral mixer 31. In other words, the spiral mixer 31 having the diffusion plate 314 can be easily manufactured. Further, since the diffusion plate 314 is disposed on the central axis L1 (same as the axis of the boss 312) of the spiral mixer 31, it is possible to diffuse the urea water in the entire circumferential direction of the outer cylinder 311. Atomization of urea water can be promoted.

(Modification 1)
Hereinafter, modifications of the exhaust purification system of the present embodiment will be described. FIG. 3 shows an exhaust purification system 11 according to the first modification. In FIG. 3, the same components as those in FIG. In FIG. 3, the engine 2 (see FIG. 1) is not shown. The exhaust purification system 11 of FIG. 3 is different from the exhaust purification system 1 of FIG. 1 in that a partition wall 81 is provided, and is otherwise the same as the exhaust purification system 1.

  The partition wall 81 is a straight cylindrical member having a cross section equivalent to the cross section of the through hole 41 and is disposed in the exhaust passage 33 between the oxidation catalyst 4 and the addition valve 6 as shown in FIG. Is done. Specifically, the partition wall 81 is arranged in the exhaust passage 33 such that one end portion 811 of the partition wall 81 is aligned with the upstream end portion of the through hole 41. The partition wall 81 may be attached to the upstream surface of the oxidation catalyst 4 or may be attached to the passage wall of the exhaust passage 33 via an attachment member (not shown).

  The length of the partition 81 is set so that a gap 100 is formed between the other end 812 of the partition 81 and the addition valve 6. In the gap 100, for example, the pressure loss when the exhaust gas passes through the oxidation catalyst 4 (portion other than the through hole 41 of the oxidation catalyst 4) and the pressure loss when the exhaust gas passes through the through hole 41 are at the same level. Have been adjusted.

  According to the first modification, the same effect as in the above embodiment can be obtained, and the partition wall 81 is provided between the through hole 41 and the addition valve 6, so that a large amount of exhaust gas flows into the through hole 41. Can be regulated. Therefore, the formation of the through hole 41 can prevent the purification of HC and CO in the exhaust gas from being lowered. Further, the presence of the partition wall 81 allows the urea water added from the addition valve 6 to effectively reach the through hole 41 (the urea water reaches a portion other than the through hole 41 of the oxidation catalyst 4). Can be suppressed). Further, a gap 100 is formed, and a certain amount of exhaust gas flows inside the partition wall 81, so that urea water attached to the partition wall 81 can be removed by the exhaust gas. Therefore, urea can be prevented from depositing on the partition wall 81.

(Modification 2)
FIG. 4 shows an exhaust purification system 12 according to the second modification. 4, the same components as those in FIG. 1 are denoted by the same reference numerals. In FIG. 4, the illustration of the engine 2 (see FIG. 1) is omitted. In the exhaust purification system 12 of FIG. 4, a diffusion plate 315 that diffuses urea water in the radial direction of the spiral mixer 31 is attached to a portion other than the tip of the boss 312. Specifically, the diffusion plate 315 is attached to the outer periphery 313a (the end portion in the radial direction) of the uppermost swirl flow plate 313. In other words, the diffusing plate 315 is attached to a position shifted in the radial direction from the axis L1 of the boss 312 (the central axis of the spiral mixer 31), that is, a position close to the outer cylinder 311 side.

  Here, FIG. 5 is a cross-sectional view when the exhaust passage 30 is cut along the line V-V in FIG. 4 (a line orthogonal to the axis L1 in the inlet region of the spiral mixer 31). FIG. 5 shows a state in which urea water that has passed through a through hole 42 to be described later collides with the diffusion plate 315 and then diffuses in the direction of the outer cylinder 311 (radial direction). It is illustrated by “73”. As shown in FIG. 5, the diffusion plate 315 is inclined obliquely toward the outer cylinder 311 (the outer cylinder 311 other than the side where the diffusion plate 315 is disposed) so that the urea water 73 diffuses in the radial direction. Has multiple faces. Note that the diffusion plate 315 may have any shape as long as it has a surface that faces obliquely toward the outer cylinder 311.

  The oxidation catalyst 4 is formed with a through hole 42 through which the urea water 7 added from the addition valve 6 passes. The through hole 42 is formed at a position facing the diffusion plate 315, that is, at the outer peripheral side (position approaching the outer periphery) of the oxidation catalyst 4. The shape of the through hole 42 is the same as the shape of the through hole 41 in FIG.

  The addition valve 6 is disposed coaxially with the through hole 42 in the exhaust passage 331 upstream of the oxidation catalyst 4. That is, the addition valve 6 is disposed on the outer peripheral side of the exhaust passage 331. In order to arrange the addition valve 6 coaxially with the through hole 42, the exhaust passage 331 has a passage wall 34 facing the through hole 42, which is substantially perpendicular to the direction in which the exhaust gas flows. The addition valve 6 is disposed on the passage wall 34.

  Further, similarly to the first modification (FIG. 3), a cylindrical partition wall 82 that restricts a large amount of exhaust gas from flowing into the through hole 42 is disposed between the through hole 42 and the addition valve 6. .

  According to the second modification, the same effect as in the above embodiment can be obtained, and the through hole 42, the partition wall 82, and the addition valve 6 are close to the outer peripheral side of the exhaust passage 30, so that the exhaust gas is allowed to flow downstream. Easy to do.

  In addition, this invention is not limited to the said embodiment, A various change is possible to the limit which does not deviate from description of a claim. For example, in the above-described embodiment, the example in which the boss of the spiral mixer is disposed on the same axis as the central axis of the exhaust passage has been described. However, the boss may be disposed at a position shifted from the central axis. In this case, the through hole of the oxidation catalyst and the addition valve are also arranged at positions shifted from the central axis. Further, the present invention may be applied to an exhaust purification system in which a DPF (Diesel Particulate Filter) with an oxidation catalyst is disposed upstream of the SCR catalyst. In this case, a through hole is formed in the DPF with an oxidation catalyst. Further, the present invention is not intended to exclude a configuration in which a diffusion plate is not provided. Even if the diffusion plate is not provided, the addition valve is provided upstream of the oxidation catalyst, so that the dispersion distance of the added urea water can be increased, and urea water is added to the passage wall of the spiral mixer. It can suppress staying.

1, 11, 12 Exhaust gas purification system (exhaust gas purification device)
2 Diesel engine (internal combustion engine)
3, 30 Exhaust passage 31 Spiral mixer (swirl flow passage)
4 Oxidation catalyst 41, 42 Through hole 5 SCRF (reduction catalyst)
6 Additive valve

Claims (8)

A reduction catalyst (5) disposed in the exhaust passage (3, 30) of the internal combustion engine (2);
An oxidation catalyst (4) disposed in the exhaust passage upstream of the reduction catalyst;
A swirl flow path (31) configured to allow the exhaust gas to pass through in a swirl flow, between the reduction catalyst and the oxidation catalyst;
An addition valve (6) for adding a reducing agent for causing a reduction reaction with the reduction catalyst to the exhaust passage;
The addition valve is disposed upstream of the oxidation catalyst;
Exhaust gas purifiers (1, 11, 12) characterized in that the oxidation catalyst is formed with through holes (41, 42) through which the reducing agent added from the addition valve passes to the swirl flow passage. ).   The diffusing portion (314, 315) disposed in an inlet region of the swirling flow passage and diffusing the reducing agent that has passed through the through hole in a radial direction of the swirling flow passage. The exhaust gas purifying apparatus according to 1.   The exhaust gas purification device according to claim 1 or 2, wherein the addition valve is disposed upstream of the oxidation catalyst and coaxially with the through hole.   The exhaust gas purification device according to any one of claims 1 to 3, wherein the inner wall (411) of the through hole is not coated with a catalyst component that promotes an oxidation reaction.   A partition wall (81, 82) is provided in the exhaust passage (33, 331) between the addition valve and the through hole, and regulates an amount of exhaust gas flowing into the through hole. The exhaust gas purification apparatus (11, 12) according to any one of 1 to 4. The swirl flow passage includes a shaft portion (312) whose axial direction is the direction in which the outer peripheral wall of the swirl flow passage extends, and a spiral swirl flow plate (313) attached to the shaft portion. ,
The diffusion part (314) is disposed at the tip on the upstream side of the shaft part,
The exhaust gas purification device (1, 11) according to claim 2, wherein the through hole (41) is formed coaxially with the shaft portion. The through hole (42) is formed at a position near the outer periphery of the oxidation catalyst,
The exhaust gas purifying device according to claim 2, wherein the diffusing portion (315) is disposed at a position on the same axis as the through hole and close to the outer peripheral wall (311) of the swirling flow passage. (12). The reducing agent is urea water;
The exhaust gas purification device according to any one of claims 1 to 7, wherein the reduction catalyst is a catalyst that reduces NOx in exhaust gas with ammonia generated from urea water.

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