JP2014058920A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device that facilitates application to various mounting spaces.SOLUTION: An exhaust emission control device 1 having a DPF 2 and a urea SCR catalyst 4 for purifying exhaust gas includes: a double exhaust pipe 6 having an outside exhaust pipe 8 and an inside exhaust pipe 7; and a return exhaust pipe 9 for connecting one exhaust pipe outlet to the other exhaust pipe inlet of the outside exhaust pipe 8 and the inside exhaust pipe 7. The DPF 2 is arranged in the inside exhaust pipe 7, the urea SCR catalyst 4 is arranged between the outside exhaust pipe 8 and the inside exhaust pipe 7, and the urea SCR catalyst 4 is divided into multiple parts in a circumferential direction of the inside exhaust pipe 7.

Description

  The present invention relates to an exhaust purification device that purifies exhaust gas.

  Diesel particulate filter (DPF) that collects PM (particulate matter) in exhaust gas and CO (carbon monoxide) and HC (carbonization) in exhaust gas as exhaust gas purification devices that purify exhaust gas such as diesel engines The thing provided with the oxidation catalyst which purifies (hydrogen) is known (refer patent documents 1 and 2).

  Patent Document 1 further includes a urea SCR (Selective Catalytic Reduction) catalyst as a NOx purification catalyst that purifies NOx (nitrogen oxide) in exhaust gas in order to comply with stricter exhaust gas regulations. Have been described.

JP 2010-071189 A Special table 2008-530446 gazette

  However, in order to provide the oxidation catalyst and the NOx purification catalyst in addition to the DPF, the vehicle needs to have a sufficient mounting space. The mounting space differs depending on the vehicle type, and there are cases where a conventional NOx purification catalyst or the like cannot be arranged depending on the size and shape of the mounting space. For this reason, if the casing shape of the catalyst is changed in accordance with the mounting space, the NOx purification catalyst needs to be recreated to a new shape, resulting in a significant cost increase.

  Therefore, an object of the present invention is to provide an exhaust purification device that can be easily adapted to various mounting spaces.

  In order to solve the above-described problems, the present invention provides an exhaust purification device having a DPF and a catalyst for purifying exhaust gas, a double exhaust pipe portion having an outer exhaust pipe and an inner exhaust pipe, an outer exhaust pipe, A return exhaust pipe connecting one exhaust pipe outlet and the other exhaust pipe inlet among the inner exhaust pipes, and a DPF is disposed inside the inner exhaust pipe, and between the outer exhaust pipe and the inner exhaust pipe Is characterized in that a catalyst is arranged and the catalyst is divided into a plurality of parts in the circumferential direction of the inner exhaust pipe.

  According to the exhaust emission control device according to the present invention, since the catalyst disposed between the outer exhaust pipe and the inner exhaust pipe is divided into a plurality of parts in the circumferential direction, the shape of the outer exhaust pipe is adapted to the mounting space for each vehicle type. Even if it is necessary to change (height or width), it can be easily adapted by changing the arrangement and number of the divided catalysts without recreating a catalyst of a new shape. Therefore, according to this exhaust purification device, it becomes easier to adapt to various mounting spaces and is advantageous for cost reduction as compared with the case where a catalyst having a new shape is created each time the shape of the outer exhaust pipe is changed. . Moreover, according to this exhaust purification device, even if there is a manufacturing failure in a part of the catalyst, it is only necessary to replace the divided part instead of the whole catalyst, and the yield of the catalyst material can be improved.

In the exhaust purification apparatus, the catalyst may be divided into two or four parts in the circumferential direction of the inner exhaust pipe.
According to this exhaust purification device, for example, when the entire catalyst is divided into four parts and the contact area to the exhaust gas is maximized to improve the NOx reduction rate, all four catalysts are used, and the outer space is limited due to the limited mounting space When changing the height and width of the exhaust pipe, it is possible to easily adapt to the mounting space according to the vehicle type by using two of the four divided catalysts and dividing it into two.

In the exhaust purification apparatus, the catalyst may be a urea SCR catalyst.
According to this exhaust gas purification apparatus, the exhaust gas purification performance can be further enhanced by employing the urea SCR catalyst effective for NOx purification.

  According to the present invention, it is possible to provide an exhaust emission control device that can be easily adapted to various mounting spaces.

It is a figure which shows the exhaust gas purification apparatus which concerns on 1st Embodiment. FIG. 2 is an end view taken along line II-II in FIG. 1. It is an end view which shows the exhaust gas purification apparatus which concerns on 2nd Embodiment. It is an end view which shows the exhaust gas purification apparatus which concerns on 3rd Embodiment. It is an end elevation which shows the exhaust gas purification apparatus which concerns on 4th Embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
As shown in FIGS. 1 and 2, the exhaust emission control device 1 according to the first embodiment purifies PM (particulate matter), NOx (nitrogen oxide), etc., of exhaust gas discharged from a diesel engine. It is a device for.

  The exhaust purification device 1 includes a double exhaust pipe portion (housing) 6 in which a DPF [Diesel particulate filter] 2 and catalysts 3 to 5 are accommodated. The double exhaust pipe section 6 has a double pipe structure composed of an inner exhaust pipe 7 and an outer exhaust pipe 8, and the inner exhaust pipe 7 and the outer exhaust pipe 8 are connected via a return exhaust pipe 9. Yes. As shown in FIG. 2, the inner exhaust pipe 7 and the outer exhaust pipe 8 are circular in cross section along the line II-II perpendicular to the flow direction of the exhaust gas. Except for being formed in a circular tube shape.

  As shown in FIGS. 1 and 2, inside the inner exhaust pipe 7, DPF 2 for removing PM (particulate matter) in the exhaust gas and diesel for purifying CO, HC, etc. in the exhaust gas. An oxidation catalyst [DOC: Diesel Oxidation Catalyst] 3 is provided. The DPF 2 is filled on the outlet 7 b side of the inner exhaust pipe 7, and the diesel oxidation catalyst 3 is filled on the inlet 7 a side of the inner exhaust pipe 7.

  The DPF 2 is made of a honeycomb body made of metal or ceramic and collects PM in the exhaust gas. Further, a catalyst for increasing the exhaust gas purification efficiency is applied to the surface of the honeycomb body. A DPF that is not coated with a catalyst may be used. The diesel oxidation catalyst 3 includes a catalyst carrier made of metal or ceramics, and purifies (detoxifies) CO, HC, and NO by an oxidation reaction.

  The inlet 7a of the inner exhaust pipe 7 is connected to the exhaust manifold of the diesel engine, and the exhaust gas that has entered from the inlet 7a passes through the diesel oxidation catalyst 3 and the DPF 2 in this order and flows to the outlet 7b. The exhaust gas purified by the diesel oxidation catalyst 3 and the DPF 2 flows into the return exhaust pipe 9 connected to the outlet 7b.

  The return exhaust pipe 9 is a pipe connecting the outlet 7 b of the inner exhaust pipe 7 and the inlet 8 a of the outer exhaust pipe 8, and the exhaust gas flowing into the return exhaust pipe 9 is connected to the exhaust gas flowing inside the inner exhaust pipe 7. Flows in the opposite direction and reaches the inlet 8a of the outer exhaust pipe 8.

  The return exhaust pipe 9 has a circular tubular linear portion 9 a extending linearly along the double exhaust pipe portion 6. The straight line portion 9a is provided with a urea injection valve 10, and the urea injection valve 10 injects urea water supplied from a urea water tank (not shown) into the exhaust gas.

  The urea injection valve 10 is provided on the upstream side of the straight portion 9a, and by injecting urea water along the flow direction of the exhaust gas in the straight portion 9a, the urea water is diffused into the exhaust gas and efficiently Mix together. The straight line portion 9a functions as a urea diffusion path for diffusing urea water into the exhaust gas.

  A urea SCR (Selective Catalytic Reduction) catalyst 4 for purifying NOx in the exhaust gas and an ammonia slip prevention catalyst 5 for preventing ammonia slip are provided between the outer exhaust pipe 8 and the inner exhaust pipe 7. .

  The urea SCR catalyst 4 and the ammonia slip prevention catalyst 5 are formed in a cylindrical shape, and are filled in a space outside the inner exhaust pipe 7 inside the outer exhaust pipe 8. The urea SCR catalyst 4 is disposed on the inlet 8 a side of the outer exhaust pipe 8, and the ammonia slip prevention catalyst 5 is disposed on the outlet 8 b side of the outer exhaust pipe 8.

  The urea SCR catalyst 4 and the ammonia slip prevention catalyst 5 are divided into four in the circumferential direction of the inner exhaust pipe 7. The urea SCR catalyst 4 is divided every 90 degrees around the inner exhaust pipe 7 in the cross section shown in FIG. 2, and is divided into four divided bodies 4A to 4D. That is, the urea SCR catalyst 4 is composed of four divided bodies 4A to 4D formed by dividing a cylinder into four in the circumferential direction.

  These divided bodies 4A to 4D are separated before the exhaust purification device 1 is assembled, and are integrated by being joined by an adhesive or the like at the time of assembly. The boundary surfaces of the divided bodies 4A to 4D may be subjected to surface processing for facilitating joining. The divided bodies 4A to 4D do not necessarily have to be joined and integrated, and may be fitted between the outer exhaust pipe 8 and the inner exhaust pipe 7 in a separable state.

  Further, the ammonia slip prevention catalyst 5 according to this embodiment is also divided into four parts in the circumferential direction like the urea SCR catalyst 4, and is composed of four divided bodies formed by dividing the cylinder into four parts.

  The exhaust gas flowing from the return exhaust pipe 9 to the inlet 8 a of the outer exhaust pipe 8 flows between the outer exhaust pipe 8 and the inner exhaust pipe 7 in the same direction as the exhaust gas flowing in the inner exhaust pipe 7. The exhaust gas flows into the urea SCR catalyst 4 in a state where urea water is added, and NOx is reduced in the urea SCR catalyst 4 by the action of ammonia generated from the urea water.

  Ammonia that has not been used for reduction by the urea SCR catalyst 4 is converted into nitrogen gas and water by being oxidized in the downstream ammonia slip prevention catalyst 5. Thereby, discharge of ammonia into the atmosphere (ammonia slip) is prevented.

  The exhaust gas passes through the urea SCR catalyst 4 and the ammonia slip prevention catalyst 5, and is then discharged from the outlet 8b of the outer exhaust pipe 8.

  According to the exhaust gas purification apparatus 1 according to the first embodiment described above, the urea SCR catalyst 4 and the ammonia slip prevention catalyst 5 disposed between the outer exhaust pipe 8 and the inner exhaust pipe 7 are divided into a plurality in the circumferential direction. Therefore, even if it is necessary to change the shape (height and width) of the outer exhaust pipe 8 in accordance with the mounting space for each vehicle type, the divided bodies 4A to 4A to 4C are formed without recreating the catalyst 4 or 5 having a new shape. It can be easily adapted by changing the arrangement and number of 4D. Therefore, according to this exhaust gas purification device 1, it becomes easier to adapt to various mounting spaces and is advantageous for cost reduction as compared with the case where a catalyst having a new shape is created each time the shape of the outer exhaust pipe 8 is changed. It is. In addition, according to this exhaust purification device 1, even if there is a manufacturing failure in a part of the catalysts 4 and 5, it is sufficient to replace them in units of the divided bodies 4A to 4D instead of the whole catalyst, thereby improving the yield of the catalyst material. be able to.

  In addition, according to the exhaust purification apparatus 1, the DPF 2 and the urea SCR catalyst 4 are respectively disposed between the inside of the inner exhaust pipe 7 and between the inner exhaust pipe 7 and the outer exhaust pipe 8 by adopting a double pipe structure. Thus, the DPF 2 and the urea SCR catalyst 4 can be integrated to reduce the size of the apparatus. Therefore, according to the exhaust gas purification device 1, the exhaust gas purification device 1 can be mounted even if the vehicle type has a small mounting space due to downsizing. Therefore, the number of vehicle types on which the DPF 2 and the urea SCR catalyst 4 can be mounted is increased. it can.

  In addition, according to the exhaust purification device 1, the DPF 2 and the urea SCR catalyst 4 are integrated and arranged close to each other, so that the heat release from the DPF 2 is suppressed and the temperature rise time during the DPF soot regeneration control is reduced. The amount of injection can be reduced, and the urea SCR catalyst 4 can be kept warm by the heat of the DPF 2, thereby shortening the warm-up time immediately after starting the engine and reducing the reducing agent injection time.

  Moreover, in this exhaust purification apparatus 1, since the return exhaust pipe 9 has the linear part 9a extended linearly, compared with the case where the return exhaust pipe 9 is formed only from a curve shape, it receives exhaust gas. Resistance can be reduced. Further, the simple structure having the straight portion 9a is advantageous for downsizing of the apparatus.

  Furthermore, in this exhaust purification device 1, since the urea injection valve 10 is provided in the straight portion 9a of the return exhaust pipe 9, urea water can be efficiently diffused in the straight portion 9a extending linearly. Moreover, since the urea injection valve 10 can be integrated in addition to the DPF 2 and the like, it is suitable for downsizing of the apparatus.

[Second Embodiment]
As shown in FIG. 3, the exhaust purification device 21 according to the second embodiment has a shape of the outer exhaust pipe 23 constituting the double exhaust pipe 22 as compared with the exhaust purification device 1 according to the first embodiment. The arrangement of the urea SCR catalyst 24 is greatly different. In addition, the same code | symbol is attached | subjected to the component same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

  Specifically, in the outer exhaust pipe 23 according to the second embodiment, the cross-sectional shape shown in FIG. 3 has an annular upper and lower end portions in order to reduce the thickness of the double exhaust pipe portion 22 in the height direction. The shape is cut by parallel straight lines. That is, the middle part of the outer exhaust pipe 23 (the part where the urea SCR catalyst 24 and the like are disposed) has a shape in which the upper and lower ends of the circular pipe are crushed and become flat. Note that the outlet side and the inlet side of the outer exhaust pipe 23 are reduced in diameter into a circular cross section as they approach the outlet or the inlet, and are connected to the return exhaust pipe 9 or the exhaust pipe on the outlet side.

  Further, the urea SCR catalyst 24 according to the second embodiment is divided into two parts in the circumferential direction of the inner exhaust pipe 7 and is divided into two divided bodies 24A and 24B. The shapes of the divided bodies 24A and 24B are the same as the divided bodies 4A to 4D in the first embodiment. The two divided bodies 24A and 24B are arranged symmetrically with the inner exhaust pipe 7 interposed therebetween.

  A filler 25 is disposed between the two divided bodies 24A and 24B. The filler 25 is disposed between the outer exhaust pipe 23 and the inner exhaust pipe 7 to prevent the exhaust gas from passing through the gaps between the divided bodies 24A and 24B. The filler 25 is provided so as to close an excess gap between the outer exhaust pipe 23 and the inner exhaust pipe 7.

  Although not shown in FIG. 3, the shape of the ammonia slip prevention catalyst is also divided in the circumferential direction like the urea SCR catalyst 24 and has the same cross-sectional shape. This is the same in the case of the third embodiment and the fourth embodiment described later.

  The filler 25 is made of a material having sufficient heat resistance. The filler 25 preferably has appropriate heat retaining properties from the viewpoint of maintaining the temperature of the DPF 3. Examples of the material of the filler 25 include a heat-resistant ceramic mat (specifically, an interlam mat [registered trademark] manufactured by Sumitomo 3M Limited).

  According to the exhaust gas purification apparatus 21 according to the second embodiment as described above, the urea SCR catalyst 24 divided in the circumferential direction is arranged on the left and right sides so that the upper and lower catalysts are eliminated. Since the thickness can be reduced, even if the mounting space is not high enough, it can be easily adapted and mounted on the vehicle.

  In addition, according to the exhaust purification device 21, the divided bodies 24A and 24B of the urea SCR catalyst 24 according to the second embodiment are the same as the divided bodies 4A to 4D according to the first embodiment. By changing this, it can be adopted in exhaust gas purification apparatuses of various types of vehicles, and the cost can be greatly reduced as compared with the case where a catalyst having a new shape is manufactured each time the housing shape is changed.

  Note that the exhaust purification device 21 may ensure the purification performance by disposing a plurality of divided bodies in the exhaust gas traveling direction by the amount corresponding to the reduced cross-sectional area of the urea SCR catalyst 24.

[Third Embodiment]
As shown in FIG. 4, the exhaust purification device 31 according to the third embodiment has a thickness in the width direction (horizontal direction) rather than the height direction, as compared with the exhaust purification device 21 according to the second embodiment. The difference is that it is made smaller.

  Specifically, the outer exhaust pipe 33 according to the third embodiment is configured so that the cross-sectional shape shown in FIG. The part is cut out by parallel straight lines. That is, the middle portion of the outer exhaust pipe 33 has a shape in which the left and right ends of the circular pipe are flattened to become a flat surface.

  Further, the urea SCR catalyst 34 according to the third embodiment is divided into two divided bodies 34A and 34B in the circumferential direction of the inner exhaust pipe 7, and the two divided bodies 34A and 34B are divided into the inner exhaust pipe 7. Are arranged symmetrically with respect to each other. A filler 35 is provided between the two divided bodies 34A and 34B. The function and configuration of the filler 35 are the same as those in the second embodiment.

  According to the exhaust emission control device 31 according to the third embodiment, the thickness in the width direction is reduced by arranging the urea SCR catalyst 34 divided into two in the circumferential direction so as to eliminate the left and right catalysts. Since the height can be reduced, even when the width of the mounting space is not sufficient, it can be easily adapted and mounted on the vehicle. Further, by making the divided bodies 34A and 34B of the urea SCR catalyst 34 according to the third embodiment common to the divided bodies according to the other embodiments, a significant cost reduction can be achieved.

  In the exhaust purification device 31, the thickness in the width direction can be further reduced by arranging the return exhaust pipe 9 closer to the outer exhaust pipe 33 than the arrangement shown in FIG. Can be reduced.

[Fourth Embodiment]
As shown in FIG. 5, the exhaust purification device 41 according to the fourth embodiment includes a urea SCR catalyst 44 including three divided bodies 44 </ b> A to 44 </ b> C as compared with the exhaust purification device 31 according to the third embodiment. The main differences are.

  Specifically, the exhaust emission control device 41 according to the fourth embodiment has a left side of the inner exhaust pipe 7 (left side in FIG. 5) in addition to the divided bodies 44A and 44B arranged above and below the inner exhaust pipe 7. It has the division body 44C arrange | positioned.

  The urea SCR catalyst 44 according to the fourth embodiment is divided into three parts 44A, 44B, and 44C. The shapes of the divided bodies 44A, 44B, and 44C are the same as the divided bodies 4A to 4D in the first embodiment. A filler 45 is disposed on the side opposite to the divided body 44C (return exhaust pipe 9 side) as viewed from the inner exhaust pipe 7, and the gap between the divided bodies 44A and 44B is closed.

  In the outer exhaust pipe 43 according to the fourth embodiment, the cross-sectional shape shown in FIG. 5 is a shape in which the right end portion of the annular ring (the end portion on the right side in FIG. 5) is cut off with a straight line. In other words, the middle part of the outer exhaust pipe 43 has a shape in which only the right side of the circular pipe along the return pipe 9 is flattened.

  According to the exhaust emission control device 41 according to the fourth embodiment, as compared with the exhaust emission purification device 1 according to the first embodiment, one of the four divided catalysts is eliminated and divided into three. Since the thickness in the width direction can be reduced, even when the width of the mounting space is not sufficient, it can be easily adapted and mounted on the vehicle. Also in this exhaust purification device 41, the thickness in the width direction can be further reduced by arranging the return exhaust pipe 9 close to the outer exhaust pipe 43.

  Furthermore, in this exhaust purification device 41, since the contact area between the catalyst and the exhaust gas can be increased as compared with the case of the second embodiment or the third embodiment described above, it is easy to ensure sufficient purification performance. Further, by making the divided bodies 44A, 44B, 44C of the urea SCR catalyst 44 according to the fourth embodiment common to the divided bodies according to the other embodiments, a significant cost reduction can be achieved.

  In addition, when the catalyst is divided into three parts as in the exhaust gas purification device 41, the structure may be such that either one of the upper and lower parts is eliminated instead of the left and right parts.

  The present invention is not limited to the embodiment described above.

  For example, in the second to fourth embodiments described above, it is not always necessary to provide a filler. By devising the shape of the outer exhaust pipe, it is possible to prevent an unnecessary gap from being generated between the outer exhaust pipe and the inner exhaust pipe. For example, in the cross-sectional shape shown in FIG. 3, the outer exhaust pipe 23 may be formed so as to eliminate the gap in which the filler 25 is disposed by denting the upper and lower sides.

  Moreover, the exhaust emission control device according to the present invention can adopt various shapes. For example, the dimensional ratios of the inner exhaust pipe, the outer exhaust pipe, the catalyst, and other components are not limited to those shown in FIGS. The inner exhaust pipe and the outer exhaust pipe may have an elliptical cross section, or may have a shape in which one or more ends of the elliptical shape are cut off with a straight line.

  The shape, number, and arrangement of the catalyst divided bodies are not limited to those described above, and a divided body obtained by dividing the cylinder into three parts every 180 ° in the circumferential direction may be adopted. A divided body may be used. In order to reduce not only the top, bottom, left and right, but also the thickness in the diagonal direction, it may be arranged so as to eliminate the diagonal catalyst. In addition, the divided catalyst bodies according to the first to fourth embodiments described above do not have to have exactly the same shape, and may have different lengths (lengths in the exhaust gas traveling direction).

  Further, the shape of the return exhaust pipe is not limited to that described above, and may be constituted only by a curved portion. The return exhaust pipe may be configured to connect the outlet of the outer exhaust pipe and the inlet of the inner exhaust pipe. In this case, the exhaust gas first enters between the outer exhaust pipe and the inner exhaust pipe, flows from the outlet of the outer exhaust pipe to the inlet of the inner exhaust pipe through the return exhaust pipe, and passes through the inside of the inner exhaust pipe to the outside. Discharged.

  The reducing agent is not limited to urea water, and may be a fuel containing HC. In this case, an HC selective reduction catalyst or the like can be employed instead of the urea SCR catalyst. The position of the reducing agent injection valve is not limited to the position shown in FIG. Further, a NOx adsorption catalyst may be employed without providing a reducing agent injection valve. When no urea water is used, it is not necessary to provide an ammonia slip prevention catalyst.

  Moreover, the exhaust emission control device according to the present invention is not limited to exhaust gas from a diesel engine, and can be used for purification of exhaust gas from various internal combustion engines.

  1, 2, 31, 41 ... Exhaust gas purification device 2 ... DPF 3 ... Diesel oxidation catalyst 4, 24, 34, 44 ... Urea SCR catalyst 4A-4D, 24A, 24B, 34A, 34B, 44A-44C ... Divided body 5 ... Ammonia slip prevention catalyst 6,22,32,42 ... Double exhaust pipe part 7 ... Inner exhaust pipe 8,23,33,43 ... Outer exhaust pipe 9 ... Return exhaust pipe 9a ... Straight part 10 ... Urea injection valve 25, 35, 45 ... Filler

Claims (3)

An exhaust purification device having a DPF and a catalyst for purifying exhaust gas,
A double exhaust pipe portion having an outer exhaust pipe and an inner exhaust pipe;
A return exhaust pipe that connects one exhaust pipe outlet and the other exhaust pipe inlet of the outer exhaust pipe and the inner exhaust pipe,
The DPF is disposed inside the inner exhaust pipe,
The exhaust gas purification apparatus, wherein the catalyst is disposed between the outer exhaust pipe and the inner exhaust pipe, and the catalyst is divided into a plurality of parts in a circumferential direction of the inner exhaust pipe.   The exhaust purification device according to claim 1, wherein the catalyst is divided into two or four in the circumferential direction of the inner exhaust pipe. The exhaust purification device according to claim 1 or 2, wherein the catalyst is a urea SCR catalyst.

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