JP5890661B2 - Exhaust purification equipment - Google Patents

Description

  The present invention relates to an exhaust emission control device.

  In recent years, a particulate filter that collects particulates in exhaust gas is provided in the middle of an exhaust pipe of an engine, and post-treatment that can selectively react NOx with ammonia even in the presence of oxygen on the downstream side of the particulate filter It has been proposed that a selective reduction catalyst as an apparatus is provided, and urea water is added as a reducing agent between the selective reduction catalyst and the particulate filter to simultaneously reduce particulates and NOx.

  In this case, since the urea water is added to the selective reduction catalyst between the particulate filter and the selective reduction catalyst, the urea water added in the exhaust gas is heated to ammonia and carbon dioxide. In order to secure sufficient reaction time until decomposition, it is necessary to increase the distance from the urea water addition position to the selective catalytic reduction catalyst. However, there is a sufficient distance between the particulate filter and the selective catalytic reduction catalyst. If they are spaced apart from each other, the mountability on the vehicle is significantly impaired.

  For this reason, a compact exhaust gas purification device as shown in FIG. 2 has already been proposed by the same applicant as the present invention. In the exhaust gas purification device shown here, an exhaust pipe 2 through which exhaust gas 1 from the engine flows is provided. In the middle of the process, a particulate filter 3 for collecting particulates in the exhaust gas 1 and selective reduction having the property of allowing NOx to selectively react with ammonia even in the presence of oxygen on the downstream side of the particulate filter 3. The catalyst 4 is held in parallel by the casings 5 and 6 and arranged in parallel, and the S-structured communication flow is provided between the outlet end of the particulate filter 3 and the inlet end of the selective catalytic reduction catalyst 4. The exhaust gas 1 connected through the passage 7 and exhausted from the outlet end of the particulate filter 3 is folded in the reverse direction and introduced into the inlet end of the adjacent selective catalytic reduction catalyst 4. The

  Here, the communication channel 7 surrounds the outlet side end of the particulate filter 3 and collects the exhaust gas 1 immediately after exiting from the outlet side end while changing the direction in a substantially perpendicular direction. A chamber 7A, a mixing pipe 7B for extracting the exhaust gas 1 collected in the gas collecting chamber 7A in a direction opposite to the exhaust flow of the particulate filter 3, and a direction in which the exhaust gas 1 guided by the mixing pipe 7B is substantially perpendicular The S-shaped structure is formed by the gas dispersion chamber 7C surrounding the inlet side end so that the dispersed exhaust gas 1 can be introduced into the inlet side end of the selective catalytic reduction catalyst 4 while being dispersed. The injector 8 for adding urea water into the mixing pipe 7B is provided at the central position of the inlet side end of the mixing pipe 7B. It is equipped toward the side end portion side.

  In the example shown here, an oxidation catalyst 9 that oxidizes unburned fuel in the exhaust gas 1 is provided in the front stage in the casing 5 in which the particulate filter 3 is held, Further, an ammonia reduction catalyst 10 as a post-treatment device that oxidizes surplus ammonia is provided at the rear stage in the casing 6 in which the selective catalytic reduction catalyst 4 is held, and a rear chamber is provided at the downstream end of the casing 6. 11 is connected.

  If such a configuration is adopted, particulates in the exhaust gas 1 are collected by the particulate filter 3, and urea water is fed from the injector 8 into the exhaust gas 1 in the middle of the mixing pipe 7 B on the downstream side. Is added to the catalyst and thermally decomposed into ammonia and carbon dioxide, and the NOx in the exhaust gas 1 is reduced and purified well by the ammonia on the selective catalytic reduction catalyst 4, so that simultaneous reduction of particulates and NOx in the exhaust gas 1 is achieved. It will be illustrated.

  At this time, the exhaust gas 1 discharged from the outlet end portion of the particulate filter 3 is folded in the reverse direction by the connecting flow path 7 and then introduced into the inlet end portion of the adjacent selective catalytic reduction catalyst 4. Therefore, a long distance from the urea water addition position to the selective catalytic reduction catalyst 4 is secured, and a sufficient reaction time is secured for ammonia to be generated from the urea water.

  In addition, the particulate filter 3 and the selective catalytic reduction catalyst 4 are arranged in parallel, and the communication flow path 7 is arranged between the particulate filter 3 and the selective catalytic reduction catalyst 4, so that the whole The configuration becomes compact, and the mountability to the vehicle is greatly improved.

  However, by adopting a structure as shown in FIG. 2, the exhaust gas 1 must be reversed and introduced into the selective catalytic reduction catalyst 4, and more specifically, the downstream portion of the connecting flow path 7. Is formed so that the exhaust gas 1 is introduced through the exhaust inlet 12 from a direction substantially orthogonal to the direction of the axis O of the selective catalytic reduction catalyst 4, and the axial axis of the selective catalytic reduction catalyst 4 is formed. The outlet end portion of the mixing pipe 7B extending in the center direction is formed so as to be bent in a substantially perpendicular direction and connected to the exhaust inlet 12.

  In this way, the exhaust gas 1 is inverted and introduced to the selective catalytic reduction catalyst 4 so that when the exhaust gas 1 is inverted, the exhaust gas 1 tends to be biased to flow outwardly in the bending direction. Since there is a concern that the exhaust gas 1 is introduced non-uniformly with respect to the catalyst 4 and the catalyst performance that should be originally exhibited may not be sufficiently extracted, the gas dispersion chamber 7C has an inlet side end face of the selective catalytic reduction catalyst 4. The depression 13 is formed so as to warp in the direction away from the exhaust gas inlet 12 and move closer to the inlet side end face of the selective catalytic reduction catalyst 4 as the exhaust gas 1 is introduced from the exhaust inlet 12. As a result, the flow of the exhaust gas 1 is suppressed, and the tendency that a relatively large amount of the exhaust gas 1 flows to the outside in the bending direction is corrected.

  Further, a recess 14 is formed at the position immediately before the bent portion formed by the mixing pipe 7B and the exhaust inlet 12 to guide the flow of the exhaust gas 1 inside in the bending direction to the outside. The recess 14 immediately before the bent portion. By swinging the inner portion in the bending direction to the outside once at a position, the curvature of the bent portion is reduced to make the bending state gentle, and the flow of the exhaust gas 1 can be bent as smoothly as possible to be led to the exhaust inlet 12. It is.

  For example, Patent Document 1 shows a general technical level related to this type of exhaust purification device.

JP 2009-68415 A

  By the way, when there is a demand to increase the NOx treatment capacity by increasing the diameter of the selective catalytic reduction catalyst 4 and the ammonia reduction catalyst 10 as the aftertreatment device of the exhaust gas purification device as shown in FIG. If the existing gas dispersion chamber 7C and the rear chamber 11 are to be used as they are, the selective reduction in which the diameter of the gas dispersion chamber 7C and the rear chamber 11 is increased as shown in FIGS. 3 (a) and 3 (b). It is conceivable that the mold catalyst 4 and the casing 6 of the ammonia reduction catalyst 10 are assembled so as to be arranged concentrically.

  However, as described above, when the gas dispersion chamber 7C and the rear chamber 11 and the casing 6 of the selective catalytic reduction catalyst 4 and the ammonia reduction catalyst 10 whose diameters are increased are arranged concentrically, the casing 6 is formed in the gas dispersion chamber 7C. The inner region of the casing 6 corresponding to the inner side of the bending direction in which the exhaust gas 1 that has passed through the mixing pipe 7B is reversed, particularly when the engine is heavily loaded (in FIG. 3 (a), The exhaust gas 1 is less likely to reach the area surrounded by the phantom line, and the selective reduction catalyst 4 and the ammonia reduction catalyst 10 located in the inner area of the casing 6 may not function sufficiently.

  In view of such circumstances, the present invention is intended to provide an exhaust emission control device that can eliminate an area in which exhaust gas is difficult to spread and can function sufficiently even if the post-treatment device has a large diameter.

The present invention relates to a post-processing device that allows exhaust gas to pass through and purifies, a casing that holds the post-processing device, an inlet side end surface of the post-processing device, and intersects with the axis of the post-processing device. An exhaust gas purifying apparatus having a gas dispersion chamber for introducing exhaust gas from a direction in which the exhaust system is disposed, and having a layout in which the exhaust gas is reversed so as to be folded back into the aftertreatment device and introduced through the gas dispersion chamber. ,
The post-treatment device is a selective reduction catalyst and an ammonia reduction catalyst having a larger diameter than the gas dispersion chamber, and the diameter of the inlet end of the casing is gradually reduced toward the gas dispersion chamber, and the casing is The exhaust gas is arranged so as to swell outward in the bending direction in which the exhaust gas is reversed with respect to the outer periphery of the gas dispersion chamber, and the axial center of the aftertreatment device is directed outward in the bending direction in which the exhaust gas is reversed. The present invention relates to an exhaust emission control device characterized by being eccentric from an axial center.

  According to the above means, the following operation can be obtained.

  When there is a demand to increase the NOx treatment capacity by increasing the diameter of the selective reduction catalyst and ammonia reduction catalyst as the aftertreatment device of the exhaust gas purification device, the existing gas dispersion chamber is used as it is for cost reduction. When the axis of the selective reduction catalyst and the ammonia reduction catalyst as the aftertreatment device is decentered from the axis of the gas dispersion chamber toward the outside in the bending direction where the exhaust gas is reversed as described above, the centrifugal force accompanying the reversal As a result, the exhaust gas that tends to go outward in the bending direction is easily dispersed from the axial center of the selective reduction catalyst and the ammonia reduction catalyst as the aftertreatment device.

  As a result, the selective reduction catalyst and ammonia reduction as the post-treatment device are different from the concentrically arranging the gas dispersion chamber and the selective reduction catalyst and ammonia reduction catalyst as the post-treatment device having an enlarged diameter. The catalyst does not swell evenly from the outer periphery of the gas dispersion chamber, but swells outward in the bending direction where the exhaust gas reverses. Therefore, even when the engine is under heavy load, the catalyst is bent in the bending direction. It is avoided that the exhaust gas hardly spreads to the region corresponding to the inner side, and the selective reduction catalyst and the ammonia reduction catalyst as the aftertreatment device function sufficiently.

  According to the exhaust emission control device of the present invention, it is possible to eliminate the region where the exhaust gas hardly spreads, and it is possible to obtain an excellent effect that it can function sufficiently even if the post-treatment device is enlarged in diameter.

It is the schematic which shows the Example of the exhaust gas purification apparatus of this invention, Comprising: (a) is a schematic sectional side view, (b) is a schematic front view. It is a general | schematic structure sectional drawing which shows an example of the conventional exhaust gas purification apparatus. It is the schematic which shows the case where the selective reduction type | mold catalyst as an aftertreatment apparatus in an example of the conventional exhaust gas purification apparatus is enlarged, (a) is a schematic sectional side view, (b) is a schematic front view.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 shows an embodiment of an exhaust emission control device according to the present invention. In the figure, the same reference numerals as those in FIGS. 2 and 3 denote the same components, and the basic configuration is shown in FIGS. However, the feature of this embodiment is that the exhaust gas 1 passing through the mixing pipe 7B is directed to the outside in the bending direction in which the exhaust gas 1 is reversed, as shown in FIG. The center O ′ of the selective reduction catalyst 4 and the ammonia reduction catalyst 10 is eccentric from the axis O of the gas dispersion chamber 7C.

  In the case of the present embodiment, the selective reduction catalyst 4 and the ammonia reduction catalyst 10 as the post-treatment device have a larger diameter than the gas dispersion chamber 7C, and therefore the selective reduction catalyst 4 and the ammonia reduction catalyst in the cylindrical casing 6. 10 is inserted, the inlet end and the outlet end of the cylindrical casing 6 are throttled by machining such as a spatula throttle and connected to the gas dispersion chamber 7C and the rear chamber 11, or the selective reduction A reducer member that is formed as a separate body and whose diameter is gradually reduced is joined by welding or the like to the inlet side end portion and the outlet side end portion of the cylindrical casing 6 in which the mold catalyst 4 and the ammonia reducing catalyst 10 are inserted, The open end of the reducer member can be connected to the gas dispersion chamber 7C and the rear chamber 11.

  Next, the operation of the above embodiment will be described.

  When there is a demand to increase the NOx treatment capacity by increasing the diameter of the selective catalytic reduction catalyst 4 and the ammonia reduction catalyst 10 as the after-treatment device of the exhaust gas purification device as shown in FIG. When the gas dispersion chamber 7C and the rear chamber 11 are used as they are, as described above, the selective reduction catalyst 4 and ammonia as the aftertreatment device are directed to the outside in the bending direction in which the exhaust gas 1 that has passed through the mixing pipe 7B is reversed. When the axial center O ′ of the reduction catalyst 10 is decentered from the axial center O of the gas dispersion chamber 7C, the exhaust gas 1 that tends to move outward in the bending direction due to the centrifugal force accompanying reversal is a selective reduction catalyst as a post-processing device. 4 and the axis O ′ of the ammonia reduction catalyst 10 are easily dispersed throughout.

  As a result, as shown in FIGS. 3 (a) and 3 (b), the gas dispersion chamber 7C and the rear chamber 11, and the casing 6 of the selective reduction catalyst 4 and the ammonia reduction catalyst 10 whose diameters are increased are concentric. Unlike the arrangement in FIG. 2, the casing 6 does not swell evenly from the outer periphery of the gas dispersion chamber 7C, but swells outward in the bending direction in which the exhaust gas 1 that has passed through the mixing pipe 7B is reversed. Therefore, even when the engine is heavily loaded, it is avoided that the exhaust gas 1 hardly spreads to the inner region of the casing 6 corresponding to the inside of the bending direction in which the exhaust gas 1 that has passed through the mixing pipe 7B is reversed. The selective catalytic reduction catalyst 4 and the ammonia reduction catalyst 10 as a whole function sufficiently.

  In this way, it is possible to eliminate the region where the exhaust gas is difficult to spread, and even if the post-treatment device is enlarged, it can function sufficiently.

  The exhaust emission control device of the present invention is not limited to the above-described embodiment, and various changes can be made without departing from the scope of the present invention.

1 exhaust gas 2 exhaust pipe 3 particulate filter 4 selective reduction catalyst (post-treatment device)
6 Casing 7C Gas dispersion chamber 10 Ammonia reduction catalyst (post-treatment device)
O axis center O 'axis center

Claims (1)

An aftertreatment device that purifies the exhaust gas by passing it through, a casing that holds the aftertreatment device, and an inlet side end face of the aftertreatment device that encloses and exhausts from a direction that intersects the axis of the aftertreatment device In the exhaust gas purification apparatus adopting a layout in which an exhaust system is provided with a gas dispersion chamber for introducing gas, and the exhaust gas is reversed so as to be folded back to the aftertreatment device and introduced through the gas dispersion chamber.
The post-treatment device is a selective reduction catalyst and an ammonia reduction catalyst having a larger diameter than the gas dispersion chamber, and the diameter of the inlet end of the casing is gradually reduced toward the gas dispersion chamber, and the casing is The exhaust gas is arranged so as to swell outward in the bending direction in which the exhaust gas is reversed with respect to the outer periphery of the gas dispersion chamber, and the axial center of the aftertreatment device is directed outward in the bending direction in which the exhaust gas is reversed. An exhaust emission control device characterized by being eccentric from a shaft center.

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