JP2007255343A - Exhaust emission control method and exhaust emission control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control method and an exhaust emission control system usable even in small-sized cars, capable of efficiently promoting the vaporization and diffusion of a depurative at a short distance in an exhaust pipe, and enabling the depurative to reach an exhaust emission control device in a uniformized state. <P>SOLUTION: In this exhaust emission control method, the depurative F consumed in the exhaust emission control device 10 disposed in the exhaust passage 4 of an internal combustion engine E is supplied into the exhaust passage 4 on the upstream side more than the exhaust emission control device 10 by an exhaust pipe inside injection device 13 and mixed with exhaust gases G. A shielding member 14 is installed in the exhaust passage 4. The depurative F is jetted to the downstream side of the shielding member 14 to promote the pulverization of the depurative F. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification method and an exhaust gas purification system that purify exhaust gas from an internal combustion engine into an exhaust passage to purify exhaust gas or regenerate an exhaust gas purification device.

  Exhaust gas regulations on automobiles are becoming stricter, and it is becoming a situation that cannot be caught up by technological development on the engine side alone. For this reason, it is indispensable to purify the exhaust gas with an aftertreatment device, and NOx (nitrogen oxide) is reduced and removed from the exhaust gas of internal combustion engines such as diesel engines and some gasoline engines and various combustion devices. Various researches and proposals have been made on NOx catalysts for the purpose and diesel particulate filter devices (hereinafter referred to as DPF devices) that remove particulate matter (hereinafter referred to as PM) in these exhaust gases. .

  Among these, as NOx reduction catalysts for diesel engines, there are ammonia selective reduction type NOx catalysts (Selective Catalystic Reduction: SCR catalysts), NOx storage reduction type catalysts and NOx direct reduction type catalysts.

  In an exhaust gas purification system equipped with an ammonia selective reduction type NOx catalyst, an ammonia-based solution such as an aqueous urea solution, ammonia, aqueous ammonia (herein, “purifying agent”) is placed in the exhaust pipe from the engine outlet to the ammonia selective reduction type NOx catalyst NOx is purified by a selective reduction reaction of the generated ammonia with NOx by mixing exhaust gas and ammonia-based solution.

  In this exhaust gas purification system, an SCR catalyst that mainly reacts with ammonia is mainly used at present, but a purifying agent to be added is an innocuous urea aqueous solution that changes to ammonia in exhaust gas instead of toxic ammonia. We are shifting to the method.

  When this aqueous urea solution is injected into the exhaust pipe, it has a large heat capacity and latent heat of vaporization, so it does not easily turn into a gas and remains in a droplet state. When this droplet state continues, diffusion in the exhaust gas Remarkably deteriorates. Therefore, urea spray is biased in the exhaust gas, urea reaches the SCR catalyst without being able to diffuse sufficiently uniformly, the ammonia changed from urea is dispersed unevenly, and unreacted ammonia is left in the atmosphere as it is in excess. When exhausted (ammonia slip) and insufficient, unreacted NOx is discharged as it is into the atmosphere.

  Further, in the exhaust gas purification system provided with the NOx occlusion reduction type catalyst, the NOx occlusion reduction type catalyst carries a noble metal catalyst having an oxidation function and a NOx occlusion material having a NOx occlusion function such as alkali metal. Thus, two functions of NOx occlusion and NOx release / purification are exhibited depending on the oxygen concentration in the exhaust gas. When the estimated NOx occlusion amount becomes the NOx occlusion saturation amount, the exhaust gas air-fuel ratio is made rich, and regeneration control for restoring NOx occlusion capability is performed. One of the regeneration controls is to the exhaust pipe. There is an exhaust pipe injection rich control that directly supplies hydrocarbons such as fuel (herein referred to as “purifier”).

  Further, in the exhaust gas purification system provided with the NOx direct reduction catalyst, the NOx direct reduction catalyst carries a metal such as rhodium (Rh) or palladium (Pd), which is a catalyst component, on a support such as β-type zeolite, NOx is reduced directly. When the NOx reduction performance deteriorates, the regeneration control for recovering the NOx reduction performance is performed by regenerating and activating the active substance of the catalyst by setting the air-fuel ratio of the exhaust gas to a rich air-fuel ratio. One of them is in-pipe injection rich control for supplying hydrocarbons such as fuel (herein referred to as “purifier”) directly to the exhaust pipe.

  Further, in an exhaust gas purification system equipped with a continuously regenerating DPF that collects PM (particulate matter) in exhaust gas, in order to regenerate the filter by burning and removing the PM collected and accumulated in the filter portion Then, hydrocarbons such as light oil fuel (herein referred to as “purifiers”) are supplied into the exhaust pipe by injection into the exhaust pipe, and this carbonization is carried out by an oxidation catalyst arranged on the upstream side of the filter or an oxidation catalyst carried on the filter. Oxidation of hydrogen raises the temperature of the filter and burns and removes the PM of the filter.

  In these exhaust pipe injections, the efficiency of NOx purification of NOx, regeneration of NOx catalyst and regeneration of continuous regeneration type DPF is reduced when the catalyst reaches the catalyst or continuous regeneration type DPF in a state where the purifier is biased. The agent is not consumed sufficiently and is discharged downstream. For this reason, it is important to supply the purifying agent into the exhaust gas substantially uniformly to make the mixed concentration of the exhaust gas and the purifying agent uniform, and various devices have been made.

  For example, in order to evenly diffuse the reducing agent in the exhaust, a throttling part is provided in the exhaust pipe downstream of the reducing agent injection device (mixing part) to create a locally high flow rate and low pressure state. Also proposed is an engine exhaust purification system that promotes vaporization of the reducing agent, or provides a stirring member in the exhaust pipe downstream of the reducing agent injection device (mixing part) to create turbulent flow and promote exhaust gas stirring. (For example, refer to Patent Document 1).

  However, in the case where the throttle part is provided, when the reducing agent is in the spray state, the flow direction changes in the central direction in the throttle part. There is a problem that it collides with the wall surface of and adheres to the liquid. Further, when the stirring member is provided, similarly, there is a problem that the reducing agent in the spray state collides with the stirring member and adheres to the liquid.

  Furthermore, an apparatus for forming a mixture of a reducing agent and an exhaust gas, comprising a mixture forming region into which the exhaust gas and the reducing agent can be introduced, wherein at least part of the wall portion of the mixture forming region is a ridge and a recess. In particular, a device and an exhaust gas purification device that are formed into a corrugated shape, in other words, cause a vortex to flow in the exhaust pipe and mix the reducing agent are proposed (for example, see Patent Document 2). ).

  However, when a corrugated tube is used, there is a problem that soot is easily accumulated in the concave portion and causes corrosion, and the rigidity of the corrugated tube is low, so that vibration of the exhaust pipe is induced.

There is also an air-assist method that mixes compressed air and purifiers and sprays them into the exhaust pipe to make them finer so that they can easily evaporate. This is possible only with For this reason, in a small car not equipped with an air tank, a method of providing a room for evaporation and diffusion by providing a long divergent tube so as to allow uniform diffusion has been considered. However, this method has a problem that the exhaust gas purification control cannot follow the exhaust gas regulation travel mode due to transient operation due to a delay in response. For this reason, it is an important issue how to efficiently evaporate and diffuse the purifying agent in a short time to reach the exhaust gas purifying device uniformly.
JP 2002-213233 A JP 2004-510909 A

  The present invention has been made to solve the above problems, and its purpose is to efficiently promote the evaporation and diffusion of the purifier within a short distance in the exhaust pipe even in a small vehicle that cannot adopt the air assist method. An object of the present invention is to provide an exhaust gas purification method and an exhaust gas purification system that can reach the exhaust gas purification device in a state where the purification agent is made uniform.

  In the exhaust gas purification method for achieving the above object, a purification agent consumed in an exhaust gas purification device disposed in an exhaust passage of an internal combustion engine is upstream of the exhaust gas purification device by an exhaust pipe injection device. In the exhaust gas purification method in which the exhaust gas is supplied into the exhaust passage on the side and mixed into the exhaust gas, a shielding member is provided in the exhaust passage, and the purification agent is injected downstream of the shielding member, It is characterized by promoting atomization.

  In addition, the downstream side of this shielding member means the downstream side of the range where at least a part of the sprayed (or sprayed) cleaning agent is caught in the vortex generated by the shielding member. The shape of the shielding member is not particularly limited as long as a part of the exhaust passage can be narrowed to generate a vortex in the exhaust gas flow. Further, the size of the shielding member does not need to cover most of the cross section of the exhaust passage, and may be a size and a position that can prevent the exhaust gas from directly hitting the injection port of the purifying agent.

  With this configuration, the shielding member provided in the exhaust passage (exhaust pipe) deliberately turbulent and slows down the flow of stable exhaust gas to generate a vortex, and the exhaust near the portion where the vortex is generated A purifier is injected into the gas. The sprayed and atomized cleaning agent stays in the stagnation region due to the vortex generated by the shielding member and the stagnation of the return flow, and gradually flows downstream. The exhaust gas temperature is not lowered, and the purifier is efficiently evaporated. Therefore, the purifier reaches the exhaust gas purification device in a state in which it is evaporated and diffused efficiently at a short distance and is uniformized in the exhaust pipe.

  Accordingly, even if the distance between the cleaning agent injection position and the exhaust gas purification device is short, the purification agent can be uniformly diffused and sent to the exhaust gas purification device. Therefore, even in the exhaust gas regulation travel mode by transient operation, the response delay is reduced, and the followability of the purification control and the regeneration control is improved. Moreover, the structure which provides this shielding member, ie, the structure which changes the cross-sectional area of an exhaust passage discontinuously, becomes simple.

  Furthermore, in the above exhaust gas purification method, when the purifying agent injected into the exhaust passage collides with the dispersing member to promote atomization of the purifying agent, atomization and uniform dispersion can be further achieved. As this dispersing member, there is a collision plate or the like in which a portion where the cleaning agent collides is appropriately inclined (for example, 30 ° to 60 °) with respect to the injection direction of the cleaning agent. When the injection direction is a direction parallel to the flow of exhaust gas, the dispersing member can be formed of a conical rod-like body with the apex of the cone facing the cleaning agent injection port.

  The surface on which the cleaning agent collides is usually flat because it is easy to process, but in order to optimize the diffusion distribution of the injected cleaning agent, a cylindrical surface, spherical surface, conical surface, etc. The curved surface can also be used.

  An exhaust gas purification system for achieving the above object includes an exhaust gas purification device in an exhaust passage of an internal combustion engine, and a purification agent consumed in the exhaust gas purification device is supplied to the exhaust gas purification device. In the exhaust gas purification system including an exhaust pipe injection device that supplies the exhaust gas into the exhaust passage on the upstream side and mixes it with the exhaust gas, a shielding member is provided in the exhaust passage on the upstream side of the injection port of the exhaust pipe injection device. Configure.

  With this configuration, since the purifying agent can be injected into or near the swirl portion of the exhaust gas generated by the shielding member, mixing with the exhaust gas is promoted by this swirl flow. Uniformization and evaporation are performed efficiently over a short distance. Therefore, even if the distance between the injection port of the in-pipe injection device and the exhaust gas purification device is short, the purifier reaches the exhaust gas purification device in a uniformly dispersed state. Further, the structure in which the shielding member is provided in the exhaust passage has a simple structure.

  Further, in the above exhaust gas purification system, when the dispersion member for promoting atomization of the purification agent is provided in the injection passage of the purification agent in the exhaust passage, the purification agent injected into the exhaust passage By colliding with the dispersing member, atomization of the purifier can be promoted, and atomization and uniform dispersion can be further achieved. As this dispersion mechanism, a collision member or the like that disperses the atomization action and the injection direction by the collision of the injection can be used.

  In the exhaust gas purification system, the exhaust gas purification device is formed with an ammonia selective reduction type NOx catalyst, and the purification agent is an ammonia-based solution. Examples of the ammonia-based solution include ammonia water, ammonia aqueous solution, urea aqueous solution and the like used in the ammonia selective reduction type NOx catalyst.

  Alternatively, in the exhaust gas purification system, the exhaust gas purification device includes an upstream oxidation catalyst and a downstream NOx storage reduction catalyst, an upstream oxidation catalyst and a downstream side. The exhaust gas purification device formed with a NOx direct reduction type catalyst or the exhaust gas purification device formed with a continuous regeneration type diesel particulate filter having an oxidation catalyst, The purification agent is configured to be a hydrocarbon.

  With these configurations, in each exhaust gas purification system, the purifying agent can be appropriately mixed uniformly into the exhaust gas and supplied to the exhaust gas purification device, so that the NOx purification and NOx occlusion can be performed efficiently. Regeneration of the reduction catalyst or NOx direct reduction catalyst and regeneration of the continuous regeneration type diesel particulate filter can be performed.

  As described above, according to the exhaust gas purification method and the exhaust gas purification system of the present invention, the evaporation and diffusion of the purification agent can be efficiently promoted at a short distance in the exhaust pipe, and the purification agent is uniformly dispersed. It can supply to an exhaust gas purification device.

  In addition, since compressed air is not used, it can also be used in small vehicles that cannot use the air assist method.

  Hereinafter, an exhaust gas purification system according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration of an exhaust gas purification system 1 according to a first embodiment of the present invention. In the exhaust gas purification system 1, an exhaust gas purification device 10 having an ammonia selective reduction type NOx catalyst 11 is disposed in an exhaust passage 4 of an engine (internal combustion engine) E.

  This ammonia selective reduction type NOx catalyst 11 has a honeycomb structure carrier (catalyst structure) formed of cordierite, aluminum oxide, titanium oxide or the like, titania-vanadium, zeolite, chromium oxide, manganese oxide, molybdenum oxide, It is formed by supporting titanium oxide, tungsten oxide or the like.

  In this ammonia selective reduction type NOx catalyst 11, ammonia-based solution (purifying agent) F such as urea aqueous solution, ammonia, ammonia water or the like is injected into the exhaust passage 4 in an oxygen-excess atmosphere, and ammonia is selectively reduced by ammonia. By supplying the NOx catalyst 11 and selectively reacting ammonia with NOx in the exhaust gas, NOx is reduced to nitrogen and purified.

  Therefore, an exhaust pipe injection device 13 is provided in the exhaust passage 4 on the upstream side of the ammonia selective reduction type NOx catalyst 11 for supplying the ammonia-based solution F serving as a NOx reducing agent by injection or spraying. The in-pipe injection device 13 directly injects the ammonia-based solution F supplied from a storage tank (not shown) via a pipe (not shown) into the exhaust passage 4.

  Further, in order to measure the temperature of the ammonia selective reduction type NOx catalyst 11, the upstream side temperature sensor 15 and the downstream side temperature sensor 16 are respectively arranged on the upstream side and the downstream side of the ammonia selective reduction type NOx catalyst 11, that is, before and after. To do. The temperature difference in the catalyst 11 is estimated from the temperature difference between the temperature sensors 15 and 16 installed at these two locations.

  Further, the control device of the exhaust gas purification system 1 is incorporated in the control device 20 of the engine E, and controls the exhaust gas purification system 1 in parallel with the operation control of the engine E. The control device of the exhaust gas purification system 1 performs injection control of the ammonia-based solution F in the exhaust pipe injection device 13.

  In this injection control, even if the injection amount of the ammonia-based solution F is changed and the flow rate of the exhaust gas G is changed depending on the operating state (the rotational speed and the load) of the engine E, the NOx in the exhaust gas G is more efficiently changed. Is controlled so that the outflow of ammonia (ammonia slip) into the purified exhaust gas Gc on the downstream side of the exhaust gas purification device 10 is minimized.

  And in this invention, as shown in FIGS. 1-3, the shielding board (shielding member) 14 is provided in the upstream of the injection port 13a of the injection apparatus 13 in the exhaust pipe 4 in the exhaust passage 4. As shown in FIG. There are no particular limitations on the shape of the shielding plate 14, the projection amount d or the blocking rate to the exhaust passage 4, the width B, the arc angle α, etc., and the exhaust gas G is prevented from directly hitting the injection port 13 a. It is only necessary that the exhaust passage has a size and arrangement that can be reduced, and a part of the exhaust passage is narrowed to generate a vortex in the exhaust gas flow. The distance between the shielding plate 14 and the injection port 13a may be in a range where at least a part of the sprayed (or sprayed) cleaning agent is caught in the vortex generated by the shielding member.

  The size and arrangement position of the shielding plate 14 can be determined by experiment or numerical calculation, but for simplicity, the injection port 13a is located at the shielding plate 14 when viewed from the axial direction upstream of the exhaust passage 4. The size and the arrangement may be such that they cannot be seen by being blocked.

  In the configuration of FIG. 1, the in-pipe injection device 13 exhausts the injection port (opening) 13 a so as to inject the ammonia-based solution F in a direction perpendicular to the flow direction of the exhaust gas G in the exhaust passage 4. It is provided along the inner wall of the passage 4. That is, the flow direction of the ammonia-based solution F injected from the injection port 13 a is set to a direction perpendicular to the axial direction of the exhaust passage 4.

  In addition, the angle of inclination of the injection center of the ammonia-based solution F, the expansion range of the injection, the position of the injection port 13a, and the like can be adopted in accordance with the structure of each exhaust gas purification system 1. In other words, for example, a configuration in which injection is performed in a direction parallel to the flow direction of the exhaust gas G other than the configuration in which injection is performed in a direction perpendicular to the flow direction of the exhaust gas G may be employed.

  According to this configuration, the shielding plate 14 is provided in the linear portion of the exhaust passage 4 to intentionally generate a vortex in the stable exhaust gas flow, and the exhaust pipe injection device 13 is disposed in the vicinity of the downstream side of the shielding plate 14. Due to the configuration in which the injection port 13a is provided to inject the ammonia-based solution F, the ammonia-based solution F is mixed and diffused with the exhaust gas G by the vortex generated by the shielding plate 14, so that the exhaust gas temperature becomes uniform and the temperature Therefore, the ammonia-based solution F is efficiently evaporated and is efficiently evaporated and diffused in a short distance in the exhaust passage 4 to reach the exhaust gas purification device 10 uniformly. Therefore, even when the distance between the injection port 13a of the exhaust pipe injection device 13 and the exhaust gas purification device 10 is short, the ammonia-based solution F can be uniformly diffused and supplied to the exhaust gas purification device 10.

  Next, a second embodiment will be described. In the second embodiment, as shown in FIGS. 4 and 5, in addition to the configuration of the exhaust gas purification system 1 of the first embodiment, an ammonia-based solution (purifying agent) is provided in the exhaust passage 4. ) Colliding plates 17 and 17A as dispersion members for promoting atomization of the ammonia-based solution F are provided in the F injection path. Due to the dispersion effect of the collision plates 17 and 17A, atomization of the ammonia-based solution F can be promoted, and further atomization and uniform dispersion can be achieved.

  The collision plates 17 and 17A only need to have a function of dispersing the ammonia-based solution F injected to the collision plates 17 and 17A. If the collision plates 17 and 17A are provided with a function of generating a vortex that makes the flow of the exhaust gas G a vortex in addition to the function of dispersing the injection, the ammonia-based solution F can be more dispersed and uniform. .

  In the configuration shown in FIG. 4, the portion where the ammonia-based solution F collides is formed by the collision plate 17 having a plane inclined appropriately (for example, 30 ° to 60 °) with respect to the injection direction. The collision plate 17 can exert a great effect when the injection direction of the ammonia-based solution F is perpendicular to or nearly perpendicular to the flow direction of the exhaust gas G.

  In the configuration shown in FIG. 5, the collision plate 17 </ b> A is formed of a conical rod-shaped body with the apex of the cone facing the cleaning agent injection port. Further, since the shielding plate 14 only needs to shield the flow from the injection port 13a portion, the shielding plate 14 is shielded only by the shaded portion, and the other portion 14a is constituted by a support portion 14a that supports the shielding portion. This configuration can have a great effect when the injection direction of the ammonia-based solution F is at an angle that is parallel or close to parallel to the flow direction of the exhaust gas G.

  Next, the exhaust gas purification systems of the third and fourth embodiments will be described. In the exhaust gas purification systems of the third and fourth embodiments, the exhaust gas purification device 10 is formed with an upstream oxidation catalyst and a downstream NOx occlusion reduction type catalyst, and the purification agent is hydrocarbon. Configured to be. Other configurations are the same as those of the first and second embodiments, respectively.

  The oxidation catalyst is formed by supporting a catalytic metal such as platinum, rhodium, or palladium on a monolith catalyst formed of a structural material such as cordierite, silicon carbide, or stainless steel. Further, the NOx occlusion reduction type catalyst carries a noble metal catalyst such as platinum (Pt) having an oxidation function and a NOx occlusion material having a NOx occlusion function such as an alkali metal, an alkaline earth metal, and a rare earth, and thereby, exhaust gas is exhausted. Two functions of NOx occlusion and NOx release / purification are exhibited depending on the oxygen concentration in the gas.

  And this NOx occlusion reduction type catalyst occludes NOx in the catalyst metal during normal operation, and when the occlusion capacity approaches saturation, the air-fuel ratio of the exhaust gas that flows in is made the rich air-fuel ratio at a proper time, and the occluded NOx And the released NOx is reduced by the three-way function of the catalyst.

  In the exhaust gas purification system equipped with this NOx occlusion reduction type catalyst, when the estimated NOx occlusion amount becomes the NOx occlusion saturation amount, the exhaust pipe injection device 13 causes the hydrocarbons such as fuel (purifier) to be directly introduced into the exhaust passage 4. F is supplied. The hydrocarbon F is oxidized by the upstream side oxidation catalyst to make the air-fuel ratio of the exhaust gas G rich, and the absorbed NOx is released. This released NOx is reduced by a noble metal catalyst. This regeneration process restores the NOx storage capacity.

  Next, exhaust gas purification systems according to fifth and sixth embodiments will be described. In the exhaust gas purification systems of the fifth and sixth embodiments, the exhaust gas purification device 10 is formed with an upstream oxidation catalyst and a downstream NOx direct reduction catalyst, and the purification agent is hydrocarbon. Configured to be. Other configurations are the same as those of the first and second embodiments, respectively.

  As in the third and fourth embodiments, this oxidation catalyst carries a catalyst metal such as platinum, rhodium or palladium on a monolith catalyst formed of a structural material such as cordierite, silicon carbide, or stainless steel. Formed. The NOx direct reduction catalyst is formed by supporting a catalyst component such as rhodium (Rh) or palladium (Pd) on a support such as β-type zeolite. In addition, cerium (Ce), which contributes to maintaining the NOx reduction ability, is reduced by reducing the metal oxidizing action, and a three-way catalyst is provided in the lower layer to promote the NOx reduction reaction, especially in the exhaust gas rich state. In order to improve the NOx purification rate, iron (Fe) is added to the single body.

The NOx direct reduction type catalyst directly reduces NOx in a lean state during normal operation. During this reduction, oxygen (O ₂ ) is adsorbed on the metal that is the active substance of the catalyst, and the reduction performance deteriorates. To do. For this reason, when the NOx reduction performance has deteriorated, hydrocarbon (purifier) F such as fuel is supplied directly to the exhaust passage 4 by the exhaust pipe injection device 13. By oxidizing this hydrocarbon F with an upstream oxidation catalyst, the air-fuel ratio of the exhaust gas G is made rich to regenerate and activate the metal that is the active substance of the catalyst.

  Next, exhaust gas purification systems according to seventh and eighth embodiments will be described. In the exhaust gas purification systems of the seventh and eighth embodiments, the exhaust gas purification device 10 is formed with a continuous regeneration type diesel particulate filter having an oxidation catalyst so that the purification agent is a hydrocarbon. Composed. Other configurations are the same as those of the first and second embodiments, respectively.

  Examples of the continuous regeneration type diesel particulate filter having this oxidation catalyst include those formed from an upstream oxidation catalyst and a downstream filter, and those formed from a filter carrying an oxidation catalyst.

  As in the third and fourth embodiments, the upstream-side oxidation catalyst is formed of a catalytic metal such as platinum, rhodium, or palladium on a monolith catalyst formed of a structural material such as cordierite, silicon carbide, or stainless steel. Is formed. The filter is formed of a monolith honeycomb type wall-through type filter in which the inlet and outlet of the channel of the porous ceramic honeycomb are alternately plugged, that is, in a checkered pattern. This filter collects PM (particulate matter) in the exhaust gas.

  The filter carrying the oxidation catalyst is formed by carrying a catalytic metal such as platinum, rhodium or palladium on a monolith honeycomb wall-through type filter, and this filter collects PM in the exhaust gas.

  Then, in order to burn and remove the PM collected and accumulated in the filter portion, a hydrocarbon (purifier) F such as light oil fuel is supplied into the exhaust passage 4 by the injection 13 in the exhaust pipe, and the upstream side of the filter The hydrocarbon F is oxidized by an oxidation catalyst disposed on the filter or an oxidation catalyst carried on the filter, whereby the temperature of the filter is raised and PM of the filter is burned and removed.

  According to the exhaust gas purification systems of the first to eighth embodiments described above, the exhaust gas purification system 1 that supplies the purifier F into the exhaust passage 4 is injected near the downstream side of the shielding plate 14. Mixing of the purifying agent F with the exhaust gas is promoted by the vortex generated in the shielding plate 14 and the collision plates 17 and 17A, and by this mixing, the purifying agent F is uniformly dispersed and evaporated in a short distance. Therefore, the purifier F efficiently evaporates and diffuses over a short distance, and reaches the exhaust gas purification device in a uniform state.

  Therefore, even if the distance between the injection position of the purification agent F and the exhaust gas purification device 10 is short, the purification agent F can be uniformly diffused and supplied to the exhaust gas purification device 10.

  In the second embodiment of the present invention, as shown in FIG. 4, a shield plate (shielding member) 14 and a collision plate (dispersion member) 17 are provided as examples, and as shown in FIG. A comparative example 1 was prepared by providing only the collision plate 17 without providing the plate 14. Further, as shown in FIG. 7, the shield plate 14 was not provided, but the step 4 b and the collision plate 17 were provided as Comparative Example 2.

  Here, in Example 1, the diameter D of the exhaust passage 4 is 90 mmφ, and the shape of the shielding plate 14 is the arc shape shown in FIG. 3, and the protruding amount d is 15 mm, 17% of the diameter D. Is 60 degrees with respect to the root portion. In Comparative Example 2, the diameter D1 of the small diameter portion 4a is 50 mmφ, and the diameter D2 of the large diameter portion 4c is 90 mmφ.

  The distance between the shielding plate 14 and the injection port 13a in Example 1 is 50 mm, and the distance between the step 4b and the injection port 13a in Comparative Example 2 is 145 mm. As for the collision plate 17, the center of the surface of the collision plate 17 where the ammonia-based solution F collides is placed at a distance of 10 mm from the wall surface. Also, it is inclined 45 ° with respect to the main injection direction of the ammonia-based solution F.

  A NOx purification test was conducted on this example and Comparative Examples 1 and 2. This NOx purification test was conducted in the ninth mode of gasoline 13 mode (60% rotation of rated rotation, 60% torque). The results are shown in FIGS.

  The equivalent ratio on the horizontal axis shown in FIGS. 8 and 9 is the ratio of ammonia that reacts with NOx in an ideal state. When the equivalence ratio is 1, the amount of ammonia generated from the sprayed urea is an amount that reacts 1: 1 with NOx in the exhaust pipe.

  According to FIG. 8 in which the NOx purification rates are compared, Example (solid line A) and Comparative Example 2 (dotted line C) change at an ideal NOx purification rate, and the NOx purification rate is 1.0 at an equivalent ratio of 1.0. Compared to the target values of 99% and 98% for the target NOx purification rate of 90% or higher, respectively, Comparative Example 1 (dashed line B) is already ideal from around the equivalent ratio of 0.5. It can be seen that the purification rate (a purification rate of 50% in the case of an equivalence ratio of 0.5) starts slightly below, and the NOx purification rate of 82% is obtained even at an equivalence ratio of 1.0.

  Further, according to FIG. 9, ammonia slip hardly appears up to an equivalence ratio of about 1.0 in Example (solid line A) and Comparative Example 2 (dotted line C), but Comparative Example 1 (one point) with a low NOx purification rate. It can be seen that this is remarkable in the chain line B).

  Therefore, in the exhaust pipe shape in which the shielding plate 14 is provided in the vicinity of the upstream side of the in-pipe injection device 13, a high NOx purification rate can be obtained as in the exhaust pipe shape with a step without providing the step 4b in the exhaust pipe. I understand that.

It is a figure showing the whole exhaust gas purification system composition of a 1st embodiment concerning the present invention. It is a fragmentary figure which shows the structure which provided the shielding board in the upstream of the injection apparatus in an exhaust pipe. It is sectional drawing of an exhaust passage which shows the relationship between a shielding board and an exhaust passage. It is a fragmentary figure which shows the structure which provided the dispersion | distribution member formed with the collision board of 2nd Embodiment. It is a fragmentary figure which shows the structure which provided the dispersion member formed with the rod-shaped body which has the cone of 2nd Embodiment in the head. It is a fragmentary figure which shows the structure which provided the dispersion member without providing the shielding board of the comparative example 1. It is a fragmentary figure which shows the structure which provided the level | step difference and the dispersion member of the comparative example 2. It is a figure which shows the NOx purification rate of an Example and Comparative Examples 1 and 2. It is a figure which shows the ammonia slip of an Example and Comparative Examples 1 and 2. FIG.

Explanation of symbols

E Engine 1 Exhaust gas purification system 4 Exhaust passage 10 Exhaust gas purification device 11 Ammonia selective reduction type NOx catalyst 13 In-pipe injection device 13a Injection port 14 Shield plate (shield member)
17 Collision plate (dispersion member)
17A Conical rod-shaped body F Ammonia-based solution (cleaning agent, droplet)
G Exhaust gas Gc Purified exhaust gas

Claims (6)

  Exhaust gas that is supplied to the exhaust gas passage upstream of the exhaust gas purifying device by an exhaust pipe injection device and that is mixed with the exhaust gas by the exhaust gas injection device, in the exhaust gas purifying device disposed in the exhaust passage of the internal combustion engine In the gas purification method, an exhaust gas purification method characterized by providing a shielding member in the exhaust passage and injecting the purification agent downstream of the shielding member to promote atomization of the purification agent.   The exhaust gas purification method according to claim 1, wherein the purification agent injected into the exhaust passage collides with a dispersion member to promote atomization of the purification agent.   In the exhaust pipe, an exhaust gas purification device is provided in the exhaust passage of the internal combustion engine, and a purification agent consumed in the exhaust gas purification device is supplied into the exhaust passage upstream of the exhaust gas purification device and mixed into the exhaust gas. The exhaust gas purification system provided with the injection apparatus WHEREIN: The exhaust-gas purification system characterized by providing the shielding member in the said exhaust passage in the upstream of the injection port of the said injection apparatus in an exhaust pipe.   The exhaust gas purification system according to claim 3, wherein a dispersion member that promotes atomization of the purification agent is provided in the injection path of the purification agent in the exhaust passage.   The exhaust gas purification system according to claim 3 or 4, wherein the exhaust gas purification device is formed with an ammonia selective reduction type NOx catalyst, and the purification agent is an ammonia-based solution. The exhaust gas purification device is formed with an exhaust gas purification device formed with an upstream oxidation catalyst and a downstream NOx occlusion reduction catalyst, an upstream oxidation catalyst and a downstream NOx direct reduction catalyst. Or an exhaust gas purification device formed with a continuous regeneration type diesel particulate filter having an oxidation catalyst, and the purification agent is a hydrocarbon. The exhaust gas purification system according to claim 3 or 4, at least.

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