JP4961847B2 - Exhaust gas purification method and exhaust gas purification system - Google Patents

Description

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

  Further, the air flow control means for imparting a turning force to the air flow, the air flow control means having a flow control body such as a valve, and a bypass passage for communicating the upstream side and the downstream side of the air flow control body, and the air flow control means. At least one injection means for injecting fuel or other liquid in a direction perpendicular to or intersecting with the central axis of the swirling airflow, and a vaporization means arranged downstream of the injection means and capable of constricting and heating the airflow A vaporizing and mixing apparatus configured to be provided has been proposed (see, for example, Patent Document 3).

  However, in this configuration, since a turning force around the main direction of the airflow is applied, fuel or the like is likely to adhere to the wall surface of the intake passage due to the centrifugal force, and the airflow control device has a special shape, so In addition, there is a problem that the pressure loss is large.

There is also an air-assist method that mixes compressed air and purifiers and sprays them in the exhaust pipe to make them finer so that they can be easily evaporated. This method is used for medium and large vehicles equipped with air tanks. This is possible only with Therefore, in a small vehicle 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 JP 2004-324585 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 a method for purifying exhaust gas that is supplied into the exhaust passage on the side and mixed into the exhaust gas, a planar shielding plate is provided around the axis perpendicular to the main direction of the exhaust gas flow in the exhaust passage. Inclined at a predetermined angle within a range of 30 to 60 degrees from the main direction of the flow of the exhaust, and provided so as to block the injection port of the exhaust pipe injection device when viewed from the axial direction upstream of the exhaust passage Thus, the exhaust gas is prevented from directly hitting the injection port, and the flow of the exhaust gas is turbulent and slowed to generate a vortex, and the purifier is injected downstream of the shielding plate. It is characterized by .

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

  According to this configuration, the shielding plate provided at a predetermined angle in the exhaust passage (exhaust pipe) deliberately turbulent and slows the flow of the stable exhaust gas to generate a vortex. A cleaning agent is injected in the vicinity of the portion where the vortex flow is generated. The sprayed and atomized cleaning agent is localized in the spraying of the cleaning agent because the cleaning agent atomized by the vortex generated by the shielding plate and the stagnation region by the return flow stays 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 board, ie, the structure which changes the cross-sectional area of an exhaust passage discontinuously, becomes simple.

Furthermore, in the above exhaust gas purification method, if the predetermined angle is 30 ° to 60 °, preferably 40 ° to 50 °, the NOx purification rate is improved by promoting the generation of eddy currents, NH It is possible to balance the effect of ₃ ) slip reduction / prevention with the negative effect of the rate of increase in exhaust pressure, which is an increase in pressure loss.

  The above exhaust gas purification method is particularly effective when the exhaust gas purification device is formed with an ammonia selective reduction type NOx catalyst and the purification agent is an ammonia-based solution.

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 provided with an exhaust pipe injection device that supplies the exhaust gas into the exhaust passage on the upstream side and mixes the exhaust gas with the exhaust gas, the exhaust gas is about the axis perpendicular to the main direction of the exhaust gas flow in the exhaust passage. A planar shielding plate inclined at a predetermined angle within a range of 30 to 60 degrees from the main direction of gas flow is provided upstream of the injection port of the exhaust pipe injection device and on the upstream side of the exhaust passage. When viewed from the direction, the injection port of the injection device in the exhaust pipe is shielded to prevent the exhaust gas from directly hitting the injection port, and the flow of the exhaust gas is turbulent and slowed to generate eddy currents. makes Constitute provided.

  With this configuration, since the purifying agent can be injected into or near the swirl portion of the exhaust gas generated by the shielding plate, mixing with the exhaust gas is promoted by this swirl flow. Uniform dispersion 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 plate is provided in the exhaust passage has a simple structure.

Further, in the above exhaust gas purification system, when the predetermined angle is set to an angle within a range of 30 degrees to 60 degrees, preferably 40 degrees to 50 degrees, the NOx purification rate is improved by promoting the generation of eddy currents, NH It is possible to balance the effect of ₃ ) slip reduction / prevention with the negative effect of the rate of increase in exhaust pressure, which is an increase in pressure loss.

  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. Based on the temperature difference between the temperature sensors 15 and 16 installed at these two locations, the temperature difference in the ammonia selective reduction type NOx catalyst 11 is estimated.

  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. 1-7, 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 in the exhaust passage 4. As shown in FIG. As shown in FIG. 3, the shielding plate 14 is provided to be inclined at a predetermined angle θ around an axis 14 c perpendicular to the main direction X of the exhaust gas G flow.

The predetermined angle θ is an angle in the range of 30 degrees to 60 degrees, preferably 40 degrees to 50 degrees. This balances the effects of improving the NOx purification rate by promoting the generation of eddy currents, reducing and preventing NH ₃ slip, and the negative effect of the exhaust pressure increase rate, which is an increase in pressure loss.

  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. Further, the distance between the shielding plate 14 and the injection port 13a may be within a range where at least a part of the sprayed (or sprayed) cleaning agent is caught in the vortex generated in the shielding plate 14.

  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 has an injection port (opening) 13 a so as to inject the ammonia-based solution F in a direction perpendicular to the direction X of the flow of the exhaust gas G in the exhaust passage 4. It is provided so as to protrude from the inner wall of the exhaust 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 X 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 X of the exhaust gas G other than the configuration in which injection is performed in a direction perpendicular to the flow direction X of the exhaust gas G may be employed.

  According to this configuration, the shielding plate 14 inclined at a predetermined angle θ is provided in the linear portion of the exhaust passage 4 to intentionally generate a vortex flow in the stable flow of the exhaust gas G, and on the downstream side of the shielding plate 14. With the configuration in which the injection port 13a of the exhaust pipe injection device 13 is provided in the vicinity to inject the ammonia solution F, the ammonia solution F is mixed and diffused with the exhaust gas G by the vortex generated by the shielding plate 14. Therefore, the exhaust gas temperature is made uniform, and a low temperature portion is not generated, so that the ammonia-based solution F is efficiently evaporated, and the exhaust gas purification device uniformly evaporates and diffuses in a short distance in the exhaust passage 4. Reach 10 Accordingly, 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. 5 to 7, 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 to make 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. 5, 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 substantially perpendicular to the flow direction X of the exhaust gas G.

  Further, in the configuration shown in FIGS. 6 and 7, the collision plate 17A is formed of a conical rod-shaped body having the apex of the cone opposed to the cleaning agent injection port. Moreover, since the shielding board 14 should just be able to shield a flow with respect to the injection port 13a part, the structure which becomes only the support part 14a except this shielding part may be sufficient. This configuration can have a great effect when the injection direction of the ammonia-based solution F becomes an angle parallel to or close to parallel to the flow direction X 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 flowing in is made rich to the rich air-fuel ratio 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.

This 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 directly supplied 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, and the metal that is the active substance of the catalyst is regenerated and activated.

  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. The purifier F is promoted to mix with the exhaust gas by the vortex generated by the shielding plate 14 and the collision plates 17 and 17A inclined by the predetermined angle θ, and this mixing shortens the dispersion and uniformization of the purifier F and evaporation. Done at 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. 5, a shield plate 14 and a collision plate (dispersing member) 17 are provided as examples, and as shown in FIG. 8, the shield plate 14 is provided. A comparative example was provided with only the collision plate 17.

  Here, in the embodiment, 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. 4, and the protruding amount d is 15 mm, 17% of the diameter D, The spread angle α is 60 degrees with respect to the root portion. Further, the predetermined angle θ around the axis 14c perpendicular to the main flow direction X of the exhaust gas is set to 45 degrees.

  In the embodiment, the distance between the shielding plate 14 and the injection port 13a is 50 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, and the collision surface is in the main direction X of the flow of the exhaust gas G. On the other hand, it is also inclined 45 degrees with respect to the main injection direction of the ammonia-based solution F.

  A NOx purification test was conducted on this example and the comparative example. 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 equivalence ratio on the horizontal axis shown in FIGS. 9 and 10 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. 9 in which the NOx purification rates are compared, in the example (solid line A), the NOx purification rate changes in an almost ideal state, and at an equivalence ratio of 1.0, the NOx purification rate is 90% or more of the target NOx purification rate. On the other hand, the target value is 99%, which is higher than the target value, but in comparison, the comparative example (dotted line B) already has an ideal purification rate from around the equivalent ratio of 0.5 (a purification rate of 50 when the equivalent ratio is 0.5). %), The NOx purification rate is 82% even at an equivalence ratio of 1.0.

  Further, according to FIG. 10, ammonia slip hardly appears up to an equivalence ratio of around 1.0 in the example (solid line A), but it is remarkable in the comparative example (dotted line B) where the NOx purification rate is low.

Thus, in the exhaust pipe shape having a predetermined angle θ inclined shield 14 in the vicinity of the upstream side of the exhaust pipe injector 13, without providing a step in the exhaust pipe, similarly to the stepped exhaust pipe shape, high NOx It can be seen that the purification rate can be obtained.

  Further, FIG. 11 shows the NOx purification rate (solid line C) and the exhaust pressure increase rate (dotted line D) when the predetermined angle (inclination angle) θ shown in FIG. 3 is changed. The exhaust pressure increase rate is defined as P0 when the shield plate 14 is attached at a predetermined angle θ of 0 degree, and P1 when the predetermined angle θ is 90 degrees. , X is an exhaust pressure actual measurement value at the measurement angle θ, and y is an exhaust pressure increase degree (% display), and is obtained from an equation of y = (x−P0) / (P1−P0) × 100. That is, y = (exhaust pressure difference from 0 degree at the measurement angle θ) / (exhaust pressure difference from 0 to 90 degrees) × 100. From FIG. 11, it is understood that when the predetermined angle θ is 30 degrees to 60 degrees, the NOx purification rate can be maintained while suppressing the exhaust pressure increase rate.

It is a figure showing the whole exhaust gas purification system composition of a 1st embodiment concerning the present invention. It is a sectional side view of the exhaust passage which shows the part which provided the shielding board. FIG. 3 is a plan sectional view of FIG. 2. FIG. 3 is a cross-sectional view of FIG. 2. It is a sectional side view of the exhaust passage which shows the structure which provided the dispersion member formed with the collision board of 2nd Embodiment. It is a sectional side view of the exhaust passage 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 cross-sectional view of FIG. It is a sectional side view of the exhaust passage which shows the structure which provided the dispersion member without providing the shielding board of a comparative example. It is a figure which shows the NOx purification rate of an Example and a comparative example. It is a figure which shows the ammonia slip of an Example and a comparative example. It is a figure which shows the relationship between the change of the inclination angle of an Example, a NOx purification rate, and an exhaust pressure raise rate.

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 Exhaust pipe injection device 13a Injection port 14 Shield plate (shield member)
14a support part 14c shaft 17 collision plate (dispersion member)
17A Conical rod-shaped body θ Predetermined angle (tilt angle)
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, the planar shielding plate is provided within a predetermined range of 30 to 60 degrees from the main direction of the exhaust gas flow around an axis perpendicular to the main direction of the exhaust gas flow in the exhaust passage. In addition to preventing the exhaust gas from directly hitting the injection port, it is provided so as to block the injection port of the injection device in the exhaust pipe when viewed from the axial direction upstream of the exhaust passage. An exhaust gas purification method characterized in that the flow of the exhaust gas is turbulent and slowed to generate a vortex and the purifier is injected downstream of the shielding plate.   2. The exhaust gas purifying method according to claim 1, wherein the sprayed purifier is collided with a collision plate provided in the purifier spray path to promote atomization of the purifier. 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. In an exhaust gas purification system including an injection device, a predetermined angle within a range of 30 to 60 degrees from a main direction of the exhaust gas flow around an axis perpendicular to the main direction of the exhaust gas flow in the exhaust passage. When the planar shielding plate inclined at an angle is viewed on the upstream side of the injection port of the exhaust pipe injection device from the axial direction upstream of the exhaust passage, the injection port of the exhaust pipe injection device is blocked, An exhaust gas purification system provided to prevent the exhaust gas from directly hitting the injection port and to generate a vortex by turbulent and slowing the flow of the exhaust gas.   The exhaust gas purification system according to claim 3, wherein a collision plate as a dispersion member for promoting 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 type catalyst, and an upstream oxidation catalyst and a downstream NOx direct reduction type catalyst. Or an exhaust gas purification device formed with a continuously regenerating 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.

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