JP2011220280A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a device, and to prevent the degradation of the performance of the denitration catalyst device caused by the adsorption of an intermediate product such as an acid ammonium sulfate, even if a large amount of sulfur components are included in fuel.SOLUTION: The exhaust emission control device 1 includes: an exhaust manifold 6 which collects exhaust gas discharged form an exhaust connecting duct 3 connected to an exhaust port 2a of an engine 2, and leads the exhaust gas to an exhaust passage 5 on the upstream side of a turbine 4a of a turbocharger 4; and the denitration catalyst device 7 arranged at the exhaust passage 5. An evaporator 8 which is connected to the exhaust passage 5 at its one end 8a, and in which the other opening end 8b is opened in the exhaust manifold 6 is arranged in the exhaust manifold 6. Furthermore, a nozzle 9 which can spray an urea aqueous solution 9a to the exhaust gas passing through the evaporator 8 is arranged in the device. The wall surface of the evaporator 8 arranged in the exhaust manifold 6 is heated by high temperature exhaust gas immediately after being discharged from the exhaust connecting duct 3, thus achieving space saving, and preventing the generation of the intermediate product.

Description

  The present invention reduces and removes nitrogen oxide (hereinafter referred to as “NOx”) in exhaust gas discharged from an internal combustion engine by reacting with a reducing agent under a denitration catalyst such as SCR (Selective Catalytic Reduction). The present invention relates to an exhaust gas purification device.

  Conventionally, for example, a denitration reactor using an SCR catalyst is installed downstream of an exhaust pipe of a diesel engine, and an aqueous solution of a reducing agent composition containing high-concentration urea and low-concentration ammonia upstream of the denitration reactor. A technique is used in which NOx in the exhaust gas is decomposed into nitrogen and water and rendered harmless by a NOx removal reactor with a nozzle for spraying the gas into the exhaust gas (for example, FIG. 1 of Patent Document 1).

  Conventionally, for example, a four-cylinder marine diesel engine 101 as shown in FIG. 6 is provided with an exhaust manifold 102 that collects exhaust gases discharged from exhaust ports 101a, 101b, 101c, and 101d and guides them to an exhaust pipe 103. It has been.

  An exhaust pipe 103 between the exhaust manifold 102 and the turbine 107a of the turbocharger 107 is supplied by spraying an aqueous solution of a reducing agent such as ammonia or an aqueous solution of a reducing agent precursor such as urea into the exhaust gas. Nozzle 104, evaporation pipe 105 for generating a reducing agent such as ammonia gas by vaporizing or hydrolyzing an aqueous solution of the reducing agent or reducing agent precursor sprayed from nozzle 104, and reducing NOx in the exhaust gas There is provided an SCR catalyst 106 that purifies by selective reduction reaction with the agent.

  Thus, the reason why the position where the SCR catalyst 106 is provided is on the upstream side of the turbine 107a is that the exhaust gas temperature is lowered on the downstream side of the turbine 107a, which is disadvantageous in terms of catalyst performance.

  However, in the case where the SCR catalyst 106 is provided upstream of the turbine 107 a of the turbocharger 107, the exhaust manifold 102 occupies a large volume in the exhaust system of the diesel engine 101, and the evaporation pipe 105 and the SCR catalyst 106 are further provided. There is a need. Therefore, since these devices occupy a considerable volume in the engine room, there is a problem that the space efficiency is poor.

Further, when sulfur is contained in the fuel, SO ₂ is generated in the exhaust gas, and when an aqueous solution such as ammonia or urea is sprayed from the nozzle 104, when the temperature of the evaporation pipe 105 is low, for example, ammonium sulfate ( An intermediate product such as (NH ₄ ) ₂ SO ₄ ) or acidic ammonium sulfate (NH ₄ HSO ₄ ) is generated, and this intermediate product is adsorbed on the SCR catalyst 106, resulting in a decrease in catalyst performance. there were.

  In particular, since marine diesel engines use fuels such as light oil and heavy oil that contain more sulfur than gasoline, there is a problem that the performance of the SCR catalyst deteriorates due to the adsorption of intermediate products.

JP 2003-260331 A

  The problems to be solved by the present invention are that the conventional exhaust gas purifying apparatus has a large volume due to the exhaust manifold and the evaporation pipe, and the space efficiency is poor, and if the fuel contains sulfur, ammonium sulfate Intermediate products such as ammonium sulfate and ammonium sulfate are generated and adsorbed on the SCR catalyst, which deteriorates the catalyst performance.

The exhaust gas purifying apparatus of the present invention is
An exhaust manifold that collects exhaust gas discharged from an exhaust communication pipe connected to an exhaust port of the engine and guides the exhaust gas to an exhaust passage upstream of the turbine of the turbocharger, and a denitration catalyst device provided in the exhaust passage ,
An evaporation pipe having one end connected to the exhaust passage and the other open end opened in the exhaust manifold is provided inside the exhaust manifold, and a reducing agent and a reducing agent precursor are provided for the exhaust gas passing through the evaporation pipe. The most important feature is that a nozzle capable of spraying an aqueous solution containing either or both of the body is provided.

  Since the exhaust gas purification apparatus of the present invention is provided with the evaporation pipe inside the exhaust manifold, the size of the apparatus can be reduced. In addition, in the exhaust gas purification apparatus of the present invention, the wall surface of the evaporation pipe is sufficiently heated by the high-temperature exhaust gas immediately after being discharged from the exhaust communication pipe, so even if the fuel contains a large amount of sulfur, The exhaust gas is not cooled by the wall surface of the evaporation pipe, and generation of intermediate products such as ammonium sulfate and acidic ammonium sulfate can be prevented. Therefore, according to the present invention, the adsorption of the intermediate product to the denitration catalyst device can be prevented, and the catalyst performance can be maintained well.

It is the schematic which showed the whole structure of the exhaust-gas purification apparatus of this invention. In FIG. 1, it is the schematic which showed the longitudinal cross-section of the exhaust manifold in which the evaporation pipe | tube was incorporated, and the cylinder head vicinity of an engine. FIG. 6 is an explanatory diagram of another embodiment in which the exhaust communication pipe is disposed in a direction in which the evaporation pipe does not exist within the range in which the exhaust communication pipe is extended in the exhaust gas discharge direction, and (a) and (b) are the exhaust communication pipes. (C) is a configuration in which the center of the evaporation pipe is shifted downward from the center position of the exhaust communication pipe, and the exhaust communication pipe is arranged in the horizontal direction. It is the figure which showed the structure in the case of doing. It is explanatory drawing of the other Example which inclined the open end side rather than the direction orthogonal to the longitudinal direction of an evaporation pipe | tube, and has arrange | positioned the exhaust communication pipe | tube, (a) is located in the side of an evaporation pipe | tube. (B) is a diagram showing a configuration when the exhaust port of the exhaust communication pipe is positioned above the evaporation pipe. It is a figure explaining the structure of the other Example provided with the switching valve for bypassing, without sending exhaust_gas | exhaustion to a denitration catalyst apparatus when a denitration process is unnecessary. It is the schematic which shows the structure of the conventional marine diesel engine.

The present invention aims to save space in an exhaust gas purifying apparatus for an engine, and prevents the performance of the denitration catalyst apparatus from being deteriorated due to adsorption of intermediate products such as ammonium sulfate and acidic ammonium sulfate even when the fuel contains sulfur. The purpose of
An exhaust manifold that collects exhaust gas discharged from an exhaust communication pipe connected to an exhaust port of the engine and guides the exhaust gas to an exhaust passage upstream of the turbine of the turbocharger, and a denitration catalyst device provided in the exhaust passage ,
An evaporation pipe having one end connected to the exhaust passage and the other open end opened in the exhaust manifold is provided inside the exhaust manifold, and a reducing agent and a reducing agent precursor are provided for the exhaust gas passing through the evaporation pipe. This was achieved by providing a nozzle capable of spraying an aqueous solution containing either or both of the bodies.

In the exhaust gas purification apparatus of the present invention,
When the exhaust communication pipe is arranged in a direction in which the evaporation pipe does not exist within the range extended in the exhaust gas discharge direction,
The high-temperature exhaust gas discharged from the exhaust communication pipe does not directly hit the evaporation pipe, but flows in the exhaust manifold in the circumferential direction of the evaporation pipe, so it is not necessary to heat the evaporation pipe from one side facing the exhaust outlet of the exhaust communication pipe Therefore, the entire outer periphery of the evaporation pipe can be efficiently heated, which is preferable.

In the exhaust gas purifying apparatus of the present invention,
When the exhaust communication pipe is configured to be inclined to the open end side from the direction orthogonal to the longitudinal direction of the evaporation pipe,
The high-temperature exhaust gas discharged from the exhaust communication pipe flows outside the evaporation pipe toward the open end, so that the exhaust in the exhaust manifold flows while heating the entire length of the evaporation pipe. It is.

Furthermore, in the exhaust gas purification apparatus of the present invention,
The exhaust communication pipe is disposed in a direction in which the evaporation pipe does not exist within a range extending in the exhaust gas discharge direction, and is inclined toward the open end side from a direction orthogonal to the longitudinal direction of the evaporation pipe. If the configuration is arranged,
The high-temperature exhaust gas discharged from the exhaust communication pipe flows spirally toward the open end of the evaporation pipe toward the open end side of the evaporation pipe, so that the exhaust manifold is heated while efficiently heating the entire circumference and the entire length of the evaporation pipe. The flow of the exhaust in the inside is further improved and is most preferable.

  Hereinafter, various modes for carrying out the present invention will be described in detail with reference to FIGS. In FIG. 1, reference numeral 1 denotes an exhaust gas purification device in which the present invention is applied to a four-cylinder marine diesel engine, and exhausts from exhaust communication pipes 3 connected to exhaust ports 2 a provided in each cylinder head of the engine 2. An exhaust manifold 6 that collects the exhaust gas that has been collected and guides the exhaust gas to an exhaust passage 5 upstream of the turbine 4 a of the turbocharger 4, and a denitration catalyst device 7 that is provided in the exhaust passage 5 are provided. Reference numeral 5a denotes an exhaust passage on the downstream side of the turbine 4a, 4b denotes a compressor of the turbocharger 4 that compresses air supplied from the air supply passage 12a, and 10 denotes compressed air supplied from the air supply passage 12. An air supply manifold that distributes to the air supply port 2b of each cylinder of the engine 2 via the air communication pipe 11 is shown.

  Inside the exhaust manifold 6 is provided an evaporation pipe 8 whose one end 8 a is connected to the exhaust passage 5 and whose other open end 8 b is opened in the exhaust manifold 6, and is discharged from the exhaust port of the exhaust communication pipe 3. A nozzle 9 is provided at a position where urea water 9a can be sprayed in the vicinity of the open end 8b with respect to the exhaust gas passing through the evaporation pipe 8.

  The denitration catalyst device 7 is mounted with an SCR catalyst that selectively reduces and removes NOx contained in the exhaust gas discharged from the engine 2 and causing environmental pollution such as acid rain and photochemical smog. As the SCR catalyst, a desired catalyst such as a metal oxide catalyst such as alumina, zirconia, vanadia / titania or a zeolite catalyst can be used, and these catalysts may be combined. Further, the SCR catalyst may be supported on a catalyst carrier having a honeycomb structure, or may be charged in a cylinder and caged.

  When NOx in exhaust gas is decomposed into nitrogen and water using an SCR catalyst to make it harmless, it is necessary to supply a reducing agent such as ammonia into the exhaust gas upstream, but ammonia water is put into the ship. Storing is dangerous. Therefore, in this embodiment, urea is stored as a reducing agent precursor in an aqueous solution state in a tank (not shown) connected to the nozzle 9, and urea water 9 a is injected from the nozzle 9 into the evaporation pipe 8 during operation. The urea is hydrolyzed using the heat of the evaporation pipe 8 to generate ammonia.

  The evaporation pipe 8 is a tubular member having one end 8 a connected to the exhaust passage 5 and the other open end 8 b opened in the exhaust manifold 6. In the embodiment of FIG. 1, a nozzle 9 for spraying urea water 9a is provided in the vicinity of the open end 8b, and a rectifier 8c for rectifying the exhaust gas in the evaporation pipe 8 is provided downstream of the nozzle 9, A static mixer 8d is provided on the downstream side of the rectifier 8c in order to sufficiently mix ammonia gas and exhaust gas generated by hydrolysis of the urea water 9a sprayed from the nozzle 9 in the evaporation pipe 8.

  Therefore, in the embodiment of FIG. 1, since the entire evaporating pipe 8 including the rectifier 8c and the static mixer 8d is incorporated inside the exhaust manifold 6, the exhaust manifold and the exhaust manifold 5 are provided in the exhaust passage 5 upstream of the turbine 4a. Space can be saved and the size of the device can be reduced compared to a conventional device in which an evaporation tube is provided.

  In general, in an engine 2 equipped with a turbocharger 4, in a transient state such as during acceleration, a transient response such as a delay in introduction of the supply air due to the turbocharger 4 rather being a hindrance to a request for increasing the output of the engine 2 In the present invention, the exhaust path to the turbocharger 4 is compared with the conventional apparatus in which the exhaust manifold and the evaporation pipe are provided in the exhaust passage 5 upstream of the turbine 4a. Therefore, exhaust control is also facilitated.

  In the embodiment of FIG. 1, the longitudinal direction of the evaporation pipe 8 is the exhaust port of the exhaust communication pipe 3 so as to face the exhaust port of the exhaust communication pipe 3 connected to the exhaust port 2 a of each cylinder of the engine 2. The evaporation pipe 8 is arranged inside the exhaust manifold 6 so as to be parallel to the arrangement direction of Accordingly, since the wall surface of the evaporation pipe 8 is heated by the high-temperature exhaust gas immediately after being discharged from the exhaust communication pipe 3, even when applied to, for example, a marine diesel engine in which the fuel contains a large amount of sulfur, the denitration catalyst device 7 can reduce the generation of intermediate products such as ammonium sulfate and acidic ammonium sulfate that cause the performance degradation, and the NOx purification performance of the SCR catalyst can be maintained well.

  Next, the positional relationship between the exhaust port 8 of the exhaust communication pipe 3 opened in the exhaust manifold 6 and the evaporation pipe 8 and the arrangement direction of the exhaust communication pipe 3 will be described. FIG. 2 is an explanatory view showing a longitudinal section in the vicinity of the cylinder head of the engine 2 and the exhaust manifold 6 in which the evaporation pipe 8 is incorporated in the embodiment of FIG. 2d is a cylinder head having an exhaust port 2a and an air supply port 2b, 2c is a cylinder block having a cylinder liner, and 2e is a piston connected to a crank 2f. An arrow 11b indicates a supply direction of the fuel directly injected into the cylinder from the fuel injection nozzle 11a, and an arrow 11c indicates an introduction direction of the air compressed by the compressor 4b of the turbocharger 4.

  In the example of FIG. 2, the center of the exhaust communication pipe 3 and the center of the evaporation pipe 8 are at the same height, and the exhaust communication pipe 3 is disposed toward the center of the evaporation pipe 8. In this case, the evaporating pipe 8 is present within the range in which the exhaust communication pipe 3 is extended in the exhaust gas discharge direction (within the dotted line indicated by the symbol A in the figure).

  Therefore, in the case of the configuration shown in FIG. 2, the exhaust gas discharged from the exhaust port of the exhaust communication pipe 3 directly hits the evaporation pipe 8 as shown by the arrow B, and then is divided into upper and lower parts and the back side of the evaporation pipe 8 Will proceed to.

  On the other hand, in the embodiment shown in FIGS. 3A and 3B, the exhaust port 3a of the exhaust communication pipe 3 is disposed upward. In this case, the evaporation pipe 8 does not exist within the range in which the exhaust communication pipe 3 is extended in the exhaust gas discharge direction (within the dotted line indicated by the symbol A in the figure).

  Further, in the embodiment shown in FIG. 3C, the center position of the evaporation pipe 8 is shifted downward from the center position of the exhaust communication pipe 3, and the exhaust communication pipe 3 is disposed in the horizontal direction. Also in this case, the evaporation pipe 8 does not exist within the range in which the exhaust communication pipe 3 is extended in the exhaust gas discharge direction (within the dotted line indicated by the symbol A in the figure).

  Therefore, when configured as shown in FIG. 3, the high-temperature exhaust gas discharged from the exhaust port 3 a of the exhaust communication pipe 3 does not directly hit the evaporation pipe 8, but the circumferential direction of the evaporation pipe 8 as shown by the arrow B Therefore, the evaporation pipe 8 is not heated only from one side facing the exhaust port 3a of the exhaust communication pipe 3, but can be efficiently heated from the entire outer periphery of the evaporation pipe 8.

  In the example of FIG. 3A, the opening end of the exhaust port 3a is formed in a direction orthogonal to the longitudinal direction of the exhaust communication pipe 3. However, in the examples of FIGS. The opening end of the exhaust port 3 a is formed obliquely with respect to the longitudinal direction of the exhaust communication pipe 3 so that the tip of the exhaust communication pipe 3 protruding inward does not hinder the flow of exhaust gas flowing in the circumferential direction of the evaporation pipe 8. (In the example of FIG. 3, for example, it is cut at 45 °), and the exhaust communication pipe 3 is arranged so that the tip of the obliquely cut open end is located on the inner peripheral surface side of the exhaust manifold 6. Has been established.

  FIG. 4 shows another example in which the exhaust communication pipes 3 are arranged so as to be inclined toward the open end 8b side of the evaporation pipe 8 from the direction orthogonal to the longitudinal direction of the evaporation pipe 8 (the direction indicated by the dotted line C in the figure). It is a figure explaining the structure of an Example. Only the exhaust manifold 6 is shown as being cut in the horizontal direction at the center position in the vertical direction.

  In the example of FIG. 4A, the exhaust communication pipe 3 is located on the side of the evaporation pipe 8, and a direction perpendicular to the longitudinal direction of the evaporation pipe 8 (the direction indicated by the dotted line C in the figure) and the exhaust communication pipe The angle θ formed by the arrangement direction 3 is, for example, 30 °.

  Therefore, in the case of the configuration as shown in FIG. 4A, the high-temperature exhaust gas discharged from the exhaust communication pipe 3 has an arrow in the figure with the outside of the evaporation pipe 8 facing the open end 8b in the exhaust manifold 6. Since it flows in the direction shown by D, the exhaust in the exhaust manifold 6 flows while heating the entire longitudinal direction of the evaporation pipe 8, which is preferable.

  Further, when adopting a configuration in which the exhaust communication pipe 3 is disposed to be inclined toward the open end 8 b side of the evaporation pipe 8, the exhaust port of the exhaust communication pipe 3 is further disposed upward of the evaporation pipe 8. Alternatively, for example, as shown in FIG. 4B, when the exhaust communication pipe 3 is extended to a position above the evaporation pipe 8, the evaporation pipe 8 is within the range in which the exhaust communication pipe 3 is extended in the exhaust gas discharge direction. It also has a configuration in which it is arranged in a direction in which no exists.

  4B, for example, when the exhaust valve provided in the exhaust port 2a of each cylinder of the engine 2 is opened, the high temperature exhausted from the exhaust communication pipe 3 into the exhaust manifold 6 is increased. Since the exhaust gas is guided to the open end 8b side while drawing a spiral trajectory around the outer periphery of the evaporation pipe 8, the entire circumference and the entire longitudinal direction of the evaporation pipe 8 can be efficiently heated, and the flow of exhaust gas in the exhaust manifold 6 Will also be good.

  As described above, according to the present invention, in the exhaust gas purifying apparatus provided with the NOx removal catalyst device in the exhaust passage upstream of the turbine of the turbocharger, one end is connected to the exhaust passage and the other open end is connected to the exhaust manifold. Equipped with an open evaporation pipe in the exhaust manifold and a nozzle capable of spraying an aqueous solution such as a reducing agent precursor to the exhaust gas passing through the evaporation pipe, saving space compared to conventional devices In addition, since the evaporation pipe does not become low temperature, even when the fuel contains a large amount of sulfur, it is possible to prevent the performance of the denitration catalyst device from being degraded due to the adsorption of the intermediate product.

  The present invention is not limited to the above-described embodiments, and it goes without saying that the embodiments may be appropriately changed within the scope of the technical idea described in each claim.

  For example, in the above-described embodiment, the exhaust gas discharged from the exhaust communication pipe 3 into the exhaust manifold 6 is always sent to the denitration catalyst device 7 to perform the denitration process. For example, as shown in FIG. When denitration treatment with a catalyst is not required, a configuration may be provided that includes a bypass path 14 for exhausting directly to the turbine 4a side of the turbocharger without the denitration catalyst device 7 and a switching valve 13 for switching the exhaust path.

  Moreover, although the structure which sprays the urea water 9a as a reducing agent precursor from the nozzle 9 to the exhaust gas in the evaporator 8 was disclosed in the said Example, the component of a reducing agent precursor is not restricted to this. Moreover, you may use the mixed aqueous solution and ammonia water of high concentration urea and low concentration ammonia.

  In the present invention, the evaporation pipe 8 in the exhaust manifold 6 is heated to a high temperature by the high-temperature exhaust gas immediately after being discharged from the exhaust communication pipe 3, so that both the reducing agent and the reducing agent precursor sprayed from the nozzle 9 are used. Alternatively, the aqueous solution containing either one is surely vaporized or hydrolyzed while passing through the evaporation tube 8 regardless of the component used. Further, the vaporized reducing agent such as ammonia gas generated in the evaporation pipe 8 can be supplied to the denitration catalyst device 7 while maintaining a high temperature state together with the exhaust gas containing NOx.

  Moreover, although the example in the case where the nozzle 9 is provided in the vicinity of the open end 8b of the evaporation pipe 8 has been disclosed in the above-described embodiment, the position where the nozzle 9 is provided is not limited to this. Also good.

  However, it is advantageous to provide the nozzle 9 in the vicinity of the open end 8b of the evaporation pipe 8 because the sprayed urea water 9a can ensure a long time for passing through the high-temperature evaporation pipe 8. If the nozzle 9 is provided in the vicinity of the open end 8b of the evaporation pipe 8, a space for providing the rectifier 8c and the static mixer 8d can be easily secured.

  The exhaust gas purification apparatus of the present invention is applicable not only to marine diesel engines but also to exhaust systems of automobile diesel engines.

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification apparatus 2 Engine 2a Exhaust port 3 Exhaust communication pipe 4 Turbocharger 4a Turbine 5 Exhaust passage 6 Exhaust manifold 7 Denitration catalyst apparatus 8 Evaporating pipe 8a One end 8b Open end 9 Nozzle 9a Urea water

Claims (3)

An exhaust manifold that collects exhaust gas discharged from an exhaust communication pipe connected to an exhaust port of the engine and guides the exhaust gas to an exhaust passage upstream of the turbine of the turbocharger, and a denitration catalyst device provided in the exhaust passage ,
An evaporation pipe having one end connected to the exhaust passage and the other open end opened in the exhaust manifold is provided inside the exhaust manifold, and a reducing agent and a reducing agent precursor are provided for the exhaust gas passing through the evaporation pipe. An exhaust gas purification apparatus comprising a nozzle capable of spraying an aqueous solution containing both or one of the bodies.   The exhaust gas purification apparatus according to claim 1, wherein the exhaust communication pipe is disposed in a direction in which the evaporation pipe does not exist within a range in which the exhaust communication pipe is extended in the exhaust gas discharge direction.   The exhaust gas purification device according to claim 1 or 2, wherein the exhaust communication pipe is disposed to be inclined toward the open end side with respect to a direction orthogonal to a longitudinal direction of the evaporation pipe.

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