WO2013136614A1

WO2013136614A1 - Exhaust gas purification device

Info

Publication number: WO2013136614A1
Application number: PCT/JP2012/082202
Authority: WO
Inventors: 孝博藤林
Original assignee: 日立造船株式会社
Priority date: 2012-03-15
Filing date: 2012-12-12
Publication date: 2013-09-19
Also published as: CN104136727B; TW201339409A; TWI576507B; KR101619098B1; KR20140129366A; JPWO2013136614A1; CN104136727A; JP5801472B2

Abstract

[Problem] An evaporation tube given a greater diameter than that of an exhaust gas channel has been the reason it is difficult to reduce device size. [Solution] An evaporation tube (18), both longitudinal ends of which are opened, is provided to an upstream side of a denitration reactor (17) and inside an exhaust gas channel (15). A nozzle (19) is provided from which an aqueous solution including a reducing agent and/or a reducing agent precursor can be sprayed into an exhaust gas that passes through the evaporation tube (18). An outlet part (18a) of the evaporation tube (18) is given a smaller diameter than that of an inlet part (18b), and a Venturi tube (15a) is formed in the exhaust gas channel (15) so as to include a position where the open end of the outlet part (18a) of the evaporation tube (18) is present. [Effects] Ample time for the hydrolysis reaction of aqueous urea to proceed can be ensured, and the diameter of a flow rate reduction zone is reduced in size.

Description

Exhaust gas purification device

The present invention relates to an exhaust gas purifying apparatus for reducing and removing 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 an SCR catalyst. .

Conventionally, for example, a denitration reactor in which an SCR catalyst is interposed in an exhaust passage of a diesel engine has been provided, and an exhaust gas purification system provided with a nozzle capable of spraying a reducing agent precursor such as urea water on the upstream side of the denitration reactor. An apparatus is used (for example, Patent Document 1).

In the apparatus as described above, the urea water sprayed into the exhaust gas from the nozzle is hydrolyzed as shown in the following formula (1) before reaching the SCR catalyst if the temperature in the exhaust passage is sufficiently high. As a result, ammonia gas (NH ₃ ) is generated.
(NH ₂ ) ₂ CO + H ₂ O → 2NH ₃ + CO ₂ ... (1)

The ammonia gas generated by the hydrolysis is supplied to the SCR catalyst, whereby a denitration reaction such as the following formulas (2) and (3) is performed between ammonia and NOx in the exhaust gas on the SCR catalyst, NOx is decomposed into nitrogen and water and detoxified.
4NH ₃ + 4NO + O ₂ → 4N ₂ + 6H ₂ O (2)
2NH ₃ + NO + NO ₂ → 2N ₂ + 3H ₂ O (3)

As described above, in the exhaust gas purification apparatus using the SCR catalyst, it is necessary to secure a time for the hydrolysis reaction of the above formula (1) to sufficiently proceed while the sprayed urea water flows in the exhaust passage.

For this reason, conventionally, in a four-cylinder marine diesel engine 102 having an exhaust manifold 101 as shown in FIG. An evaporation pipe 107 having a pipe cross-sectional area larger than that of the exhaust passage 104 is provided between the 105 and the SCR catalyst 106. The flow rate of the exhaust gas in the section in which the evaporation pipe 107 is provided is reduced and sprayed from the nozzle 105. There may be a case where the time for the hydrolysis reaction of urea water to proceed is secured.

Conventionally, as shown in FIG. 10, the reaction time is not limited to the exhaust system of the engine, but also in a device that causes a chemical reaction or a state change by adding another gas or liquid to the gas flowing in the pipe. When it is necessary to provide a section in which the gas flow rate is slowed in order to secure the change time, the mixing time of the gases, etc., a method of increasing the diameter of the piping in that section is adopted. In the example of FIG. 10, the pipe 203 in the section (the section from broken lines A to B in FIG. 10) in which the gas flow velocity is reduced is twice the diameter (2D) with respect to the diameters (D) of the front and

rear pipes

201 and 202. ).

As described above, when the difference in diameter is doubled, for example, when the velocity of the gas flowing in the pipe 201 is V ₀ , the velocity V of the gas flowing in the flow velocity reduction section 203 is V _0/4. Can be reduced.

However, when the flow velocity reduction means as described above is used, the size of the diameter of the flow velocity reduction section 203 becomes large, and there is a problem that the apparatus cannot be reduced in size. For example, in the exhaust system of the marine diesel engine 102 as shown in FIG. 9, the exhaust manifold 101 occupies a large volume, and it is necessary to provide an evaporation pipe 107 having a larger diameter. The evaporation tube 107 is a factor that hinders downsizing of the entire apparatus.

No. 6-45617

Conventionally, the problem to be solved by the present invention is to reduce the flow rate of the exhaust gas in the section from the urea water spray nozzle to the denitration reactor in order to ensure sufficient time for the urea water to be hydrolyzed. As an means, an evaporation pipe having a diameter larger than that of the exhaust passage was used, and this evaporation pipe was a factor that hindered downsizing of the apparatus.

The exhaust gas purification 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; and a denitration reactor provided in the exhaust passage;
An evaporation pipe that is upstream of the denitration reactor and that is open at both ends in the longitudinal direction is provided inside the exhaust passage, and a reducing agent and a reducing agent precursor for the exhaust gas that passes through the evaporation pipe. The main feature is that a nozzle capable of spraying an aqueous solution containing either or both of these is provided.

The exhaust gas purification apparatus of the present invention is configured such that an evaporation pipe is provided inside the exhaust passage on the upstream side of the denitration reactor and, for example, urea water or the like is sprayed from the nozzle to the exhaust gas passing through the inside of the evaporation pipe. Therefore, the flow rate of the exhaust gas passing through the inside of the evaporation pipe is reduced, and a sufficient time can be secured for the hydrolysis reaction of urea water or the like to proceed. Therefore, according to the present invention, the size of the diameter of the flow velocity reduction section can be made smaller than before.

It is a figure explaining the structure of the flow velocity reduction means of this invention. It is the figure which showed the structure of 1st Example of the exhaust gas purification apparatus of this invention. It is the enlarged view which showed the venturi of the exhaust pipe provided in the inside of the exhaust passage of the upstream of a denitration reactor, the nozzle for urea water spraying, and the exhaust passage provided in the open end vicinity of the exit part of an evaporation pipe. It is the figure which showed the structure of 2nd Example of the exhaust gas purification apparatus of this invention. It is the enlarged view which showed the urea hydrolysis catalyst provided in the vicinity of the evaporating pipe provided in the inside of the exhaust passage of the upstream of a denitration reactor, the nozzle for urea water spraying, and the exit part of an evaporating pipe. It is the figure which showed the structure of 3rd Example of the exhaust gas purification apparatus of this invention. It is the figure which showed the structure of 4th Example of the exhaust gas purification apparatus of this invention. It is the figure which showed the modification of 2nd Example of the exhaust gas purification apparatus of this invention. It is the figure which showed the structure of the conventional marine diesel engine. It is a figure explaining the structure of the conventional flow velocity reduction means.

The object of the present invention is to provide a low flow rate section for securing hydrolysis time of urea water or the like without increasing the size of the pipe diameter in the exhaust gas purification device of the engine.
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; and a denitration reactor provided in the exhaust passage;
An evaporation pipe that is upstream of the denitration reactor and that is open at both ends in the longitudinal direction is provided inside the exhaust passage, and a reducing agent and a reducing agent precursor for exhaust gas that passes through the evaporation pipe. This was realized by providing a nozzle capable of spraying an aqueous solution containing either or both of these.

In the exhaust gas purification apparatus of the present invention,
When the venturi is formed in the exhaust passage so that the diameter of the outlet portion of the evaporation pipe is smaller than the diameter of the inlet portion and the position where the open end of the outlet portion of the evaporation pipe exists is present,
By restricting the diameter of the outlet part of the evaporation pipe, the flow rate of the exhaust gas flowing in the evaporation pipe can be slowed, and the pressure near the outlet part of the evaporation pipe is increased by the action of the venturi formed in the exhaust passage. Therefore, the exhaust gas does not stay in the evaporation pipe, and a stable flow of the exhaust gas from the inlet to the outlet can be achieved.

Hereinafter, various modes for carrying out the present invention will be described in detail with reference to FIGS. FIG. 1 is a diagram for explaining the configuration of the flow velocity reducing means of the present invention.

In FIG. 1, reference numeral 1 denotes a flow velocity reduction means of the present invention that can be applied to apparatuses in various fields. The outer tube 2 through which gas flows inside is only inside the section where the flow velocity is to be reduced for some purpose. The pipe 3 is provided, and the flow velocity reduction section (the section from the broken lines A to B in FIG. 1) has a double pipe structure with the outer pipe 2 and the inner pipe 3.

The inner tube 3 is a cylindrical member whose both ends in the longitudinal direction are open, and as shown in FIG. 1, the outlet 3a on the downstream side is shaped like a nozzle and has a smaller diameter than the inlet 3b. Further, a venturi 2a is formed on the outer tube 2 so as to include a position where the open end 3aa of the nozzle-shaped outlet portion 3a exists (a position indicated by a broken line B in FIG. 1), and the tube diameter is reduced. ing.

With the configuration as described above, the gas flowing in the outer tube 2 is divided into a gas passing through the inner tube 3 and a gas passing through the outer tube 3 at the position of the broken line A. Will join.

Here, when the flow velocity of the gas at the position of the broken line A is V ₀ , the relationship between the velocity V of the gas passing inside the inner tube 3 and the velocity V ′ of the gas passing outside the inner tube 3 is V The sizes of the diameters of the outer tube 2 and the inner tube 3 are set so that <V ₀ <V ′.

In the outer pipe 2, the upstream diameter is D, the diameter of the downstream venturi 2a is Dr, the diameter of the inlet 3b in the inner pipe 3 is d, and the diameter of the nozzle-shaped outlet 3a is dr. Since the velocity V of the gas passing through the inside of the tube 3 is obtained by the equation V = V ₀ × {(dr × D) / (d × Dr)} ² , the degree of restriction of the outer tube 2 and the inner tube 3 By appropriately adjusting (Dr / D, dr / d), the flow velocity V of the gas in the inner tube 3 can be set to a desired value.

Further, in the embodiment of FIG. 1, due to the effect of the venturi 2a provided in the outer tube 2, the gas pressure near the outlet 3a of the inner tube 3 becomes lower than the gas pressure near the inlet 3b. Thereby, in the inner pipe 3, the stable flow which goes to the exit part 3a from the inlet part 3b of the inner pipe 3 can be produced, without a fluid retaining.

According to the flow velocity reduction means of the present invention having the above configuration, a stable flow velocity reduction section can be obtained without increasing the pipe diameter. The present invention can be applied to various devices regardless of the field as long as it is a piping device related to a fluid. The effect of the present invention is that the apparatus can be miniaturized while ensuring the reaction time, change time, dissolution time, evaporation time and the like.

Next, FIG. 2 is a diagram showing the configuration of the first embodiment of the exhaust gas purifying apparatus of the present invention. In FIG. 2, reference numeral 11 denotes an exhaust gas purification device in which the present invention is applied to a four-cylinder marine diesel engine. The exhaust gas purification device 11 is discharged from an exhaust communication pipe 13 connected to an exhaust port 12 a provided in each cylinder head of the engine 12. The exhaust manifold 16 that collects the exhaust gas and leads it to the exhaust passage 15 upstream of the turbine 14 a of the turbocharger 14, and the denitration reactor 17 provided in the exhaust passage 15 are provided. Reference numeral 14b denotes a compressor of the turbocharger 14 that compresses the air supplied from the supply passage 21. Reference numeral 22 denotes an air supply manifold that distributes the air compressed by the compressor 14b to an air supply port of each cylinder of the engine 12 through an air supply communication pipe.

In the exhaust passage 15 upstream of the denitration reactor 17, an evaporation pipe 18 whose both ends in the longitudinal direction are opened in the exhaust passage 15 is provided, and in the vicinity of the inlet portion 18 b of the evaporation pipe 18, an evaporation pipe is provided. A nozzle 19 capable of spraying urea water 19a is provided for the exhaust gas passing through the interior 18.

That is, in the first embodiment, the exhaust passage 15 corresponds to the outer tube 2 in FIG. 1, and the evaporation tube 18 corresponds to the inner tube 3 in FIG. The reason why the nozzle 19 is provided in the vicinity of the inlet 18b of the evaporation pipe 18 is that a long time for the sprayed urea water 19a to pass through the high-temperature evaporation pipe 18 can be secured.

The denitration reactor 17 is provided with an SCR catalyst that selectively reduces and removes NOx soot that is contained in the exhaust gas discharged from the engine 12 and causes 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 soot 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 stored in the ship. It is dangerous to keep. Therefore, in this embodiment, urea is stored as a reducing agent precursor in a tank connected to the nozzle 19 in the form of an aqueous solution, and during operation, the urea water 19a is injected from the nozzle 19 into the evaporation pipe 18, and the evaporation pipe 18 Urea is hydrolyzed using ammonia heat to generate ammonia gas.

FIG. 3 is an enlarged view showing the configuration of the evaporation pipe 18 (inner pipe) and the exhaust passage 15 (outer pipe) of the first embodiment. In the first embodiment, in order to sufficiently secure the time for the hydrolysis reaction of the urea water sprayed from the nozzle 19, the section from the broken line A to B in FIG. Yes.

The high-temperature exhaust gas collected by the exhaust manifold 16 flows into the exhaust passage 15 and is divided into one passing through the inside of the evaporation pipe 18 and one passing through the outside of the evaporation pipe 18 at the position of the broken line A. Merge at the position of the broken line B. The exhaust gas passing through the outside of the evaporation pipe 18 is not mixed with urea water at that time, but the exhaust gas passing through the inside of the evaporation pipe 18 contains ammonia gas that has been hydrolyzed. It quickly mixes with ammonia gas when it joins in place. Therefore, when introduced into the denitration reactor 17, the ammonia gas is in a state where it has spread throughout the exhaust gas.

In the first embodiment, the exhaust gas flowing outside the evaporation pipe 18 is rectified into a straight flow without swirling so that the flow of the exhaust gas is good, so that the outside of the inlet 18b of the exhaust pipe 18 is improved. A guide vane 20 is provided in the vicinity.

As shown in FIG. 3, the outlet portion 18a on the downstream side of the evaporation pipe 18 has a nozzle shape, and the pipe diameter is narrower than that of the inlet portion 18b. Further, a venturi 15a is formed in the exhaust passage 15 so as to include at least a position (a position indicated by a broken line B) where the open end 18aa of the nozzle-shaped outlet portion 18a exists, and the diameter of the exhaust passage 15 is also reduced. It is over.

In the first embodiment, due to the effect of the venturi 15a provided in the exhaust passage 15, the pressure of the exhaust gas near the nozzle-shaped outlet 18a of the evaporation pipe 18 is lower than the pressure of the exhaust gas near the inlet 18b. Thereby, in the evaporation pipe 18, the flow of the stable exhaust gas which goes to the exit part 18a from the inlet part 18b can be performed, without waste gas staying.

As in FIG. 1, the gas flow velocity at the position of the broken line A is V ₀ , the upstream diameter in the exhaust passage 15 is D, the diameter of the venturi 15a is Dr, the diameter of the upstream inlet 18b in the evaporation pipe 18 is d, When the diameter of the nozzle-shaped outlet 18a is dr, the velocity V of the exhaust gas passing through the inside of the evaporation pipe 18 is expressed by the equation V = V ₀ × {(dr × D) / (d × Dr)} ² . Desired.

Here, when the degree of restriction of the exhaust passage 15 (Dr / D value), the degree of restriction of the evaporation pipe 18 (value of dr / d) is insufficient, or when these restrictions are not provided at all, The speed of the exhaust gas passing through the inside and outside of the evaporation pipe 18 may not be stable. On the other hand, if the values of Dr / D and dr / d are too narrow, the pressure loss of the exhaust system will be too high and the engine efficiency or performance may be reduced. Therefore, the degree of restriction of the exhaust passage 15 and the evaporation pipe 18 is adjusted according to the size and shape of these pipes and the target value of the flow velocity V of the exhaust gas.

FIG. 4 is a diagram showing the configuration of the second embodiment of the exhaust gas purifying apparatus of the present invention. The difference between the exhaust gas purifying apparatus 11 of the second embodiment and the first embodiment is that the diameter of the inlet portion 18b and the outlet portion 18a of the evaporation pipe 18 are the same, and the evaporation pipe 18 (inner pipe) is connected. Urea for accelerating the hydrolysis of urea water 19a (an aqueous solution containing either or both of a reducing agent and a reducing agent precursor) sprayed from the nozzle 19 inside the evaporation pipe 18 without a restriction. This is a point where a hydrolysis catalyst 23 is provided. As the urea hydrolysis catalyst 23, for example, a catalyst having a structure in which tungsten oxide (WO 3) is added to a titanium oxide (TiO ₂ ) support can be used.

FIG. 5 is an enlarged view showing the configuration of the evaporation pipe 18 (inner pipe) and the exhaust passage 15 (outer pipe) of the second embodiment. In the second embodiment, in order to sufficiently secure the time for the hydrolysis reaction of the urea water sprayed from the nozzle 19, the section from the broken line A to B in FIG. However, the outlet 18a is not provided with a throttle. On the other hand, as shown in FIG. 5, a urea hydrolysis catalyst 23 is arranged in the vicinity of the outlet 18 a inside the evaporation pipe 18. When the urea hydrolysis catalyst 23 is arranged at the outlet 18a in this way, the flow rate of exhaust gas flowing through the evaporation pipe 18 is reduced due to pressure loss when the exhaust gas passes through the urea hydrolysis catalyst 23. Thereby, also in the structure of 2nd Example, the flow velocity of the waste gas which flows through the inside of the evaporation pipe 18 can be made slow. In addition, in the second embodiment, urea hydrolysis is promoted by the action of the urea hydrolysis catalyst 23, so that hydrolysis to ammonia can be completed within the flow velocity reduction section.

In the present invention, since the exhaust gas passing through the evaporation pipe 18 (inner pipe) has a low flow rate, the speed of urea contained in the exhaust gas is also reduced. Therefore, the time until urea passes through the urea hydrolysis catalyst 23 becomes longer, and the frequency of contact between urea and the urea hydrolysis catalyst 23 increases. Therefore, the required hydrolysis rate can be obtained even with a small amount of catalyst. In addition, since the flow rate of the exhaust gas flowing through the evaporation pipe 18 is small, the concentration of urea in the exhaust gas is increased by introducing a required amount of urea therein. Thereby, since the frequency with which urea and the urea hydrolysis catalyst 23 come into contact increases, a required hydrolysis rate can be obtained even with a small amount of catalyst.

Further, in the conventional evaporation pipe 107 as shown in FIG. 9, if the spray state of the urea water is not good, a part of the urea water adheres to the inner surface of the evaporation pipe 107, and the attached part becomes cold and the urea becomes cold. As a result, cyanuric acid, burette, melamine, and other urea-derived compounds are produced instead of ammonia, and these deposits adhere to the inner surface of the evaporation tube 107, and these deposits form exhaust gas. There was a problem of obstructing the flow. On the other hand, in the present invention, by adopting the double pipe structure as described above, when urea water adheres to the inner surface of the evaporation pipe 18, not only the heat of the exhaust gas flowing in the evaporation pipe 18 but also the evaporation pipe Since heat is also applied from the exhaust gas flowing outside 18, there is an advantage that the portion to which the urea water adheres is unlikely to cool, and the urea-derived deposit is difficult to be generated.

FIG. 6 is a view showing a configuration of a third embodiment of the exhaust gas purifying apparatus of the present invention. Reference numeral 51 denotes an exhaust gas purifying apparatus in which the present invention is applied to a four-cylinder marine diesel engine. An evaporation pipe 58 and a denitration reactor 57 having both ends in the longitudinal direction opened into the exhaust manifold 56 are continuously arranged inside the exhaust manifold 56 leading to the exhaust passage 55 upstream of the turbine 54 a of the turbocharger 54. . A nozzle 59 is provided that can spray an aqueous solution 59a containing either or both of the reducing agent and the reducing agent precursor to the exhaust gas passing through the evaporation pipe 58.

The shape of the outlet portion 58a of the evaporation pipe 58 is a nozzle shape, which is smaller than the diameter of the inlet portion 58b. Further, a venturi 56a is formed in the exhaust manifold 56 so as to include a position where the open end 58aa of the outlet portion 58a of the evaporation pipe 58 exists. Reference numeral 54 b denotes a compressor of the turbocharger 54 that compresses the air supplied from the supply passage 61. Reference numeral 62 denotes an air supply manifold that distributes the air compressed by the compressor 54b to the air supply ports of the cylinders of the engine 52 via the air supply communication pipe.

That is, in the third embodiment, the exhaust manifold 56 corresponds to the outer pipe 2 in FIG. 1 and the evaporation pipe 58 corresponds to the inner pipe 3 in FIG. 1, and the evaporation pipe 58 is incorporated in the exhaust manifold 56. However, this is different from the first embodiment.

Therefore, in the third embodiment, since all of the evaporation pipe 58 and the denitration reactor 57 are incorporated in the exhaust manifold 56, an evaporation pipe having a large pipe diameter is provided together with the exhaust manifold. Compared with the device, the device size is much more compact. Further, in general, in an engine equipped with a turbocharger, there may be a control delay such as a delay in supply air in response to a request for an increase in engine output when sudden acceleration is performed. In the configuration of the third embodiment, Since the exhaust path to the turbine 54a can be shortened, exhaust control is also facilitated.

FIG. 7 is a view showing the configuration of a fourth embodiment of the exhaust gas purifying apparatus of the present invention. The difference between the exhaust gas purifying apparatus 51 of the fourth embodiment and the third embodiment is that the diameters of the inlet 58b and outlet 58a of the evaporation pipe 58 are the same, and the evaporation pipe 58 (inner pipe) Urea for accelerating hydrolysis of urea water 59a (an aqueous solution containing either or both of a reducing agent and a reducing agent precursor) sprayed from a nozzle 59 inside the evaporation pipe 58 without a restriction. This is the point that a hydrolysis catalyst 63 is provided. The urea hydrolysis catalyst 63, similarly to the second embodiment described above, for example, can be used as the added structure carrier tungsten oxide (WO3) of titanium oxide (TiO _2).

In the fourth embodiment, the urea hydrolysis catalyst 63 is disposed in the vicinity of the outlet 58a inside the evaporation pipe 58, and the urea hydrolysis is promoted by the action of the urea hydrolysis catalyst 63. Can complete the hydrolysis to ammonia.

The present invention is not limited to the above-described embodiments, and it is needless to say 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 configuration in which the urea water 19a is sprayed from the nozzle 19 to the exhaust gas in the evaporation pipe 18 as the reducing agent precursor is disclosed, but the components of the reducing agent precursor are not limited thereto. For example, a mixed aqueous solution of high concentration urea and low concentration ammonia may be used.

Moreover, although the example which provides the nozzle 19 in the vicinity of the inlet part 18b of the evaporation pipe | tube 18 was disclosed in the said Example, the position which provides the nozzle 19 is not restricted to this, For example, you may provide in the center of the evaporation pipe | tube 18. .

Further, in the second embodiment, as shown in FIG. 5, in the case where the urea hydrolysis catalyst 23 is arranged inside the evaporation pipe 18, an example in which no restriction is provided at the outlet portion 18a of the evaporation pipe 18 is disclosed. The configuration of the second embodiment is not limited to this. For example, as in the modification shown in FIG. 8, even when the urea hydrolysis catalyst 23 is disposed inside the evaporation pipe 18, a throttle may be provided at the outlet portion 18 a of the evaporation pipe 18.

Even in the configuration of FIG. 5 in which the outlet 18a of the evaporation pipe 18 is not provided with a throttle, the flow rate of the exhaust gas can be reduced to some extent due to the pressure loss due to the urea hydrolysis catalyst 23 being arranged. Fine adjustment to the desired speed is difficult. On the other hand, when the throttle is provided at the outlet 18a of the evaporation pipe 18 as in the configuration of FIG. 8, the flow rate of the exhaust gas can be easily adjusted by designing the degree of the throttle optimally.

Thus, when the urea hydrolysis catalyst 23 and the throttle of the outlet portion 18a are used in combination, the flow rate of the exhaust gas can be easily reduced to a desired speed, and the hydrolysis of urea can be promoted by the action of the catalyst.

Further, in the third embodiment, an example in which only the nozzle 59 is provided inside the evaporation pipe 58 is disclosed, but the exhaust gas in the evaporation pipe 58 is disposed downstream of the nozzle 59 and inside the evaporation pipe 58. A rectifier may be provided to regulate the flow. Further, a static mixer may be provided inside the evaporation pipe 58 so that ammonia gas and exhaust gas generated by hydrolysis of the urea water 59a are sufficiently mixed in the evaporation pipe 58.

DESCRIPTION OF SYMBOLS 11 Exhaust gas purification device 12 Engine 12a Exhaust port 13 Exhaust communication pipe 14 Turbocharger 14a Turbine 15 Exhaust passage 15a Venturi 16 Exhaust manifold 17 Denitration reactor 18 Evaporating pipe

18a Outlet part

18b Inlet part 19 Nozzle 19a Urea water

Claims

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; and a denitration reactor provided in the exhaust passage;
An evaporation pipe that is upstream of the denitration reactor and that is open at both ends in the longitudinal direction is provided inside the exhaust passage, and a reducing agent and a reducing agent precursor for exhaust gas that passes through the evaporation pipe. An exhaust gas purification apparatus provided with a nozzle capable of spraying an aqueous solution containing either or both of the above.
A venturi is formed in the exhaust passage so that a diameter of an outlet portion of the evaporation pipe is made smaller than a diameter of an inlet portion and a position where an open end of the outlet portion of the evaporation pipe exists is included. Item 2. An exhaust gas purifying apparatus according to Item 1.
The urea hydrolysis catalyst for accelerating the hydrolysis of the aqueous solution containing either or both of the reducing agent and the reducing agent precursor sprayed from the nozzle is provided inside the evaporation pipe. Item 2. An exhaust gas purifying apparatus according to Item 1.
An exhaust pipe that collects exhaust gas discharged from the exhaust communication pipe connected to the exhaust port of the engine and leads to the exhaust passage is continuously arranged with an evaporation pipe and a denitration reactor that are open at both ends in the longitudinal direction. An exhaust gas purification apparatus comprising a nozzle capable of spraying an aqueous solution containing either or both of a reducing agent and a reducing agent precursor to exhaust gas passing through an evaporation pipe.
The vent manifold is formed in the exhaust manifold so as to include a position where the diameter of the outlet portion of the evaporation pipe is smaller than the diameter of the inlet portion and the open end of the outlet portion of the evaporation pipe exists. Item 5. The exhaust gas purifying apparatus according to Item 4.
The urea hydrolysis catalyst for accelerating the hydrolysis of the aqueous solution containing either or both of the reducing agent and the reducing agent precursor sprayed from the nozzle is provided inside the evaporation pipe. Item 5. The exhaust gas purifying apparatus according to Item 4.