Treatment device for discharge gas of engine and treatment method for discharge gas of engine

Abstract

To provide a treatment device for discharge gas of an engine with a simple device configuration, capable of safely supplying a reductant such as an ammonia aqueous solution or alcohol to a discharge gas purification device for purifying NOx (nitrogen oxide) contained in discharge gas of an engine.SOLUTION: A treatment device for discharge gas of an engine comprises a selective reduction catalyst unit 1 into which exhaust gas of an engine 101 of a ship is introduced, to which a reductant R is supplied, and which denitrifies the exhaust gas of the engine. The reductant R passes through an inner pipe 3 of a double pipe 2 and is supplied to the selective reduction catalyst unit 1 via a nozzle 4, inert gas or atmospheric air G flows through an outer pipe 5 of the double pipe 2 in the same direction as the reductant R, and the inert gas or atmospheric air G is supplied to the selective reduction catalyst unit 1 as dispersion gas for dispersing the reductant R.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an engine exhaust gas treatment apparatus and an engine exhaust gas treatment method for a ship equipped with liquefied ammonia, alcohol, etc. as cargo or engine fuel. Specifically, a reducing agent such as an aqueous ammonia solution, methanol, ethanol, or propanol can be safely supplied to an exhaust gas purification apparatus that purifies NOx (nitrogen oxides) contained in engine exhaust gas, and the present invention relates to an engine exhaust gas treatment apparatus and an engine exhaust gas treatment method having a simple device configuration.

Background Art

[0002] With the depletion of fossil fuels and global warming, alcohols such as liquefied ammonia, methanol, ethanol, and propanol, which produce little CO2 emissions, have attracted attention as marine fuels. On the other hand, as an exhaust gas purification apparatus for purifying NOx (nitrogen oxides) contained in exhaust gas discharged from an engine, an SCR (selective reduction) system is known.

[0003] Liquefied ammonia, alcohol, etc. can be used as reducing agents in addition to fuels. However, as described in Patent Documents 1 and 2 and Non-Patent Document 1, since aqueous ammonia solutions and alcohols have toxicity and flammability, sufficient safety measures need to be taken when using them as reducing agents.

[0004] In addition, since ammonia and methanol are co-produced by one process, as described in Patent Document 3, cases where they are installed on a ship as a mixed fuel and used, cases where liquefied ammonia and methanol are separately installed on the same ship, and cases where they are mixed and burned during supply to the engine are conceivable.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Non-Patent Document

[0006]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In Non-Patent Document 1, for ammonia fuel, which is an alternative fuel, when piping it through a safe area such as an engine room inside a ship, in terms of ship classification, a double pipe is used where the inert gas in the outer pipe is at a higher pressure than the fuel in the inner pipe to prevent fuel leakage. Also, when the main fuel valve is closed, the inside of the inner pipe should be purged with an inert gas, and the outside of the outer pipe should be ventilated. Similarly, for alternative fuels such as alcohol and LPG, the piping in the safe area should be a double pipe to prevent leakage.

[0008] In Patent Document 1, inside the safe area of the ship, ventilation gas is sent into the outer pipe of the double pipe from outside the safe area using a fan or blower, the ventilation gas is sent in the opposite direction to the fuel, and the leaked gas is discharged to a safe place outside the safe area through the safe area. There is a method of supplying ventilation gas by providing a duct as in Patent Document 1. However, when the fuel is toxic, before releasing the leaked gas into the atmosphere, it is necessary to send it to a facility for detoxification treatment through a return pipe, which makes the device configuration complicated. In addition, when diluting the leaked gas to a safe concentration, a large amount of ventilation gas is required, which makes the device configuration larger and more complicated.

[0009] In Patent Document 2, as a method for treating leaked gas, a method of installing a scrubber or an ammonia decomposition catalyst is mentioned. However, the addition of such equipment leads to a complication of the device configuration.

[0010] By the way, even when aqueous ammonia, alcohol, etc. are used as reducing agents in the SCR system, the pipes in the safe area should be double pipes to prevent leakage. These reducing agents, like fuel, have toxicity and flammability, so it is desirable to establish safety standards equivalent to those required for fuel pipes. In this double pipe, as described in Non-Patent Document 1 and Patent Document 1, the inside of the outer pipe can be ventilated by ventilation gas. The ventilation gas is sent in the opposite direction to the fuel and the reducing agent, and is sent to the equipment for detoxification treatment through the return pipe.

[0011] In the SCR system, a dispersion gas is required to make the reducing agent finer and more dispersed. Therefore, when aqueous ammonia, alcohol, etc. are used as reducing agents in the SCR system, both a dispersion gas for finely dispersing the reducing agent and a ventilation gas for ventilating the inside of the outer pipe of the double pipe are required. The dispersion gas is sent in the same direction as the reducing agent and supplied to the SCR system. The ventilation gas, as described above, is sent in the opposite direction to the reducing agent.

[0012] Thus, since both the dispersion gas and the ventilation gas, which are sent in opposite directions to each other, are required, the device configuration becomes complicated by providing both supply pipes respectively. Also, the fact that the ventilation gas must be sent to the equipment for detoxification treatment through the return pipe is also a factor that complicates the device configuration. Particularly in a ship where space efficiency is required, an increase in even one pipe or piece of equipment is a serious problem.

[0013] Therefore, an object of the present invention is to provide an engine exhaust gas treatment apparatus and an engine exhaust gas treatment method that can safely supply a reducing agent such as an aqueous ammonia solution or alcohol to an exhaust gas purification apparatus for purifying NOx (nitrogen oxides) contained in engine exhaust gas and have a simple apparatus configuration.

[0014] Another object of the present invention will become apparent from the following description.

Means for Solving the Problems

[0015] The above problems are solved by the following inventions. 1. A selective reduction catalyst unit is provided, into which engine exhaust gas of a ship is introduced, a reducing agent is supplied, and denitration treatment of the engine exhaust gas is performed. The reducing agent is supplied to the selective reduction catalyst unit through a nozzle via an inner pipe of a double pipe. An inert gas or air flows through an outer pipe of the double pipe in the same direction as the reducing agent. The inert gas or air is supplied to the selective reduction catalyst unit as a dispersion gas for dispersing the reducing agent. An apparatus for treating engine exhaust gas, characterized by the above. 2. An aqueous solution obtained by dissolving, in clear water, fuel remaining in a supply line of the engine fuel of the ship that has vaporized or gas volatilized from cargo in a cargo tank of the ship is used as the reducing agent. The apparatus for treating engine exhaust gas according to the above 1, characterized by the above. 3. The reducing agent is an aqueous ammonia solution, alcohol, or a mixed liquid of an aqueous ammonia solution and alcohol. The apparatus for treating engine exhaust gas according to the above 1, characterized by the above. 4. Urea water is supplied to the inner pipe of the double pipe selectively or in mixture with the reducing agent. The apparatus for treating engine exhaust gas according to the above 1, characterized by the above. 5. Inside the outer pipe of the double pipe, a level switch for detecting leakage of the reducing agent from the inner pipe, and a pressure sensor or a gas sensor are provided. The engine exhaust gas treatment apparatus according to any one of the above 1 to 4, characterized in that. 6. An engine exhaust gas treatment method for introducing ship engine exhaust gas into a selective reduction catalyst unit in which a selective reduction catalyst is arranged, supplying a reducing agent, and performing denitration treatment of the engine exhaust gas, The reducing agent is supplied to the selective reduction catalyst unit via a nozzle through the inner pipe of the double pipe. In the outer pipe of the double pipe, an inert gas or air is circulated in the same direction as the reducing agent. The inert gas or air is supplied to the selective reduction catalyst unit as a dispersion gas for dispersing the reducing agent. The engine exhaust gas treatment method characterized by the above. 7. Using an aqueous solution in which fuel remaining in the supply line of the ship's engine fuel is vaporized or gas volatilized from the cargo in the ship's cargo tank is dissolved in fresh water as the reducing agent. The engine exhaust gas treatment method according to the above 6, characterized in that. 8. Using an aqueous ammonia solution, alcohol, or a mixed liquid of an aqueous ammonia solution and alcohol as the reducing agent. The engine exhaust gas treatment method according to the above 6, characterized in that. 9. Urea water is supplied to the inner pipe of the double pipe selectively or mixed with the reducing agent. The engine exhaust gas treatment method according to the above 6, characterized in that. 10. A level switch for detecting leakage of the reducing agent from the inner pipe, and a pressure sensor or a gas sensor are provided in the outer pipe of the double pipe. The engine exhaust gas treatment method according to any one of the above 6 to 9, characterized in that.

Advantages of the Invention

[0016] In the present invention, even if the reducing agent leaks from the inner pipe of the double pipe, the leaked reducing agent is supplied to the selective reduction catalyst unit together with the inert gas or air flowing through the outer pipe, and together with the reducing agent supplied to the selective reduction catalyst unit through the inner pipe, it is used for treating engine exhaust gas. Therefore, there is no need for the conventional equipment that sends the dispersion gas and the ventilation gas in opposite directions to each other and sends the ventilation gas from the outer pipe of the double pipe to the equipment for harmless treatment through the return pipe, and the device configuration is simple. Particularly, in a ship where space efficiency is required, having even one less pipe or piece of equipment is significantly useful.

[0017] Therefore, according to the present invention, a reducing agent such as an aqueous ammonia solution or alcohol can be safely supplied to an exhaust gas purification device that purifies NOx (nitrogen oxides) contained in engine exhaust gas, and an engine exhaust gas treatment device and an engine exhaust gas treatment method with a simple device configuration can be provided.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Various features shown in each of the embodiments described below can be combined with each other. The present invention relates to an engine exhaust gas treatment apparatus and an engine exhaust gas treatment method for introducing engine exhaust gas of a ship into a selective reduction catalyst unit, supplying a reducing agent to the selective reduction catalyst unit, and performing denitration treatment of the engine exhaust gas. The engine exhaust gas treatment method of the present invention can be executed by the engine exhaust gas treatment apparatus of the present invention.

[0020] 〔First Embodiment〕 FIG. 1 is a block diagram showing the configuration of an engine exhaust gas treatment apparatus according to the first embodiment of the present invention. In FIG. 1, the liquid flow path is indicated by a solid line, and the gas flow path is indicated by a dotted line. The same applies to other figures.

[0021] Fuel is supplied from a fuel tank (not shown) to the propulsion engine 101 of the ship on which this engine exhaust gas treatment apparatus is mounted, and this fuel is burned to generate the propulsion force of the ship. Examples of the fuel for the engine 101 include liquefied fuels such as liquefied ammonia, alcohol, LNG, and LPG, or liquid fuels, but are not limited thereto, and heavy oil may be used alone or in combination. Further, the engine 101 may be a dual-fuel engine of liquefied ammonia fuel, alcohol, etc. and a fossil fuel such as heavy oil. In the dual-fuel engine, a mode of operating mainly with liquefied ammonia fuel and supplying a fossil fuel such as heavy oil as an ignition source, and a fossil fuel mode of operating only with fossil fuel can be selectively switched.

[0022] As shown in FIG. 1, the engine exhaust gas discharged from the engine 101 passes through the exhaust receiver 102 and is discharged into the atmosphere through the exhaust pipe 103.

[0023] The engine exhaust gas treatment apparatus of the present embodiment includes a selective reduction catalyst (SCR) unit 1. The selective reduction catalyst unit 1 has the engine exhaust gas passing through the exhaust receiver 102 introduced therein, and discharges this engine exhaust gas into the exhaust pipe 103.

[0024] Inside the selective reduction catalyst unit 1, a selective reduction catalyst (SCR) is installed. Engine exhaust gas is introduced, and a reducing agent R is supplied. By the selective catalytic reduction (SCR) method, NO in the engine exhaust gas X is subjected to denitrification treatment by reacting with the reducing agent R.

[0025] Examples of the reducing agent R include an aqueous ammonia solution, alcohol, or a mixed liquid of an aqueous ammonia solution and alcohol. Examples of alcohol include methanol, ethanol, and propanol. Note that these aqueous ammonia solution and methanol are toxic, and ethanol and propanol are known to be flammable.

[0026] The reducing agent R is sent from the reducing agent tank 6 by the supply pump 7 through the supply valve 8 to the inner pipe 3 of the double pipe 2 outside the safe area (outside the engine room, for example, in the fuel adjustment room). Since this reducing agent R has toxicity in the case of, for example, an aqueous ammonia solution, in the safe area (engine room), it is sent through the inner pipe 3 of the double pipe 2 to prevent leakage.

[0027] The reducing agent R passes through the inner pipe 3 of the double pipe 2, is injected into the exhaust receiver 102 or between the exhaust receiver 102 and the selective reduction catalyst through the nozzle 4, and is supplied to the selective reduction catalyst.

[0028] Note that a purge liquid or a purge gas P can be supplied to the pipe between the reducing agent tank 6 and the inner pipe 3 of the double pipe 2 through the on-off valve 9 and the check valve 10. The purge liquid or the purge gas P is supplied into the pipe to remove the reducing agent R remaining in the pipe of the reducing agent R after the supply of the reducing agent R is stopped.

[0029] When the engine fuel is liquefied ammonia or alcohol, as the reducing agent R, an aqueous solution obtained by collecting the gas vaporized from the fuel remaining in the engine fuel supply line and dissolving it in fresh water can be used. Such an aqueous solution can be stored in the reducing agent tank 6. The fresh water may be supplied from outside the ship and stored in the tank, or may be generated from seawater or the like by a water maker inside the ship. In addition, methanol does not emit CO2 during the manufacturing process, and the amount of CO2 emissions during combustion is about 15% lower than that of heavy oil or the like, so the environmental impact is small. Also, as described above, ammonia and methanol are co-produced by one process, so it is conceivable to install and use them as a mixed fuel on a ship, separately install liquefied ammonia and methanol on the same ship, or mix and burn them when supplying to the engine.

[0030] When the cargo of the ship is liquefied ammonia or alcohol, an aqueous solution obtained by dissolving the gas volatilized from the cargo in fresh water in the cargo tank can be used as the reducing agent R. Such an aqueous solution can be stored in the reducing agent tank 6.

[0031] The reducing agent tank 6 may store the reducing agent R loaded separately from the engine fuel and the cargo.

[0032] In the outer pipe 5 of the double pipe 2, an inert gas or air G flows in the same direction as the reducing agent R. The inert gas or air G is sent out from outside the engine room by the blower 11 and sent to the outer pipe 5 of the double pipe 2 through the check valve 12. As the inert gas, for example, nitrogen gas, air with a sufficiently reduced oxygen concentration, argon gas, etc. can be used. Considering safety, for example, the explosion limit, as the gas flowing in the same direction as the reducing agent R, nitrogen gas or air with a sufficiently reduced oxygen concentration is preferable.

[0033] An inert gas or air G is supplied to the selective reduction catalyst unit 1 as a dispersion gas for dispersing the reducing agent R within the selective reduction catalyst unit 1. The dispersion gas also serves as the ventilation gas within the outer pipe 5 and is used to finely disperse the reducing agent R at the nozzle 4 portion.

[0034] Even if the reducing agent R leaks from the inner pipe 3 of the double pipe 2, the leaked reducing agent R is supplied to the selective reduction catalyst unit 1 together with the inert gas or air G flowing through the outer pipe 5, and is used for the treatment of engine exhaust gas together with the reducing agent R supplied to the selective reduction catalyst unit 1 through the inner pipe 3. Therefore, in this engine exhaust gas treatment apparatus, it is not necessary to send the dispersion gas and the ventilation gas in opposite directions to each other as in the conventional fuel supply apparatus, and send the ventilation gas to a facility for performing detoxification treatment through a return pipe from the outer pipe of the double pipe, and the apparatus configuration is simple. Particularly, in a ship where space efficiency is required, having one less pipe or facility is significantly useful.

[0035] It is preferable to provide a level switch LS for detecting leakage or abnormality of the reducing agent R from the inner pipe 3, and a pressure sensor PT or a gas sensor GT within the outer pipe 5 of the double pipe 2.

[0036] The level switch LS detects leakage of the reducing agent R from the inner pipe 3 as a change in the level (liquid level position) of the reducing agent R within the outer pipe 5 when the reducing agent R cannot be pushed into the selective reduction catalyst unit 1 from the inner pipe 3. When leakage is detected, the supply pump 7 is stopped, a purge fluid (liquid or gas (the same hereinafter)) P is supplied, the flow rate of the blower 11 for the inert gas or air G is increased, and the leaked reducing agent R is sprayed into the selective reduction catalyst unit 1 and used for denitration treatment.

[0037] The pressure sensor PT detects clogging as a change in the internal pressure within the outer pipe 5 when clogging occurs at the nozzle 4 portion. When clogging is detected, the supply pump 7 is stopped, a purge fluid P is supplied, and maintenance of the pipe and the nozzle 4 is performed.

[0038] When there is a leak of the reducing agent R from the inner pipe 3, the gas sensor GT detects the leak of the reducing agent R from the inner pipe 3 as a change in the concentration of the vaporized gas from the reducing agent R in the outer pipe 5. When the leak is detected, the supply pump 7 is stopped, the purge fluid P is supplied, and the flow rate of the blower 11 for the inert gas or the atmosphere G is increased to spray the leaked reducing agent R into the selective reduction catalyst unit 1 and subject it to the denitration treatment.

[0039] 〔Second Embodiment〕 FIG. 2 is a block diagram showing the configuration of the engine exhaust gas treatment apparatus according to the second embodiment of the present invention.

[0040] In the present embodiment, as shown in FIG. 2, urea water can be supplied to the inner pipe 3 of the double pipe 2 selectively or in mixture with the reducing agent R. Since other configurations are the same as those in the first embodiment, the description thereof is incorporated herein and omitted here.

[0041] In the present embodiment, urea water U can be supplied from a urea water tank (not shown) to the pipe between the reducing agent tank 6 and the inner pipe 3 of the double pipe 2 through an on-off valve 13 and a check valve 14. The urea water U is loaded separately from the reducing agent R and stored in the urea water tank.

[0042] When the urea water U is supplied into the selective reduction catalyst unit 1, ammonia gas is generated, so that it can be used as a reducing agent for the denitration treatment of engine exhaust gas. Although the urea water U is alkaline and there is a risk of generating ammonia gas, it is stable and has no toxicity like aqueous ammonia.

[0043] Supply to the inner pipe 3 can be done in the following ways: By operating the supply pump 7, opening the supply valve 8, and closing the on-off valve 13, only the reducing agent R can be supplied; by stopping the supply pump 7, closing the supply valve 8, and opening the on-off valve 13, only the aqueous urea solution U can be supplied; or by operating the supply pump 7, opening the supply valve 8, and also opening the on-off valve 13, the reducing agent R and the aqueous urea solution U can be mixed and supplied.

[0044] In this embodiment, when the engine fuel is liquefied ammonia or alcohol and an aqueous solution of the gas remaining in the supply line of the engine fuel is used as the reducing agent R, there may be a case where the reducing agent R cannot be ensured in an amount sufficient for the denitration treatment of the engine exhaust gas in the selective reduction catalyst unit 1. This is because the gas remaining in the supply line of the engine fuel can only be recovered when the engine 101 is stopped. In this embodiment, since the aqueous urea solution U is loaded separately from the reducing agent R, as long as a sufficient amount of the aqueous urea solution U is loaded, the denitration treatment of the engine exhaust gas in the selective reduction catalyst unit 1 will not become impossible.

[0045] In this embodiment, in the Tier 3 sea area, the aqueous urea solution U and the reducing agent R are supplied to surely perform the denitration treatment in the selective reduction catalyst unit 1, satisfy the regulations, and enable in-ship treatment of the aqueous solution (reducing agent R) of the gas remaining in the supply line of the engine fuel generated on the ship. In the Tier 2 sea area, since reliable denitration treatment is not required, only the reducing agent R is supplied, and in-ship treatment of the aqueous solution (reducing agent R) of the gas remaining in the supply line of the engine fuel generated on the ship is performed.

[0046] 〔Structure of the confluence pipe〕 FIG. 3 is a schematic cross-sectional view showing the structure of the confluence pipe applied to the engine exhaust gas treatment apparatus according to the second embodiment of the present invention.

[0047] In the second embodiment, the confluence pipe of the reducing agent R and the aqueous urea solution U may be configured to confluence immediately before being supplied to the selective reduction catalyst unit 1 as shown in FIG. 3.

[0048] In this example, the pipe connection portion 15 between the double pipe 20 and the selective reduction catalyst unit 1 is preferably a sanitary structure or a flange type in consideration of the maintenance of the lance 16 leading to the nozzle 4 within the selective reduction catalyst unit 1. The sanitary structure is a structure in which fine gaps through which dust or cleaning liquid can enter are absent, making it difficult for dirt to remain, or a structure that is easily disassembled, facilitating cleaning.

[0049] In this example, the reducing agent R is supplied from the reducing agent tank 6 to the inner pipe 3 of the double pipe 2 by the supply pump 7 outside the safety area, which is the same as in the first embodiment.

[0050] It is also the same as in the first embodiment that purge liquid or purge gas P can be supplied to the pipe between the reducing agent tank 6 and the inner pipe 3 of the double pipe 2 via the on-off valve 9 and the check valve 10.

[0051] Providing a level switch LS for detecting leakage or abnormality of the reducing agent R from the inner pipe 3 in the outer pipe 5 of the double pipe 2 is the same as in the first embodiment. However, in this example, when the leakage of the reducing agent R from the inner pipe 3 is detected as a change in the level of the reducing agent R in the outer pipe 5 by the level switch LS, the leaked reducing agent R is not only sent to the selective reduction catalyst unit 1 but also returned to the reducing agent tank 6 via the on-off valve 18. The on-off valve 18 is normally closed and is opened when leakage of the reducing agent R from the inner pipe 3 is detected.

[0052] In the outer pipe 5 of the double pipe 2, outside the safety area, an inert gas or air G for the reducing agent R is sent by the blower 11 via the on-off valve 19 and flows in the same direction as the reducing agent R in the outer pipe 5.

[0053] The double pipe 2 is connected to a sealed box 17 within the safe area. Inside the box 17, the inside of the outer pipe 5 communicates with the inside of the box 17, and the inner pipe 3 passes through the box 17 as a pipe and reaches outside the box 17. Inside the box 17, the inner pipe 3 reaches outside the box 17 via the supply valve 8. A pressure sensor PT may be provided on the upstream side of the supply valve 8 in the inner pipe 3.

[0054] Note that the double pipe 2 is connected at a height position along the bottom of the box 17 so that when liquid leaks into the box 17, the leaked liquid returns to the reducing agent tank 6 side through the inside of the outer pipe 5. Also, the double pipe 2 is such that the reducing agent tank 6 side is lower than the box 17 side so that the leaked liquid inside the outer pipe 5 returns to the reducing agent tank 6 side.

[0055] Inside the box 17, a supply pipe for the urea water U joins the inner pipe 3 on the downstream side of the supply valve 8. The urea water U joins the inside of the inner pipe 3 via the on-off valve 13.

[0056] At the outlet portion from the box 17, an outer pipe surrounding the inner pipe 3 is provided, forming a double pipe 20. The outer pipe of the double pipe 20 does not communicate with the inside of the box. Urea water inert gas or air G is sent to the outer pipe of the double pipe 20 via the on-off valve 21 and flows through the inside of the outer pipe in the same direction as the urea water U toward the selective reduction catalyst unit 1. A junction portion 23 that communicates with the inside of the box 17 via the on-off valve 22 is provided between the on-off valve 21 and the outer pipe of the double pipe 20 (downstream side of the on-off valve 21). Also, a pressure alarm sensor PIA for detecting the internal pressure of the box 17 is provided in the box 17. A gas sensor GT may be provided in the box 17. U

[0057] Since the box 17 functions as the outer pipe of the double pipe, safety is ensured. The reducing agent inert gas or air G sent by the outer pipe 5 of the double pipe 2 R ​It is sent into box 17, and then through the on-off valve 22 and the confluence part 23, it is sent into the outer pipe of the double pipe 20 leading from box 17 to the selective reduction catalyst unit 1.

[0058] The double pipe 20 leading from box 17 to the selective reduction catalyst unit 1 is connected to the lance 16 in the selective reduction catalyst unit 1 by the pipe connection part 15. The pipe connection part 15 is located on the outer wall surface of the selective reduction catalyst unit 1. The lance 16 has a double pipe structure, the inner pipe is connected to the inner pipe of the double pipe 20, and the outer pipe is connected to the outer pipe of the double pipe 20. A nozzle 4 is attached to the tip of the inner pipe of the lance 16. The tip of the outer pipe of the lance 16 is open inside the selective reduction catalyst unit 1.

[0059] FIG. 4 is a longitudinal sectional view showing the structure of the pipe connection part applied to the engine exhaust gas treatment apparatus according to the second embodiment of the present invention. FIG. 5 is a cross-sectional view showing the structure of the pipe connection part applied to the engine exhaust gas treatment apparatus according to the second embodiment of the present invention.

[0060] As shown in FIGS. 4 and 5, the pipe connection part 15 can have a flange type structure. This pipe connection part 15 is composed of a first member 27 and a second member 31. The first member 27 is composed of an inner cylinder 24 connected to the inner pipe of the double pipe 20, an outer cylinder 25 connected to the outer pipe of the double pipe 20, and a disk-shaped flange part 26 formed at the ends of these inner cylinder 24 and outer cylinder 25. The second member 31 is composed of an inner cylinder 28 connected to the inner pipe of the lance 16, an outer cylinder 29 connected to the outer pipe of the lance 16, and a disk-shaped flange part 30 formed at the ends of these inner cylinder 28 and outer cylinder 29. From the viewpoint of preventing leakage of gas and liquid, it is preferable that these first member 27 and second member 31 are integrally formed by cutting from a metal round bar.

[0061] The flange portion 26 of the first member 27 and the flange portion 30 of the second member 31 are each formed with a through hole leading to the inner cylinder hole 32 at their respective central portions. Further, the flange portion 26 and the flange portion 30 are each formed with a plurality of outer cylinder holes 33 at positions inside the outer cylinders 25, 29 and outside the inner cylinders 24, 28, and a plurality of bolt holes 34 are formed at positions outside the outer cylinders 25, 29.

[0062] In this pipe connection portion 15, the first member 27 and the second member 31 are abutted against each other with the outer peripheral O-ring 35a and the inner peripheral O-ring 35b, which are packings, interposed therebetween. At this time, the through holes leading to the inner cylinder holes 32, 32 are connected to each other, the plurality of outer cylinder holes 33, 33 are connected to each other, and the plurality of bolt holes 34, 34 are connected to each other. The outer peripheral O-ring 35a seals between the plurality of outer cylinder holes 33, 33 and the outside of the pipe, and the inner peripheral O-ring 35b seals between the through holes leading to the inner cylinder holes 32, 32 and the plurality of outer cylinder holes 33, 33.

[0063] Then, bolts are passed through the plurality of bolt holes 34, 34 and fastened with nuts, whereby the first member 27 and the second member 31 are fixed to each other, and the pipe connection portion 15 is configured. The through holes leading to the inner cylinder holes 32, 32 allow the reducing agent R and the aqueous urea solution U to pass through. The plurality of outer cylinder holes 33, 33 allow the inert gas or air G for the reducing agent R and the inert gas or air G for the aqueous urea solution U to pass through. It should be noted that it is preferable that the double pipe 20 and the lance 16 connected to the pipe connection portion 15 have a larger diameter of the outer pipe only at the connection portion and a smaller diameter otherwise.

[0064] When only the reducing agent R is supplied to the selective reduction catalyst unit 1, the supply pump 7 is operated, the supply valve 8 is opened to send the reducing agent R, the on-off valve 19 and the on-off valve 22 are opened to send the inert gas or air G for the reducing agent R to send, the on-off valve 13 is closed to stop the aqueous urea solution U, and the on-off valve 21 is closed to stop the inert gas or air G for the aqueous urea solution U as well.

[0065] When only the aqueous urea solution U is supplied to the selective reduction catalyst unit 1, the supply pump 7 is stopped, the supply valve 8 is closed to stop the reducing agent R, the on-off valves 19 and 22 are closed to stop the inert gas or air G for the reducing agent R and the on-off valve 13 is opened to send the aqueous urea solution U, and the on-off valve 21 is opened to send the inert gas or air G for the aqueous urea solution U .

[0066] When the reducing agent R and the aqueous urea solution U are mixed and supplied to the selective reduction catalyst unit 1, the supply pump 7 is operated, the supply valve 8 is opened to send the reducing agent R, the on-off valves 19 and 22 are opened to send the inert gas or air G for the reducing agent R and the on-off valve 13 is opened to send the aqueous urea solution U, and the on-off valve 21 is opened to send the inert gas or air G for the aqueous urea solution U .

[0067] The pressure alarm sensor PIA detects clogging as a change in the internal pressure in the outer pipe 5 and the box 17 when clogging occurs in the inert gas or air G for the reducing agent at the nozzle 4 R . When clogging is detected, the supply pump 7 is stopped, the purge fluid P is supplied, and maintenance of the piping and the nozzle 4 is performed, etc.

[0068] The level switch LS detects leakage of the reducing agent R from the inner pipe 3 as a change in the level (liquid level position) of the reducing agent R in the outer pipe 5 when the reducing agent R cannot be pushed into the selective reduction catalyst unit 1 from the inner pipe 3. When leakage is detected, the supply pump 7 is stopped, the supply valve 8 is closed to stop the supply of the reducing agent R, the on-off valve 13 is opened to switch to the supply of the aqueous urea solution U, and the on-off valve 21 is opened to send the inert gas or air G for the aqueous urea solution U . The reducing agent R leaked into the outer pipe 5 and the box 17 of the double pipe 2 is returned to the reducing agent tank 6 by opening the on-off valve 18. Also, at this time, the purge fluid P may be supplied, and the flow rate of the blower 11 for the inert gas or air G for the reducing agent R may be increased to remove the leaked reducing agent R.

[0069] The pressure sensor PT detects clogging as a change in the internal pressure within the inner pipe 3 when clogging occurs inside the nozzle 4. When clogging is detected, the supply pump 7 is stopped, purge fluid P is supplied, and maintenance of the piping and nozzle 4 is performed.

[0070] The gas sensor GT detects leakage of the reducing agent R from the inner pipe 3 as a change in the concentration of the vaporized gas from the reducing agent R within the outer pipe 5 and inside the box 17. When leakage is detected, the supply pump 7 is stopped, purge fluid P is supplied, the flow rate of the blower 11 for the inert gas or air G is increased, and the leaked reducing agent R is sprayed into the selective reduction catalyst unit 1 for denitrification treatment.

Explanation of Signs

[0071] 1 Selective reduction catalyst unit 2 Double pipe 3 Inner pipe 4 Nozzle 5 Outer pipe 6 Reducing agent tank 7 Supply pump 8 Supply valve 9 On-off valve 10 Check valve 11 Blower 12 Check valve 13 On-off valve 14 Check valve 15 Pipe connection part 16 Lance 17 Box 18 On-off valve 19 On-off valve 20 Double pipe 21 On-off valve 22 On-off valve 23 Confluence part 24, 28 Inner cylinder 25, 29 Outer cylinder 26, 30 Flange part 27 First member 31 Second member 32 Inner cylinder hole 33 Outer cylinder hole 34 Bolt hole 35a Outer peripheral O-ring 35b Inner peripheral O-ring 101 Engine 102 Exhaust receiver 103 Exhaust pipe R Reducing agent G Inert gas or air P Purge liquid or purge gas LS Level switch PT Pressure sensor GT Gas sensor PIA Pressure alarm sensor

Claims

1. A selective reduction catalyst unit is provided, into which engine exhaust gas of a ship is introduced, a reducing agent is supplied, and a selective reduction catalyst for performing denitration treatment of the engine exhaust gas is disposed. The reducing agent is supplied to the selective reduction catalyst unit through a nozzle via an inner pipe of a double pipe. An inert gas or air flows in the outer pipe of the double pipe in the same direction as the reducing agent. The inert gas or air is supplied to the selective reduction catalyst unit as a dispersion gas for dispersing the reducing agent. An apparatus for treating engine exhaust gas, characterized by the above.

2. An aqueous solution in which fuel remaining in a supply line of engine fuel of the ship is vaporized or gas volatilized from cargo in a cargo tank of the ship is dissolved in fresh water is used as the reducing agent. The apparatus for treating engine exhaust gas according to claim 1, characterized by the above.

3. The reducing agent is an aqueous ammonia solution, alcohol, or a mixed liquid of an aqueous ammonia solution and alcohol. The apparatus for treating engine exhaust gas according to claim 1, characterized by the above.

4. Urea water is supplied to the inner pipe of the double pipe selectively or in mixture with the reducing agent. The apparatus for treating engine exhaust gas according to claim 1, characterized by the above.

5. A level switch for detecting leakage of the reducing agent from the inner pipe, and a pressure sensor or a gas sensor are provided in the outer pipe of the double pipe. The apparatus for treating engine exhaust gas according to any one of claims 1 to 4, characterized by the above.

6. An engine exhaust gas treatment method, in which engine exhaust gas of a ship is introduced into a selective reduction catalyst unit in which a selective reduction catalyst is disposed, a reducing agent is supplied, and denitration treatment of the engine exhaust gas is performed, The reducing agent is supplied to the selective reduction catalyst unit through a nozzle via an inner pipe of a double pipe. An inert gas or air is caused to flow in the outer pipe of the double pipe in the same direction as the reducing agent. The inert gas or air is supplied to the selective reduction catalyst unit as a dispersion gas for dispersing the reducing agent. An engine exhaust gas treatment method, characterized by the above.

7. An aqueous solution in which fuel remaining in a supply line of engine fuel of the ship is vaporized or gas volatilized from cargo in a cargo tank of the ship is dissolved in fresh water is used as the reducing agent. The engine exhaust gas treatment method according to claim 6, characterized by the above.

8. As the reducing agent, an aqueous ammonia solution, an alcohol, or a mixed liquid of an aqueous ammonia solution and an alcohol is used. The method for treating engine exhaust gas according to claim 6, characterized in that.

9. Urea water is supplied to the inner pipe of the double pipe selectively or in admixture with the reducing agent. The method for treating engine exhaust gas according to claim 6, characterized in that.

10. A level switch for detecting leakage of the reducing agent from the inner pipe, and a pressure sensor or a gas sensor are provided in the outer pipe of the double pipe. The method for treating engine exhaust gas according to any one of claims 6 to 9, characterized in that.

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