A methanol dual-fuel ship double-wall pipe purge residual liquid recovery system and method

Abstract

The present invention discloses a double-walled pipe purging residual liquid recovery system and method for a methanol dual-fuel ship. The system is provided with a purging unit, the connecting pipeline of the purging unit connects the outer pipe and the inner pipe of each double-walled pipe, and a nitrogen inlet is arranged at the port of the inner pipe and the outer pipe of each double-walled pipe, and the methanol gas and / or residual liquid remaining in the inner pipe and the outer pipe are purged into the methanol daily tank based on the flow direction of the methanol fuel for recycling. The present invention collects methanol gas and residual liquid, facilitates daily maintenance, and reduces the damage to the pipeline caused by the residual methanol liquid / gas.

Description

Technical Field

[0001] The invention relates to the technical field of ship equipment, and in particular to a double-walled pipe purge residual liquid recovery system and method for a methanol dual-fuel ship. Background Art

[0002] In response to global warming, international maritime environmental protection requirements have become increasingly stringent in recent years, and the requirements for greenhouse gas emission reduction from ships have become increasingly higher. Carbon reduction has become an important direction for the future development of the shipping industry. Green methanol made from carbon dioxide can well meet the increasing carbon emission requirements.

[0003] As a clean emission solution, dual-fuel diesel engines are gradually being promoted in the field of ships. They are usually arranged in the engine room, and the supply pipeline runs from the cargo hold area to the engine room area. In order to protect the safe area of ​​the engine room, a "double-wall pipe" needs to be installed to isolate the methanol supply pipeline from the safe area of ​​the engine room.

[0004] Methanol is a low-flash point fuel in liquid phase at room temperature and pressure. The methanol supply pipeline of dual-fuel diesel engine needs to be purged after the vehicle is prepared, running and stopped due to faults to prevent methanol from corroding or leaking the pipeline. Since the distance of the methanol double-wall pipe is very long, a large amount of methanol liquid and gas will gather in the double-wall pipe after the methanol supply stops, and it needs to be purged with multiple nitrogen interfaces to be purged clean; and the methanol double-wall pipe is divided into an inner pipe and an outer pipe. The connection between double-wall pipes is generally that the inner pipe is connected and the outer pipe is not connected. For the inner pipe of the double-wall pipe with leakage, the outer pipe that matches it needs to be purged accordingly to prevent the methanol gas from further corroding the outer pipe of the double-wall pipe. Summary of the invention

[0005] The purpose of the present invention is to provide a double-wall pipe purging residual liquid recovery system and method for a methanol dual-fuel ship, which is quick, convenient, safe and efficient in terms of multi-stage rated air pressure purging and residual liquid recovery, in view of the deficiencies in the prior art.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a methanol dual-fuel ship double-walled pipe purging residual liquid recovery system, including a methanol inlet, the methanol inlet is connected to a low-pressure filter, a valve group unit, a methanol booster pump unit and a first double-walled pipe in sequence through a first pipeline, the first double-walled pipe is connected to a third double-walled pipe, a generator, a fourth double-walled pipe and a second double-walled pipe in sequence, the second double-walled pipe is connected to a methanol daily tank through a second pipeline, and the connection between the first double-walled pipe and the third double-walled pipe and the connection between the second double-walled pipe and the fourth double-walled pipe is connected to a purging unit, characterized in that: the purging unit includes a first connecting pipeline and a second connecting pipeline, the end of the first connecting pipeline is connected to the outer pipe of the third double-walled pipe and is connected to a first liquid level sensor, a first normally closed discharge valve, a first check valve and a third check valve in sequence. The first connecting line has a check valve and the other end is connected to the inner tube of the fourth double-walled tube. The end of the second connecting line is connected between the first check valve and the third check valve and is connected in sequence to the second check valve, the second normally closed discharge valve and the second liquid level sensor and is connected to the outer tube at the port of the first double-walled tube at the other end. The outer tube at the port of the second double-walled tube is connected in sequence to the fourth nitrogen inlet, the fourth liquid level sensor and the fourth normally closed discharge valve through the first purge line. The outer tube of the fourth double-walled tube between the interface of the first connecting line and the fourth double-walled tube and the generator is connected to the second purge line. The second purge line is connected in sequence to the third nitrogen inlet, the third liquid level sensor and the third normally closed discharge valve. The inner tube of the fourth double-walled tube between the interface of the second purge line and the fourth double-walled tube and the interface of the first connecting line and the fourth double-walled tube is provided with a fourth check valve. The double-walled tube is divided into an outer tube and an inner tube. There is an annular cavity between the inner tube and the outer tube to prevent the methanol in the inner tube from leaking into the cabin.

[0007] Preferably, the outer tube of the first double-walled tube is connected to a third pipeline, the third pipeline is provided with a first safety valve and leads to the methanol daily tank, the outer tube of the second double-walled tube is connected to a fourth pipeline, the fourth pipeline is provided with a second safety valve and leads to the methanol daily tank, and the fourth pipeline is provided with a remote control valve in parallel with the second safety valve. The threshold of the safety valve is 16 bar, and when the inner tube of the first double-walled tube and / or the second double-walled tube leaks, the methanol gas and / or nitrogen can be discharged into the methanol daily tank through the safety valve when the pressure exceeds 16 bar.

[0008] Preferably, the valve group unit is connected to a first nitrogen inlet, and the interface between the outer tube of the first double-walled tube and the third pipeline is connected to a second nitrogen inlet. The second nitrogen inlet is located at the highest point of the first double-walled tube, so that the entire range of the outer tube of the first double-walled tube can be covered during nitrogen purging.

[0009] Preferably, the methanol inlet, low-pressure filter, valve group unit, methanol booster pump unit and methanol daily tank are all located in the fuel preparation room, and the first double-walled pipe, third double-walled pipe, generator, fourth double-walled pipe, purge unit and second double-walled pipe are all located in the engine room.

[0010] Preferably, the outer tube of the first double-walled tube is provided with a first pressure sensor, the outer tube of the second double-walled tube is provided with a second pressure sensor, and the outer tube of the third double-walled tube is provided with a third pressure sensor. The pressure sensor monitors the gas pressure value in the outer tube of the double-walled tube to monitor whether methanol gas leaks into the outer tube of the double-walled tube.

[0011] Preferably, the generator is provided with a fifth double-walled pipe connected to the third double-walled pipe, the fifth double-walled pipe leads to the electromagnetic valve group, the generator is provided with a sixth double-walled pipe connected to the fourth double-walled pipe, the sixth double-walled pipe leads to the electromagnetic valve group, and the electromagnetic valve group is connected to the fifth nitrogen inlet. The electromagnetic valve group controls the outer pipe of the fifth double-arm pipe and the outer pipe of the sixth double-arm pipe to form a loop, and the electromagnetic valve group controls the fifth nitrogen inlet to be connected to the inner pipe of the sixth double-walled pipe.

[0012] A method for recovering residual liquid from double-walled pipe purge of a methanol dual-fuel ship comprises the following steps:

[0013] S001: In the first stage of purging, the second nitrogen inlet is connected to nitrogen, and the nitrogen passes through the outer tube of the first double-walled tube and the second connecting pipeline in turn, enters the inner tube of the fourth double-walled tube via the third check valve of the first connecting pipeline, enters the inner tube of the second double-walled tube from the inner tube of the fourth double-walled tube, and enters the methanol daily tank via the second pipeline; the first stage of purging utilizes the circulation of the second check valve and the third check valve, and the blocking of the first check valve and the fourth check valve to form a passage from the outer tube of the first double-walled tube to the inner tube of the second double-walled tube, so as to purge and clean the outer tube of the first double-walled tube.

[0014] S002: In the second stage of purging, the third nitrogen inlet is connected to nitrogen, and the nitrogen enters the outer tube of the sixth double-walled tube through the outer tube of the fourth double-walled tube in turn, leads to the solenoid valve group and enters the outer tube of the fifth double-walled tube, enters the first connecting pipeline from the outer tube of the fifth double-walled tube and leads to the inner tube of the fourth double-walled tube, enters the inner tube of the second double-walled tube from the inner tube of the fourth double-walled tube and enters the methanol daily tank via the second pipeline; the second stage of purging utilizes the circulation of the first check valve and the third check valve, and the blocking of the second check valve and the fourth check valve to form a passage from the outer tube of the fourth double-walled tube to the outer tube of the third double-walled tube and the inner tube of the second double-walled tube, and the outer tube of the fourth double-arm tube and the outer tube of the third double-walled tube are purged and cleaned.

[0015] S003: In the third stage of purging, the fourth nitrogen inlet is connected to nitrogen, and the nitrogen passes through the outer tube of the second double-walled tube and enters the methanol daily tank via the second pipeline in turn; during the third stage of purging, when the fourth nitrogen inlet is connected to nitrogen, the remote control valve is set to open at the same time, forming a passage in the fourth pipeline where the remote control valve is located, and the outer tube of the second double-walled tube is purged and cleaned.

[0016] S004: The fourth stage of purging, the fifth nitrogen inlet is connected to nitrogen, the nitrogen passes through the solenoid valve group to the inner tube of the sixth double-walled tube, enters the inner tube of the fourth double-arm tube, and from the inner tube of the fourth double-arm tube to the inner tube of the second double-walled tube and the second pipeline, and finally enters the methanol daily tank;

[0017] S005: In the fifth stage of purging, the first nitrogen inlet is connected to nitrogen, and the nitrogen passes through the valve group unit, the methanol booster pump unit, the inner tube of the first double-walled tube, the inner tube of the third double-walled tube, the inner tube of the fifth double-walled tube, the solenoid valve group, the inner tube of the sixth double-walled tube, the inner tube of the fourth double-walled tube, the inner tube of the second double-walled tube and the second pipeline from the first pipeline and finally enters the methanol daily tank.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. The methanol liquid remaining in the inner and outer tubes of the first double-walled tube and the inner and outer tubes of the second double-walled tube is purged into the methanol daily tank and used again as methanol fuel, which is cyclically applicable and saves energy.

[0020] 2. The methanol is purged and collected in sections, and the purge module is used in conjunction with nitrogen inlets at different positions to ensure that the methanol residues in different sections can be purged into the methanol daily tank at the rated nitrogen pressure value, which is easy to maintain and flexible to use.

[0021] 3. The position arrangement of the pipelines and check valves in the purge unit enables the sequential purge work to be quick and efficient, effectively reducing the phenomenon of methanol liquid retention due to unclean purge, reducing the occurrence of ship operation safety accidents, and meeting the methanol mode operating requirements of methanol dual-fuel diesel engines. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a system schematic diagram of the present invention.

[0023] Figure 2 It is an enlarged schematic diagram of the purge unit in the present invention.

[0024] Among them, 11-methanol inlet, 12-low pressure filter, 13-valve group unit, 14-methanol booster pump unit, 15-purge unit, 16-generator, 17-solenoid valve group, 18-methanol daily cabin, 21-first nitrogen inlet, 22-second nitrogen inlet, 23-third nitrogen inlet, 24-fourth nitrogen inlet, 25-fifth nitrogen inlet, 31-first pipeline, 32-second pipeline, 33-third pipeline, 34-fourth pipeline, 41-first double-walled pipe, 42-second double-walled pipe, 43-third double-walled pipe, 44-fourth double-walled pipe, 45-fifth double-walled pipe, 46-sixth double-walled pipe, 51-first safety valve , 52-second safety valve, 53-remote control valve, 61-first connecting pipeline, 62-second connecting pipeline, 63-first purge pipeline, 64-second purge pipeline, 71-first liquid level sensor, 72-second liquid level sensor, 73-third liquid level sensor, 74-fourth liquid level sensor, 75-first normally closed relief valve, 76-second normally closed relief valve, 77-third normally closed relief valve, 78-fourth normally closed relief valve, 81-first pressure sensor, 82-second pressure sensor, 83-third pressure sensor, 91-first check valve, 92-second check valve, 93-third check valve, 94-fourth check valve. DETAILED DESCRIPTION

[0025] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0026] like Figure 1 to Figure 2The double-walled pipe purging residual liquid recovery system of the methanol dual-fuel ship shown in the figure comprises a methanol inlet 11, the methanol inlet 11 is sequentially connected to a low-pressure filter 12, a valve group unit 13, a methanol booster pump unit 14 and a first double-walled pipe 41 through a first pipeline 31, the first double-walled pipe 41 is sequentially connected to a third double-walled pipe 43, a generator 16, a fourth double-walled pipe 44 and a second double-walled pipe 42, the second double-walled pipe 42 is connected to a methanol daily tank 18 through a second pipeline 32, the connection between the first double-walled pipe 41 and the third double-walled pipe 43 and the connection between the second double-walled pipe 42 and the fourth double-walled pipe 44 are connected to a purge unit 15, the purge unit 15 comprises a first connecting pipeline 61 and a second connecting pipeline 62, the end of the first connecting pipeline 61 is connected to the outer pipe of the third double-walled pipe 43 and is sequentially connected to a first liquid level sensor 71, a first normally closed discharge valve 75, a first check valve 91 and a third check valve 93 and is connected to the fourth double-walled pipe 43 at the other end. The inner tube of the second double-walled tube 44 is connected to the inner tube of the second double-walled tube 44, the end of the second connecting pipeline 62 is connected between the first check valve 91 and the third check valve 93 and is connected to the second check valve 92, the second normally closed discharge valve 76 and the second liquid level sensor 72 in sequence, and is connected to the outer tube at the port of the first double-walled tube 41 at the other end, the outer tube at the port of the second double-walled tube 42 is connected to the fourth nitrogen inlet 24, the fourth liquid level sensor 74 and the fourth normally closed discharge valve 78 in sequence through the first purge pipeline 63, the outer tube of the fourth double-walled tube 44 between the interface of the first connecting pipeline 61 and the fourth double-walled tube 44 and the generator 16 is connected to the second purge pipeline 64, the second purge pipeline 64 is connected to the third nitrogen inlet 23, the third liquid level sensor 73 and the third normally closed discharge valve 77 in sequence, and the inner tube of the fourth double-walled tube 44 between the interface of the second purge pipeline 64 and the fourth double-walled tube 44 to the interface of the first connecting pipeline 61 and the fourth double-walled tube 44 is provided with a fourth check valve 94.

[0027] In the normal supply and use of methanol fuel, when the inner tube of the double-walled pipe is corroded and leaks, the outer tube of the first double-walled pipe 41 is connected to the third pipeline 33, which is provided with a first safety valve 51 and leads to the methanol daily tank 18, and the outer tube of the second double-walled pipe 42 is connected to the fourth pipeline 34, which is provided with a second safety valve 52 and leads to the methanol daily tank 18, and the fourth pipeline 34 is provided with a remote control valve 53 in parallel with the second safety valve 52. At this time, the third pipeline 33 and the fourth pipeline 34 release the leaked methanol gas into the methanol daily tank 18 through the 16bar safety valve, preventing the methanol gas from being continuously pressurized and escaping from the outer tube of the double-walled pipe.

[0028] When nitrogen is connected to the methanol liquid supply system, the valve group unit 13 is connected to the first nitrogen inlet 21, and the interface between the outer tube of the first double-walled tube 41 and the third pipeline 33 is connected to the second nitrogen inlet 22. The first nitrogen inlet 21 is connected to nitrogen with a set value of 10 bar, and is controlled by the valve group unit 13 to purge in the downstream direction of the first pipeline 31. The second nitrogen inlet 22 is close to the end position of the outer tube of the first double-walled tube 41, and the position of the second nitrogen inlet 22 is set at the highest point of the cabin.

[0029] Regarding the establishment of double-walled pipes, the methanol inlet 11, low-pressure filter 12, valve group unit 13, methanol booster pump unit 14 and methanol daily cabin 18 are all located in the fuel preparation room, and the first double-walled pipe 41, the third double-walled pipe 43, the generator 16, the fourth double-walled pipe 44, the purge unit 15 and the second double-walled pipe 42 are all located in the engine room. The fuel preparation room belongs to the dangerous area of ​​the ship, and the engine room belongs to the safe area of ​​the ship. The methanol fuel transportation pipeline in the dangerous area does not need to be protected by double-walled pipes, but the engine room is usually occupied by people, so the methanol fuel transportation pipeline passing through needs to be protected by casing pipe walls.

[0030] In order to monitor in real time whether methanol gas leakage occurs in each double-walled tube, the outer tube of the first double-walled tube 41 is provided with a first pressure sensor 81, the outer tube of the second double-walled tube 42 is provided with a second pressure sensor 82, and the outer tube of the third double-walled tube 43 is provided with a third pressure sensor 83. It should be particularly noted here that the connection between the first double-walled tube 41 and the third double-walled tube 43 is that the inner tube is connected but the outer tube is not connected, and similarly, the connection between the second double-walled tube 42 and the fourth double-walled tube 44 is also that the inner tube is connected but the outer tube is not connected, and the third double-walled tube 43, the fourth double-walled tube 44, the fifth double-walled tube 45 and the sixth double-walled tube 46 are that both the inner tube and the outer tube are connected.

[0031] Inside the generator 16, the generator 16 is provided with a fifth double-walled pipe 45 connected to the third double-walled pipe 43, the fifth double-walled pipe 45 leads to the solenoid valve group 17, the generator 16 is provided with a sixth double-walled pipe 46 connected to the fourth double-walled pipe 44, the sixth double-walled pipe 46 leads to the solenoid valve group 17, and the solenoid valve group 17 is provided with a fifth nitrogen inlet 25. The supply pipelines inside the generator 16 are all double-walled pipes, while the pipeline of the solenoid valve group 17 connected to the fifth nitrogen inlet 25 is a single-walled pipeline, which is controlled by the solenoid valve group 17 and is provided with a corresponding check valve to prevent the backflow of methanol gas. It should be further explained that the pipelines inside the solenoid valve group 17 are all connected to the inner pipe of the double-walled pipe, and the outer pipes of the fifth double-walled pipe 45 and the sixth double-walled pipe 46 are connected by additional pipelines at the port leading to the solenoid valve group 17, and the connection is located at the ports of the fifth double-walled pipe 45 and the sixth double-walled pipe 46.

[0032] The method for recovering residual liquid from double-walled pipe purge of methanol dual-fuel ship corresponding to the above embodiment comprises the following steps:

[0033] S001: First stage purge, the second nitrogen inlet 22 is connected to nitrogen, and the nitrogen passes through the outer tube of the first double-walled tube 41 and the second connecting pipeline 62 in sequence, enters the inner tube of the fourth double-walled tube 44 through the third check valve 93 of the first connecting pipeline 61, enters the inner tube of the second double-walled tube 42 from the inner tube of the fourth double-walled tube 44, and enters the methanol daily tank 18 through the second pipeline 32;

[0034] S002: The second stage of purging, the third nitrogen inlet 23 is connected to nitrogen, and the nitrogen passes through the outer tube of the fourth double-walled tube 44 in turn into the outer tube of the sixth double-walled tube 46, leads to the solenoid valve group 17 and enters the outer tube of the fifth double-walled tube 45, enters the first connecting pipeline 61 from the outer tube of the fifth double-walled tube 45 and leads to the inner tube of the fourth double-walled tube 44, enters the inner tube of the second double-walled tube 42 from the inner tube of the fourth double-walled tube 44, and enters the methanol daily tank 18 via the second pipeline 32;

[0035] S003: The third stage of purging, the fourth nitrogen inlet 24 is connected to nitrogen, and the nitrogen passes through the outer tube of the second double-walled tube 42 and enters the methanol daily tank 18 via the fourth pipeline in turn;

[0036] S004: Fourth stage purge, the fifth nitrogen inlet 25 is connected to nitrogen, and the nitrogen passes through the solenoid valve group 17 to the inner tube of the sixth double-walled tube 46, enters the inner tube of the fourth double-arm tube, and then passes from the inner tube of the fourth double-arm tube to the inner tube of the second double-walled tube 42 and the second pipeline 32, and finally enters the methanol daily tank 18;

[0037] S005: In the fifth stage of purging, the first nitrogen inlet 21 is connected to nitrogen, and the nitrogen passes through the valve group unit 13, the methanol booster pump unit 14, the inner tube of the first double-walled tube 41, the inner tube of the third double-walled tube 43, the inner tube of the fifth double-walled tube 45, the solenoid valve group 17, the inner tube of the sixth double-walled tube 46, the inner tube of the fourth double-walled tube 44, the inner tube of the second double-walled tube 42 and the second pipeline 32 from the first pipeline 31 and finally enters the methanol daily tank 18.

[0038] The methanol fuel is purged in the direction of flow, and the residual methanol and methanol gas are recovered and purged in the order of outer tube first and inner tube later. The purging in each stage remains independent and does not affect each other, ensuring that no methanol gas remains in the methanol pipeline of the ship during long-term docking and maintenance, preventing corrosion of the pipe wall caused by methanol gas.

[0039] The above description shows and describes the preferred embodiments of the present invention. As mentioned above, it should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the invention concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not depart from the spirit and scope of the present invention, and should be within the scope of protection of the claims attached to the present invention.

Claims

1. A methanol dual-fuel ship double-walled pipe purge residual liquid recovery system, comprising a methanol inlet, the methanol inlet is sequentially connected to a low-pressure filter, a valve group unit, a methanol booster pump unit and a first double-walled pipe through a first pipeline, the first double-walled pipe is sequentially connected to a third double-walled pipe, a generator, a fourth double-walled pipe and a second double-walled pipe, the second double-walled pipe is connected to a methanol daily tank through a second pipeline, and a purge unit is connected to the connection between the first double-walled pipe and the third double-walled pipe and the connection between the second double-walled pipe and the fourth double-walled pipe, characterized in that: The purge unit includes a first connecting pipeline and a second connecting pipeline, wherein the end of the first connecting pipeline is connected to the outer tube of the third double-walled tube and is sequentially connected to the first liquid level sensor, the first normally closed relief valve, the first check valve and the third check valve, and is connected to the inner tube of the fourth double-walled tube at the other end; the end of the second connecting pipeline is connected between the first check valve and the third check valve and is sequentially connected to the second check valve, the second normally closed relief valve and the second liquid level sensor, and is connected to the outer tube at the port of the first double-walled tube at the other end; The outer tube at the port of the double-walled tube is connected to a fourth nitrogen inlet, a fourth liquid level sensor and a fourth normally closed discharge valve in sequence through a first purge pipeline, the interface between the first connecting pipeline and the fourth double-walled tube and the outer tube of the fourth double-walled tube between the generator is connected to a second purge pipeline, the second purge pipeline is connected to a third nitrogen inlet, a third liquid level sensor and a third normally closed discharge valve in sequence, and the inner tube of the fourth double-walled tube between the interface between the second purge pipeline and the fourth double-walled tube and the interface between the first connecting pipeline and the fourth double-walled tube is provided with a fourth check valve; The generator is provided with a fifth double-walled pipe connected to the third double-walled pipe, the fifth double-walled pipe leads to the solenoid valve group, the generator is provided with a sixth double-walled pipe connected to the fourth double-walled pipe, the sixth double-walled pipe leads to the solenoid valve group, and the solenoid valve group is connected to a fifth nitrogen inlet; The outer tube of the first double-walled tube is connected to a third pipeline, the third pipeline is provided with a first safety valve and leads to the methanol daily tank, the outer tube of the second double-walled tube is connected to a fourth pipeline, the fourth pipeline is provided with a second safety valve and leads to the methanol daily tank, and the fourth pipeline is provided with a remote control valve in parallel with the second safety valve; The valve group unit is connected to a first nitrogen inlet, and the interface between the outer tube of the first double-walled tube and the third pipeline is connected to a second nitrogen inlet.

2. A methanol dual-fuel ship double-wall pipe purge residual liquid recovery system according to claim 1, characterized in that; The methanol inlet, low-pressure filter, valve group unit, methanol booster pump unit and methanol daily cabin are all located in the fuel preparation room, and the first double-wall pipe, third double-wall pipe, generator, fourth double-wall pipe, purge unit and second double-wall pipe are all located in the engine room.

3. A methanol dual-fuel ship double-wall pipe purge residual liquid recovery system according to claim 1, characterized in that; The outer tube of the first double-walled tube is provided with a first pressure sensor, the outer tube of the second double-walled tube is provided with a second pressure sensor, and the outer tube of the third double-walled tube is provided with a third pressure sensor.

4. A methanol dual-fuel ship double-walled pipe purge residual liquid recovery method, the recovery method is based on the methanol dual-fuel ship double-walled pipe purge residual liquid recovery system according to claim 1, characterized in that: The following steps are involved: S001: In the first stage of purging, the second nitrogen inlet is connected to nitrogen, and the nitrogen passes through the outer tube of the first double-walled tube and the second connecting pipeline in turn, enters the inner tube of the fourth double-walled tube through the third check valve of the first connecting pipeline, enters the inner tube of the second double-walled tube from the inner tube of the fourth double-walled tube, and enters the methanol daily tank through the second pipeline; S002: The second stage of purging, the third nitrogen inlet is connected to nitrogen, the nitrogen passes through the outer tube of the fourth double-walled tube in turn into the outer tube of the sixth double-walled tube, leads to the solenoid valve group and enters the outer tube of the fifth double-walled tube, enters the first connecting pipeline from the outer tube of the fifth double-walled tube and leads to the inner tube of the fourth double-walled tube, enters the inner tube of the second double-walled tube from the inner tube of the fourth double-walled tube, and enters the methanol daily tank via the second pipeline; S003: The third stage of purging, the fourth nitrogen inlet is connected to nitrogen, and the nitrogen passes through the outer pipe of the second double-walled pipe and enters the methanol daily tank through the fourth pipeline in turn; S004: The fourth stage of purging, the fifth nitrogen inlet is connected to nitrogen, the nitrogen passes through the solenoid valve group to the inner tube of the sixth double-walled tube, enters the inner tube of the fourth double-arm tube, and from the inner tube of the fourth double-arm tube to the inner tube of the second double-walled tube and the second pipeline, and finally enters the methanol daily tank; S005: In the fifth stage of purging, the first nitrogen inlet is connected to nitrogen, and the nitrogen passes through the valve group unit, the methanol booster pump unit, the inner tube of the first double-walled tube, the inner tube of the third double-walled tube, the inner tube of the fifth double-walled tube, the solenoid valve group, the inner tube of the sixth double-walled tube, the inner tube of the fourth double-walled tube, the inner tube of the second double-walled tube and the second pipeline from the first pipeline and finally enters the methanol daily tank.

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