A nitrogen supply system for methanol dual-fuel ships

Abstract

The present invention provides a nitrogen supply system for methanol dual-fuel ships. The system includes a double-line nitrogen production pipeline, which is connected in the middle by a connecting filter tube. The prepared high-concentration nitrogen is screened by a pressure sensor, a temperature sensor, a flow meter and a double check valve device connected in sequence in the distribution main pipe. The qualified nitrogen is respectively stored in the first nitrogen bottle and the second nitrogen bottle. The first distribution branch pipe and the second distribution branch pipe are connected to the methanol equipment in the dangerous area. The distribution branch pipe leading to the methanol equipment is provided with a double check valve device to prevent the backflow of methanol vapor. The third distribution branch pipe leads to the equipment in the safe area. Each corresponding equipment pipeline is provided with a stop check valve. The equipment with different nitrogen pressure requirements is depressurized through a pressure reducing valve and a safety valve, and is first pressurized by a pressurizing device and stored in a nitrogen bottle and then depressurized through a pressure reducing valve. The present invention has reasonable distribution, high safety, and stable nitrogen supply.

Description

Technical Field

[0001] The invention relates to the technical field of methanol dual-fuel ships, and in particular to a nitrogen supply system for methanol dual-fuel ships. Background Art

[0002] As emission requirements become increasingly stringent, methanol dual-fuel diesel engines and boilers are gradually being promoted in the shipbuilding field as a clean emission solution. Large methanol dual-fuel powered ships need to use nitrogen as an inert gas to purge the residues in methanol pipelines and methanol equipment and a small amount of methanol liquid and methanol vapor leaked accidentally, as well as to inert the methanol tank and methanol double-wall pipe.

[0003] Since the equipment that requires nitrogen supply in the ship also includes the main engine, generator, high-pressure pump, boiler and other equipment, the operating environment is complex, and each equipment has different requirements for the inert gas pressure, it is necessary to design a separate pipeline for each equipment.

[0004] Methanol is a gas that is toxic to humans and is highly corrosive. Once methanol gas flows back into the nitrogen system, it can easily cause immeasurable damage to the pipe body and some equipment. At the same time, once the nitrogen system leaks, the methanol evaporated gas will leak into the ship through the nitrogen system, causing great safety hazards. Summary of the invention

[0005] The purpose of the present invention is to provide a nitrogen supply system for methanol dual-fuel ships with reasonable distribution, high safety, easy replacement and maintenance of system components during use, and stable nitrogen supply in view of the shortcomings of the prior art.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a methanol dual-fuel ship nitrogen supply system, including a first air compressor and a second air compressor, the first air compressor is connected to a first stop valve, a first air filter, a first dryer, a second air filter, a third air filter and a fourth air filter in sequence through a first filter tube, the second air compressor is connected to a second stop valve, a fifth air filter, a second dryer, a sixth air filter, a seventh air filter and an eighth air filter in sequence through a second filter tube, the first filter tube and the second filter tube are combined and transmitted through the third filter tube, the third filter tube is respectively connected to the fourth filter tube and the fifth filter tube, and the fourth filter tube is provided with a a nitrogen membrane group, the fifth filter tube is provided with a second nitrogen membrane group, the fourth filter tube and the fifth filter tube are combined and connected to a main distribution pipe, the main distribution pipe is provided with a pressure sensor, a temperature sensor, a flow meter and a first double check valve device in sequence, the main distribution pipe is respectively connected to a first distribution branch pipe and a second distribution branch pipe, the first distribution branch pipe is sequentially connected to a first nitrogen bottle, a third stop valve, a second double check valve device and a first stop check valve, the first distribution branch pipe is respectively connected to a first nitrogen branch pipe, a second nitrogen branch pipe and a third nitrogen branch pipe, the first nitrogen branch pipe leads to a methanol filling station, the second nitrogen branch pipe is sequentially connected to a first pressure reducing valve and a first safety valve and leads to a methanol storage tank The third nitrogen branch pipe is connected to the second pressure reducing valve and the second safety valve in sequence and leads to the methanol daily tank. The second distribution branch pipe is connected to the second nitrogen bottle, the fourth stop valve and the third double check valve device in sequence. The second distribution branch pipe is connected to the fourth nitrogen branch pipe, the fifth nitrogen branch pipe and the sixth nitrogen branch pipe. The fourth nitrogen branch pipe is connected to the second stop check valve and leads to the methanol supply unit. The fifth nitrogen branch pipe is connected to the third stop check valve and leads to the main engine valve group. The sixth nitrogen branch pipe is connected to the fourth stop check valve and leads to the generator valve group and the high-pressure pump. The position between the fourth stop valve and the third double check valve device is connected to the third distribution branch pipe. The third distribution branch pipe The seventh nitrogen branch pipe, the eighth nitrogen branch pipe, the ninth nitrogen branch pipe, the tenth nitrogen branch pipe and the eleventh nitrogen branch pipe are connected in sequence. The seventh nitrogen branch pipe is connected in sequence with the third pressure reducing valve, the third safety valve, the fifth stop check valve and leads to the generator. The eighth nitrogen branch pipe is connected with the sixth stop check valve and leads to the main engine. The ninth nitrogen branch pipe is connected with the seventh stop check valve and leads to the high-pressure pump of the generator. The tenth nitrogen branch pipe is connected with the eighth stop check valve and leads to the boiler. The eleventh nitrogen branch pipe is connected with the pressurizing device, the third nitrogen bottle, the seventh stop valve, the fourth pressure reducing valve, the fourth safety valve and the ninth stop check valve in sequence and leads to the main engine double-wall pipe pressure test.The first air filter and the fifth air filter filter large particles of impurities, liquid water and oil, the second air filter and the sixth air filter filter small particles of impurities, suspended oil droplets and water, the third air filter and the seventh air filter filter oil mist, the fourth air filter and the eighth air filter filter dust, the prepared nitrogen is stored in the first nitrogen bottle and the second nitrogen bottle. Since the demand for nitrogen in each cabin is different, and some cabins require nitrogen as an inert gas or mixed gas to serve as methanol fuel, all terminal equipment related to methanol is divided into a dangerous area, and cabins not related to methanol are divided into a safe area. All pipelines connected to methanol-related equipment are connected with double check valves to prevent methanol vapor from flowing back.

[0007] Preferably, the first filter tube and the second filter tube are connected by a connecting filter tube, a first normally closed stop valve is provided on the connecting filter tube, one end of the connecting filter tube is located between the first stop valve of the first filter tube and the first air filter, and the other end of the connecting filter tube is located between the second stop valve of the second filter tube and the fifth air filter. The connecting filter tube uses the first filter tube and the second filter tube as spare filter tubes for each other, and when the air filter is replaced or cleaned, the normal operation of the system is ensured by the connecting filter tube.

[0008] Preferably, the first air compressor, the second air compressor, the first dryer and the second dryer are all provided with a PLC controller.

[0009] Preferably, the first nitrogen membrane group is connected to a first discharge pipe, the second nitrogen membrane group is connected to a second discharge pipe, the first discharge pipe and the second discharge pipe are combined to be connected to a third discharge pipe, and the third discharge pipe leads to the external safety zone. Nitrogen that does not meet the concentration requirements generated during the preparation of nitrogen is directly discharged to the external safety zone through the third discharge pipe.

[0010] Preferably, the first double check valve device or the second double check valve device or the third double check valve device comprises a first gas-controlled valve and a second gas-controlled valve connected in series, a ventilating branch pipe is connected between the first gas-controlled valve and the second gas-controlled valve, a third gas-controlled valve is arranged in the ventilating branch pipe, and the end of the ventilating branch pipe is connected to the external safety zone. The first double check valve is used to discharge unqualified nitrogen in the distribution main pipe to the external safety zone, and the second check valve device and the third check valve device are used to reflux and discharge methanol vapor in the first distribution branch pipe and the second distribution branch pipe to the external safety zone.

[0011] Preferably, the first distribution branch pipe is connected to the second distribution branch pipe through a connecting branch pipe, a second normally closed stop valve is provided in the middle of the connecting branch pipe, one end of the connecting branch pipe is located between the third stop valve and the second double check valve device, and the other end of the connecting branch pipe is located between the fourth stop valve and the third double check valve device and is connected to the third distribution branch pipe. The connecting branch pipe uses the first distribution branch pipe and the second distribution branch pipe as alternate distribution branches, and when the first nitrogen cylinder or the second nitrogen cylinder fails, the normal operation of the system is guaranteed by the connecting branch pipe.

[0012] Preferably, the boosting device includes a first boosting branch and a second boosting branch arranged in parallel, the first boosting branch is sequentially connected to the fifth stop valve, the first booster and the sixth stop valve, and the second boosting branch is sequentially connected to the third normally closed stop valve, the second booster and the fourth normally closed stop valve.

[0013] Preferably, the first nitrogen cylinder or the second nitrogen cylinder or the third nitrogen cylinder comprises a container, a discharge valve is provided at the bottom end of the container, a first flange interface and a second flange interface are provided at the side end of the container, and a nitrogen safety valve is provided at the top end of the container.

[0014] Preferably, the pressure values ​​of the first nitrogen cylinder and the second nitrogen cylinder are 10 bar, the input pressure value of the booster device is 10 bar, and the output pressure value of the booster device is 25 bar.

[0015] Preferably, the input value of the first pressure reducing valve is 10 bar, the output value of the first pressure reducing valve is 0.2 bar, the input value of the second pressure reducing valve is 10 bar, the output value of the second pressure reducing valve is 0.2 bar, the input value of the third pressure reducing valve is 10 bar, the output value of the third pressure reducing valve is 2 bar, the input value of the fourth pressure reducing valve is 25 bar, and the output value of the fourth pressure reducing valve is 13 bar. The nitrogen in the third distribution branch pipe is set from 10 bar to 13 bar by the cooperation of the booster device and the pressure reducing valve, and the booster device and the pressure reducing valve are cooperated to ensure stable nitrogen output.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. Ensure the reasonable allocation of multiple users and multiple pressure levels, ensure no interference in normal use, and keep the nitrogen pressure constant;

[0018] 2. Each device can be replaced in an emergency or sudden failure while ensuring the normal operation of the system;

[0019] 3. Use or set up separate pipelines for methanol-related equipment and take corresponding measures to prevent methanol vapor reflux to ensure the safety of the nitrogen system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the present invention.

[0021] Figure 2 It is a structural schematic diagram of the double check valve device in the present invention.

[0022] Figure 3 It is a structural schematic diagram of the nitrogen bottle in the present invention.

[0023] Among them, 1-dangerous area, 2-external safety area, 11-first air compressor, 110-first filter tube, 111-first stop valve, 112-first air filter, 113-first dryer, 114-second air filter, 115-third air filter, 116-fourth air filter, 12-second air compressor, 120-second filter tube, 121-second stop valve, 122-fifth air filter, 123-second dryer, 124-sixth air filter, 125-seventh air filter, 126-eighth air filter, 130-connecting filter tube, 131-third filter tube, 132-first normally closed stop valve, 133-fourth filter tube, 134-fifth filter tube, 31-first nitrogen membrane group, 311-first discharge pipe, 32-second nitrogen membrane group, 321-second discharge pipe, 33-third discharge pipe, 40-main distribution pipe, 41-pressure sensor, 42-temperature sensor, 43-flow meter, 51-first distribution branch pipe, 511-first nitrogen bottle, 512-third stop valve, 52-second distribution branch pipe, 521-second nitrogen bottle, 522-fourth stop valve, 53-third distribution branch pipe, 54-connecting branch pipe, 541-second normally closed stop valve, 61-first double check valve device, 611-first nitrogen branch pipe, 612-second nitrogen branch pipe pipe, 613-third nitrogen branch pipe, 621-fourth nitrogen branch pipe, 622-fifth nitrogen branch pipe, 623-sixth nitrogen branch pipe, 631-seventh nitrogen branch pipe, 632-eighth nitrogen branch pipe, 633-ninth nitrogen branch pipe, 634-tenth nitrogen branch pipe, 635-eleventh nitrogen branch pipe, 62-second double check valve device, 63-third double check valve device, 701-first stop check valve, 702-second stop check valve, 703-third stop check valve, 704-fourth stop check valve, 705-fifth stop check valve, 706-sixth stop check valve, 707-seventh stop check valve, 708-eighth stop check valve, 709-ninth stop check valve, 711-first safety valve, 712-second safety valve, 713-third safety valve, 714-fourth safety valve, 721-first pressure reducing valve, 722-second pressure reducing valve, 723-third pressure reducing valve, 724-fourth pressure reducing valve, 80-boosting device, 801-fifth stop valve, 802-sixth stop valve, 803-third Normally closed stop valve, 804-fourth normally closed stop valve, 805-seventh stop valve, 81-first booster branch pipe, 811-first booster, 812-second booster, 813-third nitrogen cylinder, 82-second booster branch pipe, 901-methanol filling station, 902-methanol storage tank, 903-methanol daily tank, 904-methanol supply unit, 905-main engine valve group, 906-generator valve group and high-pressure pump, 907-generator, 908-main engine, 909-generator high-pressure pump, 910-boiler,911-main engine double wall pipe pressure test, 1001-first gas control valve, 1002-second gas control valve, 1003-third gas control valve, 1004-ventilation branch pipe, 1011-first flange interface, 1012-second flange interface, 1013-container, 1014-nitrogen safety valve, 1015-relief valve. , DETAILED DESCRIPTION

[0024] 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.

[0025] like Figures 1 to 3The nitrogen supply system of the methanol dual-fuel ship shown comprises a first air compressor 11 and a second air compressor 12. The first air compressor 11 is sequentially connected to a first stop valve 111, a first air filter 112, a first dryer 113, a second air filter 114, a third air filter 115 and a fourth air filter 116 through a first filter tube 110. The second air compressor 12 is sequentially connected to a second stop valve 121, a fifth air filter 122, a second dryer 123, a sixth air filter 124, a seventh air filter 125 and an eighth air filter 126 through a second filter tube 120. The first filter tube 110 and the second filter tube 120 are combined and transmitted through a third filter tube 131. The third filter tube 131 is respectively connected to the fourth filter tube 133 and the fifth filter tube 134. 34, the fourth filter tube 133 is provided with a first nitrogen membrane group 31, the fifth filter tube 134 is provided with a second nitrogen membrane group 32, the fourth filter tube 133 and the fifth filter tube 134 are combined and connected to the main distribution pipe 40, the main distribution pipe 40 is sequentially provided with a pressure sensor 41, a temperature sensor 42, a flow meter 43 and a first double check valve device 61, the main distribution pipe 40 is respectively connected to the first distribution branch pipe 51 and the second distribution branch pipe 52, the first distribution branch pipe 51 is sequentially connected to the first nitrogen bottle 511, the third stop valve 512, the second double check valve device 62 and the first stop check valve 701, the first distribution branch pipe 51 is respectively connected to the first nitrogen branch pipe 611, the second nitrogen branch pipe 612 and the third nitrogen branch pipe 613, the first nitrogen branch pipe 611 leads to the methanol filling Station 901, the second nitrogen branch pipe 612 is connected to the first pressure reducing valve 721 and the first safety valve 711 in sequence and leads to the methanol storage tank 902, the third nitrogen branch pipe 613 is connected to the second pressure reducing valve 722 and the second safety valve 712 in sequence and leads to the methanol daily tank 903, the second distribution branch pipe 52 is connected to the second nitrogen bottle 521, the fourth stop valve 522 and the third double check valve device 63 in sequence, the second distribution branch pipe 52 is connected to the fourth nitrogen branch pipe 621, the fifth nitrogen branch pipe 622 and the sixth nitrogen branch pipe 623, the fourth nitrogen branch pipe 621 is connected to the second stop check valve 702 and leads to the methanol supply unit 904, the fifth nitrogen branch pipe 622 is connected to the third stop check valve 703 and leads to the main engine valve group 905, the sixth nitrogen branch pipe 623 The fourth stop check valve 704 is connected and leads to the generator valve group and the high-pressure pump 906. The position between the fourth stop valve 522 and the third double check valve device 63 is connected to the third distribution branch pipe 53. The third distribution branch pipe 53 is sequentially connected to the seventh nitrogen branch pipe 631, the eighth nitrogen branch pipe 632, the ninth nitrogen branch pipe 633, the tenth nitrogen branch pipe 634 and the eleventh nitrogen branch pipe 635. The seventh nitrogen branch pipe 631 is sequentially connected to the third pressure reducing valve 723, the third safety valve 713, the fifth stop check valve 705 and leads to the generator 907. The eighth nitrogen branch pipe 632 is connected to the sixth stop check valve 706 and leads to the main engine 908. The ninth nitrogen branch pipe 633 is connected to the seventh stop check valve 707 and leads to the generator high-pressure pump 909.The tenth nitrogen branch pipe 634 is connected to the eighth stop check valve 708 and leads to the boiler 910. The eleventh nitrogen branch pipe 635 is sequentially connected to the booster 80, the third nitrogen bottle 813, the seventh stop valve 805, the fourth pressure reducing valve 724, the fourth safety valve 714 and the ninth stop check valve 709 and leads to the main engine double wall pipe pressure test 911.

[0026] Furthermore, the first filter tube 110 and the second filter tube 120 are connected through a connecting filter tube 130, and a first normally closed stop valve 132 is provided on the connecting filter tube 130. One end of the connecting filter tube 130 is located between the first stop valve 111 of the first filter tube 110 and the first air filter 112, and the other end of the connecting filter tube 130 is located between the second stop valve 121 of the second filter tube 120 and the fifth air filter 122.

[0027] Furthermore, the first air compressor 11, the second air compressor 12, the first dryer 113 and the second dryer 123 are all provided with a PLC controller.

[0028] Furthermore, the first nitrogen membrane group 31 is connected to a first discharge pipe 311 , the second nitrogen membrane group 32 is connected to a second discharge pipe 321 , the first discharge pipe 311 and the second discharge pipe 321 are combined to be connected to a third discharge pipe 33 , and the third discharge pipe 33 leads to the external safety zone 2 .

[0029] Furthermore, the first double check valve device 61 or the second double check valve device 62 or the third double check valve device 63 includes a first air-controlled valve 1001 and a second air-controlled valve 1002 connected in series, a ventilation branch pipe 1004 is connected between the first air-controlled valve 1001 and the second air-controlled valve 1002, a third air-controlled valve 1003 is provided in the ventilation branch pipe 1004, and the end of the ventilation branch pipe 1004 is connected to the external safety zone 2.

[0030] Furthermore, the first distribution branch pipe 51 and the second distribution branch pipe 52 are connected through a connecting branch pipe 54, and a second normally closed stop valve 541 is provided in the middle of the connecting branch pipe 54. One end of the connecting branch pipe 54 is located between the third stop valve 512 and the second double check valve device 62, and the other end of the connecting branch pipe 54 is located between the fourth stop valve 522 and the third double check valve device 63 and is connected to the third distribution branch pipe 53.

[0031] Furthermore, the boosting device 80 includes a first boosting branch pipe 81 and a second boosting branch pipe 82 arranged in parallel, the first boosting branch pipe 81 is connected to the fifth stop valve 801, the first boosting machine 811 and the sixth stop valve 802 in sequence, and the second boosting branch pipe 82 is connected to the third normally closed stop valve 803, the second boosting machine 812 and the fourth normally closed stop valve 804 in sequence.

[0032] Furthermore, the first nitrogen bottle 511 or the second nitrogen bottle 521 or the third nitrogen bottle 813 includes a container 1013, a discharge valve 1015 is provided at the bottom end of the container 1013, a first flange interface 1011 and a second flange interface 1012 are provided at the side end of the container 1013, and a nitrogen safety valve 1014 is provided at the top end of the container 1013.

[0033] Furthermore, the pressure values ​​of the first nitrogen cylinder 511 and the second nitrogen cylinder 521 are 10 bar, the input pressure value of the booster device 80 is 10 bar, and the output pressure value of the booster device 80 is 25 bar.

[0034] Furthermore, the input value of the first pressure reducing valve 721 is 10 bar, and the output value of the first pressure reducing valve 721 is 0.2 bar, the input value of the second pressure reducing valve 722 is 10 bar, and the output value of the second pressure reducing valve 722 is 0.2 bar, the input value of the third pressure reducing valve 723 is 10 bar, and the output value of the third pressure reducing valve 723 is 2 bar, the input value of the fourth pressure reducing valve 724 is 25 bar, and the output value of the fourth pressure reducing valve 724 is 13 bar.

[0035] Air passes through the first air compressor 11 and the second air compressor 12 and enters the first filter tube 110 and the second filter tube 120 for filtering to obtain high-energy concentration nitrogen, wherein unqualified nitrogen passes through the first double check valve device 61 and is discharged to the external safety zone 2, and qualified nitrogen enters the first nitrogen bottle 511 and the second nitrogen bottle 521 for storage, and is distributed to each cabin requiring nitrogen through each corresponding nitrogen branch pipe. The cabin is divided into a safe zone and a dangerous zone 1. The main hazard source in the dangerous zone 1 is methanol. In order to prevent the reflux of methanol vapor from affecting the nitrogen branch pipe, a double check valve device is set on the nitrogen branch pipe corresponding to the dangerous zone 1, and a pressure reducing valve and an annular valve are set in the nitrogen branch pipe for equipment with a pressure value requirement lower than 10 bar. The whole valve has stable pressure reduction. For equipment with a pressure requirement higher than 10 bar, a booster is installed in the nitrogen branch pipe to first increase the pressure and then use a pressure reducing valve to reduce the pressure to provide a stable nitrogen source. In order to prevent the nitrogen branches from affecting each other, a stop check valve is installed on each branch pipe to ensure safety. At the same time, considering the failure and damage of the equipment during use, especially the air compressor and the nitrogen cylinder, the double-line processing and the connecting pipelines serve as backup equipment for each other. When the system is operating, the normally closed stop check valve in the connecting filter tube 130 or the connecting branch pipe 54 can be opened to connect the pipeline, and the pipeline that fails or needs to be replaced can be closed through the stop valve, and then replacement or maintenance work can be carried out to ensure the normal operation of the system.

[0036] 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 nitrogen supply system for a methanol dual-fuel ship, characterized in that: The invention comprises a first air compressor and a second air compressor, wherein the first air compressor is sequentially connected to a first stop valve, a first air filter, a first dryer, a second air filter, a third air filter and a fourth air filter through a first filter tube, and the second air compressor is sequentially connected to a second stop valve, a fifth air filter, a second dryer, a sixth air filter, a seventh air filter and an eighth air filter through a second filter tube, the first filter tube and the second filter tube are combined and transmitted through a third filter tube, the third filter tube is respectively connected to a fourth filter tube and a fifth filter tube, the fourth filter tube is provided with a first nitrogen membrane group, the fifth filter tube is provided with a second nitrogen membrane group, the fourth filter tube and the fifth filter tube are connected to a first filter tube, and the fifth filter tube is connected to a second filter tube. The filter tube is connected with the main distribution pipe, which is provided with a pressure sensor, a temperature sensor, a flow meter and a first double check valve device in sequence. The main distribution pipe is connected with the first distribution branch pipe and the second distribution branch pipe respectively. The first distribution branch pipe is connected with the first nitrogen bottle, the third stop valve, the second double check valve device and the first stop check valve in sequence. The first distribution branch pipe is connected with the first nitrogen branch pipe, the second nitrogen branch pipe and the third nitrogen branch pipe respectively. The first nitrogen branch pipe leads to the methanol filling station. The second nitrogen branch pipe is connected with the first pressure reducing valve and the first safety valve in sequence and leads to the methanol storage tank. The third nitrogen branch pipe is connected with the second pressure reducing valve and The second safety valve leads to the methanol daily tank, the second distribution branch is connected to the second nitrogen bottle, the fourth stop valve and the third double check valve device in sequence, the second distribution branch is connected to the fourth nitrogen branch, the fifth nitrogen branch and the sixth nitrogen branch, the fourth nitrogen branch is connected to the second stop check valve and leads to the methanol supply unit, the fifth nitrogen branch is connected to the third stop check valve and leads to the main engine valve group, the sixth nitrogen branch is connected to the fourth stop check valve and leads to the generator valve group and the high-pressure pump, the position between the fourth stop valve and the third double check valve device is connected to the third distribution branch, and the third distribution branch is connected to the seventh nitrogen branch in sequence. The gas branch pipe, the eighth nitrogen branch pipe, the ninth nitrogen branch pipe, the tenth nitrogen branch pipe and the eleventh nitrogen branch pipe, the seventh nitrogen branch pipe is connected with the third pressure reducing valve, the third safety valve, the fifth stop check valve in sequence and leads to the generator, the eighth nitrogen branch pipe is connected with the sixth stop check valve and leads to the main engine, the ninth nitrogen branch pipe is connected with the seventh stop check valve and leads to the generator high-pressure pump, the tenth nitrogen branch pipe is connected with the eighth stop check valve and leads to the boiler, the eleventh nitrogen branch pipe is connected with the pressurizing device, the third nitrogen bottle, the seventh stop valve, the fourth pressure reducing valve, the fourth safety valve and the ninth stop check valve in sequence and leads to the main engine double-wall pipe pressure test.

2. A nitrogen supply system for a methanol dual-fuel ship according to claim 1, characterized in that: The first filter tube and the second filter tube are connected through a connecting filter tube, on which a first normally closed stop valve is provided, one end of the connecting filter tube is located between the first stop valve of the first filter tube and the first air filter, and the other end of the connecting filter tube is located between the second stop valve of the second filter tube and the fifth air filter.

3. The nitrogen supply system for a methanol dual-fuel ship according to claim 1, characterized in that: The first air compressor, the second air compressor, the first dryer and the second dryer are all provided with a PLC controller.

4. The nitrogen supply system for a methanol dual-fuel ship according to claim 1, characterized in that: The first nitrogen membrane group is connected to a first discharge pipe, the second nitrogen membrane group is connected to a second discharge pipe, the first discharge pipe and the second discharge pipe are combined to be connected to a third discharge pipe, and the third discharge pipe leads to an external safety zone.

5. The nitrogen supply system for a methanol dual-fuel ship according to claim 1, characterized in that: The first double check valve device or the second double check valve device or the third double check valve device includes a first air-controlled valve and a second air-controlled valve connected in series, a ventilation branch pipe is connected between the first air-controlled valve and the second air-controlled valve, a third air-controlled valve is arranged in the ventilation branch pipe, and the end of the ventilation branch pipe is connected to an external safety zone.

6. The nitrogen supply system for a methanol dual-fuel ship according to claim 1, characterized in that: The first distribution branch pipe is connected to the second distribution branch pipe through a connecting branch pipe, a second normally closed stop valve is provided in the middle of the connecting branch pipe, one end of the connecting branch pipe is located between the third stop valve and the second double check valve device, and the other end of the connecting branch pipe is located between the fourth stop valve and the third double check valve device and is connected to the third distribution branch pipe.

7. The nitrogen supply system for a methanol dual-fuel ship according to claim 1, characterized in that: The boosting device includes a first boosting branch pipe and a second boosting branch pipe arranged in parallel, the first boosting branch pipe is sequentially connected to a fifth stop valve, a first booster and a sixth stop valve, and the second boosting branch pipe is sequentially connected to a third normally closed stop valve, a second booster and a fourth normally closed stop valve.

8. The nitrogen supply system for a methanol dual-fuel ship according to claim 1, characterized in that: The first nitrogen bottle, the second nitrogen bottle or the third nitrogen bottle comprises a container, a discharge valve is provided at the bottom end of the container, a first flange interface and a second flange interface are provided at the side end of the container, and a nitrogen safety valve is provided at the top end of the container.

9. The nitrogen supply system for a methanol dual-fuel ship according to claim 1, characterized in that: The pressure values ​​of the first nitrogen cylinder and the second nitrogen cylinder are 10 bar, the input pressure value of the booster device is 10 bar, and the output pressure value of the booster device is 25 bar.

10. The nitrogen supply system for a methanol dual-fuel ship according to claim 1, characterized in that: The input value of the first pressure reducing valve is 10 bar, and the output value of the first pressure reducing valve is 0.2 bar, the input value of the second pressure reducing valve is 10 bar, and the output value of the second pressure reducing valve is 0.2 bar, the input value of the third pressure reducing valve is 10 bar, and the output value of the third pressure reducing valve is 2 bar, the input value of the fourth pressure reducing valve is 25 bar, and the output value of the fourth pressure reducing valve is 13 bar.

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