Dual use air and nitrogen system

Abstract

The application relates to the technical field of ship engineering, and particularly discloses a nitrogen system capable of being used in combination with air, which comprises a nitrogen generator, a nitrogen main pipeline arranged along the longitudinal direction of a ship and connected with the outlet of the nitrogen generator at one end, a plurality of liquid cargo tanks connected with the nitrogen main pipeline through nitrogen branch pipelines, a first deck fan, an outlet of which is communicated with the head section of the nitrogen main pipeline through a first connecting pipeline, a second deck fan, an outlet of which is communicated with the tail section of the nitrogen main pipeline through a second connecting pipeline, a double-blind plate flange arranged in the middle of the nitrogen main pipeline and located between the first connecting pipeline and the second connecting pipeline, used for conducting or isolating the head section and the tail section, and a control system provided with a mode selection switch and electrically connected with the nitrogen generator, the first deck fan, the second deck fan and the double-blind plate flange. The application solves the problems of single function and low air replacement efficiency of the traditional air nitrogen system.

Description

Technical Field

[0001] This invention relates to the field of marine engineering technology, and in particular to a nitrogen system that can also be used for air purification. Background Technology

[0002] During the operation of liquid cargo ships, a stable inert gas environment needs to be maintained within the cargo tanks to prevent oxidation, deterioration, or the formation of explosive gas mixtures upon contact with air, thereby ensuring the ship's operational safety. Traditionally, nitrogen systems have been widely used on liquid cargo ships, achieving inert protection by supplying high-purity nitrogen into the cargo tanks. However, existing nitrogen systems have some significant limitations.

[0003] Existing nitrogen systems typically only supply nitrogen and cannot replace the nitrogen in cargo tanks with air when needed. When ships need to enter dry dock for maintenance, or when cargo tanks require internal inspection, cleaning, or repair work, air replacement must be achieved through additional equipment or complex operating procedures. This not only increases the difficulty of operation but also extends the operation time.

[0004] During air replacement, using a single blower in series will result in excessively long air exchange time, affecting the overall operational efficiency of the vessel. Conversely, using multiple blowers to supply air to the same main pipeline simultaneously can cause excessive airflow velocity within the pipeline, leading to severe pipeline vibration, significantly increased operating noise, and in severe cases, damage to pipeline accessories, creating safety hazards.

[0005] Existing nitrogen systems are often designed for specific types of liquid cargo ships, lacking versatility and flexibility. When it is necessary to retrofit older ships or adapt them to different types of new ships, large-scale modifications to the existing nitrogen pipelines are usually required. This not only increases equipment costs and construction difficulty but also prolongs the retrofit cycle.

[0006] During the switching process between the nitrogen system and the air mode, if there is no effective interlock protection mechanism, dangerous conditions can easily occur due to misoperation. For example, if the nitrogen generator and the deck fan are running at the same time, air may be mixed into the nitrogen pipeline, affecting the purity of the nitrogen, or nitrogen may flow back into the deck fan, causing equipment damage or gas leakage.

[0007] Therefore, a nitrogen system that can also be used for air exchange is proposed to solve the problems of single function and low air replacement efficiency of traditional air exchange nitrogen systems. Summary of the Invention

[0008] The purpose of this invention is to provide a nitrogen system that can also be used for air purification, in order to solve the problems mentioned in the background art.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: The present invention provides a nitrogen system that can also be used for air generation, including a nitrogen generator; The nitrogen main pipeline extends longitudinally along the ship and is connected at one end to the outlet of the nitrogen generator. Multiple liquid cargo tanks are connected to the main nitrogen pipeline via nitrogen branch lines; The outlet of the first deck fan is connected to the head section of the nitrogen main pipeline via the first connecting pipeline; The outlet of the second deck fan is connected to the tail section of the nitrogen main pipeline via a second connecting pipeline; A double blind flange is installed in the middle of the nitrogen main pipeline and located between the first connecting pipeline and the second connecting pipeline, for the purpose of connecting or isolating the head section and the tail section. The control system has a mode selection switch and is electrically connected to the nitrogen generator, the first deck fan, the second deck fan, and the double blind flange, respectively. The control system is configured as follows: In nitrogen mode, the double blind flange is in the conducting state, the first deck fan and the second deck fan are shut down, and the nitrogen generator is started to supply nitrogen to each cargo tank. In aeration mode, the nitrogen generator is stopped, and the double blind flange physically separates the main nitrogen pipeline into a bow section and a stern section that are not connected to each other. The first deck fan and the second deck fan are started, so that the first deck fan supplies air to the forward cargo tank through the bow section, and the second deck fan supplies air to the aft cargo tank through the stern section.

[0010] Preferably, the double blind flange includes a first flange, a second flange, and a rotatable or pluggable blind flange; when the blind flange is not inserted between the first flange and the second flange, the two flanges are sealed together to achieve a conductive state; when the blind flange is inserted between the first flange and the second flange, an isolation state is achieved.

[0011] Preferably, sealing gaskets are provided between the first flange and the second flange, and between the blind flange and the two flanges.

[0012] Preferably, the first connecting pipeline is provided with a first shut-off valve, and the second connecting pipeline is provided with a second shut-off valve; the control system is also electrically connected to the first shut-off valve and the second shut-off valve respectively, for closing the first shut-off valve and the second shut-off valve in nitrogen mode, and opening the first shut-off valve and the second shut-off valve in air mode.

[0013] Preferably, each nitrogen branch is equipped with a branch control valve at its inlet. The branch control valve is electrically connected to the control system and is used to independently control the gas flow in and out of the corresponding liquid cargo tank. The nitrogen generator is equipped with a main control valve at its outlet. The main control valve is electrically connected to the control system and is used to disconnect the nitrogen generator from the nitrogen main pipeline in air mode.

[0014] Preferably, the control system is a PLC or DCS control system; the mode selection switch is a physical switch or a touch screen virtual switch electrically connected to the input terminal of the control system. The control system is also connected to a status feedback sensor for detecting the status of the equipment. The status feedback sensor includes a fan operation sensor, a valve position sensor, and a blind plate position sensor. The blind plate position sensor is used to detect whether the blind plate is in the conducting or isolated position.

[0015] Preferably, the control system is configured such that: in nitrogen mode, nitrogen mode is only allowed to be started when both the first deck fan and the second deck fan are stopped, the double blind flange is in the conducting state, the main control valve is in the closed state, and all branch control valves are in the closed state; in air mode, air mode is only allowed to be started when the nitrogen generator is stopped, the main control valve is closed, the double blind flange is in the isolated state, both the first and second shut-off valves are in the open state, and all branch control valves are in the closed state.

[0016] Preferably, the control system is further configured to: lock the switching operation of another working mode when the system is operating normally in nitrogen mode or air mode; if a mode switch is required, the system must first perform a shutdown, status reset, and mode selection switch before starting the equipment in the corresponding mode.

[0017] Another aspect of the present invention includes a nitrogen mode control method and an airization mode control method; The nitrogen mode control method includes: Step S1: Switch the double blind flange to the conducting state to ensure that the first and last sections of the nitrogen main pipeline are connected. Step S2: Turn off the first deck fan and the second deck fan, and close the first shut-off valve on the first connecting pipe and the second shut-off valve on the second connecting pipe; Step S3: Open the main control valve, start the nitrogen generator, and output nitrogen; Step S4: Allow nitrogen gas to enter each liquid cargo tank through the main nitrogen gas pipeline and each nitrogen gas branch pipeline; The air-conditioning mode control method includes: Step A1: Stop the nitrogen generator and close the main control valve; Step A2: Switch the double blind flange to the isolation state to divide the nitrogen main pipeline into the head section and the tail section; Step A3: Open the first and second shut-off valves, and start the first and second deck fans; Step A4: Allow the air output from the first deck fan to enter the forward cargo tank through the bow section, and at the same time allow the air output from the second deck fan to enter the aft cargo tank through the stern section, so as to replace the nitrogen in each cargo tank.

[0018] Preferably, the air mode control method further includes step A5: real-time monitoring of oxygen concentration by oxygen content sensors in the liquid cargo tanks, and when the oxygen concentration in all liquid cargo tanks reaches the safe entry requirements, closing the first deck fan, the second deck fan, all branch control valves, the first shut-off valve and the second shut-off valve. Before starting the nitrogen mode, the control system checks the following conditions: both the first and second deck fans are stopped, the double blind flange is in the open position, the main control valve is closed, and all branch control valves are closed. The nitrogen mode is only allowed to be started when all the conditions are met. Before the air purification mode is activated, the control system checks the following conditions: the nitrogen generator is stopped, the main control valve is closed, the double blind flange is isolated, both the first and second shut-off valves are open, and all branch control valves are closed. The air purification mode is only allowed to be activated when all the conditions are met.

[0019] The beneficial effects of this invention are as follows: The nitrogen system of this invention not only possesses the traditional nitrogen supply function, but can also rapidly replace the nitrogen in the liquid cargo tank with clean, dry air when needed. This functional expansion greatly enhances the practicality and flexibility of the system, meeting the diverse gas environment requirements of ships at different operational stages; By installing double blind flanges, the main nitrogen pipeline is divided into multiple independent sections, each matched with a deck fan of appropriate displacement. This design allows each section to undergo air replacement simultaneously in aeration mode, without waiting for individual sections to complete, thus significantly shortening the overall air replacement time and improving the ship's operational efficiency. The control system achieves physical isolation and operational interlocking between nitrogen mode and air purification mode. Switching to the corresponding operating mode is only permitted when all permissible conditions are met; otherwise, the mode switching operation is invalid, and an alarm signal is issued. This interlocking design fundamentally ensures the safe isolation of the two operating conditions, completely eliminates safety hazards caused by misoperation, and improves the system's operational reliability and safety. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of air mode operation according to an embodiment of the present invention; Figure 2This is a schematic diagram of nitrogen mode operation according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the connection structure according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the control system connection structure according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the double blind flange in the open state according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the closed state structure of the double blind flange according to an embodiment of the present invention.

[0021] In the diagram: 1. Nitrogen generator; 2. Main nitrogen pipeline; 3. Cargo tank; 4. Nitrogen branch pipeline; 5. First deck fan; 6. Second deck fan; 7. Double blind flange; 701. First flange; 702. Second flange; 703. Blind flange; 704. Sealing gasket; 8. Mode selection switch; 9. First connecting pipeline; 10. Second connecting pipeline; 11. Branch control valve; 12. Main control valve; 13. Control system; 14. First shut-off valve; 15. Second shut-off valve. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0023] Reference Figures 1-6 A nitrogen system that can also be used for air purification Example 1

[0024] In this embodiment, the nitrogen system is applied to a liquid cargo ship, which is equipped with multiple liquid cargo tanks 3, which are respectively located in the front and rear areas of the hull, for storing various types of liquid cargo and ensuring the safety of liquid cargo storage.

[0025] Nitrogen generator 1 is fixedly installed in the ship's engine room area or in a specially designated nitrogen generator room. The installation location must comply with the ship's engine room equipment layout specifications and facilitate routine inspection and maintenance of the equipment.

[0026] The main nitrogen pipeline 2 extends longitudinally along the ship, with one end sealed to the outlet of the nitrogen generator 1 and the other end extending to the stern of the hull, serving as the main channel for supplying nitrogen or air. The pipeline is made of corrosion-resistant and high-pressure-resistant material suitable for marine operating conditions, which can effectively resist the erosion of harsh environments such as salt spray and humidity, and extend the service life of the pipeline.

[0027] The first deck fan 5 is fixedly installed at a predetermined position on the bow deck of the ship. The installation foundation must meet the vibration protection requirements during the operation of the fan to avoid the vibration generated by the fan affecting the stability of the pipeline connection. The outlet of the first deck fan 5 is sealed and connected to the bow section of the nitrogen main pipeline 2 through the first connecting pipeline 9. The bow section of the nitrogen main pipeline 2 is the pipeline section near the forward liquid cargo tank 3.

[0028] The second deck fan 6 is fixedly installed at a predetermined position on the stern deck of the ship. Its outlet is sealed and connected to the stern section of the nitrogen main pipeline 2 via the second connecting pipe 10. The stern section of the nitrogen main pipeline 2 is the pipeline section near the aft cargo tank 3. The first connecting pipe 9 and the second connecting pipe 10 are respectively equipped with a first shut-off valve 14 and a second shut-off valve 15, which are used to independently control the on / off of each connecting pipe, so as to achieve selective connection between the deck fan and the nitrogen main pipeline.

[0029] The first deck fan 5 and the second deck fan 6 are selected from Victormarine marine fans.

[0030] The double blind flange 7 is located in the middle of the nitrogen main pipeline 2 and between the first connecting pipeline 9 and the second connecting pipeline 10. Its core function is to realize the connection or isolation between the head section and the tail section of the nitrogen main pipeline 2, and to provide key structural support for the switching between nitrogen mode and air mode of the system.

[0031] Reference Figure 2 The specific structure of the double blind flange 7 is as follows: the first flange 701 and the second flange 702 are arranged in parallel relative to each other and are detachably connected by several sets of bolts. The structure is simple, the operation is convenient, and quick switching can be achieved.

[0032] Blind flange 703 slides between first flange 701 and second flange 702 and is connected to automatic actuator, which is hydraulically driven and electrically connected to control system 13.

[0033] When the system is in normal nitrogen mode, the blind flange 703 slides to the side of the two flanges and does not insert between the first flange 701 and the second flange 702. The first flange 701 and the second flange 702 are sealed together by the sealing gasket 704. At this time, the head section and tail section of the nitrogen main pipeline 2 are connected to form a complete nitrogen delivery channel, ensuring that nitrogen can be smoothly delivered to all liquid cargo tanks.

[0034] When the system needs to switch to air purification mode, it can be done manually by the operator or by the automatic actuator driven by the control system 13. First, loosen the bolt assembly, insert the blind flange 703 between the first flange 701 and the second flange 702, ensuring that the blind flange 703 fits tightly against the sealing surfaces of the two flanges, and then tighten the bolt assembly again. At this time, reliable sealing is achieved between the first flange 701 and the blind flange 703, and between the blind flange 703 and the second flange 702, through the sealing gasket 704. The head section and tail section of the nitrogen main pipeline 2 are isolated from each other, preventing gas from flowing between the two sections.

[0035] Each nitrogen branch line 4 is equipped with a branch control valve 11 at its inlet. The branch control valve 11 can be a solenoid valve or a manual valve, used to control the entry of nitrogen or dry air into the corresponding liquid cargo tank 3. It can be opened or closed independently according to the operational needs of the liquid cargo tank 3, so as to realize the individual control of each compartment.

[0036] A main control valve 12 is installed at the outlet of the nitrogen generator 1. The main control valve 12 is linked with the control system 13. Its core function is to quickly disconnect the nitrogen generator 1 from the nitrogen main pipeline 2 in the air mode to prevent air from flowing back into the nitrogen generator 1.

[0037] The control system 13 adopts a PLC or DCS control system, which has strong linkage control and status monitoring capabilities. The input terminal of the control system 13 is electrically connected to a mode selection switch 8, which can realize the rapid switching between nitrogen mode and air purification mode. At the same time, it is connected to the status feedback sensors of various devices, including fan operation sensors, valve position sensors, and blind plate position sensors, to obtain the operating status of each component of the system in real time.

[0038] The output terminals of the control system 13 are electrically connected to the start / stop control terminals of the nitrogen generator 1, the start / stop control terminals of the first deck fan 5 and the second deck fan 6, the automatic actuator of the double blind flange 7, and the solenoid valves of each control valve. Example 2

[0039] During normal ship operation, a stable inert nitrogen environment needs to be maintained in cargo tank 3 to prevent oxidation, deterioration, or the formation of an explosive gas mixture due to contact with air, thus ensuring ship operational safety. At this time, the operator selects the nitrogen mode via mode selection switch 8 on control system 13, and the system automatically enters the nitrogen supply working state. The specific workflow is as follows: Step S1: The control system 13 first detects the current status of the double blind flange 7. If it is an automatic double blind flange, the control system 13 drives it to switch to the conducting state; if it is a manual type, the operator manually rotates the blind flange 703 to the side of the two flanges to ensure that the first and last sections of the nitrogen main pipeline 2 are fully connected. At the same time, the position sensor confirms the conducting state to avoid the nitrogen delivery being blocked due to the pipeline not being connected.

[0040] Step S2: The control system 13 outputs a control signal to shut down the first deck fan 5 and the second deck fan 6, ensuring that both fans are in a stopped state. At the same time, the first shut-off valve 14 on the first connecting pipe 9 and the second shut-off valve 15 on the second connecting pipe 10 are closed to prevent nitrogen from leaking through the connecting pipes, ensuring that all nitrogen is used for the inertial protection of the liquid cargo tank 3 and improving the nitrogen utilization rate.

[0041] Step S3: Control system 13 opens main control valve 12. After main control valve 12 is fully open and a feedback signal is received, nitrogen generator 1 is started. Nitrogen generator 1 draws in air from the atmosphere, which is compressed by an internal compressor, cooled by a cooling system, and separated by a gas separation device. It then outputs high-purity nitrogen that meets the requirements for liquid cargo protection. The output pressure and flow rate of nitrogen are automatically adjusted by nitrogen generator 1.

[0042] Step S4: High-purity nitrogen is transported through the main nitrogen pipeline 2 to the nitrogen branch pipeline 4 inlet of each liquid cargo tank 3. The control system 13 automatically opens the branch pipeline control valve 11 of the corresponding liquid cargo tank 3 according to the liquid level, pressure and other parameters of each liquid cargo tank 3. Nitrogen slowly enters the liquid cargo tank 3, gradually replacing the air in the tank, maintaining the inert atmosphere in the tank, and keeping the oxygen content below the safe limit.

[0043] In this working mode, the first deck fan 5 and the second deck fan 6 do not participate in the operation at all. The nitrogen main pipeline 2 serves as a single nitrogen delivery channel, and its pipeline flow capacity must fully meet the maximum output demand of the nitrogen generator 1 to ensure that nitrogen can be stably and evenly delivered to each liquid cargo tank 3. Example 3

[0044] When a vessel needs to enter dry dock for maintenance, or when cargo tank 3 requires internal inspection, cleaning, or repair work, the inert nitrogen gas in cargo tank 3 must be replaced with clean, dry air to ensure the oxygen concentration inside the tank meets the safety standards for personnel entering. At this time, the operator selects the air exchange mode via mode selection switch 8 on control system 13, and the system automatically enters the air exchange working state. The specific workflow is as follows: Step A1: The control system 13 first outputs a control signal to stop the operation of the nitrogen generator 1. After the nitrogen generator 1 has completely stopped and fed back a stop signal, the main control valve 12 is closed to completely disconnect the connection between the nitrogen generator 1 and the nitrogen main pipeline 2, so as to prevent air from flowing back into the nitrogen generator 1 during the subsequent aeration operation.

[0045] Step A2: The control system 13 detects the current status of the double blind flange 7. If it is an automatic double blind flange, the control system 13 drives it to switch to the closed state; if it is a manual type, the operator manually inserts the blind flange 703 between the first flange 701 and the second flange 702 and tightens the bolt assembly to ensure that the first and last sections of the nitrogen main pipeline 2 are completely isolated. The closed state is confirmed by feedback from the position sensor to avoid air exchange between the two sections, which could lead to abnormal flow rate.

[0046] Step A3: Control system 13 opens the first shut-off valve 14 on the first connecting pipe 9 and the second shut-off valve 15 on the second connecting pipe 10, and then starts the first deck fan 5 and the second deck fan 6. The two fans operate independently and do not interfere with each other. Each deck fan draws in air from the atmosphere, filters it through the air filter installed at the fan inlet, and dries it through the dryer, before outputting clean and dry air.

[0047] Step A4: Aeration of the forward compartment. Dry air output from the first deck fan 5 enters the bow section of the nitrogen main pipeline 2 via the first connecting pipe 9. Since the double blind flange 7 is closed, the air cannot flow to the tail section of the nitrogen main pipeline 2 and can only flow along the bow section to the nitrogen branch lines 4 corresponding to each forward cargo tank 3. The control system 13, based on the number and capacity of the forward cargo tanks 3, sequentially or simultaneously opens the branch line control valves 11 corresponding to each forward cargo tank 3. Dry air continuously enters the forward cargo tanks 3, gradually replacing and expelling the nitrogen inside. The expelled nitrogen is discharged outside the tank via the vent valve of the cargo tank 3, thus aeration of the forward compartment.

[0048] Step A5: Aft compartment airing. Dry air output from the second deck fan 6 enters the tail section of the nitrogen main pipeline 2 via the second connecting pipe 10. Because the double blind flange 7 is closed, the air cannot flow to the head section of the nitrogen main pipeline 2, but can only flow along the tail section to the nitrogen branch lines 4 corresponding to each aft cargo tank 3. The control system 13 simultaneously opens the branch control valve 11 corresponding to the aft cargo tank 3, and dry air continuously enters the aft cargo tank 3, gradually replacing and expelling the nitrogen in the tank, achieving synchronous airing of the aft compartment, significantly shortening the overall air replacement time and improving operational efficiency.

[0049] Step A6: The control system 13 monitors the oxygen concentration in each cargo tank 3 in real time by connecting to the oxygen content sensor in the cargo tank 3. When the oxygen concentration in all cargo tanks 3 meets the requirements for safe entry of personnel and is maintained stably for a period of time, the control system 13 sequentially shuts down the first deck fan 5, the second deck fan 6, and closes all branch control valves 11, the first shut-off valve 14, and the second shut-off valve 15. The aeration operation is completed, and personnel can safely enter the cargo tank 3 to carry out related operations.

[0050] It should be noted that the double blind flange 7 of the present invention divides the nitrogen main pipeline 2 into two independent sections, so that the first deck fan 5 and the second deck fan 6 can supply gas to their respective corresponding pipeline sections.

[0051] If the double blind flange 7 is in the conducting state, and the two fans simultaneously supply air to the same complete nitrogen main pipeline 2, the total air flow in the pipeline will be superimposed, and the flow velocity in the pipeline will far exceed the safety design value, which will lead to problems such as severe pipeline vibration, significantly increased operating noise, and a surge in pipeline pressure loss. Example 4

[0052] To ensure the safe and stable operation of the system in both working modes and to avoid dangerous situations caused by misoperation, such as accidental switching between nitrogen mode and air purification mode, or accidental equipment startup, for example, simultaneous operation of nitrogen generator 1 and deck fans 5 and 6, which could lead to air mixing into the nitrogen pipeline and affecting nitrogen purity, or nitrogen backflow into the deck fans causing equipment damage or gas leaks, this system uses control system 13 to implement interlocking between the two working modes. The specific settings are as follows: The control system 13 monitors the operating status and location status of each device in the system in real time. Only when all the allowable conditions for the corresponding mode are met will the operator be allowed to switch to that working mode. Otherwise, the mode switching operation will be invalid, and the control system 13 will issue an alarm signal, such as an audible and visual alarm, to remind the operator to check the equipment status and troubleshoot the fault in time.

[0053] 1. All conditions for nitrogen mode to be allowed must be met: The first deck fan 5 and the second deck fan 6 are both in a stopped state, and the fan operation signal feedback is OFF; the double blind flange 7 is in a conducting state, and the position sensor feedback is "conducting"; the main control valve 12 is in a closed state and will be automatically opened by the control system after the system starts; all branch control valves 11 are in a closed state and will be opened as needed when nitrogen is delivered.

[0054] 2. All conditions for the aerosolization mode must be met: Nitrogen generator 1 is in a stopped state, and the nitrogen generator operation signal feedback is OFF; the main control valve 12 is in a closed state to ensure that the nitrogen generator is isolated from the main pipeline; the double blind flange 7 is in a closed state, and the position sensor feedback is "closed"; the first shut-off valve 14 and the second shut-off valve 15 are both in an open state; each branch control valve 11 is in a closed state and will be opened as needed when air is supplied.

[0055] Furthermore, when the system is operating normally in a certain working mode, either nitrogen mode or air mode, the control system 13 will lock the switching operation of another working mode, prohibiting direct mode switching. If it is necessary to switch the working mode, the complete operation sequence of "stop-state reset-mode switching-system restart" must be executed first, that is, first stop all equipment running in the current mode, reset all system components to the initial state, then switch the mode selection switch 8, and finally start the equipment in the corresponding mode.

[0056] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A nitrogen system that can also be used for air purification, characterized in that: Including a nitrogen generator (1); The nitrogen main pipeline (2) extends longitudinally along the ship and is connected at one end to the outlet of the nitrogen generator (1); Multiple liquid cargo tanks (3) are connected to the main nitrogen pipeline (2) via nitrogen branch lines (4); The outlet of the first deck fan (5) is connected to the head section of the nitrogen main pipeline (2) through the first connecting pipeline (9); The outlet of the second deck fan (6) is connected to the tail section of the nitrogen main pipeline (2) through the second connecting pipeline (10); A double blind flange (7) is provided in the middle of the nitrogen main pipeline (2) and located between the first connecting pipeline (9) and the second connecting pipeline (10) to enable or isolate the head section and the tail section; The control system (13) has a mode selection switch (8) and is electrically connected to the nitrogen generator (1), the first deck fan (5), the second deck fan (6) and the double blind flange (7). The control system (13) is configured as follows: In nitrogen mode, the double blind flange (7) is in the conducting state, the first deck fan (5) and the second deck fan (6) are turned off, and the nitrogen generator (1) is started to supply nitrogen to each cargo tank (3); In the air-conditioning mode, the nitrogen generator (1) is stopped, and the double blind flange (7) physically separates the nitrogen main pipeline (2) into a bow section and a stern section that are not connected to each other. The first deck fan (5) and the second deck fan (6) are started, so that the first deck fan (5) supplies air to the forward liquid cargo tank (3) through the bow section, and the second deck fan (6) supplies air to the rear liquid cargo tank (3) through the stern section.

2. The nitrogen system that can also be used for air purification according to claim 1, characterized in that: The double blind flange (7) includes a first flange (701), a second flange (702), and a rotatable or pluggable blind flange (703); when the blind flange (703) is not inserted between the first flange (701) and the second flange (702), the two flanges are sealed together to achieve a conductive state; when the blind flange (703) is inserted between the first flange (701) and the second flange (702), an isolation state is achieved. A sealing gasket (704) is provided between the first flange (701) and the second flange (702), and between the blind flange (703) and the two flanges.

3. A nitrogen system that can also be used for air purification according to claim 2, characterized in that: The first deck fan (5) and the second deck fan (6) are selected from Victormarine marine fans.

4. A nitrogen system that can also be used for air purification according to claim 1, characterized in that: The first connecting pipe (9) is provided with a first shut-off valve (14), and the second connecting pipe (10) is provided with a second shut-off valve (15); the control system (13) is also electrically connected to the first shut-off valve (14) and the second shut-off valve (15) respectively, for closing the first shut-off valve (14) and the second shut-off valve (15) in nitrogen mode, and opening the first shut-off valve (14) and the second shut-off valve (15) in air mode.

5. A nitrogen system that can also be used for air purification according to claim 1, characterized in that: Each nitrogen branch (4) is equipped with a branch control valve (11) at its inlet. The branch control valve (11) is electrically connected to the control system (13) and is used to independently control the gas flow of the corresponding liquid cargo tank (3). The nitrogen generator (1) is provided with a main control valve (12) at its outlet. The main control valve (12) is electrically connected to the control system (13) and is used to disconnect the nitrogen generator (1) from the nitrogen main pipeline (2) in the air mode.

6. A nitrogen system that can also be used for air purification according to claim 1, characterized in that: The control system (13) is a PLC or DCS control system; the mode selection switch (8) is a physical switch or a touch screen virtual switch electrically connected to the input terminal of the control system (13); The control system (13) is also connected to a status feedback sensor for detecting the status of the equipment. The status feedback sensor includes a fan operation sensor, a valve position sensor and a blind plate position sensor. The blind plate position sensor is used to detect whether the blind plate (703) is in the conducting position or the isolated position.

7. A nitrogen system that can also be used for air purification according to claim 1, characterized in that: The control system (13) is configured such that: in nitrogen mode, nitrogen mode is allowed to be started only when the first deck fan (5) and the second deck fan (6) are both in a stopped state, the double blind flange (7) is in a conducting state, the main control valve (12) is in a closed state and all branch control valves (11) are in a closed state; in air mode, air mode is allowed to be started only when the nitrogen generator (1) is in a stopped state, the main control valve (12) is in a closed state, the double blind flange (7) is in an isolated state, the first shut-off valve (14) and the second shut-off valve (15) are both in an open state and all branch control valves (11) are in a closed state.

8. A nitrogen system that can also be used for air purification according to claim 7, characterized in that: The control system (13) is also configured to lock the switching operation of another working mode when the system is operating normally in nitrogen mode or air mode; if a mode switch is required, the system must first execute the shutdown, status reset, and mode selection switch (8) before starting the equipment in the corresponding mode.

9. A control method for a nitrogen system of a liquid cargo ship according to any one of claims 1 to 8, characterized in that, This includes nitrogen mode control methods and air-gathering mode control methods; The nitrogen mode control method includes: Step S1: Switch the double blind flange (7) to the conducting state to ensure that the head section and tail section of the nitrogen main pipeline (2) are connected; Step S2: Turn off the first deck fan (5) and the second deck fan (6), and close the first shut-off valve (14) on the first connecting pipe (9) and the second shut-off valve (15) on the second connecting pipe (10); Step S3: Open the main control valve (12), start the nitrogen generator (1), and output nitrogen; Step S4: Allow nitrogen to enter each liquid cargo tank (3) through the main nitrogen pipeline (2) and each nitrogen branch pipeline (4); The air-conditioning mode control method includes: Step A1: Stop the nitrogen generator (1) and close the main control valve (12); Step A2: Switch the double blind flange (7) to the isolation state to divide the nitrogen main pipeline (2) into the head section and the tail section; Step A3: Open the first shut-off valve (14) and the second shut-off valve (15), and start the first deck fan (5) and the second deck fan (6); Step A4: The air output from the first deck fan (5) enters the forward liquid cargo tank (3) through the bow section, and the air output from the second deck fan (6) enters the aft liquid cargo tank (3) through the tail section, replacing the nitrogen in each liquid cargo tank (3).

10. The control method for a nitrogen system that can also be used for air purification according to claim 9, characterized in that: The air-conditioning mode control method further includes step A5: real-time monitoring of oxygen concentration by oxygen content sensors in the liquid cargo tank (3), and when the oxygen concentration in all liquid cargo tanks (3) reaches the safe entry requirements, closing the first deck fan (5), the second deck fan (6), all branch control valves (11), the first shut-off valve (14) and the second shut-off valve (15). Before starting the nitrogen mode, the control system (13) checks the following conditions: the first deck fan (5) and the second deck fan (6) are both in the stopped state, the double blind flange (7) is in the conducting state, the main control valve (12) is in the closed state, and all branch control valves (11) are in the closed state; the nitrogen mode is only allowed to be started when all the conditions are met. Before the air-conditioning mode is started, the control system (13) checks the following conditions: the nitrogen generator (1) is in a stopped state, the main control valve (12) is in a closed state, the double blind flange (7) is in an isolated state, the first shut-off valve (14) and the second shut-off valve (15) are both in an open state, and the branch control valves (11) are all in a closed state; the air-conditioning mode is only allowed to be started when all the conditions are met.

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