Ship liquid ammonia supply and removal method with zero ammonia residue

Abstract

A zero-ammonia-residue ship liquid ammonia supply and removal method comprises the following steps: firstly, purging a liquid ammonia supply system and the interior of a main engine by using 30barg high-pressure nitrogen to remove most ammonia fuel; the residual ammonia is further absorbed by using fresh water, the fresh water after absorbing the ammonia is completely blown away by using 30 barg of high-pressure nitrogen, and finally, the liquid ammonia supply system and the interior of the main machine are forcibly evaporated and blown by using 5 barg of heated low-pressure nitrogen, so that the effect of zero ammonia residue is finally achieved. After the device is used for removing the interiors of a liquid ammonia supply system and a main engine, zero ammonia residue can be realized, the removing effect is good, the safety of related systems and personnel on a ship can be guaranteed, the whole ammonia removing process is automatically executed after the main engine runs in an ammonia fuel mode, automatic treatment of ammonia can be realized, personnel operation is not needed, the automation degree is high, and the working efficiency is high. The operation is reliable.

Description

Technical Field

[0001] The invention belongs to the technical field of ship liquid ammonia fuel supply, and in particular relates to a ship liquid ammonia supply and removal method with zero ammonia residue. Background Art

[0002] The shipping industry has a growing demand for green and environmentally friendly ships. It is urgent to carry out the research and development of innovative technologies and the introduction of alternative fuels and other emission reduction measures in the shipping industry. Using low-carbon or even zero-carbon fuels to replace traditional marine fuels is an important measure for the shipping industry to reduce emissions. Among many new fuels, ammonia, as one of the potential zero-carbon fuels, can be stored on board at a temperature of minus 33°C, has an acceptable energy density, does not produce carbides and sulfides when burned, is easy to store and transport, has sufficient production capacity and low prices, and has become the focus of industry research.

[0003] Similar to the LNG gas supply system, after the liquid ammonia fuel supply system is used, or before it needs to be repaired, the entire supply system and the main engine must be purged with nitrogen to ensure that there is no ammonia fuel residue to avoid danger. Since LNG is in a gaseous state in the gas supply system, it is easy to blow it away. However, in the liquid ammonia supply system, ammonia is in a liquid state and is easy to accumulate and remain in the welds, bends, depressions of various equipment and pipe accessories, and blind ends of pipelines in the supply system. It is difficult to completely purge it clean, and it is also difficult to determine whether it has been purged clean. Moreover, unlike natural gas, ammonia is toxic. If it is not completely removed, it will cause the following problems: First, because ammonia is highly corrosive, residual ammonia for a long time will corrode equipment and pipelines, causing system failure and even leakage risks.

[0004] Secondly, if the liquid ammonia fuel that has not been blown away remains in the supply system or the main engine, the liquid ammonia will slowly absorb heat and evaporate over time, causing the pressure in the system to increase, and there may be a risk of system overpressure.

[0005] Third, if the supply system or main engine is not purged sufficiently during maintenance, the residual liquid ammonia will quickly evaporate and diffuse after contacting the atmosphere. Its toxicity will pose a serious threat to the personal safety of the operating and maintenance personnel, and there is even a risk of explosion. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a method for removing liquid ammonia supply from a ship with zero ammonia residue, aiming to achieve the purpose of completely purging the ammonia inside the main engine. The technical solution adopted is: A method for removing liquid ammonia supply from a ship with zero ammonia residue is disclosed. Before the liquid ammonia supply system is operated, compressed and dried air is supplied to a nitrogen generator through an air compressor and an air dryer, and the produced nitrogen is stored in a nitrogen low-pressure tank.

[0007] The nitrogen booster will store the further pressurized nitrogen in the nitrogen high-pressure tank. The fresh water buffer tank is filled with fresh water through the ship's fresh water system and maintains a water level of about 80%. The nitrogen low-pressure tank, nitrogen high-pressure tank and fresh water buffer tank are respectively filled with nitrogen and fresh water. The entire ammonia removal system is ready.

[0008] The ship can only set sail when the ammonia removal system is ready. After the main engine load reaches 25%, the main engine operation is switched from diesel mode to ammonia fuel mode, and switched back to diesel mode when the ship is about to arrive at the port. After switching back to diesel mode, the liquid ammonia supply system and the residual liquid ammonia inside the main engine are purged for the first time by high-pressure nitrogen, and most of the ammonia fuel is purged to the ammonia treatment unit; after the first purging operation, fresh water is used to absorb the residual ammonia. After the fresh water absorbs ammonia, high-pressure nitrogen is used for the second purging operation to discharge the fresh water that absorbs ammonia to the ammonia collection cabinet; after the second purging operation, low-pressure nitrogen is used for heating for the third purging operation to accelerate the evaporation of the residual fresh water after absorbing ammonia and purge it to the ammonia treatment unit. The main engine of the present invention adopts the ammonia / diesel dual-fuel main engine of WinGD manufacturer.

[0009] The above-mentioned method for supplying and removing liquid ammonia in ships with zero ammonia residue, further, the air compressor is connected to the air dryer, the nitrogen generator, and the nitrogen low-pressure tank in sequence through pipelines, the nitrogen low-pressure tank is connected to the electric heater and the main engine in sequence through one pipeline, and is connected to the nitrogen booster, the nitrogen high-pressure tank, and the main engine in sequence through another pipeline; a fifth remote control valve is provided on the passage from the electric heater to the main engine, and a first remote control valve is provided on the passage from the nitrogen high-pressure tank to the main engine.

[0010] The main engine is connected to the ammonia treatment unit and the ammonia water collection cabinet through pipelines, the ammonia water collection cabinet is connected to the ammonia treatment unit through a vent pipe, the ammonia treatment unit is connected to the vent mast, the passage from the main engine to the ammonia treatment unit is provided with a second remote control valve and an ammonia concentration transmitter, the passage from the main engine to the ammonia water collection cabinet is provided with a pressure transmitter and a fourth remote control valve. The electric heater, nitrogen high pressure tank, and fresh water buffer tank are connected to the ammonia supply pipeline inside the main engine, and the other end of the ammonia supply pipeline inside the main engine is connected to the ammonia treatment unit and the ammonia water collection cabinet respectively.

[0011] The main engine is connected to a fresh water buffer tank, and a fresh water transfer pump and a third remote control valve are arranged on the passage from the fresh water buffer tank to the main engine.

[0012] In the above-mentioned method for removing liquid ammonia supply from a ship with zero ammonia residue, further, the storage pressure of the nitrogen low-pressure tank is 10 barg.

[0013] In the above-mentioned method for supplying and removing liquid ammonia on a ship with zero ammonia residue, further, the storage pressure of the nitrogen high-pressure tank is 30 barg.

[0014] In the above-mentioned method for supplying and removing liquid ammonia in a ship with zero ammonia residue, a pressure regulating valve is further provided at the inlet of the electric heater.

[0015] The above-mentioned method for removing liquid ammonia supply in a ship with zero ammonia residue, further, the central control system controls the first remote control valve, the second remote control valve, the third remote control valve, the fourth remote control valve, and the fifth remote control valve.

[0016] The above-mentioned method for clearing liquid ammonia supply for ships with zero ammonia residue further comprises the following steps: when a high-pressure nitrogen purge operation is performed, when the ammonia concentration in the pipeline monitored by the ammonia concentration transmitter drops to 300 ppm, the first remote control valve and the second remote control valve are closed.

[0017] The above-mentioned method for supplying and removing liquid ammonia in a ship with zero ammonia residue further uses low-pressure nitrogen for heating and purging operations. When the ammonia concentration in the monitoring pipeline of the ammonia concentration transmitter drops below 1 ppm, the fifth remote control valve and the second remote control valve are closed.

[0018] The above-mentioned method for supplying and removing liquid ammonia in a ship with zero ammonia residue, further, when using low-pressure nitrogen for heating and purging operations, the pressure regulating valve adjusts the low-pressure nitrogen to 5 barg and then sends it to the electric heater to be heated to 70°C.

[0019] The beneficial effects of the present invention are: 1. After the liquid ammonia supply system and the interior of the main engine are cleaned by the present invention, zero ammonia residue can be achieved, and the ammonia cleaning effect is good.

[0020] 2. The use of the present invention can ensure the safety of relevant systems and personnel on board.

[0021] 3. After the main engine ammonia fuel mode is completed, the entire ammonia removal process is automatically executed, and automatic ammonia processing can be achieved without the need for human operation. The degree of automation is high and the operation is reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the system of the present invention; Among them, 1-air compressor, 2-air dryer, 3-nitrogen generator, 4-nitrogen low-pressure tank, 5-nitrogen booster, 6-nitrogen high-pressure tank, 7-fresh water buffer tank, 8-main engine, 9-first remote control valve, 10-second remote control valve, 11-ammonia concentration transmitter, 12-ammonia treatment unit, 13-ventilation mast, 14-third remote control valve, 15-fresh water transfer pump, 16-pressure transmitter, 17-fourth remote control valve, 18-ammonia collection cabinet, 19-fifth remote control valve, 20-pressure regulating valve, 21-electric heater. DETAILED DESCRIPTION

[0023] The present invention will be further described in conjunction with the accompanying drawings.

[0024] A method for removing liquid ammonia supply from a ship with zero ammonia residue, such as Figure 1 As shown, before the liquid ammonia supply system and the main engine are operated, the compressed and dried air is supplied to the membrane nitrogen generator 3 through the air compressor 1 and the air dryer 2, and the produced nitrogen is stored in the nitrogen low-pressure tank 4 with a storage pressure of 10 barg. Then, the nitrogen is further pressurized and stored in the nitrogen high-pressure tank 6 through the nitrogen booster 5 with a storage pressure of 30 barg. The fresh water buffer tank 7 is filled with fresh water through the ship's fresh water system and maintains a certain liquid level of water. In summary, before the liquid ammonia supply system and the main engine are operated, the nitrogen low-pressure tank, the nitrogen high-pressure tank and the fresh water buffer tank have been filled with nitrogen and fresh water respectively, and the entire ammonia removal system is ready. The main engine adopts the ammonia / diesel dual-fuel main engine of the WinGD manufacturer. The electric heater, the nitrogen high-pressure tank and the fresh water buffer tank are connected to the ammonia supply pipeline inside the main engine, and the other end of the ammonia supply pipeline inside the main engine is connected to the ammonia treatment unit and the ammonia water collection cabinet respectively.

[0025] The ship can only set sail when the ammonia removal system is ready. When the main engine load reaches 25%, it switches from diesel to ammonia fuel mode. When the ship is about to arrive at the port, after switching back to diesel mode, liquid ammonia remains in the liquid ammonia supply system and the main engine 8. At this time, the ammonia removal system of the present invention, which has been in standby mode, starts to work. Its specific process can be divided into the following four operating steps: Step 1: High-pressure nitrogen purging operation. Open the first remote control valve 9 and the second remote control valve 10, and use 30 barg high-pressure nitrogen to purge the liquid ammonia supply system and the inside of the main engine 8. During the purging process, the central control system can monitor the ammonia concentration after purging in real time through the ammonia concentration transmitter 11. When the concentration drops to about 300 ppm, the first remote control valve 9 and the second remote control valve 10 can be closed to stop the high-pressure nitrogen purging operation. After purging, the mixture containing liquid ammonia, ammonia gas and nitrogen enters the ammonia processing unit 12, where the liquid ammonia is recycled as fuel, the ammonia gas is absorbed and processed, and the remaining nitrogen is discharged into the atmosphere through the vent mast 13.

[0026] Step 2: Fresh water absorption operation. After the above-mentioned high-pressure nitrogen purging operation is completed, open the third remote control valve 14, and transport the fresh water in the fresh water buffer tank 7 to the liquid ammonia supply system and the main engine through the fresh water transfer pump 15. Taking advantage of the property that ammonia is easily soluble in water, fresh water is used to absorb the ammonia that still remains after the high-pressure nitrogen purging. As the fresh water is slowly injected into the liquid ammonia supply system and the main engine, the pressure value detected by the pressure transmitter 16 will increase accordingly. When the set value is reached, it can be known that the fresh water is full. At this time, the third remote control valve 14 and the fresh water transfer pump 15 are automatically closed through the central control system, and then the central control system automatically draws water from the fresh water system on the ship, fills the fresh water buffer tank 7 to a liquid level of about 80%, and waits for the next use. During the purging process, fresh water and nitrogen will not enter the main engine cylinder, will not intersect with diesel, and will not affect the operation of the main engine.

[0027] Step 3: Secondary purging with high-pressure nitrogen. After the above-mentioned fresh water absorption operation is completed, open the first remote control valve 9 and the fourth remote control valve 17, and use high-pressure nitrogen to purge the fresh water into the ammonia water collection cabinet 18. The air pipe of the ammonia water collection cabinet is connected to the ammonia treatment unit 12. During the operation, the fresh water after absorbing ammonia is purged into the ammonia water collection cabinet, and nitrogen also enters the ammonia water collection cabinet. The air pressure in the ammonia water collection cabinet increases accordingly. After reaching a certain pressure, the nitrogen containing a small amount of ammonia automatically enters the ammonia treatment unit through the air pipe. When the amount of nitrogen used for purging is three times the volume of the required purging pipeline, it is considered that all the fresh water has been basically purged into the ammonia water collection cabinet. The time required for 3 times the amount of nitrogen to purge the pipeline volume is calculated in advance. The central control system is set to automatically end the operation after reaching this time, and automatically close the first remote control valve 9 and the fourth remote control valve 17.

[0028] Step 4: Low-pressure nitrogen heating and purging operation. After the above-mentioned high-pressure nitrogen purging secondary operation is completed, the liquid ammonia supply system and the interior of the main engine have been basically cleaned. Open the fifth remote control valve 19 and the second remote control valve 10, and adjust the low-pressure nitrogen to 5 barg through the pressure regulating valve 20. Then, it is heated to about 70°C by the electric heater 21 and introduced into the liquid ammonia supply system and the interior of the main engine. The remaining small amount of fresh water and ammonia are forced to evaporate and pass through the ammonia treatment unit and the air mast for discharge. During the process, the ammonia concentration is monitored in real time by the ammonia concentration transmitter 11. When it drops below 1ppm, the fifth remote control valve 19 and the second remote control valve 10 are closed, and the entire ammonia removal operation is completed. At this time, the liquid ammonia supply system and the interior of the main engine are completely dry and filled with nitrogen. The ammonia has been completely removed, and there will be no safety hazards due to residual ammonia in the future.

Claims

1. A method for removing liquid ammonia from a ship with zero ammonia residue, characterized in that: Before the liquid ammonia supply system is operated, compressed and dried air is supplied to the nitrogen generator (3) through the air compressor (1) and the air dryer (2), and the produced nitrogen is stored in the nitrogen low-pressure tank (4); The nitrogen booster (5) stores the pressurized nitrogen in the nitrogen high-pressure tank (6). The fresh water buffer tank (7) is filled with fresh water through the ship's fresh water system and maintains a water level of 80%. The nitrogen low-pressure tank (4), the nitrogen high-pressure tank (6) and the fresh water buffer tank (7) are respectively filled with nitrogen and fresh water. The entire ammonia removal system is ready. The ship can only set sail when the ammonia removal system is ready. After the load of the main engine (8) reaches 25%, the main engine (8) is switched from diesel mode to ammonia fuel mode, and is switched back to diesel mode when the ship is about to arrive at the port. After switching back to diesel mode, the liquid ammonia supply system and the residual liquid ammonia inside the main engine (8) are purged for the first time by 30 barg high-pressure nitrogen, and most of the ammonia fuel is purged to the ammonia treatment unit (12); after the first purging operation, fresh water is used to absorb the residual ammonia. After the fresh water absorbs the ammonia, 30 barg high-pressure nitrogen is used for the second purging operation, and the fresh water after absorbing the ammonia is discharged to the ammonia collection cabinet (18); after the second purging operation, 5 barg low-pressure nitrogen is used for heating to perform a third purging operation, and the residual fresh water absorbing ammonia is accelerated to evaporate and purged to the ammonia treatment unit (12).

2. A method for removing liquid ammonia from a ship with zero ammonia residue according to claim 1, characterized in that: The air compressor (1) is connected to the air dryer (2), the nitrogen generator (3), and the nitrogen low-pressure tank (4) in sequence through pipelines; the nitrogen low-pressure tank (4) is connected to the electric heater (21) and the main engine (8) in sequence through a branch pipeline, and is connected to the nitrogen booster (5), the nitrogen high-pressure tank (6), and the main engine (8) in sequence through another branch pipeline; a fifth remote control valve (19) is provided on the passage from the electric heater (21) to the main engine (8), and a first remote control valve (9) is provided on the passage from the nitrogen high-pressure tank (6) to the main engine (8); The main engine (8) is connected to the ammonia treatment unit (12) and the ammonia water collection cabinet (18) through pipelines respectively; the ammonia water collection cabinet (18) is connected to the ammonia treatment unit (12) through a vent pipe; the ammonia treatment unit (12) is connected to the vent mast (13); a second remote control valve (10) and an ammonia concentration transmitter (11) are provided on the passage from the main engine (8) to the ammonia treatment unit (12); and a pressure transmitter (16) and a fourth remote control valve (17) are provided on the passage from the main engine (8) to the ammonia water collection cabinet (18); The main engine (8) is connected to a fresh water buffer tank (7), and a fresh water transfer pump (15) and a third remote control valve (14) are arranged on the passage from the fresh water buffer tank (7) to the main engine (8).

3. A method for removing liquid ammonia from a ship with zero ammonia residue according to claim 1, characterized in that: The storage pressure of the nitrogen low-pressure tank (4) is 10 barg.

4. The method for removing liquid ammonia supply from a ship with zero ammonia residue according to claim 1, characterized in that: The storage pressure of the nitrogen high pressure tank (6) is 30 barg.

5. The method for removing liquid ammonia supply from a ship with zero ammonia residue according to claim 2, characterized in that: The inlet of the electric heater (21) is provided with a pressure regulating valve (20).

6. A method for removing liquid ammonia from a ship with zero ammonia residue according to claim 2, characterized in that: The central control system controls the fresh water transfer pump (15), the first remote control valve, the second remote control valve, the third remote control valve, the fourth remote control valve and the fifth remote control valve.

7. A method for removing liquid ammonia from a ship with zero ammonia residue according to claim 2, characterized in that: When the ammonia concentration in the pipeline monitored by the ammonia concentration transmitter (11) drops to 300 ppm, the first remote control valve and the second remote control valve are closed.

8. The method for removing liquid ammonia supply from a ship with zero ammonia residue according to claim 2, characterized in that: When the ammonia concentration in the pipeline monitored by the ammonia concentration transmitter (11) drops below 1 ppm, the fifth remote control valve and the second remote control valve are closed.

9. A method for removing liquid ammonia from a ship with zero ammonia residue according to claim 5, characterized in that: The pressure regulating valve (20) adjusts the low pressure nitrogen to 5 barg and then sends it to the electric heater (21) to be heated to 70°C.

10. A method for removing liquid ammonia supply from a ship with zero ammonia residue according to claim 2, characterized in that: The electric heater (21), the nitrogen high-pressure tank (6), and the fresh water buffer tank (7) are connected to the ammonia supply pipeline inside the main engine (8), and the other end of the ammonia supply pipeline inside the main engine (8) is respectively connected to the ammonia treatment unit (12) and the ammonia water collection cabinet (18).

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