A warm-up system and a warm-up method for a liquid cargo tank of an LNG carrier

Abstract

The application discloses a kind of for LNG ship liquid cargo hold's cabin warming system, including cabin warming circulation pipeline module and with gas pipeline module, the gas dome outlet of liquid cargo hold is provided with first valve, and gas dome outlet is communicated with cabin warming circulation pipeline module and with gas pipeline module respectively by first valve, and cabin warming circulation pipeline module includes second valve, first compressor and first heat exchanger, second valve is connected by pipeline with first compressor, and first compressor is connected with first heat exchanger, and first heat exchanger is communicated with the bottom of liquid cargo hold by pipeline;With gas pipeline module includes third valve, second compressor, second heat exchanger and gas using equipment, third valve is connected by pipeline with second compressor, and second compressor is connected by pipeline with second heat exchanger, and second heat exchanger is communicated with gas using equipment by pipeline.The application carries out cabin warming operation to single or multiple specific liquid cargo hold by the setting of cabin warming circulation pipeline module and with gas pipeline module, and the flexibility of cabin warming is improved.

Description

Technical Field

[0001] This invention belongs to the field of shipbuilding technology, specifically relating to a warming system and method for LNG carrier cargo tanks. Background Technology

[0002] Membrane-type LNG carriers are specialized vessels for transporting liquefied natural gas (LNG) at -163°C. When an LNG carrier is not loaded for an extended period or requires maintenance or inspection of the cargo tanks, the tanks need to be filled with dry air at room temperature—a process known as dry air ignition—to ensure structural safety and personnel access. Prior to this, a warming and inerting process is required. To prevent the CO2 and water vapor in the inerting gas from forming dry ice or ice upon entering the cargo tanks, the tank temperature must be raised to room temperature. The warming process for LNG carrier cargo tanks involves using compressors and heaters on board to pressurize and heat the relatively cold gaseous natural gas, producing a higher-temperature, higher-pressure gaseous natural gas, which is then introduced into the cargo tanks to raise their temperature.

[0003] Traditional methods for warming LNG carrier cargo tanks have the following drawbacks:

[0004] 1. Warming operations are performed on all cargo tanks of an LNG carrier simultaneously, and it is not possible to control one or more specific cargo tanks individually.

[0005] 2. Traditional LNG carrier warming methods require all cargo tanks to be unloaded, which cannot meet the requirement of warming other cargo tanks when one or more are loaded with LNG.

[0006] 3. Traditional LNG carrier warming methods involve simultaneously warming all cargo tanks, generating a large amount of gaseous natural gas. The ship's gas-consuming equipment cannot consume this gas in time. To ensure navigational safety, excess natural gas must be burned off using a gas combustion unit (GCU), or even released into the atmosphere using a vent mast. This approach is neither safe nor environmentally friendly, and it is also economically unsustainable. Furthermore, warming operations cannot be performed when the ship is in port and the release of natural gas is prohibited. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a warming system and method for LNG carrier cargo tanks. The warming system and method of this invention improve the flexibility of warming by setting up a warming circulation pipeline module and a gas pipeline module to perform warming operations on one or more specific cargo tanks.

[0008] To achieve the above-mentioned objectives, the technical solution provided by this invention patent is as follows:

[0009] A warming system for LNG carrier cargo tanks includes a warming circulation pipeline module and a gas supply pipeline module. A first valve is installed at the gas dome outlet of the cargo tank, and the gas dome outlet is connected to both the warming circulation pipeline module and the gas supply pipeline module via the first valve. The warming circulation pipeline module includes a second valve, a first compressor, and a first heat exchanger. The second valve is connected to the first compressor via a pipeline, and the first compressor is connected to the first heat exchanger via a pipeline. The first heat exchanger is connected to the bottom of the cargo tank via a pipeline. The gas supply pipeline module includes a third valve, a second compressor, a second heat exchanger, and gas supply equipment. The third valve is connected to the second compressor via a pipeline, and the second compressor is connected to the second heat exchanger via a pipeline. The second heat exchanger is connected to the gas supply equipment via a pipeline.

[0010] Furthermore, the warm chamber circulation pipeline module and the gas pipeline module are arranged in parallel. A blind flange is provided at one end of the second valve, and a blind flange is provided on the branch line opened on the pipeline between the first valve and the third valve. When the first valve is connected to the second valve, the blind flange is removed, and the first valve and the second valve are connected through a temporary short pipe.

[0011] Furthermore, a fourth valve is installed on the pipeline between the first compressor and the first heat exchanger, and a fifth valve is installed on the pipeline connecting the first heat exchanger to the bottom of the liquid cargo tank.

[0012] Furthermore, each of the multiple liquid cargo tanks is equipped with a warm tank circulation pipeline module and a gas supply pipeline module at its gas dome outlet. The warm tank circulation pipelines of each liquid cargo tank are connected in parallel, and the gas supply pipeline modules of each liquid cargo tank are connected in parallel.

[0013] Furthermore, the gas-using equipment includes a dual-fuel marine engine, a dual-fuel generator set, a dual-fuel boiler, and a gas control unit (GCU).

[0014] A method for warming the cargo tanks of LNG carriers, the method specifically includes the following steps:

[0015] S1, Prepare a warming system for the cargo tank of an LNG carrier. The system includes a warming circulation pipeline module and a gas supply pipeline module. A first valve is installed at the gas dome outlet of the cargo tank. The gas dome outlet is connected to the warming circulation pipeline module and the gas supply pipeline module through the first valve. The warming circulation pipeline module includes a second valve, a first compressor, and a first heat exchanger. The second valve is connected to the first compressor through a pipeline, and the first compressor is connected to the first heat exchanger. The first heat exchanger is connected to the bottom of the cargo tank through a pipeline. The gas supply pipeline module includes a third valve, a second compressor, a second heat exchanger, and gas supply equipment. The third valve is connected to the second compressor through a pipeline, and the second compressor is connected to the second heat exchanger through a pipeline. The second heat exchanger is connected to the gas supply equipment through a pipeline.

[0016] S2, identify the cargo compartment of the LNG ship that needs to be heated, remove the blind flange on the gas dome outlet branch of the cargo compartment that needs to be heated, and connect the first valve and the second valve through a temporary short pipe.

[0017] S3, open the first valve, the second valve, the third valve and the fourth valve. The natural gas at the top of the liquid cargo tank flows to the warm tank circulation pipeline module and the gas supply pipeline module through the first valve at the gas dome outlet. The fifth valve on the warm tank circulation pipeline module of the liquid cargo tank that is being warmed is opened, and the fifth valve on the warm tank circulation pipeline module of the liquid cargo tank that is not being warmed is closed.

[0018] S4. When natural gas flows to the warming tank circulation pipeline module through the first valve at the gas dome outlet, the natural gas is compressed and pressurized by the first compressor, and then heated by the first heat exchanger. The heated gas is then passed through the pipeline to the bottom of the liquid cargo tank to warm the liquid cargo tank until the warming operation of the liquid cargo tank is completed.

[0019] S5, when natural gas flows to the gas pipeline module through the first valve at the gas dome outlet, the natural gas is compressed and pressurized by the second compressor. The compressed gas is heated by the second heat exchanger, and then the heated natural gas is sent to the gas-using equipment.

[0020] Furthermore, the first heat exchanger heats the natural gas in a temperature range of 32-80°C. The first heat exchanger heats the natural gas gradually. When the first heat exchanger starts heating, the gas temperature at the outlet of the first heat exchanger is 32°C. When the first heat exchanger continues to work, the gas temperature gradually rises to 80°C, thus completing the gradual warming of the liquid cargo tank.

[0021] Furthermore, the natural gas flow rate in the gas supply pipeline module is not greater than the natural gas consumption of the gas-using equipment load; when the pressure in the liquid cargo tank that is not being warmed is greater than the set value of the safe tank pressure of the liquid cargo tank, the first and third valves on the gas supply pipeline module of the liquid cargo tank that is not being warmed increase their opening degree, and the opening degree of the first, second and third valves on the gas supply pipeline module of the liquid cargo tank that is being warmed decreases, so that the pressure in the liquid cargo tank that is not being warmed is reduced to the set pressure value.

[0022] Furthermore, when the pressure in the cargo tank during warming exceeds the set safe pressure value, the first and third valves on the gas pipeline module of the cargo tank not being warmed decrease their opening, the opening of the first and third valves in the cargo tank being warmed increases, and the opening of the second valve in the cargo tank being warmed decreases, so that the pressure in the cargo tank being warmed is reduced to the set pressure value.

[0023] Based on the above technical solution, the warming system and method for LNG ship cargo tanks, as disclosed in this invention patent, have achieved the following technical advantages through practical application:

[0024] 1. The present invention provides a method for warming LNG carrier cargo tanks. By setting up a warming tank circulation pipeline module and a gas supply pipeline module, the method can perform warming operations on one or more specific cargo tanks, thereby improving the flexibility of warming and the safety of LNG carrier navigation, avoiding the resource waste caused by warming all tanks at the same time in the traditional solution, and reducing carbon emissions.

[0025] 2. The present invention provides a method for warming up LNG cargo tanks. By setting up a warming circulation pipeline module and a gas supply pipeline module, the method can warm up the remaining unloaded cargo tanks when some cargo tanks are loaded with LNG, without affecting the use of the loaded cargo tanks.

[0026] 3. The present invention provides a method for warming up LNG cargo tanks. By setting up a warming circulation pipeline module and a gas pipeline module, the method enables the warming up of one or more cargo tanks on an LNG ship without using a vent mast to discharge natural gas when only part of the cargo tank is loaded. This reduces the cost of the warming process and minimizes the waste of natural gas. Attached Figure Description

[0027] Figure 1 This is a structural diagram of the heating pipeline layout in a heating system for LNG ship cargo tanks according to the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific examples shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0029] like Figure 1 As shown, this invention pertains to a warming system for LNG carrier cargo tanks. The system includes a warming circulation pipeline module and a gas supply pipeline module. A first valve 1 is installed at the gas dome outlet of the cargo tank 8. The gas dome outlet is connected to both the warming circulation pipeline module and the gas supply pipeline module via the first valve 1. The warming circulation pipeline module includes a second valve 2, a first compressor 9, and a first heat exchanger 10. The second valve 2 is connected to the first compressor 9 via a pipeline, and the first compressor 9 is connected to the first heat exchanger 10. The first heat exchanger 10 is connected to the bottom of the liquid cargo tank 8 via a pipeline; the gas supply pipeline module includes a third valve 3, a second compressor 11, a second heat exchanger 12, and a gas supply device 13. The third valve 3 is connected to the second compressor 11 via a pipeline, the second compressor 11 is connected to the second heat exchanger 12 via a pipeline, and the second heat exchanger 12 is connected to the gas supply device 13 via a pipeline. By setting up the warm tank circulation pipeline module and the gas supply pipeline module, warming operations can be performed on one or more specific liquid cargo tanks 8, improving the flexibility of warming operations.

[0030] The warm chamber circulation pipeline module and the gas pipeline module are connected in parallel. One end of the second valve 2 is provided with a blind flange 7. A blind flange 7 is provided on the branch line opened on the pipeline between the first valve 1 and the third valve 3. When the first valve 1 is connected to the second valve 2, the blind flange 7 is removed and the first valve 1 and the second valve 2 are connected through a temporary short pipe 6.

[0031] A fourth valve 4 is installed on the pipeline between the first compressor 9 and the first heat exchanger 10, and a fifth valve 5 is installed on the pipeline connecting the first heat exchanger 10 and the bottom of the liquid cargo tank 8.

[0032] Each of the multiple liquid cargo tanks 8 is equipped with a warm tank circulation pipeline module and a gas supply pipeline module at its gas dome outlet. The warm tank circulation pipeline of each liquid cargo tank 8 is connected in parallel, and the gas supply pipeline module of each liquid cargo tank 8 is connected in parallel.

[0033] The gas-using equipment 13 includes a dual-fuel main engine, a dual-fuel generator set, a dual-fuel boiler, and a gas control unit (GCU).

[0034] A method for warming the cargo tanks of LNG carriers, the method specifically includes the following steps:

[0035] S1. Prepare a warming system for the cargo tank of an LNG carrier. The system includes a warming circulation pipeline module and a gas supply pipeline module. A first valve 1 is installed at the gas dome outlet of the cargo tank 8. The gas dome outlet is connected to the warming circulation pipeline module and the gas supply pipeline module through the first valve 1. The warming circulation pipeline module includes a second valve 2, a first compressor 9, and a first heat exchanger 10. The second valve 2 is connected to the first compressor 9 through a pipeline. The first compressor 9 is connected to the first heat exchanger 10. The first heat exchanger 10 is connected to the bottom of the cargo tank 8 through a pipeline. The gas supply pipeline module includes a third valve 3, a second compressor 11, a second heat exchanger 12, and a gas supply device 13. The third valve 3 is connected to the second compressor 11 through a pipeline. The second compressor 11 is connected to the second heat exchanger 12 through a pipeline. The second heat exchanger 12 is connected to the gas supply device 13 through a pipeline.

[0036] S2, determine the cargo compartment of the LNG ship to be heated in the cargo tank 8, remove the blind flange 7 on the gas dome outlet branch of the cargo tank 8 that needs to be heated and the blind flange 7 on the second valve 2, and connect the first valve 1 and the second valve 2 through the temporary short pipe 6.

[0037] S3, open the first valve 1, the second valve 2, the third valve 3 and the fourth valve 4. The natural gas at the top of the liquid cargo tank 8 flows to the warm tank circulation pipeline module and the gas supply pipeline module through the first valve 1 at the gas dome outlet. The fifth valve 5 on the warm tank circulation pipeline module of the liquid cargo tank 8 that is being warmed is opened, and the fifth valve 5 on the warm tank circulation pipeline module of the liquid cargo tank 8 that is not being warmed is closed.

[0038] S4, when natural gas flows to the warming chamber circulation pipeline module through the first valve 1 at the gas dome outlet, the natural gas is compressed and pressurized by the first compressor 9, and then heated by the first heat exchanger 10. The heated gas is then passed through the pipeline to the bottom of the liquid cargo tank 8 to warm the liquid cargo tank 8 until the warming operation of the liquid cargo tank 8 is completed.

[0039] S5, when natural gas flows to the gas pipeline module through the first valve 1 at the gas dome outlet, the natural gas is compressed and pressurized by the second compressor 11. The compressed gas is heated by the second heat exchanger 12, and then the heated natural gas is sent to the gas-using equipment 13 for consumption.

[0040] The first heat exchanger 10 heats natural gas at a temperature range of 32-80°C. The heating of natural gas by the first heat exchanger 10 is gradual. When the first heat exchanger 10 starts heating, the gas temperature at the outlet of the first heat exchanger 10 is 32°C. When the first heat exchanger 10 continues to work, the gas temperature gradually rises to 80°C, completing the gradual warming of the liquid cargo tank 8. Through the setting of the warming tank circulation pipeline module and the gas pipeline module, when some liquid cargo tanks 8 are loaded with LNG, the remaining unloaded liquid cargo tanks 8 are warmed up without affecting the use of the loaded liquid cargo tanks 8.

[0041] The natural gas flow rate in the gas supply pipeline module does not exceed the natural gas consumption of the gas supply equipment 13. When the pressure in the unheated cargo tank 8 exceeds the safety pressure setting value of the cargo tank 8, the first valve 1 and the third valve 3 on the gas supply pipeline module of the unheated cargo tank 8 increase their opening degree, while the opening degree of the first valve 1, the second valve 2, and the third valve 3 on the gas supply pipeline module of the heated cargo tank 8 decreases, thereby reducing the pressure in the unheated cargo tank 8 to the set pressure value. By reducing the natural gas generation rate of the heated cargo tank 8, the natural gas supply in the gas supply equipment 13 pipeline does not exceed the load consumption of the gas supply equipment 13, while ensuring the pressure stability of the cargo tank 8.

[0042] When the pressure in the cargo tank 8 during warming exceeds the set safety pressure value, the first valve 1 and the third valve 3 on the gas pipeline module of the cargo tank 8 that is not being warmed will decrease their opening, the opening of the first valve 1 and the third valve 3 of the cargo tank 8 that is being warmed will increase, and the opening of the second valve 2 of the cargo tank 8 that is being warmed will decrease, so that the pressure in the cargo tank 8 that is being warmed will decrease to the set pressure value.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A warming system for LNG carrier cargo tanks, characterized in that, The system includes a warm-tank circulation pipeline module and a gas supply pipeline module. A first valve is installed at the gas dome outlet of the liquid cargo tank. The gas dome outlet is connected to both the warm-tank circulation pipeline module and the gas supply pipeline module through the first valve. The warm-tank circulation pipeline module includes a second valve, a first compressor, and a first heat exchanger. The second valve is connected to the first compressor through a pipeline, and the first compressor is connected to the first heat exchanger. The first heat exchanger is connected to the bottom of the liquid cargo tank through a pipeline. The gas supply pipeline module includes a third valve, a second compressor, a second heat exchanger, and gas supply equipment. The third valve is connected to the second compressor through a pipeline, and the second compressor is connected to the second heat exchanger through a pipeline. The second heat exchanger is connected to the gas supply equipment through a pipeline. The warm chamber circulation pipeline module and the gas pipeline module are connected in parallel. A blind flange is provided at one end of the second valve. A blind flange is provided on the branch line opened on the pipeline between the first valve and the third valve. When the first valve is connected to the second valve, the blind flange is removed and the first valve and the second valve are connected through a temporary short pipe. A fourth valve is installed on the pipeline between the first compressor and the first heat exchanger, and a fifth valve is installed on the pipeline connecting the first heat exchanger to the bottom of the liquid cargo tank. Each of the liquid cargo tanks has a gas dome outlet equipped with a warm tank circulation pipeline module and a gas supply pipeline module. The warm tank circulation pipeline of each liquid cargo tank is connected in parallel, and the gas supply pipeline module of each liquid cargo tank is connected in parallel.

2. A warming system for LNG carrier cargo tanks according to claim 1, characterized in that, The gas-using equipment includes a dual-fuel main engine, a dual-fuel generator set, a dual-fuel boiler, and a gas control unit (GCU).

3. A method for warming the cargo tanks of LNG carriers, characterized in that, The method specifically includes the following steps: S1, Prepare a warming system for the cargo tank of an LNG carrier. The system includes a warming circulation pipeline module and a gas supply pipeline module. A first valve is installed at the gas dome outlet of the cargo tank. The gas dome outlet is connected to the warming circulation pipeline module and the gas supply pipeline module through the first valve. The warming circulation pipeline module includes a second valve, a first compressor, and a first heat exchanger. The second valve is connected to the first compressor through a pipeline, and the first compressor is connected to the first heat exchanger. The first heat exchanger is connected to the bottom of the cargo tank through a pipeline. The gas supply pipeline module includes a third valve, a second compressor, a second heat exchanger, and gas supply equipment. The third valve is connected to the second compressor through a pipeline, and the second compressor is connected to the second heat exchanger through a pipeline. The second heat exchanger is connected to the gas supply equipment through a pipeline. S2, identify the cargo compartment of the LNG ship that needs to be heated, remove the blind flange on the gas dome outlet branch of the cargo compartment that needs to be heated, and connect the first valve and the second valve through a temporary short pipe. S3, open the first valve, second valve, third valve and fourth valve, the natural gas in the top of the liquid cargo tank flows to the warm tank circulation pipeline module and the gas supply pipeline module respectively through the first valve at the gas dome outlet; the fifth valve on the warm tank circulation pipeline module of the liquid cargo tank that is being warmed is opened, and the fifth valve on the warm tank circulation pipeline module of the liquid cargo tank that is not being warmed is closed. S4. When natural gas flows to the warming tank circulation pipeline module through the first valve at the gas dome outlet, the natural gas is compressed and pressurized by the first compressor, and then heated by the first heat exchanger. The heated gas is then passed through the pipeline to the bottom of the liquid cargo tank to warm the liquid cargo tank until the warming operation of the liquid cargo tank is completed. S5, when natural gas flows to the gas pipeline module through the first valve at the gas dome outlet, the natural gas is compressed and pressurized by the second compressor. The compressed gas is heated by the second heat exchanger, and then the heated natural gas is sent to the gas-using equipment.

4. A method for warming the cargo tank of an LNG carrier according to claim 3, characterized in that, The first heat exchanger heats the natural gas in a temperature range of 32-80°C. The first heat exchanger heats the natural gas gradually. When the first heat exchanger starts heating, the gas temperature at the outlet of the first heat exchanger is 32°C. When the first heat exchanger continues to work, the gas temperature gradually rises to 80°C, thus completing the gradual warming of the liquid cargo tank.

5. A method for warming the cargo tank of an LNG carrier according to claim 3, characterized in that, The natural gas flow rate in the gas supply pipeline module is not greater than the natural gas consumption of the gas-using equipment load. When the pressure in the liquid cargo tank that is not being preheated is greater than the set value of the safe tank pressure, the first and third valves on the gas supply pipeline module of the liquid cargo tank that is not being preheated increase their opening degree, while the opening degree of the first, second, and third valves on the gas supply pipeline module of the liquid cargo tank that is being preheated decreases, so that the pressure in the liquid cargo tank that is not being preheated is reduced to the set pressure value.

6. A method for warming the cargo tank of an LNG carrier according to claim 5, characterized in that, When the pressure in the liquid cargo tank during warming exceeds the set safe pressure value, the first and third valves on the gas pipeline module of the liquid cargo tank that is not being warmed decrease their opening, the opening of the first and third valves in the liquid cargo tank that is being warmed increases, and the opening of the second valve in the liquid cargo tank that is being warmed decreases, so that the pressure in the liquid cargo tank that is being warmed is reduced to the set pressure value.

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