JP2023140783A - Cooling down method and warming up method of liquefied gas storage tank - Google Patents

Abstract

To reduce the time while inhibiting occurrence of stress in cooling down of a multiple heat-insulating structure tank for storage of a liquefied gas to reduce costs.SOLUTION: A method for cooling a tank for storing a liquefied gas, which includes an inner tank (3) and an outer tank (5), before the tank is filled with the liquefied gas, an object to be stored, includes: introducing a cooling liquefied gas (CH) into an inner tank internal space (7); measuring a temperature of the inner tank (3) and a temperature of the outer tank (5); and adjusting at least one of a temperature change speed of the inner tank (3) and a temperature change speed of the outer tank (5) based on a temperature difference between the temperature of the inner tank (3) and the temperature of the outer tank (5) to keep the temperature difference to a predetermined value or lower.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to methods for cooling down and warming up liquefied gas storage tanks.

BACKGROUND ART Conventionally, it has been proposed to use a double-shell tank including an inner tank and an outer tank as a tank for storing liquefied gas, such as cryogenic liquefied hydrogen (see, for example, Patent Document 1).

Generally, when storing low-temperature liquefied gas in a tank, in order to avoid rapid cooling of the tank by filling a room-temperature tank with a large amount of liquefied gas to be stored at once, Before filling the tank, the tank is cooled at a relatively low speed (hereinafter referred to as "cool down"). Furthermore, when it is necessary to empty the tank for maintenance or the like, the tank is heated (hereinafter referred to as "warm-up") after the liquefied gas to be stored is discharged.

Japanese Patent Application Publication No. 2019-151291

However, in the case of tanks with multiple heat insulation structures such as double-shell tanks for liquefied gas, they have high insulation properties, so even when the tank is cooled at a relatively slow rate as described above, there are large temperature differences depending on the location of the tank. can occur, resulting in large stresses. To avoid this, conventional double-shell tank cool-down requires measures such as cooling at an even slower rate, which requires a long time to cool the entire tank and requires a large amount of liquefied gas for cooling. It will take a while. Therefore, the cost required for cooldown increases. A similar problem exists with regard to warming up tanks with multiple thermal insulation structures.

In order to solve the above-mentioned problems, an object of the present disclosure is to shorten the time and reduce costs while suppressing the generation of stress during cool-down and warm-up of a multi-layered heat-insulated structure tank for storing liquefied gas. .

In order to achieve the above object, a method for cooling down a liquefied gas storage tank according to the present disclosure includes:
A method for cooling a tank including an inner tank and an outer tank for storing liquefied gas before filling it with the liquefied gas to be stored, the method comprising:
Introducing a cooling liquefied gas into the inner tank space;
Measuring the temperature of the inner tank and the temperature of the outer tank, respectively;
Based on the temperature difference between the temperature of the inner tank and the temperature of the outer tank, the temperature difference is maintained at a predetermined value or less by adjusting at least one of the temperature change rate of the inner tank and the temperature change rate of the outer tank. to do and
including.

A method for warming up a liquefied gas storage tank according to the present disclosure includes:
A method for heating a tank for storing liquefied gas, including an inner tank and an outer tank, after discharging the liquefied gas to be stored, the method comprising:
Introducing a first heating gas into the inner tank space;
Forcibly supplying a second heating gas to the space between the inner and outer tanks; Measuring the temperature of the inner tank and the temperature of the outer tank, respectively;
Based on the temperature difference between the temperature of the inner tank and the temperature of the outer tank, the temperature difference is maintained at a predetermined value or less by adjusting at least one of the temperature change rate of the inner tank and the temperature change rate of the outer tank. to do and
including.

According to the cool-down method and warm-up method for a liquefied gas storage tank according to the present disclosure, the time and cost can be reduced while suppressing the generation of stress during the cool-down and warm-up of a multi-layered heat-insulated structure tank for storing liquefied gas. Can be suppressed.

1 is a cross-sectional view showing a schematic configuration of a liquefied gas storage tank to which a cool-down method according to an embodiment of the present disclosure is applied. FIG. 2 is a schematic diagram showing an initial state before the start of a cool-down method according to an embodiment of the present disclosure. FIG. 3 is a schematic diagram showing a state during cooling of the inner tank in a cool-down method according to an embodiment of the present disclosure. FIG. 2 is a schematic diagram showing a state in which temperature difference adjustment is performed in a cool-down method according to an embodiment of the present disclosure. FIG. 2 is a schematic diagram showing a state in which a cool-down method according to an embodiment of the present disclosure has been completed. FIG. 2 is a schematic diagram showing a state at the start of a warm-up method according to an embodiment of the present disclosure. FIG. 3 is a schematic diagram showing a state in which temperature difference adjustment is performed in a warm-up method according to an embodiment of the present disclosure.

Hereinafter, preferred embodiments of the present disclosure will be described with reference to the drawings. FIG. 1 shows a liquefied gas storage tank (hereinafter simply referred to as "storage tank") 1 to which a cool-down method and a warm-up method according to an embodiment of the present disclosure are applied. This storage tank 1 is a tank for storing liquefied gas, and is configured as a double shell tank including an inner tank 3 and an outer tank 5. Note that in this specification, "cool down" means cooling the storage tank 1 before filling the storage tank 1 with the liquefied gas to be stored. Furthermore, in this specification, "warming up" means heating the low-temperature storage tank 1 in preparation for subsequent maintenance and the like after the liquefied gas to be stored is discharged.

In the present embodiment described below, liquefied hydrogen at an extremely low temperature (approximately -250° C.) will be explained as an example of the liquefied gas to be stored. However, liquefied gas can also include other types of gas, such as liquefied petroleum gas (LPG, approximately -45°C), liquefied ethylene gas (LEG, approximately -100°C), liquefied natural gas (LNG, approximately -160°C), It may be helium (LHe, about −270° C.) or the like.

The storage tank 1 is installed, for example, on a ship such as a liquefied hydrogen carrier. However, the liquefied hydrogen storage facility in which the storage tank 1 is installed is not limited to this example as long as it has a structure and function capable of storing liquefied hydrogen. The liquefied hydrogen storage facility in which the storage tank 1 is installed may be, for example, a ship that uses liquefied hydrogen as a propulsion fuel, a land-based liquefied hydrogen storage facility other than a ship, or a plant that uses liquefied hydrogen. It's fine.

The storage tank 1 is configured as a double shell tank with an inner tank 3 and an outer tank 5. Specifically, the inner tank 3 has an inner tank shell that forms a storage space (hereinafter referred to as "inner tank interior space 7") for liquefied hydrogen to be stored, and an outer circumferential surface of the inner tank shell. It has an inner tank heat insulation layer that covers the inner tank. The outer tank 5 has an outer tank shell that forms an inter-inner/outer tank space 9 that is a heat insulating layer between it and the inner tank 3, and an outer tank heat insulating layer that covers the outer peripheral surface of the outer tank shell. Note that the locations where the heat insulating layers of the inner tank 3 and the outer tank 5 are installed are not limited to this example, but are arbitrary. For example, the heat insulating layers may be installed so as to cover the inner circumferential surface of the outer tank shell. Moreover, one or both of the heat-insulating layers of the inner tank 3 and the outer tank 5 may be omitted. This storage tank 1 is normally operated with low-temperature hydrogen gas sealed in the space 9 between the inner and outer tanks, which is a heat insulating layer.

In this embodiment, a communication passage 11 is provided that communicates the inner tank space 7 with the inner and outer tank space 9. The communication path 11 is configured to be openable and closable. In the illustrated example, specifically, a vaporized gas discharge passage 13 that discharges vaporized gas of liquefied hydrogen (hereinafter simply referred to as “vaporized gas”) G1 generated in the inner tank space 7 to the outside of the storage tank 1 and a hydrogen gas introduction passage 15 that introduces hydrogen gas (hereinafter referred to as "external hydrogen gas") G2 from a hydrogen gas source (not shown) provided outside the storage tank 1 into the space 9 between the inner and outer tanks. A connecting passage 17 connecting the vaporized gas discharge passage 13 and the hydrogen gas introduction passage 15 is provided outside the storage tank 1. A communication passage 11 is formed by the vaporized gas discharge passage 13, the connection passage 17, and the hydrogen gas introduction passage 15. Further, an on-off valve 19 is provided in the communication passage 11, and the communication passage 11 is configured to be openable and closable by this on-off valve 19. In this example, the on-off valve 19 is provided in a portion of the hydrogen gas introduction passage 15 downstream of the connection point with the connection passage 17, but the position and number of the on-off valves 19 are not limited to this example. Further, the on-off valve 19 may be a valve that can be opened and closed manually, or may be a valve that is automatically opened and closed according to a set differential pressure.

Note that the specific configuration of the communication path 11 between the inner tank interior space 7 and the outer and outer tank space 9, and the specific configuration that allows the communication path 11 to be opened and closed are not limited to this example. Further, the above-mentioned "hydrogen gas source" may have any configuration as long as it can serve as a supply source of hydrogen gas, and is typically a tank that stores hydrogen gas, but for example, it may be a tank that stores liquefied hydrogen. It may also be a combination of a tank and a vaporizer.

Furthermore, in the present embodiment, a device (hereinafter simply referred to as a "gas feeding device") that forcibly feeds cooling gas, which will be described later, to the space 9 between the inner and outer tanks is provided in the communication path 11, such as a compressor or a blower. ) 31 are provided. The gas supply device 31 is a device that moves gas by applying pressure to the gas, such as a turbo or positive displacement compressor, blower, or fan. In the illustrated example, a gas supply device 31 is provided in the connection passage 17 . Further, a cooling device 33 is provided on the communication path 11, for example, on the hydrogen gas introduction path 15. The cooling device 33 includes, for example, a temperature sensor that detects gas temperature, a cooling source such as a compression refrigerator or an absorption refrigerator, a control circuit that controls these, and the like. However, the cooling device 35 may be a device having a configuration other than the above, for example, a heat exchanger. Furthermore, only the gas supply device 31 and the cooling device 33 that are necessary may be provided depending on the embodiment of the cool-down method and warm-up method described later.

Further, in this embodiment, an inner tank temperature detection device 21 that detects the temperature of the inner tank 3, an inner tank space pressure detection device 23 that monitors the pressure of the inner tank space 7, and a temperature detection device 23 that detects the temperature of the space 9 between the inner and outer tanks. The inner and outer tank space temperature detection device 25 detects the pressure in the inner and outer tank space 9, and the inner and outer tank space pressure sensor 27 detects the pressure in the inner and outer tank space 9. These detection devices consist of a sensor element that detects the physical quantity to be detected (temperature, pressure), various circuits that perform necessary processing such as signal conversion processing and arithmetic processing on the obtained detected quantity, and information necessary for these processing. The device is equipped with a memory for storing the data, a power source circuit such as a power supply element such as a battery or a power supply circuit for receiving power supply from the outside, a transmission circuit for transmitting the output signal to the outside by wire or wirelessly, and the like. Note that as such a temperature sensing device and a pressure sensing device, a device that measures parts other than those described above, such as an inner tank temperature sensing device or an outer tank temperature sensing device, may be provided. Furthermore, only the necessary temperature sensing devices and pressure sensing devices may be provided depending on the embodiment of the cool-down method and warm-up method described later.

A method for cooling down the storage tank 1 configured as described above will be described in detail below.

In this embodiment, in the storage tank 1 in the initial state at the time of starting the cool-down shown in FIG. In each of the spaces 9, hydrogen gas exists at room temperature and atmospheric pressure (0 kPaG), for example. However, the temperature and pressure of the hydrogen gas in the initial state are not limited to room temperature and atmospheric pressure. From this state, as shown in FIG. 2B, liquefied hydrogen for cooling (hereinafter simply referred to as "hydrogen for cooling") CH is introduced into the inner tank space 7. In this example, cooling hydrogen CH is sprayed into the inner tank space 7 using the sprayer 29 .

By continuing to spray the cooling hydrogen CH in this state, the temperature of the inner tank 3 is lowered. As the temperature of the inner tank 3 decreases, the temperature of the space 9 between the inner and outer tanks also decreases. Further, in the inner tank space 7, vaporized gas G1 in which the cooling hydrogen CH is vaporized is generated, and the pressure increases, while in the inner tank space 9, the pressure decreases due to the temperature drop. Since the communication passage 11 is opened as described above, the vaporized gas G1 generated in the inner tank inner space 7 flows into the inner and outer tank space 9 via the communication passage 11 due to the pressure difference between both spaces 7 and 9. do.

If the pressure difference between the two spaces exceeds a predetermined range while cooling the inner tank 3 with the communication passage 11 open, a pressure difference adjustment device is used to adjust the pressure difference between the two spaces. may be adjusted so that it falls within a predetermined range. For example, if the pressure in the space 9 between the inner and outer tanks is excessively low, the hydrogen gas supply device 31 may be used to supply the vaporized gas G1 in the inner tank space 7 to the space 9 between the inner and outer tanks. In place of or in addition to the forced supply of the vaporized gas G1, external hydrogen gas G2 may be supplied from the hydrogen gas introduction passage 15 to the space 9 between the inner and outer tanks. In the following description, the gas that is forcibly supplied to cool the space 9 between the inner and outer tanks in this manner will be collectively referred to as "cooling gas CG."

In addition, when the cooling gas CG is forcibly supplied to the space 9 between the inner and outer tanks as described above, a discharge passage (not shown) is provided to discharge the cooling gas CG from the space 9 between the inner and outer tanks. It may also be possible to prevent the pressure in the space 9 from increasing excessively.

Further, in the present embodiment, an example has been described in which the communication passage 11 is opened from the start of cool-down, that is, from the start of spraying of the cooling hydrogen CH, but the timing of opening the communication passage 11 is not limited to this. That is, spraying of the cooling hydrogen CH is started with the communication passage 11 closed, and if necessary, such as when the pressure in the space 9 between the inner and outer tanks falls below a predetermined value, the communication passage 11 is opened to spray the vaporized gas G1. may be supplied.

During the cool-down process performed in this manner, the temperature difference between the inner tank 3 and the outer tank 5 becomes too large, and the difference in the amount of thermal contraction of the constituent members becomes too large, which may generate large stress. In order to avoid this, in this embodiment, the temperature of the inner tank 3 and the temperature of the outer tank 5 are measured respectively, and the temperature difference between the temperature of the inner tank 3 and the temperature of the outer tank 5 (hereinafter simply referred to as "temperature The temperature difference is maintained at a predetermined value or less by adjusting at least one of the temperature change rate of the inner tank 3 and the outer tank 5 based on the temperature change rate of the inner tank 3 and the outer tank 5. Here, "temperature of inner tank 3" and "temperature of outer tank 5" refer to the temperature of the inner space in contact with each tank, that is, the temperature of inner tank inner space 7 for inner tank 3, and the temperature of inner tank inner space 7 for outer tank 5. includes the temperature of the space 9 between the inner and outer tanks. Also, the "predetermined value" of the temperature difference here is, for example,
It is set based on the temperature difference at the start of normal operation of the storage tank 1, and is, for example, a value larger than the temperature difference at the start of normal operation, for example, about 150K. However, the "predetermined value" is not limited to this value.

In this embodiment, as a method for adjusting the rate of temperature change in the inner tank 3, the rate of introduction of cooling hydrogen CH into the inner tank 3 is adjusted. Specifically, the cooling rate of the inner tank 3 is reduced by reducing the introduction speed of cooling hydrogen CH into the inner tank 3. Note that "reducing the introduction speed" herein includes stopping the introduction. Moreover, as a method of adjusting the temperature change rate of the outer tank 5, in this embodiment, the supply rate of the cooling gas CG to the space 9 between the inner and outer tanks is adjusted. Specifically, the temperature of the vaporized gas G1 and/or the external hydrogen gas G2 to the space 9 between the inner and outer tanks is lowered by the cooling device 33, and the supply rate of the cooling gas CG is increased by using the gas feeding device 31. This increases the cooling rate of the outer tank 5. Either one of reducing the cooling rate of the inner tank 3 and increasing the cooling rate of the outer tank 5 may be implemented, or both may be implemented in combination. As an example, FIG. 2C shows a state in which spraying of the cooling hydrogen CH to the inner tank 3 is stopped and the supply rate of the cooling gas CG to the space 9 between the inner and outer tanks is increased.

Note that the adjustment of the introduction speed of the cooling hydrogen CH into the inner tank 3 is not limited to the above example, and includes, for example, increasing the introduction speed when the inner tank 3 is insufficiently cooled. Similarly, the adjustment of the supply rate of the cooling gas CG to the space 9 between the inner and outer tanks is not limited to the above example, and includes, for example, reducing the supply rate when the outer tank 5 is cooled too much. The method of adjusting at least one of the temperature change rate of the inner tank 3 and the temperature change rate of the outer tank 5 is not limited to the example described above. For example, hydrogen gas having a higher temperature than the inner tank temperature may be supplied to the inner tank space 7.

In addition, in order to perform temperature difference control with high precision, in the inner tank 3 and the outer tank 5, the respective temperatures are measured at, for example, a predetermined location where the representative temperature of the inner tank 3 can be detected, and the outer tank 5. Select a predetermined location where the representative temperature can be detected. The term "representative temperature" as used herein means a temperature that is considered to most appropriately represent the temperature of each of the inner tank 3 and outer tank 5 in view of the overall temperature distribution of each of the inner tank 3 and outer tank 5. An example of the "representative temperature" is the average value of the overall temperature distribution of each of the inner tank 3 and the outer tank 5.

Other examples of locations in the inner tank 3 and outer tank 5 where the respective temperatures are measured include locations where the inner tank 3 is connected to other members and locations where the outer tank 5 is connected to other members. Specifically, examples of connection points with other members that perform temperature measurement include connection points with the skirt, which is a cylindrical support member that supports the storage tank 1 relative to the hull, and the center of the storage tank 1. An example of this is the connection point with a pipe-shaped tower that protrudes vertically from the top. By measuring the temperature of the connection points with other members and adjusting the temperature difference, the state of connection between the inner tank 3, outer tank 5 and other members can be effectively maintained.

As still another example of the locations where the temperature of each of the inner tank 3 and the outer tank 5 is measured, the inner space in contact with each tank 3, 5, that is, the inner tank inner space 7 for the inner tank 3, and the inner tank space 7 for the outer tank 5. An example is the space 9 between the inner and outer tanks. According to this configuration, the temperature measurement location used for steady operation of the storage tank 1 can be used, so there is no need to add a measurement device or the like.

Note that the combination of locations at which temperatures are measured in the inner tank 3 and outer tank 5 is not limited to the example described above. That is, for example, for the inner tank 3, the temperature may be measured at a connection point with other members, and for the outer tank 5, the temperature of the space 9 between the inner and outer tanks may be measured.

Further, the device used for these temperature measurements may be, for example, a temperature detection device as described above, or a differential thermometer that outputs the difference in temperature detected by individual temperature detection elements.

In this way, by supplying hydrogen gas to the space 9 between the inner and outer tanks as needed while cooling the inner tank 3 with the cooling hydrogen CH, cooling of the space 9 between the inner and outer tanks and the outer tank 5 is promoted. Therefore, compared to the case where only the inner tank 3 is cooled, the time required to cool down the entire storage tank 1 can be shortened and costs can be suppressed. Furthermore, by maintaining the temperature difference between the inner tank 3 and the outer tank 5 below a predetermined value, it is possible to suppress the difference in the amount of thermal contraction of the constituent members.

Thereafter, as shown in FIG. 2D, when the temperature of the inner tank 3 and the temperature of the space 9 between the inner and outer tanks have respectively decreased to the target temperatures, if the communication passage 11 is open, it is closed, and the cooling The spraying of hydrogen CH is stopped to complete the cool-down.

In this embodiment, an example has been described in which cool down is performed using liquefied hydrogen for cooling, but cool down may be performed using liquefied gas other than liquefied hydrogen. For example, the cooldown may be performed in stages, such as introducing liquefied nitrogen from a state in which air is present in the inner tank 3, and then replacing the nitrogen with hydrogen.

The cool down according to the present embodiment is typically performed, for example, after construction of the storage tank 1, after construction of liquefied gas storage equipment such as a ship in which the storage tank 1 is installed, or after the construction of the equipment or the storage tank 1. Maintenance is carried out after warming up the storage tank 1 and before loading it again. However, the cool-down method according to the present embodiment is also applied when carrying out an empty voyage (ballast voyage) after unloading the liquefied gas in the storage tank 1 when the storage tank 1 is installed on a ship. be able to. That is, during a ballast voyage, the temperature of the inner tank 3 may gradually rise, and in that case, the above-mentioned cool-down method can be applied. In addition, when cooling down the storage tank 1 during a ballast voyage, for example, the liquefied gas left in the inner tank 3 for cooling down without unloading is used to cool down the pumps etc. installed in the inner tank 3. A feeding device transports the liquefied gas to the top of the tank for cooling down. When a plurality of storage tanks 1 are installed, liquefied gas or vaporized gas for cooling down may be supplied from other storage tanks 1.

Next, a method for warming up the storage tank 1 according to the present embodiment will be described in detail below.

In this embodiment, liquefied hydrogen is discharged from the storage tank 1, and the on-off valve 19 of the communication passage 11 is in a closed state in the storage tank 1 in an initial state at the time of starting the warm-up shown in FIG. 3A. . For example, hydrogen gas exists in the inner tank space 7 at a pressure slightly higher than atmospheric pressure, for example, at a temperature of about 20 K, which is the freezing point, under 5 kPaG. In the space 9 between the inner and outer tanks, hydrogen gas exists at a temperature of about 110 K under a steady operating state, for example, at a pressure of -10 kPaG, which is slightly lower than atmospheric pressure. However, the temperature and pressure values of the hydrogen gas in the initial state are not limited to the above example. From this state, as shown in the figure, heating hydrogen gas (hereinafter referred to as "first heating gas") HG1 is supplied to the inner tank space 7 using the sprayer 29. Instead of the atomizer 29, the first heating gas may be supplied using another line connected to the inner tank 3, for example, a line provided for supplying liquefied gas to the storage tank 1.

During the warm-up process performed in this manner, the temperature difference between the inner tank 3 and the outer tank 5 may become too large, and the difference in the amount of thermal contraction of the constituent members may become excessive. In this embodiment, in order to avoid this, the temperature of the inner tank 3 and the temperature of the outer tank 5 are measured respectively, and the temperature difference between the temperature of the inner tank 3 and the temperature of the outer tank 5 (hereinafter simply referred to as "temperature The temperature difference is maintained at a predetermined value or less by adjusting at least one of the temperature change rate of the inner tank 3 and the outer tank 5 based on the temperature change rate of the inner tank 3 and the outer tank 5. Here, the "predetermined value" of the temperature difference is set, for example, based on the temperature difference at the end of normal operation of the storage tank 1, and is a value larger than the temperature difference at the start of normal operation, for example, 1
It is about 50K. However, the "predetermined value" is not limited to this value.

As a method for maintaining the temperature difference below a predetermined value, in this embodiment, as shown in FIG. 3B, heating gas (hereinafter referred to as "second heating gas") HG2 is also supplied to the space 9 between the inner and outer tanks. By doing so, the temperature increase rate of the outer tank 5 is increased. The second heating gas HG2 is supplied to the space 9 between the inner and outer tanks, for example, via a dedicated heating gas supply path 41. However, the second heating gas HG2 may be supplied to the space 9 between the inner and outer tanks, for example, via the hydrogen gas introduction passage 15, bypassing the cooling device 33. In order to maintain the temperature difference below a predetermined value, at least one of the supply speed of the first heating gas to the inner tank inner space 7 and the supply speed of the second heating gas HG2 to the inner and outer tank space 9 is adjusted. do.

The locations at which the temperatures of the inner tank 3 and outer tank 5 are measured during the warm-up are the same as in the case of the cool-down described above. That is, for example, a predetermined location where the representative temperature of each tank 3, 5 can be detected, a connection location of each tank 3, 5 with other members, and an inner tank space that is an inner space in contact with each tank 3, 5. 7. The temperature of the space 9 between the inner and outer tanks can be measured.

Note that the second heating gas HG2 is preferably supplied to the space 9 between the inner and outer tanks after the temperature of the inner tank 3 rises to a predetermined value or higher. The "predetermined value" of the temperature of the inner tank 3 here means a temperature at which there is no possibility of hydrogen gas condensing in the space 9 between the inner and outer tanks.

In this way, by supplying the second heating gas HG2 to the space 9 between the inner and outer tanks while heating the inner tank 3 with the first heating gas HG1, the temperature of the space 9 between the inner and outer tanks and the outer tank 5 can also be increased. Therefore, compared to the case where only the inner tank 3 is heated, the time required to warm up the entire storage tank 1 can be shortened and costs can be suppressed. Furthermore, by maintaining the temperature difference between the inner tank 3 and the outer tank 5 below a predetermined value, it is possible to suppress the difference in the amount of thermal contraction of the constituent members.

Note that although FIG. 1 shows an independent double-shell tank formed independently of the ship's hull as an example of the storage tank 1, the cool-down method and warm-up method according to this embodiment are based on this example. It is not limited to, but can be applied to any type of storage tank. For example, the cool-down method and warm-up method according to this embodiment can also be applied to a type of storage tank that is formed integrally with the hull. Moreover, the multiple structure of the storage tank may be a triple structure or more, and the cool-down method and warm-up method according to the present embodiment may be applied to the internal tank space and any other inter-tank space of such a multiple structure. Can be applied.

According to the cool-down method according to the present embodiment described above, as shown in FIG. 2B, while cooling the inner tank 3 with cooling hydrogen CH, cooling gas CG is supplied to the space 9 between the inner and outer tanks. By maintaining the temperature difference between the inner tank 3 and the outer tank 5 below a predetermined value, it is possible to suppress the generation of stress caused by the difference in the amount of thermal contraction that occurs between the constituent members, reduce the time required for cool-down, and reduce costs. can be suppressed.

In the cool-down method according to the present embodiment, the temperature change rate of the inner tank 3 may be adjusted by reducing the spray rate of the cooling liquefied hydrogen CH to the inner tank 3. Further, the temperature change rate of the outer tank 5 may be adjusted by increasing the cooling gas supply rate to the space 9 between the inner and outer tanks. According to this configuration, the temperature difference can be adjusted with a simple structure.

In the cool-down method according to the present embodiment, the temperature of the inner tank 3 and the temperature of the outer tank 5 are measured by measuring the temperature at a predetermined location where each representative temperature of the inner tank 3 and the outer tank 5 can be detected. You may go. According to this configuration, the temperature difference can be adjusted with high precision.

In the cool-down method according to the present embodiment, the temperature of the inner tank 3 and the temperature of the outer tank 5 are measured by measuring the temperature of each connection point with other members in the inner tank 3 and the outer tank 5. Good too. According to this configuration, the state of connection between the inner tank 3, outer tank 5, and other members can be effectively maintained by adjusting the temperature difference.

In the cool-down method according to the present embodiment, the temperature of the inner tank 3 and the temperature of the outer tank 5 may be measured by measuring the temperature of the inner tank space 7 and the space 9 between the inner and outer tanks. According to this configuration, the temperature measurement location used for steady operation of the storage tank 1 can be used, so there is no need to add a measurement device or the like.

According to the warm-up method according to the present embodiment, the inner tank 3 and the outer tank are heated by supplying the second heating gas HG2 to the space 9 between the inner and outer tanks while heating the inner tank 3 with the first heating gas HG1. By maintaining the temperature difference in the tank 5 below a predetermined value, it is possible to suppress the difference in the amount of thermal contraction of the constituent members, shorten the time required for warm-up, and suppress costs.

As described above, the preferred embodiments of the present disclosure have been described with reference to the drawings, but various additions, changes, or deletions can be made without departing from the spirit of the present disclosure. Accordingly, such are also included within the scope of this disclosure.

1 Liquefied gas storage tank 3 Inner tank 5 Outer tank 7 Inner tank space 9 Space between the inner and outer tanks 11 Communication path 29 Sprayer 33 Cooling device CG Cooling gas CH Cooling liquefied gas G1 Vaporized gas G2 External hydrogen gas HG1 First heating gas HG2 Second heating gas

Claims (7)

A method for cooling a tank including an inner tank and an outer tank for storing liquefied gas before filling it with the liquefied gas to be stored, the method comprising:
Introducing a cooling liquefied gas into the inner tank space;
Measuring the temperature of the inner tank and the temperature of the outer tank, respectively;
Based on the temperature difference between the temperature of the inner tank and the temperature of the outer tank, the temperature difference is maintained at a predetermined value or less by adjusting at least one of the temperature change rate of the inner tank and the temperature change rate of the outer tank. to do and
including,
How to cool down a liquefied gas storage tank. The cool-down method according to claim 1,
Adjusting at least one of the temperature change rate of the inner tank and the temperature change rate of the outer tank,
A cool-down method comprising adjusting the introduction speed of the cooling liquefied gas into the inner tank space. The cool-down method according to claim 1 or 2,
Adjusting at least one of the temperature change rate of the inner tank and the temperature change rate of the outer tank,
including adjusting the cooling gas supply rate to the space between the inner and outer tanks;
How to cool down. The cool-down method according to any one of claims 1 to 3,
Measuring the temperature of the inner tank and the temperature of the outer tank,
Measuring the temperature at a predetermined location where the representative temperature of the inner tank can be detected; Measuring the temperature at a predetermined location where the representative temperature of the outer tank can be detected;
How to cool down. The cool-down method according to any one of claims 1 to 4,
Measuring the temperature of the inner tank and the temperature of the outer tank,
Measuring the temperature of a connection point with other members in the inner tank;
Measuring the temperature of a connection point with other members in the outer tank;
Cool down methods including. The cool-down method according to any one of claims 1 to 5,
Measuring the temperature of the inner tank and the temperature of the outer tank,
Measuring the temperature of the inner tank space;
Measuring the temperature of the space between the inner and outer tanks;
Cool down methods including. A method for heating a tank for storing liquefied gas, including an inner tank and an outer tank, after discharging the liquefied gas to be stored, the method comprising:
Introducing a first heating gas into the inner tank space;
Measuring the temperature of the inner tank and the temperature of the outer tank, respectively;
Based on the temperature difference between the temperature of the inner tank and the temperature of the outer tank, the temperature difference is maintained at a predetermined value or less by adjusting at least one of the temperature change rate of the inner tank and the temperature change rate of the outer tank. to do and
including,
How to warm up a liquefied gas storage tank.

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