Cargo tank

Abstract

To provide a cargo tank reducing time for raising temperature in a tank shell.SOLUTION: A cargo tank 1 includes: a tank body 11 for storing two types of liquefied gas with different temperatures to be managed by replacing them; a piping 12 provided on a surface of the tank body 11 and through which heat medium flows to change the temperature inside the tank 11; an insulation material 13 provided on the surface of the tank body 11 so as to cover the piping 12; and a cover 14 provided on the surface of the tank body 11 so as to cover the piping 12 and the insulation material 13.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a cargo tank for containing cargo. [Background technology]

[0002] Generally, ships that transport liquefied gas such as LNG (liquefied natural gas) in cargo tanks are known. For example, an LNG ship that can efficiently cool the cargo tanks by suppressing the heel amount has been disclosed (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-34665 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, although the temperature varies depending on the type of liquefied gas, changing the temperature of the outer shell of a cargo tank requires time to heat or cool the tank if the weight of the steel material in the tank body is large, due to the large heat capacity of the tank body. Therefore, it takes time to replace the contents of the cargo tank with another substance that requires a different temperature.

[0005] Generally, tanks are cooled by spraying granular material onto the refrigerated cargo from the inside, while heating is carried out by circulating gas that has heated the refrigerated cargo inside the tank. As a result, cooling is smooth due to good heat transfer, but heating is known to take several times longer than the cooling time due to poor heat transfer.

[0006] On the other hand, low-temperature pressurized tanks that can transport CO2 are called Type C tanks, and because a minimum pressure of 0.8 MPa is required to transport liquefied CO2, the tank shell is thick and the tank weight is heavy. In other words, tanks that can transport CO2 are tanks that are difficult to cool and heat. For example, to load CO2 after transporting LNG, in order to heat the tank shell temperature to a temperature suitable for CO2 transportation (around -50°C), more weight must be taken into account compared to conventional tank heating.

[0007] Here, we will describe the thermal stress on the tank shell that occurs during cooling and heating. It is generally said that in order to keep the thermal stress of the tank steel at a safe level, the temperature gradient should be kept at about 10°C / hour. For example, this index is used for the temperature gradient during cooling, and it is expected that it will take about 7 hours to cool from -50°C to -162°C, but in the case of heating, since it is heating by gas circulation, only a temperature rise of about 2°C / hour can be expected. In other words, it will take 36 hours to heat from -162°C to -50°C. In a tank like this ship, whose tank weight is several times that of a general tank, the heating time will easily exceed 100 hours. This makes it impossible to complete the cargo replacement within the appropriate time, and measures to promote tank heating are required.

[0008] It is an object of an embodiment of the present invention to provide a cargo tank that reduces the time required to increase the temperature of the tank shell. [Means for solving the problem]

[0009] A cargo tank according to an aspect of the present invention comprises a tank body for alternately storing two types of liquefied gas having different temperatures to be managed, piping provided on the surface of the tank body through which a heat medium flows to change the temperature inside the tank body, insulation provided on the surface of the tank body so as to cover the piping, and a cover provided on the surface of the tank body so as to cover the piping and the insulation. Effect of the Invention

[0010] According to an embodiment of the present invention, a cargo tank can be provided that reduces the time required to increase the temperature of the tank shell. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view showing a configuration of a cargo tank according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing the configuration of a cargo tank according to the present embodiment. [Diagram 3] FIG. 4 is a cross-sectional view showing a configuration of a modified cargo tank according to the embodiment. [Figure 4] FIG. 1 is a diagram showing the configuration of a temperature control system according to an embodiment of the present invention. [Diagram 5] FIG. 1 is a configuration diagram showing the configuration of a ship to which a cargo tank according to this embodiment is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] (Embodiment) Fig. 1 is a perspective view showing the configuration of a cargo tank 1 according to an embodiment of the present invention. Fig. 2 is a cross-sectional view showing the configuration of the cargo tank 1 according to this embodiment. Note that the same parts in the drawings are given the same reference numerals, and duplicated explanations will be omitted as appropriate.

[0013] The cargo tank 1 is a tank that is installed on a ship and is used to load cargo. At least two types of liquefied gases that are managed at different temperatures are alternately stored in the cargo tank 1. Therefore, the temperature managed inside the cargo tank 1 is changed depending on the type of liquefied gas stored therein.

[0014] For example, the cargo is LNG and liquefied carbon dioxide. The temperature at which the LNG is managed is, for example, -162°C, and the temperature at which the liquefied carbon dioxide is managed is, for example, -50°C. The cargo may be liquefied petroleum gas (LPG) or any other liquefied gas. In addition, three or more types of liquefied gases, including two or more types of liquefied gases that have the same management temperature, may be exchanged in the cargo tank 1.

[0015] The cargo tank 1 comprises a tank body 11, piping 12, a heat insulating material 13, and a cover 14. As shown in the cross-sectional view of Fig. 2, the piping 12, the heat insulating material 13, and the cover 14 are provided in this order on the outside of the tank body 11. In Figs. 1 and 2, the piping 12, the heat insulating material 13, and the cover 14 are provided only on one side surface of the tank body 11, but it is preferable to provide them on both side surfaces of the tank body 11, and for example, both side surfaces of the cargo tank 1 are configured symmetrically.

[0016] The tank body 11 is a tank for storing cargo therein. For example, the tank body 11 is a bi-lobe tank of type C. The tank body 11 may be of any type and any shape. As shown in the cross-sectional view of FIG. 3, the tank body 11a may be a mono-lobe type (cylinder type).

[0017] The piping 12 is provided to heat the inside of the tank body 11, and forms a path through which the heat medium flows. The heat medium is heated by a heater 5 of a temperature control system 10 shown in FIG. 4. For example, the heat medium is a glycol liquid. The glycol liquid is an antifreeze liquid. The heat medium may be any substance as long as it is a fluid that flows through the piping 12.

[0018] The piping 12 is provided on the surface of the tank body 11. The piping 12 is provided so as to cover a wide area of ​​the surface of the tank body 11. For example, the piping 12 is attached to the surface of the tank body 11 so as to turn back multiple times along the longitudinal direction of the tank body 11. The piping 12 is provided so as to cover the vicinity of the equator of the tank body 11. Here, the equator is the part of the tank body 11 that bulges most in the horizontal direction. The vicinity of the equator is the area in the vicinity including the equator, for example, the part located in the middle when the height of the internal space of the tank body 11 is divided into thirds.

[0019] The shape of the path of the piping 12 provided in the tank body 11 may be any shape. The piping 12 may be branched at any point. By branching the piping 12, which is the path of the heat medium, the distance of the closed circuit of the path including the heater 5 and the tank body 11 can be shortened. This shortens the travel distance of the heat medium from the heater 5 to the tank body 11, so that the heat medium can efficiently heat the tank body 11.

[0020] The heat insulating material 13 is provided on the tank body 11 so as to cover the entire piping 12 provided on the tank body 11. The heat insulating material 13 prevents heat generated from the piping 12 from escaping to the outside (atmosphere, etc.). The heat generated from the piping 12 is trapped inside the heat insulating material 13 (the space between the tank body 11 and the heat insulating material 13), so that the tank body 11 is efficiently heated.

[0021] The cover 14 is provided on the tank body 11 so as to cover the entire insulation material 13. The cover 14 protects the tank body 11, the piping 12, and the insulation material 13 inside the cover 14. Furthermore, the cover 14, together with the insulation material 13, prevents heat generated from the piping 12 from escaping to the outside. The cover 14 may have any function. For example, the cover 14 may be painted to prevent rust due to seawater or the like, and may have the role of supporting the insulation material 13 so as not to come off.

[0022] FIG. 4 shows a temperature control system 10 according to the present embodiment. The temperature control system 10 is a system for circulating a heat medium through a pipe 12 to heat the inside of the cargo tank 1. For example, the temperature control system 10 is used when the liquefied gas contained in the cargo tank 1 is replaced from LNG to liquefied carbon dioxide gas.

[0023] The temperature control system 10 includes a cargo tank 1, a heat medium tank 2, a pump 3, a check valve 4, a heater 5, a gate valve 6, a controller 7, and piping 8.

[0024] Here, a temperature control system 10 corresponding to one cargo tank 1 will be described, but the temperature control system 10 may control the temperatures of multiple cargo tanks 1. Any number of the various devices 2-7 constituting the temperature control system 10 may be provided for temperature control of one cargo tank 1, or may be shared for temperature control of multiple cargo tanks 1. The temperature control system 10 may be configured without providing one or more of the heat medium tank 2, pump 3, check valve 4, gate valve 6, and controller 7.

[0025] The check valve 4, the heater 5, and the gate valve 6 are connected by a pipe 8 through which the heat medium flows. The pipe 8 is connected to a pipe 12 provided on the surface of the cargo tank 1. By connecting the pipe 8 and the pipe 12, a closed circuit path is formed in which the heat medium circulates alternately between the heater 5 and the cargo tank 1.

[0026] Here, the piping 8 constituting the temperature control system 10 and the piping 12 constituting the cargo tank 1 are described separately, but it is not necessary to provide these piping 8, 12 separately. For example, the piping 8 constituting the temperature control system 10 and the piping 12 constituting the cargo tank 1 may be formed as the same piping. Furthermore, in the configuration described here, the piping 8 and the piping 12 may be interpreted as being mutually interchangeable, unless this contradicts the description.

[0027] The heat medium tank 2 stores a heat medium (e.g., glycol liquid) to be circulated through the pipes 8 and 12. The heat medium tank 2 is connected to the pipe 8 via the pump 3. The heat medium lost as it circulates through the pipes 8 and 12 is replenished by pumping the heat medium in the heat medium tank 2 to the pipe 8 by the pump 3.

[0028] The check valve 4 is provided in the pipe 8 and is a valve for preventing backflow. For example, the check valve 4 is provided on the input side of the heater 5.

[0029] The heater 5 is provided in the piping 8 and heats the circulating heat medium. The heat medium heated by the heater 5 circulates through the piping 12 provided in the cargo tank 1, thereby warming the surface of the cargo tank 1. The heat medium that has circulated through the piping 12 in the cargo tank 1 returns to the heater 5. The temperature of the heat medium drops as it warms the cargo tank 1, and is heated again by the heater 5. In this way, the heater 5 continues to heat the surface of the cargo tank 1 via the heat medium until the temperature inside the cargo tank 1 reaches a predetermined temperature.

[0030] The heater 5 starts heating operation when the contents of the cargo tank 1 are replaced with a liquefied gas with a higher management temperature (for example, when replacing LNG with liquefied carbon dioxide). The heater 5 stops heating operation when the internal temperature of the cargo tank 1 reaches a temperature at which the replaced liquefied gas can be injected. For example, the temperature at which liquefied gas can be injected is a temperature at which the injected liquefied gas does not solidify (in the case of liquefied carbon dioxide, a temperature at which it does not become dry ice), that is, a temperature at which no problems occur with the injected liquefied gas. The start and end of the heating operation of the heater 5 may be automatically controlled by a computer, or may be manually performed by an operator.

[0031] The gate valve 6 is a valve for cutting off the flow of the heat medium. For example, the gate valve 6 is provided on the outlet side of the piping 12 provided in the cargo tank 1. When the piping 12 provided in the cargo tank 1 branches into two or more paths, the gate valve 6 may be provided in each of the branched piping 12. This makes it possible to individually cut off the flow of the heat medium in the branched piping 12.

[0032] The controller 7 is mainly composed of a computer, and is a device that controls the temperature control system 10. The controller 7 may control any device that constitutes the temperature control system 10. The controller 7 does not have to be provided as an independent device. For example, the controller 7 may be implemented as a part of a device such as the heater 5, or may be implemented as a part of an integrated navigation system (INS).

[0033] For example, the controller 7 controls the temperature inside the cargo tank 1 via a heat medium by controlling the heater 5. The controller 7 outputs commands to start and end heating to the heater 5. When the controller 7 determines that the inside of the cargo tank 1 has reached a predetermined temperature based on the heating time by the heater 5 or a temperature sensor or the like provided in the cargo tank 1, it outputs a command to the heater 5 to end heating. The temperature sensor may be provided anywhere in the cargo tank 1, such as inside or on the surface of the cargo tank 1.

[0034] Furthermore, the controller 7 is not limited to controlling the heater 5, and may control any device, such as the various valves 4, 6, or the pump 3, and may control any number of devices. For example, the controller 7 may control the start or end of circulation of the heat medium, the amount or speed of the heat medium flowing through the pipe 12, or the amount of heat medium replenished from the heat medium tank 2 to the pipe 12, by controlling any device.

[0035] 5 is a configuration diagram showing the configuration of a ship 20 to which the cargo tank 1 according to this embodiment is applied. Note that the ship 20 may be equipped with the temperature control system 10 shown in FIG.

[0036] For example, the ship 20 is a tanker that alternates between LNG and liquefied carbon dioxide gas. The ship 20 transports LNG on the way to a destination and transports liquefied carbon dioxide gas on the way back from the destination. In this way, it is possible to transport LNG from a production site of LNG to a destination and return carbon dioxide emitted by the use of LNG to the production site of LNG.

[0037] A plurality of cargo tanks 1 are mounted inside the hull of the ship 20. For example, three cargo tanks 1 are arranged side by side in the longitudinal direction. The piping 12 provided in each cargo tank 1 is connected to the piping 8 provided in the hull so as to be connected to each other. The piping 8 corresponds to the piping 8 of the temperature control system 10 shown in FIG. 4. The piping 8 may be provided in any manner in the hull. For example, the piping 8 may be branched or joined at any point. The piping 12 provided in each cargo tank 1 may be independent of each other without being connected to each other. In this case, each cargo tank 1 is connected to a separate heater 5 and can be heated separately and independently.

[0038] A heat medium tank 2, a pump 3, and a heater 5 are provided on the deck of the ship 20. The heat medium tank 2, the pump 3, and the heater 5 may be provided inside a building provided on the deck of the ship 20 to protect them from the external environment such as salt damage. The heater 5 is provided so as to be connected via a pipe 8 to a pipe 12 provided in each cargo tank 1. The heater 5 is not limited to being one, and multiple heaters 5 may be provided. For example, the heater may be provided corresponding to each cargo tank 1, or may be provided so as to be shared by all or some of the cargo tanks 1.

[0039] The ship 20 may be provided with a plurality of heat medium tanks 2 and pumps 3. For example, when the pipes 8, 12 through which the heat medium circulates are separated into a plurality of paths, the heat medium tanks 2 and pumps 3 are provided so that the heat medium flowing through all the paths can be replenished.

[0040] According to this embodiment, the temperature of the outer shell of the cargo tank 1 can be quickly heated by mounting the cargo tank 1, which has the pipes 12 through which a heat medium flows, on the ship 20. As a result, when the contents of the cargo tank 1 are replaced with liquefied gas that is managed at a higher temperature, the temperature inside the cargo tank 1 can be quickly raised, and the time required to replace the contents of the cargo tank 1 can be shortened.

[0041] However, additional advantages and modifications may readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific detailed representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. [Explanation of symbols]

[0042] 1...cargo tank, 2...heat medium tank, 3...pump, 4...check valve, 5...heater, 6...gate valve, 7...controller, 8...piping, 10...temperature control system, 11...tank body, 12...piping, 13...insulation material, 14 cover.

Claims

1. The tank body stores two types of liquefied gas that are managed at different temperatures, A pipe provided on a surface of the tank body through which a heat medium flows to change a temperature inside the tank body; A heat insulating material provided on a surface of the tank body so as to cover the piping; a cover provided on a surface of the tank body so as to cover the piping and the heat insulating material; A cargo tank comprising:

2. The piping, the heat insulating material, and the cover are provided on both side surfaces of the tank body, respectively.

2. A cargo tank according to claim 1 .

3. The piping is branched into two or more.

2. A cargo tank according to claim 1 .

4. The tank body of the cargo tank which alternately stores two types of liquefied gas that are managed at different temperatures, A pipe provided on a surface of the tank body through which a heat medium flows to change a temperature inside the tank body; A heat insulating material provided on a surface of the tank body so as to cover the piping; A cover provided on a surface of the tank body so as to cover the piping and the heat insulating material; A device for heating the heat medium; A cargo tank temperature control system comprising:

5. A heat transfer medium tank for replenishing the heat transfer medium 5. The cargo tank temperature control system according to claim 4, further comprising:

6. The hull and A tank body of a cargo tank provided in the hull and configured to alternately store two types of liquefied gases having different temperatures; A pipe provided on a surface of the tank body through which a heat medium flows to change a temperature inside the tank body; A heat insulating material provided on a surface of the tank body so as to cover the piping; A cover provided on a surface of the tank body so as to cover the piping and the heat insulating material; A device for heating the heat medium; A ship comprising:

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