Cargo tank

Abstract

A cargo tank (1) includes: a tank body (11) that replaces and stores two types of liquefied gases having different managed temperatures; piping (12) that is provided on the surface of the tank body (11) and through which a heat medium flows to heat the inside of the tank body (11); a flexible first heat insulating material (131) provided to cover the piping (12); and a second heat insulating material (132) having a higher heat insulating effect than the first heat insulating material (131) and being provided to cover the first heat insulating material (131).

Description

Cargo tank

[0001] The present invention relates to a cargo tank for storing cargo.

[0002] Generally, ships for loading and transporting liquefied gases such as LNG (liquefied natural gas) in cargo tanks are known. For example, an LNG ship capable of suppressing the heel amount and efficiently cooling the cargo tank is disclosed (see Patent Document 1).

[0003] However, the temperature to be controlled varies depending on the type of liquefied gas. When changing the temperature of the outer shell of the cargo tank, if the steel weight of the tank body is large, the heat capacity possessed by the tank body is large, so it takes time to heat and cool the tank. Therefore, it takes time to replace the contents of the cargo tank with another substance having a different temperature to be controlled.

[0004] Generally, cooling of the tank is performed by granule spraying (spraying) a cold cargo from the inside. On the other hand, heating is carried out by circulating a heated gas of the cold cargo in the tank. For this reason, cooling is smoothly performed because heat transfer is good, but heating has poor heat transfer and takes several times as long as the cooling time.

[0005] On the other hand, a low-temperature pressure tank capable of transporting carbon dioxide is called a type-C tank, and a pressure of at least 0.6 MPa is required to transport liquefied CO2. For this reason, the outer shell of the tank is thick and the weight of the tank increases. That is, a tank capable of transporting carbon dioxide is a tank that is difficult to cool and difficult to warm. For example, after transporting LNG, when loading carbon dioxide, the weight of the tank must be considered in order to heat the temperature of the outer shell of the tank to a temperature suitable for transporting carbon dioxide (around -50°C).

[0006] Here, we will explain the thermal stress on the tank shell that occurs during cooling or heating. Generally, it is said that in order to keep the thermal stress of the tank's steel material at a safe level, the temperature gradient should be kept to 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. On the other hand, in the case of heating, since heating is done by gas circulation, only a temperature rise of about 2°C / hour can be expected. In other words, it would theoretically take 36 hours to heat from -162°C to -50°C. Therefore, if the weight of the tank increases, it will become impossible to complete cargo transshipment operations within a reasonable time.

[0007] Japanese Patent Publication No. 2019-34665

[0008] An object of the embodiments of the present invention is to provide a cargo tank that shortens the time required to raise the temperature of the tank body.

[0009] A cargo tank according to the aspects of the present invention comprises a tank body for exchanging and storing two types of liquefied gases with different controlled temperatures; piping provided on the surface of the tank body through which a heat transfer medium flows to heat the inside of the tank body; a flexible first insulating material provided to cover the piping; and a second insulating material having a higher insulating effect than the first insulating material and provided to cover the first insulating material.

[0010] Figure 1 is a perspective view showing the configuration of a cargo tank according to the first embodiment of the present invention. Figure 2 is a configuration diagram showing the configuration of the piping portion provided on the surface of the tank body according to the first embodiment. Figure 3 is a configuration diagram showing the mounting state of the mounting fixture according to the first embodiment. Figure 4 is a plan view showing the configuration of a washer and pad according to the first embodiment. Figure 5 is an image diagram showing the state in which the piping is attached to the tank body according to the first embodiment. Figure 6 is a configuration diagram showing the configuration of the temperature control system according to the first embodiment. Figure 7 is a configuration diagram showing the configuration of a ship to which the cargo tank according to the first embodiment of this invention is applied. Figure 8 is a perspective view showing the configuration of a cargo tank according to the second embodiment of the present invention. Figure 9 is a configuration diagram showing the configuration of the piping portion provided on the surface of the tank body according to the second embodiment. Figure 10 is an image diagram showing the state in which the piping is attached to the tank body according to the second embodiment.

[0011] (First Embodiment) Figure 1 is a perspective view showing the configuration of a cargo tank 1 according to the first embodiment of the present invention. Figure 2 is a configuration diagram showing the configuration of a portion of the piping 12 provided on the surface of the tank body 11 according to this embodiment, and is a view of the tank body 11 from the front. The same parts in the drawings are denoted by the same reference numerals, and redundant explanations are omitted as appropriate.

[0012] Cargo tank 1 is a tank installed on a ship for loading cargo. Cargo tank 1 contains at least two types of liquefied gases with different controlled temperatures, which are alternately stored inside the tank. Therefore, the controlled temperature inside cargo tank 1 is changed according to the type of liquefied gas being stored.

[0013] For example, the cargo may be 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 also be liquefied petroleum gas (LPG) or any other liquefied gas. Furthermore, three or more types of liquefied gases, including two or more types of liquefied gases that are managed at the same temperature, may be transferred to cargo tank 1.

[0014] The cargo tank 1 comprises a tank body 11, piping 12, flexible insulation material 131, hardened insulation material 132, partition cover 14, heat shielding material 15, and mounting fixtures 20. Figure 1 shows the tank body with the hardened insulation material 132 removed. Although one side of the tank body 11 is shown, both sides of the tank body 11 are assumed to be symmetrical. However, the sides of the tank body 11 do not have to be symmetrical, and a heating mechanism for the tank body 11 may be provided on only one side. Furthermore, a cover may be provided to cover the entire tank body 11 covered with the hardened insulation material 132, and the cover may be painted to prevent rust caused by seawater, etc.

[0015] In Figures 1 and 2, the outbound and return sections of the U-shaped pipe 12 are attached as a set to the surface of the tank body 11. Hereafter, the outbound and return sections of the U-shaped pipe 12 may be described as separate pipes 12, that is, as two separate pipes 12.

[0016] The tank body 11 is a tank that forms the outer shell of the tank and houses cargo inside. For example, the tank body 11 is a type C bilobe-type tank. The tank body 11 can be of any type or shape. For example, the tank body 11 can be monolobe-type (cylinder-type), cylindrical or a combination of cylindrical shapes, or rectangular or a combination of rectangular shapes.

[0017] The piping 12 is provided to heat the inside of the tank body 11 and forms a path through which a heat transfer medium flows to heat the tank body 11. For example, the heat transfer medium is glycol liquid. Glycol liquid is antifreeze. Note that the heat transfer medium can 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. Specifically, multiple U-shaped pipes 12 are fixed in parallel to the surface of the tank body 11. For example, for every 1 meter of width of the surface of the tank body 11, two or three sets of U-shaped pipes 12 are arranged, with one set for each direction. Therefore, if the height of the tank body 11 is 10 meters, approximately 10 to 20 sets of pipes 12 are arranged on just one side of the tank body 11.

[0019] Furthermore, there may be any number of pipes 12, they may be of any shape, and they may be branched at any point. For example, a U-shaped pipe 12 may be made up of two or more pipes 12 joined together. It is desirable that the pipes 12 be formed so that the path of the heat transfer medium does not form a single path (a path that can be drawn in one continuous line). This is because if the path of the heat transfer medium is a single path, the heat transfer medium flowing in the latter half of the path will cool down, and the efficiency of heating the tank body 11 will decrease.

[0020] The insulating materials 131 and 132, under normal circumstances (such as during cargo transport), serve to prevent heat from entering the cargo tank 1 from the outside. When the cargo tank 1 is heated, the insulating materials 131 and 132 also serve to prevent heat generated from the piping 12 from escaping to the outside (atmosphere, etc.). This allows the tank body 11 to be heated efficiently. Note that the insulating materials 131 and 132 may also be called heat-insulating materials or heat-shielding materials, as long as they perform the above-mentioned functions.

[0021] The insulation materials 131 and 132 form a first layer and a second layer, respectively. The first layer is made of flexible insulation material 131. The second layer is made of hardened insulation material 132. The flexible insulation material 131 and the hardened insulation material 132 are separated by a partition cover 14. The partition cover 14 is optional. Furthermore, the insulation materials 131 and 132 are not limited to the configurations described herein. For example, each insulation material 131 and 132 may be formed by layering multiple materials to improve insulation performance, resulting in two or more layers of insulation material. Also, because the hardened insulation material 132 is thick, it may be formed by layering two or more layers of the same material.

[0022] The flexible insulation material 131 is an insulation material that is flexible enough to allow thermal deformation of the pipe 12. The flexibility that allows thermal deformation of the pipe 12 means that the insulation material elastically deforms in accordance with the thermal deformation of the pipe 12, so that the pipe 12 is not damaged. The flexible insulation material 131 can be any material as long as it is flexible enough to allow thermal deformation of the pipe 12. For example, the flexible insulation material 131 may be a resin such as melamine that has been molded, or it may be a foamed insulation material formed by the solidification of a spray-foamed foaming agent.

[0023] The hardened insulation material 132 has a higher insulation effect and is harder than the flexible insulation material 131. For example, the hardened insulation material 132 is a foamed plastic insulation material, such as polyurethane. However, the hardened insulation material 132 is not limited to foamed insulation materials; any type of insulation material may be used.

[0024] The flexible insulation material 131 is provided so as to cover the entire circumference of the surface of the two pipes 12 (one set of pipes 12 that make up the U-shaped pipe 12). The hardened insulation material 132 is provided so as to cover the outer circumference of the two pipes 12 that are covered with the flexible insulation material 131. The flexible insulation material 131 may also be provided together with the mounting fixture 20 and the heat shielding material 15 so as to cover the pipes 12.

[0025] The insulation materials 131 and 132 may be formed by any process. For example, they may be formed as follows: First, foam to form the flexible insulation material 131 is sprayed onto the pipe 12 so as to cover the entire circumference of the surface of the pipe 12. Next, foam to form the hardened insulation material 132 is sprayed onto the area around the hardened flexible insulation material 131. Alternatively, the flexible insulation material 131 may be formed by attaching a molded flexible insulation material 131 to the pipe 12.

[0026] The partition cover 14 covers the flexible insulation material 131 and is provided to partition the space between the flexible insulation material 131 and the hardened insulation material 132. For example, the partition cover 14 protects the piping 12 and the flexible insulation material 131 located inside. The partition cover 14, together with the insulation materials 131 and 132, also prevents heat generated from the piping 12 from escaping to the outside. Furthermore, it may also serve to support the flexible insulation material 131 so that it does not come loose. The partition cover 14 may have any function whatsoever.

[0027] The heat shield 15 is attached to the surface of the tank body 11 to prevent the piping 12 from directly contacting the tank body 11. The heat shield 15 prevents the cold from the cargo (LNG, etc.) inside the tank body 11 from being transferred to the piping 12. This prevents the heat transfer medium (e.g., glycol liquid) flowing through the piping 12 from freezing due to the cold from the cargo (LNG, etc.) inside the tank body 11 passing through the outer shell of the tank body 11, and at the same time prevents the tank body 11 from becoming partially overheated. Furthermore, if the piping 12 stretches due to thermal deformation, the heat shield 15 has the function of reducing friction between the tank body 11 and the piping 12 so as not to hinder the movement of the piping 12 due to the stretching. For example, the heat shield 15 is a plate-shaped fluororesin. The heat shield 15 is provided at the location where the piping 12 is fixed to the surface of the tank body 11.

[0028] The heat shield 15 may be installed in any section of the piping 12, but it is not necessary to install it over the entire area between the surface of the tank body 11 and the piping 12. In areas between the surface of the tank body 11 and the piping 12 where there is no heat shield 15, a flexible heat insulating material 131 is installed. The heat shield 15 may be called a heat insulating material or heat shielding material as long as it fulfills the above-mentioned role. The heat shield 15 may not be installed if there is no risk of the heat transfer medium flowing through the piping 12 freezing.

[0029] The piping 12 is fixed to the surface of the tank body 11 with a mounting bracket 20, on top of a heat-shielding material 15. The mounting bracket 20 is a device that allows the piping 12 to move relative to the tank body 11 in the event of thermal deformation of the piping 12.

[0030] The mounting fixture 20 includes a U-shaped bolt 21 and a stud bolt 22. The stud bolt 22 is a bolt fixed to the surface of the tank body 11. The U-shaped bolt 21 is a U-shaped bolt that fixes the piping 12 so as to press it against the surface of the tank body 11. The U-shaped bolt 21 is also connected to the stud bolt 22 via a washer 23. The U-shaped bolt 21 is fixed to the stud bolt 22 with a predetermined range of motion in the up, down, left, and right directions parallel to the surface of the tank body 11 (particularly in the longitudinal direction of the piping 12).

[0031] The configuration of the mounting fixture 20 will be described with reference to Figures 3 and 4. Figure 3 is a configuration diagram showing the mounting state of the mounting fixture 20. Figure 3 shows one side of the mounting portion of the U-bolt 21, but the other side is assumed to be in a similar mounting state. Figure 4 is a plan view showing the configuration of the washer 23 and pad 26.

[0032] The mounting fixture 20 is not limited to the configuration described herein; any configuration is acceptable as long as it is configured such that the pipe 12 moves relative to the tank body 11 due to thermal deformation of the pipe 12.

[0033] The U-shaped bolt 21 is fixed to the stud bolts 22 located on each side via washers 23 provided on each side. The U-shaped bolt 21 is inserted into the hole H1 of the washer 23. The hole H1 is a hole that extends in the longitudinal direction of the pipe 12. For example, the hole H1 is a rectangular shape with both ends in the longitudinal direction rounded (e.g., a semicircle). The U-shaped bolt 21 is fixed to the washer 23 with a double nut consisting of a first nut 24 and a second nut 25. Between the double nuts 24, 25 and the washer 23, there is a ring-shaped pad 26 with a hole H3 into which the U-shaped bolt 21 is inserted. For example, the pad 26 is made of fluororesin. The pad 26 is provided so that the U-shaped bolt 21 does not come out of the hole H1 of the washer 23. The double nuts 24, 25 may be single nuts. For example, a single nut can be used by tack welding or by adding a washer to prevent the nut from coming off.

[0034] The stud bolt 22 is inserted into a circular hole H2 that is slightly larger than the diameter of the stud bolt 22. The stud bolt 22 is secured to the washer 23 with a double nut consisting of a first nut 27 and a second nut 28. The double nuts 27 and 28 may also be single nuts, similar to the double nuts 24 and 25.

[0035] Furthermore, tack welding may be performed on any part of the mounting fixture 20 while it is installed. For example, tack welding may be performed on the two nuts 24 and 25 that constitute the double nut on the U-bolt 21 side, the two nuts 27 and 28 that constitute the double nut on the stud bolt 22 side, or on the washer 23 and nut 27.

[0036] The role of the washer 23 will now be explained. The washer 23 is fixed to the tank body 11 by a stud bolt 22 inserted into the hole H2. When the piping 12 stretches longitudinally due to thermal deformation, the U-shaped bolt 21 inserted into the longitudinally elongated hole H1 of the washer 23 moves within the range of the shape of the hole H1 in response to the thermal deformation of the piping 12. In this way, the U-shaped bolt 21 moves in response to the thermal deformation of the piping 12 while maintaining the state in which the piping 12 is attached to the surface of the tank body 11, thereby preventing damage to the piping 12.

[0037] The shape and size of the hole H1 provided in the washer 23 may be freely determined. Preferably, the hole H1 is long in the longitudinal direction of the pipe 12, but any shape is acceptable. For example, the shape of the pipe 12 may be elliptical, rectangular, or spindle-shaped, or any other arbitrary shape. For example, the horizontal (longitudinal) length of the hole H1 is approximately 10 mm to approximately 170 mm, and the vertical (perpendicular to the longitudinal direction) length of the hole H1 is approximately 8 mm.

[0038] Figure 5 is an illustrative diagram showing the tank body 11 with the piping 12 attached. Figure 5 shows the state with the partition cover 14 and insulation materials 131 and 132 removed. The arrows in the figure indicate the direction in which the heat transfer medium flows.

[0039] By using the U-shaped pipe 12, the inlet and outlet of the pipe 12 are located on the same side in the longitudinal direction, and the other side in the longitudinal direction becomes the U-shaped portion of the pipe 12. The inlet and outlet of the pipe 12 are fixed by being connected to the supply-side pipe 8. On the other hand, the U-shaped portion of the pipe 12 is not fixed. Thus, even if the pipe 12 undergoes thermal deformation in the longitudinal direction, the pipe 12 can extend toward the U-shaped portion. Therefore, by allowing the pipe 12 to undergo thermal deformation in the longitudinal direction, the influence on the supply-side pipe 8 connected to the pipe 12 can be reduced.

[0040] The heat insulating material 15 is provided at the location where the pipe 12 is attached by the fixture 20 (such as the U-bolt 21 and washer 23, etc.). That is, the heat insulating material 15 is provided at the portion where the adhesion between the surface of the tank body 11 and the pipe 12 is high. Thereby, freezing of the heat medium flowing through the pipe 12 is prevented by the cold heat from the cargo (such as LNG, etc.) in the cargo tank 1.

[0041] Here, for the sake of convenience of explanation, the pipe 12 attached to the tank body 11 and the supply-side pipe 8 to which the heat medium is supplied have been described separately, but these pipes 8 and 12 do not necessarily need to be clearly distinguished.

[0042] FIG. 6 is a configuration diagram showing the configuration of the temperature control system 10 according to the present embodiment. Note that the temperature control system 10 is not limited to the configuration described here and may be configured in any way.

[0043] The temperature control system 10 is a system for flowing a heat medium through the pipe 12 and heating the inside of the cargo tank 1. For example, the temperature control system 10 is used when replacing the liquefied gas stored in the cargo tank 1 from LNG to liquefied carbon dioxide gas.

[0044] 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 shut-off valve 6, a controller 7, a pipe 8, a valve 9, a recovery tank 31, and a transfer pump 32. The pipe 8 corresponds to the supply-side pipe 8 shown in FIG. 5.

[0045] Here, a temperature control system 10 corresponding to one cargo tank 1 will be described. However, the temperature control system 10 may control the temperatures of a plurality of cargo tanks 1. The various devices 2 to 7, 9, 31, 32 constituting the temperature control system 10 may be provided in any number for the temperature control of one cargo tank 1, or may be shared in the temperature control of a plurality of cargo tanks 1.

[0046] The check valve 4, the heater 5, and the shut-off 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. When the pipe 8 of the temperature control system 10 is connected to the pipe 12 provided on the cargo tank 1, a closed-circuit path is formed in which the heat medium circulates alternately between the heater 5 and the cargo tank 1.

[0047] The heat medium tank 2 stores a heat medium (for example, glycol solution) for circulating the pipes 8 and 12. The heat medium tank 2 is connected to the pipe 8 via a pump 3. The heat medium that has disappeared by circulating through the pipes 8 and 12 is replenished by the heat medium in the heat medium tank 2 being sent out to the pipe 8 by the pump 3.

[0048] 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.

[0049] The heater 5 is provided in the pipe 8 and heats the circulating heat medium. The heat medium heated by the heater 5 heats the surface of the cargo tank 1 by circulating through the pipe 12 provided on the cargo tank 1. The heat medium that has circulated through the pipe 12 of the cargo tank 1 returns to the heater 5. The heat medium cools down by heating the cargo tank 1 and is reheated by the heater 5 again. In this way, the heater 5 continuously heats the surface of the cargo tank 1 via the heat medium until the temperature inside the cargo tank 1 reaches a predetermined temperature.

[0050] Heater 5 starts heating when the contents of cargo tank 1 are replaced with a liquefied gas that requires a higher temperature (for example, when replacing LNG with liquefied carbon dioxide). Heater 5 stops heating when the internal temperature of 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 the temperature at which the injected liquefied gas does not solidify (in the case of liquefied carbon dioxide, the temperature at which it does not turn into dry ice), that is, the temperature at which no problems occur with the injected liquefied gas. The start and end of the heating operation of heater 5 may be automatically controlled by a computer or manually by an operator.

[0051] The gate valve 6 is a valve for blocking the flow of the heat transfer medium. For example, the gate valve 6 is installed on the outlet side of the piping 12 provided in the cargo tank 1. If the piping 12 provided in the cargo tank 1 branches into two or more paths, the gate valve 6 may be installed in each of the branched pipes 12. This makes it possible to individually block the flow of the heat transfer medium in the branched pipes 12.

[0052] Controller 7 is a device primarily composed of a computer that controls the temperature control system 10. Controller 7 may control any of the components of the temperature control system 10. Controller 7 does not have to be provided as a separate, independent device. For example, Controller 7 may be implemented as part of a device such as a heater 5, or as part of a ship's integrated automation system (IAS).

[0053] For example, the controller 7 controls the temperature inside the cargo tank 1 via a heat transfer medium by controlling the heater 5. The controller 7 outputs commands to the heater 5 to start and stop heating. When the controller 7 determines that the temperature inside the cargo tank 1 has reached a predetermined temperature based on the heating time by the heater 5 or a temperature sensor installed in the cargo tank 1, it outputs a command to the heater 5 to stop heating. The temperature sensor may be installed anywhere in the cargo tank 1, such as inside or on the surface of the cargo tank 1.

[0054] Furthermore, the controller 7 is not limited to controlling the heater 5, but may control any of the equipment, such as the various valves 4, 6, 9 or the various pumps 3, 32, etc., and may control any number of pieces of equipment. For example, the controller 7 may control the start or end of the circulation of the heat transfer medium, the amount or speed of the heat transfer medium flowing through the piping 12, or the amount of heat transfer medium to be replenished from the heat transfer medium tank 2 to the piping 12 by controlling any equipment.

[0055] The heat transfer fluid sealed in the pipes 8 and 12 is removed before loading cargo (e.g., LNG) to prevent freezing within the pipes 8 and 12. For example, the heat transfer fluid is injected into the pipes 8 and 12 immediately before heating the cargo tank 1, and discharged from the pipes 8 and 12 after heating the cargo tank 1. For example, immediately before heating the cargo tank 1 is when the LNG has been completely removed from the cargo tank 1, and after heating the cargo tank 1 is when the injection of carbon dioxide into the cargo tank 1 begins.

[0056] The recovery tank 31 is a tank for recovering the heat transfer medium discharged from the pipes 8 and 12. For example, the outlet for the heat transfer medium is located at the bottom of the pipe 12 installed in the cargo tank 1. The outlet of the pipe 12 is connected to the recovery tank 31 via a valve 9 so that the discharged heat transfer medium flows into the recovery tank 31. The heat transfer medium stored in the recovery tank 31 is reused when the cargo tank 1 is heated again.

[0057] Valve 9 is installed at the outlet of piping 12. When the heat transfer medium is to be discharged, valve 9 is opened. As a result, the heat transfer medium discharged from piping 12 is recovered in the recovery tank 31.

[0058] The transfer pump 32 is a pump for sending the heat transfer medium stored in the recovery tank 31 to the heat transfer medium tank 2. The transfer pump 32 is installed in the piping that allows the heat transfer medium to flow from the recovery tank 31 to the heat transfer medium tank 2.

[0059] By providing a recovery tank 31 and a transfer pump 32, the heat transfer medium discharged from the pipes 8 and 12 is recovered, and the recovered heat transfer medium is injected back into the pipes 8 and 12, thereby allowing the heat transfer medium to be reused repeatedly.

[0060] Furthermore, the system can be configured in any way as long as it is configured to recover the heat transfer medium from the pipes 8 and 12 and reuse the recovered heat transfer medium. For example, the destination of the heat transfer medium from the transfer pump 32 may be a tank for reuse that is separate from the heat transfer medium tank 2 that replenishes the heat transfer medium. Moreover, the recovery tank 31 and the transfer pump 32 do not have to be provided, and the heat transfer medium does not have to be reused.

[0061] Figure 7 is a configuration diagram showing the configuration of a vessel 30 to which the cargo tank 1 according to this embodiment is applied.

[0062] For example, ship 30 is a tanker that transports LNG and liquefied carbon dioxide by exchanging them. Ship 30 transports LNG on its way to its destination and liquefied carbon dioxide on its return trip. This allows LNG to be transported from its source to its destination, and the carbon dioxide emitted from the use of LNG can be returned to the LNG source.

[0063] A cargo tank 1 is installed inside the hull of the vessel 30. The number of cargo tanks 1 may vary, and they may be arranged in any way. The piping 12 of the cargo tank 1 is connected to piping 8 that supplies a heat transfer medium. The piping 8 may be installed in any way within the hull. For example, the piping 8 may be branched or connected at any point.

[0064] A heat transfer fluid tank 2, a pump 3, and a heater 5 are provided on the deck of the vessel 30. The heat transfer fluid tank 2, pump 3, and heater 5 may be installed inside a building on the deck of the vessel 30 to protect them from external environmental factors such as salt damage. The heater 5 is connected to the piping 12 provided to each cargo tank 1 via piping 8. There may be more than one heater 5. For example, one may be provided corresponding to each cargo tank 1, or one may be provided for common use by all or some of the cargo tanks 1.

[0065] The vessel 30 may be equipped with multiple heat transfer fluid tanks 2 and pumps 3. For example, if the pipes 8 and 12 through which the heat transfer fluid circulates are separated into multiple paths, heat transfer fluid tanks 2 and pumps 3 may be provided to replenish the heat transfer fluid flowing through all paths.

[0066] According to this embodiment, by mounting a cargo tank 1, which has a pipe 12 through which a heat transfer medium flows, on its surface, on a ship 30, the temperature of the outer shell of the cargo tank 1 can be rapidly heated. As a result, when replacing the contents of the cargo tank 1 with a liquefied gas that requires a higher temperature to be controlled, the internal temperature of the cargo tank 1 can be rapidly increased, and the time required to replace the contents of the cargo tank 1 can be shortened.

[0067] By covering the piping 12 installed in the cargo tank 1 with a flexible insulation material 131, and then covering the flexible insulation material 131 with a hardened insulation material 132 that has a high insulation effect, damage to the piping 12 due to thermal deformation can be prevented, and the piping 12 can be insulated.

[0068] By attaching the pipe 12 to the cargo tank 1 using a mounting fixture 20 configured such that the component (U-bolt 21) that secures the pipe 12 moves in response to the thermal deformation of the pipe 12, damage to the pipe 12 due to thermal deformation can be prevented.

[0069] By using a U-shaped pipe 12, the inlet and outlet of the pipe 12 are located on the same side in the longitudinal direction. Therefore, the U-shaped portion of the pipe 12 on the opposite side in the longitudinal direction is not connected to the pipe 8 that supplies the heat transfer medium. This allows the pipe 12 to stretch in the longitudinal direction due to thermal deformation, and prevents damage to the pipe 12.

[0070] By providing the heat shielding material 15 between the surface of the tank body 11 and the piping 12, it is possible to prevent the heat transfer medium flowing through the piping 12 from freezing due to the cold from the cargo (LNG, etc.) inside the cargo tank 1. (Second Embodiment) Figure 8 is a perspective view showing the configuration of a cargo tank 1A according to the second embodiment of the present invention.

[0071] Cargo tank 1A is the same as in the cargo tank 1 of the first embodiment, except that the U-shaped pipe 12 is replaced with a plurality of straight pipes 12A. Other aspects are the same as in the first embodiment.

[0072] Multiple straight pipes 12A are arranged in parallel parallel to the longitudinal direction of the cargo tank 1A and attached to the surface of the tank body 11. Pipes 8 that supply a heat transfer medium are connected to both ends of each pipe 12A in the longitudinal direction. One pipe 8 is the inlet side of the heat transfer medium, and the other pipe 8 is the outlet side of the heat transfer medium.

[0073] Figure 9 is a configuration diagram showing the configuration of the piping 12A provided on the surface of the tank body 11 according to this embodiment. Figure 9 is a view of the tank body 11 from the front.

[0074] The configuration of the piping 12A is the same as the configuration of the piping 12 according to the first embodiment shown in Figure 2, except that each piping 12A is covered with a flexible insulation material 131. Specifically, the piping 12A is covered all around its surface with a flexible insulation material 131 as a first layer, and then the entire perimeter is covered with a hardened insulation material 132 over the flexible insulation material 131.

[0075] Figure 10 is an illustrative diagram showing the tank body 11 with the piping 12A attached. Figure 10 shows the state with the partition cover 14 and insulation materials 131 and 132 removed. The arrows in the figure indicate the direction in which the heat transfer medium flows.

[0076] Multiple straight pipes 12A are arranged in parallel on the surface of the tank body 11. Both ends of the pipes 12A in the longitudinal direction are connected to supply-side pipes 8 that supply the heat transfer medium. By arranging multiple straight pipes 12A in parallel, the distance over which the heat transfer medium circulates via the heater 5 is shortened. This allows for efficient heating of the surface of the tank body 11 by the heat transfer medium.

[0077] The heat shielding material 15 is provided in the same manner as in the first embodiment, and the freezing of the heat transfer medium flowing through the piping 12A is efficiently prevented by the cold heat from the cargo in the cargo tank 1.

[0078] According to this embodiment, even when a plurality of straight pipes 12A are used, the same effects and advantages as in the first embodiment can be obtained. Furthermore, by arranging a plurality of straight pipes 12 in parallel, the distance over which the heat transfer medium circulates via the heater 5 can be shortened compared to the configuration using the U-shaped pipe 12 according to the first embodiment, and the surface of the tank body 11 can be heated efficiently by the heat transfer medium.

[0079] Furthermore, additional advantages and modifications may readily arise for those skilled in the art. Therefore, the present invention in its broader aspects is not limited to the specific detailed and representative embodiments described herein. Accordingly, various modifications can be made without departing from the spirit or scope of the general concept of the invention as defined by the appended claims and their equivalents.

Claims

1. A cargo tank comprising: a tank body for exchanging and storing two types of liquefied gases with different controlled temperatures; piping provided on the surface of the tank body through which a heat transfer medium flows to heat the inside of the tank body; a flexible first insulating material provided to cover the piping; and a second insulating material having a higher insulating effect than the first insulating material and provided to cover the first insulating material.

2. The cargo tank according to claim 1, characterized in that the piping is installed such that it moves relative to the tank body due to thermal deformation of the piping.

3. The cargo tank according to claim 1, characterized in that, in order to prevent the heat transfer medium flowing through the piping from freezing, a heat shielding material is provided between the piping and the tank body to prevent the cold heat of the liquefied gas inside the tank body from being transferred to the piping.

4. The cargo tank according to claim 3, characterized in that the heat shielding material has the function of reducing friction between the piping and the tank body.

5. The cargo tank according to claim 1, characterized in that the piping includes a U-shaped portion on one side in the longitudinal direction, and the U-shaped portion is not fixed to the tank body.

6. The cargo tank according to claim 1, characterized in that the piping includes a plurality of straight pipes arranged in parallel and parallel to the longitudinal direction of the tank body.

7. A temperature control system for a cargo tank, comprising: a tank body for exchanging and storing two types of liquefied gases with different controlled temperatures; piping provided on the surface of the tank body through which a heat transfer medium flows to change the temperature inside the tank body; a flexible first insulating material provided to cover the piping; a second insulating material having a higher insulating effect than the first insulating material and provided to cover the first insulating material; and a heater for heating the heat transfer medium.

8. The temperature control system for a cargo tank according to claim 7, further comprising a heat transfer medium tank for replenishing the heat transfer medium.

9. The cargo tank temperature control system according to claim 7, further comprising a recovery tank for storing the heat transfer medium discharged from the piping, and a pump for sending the heat transfer medium stored in the recovery tank back to the piping for reuse.

10. A vessel comprising: a hull; a tank body provided on the hull for exchanging and storing two types of liquefied gases with different controlled temperatures; piping provided on the surface of the tank body through which a heat transfer medium flows to change the temperature inside the tank body; a flexible first insulating material provided to cover the piping; a second insulating material having a higher insulating effect than the first insulating material and provided to cover the first insulating material; and a heater for heating the heat transfer medium.

Images