cargo tank

Abstract

The cargo tank (1) comprises: an outer shell (11) for alternately accommodating two liquefied gases with different temperatures, including an inner wall with a curved shape formed by the central portion in the vertical direction bulging outwards in the horizontal direction; a first filling conduit provided for injecting at least one of the two liquefied gases into the interior of the outer shell (11), and having a first ejection hole at a height above the midpoint between the height of the central portion and the height of the deepest part of the interior space of the outer shell (11) so that the ejected liquefied gas flows along the curved shape of the inner wall; and a second filling conduit provided for injecting at least one of the two liquefied gases into the interior of the outer shell (11), and having a second ejection hole so that the liquefied gas is ejected towards the bottom surface of the outer shell (11).

Description

Technical Field

[0001] This invention relates to a cargo tank for containing goods. Background Technology

[0002] Typically, ships that transport liquefied gases such as LNG (liquefied natural gas) by loading them into cargo tanks are known. For example, an LNG carrier that can suppress residual liquid and efficiently cool the cargo tanks has been disclosed (see Patent Document 1).

[0003] However, the controlled temperature varies depending on the type of liquefied gas. Therefore, problems can sometimes arise when replacing the contents of a cargo tank with a substance that requires a different controlled temperature. For example, when replacing LNG (which has a low controlled temperature) with liquefied carbon dioxide (which has a high controlled temperature), if the carbon dioxide is injected into the tank too early, it will solidify (become dry ice). To avoid this problem, the tank needs to be preheated before the replacement, but due to the large heat capacity of the tank body, preheating takes time.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2019-34665 Summary of the Invention

[0005] The purpose of this invention is to provide a cargo tank suitable for replacing two liquefied gases with different temperatures in a shorter time.

[0006] According to the present invention, a cargo tank comprises: an outer shell for replacing and containing two liquefied gases at different temperatures, including an inner wall with a curved shape formed such that its central portion in the vertical direction bulges outward in the horizontal direction; a first filling conduit configured to inject at least one of the two liquefied gases into the interior of the outer shell, and having a first ejection port at a height above the midpoint between the height of the central portion and the height of the deepest part of the interior space of the outer shell, such that the ejected liquefied gas flows along the curved shape of the inner wall; and a second filling conduit configured to inject at least one of the two liquefied gases into the interior of the outer shell, and having a second ejection port for ejecting the liquefied gas toward the bottom surface of the outer shell. Attached Figure Description

[0007] Figure 1 This is a configuration diagram showing the structure of the cargo tank according to an embodiment of the present invention.

[0008] Figure 2 This is a cross-sectional view simply showing the location of the piping of the first filling pipeline in this embodiment.

[0009] Figure 3 This is a configuration diagram showing the structure of a ship using a cargo tank according to this embodiment. Detailed Implementation

[0010] (Implementation Method) Figure 1 This is a structural diagram illustrating the configuration of the cargo tank 1 according to an embodiment of the present invention. It should be noted that the same reference numerals are used for the same parts in the drawings, and repetitive descriptions are omitted where appropriate.

[0011] Cargo tank 1 is installed on a ship and is a hold used for loading cargo. At least two liquefied gases with different controlled temperatures are replaced within cargo tank 1. Therefore, the controlled temperature inside cargo tank 1 varies depending on the type of liquefied gas contained.

[0012] Cargo tank 1 is a type C, bi-lobe compartment. Figure 1 The diagram shows one side of the double-lobed design, revealing its internal structure. The other side of the double-lobed design is also similar. Figure 1 It is symmetrically arranged. Therefore, a similar structure is also provided on the opposite side (not shown) of cargo tank 1. Figure 1 The same cargo tanks are used. It should be noted that... Figure 1 The configuration shown can be configured only on one side of the cargo tank 1, or for any equipment, only one can be installed in the cargo tank 1.

[0013] It should be noted that the cargo tank 1 can be of any type and shape. For example, the cargo tank 1 can also be a single-lobed (cylindrical) type. In this case, the cargo tank 1 is configured to be symmetrical from left to right, but the equipment located near the center of the cargo tank 1 can be only one. For example, the second filling pipe 14 can be provided at the deepest part of the bottom surface, and the third filling pipe 15 can be provided at the top.

[0014] For example, the cargo consists of LNG and liquefied carbon dioxide. The temperature for managing the LNG is, for example, -162°C, and the temperature for managing the liquefied carbon dioxide is, for example, -50°C. The cargo can be liquefied petroleum gas (LPG) or any other liquefied gas. Furthermore, three or more liquefied gases, containing two or more types of liquefied gases at the same managed temperature, can be substituted in cargo tank 1.

[0015] Cargo tank 1 includes an outer shell 11, a skeleton component 12, a first filling pipeline 13, a second filling pipeline 14, a third filling pipeline 15, three valves 16a, 16b, and 16c, and a hatch 17. It should be noted that cargo tank 1 may also include any components or equipment not described herein. For example, a pump for loading and unloading or a temperature sensor for managing the internal temperature of cargo tank 1 may be installed in cargo tank 1.

[0016] The outer shell 11 is the portion that covers the outside of the cargo tank 1. The interior space of the outer shell 11 serves as a space for containing the liquefied gas, which is the cargo in the cargo tank 1. The outer shell 11 has a shape suitable for containing liquefied gas compressed under high pressure. For example, the outer shell 11 is a curved shape formed with its central portion in the vertical direction bulging out most in the horizontal direction. For example, the cross-sectional shape of the outer shell 11 is a circle, an ellipse, or a combination of these shapes. Specifically, the outer shell 11 is a double-lobed shape or a single-lobed shape.

[0017] The rib members 12 are components that support and reinforce the outer shell 11. The rib members 12 are provided at fixed intervals on the inner wall of the outer shell 11 along its longitudinal direction. Each rib member 12 is arranged to surround the inner circumference in a direction perpendicular to the longitudinal direction of the outer shell 11.

[0018] The first filling line 13 is a piping used to inject liquefied gas (including gas in its gaseous state) as cargo into the cargo tank 1. The first filling line 13 is used when replacing a low-density liquefied gas (e.g., LNG) with a high-density liquefied gas (e.g., liquefied carbon dioxide).

[0019] The first filling conduit 13 includes: a conduit 131 extending vertically into the interior of the cargo tank 1 from the hatch 17; and a conduit 132 having a plurality of nozzles H13 for ejecting liquefied gas, respectively located on both sides (left and right sides) of the outer casing 11 in a direction perpendicular to its longitudinal dimension, extending horizontally near the equator of the inner wall of the outer casing 11. Here, the equator refers to the most bulging part of the outer casing 11 in the horizontal direction. The nozzles H13 are provided at fixed intervals in the conduit 132 along the longitudinal dimension of the outer casing 11. The nozzles H13 are arranged such that the ejected liquefied gas flows along the inner wall of the outer casing 11 from near the equator to the bottom surface. Thus, the liquefied gas ejected from the nozzles H13 flows from near the equator to the bottom surface while heating the inner wall of the outer casing 11. It should be noted that all the conduits 132 with nozzles H13 can be connected as one. For example, the pipes 132 are symmetrically arranged on the left and right sides of the inner wall of the housing 11, but the left and right pipes 132 can also be connected to each other, and the pipes 132 can also be configured to surround the inner wall.

[0020] For example, the first filling conduit 13 is fixed to the bone member 12. It should be noted that the first filling conduit 13 can be fixed to the inner wall of the outer shell 11 in any way, or it can be fixed to a part other than the bone member 12. For example, the first filling conduit 13 can be directly fixed to the outer shell 11, or a separate component can be provided for fixing the first filling conduit 13.

[0021] The second filling line 14 is a piping used to inject liquefied gas (including its gaseous state) as cargo into the cargo tank 1. The second filling line 14 is used in either the replacement of a low-density liquefied gas (e.g., LNG) with a high-density liquefied gas (e.g., liquefied carbon dioxide) or the replacement of a high-density liquefied gas (e.g., liquefied carbon dioxide) with a low-density liquefied gas (e.g., LNG). The second filling line 14 is used to improve the replacement efficiency by performing gas replacement in the cargo tank 1 in a layered manner. Specifically, the two gases to be replaced are formed into layers, and while the two layers are separated, one gas is injected into the cargo tank 1 while the other gas is discharged from the cargo tank 1. Furthermore, the second filling line 14 is also used to discharge liquefied gas (including its gaseous state) accumulated at the bottom of the cargo tank 1.

[0022] The second filling conduit 14 includes: a conduit 141 extending vertically from the hatch 17 into the interior of the cargo tank 1; and a conduit 142 having a plurality of nozzles H14 for ejecting liquefied gas, extending along the longitudinal direction of the outer casing 11 near the deepest part of the bottom surface. The nozzles H14 are provided at fixed intervals along the longitudinal direction of the outer casing 11 in the conduit 142. The nozzles H14 are arranged to eject liquefied gas toward the deepest part of the outer casing 11. The liquefied gas ejected from the nozzles H14 gradually accumulates from the deepest part of the bottom surface of the outer casing 11.

[0023] The vertically extending pipe 141 of the second filling conduit 14 and the vertically extending pipe 131 of the first filling conduit 13 are joined together as a single pipe near the hatch portion 17 inside the outer casing 11. It should be noted that the two vertically extending pipes 131 and 141 may be joined outside the outer casing 11 or remain separate without being joined.

[0024] For example, the second filling conduit 14 is fixed to the skeleton member 12. It should be noted that the second filling conduit 14 can be fixed in any manner near the bottom surface of the outer casing 11, or it can be fixed to a part other than the skeleton member 12. For example, the second filling conduit 14 can be directly fixed to the bottom surface of the outer casing 11, or a separate component can be provided for fixing the second filling conduit 14. Furthermore, the second filling conduit 14 can also be configured in the same way as the filling conduit provided in a known cargo tank (e.g., an LNG tank) containing liquefied gas.

[0025] The third filling line 15 is used to spray liquid to cool the cargo tank 1 and the cargo. For example, the third filling line 15 is used when replacing a high-density liquefied gas (e.g., liquefied carbon dioxide) with a low-density liquefied gas (e.g., LNG). In addition, the third filling line 15, like the second filling line 14, can also be used to perform gas replacement of the cargo tank 1 in layers to improve replacement efficiency.

[0026] The third filling line 15 includes a pipe that extends from the hatch 17 into the interior of the cargo tank 1 and along the longitudinal direction of the outer shell 11 near its uppermost part. The pipe has nozzles at fixed intervals along the longitudinal direction of the outer shell 11. The nozzles are configured to eject liquefied gas downwards from the upper part of the outer shell 11. The pipe of the third filling line 15 that extends from the hatch 17 into the interior of the cargo tank 1 is separate from the first filling line 13 and the second filling line 14, but it can also be configured to be connected to at least one of the first filling line 13 and the second filling line 14.

[0027] For example, the third filling pipe 15 is fixed to the skeleton member 12. It should be noted that the third filling pipe 15 can be fixed in any manner near the upper surface of the outer shell 11, or it can be fixed to a part other than the skeleton member 12. For example, the third filling pipe 15 can be directly fixed to the upper surface of the outer shell 11, or a separate member can be provided for fixing the third filling pipe 15. Furthermore, the third filling pipe 15 can also be configured similarly to the filling pipes located on the upper part of a known cargo tank (e.g., an LNG tank) containing liquefied gas. It should be noted that the third filling pipe 15 may also not be located in the cargo tank 1.

[0028] The hatch section 17 serves as the entrance and exit point for the cargo tank 1. The first filling pipe 13, the second filling pipe 14, and the third filling pipe 15 are connected to piping located outside the cargo tank 1 via the hatch section 17.

[0029] The first valve 16a and the second valve 16b are located immediately downstream of the portion of the first filling pipe 13 and the second filling pipe 14 that branches into two pipes 131 and 141. The first valve 16a is located in the first filling pipe 13. The second valve 16b is located in the second filling pipe 14. The third valve 16c is located immediately upstream of the branch that is inserted from the hatch 17.

[0030] By opening valves 16a, 16b, and 16c respectively, each filling line 13, 14, and 15 can be used independently. Furthermore, by closing valves 16a, 16b, and 16c respectively, it can be configured so that each filling line 13, 14, and 15 cannot be used independently.

[0031] It should be noted that valves 16a, 16b, and 16c can be opened and closed remotely, via computer, or manually by an operator. Furthermore, if each filling pipeline 13, 14, and 15 is configured to be used independently, valves 16a, 16b, and 16c may not be required to be installed in cargo tank 1.

[0032] Figure 2 This is a cross-sectional view simply showing the location of the piping 132 of the first filling conduit 13 in this embodiment. (Refer to...) Figure 2 The location of the nozzle H13 of the piping 132 located in the first filling pipe 13 will be described. It should be noted that the configuration described herein is not limited to any particular configuration. As long as the ejected liquefied gas flows along the inner wall toward the bottom surface, the nozzle H13 can be set in any manner.

[0033] The nozzle H13 is provided on the surface of the cylindrical pipe 132. For example, the orientation of the nozzle H13 is set such that when the horizontal direction is set to 0 degrees and the vertical direction is set to 90 degrees in the direction of the inner wall, the liquefied gas is ejected in a direction within the range of 0 degrees to 90 degrees. By setting the nozzle H13 in this way, the liquefied gas ejected from the nozzle H13 flows along the inner wall towards the bottom surface.

[0034] Next, the height of the ejector hole H13 will be explained. Here, within the internal space of the outer casing 11, the height of the uppermost part is set to 100%, the height of the equator is set to 0%, and the height of the deepest part is set to -100%. It should be noted that, as... Figure 2 As shown, the internal space of the outer shell 11 is a cross-sectional shape that occupies most of the outer shell 11, excluding spaces with special cross-sectional shapes that are part of the outer shell 11, such as hatch 17.

[0035] The height of the ejector hole H13 is preferably set in the range of -20% to 20%, and more preferably in a height of 0% (equatorial height) or higher. By setting the ejector hole H13 at a height of 0% or higher, the ejected liquefied gas can be used to heat the lower inner wall from near the equator. By setting the ejector hole H13 at a height of 20% or lower, the ejected liquefied gas can easily flow along the inner wall to the bottom surface. By setting the height of the ejector hole H13 at -20% or higher, sufficient area for the ejected liquefied gas to flow can be ensured, so as to obtain the effect of heating the inner wall with liquefied gas. Moreover, if the height of the ejector hole H13 is lower than -50% (when the height of the ejector hole H13 is lower than the midpoint between the equatorial height and the deepest point), the effect of heating the inner wall with liquefied gas may not be obtained.

[0036] Next, the method for replacing the contents of cargo tank 1 from LNG with liquefied carbon dioxide gas will be described. It should be noted that if replacing a low-density liquefied gas (i.e., a liquefied gas with a low managed temperature) with a high-density liquefied gas (i.e., a liquefied gas with a high managed temperature), the replacement can be performed in the same manner as described below. Furthermore, the replacement method described here is an example; the contents of cargo tank 1 can be replaced in any manner.

[0037] When the contents of cargo tank 1 are replaced from a low-temperature liquefied gas (e.g., LNG) to a high-temperature liquefied gas (e.g., liquefied carbonic acid), the first filling line 13 is used.

[0038] First, all the LNG in cargo tank 1 is discharged (unloading). However, even if all the LNG is discharged, methane gas will still fill cargo tank 1.

[0039] Next, the first valve 16a located in the first filling line 13 is opened, and simultaneously, the second valve 16b located in the second filling line 14 is opened. Thus, the first filling line 13 and the second filling line 14 can be used.

[0040] Preheated carbon dioxide gas (e.g., carbon dioxide at approximately 40°C) is injected into tank 1 using the first filling conduit 13. The injected carbon dioxide gas is ejected from an outlet H13 located near the equator on the inner wall. The carbon dioxide gas ejected from the outlet H13 flows along the inner wall from near the equator toward the deepest part of the bottom surface. As a result, the inner wall is heated, and the methane gas filling tank 1 is expelled. By continuing to inject carbon dioxide gas, all the methane gas is expelled from tank 1, and the interior of tank 1 is filled with carbon dioxide gas.

[0041] Furthermore, the internal temperature of cargo tank 1 is heated to a temperature suitable for injecting liquefied carbon dioxide gas. Simultaneously, the internal pressure of cargo tank 1 is increased to a pressure suitable for injecting liquefied carbon dioxide gas. For example, the temperature and pressure suitable for injecting liquefied carbon dioxide gas are those that will not cause problems even if liquefied carbon dioxide gas is injected; specifically, the temperature and pressure at which the injected liquefied carbon dioxide gas will not solidify (the temperature and pressure at which it will not become dry ice).

[0042] When all the methane gas has been discharged from tank 1 and the internal temperature and pressure of tank 1 reach the predetermined temperature and pressure suitable for the injection of liquefied carbon dioxide, the injection of liquefied carbon dioxide begins. The injection continues until the tank is full. In this way, the contents of tank 1 are replaced from LNG with liquefied carbon dioxide.

[0043] Next, the method for replacing the contents of cargo tank 1 from liquefied carbon dioxide gas with LNG will be described. It should be noted that if the contents are replaced from a high-density liquefied gas (i.e., a liquefied gas with a high managed temperature) to a low-density liquefied gas (i.e., a liquefied gas with a low managed temperature), the replacement can be performed in the same manner as described below. Furthermore, the replacement method described here is an example; the contents of cargo tank 1 can be replaced in any manner.

[0044] First, all the liquefied carbon dioxide gas in tank 1 is discharged (unloading). However, even if all the liquefied carbon dioxide gas is discharged, carbon dioxide gas will remain.

[0045] Next, the second valve 16b located in the second filling line 14 is opened. At this time, the first valve 16a located in the first filling line 13 is closed. Thus, the second filling line 14 can be used.

[0046] Methane gas is injected using the second filling pipe 14. The injected methane gas is ejected from the nozzle H14 located near the deepest part of the bottom surface. The methane gas ejected from the nozzle H14 accumulates from the deepest part. By injecting methane gas, the carbon dioxide gas remaining on the bottom surface is completely discharged from the upper part of the cargo tank 1 (e.g., hatch 17). Thus, the interior of the cargo tank 1 is filled with methane gas.

[0047] Once all the carbon dioxide gas has been discharged from cargo tank 1, LNG injection begins. LNG is injected until the cargo tank is full. In this way, the contents of cargo tank 1 are replaced from liquefied carbon dioxide gas with LNG.

[0048] Figure 3 This is a configuration diagram showing the structure of the ship 20 with the cargo tank 1 applied according to this embodiment.

[0049] For example, vessel 20 is a tanker that replaces oil tankers transporting LNG and liquefied carbon dioxide. Vessel 20 transports LNG on its way to its destination and liquefied carbon dioxide on its return trip. This allows LNG to be transported from its production site to its destination, while the carbon dioxide emitted from the use of LNG is returned to its production site.

[0050] In vessel 20, multiple cargo tanks 1 are installed inside the hull. For example, three cargo tanks 1 are arranged side by side along the length of the hull. The filling pipes 13, 14, and 15 of each cargo tank 1 are all connected to manifolds 21 via piping 22 located on the hull. Manifolds 21 are connectors used to connect to piping outside the vessel, such as on land. For example, manifolds 21 are connected to pipelines located on land during loading and unloading. Several manifolds 21 may also be installed in vessel 20.

[0051] The piping 22 connecting the various filling pipes 13, 14, and 15 to the manifold 21 can form any path. For example, the piping 22 can branch or connect at any point. In addition, various valves or pumps can be installed in the piping 22.

[0052] According to this embodiment, in the cargo tank 1, a first filling pipe 13 with a spray hole H13 near the equator on the inner wall and a second filling pipe 14 with a spray hole H14 near the bottom surface can efficiently replace two liquefied gases with different temperatures.

[0053] Specifically, by ejecting the injected liquefied gas or gaseous gas (such as liquefied carbon dioxide) from the ejector hole H13 of the first filling pipe 13, the inner wall of the cargo tank 1 can be heated from near the equator to the bottom surface. Thus, the interior of the cargo tank 1 can be heated efficiently.

[0054] It should be noted that additional advantages and modifications can sometimes be readily apparent to those skilled in the art. Therefore, the invention under a broader scope is not limited to the representative embodiments by the specific details shown in this specification. Thus, 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, characterized in that, have: The outer casing, which accommodates two liquefied gases at different temperatures, includes an inner wall with a curved shape formed by the central portion in the vertical direction bulging out most horizontally. A first filling conduit is configured to inject at least one of the two liquefied gases into the interior of the housing, and a first ejection port is provided at a height above the midpoint between the height of the central portion and the height of the deepest part of the interior space of the housing, such that the ejected liquefied gas flows along the curved shape of the inner wall; and The second filling conduit is configured to inject at least one of the two liquefied gases into the interior of the housing, and is provided with a second ejection port in such a way that the liquefied gas is ejected onto the bottom surface of the housing.

2. The cargo tank according to claim 1, characterized in that, In the internal space of the outer casing, with the height of the uppermost part set to 100%, the height of the central part set to 0%, and the height of the deepest part set to -100%, the first ejector hole is set at a height in the range of -20% to 20%.

3. The cargo tank according to claim 1, characterized in that, have: The third filling conduit is provided with a third ejector hole so that at least one of the two liquefied gases is sprayed downward from the upper part of the housing.

4. The cargo tank according to claim 3, characterized in that, have: A valve is provided in each of the first filling line, the second filling line, and the third filling line.

5. A ship, characterized in that, have: Hull; and Cargo tanks, located on the hull of the ship, The cargo tank has the following features: The outer casing, which accommodates two liquefied gases at different temperatures, includes an inner wall with a curved shape formed by the central portion in the vertical direction bulging out most horizontally. A first filling conduit is configured to inject at least one of the two liquefied gases into the interior of the housing, and a first ejection port is provided at a height above the midpoint between the height of the central portion and the height of the deepest part of the interior space of the housing, such that the ejected liquefied gas flows along the curved shape of the inner wall; and The second filling conduit is configured to inject at least one of the two liquefied gases into the interior of the housing, and is provided with a second ejection port in such a way that the liquefied gas is ejected onto the bottom surface of the housing.

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