JP7458266B2 - liquefied gas tank - Google Patents

Description

The present application relates to a liquefied gas tank that stores liquefied gas.

Flammable gases such as natural gas and hydrogen gas are liquefied by cooling or compression and stored in that state in a liquefied gas tank. The liquefied gas (liquefied flammable gas) stored in the liquefied gas tank is sucked up by a pump inside the liquefied gas tank and discharged to the outside via piping. If the liquid level of the liquefied gas is not higher than a certain level above the pump suction port, the pump cannot sufficiently suck up the liquefied gas. Furthermore, if the liquid level of the liquefied gas temporarily becomes lower than the pump suction port, what is known as air entrapment occurs.

In order to avoid such problems with the pump, a suction well may be formed on the bottom surface of the liquefied gas tank (see Patent Document 1). A suction well is a depression formed in the bottom of a liquefied gas tank. By arranging the suction port of the pump inside the suction well, even if the amount of liquefied gas decreases to some extent, the liquid level of the liquefied gas can be maintained at a level higher than the suction port of the pump by a certain level.

Japanese Patent Application Publication No. 2009-279979

The above-mentioned liquefied gas tanks are also installed on ships. In a ship equipped with a liquefied gas tank, whether the ship is transporting liquefied gas as cargo or using liquefied gas as fuel, the amount of liquefied gas in the liquefied gas tank fluctuates due to boil-off gas generated by heat entering the tank from outside, or due to the use of fuel gas as fuel. In a ship equipped with a liquefied gas tank, if the liquefied gas tank is not filled with liquefied gas, a phenomenon called "sloshing" may occur, in which the liquefied gas in the liquefied gas tank sways significantly due to rolling (sideways) and other motions during the voyage.

When sloshing occurs, the liquefied gas shakes significantly, so especially when the amount of liquefied gas in the liquefied gas tank is small, the liquefied gas in the suction well moves to the outside of the suction well, causing the liquid level of the liquefied gas in the suction well to move to the outside of the suction well. may decrease. In other words, there is a possibility that the liquid level of the liquefied gas cannot be maintained at a level higher than a certain level than the suction port of the pump.

The present application was made in view of the above-mentioned circumstances, and an object thereof is to provide a liquefied gas tank that can suppress the movement of liquefied gas within the suction well to the outside of the suction well when sloshing occurs. shall be.

A liquefied gas tank according to an aspect of the present application is mounted on a ship, and includes a storage section for storing liquefied gas, and a recessed downward from the bottom surface of the storage section, and a suction port for sucking the liquefied gas is located inside. and a top plate that covers at least a portion of the suction well or covers at least a portion of a protection area adjacent above the suction well.

With this configuration, at least a portion of the suction well or at least a portion of the protective area adjacent to and above the suction well is covered by the top plate, so the movement of liquefied gas within the suction well or around the suction well is suppressed. As a result, even if sloshing occurs, the liquefied gas within the suction well can be suppressed from moving outside the suction well.

According to the above configuration, it is possible to provide a liquefied gas tank that can suppress movement of liquefied gas within the suction well to the outside of the suction well when sloshing occurs.

FIG. 1 is a schematic diagram of a ship equipped with a liquefied gas tank. FIG. 2 is a sectional view of the vicinity of the bottom surface of the liquefied gas tank according to the first embodiment. FIG. 3 is a cross-sectional view of the vicinity of the bottom surface of a liquefied gas tank according to the second embodiment. FIG. 4 is a sectional view of the vicinity of the bottom surface of the liquefied gas tank according to the third embodiment.

First Embodiment
First, a liquefied gas tank 100 according to a first embodiment will be described. Fig. 1 is a schematic diagram of a ship 101 on which the liquefied gas tank 100 is mounted. Fig. 1(a) is a plan view of the ship 101, and Fig. 1(b) is a side view of the ship 101. In the following description, the left-right direction on the paper surface of Fig. 1(a) will be referred to as the "front-rear direction", and the up-down direction on the paper surface of Fig. 1(a) will be referred to as the "left-right direction".

The liquefied gas tank 100 stores liquefied gas that has been liquefied by cooling or compressing flammable gas such as natural gas or hydrogen gas. The ship 101 of this embodiment is a fuel ship that uses the liquefied gas (flammable gas) in the liquefied gas tank 100 as its main fuel. However, the ship 101 may also be a carrier ship that transports liquefied gas as cargo.

In this embodiment, the left-right direction is the longitudinal direction of the liquefied gas tank 100, and the longitudinal direction of the ship 101 is the longitudinal direction. That is, the liquefied gas tank 100 is mounted on the ship 101 in a "horizontal" state in which the longitudinal direction of the liquefied gas tank 100 and the longitudinal direction of the ship 101 are perpendicular to each other. However, the mounting direction is not limited to the above.

If the liquefied gas tank 100 is not filled with liquefied gas and the ship 101 undergoes rolling (rolling) at a certain period due to navigation, the liquefied gas in the liquefied gas tank 100 shakes greatly in the left and right directions, which is called "sloshing". A phenomenon occurs. In particular, when the liquefied gas tank 100 is placed horizontally, sloshing due to rolling (lateral shaking) is likely to occur.

Figure 2 is a cross-sectional view taken in the front-rear direction at the left-right central portion of the liquefied gas tank 100 according to the first embodiment, showing the vicinity of the bottom surface of the liquefied gas tank 100. As shown in Figure 2, the liquefied gas tank 100 comprises a storage section 10, a suction well 20, and a top plate 30. Below, these components will be described in order.

The storage section 10 is a part forming the outer surface of the liquefied gas tank 100, and liquefied gas is stored inside. As shown in FIG. 1, the storage section 10 has hemispherical ends at both end portions in the left-right direction, and a cylindrical shape at the center portion in the left-right direction. As an example, the horizontal dimension of the storage section 10 is 5 to 50 m, and the diameter is 3 to 20 m. However, the shape and dimensions of the storage section 10 are not limited to those described above.

The suction well 20 is a depression provided on the bottom surface of the storage section 10. That is, the suction well 20 is recessed downward from the bottom surface of the storage section 10. The suction well 20 is formed into a cylindrical shape that opens upward. As an example, the diameter of the suction well 20 is 0.2 to 2.0 m. However, the shape and dimensions of the suction well 20 are not limited to those described above. For example, the suction well 20 may have a cylindrical shape whose horizontal cross section is an ellipse whose major axis is in the left-right direction.

In the suction well 20, a suction port of a pump 102 for sucking liquefied gas is located inside the suction well 20. In this embodiment, the suction well 20 accommodates a portion of the pump 102, but may accommodate the entire pump 102. In addition, when the suction well 20 accommodates a part of the pump 102, this also includes a case where the suction port of the pump 102 is located inside the suction well 20 and the motor is located outside the storage section 10. The pump 102 of this embodiment has a suction port formed on the lower surface, and liquefied gas is sucked through the suction port. Note that the lower surface of the pump 102 and the bottom surface of the suction well 20 are separated by a certain distance in the vertical direction. The liquefied gas sucked by the pump 102 is carried out to the outside of the liquefied gas tank 100 via a pipe 103 extending upward from the pump 102. In this embodiment, the suction well 20 accommodates one pump 102, but may accommodate a plurality of pumps 102.

Note that if the liquid level of the liquefied gas is not higher than a certain level than the suction port of the pump 102, the pressure of the liquefied gas at the suction port is insufficient, and the pump 102 cannot sufficiently suction the liquefied gas. Further, if the liquid level of the liquefied gas temporarily becomes lower than the suction port of the pump 102, so-called air trapping occurs. In order to avoid such problems, the liquefied gas tank 100 is provided with a top plate 30.

The top plate 30 is a member that covers the suction well 20 from above. The top plate 30 is located near the upper end of the suction well 20. However, the top plate 30 may be located inside the suction well 20. A pump through hole 31 having an opening area through which the pump 102 can pass or through which the pump 102 can be removed is formed in the center of the top plate 30. The top plate 30 has an annular shape and covers a part of the suction well 20 (a part excluding the center of the suction well 20). In addition, the center of the pump through hole 31 and the central axis of the suction well 20 may not coincide with each other and may be offset from each other. The top plate 30 may be located below or above the upper end of the pump 102.

The diameter of the pump through hole 31 is larger than the outer diameter of the pump 102, and an annular gap is formed between the pump 102 and the top plate 30. The liquefied gas in the storage section 10 flows into the suction well 20 through this gap. On the other hand, the movement of the liquefied gas flowing into the suction well 20 to the outside of the suction well 20 is restricted by the top plate 30 . Therefore, even if the above-described sloshing occurs, the liquefied gas in the suction well 20 can be prevented from moving to the outside of the suction well 20.

Further, in this embodiment, the upper surface of the top plate 30 can be used as a foothold for the worker. If the upper surface of the top plate 30 is used as a foothold for the worker, the foothold is close to the pump 102, and the worker can easily perform maintenance work on the pump 102.

(Second embodiment)
Next, a liquefied gas tank 200 according to a second embodiment will be described. FIG. 3 is a cross-sectional view of the liquefied gas tank 200 according to the second embodiment, taken in the front-rear direction at the center in the left-right direction, showing the vicinity of the bottom surface of the liquefied gas tank 200. FIG. 3 corresponds to FIG. 2 of the first embodiment.

The liquefied gas tank 200 according to this embodiment differs from the liquefied gas tank 100 according to the first embodiment in that it includes a side wall 40. Further, the top plate 30 of this embodiment is different from that of the first embodiment. On the other hand, other than these, the liquefied gas tank 200 according to the present embodiment has the same configuration as the liquefied gas tank 100 according to the first embodiment. The liquefied gas tank 200 according to the present embodiment will be described below, focusing on the differences from the liquefied gas tank 100 according to the first embodiment.

As described above, the liquefied gas tank 200 according to this embodiment includes a sidewall 40. The sidewall 40 is arranged to surround the suction well 20 in a plan view. The sidewall 40 has a cylindrical shape and extends upward from the bottom surface of the storage unit 10. If the space adjacent to and above the suction well 20 is defined as a "protected area," the sidewall 40 is located between the inside and outside of this protected area 41. In other words, the sidewall 40 forms (demarcates) the protected area 41. Note that, if multiple suction wells 20 are provided in the storage unit 10, a single continuous protected area 41 may be formed above the multiple suction wells 20.

A plurality of communication holes 42 are formed in the side wall 40 along the circumferential direction. The flow holes 42 are formed to allow liquefied gas to flow therethrough. Therefore, the liquefied gas located outside the side wall 40 flows into the protection area 41 through the communication hole 42 . The communication hole 42 of this embodiment has an elliptical shape with a major axis in the circumferential direction. As an example, the circumferential dimension of the communication hole 42 is 0.1 to 1.0 m. However, the shape and dimensions of the communication hole 42 are not limited to those described above.

In addition, it is preferable that the flow holes 42 are formed near the lower end of the side wall 40 so that the liquefied gas can easily flow into the protected area 41. In addition, although the side wall 40 in this embodiment is formed of a material that is continuous in the circumferential direction, it may be formed of other materials.

Next, the top plate 30 will be explained. The top plate 30 of this embodiment is located at the upper end of the protection area 41 and covers the protection area 41 from above. However, a passage hole 32 through which a worker can pass is formed in the center of the top plate 30. Therefore, the top plate 30 has an annular shape and covers a part of the protection area 41 (excluding the central part of the protection area 41).

As an example, the diameter of the passage hole 32 is 0.5 to 2.0 m. Further, the passage hole 32 has a larger opening area than the circulation hole 42, and has a larger opening area than the pump through hole 31 (see FIG. 2) of the first embodiment. In this embodiment, the passage hole 32 is formed to have the same diameter as the suction well 20. Note that the shape and dimensions of the passage hole 32 are not limited to those described above.

As mentioned above, the liquefied gas passes through the flow holes 42 formed in the side wall 40, but the amount that can pass in a short period of time is limited. Therefore, once the liquefied gas has flowed into the protected area 41, it cannot quickly move outside the protected area 41 via the flow holes 42. In addition, the movement of the liquefied gas that attempts to move beyond the side wall 40 to the outside of the protected area 41 is restricted by the top plate 30. Therefore, even if sloshing occurs, the liquefied gas in the protected area 41 can be prevented from moving outside the protected area 41, and thus the liquefied gas in the suction well 20 can be prevented from moving outside the suction well 20.

Further, in this embodiment, a worker can enter the protected area 41 and the suction well 20 through the passage hole 32 . By entering the suction well 20 through the passage hole 32, an operator can easily perform maintenance work on the pump 102. However, if the gap between the pump 102 and the suction well 20 is narrow, the operator may work without entering the suction well 20 (this also applies to the third embodiment).

(Third embodiment)
Next, a liquefied gas tank 300 according to a third embodiment will be described. FIG. 4 is a sectional view of the liquefied gas tank 300 according to the third embodiment, taken in the front-rear direction at the center in the left-right direction, showing the vicinity of the bottom surface of the liquefied gas tank 300. FIG. 4 corresponds to FIG. 2 of the first embodiment and FIG. 3 of the second embodiment.

The top plate 30 and side walls 40 of this embodiment are different from those of the second embodiment. On the other hand, other than these, the liquefied gas tank 300 according to the present embodiment has the same configuration as the liquefied gas tank 200 according to the second embodiment. The liquefied gas tank 300 according to the present embodiment will be described below, focusing on the differences from the liquefied gas tank 200 according to the second embodiment.

The side wall 40 of this embodiment has a larger vertical dimension than that of the second embodiment. In addition to the circulation hole 42, the side wall 40 is formed with a passage hole 43 through which a worker can pass. The passage hole 43 of this embodiment has an elliptical shape with the major axis in the vertical direction. As an example, the vertical dimension of the passage hole 43 is 0.5 to 2.0 m. In addition, the opening area of the passage hole 43 is larger than that of the circulation hole 42, and the passage hole 43 is located above the circulation hole 42. The shape and dimensions of the passage hole 43 are not limited to those described above.

Further, the passage holes 43 are formed only in circumferential positions of the side wall 40 corresponding to the front-rear direction (that is, the longitudinal direction of the vessel 101) when viewed from the center of the protection area 41. In this embodiment, the passage holes 43 are formed at two circumferential positions of the side wall 40 corresponding to the front and rear sides when viewed from the center of the protection area 41, but are formed only at one of the circumferential positions. may have been done.

Since the opening area of the passage hole 43 is larger than that of the passage hole 42, it seems that when sloshing occurs, the liquefied gas within the protected area 41 tends to move to the outside of the protected area 41 via the passage hole 43. However, when sloshing occurs, the liquefied gas sways in the left-right direction. Therefore, if the passage hole 43 is formed only in the circumferential position of the side wall 40 that corresponds to the front and back direction when viewed from the center of the protection area 41, movement from the inside of the protection area 41 to the outside via the passage hole 43 is possible. The amount of liquefied gas produced can be suppressed.

The top plate 30 of this embodiment covers the protection area 41 from above, as in the second embodiment. However, the top plate 30 does not have a through hole 32 (see FIG. 3) formed therein. This is because, as described above, the passage hole 43 is formed in the side wall 40 and the operator can enter the protected area 41 and the suction well 20 through this passage hole 43. Note that a pump through hole 31 through which the pump 102 can pass is formed in the top plate 30. The pump through hole 31 has a smaller opening area than the passage hole 32 (see FIG. 3). The passage hole 43 may be configured so that the pump 102 can be taken out during maintenance.

According to the liquefied gas tank 300 according to the present embodiment, similarly to the liquefied gas tank 200 according to the second embodiment, when sloshing occurs, the liquefied gas inside the protection area 41 is prevented from moving to the outside of the protection area 41. In turn, it is possible to suppress the liquefied gas in the suction well 20 from moving to the outside of the suction well 20.

Furthermore, in this embodiment, a worker can enter the protection area 41 and the suction well 20 through the passage hole 43. If the operator enters the suction well 20 through the passage hole 43, the operator can easily perform maintenance or other work on the pump 102.

In addition, although the liquefied gas tanks 100, 200, and 300 based on each embodiment were demonstrated above, you may combine the component of each liquefied gas tank 100, 200, and 300. For example, the side wall 40 of the liquefied gas tank 200 according to the second embodiment or the liquefied gas tank 300 according to the third embodiment may be applied to the liquefied gas tank 100 according to the first embodiment.

(Action and Effect)
As described above, the liquefied gas tank according to the embodiment is mounted on a ship and comprises a storage section for storing liquefied gas, a suction well that is recessed downward from the bottom surface of the storage section and has a suction port located inside for sucking in the liquefied gas, and a top plate that covers at least a portion of the suction well or covers at least a portion of a protected area adjacent to and above the suction well.

According to this configuration, since at least a portion of the suction well or at least a portion of the protection area adjacent above the suction well is covered by the top plate, movement of the liquefied gas in or around the suction well is suppressed. As a result, even if sloshing occurs, it is possible to suppress the liquefied gas within the suction well from moving to the outside of the suction well.

Further, in the liquefied gas tank according to the first embodiment, a part or all of the pump having the suction port is housed in the suction well, and the top plate is located near the upper end of the suction well or inside the suction well. A pump through hole through which the pump can pass is formed in the top plate.

According to this configuration, although the structure is relatively simple, when sloshing occurs, it is possible to suppress the liquefied gas within the suction well from moving to the outside of the suction well. Furthermore, by using the top plate as a foothold, the worker can easily perform maintenance work on the pump.

Further, the liquefied gas tank according to the second embodiment and the third embodiment is arranged so as to surround the suction well in a plan view, and extends upward from the bottom surface of the storage section to form the protection area. The fuel cell further includes a side wall, and a plurality of flow holes through which the liquefied gas can flow are formed in the side wall along the circumferential direction.

According to this configuration, the liquefied gas can flow into the protection area and the suction well through the communication hole. Furthermore, when sloshing occurs, the protection wall can prevent the liquefied gas within the protection area from moving to the outside of the protection area, which in turn suppresses the liquefied gas inside the suction well from moving to the outside of the suction well. Can be done.

Further, in the liquefied gas tank according to the second embodiment, a passage hole is formed in the top plate through which a worker can pass when entering the protected area, and has a larger opening area than each of the circulation holes. There is.

According to this configuration, an operator can enter the protected area and the suction well through the passage hole formed in the top plate. Therefore, the operator can easily perform maintenance work on the pump.

In addition, in the liquefied gas tank according to the third embodiment, a pump through hole is formed in the top plate through which a pump having the suction port can pass, and a passage hole is formed in the side wall through which a worker can pass when entering the protected area and which has an opening area larger than that of each of the circulation holes.

According to this configuration, the operator can enter the protected area and the suction well through the passage hole formed in the side wall. Therefore, an operator can easily perform maintenance work on the pump.

Furthermore, in the liquefied gas tank according to the third embodiment, the passage hole is formed only in a circumferential position of the side wall corresponding to the longitudinal direction of the ship when viewed from the center of the protection area.

In this way, if the passage holes are formed only in the circumferential position of the side wall that corresponds to the longitudinal direction of the ship when viewed from the center of the protected area, when sloshing occurs, the inside of the protected area can be penetrated through the passage holes. It is possible to suppress the amount of liquefied gas that moves from the inside to the outside.

10 Storage section 20 Suction well 30 Top plate 31 Pump through hole 32 Passage hole 40 Side wall 41 Protection area 42 Distribution hole 43 Passage hole 100 Liquefied gas tank 101 Ship 102 Pump 103 Piping 200 Liquefied gas tank 300 Liquefied gas tank

Claims (5)

a storage unit that is installed on the ship and stores the liquefied gas;
A suction well that is recessed downward from the bottom surface of the storage portion and has a suction port for suctioning the liquefied gas located therein;
A sidewall that is disposed to surround the suction well in a plan view, extends upward from a bottom surface of the storage portion, and forms a protective area above the bottom surface of the storage portion;
A liquefied gas tank comprising: a top plate covering at least a portion of the protected area adjacent to and above the suction well. The liquefied gas tank according to claim 1 , wherein a plurality of circulation holes through which the liquefied gas can flow are formed in the side wall along a circumferential direction. The liquefied gas tank according to claim 2 , wherein the top plate is formed with a passage hole through which an operator can pass when entering the protected area and which has an opening area larger than that of each of the circulation holes. A pump through hole through which the pump having the suction port can pass is formed in the top plate,
The liquefied gas tank according to claim 2 , wherein the side wall is formed with a passage hole through which a worker can pass when entering the protected area, and has a larger opening area than each passage hole. The liquefied gas tank according to claim 4 , wherein the passage hole is formed only at a circumferential position of the side wall corresponding to the longitudinal direction of the ship when viewed from the center of the protected area.

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