JP2018165543A - Low-temperature liquid storage tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-temperature liquid storage tank designed to increase a maximum liquid storage amount while suppressing a height of a tank as a whole.SOLUTION: A low-temperature liquid storage tank includes an outer tank having a cylindrical outer tank side plate and an outer tank roof plate, an inner tank having a cylindrical inner tank side plate vertically disposed at an inner part of the outer tank side plate, an inner tank roof plate disposed at a lower part of the outer tank roof plate, and a knuckle plate connecting an upper end portion of the inner tank side plate and a peripheral edge portion of the inner tank roof plate, and a BOG pipe disposed to suck BOG generated by evaporation of low-temperature liquid in the inner tank from a suction port formed at a center of the inner tank roof plate, and discharge the same to the external of the inner tank, extended radially outward along the inner tank roof plate from the suction port in the inner tank, and penetrated through the inner tank roof plate and the outer tank roof plate at a position above the upper end portion of the knuckle plate. The BOG pipe includes a pipe inlet portion having the suction port, an extension portion extended radially outward along the inner tank roof plate from the pipe inlet portion, and an U-shaped curved portion once extended downward from an end of the extension portion, and then folded back and extended upward.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cryogenic liquid storage tank for storing a cryogenic liquid such as liquefied natural gas.

  Conventionally, a cryogenic liquid storage tank for storing a cryogenic liquid such as liquefied natural gas is known. For example, Patent Document 1 discloses a cylindrical prestressed concrete (hereinafter referred to as “PC”) liquid breakwater, an outer tank provided inside the PC liquid breakwater, and an inner wall of the outer tank. There is disclosed a cryogenic liquid storage tank provided with an inner tank in which a cryogenic liquid is stored.

  The PC breakwater is designed to accommodate the entire amount of the stored liquid in the inner tank in case the low temperature liquid stored in the inner tank leaks out. The outer tub has a cylindrical outer tub side plate attached to the inner peripheral surface of the PC liquid barrier, and a spherical outer tub roof plate whose peripheral edge is supported by the upper end of the PC liquid barrier. . The inner tank is a cylindrical inner tank side plate standing inward of the outer tank side plate, a spherical inner tank roof plate provided below the outer tank roof plate, and the upper end of the inner tank side plate and the inner tank It has a knuckle plate that connects the peripheral edge of the roof plate.

JP2015-96758 A

  By the way, in such a cryogenic liquid storage tank, it is desired that the maximum liquid storage amount is designed to increase as much as possible. However, the height of the cryogenic liquid storage tank cannot be easily increased at present. is there. For example, when the height of the entire tank including the roof piping exceeds a predetermined height (for example, 60 m), an aircraft warning light equipped with an explosion-proof structure is provided in the tank to indicate the presence of the tank to the flying aircraft. It is not realistic because it needs to be installed. For this reason, there is a demand for the height of the entire tank to be reduced to a height that does not require an aviation obstacle light.

  Therefore, an object of the present invention is to provide a cryogenic liquid storage tank designed to increase the maximum liquid storage amount while suppressing the height of the entire tank.

  In order to solve the above-described problems, a cryogenic liquid storage tank according to an aspect of the present invention includes an outer tank having a cylindrical outer tank side plate and an outer tank roof plate, and an inward standing of the outer tank side plate. An inner tank roof plate provided below the outer tank roof plate, and a knuckle plate that connects the upper end of the inner tank side plate and the peripheral edge of the inner tank roof plate. A BOG pipe that draws in a tank and a boil-off gas (hereinafter referred to as “BOG”) in which the low-temperature liquid has evaporated in the inner tank from a suction port disposed in the center of the inner tank roof plate and discharges it to the outside of the inner tank The inner tub roof plate and the outer tub roof plate extend in a radially outward direction from the suction port along the inner tub roof plate in the inner tub and above the upper end portion of the knuckle plate. A BOG pipe penetrating through the BOG pipe. A pipe inlet section, an extending section extending radially outward from the pipe inlet section along the inner tub roof plate, a U-curved section extending once downward from the end of the extending section, and folded and extended upward Including.

  According to said structure, since a suction inlet is arrange | positioned in the center of an inner tank roof board, BOG in an inner tank with a high temperature can be discharged | emitted from a cryogenic liquid storage tank through BOG piping. In addition, since the BOG pipe extends radially outward along the inner tank roof plate from the inlet through the inner tank, the BOG pipe is placed at a position below the top of the outer tank roof plate. Can be penetrated. For this reason, BOG piping can be arrange | positioned below rather than the top part of an outer tank roofboard.

  By the way, in the conventional tank, it is common that BOG piping is arrange | positioned so that the top part of an outer tank roof plate may be penetrated. In such a tank, the height of the entire tank including the BOG piping is higher than the top of the outer tub roof by the length protruding upward from the top of the outer tub roof in the BOG piping. With respect to such a conventional tank, according to the above configuration, since the BOG pipe can be arranged below the top of the outer tank roof plate, the maximum liquid storage amount can be increased while suppressing the height of the entire tank. Can do.

  In addition, for example, when the inner tank roof board and the BOG pipe are manufactured from different materials, a difference in thermal shrinkage occurs between the inner tank roof board and the BOG pipe when the low-temperature liquid is stored in the inner tank. However, according to the above configuration, since the BOG pipe includes the U-shaped curved portion that once extends downward from the end of the extending portion and is folded back and extends upward, it is generated between the inner tank roof plate and the BOG piping. The difference in heat shrinkage can be absorbed in the U-shaped curved portion.

  In the low-temperature liquid storage tank, a hole for discharging the liquid re-liquefied by the BOG in the BOG pipe may be formed below the U-shaped curved portion. According to this structure, the liquid which boil off gas reliquefied in BOG piping can be reliably discharged | emitted from BOG piping.

  In the cryogenic liquid storage tank, the lowermost portion of the U-shaped curved portion may be above the design liquid level of the cryogenic liquid stored in the internal space of the inner tank. According to this configuration, the cryogenic liquid stored in the inner tank can be prevented from entering the U-shaped curved portion through the hole.

  In the cryogenic liquid storage tank, the pipe inlet portion may extend vertically downward from an end portion on the center side of the inner tank roof plate in the extension portion to the suction port. After the tank construction, in order to replace the air in the inner tank of the tank with nitrogen, an air purge may be performed in which nitrogen is sent from the suction port of the BOG pipe to the inner tank. According to the above configuration, the pipe inlet portion extends vertically downward from the center side end of the inner tub roof plate in the extending portion to the suction port, so when performing the air purge, nitrogen is released downward. Thus, air can be pushed downward from above so as not to diffuse as much as possible in the inner tank.

  The cryogenic liquid storage tank is further provided with a cool down ring that is disposed in the center of the inner tank roof plate and sprays the low temperature liquid in the inner tank, and the suction port is located below the cool down ring. May be located. According to this configuration, since nitrogen is released from the suction port of the BOG pipe below the cool down ring when air purge is performed, it is possible to suppress the released nitrogen from colliding with the cool down ring and diffusing.

  According to the present invention, it is possible to provide a cryogenic liquid storage tank designed to increase the maximum liquid storage amount while suppressing the height of the entire tank.

It is a schematic sectional drawing of the tank for cryogenic liquid storage concerning one embodiment. FIG. 2 is an enlarged view of a part of the cryogenic liquid storage tank shown in FIG. 1.

  Hereinafter, a cryogenic liquid storage tank according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of a cryogenic liquid storage tank 1 according to an embodiment. The cryogenic liquid storage tank 1 is a tank in which a cryogenic liquid such as liquefied natural gas is stored. The cryogenic liquid storage tank 1 includes a cylindrical PC liquid barrier 2, an outer tank 3 provided inside the PC liquid barrier 2, and a low temperature liquid provided inside the outer tank 3. Is stored in the inner tank 4. The PC liquid barrier 2, the outer tub 3, and the inner tub 4 are installed on a reinforced concrete foundation plate 5. However, the basic version 15 may be made of PC.

  The outer tub 3 has an outer tub bottom plate 31, an outer tub side plate 32, and an outer tub roof plate 33. The outer tub 3 has an airtight structure by the outer tub bottom plate 31, the outer tub side plate 32 and the outer tub roof plate 33. The outer tank bottom plate 31 is laid on the foundation plate 5. The outer tank side plate 32 is cylindrical and is provided so as to rise from the peripheral edge of the outer tank bottom plate 31. The outer tank side plate 32 is attached to the inner peripheral surface of the cylindrical PC liquid barrier 2 provided so as to surround it. The outer tub roof plate 33 has a substantially partial spherical shape that opens downward, and the peripheral edge of the outer tub roof plate 33 is fixed to the upper end portion 21 of the PC liquid barrier 2.

  The inner tank 4 has an inner tank bottom plate 41, an inner tank side plate 42, an inner tank roof plate 43, and a knuckle plate 44. The inner tank 4 has a liquid-tight and air-tight structure by an inner tank bottom plate 41, an inner tank side plate 42, an inner tank roof plate 43, and a knuckle plate 44, and a cryogenic liquid is stored therein. The inner tank bottom plate 41 is provided on the outer tank bottom plate 31 via a cold insulating material 61. The inner tank side plate 42 is cylindrical and is erected on the inner side of the outer tank side plate 32 with a predetermined gap. A cold insulation material 62 is filled between the inner tank side plate 42 and the outer tank side plate 32. The inner tank roof plate 43 has a substantially partial spherical shape that opens downward, and is provided below the outer tank roof plate 33 with a predetermined gap therebetween. A cold insulating material 63 is filled between the inner tank roof plate 43 and the outer tank roof plate 33.

  The knuckle plate 44 connects the upper end portion of the inner tank side plate 42 and the peripheral edge portion of the inner tank roof plate 43. More specifically, the upper end of the inner tank side plate 42 is connected to the lower end of the knuckle plate 44, and the upper end of the knuckle plate 44 is connected to the peripheral edge of the inner tank roof plate 43.

  Further, the cryogenic liquid storage tank 1 includes a receiving pipe 8 that guides the cryogenic liquid from the outside to the inner tank 4. The receiving pipe 8 discharges the low-temperature liquid guided from the outside to the liquid phase bottom of the internal space of the inner tank 4. In the present embodiment, one receiving pipe 8 is provided in the cryogenic liquid storage tank 1, but a plurality of receiving pipes 8 may be provided in the cryogenic liquid storage tank 1.

  The outer tank roof plate 33 is provided with an outer through hole 33b through which the receiving pipe 8 passes. The inner tank roof plate 43 is provided with an inner through hole 43b through which the receiving pipe 8 passes. The outer through hole 33b and the inner through hole 43b are arranged so as to be aligned in the vertical direction. The outer through-hole 33b and the inner through-hole 43b are arranged so as to be at an equal distance from the center of the cryogenic liquid storage tank 1 when the cryogenic liquid storage tank 1 is viewed in plan.

  The receiving pipe 8 extends downward from the upper side of the outer tub roof plate 33 through the outer through hole 33b and the inner through hole 43b, and a discharge port 81 is provided at an end thereof. The receiving pipe 8 is supported by the outer tub roof plate 33 through the expansion and contraction pipe in the outer through hole 33b. The receiving pipe 8 is welded to the inner tank roof plate 43 through the inner through-hole 43 b and is supported by a support member 82 fixed to the inner peripheral surface of the inner tank side plate 42.

  The cryogenic liquid storage tank 1 includes a BOG pipe 9 that discharges boil-off gas generated in the inner tank 4 to the outside. The BOG pipe 9 has a suction port 91 disposed in the center of the inner tank roof plate 43, and BOG in the inner tank 4 is sucked from the suction port 91. Here, the “center of the inner tub roof plate” indicates the inner side of a half of the radius of the inner tub 4 (inner tub side plate 42) when the inner tub 4 is viewed in plan.

  The outer tub roof plate 33 and the inner tub roof plate 43 are provided with an outer through hole 33c and an inner through hole 43c through which the BOG pipe 9 passes, respectively, arranged in the vertical direction. The outer through hole 33 c and the inner through hole 43 c are located above the upper end portion 44 a of the knuckle plate 44. The BOG pipe 9 extends in the inner tank 4 from the suction port 91 along the inner tank roof plate 43 outward in the radial direction of the inner tank 4, and penetrates the inner tank roof plate 43 and the outer tank roof plate 33. The BOG pipe 9 is supported by the outer tub roof plate 33 through an expansion tube at the outer through hole 33c. The BOG pipe 9 is welded to the inner tub roof plate 43 through the inner through-holes 43 c and is supported by a plurality of support members 96 fixed to the lower surface of the inner tub roof plate 43.

  The BOG pipe 9 includes a pipe inlet portion 92 having a suction port 91 in the inner tank 4, an extending portion 93 extending from the pipe inlet portion 92 in the radially outward direction of the inner tank 4, and a suction port 91 in the extending portion 93. Has a U-shaped curved portion 94 that once extends downward from the opposite end and is folded back and extends upward toward the inner through-hole 43c. The pipe inlet portion 92 extends vertically downward from the central end of the inner tank roof plate 43 in the extending portion 93 to the suction port 91. The extending portion 93 does not necessarily have to be parallel to the radial direction of the inner tub 4 and may be in any form as long as it extends outward in the radial direction as a whole. For example, the extending portion 93 may be linear in a plan view or may include a curved portion.

  For example, the inner tank roof plate 43 and the BOG pipe 9 are made of 9% Ni steel and the BOG pipe 9 fixed to the inner tank roof board 43 is made of SUS material. May be made of different materials. In such a case, when the low temperature liquid is stored in the inner tank 4, a difference in thermal shrinkage occurs between the inner tank roof plate 43 and the BOG pipe 9. The both ends of the U-shaped bending portion 94 approach each other, and absorb the difference in heat shrinkage.

  In the lower part of the U-shaped curved portion 94, a hole 95 is formed for discharging the liquid re-liquefied by the BOG in the BOG pipe 9 to the outside. The liquid in which the BOG is liquefied in the extending portion 93 and the U-shaped curved portion 94 flows to the lower portion of the U-shaped curved portion 94, is discharged from the hole 95, and returned to the low-temperature liquid stored in the inner tank 4.

  Further, the lowermost portion of the U-shaped curved portion 94 is above the upper end portion 44 a of the knuckle plate 44. However, the lowermost portion of the U-shaped curved portion 94 may be at least above the design liquid level L of the low-temperature liquid stored in the inner tank 4. Here, the design liquid level L is the highest liquid level allowed to store the low temperature liquid in the inner tank 4. In the present embodiment, the design liquid level L is set at the position of the lower end portion 44b of the knuckle plate 44. However, the design liquid level L is not limited to this, and is lower than the lower end portion 44b of the knuckle plate 44. The position may be set. Since the lowermost portion of the U-shaped curved portion 94 is above the design liquid level L, the hole 95 formed in the U-shaped curved portion 94 is surely positioned above the liquid level of the low-temperature liquid in the inner tank 4. Can do. For this reason, the low temperature liquid stored in the inner tank 4 can be prevented from entering the U-shaped curved portion 94 through the hole 95.

  FIG. 2 is an enlarged view of the vicinity of the center of the inner tank roof plate 43 of the cryogenic liquid storage tank 1 shown in FIG. The cryogenic liquid storage tank 1 further includes a cool down ring 7 disposed in the center of the inner tank roof plate 43. The cool down ring 7 sprays a low temperature liquid in the inner tank 4 to cool the inner tank 4. For simplification, in FIG. 1 and FIG. 2, a pipe for sending the low temperature liquid to the cool down ring 7 and a member for fixing the pipe and the cool down ring 7 to the inner tank roof plate 43 are omitted. As shown in FIG. 2, the cool down ring 7 is located above the suction port 91 of the BOG pipe 9.

  By the way, the cryogenic liquid storage tank 1 of this embodiment performs an air purge in which nitrogen is sent from the suction port 91 of the BOG pipe 9 to the inner tank 4 in order to replace the air in the inner tank 4 with nitrogen after construction. In this air purge, nitrogen is supplied into the inner tank 4 from the suction port 91 located at the upper part in the inner tank 4, and the air in the inner tank 4 is pushed downward so as to achieve a piston flow. Air is discharged out of the inner tank 4 from the discharge port 81 located at the lower part. For this reason, in order to exhaust air efficiently, it is desirable that the nitrogen supplied into the inner tank 4 does not diffuse during the air purge.

  In the present embodiment, since the pipe inlet portion 92 extends vertically downward from the center side end portion of the inner tank roof plate 43 in the extending portion 93 to the suction port 91, when air purge is performed, nitrogen is directed downward. The air can be expelled from the upper side to the lower side so as not to diffuse and diffuse as much as possible in the inner tank 4. Moreover, in this embodiment, since the suction inlet 91 is located below the cool down ring 7, it can suppress that the discharge | released nitrogen collides with the cool down ring 7 and diffuses when performing an air purge.

  As described above, in the cryogenic liquid storage tank 1 of the present embodiment, since the suction port 91 is disposed at the center of the inner tank roof plate 43, the BOG in the inner tank having a high temperature is cooled through the BOG pipe 9. The liquid can be discharged from the liquid storage tank 1. In addition, since the BOG pipe 9 extends radially outward along the inner tank roof plate 43 from the suction port 91 in the inner tank 4, the BOG pipe 9 is disposed below the top 33 a of the outer tank roof plate 33. The outer tub roof plate 33 can be penetrated at the position. For this reason, the BOG piping 9 can be arrange | positioned below the top part 33a of the outer tank roof board 33. FIG.

  By the way, in the conventional tank, it is common that BOG piping is arrange | positioned so that the top part of an outer tank roof plate may be penetrated. In such a tank, the height of the entire tank including the BOG piping is higher than the top of the outer tub roof by the length protruding upward from the top of the outer tub roof in the BOG piping. With respect to such a conventional tank, in the present embodiment, as described above, the BOG pipe 9 can be disposed below the top 33a of the outer tank roof plate 33, so that the maximum liquid storage is achieved while suppressing the height of the entire tank. The amount can be increased.

  The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

  For example, the hole 95 may not be formed in the lower portion of the U-shaped curved portion 94. Further, the pipe inlet portion 92 may extend obliquely with respect to the vertical direction, or may extend in the horizontal direction. The cool down ring 7 may be positioned below the suction port 91.

DESCRIPTION OF SYMBOLS 1 Low temperature liquid storage tank 2 PC liquid barrier 3 Outer tank 32 Outer tank side plate 33 Outer tank roof plate 4 Inner tank 42 Inner tank side plate 43 Inner tank roof plate 44 Knuckle plate 7 Cool down ring 8 Receiving piping 81 Release port 9 BOG Piping 91 Suction port 92 Piping inlet portion 93 Extending portion 94 U-shaped bending portion 95 Hole

Claims (5)

An outer tank having a cylindrical outer tank side plate and an outer tank roof plate, and
A cylindrical inner tank side plate erected on the inner side of the outer tank side plate, an inner tank roof plate provided below the outer tank roof plate, and an upper end portion of the inner tank side plate and the inner tank roof plate. An inner tub having a knuckle plate connecting the peripheral portion;
A BOG pipe that sucks boil-off gas (hereinafter referred to as “BOG”) in which the low-temperature liquid is evaporated in the inner tank from a suction port disposed in the center of the inner tank roof plate, and discharges it to the outside of the inner tank, The inner tank extends radially outward from the suction port along the inner tank roof plate, and penetrates the inner tank roof plate and the outer tank roof plate at a position above the upper end portion of the knuckle plate. BOG piping,
The BOG pipe has a pipe inlet part having the suction port, an extension part extending radially outward from the pipe inlet part along the inner tub roof plate, and once extending downward from an end of the extension part and folded back. And a U-shaped curved portion extending upward.   The cryogenic liquid storage tank according to claim 1, wherein a hole for discharging the liquid re-liquefied in the BOG piping is formed in a lower portion of the U-shaped curved portion.   3. The cryogenic liquid storage tank according to claim 2, wherein a lowermost portion of the U-shaped curved portion is above a design liquid level of the cryogenic liquid stored in the internal space of the inner tank.   The said piping inlet part is a cryogenic liquid storage tank of any one of Claims 1-3 extended in the vertically downward direction from the edge part by the side of the center of the said inner tank roof board in the said extending part to the said suction inlet. It is arranged in the center of the inner tank roof plate, further comprising a cool down ring for spraying a cryogenic liquid in the inner tank,
The cryogenic liquid storage tank according to claim 1, wherein the suction port is positioned below the cool down ring.

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