JP2007308156A - Structure of mobile type low-temperature liquefied gas tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain swing of a liquid stored in a tank and prevent a pressure increase in the tank due to the swing during transportation of liquefied gas with a low boiling point, low latent heat, and low density, such as liquid hydrogen or liquid helium, at a low liquid level, and to reduce a pressure increase in the tank even if this tank is used as a fixed type liquefied gas tank. <P>SOLUTION: The mobile low-temperature liquefied gas tank has a plurality of breakwater plates 8 arranged in the tank 5 and perpendicular to the lengthwise direction of the tank 5 with a space in a vertical direction and the lengthwise direction. In such a gas tank, a plurality of lower breakwater plates 9 each having a communication hole 9a are disposed in the lower part of the tank 5 at intervals perpendicularly to the lengthwise direction and away from the breakwater plates 8. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a mobile low temperature suitable for transporting liquefied gas (e.g., liquid helium, liquid hydrogen) having a low boiling point, low density, and low latent heat mainly on a truck, rail freight vehicle, or ship. The present invention relates to the structure of a liquefied gas tank (movable cryogenic container).

For mobile low-temperature liquefied gas tanks for transporting high-density liquefied gas such as LPG (liquefied petroleum gas) and LNG (liquefied natural gas), the wave protection plate ( Baffle plate) is provided. That is, as shown in FIG. 5, in the case of a horizontal tank, the wave preventing plate 8 is perpendicular to the traveling direction of the vehicle (in this case, the longitudinal direction in the tank) and has an area of 40% or more of the transverse area of the tank 5. It is specified that the upper space 5A in the tank 5 is provided at a position in the vertical direction at which the cross-sectional area of the tank 5 is 20% or less so that there is one sheet with a tank internal volume of 3 m ³ or less. This regulation is intended for high-density liquefied gas as described above. For the purpose of reducing momentum changes due to disturbance to the tank 5, such as acceleration and vibration during start and stop during truck transportation, for example. Yes.

  As a prior art of this type of low-temperature liquefied gas tank, a gas pipe communicating with the atmosphere is provided in a low-temperature refrigerant container, and the gas-liquid two-phase gas in the low-temperature refrigerant container is connected to this gas pipe by centrifugal force and gravity. There has been proposed a low-temperature apparatus provided with a gas-liquid separator composed of a spiral tube that separates a gas phase and a liquid phase (see, for example, Patent Document 1). In this low-temperature apparatus, as a means for returning the particulate liquid generated in a low-temperature refrigerant container such as liquid helium into the liquid, a two-phase gas-liquid is caused to flow in the helical pipe, thereby The gas phase and the liquid phase are separated by the centrifugal force generated when passing through, and the liquid phase flows along the spiral tube due to the centrifugal force and gravity, and in the gas pipe where the centrifugal force disappears, The liquid phase can be returned to the liquid along the wall of the gas pipe. On the other hand, the gas phase collects at substantially the center of the gas pipe having a small centrifugal force and rises above the gas pipe. Only this gas phase, that is, gas, can be discharged into the atmosphere or into the refrigerator.

  In addition, as a prior art of the low temperature apparatus in Patent Document 1, with regard to mobile type sloshing, by providing a baffle plate in a liquid helium container, the sloshing of liquid helium can be reduced during traveling, and as a result, the liquid helium during traveling is reduced. RCVan Meerbeke's “Thermal Stratification and Sloshing in Liquid Helium Trailers”; Advances in Cryogenic Engineering. Vol 13, 199, which has been shown to reduce consumption, is cited.

  As another prior art, a cylindrical liquid storage that can prevent the occurrence of abnormally large sloshing phenomenon by installing a partition wall with flow holes in which liquid can freely move in the storage tank and dividing the tank body vertically into multiple tanks A tank structure has been proposed (see, for example, Patent Document 2).

Further, as another prior art, a ship having a structure in which a partition is provided in a liquid tank mounted on the ship so as to prevent the wave of liquid due to rolling and pitching of the ship, and mutual communication holes are formed in these partitions. A liquid tank for mounting has been proposed (see, for example, Patent Document 3).
JP-A-9-189399 (0004, 0009 to 0015, 0019 to 0021 and FIG. 1) Japanese Patent Laying-Open No. 2005-280837 (0005/0006/0012 to 0014 and FIG. 1) JP 51-61980 (pages 3 and 4 and FIGS. 3 and 4)

  By the way, transportation of liquid hydrogen will become a very important issue in the future for the beginning of a society that consumes hydrogen energy, including fuel cells. Liquid hydrogen will be transported using a mobile cryogenic liquefied gas tank. In this case, so-called small-port delivery is expected in which liquid hydrogen stored in a relatively large (eg, ISO 40 ft container) liquefied gas tank is distributed to a plurality of hydrogen stations. However, the amount of liquid hydrogen in the liquefied gas tank decreases in stages. In particular, when the transportation is performed at a low liquid level (for example, the liquid level is 10 to 50%), the sloshing (swing) of the stored liquid in the tank becomes intense when the vehicle starts and stops. As a result, the oscillating liquid comes into contact with the high-temperature part (ceiling surface, etc.) of the tank, and the evaporation of the stored liquid is promoted due to the influence of intrusion heat, so that the pressure in the tank rises and may exceed the tank design pressure. . Even when the liquid level of the stored liquid in the tank is relatively high, when transporting liquefied gas with low boiling point, low latent heat and low density such as liquid hydrogen and liquid helium, In the conventional tank structure with a wave barrier only on the side, the stored liquid sloshing when the vehicle starts and stops, so that the liquid becomes small particles from the liquid surface and is pushed into the atmosphere together with the gas. The same phenomenon as when the intrusion heat increases may occur.

  The present invention has been made in view of the above-mentioned points, and when the low boiling point / low latent heat / low density liquefied gas such as liquid hydrogen or liquid helium is transported at a low liquid level, the stored liquid in the tank is swung. Providing a structure of mobile cryogenic liquefied gas tank (movable cryogenic container) that can suppress and prevent pressure rise due to rocking and reduce pressure rise in the tank even when used as a stationary liquefied gas tank It is something to try.

  In order to achieve the above object, the structure of the mobile cryogenic liquefied gas tank according to the present invention includes a plurality of wave blocking plates in a direction perpendicular to the longitudinal direction in the tank, a space in the upper part and the lower part, and a longitudinal part. In the structure of the mobile cryogenic liquefied gas tank provided with an interval in the direction, a plurality of lower wave breakers having communication holes are perpendicular to the longitudinal direction of the lower part in the tank and from each wave breaker It is characterized in that it is provided so as to be spaced apart in the tank longitudinal direction.

  According to the structure of the mobile low-temperature liquefied gas tank having the above-described configuration, the lower wave-breaking plate can be used for transporting a low-boiling point, low latent heat, low-density liquefied gas such as liquid hydrogen or liquid helium at a low liquid level. However, since the rocking of the stored liquid at the time of starting and stopping is reduced together with the upper side wave preventing plate, the rocking of the stored liquid is suppressed (see the simulation of FIG. 6), and the increase in the pressure in the tank is prevented. Further, since the lower wave preventing plate is provided apart from the upper wave preventing plates, heat input from the outside of the tank via the wave preventing plate does not increase.

  According to a second aspect of the present invention, the lower wave-breaking plate is formed at a position substantially below the middle position between the wave-breaking plates and at a position substantially below the middle position between the wave-breaking plate at the foremost position and the front wall in the tank and at the last position. A horizontal wave-breaking plate can be provided at a position substantially below the middle position between the corrugated plate and the rear wall in the tank, and a horizontal wave-breaking plate at a substantially middle position in the vertical direction of the front and rear wall surfaces in the tank.

  With this configuration, even when the liquid level of the liquid stored in the tank is low and the acceleration is received, the liquid stored in the tank is shown in the simulation in the lower part of FIG. 6 (case 2). By suppressing the oscillation of the liquid, there is no risk of the stored liquid coming into contact with the high temperature part such as the ceiling surface in the tank, so the stored liquid is heated by the heat capacity of the high temperature part tank wall, and the pressure in the tank is reduced. A significant increase is prevented.

  According to a third aspect of the present invention, the lower end portion of each of the wave preventing plates and the upper end portion of the lower wave preventing plate can be configured to overlap in the height direction of the tank. By configuring in this way, the stored liquid in the tank is prevented from exceeding the upper end portion of each lower wave preventing plate due to the swinging, so that the swinging of the stored liquid is further suppressed.

  According to a fourth aspect of the present invention, a metal plate (such as a copper plate or an aluminum plate) having a high thermal conductivity can be attached to at least one surface of each of the wave preventing plates.

  With this configuration, when used as a stationary liquefied gas tank, as shown in FIG. 3, the liquid in the tank undergoes natural convection in the stationary evaporative gas sealing (sealed) state, as shown in FIG. As a result, a stratification (high temperature layer) is formed on the liquid surface portion at a saturation temperature corresponding to the gas phase pressure, and the deep portion of the liquid becomes supercooled. In this state, when the upper part of a metal plate (for example, a copper plate) having a high thermal conductivity is attached to each wave preventing plate on the upper side and hung downward in the stored liquid, the high temperature layer is passed through the metal plate to the supercooling part ( The cooling heat from the bulk layer) is conducted and cooled, so that the increase in pressure in the tank is reduced.

Since the structure of the mobile low-temperature liquefied gas tank according to the present invention is configured as described above, the following excellent effects are obtained. That is,
Even when transporting low boiling point, low latent heat, and low density liquefied gas such as liquid hydrogen at a low liquid level, the lower wave breaker, together with the wave breaker on the upper side, swings the stored liquid when starting and stopping. Therefore, the stored liquid is prevented from swinging and the tank pressure is prevented from increasing. Further, since the lower wave preventing plate is provided apart from the upper wave preventing plates, heat input from the outside of the tank via the wave preventing plate does not increase.

  Hereinafter, the structure of a mobile low-temperature liquefied gas tank according to the present invention will be described with reference to the drawings, citing embodiments.

  FIG. 1 is a perspective view showing a structure of a liquid hydrogen container tank according to an embodiment of the present invention, with a part removed and showing a part in the tank, and FIG. 2 conceptually showing the structure of the container tank of FIG. It is a longitudinal cross-sectional view shown.

  As shown in FIG. 1, the mobile liquid hydrogen container tank 1 is used by being mounted on a truck bed or a railcar freight vehicle, and is supported in a container frame 2 via front and rear pedestals 2a. Yes. The container tank 1 includes an outer tank 3 and an inner tank 5, and the inner tank 5 is supported by a plurality of tension rods 6 in a central space in the outer tank 3. A space between the outer tank 3 and the inner tank 5 is formed in the vacuum heat insulating layer 4. An operation box 7 is integrally provided at the rear part of the outer tank 3, and this operation box 7 is also supported in the container frame 2.

As shown in FIG. 2, the inner tank 5 is similar to the outer tank 3 in that the front and rear surfaces 5 a and 5 b are hemispherical surfaces with the central portion projecting outward, the side circumferential surface is circular in cross section and longer than the diameter. It consists of a long cylindrical body. Near the upper part in the inner tank 5, in this example, four wave blocking plates 8 are provided at intervals in the longitudinal direction. The longitudinal direction of the inner tank 5 is the traveling direction of the truck and the railway vehicle. The wave preventing plate 8 is in accordance with the provisions of the High Pressure Gas Safety Law, and is disposed at right angles to the longitudinal direction in the inner tank 5 as with the wave preventing plate 8 shown in FIG. Is disposed at a position that is 40% or more of the cross-sectional area of the inner tank 5 and the cross-sectional area of the upper space portion 5A is 20% or less of the cross-sectional area of the inner tank 5. For this reason, the lower space part 5B of each wave preventing plate 8 is larger than the upper space part 5A. Further, the wave preventing plate 8 is provided at a ratio of one sheet per 3.3 m ³ or less of the volume in the inner tank 5.

  At the lower part (closer to the bottom) in the inner tank 5, a lower wave-breaking plate 9 is erected on the tank bottom surface with a space in the longitudinal direction and spaced from the wave-breaking plate 8. In the case of this example, the lower wave-breaking plate 9 is located below the intermediate position between the adjacent wave-breaking plates 8 and 8 and below the foremost wave-breaking plate 8 and the tank front surface 5a and the last wave-breaking plate 8 and the tank. It arrange | positions below between the rear surfaces 5b. The height of each lower wave-breaking plate 9 is slightly lower than the lower end of the wave-breaking plate 8, and a communication hole 9 a is formed near the lower end at the center in the width direction of each lower wave-breaking plate 9. The pitch and area of the lower wave preventing plate 9 are not limited and are determined in consideration of the magnitude of the disturbance. Further, a horizontal wave breaking plate 10 is provided opposite to each other at an intermediate position in the vertical direction between the tank front surface 5a and the tank rear surface 5b and separated from the wave blocking plate 8 and the lower wave blocking plate 9.

  Furthermore, in the present embodiment, considering the reduction in pressure rise when the mobile liquid hydrogen container tank 1 is used as a stationary liquid hydrogen container, a metal plate (copper plate) 11 having a high thermal conductivity is connected to each wave-protecting plate 8 and each It is affixed on both surfaces of the lower wave-shielding board 9, respectively.

  Here, FIG. 3 is a schematic diagram showing the action and effect when the upper part of the copper plate 11 is attached to each upper-side wave preventing plate 8 and hung downward in the liquid hydrogen H. FIG. In other words, when the mobile liquid hydrogen container tank 1 is used as a stationary liquid hydrogen container, as shown in FIG. 3, the copper plate 11 causes the evaporative gas sealed (sealed) in the stationary state to move outwardly from the inner tank 5. The liquid hydrogen H in the tank 5 undergoes natural convection due to intrusion heat from the water, and a stratification (high temperature layer) is formed on the liquid surface portion Hu at a saturation temperature corresponding to the gas phase pressure, and the deep portion Hd in the liquid hydrogen H is excessive. It becomes cool. In this state, when the copper plate 11 is attached to each of the wave preventing plates 8 on the upper side and hung downward in the liquid hydrogen H, the high-temperature layer receives the cooling heat from the supercooling portion (bulk layer) via the copper plate 11. Conducted and cooled, the increase in the pressure in the tank 5 is reduced.

The size of the inner tank 5 is 15 m ³ , the inner diameter is 2.1 m, the inner length is 4.6 m, the average width of the wave-breaking plate 8 is 1 m, the thickness is 4 mm, and the number of sheets is four. The thickness of the copper plate 11 Is ² mm and the effective area is 0.004 m ^2, and is attached to both surfaces of the wave-breaking plate 8. And ・ Invasion heat into the inner tank 5: 40 W ・ The thermal conductivity of the copper plate 11 is about 1000 W / mK @ 20K (The thermal conductivity of copper is dramatically higher than that at room temperature, and the thermal conductivity of liquid hydrogen Greater than 0.2W / (mK))
-Temperature difference between the high temperature layer and the supercooling part: 3K (2.3atm saturation temperature 23K-supercooling temperature 20K)-Heat conduction length of the copper plate 11 1m
If a trial calculation is made based on the above assumptions, the possible heat transfer amount per wave-breaking plate 8 is 12 W, and the total heat transfer amount is 48 W.

In addition, about heat balance by evaporative gas sealing (livestock pressure) period,
External heat input = latent heat of liquid evaporation + internal energy change of liquid / gas + high temperature layer temperature increase + tank wall temperature increase
This ratio greatly affects the shape of the inner tank 5, the liquid level of the liquid hydrogen H, the settling time, etc., but is 8 W when the temperature rise of the high temperature layer is assumed to be 20%. Therefore, this amount of heat is the amount of heat that can be sufficiently cooled by a metal plate such as the copper plate 11 or an aluminum plate.

  FIG. 4 shows another embodiment of the mobile low temperature gas tank structure according to the present invention. The low temperature gas tank 1 ′ of this example is different from the low temperature gas tank 1 of the above embodiment in that the height of the lower wave breaker 9 is high. The height is made higher than the lower end of the wave preventing plate 8 and the horizontal wave preventing plate 11 is omitted. Since the upper end portion of the lower wave preventing plate 9 is wrapped with the lower end portion of the wave preventing plate 8, particularly when the liquid level of the liquid hydrogen H in the inner tank 5 is lowered from the upper end of the lower wave preventing plate 9, The liquid hydrogen H does not easily exceed the upper end of the lower wave-breaking plate 9, and the swing when the liquid hydrogen H is subjected to acceleration is further suppressed. For this reason, the front and rear horizontal wave blocking plates 10 are omitted.

  Also, as shown in FIGS. 4B and 4C, a plurality of reinforcing holes 8a projecting so that the edge of the hole is curved in one direction are formed in the upper wave preventing plate 8 at regular intervals. The one or two thin rods 12 (FIG. 4 (a)) that are omitted connect the wave preventing plates 8 using one or two reinforcing holes 8a. Further, the lower end 8b of the wave preventing plate 8 is bent to one side to increase the strength (rigidity). Therefore, the deformation of the wave preventing plate 8 due to the fluctuation of the liquid level is unlikely to occur, but such a reinforcing structure is effective in the case of a high-density liquefied gas such as LPG or LNG. It may be omitted in gas tanks dedicated to high density liquefied gas.

  FIG. 6 is a diagram showing a simulation compared with the conventional tank structure (FIG. 5) in order to confirm the effect of suppressing the liquid level fluctuation by the tank structure (FIG. 2) of the above embodiment according to the present invention. . The inner tank 5 has an inner diameter of 2.1 m × inner length of 4.6 m, liquid hydrogen level of 50%, acceleration in the traveling direction of 0.4 G (braking at a traveling speed of 100 km / h in 7 seconds) This is a simulation in the case of applying the action (corresponding to the deceleration acceleration to stop). The thermal analysis model uses STAR-CD. Case 1 is a conventional structure and case 2 is the present invention.

  In case 2, it is confirmed that the rise of the liquid level is mainly suppressed by the lower wave-breaking plate 9, and the raised liquid prevents heat exchange (increased heat input) due to contact with the upper wall in the tank. .

It is the perspective view which showed the structure of the liquid hydrogen container tank which concerns on an Example at this invention, and represented a part in a tank by removing a part. It is a longitudinal cross-sectional view which shows notionally the structure of the container tank of FIG. FIG. 6 is a schematic diagram showing the action and effect when the upper part of the copper plate 11 is attached to each upper-side wave preventing plate 8 and hung downward in the liquid hydrogen H. 2A and 2B show another embodiment of the mobile cryogenic gas tank structure according to the present invention, in which FIG. 2A is a longitudinal sectional view corresponding to FIG. 2, FIG. It is a cc line expanded sectional view of. The conventional tank structure by prescription | regulation of the high pressure gas security law is shown, (a) is a longitudinal cross-sectional view, (b) is the bb sectional view taken on the line of (a). 7 is a diagram showing a simulation compared with a conventional tank structure (FIG. 5) in order to confirm the effect of suppressing the liquid level fluctuation by the tank structure (FIG. 2) of the above embodiment according to the present invention.

Explanation of symbols

1.1 'mobile liquid hydrogen container tank (mobile low temperature liquefied gas tank)
2 Container frame 2a pedestal 3 Outer tank tank 4 Vacuum heat insulating layer 5 Inner tank tank 6 Tension rod 7 Operation box 8 Wave breaker 9 Lower wave breaker 10 Horizontal wave breaker 11 Copper plate (high thermal conductivity metal plate)
12 rods

Claims (4)

  In the structure of a mobile cryogenic liquefied gas tank having a plurality of wave blocking plates in a direction perpendicular to the longitudinal direction in the tank, with spaces in the upper and lower portions and spaced in the longitudinal direction, there are communication holes. A mobile low temperature characterized in that a plurality of lower wave-breaking plates are provided in a direction perpendicular to the longitudinal direction of the lower part in the tank and spaced apart from each wave-breaking plate in the tank longitudinal direction. Structure of liquefied gas tank.   The lower wave-breaking plate includes a lower position between the wave-breaking plates and a position between the wave-breaking plate at the frontmost position and a front wall in the tank. 2. The structure of a mobile cryogenic liquefied gas tank according to claim 1, wherein a horizontal wave preventing plate is provided at a substantially intermediate position in the vertical direction of each of the front and rear wall surfaces in the tank.   The structure of the mobile cryogenic liquefied gas tank according to claim 1 or 2, wherein a lower end portion of each of the wave preventing plates and an upper end portion of the lower wave preventing plate are overlapped with each other in a tank height direction.   The structure of the mobile cryogenic liquefied gas tank according to any one of claims 1 to 3, wherein a metal plate having a high thermal conductivity is attached to at least one surface of each of the wave preventing plates.

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