Re-liquefaction device

Abstract

To provide a re-liquefaction device capable of sufficiently re-liquefying boil-off gas even when a vertical height of a tank is not very large.SOLUTION: According to one embodiment, a re-liquefaction device 2A for a tank 1 that stores liquefied gas, comprises: a circulation path 3 provided with a pump 4 that circulates liquefied gas below a saturation temperature at the pressure of a gas layer in the tank 1; and an agitation device 5 provided in the circulation path 3 on the downstream side with respect to the pump 4. The re-liquefaction device 2A further comprises: a boil-off gas treatment path 6 that guides boil-off gas generated in the tank 1 to the agitator 5; and a compressor 7 that is provided in the boil-off gas treatment path 6 and enables the boil-off gas to be sent into the agitation device 5. The agitation device 5 condenses the boil-off gas by agitating the boil-off gas and the liquefied gas.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a reliquefaction device for a tank that stores liquefied gas. [Background technology]

[0002] Conventionally, there has been known a reliquefaction device that reliquefies boil-off gas generated in a tank that stores liquefied gas. For example, Patent Document 1 discloses a reliquefaction device that reliquefies boil-off gas by ejecting the boil-off gas as bubbles into the liquefied gas in the tank. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-46295 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the reliquefaction device of Patent Document 1, the bubbles are reliquefied as they rise through the liquefied gas, so if the vertical height of the tank is not very large, there is a risk that the boil-off gas will not be sufficiently reliquefied.

[0005] Therefore, an object of the present disclosure is to provide a reliquefaction device that can sufficiently reliquefy boil-off gas even when the vertical height of the tank is not particularly large. [Means for solving the problem]

[0006] The present disclosure provides a reliquefaction device for a tank that stores liquefied gas, the reliquefaction device comprising: a circulation path provided with a pump that circulates liquefied gas that is below a saturation temperature at the pressure of a gas layer in the tank; a stirring device provided in the circulation path downstream of the pump; a boil-off gas treatment path that guides boil-off gas generated in the tank to the stirring device; and a compressor provided in the boil-off gas treatment path that enables the boil-off gas to be sent into the stirring device, wherein the stirring device condenses the boil-off gas by stirring the boil-off gas and the liquefied gas. Effect of the Invention

[0007] According to the present disclosure, a reliquefaction device is provided that can sufficiently reliquefy boil-off gas even when the vertical height of the tank is not particularly large. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a reliquefaction device according to an embodiment. [Diagram 2] FIG. 13 is a schematic diagram of a reliquefaction device according to a modified example. [Diagram 3] FIG. 13 is a schematic diagram of a reliquefaction device according to another modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] FIG. 1 shows a reliquefaction device 2A for a tank 1 that stores liquefied gas according to one embodiment. In this embodiment, the tank 1 and the reliquefaction device 2A are mounted on a ship that uses liquefied gas as fuel. However, the tank 1 and the reliquefaction device 2A may also be installed on land. In this embodiment, the liquefied gas is liquefied hydrogen. However, the liquefied gas may also be LNG (Liquefied Natural Gas), LPG (Liquefied Petroleum Gas), or the like.

[0010] In this embodiment, the tank 1 is a double-shell tank including an inner tank 11 and an outer tank 12. A vacuum layer is formed between the inner tank 11 and the outer tank 12. However, the tank 1 may be a single-shell tank covered with a heat insulating material. Also, in this embodiment, the tank 1 is horizontally cylindrical. However, the tank 1 may be vertically cylindrical. Alternatively, the tank 1 may be spherical or approximately rectangular.

[0011] Boil-off gas (BOG) is generated by evaporation of the liquefied gas in the tank 1. That is, in the tank 1, a liquid layer is formed by the liquefied gas, and a gas layer is formed by the boil-off gas.

[0012] The liquefied gas is sufficiently cooled when it is poured into the tank 1. For this reason, for a while after the liquefied gas is poured into the tank 1 while the liquid level of the liquefied gas is kept high, for example, for several weeks, a temperature layer is formed in the liquefied gas in the tank 1, and the temperature near the liquid level of the upper layer of the liquefied gas is the saturation temperature at the pressure of the gas layer in the tank 1 and is kept in equilibrium, but in the lower layer of the liquefied gas, it is possible to keep the temperature of the liquefied gas below the saturation temperature at the pressure of the gas layer in the tank 1. For example, the pressure of the gas layer in the tank 1 is equal to or higher than atmospheric pressure, and the temperature of the liquefied gas, liquefied hydrogen, which is the liquefied gas in the tank 1, is equal to or higher than 20K.

[0013] The reliquefaction device 2A includes a circulation path 3 that circulates the liquefied gas at a temperature lower than the saturation temperature at the pressure of the gas layer in the tank 1. The circulation path 3 is provided with a pump 4, and a stirring device 5 is provided downstream of the pump 4.

[0014] In this embodiment, the pump 4 is provided in the circulation path 3 downstream of the upstream end of the circulation path 3, and the pump 4 and the agitator 5 are disposed outside the tank 1. Therefore, the upstream end of the circulation path 3 is connected to the inner tank 11 of the tank 1, and the downstream part of the circulation path 3 penetrates the tank 1 from the outside to the inside. In the illustrated example, the downstream end of the circulation path 3 opens near the bottom of the inner tank 11 of the tank 1, but the downstream end of the circulation path 3 may be configured to be able to spray the liquefied gas in the gas layer in the tank 1.

[0015] Furthermore, in this embodiment, the pump 4 and the stirring device 5 are disposed in the vacuum insulation pod 8. The vacuum insulation pod 8 has a vacuum layer formed between its inner wall and outer wall. The inner vessel 11 of the tank 1 and the pump 4 are connected by an outlet path 31. The inside of the vacuum insulation pod 8 is filled with liquefied hydrogen or hydrogen gas, which is the same as the liquefied gas stored in the tank 1. The portion of the outlet path 31 located in the outer vessel 12 of the tank 1 is composed of a single pipe, the portion between the outer vessel 12 and the inner or outer wall of the vacuum insulation pod 8 is composed of a vacuum insulation double pipe, and the portion located within the inner or outer wall of the vacuum insulation pod 8 is composed of a single pipe.

[0016] Alternatively, the inner vessel 11 of the tank 1 and the vacuum insulation pod 8 may be connected by the outlet passage 31, the inside of the vacuum insulation pod 8 may be filled with liquefied gas discharged from the inner vessel 11 of the tank 1 through the outlet passage 31, and the pump 4 may suck in the liquefied gas in the vacuum insulation pod 8. In this case, the outlet passage 31 and the inside of the vacuum insulation pod 8 may form the upstream portion of the circulation passage 3.

[0017] The pump 4 sucks the liquefied gas in the tank 1 through the outlet path 31. The liquefied gas discharged from the pump 4 flows into the agitator 5 through the discharge path 32, and the liquefied gas flowing out from the agitator 5 is returned into the tank 1 through the return path 33.

[0018] The discharge path 32 is constructed of a single pipe since it is located inside the inner wall of the vacuum insulation pod 8. In the return path 33, the portion located inside the inner wall or outer wall of the vacuum insulation pod 8 is constructed of a single pipe, the portion between the inner wall or outer wall of the vacuum insulation pod 8 and the outer tank 12 of the tank 1 is constructed of a vacuum insulation double pipe, and the portion located inside the outer tank 12 of the tank 1 is constructed of a single pipe.

[0019] Furthermore, the reliquefaction device 2A includes a boil-off gas treatment path 6 that guides the boil-off gas generated in the tank 1 to the agitator 5. The boil-off gas treatment path 6 is provided with a compressor 7 that enables the boil-off gas to be fed into the agitator 5. In other words, the compressor 7 pressurizes the boil-off gas to a pressure higher than the outlet pressure of the pump 4.

[0020] The agitator 5 agitates the boil-off gas and the liquefied gas, thereby condensing the boil-off gas. The configuration of the agitator 5 is not particularly limited, and various configurations can be adopted. The liquefied gas containing the condensed liquid of the boil-off gas is returned to the tank 1 through the return line 33. Instead of disposing the agitator 5 in the vacuum insulation pod 8, the surface of the agitator 5 may be covered with a vacuum insulation structure.

[0021] The compressor 7 is disposed outside the tank 1. In the boil-off gas treatment path 6, the portion between the inner tank 11 and the outer tank 12 of the tank 1 is configured with a single pipe, the portion between the outer tank 12 of the tank 1 and the inner or outer wall of the vacuum insulation pod 8 is configured with a vacuum insulation double pipe, and the portion located within the inner or outer wall of the vacuum insulation pod 8 is configured with a single pipe.

[0022] As described above, in the reliquefaction apparatus 2A of this embodiment, the boil-off gas is condensed by being stirred with the liquefied gas by the stirring device 5, so that the boil-off gas can be sufficiently reliquefied even if the vertical height of the tank 1 is not so large. Moreover, the boil-off gas is condensed by utilizing the cold heat of the liquefied gas that is less than the saturation temperature at the pressure of the gas layer in the tank 1, so that the condensed liquefied gas, i.e., the reliquefied boil-off gas, is prevented from vaporizing again after being returned to the tank 1.

[0023] Furthermore, in this embodiment, since the pump 4, the agitator 5 and the compressor 7 are disposed outside the tank 1, maintenance of the pump 4, the agitator 5 and the compressor 7 can be easily performed.

[0024] <Modification> The present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present disclosure.

[0025] For example, as in a modified reliquefaction apparatus 2B shown in Fig. 2, the agitator 5 may be disposed inside the tank 1, and the pump 4 and the compressor 7 may be disposed outside the tank 1. According to this configuration, the assembly of the tank 1 and the reliquefaction apparatus 2B can be made compact.

[0026] 3, the pump 4 and the agitator 5 may be disposed inside the tank 1, and the compressor 7 may be disposed outside the tank 1. In this modification, the outlet path 31 and the vacuum insulation pod 8 are omitted, and the pump 4 is provided in the circulation path 3 at the upstream end of the circulation path 3. With this configuration, the assembly of the tank 1 and the reliquefaction device 2C can be significantly made compact. In FIG. 3, the circulation path 3 penetrates from the inside to the outside of the tank 1, and then penetrates from the outside to the inside, but the entire circulation path 3 may be disposed inside the tank 1.

[0027] <Summary> In a first aspect, the present disclosure provides a reliquefaction device for a tank for storing liquefied gas, the reliquefaction device comprising: a circulation path provided with a pump for circulating liquefied gas below a saturation temperature at the pressure of a gas layer in the tank; a stirring device provided in the circulation path downstream of the pump; a boil-off gas treatment path for directing boil-off gas generated in the tank to the stirring device; and a compressor provided in the boil-off gas treatment path for enabling the boil-off gas to be sent into the stirring device, wherein the stirring device condenses the boil-off gas by stirring the boil-off gas and the liquefied gas.

[0028] According to the above configuration, the boil-off gas is condensed by being stirred with the liquefied gas by the stirring device, so that the boil-off gas can be sufficiently re-liquefied even if the height of the tank in the vertical direction is not so large. Moreover, the boil-off gas is condensed by utilizing the cold heat of the liquefied gas that is less than the saturation temperature at the pressure of the gas layer in the tank, so that the condensed liquefied gas, i.e., the re-liquefied boil-off gas, is prevented from vaporizing again after being returned to the tank.

[0029] As a second aspect, in the first aspect, the pump, the agitator, and the compressor may be disposed outside the tank. With this configuration, maintenance of the pump, the agitator, and the compressor can be easily performed.

[0030] As a third aspect, in the first aspect, the agitator may be disposed inside the tank, and the pump and the compressor may be disposed outside the tank. With this configuration, the assembly of the tank and the reliquefaction device can be made compact.

[0031] As a fourth aspect, in the first aspect, the pump and the agitator may be disposed inside the tank, and the compressor may be disposed outside the tank. With this configuration, the assembly of the tank and the reliquefaction device can be significantly made compact.

[0032] As a fifth aspect, in any one of the first to fourth aspects, for example, the liquefied gas may be liquefied hydrogen. [Explanation of symbols]

[0033] 1 Tank 2A,2B,2C Reliquefaction equipment 3 Circulation route 4. Pump 5. Mixing device 6 Boil-off gas treatment line 7 Compressor

Claims

1. A reliquefaction device for a tank that stores liquefied gas, comprising: a circulation path provided with a pump for circulating the liquefied gas having a temperature lower than a saturation temperature at the pressure of the gas layer in the tank; a stirring device provided in the circulation path downstream of the pump; A boil-off gas treatment path that guides the boil-off gas generated in the tank to the stirring device; A compressor provided in the boil-off gas treatment passage and capable of feeding the boil-off gas into the stirring device; The stirring device stirs the boil-off gas and the liquefied gas to condense the boil-off gas.

2. The reliquefaction apparatus of claim 1 , wherein the pump, the agitator and the compressor are located outside the tank.

3. The reliquefaction apparatus of claim 1 , wherein the agitator is disposed within the tank, and the pump and compressor are disposed outside the tank.

4. The reliquefaction apparatus of claim 1 , wherein the pump and the agitator are disposed within the tank, and the compressor is disposed outside the tank.

5. 5. The reliquefaction apparatus according to claim 1, wherein the liquefied gas is liquefied hydrogen.

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