Storage facility for low-temperature liquefied gas

Abstract

To provide a storage tank facility for low temperature liquefied gas in which backflow of gas does not occur in an economizer line.SOLUTION: A cryogenic liquefied gas storage facility includes a tank that stores cryogenic liquefied gas, a liquid feeding line that feeds the cryogenic liquefied gas from the tank, an economizer line that includes a first end communicating with an upper space in the tank at a first position, a second end connected to the liquid feeding line, and a first valve and feeds gas in the tank to the liquid feeding line by an opening operation of the first valve, and a discharge line that includes a first end communicating with the upper space in the tank at a second position different from the first position and a second valve and discharges the gas in the tank to the atmosphere by an opening operation of the second valve.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a storage tank facility for low-temperature liquefied gas. [Background technology]

[0002] A low-temperature liquefied gas such as liquefied hydrogen is transported from a low-temperature liquefied gas production facility to a supply destination of the low-temperature liquefied gas (hereinafter simply referred to as the "supply destination"), for example, by tank truck, and is supplied from the tank truck to a storage tank facility at the supply destination (hereinafter simply referred to as the "storage tank facility"). Figures 4 to 6 show storage tank facilities of the prior art. As shown in Figure 4, storage tank facility 100 includes a tank 101 that can store the low-temperature liquefied gas supplied from tank truck R in a liquid state, and a liquid supply line 102. A supply evaporator 103 is provided on liquid supply line 102. The low-temperature liquefied gas in tank 101 is supplied to supply evaporator 103, as shown by arrow X1 in Figure 4, and is evaporated in supply evaporator 103 and supplied to a point of use in a gasified state.

[0003] When the low-temperature liquefied gas in the tank 101 is supplied to the point of use, the liquid level 1 of the low-temperature liquefied gas in the tank 101 drops. The low-temperature liquefied gas in the tank 101 is supplied to the point of use via the liquid supply line 102 while the pressure inside the tank 101 is maintained at a set pressure. Therefore, when the liquid level 1 of the low-temperature liquefied gas in the tank 101 drops, it is necessary to pressurize the inside of the tank 101 to maintain the pressure inside the tank 101 at the set pressure. For this reason, the storage tank facility 100 is provided with a pressurization line 104.

[0004] A pressurization evaporator 105 is provided in the pressurization line 104. When the pressure inside the tank 101 drops, low-temperature liquefied gas is taken out of the tank 101 and supplied to the pressurization evaporator 105, as shown by arrow X2 in FIG. 4. The low-temperature liquefied gas evaporates in the pressurization evaporator 105, becomes pressurized gas, and is sent to an upper space (gas phase) G inside the tank 101. This pressurizes the inside of the tank 101, and the low-temperature liquefied gas inside the tank 101 is supplied to a point of use via the liquid supply line 102.

[0005] If the supply of cryogenic liquefied gas to a point of use is stopped or the amount of cryogenic liquefied gas supplied is reduced, the cryogenic liquefied gas in the tank 101 vaporizes due to natural evaporation or external heat intrusion. If the vaporized gas accumulates in the upper space (gas phase) G of the tank 101, the pressure in the tank 101 may rise and exceed the set pressure. The tank storage facility 100 is equipped with an economizer line 106 to reduce the pressure in the tank 101 when the pressure in the tank 101 exceeds the set pressure. If the pressure in the tank 101 exceeds the set pressure, the supply of pressurized gas to the tank 101 through the pressurization line 104 is stopped. At the same time, as shown by arrow X3 in FIG. 5 , excess gas causing a pressure increase in the tank 101 is sent to the liquid supply line 102 via the economizer line 106. The gas sent to the liquid supply line 102 is supplied to the point of use together with the cryogenic liquefied gas flowing through the liquid supply line 102. This allows the pressure inside the tank 101 to be reduced without unnecessary loss of the low-temperature gas inside the storage tank.

[0006] Even if an attempt is made to reduce the pressure inside the tank 101 by operating the economizer line 106, if the supply of liquefied gas to the point of use is stopped for a long period of time, an abnormal situation may occur, such as the pressure inside the tank 101 continuing to rise. The tank storage facility 100 is provided with a discharge line 107 to release the gas inside the tank 101 into the atmosphere when an abnormal situation occurs. When an abnormal situation occurs, the gas inside the tank 101 is released into the atmosphere via the discharge line 107, as shown by arrow X4 in FIG. 6. This allows the pressure inside the tank 101 to be reduced (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 8-128595 Summary of the Invention [Problem to be solved by the invention]

[0008] In the conventional tank storage facility 100, a portion of the economizer line 106 connected to the tank 101 is also used as the discharge line 107. Therefore, when the discharge line 107 operates while the economizer line 106 is in operation, releasing the gas in the tank 101 into the atmosphere, the pressure in the economizer line 106 drops at the point where it branches off from the upstream discharge line 107. This creates a pressure difference between the upstream and downstream sides (the liquid supply line 102 side) of the economizer line 106. Depending on the properties of the low-temperature liquefied gas or the usage environment, this pressure difference can cause a backflow of gas. If a backflow occurs in the economizer line 106, as shown by arrow X5 in FIG. 6 , and the gas flows in the opposite direction from the liquid supply line 102 and into the tank 101, this can potentially cause a pressure increase in the tank 101.

[0009] An object of the present disclosure is to provide a storage tank facility for low-temperature liquefied gas in which gas backflow does not occur in the economizer line. [Means for solving the problem]

[0010] The low-temperature liquefied gas storage tank equipment according to the present disclosure comprises: a tank for storing low-temperature liquefied gas; a liquid transfer line for transferring the low-temperature liquefied gas from the tank; an economizer line having a first end communicating with an upper space in the tank at a first position, a second end connected to the liquid transfer line, and a first valve, the economizer line transferring gas in the tank to the liquid transfer line when the first valve is opened; and a discharge line having a first end communicating with the upper space in the tank at a second position different from the first position, and a second valve, the discharge line releasing the gas in the tank to the atmosphere when the second valve is opened. [Effects of the Invention]

[0011] According to the low-temperature liquefied gas storage tank facility of the present disclosure, backflow of gas in the economizer line can be prevented. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing a storage tank facility for low-temperature liquefied gas according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram showing a gas flow when an economizer line is operating in a low-temperature liquefied gas storage tank facility according to an embodiment of the present disclosure. [Figure 3] FIG. 3 is a schematic diagram showing the gas flow when the economizer line and the discharge line are in operation in a low-temperature liquefied gas storage tank facility according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a schematic diagram showing a conventional low-temperature liquefied gas storage tank facility. [Figure 5] FIG. 5 is a schematic diagram showing the gas flow when the economizer line is operating in a conventional low-temperature liquefied gas storage tank facility. [Figure 6] FIG. 6 is a schematic diagram showing the gas flow when the economizer line and the discharge line are in operation in a conventional low-temperature liquefied gas storage tank facility. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Outline of the embodiment] First, an overview of the low-temperature liquefied gas storage tank facility according to the present disclosure will be listed and described.

[0014] The low-temperature liquefied gas storage tank equipment according to the present disclosure comprises: a tank for storing low-temperature liquefied gas; a liquid transfer line for transferring the low-temperature liquefied gas from the tank; an economizer line having a first end communicating with an upper space in the tank at a first position, a second end connected to the liquid transfer line, and a first valve, the economizer line transferring gas in the tank to the liquid transfer line when the first valve is opened; and a discharge line having a first end communicating with the upper space in the tank at a second position different from the first position, and a second valve, the discharge line releasing the gas in the tank to the atmosphere when the second valve is opened.

[0015] Storage tank facilities for low-temperature liquefied gases, such as liquefied hydrogen, are equipped with an economizer line and a discharge line as a means for discharging gas from the upper space of the tank to reduce the pressure inside the tank when the pressure inside the tank increases. If the economizer line and the discharge line were connected to the tank separately and corresponding gas outlets were formed on the tank, heat would be more likely to enter the tank from the outside. The tanks in storage tank facilities are required to have a highly insulated structure in order to store the low-temperature liquefied gas in a low-temperature liquid state. Therefore, to improve the insulation of the tank, it is necessary to reduce the number of gas outlets formed on the tank. It is generally recognized by those skilled in the art that the economizer line and the discharge line share a common connection to the tank, as in storage tank facilities of the prior art.

[0016] However, the inventors' investigations revealed that if a portion of the economizer line connected to the tank is also used as a discharge line, as described above, when gas in the tank is released into the atmosphere through the discharge line, the gas flow in the economizer line may backflow in the direction opposite to the direction of the liquid supply line. If gas backflow occurs in the economizer line, gas may flow into a tank where a pressure abnormality is occurring, causing a pressure increase inside the tank. Therefore, the inventors' investigations revealed that in order to improve the safety of storage tank facilities, the economizer line needs to be a separate pipe that is independent of the discharge line.

[0017] In the low-temperature liquefied gas storage tank facility disclosed herein, the economizer line and the discharge line are independent pipes, with their respective first ends communicating with the upper space in the tank at different positions. Because the economizer line is a separate pipe from the discharge line, the flow of gas in the economizer line is not affected by the flow of gas in the discharge line. Therefore, even if the gas in the tank is discharged to the atmosphere through the discharge line while the gas in the tank is being sent to the liquid supply line through the economizer line, no backflow of gas occurs in the economizer line. As a result, even if the pressure in the tank abnormally increases, the pressure in the tank can be reduced through the economizer line and the discharge line, ensuring the safety of the storage tank facility.

[0018] In the storage tank facility for low-temperature liquefied gas according to the present disclosure, the piping constituting the economizer line may be configured to have an inner diameter smaller than that of the piping constituting the discharge line. This configuration of the storage tank facility for low-temperature liquefied gas has the effect of reducing the piping space in the insulated space of the tank and reducing the amount of heat entering through the piping.

[0019] The low-temperature liquefied gas storage tank facility according to the present disclosure may further include a control device that controls the first valve and the second valve, and the control device controls the first valve and the second valve so that the first valve opens when the pressure in the tank exceeds a set pressure, and the second valve opens when the pressure in the tank exceeds a control pressure that is higher than the set pressure. With this configuration of low-temperature liquefied gas storage tank facility, decompression through the economizer line and gas release through the release line can be automatically performed according to the pressure in the tank.

[0020] The cryogenic liquefied gas storage tank equipment according to the present disclosure may be configured so that the cryogenic liquefied gas has a specific gravity of 1 kg / L or less. In conventional storage tank equipment, if the specific gravity of the cryogenic liquefied gas stored in the tank is high, the gas in the economizer line is likely to be drawn into the flow of the cryogenic liquefied gas sent from the tank to the liquid supply line. Therefore, if the specific gravity of the cryogenic liquefied gas is high, backflow is unlikely to occur even if a pressure difference between the upstream and downstream sides of the economizer line, which would cause backflow, occurs. However, if the specific gravity of the cryogenic liquefied gas stored in the tank is low, the gas in the economizer line is likely to be drawn into the flow of the cryogenic liquefied gas sent from the tank to the liquid supply line. Therefore, if the specific gravity of the cryogenic liquefied gas is low, backflow is likely to occur when a pressure difference between the upstream and downstream sides of the economizer line occurs, and it is highly necessary to prevent backflow. This configuration of the cryogenic liquefied gas storage tank equipment allows safe storage of cryogenic liquefied gas with a specific gravity of 1 kg / L or less.

[0021] The storage tank facility for low-temperature liquefied gas according to the present disclosure may be configured so that the low-temperature liquefied gas is liquefied hydrogen. With this configuration of the storage tank facility for low-temperature liquefied gas, liquefied hydrogen, which has a low specific gravity, can be safely stored.

[0022] [Specific example of embodiment] Next, an example of a specific embodiment of a low-temperature liquefied gas storage tank facility (hereinafter simply referred to as "storage tank facility") according to the present disclosure will be described with reference to the accompanying drawings. In the present disclosure, the same or corresponding parts in the drawings will be designated by the same reference numerals, and their description will not be repeated.

[0023] <Low temperature liquefied gas> In this disclosure, low-temperature liquefied gas refers to a fluid that liquefies at a temperature of 120 K (approximately -153°C) or less. Examples of low-temperature liquefied gas include liquefied natural gas, liquefied oxygen, liquefied nitrogen, liquefied hydrogen, and liquefied helium, but the low-temperature liquefied gas is not limited to these examples. The storage tank equipment according to this disclosure is suitable for use in storing low-temperature liquefied gases with a specific gravity of 1 kg / L or less. Examples of low-temperature liquefied gases with a specific gravity of 1 kg / L or less include liquefied natural gas, liquefied nitrogen, liquefied hydrogen, and liquefied helium, but the low-temperature liquefied gases with a specific gravity of 1 kg / L or less are not limited to these examples.

[0024] <Storage tank equipment> 1 to 3 show a storage tank facility 1 of this embodiment. As shown in Fig. 1, the storage tank facility 1 includes at least a tank 7 for storing low-temperature liquefied gas, a filling line 2 for filling the tank 7 with the low-temperature liquefied gas from a transport vehicle for transporting the low-temperature liquefied gas, such as a tank truck R, a liquid transfer line 3 for supplying the low-temperature liquefied gas from the tank 7 to a point of use, a pressure line 4 for supplying pressurized gas that pressurizes the inside of the tank 7 to the tank 7, an economizer line 5 for mixing the gas in the tank 7 with the liquid transfer line 3 and supplying it to the point of use, and a release line 6 for releasing the gas in the tank 7 to the atmosphere.

[0025] <Tank> The tank 7 is a sealed container capable of storing cryogenic liquefied gas in a liquid state at a low temperature. The tank 7 has a highly insulated structure in order to maintain the cryogenic liquefied gas in a liquid state. An example of a tank 7 with a highly insulated structure is a vacuum insulated tank, as shown in FIG. 1, which includes an inner tank 70 that stores the cryogenic liquefied gas and an outer tank 71 that stores the inner tank 70, with the space between the inner tank 70 and the outer tank 71 being a vacuum insulation layer 72. The space between the inner tank 70 and the outer tank 71 may be filled with an insulating material. The cryogenic liquefied gas stored in the inner tank 70 is maintained in a liquid state by being insulated by the vacuum insulation layer 72 that covers the inner tank 70. In this disclosure, "inside the tank" basically means "inside the inner tank of the tank."

[0026] <Filling line> The filling line 2 is a pipe through which low-temperature liquefied gas flows when the low-temperature liquefied gas is filled into the tank 7 from a tank truck R or the like. The material of the pipe is not particularly limited, and materials conventionally used for this type of pipe, such as stainless steel, can be used. The filling line 2 has a highly insulated structure so that the low-temperature liquefied gas can be supplied to the tank 7 in a low-temperature liquid state. An example of a pipe with a highly insulated structure is a vacuum-insulated multi-wall pipe, such as a double pipe in which a vacuum insulation layer is formed between an outer pipe and an inner pipe. The space between the outer pipe and the inner pipe may be filled with an insulating material.

[0027] As shown in Figure 1, one end of the filling line 2, that is, a first end E1, is connected to a filling hose 20 via a pipe joint. The filling line 2 branches into a first filling line 2A and a second filling line 2B. The first filling line 2A is a pipe for filling the inner vessel 70 of the tank 7 from below with low-temperature liquefied gas. The second filling line 2B is a pipe for filling the inner vessel 70 of the tank 7 from above with low-temperature liquefied gas.

[0028] In the filling line 2, a second end E2 opposite to the first end E1 and on the first filling line 2A side is connected to the lower part of the inner tank 70 of the tank 7. The lower part of the inner tank 70 refers to a part of the inner tank 70 that is below the liquid level 1 of the low-temperature liquefied gas in the inner tank 70. The second end E2 of the filling line 2 is connected, for example, to the bottom of the inner tank 70. In the filling line 2, a third end E3 opposite to the first end E1 and on the second filling line 2B side is connected to the upper part of the inner tank 70 of the tank 7. The upper part of the inner tank 70 refers to a part of the inner tank 70 that is above the liquid level 1 of the low-temperature liquefied gas in the inner tank 70. For example, the third end E3 of the filling line 2 is connected to the top of the inner tank 70, and communicates with an upper space G that becomes a gas phase within the inner tank 70.

[0029] When low-temperature liquefied gas is filled into the tank 7 from a tank truck R or the like via the first filling line 2A, the pressure inside the tank 7 rises. On the other hand, when low-temperature liquefied gas is filled into the tank 7 from a tank truck R or the like via the second filling line 2B, the pressure inside the tank 7 drops. The low-temperature liquefied gas is filled into the inner tank 70 via the first filling line 2A and the second filling line 2B until the liquid level l reaches a predetermined position. The position of the liquid level l of the low-temperature liquefied gas inside the tank 7 is measured by a level gauge.

[0030] <Liquid transfer line> The liquid supply line 3 is a pipe through which the low-temperature liquefied gas flows when the low-temperature liquefied gas in the tank 7 is supplied to a usage point. The material of the pipe is not particularly limited, and a material conventionally used for this type of pipe, such as stainless steel, can be used.

[0031] 1, one end of the liquid supply line 3, that is, a first end E4, is disposed from an upper portion (e.g., the top) of the inner tank 70 of the tank 7 to a lower space L that becomes a liquid phase within the inner tank 70, and is in communication with the lower space (liquid phase) L. The liquid supply line 3 sends out the low-temperature liquefied gas in the tank 7 from the tank 7 via the first end E4, as indicated by an arrow X1 in FIG.

[0032] A supply evaporator 8 is provided on the liquid transfer line 3. The supply evaporator 8 is, for example, a heat exchanger that uses outside air as a heat source. The low-temperature liquefied gas in the tank 7 is supplied to the supply evaporator 8 via the liquid transfer line 3, where it is evaporated and gasified and supplied to the point of use. A supply valve 15 is provided on the liquid transfer line 3. The supply valve 15 can switch the liquid transfer line 3 between a connected state (line open) and a closed state (line closed), for example, manually.

[0033] <Pressure line> When the cryogenic liquefied gas in the tank 7 is supplied to the point of use, the liquid level l of the cryogenic liquefied gas in the tank 7 drops. The cryogenic liquefied gas in the tank 7 is supplied to the point of use via the liquid supply line 3 while the pressure inside the tank 7 is maintained at a set pressure. Therefore, when the liquid level l of the cryogenic liquefied gas in the tank 7 drops, it is necessary to pressurize the tank 7 to prevent the pressure inside the tank 7 from decreasing, thereby maintaining the pressure inside the tank 7 at the set pressure. The pressurized line 4 is a pipe that supplies pressurized gas to the tank 7 to pressurize the tank 7, thereby maintaining the pressure inside the tank 7 at the set pressure. The material of the pipe is not particularly limited, and materials conventionally used for this type of pipe, such as stainless steel, can be used. The pressure inside the tank 7 is measured by a pressure gauge. The measurement result of the pressure gauge is sent to the control device 10, which monitors the pressure inside the tank 7.

[0034] As shown in FIG. 1 , a portion of the pressurized line 4 is shared with the first filling line 2A. One end of the pressurized line 4, a first end E2, is connected to the lower part of the inner tank 70 of the tank 7. The other end of the pressurized line 4, a second end E5 opposite the first end E2, is connected to the upper part of the inner tank 70 of the tank 7. For example, the first end E2 of the pressurized line 4 is connected to the bottom of the inner tank 70, and the second end E5 of the pressurized line 4 is connected to the top of the inner tank 70 and communicates with the upper space (gas phase) G within the inner tank 70. A pressurizing valve 16, a pressurizing evaporator 9, and an automatic pressurizing valve 11 as a third valve are provided in this order in the portion of the pressurized line 4 branching off from the first filling line 2A.

[0035] The pressurization valve 16 can be switched, for example, manually, between a communicating state (line open) and a closed state (line closed) of the pressurization line 4. The low-temperature liquefied gas taken out from the tank 7 is supplied to the pressurization evaporator 9 through the pressurization valve 16.

[0036] The pressurizing evaporator 9 is a heat exchanger that uses, for example, outside air as a heat source. The pressurizing evaporator 9 generates pressurized gas by vaporizing the low-temperature liquefied gas through heat exchange with the outside air. The pressurized gas generated in the pressurizing evaporator 9 is sent to the upper space (gas phase) G in the tank 7 through the automatic pressurizing valve 11.

[0037] The automatic pressurization valve 11 can adjust the flow rate (pressure) of the pressurized gas supplied from the pressurization evaporator 9 to the tank 7. The automatic pressurization valve 11 is an adjustment valve whose opening / closing operation and valve opening degree are controlled by external power, for example, upon receiving a control signal from the control device 10. When the automatic pressurization valve 11 automatically opens under the control of the control device 10, the low-temperature liquefied gas is extracted from the tank 7 and supplied to the pressurization evaporator 9, as indicated by arrow X2 in FIG. 1 . The low-temperature liquefied gas is evaporated in the pressurization evaporator 9 and sent as pressurized gas to the upper space (gas phase) G within the tank 7. The control device 10 adjusts the valve opening of the automatic pressurization valve 11, and pressurized gas is sent to the tank 7 at a flow rate (pressure) sufficient to maintain the pressure within the tank 7 at a set pressure, whereby the low-temperature liquefied gas within the tank 7 is supplied to a point of use via the liquid supply line 3. Note that the automatic pressurization valve 11 does not have to be an adjustment valve operated under the control of the control device 10. The automatic pressurizing valve 11 may be an adjusting valve that includes a pressure adjusting spring and adjusts the flow rate (pressure) of the pressurized gas by the force of the spring.

[0038] <Economizer line> Tank 7 is a sealed container in which a high degree of vacuum is maintained, but if the supply of cryogenic liquefied gas to the point of use is stopped or the amount of cryogenic liquefied gas supplied is reduced, the cryogenic liquefied gas in tank 7 will vaporize due to heat intrusion from the outside or natural evaporation. If the vaporized gas accumulates in the upper space (gas phase) G within tank 7, the pressure within tank 7 will increase and may exceed the set pressure. Economizer line 5 is a pipe that, when the pressure within tank 7 exceeds the set pressure, discharges excess gas from tank 7 that causes the pressure within tank 7 to increase, thereby reducing the pressure within tank 7 to the set pressure. There are no particular restrictions on the material of the pipe, and materials conventionally used for this type of piping, such as stainless steel, can be used.

[0039] As shown in FIG. 1 , one end of the economizer line 5, that is, a first end E6, is connected to the upper part of the inner tank 70 of the tank 7. For example, the first end E6 of the economizer line 5 is connected to the top of the inner tank 70 and communicates with the upper space (gas phase) G within the inner tank 70. The other end of the economizer line 5, that is, a second end E7 opposite to the first end E6, is connected to the liquid feed line 3. For example, the second end E7 of the economizer line 5 is connected to an upstream portion of the liquid feed line 3 that is close to the inner tank 70 side.

[0040] An automatic pressure-reducing valve 12 is provided as a first valve in the economizer line 5. The automatic pressure-reducing valve 12 can adjust the flow rate (pressure) of gas supplied from the tank 7 to the liquid supply line 3. The automatic pressure-reducing valve 12 is an adjustment valve whose opening and closing operation and valve opening degree are controlled by external power, for example, in response to a control signal from the control device 10. When the pressure in the tank 7 exceeds a set pressure, the automatic pressure-reducing valve 11 automatically closes under the control of the control device 10, thereby stopping the supply of pressurized gas to the tank 7 through the pressurization line 4. At the same time, the automatic pressure-reducing valve 12 automatically opens under the control of the control device 10. As shown by arrow X3 in FIG. 2 , excess gas that causes a pressure increase in the tank 7 is mixed with the low-temperature liquefied gas flowing through the liquid supply line 3 via the economizer line 5 and supplied to the point of use. This allows the pressure in the tank 7 to be reduced without wastefully discharging the low-temperature liquefied gas. The automatic pressure-reducing valve 12 does not have to be an adjustment valve operated under the control of the control device 10. The automatic pressure reducing valve 12 may be an adjusting valve that is provided with a pressure adjusting spring and adjusts the flow rate (pressure) of the gas by the force of the spring.

[0041] 1 , a first end E6 of the economizer line 5 is connected to an upper space (gas phase) G in the tank 7 at a position different from a first end E5 of a discharge line 6, which will be described later. That is, the first end E6 of the economizer line 5 is connected to an upper part of the inner tank 70 of the tank 7 at a first position P1 and communicates with the upper space (gas phase) G in the inner tank 70, while the first end E5 of the discharge line 6 is connected to an upper part of the inner tank 70 of the tank 7 at a second position P2 away from the first position P1 and communicates with the upper space (gas phase) G in the inner tank 70.

[0042] In this way, the economizer line 5 is a separate pipe from the discharge line 6, and does not share a portion of the same, so the flow of gas in the economizer line 5 is not affected by the flow of gas in the discharge line 6. Therefore, as shown in FIG. 3 , even if the gas in the tank 7 is discharged to the atmosphere through the discharge line 6 while the gas in the tank 7 is being sent to the liquid feed line 3 through the economizer line 5, a backflow of gas does not occur in the economizer line 5, as in the storage tank facility of the prior art. As a result, when the pressure in the tank 7 rises, the pressure in the tank 7 can be appropriately reduced by the economizer line 5 and the discharge line 6, ensuring the safety of the storage tank facility 1.

[0043] The piping that constitutes the economizer line 5 may be of the same diameter as the piping that constitutes the discharge line 6, or may be thinner than the piping that constitutes the discharge line 6. The economizer line 5 mixes excess gas that causes a pressure increase in the tank 7 with the low-temperature liquefied gas in a liquid state flowing through the liquid feed line 3 and discharges it. Therefore, the economizer line 5 does not need to carry a large amount of gas, and using a piping that is thinner than the piping that constitutes the discharge line 6 has the effect of reducing the space required for the vacuum insulation layer 72, which serves as an insulating space for the tank 7, and also reducing heat penetration through the piping. The inner diameter of the piping that constitutes the economizer line 5 is, for example, 17 mm or more and 25 mm or less.

[0044] <Release line> The discharge line 6 is a pipe for releasing the gas in the tank 7 to the atmosphere to reduce the pressure in the tank 7 in the event of an abnormal situation, such as the pressure in the tank 7 continuing to rise even after the pressure in the tank 7 has been reduced by the operation of the economizer line 5. The material of the pipe is not particularly limited, and a material conventionally used for this type of pipe, such as stainless steel, can be used.

[0045] 1, a portion of the discharge line 6 is shared with the pressurized line 4. One end of the discharge line 6, a first end E5, is connected to the top of the inner tank 70 of the tank 7 and communicates with the upper space (gas phase) G within the inner tank 70. The discharge line 6 is provided with at least one of an automatic discharge valve 13 and a discharge valve 14 as a second valve. In this embodiment, the discharge line 6 branches into a first discharge line 6A and a second discharge line 6B, and the automatic discharge valve 13 is provided on the first discharge line 6A and the discharge valve 14 is provided on the second discharge line 6B.

[0046] The automatic release valve 13 can adjust the flow rate (pressure) of gas released from the tank 7 to the atmosphere. The automatic release valve 13 is an adjustment valve whose opening / closing operation and valve opening degree are controlled by external power upon receiving a control signal from, for example, the control device 10. When the pressure inside the tank 7 continues to rise above the set pressure and exceeds a management pressure higher than the set pressure, the automatic release valve 13 automatically opens under the control of the control device 10, and the gas inside the tank 7 is released to the atmosphere via the first release line 6A, as shown by arrow X4 in FIG. 3. Note that the automatic release valve 13 does not have to be an adjustment valve that operates under the control of the control device 10. The automatic release valve 13 may be an adjustment valve equipped with a pressure adjustment spring that adjusts the flow rate (pressure) of the gas by the force of the spring.

[0047] The discharge valve 14 can be manually switched between a communicating state (line open) and a closed state (line closed) of the second discharge line 6B. When the pressure inside the tank 7 exceeds the set pressure and continues to rise, exceeding a control pressure higher than the set pressure, the discharge valve 14 can be manually opened to release the gas inside the tank 7 into the atmosphere via the second discharge line 6B, as shown by arrow X4 in Figure 3.

[0048] The discharge line 6 needs to allow a large amount of gas to flow through it in order to quickly release the gas in the tank 7 into the atmosphere. Therefore, the piping that constitutes the discharge line 6 can be thicker than the piping that constitutes the economizer line 5. The inner diameter of the piping that constitutes the discharge line 6 is, for example, 28 mm or more and 40 mm or less.

[0049] <Control device> The control device 10 can be configured, for example, by a microcomputer equipped with a processor, memory, etc. A pressure gauge that measures the pressure inside the tank 7 is connected to the control device 10, and upon receiving an input signal from the pressure gauge, the control device 10 controls the opening and closing operations and valve opening degrees of the valves 11, 12, and 13, thereby switching the lines 4, 5, and 6.

[0050] For example, when the pressure inside the tank 7 falls below a set pressure, the control device 10 opens the automatic pressurizing valve 11 so that the pressure inside the tank 7 is maintained at the set pressure. This causes the inside of the tank 7 to be pressurized by the pressurizing line 4. The same applies when the automatic pressurizing valve 11 is not controlled by the control device 10 but is instead controlled by a pressure adjustment spring.

[0051] When the pressure inside the tank 7 exceeds the set pressure, the control device 10 closes the automatic pressurizing valve 11 and opens the automatic depressurizing valve 12. This stops pressurizing the inside of the tank 7 through the pressurizing line 4, and depressurizes the inside of the tank 7 through the economizer line 5. When the pressure inside the tank 7 returns to the set pressure, the control device 10 closes the automatic depressurizing valve 12. This stops depressurizing the inside of the tank 7 through the economizer line 5. The same applies when the automatic depressurizing valve 12 is not controlled by the control device 10 but is instead controlled by a pressure adjustment spring to adjust the pressure.

[0052] Even if the pressure inside the tank 7 is reduced by the economizer line 5, if the pressure inside the tank 7 exceeds the control pressure, the control device 10 opens the automatic discharge valve 13. This reduces the pressure inside the tank 7 through the discharge line 6. When the pressure inside the tank 7 returns to the set pressure, the control device 10 closes the automatic pressure reducing valve 12 and the automatic discharge valve 13. The same applies when the automatic discharge valve 13 is not controlled by the control device 10 but is instead controlled by a pressure adjustment spring to adjust the pressure.

[0053] In the above-described embodiment, in addition to the above-described valves, various valves such as automatic valves, manual valves, and safety valves may be provided at appropriate locations in the filling line 2, the liquid supply line 3, the pressurizing line 4, the economizer line 5, and the discharge line 6, as needed.

[0054] The embodiments disclosed herein are illustrative in all respects and should not be construed as limiting. The scope of the present invention is defined by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0055] 1 Storage tank equipment 3 Liquid delivery line 4 Pressure lines 5 Economizer Line 6. Release Line 7. Tank 3 Liquid delivery line 4 Pressure lines 7. Evaporator 10 Control device 12 Automatic pressure reducing valve (first valve) 13 Automatic discharge valve (second valve) G Headspace inside the tank (gas phase) L Lower space inside the tank (liquid phase) E4 First end of the liquid delivery line E5 First end of discharge line E6 First end of economizer line E7 Second end of economizer line P1 First position P2 Second position

Claims

1. a tank for storing cryogenic liquefied gas; a liquid transfer line for transferring the low-temperature liquefied gas from the tank; an economizer line having a first end communicating with an upper space in the tank at a first position, a second end connected to the liquid supply line, and a first valve for supplying gas in the tank to the liquid supply line by opening the first valve; a discharge line having a first end communicating with an upper space in the tank at a second position different from the first position, and a second valve for discharging gas in the tank to the atmosphere by opening the second valve; A low-temperature liquefied gas storage tank facility equipped with:

2. 2. The low-temperature liquefied gas storage tank facility according to claim 1, wherein the inner diameter of the pipe constituting the economizer line is smaller than the inner diameter of the pipe constituting the discharge line.

3. a control device that controls the first valve and the second valve; 2. The low-temperature liquefied gas storage tank facility of claim 1, wherein the control device controls the first valve and the second valve so that the first valve opens when the pressure in the tank exceeds a set pressure, and the second valve opens when the pressure in the tank exceeds a management pressure that is higher than the set pressure.

4. 4. The low-temperature liquefied gas storage tank facility according to claim 1, wherein the low-temperature liquefied gas has a specific gravity of 1 kg / L or less.

5. 5. The low-temperature liquefied gas storage tank facility according to claim 4, wherein the low-temperature liquefied gas is liquefied hydrogen.

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