Low-temperature liquefied gas storage tank facilities

Abstract

To provide a storage tank facility for low-temperature liquefied gas in which no backflow of gas occurs in an economizer line. [Solution] A low-temperature liquefied gas storage facility includes a tank for storing low-temperature liquefied gas, a liquid delivery line for delivering 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 delivery line, and a first valve, the economizer line delivering gas in the tank to the liquid delivery 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.

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 "supply destination"), for example by a tank truck, and is supplied from the tank truck to a storage tank facility at the supply destination (hereinafter simply referred to as "storage tank facility"). Figs. 4 to 6 show storage tank facilities of the prior art. As shown in Fig. 4, the storage tank facility 100 includes a tank 101 and a liquid delivery line 102 that can store the low-temperature liquefied gas supplied from the tank truck R in a liquid state. A supply evaporator 103 is provided in the liquid delivery line 102. The low-temperature liquefied gas in the tank 101 is supplied to the supply evaporator 103 as shown by the arrow X1 in Fig. 4, and is evaporated in the 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 a 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 by maintaining the inside of the tank 101 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. Therefore, 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, the low-temperature liquefied gas is taken out of the tank 101 and supplied to the pressurization evaporator 105, as shown by the arrow X2 in Fig. 4. The low-temperature liquefied gas evaporates in the pressurization evaporator 105, and becomes a pressurized gas, which is sent to the upper space (gas phase) G inside the tank 101. This causes the inside of the tank 101 to be pressurized, and the low-temperature liquefied gas inside the tank 101 is supplied to the point of use via the liquid supply line 102.

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

[0006] Even if an attempt is made to reduce the pressure in 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 in the tank 101 continuing to rise. The tank storage facility 100 is provided with a discharge line 107 in order to release the gas in the tank 101 to the atmosphere when an abnormal situation occurs. When an abnormal situation occurs, the gas in the tank 101 is released to the atmosphere via the discharge line 107, as shown by the arrow X4 in FIG. 6. This makes it possible to reduce the pressure in the tank 101 (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 storage tank facility 100 of the prior art, a part of the economizer line 106 connected to the tank 101 is shared with the discharge line 107. Therefore, when the discharge line 107 operates to discharge the gas in the tank 101 to the atmosphere while the economizer line 106 is operating, the pressure of the economizer line 106 drops at the point where it branches off from the upstream discharge line 107. This causes a pressure difference between the upstream side and the downstream side (the liquid supply line 102 side) in the economizer line 106, and depending on the properties of the low-temperature liquefied gas or the usage environment, this pressure difference causes a backflow of gas. In the economizer line 106, as shown by the arrow X5 in FIG. 6, if a backflow occurs and the gas flows in the opposite direction to the original direction of the liquid supply line 102 and flows into the tank 101, this may cause a pressure rise in the tank 101.

[0009] An object of the present disclosure is to provide a low-temperature liquefied gas storage tank facility in which no backflow of gas occurs in an 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 delivery line for delivering 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 delivery line, and a first valve, the economizer line delivering gas in the tank to the liquid delivery line by opening the first valve, 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 by opening the second valve. Effect 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 description 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 an example of the present disclosure. [Diagram 2] FIG. 2 is a schematic diagram showing a gas flow when an economizer line is in operation in a low-temperature liquefied gas storage tank facility according to an embodiment of one example of the present disclosure. [Diagram 3] FIG. 3 is a schematic diagram showing a gas flow when an economizer line and a discharge line are in operation in a low-temperature liquefied gas storage tank facility according to an embodiment of an example of the present disclosure. [Figure 4] FIG. 4 is a schematic diagram showing a conventional low-temperature liquefied gas storage tank facility. [Diagram 5] FIG. 5 is a schematic diagram showing a gas flow when an economizer line is in operation 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 PREFERRED EMBODIMENTS

[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 delivery line for delivering 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 delivery line, and a first valve, the economizer line delivering gas in the tank to the liquid delivery line by opening the first valve, 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 by opening the second valve.

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

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

[0017] According to the low-temperature liquefied gas storage tank facility of the present disclosure, the economizer line and the discharge line are independent pipes, each of which has a first end communicating with the upper space in the tank at a different position. Since the economizer line is a pipe separate 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 rises abnormally, the pressure in the tank can be reduced by the economizer line and the discharge line, and the safety of the storage tank facility can be ensured.

[0018] The low-temperature liquefied gas storage tank equipment according to the present disclosure may be configured such that the pipe constituting the economizer line has an inner diameter smaller than that of the pipe constituting the discharge line. This configuration of the low-temperature liquefied gas storage tank equipment has the effect of reducing the piping space in the thermally 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 for controlling the first valve and the second valve, and the control device may be configured to control 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 higher than the set pressure. With this configuration of the low-temperature liquefied gas storage tank facility, pressure reduction through the economizer line and gas release through the release line can be automatically performed according to the pressure in the tank.

[0020] The low-temperature liquefied gas storage tank equipment according to the present disclosure may be configured such that the low-temperature liquefied gas has a specific gravity of 1 kg / L or less. In the storage tank equipment of the prior art, when the specific gravity of the low-temperature liquefied gas stored in the tank is high, the gas in the economizer line is easily drawn into the flow of the low-temperature liquefied gas sent from the tank to the liquid sending line. Therefore, when the specific gravity of the low-temperature liquefied gas is high, backflow is unlikely to occur even if a pressure difference occurs between the upstream and downstream sides of the economizer line, which causes backflow. However, when the specific gravity of the low-temperature liquefied gas stored in the tank is low, the gas in the economizer line is hardly drawn into the flow of the low-temperature liquefied gas sent from the tank to the liquid sending line. Therefore, when the specific gravity of the low-temperature liquefied gas is low, backflow is likely to occur when a pressure difference occurs between the upstream and downstream sides of the economizer line, and it is highly necessary to prevent backflow. According to the low-temperature liquefied gas storage tank equipment of this configuration, low-temperature liquefied gas with a specific gravity of 1 kg / L or less can be safely stored.

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

[0022] [Specific example of embodiment] Next, 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 are designated by the same reference characters, and the description thereof will not be repeated.

[0023] <Low temperature liquefied gas> In the present disclosure, low-temperature liquefied gas means a fluid that liquefies at a temperature of 120K (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 the present disclosure is suitable for use in storing low-temperature liquefied gases having a specific gravity of 1kg / L or less among low-temperature liquefied gases. Examples of low-temperature liquefied gases having a specific gravity of 1kg / L or less include liquefied natural gas, liquefied nitrogen, liquefied hydrogen, and liquefied helium, but the low-temperature liquefied gases having a specific gravity of 1kg / L or less are not limited to these examples.

[0024] <Storage tank equipment> A storage tank facility 1 according to the present embodiment is shown in Figures 1 to 3. As shown in Figure 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 low-temperature liquefied gas from a transport vehicle such as a tank truck R for transporting the low-temperature liquefied gas, a liquid delivery line 3 for supplying the low-temperature liquefied gas from the tank 7 to a point of use, a pressurization line 4 for supplying the pressurized gas that pressurizes the tank 7 to the tank 7, an economizer line 5 for mixing the gas in the tank 7 with the liquid delivery line 3 and supplying it to the point of use, and a discharge line 6 for discharging the gas in the tank 7 to the atmosphere.

[0025] <Tank> The tank 7 is a sealed container capable of storing the low-temperature liquefied gas in a liquid state at a low temperature. The tank 7 has a highly insulated structure in order to maintain the low-temperature liquefied gas in a liquid state. As shown in FIG. 1, the tank 7 having a highly insulated structure is exemplified by a tank having a vacuum insulation structure, which includes an inner tank 70 for storing the low-temperature liquefied gas and an outer tank 71 for storing the inner tank 70, and in which the space between the inner tank 70 and the outer tank 71 is a vacuum insulation layer 72. The space between the inner tank 70 and the outer tank 71 may be filled with a heat insulating material. The low-temperature liquefied gas stored in the inner tank 70 is insulated by the vacuum insulation layer 72 that covers the inner tank 70, and is maintained in a liquid state. 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 a material 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 a heat insulating material.

[0027] As shown in Fig. 1, one end of the filling line 2, 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, the second end E2 on the side of the first filling line 2A, opposite to the first end E1, is connected to the lower part of the inner tank 70 of the tank 7. The lower part of the inner tank 70 is a part of the inner tank 70 below the liquid level l of the low-temperature liquefied gas in the inner tank 70. The second end E2 of the filling line 2 is connected to, for example, the bottom of the inner tank 70. In the filling line 2, the third end E3 on the side of the second filling line 2B, opposite to the first end E1, is connected to the upper part of the inner tank 70 of the tank 7. The upper part of the inner tank 70 is a part of the inner tank 70 above the liquid level l 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 the upper space G that becomes a gas phase in 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 through the first filling line 2A and the second filling line 2B until the position of the liquid level l reaches a predetermined position. The position of the liquid level l of the low-temperature liquefied gas in the tank 7 is measured by a liquid level gauge.

[0030] <Liquid delivery line> The liquid delivery 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 that has been 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., a top portion) of the inner tank 70 of the tank 7 to a lower space L which becomes a liquid phase in the inner tank 70, and is in communication with the lower space (liquid phase) L. As shown by an arrow X1 in FIG. 1, 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.

[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, and is evaporated in the supply evaporator 8 and supplied to the point of use in a gasified state. A supply valve 15 is provided on the liquid transfer line 3. The supply valve 15 can manually switch the liquid transfer line 3 between a connected state (line open) and a closed state (line closed), for example.

[0033] <Pressure line> When the low-temperature liquefied gas in the tank 7 is supplied to the point of use, the liquid level 1 of the low-temperature liquefied gas in the tank 7 drops. The low-temperature liquefied gas in the tank 7 is supplied to the point of use through the liquid supply line 3 by maintaining the inside of the tank 7 at a set pressure. Therefore, when the liquid level 1 of the low-temperature liquefied gas in the tank 7 drops, it is necessary to pressurize the inside of the tank 7 so that the pressure in the tank 7 does not drop, and to maintain the pressure in the tank 7 at the set pressure. The pressurized line 4 is a pipe for supplying pressurized gas to the tank 7 to pressurize the inside of the tank 7, thereby maintaining the pressure in the tank 7 at the set pressure. The material of the pipe is not particularly limited, and a material that has been conventionally used for this type of pipe, such as stainless steel, can be used. The pressure in the tank 7 is measured by a pressure gauge. The measurement result of the pressure gauge is transmitted to the control device 10, and the control device 10 monitors the pressure in the tank 7.

[0034] As shown in FIG. 1, a portion of the pressurized line 4 is shared with the first filling line 2A. In the pressurized line 4, a first end E2, which is one end, is connected to the lower part of the inner tank 70 of the tank 7. In the pressurized line 4, a second end E5, which is the other end opposite to 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 in the inner tank 70. In the pressurized line 4, a pressurizing valve 16, a pressurizing evaporator 9, and an automatic pressurizing valve 11 as a third valve are provided in this order at a portion branching off from the first filling line 2A.

[0035] The pressurizing valve 16 can be switched, for example manually, between a communicating state (line open) and a closed state (line closed) of the pressurizing line 4. The low-temperature liquefied gas taken out of the tank 7 is supplied to the pressurizing evaporator 9 through the pressurizing 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 pressurizing valve 11 can adjust the flow rate (pressure) of the pressurized gas supplied from the pressurizing evaporator 9 to the tank 7. The automatic pressurizing valve 11 is an adjustment valve whose opening / closing operation and valve opening degree are controlled by an external power upon receiving a control signal from the control device 10, for example. When the automatic pressurizing valve 11 is automatically opened under the control of the control device 10, the low-temperature liquefied gas is taken out from the tank 7 and supplied to the pressurizing evaporator 9 as shown by the arrow X2 in FIG. 1. The low-temperature liquefied gas is evaporated in the pressurizing evaporator 9 and sent to the upper space (gas phase) G in the tank 7 as a pressurized gas. The control device 10 adjusts the valve opening degree of the automatic pressurizing valve 11, and pressurized gas is sent to the tank 7 at a flow rate (pressure) that can maintain the pressure in the tank 7 at the set pressure, so that the low-temperature liquefied gas in the tank 7 is supplied to the point of use via the liquid supply line 3. The automatic pressurizing valve 11 does not have to be an adjustment valve that operates under the control of the control device 10. The automatic pressurizing valve 11 may be an adjusting valve equipped with a pressure adjusting spring, which adjusts the flow rate (pressure) of the pressurized gas by the force of the spring.

[0038] <Economizer line> The tank 7 is a sealed container in which a high degree of vacuum is maintained, but if the supply of low-temperature liquefied gas to the point of use is stopped or the supply amount of low-temperature liquefied gas is reduced, the low-temperature liquefied gas in the 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 in the tank 7, the pressure in the tank 7 will increase and may exceed the set pressure. The economizer line 5 is a pipe for discharging excess gas that causes a pressure increase in the tank 7 from the tank 7 when the pressure in the tank 7 exceeds the set pressure, and reducing the pressure in the tank 7 to the set pressure. The material of the pipe is not particularly limited, and a material that has been conventionally used for this type of pipe, such as stainless steel, can be used.

[0039] 1, in the economizer line 5, a first end E6, which is one end, 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 in the inner tank 70. In the economizer line 5, a second end E7, which is the other end opposite to the first end E6, is connected to the liquid supply line 3. For example, the second end E7 of the economizer line 5 is connected to an upstream portion of the liquid supply line 3 close to the inner tank 70 side.

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

[0041] 1, the economizer line 5 has a first end E6 that communicates with an upper space (gas phase) G in the tank 7 at a position different from a first end E5 of a discharge line 6 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, since the economizer line 5 is a separate pipe from the discharge line 6 and does not share a portion with the discharge line 6, 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, when the gas in the tank 7 is being sent to the liquid feed line 3 through the economizer line 5, even if the gas in the tank 7 is released to the atmosphere through the discharge line 6, 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 lowered by the economizer line 5 and the discharge line 6, and the safety of the storage tank facility 1 can be ensured.

[0043] The pipe constituting the economizer line 5 may be of the same diameter as the pipe constituting the discharge line 6, or may be thinner than the pipe constituting the discharge line 6. The economizer line 5 discharges excess gas that causes a pressure rise in the tank 7 by mixing it with the low-temperature liquefied gas in a liquid state flowing through the liquid feed line 3. Therefore, the economizer line 5 does not need to have a large amount of gas flowing, and a thinner pipe than the pipe constituting the discharge line 6 has the effect of reducing the space of the vacuum insulation layer 72 that serves as the insulation space of the tank 7 and reducing heat penetration from the pipe. The inner diameter of the pipe constituting 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 discharging the gas in the tank 7 to the atmosphere to reduce the pressure in the tank 7 in the event of an abnormality, 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 upper part of the inner tank 70 of the tank 7 and communicates with an upper space (gas phase) G in the inner tank 70. At least one of an automatic discharge valve 13 and a discharge valve 14 is provided in the discharge line 6 as a second valve. In this embodiment, the discharge line 6 branches into a first discharge line 6A and a second discharge line 6B, the automatic discharge valve 13 is provided in the first discharge line 6A, and the discharge valve 14 is provided in the second discharge line 6B.

[0046] The automatic release valve 13 can adjust the flow rate (pressure) of the 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 an external power upon receiving a control signal from the control device 10, for example. When the pressure in the tank 7 continues to rise beyond 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 in the tank 7 is released to the atmosphere through the first release line 6A as shown by the arrow X4 in FIG. 3. 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 that includes a pressure adjustment spring and adjusts the flow rate (pressure) of the gas by the force of the spring.

[0047] The discharge valve 14 can manually switch the second discharge line 6B between a communicating state (line open) and a closed state (line closed). When the pressure in the tank 7 exceeds the set pressure and continues to rise and exceeds a management pressure higher than the set pressure, the discharge valve 14 is manually opened, whereby the gas in the tank 7 is discharged to the atmosphere via the second discharge line 6B as shown by the arrow X4 in FIG. 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 to the atmosphere. Therefore, the piping constituting the discharge line 6 can be thicker than the piping constituting the economizer line 5. The inner diameter of the piping constituting 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, a 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.

[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 pressure adjusted using a pressure adjustment spring.

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

[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, not the above description, and is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0055] 1 Storage tank equipment 3. Liquid delivery line 4. Pressurized Line 5 Economizer Line 6. Release Line 7. Tank 3. Liquid delivery line 4. Pressurized Line 7. Evaporator 10 Control device 12 Automatic pressure reducing valve (first valve) 13 Automatic release 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 low-temperature liquefied gas; a liquid delivery line for delivering the low-temperature liquefied gas from the tank; an economizer line including 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, the economizer line being configured to supply 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, the discharge line discharging the gas in the tank to the atmosphere by opening the second valve; a pressurization line including an end connected to a lower portion of the tank for extracting low-temperature liquefied gas from the tank, a pressurization evaporator for generating pressurized gas for pressurizing the inside of the tank by vaporizing the low-temperature liquefied gas, and a third valve, a portion of the end side communicating with an upper space in the tank being shared with the discharge line, and the pressurization line for supplying the pressurized gas to the tank by opening the third valve; Equipped with A low-temperature liquefied gas storage tank facility configured such that when the pressure in the tank exceeds a set pressure, the third valve closes and the first valve opens, so that the gas in the tank is mixed with the low-temperature liquefied gas in the liquid supply line and supplied to a point of use, and when the pressure in the tank exceeds a control pressure that is higher than the set pressure, the second valve opens.

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

3. A control device that controls the first valve, the second valve, and the third valve, The low-temperature liquefied gas storage tank equipment of claim 1, wherein the control device controls the first valve, the second valve, and the third valve so that the third valve closes and 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 higher than the set pressure.

4. The low-temperature liquefied gas storage tank facility according to any one of claims 1 to 3, wherein the low-temperature liquefied gas has a specific gravity of 1 kg / L or less.

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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