Gas pumping system and gas pumping method

Abstract

To facilitate compression of a hydrogen gas having a room temperature to a cryogenic temperature.SOLUTION: A gas pressure-feeding system in one embodiment pressure-feeds a hydrogen gas evaporated in a tank storing liquefied hydrogen from the tank to a pressure-feeding destination outside the tank. The gas pressure-feeding system includes: a gas supply line for supplying the hydrogen gas from the tank to the pressure-feeding destination; a first compressor provided in the gas supply line; a second compressor provided in a portion downstream of the first compressor in the gas supply line; a thermometer measuring a temperature of the hydrogen gas flowing in the gas supply line; and a control device controlling the first compressor and the second compressor. The control device operates the second compressor with the first compressor stopped when the temperature measured by the thermometer is a predetermined threshold value or higher, and operates the first compressor when the temperature measured by the thermometer is lower than the threshold value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a gas pumping system and a gas pumping method for pumping boil-off gas generated in a tank storing a cryogenic liquid to the outside of the tank.

Background Art

[0002] Conventionally, a system for pumping boil-off gas generated in a storage tank storing liquefied natural gas (hereinafter, LNG) to a power generation plant or the like outside the tank has been known. For example, Patent Document 1 discloses a pumping system including a storage tank for storing LNG, a compressor, and a discharge line connecting the upper part of the storage tank and the compressor to discharge boil-off gas. The boil-off gas guided from the tank to the compressor is compressed by the compressor and then supplied to a power generation plant or the like.

[0003] In this type of system, immediately after the compressor starts, the temperature of the pipe connecting the tank to the compressor is usually normal temperature. Therefore, immediately after the compressor starts, boil-off gas that has warmed up to near normal temperature during flow through the pipe is guided to the suction port of the compressor. As time elapses from the start of the compressor, the temperature of the pipe gradually decreases due to the guided boil-off gas. As a result, the temperature of the boil-off gas guided to the suction port of the compressor stabilizes at around minus one hundred degrees. Thus, the temperature of the boil-off gas guided to the compressor can vary over a wide range from minus one hundred degrees to normal temperature.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, while the boiling point of LNG is approximately -161°C, the boiling point of liquefied hydrogen is approximately -253°C. Therefore, when using the pressurized transport system described in Patent Document 1 to pump hydrogen gas from a tank storing liquefied hydrogen to the outside, the temperature of the hydrogen gas introduced into the compressor's intake will fluctuate over a fairly wide range, from room temperature to extremely low temperatures of several hundred degrees minus. However, manufacturing a compressor that can compress hydrogen gas at any temperature from room temperature to several hundred degrees minus is costly.

[0006] Therefore, the purpose of this disclosure is to provide a gas pumping system and a gas pumping method that can easily achieve the compression of hydrogen gas from room temperature to cryogenic temperatures. [Means for solving the problem]

[0007] To solve the above problems, a gas pumping system according to one aspect of the present disclosure is a gas pumping system that pumps hydrogen gas evaporated in a tank storing liquefied hydrogen from the tank to a pumping destination outside the tank, comprising: a gas supply line for supplying hydrogen gas from the tank to the pumping destination; a first compressor provided in the gas supply line; a second compressor provided in the gas supply line on the downstream side of the first compressor; a thermometer for measuring the temperature of the hydrogen gas flowing through the gas supply line; and a control device for controlling the first compressor and the second compressor, wherein the control device operates the second compressor with the first compressor stopped when the temperature measured by the thermometer is above a predetermined threshold, and operates the first compressor when the temperature measured by the thermometer is below the threshold.

[0008] Furthermore, a gas pumping method according to one aspect of the present disclosure is a gas pumping method for pumping hydrogen gas evaporated in a tank storing liquefied hydrogen from the tank to a pumping destination outside the tank, comprising a gas supply line for leading hydrogen gas from the tank to the pumping destination, a first compressor provided in the gas supply line, and a second compressor provided in the gas supply line on the downstream side of the first compressor, wherein the temperature of the hydrogen gas supplied by the gas supply line is measured, and if the measured temperature is above a predetermined threshold, the second compressor is operated with the first compressor stopped, and if the measured temperature is below the threshold, the first compressor is operated. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide a gas pumping system and a gas pumping method that can easily achieve the compression of hydrogen gas from room temperature to cryogenic temperatures. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram showing the overall configuration of a gas pumping system according to one embodiment of the present disclosure. [Figure 2] Figure 2 is a block diagram showing the control system of the gas pumping system shown in Figure 1. [Figure 3] Figure 3 is a flowchart showing the control flow by the control device when the first operating mode is selected. [Figure 4] Figure 4 is a flowchart showing the control flow by the control device when switching from the first operating mode to the second operating mode. [Figure 5] Figure 5 is a flowchart showing the control flow by the control device when switching from the first operating mode to the third operating mode. [Figure 6] Figure 6 is a flowchart showing the control flow by the control device when switching from the first operating mode to the fourth operating mode. [Figure 7]Figure 7 is a flowchart showing the control flow by the control device when the fifth operating mode is determined. [Modes for carrying out the invention]

[0011] Embodiments of this disclosure will be described below with reference to the drawings.

[0012] Figure 1 is a schematic diagram showing the overall configuration of a gas pumping system 1 according to one embodiment of the present disclosure.

[0013] The gas pumping system 1 pumps the hydrogen gas evaporated in the tank 2, which stores liquefied hydrogen, i.e., the boil-off gas, from the tank 2 to a destination 3 outside the tank 2. The destination 3 to which the hydrogen gas is pumped by the gas pumping system 1 is, for example, a hydrogen gas consumption facility or hydrogen gas storage facility such as a power plant.

[0014] The gas pumping system 1 includes a gas supply line 10 that supplies hydrogen gas from tank 2 to destination 3. Gas supply line 10 and the other lines 11, 30, 31, and 50 described later are each combinations of one or more pipes and pieces of equipment. Hereinafter, the side of gas supply line 10 and the other lines 11, 30, 31, and 50 described later that is on the tank 2 side, that is, the side from which the hydrogen gas flows, will be referred to as the "upstream," and the side opposite to tank 2, that is, the side from which the hydrogen gas flows, will be referred to as the "downstream."

[0015] The upstream end 10a of the gas supply line 10 is connected to the top of the tank 2. The downstream end 10b of the gas supply line 10 is connected to the pumping destination 3. The gas supply line 10 is equipped with, in order from upstream to downstream, a first compressor 21A, a thermometer 22A, an on-off valve 23A, an on-off valve 24, a heater 25, a buffer tank 26, and a second compressor 27.

[0016] The first compressor 21A is a compressor for low-temperature gas that can compress hydrogen gas at a temperature extremely lower than normal temperature. In this specification, normal temperature refers to a temperature equivalent to the outside air temperature, for example, a temperature in the range of -10°C or higher and +40°C or lower. Since hydrogen gas at around -240°C can be supplied to the suction port of the first compressor 21A, the first compressor 21A is manufactured using a low-temperature steel material that can withstand low-temperature gas at a temperature of -200°C or lower. The low-temperature steel material is, for example, a stainless steel material.

[0017] In this embodiment, when the first compressor 21A operates, an allowable temperature range of the gas supplied to the suction port of the first compressor 21A is preset. The allowable temperature range of the first compressor 21A is, for example, in the range of -250°C or higher and -100°C or lower, preferably in the range of -250°C or higher and -150°C or lower, and more preferably in the range of -250°C or higher and -200°C or lower. The reason for setting an upper limit on the temperature of the gas supplied to the suction port of the first compressor 21A when the first compressor 21A operates is to prevent the gas temperature discharged from the discharge port of the first compressor 21A from becoming too high. High-temperature countermeasures are not required for the first compressor 21A and the piping and equipment on the downstream side of the first compressor 21A in the gas supply line 10.

[0018] Note that the preset allowable temperature range is the allowable temperature range when the first compressor 21A operates, and does not regulate the supply of gas at a temperature outside the allowable temperature range to the suction port of the first compressor 21A when the first compressor 21A is in a stopped state. That is, when the first compressor 21A is in a stopped state, gas at normal temperature may be supplied to the suction port of the first compressor 21A.

[0019] Also, when the first compressor 21A is stopped, the hydrogen gas led from the tank 2 to the suction port of the first compressor 21A can pass through the inside of the first compressor 21A from the suction port to the discharge port. The first compressor 21A is, for example, a centrifugal compressor. However, the first compressor 21A may be another type of compressor such as a screw type as long as it is configured to allow passage through its interior when the first compressor 21A is stopped.

[0020] The start and stop of the first compressor 21A are controlled by a control device 60 described later.

[0021] The thermometer 22A measures the temperature of the hydrogen gas flowing through the gas supply line 10. The thermometer 22A is disposed in a portion between the first compressor 21A and the heater 25 in the gas supply line 10. That is, the thermometer 22A measures the temperature of the hydrogen gas immediately after being discharged from the first compressor 21A.

[0022] The opening and closing of each valve of the on-off valve 23A and the on-off valve 24 are controlled by a control device 60 described later. In the following description, the on-off valve 23A may be referred to as the first on-off valve 23A.

[0023] The heater 25 raises the temperature of the inflowing hydrogen gas. For example, the heater 25 raises the temperature of the inflowing hydrogen gas to room temperature.

[0024] The buffer tank 26 temporarily stores the hydrogen gas flowing out from the heater 25. The buffer tank 26 suppresses a rapid decrease in the pressure on the suction port side of the second compressor 27 when the second compressor 27 starts.

[0025] The second compressor 27 is a compressor for normal temperature gas for compressing normal temperature hydrogen gas. Since the hydrogen gas heated to room temperature by the heater 25 is led to the second compressor 27, it is not necessary to be manufactured using low-temperature steel materials.

[0026] In this embodiment, the main role of the second compressor 27 is to pre-cool the first compressor 21A and the piping upstream of the first compressor 21A in the gas supply line 10. In this embodiment, basically, after pre-cooling is complete, the second compressor 27 is stopped and hydrogen gas is pumped by the first compressor 21A. This is because pumping a relatively low-temperature fluid has a higher pumping efficiency, i.e., a higher pumping gas capacity relative to power, compared to pumping a relatively high-temperature fluid. Therefore, basically, the second compressor 27 only needs to pump hydrogen gas until pre-cooling is complete, so the second compressor 27 does not need to have the same capacity as the first compressor 21A. For example, the discharge rate of the second compressor 27 in the reference state (i.e., at a temperature of 0°C and atmospheric pressure) is 50% or less of the discharge rate of the first compressor 21A in the reference state, preferably 25% or less. The smaller the capacity of the second compressor 27, the more space can be saved for its installation.

[0027] Furthermore, the second compressor 27 is, for example, a centrifugal compressor. However, the second compressor 27 may be another type of compressor, such as a screw compressor.

[0028] The starting and stopping of the second compressor 27 are controlled by the control device 60, which will be described later.

[0029] Furthermore, the gas pumping system 1 includes a bypass line 30 that bypasses the second compressor 27. The bypass line 30 branches off from a branching point 30a located between the first compressor 21A and the second compressor 27 in the gas supply line 10 and connects to the downstream portion of the second compressor 27 in the gas supply line 10. More specifically, the upstream end 30a of the bypass line 30 is connected to the portion of the gas supply line 10 between the thermometer 22A and the on-off valve 23A. The downstream end 30b of the bypass line 30 is connected to the downstream portion of the second compressor 27 in the gas supply line 10.

[0030] A shut-off valve 41A is provided in the bypass line 30. In the following description, the shut-off valve 41A may be referred to as the second shut-off valve 41A. The opening and closing of the shut-off valve 41A is controlled by the control device 60 described later.

[0031] Furthermore, the gas pumping system 1 includes a first compressor 21B, a thermometer 22B, an on-off valve 23B, and an on-off valve 41B, which are installed in parallel with the first compressor 21A, thermometer 22A, on-off valve 23A, and on-off valve 41A.

[0032] Specifically, the gas pumping system 1 includes a parallel line 11 and a connecting line 31. The upstream end 11a of the parallel line 11 is connected to the upstream portion of the first compressor 21A in the gas supply line 10. The downstream end 11b of the parallel line 11 is connected to the portion of the gas supply line 10 between the on-off valve 23A and the on-off valve 24. The parallel line 11 is provided with the first compressor 21B, thermometer 22B, and on-off valve 23B in order from upstream to downstream.

[0033] Furthermore, one end 31a of the connecting line 31 is connected to the portion of the parallel line 11 between the thermometer 22B and the on-off valve 23B. The other end 31b of the connecting line 31 is connected to the downstream portion of the on-off valve 41A in the parallel line 11. The connecting line 31 is provided with the on-off valve 41B described above.

[0034] Thus, the first compressor 21A, thermometer 22A, on-off valve 23A, and on-off valve 41A are in a parallel relationship with the first compressor 21B, thermometer 22B, on-off valve 23B, and on-off valve 41B. The first compressor 21B, thermometer 22B, on-off valve 23B, and on-off valve 41B have the same configuration as the first compressor 21A, thermometer 22A, on-off valve 23A, and on-off valve 41A, respectively. For this reason, the explanation of the first compressor 21B, thermometer 22B, on-off valve 23B, and on-off valve 41B will be omitted.

[0035] Furthermore, the gas pumping system 1 includes a direct line 50 that bypasses both the first compressors 21A and 21B. A shut-off valve 51 is provided in the direct line 50. The opening and closing of the shut-off valve 51 is controlled by a control device 60, which will be described later.

[0036] The gas pumping system 1 also includes a control device 60. The control device 60 is communicatively connected to thermometers 22A, 22B, first compressors 21A, 21B, second compressor 27, and on-off valves 23A, 23B, 24, 41A, 41B, and 51. The control device 60 controls the starting and stopping of the first compressors 21A, 21B and the second compressor 27, respectively. The control device 60 also controls the opening and closing of the on-off valves 23A, 23B, 24, 41A, 41B, and 51.

[0037] The control device 60 has hardware components such as an arithmetic processor and memory. The arithmetic processor includes, for example, a processor. The memory includes volatile memory, non-volatile memory, and the like. The control device 60 may consist of a single control device 60 that provides centralized control, or it may consist of multiple control devices 60 that cooperate with each other to provide distributed control.

[0038] Figure 2 is a block diagram showing the control system of the gas pumping system 1 shown in Figure 1. Functionally, the control device 60 includes a mode determination unit 61, a determination unit 62, and a control unit 63. The mode determination unit 61, the determination unit 62, and the control unit 63 can be realized by a processor performing calculations using volatile memory based on a program stored in non-volatile memory.

[0039] The mode determination unit 61 determines one operating mode from among a predetermined set of operating modes. Each operating mode relates to which of the first compressors 21A, 21B, and the second compressor 27 is operated to pump hydrogen gas. The determination of the operating mode by the mode determination unit 61 also includes switching from one operating mode to another. In this embodiment, the mode determination unit 61 determines the operating mode to be executed from among five predetermined operating modes, the first to fifth operating modes.

[0040] The first operating mode is an operating mode in which only the first compressor 21A is operated. The second operating mode is an operating mode in which both compressors, the first compressor 21A and 21B, are operated. The second operating mode is used, for example, when it is desired to compress low-temperature hydrogen gas in the same way as the first operating mode, but to increase the gas volume pumped per unit time compared to the first operating mode. The third operating mode is an operating mode in which only the first compressor 21B is operated. The third operating mode is used, for example, when the first compressor 21A is unavailable or needs to be inspected. The fourth operating mode is an operating mode in which all of the first compressors 21A and 21B and the second compressor 27 are operated. The fourth operating mode is used, for example, when it is necessary to quickly pump a larger amount of hydrogen gas from tank 2 to destination 3 than in the second operating mode, even if it reduces pumping efficiency. The fifth operating mode is an operating mode in which only the second compressor 27 is operated. The fifth operating mode is executed when both the first compressors 21A and 21B are unavailable, for example, when there is a malfunction in both of the first compressors 21A and 21B or when both are undergoing inspection.

[0041] In this embodiment, the operating mode is determined by the operator's manual operation. Specifically, the gas pumping system 1 is equipped with an input device 70 that receives operator input. As shown in Figure 2, the control device 60 is communicatively connected to the input device 70. The mode determination unit 61 determines the operating mode based on the information received from the input device 70. For example, the input device 70 is a known input device such as a keyboard, touch panel, or group of button switches. Alternatively, the operating mode may be determined automatically based on a program stored in non-volatile memory, without the operator's manual operation.

[0042] The determination unit 62 determines whether the temperature measured by thermometer 22A or thermometer 22B is below a predetermined threshold. The threshold is set, for example, to a temperature between -200°C and -100°C.

[0043] The control unit 63 controls the first compressors 21A, 21B, the second compressor 27, and the on-off valves 23A, 23B, 24, 41A, 41B, 51 based on the operating mode determined by the mode determination unit 61 and the determination result by the determination unit 62.

[0044] Next, the control of the control device 60 when each operating mode is determined will be explained with reference to Figures 3 to 6.

[0045] (First operating mode) First, in a gas pumping system 1 where hydrogen gas is not being pumped, the control flow by the control device 60 when the mode determination unit 61 determines the operating mode to be executed as the first operating mode will be explained with reference to Figure 3.

[0046] When the mode determination unit 61 determines the first operating mode, if the open / closed state of each on-off valve 23A, 23B, 24, 41A, 41B, 51 is not in the initial state, the control unit 63 controls each on-off valve 23A, 23B, 24, 41A, 41B, 51 so that the open / closed state of each on-off valve 23A, 23B, 24, 41A, 41B, 51 returns to the initial state (step S1). Here, the initial state is when on-off valves 23A and 24 are open and on-off valves 23B, 41A, 41B, 51 are closed.

[0047] Next, the control unit 63 starts the second compressor 27 (step S2). As a result, the hydrogen gas in tank 2 is supplied from tank 2 to destination 3 through the gas supply line 10. That is, the hydrogen gas leaving tank 2 passes through the inside of the stopped first compressor 21A and then reaches the heater 25. The hydrogen gas heated by the heater 25 passes through the buffer tank 26, is compressed by the second compressor, and then supplied to destination 3. In this way, while the second compressor 27 is operating, the first compressor 21A and the piping upstream of the first compressor 21A in the gas supply line 10 are pre-cooled.

[0048] While the second compressor 27 is operating, the control device 60 receives information regarding the temperature measured by the thermometer 22A. The determination unit 62 determines whether the temperature measured by the thermometer 22A is below a predetermined threshold (step S3).

[0049] If the determination unit 62 determines that the temperature measured by the thermometer 22A is not below a predetermined threshold (step S3: NO), the pumping of hydrogen gas by the second compressor 27 is continued, and the determination unit 62 repeats the determination.

[0050] If the determination unit 62 determines that the temperature measured by the thermometer 22A is below a predetermined threshold (step S3: YES), the control unit 63 stops the second compressor 27 (step S4). The control unit 63 also closes the on-off valve 23A and opens the on-off valve 41A (step S5).

[0051] Subsequently, the control unit 63 starts the first compressor 21A (step S6). In this way, the hydrogen gas in tank 2 is compressed by the first compressor 21A and then pumped to the destination 3 through the bypass line 30.

[0052] (Switching from the first operating mode to the second operating mode) Next, with reference to Figure 4, the control flow by the control device 60 when the mode determination unit 61 switches the operating mode from the first operating mode to the second operating mode in the gas pumping system 1 will be explained.

[0053] In the first operating mode after step S6 shown in Figure 1, the on-off valves 24 and 41A are open, and the on-off valves 23A, 23B, 41B, and 51 are closed. When the mode determination unit 61 switches the operating mode from the first operating mode to the second operating mode, the control unit 63 opens the on-off valve 23B (step S11) and starts the second compressor 27 (step S12).

[0054] While the second compressor 27 is operating, the control device 60 receives information regarding the temperature measured by the thermometer 22B. The determination unit 62 determines whether the temperature measured by the thermometer 22B is below a predetermined threshold (step S13).

[0055] If the determination unit 62 determines that the temperature measured by the thermometer 22B is not below a predetermined threshold (step S13: NO), the pumping of hydrogen gas by the second compressor 27 is continued, and the determination unit 62 repeats the determination.

[0056] If the determination unit 62 determines that the temperature measured by the thermometer 22B is below a predetermined threshold (step S13: YES), the control unit 63 stops the second compressor 27 (step S14). The control unit 63 also closes the on-off valve 23B and opens the on-off valve 41B (step S15).

[0057] Subsequently, the control unit 63 starts the first compressor 21B (step S16). In this way, the hydrogen gas in tank 2 is pumped to destination 3 by both the first compressors 21A and 21B. Specifically, the hydrogen gas introduced to the first compressor 21A is compressed by the first compressor 21A and then pumped to destination 3 through the bypass line 30, and the hydrogen gas introduced to the first compressor 21B is compressed by the first compressor 21B and then pumped to destination 3 through the bypass line 30.

[0058] (Switching from the first operating mode to the third operating mode) Next, with reference to Figure 5, the control flow by the control device 60 when the mode determination unit 61 switches the operating mode from the first operating mode to the third operating mode in the gas pumping system 1 will be explained.

[0059] In the first operating mode after step S6 shown in Figure 1, the on-off valves 24 and 41A are open, and the on-off valves 23A, 23B, 41B, and 51 are closed. When the mode determination unit 61 switches the operating mode from the first operating mode to the third operating mode, the control unit 63 opens the on-off valve 23B (step S21) and starts the second compressor 27 (step S22).

[0060] While the second compressor 27 is operating, the control device 60 receives information regarding the temperature measured by the thermometer 22B. The determination unit 62 determines whether the temperature measured by the thermometer 22B is below a predetermined threshold (step S23).

[0061] If the determination unit 62 determines that the temperature measured by the thermometer 22B is not below a predetermined threshold (step S23: NO), the pumping of hydrogen gas by the first compressor 21A and the second compressor 27 is continued, and the determination unit 62 repeats the determination.

[0062] If the determination unit 62 determines that the temperature measured by the thermometer 22B is below a predetermined threshold (step S23: YES), the control unit 63 stops the first compressor 21A and the second compressor 27 (step S24). The control unit 63 also closes the on-off valves 23B and 41A and opens the on-off valve 41B (step S25).

[0063] Subsequently, the control unit 63 starts the first compressor 21B (step S26). In this way, the hydrogen gas in tank 2 is compressed by the first compressor 21B and then pumped to the destination 3 through the bypass line 30.

[0064] (Switching from the first operating mode to the fourth operating mode) Next, with reference to Figure 6, the control flow by the control device 60 when the mode determination unit 61 switches the operating mode from the first operating mode to the fourth operating mode in the gas pumping system 1 will be explained.

[0065] In the first operating mode after step S6 shown in Figure 1, the on-off valves 24 and 41A are open, and the on-off valves 23A, 23B, 41B, and 51 are closed. When the mode determination unit 61 switches the operating mode from the first operating mode to the fourth operating mode, the control unit 63 opens the on-off valve 23B (step S31) and starts the second compressor 27 (step S32).

[0066] While the second compressor 27 is operating, the control device 60 receives information regarding the temperature measured by the thermometer 22B. The determination unit 62 determines whether the temperature measured by the thermometer 22B is below a predetermined threshold (step S33).

[0067] If the determination unit 62 determines that the temperature measured by the thermometer 22B is not below a predetermined threshold (step S33: NO), the pumping of hydrogen gas by the first compressor 21A and the second compressor 27 is continued, and the determination unit 62 repeats the determination.

[0068] If the determination unit 62 determines that the temperature measured by the thermometer 22B is below a predetermined threshold (step S33: YES), the control unit 63 closes the on-off valve 23B and opens the on-off valves 41B and 51 (step S34).

[0069] Subsequently, the control unit 63 starts the first compressor 21B (step S35). In this way, the hydrogen gas in tank 2 is pumped to destination 3 by the first compressors 21A and 21B and the second compressor 27. Specifically, the hydrogen gas introduced to the first compressor 21A is compressed by the first compressor 21A and then pumped to destination 3 through the bypass line 30, and the hydrogen gas introduced to the first compressor 21B is compressed by the first compressor 21B and then pumped to destination 3 through the bypass line 30. The hydrogen gas introduced to the second compressor 27 through the direct line 50 is compressed by the second compressor 27 and then pumped to destination.

[0070] (Fifth operating mode) Next, with reference to Figure 7, the control flow by the control device 60 when the mode determination unit 61 determines the operating mode to the fifth operating mode in the gas pumping system 1, which is not currently pumping hydrogen gas, will be explained.

[0071] In the initial state, on-off valves 23A and 24 are open, and on-off valves 23B, 41A, 41B, and 51 are closed.

[0072] When the mode determination unit 61 determines the operating mode to the fifth operating mode, the control unit 63 closes the on-off valve 23A and opens the on-off valve 51 (step S41).

[0073] Subsequently, the control unit 63 starts the second compressor 27 (step S42). In this way, the hydrogen gas in tank 2 is pumped to the destination 3 by the second compressor 27. That is, the hydrogen gas that is guided to the second compressor 27 through the direct line 50 is compressed by the second compressor 27 and then pumped to the destination.

[0074] As described above, according to this embodiment, if the temperature measured by the thermometer 22A is above a predetermined threshold, the control device 60 stops the first compressor 21A and operates the second compressor 27. Also, if the temperature measured by the thermometer 22A is below the threshold, the control device 60 operates the first compressor 21A. In other words, the first compressor 21A can be used for low temperatures from the temperature of liquefied hydrogen down to the threshold, and the second compressor 27 can be used for high temperatures from the threshold down to room temperature.

[0075] For example, immediately after starting to pump hydrogen gas from tank 2 to destination 3, hydrogen gas that has risen to room temperature on its way from tank 2 to the first compressor 21A can be compressed by the second compressor 27. After the temperature of the hydrogen gas flowing through the gas supply line 10 has sufficiently decreased, the hydrogen gas can be compressed by the first compressor 21A.

[0076] Furthermore, the second compressor 27 is located downstream of the first compressor 21A in the gas supply line 10, and hydrogen gas passes through the stopped first compressor 21A while the second compressor 27 is operating. This allows the first compressor 21A to be pre-cooled by the hydrogen gas before it is compressed by the second compressor 27 while the second compressor 27 is operating. As a result, after the temperature of the hydrogen gas flowing through the gas supply line 10 has sufficiently decreased, the first compressor 21A can be immediately started and the hydrogen gas can be compressed by the first compressor 21A.

[0077] Therefore, according to this embodiment, it is possible to compress hydrogen gas from room temperature to cryogenic temperatures without having to prepare a compressor that can compress hydrogen gas at any temperature from room temperature to cryogenic temperatures.

[0078] Furthermore, according to this embodiment, the thermometer 22A is installed in the gas supply line 10 between the first compressor 21A and the second compressor 27. This makes it possible to determine from the temperature of the hydrogen gas discharged from the first compressor 21A that the first compressor 21A has been pre-cooled to the desired temperature. Therefore, it is easy to set the threshold for the timing of operating the first compressor 21A to the point when the pre-cooling of the first compressor 21A is complete.

[0079] Furthermore, according to this embodiment, the control device 60 controls the first on-off valve 23A and the second on-off valve 41A so that when the temperature measured by the thermometer 22A is above a predetermined threshold, the first on-off valve 23A is opened while the second on-off valve 41A is closed, and when the temperature measured by the thermometer 22A is below the threshold, the first on-off valve 23A is closed and the second on-off valve 41A is opened. As a result, the hydrogen gas compressed by the first compressor 21A can be guided to the pumping destination 3 without passing through the second compressor 27.

[0080] Furthermore, according to this embodiment, since a heater 25 is provided in the portion of the gas supply line 10 between the first on-off valve 23A and the second compressor 27, the heater 25 can raise the temperature of the hydrogen gas supplied to the second compressor 27 so that it falls within the allowable temperature range of the second compressor 27.

[0081] <Other Embodiments> This disclosure is not limited to the embodiments described above, and various modifications are possible without departing from the gist of this disclosure.

[0082] For example, in the above embodiment, the thermometer 22A was located in the gas supply line 10 between the first compressor 21A and the second compressor 27, but the location of the thermometer 22A is not limited to this. For example, the thermometer 22A may be located in the first compressor 21A. In other words, the thermometer 22A may measure the temperature of the hydrogen gas passing through the first compressor 21A.

[0083] Furthermore, for example, the thermometer 22A may be provided in the upstream portion of the first compressor 21A in the gas supply line 10.

[0084] Furthermore, although the gas pumping system 1 is equipped with a bypass line 30 in the above embodiment, the gas pumping system 1 does not need to be equipped with a bypass line 30. In this case, for example, the second compressor 27 may be configured to allow gas to pass through the inside of the second compressor 27A from the inlet to the discharge port while the second compressor 27 is stopped. While the second compressor 27 is stopped, hydrogen gas compressed by the first compressor 21A may pass through the inside of the second compressor 27.

[0085] Furthermore, although the second compressor 27 was described as a compressor for ambient temperature in the above embodiment, the second compressor 27 may compress hydrogen gas at a temperature lower than ambient temperature. The second compressor 27 only needs to be able to compress hydrogen gas at a temperature above a threshold. The gas supply system 1 is equipped with a heater 25 provided in the portion between the first on-off valve 23A and the second compressor 27 in the gas supply line 10, but the gas supply system 1 does not need to be equipped with a heater 25.

[0086] Furthermore, in the above embodiment, the control device 60 controlled the starting and stopping of the first compressors 21A, 21B and the second compressor 27, but the operator may manually start and stop the first compressors 21A, 21B and the second compressor 27. Also, in the above embodiment, the control device 60 controlled the opening and closing of the on-off valves 23A, 23B, 24, 41A, 41B, and 51, but the operator may manually open and close the on-off valves 23A, 23B, 24, 41A, 41B, and 51.

[0087] Furthermore, in the above embodiment, the gas pumping system 1 is equipped with two first compressors 21A and 21B, but it may be equipped with only one first compressor, or with three or more first compressors. In addition, the gas pumping system 1 may be equipped with two or more second compressors.

[0088] Furthermore, the control flow described with Figures 3-7 is merely illustrative. For example, the second to fourth operating modes do not necessarily have to be determined by switching from the first operating mode; each of the second to fourth operating modes may be determined from a state where hydrogen gas is not being pumped.

[0089] The functions of the elements disclosed herein can be performed using circuits or processing circuits, including general-purpose processors, dedicated processors, integrated circuits, ASICs (Application Specific Integrated Circuits), conventional circuits, or any combination thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuits. In this disclosure, a circuit, unit, or means is hardware that performs the enumerated functions, or hardware programmed to perform the enumerated functions. The hardware may be hardware disclosed herein, or other known hardware that is programmed or configured to perform the enumerated functions. If the hardware is a processor, which is considered a type of circuit, then the circuit, means, or unit is a combination of hardware and software, where the software is used to configure the hardware or processor.

[0090] A gas pumping system according to one aspect of the present invention is a gas pumping system that pumps hydrogen gas evaporated in a tank storing liquefied hydrogen from the tank to a pumping destination outside the tank, comprising: a gas supply line for supplying hydrogen gas from the tank to the pumping destination; a first compressor provided in the gas supply line; a second compressor provided in the gas supply line on the downstream side of the first compressor; a thermometer for measuring the temperature of the hydrogen gas flowing through the gas supply line; and a control device for controlling the first compressor and the second compressor, wherein the control device operates the second compressor with the first compressor stopped if the temperature measured by the thermometer is above a predetermined threshold, and operates the first compressor if the temperature measured by the thermometer is below the threshold.

[0091] According to the above configuration, the control device operates the second compressor while stopping the first compressor if the temperature measured by the thermometer is above a predetermined threshold. Conversely, the control device operates the first compressor if the temperature measured by the thermometer is below the threshold. In other words, the first compressor can be used for low temperatures from the temperature of liquefied hydrogen down to the threshold, and the second compressor can be used for high temperatures from the threshold down to room temperature.

[0092] Furthermore, the second compressor is located downstream of the first compressor in the gas supply line, and hydrogen gas passes through the first compressor while it is stopped, while the second compressor is operating. This allows the first compressor to be pre-cooled by the hydrogen gas before it is compressed by the second compressor while it is operating. As a result, after the temperature of the hydrogen gas flowing through the gas supply line has dropped sufficiently, the first compressor can be started immediately and the hydrogen gas can be compressed by the first compressor.

[0093] Therefore, with the above configuration, it is possible to compress hydrogen gas from room temperature to cryogenic temperatures without having to prepare a compressor that can compress hydrogen gas at any temperature from room temperature to cryogenic temperatures.

[0094] Furthermore, in the above configuration, the thermometer may be installed in the gas supply line between the first compressor and the second compressor, or on the first compressor. With this configuration, the temperature of the hydrogen gas discharged from the first compressor, or the temperature of the hydrogen gas passing through the first compressor, can be measured by the thermometer, and it can be determined from the temperature measured that the first compressor has been pre-cooled to the desired temperature. For this reason, it is easy to set the threshold for the timing of operating the first compressor to the point when the pre-cooling of the first compressor is completed.

[0095] Furthermore, in the above configuration, the system may further include a bypass line that branches off from a branching point located between the first and second compressors in the gas supply line and connects to the downstream portion of the second compressor in the gas supply line, a first on-off valve provided in the portion of the gas supply line between the branching point and the second compressor, and a second on-off valve provided in the bypass line, wherein the control device may control the first on-off valve and the second on-off valve to close the second on-off valve and open the first on-off valve when the temperature measured by the thermometer is above a predetermined threshold, and to close the first on-off valve and open the second on-off valve when the temperature measured by the thermometer is below the threshold. With this configuration, hydrogen gas compressed by the first compressor can be guided to the destination without passing through the second compressor.

[0096] Furthermore, the above configuration may include a heater provided in the gas supply line between the first shut-off valve and the second compressor. With this configuration, the heater can raise the temperature of the hydrogen gas supplied to the second compressor so that it falls within the allowable temperature range of the second compressor.

[0097] Furthermore, a gas pumping method according to one aspect of the present invention is a gas pumping method for pumping hydrogen gas evaporated in a tank storing liquefied hydrogen from the tank to a pumping destination outside the tank, comprising a gas supply line for leading hydrogen gas from the tank to the pumping destination, a first compressor provided in the gas supply line, and a second compressor provided in the gas supply line on the downstream side of the first compressor, wherein the temperature of the hydrogen gas supplied by the gas supply line is measured, and if the measured temperature is above a predetermined threshold, the second compressor is operated with the first compressor stopped, and if the measured temperature is below the threshold, the first compressor is operated.

[0098] According to the method described above, if the measured temperature is above a predetermined threshold, the first compressor is stopped and the second compressor is started. If the measured temperature is below the threshold, the first compressor is started. In other words, the first compressor can be used for low temperatures from the temperature of liquefied hydrogen down to the threshold, and the second compressor can be used for high temperatures from the threshold down to room temperature.

[0099] Furthermore, the second compressor is located downstream of the first compressor in the gas supply line, and hydrogen gas passes through the first compressor while it is stopped, while the second compressor is operating. This allows the first compressor to be pre-cooled by the hydrogen gas before it is compressed by the second compressor while it is operating. As a result, after the temperature of the hydrogen gas flowing through the gas supply line has dropped sufficiently, the first compressor can be started immediately and the hydrogen gas can be compressed by the first compressor.

[0100] Therefore, according to the above method, it is possible to compress hydrogen gas from room temperature to cryogenic temperatures without having to prepare a compressor that can compress hydrogen gas at any temperature from room temperature to cryogenic temperatures. [Explanation of Symbols]

[0101] 1: Gas pressure supply system 2: Tank 3: Destination of pumped material 10: Gas supply line 11: Parallel lines 21A: First Compressor 21B: First Compressor 22A:Thermometer 22B:Thermometer 23A: Shut-off valve, 1st shut-off valve 23B: Shut-off valve 24: Shut-off valve 25:Warmer 26: Buffer Tank 27: Second Compressor 30: Bypass Line 31: Connection line 41A: Shut-off valve, second shut-off valve 41B: Shut-off valve 50: Direct Line 51: Shut-off valve 60: Control device 61: Mode determination unit 62: Judgment section 63: Control Unit

Claims

1. A gas pumping system for pumping hydrogen gas evaporated in a tank that stores liquefied hydrogen from the tank to a destination outside the tank, A gas supply line that supplies hydrogen gas from the tank to the destination, A first compressor installed in the aforementioned gas supply line, A second compressor is provided in the downstream portion of the first compressor in the gas supply line, A thermometer for measuring the temperature of hydrogen gas flowing through the aforementioned gas supply line, The system comprises a control device for controlling the first compressor and the second compressor, The control device is If the temperature measured by the thermometer is above a predetermined threshold, the second compressor is operated with the first compressor stopped. A gas pumping system that operates the first compressor when the temperature measured by the thermometer is below the threshold.

2. The gas pumping system according to claim 1, wherein the thermometer is provided in the portion of the gas supply line between the first compressor and the second compressor, or on the first compressor.

3. A bypass line branches off from a branching point located between the first compressor and the second compressor in the gas supply line and connects to the downstream portion of the second compressor in the gas supply line, A first on-off valve is provided in the portion of the gas supply line between the branching point and the second compressor, The bypass line further comprises a second on / off valve, The control device is If the temperature measured by the thermometer is above a predetermined threshold, the first on-off valve is opened while the second on-off valve is closed. A gas pumping system according to claim 1 or 2, wherein the first on-off valve and the second on-off valve are controlled to close the first on-off valve and open the second on-off valve when the temperature measured by the thermometer is below the threshold.

4. The gas pumping system according to claim 3, further comprising a heater provided in the portion of the gas supply line between the first on-off valve and the second compressor.

5. A gas pumping method for pumping hydrogen gas evaporated in a tank storing liquefied hydrogen from the tank to a destination outside the tank, A system comprising: a gas supply line for guiding hydrogen gas from the tank to the destination; a first compressor provided in the gas supply line; and a second compressor provided in the gas supply line on the downstream side of the first compressor, The temperature of the hydrogen gas supplied by the aforementioned gas supply line is measured. A gas pumping method comprising: operating the second compressor with the first compressor stopped if the measured temperature is above a predetermined threshold; and operating the first compressor if the measured temperature is below the threshold.

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