Compressor unit

Abstract

The control unit of the compressor unit controls the demand end switching means so as to be in a second switching state in which hydrogen gas is sent to the output flow path toward the high-pressure demand end when the temperature (TS1) of hydrogen gas located on the upstream side with respect to the branch point in the intermediate flow path or the output flow path is less than a first temperature threshold value (T1). When the demand-end switching means is in the second switching state, the control unit controls the return valve so that the temperature TS2 falls within a predetermined temperature range (a range higher than a reference temperature based on the liquefaction temperature of air and lower than 0 DEG C) by referring to the temperature TS2 of the hydrogen gas between the connection part of the return flow path and the first compression stage of the first stage.

Description

Technical Field

[0001] The present invention relates to a reciprocating compressor unit. Background Art

[0002] In recent years, research into hydrogen as a fuel for power generation and automobiles has been underway for environmental reasons, leading to a growing demand for hydrogen. Furthermore, low-temperature boil-off gas (BOG) from sources like liquefied natural gas (LNG) and liquefied hydrogen (LH2) is recovered by compressors and supplied to demanding engines and other sources. The boil-off gas produced by LH2 is particularly cold. Therefore, direct intake of the boil-off gas by the compressor is subject to limitations such as the need to select materials suitable for extremely low temperatures, employ design considerations for thermal deformation, and implement rigorous thermal insulation.

[0003] Patent Document 1 also points out the following problem: "In recent years, hydrogen has attracted attention as a new energy source. It is envisioned that, when used as an energy source, hydrogen would be stored and transported in a liquefied state, similar to natural gas. However, hydrogen has a lower liquefaction temperature than air. Therefore, if equipment such as reciprocating compressors designed for natural gas, etc., were directly adapted for hydrogen, there is a risk of adverse effects caused by the extremely low temperature of liquefied hydrogen. For example, this could result in the formation of liquefied air around the equipment supplying liquefied hydrogen."

[0004] In this regard, Patent Document 1 describes the following: "The reciprocating compressor contains a compression section for compressing gas in a container section. Furthermore, the container section forms a vacuum region around the compression section. Thus, the compression section is thermally insulated from the external region based on the vacuum region. That is, even when extremely low-temperature gas is supplied to the compression section, the peripheral region of the reciprocating compressor will not be excessively cooled. Therefore, the generation of liquefied air can be suppressed." However, in general, it is very difficult to achieve high-performance thermal insulation for power machinery that is accompanied by vibrations during operation or equipment that must be regularly maintained through inspection openings (such as reciprocating compressors).

[0005] Patent Documents 2 and 3 propose technologies for adjusting the intake gas temperature using a preheater for screw compressors. Furthermore, Patent Document 4 discloses a reciprocating compressor and a heat exchanger for exchanging heat between boil-off gas before it is drawn into the compressor section and boil-off gas after it is discharged from the compressor section. However, since this heat exchanger is used to reliquefy boil-off gas compressed in the compressor section, boil-off gas cooled by a cooler located downstream of the compressor section is introduced into the heat exchanger.

[0006] On the other hand, Patent Document 5 points out the following problem: "In the past, when BOG (boil-off gas) evaporated in an LNG cryogenic storage tank was compressed and supplied to factory equipment by a cryogenic gas multi-stage compressor, the temperature of the BOG tended to fluctuate over a wide range from more than 100 degrees below zero to room temperature. In particular, right after the multi-stage compressor was started, the suction side temperature would rise to near room temperature. If compression was continued in this manner, the output temperature would become higher than the allowable temperature, making it impossible to operate."

[0007] Since liquefied hydrogen has a lower boiling point than LNG, the problems it causes may be more serious than those disclosed in Patent Document 5. Reciprocating compressors that handle boil-off gas from liquefied hydrogen must operate over a wide temperature range, from cryogenic temperatures to room temperature.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 2020-172870

[0011] Patent Document 2: Japanese Patent Publication No. 7085079

[0012] Patent Document 3: Japanese Patent Application Laid-Open No. 2001-65795

[0013] Patent Document 4: Japanese Patent Application Publication No. 2019-27590

[0014] Patent Document 5: Japanese Patent Application Laid-Open No. 4-12178 Summary of the Invention

[0015] An object of the present invention is to appropriately protect components of a reciprocating compressor unit that processes boil-off gas of liquefied hydrogen from wide temperature variations of the boil-off gas.

[0016] One aspect of the present invention relates to a reciprocating compressor unit that recovers boil-off gas, i.e., hydrogen, from a liquefied hydrogen storage tank and supplies at least a portion of the hydrogen to a high-pressure demand end (D1) comprising at least one of an engine, a power generation device, and a boiler. The compressor unit includes a plurality of compression stages, a crank mechanism, a reflux unit (SB1), a low-pressure gas discharge path, a demand end switching unit (CV1), a check valve, a first temperature sensor, a second temperature sensor, and a control unit.

[0017] The plurality of compression stages compress the hydrogen gas sucked in from the intake channel. The crank mechanism drives the plurality of compression stages. The reflux section (SB1) includes a reflux channel and a reflux valve. The reflux channel is a channel that returns the hydrogen gas output to the output channel on the output side of the plurality of compression stages, or the hydrogen gas flowing in the intermediate channel between the plurality of compression stages, to the intake channel. The reflux valve adjusts the reflux rate in the reflux channel. The low-pressure gas discharge path is a channel that branches from a branch point provided in the intermediate channel or the output channel and is capable of discharging hydrogen gas to a low-pressure demand end (D2), which is capable of processing hydrogen gas at a lower pressure than the hydrogen gas required by the high-pressure demand end (D1). The demand end switching unit (CV1) is provided in the low-pressure gas discharge path or the branch point. The check valve is located downstream of the branch point. The first temperature sensor is arranged in the intermediate channel or the output channel upstream of the branch point. The second temperature sensor is arranged between a connection portion of the return flow passage in the intake flow passage and a first compression stage that is the first stage among the plurality of compression stages. The control unit controls the demand-side switching unit (CV1) and the return valve.

[0018] In the compressor unit according to one aspect, during startup and when the temperature TS1 obtained by the first temperature sensor is greater than a specified first temperature threshold T1 greater than 0°C, the control unit controls the demand-side switching unit (CV1) to enter a first switching state in which hydrogen gas is allowed to flow through the low-pressure gas discharge path. Furthermore, when the temperature TS1 obtained by the first temperature sensor is less than the first temperature threshold T1, the control unit controls the demand-side switching unit (CV1) to enter a second switching state in which hydrogen gas is sent to the output flow path toward the high-pressure demand end (D1). Furthermore, when the demand-side switching unit (CV1) is in the second switching state, the control unit controls the return valve with reference to the intake temperature TS2 obtained by the second temperature sensor so that the intake temperature TS2 falls within a predetermined temperature range.

[0019] The predetermined temperature range is set to a range higher than a reference temperature based on the liquefaction temperature of air and lower than 0°C.

[0020] Another aspect of the present invention relates to another reciprocating compressor unit that recovers boil-off gas, i.e., hydrogen, from a liquefied hydrogen storage tank and supplies at least a portion of the hydrogen to a high-pressure demand end (D1) comprising at least one of an engine, a power generation device, and a boiler. The compressor unit includes a plurality of compression stages, a crank mechanism, a reflux unit (SB1), a low-pressure gas discharge path, a demand end switching unit (CV1), a check valve, a first temperature sensor, a second temperature sensor, a pressure sensor, and a control unit.

[0021] The plurality of compression stages compress the hydrogen gas sucked in from the intake channel. The crank mechanism drives the plurality of compression stages. The reflux section (SB1) includes a reflux channel and a reflux valve. The reflux channel is a channel that returns the hydrogen gas output to the output channel on the output side of the plurality of compression stages, or the hydrogen gas flowing in the intermediate channel between the plurality of compression stages, to the intake channel. The reflux valve adjusts the reflux rate in the reflux channel. The low-pressure gas discharge path is a channel that branches from a branch point provided in the intermediate channel and is capable of discharging hydrogen gas to a low-pressure demand end (D2), which is capable of processing hydrogen gas at a lower pressure than the hydrogen gas required by the high-pressure demand end (D1). The demand end switching unit (CV1) is provided in the low-pressure gas discharge path or the branch point. The check valve is provided in the intermediate channel downstream of the branch point. The first temperature sensor is arranged in the intermediate channel upstream of the branch point. The second temperature sensor is arranged between the connection portion of the return flow passage in the intake flow passage and the first compression stage. The pressure sensor is provided in the low-pressure gas discharge passage. The control unit controls the demand-side switching unit (CV1) and the return valve.

[0022] In the compressor unit according to another aspect, during startup, when the temperature TS1 obtained by the first temperature sensor is greater than a predetermined first temperature threshold value T1 greater than 0° C., the control unit controls the demand-side switching unit (CV1) to a first switching state in which hydrogen gas output from a first compression stage, which is located at the front of the plurality of compression stages, flows through the low-pressure gas discharge path. Furthermore, when the temperature TS1 obtained by the first temperature sensor is less than the first temperature threshold value T1, the control unit controls the demand-side switching unit (CV1) to a third switching state in which hydrogen gas flows through both the low-pressure gas discharge path and downstream of the branch point in the intermediate flow channel. Furthermore, when the demand-side switching unit (CV1) is in the third switching state, the control unit controls the demand-side switching unit (CV1) so that the pressure PS2 obtained by the pressure sensor falls within a predetermined range, and controls the return valve with reference to the intake temperature TS2 obtained by the second temperature sensor so that the intake temperature TS2 falls within a predetermined temperature range.

[0023] The predetermined temperature range is set to a range higher than a reference temperature based on the liquefaction temperature of air and lower than 0°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a diagram schematically showing the configuration of a compressor unit according to the first embodiment.

[0025] Figure 2 This is a flowchart showing the operation control executed by the control unit during the operation of the compressor unit.

[0026] Figure 3 This is a diagram schematically showing a partial configuration of a compressor unit according to a modified example of the first embodiment.

[0027] Figure 4 This is a diagram schematically showing a partial configuration of a compressor unit according to a modified example of the first embodiment.

[0028] Figure 5 This is a diagram schematically showing a partial configuration of a compressor unit according to the second embodiment.

[0029] Figure 6 This is a flowchart showing the operation control executed by the control unit during the operation of the compressor unit.

[0030] Figure 7 This is a diagram schematically showing a partial configuration of a compressor unit according to a modified example of the second embodiment.

[0031] Figure 8This is a diagram schematically showing a partial configuration of a compressor unit according to a third embodiment.

[0032] Figure 9 This is a diagram schematically showing a partial configuration of a compressor unit according to a modified example of the third embodiment.

[0033] Figure 10 This is a diagram schematically showing a partial configuration of a compressor unit according to a fourth embodiment.

[0034] Figure 11 This is a flowchart showing the operation control executed by the control unit during the operation of the compressor unit.

[0035] Figure 12 This is a diagram schematically showing a partial configuration of a compressor unit according to a modified example of the fourth embodiment.

[0036] Figure 13 This is a diagram schematically showing a partial configuration of a compressor unit according to the fifth embodiment.

[0037] Figure 14 This is a flowchart showing the operation control executed by the control unit during the operation of the compressor unit.

[0038] Figure 15 This is a flowchart showing the operation control executed by the control unit during the operation of the compressor unit.

[0039] Figure 16 This is a diagram schematically showing a partial configuration of a compressor unit according to a modified example of the fifth embodiment.

[0040] Figure 17 This is a flowchart showing the operation control executed by the control unit during the operation of the compressor unit.

[0041] Figure 18 This is a diagram schematically showing a partial configuration of a compressor unit according to a modified example of the fifth embodiment.

[0042] Figure 19 This is a flowchart showing the operation control executed by the control unit during the operation of the compressor unit.

[0043] Figure 20 This is a diagram schematically showing a partial configuration of a compressor unit according to a modified example of the fifth embodiment.

[0044] Figure 21 This is a diagram schematically showing a partial configuration of a compressor unit according to the sixth embodiment.

[0045] Figure 22 This is a flowchart showing the operation control executed by the control unit during the operation of the compressor unit.

[0046] Figure 23 This is a diagram schematically showing a partial configuration of a compressor unit according to the seventh embodiment.

[0047] Figure 24 This is a flowchart showing the operation control executed by the control unit during the operation of the compressor unit.

[0048] Figure 25 This is a diagram schematically showing a partial configuration of a compressor unit according to a modified example of the seventh embodiment.

[0049] Figure 26 This is a diagram schematically showing a partial configuration of a compressor unit according to a modified example of the first embodiment.

[0050] Figure 27 This is a diagram schematically showing a partial configuration of a compressor unit according to a modified example of the first embodiment. DETAILED DESCRIPTION

[0051] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are merely illustrative of the present invention, and the present invention is not limited to the following embodiments except for its basic configuration.

[0052] (First embodiment)

[0053] The compressor unit in this embodiment is a reciprocating compressor unit that recovers boil-off gas (hydrogen) from a liquefied hydrogen storage tank, compresses the recovered hydrogen, and supplies it to a demand source. The temperature of the boil-off gas is approximately -253°C.

[0054] like Figure 1 As shown, the compressor unit 10 includes: a plurality of compression stages (a first compression stage 12 and a subsequent compression stage 14 ) for compressing hydrogen gas sucked into the flow path 21 ; and a crank mechanism 16 for driving the first compression stage 12 and the subsequent compression stage 14 .

[0055] The first compression stage 12 is connected to the liquefied hydrogen storage tank 23 via the suction flow path 21 . Therefore, boil-off gas of the liquefied gas generated in the liquefied hydrogen storage tank 23 is sucked into the first compression stage 12 through the suction flow path 21 .

[0056] The first compression stage 12 includes a reciprocating compression mechanism. The first compression stage 12 includes a piston that reciprocates within a cylinder and is connected to the crank mechanism 16 via a piston rod connected to the piston. Alternatively, the first compression stage 12 may include an oil-free compression mechanism that does not utilize lubricating oil. Furthermore, the first compression stage 12 may have either a double-acting or single-acting structure.

[0057] In addition, Figure 1 In the figure, the first compression section 12 is shown as a trapezoid for convenience, but the first compression section 12 may also be configured such that the hydrogen gas is compressed by the reciprocating movement of pistons in a plurality of cylinders, thereby increasing the pressure of the hydrogen gas. This is also true for other embodiments.

[0058] The subsequent compression section 14 is connected to the first compression section 12 via the intermediate flow channel 22 and is equipped with a compression mechanism for further compressing the hydrogen compressed in the first compression section 12. The hydrogen compressed by the subsequent compression section 14 is output to the output flow channel 24. The hydrogen flowing into the output flow channel 24 is sent to the high-pressure demand end D1 or the low-pressure demand end D2 based on the switching of the demand end switching unit CV1. The hydrogen output from the compressor unit does not necessarily have to be supplied directly to the high-pressure demand end D1. The hydrogen can also be supplied to the high-pressure demand end D1 by various means such as transporting the gas cylinder or gas piping connected to the gas cylinder after filling it into the gas cylinder.

[0059] The high-pressure demand end D1 includes at least one of an engine, a power generation device, and a boiler, but may also include, in addition to these devices, devices such as a flame device and a bleed valve that discharge gas to the atmosphere.

[0060] Low-pressure demand side D2 is equipment capable of handling hydrogen at a lower pressure than that requested by high-pressure demand side D1. Low-pressure demand side D2 may include, for example, engines, power generation equipment, boilers, and other equipment that utilize gas as energy. In addition to these, it may also include equipment that utilizes gas at approximately atmospheric pressure, such as flame equipment and gas relief valves.

[0061] The subsequent compression stage 14 also includes a reciprocating compression mechanism similar to the first compression stage 12. The subsequent compression stage 14 also includes a piston that reciprocates in a cylinder and is connected to the crank mechanism 16 via a piston rod connected to the piston.

[0062] In addition, the leakage gas discharge part can also be connected to the subsequent compression section 14, and the leakage gas discharge part returns the leakage gas generated in the compression section 14 to the suction flow channel 21. Figure 1 For convenience, the subsequent compression stage 14 is represented by a trapezoid. However, the subsequent compression stage 14 does not necessarily have to employ a single-stage compression mechanism; a multi-stage compression mechanism may also be employed. Specifically, the subsequent compression stage 14 may be configured such that the hydrogen gas is sequentially compressed by the reciprocating motion of pistons within multiple cylinders connected in series, thereby increasing the pressure of the hydrogen gas. This applies to other embodiments as well. Within the subsequent compression stage 14, the compression stage that outputs hydrogen gas at room temperature may employ either a non-oiled or lubricated system.

[0063] like Figure 1 As shown, the compressor unit 10 includes: a reflux section SB1, which returns a portion of the hydrogen gas output from the subsequent compression section 14 to the output flow channel 24 to the intake flow channel 21. The reflux section SB1 includes: a reflux flow channel 18a; and a reflux valve 18b, which is arranged in the reflux flow channel 18a and includes a valve capable of adjusting the opening. One end of the reflux flow channel 18a is connected to the output flow channel 24, and the other end is connected to the intake flow channel 21. In other words, the hydrogen gas flowing in the reflux flow channel 18a merges with the hydrogen gas from the liquefied hydrogen storage tank 23 in the intake flow channel 21. The reflux valve 18b adjusts the reflux amount in the reflux flow channel 18a.

[0064] Furthermore, the compressor unit 10 includes a low-pressure gas discharge path 53 at a branch point P located at the output flow path 24. B Branch point P is connected to the low pressure demand end D2; and the demand end switching unit CV1 switches the supply destination of the hydrogen output from the subsequent compression section 14 to the high pressure demand end D1 or the low pressure demand end D2. B It is arranged at a position upstream of the position connected to the return flow path 18a in the output flow path 24. B A check valve 54 is provided at the downstream side. The check valve 54 can also be provided at the downstream side relative to the connection portion of the return flow channel 18a. The check valve 54 is a valve that allows hydrogen to flow from the branch point P B Therefore, the compressor unit 10 can prevent the hydrogen from flowing back from the high pressure demand end D1 to the branch point P. B The gas flows into the low-pressure gas discharge passage 53 .

[0065] The demand-side switching unit CV1 includes a regulating valve 56a that can be opened and closed and can adjust the opening degree. In this embodiment, as an example, it is provided in the low-pressure gas discharge path 53. However, the demand-side switching unit CV1 can be provided at the branch point P B , can also be set in the output channel 24 relative to the branch point P B The downstream portion. Furthermore, in this embodiment, the demand-side switching unit CV1 including the regulating valve 56a is employed, but the present invention is not limited thereto. For example, a demand-side switching unit CV1 including an on-off valve (on-off valve) capable of taking two positions, fully open and fully closed, may also be employed.

[0066] The demand-side switching unit CV1 is configured to switch the flow path of hydrogen between a state in which the hydrogen output from the subsequent compression section 14 is sent to the high-pressure demand end D1 (second switching state) and a state in which the hydrogen is sent to the low-pressure demand end D2 (first switching state).

[0067] The compressor unit 10 includes an upstream temperature sensor (second temperature sensor) 45 and an intermediate temperature sensor (first temperature sensor) 46. The upstream temperature sensor 45 is located in the intake passage 21 between the connection of the return passage 18a and the first compression stage 12. Therefore, when hydrogen gas flows through the return passage 18a, the upstream temperature sensor 45 can detect the temperature TS2 of the hydrogen gas that is drawn into the first compression stage 12 after the hydrogen gas from the return passage 18a merges with the hydrogen gas from the liquefied hydrogen storage tank 23.

[0068] The intermediate temperature sensor 46 is disposed in the intermediate flow passage 22 connecting the first compression stage 12 and the second compression stage 14 . Therefore, the intermediate temperature sensor 46 can obtain the temperature TS1 of the hydrogen gas flowing in the intermediate flow passage 22 .

[0069] The upstream temperature sensor 45 and the intermediate temperature sensor 46 each transmit the acquired temperature information to the control unit 50. The control unit 50 is configured to include a microprocessor including an MPU / CPU, an ASIC, a ROM, a RAM, etc., and controls various operations of the compressor unit 10 by executing firmware and the like pre-stored in the memory. The control unit 50 includes a first control unit 50a and a second control unit 50b, each serving as a functional unit. The first control unit 50a is a functional unit configured to control the demand-side switching unit CV1 with reference to the hydrogen temperature TS1 acquired by the intermediate temperature sensor 46. The second control unit 50b is a functional unit configured to control the return valve 18b with reference to the hydrogen temperature TS2 acquired by the upstream temperature sensor 45.

[0070] Here, refer to Figure 2 The operation control performed by the controller 50 during the operation of the compressor unit 10 according to the present embodiment will be described.

[0071] The control unit 50 determines whether the compressor unit 10 is already being driven or, if it is not being driven, whether there is a driving instruction.

[0072] When a start-up command is issued for the compressor unit 10, the control unit 50 activates the crank mechanism 16. This drives the first compression stage 12 and the subsequent compression stage 14 (step ST1). The first compression stage 12 and the subsequent compression stage 14 reciprocate the pistons within the cylinders based on the operation of the crank mechanism 16. As a result, hydrogen gas from the intake flow passage 21 is drawn into the first compression stage 12, and hydrogen gas from the intermediate flow passage 22 is drawn into the subsequent compression stage 14. In this manner, hydrogen gas is compressed in the compressor unit 10.

[0073] During the startup of the compressor unit 10, the temperature TS1 of the hydrogen gas flowing in the intermediate flow passage 22 (output from the first compression stage 12) is measured by the intermediate temperature sensor (first temperature sensor) 46. At this time, the control unit 50 refers to the temperature TS1 to determine whether the temperature TS1 is greater than a specified first temperature threshold T1 (step ST2). Here, the specified first temperature threshold T1 is a temperature greater than 0°C.

[0074] If the control unit 50 determines "yes" in step ST2 (temperature TS1 ≥ threshold T1), the first control unit 50a controls the demand-side switching unit CV1 so that the hydrogen gas output from the subsequent compression stage 14 to the output flow path 24 flows to the low-pressure gas discharge path 53 (step ST3). Consequently, the hydrogen gas output from the subsequent compression stage 14 to the output flow path 24 is delivered to the low-pressure demand end D2 via the low-pressure gas discharge path 53 (first switching state). Specifically, during startup (step ST2: "yes"), when the hydrogen gas in the piping downstream of the first compression stage 12 is at room temperature or a higher temperature than room temperature (step ST2: "yes"), the compressed hydrogen gas is not delivered to the high-pressure demand end D1 but to the low-pressure demand end D2 (step ST3). This protects the compressor from excessive increases in the output temperature caused by boosting the pressure to a high level in the subsequent compression stage 14 during startup, even when the intake gas temperature in the subsequent compression stage 14 is high.

[0075] On the other hand, if the control unit 50 determines "no" in step ST2 (temperature TS1 < threshold T1), the first control unit 50a controls the demand-side switching unit CV1 so that the hydrogen gas output from the subsequent compression stage 14 to the output flow channel 24 flows to the high-pressure demand end D1 (step ST4). In other words, the supply destination of the hydrogen gas output from the subsequent compression stage 14 to the output flow channel 24 is switched from the low-pressure demand end D2 to the high-pressure demand end D1 (a second switching state). The first switching state corresponds to the startup period of the compressor unit 10, while the second switching state corresponds to the steady-state operation period of the compressor unit 10.

[0076] During the steady-state operation of the compressor unit 10, the temperature (suction temperature) TS2 of the hydrogen gas sucked into the first compression stage 12 is acquired by the upstream temperature sensor (second temperature sensor) 45. The control unit 50 can start the reflux control (step ST5) with reference to the suction temperature TS2. That is, when the demand-side switching unit CV1 is in the second switching state (step ST4), the hydrogen gas in the suction flow path 21 is heated so that the suction temperature TS2 falls within the predetermined temperature range (T TH1 ≤TS2≤T TH2 ).

[0077] In more detail, in TS2 <T TH1 In the case of TS2>T TH2 In this case, the operation of returning part of the gas in the discharge flow path 24 to the suction flow path 21 is not performed or the amount of the gas returned is reduced.

[0078] Here, the predetermined temperature range is set to a range higher than a reference temperature based on the liquefaction temperature of air and lower than 0° C. That is, the lower limit value T of the predetermined temperature range is set to TH1 and upper limit value T TH2 It is set in a range higher than the reference temperature and lower than 0°C.

[0079] When the second control unit 50b controls the reflux valve 18b to be in the open state and performs reflux control (executes step ST5) as described above, the hydrogen gas from the liquefied hydrogen storage tank 23 is not directly introduced into the first compression stage 12. In this case, the hydrogen gas from the liquefied hydrogen storage tank 23 merges with the hydrogen gas compressed by the subsequent compression stage 14, and the hydrogen gas with a higher temperature is introduced into the first compression stage 12. In addition, the intake temperature TS2 is adjusted to the lower limit value T of the predetermined temperature range. TH1 As described above, the predetermined temperature range is set to a range higher than the reference temperature based on the liquefaction temperature of air. Therefore, the first compression stage 12 can be prevented from coming into contact with extremely low-temperature hydrogen (temperatures below the predetermined temperature range). This also prevents the density of the hydrogen gas drawn into the first compression stage 12 from becoming excessively high.

[0080] The compressor unit 10 having the above-described configuration can be protected in an environment where the boil-off gas (hydrogen gas) is at a low temperature, and can also be protected during the startup period where the boil-off gas (hydrogen gas) is at a normal temperature.

[0081] Here, each includes a reciprocating compressor in the compression stages 12 and 14, which output boil-off gas (hydrogen) at a pressure corresponding to the pressure of the boil-off gas's supply destination. Under these circumstances, in the compressor unit 10 of this embodiment, during startup, when the hydrogen gas in the piping on the liquefied hydrogen storage tank 23 side rises to a positive temperature range (normal temperature), the controller 50 switches the demand-side switching element CV1 to the first switching state. By switching the demand-side switching element CV1 to the first switching state by the controller 50, the hydrogen gas output from the subsequent compression stage 14 flows to the low-pressure demand end D2. Thus, the hydrogen gas is sent to the low-pressure demand end D2, which processes the hydrogen gas at a relatively low pressure. This allows the compression ratio in the compression stages 12 and 14 to be kept low, preventing excessive temperature increases in the hydrogen gas due to the temperature increase in the compression stages 12 and 14. Consequently, the compression stages 12 and 14 can be protected.

[0082] Furthermore, during the startup of the compressor unit 10, even if the hydrogen in the piping on the liquefied hydrogen storage tank 23 side is at room temperature, the startup of the compressor unit 10 can be performed quickly by discharging the hydrogen from the compression stages 12 and 14 to the low-pressure demand end D2 as described above.

[0083] On the other hand, the compressor unit 10 according to this embodiment can control the suction temperature TS2 within the predetermined temperature range (T TH1 ≤TS2≤T TH2 ). In addition, in the compressor unit 10, the lower limit value T of the above temperature range is TH1 The temperature is set to a range higher than the reference temperature based on the liquefaction temperature of air. Therefore, liquefaction of oxygen used as the combustion-supporting gas on the outer surface of the suction portion of the first compression stage 12 or around the device supplying hydrogen can be avoided.

[0084] In addition, in the compressor unit 10, a check valve 54 is provided in the output flow channel 24, thereby preventing hydrogen from flowing back from the high-pressure demand end D1 side in the output flow channel 24 to the subsequent compression section 14, thereby properly protecting the compressor (the first compression section 12 and the subsequent compression section 14).

[0085] Furthermore, if the compressor unit 10 is used, efficient hydrogen recovery and supply can be achieved.

[0086] In addition, Figure 1 In the compressor unit shown, the subsequent compression stage 14 uses a compression mechanism with one stage, but a compression mechanism with multiple stages can also be used. Figure 3As shown, a subsequent compression stage 14 including a subsequent first compression stage 14a and a subsequent second compression stage 14b may be used. However, a compression mechanism having three or more stages may be used as the subsequent compression stage 14. That is, a compression mechanism having four or more stages may be used as the entire compressor unit 10.

[0087] In addition, Figure 1 In the compressor unit 10 shown in FIG. 1 , the intermediate temperature sensor (first temperature sensor) 46 is provided in the intermediate flow passage 22. However, the position of the intermediate temperature sensor 46 is not limited thereto. Figure 4 As shown, the intermediate temperature sensor 46 can also be arranged in the output flow channel 24 relative to the branch point P B In this case, the temperature of the hydrogen gas in the intermediate flow channel 22 can be estimated by the intermediate temperature sensor 46 disposed in the output flow channel 24, and the determination in step ST2 can be performed using the estimated temperature of the hydrogen gas in the intermediate flow channel 22.

[0088] (Second embodiment)

[0089] like Figure 5 As shown, the compressor unit 10 involved in the second embodiment differs from the first embodiment described above in that the compressor unit 10 is provided with a preheater 71 capable of exchanging heat between the hydrogen gas flowing in the suction flow path 21 (hydrogen gas sucked into the first compression stage 12) and the hydrogen gas output from the subsequent compression stage 14 to the output flow path 24. Figure 5 In the present invention, the same components as those in the first embodiment are denoted by the same reference numerals and descriptions of the overlapping components are omitted below.

[0090] like Figure 5 As shown, the output flow channel 24 includes a first flow channel 24a and a second flow channel 24b that branch off from each other at the upstream side of the portion connected to the return flow channel 18a, and the preheater 71 is provided between one of the flow channels, the first flow channel 24a, and the suction flow channel 21. Thus, the preheater 71 can perform heat exchange between the hydrogen gas flowing in the first flow channel 24a and the hydrogen gas flowing in the suction flow channel 21.

[0091] A flow control unit FCV1 is provided at the branch point between the first flow channel 24a and the second flow channel 24b on the output flow channel 24. In the present embodiment, as an example, the flow control unit FCV1 includes a three-way valve 72a. The flow control unit FCV1 can cause the hydrogen gas output from the subsequent compression section 14 to flow to one of the first flow channel 24a and the second flow channel 24b, and can also adjust the amount of hydrogen gas flowing in the first flow channel 24a while causing the hydrogen gas to flow to both the first flow channel 24a and the second flow channel 24b. However, as far as the flow control unit FCV1 is concerned, it is sufficient that it can appropriately branch into the first flow channel 24a and the second flow channel 24b, and is not limited to the three-way valve 72a.

[0092] The compressor unit 10 according to this embodiment further includes a downstream temperature sensor (third temperature sensor) 48 disposed in the discharge flow passage 24 downstream of the preheater 71. The downstream temperature sensor 48 can obtain the temperature TS3 of the hydrogen gas flowing in the portion of the discharge flow passage 24 downstream of the preheater 71. The temperature information obtained by the downstream temperature sensor 48 is transmitted to the control unit 50.

[0093] In the compressor unit 10, the control unit 50 includes a first control unit 50a and a second control unit 50b, as well as a third control unit 50c as a functional unit. The third control unit 50c is configured to control the flow control unit FCV1 with reference to the hydrogen gas temperature TS3 obtained by the downstream temperature sensor 48.

[0094] Here, refer to Figure 6 The operation control performed by the controller 50 during the operation of the compressor unit 10 according to this embodiment will be described. In the following description, the operation of the controller 50 during startup (steps ST1 to ST3) is the same as that of the first embodiment, and thus description thereof will be omitted.

[0095] In the case of a steady-state operation (temperature TS1 < threshold T1 , “No” in step ST2 ), the control unit 50 controls the demand-side switching unit CV1 to allow hydrogen to flow to the high-pressure demand side D1 (step ST4 ).

[0096] The control unit 50 refers to the suction temperature TS2 acquired by the upstream temperature sensor 45 and starts the preheater control (step ST6). <T TH1 In this case, the third control unit 50c controls the flow control unit FCV1 so that the hydrogen gas output from the subsequent compression stage 14 to the output flow channel 24 flows into the first flow channel 24a and passes through the preheater 71 (step ST6). The control unit 50 then determines whether the temperature TS3 obtained by the downstream temperature sensor 48 while the hydrogen gas passes through the preheater 71 is greater than the temperature T TH3(Step ST7). If the control unit 50 determines "Yes" in step ST7 (temperature TS3>T TH3 ), the third control unit 50c maintains the state of hydrogen flowing into the preheater 71. Heat exchange in the preheater 71 is continued. TH2 In this case, preheater control is not performed.

[0097] On the other hand, if the control unit 50 determines "No" in step ST7 (temperature TS3 ≤ T TH3 ), the flow rate regulating unit FCV1 is controlled so that the inflow of hydrogen gas to the preheater 71 is constant (step ST8), and then the reflux control is started (step ST5). That is, the second control unit 50b controls the reflux valve 18b so that part of the gas in the output flow channel 24 is returned to the intake flow channel 21. Thus, when the control unit 50 determines "No" in step ST7, in addition to performing hydrogen heating by the preheater 71, hydrogen heating using the reflux unit SB1 is also performed. As a result, the intake temperature TS2 is adjusted to the lower limit value T of the predetermined temperature range. TH1 above.

[0098] The compressor unit 10 with the above-described configuration prioritizes heating of the hydrogen gas in the intake flow path 21 by the preheater 71 over heating by the reflux unit 18. If heating is insufficient, compensatory control is performed by heating by the reflux unit SB1. This minimizes the power loss associated with returning the hydrogen gas to the intake side, compared to heating by the reflux unit SB1 alone. Consequently, the compressor unit 10 can suppress a decrease in processing efficiency and maintain the intake temperature TS2 within a constant range.

[0099] In addition, the compressor unit 10 obtains the temperature TS3 of the hydrogen located on the downstream side relative to the preheater 71 in the output flow channel 24 by the downstream temperature sensor 48, and based on the temperature TS3 of the hydrogen obtained by the downstream temperature sensor 48, the flow adjustment unit FCV1 is controlled by the third control unit 50c, thereby suppressing the excessive temperature drop of the hydrogen supplied to the high-pressure demand end D1.

[0100] Furthermore, if the compressor unit 10 is used, efficient recovery and supply of hydrogen can be achieved.

[0101] In addition, Figure 5 In the compressor unit 10 shown in FIG. 1 , as an example, the output flow path 24 is branched into the first flow path 24a and the second flow path 24b and the preheater 71 is provided in the first flow path 24a. However, the arrangement of the preheater 71 is not limited to this. For example, Figure 7As shown, the preheater 71 is provided so that the intake flow passage 21 branches into the first flow passage 21a and the second flow passage 21b, and the preheater 71 is connected to one of the branched flow passages (the first flow passage 21a) and the output flow passage 24. In this case, a flow control unit FCV1 capable of adjusting the amount of hydrogen gas flowing into the preheater 71 may be provided at the branch point between the first flow passage 21a and the second flow passage 21b in the intake flow passage 21.

[0102] In addition, Figure 5 and Figure 7 In the illustrated compressor unit 10, a compression mechanism having one stage is employed in the subsequent compression stage 14, but a compression mechanism having multiple stages may be employed. That is, the compressor unit 10 as a whole may also employ a compression mechanism having three or more stages.

[0103] (Third embodiment)

[0104] like Figure 8 As shown, the compressor unit 10 according to the third embodiment differs from the second embodiment in that a preheater 71 capable of performing heat exchange between hydrogen gases is provided between the intermediate flow channel 22 and the suction flow channel 21. Figure 8 In the present invention, the same components as those in the second embodiment are denoted by the same reference numerals and descriptions of the overlapping components are omitted below.

[0105] In the compressor unit 10, the intermediate flow passage 22 is branched into a first flow passage 22a and a second flow passage 22b at a portion downstream of the location where the intermediate temperature sensor 46 is located. In the compressor unit 10 according to this embodiment, the preheater 71 is provided so as to be connected to the first flow passage 22a and the suction flow passage 21 in the intermediate flow passage 22.

[0106] The flow rate control unit FCV1 is provided at a junction between the first flow channel 22a and the second flow channel 22b in the intermediate flow channel 22. Furthermore, in the compressor unit 10, a downstream temperature sensor 48 is provided between the preheater 71 and the subsequent compression stage 14. The downstream temperature sensor 48 detects the temperature TS3 of the hydrogen gas drawn into the subsequent compression stage 14.

[0107] In the operation of the compressor unit 10 according to this embodiment, the control unit 50 performs the same control as in the second embodiment. Figure 6 Same controls as described.

[0108] The compressor unit 10 having the above-described configuration includes a preheater 71 capable of performing heat exchange between the hydrogen gas before being drawn into the first compression stage 12 and the hydrogen gas flowing through the intermediate flow passage 22. Furthermore, similar to the second embodiment described above, the compressor unit 10 prioritizes heating the hydrogen gas in the intake flow passage 21 by the preheater 71 over heating by the reflux unit SB1. If heating is insufficient, the reflux unit SB1 performs compensatory control. This minimizes the power loss associated with returning the compressed hydrogen gas to the intake side, compared to a case where heating is performed solely by the reflux unit SB1. Furthermore, due to the decrease in gas temperature at the inlet of the subsequent compression stage 14 (specifically, the compression mechanism located one stage after the first compression stage 12), the gas volume decreases, and the compression power in the subsequent compression stage 14 also decreases. Consequently, the compressor unit 10 can suppress a decrease in processing efficiency and maintain the intake temperature TS2 within a constant range.

[0109] In addition, the compressor unit 10 obtains the temperature TS3 of the hydrogen located on the downstream side relative to the preheater 71 in the intermediate flow channel 22 by the downstream temperature sensor 48, and based on the temperature TS3 of the hydrogen obtained by the downstream temperature sensor 48, the flow adjustment unit FCV1 is controlled by the third control unit 50c, thereby suppressing the excessive temperature drop of the hydrogen supplied to the high-pressure demand end D1.

[0110] Furthermore, if the compressor unit 10 is used, efficient recovery and supply of hydrogen can be achieved.

[0111] In addition, Figure 8 In the compressor unit 10 shown, the subsequent compression stage 14 uses a compression mechanism having one stage, but a compression mechanism having multiple stages may also be used. Figure 9 As shown, a subsequent compression section 14 having a subsequent first compression section 14a and a subsequent second compression section 14b may also be used. In this case, the portion between the subsequent first compression section 14a and the subsequent second compression section 14b in the intermediate flow channel 22 may be branched into a first flow channel 22a and a second flow channel 22b. Moreover, a flow control unit FCV1 may be provided at a branch point between the first flow channel 22a and the second flow channel 22b, etc. When this structure is adopted, heat exchange can be performed between the hydrogen output from the subsequent first compression section 14a and the hydrogen flowing in the intake flow channel 21.

[0112] However, a compression mechanism having three or more stages may be employed as the subsequent compression stage 14. That is, a compression mechanism having four or more stages may be employed as the entire compressor unit 10. When such a configuration having four or more stages is employed, a preheater 71 may be provided on the suction side of the last stage of the compression mechanism in the intermediate flow passage 22.

[0113] (Fourth embodiment)

[0114] Figure 10 The compressor unit 10 according to the fourth embodiment further includes another low-pressure gas discharge path, namely, a second low-pressure gas discharge path 83. The second low-pressure gas discharge path 83 is located at another branch point P of the intermediate flow passage 22. B 2 is branched and connected to the second low-pressure demand end (another low-pressure demand end) D3.

[0115] The compressor unit 10 according to the fourth embodiment differs from the first embodiment in that hydrogen is sent to the low-pressure demand end D2 and the second low-pressure demand end D3 during the startup period. Figure 10 In the present invention, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant descriptions are omitted below.

[0116] The second low-pressure demand end D3 is a device capable of processing hydrogen gas at a lower pressure than the hydrogen gas requested by the high-pressure demand end D1. The second low-pressure demand end D3 may include, for example, equipment that utilizes gas as energy, such as engines, power generation equipment, and boilers. In addition to these devices, it may also include equipment that utilizes gas at approximately atmospheric pressure, such as flame equipment and gas relief valves.

[0117] The compressor unit 10 also includes: a second demand-side switching unit CV2, which switches the flow path for outputting hydrogen from the first compression section 12 to the flow path to the subsequent compression section 14 or to the second low-pressure gas flow path 83. The second demand-side switching unit CV2 is another demand-side switching unit. In the present embodiment, the second demand-side switching unit CV2 includes, as an example, a regulating valve 86a and is arranged in the second low-pressure gas discharge path 83. In addition, in the present embodiment, a second demand-side switching unit CV2 including a regulating valve 86a capable of adjusting the opening is adopted, but is not limited to this. For example, a second demand-side switching unit CV2 including an on-off valve (open-off valve) capable of obtaining two positions of fully open and fully closed can also be adopted.

[0118] In the compressor unit 10, the control unit 50 includes a first control unit 50a and a second control unit 50b, as well as a fourth control unit 50d as a functional unit. The fourth control unit 50d is configured to control the second demand-side switching unit CV2 with reference to the hydrogen gas temperature TS1 obtained by the intermediate temperature sensor 46.

[0119] Here, refer to Figure 11The operation control performed by the controller 50 during the operation of the compressor unit 10 according to the present embodiment will be described. In the following description, a portion of the description overlapping with that of the first embodiment will be omitted.

[0120] If the control unit 50 determines "yes" in step ST2 (temperature TS1 ≥ threshold T1), that is, during the startup period, the first control unit 50a controls the demand-side switching unit CV1 to the first switching state, so that the hydrogen gas output from the subsequent compression stage 14 to the output flow channel 24 flows to the low-pressure demand end D2. Furthermore, the fourth control unit 50d controls the second demand-side switching unit CV2 to cause a portion of the hydrogen gas output from the first compression stage 12 to the intermediate flow channel 22 to flow to the second low-pressure demand end D3 (step ST9). Thus, while the hydrogen gas output from the subsequent compression stage 14 to the output flow channel 24 flows to the low-pressure demand end D2 in the first switching state, a portion of the hydrogen gas output from the first compression stage 12 to the intermediate flow channel 22 flows to the second low-pressure demand end D3 through the second low-pressure gas discharge path 83.

[0121] On the other hand, if the control unit 50 determines "No" in step ST2 (temperature TS1 < threshold T1), the fourth control unit 50d controls the demand-side switching unit CV1 and the second demand-side switching unit CV2 to direct the hydrogen output from the subsequent compression stage 14 to the output flow channel 24 to the high-pressure demand end D1 (step ST10). That is, in steady-state operation, the hydrogen compressed by the first compression stage 12 and the subsequent compression stage 14 is delivered to the high-pressure demand end D1 (second switching state). In steady-state operation, step ST5 (the step of initiating reflux control) executed by the second control unit 50b is the same as in the first embodiment described above.

[0122] In the compressor unit 10 having the above-described structure, the control unit 50 controls the demand-side switching unit CV1 so as to be able to switch to the first switching state or the second switching state. Thus, when the compressor unit 10 is in the first switching state, it is not only possible to discharge hydrogen to the low-pressure gas discharge path 53, but also possible to discharge hydrogen to the second low-pressure gas discharge path (another low-pressure gas discharge path) 83. Therefore, the compressor unit 10 involved in this embodiment can reduce the pressure of the hydrogen in the intermediate flow channel 22 compared to the case where the second low-pressure gas discharge path 83 is not provided. Thus, the compressor unit 10 can reduce the suction pressure of the subsequent compression section 14 arranged on the downstream side of the intermediate flow channel 22, thereby further reducing the power during startup.

[0123] Furthermore, if the compressor unit 10 is used, efficient recovery and supply of hydrogen can be achieved.

[0124] In addition, Figure 10 In the compressor unit 10 shown, the subsequent compression stage 14 uses a compression mechanism having one stage, but a compression mechanism having multiple stages may also be used. Figure 12 As shown, a subsequent compression section 14 having a subsequent first compression section 14a and a subsequent second compression section 14b may also be used. Figure 12 In the compressor unit 10 shown, the gas flow path between the first compression stage 12 and the subsequent second compression stage 14b is the intermediate flow path 22. In the case of adopting this structure, the branch point P of the low-pressure gas discharge path 53 can be branched. B , is arranged in a position between the subsequent first compression section 14 a and the subsequent second compression section 14 b in the intermediate flow channel 22 rather than in the output flow channel 24 .

[0125] However, a compression mechanism having three or more stages may be used as the subsequent compression stage 14. That is, a compression mechanism having four or more stages may be used as the entire compressor unit 10. In this case, the gas flow path between the first compression stage 12 and the last stage of the compression mechanism constituting the subsequent compression stage 14 is the intermediate flow path 22. When a configuration having four or more stages is adopted, a branch point P may be arranged at the position of the suction side of the last stage of the compression mechanism in the intermediate flow path 22. B .

[0126] (Fifth embodiment)

[0127] At once Figure 13 The structure of the compressor unit 10 according to the fifth embodiment shown in FIG. 1 is different from that of the second embodiment in that the structure of the subsequent compression stage 14 is different from that of the first embodiment shown in FIG. Figure 10 The compressor unit 10 of the fourth embodiment shown in FIG. Furthermore, the hydrogen treatment of the compressor unit 10 differs from that of the compressor unit 10 of the fourth embodiment in that during startup, hydrogen is delivered only to the low-pressure demand port D2, while during steady-state operation, hydrogen is delivered to the second low-pressure demand port D3 and the high-pressure demand port D1. Other aspects are the same as those of the fourth embodiment, and therefore, the same reference numerals are used for the same components as those of the fourth embodiment, and redundant descriptions are omitted below.

[0128] The compressor unit 10 includes an adjustment unit 41 for adjusting the hydrogen gas processing capacity of the subsequent compression stage 14. The adjustment unit 41 adjusts the gas processing capacity by a method other than adjusting the rotational speed of the crank mechanism 16. In this embodiment, as an example, an open / close intake valve unloader 61 is installed in the cylinder portion of the subsequent compression stage 14 to adjust the gas flow rate sent to the high-pressure demand end D1.

[0129] The compressor unit 10 also includes an intermediate pressure sensor (second pressure sensor) 47, a discharge path pressure sensor (pressure sensor) 49, and an output path pressure sensor (fourth pressure sensor) 87. The intermediate pressure sensor 47 is located on the suction side of the subsequent compression stage 14 in the intermediate flow passage 22 and obtains the pressure PS1 of the hydrogen gas flowing in this portion. The output path pressure sensor 87 is located in the output flow passage 24 and obtains the pressure PS4 of the hydrogen gas flowing in the output flow passage 24. The discharge path pressure sensor 49 is located in the second low-pressure gas discharge passage 83 and obtains the pressure PS2 of the hydrogen gas flowing in the second low-pressure gas discharge passage 83. Each pressure sensor 47, 87, and 49 transmits the obtained pressure information to the control unit 50.

[0130] The control unit 50 includes a first control unit 50a, a second control unit 50b, and a fourth control unit 50d, as well as a fifth control unit 50e as a functional unit. The control unit 50 accepts inputs such as the pressure PS4 at the high-pressure demand end D1, the pressure PS2 at the second low-pressure demand end D3, and the pressure PS1 at the inlet of the subsequent compression stage 14. Furthermore, the control unit 50 may also accept inputs of set values ​​for an intermediate pressure range (pressure thresholds a1 and a2). Furthermore, the fifth control unit 50e is configured to control the intake valve unloader 61, which serves as the adjustment unit 41, so that the pressure PS1 at the inlet of the subsequent compression stage 14, which varies in response to changes in the gas demand at the second low-pressure demand end D3 or the gas demand at the high-pressure demand end D1, falls within a predetermined range of values.

[0131] The cylinder portion of the subsequent compression stage 14 has two chambers: a push-compression chamber that compresses during the piston's push stroke, and a pull-compression chamber that compresses during the piston's pull stroke. The compressor unit 10 includes a capacity adjustment device for individually loading and unloading each compression chamber in the cylinder portion. Loading both chambers results in a 100% load, while loading only one chamber results in a 50% load. The fifth control unit 50e issues a load or unload command to the intake valve unloader 61 based on the pressure at the inlet of the subsequent compression stage 14, as detected by the second pressure sensor 47.

[0132] In the compressor unit 10, if the supply flow to the second low-pressure demand end D3 increases, the amount of gas processed in the subsequent compression stage 14 decreases compared to a case where the supply flow is not increased. Consequently, the pressure at the inlet of the subsequent compression stage 14 decreases. Specifically, the pressure differential between the inlet and outlet of the subsequent compression stage 14 increases as the supply flow to the second low-pressure demand end increases. This increases the load acting on internal components such as the piston that reciprocates for compression within the cylinder portion of the compression stage.

[0133] If the pressure PS1 at the inlet of the subsequent compression stage 14 drops below the preset pressure threshold a1, the inlet pressure PS1 can be increased by reducing the load of each compression chamber in the cylinder portion of the subsequent compression stage 14 from 100% to 50%. This reduces the load on the internal components. Furthermore, if the inlet pressure PS1 rises above the preset pressure threshold a2 under a 50% load, this is similar to the situation where the output pressure of the first compression stage 12 rises. Therefore, by increasing the load of the subsequent compression stage 14 to 100%, the load on the internal components of the first compression stage 12 can be reduced.

[0134] Here, refer to Figure 14 The operation control performed by the controller 50 during the operation of the compressor unit 10 according to the present embodiment will be described. In the following description, a portion of the description overlapping with that of the first embodiment will be omitted.

[0135] If the control unit 50 determines "yes" in step ST2 (temperature TS1 ≥ threshold T1), the first control unit 50a controls the demand-side switching unit (CV1) to be in the first switching state. Furthermore, during startup, the second demand-side switching unit (CV2) is closed to prevent hydrogen from flowing to the second low-pressure demand end D3. As a result, hydrogen output from the subsequent compression stage 14 to the output flow channel 24 flows only to the low-pressure demand end D2 (step ST3). Thus, hydrogen output from the subsequent compression stage 14 to the output flow channel 24 flows to the low-pressure demand end D2 via the low-pressure gas discharge path 53 (first switching state).

[0136] In the steady-state operating state (temperature TS1 < threshold T1, "No" in step ST2), the control unit 50 sets the demand-side switching element CV1 to the second switching state to supply hydrogen to the high-pressure demand side D1 (step ST4). Furthermore, the second control unit 50b begins controlling the return valve 18b (step ST5).

[0137] Furthermore, the fourth control unit 50d and the fifth control unit 50e control the second demand-side switching unit CV2 and the adjustment unit 41 (intake valve unloader) based on the fluctuation in the gas demand at the second low-pressure demand end D3 or the gas demand at the high-pressure demand end D1 (step ST11). Specifically, the fourth control unit 50d controls the second demand-side switching unit CV2 based on the fluctuation in the gas demand at the second low-pressure demand end D3 or the gas demand at the high-pressure demand end D1 to discharge hydrogen into the second low-pressure gas discharge path 83. The fifth control unit 50e controls the adjustment unit 41 so that the pressure PS1 at the inlet of the subsequent compression stage 14 falls within a predetermined threshold range. Specifically, the load change is performed via the intake valve unloader 61.

[0138] Reference Figure 15 The load change of the intake valve unloader 61 will be described in detail. If the demand from the second low-pressure demand end D3 increases (in other words, the demand from the high-pressure demand end D1 decreases), the pressure PS1 detected by the intermediate pressure sensor 47 decreases. In this case, if the pressure PS1 falls below the pressure threshold a1 ("Yes" in step ST21), the fifth control unit 50e controls the intake valve unloader 61 to change the load from 100% to 50% (step ST22). At a load of 50%, if the demand from the second low-pressure demand end D3 decreases (in other words, the demand from the high-pressure demand end D1 increases), the pressure PS1 detected by the intermediate pressure sensor 47 increases. Subsequently, if the pressure PS1 exceeds the pressure threshold a2 ("Yes" in step ST23), the fifth control unit 50e controls the intake valve unloader 61 to change the load from 50% to 100% (step ST24). In addition, if the amount at the second low-pressure demand end D3 is not changed but is changed according to the demand at the high-pressure demand end D1 , the amount of the reflux flow through the reflux portion SB1 can be used for adjustment.

[0139] The compressor unit 10, especially when the demand at the second low-pressure demand end D3 increases, prevents excessive pressure drops at the inlet of the subsequent compression stage 14, thereby preventing the effects of excessive pressure differentials within its internal components. In other words, without this control, a compressor with a large margin to absorb such fluctuations would be required. However, the compressor unit 10 can reduce this margin.

[0140] exist Figure 16 The compressor unit 10 shown is provided with, for example, Figure 13 Different Adjustment Unit 41. In this embodiment, as an example, an adjustment unit 41 is used that includes a reflux unit (second reflux unit) SB2 for adjusting the hydrogen processing amount by adjusting the gas flow rate sent from the subsequent compression stage 14 to the high-pressure demand end D1.

[0141] The second recirculation section SB2 includes a second recirculation passage 43a and a second recirculation valve 43b, which is disposed in the second recirculation passage 43a and has an adjustable opening. One end of the second recirculation passage 43a is connected to a portion of the output passage 24 upstream of the location of the check valve 54, and the other end is connected to the intermediate passage 22. Therefore, a portion of the hydrogen gas output from the subsequent compression stage 14 is returned to the intake side of the subsequent compression stage 14 in the intermediate passage 22. The second recirculation valve 43b adjusts the amount of recirculation in the second recirculation passage 43a.

[0142] The compressor unit 10 also includes an intermediate pressure sensor (second pressure sensor) 47, a discharge path pressure sensor (pressure sensor) 49, and an output path pressure sensor (fourth pressure sensor) 87. The intermediate pressure sensor 47 is located on the suction side of the subsequent compression stage 14 in the intermediate flow passage 22 and obtains the pressure PS1 of the hydrogen gas flowing in this portion. The output path pressure sensor 87 is located in the output flow passage 24 and obtains the pressure PS4 of the hydrogen gas flowing in the output flow passage 24. The discharge path pressure sensor 49 is located in the second low-pressure gas discharge passage 83 and obtains the pressure PS2 of the hydrogen gas flowing in the second low-pressure gas discharge passage 83. Each pressure sensor 47, 87, and 49 transmits the obtained pressure information to the control unit 50.

[0143] The control unit 50 includes a first control unit 50a, a second control unit 50b, and a fourth control unit 50d, as well as a fifth control unit 50e as a functional unit. The control unit 50 can receive inputs such as the pressure PS4 at the high-pressure demand end D1, the pressure PS2 at the second low-pressure demand end D3, and the pressure PS1 at the inlet of the subsequent compressor stage 14. It can also receive inputs such as the set values ​​for the intermediate pressures (pressure thresholds a1 and a2). Furthermore, the fifth control unit 50e is a functional unit configured to control the adjustment unit 41 (second return valve 43b) so that the pressure PS1 at the inlet of the subsequent compressor stage 14, which changes in accordance with the gas demand at the second low-pressure demand end D3 or the gas demand at the high-pressure demand end D1, reaches a predetermined value. The set value for the inlet pressure of the subsequent compressor stage 14 can be calculated based on the values ​​of PS4 and PS2.

[0144] Here, refer to Figure 14 The operation control performed by the controller 50 during the operation of the compressor unit 10 according to the present embodiment will be described. Note that in the following description, some of the descriptions that overlap with those of the first embodiment will be omitted.

[0145] In a steady-state operation state (temperature TS1 < threshold T1, "No" in step ST2), the control unit 50 controls the demand-side switching unit CV1 to supply hydrogen to the high-pressure demand side D1 (step ST4). Furthermore, the second control unit 50b controls the recirculation valve 18b to initiate recirculation control (step ST5).

[0146] Furthermore, the fourth control unit 50d and the fifth control unit 50e control the second demand-side switching unit CV2 and the adjustment unit 41 (second return valve 43b) based on the amount of gas demanded by the second low-pressure demand end D3 or the amount of gas demanded by the high-pressure demand end D1 (step ST11). Specifically, the fourth control unit 50d controls the second demand-side switching unit CV2 based on the amount of gas demanded by the second low-pressure demand end D3 or the amount of gas demanded by the high-pressure demand end D1 to discharge hydrogen gas to the second low-pressure gas discharge path 83. The fifth control unit 50e adjusts the opening of the second return valve 43b to adjust the gas processing capacity in the subsequent compression stage 14.

[0147] Reference Figure 17 The opening adjustment of the second return valve 43b will be described in detail. If the demand from the second low-pressure demand end D3 increases (in other words, if the demand from the high-pressure demand end D1 decreases), the pressure PS1 detected by the intermediate pressure sensor 47 decreases. Consequently, if the pressure PS1 falls below the pressure threshold a11 ("Yes" in step ST31), the fourth control unit 50d and the fifth control unit 50e control the flow rate of the return flow from the second return flow section SB2 to increase (step ST32). On the other hand, if the demand from the second low-pressure demand end D3 decreases (in other words, if the demand from the high-pressure demand end D1 increases), the pressure PS1 detected by the intermediate pressure sensor 47 increases. Consequently, if the pressure PS1 exceeds the pressure threshold a2 ("Yes" in step ST33), the fourth control unit 50d and the fifth control unit 50e control the flow rate of the return flow from the second return flow section SB2 to decrease (step ST34). In addition, if the amount at the second low-pressure demand end D3 is not changed but is changed according to the demand at the high-pressure demand end D1 , the amount of the reflux flow through the reflux portion SB1 can be used for adjustment.

[0148] As described above, the suction pressure of the subsequent compression section 14 is maintained approximately constant by discharging hydrogen to the second low-pressure demand end D3 and adjusting the gas processing volume in the subsequent compression section 14 based on the second reflux section SB2 in response to changes in the gas demand at the second low-pressure demand end D3 or the gas demand at the high-pressure demand end D1.

[0149] Furthermore, when the required amount (demand) of hydrogen at the high-pressure demand end D1 is reduced, the compressor unit 10 discharges hydrogen to the second low-pressure demand end D3. Thus, the compressor unit 10 maintains a constant pressure in the liquefied hydrogen storage tank 23 by balancing the amount of boil-off gas (hydrogen) generated from the liquefied hydrogen storage tank 23 with the amount of hydrogen delivered from the compressor unit 10.

[0150] Furthermore, the compressor unit 10 includes the adjustment unit 41 (second reflux section SB2), which allows it to maintain a substantially constant suction pressure in the subsequent compression stage 14. This allows the compressor unit 10 to maintain a constant pressure balance across the various stages of the subsequent compression stage, thereby achieving high compressor reliability. Specifically, if the pressure balance in the subsequent compression stage 14 cannot be maintained constant, a compressor with a large margin to accommodate such fluctuations would be required. However, the compressor unit 10 does not require a compressor with such a large margin.

[0151] Furthermore, the use of the compressor unit 10 enables efficient hydrogen recovery and supply. Furthermore, by utilizing the gas heated by compression in the compressor, the compressor serves as a heat source to heat the extremely low-temperature intake gas to an appropriate temperature. This also prevents excessive CO2 emissions compared to a heater upstream of the compressor that utilizes, for example, the heat of fossil fuel combustion.

[0152] like Figure 18 As shown, in the compressor unit 10, it is possible to use Figure 13 The same open and close type suction valve unloader 61 and Figure 16 The adjustment unit 41 is constituted by the similar second recirculation portion SB2.

[0153] like Figure 19 As shown, during the control of the adjustment unit 41, when the state (valve opening) of the second return valve 43b input to the control unit 50 is greater than a preset opening threshold b1 (a large amount of reflux) ("YES" in step ST41), the intake valve unloader 61 is controlled to reduce the load of the subsequent compression stage 14 (from 100% to 50%) (step ST42). If the opening of the second return valve 43b is less than the opening threshold b2 ("YES" in step ST43), the intake valve unloader 61 is controlled to increase the load of the subsequent compression stage 14 (from 50% to 100%) (step ST44). This allows power reduction by reducing the load of the subsequent compression stage 14 in the event of excessive reflux.

[0154] Furthermore, if the compressor unit 10 is used, efficient recovery and supply of hydrogen can be achieved.

[0155] like Figure 20 As shown, the compressor unit 10 may include a stepless capacity adjustment device 64 b as the adjustment unit 41 provided in the subsequent compression stage 14 .

[0156] The stepless capacity adjustment device 64b includes an intake valve unloader 61b, a drive device 62b, and a detector 63b for detecting the rotation of the crank mechanism. The intake valve unloader 61b is driven by a hydraulic or electric drive device 62b and can maintain or release the open state of the intake valve plate at a speed higher than the reciprocating time required for the piston. Furthermore, the control unit 50 performs computational processing to estimate the piston position based on a signal from the detector 63b located in the crank mechanism 16.

[0157] An intake valve is installed between the intake passage and the compression chamber in the cylinder portion of the subsequent compression stage 14. This intake valve comprises a valve plate that opens and closes the gas passage, and a valve body that houses the valve plate. The cylinder intake valve has a similar structure to a check valve: when the upstream pressure is higher than the downstream pressure, the valve plate opens due to the pressure differential. When the downstream pressure is higher, the valve plate stops the flow of gas.

[0158] When the intake valve unloader 61b is actuated, the valve plate of the intake valve is maintained in an open position, disabling its check valve function. Furthermore, when the unloader is not actuated, if the piston enters the intake stroke, the pressure in the compression chamber is lower than that in the intake passage, causing the intake valve to open and allowing gas to enter the compression chamber. If the piston enters the compression stroke, the pressure in the compression chamber is higher than that in the intake passage, causing the intake valve to close.

[0159] At the beginning of the compression stroke, the stepless capacity adjustment device 64b maintains an open state. Subsequently, a portion of the gas introduced into the compression chamber is returned to the suction passage. Then, midway through the compression stroke, the open state is released, closing the suction valve. The gas remaining in the compression chamber is compressed and discharged. During the next piston suction stroke, the drive unit is driven again, initiating the piston's compression stroke. Finally, the open state is released. This process is repeated in accordance with the reciprocating motion of the piston.

[0160] If the release time is advanced, the amount of gas delivered increases, while if it is delayed, the amount of gas delivered decreases, thereby achieving the same function as the second return valve. Moreover, since the amount of compressed gas is adjusted, the power reduction effect is large.

[0161] In addition, in Figure 12 When a configuration is adopted in which the subsequent compression stage 14 includes a plurality of compression mechanisms as shown, the second reflux portion 43 and / or the capacity adjustment device 64b may be provided for at least one of the compression mechanisms.

[0162] (Sixth embodiment)

[0163] Secondly, refer to Figure 21The compressor unit 10 according to the sixth embodiment will be described. The compressor unit 10 has the following structure: Figure 1 The compressor unit 10 involved in the first embodiment shown in the figure is different in that the low-pressure gas discharge path 53 is located in the intermediate flow channel 22. In addition, regarding the treatment of hydrogen, it is different from the compressor unit 10 involved in the first embodiment in that hydrogen is supplied to the low-pressure demand end D2 via the low-pressure gas discharge path 53 during either the startup period or the steady-state operation period. Figure 21 In the present invention, the same components as those in the first embodiment are denoted by the same reference numerals and descriptions of the overlapping components are omitted below.

[0164] In the compressor unit 10 according to the present embodiment, the branch point P from which the low-pressure gas discharge path 53 branches is B The intermediate pressure sensor 47 is located downstream of the intermediate temperature sensor 46 in the intermediate flow passage 22. Furthermore, the intermediate pressure sensor 47 is located downstream of the intermediate flow passage 22. The intermediate pressure sensor 47 obtains the pressure PS1 of the hydrogen gas drawn into the subsequent compression stage 14 and transmits it to the control unit 50.

[0165] The compressor unit 10 also includes a discharge line pressure sensor 49. This sensor is located downstream of the location where the demand-side switching unit CV1 is located in the low-pressure gas discharge line 53. The sensor 49 measures the pressure PS2 of the hydrogen gas discharged to the low-pressure demand end D2 through the low-pressure gas discharge line 53 and transmits it to the control unit 50.

[0166] Here, refer to Figure 22 The operation control performed by the controller 50 during the operation of the compressor unit 10 according to the present embodiment will be described. Note that in the following description, some of the descriptions that overlap with those of the first embodiment will be omitted.

[0167] During startup of the compressor unit 10, if the control unit 50 determines that the temperature TS1 of the hydrogen gas flowing through the intermediate flow passage 22 (output from the first compression stage 12) is greater than or equal to the threshold value T1 (step ST2: "Yes"), the first control unit 50a controls the demand-side switching unit CV1 so that the hydrogen gas output from the first compression stage 12 to the intermediate flow passage 22 flows to the low-pressure gas discharge path 53 (steps ST1 to ST3). In other words, the first switching state is established in which the hydrogen gas is delivered to the low-pressure demand end D2.

[0168] If the control unit 50 determines that the system is in a steady-state operating state (temperature TS1 < threshold value T1), the first control unit 50a controls the demand-side switching unit CV1 to allow hydrogen to flow to both the high-pressure demand end D1 and the low-pressure demand end D2 (step ST12). Specifically, during step ST12, the compressor unit 10 of this embodiment controls the system by adjusting the opening of the demand-side switching unit CV1, which includes the regulating valve 56a, to allow hydrogen to flow to both the high-pressure demand end D1 and the low-pressure demand end D2.

[0169] In the state where hydrogen is delivered to both the high-pressure demand end D1 and the low-pressure demand end D2 (third switching state), the control unit 50 determines whether the pressure PS2 obtained by the discharge path pressure sensor 49 falls within a preset range (step ST13). If the control unit 50 determines "No" in step ST13 (P TH1 ≥PS2 or PS2>P TH2 ), the first control unit 50a controls the demand-side switching unit CV1 so that the pressure PS2 falls within the above-mentioned pre-set range (step ST14).

[0170] On the other hand, when the control unit 50 determines "Yes" in step ST13 (P TH1 <PS2≤P TH2 ), refers to the suction temperature TS2 acquired by the upstream temperature sensor 45, and performs the backflow control (step ST5). That is, at TS2 <T TH1 In this case, the second control unit 50b controls the return valve 18b to return part of the gas in the output flow channel 24 to the intake flow channel 21. As a result, when the demand-side switching unit CV1 is in the third switching state, the hydrogen gas in the intake flow channel 21 is heated so that the intake temperature TS2 falls within the predetermined temperature range (T TH1 ≤TS2≤T TH2 ). In addition, when TS2>T TH2 In this case, the operation of returning part of the gas in the outlet flow channel 24 to the intake flow channel 21 is not performed. Here, the predetermined temperature range is set to a range higher than the reference temperature based on the liquefaction temperature of air and lower than 0°C, similarly to the first embodiment. That is, the lower limit value T of the predetermined temperature range is TH1 and upper limit value T TH2 It is set in a range higher than the reference temperature and lower than 0°C.

[0171] The compressor unit 10 having the above-mentioned structure can properly protect its constituent equipment from the wide temperature changes of the evaporated gas (hydrogen) from the liquefied hydrogen storage tank 23. That is, the compressor unit 10 is configured so that during startup, even if the hydrogen in the piping on the side of the liquefied hydrogen storage tank 23 rises to the positive temperature range, the demand-side switching unit CV1 is controlled so that the hydrogen flows to the first switching state of the low-pressure demand end D2. As a result, the compressor unit 10 can suppress the compression ratio in the subsequent compression section 14 to a lower level compared to the case where hydrogen flows only to the high-pressure demand end D1 from the output flow channel 24, and can suppress the excessive temperature rise of the hydrogen caused by the subsequent compression section 14 compressing the hydrogen and heating it up. That is, the subsequent compression section 14 can be protected. In addition, the startup work of the compressor unit 10 can also be carried out quickly.

[0172] On the other hand, when the demand-side switching element CV1 of the compressor unit 10 is in the third switching state, the first control unit 50a controls the demand-side switching element CV1 so that the pressure PS2 obtained by the discharge path pressure sensor 49 falls within a predetermined range. Furthermore, in this case, the second control unit 50b controls the return valve 18b so that the suction temperature TS2 obtained by the upstream temperature sensor 45 falls within the predetermined temperature range. This allows the compressor unit 10 to be protected even in low-temperature hydrogen environments.

[0173] Furthermore, if the compressor unit 10 is used, efficient recovery and supply of hydrogen can be achieved.

[0174] In addition, Figure 21 In the illustrated compressor unit 10 , the subsequent compression stage 14 adopts a compression mechanism having one stage, but a compression mechanism having multiple stages may also be adopted.

[0175] (Seventh embodiment)

[0176] like Figure 23 As shown, the compressor unit 10 according to the seventh embodiment differs from the sixth embodiment in that a regulating unit 41 for regulating the hydrogen processing amount of the subsequent compression stage 14 is provided. Figure 23 In the embodiment 6, the same components as those in the embodiment 6 are denoted by the same reference numerals and descriptions of the overlapping components are omitted below.

[0177] The adjustment unit 41 adjusts the hydrogen gas processing capacity of the subsequent compression stage 14. The adjustment unit 41 adjusts the gas processing capacity by a method other than adjusting the rotational speed of the crank mechanism 16. In this embodiment, as an example, the adjustment unit 41 is configured by employing a reflux unit (second reflux unit SB2) that adjusts the hydrogen gas processing capacity by adjusting the flow rate of gas sent from the subsequent compression stage 14 to the high-pressure demand end D1.

[0178] The second recirculation section SB2 includes a second recirculation passage 43a and a second recirculation valve 43b, which is arranged in the second recirculation passage 43a and has an adjustable opening. One end of the second recirculation passage 43a is connected to a portion of the output passage 24 upstream of the connection with the recirculation passage 18a, and the other end is connected to the intermediate passage 22. Therefore, a portion of the hydrogen gas output from the subsequent compression stage 14 is returned to the intake side of the subsequent compression stage 14 in the intermediate passage 22. The second recirculation valve 43b adjusts the amount of recirculation in the second recirculation passage 43a.

[0179] The control unit 50 includes a first control unit 50a and a second control unit 50b, as well as a fifth control unit 50e. The fifth control unit 50e is a functional unit configured to control the adjustment unit 41 (second return valve 43b) based on the change in pressure PS1 obtained by the intermediate pressure sensor 47.

[0180] Here, refer to Figure 24 The operation control performed by the controller 50 during the operation of the compressor unit 10 according to the present embodiment will be described. In the following description, overlapping descriptions with those of the sixth embodiment will be omitted.

[0181] When the control unit 50 determines that the compressor is in a steady-state operation state (temperature TS1 < threshold value T1), the first control unit 50a controls the demand-side switching unit CV1 so that hydrogen flows to both the high-pressure demand end D1 and the low-pressure demand end D2 (step ST12). After the first control unit 50a executes step ST12, the fifth control unit 50e controls the adjustment unit 41 (second return valve 43b) according to the change in pressure PS1 (step ST15). By controlling the second return valve 43b according to the change in pressure PS1 by the fifth control unit 50e, the processing capacity of the subsequent compression stage 14 is adjusted. This embodiment differs from the sixth embodiment described above in that the fifth control unit 50e controls the adjustment unit 41 (second return valve 43b).

[0182] Each control after step ST15 during the operation of the compressor unit 10 according to the present embodiment is the same as that of the sixth embodiment.

[0183] With the compressor unit 10 having the above configuration, when the demand-side switching unit CV1 is in the third switching state, the fifth control unit 50e includes the adjustment unit 41 (second return valve 43b), thereby maintaining the suction pressure of the subsequent compression stage 14 at a substantially constant level. Therefore, the compressor unit 10 can maintain a constant pressure balance across the various stages of the subsequent compression stage, thereby achieving high compressor reliability. Specifically, if the pressure balance in the subsequent compression stage 14 cannot be maintained constant, a compressor with a large margin to absorb such fluctuations would be required. However, the compressor unit 10 does not require a compressor with such a large margin.

[0184] Furthermore, if the compressor unit 10 is used, efficient recovery and supply of hydrogen can be achieved.

[0185] In addition, Figure 23 In the illustrated compressor unit 10, a single-stage compression mechanism is employed for the subsequent compression stage 14. However, a multi-stage compression mechanism may also be employed. In this case, an adjustment unit 41 may be provided for each of the multiple stages of the compression mechanism, or a single adjustment unit 41 may be provided for the entire multi-stage compression mechanism.

[0186] also, Figure 23 The compressor unit 10 shown in FIG. 1 includes the second reflux portion SB2 as an example of the adjustment unit 41, but the adjustment unit 41 is not limited thereto. Figure 25 As shown, the compressor unit 10 may include a stepless capacity adjustment device 64b provided in the subsequent compression stage 14 as the adjustment unit 41. The stepless capacity adjustment device 64b may be configured similarly to the above-described device, including a suction valve unloader 61b, a drive device 62b, and a detector 63b for detecting the rotation of the crank mechanism.

[0187] In addition, when the subsequent compression stage 14 is configured as a plurality of compression mechanisms as described above, the capacity adjustment device 64 may be provided in each compression mechanism or in a portion of the compression mechanisms as the adjustment device 41 .

[0188] In addition, you can also Figure 23 The second reflux section SB2 used in the compressor unit 10 shown in FIG. Figure 25 The capacity adjustment device 64 b used in the compressor unit 10 shown is also provided in the subsequent compression section 14 .

[0189] (Variation)

[0190] use Figure 26 The configuration of the compressor unit 10 according to a modified example of the first embodiment will be described. Figure 26In the embodiment 1, a part of the same structure as that of the first embodiment is omitted. In addition, the description of the overlapping parts is omitted below.

[0191] In the compressor unit 10 according to this variation, the subsequent compression stage 14 can employ a compression mechanism having multiple stages. Specifically, the compressor unit 10 according to this variation can employ a subsequent compression stage 14 having a first subsequent compression stage 14a and a second subsequent compression stage 14b. However, a compression mechanism having three or more stages can also be employed as the subsequent compression stage 14. In other words, the compressor unit 10 as a whole can employ a compression mechanism having four or more stages.

[0192] Furthermore, in the compressor unit 10 according to this modification, the return flow passage 18a may be connected to a portion of the intermediate flow passage 22 between the subsequent first compression stage 14a and the subsequent second compression stage 14b. This allows a portion of the hydrogen gas heated by the subsequent first compression stage 14a to be returned to the intake flow passage 21 via the return portion SB1.

[0193] Furthermore, an intermediate cooling section 74 may be provided between the subsequent first compression stage 14a and the subsequent second compression stage 14b in the intermediate flow passage 22. Thus, the hydrogen gas heated by the compression in the subsequent first compression stage 14a can be cooled and sent to the subsequent second compression stage 14b, thereby protecting the subsequent second compression stage 14b.

[0194] use Figure 27 The configuration of the compressor unit 10 according to another modified example of the first embodiment will be described. Figure 27 In the embodiment 1, a part of the same structure as that of the first embodiment is omitted. In addition, the description of the overlapping parts is omitted below.

[0195] The compressor unit 10 according to this modification is Figure 26 The modified example shown also employs the subsequent compression stage 14 including the subsequent first compression stage 14a and the subsequent second compression stage 14b. As the subsequent compression stage 14, a compression mechanism having three or more stages may be employed.

[0196] The reflux passage 18a is connected to a portion between the subsequent first compression stage 14a and the subsequent second compression stage 14b in the intermediate passage 22. This allows a portion of the hydrogen gas heated by the subsequent first compression stage 14a to return to the intake passage 21 via the reflux portion SB1.

[0197] The compressor unit 10 further includes a second reflux portion SB2 serving as an adjustment unit 41, located downstream of the branch portion of the reflux flow channel 18a in the intermediate flow channel 22. Specifically, the second reflux portion SB2 includes a second reflux flow channel 43a for returning hydrogen gas output from the subsequent second compression stage 14b, located downstream of the branch portion of the reflux flow channel 18a in the intermediate flow channel 22, to the upstream side of the subsequent second compression stage 14b (more precisely, the suction side of the subsequent second compression stage 14b), and a second reflux valve 43b for adjusting the reflux amount in the second reflux flow channel 43a.

[0198] When the demand-side switching unit (CV1) is in the second switching state, the control unit 50 controls the second return valve 43b so that a flow rate equivalent to the return flow rate of the return portion SB1 is returned to the upstream side of the subsequent second compression stage 14b. This maintains a constant pressure balance in the subsequent second compression stage 14b.

[0199] exist Figure 27 Alternatively, the return flow channel 18a may be connected to a portion of the intermediate flow channel 22 between the first compression stage 12 and the subsequent first compression stage 14a. In this case, the second return flow channel 43a may be configured so that the hydrogen gas output from the subsequent first compression stage 14a is returned to the upstream side of the subsequent first compression stage 14a. Alternatively, the second return flow channel 43a may be configured so that the hydrogen gas output from the subsequent second compression stage 14b is returned to the upstream side of the subsequent first compression stage 14a.

[0200] The embodiments disclosed this time should be interpreted in all respects as illustrative and non-restrictive. The present invention is not limited to the embodiments described above, and various changes and improvements can be made without departing from the spirit of the present invention.

[0201] (Summarize)

[0202] A reciprocating compressor unit according to one embodiment of the present invention is a reciprocating compressor unit that recovers boil-off gas, i.e., hydrogen, from a liquefied hydrogen storage tank and supplies at least a portion of the hydrogen to a high-pressure demand end (D1) comprising at least one of an engine, a power generation device, and a boiler. The compressor unit includes: a plurality of compression stages, a crank mechanism, a reflux unit (SB1), a low-pressure gas discharge path, a demand end switching unit (CV1), a check valve, a first temperature sensor, a second temperature sensor, and a control unit.

[0203] The plurality of compression stages compress the hydrogen gas sucked in from the intake channel. The crank mechanism drives the plurality of compression stages. The reflux section (SB1) includes a reflux channel and a reflux valve. The reflux channel is a channel that returns the hydrogen gas output to the output channel on the output side of the plurality of compression stages, or the hydrogen gas flowing in the intermediate channel between the plurality of compression stages, to the intake channel. The reflux valve adjusts the reflux rate in the reflux channel. The low-pressure gas discharge path is a channel that branches from a branch point provided in the intermediate channel or the output channel and is capable of discharging hydrogen gas to a low-pressure demand end (D2), which is capable of processing hydrogen gas at a lower pressure than the hydrogen gas required by the high-pressure demand end (D1). The demand end switching unit (CV1) is provided in the low-pressure gas discharge path or the branch point. The check valve is located downstream of the branch point. The first temperature sensor is arranged in the intermediate channel or the output channel upstream of the branch point. The second temperature sensor is arranged between a connection portion of the return flow passage in the intake flow passage and a first compression stage that is the first stage among the plurality of compression stages. The control unit controls the demand-side switching unit (CV1) and the return valve.

[0204] In the compressor unit according to the present invention, the control unit is configured to, during startup and when the temperature TS1 obtained by the first temperature sensor is greater than a predetermined first temperature threshold T1 greater than 0°C, control the demand-side switching unit (CV1) to a first switching state in which hydrogen gas is allowed to flow through the low-pressure gas discharge path. Furthermore, when the temperature TS1 obtained by the first temperature sensor is less than the first temperature threshold T1, control the demand-side switching unit (CV1) to a second switching state in which hydrogen gas is sent to the output flow path toward the high-pressure demand end (D1). Furthermore, when the demand-side switching unit (CV1) is in the second switching state, the control unit is configured to control the return valve with reference to the intake temperature TS2 obtained by the second temperature sensor so that the intake temperature TS2 falls within a predetermined temperature range.

[0205] The predetermined temperature range is set to a range higher than a reference temperature based on the liquefaction temperature of air and lower than 0°C.

[0206] The above technical solution can protect the compressor unit in an environment where BOG (hydrogen) is at a low temperature, and can also protect the compressor unit during the startup period when BOG (hydrogen) is at a normal temperature.

[0207] Here, the reciprocating compressor outputs BOG from the compressor at a pressure corresponding to the pressure on the demand side. Under such a premise, the above technical solution is constructed as follows: during startup, even if the hydrogen in the piping on the side of the liquefied hydrogen storage tank rises to a positive temperature zone (normal temperature), the control unit will switch the demand side switching unit (CV1) to the first switching state so that the hydrogen output from the compression section is sent to the low-pressure demand end (D2). Thus, by discharging hydrogen to the low-pressure demand end that treats hydrogen at a relatively low pressure, the compression ratio in the compression section can be suppressed to a low level, and excessive temperature rise of hydrogen caused by increasing the pressure due to compressing hydrogen in the compression section can be prevented. That is, the compression section can be protected. In addition, during the startup of the unit, even if the hydrogen in the above piping is at normal temperature, the startup work of the compressor unit can be quickly performed by discharging hydrogen from the compression section to the low-pressure demand end as described above.

[0208] On the other hand, in the above technical solution, when the demand-side switching unit (CV1) is in the second switching state, the control unit controls the return valve so that the intake temperature TS2 falls within the predetermined temperature range. Therefore, based on the hydrogen gas returned to the intake flow path from the return unit, the intake temperature TS2 can be controlled within the predetermined temperature range. Furthermore, in the above technical solution, since the predetermined temperature range is set to a range higher than a reference temperature based on the liquefaction temperature of air, liquefaction of oxygen used as an auxiliary gas on the outer surface of the intake section of the first compression stage or around the device supplying hydrogen gas can be avoided.

[0209] In the compressor unit according to the above technical solution, the check valve may be provided in the output flow passage, and the branch point may be provided in the output flow passage at a position upstream of the check valve.

[0210] In the above technical solution, a specific structure is adopted in which a check valve is provided in the output flow channel and a branch point is provided at a position upstream of the check valve in the output flow channel. Since the control unit switches the demand-side switching unit (CV1) between the first switching state and the second switching state according to the first temperature TS1, and since the return valve is controlled according to the suction temperature TS2 when the demand-side switching unit (CV1) is in the second switching state, the same effect as the above technical solution can be obtained.

[0211] Furthermore, in the above technical solution, since a check valve is provided in the output flow passage, it is possible to prevent hydrogen from flowing back from the output flow passage to the compression section, thereby more appropriately protecting the compressor.

[0212] The compressor unit according to the above technical solution may further include a preheater, a third temperature sensor, and a flow control unit (FCV1). The preheater may be capable of performing heat exchange between the hydrogen gas before being drawn into the first compression stage and the hydrogen gas after being output to the output flow channel. The third temperature sensor may be positioned downstream of the preheater in the output flow channel. The flow control unit (FCV1) may be configured to adjust the flow of hydrogen gas into the preheater.

[0213] In the compressor unit according to the present technical solution, the control unit may be configured to increase the flow rate of hydrogen gas into the preheater when the demand-side switching unit (CV1) is in the second switching state, so that the preheater prioritizes heating of the hydrogen gas in the intake flow path over heating by the return unit (SB1), and to control the flow control unit (FCV1) so that the temperature TS3 on the downstream side of the preheater obtained by the third temperature sensor does not fall below a threshold. Furthermore, the control unit may be configured to control the flow control unit (FCV1) and the return valve so that the intake temperature TS2 falls within the predetermined temperature range when the intake temperature TS2 is lower than the predetermined temperature range.

[0214] In this technical solution, the preheater prioritizes hydrogen heating in the intake flow path over heating by the reflux unit. In the event of insufficient heating, the reflux unit provides compensatory control. This minimizes the power loss associated with returning the compressed gas to the intake side, compared to heating by the reflux unit alone. This reduces the reduction in processing efficiency and maintains the intake temperature within a constant range.

[0215] In addition, in the above technical solution, the temperature TS3 of the hydrogen on the downstream side of the preheater is obtained by the third temperature sensor, and the control unit controls the flow adjustment unit (FCV1) according to the temperature TS3 of the hydrogen obtained by the third temperature sensor, thereby suppressing the excessive temperature drop of the hydrogen supplied to the demand end.

[0216] The compressor unit according to the above technical solution may further include a preheater, a third temperature sensor, and a flow control unit (FCV1). The preheater can enable heat exchange between the hydrogen gas before being drawn into the first compression stage and the hydrogen gas flowing through the intermediate flow channel. The third temperature sensor can be positioned downstream of the preheater in the intermediate flow channel. The flow control unit (FCV1) can be configured to adjust the flow of hydrogen gas into the preheater.

[0217] In the compressor unit according to the present technical solution, the control unit may be configured to increase the flow rate of hydrogen gas into the preheater when the demand-side switching unit (CV1) is in the second switching state, so that the preheater prioritizes heating of the hydrogen gas in the intake flow path over heating by the return unit (SB1), and to control the flow control unit (FCV1) so that the temperature TS3 on the downstream side of the preheater obtained by the third temperature sensor does not fall below a threshold. Furthermore, the control unit may be configured to control the flow control unit (FCV1) and the return valve so that the intake temperature TS2 falls within the predetermined temperature range when the intake temperature TS2 is lower than the predetermined temperature range.

[0218] The above-mentioned technical solution includes a preheater capable of exchanging heat between the hydrogen gas before being drawn into the first compression stage and the hydrogen gas flowing through the intermediate flow path. Furthermore, in this technical solution, heating of the hydrogen gas in the intake flow path by the preheater is prioritized over heating by the reflux unit. In the event of insufficient heating, the heating by the reflux unit provides compensatory control. This minimizes the power loss associated with returning the compressed gas to the intake side, compared to heating by the reflux unit alone. This technical solution thus suppresses a decrease in processing efficiency and maintains the intake temperature within a constant range.

[0219] In addition, in the above technical solution, the temperature TS3 of the hydrogen on the downstream side of the preheater is obtained by the third temperature sensor, and the control unit controls the flow adjustment unit (FCV1) according to the temperature TS3 of the hydrogen obtained by the third temperature sensor, thereby suppressing the excessive temperature drop of the hydrogen supplied to the demand end.

[0220] In the compressor unit involved in the above technical solution, the check valve can be arranged in the output flow channel, and the branch point can be arranged in the output flow channel and located on the upstream side relative to the check valve. The compressor unit involved in this technical solution may also include: another low-pressure gas discharge path and a second demand end switching unit (CV2). The other low-pressure gas discharge path can branch from another branch point arranged in the intermediate flow channel, and can discharge hydrogen to another low-pressure demand end (D3), and the other low-pressure demand end (D3) can process hydrogen with a lower pressure than the hydrogen required by the high-pressure demand end (D1). The second demand end switching unit (CV2) can be arranged in the other low-pressure gas discharge path or the other branch point.

[0221] In the compressor unit according to the present technical solution, the control unit may be configured to: when the demand-side switching unit (CV1) is in the first switching state, control the second demand-side switching unit (CV2) so that the hydrogen in the intermediate flow channel flows to the other low-pressure gas discharge path. Furthermore, the control unit may be configured to: when the demand-side switching unit (CV1) is in the second switching state, control the second demand-side switching unit (CV2) so that the hydrogen is delivered to the output flow channel toward the high-pressure demand end (D1).

[0222] In the above technical solution, a configuration is adopted in which the two demand-side switching units (CV1) and (CV2) are controlled by a control unit and can be switched between a first switching state and a second switching state. This configuration allows hydrogen to be discharged not only to the low-pressure gas discharge path but also to the other low-pressure gas discharge path. This reduces the hydrogen pressure in the intermediate flow path compared to a case where the other low-pressure gas discharge path is not provided. Consequently, the above technical solution can reduce the suction pressure of the compression stage located downstream of the intermediate flow path, thereby further reducing power consumption during startup.

[0223] In the compressor unit involved in the above technical solution, the check valve can be arranged in the output flow channel, and the branch point can be arranged in a position in the output flow channel that is located upstream relative to the check valve. The compressor unit involved in this technical solution may also include: another low-pressure gas discharge path, a second demand end switching unit (CV2), and an adjustment unit. The other low-pressure gas discharge path branches off from another branch point in the intermediate flow channel and is capable of discharging hydrogen to another low-pressure demand end (D3), and the other low-pressure demand end (D3) is capable of processing hydrogen with a lower pressure than the hydrogen required by the high-pressure demand end (D1). The second demand end switching unit (CV2) can be arranged in the other low-pressure gas discharge path or the other branch point. The adjustment unit can adjust the hydrogen processing capacity of the subsequent compression sections other than the first compression section in the multiple compression sections.

[0224] In the compressor unit involved in the present technical solution, the control unit can be configured as follows: when the demand-side switching unit (CV1) is in the second switching state, the second demand-side switching unit (CV2) is controlled to discharge hydrogen to the other low-pressure gas discharge path according to the demand of the other low-pressure demand end (D3) or the change in the demand of the high-pressure demand end (D1), and the adjustment unit is controlled to adjust the processing capacity of the subsequent compression stage.

[0225] The above technical solution discharges hydrogen to another low-pressure demand end when the required amount (demand) of hydrogen at the high-pressure demand end is reduced. By balancing the amount of evaporated gas generated from the liquefied hydrogen storage tank and the amount of hydrogen sent from the compressor unit, the pressure of the liquefied hydrogen storage tank can be kept constant.

[0226] Furthermore, the above technical solution, because it includes an adjustment unit, can maintain the suction pressure of the subsequent compression stage at a substantially constant level. Therefore, the above technical solution can maintain a constant pressure balance across the various stages of the subsequent compression stage, thereby achieving high compressor reliability. Specifically, if the pressure balance in the subsequent compression stage cannot be maintained constant, a compressor with a large margin to accommodate fluctuations as much as possible would be necessary. However, the above technical solution does not require a compressor with such a large margin.

[0227] In the compressor unit according to the above technical solution, the adjustment unit may include a second reflux section (SB2). In the case where the reflux section (SB1) returns the hydrogen gas output to the output flow channel to the intake flow channel, the second reflux section (SB2) may include: a second reflux flow channel for returning the hydrogen gas from the upstream side of a branching section on the output flow channel branched from the reflux flow channel to the intake side of the subsequent compression stage; and a reflux valve for adjusting the reflux amount in the second reflux flow channel.

[0228] In the compressor unit involved in the present technical solution, the control unit can be configured to: when the demand-end switching unit (CV1) is in the second switching state, control the second return valve so that a flow rate equivalent to the demand amount of the other low-pressure demand end (D3) or the change in the demand amount of the high-pressure demand end (D1) returns to the suction side of the subsequent compression section.

[0229] Because the above technical solution includes the second reflux section, even when the demand at the high-pressure demand end (D1) decreases, the compressed hydrogen gas is returned to the suction side of the subsequent compression stage through the second reflux section, thereby maintaining the suction pressure of the subsequent compression stage substantially constant. Thus, the above technical solution can maintain a constant pressure balance across the various stages of the subsequent compression stage, thereby achieving high compressor reliability.

[0230] In the compressor unit according to the above technical solution, the adjustment unit may include a second reflux section (SB2). In the case where the reflux section (SB1) returns the hydrogen gas flowing through the intermediate flow channel to the suction flow channel, the adjustment unit may include: a second reflux flow channel for returning the hydrogen gas output from the compression section located downstream of a branching section on the intermediate flow channel branched from the reflux flow channel to the upstream side of the compression section; and a second reflux valve for adjusting the reflux amount in the second reflux flow channel.

[0231] In the compressor unit involved in the present technical solution, the control unit can be configured to: when the demand-side switching unit (CV1) is in the second switching state, control the second return valve so that a flow rate equivalent to the return amount of the return unit (SB1) returns to the upstream side of the compression section.

[0232] Because the above technical solution includes the second reflux section, even if the processing capacity of the compression stage is reduced due to the return of hydrogen gas to the suction passage by the reflux section, the compressed hydrogen gas is returned to the upstream side of the compression stage by the second reflux section, thereby maintaining the suction pressure of the compression stage at a substantially constant level. Thus, the above technical solution can achieve high reliability for the compressor.

[0233] In the compressor unit according to the above technical solution, the adjustment unit may include an on-off type suction valve unloader. The on-off type suction valve unloader may be installed in the cylinder portion of the subsequent compression stage.

[0234] In the compressor unit involved in the present technical solution, the control unit can be configured to: when the demand-end switching unit (CV1) is in the second switching state, control the suction valve unloader so that a flow rate equivalent to the demand amount of the other low-pressure demand end (D3) or the change in the demand amount of the high-pressure demand end (D1) returns to the suction side of the subsequent compression section.

[0235] Because the above technical solution includes the second reflux section, even when the demand at the high-pressure demand end (D1) decreases, the compressed hydrogen gas is returned to the suction side of the subsequent compression stage through the second reflux section, thereby maintaining the suction pressure of the subsequent compression stage at a substantially constant level. Thus, the above technical solution can maintain a constant pressure balance across the various stages of the subsequent compression stage, thereby achieving high compressor reliability.

[0236] In the compressor unit according to the above technical solution, the adjustment unit may include a stepless capacity adjustment device. The stepless capacity adjustment device may include a suction valve unloader and a drive device. The suction valve unloader may be mounted on the cylinder portion of the subsequent compression stage. The drive device may be a hydraulic or electric drive device that opens and closes the suction valve unloader.

[0237] In the compressor unit involved in the present technical solution, the control unit can be configured to: when the demand-end switching unit (CV1) is in the second switching state, the hydrogen gas sucked into the intake side from the inside of the cylinder is returned at a flow rate equivalent to the change in the demand of the other low-pressure demand end (D3) or the demand of the high-pressure demand end (D1), thereby controlling the period during which the intake valve unloader works in conjunction with the rotational movement of the crankshaft, thereby adjusting the processing capacity of the subsequent compression section.

[0238] The above technical solution employs a configuration including a second low-pressure gas discharge path and an adjustment unit equipped with an intake valve unloader. Therefore, when the demand-side switching unit (CV1) is in the second switching state, the control unit controls the capacity adjustment device to return a portion of the hydrogen gas within the cylinder to the intake side. This reduces the amount of hydrogen gas processed in the subsequent compression stage, further reducing power consumption.

[0239] Another embodiment of the present invention relates to a reciprocating compressor unit that recovers boil-off gas, or hydrogen, from a liquefied hydrogen storage tank and supplies at least a portion of the hydrogen to a high-pressure demand end (D1) comprising at least one of an engine, a power generation device, and a boiler. The compressor unit includes a plurality of compression stages, a crank mechanism, a reflux unit (SB1), a low-pressure gas discharge path, a demand end switching unit (CV1), a check valve, a first temperature sensor, a second temperature sensor, a pressure sensor, and a control unit.

[0240] The plurality of compression stages compress the hydrogen gas sucked in from the intake channel. The crank mechanism drives the plurality of compression stages. The reflux section (SB1) includes a reflux channel and a reflux valve. The reflux channel is a channel that returns the hydrogen gas output to the output channel on the output side of the plurality of compression stages, or the hydrogen gas flowing in the intermediate channel between the plurality of compression stages, to the intake channel. The reflux valve adjusts the reflux rate in the reflux channel. The low-pressure gas discharge path is a channel that branches from a branch point provided in the intermediate channel and is capable of discharging hydrogen gas to a low-pressure demand end (D2), which is capable of processing hydrogen gas at a lower pressure than the hydrogen gas required by the high-pressure demand end (D1). The demand end switching unit (CV1) is provided in the low-pressure gas discharge path or the branch point. The check valve is provided in the intermediate channel downstream of the branch point. The first temperature sensor is arranged in the intermediate channel upstream of the branch point. The second temperature sensor is arranged between the connection portion of the return flow passage in the intake flow passage and the first compression stage. The pressure sensor is provided in the low-pressure gas discharge passage. The control unit controls the demand-side switching unit (CV1) and the return valve.

[0241] In the compressor unit according to the present technical solution, the control unit is configured to, during startup and when the temperature TS1 obtained by the first temperature sensor is greater than a predetermined first temperature threshold value T1 greater than 0°C, control the demand-side switching unit (CV1) to enter a first switching state in which hydrogen gas output from a first compression stage located at the front of the plurality of compression stages flows through the low-pressure gas discharge path. Furthermore, when the temperature TS1 obtained by the first temperature sensor is less than the first temperature threshold value T1, the control unit is configured to control the demand-side switching unit (CV1) to enter a third switching state in which hydrogen gas flows through both the low-pressure gas discharge path and downstream of the branch point in the intermediate flow channel. In addition, the control unit is configured to: when the demand-side switching unit (CV1) is in the third switching state, control the demand-side switching unit (CV1) so that the pressure PS2 obtained by the pressure sensor falls within a predetermined range, and control the return valve with reference to the suction temperature TS2 obtained by the second temperature sensor so that the suction temperature TS2 falls within a predetermined temperature range.

[0242] The predetermined temperature range is set to a range higher than a reference temperature based on the liquefaction temperature of air and lower than 0°C.

[0243] In the above technical solution, during startup, even when the hydrogen in the piping on the side of the liquefied hydrogen storage tank rises to a positive temperature zone (normal temperature), the control unit controls the demand-side switching unit (CV1) to become the first switching state in which the hydrogen is sent to both the downstream side of the branch point in the intermediate flow channel and the low-pressure demand end (D2) from the branch point. Thus, in the above technical solution, compared with the case where hydrogen is sent only to the high-pressure demand end (D1) from the output flow channel, the compression ratio in the compression section can be suppressed to a lower level, and the excessive temperature rise of the hydrogen that is heated by compressing the hydrogen in the compression section can be prevented. That is, the compression section can be protected. In addition, during the startup of the unit, even if the hydrogen in the piping is at normal temperature, the startup work of the compressor unit can be quickly performed by sending hydrogen toward both the high-pressure demand end (D1) and the low-pressure demand end (D2) as described above.

[0244] On the other hand, the above technical solution adopts the following structure, that is, when the demand-side switching unit (CV1) is in the third switching state, the control unit controls the demand-side switching unit (CV1) so that the pressure PS2 of the obtained hydrogen falls within the predetermined range, and the control unit controls the return valve so that the intake temperature TS2 falls within the above-mentioned predetermined temperature range. Therefore, in a low-temperature environment of hydrogen, the compressor unit can be protected.

[0245] The compressor unit according to the above technical solution may further include an adjustment unit and a second pressure sensor. The adjustment unit may adjust the hydrogen processing capacity of subsequent compression stages, excluding the first compression stage, among the plurality of compression stages. The second pressure sensor may be disposed in the intermediate flow channel between the first compression stage and the subsequent compression stages.

[0246] In the compressor group involved in the present technical solution, the control unit is configured to: when the demand-end switching unit (CV1) is in the third switching state, control the adjustment unit to adjust the processing volume of the subsequent compression stage according to the change in pressure PS1 in the intermediate flow channel obtained by the second pressure sensor.

[0247] In the above technical solution, when the demand-side switching unit (CV1) is in the third switching state, the control unit can reduce the processing volume of hydrogen in the subsequent compression stage by controlling the adjustment unit, thereby reducing the power of the subsequent compression stage.

[0248] As described above, the compressor unit according to each of the above-mentioned aspects can appropriately protect its constituent devices from the wide temperature variation of the boil-off gas of liquefied hydrogen.

Claims

1. A compressor unit, characterized in that The following reciprocating compressor units: The compressor unit recovers boil-off gas, i.e., hydrogen, from a liquefied hydrogen storage tank and supplies at least a portion of the hydrogen to a high-pressure demand end (D1) comprising at least one of an engine, a power generation device, and a boiler, and includes: Multiple compression sections compress the hydrogen gas sucked in from the suction flow channel; a crank mechanism for driving the plurality of compression sections; a reflux section (SB1) comprising a reflux passage and a reflux valve, wherein the reflux passage returns hydrogen gas output to the output passage on the output side of the plurality of compression stages or hydrogen gas flowing in the intermediate passage between the plurality of compression stages to the intake passage, and the reflux valve adjusts the reflux amount in the reflux passage; a low-pressure gas discharge path branching from a branch point provided in the intermediate flow channel or the output flow channel and capable of discharging hydrogen to a low-pressure demand end (D2), wherein the low-pressure demand end (D2) is capable of processing hydrogen at a lower pressure than the hydrogen required by the high-pressure demand end (D1); a demand-side switching unit (CV1), which is arranged at the low-pressure gas discharge path or the branch point; a check valve located on a downstream side relative to the branch point; a first temperature sensor disposed in the intermediate flow channel or the output flow channel and located upstream of the branch point; a second temperature sensor disposed between a connection portion of the return flow passage in the intake flow passage and a first compression stage that is the first stage among the plurality of compression stages; and The control unit controls the demand-side switching unit (CV1) and the return valve; wherein, The control unit is configured as follows: During startup, when the temperature TS1 acquired by the first temperature sensor is greater than or equal to a predetermined first temperature threshold T1 greater than 0° C., controlling the demand-side switching unit (CV1) to enter a first switching state in which hydrogen gas is allowed to flow through the low-pressure gas discharge path; When the temperature TS1 obtained by the first temperature sensor is less than the first temperature threshold T1, the demand-side switching unit (CV1) is controlled to be in a second switching state in which hydrogen is delivered to the output flow channel toward the high-pressure demand end (D1); and When the demand-side switching unit (CV1) is in the second switching state, the return valve is controlled with reference to the suction temperature TS2 obtained by the second temperature sensor so that the suction temperature TS2 falls within a predetermined temperature range, wherein The predetermined temperature range is set to a range higher than a reference temperature based on the liquefaction temperature of air and lower than 0°C.

2. The compressor unit according to claim 1, characterized in that The check valve is arranged in the output flow channel, The branch point is provided at a position upstream of the check valve in the output flow passage.

3. The compressor unit according to claim 2, characterized in that Also includes: a preheater capable of performing heat exchange between the hydrogen gas before being drawn into the first compression stage and the hydrogen gas after being output to the output flow channel; a third temperature sensor disposed downstream of the preheater in the output flow channel; and A flow adjustment unit (FCV1) is capable of adjusting the flow state of hydrogen into the preheater; wherein, The control unit is configured as follows: When the demand-side switching unit (CV1) is in the second switching state, The flow rate of hydrogen gas into the preheater is increased so that the preheater heats the hydrogen gas in the intake flow passage in priority to the heats performed by the reflux unit (SB1), and the flow rate regulating unit (FCV1) is controlled so that the temperature TS3 on the downstream side of the preheater obtained by the third temperature sensor does not fall below a threshold value; and When the intake temperature TS2 is lower than the predetermined temperature range, the flow rate adjustment unit (FCV1) and the return valve are controlled so that the intake temperature TS2 falls within the predetermined temperature range.

4. The compressor unit according to claim 2, characterized in that Also includes: a preheater to enable heat exchange between the hydrogen gas before being sucked into the first compression stage and the hydrogen gas circulating in the intermediate flow channel; A third temperature sensor is arranged downstream of the preheater in the intermediate flow channel; and A flow adjustment unit (FCV1) is capable of adjusting the flow state of hydrogen into the preheater; wherein, The control unit is configured as follows: When the demand-side switching unit (CV1) is in the second switching state, The flow rate of hydrogen gas into the preheater is increased so that the preheater heats the hydrogen gas in the intake flow passage in priority to the heats performed by the reflux unit (SB1), and the flow rate regulating unit (FCV1) is controlled so that the temperature TS3 on the downstream side of the preheater obtained by the third temperature sensor does not fall below a threshold value; and When the intake temperature TS2 is lower than the predetermined temperature range, the flow rate adjustment unit (FCV1) and the return valve are controlled so that the intake temperature TS2 falls within the predetermined temperature range.

5. The compressor unit according to claim 1, characterized in that The check valve is arranged in the output flow channel, The branch point is provided in the output flow passage on the upstream side relative to the check valve. The compressor unit further comprises: another low-pressure gas discharge path, branching from another branch point provided in the intermediate flow channel and capable of discharging hydrogen to another low-pressure demand end (D3), wherein the other low-pressure demand end (D3) is capable of processing hydrogen at a lower pressure than the hydrogen required by the high-pressure demand end (D1); and, The second demand-side switching unit (CV2) is provided at the other low-pressure gas discharge path or the other branch point; wherein, The control unit is configured as follows: When the demand-side switching unit (CV1) is in the first switching state, the second demand-side switching unit (CV2) is controlled so that the hydrogen in the intermediate flow channel flows to the other low-pressure gas discharge path; and When the demand-side switching unit (CV1) is in the second switching state, the second demand-side switching unit (CV2) is controlled so that hydrogen is delivered to the output flow channel toward the high-pressure demand end (D1).

6. The compressor unit according to claim 1, characterized in that The check valve is arranged in the output flow channel, The branch point is provided at a position upstream of the check valve in the output flow channel. The compressor unit further comprises: another low-pressure gas discharge path, branching from another branch point in the intermediate flow channel and capable of discharging hydrogen to another low-pressure demand end (D3), wherein the other low-pressure demand end (D3) is capable of processing hydrogen at a lower pressure than the hydrogen required by the high-pressure demand end (D1); A second demand-side switching unit (CV2) is provided at the other low-pressure gas discharge path or the other branch point; and An adjusting unit is used to adjust the hydrogen processing capacity of subsequent compression stages except the first compression stage in the plurality of compression stages; wherein, The control unit is configured as follows: When the demand-side switching unit (CV1) is in the second switching state, the second demand-side switching unit (CV2) is controlled to discharge hydrogen to the other low-pressure gas discharge path according to the demand of the other low-pressure demand end (D3) or the change in the demand of the high-pressure demand end (D1), and the adjustment unit is controlled to adjust the processing capacity of the subsequent compression stage.

7. The compressor unit according to claim 6, characterized in that When the reflux portion (SB1) returns the hydrogen gas output to the output flow channel to the intake flow channel, The adjustment unit includes a second reflux unit (SB2), and the second reflux unit (SB2) includes: a second reflux flow passage for returning hydrogen gas from an upstream side of a branch portion on the output flow passage branched from the reflux flow passage to a suction side of the subsequent compression stage; and The second reflux valve adjusts the reflux amount in the second reflux flow passage, wherein: The control unit is configured as follows: When the demand-side switching unit (CV1) is in the second switching state, the second return valve is controlled so that a flow rate corresponding to the demand amount of the other low-pressure demand end (D3) or the change in the demand amount of the high-pressure demand end (D1) returns to the suction side of the subsequent compression section.

8. The compressor unit according to claim 1, characterized in that When the reflux portion (SB1) returns the hydrogen gas flowing in the intermediate flow channel to the intake flow channel, The adjustment unit includes a second reflux unit (SB2), and the second reflux unit (SB2) includes: a second reflux flow passage for returning hydrogen gas outputted from a compression section located downstream of a branch portion of the intermediate flow passage branched from the reflux flow passage to an upstream side of the compression section; and The second reflux valve adjusts the reflux amount in the second reflux flow passage, wherein: The control unit is configured as follows: When the demand-side switching unit (CV1) is in the second switching state, the second return valve is controlled so that a flow rate equivalent to the return amount of the return portion (SB1) is returned to the upstream side of the compression stage.

9. The compressor unit according to claim 6, characterized in that The adjustment unit comprises: An open-close type suction valve unloader is installed on the cylinder portion of the subsequent compression section, wherein: The control unit is configured as follows: When the demand-side switching unit (CV1) is in the second switching state, the suction valve unloader is controlled so that a flow rate corresponding to the demand of the other low-pressure demand end (D3) or the change in the demand of the high-pressure demand end (D1) is returned to the suction side of the subsequent compression section.

10. The compressor unit according to claim 6, characterized in that The adjustment unit is provided with a stepless capacity adjustment device, and the stepless capacity adjustment device includes: a suction valve unloader mounted on the cylinder portion of the subsequent compression section; and A hydraulic or electric drive device opens and closes the suction valve unloader, wherein: The control unit is configured as follows: When the demand-side switching unit (CV1) is in the second switching state, the period during which the intake valve unloader operates in conjunction with the rotational movement of the crankshaft is controlled by returning the hydrogen gas sucked from the inside of the cylinder to the intake side at a flow rate corresponding to the change in the demand at the other low-pressure demand end (D3) or the demand at the high-pressure demand end (D1), thereby adjusting the processing capacity of the subsequent compression section.

11. A compressor unit, characterized in that The following reciprocating compressor units: The compressor unit recovers boil-off gas, i.e., hydrogen, from a liquefied hydrogen storage tank and supplies at least a portion of the hydrogen to a high-pressure demand end (D1) comprising at least one of an engine, a power generation device, and a boiler, and includes: Multiple compression sections compress the hydrogen gas sucked in from the suction flow channel; a crank mechanism for driving the plurality of compression sections; a reflux section (SB1) comprising a reflux passage and a reflux valve, wherein the reflux passage returns hydrogen gas output to the output passage on the output side of the plurality of compression stages or hydrogen gas flowing in the intermediate passage between the plurality of compression stages to the intake passage, and the reflux valve adjusts the reflux amount in the reflux passage; a low-pressure gas discharge path branching from a branch point provided in the intermediate flow channel and capable of discharging hydrogen to a low-pressure demand end (D2), wherein the low-pressure demand end (D2) is capable of processing hydrogen at a lower pressure than the hydrogen required by the high-pressure demand end (D1); a demand-side switching unit (CV1), which is arranged at the low-pressure gas discharge path or the branch point; a check valve disposed in the intermediate flow channel on a downstream side relative to the branch point; a first temperature sensor disposed in the intermediate flow channel upstream of the branch point; a second temperature sensor disposed in the suction flow passage between a connection portion of the return flow passage and the first compression stage; a pressure sensor disposed in the low-pressure gas discharge path; and The control unit controls the demand-side switching unit (CV1) and the return valve; wherein, The control unit is configured as follows: During startup, when the temperature TS1 acquired by the first temperature sensor is greater than or equal to a predetermined first temperature threshold value T1 greater than 0° C., controlling the demand-side switching unit (CV1) to enter a first switching state in which hydrogen gas output from a first compression stage located at the front of the plurality of compression stages flows through the low-pressure gas discharge path; When the temperature TS1 obtained by the first temperature sensor is less than the first temperature threshold T1, the demand-side switching unit (CV1) is controlled to be in a third switching state in which hydrogen gas flows through both the low-pressure gas discharge path and the downstream side of the branch point in the intermediate flow channel; and When the demand-side switching unit (CV1) is in the third switching state, the demand-side switching unit (CV1) is controlled so that the pressure PS2 obtained by the pressure sensor falls within a predetermined range, and the return valve is controlled with reference to the suction temperature TS2 obtained by the second temperature sensor so that the suction temperature TS2 falls within a predetermined temperature range, wherein: The predetermined temperature range is set to a range higher than a reference temperature based on the liquefaction temperature of air and lower than 0°C.

12. The compressor unit according to claim 11, characterized in that Also includes: an adjusting unit, for adjusting the hydrogen processing capacity of subsequent compression stages except the first compression stage among the plurality of compression stages; as well as, The second pressure sensor is arranged between the first compression section and the subsequent compression section in the intermediate flow channel; wherein, The control unit is configured as follows: When the demand-side switching unit (CV1) is in the third switching state, the adjustment unit is controlled to adjust the processing volume of the subsequent compression stage according to the change in pressure PS1 in the intermediate flow channel obtained by the second pressure sensor.

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