Compressor Unit

Abstract

To properly protect a reciprocating-type compressor unit from a boil-off gas of liquefied hydrogen at cryogenic-temperature.SOLUTION: A compressor unit 10 comprises: a first spillback valve 18b; adjustment means 41 for adjusting a treatment amount of a hydrogen gas by a succeeding compression stage 14; an upstream-side temperature sensor 45; and a control part 50. The control part 50 can perform first control for controlling the first spillback valve 18b so that the suction temperature falls within a preset temperature range, referring to a suction temperature which is acquired by the upstream-side temperature sensor 45, and second control for controlling the adjustment means 41 so that the treatment amount of the succeeding compression stage 14 is adjusted according to a change amount of pressure in an intermediate flow passage 22 which is generated by the first control. The preset temperature range is set within a range in which the temperature is higher than a reference temperature based on an air liquefaction temperature and lower than 0°C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, with environmental considerations in mind, hydrogen has been considered for use as a fuel for power generation, automobiles, and the like, and the demand for hydrogen has been increasing. Furthermore, low-temperature boil-off gas (BOG) from liquefied natural gas (LNG), liquid hydrogen (LH2), and the like is recovered using compressors and supplied to users such as engines. In particular, the boil-off gas generated from LH2 has an extremely low temperature. Therefore, if a compressor is configured to directly suck in the boil-off gas, it is subject to constraints such as the need to select materials suitable for extremely low temperatures, adopt design conditions that take into account the amount of thermal deformation, and implement strict insulation treatment. For example, Patent Document 1 discloses a reciprocating compressor for compressing hydrogen gas.

[0003] Furthermore, Figure 9 of Patent Document 2 discloses a tandem screw compressor unit capable of compressing hydrogen gas. This compressor unit is provided with an intermediate-stage spillback valve and a rear-stage spillback valve. The intermediate-stage spillback valve is controlled based on the pressure detected by a pressure sensor disposed in the intermediate stage, and the rear-stage spillback valve is controlled based on the pressure detected by a pressure sensor disposed in the discharge flow path.

[0004] Furthermore, Patent Document 3 discloses a multi-stage compressor for compressing boil-off gas of liquefied natural gas. In this multi-stage compressor, a cooler is provided between a low-pressure stage compressor section and a high-pressure stage compressor section, and the cooler is used when the temperature of the gas discharged from the low-pressure stage compressor becomes high. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-172870 [Patent Document 2] Patent No. 7085079 [Patent Document 3] Japanese Patent Application Publication No. 4-12178 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, Patent Document 1 points out the following problem: "In recent years, hydrogen has been attracting attention as a new energy source. When using hydrogen as an energy source, it is expected that it will be stored and transported in a liquefied state, just like natural gas. However, hydrogen has the characteristic that its liquefaction temperature is lower than that of air. Therefore, if equipment such as reciprocating compressors designed for natural gas, etc., is applied to hydrogen as is, there is a possibility that problems will arise due to the extremely low temperature of liquid hydrogen. For example, liquefied air will be generated around the equipment to which liquid hydrogen is supplied."

[0007] In response to this, Patent Document 1 explains that "In this reciprocating compressor, a compression section that compresses gas is housed in a container section. This container section forms a vacuum region around the compression section. Thus, the compression section is thermally insulated from the external region by the vacuum region. In other words, even when extremely low-temperature gas is provided to the compression section, the region around the reciprocating compressor is not excessively cooled. Therefore, the generation of liquefied air can be suppressed."

[0008] However, it is generally very difficult to achieve high-performance insulation for moving machinery that vibrates during operation or for equipment that requires regular maintenance through an inspection opening (such as a reciprocating compressor).For this reason, the technology disclosed in Patent Document 1 makes it difficult to adequately protect a reciprocating compressor unit.

[0009] The present invention has been made in view of the above problems, and an object of the present invention is to appropriately protect a reciprocating compressor unit from boil-off gas of liquefied hydrogen, which is at an extremely low temperature. [Means for solving the problem]

[0010] The compressor unit of the present invention is a reciprocating compressor unit that recovers hydrogen gas, which is boil-off gas, from a liquid hydrogen storage tank and supplies at least a portion of it to a demand destination including at least one of an engine, a power generation facility, or a boiler, and comprises: a first compression stage that compresses the hydrogen gas; one or more subsequent compression stages that further compress the hydrogen gas discharged from the first compression stage; a crank mechanism that drives the first compression stage and the subsequent compression stage; a first spillback flow path that returns the hydrogen gas discharged from the first compression stage to the suction flow path; a first spillback section that includes a first spillback valve that adjusts the amount of spillback in the first spillback flow path; adjustment means that adjusts the amount of hydrogen gas processed by the subsequent compression stage; a pressure sensor that is arranged in an intermediate flow path between the first compression stage and the subsequent compression stage; an upstream temperature sensor that is arranged in the suction flow path between the connection portion of the first spillback flow path and the first compression stage; and a control unit that controls the first spillback valve and the adjustment means. The first compression stage and the subsequent compression stage each include a cylinder section, a piston, a piston rod connecting the piston to the crank mechanism, and a rod packing sealing the gap between the piston rod and the cylinder section. The first compression stage is air-cooled and oil-free. At least a portion of the subsequent compression stage has a leak gas discharge section that returns leak gas from the rod packing to the suction flow path. The control unit is capable of executing a first control that controls the first spillback valve based on the suction temperature acquired by the upstream temperature sensor so that the suction temperature falls within a predetermined temperature range, and a second control that controls the adjustment means so that the throughput of the subsequent compression stage is adjusted in accordance with the amount of change in pressure in the intermediate flow path caused by the first control. The predetermined temperature range is set to be higher than a reference temperature based on the liquefaction temperature of air and lower than 0°C.

[0011] The compressor unit according to the present invention can protect the compressor unit in low-temperature environments. More specifically, in the first control, the flow rate of hydrogen gas returned to the suction passage by the first spillback section can be adjusted to adjust the suction temperature of the hydrogen gas before it is suctioned into the first compression stage. Furthermore, since the temperature range of the hydrogen gas suctioned into the first compression stage is adjusted to be higher than a reference temperature based on the liquefaction temperature of air, liquefaction of oxygen, a combustion-supporting gas, can be prevented in the suction section or suction passage of the first compression stage. Furthermore, by setting the suction temperature within a preset temperature range higher than the reference temperature based on the liquefaction temperature of air and lower than 0°C, a decrease in the processing efficiency of the hydrogen gas can be suppressed.

[0012] In addition, since the first spillback section bypasses only the first compression stage, deterioration in the power of the compressor unit can be suppressed compared to when hydrogen gas is spilled back from the discharge flow path of the subsequent compression stage to the suction flow path, i.e., when the highest pressure hydrogen gas is returned to the suction flow path 21.

[0013] Furthermore, since the adjustment means adjusts the throughput of the subsequent compression stage in response to the spillback operation of the first spillback section, excessive compression operation in the subsequent compression stage can be suppressed, thereby reducing the power consumption of the compressor unit.

[0014] In addition, at least the first compression stage is oil-free, which avoids the risk of oil freezing.Furthermore, the pressure increases in subsequent compression stages, making hydrogen gas more likely to leak, but hydrogen gas that leaks in subsequent compression stages is recovered into the suction flow path by the leak gas discharge section, reducing the loss of product gas during compression.

[0015] The compressor unit may include a downstream temperature sensor disposed in the intermediate flow path, a low-pressure gas discharge path branching from a branch point provided in a discharge flow path on the discharge side of the subsequent compression stage and capable of discharging hydrogen gas to a low-pressure demander that can process hydrogen gas at a pressure lower than that required by the demander, a switching device provided in the low-pressure gas discharge path or the branch point, and a check valve located downstream of the branch point. In this case, the control unit may control the switching device to a first switching state in which hydrogen gas discharged from the subsequent compression stage is circulated through the low-pressure gas discharge path when a temperature detected by the downstream temperature sensor is higher than a predetermined first temperature T1 higher than 0°C during startup, and control the switching device to a second switching state in which hydrogen gas discharged from the subsequent compression stage is sent to the discharge flow path toward the demander when the temperature detected by the downstream temperature sensor becomes lower than the first temperature T1, and may execute the first control and the second control on the condition that the switching device is in the second switching state.

[0016] In this embodiment, if the hydrogen gas in the piping on the liquid hydrogen storage tank side rises to a positive temperature range during startup, the hydrogen gas discharged from the subsequent compression stage is sent to a low-pressure demand destination, thereby more effectively preventing an excessive temperature rise in the hydrogen gas in the subsequent compression stage. In other words, in a reciprocating compressor unit, hydrogen gas is delivered at a pressure corresponding to the pressure set by the hydrogen gas supply destination. Therefore, by controlling the switching means so that hydrogen gas is delivered to a low-pressure demand destination, the discharge gas pressure from the subsequent compression stage is reduced. This more reliably protects the subsequent compression stage. Furthermore, the compressor unit can be quickly started up. Furthermore, the compressor unit can be protected in low-temperature environments.

[0017] The compressor unit may further include a downstream temperature sensor disposed in the intermediate flow path, a cooler section provided between the first compression stage and the subsequent compression stage, and cooler switching means capable of switching between a path for introducing hydrogen gas into the cooler section and a path for introducing hydrogen gas into the subsequent compression stage without passing through the cooler section. In this case, the control unit may control the cooler switching means to enter a first switching state in which hydrogen gas discharged from the first compression stage is circulated through the cooler section and cooled when the temperature detected by the downstream temperature sensor is higher than a predetermined first temperature T1 higher than 0°C during startup, and control the cooler switching means to enter a second switching state in which hydrogen gas discharged from the first compression stage is sent to the subsequent compression stage without passing through the cooler section when the temperature detected by the downstream temperature sensor becomes lower than the first temperature T1, and may execute the first control and the second control on the condition that the cooler switching means is in the second switching state.

[0018] In this embodiment, if the hydrogen gas in the pipe on the liquid hydrogen storage tank side rises to a positive temperature range during startup, the hydrogen gas discharged from the first compression stage is cooled by the cooler unit, preventing an excessive temperature rise in the hydrogen gas in the subsequent compression stages. In other words, the subsequent compression stages can be protected. Furthermore, the compressor unit can be started up quickly. Furthermore, the compressor unit can be protected in low-temperature environments.

[0019] The adjustment means may include, in at least one subsequent compression stage, a second spillback section including a second spillback flow path that returns hydrogen gas flowing through the discharge side of the subsequent compression stage to the suction side of the subsequent compression stage and a second spillback valve that adjusts the amount of spillback in the second spillback flow path, and a suction valve unloader attached to a cylinder section of the subsequent compression stage. In this case, in the second control, the control unit may control the second spillback valve in accordance with the amount of change in pressure in the intermediate flow path caused by the first control, and when the opening degree of the second spillback valve reaches a predetermined value, may also drive the suction valve unloader to reduce the throughput of the cylinder section, thereby reducing the amount of hydrogen returned to the suction side of the subsequent compression stage through the second spillback section.

[0020] In this embodiment, it is possible to further reduce the power required to compress the gas.

[0021] The adjusting means may include, in at least one subsequent compression stage, a stepless capacity adjusting device having a suction valve unloader attached to a cylinder portion of the subsequent compression stage and a hydraulic or electric drive device for opening and closing the suction valve unloader. In this case, the control unit may drive the drive device so that the operation timing of the suction valve unloader is adjusted in conjunction with the rotational movement of a crankshaft in the crank mechanism. In addition, in the second control, the control unit may control the drive device in accordance with the amount of change in pressure in the intermediate flow path caused by the first control to adjust the throughput of the subsequent compression stage.

[0022] In this embodiment, the timing and duration of the operation of the intake valve unloader are controlled to return a portion of the hydrogen gas in the cylinder to the intake side, thereby reducing the amount of gas processed in the subsequent compression stage, thereby further reducing power consumption. [Effects of the Invention]

[0023] As described above, according to the present invention, a reciprocating compressor unit can be appropriately protected from boil-off gas of liquefied hydrogen, which is at an extremely low temperature. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a diagram schematically illustrating a compressor unit according to a first embodiment. [Figure 2] FIG. 3 is a diagram illustrating a first compression stage of the compressor unit. [Figure 3] FIG. 3 is a schematic diagram of a subsequent compression stage in the compressor unit. [Figure 4] 5A and 5B are diagrams for explaining the operation of the compressor unit. [Figure 5] FIG. 4 is a diagram schematically illustrating a compressor unit according to a modified example of the first embodiment. [Figure 6] FIG. 4 is a diagram schematically illustrating a compressor unit according to a modified example of the first embodiment. [Figure 7] FIG. 4 is a diagram schematically illustrating a compressor unit according to a modified example of the first embodiment. [Figure 8] FIG. 6 is a diagram schematically illustrating a compressor unit according to a second embodiment. [Figure 9] 5A and 5B are diagrams for explaining the operation of the compressor unit. [Figure 10] FIG. 10 is a diagram schematically illustrating a compressor unit according to a third embodiment. [Figure 11] 5A and 5B are diagrams for explaining the operation of the compressor unit. [Figure 12] FIG. 10 is a diagram schematically illustrating a compressor unit according to a fourth embodiment. [Figure 13] 5A and 5B are diagrams for explaining the operation of the compressor unit. [Figure 14] 5A and 5B are diagrams for explaining the operation of the compressor unit. [Figure 15] FIG. 10 is a diagram schematically illustrating a compressor unit according to a fifth embodiment. [Figure 16]FIG. 10 is a diagram schematically illustrating a compressor unit according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0026] (First embodiment) The compressor unit according to this embodiment is configured to recover boil-off hydrogen gas from a liquid hydrogen storage tank, compress the recovered hydrogen gas, and supply it to a consumer. The boil-off hydrogen gas has a temperature of approximately -253°C.

[0027] As shown in FIG. 1, the compressor unit 10 includes a first compression stage 12 that compresses hydrogen gas in an intake passage 21, a subsequent compression stage 14 that is connected to the first compression stage 12 via an intermediate passage 22, and a crank mechanism 16 that drives the first compression stage 12 and the subsequent compression stage 14.

[0028] The first compression stage 12 is connected to the liquid hydrogen storage tank 23 via the suction passage 21. Therefore, boil-off gas of the liquefied gas generated in the liquid hydrogen storage tank 23 is sucked into the first compression stage 12 through the suction passage 21.

[0029] The first compression stage 12 is configured by a reciprocating compression mechanism. That is, as shown in Fig. 2, the first compression stage 12 has a cylinder portion 211, a piston 212 arranged in the cylinder portion 211, a piston rod 213 connected to the piston 212, a pair of suction valves 214, and a pair of discharge valves 215. Within the cylinder portion 211, compression chambers 216 are formed between a front head 211a and the piston 212, and between a rear head 211b and the piston 212. The first compression stage 12 is configured by an air-cooled, oil-free compression mechanism that does not use lubricating oil.

[0030] A rod packing 217 is provided in rear head 211b of cylinder section 211 to prevent leakage of hydrogen gas from compression chamber 216. Rod packing 217 is configured to seal between piston rod 213 and cylinder section 211, and has packing ring 217a arranged to surround piston rod 213, and case 217b that holds packing ring 217a.

[0031] The piston 212 is connected to the crank mechanism 16 via a piston rod 213. The reciprocating movement of the piston 212 within the cylinder portion 211 compresses the hydrogen gas within a compression chamber 216. Although FIG. 2 shows the first compression stage 12 having a double-acting structure, the first compression stage 12 may also have a single-acting structure in which a compression chamber is provided only on the front head side or the rear head side.

[0032] 1, for convenience, the first compression stage 12 is shown as a single trapezoid, but the first compression stage 12 may have a plurality of cylinder sections 211. That is, the first compression stage 12 may be configured such that hydrogen gas is compressed and pressurized by pistons 212 in a plurality of cylinder sections 211 connected in parallel. The same applies to other embodiments.

[0033] The subsequent compression stage 14 is a compression mechanism for further compressing the hydrogen gas discharged from the first compression stage, and the hydrogen gas compressed by the subsequent compression stage 14 is discharged to a discharge flow path 24. The hydrogen gas flowing through the discharge flow path 24 is sent to a consumer 26 directly or indirectly via other equipment. Examples of the consumer 26 include power generation equipment, boilers, engines of ships, etc., and may also include equipment for releasing gas into the atmosphere, such as flare equipment and vents.

[0034] 3, the subsequent compression stage 14 is configured by a reciprocating compression mechanism, similar to the first compression stage 12. A piston 212 of the subsequent compression stage 14 is also connected to the crank mechanism 16 via a piston rod 213. The subsequent compression stage 14 is configured similarly to the first compression stage 12, but is further provided with a leakage gas discharge part 29 that returns leakage gas from the rod packing 217 to the suction passage 21. The leakage gas discharge part 29 may be formed by a pipe member provided to connect the rod packing 217 and the suction passage 21 to each other.

[0035] 1, the subsequent compression stage 14 is shown as a single trapezoid for convenience, but the subsequent compression stage 14 does not necessarily have to be a single stage and may have a compression mechanism with multiple compression stages. That is, the subsequent compression stage 14 may be configured such that hydrogen gas is sequentially compressed and pressurized by pistons 212 in multiple cylinder portions 211. The same applies to other embodiments. In the subsequent compression stage 14, the compression stage that discharges room temperature hydrogen gas may be either an oil-free type or a lubricated type.

[0036] As shown in FIG. 1, the compressor unit 10 includes a first spillback section 18 that returns a portion of the hydrogen gas discharged from the first compression stage 12 to the suction passage 21. The first spillback section 18 includes a first spillback passage 18a and a first spillback valve 18b, which is an adjustable valve disposed in the first spillback passage 18a. One end of the first spillback passage 18a is connected to the intermediate passage 22, and the other end is connected to the suction passage 21. That is, the hydrogen gas that flows through the first spillback passage 18a merges with hydrogen gas from the liquid hydrogen storage tank 23 in the suction passage 21. The first spillback valve 18b adjusts the amount of spillback in the first spillback passage 18a.

[0037] The compressor unit 10 is equipped with an adjustment means 41 that adjusts the amount of hydrogen gas processed by the subsequent compression stage 14. The adjustment means 41 adjusts the gas processing amount by a method other than adjusting the rotation speed of the crank mechanism 16, and in this embodiment is configured by a spillback section (second spillback section 43) that adjusts the amount of hydrogen gas processed so that the gas flow rate sent from the subsequent compression stage 14 to the demand destination 26 is adjusted.

[0038] The second spillback section 43 has a second spillback passage 43a and a second spillback valve 43b, which is an adjustable valve disposed in the second spillback passage 43a. One end of the second spillback passage 43a is connected to the discharge passage 24, and the other end is connected to the intermediate passage 22. Therefore, a portion of the hydrogen gas discharged from the subsequent compression stage 14 is returned to the intermediate passage 22. The second spillback valve 43b adjusts the amount of spillback in the second spillback passage 43a.

[0039] The suction passage 21 is provided with a temperature sensor (upstream temperature sensor 45) that detects the temperature of the hydrogen gas flowing through the suction passage 21. The upstream temperature sensor 45 is disposed in the suction passage 21 between the connection portion of the first spillback passage 18a and the first compression stage 12. Therefore, when hydrogen gas flows through the first spillback passage 18a, the upstream temperature sensor 45 can acquire the temperature of the hydrogen gas that is drawn into the first compression stage 12 after the hydrogen gas from the first spillback passage 18a is joined with the hydrogen gas from the liquid hydrogen storage tank 23.

[0040] The intermediate flow path 22 is provided with a pressure sensor 47 that detects the pressure of the hydrogen gas flowing through the intermediate flow path 22. The pressure sensor 47 is located in the intermediate flow path 22 between the connection portion of the first spillback flow path 18a and the subsequent compression stage 14. Therefore, the pressure sensor 47 can detect the pressure of the hydrogen gas that has had its pressure adjusted by the first spillback portion 18 and is introduced into the subsequent compression stage 14.

[0041] The pressure sensor 47 outputs a signal indicating the detected pressure, and the upstream temperature sensor 45 outputs a signal indicating the acquired temperature (suction temperature TS2). The signals from the pressure sensor 47 and the upstream temperature sensor 45 are input to the control unit 50. The control unit 50 is a computer that controls various operations of the compressor unit 10, and the functions of the control unit 50 executed by this computer include a first control unit 50a and a second control unit 50b. The first control unit 50a is a functional unit configured to control the first spillback valve 18b while referring to the suction temperature TS2 acquired by the upstream temperature sensor 45. The second control unit 50b is a functional unit configured to control the adjustment means 41 based on the detected pressure of the pressure sensor 47.

[0042] Here, the operation of the compressor unit 10 according to this embodiment will be described with reference to FIG.

[0043] Operation of the crank mechanism 16 causes the piston 212 to reciprocate within the cylinder portion 211 in the first compression stage 12 and the subsequent compression stage 14. As a result, in the first compression stage 12, hydrogen gas in the intake passage 21 is sucked into the first compression stage 12, and in the subsequent compression stage 14, hydrogen gas in the intermediate passage 22 is sucked into the subsequent compression stage 14, thereby compressing the hydrogen gas (step ST11).

[0044] When the first compression stage 12 is operating, the temperature of the hydrogen gas sucked into the first compression stage 12 (suction temperature TS2) is acquired by the upstream temperature sensor 45 (step ST12). At this time, the first control unit 50a refers to the suction temperature TS2, and executes a first control to control the first spillback valve 18b so that the suction temperature TS2 falls within a predetermined temperature range (TTH1≦TS2≦TTH2) (step ST13).

[0045] More specifically, in the first control, when TS2 < TTH1, the second control unit 50b controls the first spillback valve 18b so that a part of the gas in the intermediate flow path 22 is returned to the suction flow path 21 or the amount of return increases. Thereby, the suction temperature TS2 is made within the above temperature range. When TS2 > TTH2, the operation of returning a part of the gas in the intermediate flow path 22 to the suction flow path 21 is not performed or the amount of return is reduced.

[0046] Here, the predetermined temperature range is set higher than the reference temperature based on the liquefaction temperature of air and within the range of less than 0°C. That is, the lower limit value TTH1 and the upper limit value TTH2 of the predetermined temperature range are set higher than the reference temperature and within the range of less than 0°C.

[0047] Thereby, the suction temperature TS2, which is the temperature of the hydrogen gas inhaled into the first compression stage 12, can be kept within an appropriate range. The hydrogen gas from the liquid hydrogen storage tank 23 is not directly introduced into the first compression stage 12, but the hydrogen gas that has been compressed in the first compression stage 12 and the hydrogen gas that has been heated after confluence are introduced. Therefore, it is possible to prevent the first compression stage 12 from being exposed to extremely low-temperature hydrogen gas. Moreover, since the suction temperature TS2 is adjusted to be higher than the reference temperature based on the liquefaction temperature of air, it is also possible to prevent the liquefaction of oxygen. In addition, since it is adjusted within the range of less than 0°C, it is also possible to prevent the density of the hydrogen gas inhaled into the first compression stage 12 from decreasing excessively.

[0048] When the first control is performed, the flow rate of the hydrogen gas introduced into the subsequent compression stage 14 among the hydrogen gas discharged from the first compression stage 12 changes. Therefore, during the operation of the subsequent compression stage 14, the pressure (intermediate pressure) of the hydrogen gas introduced into the subsequent compression stage 14 is detected by the pressure sensor 47 (step ST14).

[0049] At this time, the second control unit 50b executes second control to control the adjusting means 41 so as to adjust the throughput of the subsequent compression stage 14 in accordance with the change in pressure (intermediate pressure) in the intermediate flow path 22 caused by the first control (step ST15). Specifically, in the second control, when the pressure detected by the pressure sensor 47 is lower than the target value, the second control unit 50b controls the second spillback valve 43b to increase the opening by a predetermined value, and when the detected pressure is higher than the target value, the second control unit 50b controls the second spillback valve 43b to decrease the opening by a predetermined value. This keeps the pressure at the suction port of the subsequent compression stage 14 within a predetermined range, thereby suppressing excessive compression in the subsequent compression stage 14. The hydrogen gas compressed in the subsequent compression stage 14 is sent to a consumer through the discharge flow path 24.

[0050] As described above, this embodiment can protect the compressor unit 10 in low-temperature environments, thereby contributing to stable recovery of hydrogen gas. Specifically, in the first control, the flow rate of hydrogen gas returned to the suction passage 21 by the first spillback section 18 is adjusted, thereby adjusting the suction temperature TS2 of the hydrogen gas suctioned into the first compression stage 12. Furthermore, the temperature range of the hydrogen gas suctioned into the first compression stage 12 is adjusted to be higher than a reference temperature based on the liquefaction temperature of air, thereby preventing liquefaction of oxygen, a combustion-supporting gas, in the suction section of the first compression stage 12 or the suction passage 21. In other words, liquefaction of oxygen on the outer surface of the hydrogen gas inlet (around the device to which hydrogen gas is supplied) can be prevented. Furthermore, the suction temperature TS2 is adjusted to a predetermined temperature range higher than a reference temperature based on the liquefaction temperature of air and lower than 0°C, thereby preventing a decrease in the hydrogen gas processing efficiency.

[0051] Furthermore, since the first spillback section 18 bypasses only the first compression stage 12, deterioration in the power of the compressor unit 10 can be suppressed compared to when hydrogen gas is spilled back from the discharge passage 24 of the subsequent compression stage 14 to the suction passage 21, i.e., when the highest pressure hydrogen gas is returned to the suction passage 21.

[0052] Furthermore, because at least the first compression stage 12 is oil-free, the risk of oil freezing can be avoided. Furthermore, the pressure increases in subsequent compression stages, making it more likely that hydrogen gas will leak. However, hydrogen gas leaked in the subsequent compression stage 14 is recovered into the suction passage 21 by the leak gas discharge part 29, reducing the loss of product gas during compression. This contributes to efficient recovery of hydrogen gas. The leak gas discharge part 29 may also be provided in the first compression stage 12.

[0053] Although the compressor unit 10 shown in Fig. 1 has a single compression mechanism in the subsequent compression stage 14, as described above, the compressor unit 10 may have a compression mechanism with multiple compression stages. In this case, for example, as shown in Fig. 5, the second spillback section 43 may be provided only in the first compression mechanism, or as shown in Fig. 6, the second spillback flow path 43a may bypass all compression mechanisms constituting the subsequent compression stage 14, or as shown in Fig. 7, the second spillback section 43 may be provided in each compression mechanism of the subsequent compression stage 14. The compressor unit 10 may have a so-called tandem structure in which the first compression stage 12 and the subsequent compression stage 14 are arranged in the piston rod direction.

[0054] (Second embodiment) 8, the compressor unit 10 of the second embodiment differs from the first embodiment in that the intermediate flow path 22 is provided with a temperature sensor (downstream temperature sensor 46) that detects the temperature of the hydrogen gas flowing through the intermediate flow path 22, and is provided with a low-pressure gas discharge path 53 that can discharge the hydrogen gas to a low-pressure demand destination 52. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0055] As the low-pressure demand destination 52, various facilities may be used as long as they can process hydrogen gas at a pressure lower than that of hydrogen gas required by the demand destination 26. For example, facilities that release gas into the atmosphere, such as flare facilities and vents, and other facilities that use a supply pressure approximately at atmospheric pressure may be used.

[0056] Low-pressure gas discharge path 53 branches off from discharge flow path 24, and a check valve 54 is provided in discharge flow path 24 at a location downstream of branch point 24a where low-pressure gas discharge path 53 branches off. This check valve 54 is a valve that allows hydrogen gas to flow from branch point 24a to demand destination 26, but prevents hydrogen gas from flowing in the reverse direction. Therefore, it is possible to prevent hydrogen gas from flowing back from demand destination 26 to branch point 24a and into low-pressure gas discharge path 53.

[0057] The compressor unit 10 is provided with a switching means 56 for switching the flow state of hydrogen gas in the low-pressure gas discharge channel 53. The switching means 56 is configured by an on-off valve 56a and is provided in the low-pressure gas discharge channel 53. The switching means 56 switches the flow state of hydrogen gas in the low-pressure gas discharge channel 53 between a state (first switching state) in which hydrogen gas discharged from the subsequent compression stage 14 flows into the low-pressure gas discharge channel 53 and a state (second switching state) in which hydrogen gas discharged from the subsequent compression stage 14 is sent to the consumer 26 through the discharge flow path 24 without flowing into the low-pressure gas discharge channel 53. In the first switching state, the on-off valve 56a is open, and therefore hydrogen gas flows into the low-pressure gas discharge channel 53. On the other hand, although the pressure of hydrogen gas at the consumer 26 is higher than the pressure of hydrogen gas at the low-pressure consumer 52, the check valve 54 prevents hydrogen gas from flowing toward the consumer 26. In the second switching state, the on-off valve 56a is closed, and therefore the hydrogen gas does not flow through the low-pressure gas discharge path 53. Therefore, the hydrogen gas discharged from the subsequent compression stage 14 is sent to the consumer 26.

[0058] The switching means 56 is not limited to the on-off valve 56a provided in the low-pressure gas discharge path 53. For example, the switching means 56 may be configured by a three-way valve (not shown) and provided at the branch point 24a. In this case, the three-way valve can be in either a state (second switching state) in which the hydrogen gas discharged from the subsequent compression stage 14 flows toward the demand destination 26, or a state (first switching state) in which the hydrogen gas discharged from the subsequent compression stage 14 flows toward the low-pressure demand destination 52.

[0059] The functions of the control unit 50 include a switching control unit 50c that controls the switching means 56.

[0060] The switching control unit 50c controls the switching means 56 to be in the first switching state when the temperature TS1 detected by the downstream temperature sensor 46 is higher than a predetermined first temperature T1, which is a temperature higher than 0°C, during startup. When the switching means 56 is in the first switching state, hydrogen gas discharged from the subsequent compression stage 14 is allowed to flow through the low-pressure gas discharge path 53, so that hydrogen gas at a relatively low pressure is discharged from the subsequent compression stage 14. As a result, if the temperature of the intake gas of the subsequent compression stage 14 is high during startup, the compressor can be protected from an excessive rise in discharge temperature caused by increasing the pressure to a high level.

[0061] Furthermore, the switching control unit 50c controls the switching means 56 so that the switching means 56 enters the second switching state when the temperature TS1 detected by the downstream temperature sensor 46 becomes less than the first temperature T1. When the switching means 56 is in the second switching state, hydrogen gas does not flow through the low-pressure gas discharge path 53, and therefore the hydrogen gas discharged from the subsequent compression stage 14 flows toward the demand destination 26 through the discharge path 24. In this case, the pressure of the hydrogen gas discharged from the subsequent compression stage 14 becomes relatively high, but because the temperature of the hydrogen gas introduced into the subsequent compression stage 14 is not high, the temperature in the subsequent compression stage 14 does not become excessively high.

[0062] Here, the operation of the compressor unit 10 according to this embodiment will be described with reference to FIG.

[0063] When the compressor unit 10 is started, compression of hydrogen gas begins in the first compression stage 12 (step ST21). When the compressor unit 10 is started, the temperature of the piping between the liquid hydrogen storage tank 23 and the first compression stage 12 may be at room temperature, so when the compressor unit 10 is started, the switching means 56 is switched to the first switching state. Therefore, the hydrogen gas discharged from the subsequent compression stage 14 is sent to the low-pressure demand destination 52 through the low-pressure gas discharge path 53 (step ST22).

[0064] In this state, it is determined whether the detected temperature TS1 of the downstream temperature sensor 46 has become less than the first temperature T1 (step ST23). As long as the detected temperature TS1 is equal to or greater than the first temperature T1 (NO in step ST23), step ST23 is repeatedly executed. When the detected temperature TS1 becomes less than the first temperature T1 (YES in step ST23), the switching control unit 50c of the control unit 50 controls the switching means 56 to enter the second switching state (step ST24). This stops the state in which hydrogen gas discharged from the subsequent compression stage 14 flows into the low-pressure gas discharge path 53 (start-up operation), and the system enters steady operation in which hydrogen gas is supplied to the demand destination 26.

[0065] In steady operation, the temperature of the hydrogen gas sucked into the first compression stage 12 (suction temperature TS2) is acquired by the upstream temperature sensor 45 (step ST12). At this time, the first control unit 50a refers to the suction temperature TS2 and executes the first control to control the first spillback valve 18b, as in the first embodiment (step ST13).

[0066] As a result of the first control being performed, the flow rate of the hydrogen gas discharged from the first compression stage 12 and introduced into the subsequent compression stage 14 changes, and therefore the pressure (intermediate pressure) of the hydrogen gas introduced into the subsequent compression stage 14 is detected by the pressure sensor 47 (step ST14). At this time, the second control unit 50b performs the second control, which controls the adjustment means 41 so that the throughput of the subsequent compression stage 14 is adjusted in accordance with the amount of change in the pressure (intermediate pressure) in the intermediate flow path 22 caused by the first control (step ST15), as in the first embodiment.

[0067] Therefore, in this embodiment, when the hydrogen gas in the piping on the liquid hydrogen storage tank 23 side rises to a positive temperature range during startup, the hydrogen gas discharged from the subsequent compression stage 14 is sent to the low-pressure demand destination 52. This more effectively prevents an excessive temperature rise in the hydrogen gas in the subsequent compression stage 14. That is, in the reciprocating compressor unit 10, hydrogen gas is delivered at a pressure corresponding to the pressure set by the hydrogen gas supply destination. Therefore, by controlling the switching means 56 so that hydrogen gas is delivered to the low-pressure demand destination 52, the discharge gas pressure from the subsequent compression stage 14 is reduced, and the compressor is protected from an excessive rise in discharge temperature due to the pressure being increased to a high pressure. This more reliably protects the subsequent compression stage 14. Furthermore, the compressor unit 10 can be quickly started up. Furthermore, the compressor unit 10 can be protected in low-temperature environments.

[0068] Although the description of other configurations, actions, and effects will be omitted, the description of the first embodiment can be applied to the second embodiment.

[0069] (Third embodiment) 10, the compressor unit 10 according to the third embodiment differs from the first embodiment in that it is provided with a cooler section 58 and a cooler switching means 59. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0070] The cooler unit 58 is disposed between the first compression stage 12 and the subsequent compression stage 14. That is, in the third embodiment, the intermediate flow path 22 has branched flow paths (first flow path 22a and second flow path 22b) at a midpoint thereof, and the cooler unit 58 is disposed in one of the flow paths (first flow path 22a).

[0071] The cooler switching means 59 is configured to be able to switch the path of the hydrogen gas between a state (first switching state) in which the hydrogen gas discharged from the first compression stage 12 flows into the subsequent compression stage 14 via the cooler unit 58, and a state (second switching state) in which the hydrogen gas flows into the subsequent compression stage 14 without passing through the cooler unit 58. The cooler switching means 59 includes a first opening / closing valve 59a provided in the first flow path 22a and a second opening / closing valve 59b provided in the second flow path 22b. Note that the cooler switching means 59 is not limited to a configuration having two opening / closing valves 59a, 59b. For example, the cooler switching means 59 may be configured as a three-way valve arranged at the connection between the first flow path 22a and the second flow path 22b.

[0072] The connection portion of the first spillback flow path 18a in the intermediate flow path 22 may be located upstream or downstream of the connection portion with the first flow path 22a and the second flow path 22b, as long as it is between the first compression stage 12 and the subsequent compression stage 14.

[0073] The functions of the control unit 50 include a cooler control unit 50d that can control the switching of the cooler switching means 59.

[0074] When the temperature TS1 detected by the downstream temperature sensor 46 at startup is higher than a predetermined first temperature T1 that is higher than 0°C, the cooler control unit 50d controls the cooler switching means 59 so that hydrogen gas flows through the cooler unit 58. In other words, when the temperature TS1 detected by the downstream temperature sensor 46 is higher than the first temperature T1, the cooler switching means 59 is controlled so that the hydrogen gas discharged from the first compression stage 12 is cooled by the cooler unit 58 before being drawn into the subsequent compression stage 14.

[0075] Furthermore, the cooler control unit 50d controls the cooler switching means 59 so that hydrogen gas does not flow into the cooler unit 58 when the detected temperature TS1 of the downstream temperature sensor 46 becomes lower than the first temperature T1.

[0076] Here, the operation of the compressor unit 10 according to this embodiment will be described with reference to FIG.

[0077] When the compressor unit 10 is started, compression of hydrogen gas begins in the first compression stage 12 (step ST31). When the compressor unit 10 is started, the temperature of the piping between the liquid hydrogen storage tank 23 and the first compression stage 12 may be at room temperature, so when the compressor unit 10 is started, the cooler switching means 59 is switched to the first switching state. Therefore, the hydrogen gas discharged from the first compression stage 12 flows into the first flow path 22a of the intermediate flow path 22, is cooled in the cooler section 58, and is then introduced into the subsequent compression stage 14 (step ST32).

[0078] In this state, it is determined whether the detected temperature TS1 of the downstream temperature sensor 46 has become less than the first temperature T1 (step ST33). As long as the detected temperature TS1 is equal to or greater than the first temperature T1 (NO in step ST33), step ST33 is repeatedly executed. When the detected temperature TS1 becomes less than the first temperature T1 (YES in step ST33), the cooler control unit 50d of the control unit 50 controls the cooler switching unit 59 to enter the second switching state (step ST34). This stops the state (start-up operation) in which the hydrogen gas discharged from the first compression stage 12 is cooled by the cooler unit 58, and the system enters steady operation in which the hydrogen gas discharged from the first compression stage 12 is introduced into the subsequent compression stage 14 without being cooled by the cooler unit 58.

[0079] In steady-state operation, the temperature of the hydrogen gas taken into the first compression stage 12 (suction temperature TS2) is acquired by the upstream temperature sensor 45 (step ST12). At this time, the first control unit 50a executes the first control as in the first embodiment (step ST13). This allows the suction temperature TS2 of the hydrogen gas taken into the first compression stage 12 to be kept within an appropriate range.

[0080] By performing the first control, the flow rate of the hydrogen gas discharged from the first compression stage 12 and introduced into the subsequent compression stage 14 changes. Therefore, the pressure (intermediate pressure) of the hydrogen gas introduced into the subsequent compression stage 14 is detected by the pressure sensor 47 (step ST14), and the second control unit 50b executes the second control to control the adjustment means 41 (step ST15), similar to the first embodiment.

[0081] Therefore, according to this embodiment, when the hydrogen gas in the piping on the liquid hydrogen storage tank 23 side rises to a positive temperature range at startup, the hydrogen gas discharged from the first compression stage 12 is cooled by the cooler unit 58, preventing an excessive temperature rise of the hydrogen gas in the subsequent compression stage 14. This contributes to stable recovery of hydrogen gas. In other words, the subsequent compression stage 14 can be protected. Furthermore, the compressor unit 10 can be started up quickly. Furthermore, the compressor unit 10 can be protected in low-temperature environments.

[0082] Although the description of other configurations, actions, and effects will be omitted, the descriptions of the first and second embodiments can be applied to the third embodiment.

[0083] (Fourth embodiment) 12, the compressor unit 10 according to the fourth embodiment differs from the first embodiment in that the adjustment means 41 includes a second spillback section 43, an on-off type suction valve unloader 61, and a drive device 62. Note that the same components as those in the first to third embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0084] When suction valve unloader 61 is driven by drive device 62, the valve plate of suction valve 214 is maintained in an open state, and the check valve is unable to function. When piston 212 undergoes a suction stroke without unloader 61 being driven, the pressure in compression chamber 216 drops below the pressure in intermediate passage 22, which is the suction side passage, and suction valve 214 is open. This allows gas to be introduced into compression chamber 216. When piston 212 undergoes a compression stroke, the pressure in compression chamber 216 rises above the pressure in intermediate passage 22, and suction valve 214 is closed.

[0085] The adjustment means 41 is provided in at least one subsequent compression stage 14, and the suction valve unloader 61 is attached to the suction valve 214 of that subsequent compression stage 14. The suction valve unloaders are attached to the front head side compression chamber and the rear head side compression chamber of the cylinder section 211, and can be operated independently. A state in which neither is operated is called 100% load, and a state in which either one is operated is called 50% load.

[0086] Suction valve unloader 61 is driven by a driver 62 using a gas such as air or nitrogen. Driven by driver 62, suction valve unloader 61 sets suction valve 214 (see FIG. 3) in a state in which compression chamber 216 opens and closes relative to suction passage 21 (loaded state) depending on the pressure difference between compression chamber 216 and suction passage 21, or in a state in which the space between compression chamber 216 and suction passage 21 is maintained open (unloaded state). For example, if gas such as air or nitrogen is not supplied to driver 62, suction valve unloader 61 sets suction valve 214 in a free state so that compression chamber 216 can open and close depending on the pressure difference between compression chamber 216 and suction passage 21. On the other hand, when air or a gas such as nitrogen is applied to the drive unit 62, the compression chamber 216 would normally be closed due to the pressure difference between the compression chamber 216 and the suction passage 21, but the suction valve unloader 61 forcibly keeps the suction valve 214 open.

[0087] Furthermore, a signal indicating the state of the unloader and an opening signal of the second spillback valve 43b are sent to the control unit 50 and used for control by the control unit 50. That is, the control unit 50 estimates the amount of gas to be spilled back from the opening of the second spillback valve 43b, and when the opening of the second spillback valve 43b exceeds a preset opening threshold (e.g., approximately 50%), the control unit 50 reduces the load of the subsequent compression stage 14 to 50% by the suction valve unloader 61. This reduces the discharge volume of the subsequent compression stage 14, thereby reducing the amount of spillback in the second spillback unit 43. This makes it possible to reduce the power of the subsequent compression stage 14 compared to when the suction valve 214 is in a free state.

[0088] 13, the first control unit 50a of the control unit 50 refers to the suction temperature TS2 and executes first control to control the first spillback valve 18b so that the suction temperature TS2 falls within a predetermined temperature range (step ST13). When the first control is executed, the flow rate of the hydrogen gas discharged from the first compression stage 12 that is introduced into the subsequent compression stage 14 changes, and therefore, during the operation of the subsequent compression stage 14, the pressure (intermediate pressure) of the hydrogen gas introduced into the subsequent compression stage 14 is detected by the pressure sensor 47 (step ST14).

[0089] The second control unit 50b of the control unit 50 controls the second spillback valve 43b in accordance with the amount of change in pressure in the intermediate flow path 22 caused by the first control (step ST15). For example, when the pressure detected by the pressure sensor 47 is lower than a target value, the second control unit 50b controls the second spillback valve 43b so that the opening degree increases by a predetermined value. Then, when the opening degree of the second spillback valve 43b reaches a preset value, the second control unit 50b controls the drive device 62 so that the suction valve unloader 61 is also used (step ST16).

[0090] Specifically, as shown in FIG. 14, the control unit 50 compares the opening of the second spillback valve 43b input to the control unit 50 with a preset opening threshold b1. If the state (valve opening) of the second spillback valve 43b is greater than the opening threshold b1 (i.e., if the spillback amount is large) (Yes in step ST41), the control unit 50 controls the suction valve unloader 61 (e.g., the suction valve unloader on the front head side) to reduce the load (step ST42). This reduces the load of the subsequent compression stage 14 (from 100% to 50%). If the opening of the second spillback valve 43b is smaller than the opening threshold b2 (Yes in step ST43), the control unit 50 controls the suction valve unloader 61 to increase the load (step ST44). This increases the load of the subsequent compression stage 14 (from 50% to 100%). This allows power reduction by lowering the load on the subsequent compression stage 14 in the event of excessive spillback.

[0091] Although the description of other configurations, actions, and effects will be omitted, the descriptions of the first to third embodiments can be applied to the fourth embodiment.

[0092] (Fifth embodiment) In the fourth embodiment, the adjustment means 41 includes a second spillback section 43, an on-off suction valve unloader 61, and a drive device 62. In contrast, in a compressor unit 10 according to a fifth embodiment, as shown in FIG. 15, the adjustment means 41 does not include the second spillback section 43, but includes a stepless capacity adjustment device 64b. The functions of the control unit 50 include a stepless capacity adjustment control unit 50e that can control the stepless capacity adjustment device 64b. Note that the same components as those in the first to fourth embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0093] The stepless capacity adjuster 64b has a suction valve unloader 61b, a drive unit 62b, and a detector 63b that detects the rotation of the crankshaft in the crank mechanism 16. The suction valve unloader 61b is driven by a hydraulic or electric drive unit 62b, and can maintain or release the open state of the valve plate of the suction valve 214 faster than the time it takes for the piston 212 to reciprocate. In addition, the control unit 50 performs calculations to estimate the position of the piston 212 based on a signal sent from the detector 63b installed in the crank mechanism 16.

[0094] In the cylinder section 211 of the subsequent compression stage 14, an intake valve 214 is installed between the intermediate flow path 22, which is the intake side flow path, and the compression chamber 216. The intake valve 214 is composed of a valve plate that opens and closes the gas passage and a valve body that houses the valve plate. Similar to a check valve, when the upstream pressure is higher than the downstream pressure, the valve plate opens due to the pressure difference, and when the downstream pressure is higher, gas does not flow.

[0095] When suction valve unloader 61b is driven by drive unit 62b, the valve plate of suction valve 214 is maintained in an open state, and the check valve is unable to function. When piston 212 undergoes a suction stroke without driving unloader 61b, the pressure in compression chamber 216 drops below the pressure in intermediate passage 22, which is the suction-side passage, and suction valve 214 opens. This allows gas to be introduced into compression chamber 216. When piston 212 undergoes a compression stroke, the pressure in compression chamber 216 rises above the pressure in intermediate passage 22, and suction valve 214 closes.

[0096] The stepless capacity adjustment control unit 50e of the control unit 50 drives the drive unit 62b to adjust the operation timing of the suction valve unloader 61b in conjunction with the rotational movement of the crankshaft in the crank mechanism 16. Specifically, at the beginning of the compression stroke, the stepless capacity adjustment unit 64b maintains the open state of the suction valve 214, thereby returning a portion of the gas introduced into the compression chamber 216 to the intermediate flow path 22. Then, by releasing the open state midway through the compression stroke, the suction valve 214 closes, and the gas remaining in the compression chamber 216 at that time is compressed and discharged. At the next suction stroke of the piston, the drive unit 62b is again driven, and the open state is released after the compression stroke of the piston 212 begins. This process is repeated in accordance with the reciprocating motion of the piston.

[0097] If the timing of this release is made earlier, the discharge amount increases, and if it is made later, the discharge amount decreases, so that it can perform the same function as the second spillback section 43. In other words, since the throughput of the subsequent compression stage 14 is adjusted according to the amount of change in pressure in the intermediate flow path 22 caused by the first control, the effect of reducing power is significant.

[0098] Although the description of other configurations, actions, and effects will be omitted, the descriptions of the first to fourth embodiments can be applied to the fifth embodiment.

[0099] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The present invention is not limited to the above-described embodiments, and various modifications and improvements can be made without departing from the spirit of the present invention.

[0100] For example, the compressor unit 10 shown in FIG. 1 may further include a leading compression stage 15 upstream of the first compression stage 12, as shown in FIG. 16. In this case, the first spillback section 18 is provided downstream of the first compression stage 12, which is the second compression stage from the beginning. Even with the configuration shown in FIG. 16, deterioration in the power of the compressor unit 10 can be suppressed more effectively than if hydrogen gas were to spill back from the discharge flow path 24 of the subsequent compression stage 14 to the suction flow path 21. The number of leading compression stages 15 may be two or more. This also applies to the other figures. [Explanation of symbols]

[0101] 10: Compressor unit 12: First compression stage 14: Subsequent compression stage 16: Crank mechanism 18: First spillback section 18a: First spillback channel 18b: First spillback valve 21: Suction passage 22: Intermediate flow path 23: Liquid hydrogen storage tank 24: Discharge flow path 24a: Branch point 26: Demand destination 29: Leak gas exhaust section 41: Adjustment means 43: Second spillback section 43a: Second spillback channel 43b: Second spillback valve 45: Upstream temperature sensor 46: Downstream temperature sensor 47: Pressure sensor 50: Control unit 50e: Stepless capacity adjustment control unit 52: Low-voltage demand destination 53: Low pressure gas discharge channel 54: Check valve 56: Switching method 58: Cooler section 59: Cooler switching means 61: Suction valve unloader 62: Drive unit 64b: Stepless capacity adjustment device

Claims

1. A reciprocating compressor unit that recovers boil-off hydrogen gas from a liquid hydrogen storage tank and supplies at least a portion of the recovered hydrogen gas to a demand destination including at least one of an engine, a power generation facility, or a boiler, a first compression stage for compressing hydrogen gas; one or more subsequent compression stages for further compressing the hydrogen gas discharged from the first compression stage; a crank mechanism that drives the first compression stage and the subsequent compression stage; a first spillback section including a first spillback flow path that returns hydrogen gas discharged from the first compression stage to the suction flow path, and a first spillback valve that adjusts the amount of spillback in the first spillback flow path; an adjusting means for adjusting the throughput of hydrogen gas through the subsequent compression stage; a pressure sensor disposed in an intermediate flow path between the first compression stage and the subsequent compression stage; an upstream temperature sensor disposed in the intake passage between a connection portion of the first spillback passage and the first compression stage; a control unit that controls the first spillback valve and the adjusting means; Equipped with The first compression stage and the subsequent compression stage each include: A cylinder portion; The piston and a piston rod connecting the piston to the crank mechanism; a rod packing that seals between the piston rod and the cylinder portion; Equipped with the first compression stage is air-cooled and oil-free; At least a portion of the subsequent compression stage has a leak gas discharge portion that returns leak gas from a rod packing to the suction flow path, The control unit A first control that refers to the suction temperature acquired by the upstream temperature sensor and controls the first spillback valve so that the suction temperature is within a predetermined temperature range; a second control for controlling the adjusting means so that the throughput of the subsequent compression stage is adjusted in accordance with the amount of change in pressure in the intermediate flow path caused by the first control; is executable, The compressor unit, 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. a downstream temperature sensor disposed in the intermediate flow path; a low-pressure gas discharge path that branches off from a branch point provided in the discharge flow path on the discharge side of the subsequent compression stage and that can discharge hydrogen gas to a low-pressure demander that can process hydrogen gas at a pressure lower than the hydrogen gas pressure required by the demander; a switching means provided in the low-pressure gas discharge path or the branch point; a check valve located downstream of the branch point; Equipped with The control unit When the temperature detected by the downstream temperature sensor is higher than a predetermined first temperature T1 that is higher than 0°C during startup, the switching means is controlled to be in a first switching state in which hydrogen gas discharged from the subsequent compression stage is circulated through the low-pressure gas discharge path; When the detected temperature of the downstream temperature sensor becomes lower than the first temperature T1, the switching means is controlled to enter a second switching state in which the hydrogen gas discharged from the subsequent compression stage is sent to the discharge flow path toward the demand destination. The compressor unit according to claim 1 , wherein the first control and the second control are executed on the condition that the switching means is in the second switching state.

3. a downstream temperature sensor disposed in the intermediate flow path; a cooler section provided between the first compression stage and the subsequent compression stage; a cooler switching means capable of switching between a path for allowing hydrogen gas to flow into the cooler section and a path for allowing hydrogen gas to flow into the subsequent compression stage without passing through the cooler section; Furthermore, The control unit When the temperature detected by the downstream temperature sensor is higher than a predetermined first temperature T1 that is higher than 0°C during startup, the cooler switching means is controlled to enter a first switching state in which the hydrogen gas discharged from the first compression stage flows through the cooler section and is cooled; When the temperature detected by the downstream temperature sensor becomes lower than the first temperature T1, the cooler switching means is controlled to enter a second switching state in which the hydrogen gas discharged from the first compression stage is sent to the subsequent compression stage without passing through the cooler unit; The compressor unit according to claim 1 , wherein the first control and the second control are executed on the condition that the cooler switching means is in the second switching state.

4. The adjusting means In at least one subsequent compression stage, a second spillback section including a second spillback flow path that returns hydrogen gas flowing through the discharge side of the subsequent compression stage to the suction side of the subsequent compression stage, and a second spillback valve that adjusts the amount of spillback in the second spillback flow path; a suction valve unloader attached to a cylinder portion of the subsequent compression stage; Equipped with 4. The compressor unit according to claim 1, wherein in the second control, the control unit controls the second spillback valve in accordance with a change in pressure in the intermediate flow path caused by the first control, and when the opening degree of the second spillback valve reaches a preset value, the control unit also drives the suction valve unloader to reduce the processing volume of the cylinder unit, thereby reducing the amount of gas returned to the suction side of the subsequent compression stage through the second spillback section.

5. The adjusting means In at least one subsequent compression stage, a suction valve unloader attached to a cylinder portion of the subsequent compression stage; a hydraulic or electric drive device for opening and closing the suction valve unloader; A stepless capacity adjusting device having the control unit drives the drive device so that the operation timing of the suction valve unloader is adjusted in conjunction with the rotational movement of a crankshaft in the crank mechanism, 4. The compressor unit according to claim 1, wherein in the second control, the control unit controls the drive device in accordance with a change in pressure in the intermediate flow path caused by the first control, and adjusts a throughput of the subsequent compression stage.

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