Compressor unit

Abstract

The compressor unit includes a first return valve, an adjustment unit that adjusts a hydrogen gas treatment amount in a subsequent compression stage, an upstream temperature sensor, and a control unit. The control unit is capable of executing: a first control for controlling the first return valve so that the suction temperature is within a predetermined temperature range by referring to the suction temperature acquired by the upstream-side temperature sensor; and a second control for controlling the adjustment means in such a manner that the amount of throughput of the subsequent compression stage is adjusted in accordance with the amount of pressure change in the intermediate flow path generated by the first control. The predetermined temperature range is set in a range higher than a reference temperature based on the liquefaction temperature of the air and lower than 0 DEG C.

Description

Technical Field

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

[0002] In recent years, research has been underway to use hydrogen as a fuel for power generation and automobiles, etc., for environmental reasons, and the demand for hydrogen is increasing. In addition, low-temperature boil-off gas (BOG) such as liquefied natural gas (LNG) and liquid hydrogen (LH2) is recovered by a compressor and supplied to demanders such as engines. In particular, the boil-off gas generated by LH2 has a very low temperature. Therefore, if a structure is adopted in which the compressor directly absorbs the boil-off gas, it is necessary to select materials suitable for extremely low temperatures, or to adopt design conditions that take into account thermal deformation or to implement strict thermal insulation treatment, etc., which is limited. For example, the following patent document 1 discloses a reciprocating compressor for compressing hydrogen.

[0003] In addition, the following patent document 2 Figure 9 Disclosed is a tandem screw compressor unit capable of compressing hydrogen. The compressor unit is equipped with an intermediate-stage return valve and a post-stage return valve. The intermediate-stage return valve is controlled based on the pressure detected by a pressure sensor located in the intermediate stage, while the post-stage return valve is controlled based on the pressure detected by a pressure sensor located in the discharge flow path.

[0004] Patent Document 3 below discloses a multi-stage compressor for compressing boil-off gas from liquefied natural gas. This multi-stage compressor includes a cooler between the low-pressure stage compressor and the high-pressure stage compressor. The cooler is used when the temperature of the gas discharged from the low-pressure stage compressor rises.

[0005] Patent Document 1, listed below, points out the following problem: "In recent years, hydrogen has attracted considerable 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 use with natural gas were directly adapted for use with hydrogen, the extremely low temperature of the liquid hydrogen could cause problems. For example, liquefied air could form around the equipment supplying the liquid hydrogen."

[0006] Patent Document 1 explains this as follows: "In this reciprocating compressor, a compression section for compressing gas is housed within a container. Furthermore, the container forms a vacuum region around the compression section. Thus, the compression section is thermally isolated from the outside by the vacuum region. In other words, even when extremely low-temperature gas is supplied to the compression section, the area surrounding the reciprocating compressor is not excessively cooled. Consequently, the generation of liquefied air can be suppressed."

[0007] However, achieving high-performance thermal insulation is generally very difficult for power machinery that generates vibrations during operation and equipment that requires regular maintenance through inspection openings (such as reciprocating compressors). Therefore, the technology disclosed in Patent Document 1 is difficult to properly protect reciprocating compressor units.

[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. 4-12178 Summary of the Invention

[0013] An object of the present invention is to appropriately protect a reciprocating compressor unit from boil-off gas of cryogenic liquid hydrogen.

[0014] One aspect of the present invention relates to a compressor unit that is a reciprocating compressor unit as follows: the compressor unit recovers evaporated gas, i.e., hydrogen, from a liquid hydrogen storage tank and supplies at least a portion of the hydrogen to a demander including at least one of an engine, a power generation device and a boiler, and includes: a first compression section that compresses the hydrogen; one or more subsequent compression sections that further compress the hydrogen discharged from the first compression section; a crank mechanism that drives the first compression section and the subsequent compression sections; a first reflux section that includes: a first reflux flow path for returning a portion of the hydrogen discharged from the first compression section to an intake flow path; and a first reflux valve that adjusts the reflux amount in the first reflux flow path; a regulating unit that adjusts the hydrogen processing amount of the subsequent compression section; a pressure sensor that is arranged in an intermediate flow path between the first compression section and the subsequent compression section; an upstream temperature sensor that is arranged in the intake flow path between the connection portion of the first reflux flow path and the first compression section; and a control section that controls the first reflux valve and the regulating unit, respectively. The first compression stage and the subsequent compression stage each include: a cylinder; a piston; a piston rod connecting the piston to the crank mechanism; and a rod seal sealing the piston rod and the cylinder. The first compression stage is air-cooled and oil-free. At least a portion of the subsequent compression stage has a leakage gas discharge portion that returns leakage gas from the rod seal to the intake flow path. The control unit is capable of performing the following controls: a first control for controlling the first return valve with reference to the intake temperature acquired by the upstream temperature sensor so that the intake temperature falls within a predetermined temperature range; and a second control for controlling the regulating unit so that the processing volume of the subsequent compression stage is adjusted according to the pressure change in the intermediate flow path generated by the first control. The predetermined temperature range is set to a range that is higher than a reference temperature based on the liquefaction temperature of air and lower than 0°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the compressor unit according to the first embodiment.

[0016] Figure 2 It is a schematic diagram of the first compression section in the compressor unit.

[0017] Figure 3 is a schematic diagram of a subsequent compression section in the compressor train.

[0018] Figure 4 It is a diagram for explaining the operation of the compressor unit.

[0019] Figure 5 It is a schematic diagram of a compressor unit according to a modified example of the first embodiment.

[0020] Figure 6 It is a schematic diagram of a compressor unit according to a modified example of the first embodiment.

[0021] Figure 7 It is a schematic diagram of a compressor unit according to a modified example of the first embodiment.

[0022] Figure 8 It is a schematic diagram of a compressor unit according to a second embodiment.

[0023] Figure 9 It is a diagram for explaining the operation of the compressor unit.

[0024] Figure 10 It is a schematic diagram of a compressor unit according to a third embodiment.

[0025] Figure 11 It is a diagram for explaining the operation of the compressor unit.

[0026] Figure 12 It is a schematic diagram of a compressor unit according to a fourth embodiment.

[0027] Figure 13 It is a diagram for explaining the operation of the compressor unit.

[0028] Figure 14 It is a diagram for explaining the operation of the compressor unit.

[0029] Figure 15 It is a schematic diagram of a compressor unit according to a fifth embodiment.

[0030] Figure 16 It is a schematic diagram of a compressor unit according to another embodiment. DETAILED DESCRIPTION

[0031] Hereinafter, the embodiment will be described with reference to the drawings. Note that the following embodiment is an example of a specific embodiment of the present invention and does not limit the technical scope of the present invention.

[0032] (First embodiment)

[0033] The compressor unit according to this embodiment recovers boil-off gas (hydrogen) from a liquid hydrogen storage tank, compresses the recovered hydrogen, and supplies it to a customer. The boil-off gas (hydrogen) has a temperature of approximately -253°C.

[0034] like Figure 1 As shown, the compressor unit 10 includes: a first compression stage 12 for compressing hydrogen in the suction flow path 21; a subsequent compression stage 14 connected to the first compression stage 12 via an intermediate flow path 22; and a crank mechanism 16 for driving the first compression stage 12 and the subsequent compression stage 14.

[0035] The first compression stage 12 is connected to the liquid hydrogen storage tank 23 via the intake flow path 21 . Therefore, boil-off gas generated from the liquefied gas in the liquid hydrogen storage tank 23 is sucked into the first compression stage 12 through the intake flow path 21 .

[0036] The first compression section 12 includes a reciprocating compression mechanism. Figure 2 As shown, the first compression stage 12 comprises a cylinder 211; a piston 212 disposed within the cylinder 211; a piston rod 213 connected to the piston 212; a pair of intake valves 214; and a pair of discharge valves 215. Compression chambers 216 are formed within the cylinder 211, between the front cover 211a and the piston 212, and between the rear cover 211b and the piston 212. The first compression stage 12 is air-cooled and includes a non-lubricated compression mechanism that does not utilize lubricating oil.

[0037] A rod seal 217 is provided on the rear cover 211b of the cylinder 211 to prevent hydrogen gas from leaking from the compression chamber 216. The rod seal 217 is configured to seal between the piston rod 213 and the cylinder 211. The rod seal 217 includes a seal ring 217a disposed around the piston rod 213 and a housing 217b that holds the seal ring 217a.

[0038] The piston 212 is connected to the crank mechanism 16 via the piston rod 213. As the piston 212 reciprocates in the cylinder 211, hydrogen is compressed in the compression chamber 216. Figure 2 2 shows the first compression section 12 of a double-acting structure, but the first compression section 12 may also adopt a single-acting structure in which a compression chamber is provided only on the front cover side or the rear cover side.

[0039] In addition, Figure 1 In the figure, the first compression stage 12 is shown as a trapezoid for convenience. However, the first compression stage 12 may include multiple cylinders 211 instead of just one cylinder 211. In other words, the first compression stage 12 may also be configured such that the hydrogen gas is compressed and pressurized by pistons 212 in each of the multiple cylinders 211 connected in parallel. This is also true for other embodiments.

[0040] The subsequent compression stage 14 is a compression mechanism for further compressing the hydrogen discharged from the first compression stage. The hydrogen compressed by the subsequent compression stage 14 is discharged into a discharge flow path 24. The hydrogen flowing through the discharge flow path 24 is delivered directly or indirectly through other equipment to a consumer 26. Examples of the consumer 26 include power generation equipment, boilers, and engines such as ships. Other examples include flame equipment, exhaust ports, and other equipment that releases gas to the atmosphere.

[0041] like Figure 3As shown, the subsequent compression stage 14, like the first compression stage 12, includes a reciprocating compression mechanism. The 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 has the same configuration as the first compression stage 12, but is further provided with a leakage gas discharge portion 29 that returns leakage gas from the rod seal 217 to the suction flow path 21. The leakage gas discharge portion 29 may also include a pipe member that is provided to connect the rod seal 217 and the suction flow path 21.

[0042] In addition, Figure 1 For convenience, the subsequent compression stage 14 is depicted as a trapezoid. However, the subsequent compression stage 14 does not necessarily need to be a single-stage type and may also include a multi-stage compression mechanism. Specifically, the subsequent compression stage 14 may employ a configuration in which pistons 212 in each of multiple cylinders 211 sequentially compress hydrogen gas to increase its pressure. This is also true for other embodiments. In the subsequent compression stage 14, the compression stage that discharges room-temperature hydrogen gas may be either oil-free or lubricated.

[0043] like Figure 1 As shown, the compressor unit 10 includes a first reflux portion 18 that returns a portion of the hydrogen gas discharged from the first compression section 12 to the suction flow path 21. The first reflux portion 18 includes: a first reflux flow path 18a; and a first reflux valve 18b formed by a valve that is arranged in the first reflux flow path 18a and can adjust the opening. One end of the first reflux flow path 18a is connected to the intermediate flow path 22, and the other end is connected to the suction flow path 21. That is, the hydrogen gas flowing through the first reflux flow path 18a merges with the hydrogen gas from the liquid hydrogen storage tank 23 in the suction flow path 21. The first reflux valve 18b adjusts the reflux amount (the flow rate in the first reflux flow path 18a) in the first reflux flow path 18a.

[0044] The compressor unit 10 includes a regulating unit 41 for adjusting the hydrogen processing capacity of the subsequent compression stage 14. The regulating unit 41 is a unit that adjusts the gas processing capacity by a method other than adjusting the number of revolutions of the crank mechanism 16. In this embodiment, the regulating unit 41 includes a reflux section (a second reflux section 43) that adjusts the hydrogen processing capacity and thereby adjusts the gas flow rate sent from the subsequent compression stage 14 to the demander 26.

[0045] The second reflux section 43 includes a second reflux passage 43a and a second reflux valve 43b, which is a valve disposed in the second reflux passage 43a and has an adjustable opening. One end of the second reflux 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 reflux valve 43b adjusts the reflux amount (the flow rate in the second reflux passage 43a) in the second reflux passage 43a.

[0046] The intake passage 21 is provided with a temperature sensor (upstream temperature sensor 45) for detecting the temperature of the hydrogen gas flowing through the intake passage 21. The upstream temperature sensor 45 is positioned in the intake passage 21 between the connection between the first recirculation passage 18a and the first compression stage 12. Therefore, when hydrogen flows through the first recirculation passage 18a, the upstream temperature sensor 45 can detect the temperature of the hydrogen gas, which is the result of the merging of the hydrogen gas from the first recirculation passage 18a and the hydrogen gas from the liquid hydrogen storage tank 23, i.e., the hydrogen gas being drawn into the first compression stage 12.

[0047] A pressure sensor 47 is provided in the intermediate flow passage 22 for detecting the pressure of the hydrogen gas flowing through the intermediate flow passage 22. The pressure sensor 47 is located between the connection portion of the first reflux flow passage 18a and the subsequent compression stage 14 in the intermediate flow passage 22. Therefore, the pressure sensor 47 can detect the pressure of the hydrogen gas after pressure regulation by the first reflux section 18, that is, the pressure of the hydrogen gas introduced into the subsequent compression stage 14.

[0048] 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. The functions of the control unit 50 executed by the 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 return valve 18b with reference 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 regulating unit 41 based on the detected pressure of the pressure sensor 47.

[0049] Here, refer to Figure 4 The operation of the compressor unit 10 according to this embodiment will be described.

[0050] The crank mechanism 16 operates to reciprocate the piston 212 within the cylinder 211 in the first compression stage 12 and the subsequent compression stage 14. As a result, hydrogen gas from the intake passage 21 is drawn into the first compression stage 12 and compressed there. Furthermore, hydrogen gas from the intermediate passage 22 is drawn into the subsequent compression stage 14 and compressed there (step ST11).

[0051] When the first compression stage 12 is operating, the upstream temperature sensor 45 obtains the temperature of the hydrogen gas drawn into the first compression stage 12 (intake temperature TS2) (step ST12). At this time, the first control unit 50a refers to the intake temperature TS2 and executes a first control of the first return valve 18b so that the intake temperature TS2 falls within a predetermined temperature range (TTH1 ≤ TS2 ≤ TTH2) (step ST13).

[0052] More specifically, in the first control, when TS2 < TTH1, the first control unit 50a controls the first reflux valve 18b such that a part of the gas in the intermediate flow path 22 is returned to the suction flow path 21 or the amount of the returned gas is increased. Accordingly, the suction temperature TS2 falls within the above temperature range. In addition, 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 the returned gas is reduced.

[0053] Here, the predetermined temperature range is set in a range higher than the reference temperature based on the liquefaction temperature of air and lower than 0°C. That is, the lower limit value TTH1 and the upper limit value TTH2 of the predetermined temperature range are set in a range higher than the above reference temperature and lower than 0°C. In addition, the reference temperature may be a temperature within a specified range relative to the liquefaction temperature of air (for example, from the liquefaction temperature of air to the liquefaction temperature of air + 50°C).

[0054] Thereby, the temperature of the hydrogen gas sucked into the first compression stage 12, that is, the suction temperature TS2, can be made to be within an appropriate range. In the first compression stage 12, hydrogen gas from the liquid hydrogen storage tank 23 is not directly introduced, but hydrogen gas that is heated by converging a part of the hydrogen gas compressed in the first compression stage 12 is introduced. Therefore, it is possible to prevent the first compression stage 12 from coming into contact with 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 a range lower than 0°C, it is also possible to prevent the density of the hydrogen gas sucked into the first compression stage 12 from being excessively reduced.

[0055] 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, 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).

[0056] At this point, the second control unit 50b executes a second control of the regulating unit 41 (step ST15) to adjust the processing capacity of the subsequent compression stage 14 based on the change in the gas pressure (intermediate pressure) in the intermediate flow path 22 generated by the first control. Specifically, during the second control, the second control unit 50b controls the second return valve 43b to increase its opening by a specified value when the pressure detected by the pressure sensor 47 is below the target value; and controls the second return valve 43b to decrease its opening by a specified value when the pressure detected is above the target value. This ensures that the pressure at the intake port of the subsequent compression stage 14 falls within a specified range, thereby suppressing excessive compression in the subsequent compression stage 14. The hydrogen compressed in the subsequent compression stage 14 is delivered to the consumer via the discharge flow path 24.

[0057] As described above, in this embodiment, the compressor unit 10 can be protected in a low-temperature environment, thereby contributing to the stable recovery of hydrogen. Specifically, in the first control, since the flow rate of hydrogen returned to the intake flow path 21 is adjusted by the first reflux unit 18, the intake temperature TS2 of the hydrogen gas sucked into the first compression stage 12 can be adjusted. In addition, the temperature range of the hydrogen gas sucked into the first compression stage 12 is adjusted to be higher than the reference temperature based on the liquefaction temperature of air. Therefore, the liquefaction of oxygen used as an auxiliary gas in the intake portion or intake flow path 21 of the first compression stage 12 can be avoided. In other words, the liquefaction of oxygen on the outer surface of the hydrogen inflow portion (around the device to which hydrogen is supplied) can be avoided. In addition, since the intake temperature TS2 is adjusted to a predetermined temperature range that is higher than the reference temperature based on the liquefaction temperature of air and lower than 0°C, the reduction in hydrogen processing efficiency can be suppressed.

[0058] Furthermore, the first reflux portion 18 bypasses only the first compression stage 12. Therefore, compared to a case where hydrogen is refluxed from the discharge flow path 24 of the subsequent compression stage 14 to the intake flow path 21, that is, a case where the hydrogen gas with the highest pressure is returned to the intake flow path 21, deterioration in the power of the compressor unit 10 can be suppressed.

[0059] Furthermore, since at least the first compression stage 12 employs an oil-free design, the risk of oil freezing is avoided. Furthermore, while the pressure increases with subsequent compression stages, hydrogen is more likely to leak. However, hydrogen leaking in the subsequent compression stage 14 is recovered by the leaked gas discharge unit 29 into the intake flow path 21, thus minimizing product gas loss during compression. This contributes to efficient hydrogen recovery. Alternatively, the leaked gas discharge unit 29 may also be provided in the first compression stage 12.

[0060] in addition, Figure 1The subsequent compression section 14 of the compressor unit 10 shown in FIG has a single-stage compression mechanism, but as mentioned above, it is also possible to have a compression mechanism with multiple compression stages. In this case, for example, Figure 5 As shown, the second reflux portion 43 may be provided only in the frontmost compression mechanism in the subsequent compression section 14, or as shown in FIG. Figure 6 As shown, the second return flow path 43a may be used to bypass all compression mechanisms of the subsequent compression stage 14, or as shown in FIG. Figure 7 As shown, a second reflux portion 43 may be provided for each compression mechanism in the subsequent compression stage 14. The compressor unit 10 may adopt a so-called series structure, that is, the first compression stage 12 and the subsequent compression stage 14 are arranged along the extension direction of the piston rod.

[0061] (Second embodiment)

[0062] like Figure 8 As shown, the compressor unit 10 of the second embodiment differs from the first embodiment in that a temperature sensor (downstream temperature sensor 46) for detecting the temperature of the hydrogen gas flowing through the intermediate flow path 22 is provided in the intermediate flow path 22, and a low-pressure gas discharge passage 53 capable of discharging the hydrogen gas to a low-pressure demander 52 is also provided. The same reference numerals are attached to the same components as those of the first embodiment, and their detailed descriptions are omitted.

[0063] As the low-pressure demander 52, any device can be used as long as it can process hydrogen at a pressure lower than the hydrogen pressure required by the demander 26. For example, a flame device, an exhaust port, or other device that releases gas to the atmosphere, as well as other devices that are used to supply pressure at approximately atmospheric pressure, can be used.

[0064] The low-pressure gas discharge passage 53 branches off from the discharge flow path 24. A check valve 54 is provided in the discharge flow path 24, downstream of the branch point 24a where the low-pressure gas discharge passage 53 branches off. This check valve 54 allows hydrogen gas to flow from the branch point 24a toward the consumer 26, while preventing hydrogen gas from flowing in the opposite direction. This prevents hydrogen gas from flowing back from the consumer 26 to the branch point 24a and into the low-pressure gas discharge passage 53.

[0065] The compressor unit 10 is provided with a switching unit 56 for switching the flow state of hydrogen gas in the low-pressure gas discharge passage 53. The switching unit 56 includes an on-off valve 56a and is disposed in the low-pressure gas discharge passage 53. The switching unit 56 switches the flow state of hydrogen gas in the low-pressure gas discharge passage 53 between a first switching state, in which hydrogen gas discharged from the subsequent compression stage 14 flows to the low-pressure gas discharge passage 53, and a second switching state, in which hydrogen gas discharged from the subsequent compression stage 14 is not discharged to the low-pressure gas discharge passage 53 but is instead delivered to the demander 26 via the discharge flow path 24. In the first switching state, the on-off valve 56a is open, allowing hydrogen gas to flow to the low-pressure gas discharge passage 53. Meanwhile, although the hydrogen pressure at the demander 26 is higher than that at the low-pressure demander 52, the check valve 54 prevents hydrogen gas from flowing to the demander 26. In the second switching state, the on-off valve 56a is closed, and the hydrogen gas does not flow into the low-pressure gas discharge passage 53. Therefore, the hydrogen gas discharged from the subsequent compression stage 14 is delivered to the demander 26.

[0066] Furthermore, the switching unit 56 is not limited to the on-off valve 56a provided in the low-pressure gas discharge passage 53. For example, the switching unit 56 may comprise a three-way valve (not shown) and be provided at the branch point 24a. In this case, the three-way valve can be in either a state where the hydrogen discharged from the subsequent compression stage 14 flows to the demand side 26 (a second switching state) or a state where the hydrogen discharged from the subsequent compression stage 14 flows to the low-pressure demand side 52 (a first switching state).

[0067] The functions of the control unit 50 include a switching control unit 50 c that controls the switching unit 56 .

[0068] During startup of the compressor unit 10, when the temperature TS1 detected by the downstream temperature sensor 46 is higher than a predetermined first temperature T1 (this first temperature T1 is higher than 0°C), the switching control unit 50c controls the switching unit 56 to enter a first switching state. When the switching unit 56 is in the first switching state, hydrogen discharged from the subsequent compression stage 14 is allowed to flow through the low-pressure gas discharge passage 53, thereby discharging low-pressure hydrogen from the subsequent compression stage 14. Consequently, during startup, if the intake gas temperature in the subsequent compression stage 14 is high, the compressor can be protected from the effects of an excessive increase in discharge temperature due to boosting the pressure to a higher level.

[0069] Furthermore, when the temperature TS1 detected by the downstream temperature sensor 46 is lower than the first temperature T1, the switching control unit 50c controls the switching unit 56 so that it enters the second switching state. When the switching unit 56 is in the second switching state, hydrogen gas does not flow into the low-pressure gas discharge passage 53. Therefore, the hydrogen gas discharged from the subsequent compression stage 14 flows to the demander 26 via the discharge flow path 24. In this case, the pressure of the hydrogen gas discharged from the subsequent compression stage 14 is 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.

[0070] Here, refer to Figure 9 The operation of the compressor unit 10 according to this embodiment will be described.

[0071] When the compressor unit 10 starts up, hydrogen compression begins in the first compression stage 12 (step ST21). During the startup of the compressor unit 10, the temperature of the piping from the liquid hydrogen storage tank 23 to the first compression stage 12 may sometimes reach room temperature. Therefore, during the startup of the compressor unit 10, the switching unit 56 is switched to the first switching state. Consequently, hydrogen discharged from the subsequent compression stage 14 is delivered to the low-pressure demander 52 via the low-pressure gas discharge passage 53 (step ST22).

[0072] In this state, a determination is made as to whether the temperature TS1 detected by the downstream temperature sensor 46 is lower than the first temperature T1 (step ST23). As long as the detected temperature TS1 is higher than the first temperature T1 (no in step ST23), step ST23 is repeatedly executed. If the detected temperature TS1 is lower than the first temperature T1 (yes in step ST23), the switching control unit 50c of the control unit 50 controls the switching unit 56 to enter the second switching state (step ST24). Consequently, the flow of hydrogen discharged from the subsequent compression stage 14 to the low-pressure gas discharge passage 53 (startup operation) ceases, and steady-state operation is resumed, with hydrogen being supplied to the demander 26.

[0073] During steady-state operation, the temperature of the hydrogen gas drawn into the first compression stage 12 (intake temperature TS2) is acquired by the upstream temperature sensor 45 (step ST12). At this time, the first control unit 50a refers to the intake temperature TS2 and, similarly to the first embodiment, executes the first control of the first recirculation valve 18b (step ST13).

[0074] By performing the first control, the flow rate of hydrogen gas discharged from the first compression stage 12 and introduced into the subsequent compression stage 14 changes. Therefore, the pressure sensor 47 detects the pressure (intermediate pressure) of the hydrogen gas introduced into the subsequent compression stage 14 (step ST14). At this time, the second control unit 50b, similar to the first embodiment, performs the second control of controlling the adjustment unit 41 so that the processing capacity of the subsequent compression stage 14 is adjusted according to the amount of change in the pressure (intermediate pressure) in the intermediate flow path 22 caused by the first control (step ST15).

[0075] Therefore, in the present embodiment, during startup and when the hydrogen in the piping on the side of the liquid hydrogen storage tank 23 rises to a positive temperature range (a temperature range higher than 0°C), the hydrogen discharged from the subsequent compression section 14 is sent to the low-pressure demand side 52. Therefore, it is possible to more effectively prevent the hydrogen temperature in the subsequent compression section 14 from rising excessively. That is, in the reciprocating compressor unit 10, hydrogen of a pressure corresponding to the pressure set according to the hydrogen supply destination is sent out. Therefore, by controlling the switching unit 56 in such a way as to send hydrogen to the low-pressure demand side 52, the compressor is protected from the influence of excessive rise in discharge temperature caused by the exhaust gas pressure of the subsequent compression section 14 being reduced and thus increased to a higher pressure. Accordingly, the subsequent compression section 14 can be protected more reliably. In addition, the startup work of the compressor unit 10 can also be performed quickly. In addition, the compressor unit 10 can be protected in a low-temperature environment.

[0076] In addition, although the description of other configurations, functions, and effects is omitted, the description of the first embodiment can be applied to the second embodiment.

[0077] (Third embodiment)

[0078] like Figure 10 As shown, the compressor unit 10 of the third embodiment differs from the first embodiment in that a cooler portion 58 and a cooler switching unit 59 are provided. Components identical to those of the first embodiment are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0079] The cooler section 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 flow paths (the first flow path 22a and the second flow path 22b) that branch at a midpoint thereof, and the cooler section 58 is disposed in one of the flow paths (the first flow path 22a).

[0080] The cooler switching unit 59 is capable of switching the path of the hydrogen between a first switching state and a second switching state, wherein the first switching state is a state in which the hydrogen discharged from the first compression section 12 flows into the subsequent compression section 14 via the cooler portion 58, and the second switching state is a state in which the hydrogen flows into the subsequent compression section 14 without passing through the cooler portion 58. The cooler switching unit 59 includes a first on-off valve 59a provided in the first flow path 22a and a second on-off valve 59b provided in the second flow path 22b. In addition, the cooler switching unit 59 is not limited to a configuration having two on-off valves 59a and 59b. For example, the cooler switching unit 59 may have a three-way valve arranged at the connection portion between the first flow path 22a and the second flow path 22b.

[0081] The connection portion of the first return flow path 18a in the intermediate flow path 22 may be located upstream or downstream of the connection portion between 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.

[0082] The functions of the control unit 50 include a cooler control unit 50 d capable of switching and controlling a cooler switching unit 59 .

[0083] During startup, when the temperature TS1 detected by the downstream temperature sensor 46 is higher than a predetermined first temperature T1 (the first temperature T1 is higher than 0° C.), the cooler control unit 50 d controls the cooler switching unit 59 so that hydrogen gas flows to the cooler unit 58. Specifically, when the temperature TS1 detected by the downstream temperature sensor 46 is higher than the first temperature T1, the cooler switching unit 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.

[0084] Furthermore, the cooler control unit 50 d controls the cooler switching means 59 so that hydrogen gas does not flow into the cooler unit 58 when the temperature TS1 detected by the downstream temperature sensor 46 is lower than the first temperature T1 .

[0085] Here, refer to Figure 11 The operation of the compressor unit 10 according to this embodiment will be described.

[0086] When the compressor train 10 starts up, hydrogen compression begins in the first compression stage 12 (step ST31). During the startup of the compressor train 10, the temperature of the piping from the liquid hydrogen storage tank 23 to the first compression stage 12 may sometimes reach room temperature. Therefore, during the startup of the compressor train 10, the cooler switching unit 59 is switched to the first switching state. Consequently, hydrogen 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 then is introduced into the subsequent compression stage 14 (step ST32).

[0087] In this state, it is determined whether the temperature TS1 detected by the downstream temperature sensor 46 is lower than the first temperature T1 (step ST33). As long as the detected temperature TS1 is higher than the first temperature T1 (no in step ST33), step ST33 is repeatedly executed. If the detected temperature TS1 is lower 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 so that the cooler switching unit 59 enters the second switching state (step ST34). Accordingly, the state in which the hydrogen discharged from the first compression stage 12 is cooled by the cooler unit 58 (start-up operation) is stopped, and the state becomes a steady-state operation in which the hydrogen discharged from the first compression stage 12 is not cooled by the cooler unit 58 and is introduced into the subsequent compression stage 14.

[0088] During steady-state operation, the temperature of the hydrogen gas drawn into the first compression stage 12 (intake temperature TS2) is acquired by the upstream temperature sensor 45 (step ST12). At this point, the first control unit 50a executes the first control (step ST13) similar to the first embodiment. This allows the intake temperature TS2 of the hydrogen gas drawn into the first compression stage 12 to be within an appropriate range.

[0089] By performing the first control, the flow rate of hydrogen gas introduced into the subsequent compression stage 14 from the hydrogen gas discharged from the first compression stage 12 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 of controlling the regulating unit 41 in the same manner as in the first embodiment (step ST15).

[0090] Therefore, according to this embodiment, during startup and when the hydrogen gas in the piping on the liquid hydrogen storage tank 23 side rises to a positive temperature range, the cooler unit 58 cools the hydrogen gas discharged from the first compression stage 12. This prevents the hydrogen gas temperature in the subsequent compression stage 14 from rising excessively. This contributes to stable hydrogen recovery. In other words, the subsequent compression stage 14 can be protected. Furthermore, the startup operation of the compressor unit 10 can be performed quickly. Furthermore, the compressor unit 10 can be protected in low-temperature environments.

[0091] In addition, although the description of other configurations, functions, and effects is omitted, the description of the first and second embodiments can be applied to the third embodiment.

[0092] (Fourth embodiment)

[0093] like Figure 12As shown, the compressor unit 10 according to the fourth embodiment differs from the first embodiment in that the regulating unit 41 includes a second reflux portion 43, an on-off type suction valve unloader 61, and a driving device 62. The same reference numerals are used for the same components as those in the first to third embodiments, and detailed descriptions thereof are omitted.

[0094] When the intake valve unloader 61 is driven by the drive device 62, the valve plate of the intake valve 214 is maintained in an open position, rendering the check valve inoperable. Specifically, when the unloader 61 is not driven and the piston 212 is in the intake stroke, the pressure in the compression chamber 216 is lower than the pressure in the intake passage, or intermediate flow path 22, and the intake valve 214 is therefore open. This allows gas to flow into the compression chamber 216. On the other hand, when the piston 212 is in the compression stroke, the pressure in the compression chamber 216 is higher than the pressure in the intermediate flow path 22, and the intake valve 214 is therefore closed. Consequently, when the intake valve unloader 61 is driven by the drive device 62, the check valve becomes inoperable.

[0095] The regulating unit 41 is provided in at least one subsequent compression stage 14, and the suction valve unloader 61 is mounted on the suction valve 214 of the subsequent compression stage 14. The suction valve unloaders are mounted in the front cover-side compression chamber and the rear cover-side compression chamber of the cylinder portion 211, respectively, and are capable of independent operation. A state in which both unloads are inoperative is referred to as 100% load, while a state in which one unloads is inoperative is referred to as 50% load.

[0096] The suction valve unloader 61 is driven by a driving device 62 using a gas such as air or nitrogen. The suction valve unloader 61 is driven by the driving device 62, thereby opening the suction valve 214 (see Figure 3 ) is set to a state where the compression chamber 216 is opened and closed relative to the intake passage 21 in response to the pressure differential between the compression chamber 216 and the intake passage 21 (a loaded state), or a state where the compression chamber 216 and the intake passage 21 are maintained open (unloaded state). For example, if a gas such as air or nitrogen is not applied to the driving device 62, the intake valve unloader 61 sets the intake valve 214 to a free state, allowing the compression chamber 216 to be opened and closed in response to the pressure differential between the compression chamber 216 and the intake passage 21. On the other hand, if a gas such as air or nitrogen is applied to the driving device 62, the compression chamber 216 should be closed in response to the pressure differential between the compression chamber 216 and the intake passage 21. However, the intake valve unloader 61 forcibly maintains the intake valve 214 in an open state.

[0097] Furthermore, a signal indicating the state of the intake valve unloader 61 and the opening signal of the second return valve 43b are transmitted to the control unit 50 and utilized for control within the control unit 50. Specifically, the control unit 50 estimates the amount of gas to be recirculated based on the opening of the second return valve 43b. If the opening of the second return valve 43b exceeds a preset opening threshold (e.g., approximately 50%), the control unit 50 uses the intake valve unloader 61 to reduce the load of the subsequent compression stage 14 to 50%. This reduces the discharge volume of the subsequent compression stage 14, thereby reducing the amount of recirculation in the second recirculation section 43. Consequently, the power of the subsequent compression stage 14 can be reduced compared to when the intake valve 214 is in the free state.

[0098] like Figure 13 As shown, the first control unit 50a of the control unit 50 refers to the intake temperature TS2 and executes a first control to control the first recirculation valve 18b so that the intake temperature TS2 falls within a predetermined temperature range (step ST13). This first control changes the flow rate of hydrogen gas discharged from the first compression stage 12 and introduced into the subsequent compression stage 14. 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).

[0099] The second control unit 50b of the control unit 50 controls the second return valve 43b based on the pressure change in the intermediate flow path 22 caused by the first control (step ST15). For example, if the pressure detected by the pressure sensor 47 is lower than the target value, the second return valve 43b is controlled to increase its opening by a specified value. Furthermore, the second control unit 50b controls the drive device 62 so that when the opening of the second return valve 43b reaches a preset value, the intake valve unloader 61 is also driven (step ST16).

[0100] Specifically, if Figure 14As shown, the control unit 50 compares the opening of the second return valve 43b input to the control unit 50 with a preset opening threshold b1. If the state (valve opening) of the second return valve 43b exceeds the opening threshold b1 (a large amount of backflow) (YES in step ST41), the control unit 50 controls the drive unit 62 to reduce the load on the intake valve unloader 61 (e.g., the intake valve unloader on the front cover side) (step ST42). This reduces the load on the subsequent compression stage 14 (from 100% to 50%). If the opening of the second return valve 43b is less than the opening threshold b2 (YES in step ST43), the control unit 50 controls the drive unit 62 to increase the load on the intake valve unloader 61 (step ST44). This increases the load on the subsequent compression stage 14 (from 50% to 100%). This allows power reduction by reducing the load on the subsequent compression stage 14 in the event of excessive backflow.

[0101] In addition, although the description of other configurations, functions, and effects is omitted, the description of the first to third embodiments can be applied to the fourth embodiment.

[0102] (Fifth embodiment)

[0103] In the fourth embodiment, the regulating unit 41 includes the second reflux portion 43, the on-off type suction valve unloader 61, and the driving device 62. In contrast, the compressor unit 10 according to the fifth embodiment is as follows. Figure 15 As shown, the regulating unit 41 does not include the second reflux unit 43 but instead includes a stepless capacity adjustment device 64b. The control unit 50 includes a stepless capacity adjustment control unit 50e capable of controlling the stepless capacity adjustment device 64b. Components identical to those in the first to fourth embodiments are denoted by the same reference numerals, and detailed descriptions thereof are omitted.

[0104] The stepless capacity adjustment device 64b includes a suction valve unloader 61b, a drive device 62b, and a detector 63b for detecting the rotation of the crankshaft of the crank mechanism 16. The suction valve unloader 61b is driven by a hydraulic or electrical drive device 62b and can maintain or release the valve plate of the suction valve 214 in an open state in a time shorter than the time required for the reciprocating motion of the piston 212. Furthermore, the control unit 50 performs computational processing to estimate the position of the piston 212 based on a signal transmitted from the detector 63b provided in the crank mechanism 16.

[0105] In the cylinder portion 211 of the subsequent compression stage 14, an intake valve 214, located between the intermediate flow path 22 (the suction-side flow path) and the compression chamber 216, comprises a valve plate that opens and closes the gas passage, and a valve body that houses the valve plate. Like a check valve, intake valve 214 employs a structure where, when the upstream pressure is higher than the downstream pressure, the valve plate opens due to the resulting pressure difference. When the downstream pressure is higher, gas is not allowed to flow.

[0106] When the intake valve unloader 61b is driven by the drive device 62b, the valve plate of the intake valve 214 is maintained in an open position, rendering the check valve inoperable. Furthermore, when the unloader 61b is not driven and the piston 212 is in the intake stroke, the pressure in the compression chamber 216 is lower than the pressure in the intermediate flow path 22, the intake passage, and therefore the intake valve 214 is open. This allows gas to be introduced into the compression chamber 216. On the other hand, when the piston 212 is in the compression stroke, the pressure in the compression chamber 216 is higher than the pressure in the intermediate flow path 22, and therefore the intake valve 214 is closed.

[0107] The stepless capacity adjustment control unit 50e of the control unit 50 drives the drive device 62b in such a way that the timing of the operation of the intake valve unloader 61b is adjusted in conjunction with the rotational movement of the crankshaft in the crank mechanism 16. Specifically, in the initial stage after the start of the compression stroke, the stepless capacity adjustment device 64b maintains the intake valve 214 in an open state. As a result, a portion of the gas introduced into the compression chamber 216 is returned to the intermediate flow path 22. Furthermore, midway through the compression stroke, the intake valve 214 is closed by releasing the open state, and the gas remaining in the compression chamber 216 is compressed and discharged. During the next piston intake stroke, the drive device 62b is driven again, and the open state is released after the compression stroke of the piston 212 begins. This action is repeated in conjunction with the reciprocating motion of the piston.

[0108] If the release timing is advanced, the delivery amount increases, while if it is delayed, the delivery amount decreases, thereby achieving the same function as the second reflux unit 43. In other words, since the processing capacity of the subsequent compression stage 14 is adjusted according to the pressure change in the intermediate flow path 22 caused by the first control, the power reduction effect is significant.

[0109] In addition, although the description of other configurations, functions, and effects is omitted, the description of the first to fourth embodiments can be applied to the fifth embodiment.

[0110] The embodiments disclosed herein are illustrative in all respects and should not be construed as limiting. 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.

[0111] For example, Figure 1 The compressor unit 10 shown is as follows Figure 16 As shown, the front compression section 15 can be further provided on the upstream side of the first compression section 12. In this case, the first reflux section 18 is provided on the downstream side of the first compression section 12, that is, the second compression section from the front. Figure 16 The illustrated method can also suppress the deterioration of the power of the compressor unit 10 compared to the case where hydrogen is refluxed from the discharge flow path 24 of the subsequent compression stage 14 to the intake flow path 21. In addition, the number of the first compression stage 15 can be two or more. The same applies to the other figures.

[0112] Here, the above-mentioned embodiment will be briefly described.

[0113] (1) The compressor unit involved in the embodiment is a reciprocating compressor unit as follows: the compressor unit recovers evaporated gas, i.e., hydrogen, from a liquid hydrogen storage tank and supplies at least a portion of the hydrogen to a demander including at least one of an engine, a power generation device and a boiler, and includes: a first compression section for compressing hydrogen; one or more subsequent compression sections for further compressing the hydrogen discharged from the first compression section; a crank mechanism for driving the first compression section and the subsequent compression sections; a first reflux section including: a first reflux flow path for returning a portion of the hydrogen discharged from the first compression section to the intake flow path; and a first reflux valve for regulating the reflux amount in the first reflux flow path; a regulating unit for regulating the hydrogen processing amount of the subsequent compression section; a pressure sensor arranged in an intermediate flow path between the first compression section and the subsequent compression section; an upstream temperature sensor arranged in the intake flow path between the connection portion of the first reflux flow path and the first compression section; and a control section for controlling the first reflux valve and the regulating unit, respectively. The first compression stage and the subsequent compression stage each include: a cylinder; a piston; a piston rod connecting the piston to the crank mechanism; and a rod seal sealing the piston rod and the cylinder. The first compression stage is air-cooled and oil-free. At least a portion of the subsequent compression stage has a leakage gas discharge portion that returns leakage gas from the rod seal to the intake flow path. The control unit is capable of performing the following controls: a first control for controlling the first return valve with reference to the intake temperature acquired by the upstream temperature sensor so that the intake temperature falls within a predetermined temperature range; and a second control for controlling the regulating unit so that the processing volume of the subsequent compression stage is adjusted according to the pressure change in the intermediate flow path generated by the first control. The predetermined temperature range is set to a range that is higher than a reference temperature based on the liquefaction temperature of air and lower than 0°C.

[0114] According to the compressor unit, the compressor unit can be protected in a low-temperature environment. More specifically, in the first control, by using the first reflux unit to adjust the flow rate of hydrogen gas returned to the intake flow path, the intake temperature of the hydrogen gas before being sucked into the first compression stage can be adjusted. In addition, the temperature range of the hydrogen gas sucked into the first compression stage is adjusted to be higher than the reference temperature based on the liquefaction temperature of air. Therefore, it is possible to avoid the liquefaction of oxygen gas used as a combustion-supporting gas in the intake portion or intake flow path of the first compression stage. In addition, by setting the intake temperature within a predetermined temperature range that is higher than the reference temperature based on the liquefaction temperature of air and lower than 0°C, it is possible to suppress a decrease in the hydrogen processing efficiency.

[0115] In addition, since the first reflux portion only bypasses the first compression stage, the deterioration of the power of the compression unit can be suppressed compared to the case where hydrogen is refluxed from the discharge flow path of the subsequent compression stage to the intake flow path, that is, the case where the hydrogen with the highest pressure is returned to the intake flow path 21.

[0116] Furthermore, since the adjustment unit adjusts the processing capacity of the subsequent compression stage according to the reflux operation of the first reflux portion, it is possible to suppress excessive compression operation in the subsequent compression stage, thereby reducing the power consumption of the compressor unit.

[0117] Furthermore, since at least the first compression stage utilizes an oil-free design, the risk of oil freezing is avoided. Furthermore, while the pressure in subsequent compression stages increases, hydrogen is more likely to leak. However, any hydrogen leaking in subsequent compression stages is recovered by the leaked gas discharge unit and returned to the intake flow path, minimizing product gas loss during compression.

[0118] (2) The compressor unit may also include: a downstream side temperature sensor, which is arranged in the intermediate flow path; a low-pressure gas discharge channel, which branches from a branch point of the discharge flow path arranged on the discharge side relative to the subsequent compression section, and is capable of discharging hydrogen to a low-pressure demander, which is capable of processing hydrogen with a pressure lower than the hydrogen pressure required by the demander; a switching unit, which is arranged in the low-pressure gas discharge channel or the branch point; and a check valve, which is located on the downstream side relative to the branch point. In this case, the control unit may also: (i) during startup and when the detected temperature of the downstream side temperature sensor is higher than a specified first temperature T1 higher than 0°C, control the switching unit in a manner such that the hydrogen gas discharged from the subsequent compression section flows to the low-pressure gas discharge channel in a first switching state; (ii) when the detected temperature of the downstream side temperature sensor is lower than the first temperature T1, control the switching unit in a manner such that the hydrogen gas discharged from the subsequent compression section is transported to the discharge flow path toward the demand side; and (iii) execute the first control and the second control on the condition that the switching unit is in the second switching state.

[0119] In this technical solution, when the hydrogen in the piping on the side of the liquid hydrogen storage tank rises to a positive temperature range during startup, the hydrogen discharged from the subsequent compression section is sent to the low-pressure demand side. Therefore, it is possible to more effectively prevent the hydrogen temperature in the subsequent compression section from rising excessively. That is, in the reciprocating compressor unit, hydrogen is delivered at a pressure corresponding to the pressure set according to the hydrogen supply destination. Therefore, by controlling the switching unit in such a way as to deliver hydrogen to the low-pressure demand side, the exhaust gas pressure of the subsequent compression section is reduced. Accordingly, the subsequent compression section can be protected more reliably. In addition, the startup work of the compressor unit can also be performed quickly. In addition, the compressor unit can be protected in a low-temperature environment.

[0120] (3) The compressor unit may further include: a downstream temperature sensor disposed in the intermediate flow path; a cooler section disposed between the first compression stage and the subsequent compression stage; and a cooler switching unit capable of switching between a path for hydrogen gas to flow into the cooler section and a path for hydrogen gas to flow into the subsequent compression stage without passing through the cooler section. In this case, the control unit may: (i) during startup and when the temperature detected by the downstream temperature sensor is higher than a predetermined first temperature T1 higher than 0°C, control the cooler switching unit to a first switching state in which hydrogen gas discharged from the first compression stage flows to the cooler section and is cooled; (ii) when the temperature detected by the downstream temperature sensor is lower than the first temperature T1, control the cooler switching unit to a second switching state in which hydrogen gas discharged from the first compression stage is fed to the subsequent compression stage without passing through the cooler section; and (iii) subject to the cooler switching unit being in the second switching state, execute the first control and the second control.

[0121] In this technical solution, if the hydrogen gas in the piping on the liquid hydrogen storage tank side rises to a positive temperature during startup, the cooler unit cools the hydrogen gas discharged from the first compression stage. This prevents the hydrogen gas temperature in the subsequent compression stages from rising excessively. This protects the subsequent compression stages. Furthermore, the compressor unit can be started quickly, protecting the compressor unit in low-temperature environments.

[0122] (4) The regulating unit may also include, in at least one subsequent compression stage, a second reflux section including a second reflux flow path for returning hydrogen gas flowing through the discharge side of the subsequent compression stage to the suction side of the subsequent compression stage; a second reflux valve for regulating the reflux amount in the second reflux flow path; and a suction valve unloader installed in the cylinder section of the subsequent compression stage. In this case, in the second control, the control section is configured to control the second reflux valve based on the pressure change in the intermediate flow path generated by the first control, and when the opening of the second reflux valve reaches a predetermined value, the suction valve unloader is also driven, thereby reducing the processing volume of the cylinder section, thereby reducing the amount of hydrogen gas returned to the suction side of the subsequent compression stage through the second reflux section.

[0123] In this technical solution, the power of compressed gas can be further reduced.

[0124] (5) The regulating unit may also include, in at least one subsequent compression stage, a stepless capacity regulating device having a suction valve unloader mounted on the cylinder portion of the subsequent compression stage and a hydraulic or electrical drive device for opening and closing the suction valve unloader. In this case, the control unit is configured to drive the drive device in such a manner that the timing of the operation of the suction valve unloader is adjusted in conjunction with the rotational movement of the crankshaft in the crank mechanism. Furthermore, in the second control, the control unit controls the drive device based on the pressure change in the intermediate flow path generated by the first control, thereby adjusting the processing capacity of the subsequent compression stage.

[0125] In this technical solution, the timing and duration of the suction valve unloader's operation are controlled, allowing some of the hydrogen in the cylinder to be returned to the suction side. This reduces the amount of gas processed in the subsequent compression stage, thereby further reducing power.

[0126] As described above, the reciprocating compressor unit can be appropriately protected from the boil-off gas of extremely low-temperature liquid hydrogen.

[0127] This application is based on Japanese patent application No. 2023-020152 filed on February 13, 2023, the contents of which are incorporated herein by reference.

[0128] While the present invention has been appropriately and fully described above with reference to the accompanying drawings and through the embodiments, it should be appreciated that those skilled in the art can readily modify and / or improve the above-described embodiments. Therefore, any modified or improved embodiments implemented by those skilled in the art, as long as they do not depart from the scope of protection of the claims set forth therein, should be construed as being included within the scope of protection of the claims.

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 liquid hydrogen storage tank and supplies at least a portion of the hydrogen to a demander including at least one of an engine, a power generation device, and a boiler, and includes: The first compression stage compresses hydrogen; One or more subsequent compression stages to further compress the hydrogen discharged from the first compression stage; a crank mechanism for driving the first compression section and the subsequent compression sections; The first reflux section includes: a first reflux passage for returning a portion of the hydrogen gas discharged from the first compression section to the suction passage; and a first reflux valve for adjusting a reflux amount in the first reflux passage; A regulating unit for regulating the hydrogen processing capacity of the subsequent compression section; a pressure sensor disposed in an intermediate flow path between the first compression section and the subsequent compression section; an upstream temperature sensor disposed in the suction flow path between a connection portion of the first return flow path and the first compression stage; and The control unit controls the first return valve and the regulating unit respectively, wherein: The first compression section and the subsequent compression section each include: Cylinder; piston; a piston rod connecting the piston to the crank mechanism; and A rod seal seals the piston rod and the cylinder. The first compression stage is air-cooled and oil-free. At least a portion of the subsequent compression stage includes a leaked gas discharge portion for returning leaked gas from the rod seal to the suction flow path. The control unit can perform the following control: a first control of referring to the suction temperature acquired by the upstream temperature sensor and controlling the first return valve so that the suction temperature falls within a predetermined temperature range; and The second control controls the regulating unit so that the processing volume of the subsequent compression stage is regulated according to the pressure change in the intermediate flow path caused by the first control. 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 Also includes: a downstream temperature sensor, disposed in the intermediate flow path; a low-pressure gas discharge passage branching from a branch point of the discharge flow path provided on the discharge side relative to the subsequent compression stage, capable of discharging hydrogen to a low-pressure demander capable of processing hydrogen at a pressure lower than the hydrogen pressure required by the demander; a switching unit, provided in the low-pressure gas discharge passage or the branch point; and a check valve located on the downstream side relative to the branch point, wherein The control unit is configured as follows: During startup and when the temperature detected by the downstream temperature sensor is higher than a predetermined first temperature T1 higher than 0° C., controlling the switching unit to be in a first switching state in which hydrogen gas discharged from the subsequent compression stage flows to the low-pressure gas discharge passage; When the temperature detected by the downstream temperature sensor is lower than the first temperature T1, the switching unit is controlled so as to be in a second switching state in which the hydrogen gas discharged from the subsequent compression stage is delivered to the discharge flow path toward the demand side; and The first control and the second control are executed on the condition that the switching unit is in the second switching state.

3. The compressor unit according to claim 1, characterized in that Also includes: a downstream temperature sensor, disposed in the intermediate flow path; a cooler portion disposed between the first compression stage and the subsequent compression stage; and The cooler switching unit is capable of switching between a path for hydrogen to flow into the cooler section and a path for hydrogen to flow into the subsequent compression section without passing through the cooler section, wherein The control unit is configured as follows: During startup, when the temperature detected by the downstream temperature sensor is higher than a predetermined first temperature T1 higher than 0° C., controlling the cooler switching unit to be in a first switching state in which hydrogen gas exhausted from the first compression stage flows to the cooler portion for cooling; When the temperature detected by the downstream temperature sensor is lower than the first temperature T1, the cooler switching unit is controlled so as to be in a second switching state in which the hydrogen gas discharged from the first compression stage is transported to the subsequent compression stage without passing through the cooler portion; and The first control and the second control are executed on the condition that the cooler switching unit is in the second switching state.

4. The compressor unit according to any one of claims 1 to 3, characterized in that The conditioning unit comprises, in at least one subsequent compression section: The second reflux section includes: a second reflux passage for returning the hydrogen gas flowing through the discharge side of the subsequent compression stage to the suction side of the subsequent compression stage; and a second reflux valve for adjusting the reflux amount in the second reflux passage; and The suction valve unloader is installed in the cylinder of the subsequent compression section. In the second control, the control section is configured to control the second return valve based on the pressure change in the intermediate flow path generated by the first control, and when the opening of the second return valve reaches a predetermined value, the suction valve unloader is also driven, thereby reducing the processing volume of the cylinder section, thereby reducing the amount returned to the suction side of the subsequent compression stage through the second return section.

5. The compressor unit according to any one of claims 1 to 3, characterized in that The conditioning unit comprises, in at least one subsequent compression section: The stepless capacity adjustment device comprises: a suction valve unloader mounted on the cylinder portion of the subsequent compression stage; and a hydraulic or electrical drive device for opening and closing the suction valve unloader. The control unit is configured to drive the drive device so that the operation timing of the intake valve unloader is adjusted in conjunction with the rotational movement of the crankshaft in the crank mechanism. In the second control, the control unit controls the driving device according to the amount of pressure change in the intermediate flow path caused by the first control, thereby adjusting the processing capacity of the subsequent compression stage.

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