Reciprocating compressor and method for controlling reciprocating compressor

Abstract

This reciprocating compressor comprises a hydrogen gas flow path, a compressor body, a nitrogen gas supply path, a first valve, a nitrogen gas discharge path, a second valve, a control unit that controls the first valve and the second valve, and a pressure sensor. When the compressor body is stopped, the control unit executes a first valve operation, a second valve operation, and a third valve operation. The first valve operation is a valve operation for opening the first valve so that nitrogen gas higher than atmospheric pressure is supplied into a cylinder part in a state in which the second valve is closed. The second valve operation is a valve operation for closing the first valve and opening the second valve on condition that a pressure condition for the pressure between the first valve and the second valve in the hydrogen gas flow path to be a predetermined pressure is satisfied. The third valve operation is a valve operation for closing the second valve on condition that a pressure value detected by the pressure sensor is equal to or less than a threshold value.

Description

Reciprocating Compressor and Control Method for Reciprocating Compressor

[0001] The present invention relates to a reciprocating compressor for compressing hydrogen gas and a control method therefor.

[0002] Patent Document 1 discloses a hydrogen station including an H2 receiving unit, a hydrogen station package unit, a dispenser unit, and a purge N2 unit. In the hydrogen station disclosed in Patent Document 1, the purge N2 unit stores nitrogen gas (N2 gas) for purging impurities such as air in addition to hydrogen gas (H2 gas) remaining in the flow path and valves within the hydrogen station package unit. Further, the purge N2 unit is configured to be able to supply N2 gas to the hydrogen station package unit via the H2 receiving unit if necessary. By supplying N2 gas from the purge N2 unit to the hydrogen station package unit in this way, an attempt is made to purge H2 gas and the like remaining in the flow path including the compressor unit.

[0003] By the way, when discharging H2 gas, there may be a case where simply supplying N2 gas into the flow path cannot sufficiently replace H2 gas with N2 gas. In particular, for the inside of the mechanism of the compressor body or the deep part of the piping, etc., it may be difficult to replace the remaining H2 gas with N2 gas, and there may be a case where the H2 gas cannot be completely discharged.

[0004] Japanese Unexamined Patent Application Publication No. 2021-156435

[0005] The present invention has been made in view of the above problems, and an object thereof is to more reliably discharge hydrogen gas remaining in the cylinder part of the compressor body.

[0006] A reciprocating compressor according to one aspect of the present invention is a reciprocating compressor for compressing hydrogen gas, comprising a hydrogen gas passage, a compressor body, a nitrogen gas supply passage, a first valve, a nitrogen gas discharge passage, a second valve, a control unit, and a pressure sensor. The hydrogen gas passage is a passage provided for the flow of the hydrogen gas. The compressor body is provided in the hydrogen gas passage. The nitrogen gas supply passage is connected to the suction-side passage of the compressor body in the hydrogen gas passage and is provided for supplying nitrogen gas into the cylinder portion of the compressor body during nitrogen purging. The first valve is provided in the nitrogen gas supply passage. The nitrogen gas discharge passage is connected to the discharge-side passage of the compressor body in the hydrogen gas passage and is provided for discharging nitrogen gas that has flowed out from the cylinder portion of the compressor body during nitrogen purging. The second valve is provided in the nitrogen gas discharge passage. The control unit is configured to control the first valve and the second valve. The pressure sensor is located downstream of the connection point of the nitrogen gas supply path in the hydrogen gas flow path.

[0007] When the compressor body is stopped, the control unit is configured to perform a first valve operation, a second valve operation, and a third valve operation. The first valve operation is to open the first valve so that nitrogen gas at a pressure higher than atmospheric pressure is supplied into the cylinder section when the second valve is closed. The second valve operation is to close the first valve and open the second valve when a pressure condition is met in which the pressure between the first valve and the second valve in the hydrogen gas flow path becomes a predetermined pressure. The third valve operation is to close the second valve when the pressure value detected by the pressure sensor falls below a threshold.

[0008] This is a diagram showing the configuration of a reciprocating compressor according to Embodiment 1. This is a schematic diagram showing the internal structure of the compressor body. This is a flowchart showing the control method of the reciprocating compressor executed by the control unit. This is a diagram showing a partial configuration of a reciprocating compressor according to Embodiment 2. This is a diagram showing a partial configuration of a reciprocating compressor according to Embodiment 3. This is a diagram showing a partial configuration of a reciprocating compressor according to Embodiment 4. This is a diagram showing a partial configuration of a reciprocating compressor according to Embodiment 5.

[0009] The embodiments of the present invention will be described below with reference to the drawings. The forms described below are merely examples of the present invention, and the present invention is not limited to these forms except for its essential configuration.

[0010] [Embodiment 1] 1. Configuration of the reciprocating compressor 1 The reciprocating compressor 1 according to this embodiment compresses hydrogen gas (H2 gas) supplied from a gas supply source 50. The configuration of the reciprocating compressor 1 will be explained with reference to Figures 1 and 2.

[0011] As shown in Figure 1, the reciprocating compressor 1 comprises a hydrogen gas passage 10, a compressor body 13, a nitrogen gas supply passage 16, a nitrogen gas supply passage on-off valve (first valve) 17, a gas discharge passage 18, a gas discharge passage on-off valve (second valve) 19, a pressure sensor 21, and a control unit 20. The hydrogen gas passage 10 is a passage provided for the flow of hydrogen gas supplied from the gas supply source 50. The hydrogen gas passage 10 includes an intake-side passage (the passage on the suction side of the compressor body 13) 11 and a discharge-side passage (the passage on the discharge side of the compressor body 13) 12. The intake-side passage 11 is the portion from the point connected to the gas supply source 50 to the compressor body 13. The discharge-side passage 12 is the discharge-side portion of the compressor body 13.

[0012] As described above, the compressor body 13 has the suction side passage 11 of the hydrogen gas passage 10 connected to the suction side and the discharge side passage 12 of the hydrogen gas passage 10 connected to the discharge side. The compressor body 13 includes two compression stages 14 and 15 arranged in series in the direction of hydrogen gas (H2 gas) flow. The first compression stage 14, located upstream in the direction of H2 gas flow, has the suction side passage 11 connected to the suction side and the connecting passage 22 connected to the discharge side. The second compression stage 15, located downstream in the direction of H2 gas flow, has the connecting passage 22 connected to the suction side and the discharge side passage 12 connected to the discharge side. Each of the first compression stage 14 and the second compression stage 15 is composed of a reciprocating compression mechanism and is driven by a crank mechanism (not shown).

[0013] As shown in Figure 2, the first compression stage 14 includes a cylinder section 140, a piston 141 disposed within the cylinder section 140, a piston rod 142 connected to the piston 141, a pair of cylinder suction valves 143, and a pair of cylinder discharge valves 144. Within the cylinder section 140, compression chambers 145 are formed between the front head 140a and the piston 141, and between the rear head 140b and the piston 141.

[0014] The rear head 140b of the cylinder section 140 is provided with a rod packing 146 to prevent H2 gas leakage from the compression chamber 145. The rod packing 146 is provided to seal the space between the piston rod 142 and the cylinder section 140. The rod packing 146 has a packing ring 146a arranged to surround the piston rod 142 and a case 146b that holds the packing ring 146a.

[0015] Although only the first compression stage 14 is shown in Figure 2, the second compression stage 15 has the same structure.

[0016] The nitrogen gas supply passage 16 is connected to the suction-side passage 11 in the hydrogen gas passage 10 and supplies nitrogen gas (N2 gas) into the cylinder section 140 of the compressor body 13 when H2 gas remaining in the system is discharged. In the following description, the process of supplying N2 gas into the system to replace H2 gas with N2 gas is called "nitrogen purging". The suction-side passage 11 is provided with a suction-side passage on-off valve 24 and a check valve 26 in order from the upstream side in the direction of H2 gas flow. The nitrogen gas supply passage 16 is connected to the suction-side passage 11 at a point between the section where the suction-side passage on-off valve 24 is provided and the section where the check valve 26 is provided.

[0017] In this embodiment, the reciprocating compressor 1 is supplied with N2 gas at a pressure of 0.01 MPaG or higher (N2 gas at a pressure higher than atmospheric pressure) from the nitrogen gas supply passage 16.

[0018] The nitrogen gas supply passage shut-off valve 17 is installed in the nitrogen gas supply passage 16. The nitrogen gas supply passage shut-off valve 17 switches the supply of N2 gas to the suction side passage 11 between supply and cessation by opening and closing its position.

[0019] The gas discharge passage 18 is connected to the discharge-side passage 12 in the hydrogen gas passage 10 and is a nitrogen gas discharge passage that discharges N2 gas that flows out from the cylinder section 140 of the compressor body 13 during nitrogen purging. The gas discharge passage 18 also serves as a hydrogen gas vent line that discharges H2 gas from within the system. In other words, the gas discharge passage 18 is configured to combine the functions of a nitrogen gas discharge passage and a hydrogen gas vent line. Specifically, the discharge-side passage 12 is equipped with a cooler 33, a check valve 27, and a discharge-side passage on / off valve 25 in order from the upstream side in the direction of H2 gas flow. The gas discharge passage 18 is connected to the discharge-side passage 12 at a point between the section where the check valve 27 is installed and the section where the discharge-side passage on / off valve 25 is installed.

[0020] In this embodiment, a gas discharge passage 18 is provided that serves both as a nitrogen gas discharge passage and a hydrogen gas vent line; however, the nitrogen gas discharge passage and the hydrogen gas vent line may be provided independently.

[0021] The gas discharge passage on / off valve 19 is installed in the gas discharge passage 18. The gas discharge passage on / off valve 19 can switch between discharging / stopping N2 gas and H2 gas through the gas discharge passage 18 by opening and closing it.

[0022] The pressure sensor 21 is located downstream of the connection point of the nitrogen gas supply passage 16 in the hydrogen gas flow path 10. In this embodiment, the pressure sensor 21 is located in the discharge flow path 12.

[0023] The control unit 20 is configured to have a microprocessor that includes an MPU / CPU and ASIC, as well as memory such as ROM and RAM. The control unit 20 is configured to control the opening and closing of the nitrogen gas supply valve 17, the gas discharge valve 19, the suction side flow path valve 24, and the discharge side flow path valve 25 by executing firmware or the like that is pre-stored in the memory.

[0024] The reciprocating compressor 1 further comprises four buffer tanks 28-31, a cooler 32 provided in the connecting passage 22, and two spillback passages 34. The four buffer tanks 28-31 are provided to suppress pulsation of H2 gas during compression of the H2 gas. Buffer tank 28 is provided on the suction side of the first compression stage 14, and buffer tank 30 is provided on the discharge side of the first compression stage 14. Buffer tank 29 is provided on the suction side of the second compression stage 15, and buffer tank 31 is provided on the discharge side of the second compression stage 15.

[0025] In this embodiment, a spillback passage 34 is provided that connects the discharge-side passage 12 and the connecting passage 22 across the second compression stage 15, and another spillback passage 34 is provided that connects the connecting passage 22 and the suction-side passage 11 across the first compression stage 14. Each spillback passage 34 is provided with a spillback valve 35.

[0026] The opening degree of the spillback valve 35 is adjusted by the control unit 20. By adjusting the opening degree of each spillback valve 35, the amount of H2 gas returned to the suction side of each compression stage 14, 15 via the spillback passage 34 is adjusted. This makes it possible to adjust the discharge pressure of each compression stage 14, 15.

[0027] 2. Control Method of the Reciprocating Compressor 1 Executed by the Control Unit 20 The control method of the reciprocating compressor 1 executed by the control unit 20 will be explained with reference to Figures 3 and 4.

[0028] As shown in Figure 3, the control unit 20 issues a command signal to a motor (not shown) that drives the crank mechanism to stop the compressor body 13 (first compression stage 14 and second compression stage 15) (step S1). With the compressor body 13 stopped, the control unit 20 closes the suction-side flow path on / off valve 24, the discharge-side flow path on / off valve 25, and the two spillback valves 35 (step S2). This creates a closed space consisting of the hydrogen gas flow path 10, the cylinder portion 140 of the compressor body 13, and the connecting flow path 22.

[0029] Next, the control unit 20 opens the gas discharge valve 19 (step S3). As a result, some of the H2 gas remaining in the hydrogen gas passage 10, the cylinder section 140 of the compressor body 13, and the connecting passage 22 is discharged out of the system through the gas discharge passage 18. This depressurizes the system, including the cylinder section 140.

[0030] Next, the control unit 20 performs the first valve operation (step S4). Specifically, the control unit 20 closes the gas discharge passage on / off valve 19 (step S5) and opens the nitrogen gas supply passage on / off valve 17 (indicated as "N2 gas supply passage on / off valve 17" in Figure 3) (step S6). As a result, N2 gas at a pressure higher than atmospheric pressure (0.01 MPaG or higher) is supplied to the space formed by the hydrogen gas passage 10, the cylinder section 140 of the compressor body 13, and the connecting passage 22. Note that even when supplying N2 gas, the suction-side passage on / off valve 24, the discharge-side passage on / off valve 25, and the gas discharge passage on / off valve 19 are closed, so the supplied N2 gas is only filled into the above space and is not discharged outside the system. Therefore, the supplied N2 gas reaches every corner of the system, including the cylinder section 140 of the compressor body 13.

[0031] The control unit 20 keeps the nitrogen gas supply valve 17 open until it determines that the supply of N2 gas is complete (Step S7: NO). The control unit 20 may determine that the supply of N2 gas is complete (Step S7) by, for example, whether the detected value (pressure P) of the pressure sensor 21 provided in the discharge-side flow path 12 has reached a predetermined second threshold.

[0032] Furthermore, the control unit 20 may determine the completion of N2 gas supply (step S7) by determining whether a predetermined time has elapsed after opening the nitrogen gas supply valve 17 (step S6). Specifically, the control unit 20 starts timing approximately simultaneously with opening the nitrogen gas supply valve 17 (step S6) and begins measuring the time during which N2 gas is being supplied. When the control unit 20 determines that the measured time has reached a predetermined threshold, it terminates the timing and closes the nitrogen gas supply valve 17 (step S9).

[0033] As described above, in the reciprocating compressor 1 according to this embodiment, the pressure P detected by the pressure sensor 21 provided in the discharge-side flow path 12 may be used as a criterion for determining whether or not the pressure conditions in the system have been met (determination in step S7). Alternatively, the elapsed time after opening the nitrogen gas supply passage on / off valve 17 (step S6) may be used as a criterion for determining whether or not the pressure conditions in the system have been met (determination in step S7).

[0034] If the control unit 20 determines that the supply of N2 gas is complete (step S7: YES), it executes a second valve operation (step S8). The second valve operation (step S8) includes a valve operation to close the nitrogen gas supply passage on-off valve 17 (step S9) and a valve operation to open the gas discharge passage on-off valve 19 (step S10). As a result, the supply of N2 gas into the cylinder section 140 of the compressor body 13 is stopped, and the N2 gas and H2 gas mixed in the system are discharged out of the system through the gas discharge passage 18. As described above, the N2 gas supplied from the nitrogen gas supply passage 16 has a pressure higher than atmospheric pressure (0.01 MPaG or higher), so the pressure in the system until the gas discharge passage on-off valve 19 is opened is also higher than atmospheric pressure. For this reason, simply opening the gas discharge passage on-off valve 19 is enough to discharge the gas (N2 gas, H2 gas) in the system out of the system through the gas discharge passage 18. It is desirable to leave a predetermined time between the execution of step S9 and the execution of step S10. That is, by providing a waiting time between step S9 and step S10, both the nitrogen gas supply valve 17 and the gas discharge valve 19 are closed, thereby creating a sealed space in the hydrogen gas flow path 10, which is effective in allowing the supplied N2 gas to reach every corner of the system.

[0035] The control unit 20 maintains the open state of the gas discharge valve 19 until the pressure P detected by the pressure sensor 21 reaches a predetermined threshold Pth (step S11: NO). When the control unit 20 determines that the pressure P has reached the threshold Pth (step S11: YES), it closes the gas discharge valve 19 (step S12) and terminates the nitrogen purge control. In other words, the control unit 20 terminates the nitrogen purge control by executing a third valve operation to close the gas discharge valve 19.

[0036] Although not specifically shown in Figure 3, the control may be performed by repeating steps S4 to S12 multiple times. This makes it possible to further reduce the amount of H2 gas remaining in the system, including the cylinder portion 140 of the compressor body 13 (in other words, the H2 gas concentration).

[0037] In this embodiment, instead of the nitrogen gas supply valve 17, a three-way valve (first valve) may be provided at the connection point of the nitrogen gas supply passage 16 in the suction-side passage 11. In this case, in step S6 of Figure 3, the three-way valve is controlled so that H2 gas flows from the nitrogen gas supply passage 16 to the hydrogen gas passage 10 (corresponding to the opening operation of the nitrogen gas supply valve 17). In step S9, the three-way valve is controlled so that H2 gas does not flow from the nitrogen gas supply passage 16 to the hydrogen gas passage 10 (corresponding to the closing operation of the nitrogen gas supply valve 17). Alternatively, instead of the gas discharge valve 19, a three-way valve (second valve) may be provided at the connection point of the gas discharge passage 18 in the discharge-side passage 12. In this case, in steps S3 and S10, the three-way valve is controlled so that the gas discharge passage 18 and the discharge-side passage 12 are in communication (corresponding to the opening operation of the gas discharge valve 19). In steps S5 and S12, the three-way valve is controlled so that the gas discharge passage 18 and the discharge-side passage 12 are blocked (corresponding to the closing operation of the gas discharge passage on / off valve 19).

[0038] 3. Effects In the reciprocating compressor 1 according to this embodiment, the control unit 20 performs a first valve operation (step S4) to supply N2 gas into the cylinder section 140. After that, it waits for the determination in step S7 to be "YES". When the determination in step S7 is YES, the gas discharge passage opening valve (second valve) 19 is opened (step S9) by performing a second valve operation (step S8). In the reciprocating compressor 1, the N2 gas supplied between the execution of the first valve operation (step S4) and the execution of the second valve operation (step S8) reaches every corner of the system, including the inside of the cylinder section 140. Therefore, in the reciprocating compressor 1, N2 gas is reliably mixed with the H2 gas remaining in the cylinder section 140. Therefore, compared to a configuration in which H2 gas is discharged by continuously flowing N2 gas from the nitrogen gas supply passage 16 to the gas discharge passage 18 in the reciprocating compressor 1, it is possible to more reliably prevent H2 gas from remaining in the cylinder section 140.

[0039] Furthermore, in the reciprocating compressor 1 according to this embodiment, the control unit 20 determines whether or not the supply of N2 gas has been completed based on the detected value (pressure P) of the pressure sensor 21 provided in the discharge-side passage 12 of the hydrogen gas passage 10 (step S7). If it is determined that the supply has been completed (step S7: YES), the second valve operation (step S8) is performed. Thus, in the reciprocating compressor 1, by providing the pressure sensor 21 in the discharge-side passage 12, it is possible to confirm that N2 gas has filled the entire hydrogen gas passage 10, and the opening and closing timing of the nitrogen gas supply passage valve (first valve) 17 and the gas discharge passage valve (second valve) 19 can be appropriately determined.

[0040] Furthermore, in the reciprocating compressor 1 according to this embodiment, if the nitrogen purging performed by executing the first valve operation (step S4) to the third valve operation (step S12) is performed multiple times, the amount of H2 gas remaining in the cylinder portion 140 of the compressor body 13 can be reduced to an extremely small amount.

[0041] Furthermore, in the reciprocating compressor 1 according to this embodiment, the spillback valve 35 is closed before the first valve operation (step S4) is performed, so that the N2 gas supplied from the nitrogen gas supply passage 16 to the hydrogen gas passage 10 is prevented from being dispersed and flowing into the spillback passage 34. Therefore, the N2 gas can be reliably filled into the cylinder portion 140 of the compressor body 13.

[0042] [Embodiment 2] The reciprocating compressor 1 according to Embodiment 2 will be described with reference to Figure 4. The reciprocating compressor 1 according to this embodiment differs from Embodiment 1 in the arrangement of the spillback passage 34. However, the other configurations are the same as those of Embodiment 1, so the differences from Embodiment 1 will be mainly described below.

[0043] As shown in Fig. 4, in the reciprocating compressor 1 according to the present embodiment, the spillback flow path 34 is provided so as to directly connect the discharge-side flow path 12 and the suction-side flow path 11. That is, in the above-described Embodiment 1, two spillback flow paths 34 were formed, whereas in the present embodiment, one spillback flow path 34 is formed. The point that the spillback valve 35 is provided in the spillback flow path 34 is the same as above.

[0044] In the reciprocating compressor 1 according to the present embodiment as well, nitrogen purge control is executed using the method described with reference to Fig. 3.

[0045] Even in the reciprocating compressor 1 according to the present embodiment having the above-described configuration, the same effects as those of the reciprocating compressor 1 according to the above-described Embodiment 1 can be obtained.

[0046] [Embodiment 3] The reciprocating compressor 1 according to Embodiment 3 will be described with reference to Fig. 5. The reciprocating compressor 1 according to the present embodiment is different from the above-described Embodiment 1 in that the H₂ gas supplied from the gas supply source 50 is at an extremely low temperature and that a preheater 51 is provided at the upstream end of the hydrogen gas flow path 10. Since the other configurations are the same as those of the above-described Embodiment 1, the differences from the above-described Embodiment 1 will be mainly described below.

[0047] In the reciprocating compressor 1 according to the present embodiment, as the gas supply source 50, a gas supply source that supplies BOG (boil-off gas) generated from liquefied hydrogen is adopted. The BOG supplied from the gas supply source 50 is a low-temperature H₂ gas because it is generated from liquefied hydrogen.

[0048] As shown in Fig. 5, the reciprocating compressor 1 according to the present embodiment further includes a preheater (heating device) 51 provided in a portion upstream of the location where the nitrogen gas supply path 16 in the hydrogen gas flow path 10 is connected. The preheater 51 heats the BOG (H₂ gas) introduced from the gas supply source 50 to a temperature higher than the temperature at which N₂ gas liquefies or solidifies.

[0049] In the reciprocating compressor 1 according to this embodiment, a preheater 51 is provided to heat the BOG supplied from the gas supply source 50 to the above temperature after the operation of the third valve (step S12 in Figure 3) and when the compressor body 13 is started. This prevents the N2 gas in the system, including the cylinder portion 140 of the compressor body 13, from liquefying or solidifying even when the operation of supplying H2 gas into the system to replace N2 gas with H2 gas (hereinafter referred to as "hydrogen purging") is performed.

[0050] Furthermore, since the reciprocating compressor 1 according to this embodiment has the same configuration as the embodiment 1 described above, except that it is equipped with a preheater 51, the same effects as the embodiment 1 can be obtained.

[0051] [Embodiment 4] The reciprocating compressor 1 according to Embodiment 4 will be described with reference to Figure 6. The reciprocating compressor 1 according to this embodiment differs from Embodiment 1 in that it selectively receives H2 gas from one of two types of gas supply sources 52 and 53. The other configurations are the same as those of Embodiment 1, so the differences from Embodiment 1 will be mainly described below.

[0052] As shown in Figure 6, the reciprocating compressor 1 employs a first gas supply source 52 and a second gas supply source 53 as the gas supply source 50. The first gas supply source 52 is a gas supply source that supplies BOG (H2 gas) generated from liquefied hydrogen, similar to the gas supply source 50 in the above embodiment 3.

[0053] The second gas supply source 53 is a gas supply source that supplies H2 gas at a temperature higher than the temperature at which N2 gas liquefies or solidifies to the hydrogen gas flow path 10. Specific examples of the second gas supply source 53 include a water electrolysis device and a tank for storing separately generated H2 gas.

[0054] An on-off valve 54 is provided at the connection point of the first gas supply source 52 to the hydrogen gas flow path 10, and an on-off valve 55 is provided at the connection point of the second gas supply source 53 to the hydrogen gas flow path 10. In the reciprocating compressor 1 according to this embodiment, after the execution of the third valve operation (step S12 in Figure 3) and when starting the compressor body 13, the on-off valve 55 is opened with the on-off valve 54 closed. As a result, H2 gas at a temperature higher than the temperature at which N2 gas liquefies or solidifies is supplied to the hydrogen gas flow path 10. Therefore, it is possible to prevent the N2 gas remaining in the system, including the cylinder portion 140 of the compressor body 13, from liquefying or solidifying after the execution of hydrogen purging.

[0055] Furthermore, if any N2 gas remaining in the system after the compressor body 13 has been started is discharged, the on-off valve 54 may be opened. In this case, the on-off valve 55 will be closed.

[0056] In this embodiment, two on-off valves 54 and 55 are provided, but a three-way valve may be used as the switching valve that switches between the supply of H2 gas from the first gas supply source 52 and the supply of H2 gas from the second gas supply source 53.

[0057] The reciprocating compressor 1 according to this embodiment has the same configuration as the embodiment 1 described above, except that it is equipped with two types of gas supply sources 52 and 53 as gas supply sources 50, and therefore the same effects as the embodiment 1 can be obtained.

[0058] Furthermore, in this embodiment, when the compressor body 13 is started after nitrogen purging, valve operation is performed so that H2 gas from the second gas supply source 53 is supplied. In other words, hydrogen purging is performed using the H2 gas from the second gas supply source 53. Therefore, similar to embodiment 3 above, it is possible to prevent the N2 gas remaining in the system, including the cylinder portion 140 of the compressor body 13, from liquefying or solidifying before discharge.

[0059] [Embodiment 5] The reciprocating compressor 1 according to Embodiment 5 will be described with reference to Figure 7. The reciprocating compressor 1 according to this embodiment differs from Embodiment 1 in that it is equipped with a mechanism that can forcibly open the cylinder suction valve 143 of the compressor body 13 when the first valve operation (step S4) is performed. The other configurations are the same as those of Embodiment 1, so the differences from Embodiment 1 will be mainly described below.

[0060] As shown in Figure 7, the reciprocating compressor 1 according to this embodiment further comprises a suction valve unloader 36 attached to the cylinder suction valve 143 (see Figure 2) of each compressor body 13, and a drive device 37 that drives each suction valve unloader 36. The drive device 37 drives the suction valve unloader 36 based on a command from the control unit 20 (see Figure 1).

[0061] In the reciprocating compressor 1 according to this embodiment, when the first valve operation (step S4) is performed, the drive device 37 drives the suction valve unloader 36 based on a command from the control unit 20. As a result, the suction valve unloader 36 forcibly opens the valve plate of the cylinder suction valve 143 (see Figure 2). Therefore, in the reciprocating compressor 1 according to this embodiment, the state in which the cylinder suction valve 143 of each compressor body 13 is open is maintained while the first valve operation (step S4) is performed.

[0062] The reciprocating compressor 1 according to this embodiment has the same configuration as the embodiment 1 described above, except that it includes a suction valve unloader 36 and a drive device 37, and therefore the same effects as the embodiment 1 can be obtained.

[0063] Furthermore, in the reciprocating compressor 1 according to this embodiment, the suction valve unloader 36 performs a first valve operation (step S4) in which the cylinder suction valve 1143 is forcibly opened. Therefore, even when the compressor body 13 is relatively large, N2 gas can be quickly introduced into the cylinder section 140 during nitrogen purging. Thus, in the above-described reciprocating compressor 1, N2 gas can be distributed throughout the cylinder section 140 relatively quickly, regardless of the size of the compressor body 13.

[0064] [Modification] Each of the reciprocating compressors 1 in Embodiments 1 to 5 above is provided with a spillback passage 34 and a spillback valve 35, but each reciprocating compressor 1 does not necessarily have to be provided with a spillback passage 34 and a spillback valve 35.

[0065] Furthermore, although each of the reciprocating compressors 1 in Embodiments 1 to 5 is equipped with buffer tanks 28 to 31, each reciprocating compressor 1 does not necessarily have to be equipped with buffer tanks 28 to 31.

[0066] Furthermore, although each of the reciprocating compressors 1 in Embodiments 1 to 5 is provided with a gas discharge passage 18 that serves as both a nitrogen gas discharge passage and a hydrogen gas vent line, each reciprocating compressor 1 may also be provided with a separate nitrogen gas discharge passage and a hydrogen gas vent line.

[0067] Furthermore, the embodiments and modifications disclosed herein should be considered in all respects as illustrative and not restrictive. The present invention is not limited to the above embodiments and modifications, and various modifications and improvements are possible without departing from the spirit of the invention.

[0068] [Summary] A reciprocating compressor according to one aspect of the present invention is a reciprocating compressor for compressing hydrogen gas, comprising a hydrogen gas passage, a compressor body, a nitrogen gas supply passage, a first valve, a nitrogen gas discharge passage, a second valve, a control unit, and a pressure sensor. The hydrogen gas passage is a passage provided for the flow of the hydrogen gas. The compressor body is provided in the hydrogen gas passage. The nitrogen gas supply passage is connected to the suction-side passage of the compressor body in the hydrogen gas passage and is provided for supplying nitrogen gas into the cylinder portion of the compressor body during nitrogen purging. The first valve is provided in the nitrogen gas supply passage. The nitrogen gas discharge passage is connected to the discharge-side passage of the compressor body in the hydrogen gas passage and is provided for discharging nitrogen gas that has flowed out from the cylinder portion of the compressor body during nitrogen purging. The second valve is provided in the nitrogen gas discharge passage. The control unit is configured to control the first valve and the second valve. The pressure sensor is located downstream of the connection point of the nitrogen gas supply path in the hydrogen gas flow path.

[0069] When the compressor body is stopped, the control unit is configured to perform a first valve operation, a second valve operation, and a third valve operation. The first valve operation is to open the first valve so that nitrogen gas at a pressure higher than atmospheric pressure is supplied into the cylinder section when the second valve is closed. The second valve operation is to close the first valve and open the second valve when a pressure condition is met in which the pressure between the first valve and the second valve in the hydrogen gas flow path becomes a predetermined pressure. The third valve operation is to close the second valve when the pressure value detected by the pressure sensor falls below a threshold.

[0070] In the reciprocating compressor according to the above embodiment, the control unit executes the first valve operation to supply nitrogen gas into the cylinder section. After that, it waits for the pressure between the first valve and the second valve to reach a predetermined pressure. When the pressure between the first valve and the second valve reaches the predetermined pressure, the second valve is opened by executing the second valve operation. Therefore, in the above reciprocating compressor, the nitrogen gas supplied between the execution of the first valve operation and the execution of the second valve operation reaches every corner of the cylinder section and is reliably mixed with the hydrogen gas remaining in the cylinder section. Thus, the above reciprocating compressor can more reliably prevent hydrogen gas from remaining in the cylinder section compared to a method of discharging hydrogen gas by continuously flowing nitrogen gas from the nitrogen gas supply passage to the nitrogen gas discharge passage.

[0071] In the reciprocating compressor according to the above embodiment, the pressure sensor may be provided in the discharge-side flow path of the compressor body. In this case, the control unit may be configured to determine whether or not the pressure condition has been met based on the pressure value detected by the pressure sensor.

[0072] In the reciprocating compressor according to the above embodiment, the control unit determines whether the above pressure condition is met based on the detected value (pressure value) of a pressure sensor installed in the discharge-side flow path of the compressor body in the hydrogen gas flow path. The reciprocating compressor executes the operation of the second valve based on the determination result of whether the above pressure condition is met. Therefore, in the reciprocating compressor, by installing the pressure sensor in the discharge-side flow path of the compressor body, it is possible to determine whether nitrogen gas has filled the entire cylinder part of the compressor body, and the opening and closing timing of the first valve and the second valve can be appropriately determined.

[0073] In the reciprocating compressor according to the above embodiment, the control unit may be configured to perform the first valve operation to the third valve operation multiple times.

[0074] In the reciprocating compressor according to the above embodiment, nitrogen purging is performed multiple times by executing the first valve operation to the third valve operation, so that hydrogen does not remain in the cylinder part of the compressor body more reliably.

[0075] In the reciprocating compressor according to the above embodiment, the control unit may be configured to forcibly open the cylinder suction valve of the cylinder section during the first valve operation.

[0076] In the reciprocating compressor according to the above embodiment, the cylinder suction valve is forcibly opened when the first valve operation is performed, so that nitrogen gas can be distributed throughout the entire cylinder relatively quickly, and hydrogen gas inside the cylinder can be discharged quickly.

[0077] In the reciprocating compressor according to the above embodiment, a spillback passage may be further provided to return the hydrogen gas discharged into the discharge-side passage of the compressor body back into the suction-side passage of the compressor body. In this case, the control unit may be configured to close the spillback valve provided in the spillback passage during the operation of the first valve.

[0078] In the reciprocating compressor according to the above embodiment, the spillback valve is kept closed when the first valve operation is performed, so that nitrogen gas supplied from the nitrogen gas supply passage to the hydrogen gas passage is prevented from being dispersed and flowing into the spillback passage. Therefore, nitrogen gas can be reliably filled into the cylinder section.

[0079] In the reciprocating compressor according to the above embodiment, the hydrogen gas may be boil-off gas produced from liquefied hydrogen. In this case, a heating device may be further provided in the portion of the hydrogen gas flow path upstream of the point where the nitrogen gas supply path is connected. The heating device is provided to heat the hydrogen gas introduced into the hydrogen gas flow path to a temperature higher than the temperature at which the nitrogen gas liquefies or solidifies.

[0080] In the reciprocating compressor according to the above embodiment, a heating device is further provided, which prevents liquefaction and solidification caused by nitrogen gas coming into contact with hydrogen gas, which is an extremely cold boil-off gas.

[0081] In the reciprocating compressor according to the above embodiment, a first gas supply source and a second gas supply source may be provided as the hydrogen gas supply source. The first gas supply source is provided to supply the hydrogen gas, which is a boil-off gas generated from liquefied hydrogen. The second gas supply source is provided to supply the hydrogen gas at a temperature higher than the temperature at which nitrogen gas liquefies or solidifies. Furthermore, a switching valve may be provided at the upstream end of the hydrogen gas flow path and is provided to selectively switch the hydrogen gas supply source to the hydrogen gas flow path between the first gas supply source and the second gas supply source. In this case, the control unit may be configured to control the switching valve after the execution of the third valve operation and when the compressor body is started up, so that the hydrogen gas from the second gas supply source is introduced into the hydrogen gas flow path.

[0082] In the reciprocating compressor according to the above embodiment, the control unit controls the switching valve so that hydrogen gas from the second gas supply source is introduced after the operation of the third valve and when the compressor body is started, thereby preventing nitrogen gas remaining in the cylinder and other parts from liquefying or solidifying.

[0083] A control method for a reciprocating compressor according to one aspect of the present invention is a control method for a reciprocating compressor that compresses hydrogen gas. The reciprocating compressor controlled by the control method according to this aspect comprises a hydrogen gas passage, a compressor body, a nitrogen gas supply passage, a first valve, a nitrogen gas discharge passage, a second valve, and a pressure sensor. The hydrogen gas passage is a passage provided for the flow of the hydrogen gas. The compressor body is provided in the hydrogen gas passage. The nitrogen gas supply passage is connected to the suction-side passage of the compressor body in the hydrogen gas passage and is provided for supplying nitrogen gas into the cylinder part of the compressor body during nitrogen purging. The first valve is provided in the nitrogen gas supply passage. The nitrogen gas discharge passage is connected to the discharge-side passage of the compressor body in the hydrogen gas passage and is provided for discharging nitrogen gas that has flowed out from the cylinder part of the compressor body during nitrogen purging. The second valve is provided in the nitrogen gas discharge passage. The pressure sensor is located downstream of the connection point of the nitrogen gas supply path in the hydrogen gas flow path.

[0084] The control method for a reciprocating compressor according to this embodiment comprises a first valve operation step, a second valve operation step, and a third valve operation step, which are executed when the compressor body is stopped. In the first valve operation step, the first valve is opened so that nitrogen gas at a pressure higher than atmospheric pressure is supplied into the cylinder section when the second valve is closed. In the second valve operation step, after the execution of the first valve operation step, the pressure between the first valve and the second valve in the hydrogen gas flow path is detected, and when the pressure reaches a predetermined pressure, the first valve is closed and the second valve is opened. In the third valve operation step, after the execution of the second valve operation step, the second valve is closed when the pressure value detected by the pressure sensor falls below a threshold.

[0085] In the control method for a reciprocating compressor according to the above embodiment, when the compressor body is stopped, the first valve operation step is executed to supply nitrogen gas into the cylinder section. After that, the system waits for the pressure between the first valve and the second valve to reach a predetermined pressure. When the pressure between the first valve and the second valve reaches the predetermined pressure, the second valve is opened by executing the second valve operation step. Therefore, in the above control method, when the compressor body is stopped, the nitrogen gas supplied between the execution of the first valve operation step and the execution of the second valve operation step reaches every corner of the cylinder section and is reliably mixed with the hydrogen gas remaining in the cylinder section. Thus, the above control method can more reliably prevent hydrogen gas from remaining in the cylinder section compared to a method that discharges hydrogen gas by continuously flowing nitrogen gas from the nitrogen gas supply passage to the nitrogen gas discharge passage.

[0086] In the control method according to the above embodiment, the control sensor may be provided in the discharge-side flow path of the compressor body in the reciprocating compressor that is the target of the control method. In this case, in the control method according to the above embodiment, in the second valve operation step, it may be determined whether the pressure between the first valve and the second valve in the hydrogen gas flow path has reached the predetermined pressure based on the pressure value detected by the pressure sensor.

[0087] In the control method for a reciprocating compressor according to the above embodiment, it is determined whether the above pressure condition has been met based on the detected value (pressure value) of a pressure sensor installed in the discharge-side flow path of the compressor body in the hydrogen gas flow path. In the above control method, the second valve operation step is executed based on the result of the determination of whether the above pressure condition has been met. Therefore, in the above control method, by using the detected value of a pressure sensor installed in the discharge-side flow path of the compressor body, it is possible to determine whether nitrogen gas has filled the entire cylinder part of the compressor body, and the opening and closing timing of the first valve and the second valve can be appropriately determined.

[0088] In the control method for a reciprocating compressor according to the above embodiment, the cylinder suction valve of the cylinder section may be forcibly opened in the first valve operation step.

[0089] In the control method for a reciprocating compressor according to the above embodiment, the cylinder suction valve is forcibly opened when the first valve operation step is executed, so that nitrogen gas can be distributed throughout the entire cylinder relatively quickly, and hydrogen gas inside the cylinder can be discharged quickly.

[0090] The reciprocating compressor controlled by the control method according to the above embodiment may further include a spillback passage that returns the hydrogen gas discharged into the discharge-side passage of the compressor body back into the suction-side passage of the compressor body. In this case, the control method according to the above embodiment may close a spillback valve provided in the spillback passage in the first valve operation step.

[0091] In the control method for a reciprocating compressor according to the above embodiment, the spillback valve is kept closed when the first valve operation step is executed, so that nitrogen gas supplied from the nitrogen gas supply passage to the hydrogen gas passage is prevented from being dispersed and flowing into the spillback passage. Therefore, nitrogen gas can be reliably filled into the cylinder section.

[0092] In the control method for a reciprocating compressor according to the above embodiment, the hydrogen gas may be boil-off gas produced from liquefied hydrogen. In this case, the control method according to the above embodiment may further include a high-temperature gas introduction step after the execution of the third valve operation step and when starting the compressor body. In the high-temperature gas introduction step, the hydrogen gas, which is at a temperature higher than the temperature at which nitrogen gas liquefies or solidifies, is introduced into the hydrogen gas flow path.

[0093] In the control method for a reciprocating compressor according to the above embodiment, the high-temperature gas introduction step is performed after the execution of the third valve operation step and when the compressor body is started, so that liquefaction and solidification due to contact between nitrogen gas and hydrogen gas, which is an extremely low-temperature boil-off gas, can be prevented.

[0094] Furthermore, in the control method according to the above embodiment, the high-temperature hydrogen gas is introduced into the hydrogen gas flow path after the execution of the third valve operation step and when the compressor body is started. Therefore, in the above control method, the nitrogen gas remaining in the cylinder and other parts can be prevented from liquefying or solidifying due to the introduced high-temperature hydrogen gas.

[0095] As described above, in each of the above embodiments, hydrogen gas remaining in the cylinder portion of the compressor body can be discharged more reliably.

Claims

1. A reciprocating compressor for compressing hydrogen gas, comprising: a hydrogen gas passage provided for the flow of the hydrogen gas; a compressor body provided in the hydrogen gas passage; a nitrogen gas supply passage connected to the suction-side passage of the compressor body in the hydrogen gas passage and provided for supplying nitrogen gas into the cylinder section of the compressor body during nitrogen purging; a first valve provided in the nitrogen gas supply passage; a nitrogen gas discharge passage connected to the discharge-side passage of the compressor body in the hydrogen gas passage and provided for discharging nitrogen gas that has flowed out from the cylinder section of the compressor body during nitrogen purging; a second valve provided in the nitrogen gas discharge passage; a control unit configured to control the first valve and the second valve; and a pressure sensor provided downstream of the connection point of the nitrogen gas supply passage in the hydrogen gas passage. A reciprocating compressor, wherein, when the compressor body is stopped, the control unit is configured to perform a first valve operation, which opens the first valve so that nitrogen gas at a pressure higher than atmospheric pressure is supplied into the cylinder section when the second valve is closed; a second valve operation, which closes the first valve and opens the second valve on the condition that a pressure condition is met such that the pressure between the first valve and the second valve in the hydrogen gas flow path becomes a predetermined pressure; and a third valve operation, which closes the second valve on the condition that the pressure value detected by the pressure sensor falls below a threshold.

2. The reciprocating compressor according to claim 1, wherein the pressure sensor is provided in the discharge-side flow path of the compressor body, and the control unit is configured to determine whether or not the pressure condition has been met based on the pressure value detected by the pressure sensor.

3. The reciprocating compressor according to claim 1 or 2, wherein the control unit is configured to perform the first valve operation to the third valve operation multiple times.

4. The reciprocating compressor according to claim 1 or 2, wherein the control unit is configured to forcibly open the cylinder suction valve of the cylinder section during the first valve operation.

5. The reciprocating compressor according to claim 1, further comprising a spillback passage provided to return the hydrogen gas discharged into the discharge-side passage of the compressor body back into the suction-side passage of the compressor body, wherein the control unit is configured to close a spillback valve provided in the spillback passage during the operation of the first valve.

6. The reciprocating compressor according to claim 1, wherein the hydrogen gas is a boil-off gas produced from liquefied hydrogen, and further comprises a heating device provided in the portion of the hydrogen gas flow path upstream of the point where the nitrogen gas supply path is connected, which is provided to heat the hydrogen gas introduced into the hydrogen gas flow path to a temperature higher than the temperature at which the nitrogen gas liquefies or solidifies.

7. The reciprocating compressor according to claim 1, wherein the hydrogen gas supply source comprises a first gas supply source provided to supply the hydrogen gas which is a boil-off gas generated from liquefied hydrogen, and a second gas supply source provided to supply the hydrogen gas at a temperature higher than the temperature at which nitrogen gas liquefies or solidifies, and further comprises a switching valve provided at the upstream end of the hydrogen gas flow path, which is provided to selectively switch the hydrogen gas supply source to the hydrogen gas flow path between the first gas supply source and the second gas supply source, and the control unit is configured to control the switching valve after the execution of the third valve operation and when the compressor body is started up, so that the hydrogen gas from the second gas supply source is introduced into the hydrogen gas flow path.

8. A control method for a reciprocating compressor for compressing hydrogen gas, the reciprocating compressor comprising: a hydrogen gas flow path provided for the flow of hydrogen gas; a compressor body provided in the hydrogen gas flow path; a nitrogen gas supply path connected to the suction-side flow path of the compressor body in the hydrogen gas flow path and provided for supplying nitrogen gas into the cylinder section of the compressor body during nitrogen purging; a first valve provided in the nitrogen gas supply path; a nitrogen gas discharge path connected to the discharge-side flow path of the compressor body in the hydrogen gas flow path and provided for discharging nitrogen gas that has flowed out from the cylinder section of the compressor body during nitrogen purging; a second valve provided in the nitrogen gas discharge path; and a pressure sensor provided downstream of the connection portion of the nitrogen gas supply path in the hydrogen gas flow path, wherein, when the compressor body is stopped, the first valve is opened so that nitrogen gas at a pressure higher than atmospheric pressure is supplied into the cylinder section when the second valve is closed. A control method for a reciprocating compressor, comprising: a second valve operation step, when the compressor body is stopped and after the first valve operation step has been performed, detecting the pressure between the first valve and the second valve in the hydrogen gas flow path, and closing the first valve and opening the second valve when the pressure reaches a predetermined pressure; and a third valve operation step, when the compressor body is stopped and after the second valve operation step has been performed, closing the second valve when the pressure value detected by the pressure sensor falls below a threshold.

9. The control method for a reciprocating compressor according to claim 8, wherein the pressure sensor is provided in the discharge-side flow path of the compressor body, and in the second valve operation step, it is determined whether the pressure between the first valve and the second valve in the hydrogen gas flow path has reached the predetermined pressure based on the pressure value detected by the pressure sensor.

10. A control method for a reciprocating compressor according to claim 8 or 9, wherein in the first valve operation step, the cylinder suction valve of the cylinder section is forcibly opened.

11. The reciprocating compressor further comprises a spillback passage that returns the hydrogen gas discharged into the discharge passage of the compressor body to the suction passage of the compressor body, and in the first valve operation step, a spillback valve provided in the spillback passage is closed, the control method for a reciprocating compressor according to claim 8.

12. A control method for a reciprocating compressor according to claim 8, further comprising a high-temperature gas introduction step of introducing the hydrogen gas, which is at a temperature higher than the temperature at which nitrogen gas liquefies or solidifies, into the hydrogen gas flow path after the execution of the third valve operation step and when the compressor body is started.

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