Compressor unit and method for controlling compressor unit

Abstract

This compressor unit comprises: a first compressor installed in a first flow path; and a second compressor installed in a second flow path which is parallel to the first flow path. A first suction-side on-off valve and a first discharge-side on-off valve are installed in the first flow path. The compressor unit further comprises: a communication flow path that sends hydrogen gas present in the flow path between the first suction-side on-off valve and the first discharge-side on-off valve to the second compressor; and a communication flow path on-off valve that is installed in the communication flow path. A control unit is configured to close the first suction-side on-off valve and the first discharge-side on-off valve and open the communication flow path on-off valve in a state in which the first compressor is stopped and the second compressor is operated.

Description

Compressor Unit and Control Method of Compressor Unit

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

[0002] Patent Document 1 discloses a compressor unit that compresses hydrogen gas generated by a hydrogen gas generation unit and discharges it to a destination. The compressor unit includes three compressors connected in parallel. The compressor unit also includes a spillback flow path formed for each compressor. Further, the compressor unit also includes a circulation flow path that connects the discharge-side flow path and the suction-side flow path of the three compressors.

[0003] By the way, when the compressor stops, the valves before and after the compressor are closed, so the system is in a high-pressure state. If an attempt is made to start the compressor without reducing the pressure inside the system, a large amount of power is required, or it becomes necessary to use a large motor accordingly. In particular, when using a seal gas (such as hydrogen gas or nitrogen gas) as a sealing means for the compressor, it is necessary to continue supplying the seal gas even during stoppage, so the pressure inside the system tends to rise.

[0004] For this reason, as shown in FIG. 7, it is conceivable to provide a flare facility for discharging hydrogen gas remaining in the system to the outside of the system when the compressor 90 stops. Specifically, in a compressor unit that compresses hydrogen gas from a hydrogen supply source 950 with a compressor 90 and supplies it to a destination 951, when the compressor 90 stops, the suction-side on-off valve 93 provided in the suction-side flow path portion 92 and the discharge-side on-off valve 95 provided in the discharge-side flow path portion 94 are closed. In this state, the hydrogen gas existing downstream of the discharge-side on-off valve 95 can be discarded to the outside of the system using the flare facility. Therefore, it becomes possible to reduce the starting power required when starting the compressor.

[0005] However, when discarding hydrogen gas to the outside of the system using the flare facility when the compressor stops, the hydrogen gas that should originally be sent to the destination is wasted.

[0006] As one solution to the above-mentioned problems, Patent Document 2 discloses a method for operating a compressor unit in which, while the main compressor is shut down, another compressor sends gas to the suction and discharge passages of the main compressor.

[0007] In the operating method disclosed in Patent Document 2, when the main compressor is stopped, it is necessary to have the separate compressor installed to supply gas to the suction and discharge passages of the main compressor, which increases costs due to the addition of the compressor. Furthermore, when supplying gas to the suction passage (low-pressure space) upstream of the main compressor, the pressure in the upstream passage increases. On the other hand, when supplying gas to the discharge passage (high-pressure space) downstream of the main compressor, a relatively large compressor is required as the separate compressor.

[0008] European Patent Application Publication No. 4105491, Specification of Japanese Patent No. 7331242

[0009] This invention has been made in view of the above problems, and aims to reduce the power required to start the compressor without discarding hydrogen gas outside the compressor system when the compressor is stopped.

[0010] A compressor unit according to one aspect of the present invention is a compressor unit that inhales hydrogen gas from a hydrogen supply source and supplies the inhaled hydrogen gas to a customer, and comprises a first compressor, a second compressor, a first suction valve and a first discharge valve, a connecting passage, a connecting passage on / off valve, and a control unit. The first compressor is provided in a first passage for circulating the hydrogen gas from the hydrogen supply source. The second compressor is provided in a second passage that is in parallel with the first passage to the hydrogen supply source. The first suction valve and the first discharge valve are provided in the first passage. The connecting passage is a passage for sending the hydrogen gas present between the first suction valve and the first discharge valve to the second compressor. The connecting passage on / off valve is provided in the connecting passage. The control unit controls the opening and closing of the connecting passage on / off valve.

[0011] In the compressor unit according to this embodiment, the control unit is configured to open the connecting flow path valve when the first compressor is stopped and the second compressor is in operation.

[0012] This is a diagram showing the configuration of a compressor unit according to Embodiment 1. This is a flowchart showing a control method executed by the control unit when the first compressor is stopped. This is a flowchart showing a control method executed by the control unit when the first compressor is started. This is a flowchart showing a control method executed by the control unit when the first compressor is stopped in a configuration in which the first and second compressors utilize seal gas as a sealing means. This is a diagram showing a partial configuration of a compressor unit according to a modified example of Embodiment 1. This is a diagram showing the configuration of a compressor unit according to Embodiment 2. This is a diagram showing a partial configuration of a compressor unit according to a modified example of Embodiment 2. This is a diagram showing the configuration of a compressor unit according to the prior art.

[0013] 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.

[0014] [Embodiment 1] 1. Configuration of Compressor Unit 1 The compressor unit 1 according to Embodiment 1 inhales hydrogen gas from a hydrogen supply source 50 and supplies the inhaled hydrogen gas to a customer 51. The hydrogen supply source 50 may be a part that has a water electrolysis device and supplies hydrogen gas produced by the water electrolysis device, or it may be a part that supplies boil-off gas generated from liquefied hydrogen. However, the hydrogen supply source 50 is not limited to these and may be a part that supplies hydrogen gas from various sources.

[0015] As shown in Figure 1, the compressor unit 1 includes a first compressor 11 provided in the first flow path 10, a second compressor 21 provided in the second flow path 20, a first suction-side valve (hereinafter referred to as the "first suction-side on-off valve 14") and a first discharge-side valve (hereinafter referred to as the "first discharge-side on-off valve 15") provided in the first flow path 10, a connecting flow path 30, a connecting flow path on-off valve 31, and a control unit 40. The first flow path 10 and the second flow path 20 branch off from a supply flow path 52 extending from the hydrogen supply source 50 and are connected to a delivery flow path 53 that sends hydrogen gas to the customer 51. That is, the first flow path 10 and the second flow path 20 are provided in a parallel relationship in the hydrogen gas path between the hydrogen supply source 50 and the customer 51.

[0016] The first compressor 11 is provided in the first flow path 10. The second compressor 21 is provided in the second flow path 20. The first flow path 10 has a first suction-side flow path 12 which is on the suction side with respect to the first compressor 11, and a first discharge-side flow path 13 which is on the discharge side with respect to the first compressor 11. The second flow path 20 also has a second suction-side flow path 22 which is on the suction side with respect to the second compressor 21, and a second discharge-side flow path 23 which is on the discharge side with respect to the second compressor 21.

[0017] In this embodiment, the first compressor 11 and the second compressor 21 are both screw compressors. However, other types of compressors such as reciprocating compressors and turbo compressors can also be used.

[0018] Furthermore, in this embodiment, the compressor unit 1 comprises two compressors arranged in parallel (a first compressor 11 and a second compressor 21), but it may also comprise three or more compressors arranged in parallel.

[0019] The first suction-side on-off valve 14 and the first discharge-side on-off valve 15 are provided in the first flow path 10. Specifically, the first suction-side on-off valve 14 is provided in the first suction-side flow path 12, and the first discharge-side on-off valve 15 is provided in the first discharge-side flow path 13.

[0020] The second flow path 20 is provided with a second suction-side on-off valve 24 and a second discharge-side on-off valve 25. Specifically, the second suction-side on-off valve 24 is provided in the second suction-side flow path 22, and the second discharge-side on-off valve 25 is provided in the second discharge-side flow path 23.

[0021] The connecting passage 30 is a passage for drawing hydrogen gas present in the portion of the first passage 10 between the first suction-side on-off valve 14 and the first discharge-side on-off valve 15 into the second compressor 21. Specifically, the connecting passage 30 branches off from the portion of the first suction-side passage 12 between the first suction-side on-off valve 14 and the first compressor 11 (location P1) and connects to the second suction-side passage 22 of the second passage 20 (location P2). Location P2 is on the side of the second compressor 21 than the second suction-side on-off valve 24 in the second suction-side passage 22.

[0022] The connecting passage on / off valve 31 is installed in the connecting passage 30 and controls the opening and closing of the connecting passage 30.

[0023] The control unit 40 is configured with a microprocessor that includes an MPU / CPU and ASIC, and memory such as ROM and RAM. The control unit 40 controls the opening and closing of the first suction-side on-off valve 14, the first discharge-side on-off valve 15, the second suction-side on-off valve 24, the second discharge-side on-off valve 25, and the connecting flow path on-off valve 31 by executing firmware or the like that which is pre-stored in the memory.

[0024] The compressor unit 1 further comprises a pressure sensor 32, a first spillback section 16, and a second spillback section 26. The pressure sensor 32 detects the pressure of hydrogen gas in the portion of the first flow path 10 between the first compressor 11 and the first suction-side on-off valve 14. In this embodiment, the pressure sensor 32 is provided at a location between location P1 and the connecting flow path on-off valve 31 in the connecting flow path 30. Alternatively, the pressure sensor 32 may be provided at a location between the first suction-side on-off valve 14 and the first compressor 11 in the first suction-side flow path 12.

[0025] The first spillback section 16 includes a first spillback passage 17 that connects the first discharge passage 13 and the first suction passage 12, and a first spillback valve 18 provided in the first spillback passage 17. The amount of spillback from the first discharge passage 13 to the first suction passage 12 is adjusted by adjusting the opening degree of the first spillback valve 18.

[0026] The first spillback passage 17 is configured as part of the first passage 10 through which hydrogen gas from the hydrogen supply source 50 flows. Therefore, the first spillback passage 17 is also included in the passage portion of the first passage 10 between the first suction-side on-off valve 14 and the first discharge-side on-off valve 15, and hydrogen gas is present in this passage.

[0027] The second spillback section 26 includes a second spillback passage 27 that connects the second discharge passage 23 and the second suction passage 22, and a second spillback valve 28 provided in the second spillback passage 27. The amount of spillback from the second discharge passage 23 to the second suction passage 22 is adjusted by adjusting the opening degree of the second spillback valve 28.

[0028] The control unit 40 acquires information regarding the pressure detected by the pressure sensor 32 and also controls the opening and closing of the second suction valve 24, the second discharge valve 25, the first spillback valve 18, and the second spillback valve 28. The control unit 40 also controls the operation / stopping of the first compressor 11 and the second compressor 21.

[0029] 2. Control performed by the control unit 40 The control performed by the control unit 40 to reduce the power required to start the first compressor 11 without discarding hydrogen gas outside the compressor unit 1 system when the first compressor 11 is stopped will be explained below. The following explanation will be divided into control performed when the first compressor 11 is stopped and control performed when the first compressor 11 is started.

[0030] (1) When the first compressor 11 is stopped, if the second compressor 21 is running and a stop command for the first compressor 11 is received, the control unit 40 performs control in the manner shown in Figure 2.

[0031] As shown in Figure 2, when the control unit 40 receives a command to stop the first compressor 11 while maintaining the operating state of the second compressor 21 as described above, it stops the first compressor 11 (step S1).

[0032] After stopping the first compressor 11 by executing step S1, the control unit 40 closes the first suction-side on-off valve 14 and the first discharge-side on-off valve 15 (step S2).

[0033] Furthermore, the control unit 40 fully opens the first spillback valve 18 when step S2 is executed (step S3). In the state before the first compressor 11 is stopped, the first spillback valve 18 may be closed or open to a predetermined degree, but the execution of step S3 causes the first spillback valve 18 to be fully open. As a result, the first suction-side flow path 12 and the first discharge-side flow path 13 are connected as a single communication space in the portion between the first suction-side on-off valve 14 and the first discharge-side on-off valve 15.

[0034] Next, the control unit 40 determines, based on the information detected from the pressure sensor 32, whether the pressure of the hydrogen gas in the portion of the first suction-side passage 12 closer to the first compressor 11 than the first suction-side on-off valve 14 and the pressure of the hydrogen gas in the portion of the first discharge-side passage 13 closer to the first compressor 11 than the first discharge-side on-off valve 15 have been equalized (step S4). The determination of whether the pressure has been equalized can be made, for example, by determining that the degree of increase in the pressure P (hydrogen gas pressure in the first suction-side passage 12) detected by the pressure sensor 32 is less than a predetermined degree, or by determining that the pressure P falls within a predetermined range.

[0035] The control unit 40 determines, by determining whether the pressure has become uniform (step S4), whether a portion of the hydrogen gas that was present in the portion of the first discharge-side passage 13 on the side of the first compressor 11 to the first discharge-side on-off valve 15 immediately after the first compressor 11 stopped has moved to the first suction-side passage 12. In this embodiment, the movement of hydrogen gas from the discharge side to the suction side of the first compressor 11 mainly occurs via the spillback passage 17, but a portion may also occur via the mechanism of the first compressor 11.

[0036] When the control unit 40 determines that the pressure has become uniform (step S4: YES), it opens the connecting passage on-off valve 31 (step S5). At this time, the second compressor 21, which is connected to the connecting passage 30, is in operation, so the hydrogen gas present in the area between the first suction-side on-off valve 14 and the first discharge-side on-off valve 15, as well as in the first spillback passage 17, is drawn into the second compressor 21 via the connecting passage 30 by the suction action of the second compressor 21.

[0037] After opening the communication channel on / off valve 31, the control unit 40 monitors the pressure P and determines whether the pressure P has fallen below a predetermined threshold Pth (step S6).

[0038] If the control unit 40 determines that the pressure P has fallen below the threshold Pth (step S6: YES), it closes the connecting passage on / off valve 31 (step S7). This completes the recovery of hydrogen gas present on the suction and discharge sides of the first compressor 11.

[0039] (2) When the first compressor 11 is started Next, we will explain the case in which hydrogen gas present on the suction side and discharge side of the first compressor 11 is recovered when the first compressor 11 is started. In the following explanation, it is assumed that the second compressor 21 is in continuous operation before and after the first compressor 11 is started.

[0040] As shown in Figure 3A, when the control unit 40 receives a start command for the first compressor 11 while the second compressor 21 is operating, it executes control to recover hydrogen gas present on the suction side and discharge side of the first compressor 11 prior to starting the first compressor 11. Specifically, when the control unit 40 receives a start command for the first compressor 11, it opens the connecting passage on-off valve 31 (step S11). At this time, the control unit 40 confirms that both the first suction side on-off valve 14 and the first discharge side on-off valve 15 are closed and the first spillback valve 18 is open. As the control unit 40 executes step S11, hydrogen gas present on the suction side and discharge side of the first compressor 11, as well as in the first spillback passage 17, is drawn into the suction side of the second compressor 21 via the connecting passage 30.

[0041] After opening the communication channel on / off valve 31, the control unit 40 determines whether the pressure P has fallen below a predetermined threshold Pth (step S12).

[0042] If the control unit 40 determines that the pressure P has fallen below the threshold Pth (step S12: YES), it closes the connecting passage on / off valve 31 (step S13). This completes the recovery of hydrogen gas present on the suction and discharge sides of the first compressor 11.

[0043] Here, the first spillback valve 18 is in the open state, and both the first suction-side on-off valve 14 and the first discharge-side on-off valve 15 are in the closed state. Next, the control unit 40 opens the first suction-side on-off valve 14 (step S14). Then, the first compressor 11 is started (step S15).

[0044] After the first compressor 11 reaches a steady operating state, the control unit 40 opens the first discharge-side on-off valve 15 (step S16).

[0045] As described above, the startup control of the first compressor 11 after recovering the hydrogen gas existing on the suction side and the discharge side of the first compressor 11 is completed. Note that the timing of opening the first discharge-side on-off valve 15 does not necessarily have to be after the startup of the first compressor 11, and it may be the timing of opening the first suction-side on-off valve 14 or the timing of starting the first compressor 11.

[0046] 3. Effects In the compressor unit 1 according to the present embodiment, in a state where the first compressor 11 is stopped and the second compressor 21 is operating, the control unit 40 closes the first suction-side on-off valve 14 and the first discharge-side on-off valve 15, and opens the communication flow path on-off valve 31. As a result, the hydrogen gas existing between the first suction-side on-off valve 14 and the first discharge-side on-off valve 15 is sucked into the suction side of the operating second compressor 21 by the suction action of the second compressor 21. Therefore, in the compressor unit 1, in a state where the first compressor 11 is stopped, the hydrogen gas remaining on the intake side and the discharge side of the first compressor 11 can be suppressed to a low pressure without being discarded outside the system of the compressor unit 1. Therefore, in the compressor unit 1, the power required to restart the first compressor 11 can be reduced without wasting the hydrogen gas remaining on the intake side and the discharge side of the first compressor 11.

[0047] Further, in the compressor unit 1, the communication flow path 30 is provided so as to branch from a location P1 between the first suction-side on-off valve 14 and the first compressor 11 in the first flow path 10. Therefore, the hydrogen gas remaining on the intake side and the discharge side of the first compressor 11 can be sucked into the second compressor 21 by the suction action of the second compressor 21.

[0048] Further, in the compressor unit 1, the communication flow path 30 is connected to the suction side flow path (second suction side flow path 22) of the second compressor 21. Therefore, the hydrogen gas in the flow paths of the stopped first compressor 11 and the first suction side flow path 12 and the first discharge side flow path 13 connected thereto can be sucked into the operating second compressor 21.

[0049] Further, in the compressor unit 1, the communication flow path opening / closing valve 31 is opened after waiting for the pressure P acquired from the pressure sensor 32 to reach a pressure within a predetermined range. That is, in the compressor unit 1, before opening the communication flow path opening / closing valve 31, it is determined whether or not the pressure P has reached a pressure within a predetermined range (the control unit 40 executes a determination step). The fact that the pressure P is within the predetermined range indicates that a part of the hydrogen gas that was present on the discharge side of the first compressor 11 immediately after the stop of the first compressor 11 has moved to the suction side. Therefore, in the compressor unit 1, a part of the hydrogen gas that was present on the discharge side immediately after the stop of the first compressor 11 can also be surely made to flow into the suction side of the second compressor 21 through the communication flow path 30 connected to the first suction side flow path 12.

[0050] In the compressor unit 1 according to the present embodiment, when using a seal gas (such as hydrogen gas or nitrogen gas) as the seal means of the compressor, it is necessary to continue supplying the seal gas even while the first compressor 11 is stopped. For this reason, as shown in FIG. 3B, when the pressure P detected by the pressure sensor 32 becomes equal to or higher than the threshold value Pth2 (step S21: YES), the communication flow path opening / closing valve 31 is opened (step S22), and the hydrogen gas may be sent to the second compressor 21 through the communication flow path 30. After opening the communication flow path opening / closing valve 31, the control unit 40 monitors the pressure P and determines whether or not the pressure P has become equal to or lower than a predetermined threshold value Pth (step S23). When it is determined that the pressure P has become equal to or lower than the threshold value Pth (step S23: YES), the communication flow path opening / closing valve 31 is closed (step S24).

[0051] In the compressor unit 1 according to this embodiment, when a stop command for the first compressor 11 is received while the second compressor 21 is operating, the following operations are performed: stopping the first compressor 11 (step S1 in Figure 2), closing the first suction-side on-off valve 14 and the first discharge-side on-off valve 15 (step S2), and fully opening the first spillback valve 18 (step S3). These operations may be performed simultaneously or in a different order than the steps in Figure 2.

[0052] In the compressor unit 1 according to this embodiment, with the second compressor 21 stopped and the first compressor 11 running, the control unit 40 may close the second suction-side on-off valve 24 and the second discharge-side on-off valve 25, and open the connecting passage on-off valve 31. This allows the hydrogen gas present between the second suction-side on-off valve 24 and the second discharge-side on-off valve 25 to be drawn into the suction side of the running first compressor 11 by the suction action of the first compressor 11. In the compressor unit 1, if there is a restriction on the flow direction of the connecting passage on-off valve 31, another on-off valve is provided on the connecting passage 30, and the control unit 40 may control the opening and closing operation of this other on-off valve instead of the opening and closing operation of the connecting passage on-off valve 31. In other words, in step S5 of Figure 2, the control unit 40 opens the other on-off valve from a closed state, thereby allowing the hydrogen gas present between the second suction-side on-off valve 24 and the second discharge-side on-off valve 25 to be drawn into the first compressor 11 via the connecting passage 30. In addition, another connecting passage is provided in parallel with the connecting passage 30, and the control unit 40 can open another connecting passage on-off valve provided in this other connecting passage instead of opening and closing the connecting passage on-off valve 31. This allows the hydrogen gas present in the portion between the second suction-side on-off valve 24 and the second discharge-side on-off valve 25 to be drawn into the first compressor 11.

[0053] [Modification of Embodiment 1] The configuration of the compressor unit 1 according to a modification of Embodiment 1 will be described with reference to Figure 4. In this modification, the compressor unit 1 differs from Embodiment 1 in that the branching point (point P3) of the communication channel 30 to the first channel 10 is located differently. The other configurations are the same as those of Embodiment 1, and the control method executed by the control unit 40 (see Figure 1), which is not shown in Figure 4, is the same as that of Embodiment 1.

[0054] As shown in Figure 4, the communication passage 30 of the compressor unit 1 according to this modified example is configured to branch off from a point P3 between the first discharge-side on-off valve 15 and the first compressor 11 in the first discharge-side passage 13. More specifically, the point P3 where the communication passage 30 branches off is located closer to the first discharge-side on-off valve 15 than the point P11 where the first spillback passage 17 in the first discharge-side passage 13 branches off.

[0055] In the compressor unit 1 according to this modified example, even when the first compressor 11 is stopped and the second compressor 21 is running, hydrogen gas present between the first suction-side on-off valve 14 and the first discharge-side on-off valve 15 can be flowed into the second compressor 21.

[0056] Furthermore, when transferring hydrogen gas remaining on the suction and discharge sides of the first compressor 11 to the second compressor 21, the first spillback valve 18 is fully opened as described above. Therefore, hydrogen gas remaining in the portion of the first suction side flow path 12 between the first suction side on-off valve 14 and the first compressor 11 can also be sent to the second compressor 21 via the first spillback flow path 17.

[0057] In this modified compressor unit 1, the connecting passage 30 is configured to branch off from point P3 between the first discharge-side on-off valve 15 and the first compressor 11 in the first discharge-side passage 13. Therefore, it is not necessarily required to perform step S4 of the flowchart shown in Figure 2. That is, since the connecting passage 30 is provided to branch off from point P3 on the discharge side, which is under high pressure immediately after the first compressor 11 stops, it is not necessary to wait for the hydrogen gas pressure in the first suction-side passage 12 and the first discharge-side passage 13 to equalize.

[0058] The compressor unit 1 having the above configuration differs from the embodiment 1 in that the branching point (point P3) of the communication passage 30 to the first passage 10 is located therein, but the other configurations are the same, and hydrogen gas is recovered using the same control method as the embodiment 1. Therefore, the compressor unit 1 according to this modified example can obtain the same effects as the embodiment 1.

[0059] [Embodiment 2] The configuration of the compressor unit 1 according to Embodiment 2 will be described with reference to Figure 5. The compressor unit 1 according to this embodiment differs from Embodiment 1 in that it includes a connection point (location P4) of the communication passage 30 and a second communication passage 33. The other configurations are the same as those of Embodiment 1, and the control method executed by the control unit 40 (see Figure 1) is the same as that of Embodiment 1.

[0060] As shown in Figure 5, in the compressor unit 1 according to this embodiment, similar to the embodiment 1 described above, the first flow path 10 and the second flow path 20 are arranged in a parallel relationship in the hydrogen gas path between the hydrogen supply source 50 and the demand destination 51. Furthermore, the first suction-side flow path 12 in the first flow path 10 and the second suction-side flow path 22 in the second flow path 20 are fluidly connected at the portion on the hydrogen supply source 50 side.

[0061] In the compressor unit 1 according to this embodiment, the communication passage 30 is connected to a point P4 in the first suction-side passage 12 that is on the side of the hydrogen supply source 50 than the first suction-side on-off valve 14. The point P1 where the communication passage 30 branches off from the first suction-side passage 12 is located in the same position as in the embodiment 1 described above.

[0062] As shown in Figure 5, in this embodiment, the pressure sensor 32 is provided in the first suction-side passage 12. However, the location where the pressure sensor 32 is provided may be the connecting passage 30, as in the above embodiment.

[0063] The second connecting passage 33 is a passage for allowing hydrogen gas present in the portion of the second passage 20 between the second suction-side shut-off valve 24 and the second discharge-side shut-off valve 25 to flow into the operating first compressor 11 when the second compressor 21 is stopped. Specifically, the second connecting passage 33 branches off from a point (point P5) between the connection point P12 of the second suction-side shut-off valve 24 in the second suction-side passage 22 and the second spillback passage 27, and is connected to a point P6 on the hydrogen supply source 50 side of the second suction-side shut-off valve 24 in the second suction-side passage 22. The second connecting passage 33 is provided with a second connecting passage shut-off valve 34 that controls the opening and closing of the second connecting passage 33. The second connecting passage shut-off valve 34 is controlled to open and close by a control unit 40 (see Figure 1).

[0064] The compressor unit 1 according to this embodiment, having the configuration described above, has a connection point in the communication passage 30 that is upstream of the first suction-side on-off valve 14 in the first suction-side passage 12, but the other configurations are the same as in Embodiment 1. Also, the control method executed by the control unit 40 (see Figure 1) is the same as in Embodiment 1. Therefore, the compressor unit 1 according to this embodiment can obtain the same effects as in Embodiment 1.

[0065] However, the compressor unit 1 according to this embodiment differs from embodiment 1 in that the suction action of the second compressor 21 is generated in the hydrogen gas present in the portion of the first flow path 10 between the first suction-side on-off valve 14 and the first discharge-side on-off valve 15, via the connecting flow path 30 and the portion of the first suction-side flow path 12 upstream of the first suction-side on-off valve 14.

[0066] Furthermore, in the compressor unit 1 according to this embodiment, the connecting passage 30 bypasses the first suction-side on-off valve 14 and is connected to the portion of the first suction-side passage 12 on the hydrogen supply source 50 side (location P4), thereby fluidly connecting to the second suction-side passage 22 in the second passage 20. Therefore, the connecting passage 30 can be configured with a simple structure, and hydrogen gas remaining on the intake and discharge sides of the first compressor 11 can not be wasted.

[0067] Furthermore, the compressor unit 1 according to this embodiment includes a second communication passage 33 formed to bypass the second suction-side on-off valve 24. Therefore, in the compressor unit 1, even when the second compressor 21 is stopped and the first compressor 11 is running, hydrogen gas present in the portion between the second suction-side on-off valve 24 and the second discharge-side on-off valve 25 can be drawn into the first compressor 11 by the suction action of the first compressor 11. For this reason, in the compressor unit 1 according to this embodiment, the power required to restart the compressors 11 and 21 can be reduced without wasting residual hydrogen gas, not only when the first compressor 11 is stopped and the second compressor 21 is running, but also when the second compressor 21 is stopped and the first compressor 11 is running.

[0068] In the compressor unit 1 according to this embodiment, the second communication channel 33 is not an essential component.

[0069] [Modification of Embodiment 2] The configuration of the compressor unit 1 according to a modification of Embodiment 2 will be described with reference to Figure 6. In this modification, the compressor unit 1 differs from Embodiment 2 in that the location of the branch point (location P3) of the connecting passage 30 to the first passage 10 and the location of the branch point (location P7) of the second connecting passage 33 to the second passage 20 are different. The other configurations are the same as those of Embodiment 2, and the control method executed by the control unit 40 (see Figure 1) is the same as that of Embodiment 1.

[0070] As shown in Figure 6, the communication passage 30 of the compressor unit 1 according to this modified example is configured to branch off from a point P3 between the first discharge-side on-off valve 15 and the first compressor 11 in the first discharge-side passage 13. More specifically, the point P3 where the communication passage 30 branches off is located closer to the first discharge-side on-off valve 15 than the point P11 where the first spillback passage 17 in the first discharge-side passage 13 branches off.

[0071] In the compressor unit 1 according to this modified example, even when the first compressor 11 is stopped and the second compressor 21 is running, hydrogen gas present between the first suction-side on-off valve 14 and the first discharge-side on-off valve 15 can be diverted to the second compressor 21 by bypassing the first suction-side on-off valve 14.

[0072] Furthermore, when sending the hydrogen gas remaining on the suction and discharge sides of the first compressor 11 to the second compressor 21, the first spillback valve 18 is fully opened as described above. Therefore, the hydrogen gas remaining in the portion of the first suction side passage 12 between the first suction side on-off valve 14 and the first compressor 11 can also be allowed to flow into the second compressor 21 via the first spillback passage 17.

[0073] The second connecting passage 33 is a passage for allowing hydrogen gas present in the portion of the second passage 20 between the second suction-side shut-off valve 24 and the second discharge-side shut-off valve 25 to flow into the operating first compressor 11 when the second compressor 21 is stopped. The second connecting passage 33 is configured to branch off from point P7 in the second discharge-side passage 23 between the second discharge-side shut-off valve 25 and the second compressor 21. More specifically, point P7 where the second connecting passage 33 branches off is located closer to the second discharge-side shut-off valve 25 than point P13 where the second spillback passage 27 in the second discharge-side passage 23 branches off.

[0074] In the compressor unit 1 according to this modified example, even when the first compressor 11 is stopped and the second compressor 21 is running, hydrogen gas present in the area between the first suction valve 14 and the first discharge valve 15 can be diverted to the second compressor 21 by bypassing the first suction valve 14.

[0075] Furthermore, in the compressor unit 1, similar to the embodiment 2 described above, when the second compressor 21 is stopped and the first compressor 11 is running, hydrogen gas present in the portion between the second suction valve 24 and the second discharge valve 25 can be diverted to the first compressor 11 by bypassing the second suction valve 24.

[0076] Furthermore, when the first compressor 11 is stopped, the first spillback valve 18 is fully open, so the portion of the first suction-side passage 12 between the first suction-side on-off valve 14 and the first compressor 11, and the portion of the first discharge-side passage 13 between the first discharge-side on-off valve 15 and the first compressor 11 become a single continuous passage. Therefore, hydrogen gas remaining on the intake and discharge sides of the first compressor 11 can be drawn into the second compressor 21 by the suction action of the second compressor 21 via the connecting passage 30.

[0077] Furthermore, when the second compressor 21 is stopped, the second spillback valve 28 is fully open, so the portion between the second suction-side on-off valve 24 and the second compressor 21 in the second suction-side passage 22 and the portion between the second discharge-side on-off valve 25 and the second compressor 21 in the second discharge-side passage 23 become a single continuous passage. Therefore, hydrogen gas remaining in the intake and discharge portions of the second compressor 21 can be drawn into the first compressor 11 by the suction action of the first compressor 11 via the second connecting passage 33.

[0078] The compressor unit 1 having the above configuration differs from the embodiment 2 in that the location of the branch point (location P3) of the connecting passage 30 to the first passage 10 and the location of the branch point (location P7) of the second connecting passage 33 to the second passage 20 are the same, but the other configurations are the same, and since hydrogen gas is recovered using the same control method as the embodiment 2, the same effects as the embodiment 2 can be obtained.

[0079] In addition, in the compressor unit 1 according to this modified example, the communication passage 30 is configured to branch off from point P3 between the first discharge-side on-off valve 15 and the first compressor 11 in the first discharge-side passage 13, so it is not necessarily required to perform step S4 of the flowchart shown in Figure 2.

[0080] [Other Modifications] In embodiments 1 and 2 described above, the connecting passage 30 is provided so as to branch off from location P1 in the first suction-side passage 12, and in the modified embodiment 1 and the modified embodiment 2 described above, the connecting passage 30 is provided so as to branch off from location P3 in the first discharge-side passage 13. However, the present invention is not limited thereto. For example, the connecting passage 30 may be branched off from the first spillback passage 17. Also, in cases where a reciprocating compressor is used as the first compressor 11, one end of the connecting passage 30 may be connected to the leak gas discharge section of the compressor.

[0081] Furthermore, in the embodiments 1 and 2 described above and their variations, a first flow path 10 and a second flow path 20 are provided in parallel with each other, with a first compressor 11 in the first flow path 10 and a second compressor 21 in the second flow path 20. However, the present invention is not limited thereto. For example, three or more flow paths are provided in parallel with each other, and a compressor is provided in each flow path. In this case, if there are multiple compressors in operation, hydrogen gas may be drawn into these multiple compressors. Also, the compressors provided in each flow path may be provided in multiple stages.

[0082] Furthermore, in the embodiments 1 and 2 described above and their variations, a first spillback section 16 is provided to connect the suction side and discharge side of the stopped first compressor 11, but it is not always necessary to use the spillback section to equalize the pressure. For example, pressure equalization may be achieved by allowing hydrogen gas to flow from the discharge side to the suction side through the mechanism of the first compressor 11.

[0083] In the embodiments 1 and 2 described above and their variations, a check valve may be used as the first discharge valve in the first discharge valve 15. This check valve is for preventing backflow of hydrogen gas discharged from the first compressor 11. The first discharge valve 15 and the check valve may be used in combination as the first discharge valve. Similarly, a check valve may be used in place of the second discharge valve 25, or in combination with the second discharge valve 25.

[0084] In the embodiments 1 and 2 described above and their variations, a check valve may be used as the first suction valve instead of the first suction valve 14. The check valve is for preventing backflow of hydrogen gas drawn into the first compressor 11. The first suction valve 14 and the check valve may be used in combination as the first suction valve. Similarly, a check valve may be used in place of the second suction valve 24, or in combination with the second suction valve 24.

[0085] It should be noted that the embodiments and modifications disclosed herein are illustrative and not restrictive in all respects. 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.

[0086] [Summary] A compressor unit according to one aspect of the present invention is a compressor unit that inhales hydrogen gas from a hydrogen supply source and supplies the inhaled hydrogen gas to a customer, and comprises a first compressor, a second compressor, a first suction valve and a first discharge valve, a connecting passage, a connecting passage on / off valve, and a control unit. The first compressor is provided in a first passage for circulating the hydrogen gas from the hydrogen supply source. The second compressor is provided in a second passage that is in parallel with the first passage to the hydrogen supply source. The first suction valve and the first discharge valve are provided in the first passage. The connecting passage is a passage for sending the hydrogen gas present between the first suction valve and the first discharge valve to the second compressor. The connecting passage on / off valve is provided in the connecting passage. The control unit controls the opening and closing of the connecting passage on / off valve.

[0087] In the compressor unit according to this embodiment, the control unit is configured to open the connecting flow path valve when the first compressor is stopped and the second compressor is in operation.

[0088] In the compressor unit according to the above embodiment, when the first compressor is stopped and the second compressor is running, the control unit closes the first suction valve and the first discharge valve, and opens the connecting flow path valve. As a result, the hydrogen gas present between the first suction valve and the first discharge valve is drawn into the suction side of the second compressor by the suction action of the second compressor. Therefore, in the compressor unit according to the above embodiment, when the first compressor is stopped, the hydrogen gas remaining on the intake and discharge sides of the first compressor is not discarded outside the compressor unit system, and the pressure within the system can be kept low. Consequently, in the compressor unit according to the above embodiment, the hydrogen gas remaining on the intake and discharge sides of the first compressor is not wasted, and the power required to restart the first compressor can be reduced.

[0089] In the compressor unit according to the above embodiment, the communication passage may be provided so as to branch off from between the first suction valve and the first discharge valve in the first passage.

[0090] In the compressor unit according to the above embodiment, the connecting passage is provided to branch off from between the first suction valve and the first discharge valve in the first passage, so that hydrogen gas remaining on the intake and discharge sides of the first compressor can be drawn into the suction side of the second compressor by the suction action of the second compressor.

[0091] In the compressor unit according to the above embodiment, the communication channel may be connected to the suction side portion of the second compressor in the second channel.

[0092] In the compressor unit according to the above embodiment, since the connecting passage is connected to the suction passage of the second compressor, hydrogen gas in the first compressor, which is stopped, and the suction passage and discharge passage connected to it can be drawn into the second compressor, which is in operation.

[0093] In the compressor unit according to the above embodiment, the communication passage may be connected to a portion of the first passage that is closer to the hydrogen supply source than the first suction valve.

[0094] In the compressor unit according to the above embodiment, the connecting passage bypasses the first suction valve and connects to the hydrogen supply source side portion of the suction passage of the first compressor, thereby fluidly connecting to the suction passage of the second compressor. Therefore, the connecting passage can be configured with a simple structure, and hydrogen gas remaining on the intake and discharge sides of the first compressor can not be wasted.

[0095] In the compressor unit according to the above embodiment, a pressure sensor may be further provided between the first compressor and the first suction valve in the first flow path, or between the first compressor and the first discharge valve in the first flow path. In this case, the control unit may be configured to open the connecting flow path on / off valve when it determines that the pressure obtained from the pressure sensor is within a predetermined range.

[0096] In the compressor unit according to the above embodiment, the connecting passage valve is opened after waiting for the pressure obtained from the pressure sensor to fall within a predetermined range. When the pressure falls within this predetermined range, it indicates that some of the hydrogen gas that was present on the discharge side immediately after the first compressor stopped has moved to the suction side. Therefore, in the above compressor unit, even if the connecting passage is connected to the suction side of the first compressor, some of the hydrogen gas that was present on the discharge side immediately after the first compressor stopped can be reliably drawn into the second compressor via the connecting passage.

[0097] In the compressor unit according to the above embodiment, the first discharge valve may be a first discharge valve that is an on / off valve, and the control unit may control the opening and closing of the first discharge valve. In this case, the control unit may be configured to close the first discharge valve and open the connecting flow path valve when the first compressor is stopped and the second compressor is running.

[0098] In the compressor unit according to the above embodiment, a first discharge-side on-off valve is used as the first discharge-side valve. Even in this case, the power required to restart the first compressor can be reduced without wasting the hydrogen gas remaining on the intake and discharge sides of the first compressor.

[0099] In the compressor unit according to the above embodiment, the first suction valve may be a first suction valve that is an on / off valve, and the control unit may control the opening and closing of the first suction valve. In this case, the control unit may be configured to close the first suction valve and open the connecting flow path valve when the first compressor is stopped and the second compressor is running.

[0100] In the compressor unit according to the above embodiment, a first suction-side on-off valve is used as the first suction-side valve. Even in this case, the power required to restart the first compressor can be reduced without wasting the hydrogen gas remaining on the intake and discharge sides of the first compressor.

[0101] In the compressor unit according to the above embodiment, the first compressor may be a screw compressor.

[0102] The compressor unit according to the above embodiment can reduce the power required to restart the first compressor without wasting the hydrogen gas remaining on the intake and discharge sides of the first compressor, even when a screw compressor is used as the first compressor.

[0103] A control method for a compressor unit according to one aspect of the present invention is a control method for a compressor unit that inhales hydrogen gas from a hydrogen supply source and supplies the inhaled hydrogen gas to a customer. The compressor unit controlled by the control method according to this aspect comprises a first compressor, a second compressor, a first suction valve and a first discharge valve, a connecting passage, and a connecting passage on / off valve. The first compressor is provided in a first passage for circulating the hydrogen gas from the hydrogen supply source. The second compressor is provided in a second passage that is in parallel with the first passage to the hydrogen supply source. The first suction valve and the first discharge valve are provided in the first passage. The connecting passage is a passage for sending the hydrogen gas present between the first suction valve and the first discharge valve to the second compressor. The connecting passage on / off valve is provided in the connecting passage.

[0104] The control method for the compressor unit according to this embodiment includes a valve opening step in which the connecting flow path on / off valve is opened when the operating state of the second compressor is maintained and the first compressor is stopped.

[0105] In the compressor unit control method according to the above embodiment, when the first compressor is stopped and the second compressor is running, the control unit includes a valve opening step that closes the first suction valve and the first discharge valve and opens the connecting flow path valve. As a result, the hydrogen gas present between the first suction valve and the first discharge valve is drawn into the suction side of the second compressor by the suction action of the second compressor. Therefore, in the compressor unit control method according to the above embodiment, when the first compressor is stopped, the hydrogen gas remaining on the intake and discharge sides of the first compressor is not discarded outside the compressor unit system, and the pressure within the system can be kept low. Consequently, in the compressor unit control method according to the above embodiment, the hydrogen gas remaining on the intake and discharge sides of the first compressor is not wasted, and the power required to restart the first compressor can be reduced.

[0106] In the control method for the compressor unit according to the above embodiment, the first discharge valve may be a first discharge on-off valve. A compressor unit having this configuration may further include a valve closing step of closing the first discharge on-off valve when the operating state of the second compressor is maintained and the first compressor is stopped.

[0107] The control method for a compressor unit according to the above embodiment controls a compressor unit in which a first discharge-side on / off valve is used as the first discharge-side valve. In this case as well, by performing the valve closing step and the valve opening step, the power required to restart the first compressor can be reduced without wasting the hydrogen gas remaining on the intake and discharge sides of the first compressor.

[0108] In the control method for the compressor unit according to the above embodiment, the first suction valve may be a first suction valve that is an on-off valve. For a compressor unit having this configuration, the method may further include a valve closing step of closing the first suction valve when the operating state of the second compressor is maintained and the first compressor is stopped.

[0109] The control method for a compressor unit according to the above embodiment controls a compressor unit in which a first suction-side on-off valve is used as the first suction-side valve. In this case as well, by performing the valve closing step and the valve opening step, the power required to restart the first compressor can be reduced without wasting the hydrogen gas remaining on the intake and discharge sides of the first compressor.

[0110] In the control method for the compressor unit according to the above embodiment, the compressor unit may further include a pressure sensor provided between the first compressor and the first suction valve in the first flow path, or between the first compressor and the first discharge valve in the first flow path. For a compressor unit having this configuration, when the operating state of the second compressor is maintained and the first compressor is stopped, the method may further include a determination step of determining whether the pressure obtained from the pressure sensor has fallen within a predetermined range before executing the valve opening step.

[0111] In the compressor unit control method according to the above embodiment, the control target is a compressor unit in which a connecting passage bypasses the first suction valve and connects to the hydrogen supply source side portion of the suction passage of the first compressor, thereby fluidly connecting to the suction passage of the second compressor. In this case as well, since the method further includes the determination step of making the determination before executing the valve opening step, a simple connecting passage can be used in the target compressor unit, and hydrogen gas remaining on the intake and discharge sides of the first compressor can not be wasted.

[0112] In the control method for the compressor unit according to the above embodiment, the first discharge valve may be a first discharge on-off valve which is an on-off valve, and the first suction valve may be a first suction on-off valve which is an on-off valve. For a compressor unit having this configuration, when the operating state of the second compressor is maintained and the first compressor is stopped, after executing the valve closing step of closing the first suction on-off valve and the first discharge on-off valve, and before executing the valve opening step, the determination step of determining whether the pressure obtained from the pressure sensor has come within a predetermined range may be executed.

[0113] The control method for the compressor unit according to the above embodiment performs the determination step after the valve closing step but before the valve opening step, so that hydrogen gas remaining on the intake and discharge sides of the first compressor is not wasted.

[0114] As described above, in each of the above embodiments, it is possible to reduce the power required to start the compressor without discarding hydrogen gas outside the compressor system when the compressor is stopped.

Claims

1. A compressor unit for drawing in hydrogen gas from a hydrogen supply source and supplying the drawn-in hydrogen gas to a customer, comprising: a first compressor provided in a first flow path for circulating the hydrogen gas from the hydrogen supply source; a second compressor provided in a second flow path parallel to the first flow path with respect to the hydrogen supply source; a first suction valve and a first discharge valve provided in the first flow path; a connecting flow path provided to send the hydrogen gas present between the first suction valve and the first discharge valve to the second compressor; a connecting flow path on / off valve provided in the connecting flow path; and a control unit for controlling the opening and closing of the connecting flow path on / off valve, wherein the control unit is configured to open the connecting flow path on / off valve when the first compressor is stopped and the second compressor is in operation.

2. The compressor unit according to claim 1, wherein the connecting passage is provided to branch off from between the first suction valve and the first discharge valve in the first passage.

3. The compressor unit according to claim 1, wherein the connecting passage is connected to the suction side portion of the second compressor in the second passage.

4. The compressor unit according to claim 1, wherein the connecting passage is connected to the portion of the first passage on the hydrogen supply source side of the first suction valve.

5. The compressor unit according to any one of claims 1 to 4, further comprising a pressure sensor provided between the first compressor and the first suction valve in the first flow path or between the first compressor and the first discharge valve in the first flow path, wherein the control unit is configured to open the connecting flow path on / off valve when it determines that the pressure obtained from the pressure sensor is within a predetermined range.

6. The compressor unit according to any one of claims 1 to 4, wherein the first discharge valve is a first discharge valve that is an on / off valve, the control unit controls the opening and closing of the first discharge valve, and the control unit is configured to close the first discharge valve and open the connecting flow path valve when the first compressor is stopped and the second compressor is running.

7. The compressor unit according to any one of claims 1 to 4, wherein the first suction valve is a first suction valve that is an on / off valve, the control unit controls the opening and closing of the first suction valve, and the control unit is configured to close the first suction valve and open the connecting flow path valve when the first compressor is stopped and the second compressor is running.

8. The compressor unit according to any one of claims 1 to 4, wherein the first compressor is a screw compressor.

9. A control method for a compressor unit that inhales hydrogen gas from a hydrogen supply source and supplies the inhaled hydrogen gas to a customer, wherein the compressor unit comprises: a first compressor provided in a first flow path for circulating the hydrogen gas from the hydrogen supply source; a second compressor provided in a second flow path parallel to the first flow path with respect to the hydrogen supply source; a first suction valve and a first discharge valve provided in the first flow path; a connecting flow path provided to send the hydrogen gas present between the first suction valve and the first discharge valve to the second compressor; and a connecting flow path on / off valve provided in the connecting flow path, wherein the control method for the compressor unit comprises a valve opening step of opening the connecting flow path on / off valve when the operating state of the second compressor is maintained and the first compressor is stopped.

10. The control method for a compressor unit according to claim 9, further comprising a valve closing step of closing the first discharge valve when the first discharge valve is a first discharge valve that is an on / off valve, and the second compressor is in an operating state and the first compressor is stopped.

11. The control method for a compressor unit according to claim 9, further comprising a valve closing step of closing the first suction valve when the first suction valve is a first suction valve that is an on / off valve, and the second compressor is in an operating state and the first compressor is stopped.

12. The compressor unit further comprises a pressure sensor provided between the first compressor and the first suction valve in the first flow path or between the first compressor and the first discharge valve in the first flow path, and further comprises a determination step of determining whether the pressure obtained from the pressure sensor has fallen within a predetermined range before executing the valve opening step, when the operating state of the second compressor is maintained and the first compressor is stopped.

13. A control method for a compressor unit according to claim 12, wherein the first discharge valve is a first discharge valve that is an on / off valve, the first suction valve is a first suction valve that is an on / off valve, and when the operating state of the second compressor is maintained and the first compressor is stopped, the determination step of determining whether the pressure obtained from the pressure sensor has come within a predetermined range is performed after the valve closing step of closing the first suction valve and the first discharge valve, but before the valve opening step is performed.

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