Reciprocating compressor, compressor unit, and operating method of reciprocating compressor

Abstract

This system suppresses excessive drops in suction pressure when the supply flow rate of the target gas from upstream sources fluctuates. [Solution] The reciprocating compressor 20 comprises two compression units 1 and 2 arranged in parallel in the flow direction of the target gas, and a pressure sensor 31 for measuring the pressure of the target gas. The compression units 1 and 2 are equipped with suction valve unloaders that can switch between load operation and no-load operation of the target gas in each compression chamber. The compressor further comprises a drive control unit 8a for switching the suction valve unloaders of the compression units. When each compression chamber is switched to load operation or no-load operation, the compression units 1 and 2 are in a load state of 100%, 75%, 50%, or 25%. The drive control unit 8a sets the load state to 100%, 50%, or 75% when the pressure measured by the pressure sensor 31 is above a first threshold, and sets the load state to 25% when the pressure measured by the pressure sensor 31 is below the first threshold.

Description

[Technical Field]

[0001] The present invention relates to a reciprocating compressor, a compressor unit, and a method of operating a reciprocating compressor. [Background Art]

[0002] In recent years, considering the environment, the use of hydrogen as a fuel for power generation, automobiles, and the like has been considered, and the demand for hydrogen is increasing. Patent Document 1 discloses a two-stage reciprocating compressor. In this reciprocating compressor, two compression chambers (a compression chamber on the head end side and a compression chamber on the connecting rod side) are provided respectively in the first-stage and second-stage compression mechanisms. Each compression chamber is provided with a suction valve unloader capable of switching between loaded and unloaded states, and by switching the loaded and unloaded states of the four compression chambers, various states of 100% load, 75% load, 50% load, 25% load and 0% load can be obtained. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 2009-30454 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] Incidentally, there are cases where a device that supplies gas toward the reciprocating compressor is provided upstream of the reciprocating compressor. When the supply amount of gas from the device decreases, the suction pressure of the reciprocating compressor will decrease. In this case, if the operation of the reciprocating compressor is continued with the load state kept constant, the reciprocating compressor will excessively suck gas from the device, which promotes a further decrease in the suction pressure. Note that Patent Document 1 does not disclose criteria relating to switching of the load state, so the problem of promoted reduction in suction pressure cannot be solved only with the technology disclosed in Patent Document 1.

[0005] The present invention has been made in view of the above problems, and aims to provide a reciprocating compressor that can suppress an excessive drop in suction pressure when the supply flow rate of the target gas from upstream equipment fluctuates. [Means for solving the problem]

[0006] The reciprocating compressor according to the present invention is a reciprocating compressor used in an environment in which a fluctuating element that causes fluctuations in the suction pressure of a target gas exists upstream, and comprises two compression units arranged in parallel in the flow direction of the target gas, and a pressure sensor provided upstream of the two compression units for measuring the pressure of the target gas. Each of the two compression units comprises one piston, one cylinder housing the piston and forming compression chambers on both sides of the piston, and a suction valve unloader provided at the suction portion of each compression chamber, which can switch between load operation and unload operation of the target gas in each compression chamber. The reciprocating compressor further comprises a drive control unit that switches the suction valve unloaders of the two compression units. By switching each compression chamber of the two compression units between load operation and unload operation, the two compression units can be in a 100% load state, a 75% load state, a 50% load state, or a 25% load state. The drive control unit is configured to perform a first load control to set the load to 100%, 50%, or 75% when the pressure measured by the pressure sensor is equal to or greater than a first threshold, and to perform a second load control to set the load to 25% when the pressure measured by the pressure sensor is less than the first threshold.

[0007] In the aforementioned reciprocating compressor, in environments where the suction pressure of the target gas may fluctuate, the load state of the two compression sections is reduced to 25% in accordance with a decrease in the pressure measured by pressure sensors located upstream of the two compression sections. This prevents the processing capacity of the reciprocating compressor from becoming excessive. As a result, it is possible to suppress an excessive decrease in the pressure of the target gas drawn into the two compression sections. Therefore, it can handle cases where the amount of target gas drawn in fluctuates greatly due to fluctuating factors. Moreover, a low suction state can be obtained by a simple method of switching the suction valve unloader.

[0008] The drive control unit may, during the execution of the first load control, set the load state to 100% if the pressure measured by the pressure sensor is greater than or equal to a second threshold which is a threshold higher than the first threshold, or it may set the load state to either 50% or 75% if the pressure measured by the pressure sensor is greater than or equal to the first threshold but less than the second threshold.

[0009] In this embodiment, load states between a 25% load state and a 100% load state are set, enabling more precise load control according to the magnitude of the pressure of the target gas drawn into the two compression sections. When the measured pressure is above the first threshold and below the second threshold, the load state may be set to 50%, or to 75%, or the system may switch between the 50% load state and the 75% load state depending on the measured pressure.

[0010] The drive control unit may, during the execution of the first load control, set the load state to 50% if the pressure measured by the pressure sensor is higher than the first threshold and lower than the second threshold (i.e., less than or equal to the first threshold), and set the load state to 75% if it is higher than or equal to the third threshold and less than the second threshold.

[0011] In this embodiment, the load state between a 25% load state and a 100% load state is set to either a 50% or 75% load state depending on the height of the pressure measured by the pressure sensor, thereby enabling more precise load control.

[0012] The drive control unit may switch the suction valve unloader so that, when changing from the first load control to the second load control, it passes through the 100% load state, the 75% load state, the 25% load state, and an intermediate load state.

[0013] In this embodiment, an intermediate load state is passed through when changing from the first load control to the second load control, thus suppressing fluctuations in the capacity of the two compression sections when the load state changes. Therefore, the impact on pressure fluctuations of the target gas drawn into the two compression sections can be reduced. Furthermore, if an intermediate load state is not set, the pressure measured by the pressure sensor is likely to change abruptly from a 100% load state or a 75% load state to a 25% load state, leading to large load fluctuations. However, by passing through an intermediate load state, such a situation can be prevented.

[0014] The reciprocating compressor may further include a storage unit that stores the compression unit having the compression chamber on which the load operation was performed, among the two compression units, when the load state is 25%. In this case, the drive control unit may read the compression unit stored in the storage unit when maintaining the 25% load state for a certain period of time, when switching from a load state other than 25% to the 25% load state, or when restarting the reciprocating compressor and operating it in the 25% load state, and drive the suction valve unloader so that a compression unit other than the read-out compression unit becomes the load operation.

[0015] In this embodiment, when operating under a 25% load, the two compression sections can be used alternately, thus preventing an uneven load on one of the compression sections (or its internal components).

[0016] The reciprocating compressor may include a compression stage composed of the two compression sections, and a downstream compression stage composed of one compression section that draws in the target gas discharged from the compression stage. In this case, the one compression section may include one piston and one cylinder that houses the one piston and forms compression chambers on one or both sides of the one piston.

[0017] In this embodiment, it is possible to prevent the processing capacity of the compression stage from becoming excessive when the flow rate of the target gas drawn into the compression stage having two compression sections is reduced, and the pressure of the target gas can be increased by the subsequent compression stage.

[0018] The compressor unit according to the present invention comprises a reciprocating compressor, a screw-type or turbo-type upstream compressor positioned upstream of the reciprocating compressor, and a discharge volume adjustment means for adjusting the discharge volume of the upstream compressor, wherein the upstream compressor, whose discharge volume is adjusted by the discharge volume adjustment means, functions as the variable element.

[0019] The reciprocating compressor may be located downstream of a storage tank for temporarily storing hydrogen gas generated using renewable energy. In this case, the storage tank may function as a variable element that changes the suction pressure in accordance with fluctuations in the pressure inside the storage tank.

[0020] The target gas may also be hydrogen gas.

[0021] A method for operating a reciprocating compressor according to the present invention is a method for operating a reciprocating compressor used in an environment where there is a varying element that varies the suction pressure of a target gas upstream, wherein the reciprocating compressor comprises two compression units arranged in parallel in the flow direction of the target gas, and a pressure sensor provided upstream of the two compression units for measuring the pressure of the target gas, each of the two compression units respectively comprises one piston, one cylinder that accommodates the piston and forms compression chambers on both sides of the piston, and suction valve unloaders respectively provided at suction portions of each compression chamber and capable of switching between loaded operation and unloaded operation of the target gas in each compression chamber, in the operating method, each compression chamber of the two compression units is switched to the loaded operation or the unloaded operation, so that the two compression units can be set to a 100% load state, a 75% load state, a 50% load state or a 25% load state, when the pressure measured by the pressure sensor is equal to or higher than a first threshold, a first load control is performed to set the two compression units to the 100% load state, the 50% load state or the 75% load state, and when the pressure measured by the pressure sensor is less than the first threshold, a second load control is performed to set the two compression units to the 25% load state. [Effects of the Invention]

[0022] As described above, according to the reciprocating compressor of the present invention, an excessive decrease in suction pressure can be suppressed. Brief Description of the Drawings

[0023] [Figure 1] It is a diagram schematically showing a hydrogen gas flow path system to which the reciprocating compressor according to the first embodiment is applied. [Figure 2] It is a diagram schematically showing the configuration of two compression units provided in the reciprocating compressor. [Figure 3] (a) is a diagram explaining a 0% load state, (b) is a diagram explaining a 25% load state, (c) is a diagram explaining a 50% load state, (d) is a diagram explaining a 75% load state, and (e) is a diagram explaining a 100% load state. [Figure 4]It is a diagram for explaining first load control and second load control by the drive control unit. [Figure 5] It is a diagram for explaining a first modification of the first load control and the second load control by the drive control unit. [Figure 6] It is a diagram for explaining a second modification of the first load control and the second load control by the drive control unit. [Figure 7] It is a diagram for explaining a third modification of the first load control and the second load control by the drive control unit. [Figure 8] It is a diagram schematically showing a compressor unit according to a second embodiment. [Figure 9] It is a diagram schematically showing a compressor unit according to another embodiment. [Figure 10] It is a diagram schematically showing a compressor unit according to another embodiment. DETAILED DESCRIPTION OF EMBODIMENTS

[0024] Hereinafter, modes for carrying out the present invention will be described in detail with reference to the drawings.

[0025] (First Embodiment) As shown in Figure 1, a reciprocating compressor 20 according to the present embodiment receives hydrogen gas obtained by a water electrolysis device 21, boosts the pressure of the received hydrogen gas, and supplies the pressure-increased hydrogen gas to a demand destination thereof. The water electrolysis device 21 is configured to generate hydrogen gas using, for example, electric power generated using renewable energy. Examples of renewable energy include solar light, wind power, hydropower, wave power, tidal power, geothermal energy, solar heat, heat present in the atmosphere and other heat existing in nature, or biomass. Note that the water electrolysis device 21 is not limited to one that generates hydrogen gas using electric power obtained using renewable energy.

[0026] The hydrogen gas obtained from the water electrolysis device 21 is stored in the storage tank 22. The reciprocating compressor 20 is connected to the storage tank 22 and used for this purpose. Specifically, the reciprocating compressor 20 draws in the target gas, which is hydrogen gas, sent from the storage tank 22, and pressurizes this target gas.

[0027] In the water electrolysis device 21, hydrogen gas is generated using electricity produced from renewable energy, so the amount of hydrogen gas stored in the storage tank 22 is prone to fluctuations. As a result, the pressure inside the storage tank 22 is prone to fluctuations, and therefore the flow rate of hydrogen gas supplied to the reciprocating compressor 20 fluctuates in accordance with the pressure fluctuations inside the storage tank 22. In other words, the reciprocating compressor 20 is used in environments where there are fluctuating factors that cause changes in the suction pressure of the target gas.

[0028] The reciprocating compressor 20 includes an intake passage 23 connected to a storage tank 22, a compression stage 25 connected to the intake passage 23, a downstream compression stage 27 connected to the compression stage 25 through a connecting passage 26, and a discharge passage 28 connected to the downstream compression stage 27.

[0029] The compression stage 25 comprises two compression sections 1 and 2 connected in parallel to each other in the intake passage 23. That is, the two compression sections 1 and 2 are arranged in parallel in the direction of the flow of the target gas.

[0030] As shown in Figure 2, one compression unit 1 has a first-stage compression mechanism 1A, and the other compression unit 2 has a second-stage compression mechanism 2A. That is, the compression stage 25 includes one first-stage compression mechanism 1A and one second-stage compression mechanism 2A.

[0031] As shown in Figure 2, the first-stage compression mechanism 1A comprises one piston 3 and one cylinder 5 that houses the piston 3 and forms compression chambers HE and CE on both sides of the piston 3. Similarly, the second-stage compression mechanism 2A also comprises one piston 3 and one cylinder 5 that houses the piston 3 and forms compression chambers HE and CE on both sides of the piston 3.

[0032] Each piston 3 is connected to a crank mechanism 4, and this crank mechanism 4 is driven by a drive motor M, which in turn compresses the target gas in the compression chambers HE and CE of the first-stage compression mechanism 1A and the second-stage compression mechanism 2A, respectively.

[0033] Each cylinder 5 contains a compression chamber HE on the head end side and a compression chamber CE on the connecting rod side. Therefore, the compression stage 25 has a total of four compression chambers HE and CE, and these four compression chambers HE and CE are in parallel with respect to the intake passage 23.

[0034] Since the four compression chambers HE and CE of the first-stage compression mechanism 1A and the second-stage compression mechanism 2A are connected in parallel to the intake passage 23, the target gas flowing through the intake passage 23 is divided among these four compression chambers HE and CE before being drawn into each respective compression chamber HE and CE.

[0035] The subsequent compression stage 27, although not shown in the figure, comprises one piston and one cylinder that houses the piston and forms compression chambers on one or both sides of the piston. In other words, the subsequent compression stage 27 is composed of a reciprocating compression mechanism. The piston of this subsequent compression stage 27 may also be connected to the crank mechanism 4 and driven by the drive motor M. The target gas, which has been compressed in the compression stage 25, is introduced into the compression chamber of the subsequent compression stage 27.

[0036] As shown in Figure 1, a pressure sensor 31 for measuring the pressure of the target gas is located in the intake passage 23. The pressure sensor 31 outputs a signal indicating the measured pressure. This signal is input to the controller 8, which will be described later. Note that the location of the pressure sensor 31 is not particularly limited as long as it is upstream of the compression stage 25.

[0037] A spillback passage 32 is connected to the connection passage 26. The spillback passage 32 is a passage for returning a portion of the target gas discharged from the compression stage 25 back to the intake passage 23. A flow control valve 33 is provided in the spillback passage 32. The flow control valve 33 operates to adjust its opening in response to commands from the controller 8, which will be described later. The flow control valve 33 may be controlled so that the pressure measured by the pressure sensor 31 falls within a predetermined range. Alternatively, the flow control valve 33 may be controlled, for example, so that the pressure on the discharge side of the compression stage 25 falls within a predetermined range.

[0038] As shown in Figure 2, each compression chamber HE and CE of the compression stage 25 is provided with a suction valve unloader 7. In other words, there are four suction valve unloaders 7. The suction valve unloader 7 is an actuator for switching the state of the suction valve (not shown) provided in each compression chamber. The suction valve unloader 7 is configured to switch the suction valve between a constrained state and a free state. When the suction valve is constrained, the compression chambers HE and CE and the flow path on their suction side are in communication, so in these compression chambers HE and CE, the target gas is not compressed regardless of the operation of the piston 3, resulting in no-load operation. The state of the suction valve unloader 7 at this time is called the unloaded state. On the other hand, when the suction valve is free, the suction valve opens and closes in accordance with the differential pressure between the compression chambers HE and CE and the flow path on their suction side. In this case, the compression chambers HE and CE are in load operation, where the target gas is compressed in conjunction with the operation of the piston 3. The state of the suction valve unloader 7 at this time is called the loaded state. In this context, the intake passage refers to the intake passage 23 for the compression chambers HE and CE of the first-stage compression mechanism 1A. The same applies to the second-stage compression mechanism 2A.

[0039] Each of the four suction valve unloaders is connected to an air piping system equipped with a solenoid valve (not shown). Compressed air is supplied to the air piping from an air source (not shown). The solenoid valves are opened and closed by commands from the controller 8.

[0040] Here, the suction valve unloaders 7 provided in the compression chamber HE on the head end side and the compression chamber CE on the connecting rod side formed in the cylinder 5 of the first-stage compression mechanism 1A are designated as suction valve unloader 71a and suction valve unloader 71b. Also, the suction valve unloaders 7 provided in the compression chamber HE on the head end side and the compression chamber CE on the connecting rod side formed in the cylinder 5 of the second-stage compression mechanism 2A are designated as suction valve unloader 72b and suction valve unloader 72a.

[0041] The opening and closing operation of the solenoid valve (not shown) supplies instrument air to each of the suction valve unloaders 71a, 71b, 72a, and 72b, thereby switching between the loaded and unloaded states of the suction valve unloaders 71a, 71b, 72a, and 72b.

[0042] For example, when instrument air is supplied to the suction valve unloader 71a, the suction valve becomes locked. As a result, the corresponding compression chamber HE communicates with the suction-side flow path, and thus the compression chamber HE operates under no load. Conversely, when instrument air is not supplied, the suction valve of the suction valve unloader 71a is released, and the suction valve opens and closes due to the differential pressure across it. As a result, the corresponding compression chamber HE operates under load. The same applies to the other suction valve unloaders 71b, 72a, and 72b.

[0043] Figures 3(a) to 3(e) show examples of the operating states (loaded operation and unloaded operation) of each compression chamber HE and CE from a 0% load state to a 100% load state. As shown in Figure 3(a), when all compression chambers HE and CE are in the unloaded operation state, the compression stage 25 (two compression sections 1 and 2) is in the 0% load state. As a result, all compression chambers HE and CE in both the two compression sections 1 and 2 are in unloaded operation.

[0044] Furthermore, as shown in Figure 3(b), when one compression chamber CE is operating under load and the remaining three compression chambers HE and CE are operating without load, the compression stage 25 (the two compression sections 1 and 2) is under a 25% load.

[0045] Furthermore, as shown in Figure 3(c), when the two compression chambers CE are operating under load and the remaining compression chamber HE is operating without load, the compression stage 25 (the two compression sections 1 and 2) is in a 50% load state.

[0046] Furthermore, as shown in Figure 3(d), when three compression chambers HE and CE are operating under load and the remaining compression chamber HE is operating without load, the compression stage 25 (two compression sections 1 and 2) is in a 75% load state.

[0047] Furthermore, as shown in Figure 3(e), when all compression chambers HE and CE are under load, the compression stage 25 (the two compression sections 1 and 2) is under 100% load.

[0048] The controller 8 is composed of a microcomputer equipped with a CPU that performs arithmetic processing, a ROM that stores processing programs and data, and RAM that temporarily stores data. The controller 8 performs predetermined functions by executing processing programs. These functions include the drive control unit 8a and the storage unit 8b (see Figures 1 and 2).

[0049] The drive control unit 8a is a functional unit configured to switch the suction valve unloaders 7 according to the pressure measured by the pressure sensor 31. The controller 8 stores a threshold value for switching the suction valve unloaders 7, and the drive control unit 8a compares this threshold value with the pressure measured by the pressure sensor 31, and according to the result of this comparison, sets some of the four suction valve unloaders 7 to the unloaded state.

[0050] As shown in Figure 4, in this embodiment, a first threshold, a second threshold, and a third threshold are stored for the pressure measured by the pressure sensor 31. The second threshold is higher than the first threshold, and the third threshold is higher than the first threshold and lower than the second threshold.

[0051] The drive control unit 8a is capable of performing first load control and second load control. First load control is performed when the pressure measured by the pressure sensor 31 is equal to or greater than a first threshold, and second load control is performed when the pressure measured by the pressure sensor 31 is less than the first threshold.

[0052] When the first load control is performed, the drive control unit 8a sets the compression stage 25 (two compression units 1 and 2) to a 100% load state, a 75% load state, or a 50% load state. Specifically, if the pressure measured by the pressure sensor 31 is above the first threshold and below the third threshold, the drive control unit 8a sets it to a 50% load state; if the pressure measured by the pressure sensor 31 is above the third threshold and below the second threshold, it sets it to a 75% load state; and if the pressure measured by the pressure sensor 31 is above the second threshold, it sets it to a 100% load state.

[0053] When the second load control is performed, the drive control unit 8a sets the compression stage 25 (the two compression sections 1 and 2) to a 25% load state. However, when the pressure measured by the pressure sensor 31 is lower than a predetermined value less than the first threshold, the drive control unit 8a may set the compression stage 25 to a 0% load state.

[0054] Thus, during the operation of the reciprocating compressor 20, a signal indicating the measured pressure from the pressure sensor 31 is constantly input to the controller 8, and the switching control of the suction valve unloader 7 is performed so that the load state corresponding to the measured pressure indicated by this input signal is selected. The reciprocating compressor 20 in this embodiment sucks in the target gas, which is hydrogen gas sent from the storage tank 22, and pressurizes it. However, the storage tank 22 stores hydrogen gas derived from renewable energy, and its pressure is prone to fluctuations. For this reason, the load state of the compression stage 25 (two compression sections 1 and 2) is changed in accordance with the pressure fluctuations of the hydrogen gas sent from the storage tank 22.

[0055] Furthermore, while the reciprocating compressor 20 is in operation, a signal indicating the measured pressure from the pressure sensor 31 is constantly input to the controller 8. Therefore, when the measured pressure starts to drop from above the second threshold, it does not suddenly drop below the first threshold. Instead, a pressure above the third threshold and below the second threshold is detected, followed by a pressure above the first threshold and below the third threshold, and then it drops to below the first threshold. In this case, the load state of the compression stage 25 (two compression sections 1 and 2) progresses from 100% load to 75% load, then 50% load, and finally to 25% load. In other words, the suction valve unloader 7 is switched to pass through intermediate load states. Similarly, when the load is reduced from 75% to 25%, it also passes through a 50% load state. Therefore, the influence of pressure fluctuations on the target gas drawn into the compression stage 25 (two compression sections 1 and 2) can be suppressed.

[0056] When the compression stage 25 (two compression units 1 and 2) is under a 25% load, the memory unit 8b stores which of the two compression units 1 and 2 has the compression chambers HE and CE that have been operated under load. For example, in the case of the 25% load state shown in Figure 3(b), the memory unit 8b stores the compression unit 1 having the first stage compression mechanism 1A.

[0057] The drive control unit 8a reads out the compression units 1 and 2 stored in the memory unit 8b when maintaining a 25% load state for a certain period of time for one of the compression units 1 and 2, when switching from a load state other than 25% to a 25% load state, or when restarting the reciprocating compressor 20 and operating it in a 25% load state. In other words, the drive control unit 8a reads out the compression units 1 and 2 stored in the memory unit 8b each time it operates in a 25% load state.

[0058] Furthermore, the drive control unit 8a drives the suction valve unloader 7 so that a compression unit 2,1 other than the one read out, is operated under a 25% load. For example, if compression unit 1 is stored in the storage unit 8b, the drive control unit 8a drives the suction valve unloader 7 so that load operation is performed in the compression chambers HE and CE of compression unit 2. The drive control unit 8a may also alternately switch between compression units 1 and 2 at regular intervals to maintain a 25% load state.

[0059] As described above, in this embodiment, in an environment where the suction pressure of the target gas may fluctuate, the load state of the two compression units 1 and 2 is reduced to 25% in accordance with the decrease in the pressure measured by the pressure sensor 31 located upstream of the two compression units 1 and 2. This prevents the processing capacity of the reciprocating compressor 20 from becoming excessive. As a result, it is possible to suppress an excessive decrease in the pressure of the target gas drawn into the two compression units 1 and 2. Therefore, it is possible to deal with cases where the amount of target gas drawn in fluctuates greatly due to fluctuating factors. Moreover, a low suction state can be obtained by a simple method of switching the suction valve unloader 7.

[0060] Furthermore, in this embodiment, since load states between a 25% load state and a 100% load state are set, more precise load control is possible according to the magnitude of the pressure of the target gas drawn into the two compression sections 1 and 2.

[0061] Furthermore, in this embodiment, an intermediate load state is passed through when changing from the first load control to the second load control, so fluctuations in the capacity of the two compression units 1 and 2 are suppressed when the load state is changed. Therefore, the impact on pressure fluctuations of the target gas drawn into the two compression units 1 and 2 can be suppressed. Also, if an intermediate load state is not set, a sudden change from a 100% load state or a 75% load state to a 25% load state tends to cause large load fluctuations. However, by passing through an intermediate load state, such a situation can be prevented.

[0062] Furthermore, in this embodiment, when operating under a 25% load, the two compression units 1 and 2 can be used alternately by referring to the compression units 1 and 2 stored in the memory unit 8b. This prevents an uneven distribution of load on one of the compression units 1 and 2 (or its internal components).

[0063] Furthermore, in this embodiment, since a downstream compression stage 27 is provided, it is possible to prevent the processing capacity of the compression stage 25 from becoming excessive when the flow rate of the target gas drawn into the compression stage 25 is reduced, and the downstream compression stage 27 can further increase the pressure of the target gas.

[0064] Furthermore, in this embodiment, neither the compression stage 25 nor the subsequent compression stage 27 is equipped with a stepless capacity adjustment mechanism or a head-end unloader (clearance pocket). Therefore, cost reduction is possible.

[0065] Furthermore, in this embodiment, the reciprocating compressor 20 is equipped with two compression stages, a compression stage 25 and a subsequent compression stage 27, but it may also be equipped with three or more compression stages.

[0066] In this embodiment, a third threshold is set, but the third threshold may be omitted. In this case, if the pressure measured by the pressure sensor 31 is greater than or equal to the first threshold and less than the second threshold, the load state may be set to 50%, as shown in Figure 5, or to 75%, as shown in Figure 6.

[0067] Furthermore, although a second threshold is set in this embodiment, the second threshold may be omitted. In this case, as shown in Figure 7, when the measured pressure is equal to or greater than the first threshold, the compression stage 25 (two compression sections 1 and 2) is in a 100% load state, and when the measured pressure is less than the first threshold, the compression stage 25 (two compression sections 1 and 2) is in a 25% load state.

[0068] In the case shown in Figure 7, when the measured pressure is above the first threshold (when the first load control is performed), the opening degree of the flow control valve 33 of the spillback passage 32 may be adjusted based on the measured pressure. That is, even if only a 100% load state is possible when the first load control is performed, a load state that is substantially the same as a 50% load state or a 75% load state can be created by controlling the flow control valve 33 of the spillback passage 32. However, from the viewpoint of efficiency, it is preferable that a 50% or 75% load state can be created by the suction valve unloader 7.

[0069] In this embodiment, the operator of the reciprocating compressor 20 may perform first load control and second load control based on the pressure measured by the pressure sensor 31. That is, the operator performs second load control when the pressure measured by the pressure sensor 31 is less than the first threshold. If the pressure measured by the pressure sensor 31 is greater than or equal to the first threshold and less than the third threshold, the load state is set to 50%. If the pressure measured by the pressure sensor 31 is greater than or equal to the third threshold and less than the second threshold, the load state is set to 75%. If the pressure measured by the pressure sensor 31 is greater than or equal to the second threshold, the load state is set to 100%. The same applies to the following embodiments.

[0070] (Second Embodiment) As shown in Figure 8, the second embodiment is a compressor unit 40 comprising a reciprocating compressor 20 and a pre-stage compressor 35. Here, the same reference numerals are used for components identical to those in the first embodiment, and their detailed descriptions are omitted.

[0071] The pre-compressor 35 is located in the intake passage 23. That is, it draws in the target gas sent from the storage tank 22 and compresses the drawn-in target gas. The reciprocating compressor 20 compresses the target gas that has been compressed by the pre-compressor 35.

[0072] The pre-stage compressor 35 is a screw-type or turbo-type compressor and is a device independent of the reciprocating compressor 20. The compressor unit 40 may further be provided with a discharge volume adjustment means 42 for adjusting the discharge volume of the pre-stage compressor 35.

[0073] The discharge volume adjustment means 42 may have at least one of a VFD (variable speed drive) 42a or a spillback means 42b. In Figure 8, for convenience, the discharge volume adjustment means 42 having both a VFD 42a and a spillback means 42b is shown, but one of the VFD 42a or the spillback means 42b may be omitted. Also, the discharge volume adjustment means 42 may have a slide valve instead of a VFD 42a.

[0074] Fluctuations in the discharge volume from the upstream compressor 35 can cause fluctuations in the suction pressure of the reciprocating compressor 20. In other words, the upstream compressor 35 can function as a fluctuating element. However, since the drive control unit 8a of the reciprocating compressor 20 adjusts the load state of the compression stage 25 (two compression sections 1 and 2) according to the pressure measured by the pressure sensor 31, even if a fluctuating element exists upstream of the reciprocating compressor 20, it is possible to suppress an excessive drop in the pressure of the target gas drawn into the reciprocating compressor 20.

[0075] The other configurations, functions, and effects will not be described here, but the description of the first embodiment can be applied to the second embodiment.

[0076] (Other embodiments) It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The present invention is not limited to the above embodiments, and various modifications and improvements are possible without departing from its spirit. For example, in the first embodiment, the reciprocating compressor 20 is configured so that hydrogen gas from the storage tank 22 is directly drawn into a compression stage 25 having two compression sections 1 and 2, but it is not limited to this. For example, as shown in Figure 9, the reciprocating compressor 20 may be provided with a compression stage 25 having two compression sections 1 and 2 as a downstream compression stage. In this case, the reciprocating compressor 20 further includes a compression stage 45 upstream of the compression stage 25, which consists of one piston and one cylinder housing the piston. This compression stage 45 varies its discharge amount according to the flow rate of hydrogen gas introduced from the storage tank 22.

[0077] In a configuration in which a compression stage 45 is provided, as shown in Figure 9, the pressure sensor 31 may be located upstream of the compression stage 45, which is the first compression stage, or, as shown in Figure 10, the position of the pressure sensor 31 may be between the compression stage 45 and the compression stage 25. In the compressor unit 40 of Figures 9 and 10, a subsequent compression stage 27 may be provided or omitted. If a subsequent compression stage 27 is not provided, the discharge passage 28 is connected to the compression stage 25 instead of the connection passage 26. In addition, in a reciprocating compressor 20, two or more compression stages having the same structure as the compression stage 45 may be provided in series upstream of the compression stage 25. [Explanation of Symbols]

[0078] 1: Compression section 2: Compression section 3: Piston 5: Cylinder 7: Suction valve unloader 8a: Drive control unit 8b: Storage section 20: Reciprocating compressor 22: Storage tank 25: Compression Stage 27: Post-compression stage 31: Pressure sensor 35: Front-stage compressor 40: Compressor Unit 42:Discharge amount adjustment means 71a: Suction valve unloader 71b: Suction valve unloader 72a: Suction valve unloader 72b: Suction valve unloader CE: Compression chamber HE: Compression chamber

Claims

1. A reciprocating compressor used in an environment where a fluctuating element exists upstream that causes fluctuations in the suction pressure of the target gas, Two compression units arranged in parallel in the flow direction of the target gas, A pressure sensor is provided upstream of the two compression sections to measure the pressure of the target gas, Equipped with, The two compression sections mentioned above are, One piston and, A cylinder housing the piston and forming compression chambers on both sides of the piston, A suction valve unloader is provided at the suction section of each compression chamber, and is capable of switching between load operation and no-load operation of the target gas in each compression chamber. Equipped with, The system further includes a drive control unit that switches the suction valve unloaders of the two compression units, By switching each compression chamber of the two compression units to either load operation or no-load operation, the two compression units will be in a 100% load state, a 75% load state, a 50% load state, or a 25% load state. The drive control unit, When the pressure measured by the pressure sensor is equal to or greater than a first threshold, a first load control is executed to set the load state to 100%, 50%, or 75%. A reciprocating compressor configured to perform a second load control that sets the load state to 25% when the pressure measured by the pressure sensor is less than the first threshold.

2. The drive control unit, when executing the first load control, The 100% load state is set when the pressure measured by the pressure sensor is equal to or greater than a second threshold, which is a threshold higher than the first threshold. The reciprocating compressor according to claim 1, wherein the load state is set to either 50% or 75% when the pressure measured by the pressure sensor is greater than or equal to the first threshold and less than the second threshold.

3. The drive control unit, when executing the first load control, The reciprocating compressor according to claim 2, wherein the load state is set to 50% when the pressure measured by the pressure sensor is higher than the first threshold and lower than the second threshold, and is less than or equal to the first threshold, and the load state is set to 75% when it is greater than or equal to the third threshold and less than the second threshold.

4. The reciprocating compressor according to claim 1, wherein when the drive control unit changes from the first load control to the second load control, it switches the suction valve unloader so that it passes through the 100% load state, the 75% load state, the 25% load state, and an intermediate load state.

5. The system further includes a storage unit that stores the compression unit having the compression chamber on which the load operation was performed, when the load condition is 25%. The drive control unit, When maintaining a 25% load state for a certain period of time, when switching from a load state other than 25% to the 25% load state, or when restarting the reciprocating compressor and operating it in the 25% load state, the compression unit stored in the memory unit is read out. The reciprocating compressor according to any one of claims 1 to 4, wherein the suction valve unloader is driven so that a compression unit other than the one read out becomes the load-operated unit.

6. A compression stage comprising the two compression sections, A subsequent compression stage comprising a single compression unit that inhales the target gas discharged from the aforementioned compression stage, Equipped with, The aforementioned one compression section, One piston and, A cylinder housing the aforementioned piston and forming compression chambers on one or both sides of the aforementioned piston, A reciprocating compressor according to any one of claims 1 to 4, comprising:

7. A reciprocating compressor according to any one of claims 1 to 4, A screw-type or turbo-type upstream compressor is positioned upstream of the aforementioned reciprocating compressor, Discharge volume adjustment means for adjusting the discharge volume of the preceding compressor, Equipped with, A compressor unit in which the preceding compressor, whose discharge volume is adjusted by the discharge volume adjustment means, functions as the variable element.

8. A reciprocating compressor according to any one of claims 1 to 4, The aforementioned reciprocating compressor is installed downstream of a storage tank for temporarily storing hydrogen gas generated using renewable energy. The storage tank functions as a variable element that changes the suction pressure in accordance with fluctuations in the pressure inside the storage tank, and is a reciprocating compressor.

9. The reciprocating compressor according to any one of claims 1 to 4, wherein the target gas is hydrogen gas.

10. A method for operating a reciprocating compressor used in an environment where a fluctuating element exists upstream that causes fluctuations in the suction pressure of the target gas, The aforementioned reciprocating compressor, Two compression units arranged in parallel in the flow direction of the target gas, A pressure sensor is provided upstream of the two compression sections to measure the pressure of the target gas, Equipped with, The two compression sections mentioned above are, One piston and, A cylinder housing the piston and forming compression chambers on both sides of the piston, A suction valve unloader is provided at the suction section of each compression chamber, and is capable of switching between load operation and no-load operation of the target gas in each compression chamber. Equipped with, The aforementioned driving method, By switching each compression chamber of the two compression units between load operation and no-load operation, the two compression units can be operated under 100% load, 75% load, 50% load, or 25% load conditions. When the pressure measured by the pressure sensor is equal to or greater than a first threshold, a first load control is executed to set the load state to 100%, 50%, or 75%. A method for operating a reciprocating compressor, comprising: executing a second load control that sets the load state to 25% when the pressure measured by the pressure sensor is less than the first threshold.

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