Compressor unit

Abstract

To provide a reciprocating-type compressor unit which can properly protect its constituent apparatus from a wide temperature change of a boil-off gas of a hydrogen gas.SOLUTION: In a compressor unit 10, when a temperature TS1 acquired by an intermediate temperature sensor 46 at activation is equal to or higher than a threshold T1, a control part 50 brings first switching means CV1 into a first switching state so that a hydrogen gas discharged from a first compression stage 12 circulates to a cooler part 58. When the detection temperature TS1 is lower than the threshold T1, the control part brings the first switching means CV1 into a second switching state so that the hydrogen gas discharged from the first compression stage 12 does not pass through the cooler part 58. When the first switching means CV1 is in the second switching state, the control part 50 controls a spillback valve 18b so that a suction temperature TS2 falls within a preset temperature range. The temperature range is set within a range in which the suction temperature is higher than a reference temperature based on an air liquefaction temperature and lower than 0°C.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] In recent years, in consideration of the environment, it has been considered to use hydrogen as a fuel for power generation, automobiles, etc., and the demand for hydrogen is increasing. In addition, it has been practiced to recover cryogenic boil-off gas (BOG) such as liquefied natural gas (LNG) and liquid hydrogen (LH2) by a compressor and supply it to a demand destination such as an engine. In particular, the boil-off gas generated from LH2 is extremely low in temperature. For this reason, if the compressor is configured to directly inhale the boil-off gas, it is necessary to select a material suitable for extremely low temperatures, adopt design conditions considering the amount of thermal deformation, or perform strict heat treatment, etc. Constraints such as this apply.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the following problems are pointed out in Patent Document 1. "In recent years, hydrogen has attracted attention as a new energy source. Even when hydrogen is used as an energy source, it is assumed that it will be in a liquefied state during storage and transportation, like natural gas. However, hydrogen has the property that its liquefaction temperature is lower than that of air. Therefore, if equipment such as a reciprocating compressor for natural gas etc. is directly applied to hydrogen, problems caused by extremely low-temperature liquid hydrogen may occur. For example, liquefied air may be generated around the device to which liquid hydrogen is supplied."

[0005] In contrast, Patent Document 1 explains that "This reciprocating compressor has a compression part for compressing gas housed in a container part. And this container part forms a vacuum region around the compression part. Then, the compression part is thermally insulated from the external region by the vacuum region. That is, even when an extremely low-temperature gas is provided to the compression part, the peripheral region of the reciprocating compressor is not excessively cooled. Therefore, the generation of liquefied air can be suppressed."

[0006] However, generally, in machinery with vibrations during operation, and equipment that requires regular maintenance through inspection openings (such as reciprocating compressors etc.), it is very difficult to achieve high-performance heat insulation.

[0007] In Patent Documents 2 and 3, technologies for adjusting the temperature of the suction gas using a preheater are proposed for screw compressors. Also, Patent Document 4 discloses a reciprocating compressor, and shows a heat exchanger that exchanges heat between the boil-off gas before being inhaled into the compression part and the boil-off gas after being discharged from the compression part. However, since this heat exchanger is for reliquefying the boil-off gas after being compressed in the compression part, the boil-off gas cooled by a cooler arranged downstream of the compression part is introduced into the heat exchanger.

[0008] On the other hand, Patent Document 5 also points out the following problem. "Conventionally, when the BOG (boil-off gas) evaporated in the LNG cryogenic storage tank is compressed by a cryogenic gas multistage compressor and supplied to the plant, the temperature of the BOG easily fluctuates within a wide range from minus one hundred degrees to room temperature. Especially immediately after starting the multistage compressor, the temperature on the suction side rises to near room temperature, and if this is compressed as it is, the discharge temperature will exceed the allowable temperature and the operation cannot be carried out."

[0009] In the case of liquefied hydrogen, since the boiling point is lower than that of LNG, the problem disclosed in Patent Document 5 can be more serious. In a reciprocating compressor that handles the boil-off gas of liquefied hydrogen, it is necessary to cope with a wide temperature range from an extremely low temperature state to room temperature.

[0010] Therefore, the present invention has been made in view of the above problems, and an object thereof is to appropriately protect the constituent devices of a reciprocating compressor unit that handles the boil-off gas of liquefied hydrogen from a wide temperature change of the boil-off gas.

Means for Solving the Problems

[0011] The compressor unit according to one aspect of the present invention is a reciprocating compressor unit that recovers hydrogen gas, which is boil-off gas, from a liquid hydrogen storage tank and supplies at least a part of it to a demand destination including at least one of an engine, a power generation facility, or a boiler. And the compressor unit according to this aspect includes a plurality of compression stages, a crank mechanism, a cooler section, a first switching means, a spillback section, a first temperature sensor, a second temperature sensor, and a control section.

[0012] The plurality of compression stages compress the hydrogen gas inhaled from the suction flow path. The crank mechanism drives the plurality of compression stages. The cooler section is provided in an intermediate flow path between the plurality of compression stages. The first switching means switches the inflow state of the hydrogen gas to the cooler section. The spillback section includes a spillback flow path that returns the hydrogen gas discharged into the discharge flow path on the discharge side of the plurality of compression stages or the hydrogen gas flowing through the intermediate flow path to the suction flow path, and a spillback valve that adjusts the spillback amount in the spillback flow path. The first temperature sensor is disposed in the intermediate flow path. The second temperature sensor is disposed in the suction flow path between the connection portion of the spillback flow path and the first compression stage, which is the foremost stage among the plurality of compression stages. The control unit controls the first switching means and the spillback valve respectively.

[0013] In the compressor unit according to this aspect, each of the first compression stage and the subsequent compression stages excluding the first compression stage among the plurality of compression stages includes a cylinder section, a piston, a piston rod, and a rod packing. The piston rod connects the piston to the crank mechanism. The rod packing seals between the piston rod and the cylinder section.

[0014] The first compression stage is air-cooled and oil-free.

[0015] The control unit controls the first switching means and the spillback valve as follows.

[0016] When starting up and the temperature TS1 acquired by the first temperature sensor is equal to or higher than a predetermined first temperature threshold T1 greater than 0°C, the control unit controls the first switching means to be in a first switching state in which the hydrogen gas discharged from the first compression stage is circulated through the cooler section for cooling.

[0017] When the temperature TS1 acquired by the first temperature sensor is less than the first temperature threshold T1, the control unit controls the first switching means so as to enter a second switching state in which hydrogen gas is sent to a compression stage downstream of the location where the cooler unit is provided without passing through the cooler unit.

[0018] When the first switching means is in the second switching state, the control unit refers to the suction temperature TS2 acquired by the second temperature sensor and controls the spillback valve so that the suction temperature TS2 is within a predetermined temperature range.

[0019] In the compressor unit according to this aspect, the predetermined temperature range is set higher than a reference temperature based on the liquefaction temperature of air and in a range less than 0°C.

[0020] In the above aspect, the compressor unit can be protected in a low-temperature environment. More specifically, when the hydrogen gas in the piping on the liquid hydrogen storage tank side has risen to the positive temperature region at startup, by cooling the hydrogen gas upstream of the cooler unit in the intermediate flow path with the cooler unit, it is possible to prevent hydrogen gas with an excessively increased temperature from being sent to the downstream compression stage (subsequent compression stage). That is, in the compressor unit, the subsequent compression stage can be protected. Also, in the compressor unit, even when it is at startup and the first switching means is in the first switching state, since hydrogen gas within the predetermined temperature range is sent to the downstream compression stage, the compressor unit can be started up promptly.

[0021] Further, in the compressor unit according to the above aspect, when the first switching means is in the second switching state, the suction temperature TS2 of the hydrogen gas sucked into the first compression stage can be adjusted by the hydrogen gas returned to the suction flow path by the spillback section. For this reason, in the compressor unit, by setting the temperature range of the hydrogen gas sucked into the first compression stage higher than the reference temperature based on the liquefaction temperature of air, it is possible to avoid the liquefaction of oxygen gas, which is a combustion-supporting gas.

[0022] Further, in the compressor unit according to the above aspect, since the first compression stage is oil-free, the risk of oil freezing can be avoided.

[0023] In the compressor unit according to the above aspect, a preheater, a third temperature sensor, and a flow rate adjusting means may be further provided. The preheater can exchange heat between the hydrogen gas before being inhaled into the first compression stage, the hydrogen gas after being discharged into the discharge flow path, or the hydrogen gas flowing through the intermediate flow path. The third temperature sensor is disposed downstream of the preheater in the discharge flow path. The flow rate adjusting means can adjust the inflow state of the hydrogen gas to the preheater.

[0024] When the first switching means is in the second switching state, the control unit may control the flow rate adjusting means and the spillback valve as follows.

[0025] In the second switching state, the control unit may increase the inflow amount of the hydrogen gas to the preheater so that the preheater can preferentially heat the hydrogen gas in the suction flow path over the heating by the spillback section, and control the flow rate adjusting means so that the temperature TS3 on the downstream side of the preheater obtained by the third temperature sensor does not become equal to or lower than the threshold value.

[0026] In the second switching state, when the suction temperature TS2 becomes equal to or lower than the set value temperature, the control unit may control the flow rate adjusting means and the spillback valve so that the suction temperature TS2 is within a predetermined temperature range.

[0027] In the compressor unit according to the above aspect, in the second switching state, by preferentially heating the suction temperature TS2 by the preheater over the heating by the spillback section and supplementing with the preheater when the heating is insufficient, the loss of power for returning the compressed hydrogen gas to the suction side of the first compression stage is minimized, thereby suppressing a decrease in processing efficiency and managing the suction temperature of the hydrogen gas to the subsequent compression stage within a certain range.

[0028] Further, in the compressor unit, a third temperature sensor is arranged downstream of the preheater, and by managing the temperature of the hydrogen gas on the downstream side of the preheater using the detected temperature TS3 by the third temperature sensor, an excessive temperature drop of the hydrogen gas can be suppressed.

[0029] In the compressor unit according to the above aspect, a preheater and a third temperature sensor may be further provided. The preheater can exchange heat between the hydrogen gas before being sucked into the first compression stage and the hydrogen gas flowing between the first compression stage and the subsequent compression stage in the intermediate flow path. The third temperature sensor is arranged downstream of the preheater in the intermediate flow path.

[0030] Also, in the compressor unit according to the above aspect, the first switching means may be capable of switching the hydrogen gas discharged from the first compression stage to any one of the inflow state of the hydrogen gas to the cooler section, the direct inflow state of the hydrogen gas to the subsequent compression stage, and the inflow state of the hydrogen gas to the preheater.

[0031] Furthermore, in the compressor unit according to the above aspect, when the first switching means is in the second switching state, the control unit may control the spillback valve and the first switching means as follows.

[0032] The control unit may control the spillback valve and the first switching means so that the hydrogen gas in the suction flow path is within the predetermined temperature range by using a combination of heating of the hydrogen gas in the suction flow path by the spillback section and heating by the preheater in the second switching state.

[0033] The control unit may control the first switching means so as not to further increase the inflow of hydrogen gas to the preheater when the temperature TS3 on the downstream side of the preheater obtained by the third temperature sensor is less than the threshold value in the second switching state.

[0034] In the compressor unit according to the above aspect, when the first switching means is in the second switching state, in addition to heating the hydrogen gas in the suction passage by the spillback section, heating by the preheater is also used in combination. Therefore, compared with the case where only heating by the spillback section is performed, by using heating by the preheater in combination, the loss of power for returning the compressed hydrogen gas to the suction side of the subsequent compression stage can be minimized, and the decrease in processing efficiency can be suppressed while managing the suction temperature of the hydrogen gas to the subsequent compression stage within a certain range.

[0035] Further, in the compressor unit, a third temperature sensor is arranged downstream of the preheater, and by managing the temperature on the downstream side of the preheater using the detected temperature TS3 by the third temperature sensor, an excessive temperature drop of the hydrogen gas can be suppressed.

[0036] In the compressor unit according to the above aspect, a low-pressure gas discharge passage, a third switching means, and an adjustment means may be further provided. The low-pressure gas discharge passage branches from a branch point provided in the intermediate passage and can discharge hydrogen gas to an intermediate-stage demand destination that can process hydrogen gas at a pressure lower than the pressure of the hydrogen gas required by the demand destination. The third switching means is provided at the low-pressure gas discharge passage or the branch point. The adjustment means adjusts the processing amount of the hydrogen gas by the subsequent compression stage.

[0037] In the compressor unit according to the above aspect, when the first switching means is in the second switching state, in parallel with the control of the spillback valve, the control unit controls the third switching means so that hydrogen gas is discharged to the low-pressure gas discharge passage according to the required amount of the intermediate-stage demand destination or the variation in the required amount of the demand destination, and controls the adjustment means so that the processing amount of the subsequent compression stage is adjusted.

[0038] In the compressor unit according to the above aspect, when the required amount (demand amount) at the demand destination is reduced, by discharging hydrogen gas to the intermediate-stage demand destination, the amount of boil-off gas (hydrogen gas) generated from the liquid hydrogen storage tank and the amount of hydrogen gas sent out by the first compression stage are balanced, so that the pressure of the liquid hydrogen storage tank can be kept constant.

[0039] Further, in the compressor unit, the processing amount of hydrogen gas in the subsequent compression stage is reduced by the adjustment means, and thereby the compression ratio of the subsequent compression stage is suppressed to reduce the processing amount of hydrogen gas in the subsequent compression stage, and the power of the subsequent compression stage can be reduced.

[0040] In the compressor unit according to the above aspect, the subsequent compression stage may be composed of two or more compression stages. Further, the compressor unit according to the above aspect may further include a low-pressure gas discharge path, a third switching means, and an adjustment means. The low-pressure gas discharge path branches from a branch point provided in the intermediate flow path and can discharge hydrogen gas to an intermediate-stage demand destination capable of processing hydrogen gas having a pressure lower than the pressure of the hydrogen gas required at the demand destination. The third switching means is provided at the low-pressure gas discharge path or the branch point. The adjustment means adjusts the processing amount of hydrogen gas by the compression stage on the downstream side of the branch point among the two or more compression stages constituting the subsequent compression stage.

[0041] In the compressor unit according to the above aspect, when the first switching means is in the second switching state, the control unit controls the third switching means so that hydrogen gas is discharged to the low-pressure gas discharge path in accordance with the required amount of the intermediate-stage demand destination or the variation in the required amount of the demand destination in parallel with the control of the spillback valve, and controls the adjustment means so that the processing amount of the compression stage on the downstream side in the subsequent compression stage is adjusted.

[0042] In the compressor unit according to the above aspect, when the required amount (demand amount) at the demand destination is reduced, by discharging hydrogen gas to the intermediate-stage demand destination, the amount of boil-off gas (hydrogen gas) generated from the liquid hydrogen storage tank and the amount of hydrogen gas sent out by the first compression stage are balanced, so that the pressure of the liquid hydrogen storage tank can be kept constant.

[0043] Further, in the compressor unit, the adjustment means reduces the amount of hydrogen gas flowing into the downstream compression stage, thereby suppressing the compression ratio of the downstream compression stage in the subsequent compression stage, reducing the processing amount of hydrogen gas in the compression stage, and reducing the power of the compression stage.

[0044] In the compressor unit according to the above aspect, the adjustment means may include a second spillback section. The second spillback section includes a second spillback flow path for returning hydrogen gas to the suction side of the subsequent compression stage upstream of the spillback flow path, and a second spillback valve for adjusting the spillback amount in the second spillback flow path.

[0045] In the compressor unit according to the above aspect, when the first switching means is in the second switching state, the control unit may control the second spillback valve so that a flow rate corresponding to the change in the required amount of the intermediate-stage demand destination or the required amount of the demand destination is returned to the suction side of the subsequent compression stage by the second spillback section.

[0046] In the compressor unit according to the above aspect, when the required amount (demand amount) at the demand destination is reduced, by reducing the amount of hydrogen gas returned to the suction side of the subsequent compression stage by the second spillback section, while balancing the amount of boil-off gas (hydrogen gas) generated from the liquid hydrogen storage tank and the amount of hydrogen gas sent out by the first compression stage, the processing amount of hydrogen gas in the subsequent compression stage can be reduced, and the power of the subsequent compression stage can be reduced.

[0047] In the compressor unit according to the above aspect, the adjustment means may further include an on-off type suction valve unloader attached to the cylinder part of the subsequent compression stage.

[0048] In the compressor unit according to the above aspect, when the first switching means is in the second switching state, the control unit may control the suction valve unloader as follows.

[0049] When the opening degree of the second spillback valve becomes larger than a preset opening degree threshold value b1 in the second switching state, the control unit may control the suction valve unloader so that the suction valve unloader is controlled to reduce the load amount of the subsequent compression stage.

[0050] When the opening degree of the second spillback valve becomes smaller than the opening degree threshold value b2 in the second switching state, the control unit may control the suction valve unloader so that the load amount of the subsequent compression stage is increased.

[0051] In the above aspect, since the second spillback part is provided, even when the required amount of the high-pressure demand destination (D1) decreases, the hydrogen gas after compression is returned to the suction side of the subsequent compression stage by the second spillback part, so that the suction pressure of the subsequent compression stage can be kept substantially constant. Therefore, in the above aspect, the pressure balance of each stage of the subsequent compression stage is always constant, and high reliability of the compressor can be obtained.

[0052] In the compressor unit according to the above aspect, the adjustment means may include a suction valve unloader, a driving device, and a stepless capacity adjustment device. The suction valve unloader is attached to the cylinder part of the subsequent compression stage. The driving device is a hydraulic type or an electric type for opening and closing the suction valve unloader. The stepless capacity adjustment device includes a control device that controls the timing of the operation of the suction valve unloader in conjunction with the rotational movement of the crankshaft.

[0053] In the compressor unit according to the above aspect, when the first switching means is in the second switching state, the control unit causes the hydrogen gas sucked from the inside of the cylinder part to the suction side to be returned according to the flow rate corresponding to the required amount of the intermediate-stage demand destination or the variation in the required amount of the demand destination, and controls the capacity adjustment device so that the processing amount of the subsequent compression stage is adjusted.

[0054] In the compressor unit according to the above aspect, in the second switching state, the operation timing and operation time of the suction valve unloader are controlled, and a part of the hydrogen gas in the cylinder part is returned to the suction side, so that the processing amount of the hydrogen gas in the subsequent compression stage can be reduced. Thereby, more power can be reduced.

[0055] In the compressor unit according to the above aspect, at least a part of the subsequent compression stage may have a leak gas discharge part that returns the leak gas from the rod packing to the suction flow path.

[0056] In the compressor unit, the pressure becomes higher in the subsequent compression stages, and the hydrogen gas is more likely to leak. However, in the compressor unit according to the above aspect, the hydrogen gas leaked in the subsequent compression stage is recovered to the suction flow path side by the leak gas discharge part, so that the loss of the product gas (hydrogen gas) during compression can be reduced.

Effects of the Invention

[0057] The compressor unit according to each of the above aspects can appropriately protect its constituent devices from a wide temperature change of the boil-off gas of liquefied hydrogen.

Brief Description of the Drawings

[0058]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

MODE FOR CARRYING OUT THE INVENTION

[0059] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below are illustrative of the present invention, and the present invention is not limited to the following embodiments except for its essential configuration.

[0060] (First Embodiment) The compressor unit according to the present embodiment is a reciprocating compressor unit, which is configured to recover hydrogen gas, which is boil-off gas, from a liquid hydrogen storage tank, compress the recovered hydrogen gas, and supply it to a demand destination. The temperature of the boil-off gas, which is hydrogen gas, is about -253°C.

[0061] As shown in FIG. 1, the compressor unit 10 includes a plurality of compression stages (first compression stage 12, subsequent compression stage 14) that compress the hydrogen gas in the suction flow path 21, and a crank mechanism 16 that drives the first compression stage 12 and the subsequent compression stage 14.

[0062] The first compression stage 12 is connected to the liquid hydrogen storage tank 23 via the suction flow path 21. Therefore, the boil-off gas of the liquefied gas generated in the liquid hydrogen storage tank 23 is sucked into the first compression stage 12 through the suction flow path 21.

[0063] The first compression stage 12 is constituted by a reciprocating compression mechanism. As shown in FIG. 2, the first compression stage 12 includes a piston 212 disposed in a cylinder portion 211, a piston rod 213 connected to the piston 212, a pair of suction valves 214, and a pair of discharge valves 215. A compression chamber 216 is formed between the front head 211a and the piston 212 and between the rear head 211b and the piston 212 in the cylinder portion 211. The first compression stage 12 is an air-cooled and oil-free compression mechanism that does not use lubricating oil.

[0064] A rod packing 217 for preventing leakage of hydrogen gas from the compression chamber 216 is provided on the rear head 211b of the cylinder portion 211. The rod packing 217 is configured to seal between the piston rod 213 and the cylinder portion 211, and includes a packing ring 217a disposed so as to surround the piston rod 213 and a case 217b that holds the packing ring 217a.

[0065] The piston 212 is connected to the crank mechanism 16 via the piston rod 213. When the piston 212 reciprocates in the cylinder portion 211, the hydrogen gas is compressed in the compression chamber 216. Although FIG. 2 shows the first compression stage 12 having a double-acting structure, the first compression stage 12 may adopt a single-acting structure.

[0066] In FIG. 1, for the sake of convenience, the first compression stage 12 is shown as a single trapezoid, but the first compression stage 12 may have a plurality of cylinder parts 211. That is, the first compression stage 12 may be configured such that hydrogen gas is compressed and pressurized by the reciprocating motion of pistons 212 in a plurality of cylinder parts 211 connected in parallel. Further, it may have a compression mechanism with a plurality of compression stages. That is, the first compression stage 12 may be configured such that hydrogen gas is sequentially compressed and pressurized by pistons 212 in a plurality of cylinder parts 211. The same applies to other embodiments.

[0067] The subsequent compression stage 14 is connected to the first compression stage 12 via the intermediate flow path 22 and is a compression mechanism for further compressing the hydrogen gas discharged from the first compression stage 12. Then, the hydrogen gas compressed in the subsequent compression stage 14 is discharged into the discharge flow path 24. The hydrogen gas flowing in the discharge flow path 24 is sent to the demand destination D1. The hydrogen gas discharged from the compressor unit does not necessarily have to be directly supplied to the demand destination D1. For example, after being filled into a cylinder or the like, it may be supplied to the demand destination D1 by various means such as transporting the cylinder or gas piping connected to the cylinder. The high-pressure demand destination D1 includes at least one of an engine, a power generation facility, or a boiler. In addition to these, for example, facilities that release gas into the atmosphere such as flare facilities and vents may be included.

[0068] As shown in FIG. 3, the subsequent compression stage 14 is also configured by a reciprocating compression mechanism, similar to the first compression stage 12. The piston 212 of the subsequent compression stage 14 is also connected to the crank mechanism 16 via the piston rod 213. In the subsequent compression stage 14, a leak gas discharge part 29 for returning leak gas from the rod packing 217 to the suction flow path 21 is further provided. The leak gas discharge part 29 may be constituted by a pipe member provided so as to connect the rod packing 217 and the suction flow path 21 to each other.

[0069] In addition, in FIG. 1, for the sake of convenience, the subsequent compression stage 14 is shown as a single trapezoid, but the subsequent compression stage 14 does not necessarily have to be a single-stage type and may have a compression mechanism with a plurality of compression stages. That is, the subsequent compression stage 14 may be configured such that hydrogen gas is sequentially compressed and pressurized by the reciprocating motion of the pistons 212 in a plurality of cylinder parts 211. The same applies to other embodiments. Regarding the compression stage that discharges hydrogen gas at normal temperature in the subsequent compression stage 14, it may be an oil-free type or a lubricated type.

[0070] As shown in FIG. 1, the compressor unit 10 includes a spillback part SB1 that returns a part of the hydrogen gas discharged from the subsequent compression stage 14 to the suction passage 21 through the discharge passage 24. The spillback part SB1 includes a spillback passage 18a and a spillback valve 18b including a valve with an adjustable opening degree disposed in the spillback passage 18a. One end part of the spillback passage 18a is connected to the discharge passage 24, and the other end part is connected to the suction passage 21. That is, the hydrogen gas flowing through the spillback passage 18a merges with the hydrogen gas from the liquid hydrogen storage tank 23 in the suction passage 21. The spillback valve 18b adjusts the spillback amount in the spillback passage 18a.

[0071] The compressor unit 10 includes a cooler part 58 provided in an intermediate passage 22 between the first compression stage 12 and the subsequent compression stage 14. The intermediate passage 22 has branched passages (a first passage 22a and a second passage 22b) at an intermediate part thereof, and the cooler part 58 is disposed in one of the passages (the first passage 22a).

[0072] At the branch point between the first flow path 22a and the second flow path 22b in the intermediate flow path 22, a first switching means CV1 is provided. However, the first switching means CV1 may be provided in the first flow path 22a or in the second flow path 22b. In the present embodiment, the first switching means CV1 is constituted by a three-way valve 59a as an example. The first switching means CV1 circulates the hydrogen gas discharged from the first compression stage 12 to the cooler section 58 for cooling and then allows it to flow into the subsequent compression stage 14 (first switching state), and allows the hydrogen gas discharged from the first compression stage 12 to flow into the subsequent compression stage 14 without passing through the cooler section 58 (second switching state). It is possible to switch the flow path of the hydrogen gas between these two states. In the present embodiment, the first switching means CV1 constituted by the three-way valve 59a is adopted as an example, but it is not limited thereto. For example, it is also possible to adopt an on-off valve that can take two positions of fully open / fully closed, or a regulating valve that can adjust the flow rate of the hydrogen gas to the first flow path 22a and the flow rate of the hydrogen gas to the second flow path 22b.

[0073] The compressor unit 10 includes an upstream temperature sensor (second temperature sensor) 45 and an intermediate temperature sensor (first temperature sensor) 46. The upstream temperature sensor 45 is a temperature sensor that detects the temperature of the hydrogen gas flowing through the suction flow path 21. The upstream temperature sensor 45 is disposed in the suction flow path 21 between the connection portion of the spillback flow path 18a and the first compression stage 12. Therefore, when hydrogen gas flows through the spillback flow path 18a, the upstream temperature sensor 45 can acquire the temperature TS2 of the hydrogen gas that is the hydrogen gas from the liquid hydrogen storage tank 23 after the hydrogen gas from the spillback flow path 18a has merged and is inhaled into the first compression stage 12.

[0074] The intermediate temperature sensor 46 is a temperature sensor that detects the temperature of the hydrogen gas flowing through the intermediate flow path 22. The intermediate temperature sensor 46 is located in the intermediate flow path 22 between the first compression stage 12 and the branch point between the first flow path 22a and the second flow path 22b in the intermediate flow path 22. Therefore, the intermediate temperature sensor 46 can acquire the temperature of the hydrogen gas flowing through the intermediate flow path 22.

[0075] Each of the upstream temperature sensor 45 and the intermediate temperature sensor 46 sends the acquired temperature information to the control unit 50. The control unit 50 is configured with a microprocessor including an MPU / CPU, an ASIC, a ROM, a RAM, etc., and controls various operations of the compressor unit 10 by executing firmware and the like pre-stored in the memory. The functions of the control unit 50 include a first control unit 50a and a second control unit 50b. The first control unit 50a is a functional unit configured to control the first switching means 59 with reference to the temperature TS1 of the hydrogen gas acquired by the intermediate temperature sensor 46. The second control unit 50b is a functional unit configured to control the spillback valve 18b with reference to the temperature TS2 of the hydrogen gas acquired by the upstream temperature sensor 45.

[0076] Here, regarding the operation control executed by the control unit 50 in the operation of the compressor unit 10 according to the present embodiment, it will be described with reference to FIG. 4.

[0077] The control unit 50 determines whether the compressor unit 10 is already in operation or not, and determines the presence or absence of a drive command when it is not in operation.

[0078] When there is a start command for the compressor unit 10, the control unit 50 operates the crank mechanism 16, whereby the first compression stage 12 and the subsequent compression stage 14 are driven (step ST1). The first compression stage 12 and the subsequent compression stage 14 cause the piston 212 to reciprocate in the cylinder unit 211 by the operation of the crank mechanism 16. As a result, the hydrogen gas in the suction flow path 21 is sucked into the first compression stage 12, the hydrogen gas in the intermediate flow path 22 is sucked into the subsequent compression stage 14, and the hydrogen gas is compressed.

[0079] When the compressor unit 10 is started, the temperature TS1 of the hydrogen gas flowing through the intermediate flow path 22 (discharged from the first compression stage 12) is acquired by the intermediate temperature sensor (first temperature sensor) 46. At this time, the control unit 50 refers to the temperature TS1 and determines whether the temperature TS1 is equal to or higher than a predetermined first temperature threshold value T1 (step ST2). Here, the first temperature threshold value T1 is a temperature higher than 0°C.

[0080] When the control unit 50 determines YES (TS1 ≥ threshold value T1) in step ST2, the first control unit 50a controls the first switching means CV1 so that the hydrogen gas discharged from the first compression stage 12 flows into the first flow path 22a (step ST3). As a result, the hydrogen gas discharged from the first compression stage 12 is cooled by the cooler unit 58 and sent to the subsequent compression stage 14 (first switching state).

[0081] On the other hand, when the control unit 50 determines NO (TS1 < threshold value T1) in step ST2, the first control unit 50a controls the first switching means CV1 so that the hydrogen gas discharged from the first compression stage 12 flows into the second flow path 22b without passing through the first flow path 22a (step ST4). That is, the first control unit 50a controls the first switching means CV1 so that the inflow of hydrogen gas into the cooler unit 58 is stopped. As a result, the hydrogen gas discharged from the first compression stage 12 is sent to the subsequent compression stage 14 without passing through the cooler unit 58 (second switching state).

[0082] When the compressor unit 10 is driven, the temperature (suction temperature) TS2 of the hydrogen gas sucked into the first compression stage 12 is acquired by the upstream temperature sensor (second temperature sensor) 45. The control unit 50 starts the spillback control while referring to the suction temperature TS2 (step ST5). That is, when TS2 < T TH1 in the case of, the second control unit 50b controls the spillback valve 18b so that a part of the gas in the discharge flow path 24 is returned to the suction flow path 21. As a result, when the first switching means CV1 is in the second switching state, the suction temperature TS2 is within a predetermined temperature range (T TH1 ≤ TS2 ≤ T TH2) The hydrogen gas in the suction passage 21 is heated so as to be

[0083] More specifically, when TS2 < T TH1 , the second control unit 50b controls the spillback valve 18b to return a part of the gas in the discharge passage 24 to the suction passage 21 or increase the amount of return, so that the suction temperature TS2 is within the above temperature range. When TS2 > T TH2 , the operation of returning a part of the gas in the discharge passage 24 to the suction passage 21 is not performed or the amount of return is reduced.

[0084] Here, the predetermined temperature range is set higher than the reference temperature based on the liquefaction temperature of air and in the range less than 0°C. That is, the lower limit value T TH1 and the upper limit value T TH2 of the predetermined temperature range are set higher than the above reference temperature and within the range less than 0°C.

[0085] When the second control unit 50b opens the spillback valve 18b as described above (executes step ST5), the hydrogen gas from the liquid hydrogen storage tank 23 is not directly introduced into the first compression stage 12, but the hydrogen gas compressed in the subsequent compression stage 14 and the heated hydrogen gas after confluence are introduced into the first compression stage 12. Therefore, it is possible to prevent the first compression stage 12 from being exposed to hydrogen gas at an extremely low temperature (temperature lower than T TH1 ). Moreover, since the suction temperature TS2 is adjusted to be equal to or higher than the lower limit temperature T TH1 , it is also possible to prevent the liquefaction of oxygen gas. In addition, since the suction temperature TS2 is adjusted to be equal to or lower than the upper limit temperature T TH2 , it is also possible to prevent the density of the hydrogen gas sucked into the first compression stage 12 from decreasing excessively.

[0086] The compressor unit 10 having the above configuration is in an environment where the hydrogen gas in the intermediate passage 22 has risen to the positive temperature region, or the hydrogen gas in the suction passage 21 is at the lower limit temperature T TH1Protection is achieved even in a low-temperature environment or the like where the temperature is below a certain level. Specifically, when the hydrogen gas in the intermediate flow path 22 of the compressor unit 10 has risen to the positive temperature region, by cooling the hydrogen gas discharged from the first compression stage 12 with the cooler unit 58, it is possible to prevent the hydrogen gas whose temperature has risen excessively from being sent to the subsequent compression stage 14. That is, the subsequent compression stage 14 can be protected. Also, in the compressor unit 10, even at startup, since the hydrogen gas cooled by the cooler unit 58 is sent to the subsequent compression stage 14, startup can be carried out promptly.

[0087] Also, in the compressor unit 10, when the first switching means CV1 is in the second switching state, the suction temperature TS2 of the hydrogen gas sucked into the first compression stage 12 is adjusted within the above-mentioned predetermined temperature range by the hydrogen gas returned to the suction flow path 21 by the spillback unit SB1. For this reason, the temperature of the hydrogen gas sucked into the first compression stage 12 is made equal to or higher than the above-mentioned lower limit temperature T TH1 By doing so, it is possible to avoid the liquefaction of oxygen gas, which is a combustion-supporting gas.

[0088] Also, in the compressor unit 10, since the first compression stage 12 is oil-free, the risk of oil freezing can be avoided. Further, in a plurality of compression stages, the pressure becomes higher in the subsequent compression stages, and hydrogen gas is more likely to leak. However, since the hydrogen gas leaked in the subsequent compression stage 14 is recovered by the leak gas discharge unit 29 into the suction flow path 21, product loss (loss of hydrogen gas) during compression can be reduced.

[0089] Furthermore, if the compressor unit 10 is adopted, efficient recovery / supply of hydrogen gas is possible.

[0090] In the compressor unit 10 shown in FIG. 1, although the three-way valve 59a is taken as an example of the first switching means CV1 for switching between the first flow path 22a and the second flow path 22b in the intermediate flow path 22, the specific example of the first switching means CV1 is not limited to this. For example, as shown in FIG. 5, the first switching means CV1 including the first regulating valve 59b provided in the first flow path 22a and the second regulating valve 59c provided in the second flow path 22b may be configured.

[0091] Also, in the compressor unit 10 shown in FIG. 1, the subsequent compression stage 14 has a single-stage compression mechanism, but it may have a multi-stage compression mechanism. For example, as shown in FIG. 6, the subsequent compression stage 14 may be constituted by a subsequent first compression stage 14a and a subsequent second compression stage 14b. When this configuration is adopted, for example, as shown in FIG. 7, the intermediate temperature sensor 46 may be arranged in the third flow path 22c between the subsequent first compression stage 14a and the subsequent second compression stage 14b in the intermediate flow path 22. In this case, the temperature of the hydrogen gas discharged from the first compression stage 12 can be estimated by the intermediate temperature sensor 46 arranged on the downstream side of the subsequent first compression stage 14a.

[0092] Also, in the compressor unit 10 shown in FIG. 1, although the cooler section 58 is provided in the intermediate flow path 22 between the first compression stage 12 and the subsequent compression stage 14, the position where the cooler section 58 is provided is not limited to this. For example, as shown in FIG. 8, a branched flow path (the first flow path 22a and the second flow path 22b) may be provided in a portion between the subsequent first compression stage 14a and the subsequent second compression stage 14b of the subsequent compression stage 14 in the intermediate flow path 22, and the cooler section 58 may be provided in the first flow path 22a. Also, for the first switching means CV1, the form shown in FIG. 5 may be adopted.

[0093] (Second Embodiment) As shown in FIG. 9, the compressor unit 10 according to the second embodiment is different from the first embodiment in that it includes a preheater 71 capable of exchanging heat between the hydrogen gas flowing through the suction flow path 21 (the hydrogen gas sucked into the first compression stage 12) and the hydrogen gas after being discharged from the subsequent compression stage 14 into the discharge flow path 24. In FIG. 9, the same components as those in the first embodiment are denoted by the same reference numerals, and the description of the overlapping parts will be omitted below.

[0094] As shown in FIG. 9, the discharge flow path 24 has branched flow paths (a first flow path 24a and a second flow path 24b) at a portion upstream of the position where the spillback flow path 18a is connected, and the preheater 71 is provided between one of the flow paths (the first flow path 24a) and the suction flow path 21. Thereby, in the preheater 71, heat exchange is possible between the hydrogen gas flowing through the first flow path 24a of the discharge flow path 24 and the hydrogen gas flowing through the suction flow path 21.

[0095] A flow rate adjusting means FCV1 is provided at the branch point between the first flow path 24a and the second flow path 24b in the discharge flow path 24. However, the flow rate adjusting means FCV1 may be provided in the first flow path 24a or the second flow path 24b. The flow rate adjusting means FCV1 is constituted by a three-way valve 72a as an example in the present embodiment, and it is possible to flow the hydrogen gas discharged from the subsequent compression stage 14 to one of the first flow path 24a and the second flow path 24b, and it is also possible to adjust the amount of hydrogen gas flowing through the first flow path 24a while flowing through both the first flow path 24a and the second flow path 24b.

[0096] The compressor unit 10 according to the present embodiment also includes a downstream temperature sensor (third temperature sensor) 48 disposed downstream of the preheater 71 in the discharge flow path 24. The downstream temperature sensor 48 can acquire the temperature of the hydrogen gas flowing through a portion downstream of the preheater 71 in the discharge flow path 24. The temperature information acquired by the downstream temperature sensor 48 is sent to the control unit 50.

[0097] In the compressor unit 10, the functions of the control unit 50 include a third control unit 50c in addition to the first control unit 50a and the second control unit 50b. The third control unit 50c is a functional unit configured to control the flow rate adjustment means FCV1 with reference to the temperature TS3 of the hydrogen gas acquired by the downstream temperature sensor 48.

[0098] Here, regarding the operation control executed by the control unit 50 in the operation of the compressor unit 10 according to the present embodiment, it will be described with reference to FIG. 10. In the following description, some descriptions overlapping with the above first embodiment will be omitted.

[0099] When the control unit 50 is in the steady operation state (TS1 < threshold value T1), it controls the first switching means CV1 to stop the inflow of hydrogen gas into the cooler unit 58 (step ST4). The control steps up to here are the same as those in the above first embodiment.

[0100] The control unit 50 starts preheater control while referring to the suction temperature TS2 acquired by the upstream temperature sensor 45 (step ST6). That is, when TS2 < T TH1 in the case of, the third control unit 50c controls the flow rate adjustment means FCV1 so that the hydrogen gas discharged from the subsequent compression stage 14 flows into the first flow path 24a and passes through the preheater 71 (step ST6). Then, in the state where the hydrogen gas passes through the preheater 71, the control unit 50 determines whether the temperature TS3 acquired by the downstream temperature sensor 48 is greater than the temperature T TH3 (step ST7). When the control unit 50 determines YES (TS3 > T TH3 ) in step ST7, the third control unit 50c continues the state where hydrogen gas flows into the preheater 71. Thereby, heat exchange in the preheater 71 is continuously executed. When TS2 > T TH2 is the case, preheater control is not performed.

[0101] On the other hand, when the control unit 50 determines NO (TS3 ≤ T TH3) If it is determined that the temperature is lower than the lower limit value of the predetermined temperature range, the flow rate control means FCV1 is controlled so that the inflow rate of hydrogen gas into the preheater 71 is fixed (step ST8), and then spillback control is started (step ST5). That is, the second control unit 50b controls the spillback valve 18b so that a part of the gas in the discharge passage 24 is returned to the suction passage 21. In this way, when it is determined as NO in step ST7, in addition to heating the hydrogen gas by the preheater 71, heating of the hydrogen gas using the spillback unit SB1 is also performed. As a result, the suction temperature TS2 is adjusted to be equal to or higher than the lower limit value T TH1 of the predetermined temperature range.

[0102] In the compressor unit 10 having the above configuration, when the first switching means CV1 is in the second switching state (when the compressor unit 10 is in the steady operation state), the heating of the hydrogen gas in the suction passage 21 by the preheater 71 is given priority over the heating by the spillback unit SB1, and when the heating is insufficient, the heating by the spillback unit SB1 is used for compensation control. Therefore, in the compressor unit 10 according to the present embodiment, the loss of power for returning the hydrogen gas compressed in the subsequent compression stage 14 to the suction passage 21 can be minimized. Therefore, the temperature of the hydrogen gas sent to the subsequent compression stage 14 can be managed within a certain range while suppressing a decrease in processing efficiency.

[0103] Also, in the compressor unit 10, a downstream temperature sensor 48 is arranged downstream of the preheater 71 in the discharge passage 24, and by managing the temperature of the hydrogen gas on the downstream side of the preheater 71 using the detected temperature TS3 acquired by the downstream temperature sensor 48, an excessive temperature drop of the hydrogen gas supplied to the demand destination can be suppressed. Effects such as not having to use an expensive low-temperature specification for the supply pipe to the demand destination can also be expected.

[0104] Furthermore, if the compressor unit 10 is adopted, efficient recovery / supply of hydrogen gas is possible.

[0105] In the compressor unit 10 shown in FIG. 9, as an example, the discharge flow path 24 is branched into a first flow path 24a and a second flow path 24b, and the preheater 71 is provided in the first flow path 24a. However, the arrangement form of the preheater 71 is not limited to this. For example, as shown in FIG. 11, the suction flow path 21 may be branched into a first flow path 21a and a second flow path 21b, and the preheater 71 may be provided between one of the branched flow paths (the first flow path 21a) and the discharge flow path 24. In this case, a flow rate adjusting means FCV1 capable of adjusting the amount of hydrogen gas flowing into the preheater 71 may be provided at a branch point between the first flow path 21a and the second flow path 21b in the suction flow path 21.

[0106] In the compressor unit 10 shown in FIG. 9, as an example, a configuration including two compression stages of the first compression stage 12 and the subsequent compression stage 14 is taken, but it is not limited to this. For example, one or more compression stages may be added between the subsequent compression stage 14 and the flow rate adjusting means FCV1. Similarly, in the compressor unit 10 shown in FIG. 11, one or more compression stages may be added between the subsequent compression stage 14 and the preheater 71.

[0107] (Third Embodiment) As shown in FIG. 12, the compressor unit 10 according to the third embodiment is different from the second embodiment in that the preheater 71 is provided so that heat exchange between hydrogen gases is possible between the intermediate flow path 22 and the suction flow path 21. In FIG. 12, the same components as those in the first embodiment and the second embodiment are denoted by the same reference numerals, and the description of the overlapping parts will be omitted below.

[0108] In the compressor unit 10, the intermediate flow path 22 has a fourth flow path 22d in addition to the first flow path 22a and the second flow path 22b. The fourth flow path 22d is configured to branch separately from the first flow path 22a and the second flow path 22b. In the compressor unit 10 according to the present embodiment, the preheater 71 is provided between the fourth flow path 22d and the suction flow path 21 in the intermediate flow path 22.

[0109] The first switching means CV1 includes a first control valve 59b provided in the first flow path 22a, a second control valve 59c provided in the second flow path 22b, and a third control valve 59d provided in the fourth flow path 22d. Therefore, in the compressor unit 10, by controlling the first control valve 59b, the second control valve 59c, and the third control valve 59d, the hydrogen gas discharged from the first compression stage 12 selectively flows into the first flow path 22a, the second flow path 22b, and the fourth flow path 22d. In this embodiment, control valves 59b, 59c, and 59d are provided in each of the first flow path 22a, the second flow path 22b, and the fourth flow path 22d. However, on-off valves that simply perform opening and closing may be provided instead.

[0110] Although not shown, the first control unit 50a of the control unit 50 (see FIG. 1 etc.) can control the first control valve 59b, the second control valve 59c, and the third control valve 59d that constitute the first switching means CV1 respectively.

[0111] In the compressor unit 10 according to this embodiment, the downstream temperature sensor 48 is arranged on the downstream side of the preheater 71 and the cooler section 58 in the intermediate flow path 22.

[0112] In the operation of the compressor unit 10 according to this embodiment, the control unit 50 executes the same control as in the second embodiment. That is, the same control as that described with reference to FIG. 10 is executed.

[0113] When the first switching means CV1 (the first regulating valve 59a, the second regulating valve 59b, the third regulating valve 59d) of the compressor unit 10 having the above configuration is in the second switching state, the hydrogen gas flowing through the suction passage 21 is heated by combining the heating by the preheater 71 and the heating by the spillback portion SB1. Therefore, compared with the case where only the spillback portion SB1 heats the hydrogen gas in the suction passage 21, the power loss of returning the compressed hydrogen gas to the suction side of the first compression stage 12 can be minimized. Further, since the gas flowing through the fourth passage 22d is cooled by the preheater 71, the suction gas temperature of the subsequent compression stage 14 decreases. For this reason, the power at the subsequent compression stage also decreases. By these means, the suction temperature TS2 of the hydrogen gas to the first compression stage 12 can be managed within a certain range while suppressing a decrease in processing efficiency.

[0114] Also, in the compressor unit 10, a downstream temperature sensor 48 is arranged downstream of the preheater 71 in the intermediate passage 22, and by managing the temperature on the downstream side of the preheater 71 using the detected temperature TS3 acquired by the downstream temperature sensor 48, it is possible to prevent the temperature of the hydrogen gas sucked into the subsequent compression stage 14 from decreasing excessively.

[0115] Furthermore, if the compressor unit 10 is adopted, efficient recovery / supply of hydrogen gas is possible.

[0116] In the compressor unit 10 shown in FIG. 12, as an example, a fourth passage 22d that branches separately from the first passage 22a and the second passage 22b is provided in the intermediate passage 22, and a preheater 71 is provided between the fourth passage 22d and the suction passage 21. However, the arrangement form of the preheater 71 is not limited to this. For example, as shown in FIG. 13, the suction passage 21 may be branched into a first passage 21a and a second passage 21b, and a preheater 71 may be provided between one of the branched passages (the first passage 21a) and the second passage 22b of the intermediate passage 22. In this case, a flow rate adjusting means 72 capable of adjusting the amount of hydrogen gas flowing into the preheater 71 may be provided at a branch point between the first passage 21a and the second passage 21b in the suction passage 21 or the like.

[0117] In addition, in the compressor unit 10 shown in FIG. 12, although an example of a configuration is provided in which there are two compression stages, i.e., the first compression stage 12 and the subsequent compression stage 14, the present invention is not limited thereto. For example, one or more compression stages may be added between the subsequent compression stage 14 and the connection portion of the spillback flow path 18a in the discharge flow path 24.

[0118] (Fourth Embodiment) As shown in FIG. 14, the compressor unit 10 according to the fourth embodiment is different from the first embodiment in that a low-pressure gas discharge path 53 capable of discharging hydrogen gas to the intermediate-stage demand destination D2 is provided, and adjustment means 41 for adjusting the processing amount of hydrogen gas by the subsequent compression stage 14 is provided. In FIG. 14, the same components as those in the first embodiment are denoted by the same reference numerals, and the description of the overlapping parts will be omitted hereinafter.

[0119] The intermediate-stage demand destination D2 is a facility capable of processing hydrogen gas at a pressure lower than the pressure of the hydrogen gas required at the demand destination D1. For example, in addition to facilities that utilize gas such as engines, power generation facilities, and boilers as energy sources, facilities that utilize gas at approximately atmospheric pressure, such as flare facilities and vents, may be included.

[0120] The low-pressure gas discharge path 53 branches at the branch point P B in the intermediate flow path 22. The branch point P B may be provided at any position in the intermediate flow path 22 including the first flow path 22a and the second flow path 22b as long as it is between the first compression stage 12 and the subsequent compression stage 14.

[0121] Furthermore, a pressure sensor 47 is disposed in the intermediate flow path 22. The pressure sensor 47 acquires the pressure of the hydrogen gas in the intermediate flow path 22 and sends the acquired pressure information to the control unit 50.

[0122] The compressor unit 10 is provided with a third switching means CV3 for switching the flow state of hydrogen gas in the low-pressure gas discharge passage 53. The third switching means CV3 is constituted by an on-off valve 56a and is provided in the low-pressure gas discharge passage 53 as an example in the present embodiment. The third switching means CV3 mutually adjusts the amount of hydrogen gas sent to the subsequent compression stage 14 and the amount of hydrogen gas sent to the low-pressure gas discharge passage 53 when the first switching means CV1 is in the second switching state.

[0123] In the present embodiment, the third switching means CV3 constituted by the on-off valve 56a is adopted as an example, but the present invention is not limited thereto. For example, it is also possible to adopt the third switching means CV3 constituted by a three-way valve or the like.

[0124] A pressure sensor 49 is disposed at a portion downstream of the third switching means CV3 in the low-pressure gas discharge passage 53. The pressure sensor 49 acquires the pressure of the hydrogen gas flowing in the low-pressure gas discharge passage 53 toward the intermediate-stage demand destination D2 and sends the acquired pressure information to the control unit 50.

[0125] The adjustment means 41 adjusts the processing amount of hydrogen gas by the subsequent compression stage 14 on the downstream side of the branch point P B The adjustment means 41 adjusts the gas processing amount by a method other than adjusting the rotation speed of the crank mechanism 16. In the present embodiment, as an example, the adjustment means 41 is constituted by a spillback portion (second spillback portion SB2) that adjusts the processing amount of hydrogen gas so that the gas flow rate sent from the subsequent compression stage 14 toward the demand destination 26 is adjusted.

[0126] The second spillback section SB2 includes a second spillback channel 43a and a second spillback valve 43b with adjustable opening degree disposed in the second spillback channel 43a. One end of the second spillback channel 43a is connected to the discharge channel 24 upstream of the spillback channel 18. The other end is connected to the intermediate channel 22. Therefore, a part of the hydrogen gas discharged from the subsequent compression stage 14 is returned to the intermediate channel 22, that is, the suction side of the subsequent compression stage 14. The second spillback valve 43b adjusts the spillback amount in the second spillback channel 43a.

[0127] Information regarding the required amount of hydrogen gas is input to the control unit 50 from the demand destination D1 and the intermediate-stage demand destination D2, respectively. And the functions of the control unit 50 include a fourth control unit 50d and a fifth control unit 50e in addition to the first control unit 50a and the second control unit 50b. The fourth control unit 50d is a functional unit configured to control the third switching means CV3 according to the change in the required amount of hydrogen gas input from the intermediate-stage demand destination D2 or the change in the required amount of hydrogen gas input from the demand destination D1. The fifth control unit 50e is a functional unit configured to control the second spillback valve 43b according to the change in the required amount of hydrogen gas input from the intermediate-stage demand destination D2 or the change in the required amount of hydrogen gas input from the demand destination D1.

[0128] Here, regarding the operation control executed by the control unit 50 in the operation of the compressor unit 10 according to the present embodiment, it will be described with reference to FIG. 15. In the following description, some descriptions overlapping with the above first embodiment are omitted.

[0129] When in the steady operation state (TS1 < threshold value T1), the control unit 50 controls the first switching means CV1 to stop the inflow of hydrogen gas into the cooler unit 58 (step ST4). The control steps up to this point are the same as those in the above first embodiment.

[0130] The control unit 50 starts the spillback control while referring to the suction temperature TS2 acquired by the upstream temperature sensor 45 (step ST5). That is, TS2 < TTH1 In this case, the first control unit 50a controls the spillback valve 18b so that a part of the hydrogen gas discharged from the subsequent compression stage 14 is returned to the suction passage 21 (step ST5). As a result, the temperature of the hydrogen gas flowing through the suction passage 21 (suction temperature TS2) is within the above-mentioned predetermined temperature range (T TH1 ≦TS2≦T TH2 ), and the hydrogen gas in the suction passage 21 is heated so as to fall within this range. When TS2>T TH2 , the operation of returning a part of the gas in the discharge passage 24 to the suction passage 21 is not performed, or the amount returned is reduced.

[0131] Also, in the present embodiment, in parallel with the execution of step ST5, the third switching means CV3 is controlled so that the hydrogen gas flowing through the intermediate passage 22 is discharged to the intermediate-stage demand destination D2 through the low-pressure gas discharge passage 53 (step ST11). Further, in the present embodiment, in parallel with the execution of step ST5 and step ST11, the adjustment means 41 (second spillback valve 43b) is controlled so that a part of the hydrogen gas discharged from the subsequent compression stage 14 returns to the intermediate passage 22 (step ST12). As described above, the control of the third switching means CV3 and the adjustment means 41 is executed according to the change in the required amount of hydrogen gas from the intermediate-stage demand destination D2 or the required amount of hydrogen gas from the demand destination D1.

[0132] When the required amount (demand amount) of hydrogen gas at the demand destination D1 is reduced during steady operation (when the first switching means CV1 is in the second switching state), the compressor unit 10 having the above configuration discharges hydrogen gas to the intermediate-stage demand destination D2, thereby balancing the amount of boil-off gas (hydrogen gas) generated from the liquid hydrogen storage tank 23 and the amount of hydrogen gas sent by the first compression stage 12, and the pressure of the liquid hydrogen storage tank 23 can be kept constant.

[0133] Also, in the compressor unit 10, the adjustment means 41 (the second spillback portion SB2) reduces the processing amount of hydrogen gas in the subsequent compression stage 14, and by suppressing the compression ratio of the subsequent compression stage 14 in this way, the processing amount of hydrogen gas in the subsequent compression stage 14 can be reduced. Therefore, in the compressor unit 10, the power of the subsequent compression stage 14 can be reduced.

[0134] Furthermore, if the compressor unit 10 is adopted, efficient recovery / supply of hydrogen gas is possible.

[0135] In the compressor unit 10 shown in FIG. 14, the subsequent compression stage 14 has a single-stage compression mechanism, but it may have a multi-stage compression mechanism. For example, as shown in FIG. 16, the subsequent compression stage 14 may be constituted by a subsequent first compression stage 14a and a subsequent second compression stage 14b. When this configuration is adopted, one end portion of the second spillback flow path 43a may be connected to a third flow path 22c between the subsequent first compression stage 14a and the subsequent second compression stage 14b in the intermediate flow path 22. In this case, a part of the hydrogen gas discharged from the subsequent first compression stage 14a is returned to the suction side of the subsequent first compression stage 14a.

[0136] Also, when the subsequent compression stage 14 has a subsequent first compression stage 14a and a subsequent second compression stage 14b, as shown in FIG. 17, one end portion of the second spillback flow path 43a may be connected to the discharge flow path 24, and the other end portion may be connected to a portion upstream of the subsequent first compression stage 14a in the intermediate flow path 22. In this case, a part of the hydrogen gas discharged from the subsequent second compression stage 14b is returned to the suction side of the subsequent first compression stage 14a.

[0137] Further, when the subsequent compression stage 14 has a subsequent first compression stage 14a and a subsequent second compression stage 14b, as shown in FIG. 18, a second spillback portion SB2 may be provided for each of the subsequent first compression stage 14a and the subsequent second compression stage 14b. In this case, a part of the hydrogen gas discharged from the subsequent first compression stage 14a to the third flow path 22c is returned to the suction side of the subsequent first compression stage 14a, and a part of the hydrogen gas discharged from the subsequent second compression stage 14b to the discharge flow path 24 is returned to the third flow path 22c.

[0138] Furthermore, in the compressor unit 10 shown in FIGS. 16 to 18, a configuration is adopted in which the low-pressure gas discharge path 53 branches from a portion upstream of the subsequent first compression stage 14a in the intermediate flow path 22. However, regarding the position of the branch point P B where the low-pressure gas discharge path 53 branches, it is not limited thereto. For example, as shown in FIG. 19, the low-pressure gas discharge path 53 may branch from a branch point P B at which the third flow path 22c arranged between the subsequent first compression stage 14a and the subsequent second compression stage 14b in the intermediate flow path 22 is located. In the compressor unit 10 shown in FIG. 19, as an example, an intermediate cooler portion 74 may be provided at a portion upstream of the branch point P B in the third flow path 22c. Thereby, the hydrogen gas whose temperature has risen due to the compression of the subsequent first compression stage 14a can be cooled and sent to the subsequent second compression stage 14b. In this case, the adjustment means 41 adjusts the processing amount of the hydrogen gas by the compression stage 14b on the downstream side of the branch point P B among the two compression stages 14a and 14b constituting the subsequent compression stage.

[0139] In the compressor unit 10 shown in each of FIGS. 16 to 19, leak gas discharge portions 29 are provided for each of the subsequent first compression stage 14a and the subsequent second compression stage 14b included in the subsequent compression stage 14. However, a configuration may be adopted in which leak gas discharge portions 29 are provided for some of the plurality of compression stages constituting the subsequent compression stage 14.

[0140] (Fifth Embodiment) As shown in FIG. 20, the compressor unit 10 may be configured with an on-off suction valve unloader 61 and an adjusting means 41 using a second spillback portion SB2 similar to that shown in FIG. 19 in combination.

[0141] As shown in FIG. 21, in the control of the adjusting means 41, when the state (valve opening degree) of the second spillback valve 43b input to the control unit 50 becomes larger than a preset opening threshold value b1 (when the spillback amount is large) (Yes in step ST41), the suction valve unloader 61 is controlled to reduce the load amount of the subsequent compression stage 14 (from 100% to 50%) (step ST42). When the opening degree of the second spillback valve 43b becomes smaller than the opening threshold value b2 (Yes in step ST43), the suction valve unloader 61 is controlled to increase the load amount of the subsequent compression stage 14 (from 50% to 100%) (step ST44). Thereby, when the spillback is excessive, the power can be reduced by reducing the load of the subsequent compression stage 14.

[0142] As shown in FIG. 22, the compressor unit 10 may be provided with a stepless capacity adjusting device 64b provided in the subsequent compression stage 14 as the adjusting means 41.

[0143] The stepless capacity adjusting device 64b includes a suction valve unloader 61b, a driving device 62b, and a detector 63b for detecting the rotation of the crank mechanism. The suction valve unloader 61b is driven by a hydraulic or electric driving device 62b and can maintain or release the open state of the valve plate of the suction valve at a speed higher than the time taken for the piston to reciprocate. Further, based on the signal sent from the detector 63b installed in the crank mechanism, the control unit performs arithmetic processing for estimating the position of the piston.

[0144] In the cylinder part of the subsequent compression stage 14, the suction valve installed between the suction passage and the compression chamber is composed of a valve plate that opens and closes the gas passage and a valve body that houses it. Similar to a check valve, when the upstream pressure is higher than the downstream side, the valve plate is in an open state due to the differential pressure. When the downstream pressure is high, the gas does not flow.

[0145] When the suction valve unloader 61b is driven, the valve plate of the suction valve is maintained in an open state, creating a state where the check valve function cannot be performed. When the piston is in the suction stroke without driving the unloader, the pressure in the compression chamber drops below that in the suction passage, so the suction valve opens and gas is introduced into the compression chamber side. When the piston is in the compression stroke, the pressure in the compression chamber rises above that in the suction passage, so the suction valve closes.

[0146] At the initial stage when the compression stroke starts, the stepless capacity adjustment device 64b maintains the open state, returns part of the gas introduced into the compression chamber to the suction passage side, and releases the open state during the middle of the compression stroke, so that the suction valve closes. At this time, the gas remaining in the compression chamber is compressed and sent out. During the next piston suction stroke, the drive part is driven again, and the open state is released after the compression stroke of the piston starts. This is repeated in accordance with the reciprocating motion of the piston.

[0147] If the timing of this release is advanced, the delivery volume increases, and if it is delayed, the delivery volume decreases. Therefore, it can perform the same function as the second spillback valve. Furthermore, since the amount of gas to be compressed is adjusted, the effect of reducing power is significant.

[0148] [Other Modification Examples] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The present invention is not limited to the above embodiments, and various changes, improvements, etc. are possible without departing from the gist thereof.

[0149] For example, as shown in FIG. 23, in the compressor unit 10, the spillback portion SB1 may be configured to return a part of the hydrogen gas flowing through the third flow path 22c between two adjacent subsequent compression stages 14 (subsequent first compression stage 14a and subsequent second compression stage 14b) in the intermediate flow path 22 to the suction flow path 21. Even in this case, the first compression stage 12 is prevented from being exposed to the extremely low temperature hydrogen gas. In the compressor unit 10, the number of subsequent compression stages 14 may be three or more, and the spillback portion SB1 may be provided in any intermediate flow path between the subsequent compression stages 14.

[0150] As shown in FIG. 24, in the compressor unit 10, a fourth flow path 22d branched separately from the third flow path 22c may be provided in the intermediate flow path 22, and the preheater 71 may be arranged to heat-exchange the hydrogen gas flowing through the suction flow path 21 (the hydrogen gas sucked into the first compression stage 12) and the hydrogen gas flowing through the fourth flow path 22d. Other configurations are substantially the same as those in FIG. 23. The number of subsequent compression stages 14 may be three or more, and the preheater 71 may be provided in any intermediate flow path between the subsequent compression stages 14.

Description of Reference Numerals

[0151] 10 Compressor unit 12 First compression stage 14 Subsequent compression stage 16 Crank mechanism 18a Spillback flow path 18b Spillback valve 21 Suction flow path 22 Intermediate flow path 23 Liquid hydrogen storage tank 24 Discharge flow path 29 Leak gas discharge portion 41 Adjusting means 43 Second spillback portion 43a Second spillback flow path 43b Second spillback valve 45 Upstream temperature sensor (second temperature sensor) 46 Intermediate temperature sensor (first temperature sensor) 47 Pressure sensor 48 Downstream temperature sensor (third temperature sensor) 50 Control unit 53 Low-pressure gas discharge path 58 Cooler section 61 Suction valve unloader 62 Driving device 64 Capacity adjustment device 71 Preheater 211 Cylinder section 212 Piston 213 Piston rod CV1 First switching means CV3 Third switching means D1 Demand leader D2 Intermediate-stage demand leader FCV1 Flow rate adjustment means SB1 Spillback section P B Branch point

Claims

1. A reciprocating compressor unit that recovers hydrogen gas, which is boil-off gas, from a liquid hydrogen storage tank and supplies at least a part of the recovered hydrogen gas to a customer including at least one of an engine, a power generation facility, or a boiler, including a plurality of compression stages that compress hydrogen gas inhaled from a suction flow path, a crank mechanism that drives the plurality of compression stages, a cooler section provided in an intermediate flow path between the plurality of compression stages, a first switching means for switching the inflow state of hydrogen gas to the cooler section, a spillback flow path that returns hydrogen gas discharged from a discharge flow path on the discharge side of the plurality of compression stages or hydrogen gas flowing through the intermediate flow path to the suction flow path, and a spillback section including a spillback valve for adjusting the spillback amount in the spillback flow path, a first temperature sensor disposed in the intermediate flow path, a second temperature sensor disposed in the suction flow path between a connection portion of the spillback flow path and a first compression stage, which is the foremost stage among the plurality of compression stages, a control unit that controls the first switching means and the spillback valve respectively, and comprising, each of the first compression stage and subsequent compression stages excluding the first compression stage among the plurality of compression stages, includes a cylinder section, a piston, a piston rod that connects the piston to the crank mechanism, and a rod packing that seals between the piston rod and the cylinder section, and comprising, the first compression stage is air-cooled and oil-free, the control unit, When starting up and when the temperature TS1 acquired by the first temperature sensor is equal to or higher than a predetermined first temperature threshold T1 greater than 0°C, the first switching means is controlled to be in a first switching state in which the hydrogen gas discharged from the first compression stage is circulated through the cooler section and cooled. When the temperature TS1 acquired by the first temperature sensor becomes less than the first temperature threshold T1, the first switching means is controlled to be in a second switching state in which the hydrogen gas is sent to a compression stage downstream of the location where the cooler section is provided without passing through the cooler section. When the first switching means is in the second switching state, the suction temperature TS2 acquired by the second temperature sensor is referred to, and the spillback valve is controlled so that the suction temperature TS2 is within a predetermined temperature range. The predetermined temperature range is set higher than a reference temperature based on the liquefaction temperature of air and within a range less than 0°C, a compressor unit.

2. A preheater capable of heat-exchanging the hydrogen gas before being inhaled into the first compression stage, the hydrogen gas after being discharged into the discharge flow path, or the hydrogen gas flowing through the intermediate flow path. A third temperature sensor disposed downstream of the preheater in the discharge flow path. Flow rate adjusting means capable of adjusting the inflow state of hydrogen gas into the preheater. Further comprising. The control unit. When the first switching means is in the second switching state. While increasing the inflow amount of hydrogen gas into the preheater so that the heating of the hydrogen gas in the suction flow path by the preheater takes precedence over the heating by the spillback section, the flow rate adjusting means is controlled so that the temperature TS3 on the downstream side of the preheater acquired by the third temperature sensor does not become equal to or lower than the threshold value. When the suction temperature TS2 becomes equal to or lower than the set value temperature, the flow rate adjusting means and the spillback valve are controlled so that the suction temperature TS2 is within a predetermined temperature range, the compressor unit according to claim 1.

3. A preheater capable of heat-exchanging the hydrogen gas before being inhaled into the first compression stage and the hydrogen gas flowing between the first compression stage and the subsequent compression stage in the intermediate flow path; A third temperature sensor disposed downstream of the preheater in the intermediate flow path; and further comprising: The first switching means can switch the hydrogen gas discharged from the first compression stage to any one of the inflow state of hydrogen gas to the cooler section, the direct inflow state of hydrogen gas to the subsequent compression stage, and the inflow state of hydrogen gas to the preheater; The control unit: When the first switching means is in the second switching state, the spillback valve and the first switching means are controlled so that the hydrogen gas in the suction flow path is within the predetermined temperature range by the combined use of heating of the hydrogen gas in the suction flow path by the spillback section and heating by the preheater; When the temperature TS3 on the downstream side of the preheater acquired by the third temperature sensor is less than the threshold value, the first switching means is controlled so as not to further increase the inflow of hydrogen gas to the preheater. The compressor unit according to claim 1.

4. A low-pressure gas discharge path that branches from a branch point provided in the intermediate flow path and can discharge hydrogen gas to an intermediate-stage demand destination that can process hydrogen gas at a pressure lower than the pressure of the hydrogen gas required at the demand destination; Third switching means provided in the low-pressure gas discharge path or the branch point; Adjusting means for adjusting the processing amount of hydrogen gas by the subsequent compression stage; and further comprising: The control unit: When the first switching means is in the second switching state, in parallel with the control of the spillback valve, while controlling the third switching means so that hydrogen gas is discharged to the low-pressure gas discharge path according to the required amount of the intermediate-stage demand destination or the variation in the required amount of the demand destination, the adjusting means is controlled so that the throughput of the subsequent compression stage is adjusted. The compressor unit according to claim 1.

5. The subsequent compression stage is composed of two or more compression stages. A low-pressure gas discharge path that branches from a branch point provided in the intermediate flow path and discharges hydrogen gas to an intermediate-stage demand destination capable of processing hydrogen gas at a pressure lower than the pressure of the hydrogen gas required by the demand destination. A third switching means provided in the low-pressure gas discharge path or the branch point. Adjusting means for adjusting the throughput of the compression stage on the downstream side of the branch point among the two or more compression stages constituting the subsequent compression stage. Further comprising The control unit When the first switching means is in the second switching state, in parallel with the control of the spillback valve, while controlling the third switching means so that hydrogen gas is discharged to the low-pressure gas discharge path according to the required amount of the intermediate-stage demand destination or the variation in the required amount of the demand destination, the adjusting means is controlled so that the throughput of the downstream compression stage in the subsequent compression stage is adjusted. The compressor unit according to claim 1.

6. The adjusting means Comprises a second spillback flow path that returns hydrogen gas to the suction side of the subsequent compression stage upstream of the spillback flow path, and a second spillback valve that adjusts the spillback amount in the second spillback flow path, and a second spillback section. The control unit When the first switching means is in the second switching state, the second spillback valve is controlled so that a flow rate corresponding to the required amount of the intermediate-stage demand destination or the variation in the required amount of the demand destination is returned to the suction side of the subsequent compression stage. The compressor unit according to claim 4 or 5.

7. The adjusting means further includes an on-off type suction valve unloader attached to the cylinder part of the subsequent compression stage, The control unit When the first switching means is in the second switching state, if the opening degree of the second spillback valve becomes larger than a preset opening degree threshold value b1, the suction valve unloader is controlled to reduce the load amount of the subsequent compression stage. When the opening degree of the second spillback valve becomes smaller than the opening degree threshold value b2, the control is executed so that the suction valve unloader is controlled to increase the load amount of the subsequent compression stage. The compressor unit according to claim 6.

8. The adjusting means a suction valve unloader attached to the cylinder part of the subsequent compression stage, a hydraulic or electric drive device for opening and closing the suction valve unloader, a stepless capacity adjustment device including a control device for controlling the timing of the suction valve unloader to operate in conjunction with the rotational movement of the crankshaft, and The control unit When the first switching means is in the second switching state, the capacity adjustment device is controlled according to the flow rate corresponding to the required amount of the intermediate-stage demand destination or the variation in the required amount of the demand destination, so that the hydrogen gas inhaled from the inside of the cylinder part to the suction side is returned, thereby adjusting the throughput of the subsequent compression stage. The compressor unit according to claim 4 or 5.

9. The compressor unit according to claim 1, wherein at least a part of the subsequent compression stage has a leak gas discharge portion that returns leak gas from the rod packing to the suction flow path.

Images