Liquefied hydrogen facility
Patent Information
- Application Number
- PCT/JP2025/012042
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-03-26
- Publication Date
- 2026-10-01
Smart Images
Figure JP2025012042_01102026_PF_FP_ABST
Abstract
Description
Liquid hydrogen equipment
[0001] The present disclosure relates to liquid hydrogen equipment.
[0002] Boil-off gas generated from a liquid hydrogen storage tank that stores liquid hydrogen may be treated by being combusted in a combustion engine. In this case, an oil-filled compressor may be used as a compressor for supplying boil-off gas to the combustion engine. In the oil-filled compressor, oil is supplied into a compression chamber, and the gas heated by compression is cooled. As a result, the oil-filled compressor discharges oil-containing gas in which oil components are mixed with the boil-off gas.
[0003] For operation control, an oil-filled compressor may recirculate a part of the discharged gas to the upstream side via a spillback line. That is, the oil-containing gas, which is a part of the discharged gas, also flows into the portion of the upstream section of the oil-filled compressor to which the spillback line is connected. When the oil-filled compressor is in operation, the oil-filled compressor sucks in the oil-containing gas, so that the inflow of the oil-containing gas to the upstream side of the oil-filled compressor is suppressed.
[0004] Patent Document 1 discloses a compressor that cools a gas via a cooled cylinder while preventing oil from mixing into the gas when compressing the gas, by circulating a coolant through a flow path provided in a cylinder.
[0005] Japanese Unexamined Patent Publication No. 2020-041510
[0006] If the oil-filled compressor abnormally stops, the oil-containing gas that has recirculated to the upstream side of the oil-filled compressor via the spillback line will not be sucked into the oil-filled compressor, and may flow into the upstream liquid hydrogen storage tank side. Generally, a liquid hydrogen storage tank is regarded as an oil-free area where high purity of liquid hydrogen is required, and it is necessary to prevent the inflow of oil-containing gas.
[0007] On the other hand, the compressor disclosed in Patent Document 1 cools compressed gas from the outside of the cylinder, and thus has inferior cooling performance compared to an oil-filled compressor.
[0008] The object of this disclosure is to provide a liquefied hydrogen facility that uses an oil-lubricated compressor that supplies oil into the compression chamber, while suppressing the inflow of oil-containing gas into the oil-free zone upstream of the oil-lubricated compressor.
[0009] This disclosure provides a liquefied hydrogen facility comprising: a liquefied hydrogen storage tank for storing liquefied hydrogen; a first gas discharge line connected to the gas phase of the liquefied hydrogen storage tank, which discharges boil-off gas from the liquefied hydrogen storage tank to an oil-free zone; a second gas discharge line branching from the first gas discharge line, which discharges boil-off gas from the liquefied hydrogen storage tank to an oil-free zone; an oil-lubricated compressor provided in the second gas discharge line, which has a compression chamber to which oil is supplied, and which compresses and discharges the gas discharged from the liquefied hydrogen storage tank; a spillback line connecting the upstream and downstream sides of the oil-lubricated compressor; a spillback valve provided in the spillback line for opening and closing the spillback line; and a valve in the compressor inlet piping located upstream of the portion to which the spillback line is connected, which prevents the gas from flowing from the second gas discharge line to the first gas discharge line.
[0010] According to the liquefied hydrogen equipment described herein, the second gas discharge line includes an oil-lubricated compressor, so the gas discharged from the oil-lubricated compressor may become an oil-containing gas that contains oil supplied in the compression chamber. As a result, the oil-containing gas discharged from the oil-lubricated compressor may be recirculated into the compressor inlet piping via the spillback line. During normal operation, the oil-containing gas recirculated into the compressor inlet piping is drawn into the oil-lubricated compressor and does not flow into the first gas discharge line. However, when the oil-lubricated compressor is stopped, the oil-containing gas is not drawn into the stopped oil-lubricated compressor and may flow upstream, i.e., into the first gas discharge line, due to the pressure difference, potentially resulting in the discharge of oil-containing gas into the oil-free zone.
[0011] However, according to the liquefied hydrogen equipment described herein, the compressor inlet piping has a valve upstream of the section to which the spillback line is connected, which prevents gas from flowing into the first gas discharge line. As a result, the valve prevents oil-containing gas from flowing into the first gas discharge line. Therefore, oil-containing gas is prevented from flowing into the oil-free zone.
[0012] Figure 1 is a schematic diagram showing a liquefied hydrogen facility according to one embodiment of the present disclosure. Figure 2 is a flowchart showing the operation of the liquefied hydrogen facility. Figure 3 is a time chart schematically explaining the operation of the liquefied hydrogen facility. Figure 4 is a diagram showing a valve according to a modified example. Figure 5 is a diagram showing a valve according to another modified example. Figure 6 is a diagram showing a valve according to yet another modified example.
[0013] Hereinafter, a liquefied hydrogen facility according to one embodiment of this disclosure will be described with reference to the attached drawings.
[0014] Figure 1 schematically shows a liquefied hydrogen facility 1 according to one embodiment of the present disclosure. The liquefied hydrogen facility 1 according to the present disclosure is installed on a liquefied hydrogen carrier that transports liquefied hydrogen LH2 as cargo. In addition, the liquefied hydrogen facility may be installed on land. For example, the liquefied hydrogen facility may be a liquefied gas-fueled ship that is propelled using liquefied hydrogen gas as fuel, or it may be a land-based liquefied hydrogen gas facility or liquefied hydrogen gas plant.
[0015] As shown in Figure 1, the liquefied hydrogen facility 1 includes one or more liquefied hydrogen storage tanks 2 in which liquefied hydrogen is stored, and a combustion engine 3 that burns the boil-off gas generated from the liquefied hydrogen in the liquefied hydrogen storage tanks 2 as fuel. In this embodiment, the liquefied hydrogen facility 1 has multiple liquefied hydrogen storage tanks 2.
[0016] In this embodiment, the combustion engine 3 is a boiler supplied with boil-off gas as fuel, which generates steam. The generated steam is used to propel the liquefied hydrogen carrier, for example, to drive a steam turbine, which rotates the main shaft and propeller, generating the power necessary for the operation of the liquefied hydrogen carrier. Alternatively, a generator may be driven by the steam turbine, in which case the liquefied hydrogen carrier may have an electric propulsion system in which the generated electricity is supplied to a motor that rotates a screw. Furthermore, an internal combustion engine, such as an engine, may be used as the combustion engine 3. In this case as well, the screw may be driven directly by the combustion engine 3, or the electricity generated by driving a generator may be supplied to the electric propulsion system.
[0017] The liquefied hydrogen facility 1 has a first gas discharge line 30 through which boil-off gas is discharged from the liquefied hydrogen storage tank 2 to the onshore cargo handling facility 8, and a second gas discharge line 40 through which it is discharged to the combustion engine 3. The liquefied hydrogen facility 1 further has an inert gas supply line 32 that supplies inert gas to the liquefied hydrogen storage tank 2.
[0018] The inert gas supply line 32 is equipped with an inert gas generator 4 that generates inert gases such as nitrogen and combustion gases mainly composed of carbon dioxide, for example, in the liquefied hydrogen storage tank 2. For example, during maintenance of the liquefied hydrogen storage tank 2, in the process of replacing the atmosphere inside the liquefied hydrogen storage tank 2 from liquefied hydrogen to air, inert gas is supplied to the liquefied hydrogen storage tank 2 via the inert gas supply line 32 in order to temporarily replace it with inert gas.
[0019] The cargo handling equipment 8 is, for example, equipment for handling liquefied hydrogen between the liquefied hydrogen storage tank 2 and the tank on land. In this embodiment, the cargo handling equipment 8 is equipment for filling the liquefied hydrogen storage tank 2 of the liquefied hydrogen carrier with liquefied hydrogen stored in the tank on land.
[0020] A compressor 7 is provided in the first gas discharge line 30. The compressor 7 draws boil-off gas from the liquefied hydrogen storage tank 2, compresses it, and discharges it toward the cargo handling equipment 8. In this embodiment, both the liquefied hydrogen storage tank 2 and the cargo handling equipment 8 are required to maintain high purity hydrogen, and the mixing of oil and other substances is prohibited, making them oil-free zones. Therefore, the first gas discharge line 30, including the compressor 7, is an oil-free zone. Accordingly, an oil-free compressor is used as the compressor 7, in which no oil is supplied to the compression chamber 7a.
[0021] The first gas discharge line 30 includes, in addition to the liquefied hydrogen storage tank 2, a compressor inlet pipe 31 connecting the gas phase of the liquefied hydrogen storage tank 2 to the oil-free compressor 7, and a cargo handling equipment inlet pipe 33 connecting the oil-free compressor 7 to the cargo handling equipment 8. The compressor inlet pipe 31 has multiple branch pipes 31a, the upstream end of which is branched to correspond to each of the multiple liquefied hydrogen storage tanks 2. Each branch pipe 31a is connected to the gas phase of the corresponding liquefied hydrogen storage tank 2. Therefore, the first gas discharge line 30 may also be a gas discharge line for cargo handling.
[0022] The second gas discharge line 40 branches off from the first gas discharge line 30. Specifically, the second gas discharge line 40 branches off from the downstream side of the section where multiple branch pipes 31a of the compressor inlet piping 31 converge, that is, from the side of the oil-free compressor 7.
[0023] The second gas discharge line 40 is equipped with a compressor 11 that compresses the boil-off gas supplied from the liquefied hydrogen storage tank 2 and discharges it to the combustion engine 3.
[0024] In this embodiment, the second gas discharge line 40 is used not only to discharge boil-off gas generated from liquefied hydrogen, but also to discharge the inert gas in the liquefied hydrogen storage tank 2 that has been replaced during maintenance. Here, hydrogen gas has a molecular weight of approximately 2, nitrogen gas as the inert gas has a molecular weight of approximately 28, and when combustion gas is used as the inert gas, carbon dioxide, which accounts for a relatively large proportion, has a molecular weight of approximately 44. Thus, the compressor 11 needs to have the ability to compress multiple types of gases that have significantly different molecular weights and also significantly different specific heat ratios. For this reason, an oil-lubricated compressor is used as the compressor 11, which can reduce the temperature of the gas by supplying oil into the compression chamber 11a.
[0025] In this embodiment, the oil-lubricated compressor 11 is a screw-type compressor and has a pair of screws that mesh with each other. The pair of screws includes a drive screw and a driven screw driven by the drive screw. Because oil is supplied between the drive screw and the driven screw, they constantly mesh and rotate together, supporting each other, making them more resistant to vibration than when they rotate with clearance between them. Furthermore, both screws are cooled by the oil.
[0026] In contrast, in the case of an oil-free compressor where oil is not supplied to the compression chamber, the gas in the compression chamber is not oil-cooled. Due to the differences in the specific heat ratios of the various gases, as well as the differences in the compression ratio in the compressor due to differences in pressure loss in the compressor piping and suction nozzle, the temperature of the compressed gas varies greatly. This makes it difficult to set the clearance between moving parts such as a pair of screws, and it is not possible to stably compress these various gases due to vibrations in the moving parts.
[0027] Therefore, the oil-lubricated compressor 11 discharges an oil-containing gas, which is formed when oil is mixed with the boil-off gas as it is compressed in the compression chamber 11a. The oil-containing gas compressed by the oil-lubricated compressor 11 can be heated up by the compression, but it is cooled by the oil supplied to the compression chamber 11a.
[0028] The second gas discharge line 40 has a compressor inlet pipe 41 that branches off from the first gas discharge line 30 and is connected to the oil-lubricated compressor 11, and a compressor outlet pipe 42 that connects the oil-lubricated compressor 11 to the combustion engine 3.
[0029] The compressor inlet piping 41 is equipped with, in order from the upstream side, a valve 21, a filter 17, and a compressor inlet check valve 18. The compressor inlet piping 41 includes an inlet first pipe 41a located on the upstream side and equipped with the valve 21, and an inlet second pipe 41b located on the downstream side and equipped with the filter 17 and the compressor inlet check valve 18.
[0030] Valve 21 has a check valve portion 21a and a shut-off valve portion 21b. In other words, valve 21 is a check valve with a shut-off valve function, and in this embodiment, a screw-type check valve is used. The check valve portion 21a of valve 21 is a pressure-sensitive check valve that closes when the pressure on the downstream side becomes higher than the pressure on the upstream side, preventing gas from flowing from the downstream side to the upstream side. The shut-off valve portion 21b of valve 21 operates by manually tightening the operating part to shut off the upstream and downstream sides.
[0031] The filter 17 removes foreign matter from the gas drawn into the compressor 11.
[0032] The compressor inlet check valve 18 is a pressure-sensitive check valve that closes when the downstream pressure becomes higher than the upstream pressure, preventing gas from flowing from the downstream to the upstream side. In other words, the compressor inlet check valve 18 prevents the high-pressure gas compressed by the compressor 11 from flowing back upstream from the compressor 11 inlet.
[0033] The compressor outlet piping 42 is provided with, in order from the upstream side, a first gas-liquid separator 12, a gas cooler 13, and a second gas-liquid separator 14. The compressor outlet piping 42 includes a first outlet pipe 42a connecting the oil-lubricated compressor 11 and the first gas-liquid separator 12, a second outlet pipe 42b connecting the first gas-liquid separator 12 and the gas cooler 13, a third outlet pipe 42c connecting the gas cooler 13 and the second gas-liquid separator 14, a fourth outlet pipe 42d connected to the second gas-liquid separator 14, and a fifth outlet pipe 42e connecting the fourth outlet pipe 42d and the combustion engine 3.
[0034] The first gas-liquid separator 12 and the second gas-liquid separator 14 gradually remove and recover oil from the oil-containing gas. The recovered oil is then supplied back to the oil-lubricated compressor 11. However, the first gas-liquid separator 12 and the second gas-liquid separator 14 cannot completely remove the oil from the oil-containing gas. Therefore, the gas supplied downstream from the second gas-liquid separator 14 may still contain oil.
[0035] The gas cooler 13 cools the oil-containing gas that is discharged from the oil-lubricated compressor 11 and has passed through the first gas-liquid separator 12.
[0036] The second gas discharge line 40 further includes a spillback line 43 connecting the outlet fourth pipe 42d and the inlet second pipe 41b. The spillback line 43 is equipped with a spillback valve 20. The spillback valve 20 is an electronically controlled valve whose operation is controlled by a controller 50. The spillback valve 20 is controlled by the controller 50 to adjust its opening so that the oil-lubricated compressor 11 operates at a desired compression ratio. Therefore, when the oil-lubricated compressor 11 is operating normally, a portion of the oil-containing gas discharged from the oil-lubricated compressor 11 is returned to the inlet second pipe 41b via the spillback line 43.
[0037] The second gas discharge line 40 further includes an oil supply line 44 that supplies the oil removed from the oil-containing gas by the first gas-liquid separator 12 to the oil-lubricated compressor 11.
[0038] The oil supply line 44 is equipped with an oil cooler 15, an oil pump 16, and an oil filter 19, arranged in order from the first gas-liquid separator 12 towards the oil-lubricated compressor 11.
[0039] The oil cooler 15 cools the oil recovered from the oil-containing gas by the first gas-liquid separator 12. Here, the oil-containing gas supplied to the first gas-liquid separator 12 is the gas discharged from the oil-lubricated compressor 11, and its temperature rises due to compression. Therefore, in order to supply the oil recovered by the first gas-liquid separator 12 back to the oil-lubricated compressor 11, the oil cooler 15 is used to cool the oil whose temperature has risen.
[0040] The oil pump 16 pressurizes the oil cooled by the oil cooler and discharges it toward the oil-lubricated compressor 11. The oil filter 19 removes foreign matter from the oil. Therefore, the oil recovered by the first gas-liquid separator 12 is cooled, pressurized, and further decontaminated by the oil supply line 44 before being supplied to the compression chamber 11a of the oil-lubricated compressor 11.
[0041] In this embodiment, the compressor unit 10 consists of the inlet second pipe 41b to the outlet fourth pipe 42d, that is, the oil-lubricated compressor 11, the first gas-liquid separator 12, the gas cooler 13, the second gas-liquid separator 14, the oil cooler 15, the oil pump 16, the oil filter 19, the filter 17, the compressor inlet check valve 18, the spillback valve 20, the inlet second pipe 41b of the compressor inlet piping 41, the outlet first pipe 42a to the outlet fourth pipe 42d of the compressor outlet piping 42, the spillback line 43, and the oil supply line 44.
[0042] In other words, the compressor unit 10 is connected to the first gas discharge line 30 via the first inlet pipe 41a of the compressor inlet piping 41, and is connected to the combustion engine 3 via the fifth outlet pipe 42e of the compressor outlet piping 42. The gas flowing through the compressor unit 10 may be an oil-containing gas, meaning that the second gas discharge line 40 is configured as an oil-free zone at least inside the compressor unit 10.
[0043] The liquid hydrogen facility 1 further includes a controller 50 that controls the operation of the liquid hydrogen facility 1, specifically the operation of the compressor unit 10. The controller 50 is configured by a storage unit 51 such as a hard disk, an arithmetic processing circuit 52 that controls the operation of the compressor unit 10, a well-known computer including a memory and an input / output device, and software installed in the computer.
[0044] The controller 50 executes operation control related to the liquid hydrogen facility 1 by executing a program stored in the storage unit 51. Functions related to the operation control of the liquid hydrogen facility 1 executed by the controller 50 can be programmed using general-purpose processors, special-purpose processors, integrated circuits, ASICs (Application Specific Integrated Circuits), FPGAs (Field Programmable Gate Arrays), conventional circuits, and / or one or more programs stored in one or more memories, or can be implemented using one or more circuits or processing circuits, including combinations thereof, otherwise configured to perform the disclosed functions. A processor is considered a processing circuit or circuit because it includes transistors and other circuits. The processor may be a programmed processor that executes a program stored in a memory. In the present disclosure, a circuit, unit, or means is hardware that performs the recited functions alone or in combination with each other, or hardware programmed to perform the recited functions alone or in combination with each other. The hardware may be any hardware disclosed in the present specification as long as it is programmed or configured to perform the recited functions.
[0045] A computer program containing computer instructions is stored in memory. These computer instructions provide logic and routines that enable hardware (e.g., processing circuitry or circuits) to perform the methods disclosed herein. The computer program can be implemented in a known format on a computer-readable storage medium, a computer program product, a memory device, a recording medium such as a CD-ROM or DVD, and / or in a memory of FPGAs or ASICs.
[0046] The arithmetic processing circuit 52 includes a compressor operating state determination circuit 53 and an oil-flooded compressor control circuit 54.
[0047] The compressor operating state determination circuit 53 determines whether the oil-flooded compressor 11 is operating normally. For example, the compressor operating state determination circuit 53 may determine whether the operating state of the oil-flooded compressor 11 is normal or abnormal based on the actual compression ratio of the oil-flooded compressor 11 in response to a control instruction such as a compression ratio issued by the oil-flooded compressor control circuit 54. In the present embodiment, the compressor operating state determination circuit 53 is provided in the controller 50, but may alternatively be provided in the oil-flooded compressor 11. In this case, the compressor operating state determination circuit 53 may detect a mechanical operating state such as the rotation speed of the oil-flooded compressor 11 to determine the operating state of the oil-flooded compressor 11.
[0048] The oil-flooded compressor control circuit 54 controls the compression ratio of the oil-flooded compressor 11 by adjusting the opening degree of the spillback valve 20 to prevent the inlet pressure of the oil-flooded compressor 11 from becoming negative, while also controlling the operation of the oil-flooded compressor 11. Furthermore, when stopping the oil-flooded compressor 11 due to an abnormality, the oil-flooded compressor control circuit 54 controls the spillback valve 20 to fully open. This prevents the pressure on the downstream side of the oil-flooded compressor 11 from becoming excessively high.
[0049] Next, the operation of the liquefied hydrogen equipment 1 will be explained with reference to Figure 2. Figure 2 is a flowchart showing the operation of the liquefied hydrogen equipment 1. Specifically, when the boil-off gas generated in the liquefied hydrogen storage tank 2 is being burned in the combustion engine 3, and the oil-lubricated compressor 11 is stopped due to a predetermined malfunction, the operation of the liquefied hydrogen equipment 1 will be explained to prevent oil-containing gas from flowing into the first gas discharge line 30, i.e., the oil-free zone, from the second gas discharge line 40.
[0050] As shown in Figure 2, in step S001, the compressor operating state determination circuit 53 determines whether or not there is an abnormality in the oil-lubricated compressor 11. If step S001 is NO, this control is terminated.
[0051] If step S001 is YES, in step S002, the oil-lubricated compressor control circuit 54 controls the oil-lubricated compressor 11 to stop. Specifically, the oil-lubricated compressor control circuit 54 stops the drive source that rotates the oil-lubricated compressor 11. In this case, the oil-lubricated compressor 11 does not stop immediately, but can continue to operate for a while due to inertia and discharge boil-off gas downstream.
[0052] Next, in step S003, the oil-lubricated compressor control circuit 54 controls the spillback valve 20 to open from a predetermined opening to fully open. As a result, the oil-containing gas discharged from the oil-lubricated compressor 11 is returned to the inlet second pipe 41b via the spillback line 43. At this time, although the oil-lubricated compressor 11 continues to operate for a while due to inertia, the gas suction force at the inlet of the oil-lubricated compressor 11 decreases.
[0053] As the suction force at the inlet of the oil-lubricated compressor 11 decreases, if the pressure in the second inlet pipe 41b becomes higher than the pressure in the first inlet pipe 41a, in step S004, the check valve portion 21a of the valve 21 is activated to prevent oil-containing gas from flowing from the second inlet pipe 41b to the first inlet pipe 41a.
[0054] Next, in step S005, the valve 21 is closed by manually tightening the shut-off valve portion 21b of the valve 21, thereby blocking the flow in the inlet first pipe 41a. This completely prevents the inflow of oil-containing gas into the inlet first pipe 41a, and prevents the inflow of oil-containing gas from the second gas discharge line 40 into the first gas discharge line 30, which is an oil-free zone.
[0055] The above operation will be explained with reference to the time chart shown in Figure 3. Figure 3(a) shows the discharge pressure, i.e., the operating state, of the oil-lubricated compressor 11. Figure 3(b) shows the opening degree of the spillback line. Figure 3(c) shows the differential pressure obtained by subtracting the downstream pressure from the upstream pressure of the valve 21, specifically the check valve portion 21a. Figure 3(d) shows the opening degree of the shut-off valve portion 21b of the valve 21.
[0056] In the example shown in Figure 3, the discharge pressure of the oil-lubricated compressor 11 remains constant until time t1, the spillback valve 20 is controlled to a predetermined opening, the differential pressure across the check valve portion 21a is positive, meaning the check valve portion 21a is not operating and the shut-off valve portion 21b is fully open.
[0057] As shown in Figure 3(a), at time t1, an abnormality occurs in the oil-lubricated compressor 11, and the discharge pressure begins to decrease. At time t2, the discharge pressure falls below a predetermined threshold, and the compressor operating state determination circuit 53 determines that an abnormality has occurred in the oil-lubricated compressor 11.
[0058] As a result, from time t2 onward, as shown in Figure 4(b), the oil-lubricated compressor control circuit 54 controls the oil-lubricated compressor 11 to stop, and controls the opening of the spillback valve 20 to change from a predetermined opening to fully open.
[0059] As the oil-lubricated compressor 11 stops operating and the spillback valve 20 opens, the pressure in the inlet second pipe 41b increases, and the differential pressure across valve 21 gradually decreases. When the differential pressure across valve 21 changes from positive to negative, the check valve portion 21a of valve 21 activates, preventing oil-containing gas from flowing from the inlet second pipe 41b side to the inlet first pipe 41a side.
[0060] Next, between times t3 and t4, the shut-off valve portion 21b of the valve 21 is manually activated to shut off the gas flow between the second inlet pipe 41b and the first inlet pipe 41a in the compressor inlet piping 41.
[0061] At time t5, when the operation of the oil-lubricated compressor 11 has completely stopped, and the gas pressure in the inlet first pipe 41a and the gas pressure in the inlet second pipe 41b have been equalized, and the differential pressure across the valve 21 has become zero, the check valve portion 21a no longer functions, but the shut-off valve portion 21b still functions, preventing oil-containing gas from flowing from the second gas discharge line 40 to the first gas discharge line 30.
[0062] The liquefied hydrogen equipment 1 according to this embodiment provides the following effects.
[0063] (1) The liquefied hydrogen equipment 1 includes: a liquefied hydrogen storage tank 2 in which liquefied hydrogen is stored; a first gas discharge line 30 connected to the gas phase of the liquefied hydrogen storage tank 2, through which boil-off gas from the liquefied hydrogen storage tank 2 is discharged to an oil-free zone; a second gas discharge line 40 branching off from the first gas discharge line 30, through which boil-off gas from the liquefied hydrogen storage tank 2 is discharged to an oil-free zone; an oil-lubricated compressor 11 provided in the second gas discharge line 40, having a compression chamber 11a to which oil is supplied, and compressing and discharging the gas discharged from the liquefied hydrogen storage tank 2; a spillback line 43 connecting the upstream and downstream sides of the oil-lubricated compressor 11; and a spillback valve 20 provided in the spillback line 43, which opens and closes the spillback line 43. In the compressor inlet piping 41 located upstream of the oil-lubricated compressor 11 in the second gas discharge line 40, there is a valve 21 upstream of the part to which the spillback line 43 is connected, which prevents gas from flowing from the second gas discharge line 40 to the first gas discharge line 30.
[0064] Since the second gas discharge line 40 includes an oil-lubricated compressor 11, the gas discharged from the oil-lubricated compressor 11 may become an oil-containing gas that contains the oil supplied in the compression chamber 11a. As a result, the oil-containing gas discharged from the oil-lubricated compressor 11 may be recirculated into the inlet second pipe 41b via the spillback line 43. During normal operation, the oil-containing gas recirculated into the inlet second pipe 41b is drawn into the oil-lubricated compressor 11 and does not flow into the first gas discharge line 30. However, when the oil-lubricated compressor 11 is stopped, the oil-containing gas is not drawn into the stopped oil-lubricated compressor 11 and may flow upstream, i.e., into the first gas discharge line 30, due to the pressure difference, potentially resulting in the discharge of oil-containing gas into the oil-free zone.
[0065] However, according to the liquefied hydrogen equipment 1 of this disclosure, the compressor inlet piping 41 has a valve 21 upstream of the portion to which the spillback line 43 is connected, i.e., in the inlet first piping 41a, which prevents gas from flowing into the first gas discharge line 30. As a result, the valve 21 prevents oil-containing gas from flowing into the first gas discharge line 30. Therefore, oil-containing gas is prevented from flowing into the oil-free zone.
[0066] Furthermore, the statement that the second gas discharge line 40 is branched from the first gas discharge line 30 includes not only the case where it is branched from the compressor inlet piping 31, but also the case where it is directly connected to the gas phase section of the liquefied hydrogen storage tank 2.
[0067] (2) The valve 21 may include a check valve portion 21a that is activated by the pressure difference between the upstream and downstream sides of the valve 21. As a result, since the valve 21 that prevents gas from flowing into the first gas discharge line 30 includes a check valve portion 21a, even if conditions are such that oil-containing gas is likely to flow back from the inlet second pipe 41b to the inlet first pipe 41a due to the pressure difference across the valve 21, the check valve portion 21a can be activated in a responsive manner to prevent backflow.
[0068] (3) The valve 21 may include a shut-off valve portion 21b. As a result, since the valve 21 that prevents gas from flowing into the first gas discharge line 30 includes a shut-off valve portion 21b, once shut off, the shut-off state by the valve 21 is maintained even if the upstream and downstream sides of the valve 21 are pressurized, thereby reliably preventing backflow of oil-containing gas from the inlet second pipe 41b to the inlet first pipe 41a.
[0069] (4) The valve 21 may be a check valve having a shut-off valve function. That is, the valve 21 may have a shut-off valve portion 21b and a check valve portion 21a. As a result, the valve 21 that prevents gas from flowing into the first gas discharge line 30 includes a shut-off valve portion 21b and a check valve portion 21a, so that after conditions are created in which backflow is likely to occur due to the differential pressure across the valve 21, the check valve portion 21a is activated in a responsive manner, and then the shut-off valve portion 21b is activated, thereby maintaining the shut-off state even when the upstream and downstream pressures of the valve 21 are equalized.
[0070] (5) The liquefied hydrogen storage tank 2 is replaced with an inert gas during maintenance, and the oil-lubricated compressor 11 may also compress and discharge the inert gas discharged from the liquefied hydrogen storage tank 2. As a result, the gas discharged from the liquefied hydrogen storage tank 2 may be an inert gas in addition to the boil-off gas generated from liquefied hydrogen. The molecular weight of the inert gas is significantly different from that of the boil-off gas generated from liquefied hydrogen. However, since an oil-lubricated compressor 11 is used in this disclosure, these multiple gases can be stably compressed and discharged. In other words, in the case of an oil-free compressor in which oil is not supplied to the compression chamber, the gas in the compression chamber is not oil-cooled, and the temperature of the compressed gas varies greatly due to the differences in the specific heat ratio of each of the multiple gases, as well as the differences in the compression ratio in the compressor due to the differences in pressure loss in the compressor piping and suction nozzle. This makes it difficult to set the clearance of the movable parts, and it is not possible to stably compress these multiple gases due to vibrations of the movable parts, etc.
[0071] (6) The first gas discharge line may be equipped with an oil-free compressor that does not supply oil to the compression chamber. As a result, since no oil-containing gas flows into the first gas discharge line 30, oil-free gas can be compressed and discharged using the oil-free compressor 7. For example, when filling the liquefied hydrogen storage tank 2 with liquefied hydrogen from an external source, boil-off gas etc. inside the liquefied hydrogen storage tank 2 can be discharged to the external cargo handling equipment 8 via the oil-free compressor 7 while maintaining the hydrogen at a high purity.
[0072] (7) The first gas discharge line 30 may be a gas discharge line for cargo handling that is connected to the external cargo handling equipment 8 when liquefied hydrogen is being handled between the liquefied hydrogen storage tank 2 and the external cargo handling equipment 8. As a result, by implementing the first gas discharge line 30 as a gas discharge line for cargo handling, boil-off gas containing oil-free hydrogen maintained at high purity can be discharged to the cargo handling equipment 8 during cargo handling.
[0073] (8) The spillback valve 20 is automatically controlled to be fully open when an abnormality occurs in the oil-lubricated compressor 11, and the valve 21 may have a check valve portion 21a that operates due to the pressure difference between the upstream and downstream sides of the valve 21. As a result, when the spillback valve 20 is automatically controlled to be fully open when an abnormality occurs in the oil-lubricated compressor 11, the pressure of the oil-containing gas discharged from the oil-lubricated compressor 11 tends to increase downstream of the valve 21. As a result, the pressure difference between the upstream and downstream sides of the valve 21 increases, and the check valve portion 21a operates, preventing the oil-containing gas from flowing upstream of the valve 21.
[0074] The liquefied hydrogen equipment 1 according to this disclosure is not limited to the configuration of the above embodiment, and various modifications are possible.
[0075] In the above embodiment, the valve 21 is described as a check valve having a shut-off valve function, specifically in the case where the shut-off valve function is activated manually, but it is not limited to this. The valve 21 may also be an electronically controlled valve whose operation is controlled by a controller 50. In this case, the controller 50 has a shut-off valve portion control circuit 55, which is shown by the dashed line in Figure 1. The shut-off valve portion control circuit 55 may control the opening degree of the shut-off valve portion 21b of the valve 21.
[0076] In the above embodiment, the valve 21 is configured to have a shut-off valve portion 21b and a check valve portion 21a, but it is not limited to this. As shown in Figure 4, the valve 21 may be configured to be divided into a check valve 23 and a shut-off valve 22 separate from the check valve 23. In this case, it is desirable to place the shut-off valve 22 upstream of the check valve 23. With this arrangement, since the shut-off valve 22 is located upstream of the check valve 23, even when the upstream and downstream sides of the check valve 23 are in communication when the check valve 23 and the shut-off valve 22 are operated and the upstream and downstream sides are equalized, the shut-off valve 22 located upstream can reliably prevent oil-containing gas that may be present upstream of the check valve 23 from flowing into the first gas discharge line 30.
[0077] Alternatively, as shown in Figure 5, only a check valve 23 may be provided as the valve 21. In this case as well, depending on the differential pressure across the valve 21, the check valve 23 can be activated, for example, immediately after the oil-lubricated compressor 11 stops, thereby preventing oil-containing gas from flowing into the first gas discharge line 30.
[0078] Alternatively, as shown in Figure 6, only a shut-off valve 22 may be provided as the valve 21. In this case, when an abnormality in the oil-lubricated compressor 11 is detected, the shut-off valve 22 can be immediately closed manually or by the controller 50 to prevent oil-containing gas from flowing into the first gas discharge line 30.
[0079] If valve 21 is composed solely of a shut-off valve 22, the spillback valve 20 may be automatically controlled to close completely or manually closed completely when an abnormality occurs in the oil-lubricated compressor 11. As a result, when an abnormality occurs in the oil-lubricated compressor 11, the spillback valve 20 is completely closed, reducing the pressure difference between the upstream and downstream sides of valve 21 and making it easier to equalize the pressure. Here, if valve 21 is a check valve, it will not function as a check valve when the upstream and downstream pressures are equalized. However, by configuring valve 21 with a shut-off valve 22, the shut-off state is maintained even when the upstream and downstream sides of valve 21 are equalized, thus preventing oil-containing gas that may be present downstream of valve 21 from flowing upstream of valve 21.
[0080] In the above embodiment, the second gas discharge line 40 is configured to supply boil-off gas to the combustion engine 3, but it is not limited to this. The boil-off gas may also be supplied to other boil-off gas processing equipment via the second gas discharge line 40. Furthermore, depending on the concentration and amount of hydrogen gas contained in the boil-off gas, it may be released into the atmosphere.
[0081] The liquefied hydrogen equipment relating to this disclosure provides the following aspects.
[0082] [Aspect 1] A liquefied hydrogen facility comprising: a liquefied hydrogen storage tank for storing liquefied hydrogen; a first gas discharge line connected to the gas phase of the liquefied hydrogen storage tank, for which boil-off gas from the liquefied hydrogen storage tank is discharged to an oil-free zone; a second gas discharge line branching from the first gas discharge line, for which boil-off gas from the liquefied hydrogen storage tank is discharged to an oil-free zone; an oil-lubricated compressor provided in the second gas discharge line, having a compression chamber to which oil is supplied, for compressing and discharging gas discharged from the liquefied hydrogen storage tank; a spillback line connecting the upstream and downstream sides of the oil-lubricated compressor; a spillback valve provided in the spillback line for opening and closing the spillback line; and a valve in the compressor inlet piping located upstream of the portion to which the spillback line is connected, in the second gas discharge line, on the upstream side of the portion to which the spillback line is connected, for preventing the gas from flowing from the second gas discharge line to the first gas discharge line.
[0083] [Aspect 2] The liquefied hydrogen equipment according to aspect 1, wherein the valve is a check valve that operates due to the pressure difference between the upstream and downstream sides of the valve.
[0084] [Aspect 3] The liquefied hydrogen equipment according to aspect 1, wherein the valve is a shut-off valve.
[0085] [Aspect 4] The liquefied hydrogen equipment according to Aspect 1, wherein the valve is a check valve having a shut-off valve function.
[0086] [Aspect 5] The liquefied hydrogen equipment according to aspect 1, wherein the valve includes a check valve and a shut-off valve located upstream of the check valve.
[0087] [Aspect 6] The liquefied hydrogen storage tank is replaced with an inert gas during maintenance, and the oil-lubricated compressor also compresses and discharges the inert gas discharged from the liquefied hydrogen storage tank, according to any one of claims 1 to 5.
[0088] [Aspect 7] The liquefied hydrogen equipment according to any one of claims 1 to 6, wherein the first gas discharge line is equipped with an oil-free compressor that does not supply oil to the compression chamber.
[0089] [Aspect 8] The liquefied hydrogen equipment according to any one of claims 1 to 7, wherein the first gas discharge line is a gas discharge line for cargo handling that is connected to an external cargo handling facility when the liquefied hydrogen is being handled between the liquefied hydrogen storage tank and the external cargo handling facility.
[0090] [Aspect 9] The spillback valve is automatically controlled to be fully open when an abnormality occurs in the oil-lubricated compressor, and the valve is a check valve that operates due to the pressure difference between the upstream and downstream sides of the valve, as described in Aspect 1 and any one of Aspects 6 to 8.
[0091] [Aspect 10] The spillback valve is automatically controlled to be fully closed when an abnormality occurs in the oil-lubricated compressor, and the valve is a shut-off valve, the liquefied hydrogen equipment according to any one of aspects 1 and 6 to 8.
[0092] 1. Liquefied hydrogen equipment 2. Liquefied hydrogen storage tank 3. Combustion engine 4. Inert gas generator 7. Oil-free compressor 7a. Compression chamber 8. Cargo handling equipment 10. Compressor unit 11. Oil-lubricated compressor 11a. Compression chamber 20. Spillback valve 21. Valve 21a. Check valve section 21b. Shut-off valve section 30. First gas discharge line 31. Compressor inlet piping 32. Inert gas supply line 33. Cargo handling equipment inlet piping 40. Second gas discharge line 41. Compressor inlet piping 41a. First inlet piping 41b. Second inlet piping 42. Compressor outlet piping 43. Spillback line 44. Oil supply line 50. Controller 53. Compressor operating state determination circuit 54. Oil-lubricated compressor control circuit
Claims
1. A liquefied hydrogen facility comprising: a liquefied hydrogen storage tank for storing liquefied hydrogen; a first gas discharge line connected to the gas phase of the liquefied hydrogen storage tank, for discharging boil-off gas from the liquefied hydrogen storage tank to an oil-free zone; a second gas discharge line branching from the first gas discharge line, for discharging boil-off gas from the liquefied hydrogen storage tank to an oil-free zone; an oil-lubricated compressor provided in the second gas discharge line, having a compression chamber to which oil is supplied, for compressing and discharging gas discharged from the liquefied hydrogen storage tank; a spillback line connecting the upstream and downstream sides of the oil-lubricated compressor; a spillback valve provided in the spillback line for opening and closing the spillback line; and a valve in the compressor inlet piping located upstream of the portion to which the spillback line is connected, in the second gas discharge line, on the upstream side of the portion to which the spillback line is connected, for preventing the gas from flowing from the second gas discharge line to the first gas discharge line.
2. The liquefied hydrogen equipment according to claim 1, wherein the valve is a check valve that operates due to the pressure difference between the upstream and downstream sides of the valve.
3. The liquefied hydrogen equipment according to claim 1, wherein the valve is a shut-off valve.
4. The liquefied hydrogen equipment according to claim 1, wherein the valve has a shut-off valve function and is a check valve that operates due to the pressure difference between the upstream and downstream sides of the valve.
5. The liquefied hydrogen equipment according to claim 1, wherein the valve includes a check valve that is operated by the pressure difference between the upstream and downstream sides of the valve, and a shut-off valve located upstream of the check valve.
6. The liquefied hydrogen storage tank is replaced with an inert gas during maintenance, and the oil-lubricated compressor also compresses and discharges the inert gas discharged from the liquefied hydrogen storage tank, as described in claim 1 or 2.
7. The liquefied hydrogen facility according to claim 1 or 2, wherein the first gas discharge line is equipped with an oil-free compressor that does not supply oil to the compression chamber.
8. The liquefied hydrogen equipment according to claim 1 or 2, wherein the first gas discharge line is a gas discharge line for cargo handling connected to an external cargo handling facility when the liquefied hydrogen is being handled between the liquefied hydrogen storage tank and the external cargo handling facility.
9. The spillback valve is automatically controlled to be fully open when an abnormality occurs in the oil-lubricated compressor, and the valve is a check valve that operates due to the pressure difference between the upstream and downstream sides of the valve, as described in claim 1.
10. The spillback valve is automatically controlled to be fully closed when an abnormality occurs in the oil-lubricated compressor, and the valve is a shut-off valve, as described in claim 1.