The present disclosure relates to a maintenance method of equipment that handles liquefied hydrogen.
As a technology to handle liquefied gas at low temperatures, Patent Literature 1 discloses a method of shipping LNG from an LNG receiving terminal tank and a device for this purpose.
In the technology, a lorry is connected to the LNG receiving terminal via a flexible hose. When the LNG loading operation from the LNG receiving terminal to the lorry is completed, nitrogen gas flows from a nitrogen gas supply facility into the flexible hose, thereby purging the LNG remaining in the flexible hose and disconnecting the lorry from the LNG receiving terminal.
In the technology described in Patent Literature 1, nitrogen gas is used to perform purge when the lorry is disconnected from the LNG receiving terminal, but if such purge technology is applied to equipment that handles liquefied hydrogen, there is a possibility that nitrogen may solidify when exposed to the cold energy of liquefied hydrogen.
An object of the present disclosure is to provide a maintenance method of equipment capable of preventing nitrogen gas from solidifying when the equipment is separated from a flow path of liquefied hydrogen.
An equipment maintenance method according to one aspect of the present disclosure is an equipment maintenance method in a flow path having a first valve, a second valve, equipment, a third valve, and a fourth valve disposed in order along a direction in which liquefied hydrogen flows, and includes: filling hydrogen gas between the first valve and the fourth valve in the flow path; filling nitrogen gas between the second valve and the third valve in the flow path from a state where the hydrogen gas is filled between the first valve and the fourth valve in the flow path; and decoupling and sealing the flow path between the second valve and the equipment and between the third valve and the equipment, and separating the equipment from the flow path with the nitrogen gas filled between the second valve and the third valve in the flow path.
The present disclosure provides a maintenance method of equipment capable of preventing nitrogen gas from solidifying when the equipment is separated from a flow path of liquefied hydrogen.
An embodiment of an equipment maintenance method according to the present disclosure will be described in detail below with reference to the drawings. The equipment according to the present disclosure is a member or device that handles liquefied hydrogen. In the following embodiment, a description will be given based on an example in which a pump is used as the equipment.
The liquefied hydrogen tank 100 is a tank that can store liquefied hydrogen, and is disposed on land. As one example, the liquefied hydrogen tank 100 is a ground-mounted flat-bottom tank. The hydrogen utilization facility 101 is a facility that utilizes the liquefied hydrogen stored in the liquefied hydrogen tank 100. As one example, the hydrogen utilization facility 101 includes a lorry that transports liquefied hydrogen. The plurality of pumps 50 has a function of sending the liquefied hydrogen stored in the liquefied hydrogen tank 100 to the hydrogen utilization facility 101. Note that as shown in
The liquefied hydrogen system 1S further includes two attachment and detachment mechanisms 1. Each of the attachment and detachment mechanisms 1 separates a part including the pump 50 from the flow path LS when performing maintenance on the pump 50.
Next, the configuration and function of the attachment and detachment mechanism 1 will be described in detail, taking the periphery of one of the pumps 50 in
The attachment and detachment mechanism 1 includes a first valve 91, a second valve 92, a third valve 93 and a fourth valve 94.
The first valve 91, the second valve 92, the third valve 93, and the fourth valve 94 are disposed in order from the liquefied hydrogen tank 100 side. Each valve opens and closes a part of the flow path LS. The pump 50 is disposed between the second valve 92 and the third valve 93.
Hereinafter, in the flow path LS, a section between the first valve 91 and the second valve 92 is referred to as a first section LS1, a section between the second valve 92 and the pump 50 is referred to as a second section LS2, a section between the pump 50 and the third valve 93 is referred to as a third section LS3, and a section between the third valve 93 and the fourth valve 94 is referred to as a fourth section LS4.
The attachment and detachment mechanism 1 further includes a hydrogen supply and discharge unit 70, a hydrogen supply and discharge unit 71, a nitrogen supply unit 80, and a nitrogen discharge unit 81.
Each supply and discharge unit supplies gas to the flow path LS and discharges gas from the flow path LS. Specifically, the hydrogen supply and discharge unit 70 communicates with the first section LS1 and supplies hydrogen gas to the flow path LS. In addition, the hydrogen supply and discharge unit 70 discharges hydrogen gas from the first section LS1. The hydrogen supply and discharge unit 70 includes a hydrogen gas tank 70A, a flow path 70B, and a hydrogen valve 70C. The hydrogen gas tank 70A stores hydrogen gas. The flow path 70B communicates the hydrogen gas tank 70A with the first section LS1. The hydrogen valve 70C opens and closes the flow path 70B.
The hydrogen supply and discharge unit 71 communicates with the fourth section LS4 and supplies hydrogen gas to the flow path LS. In addition, the hydrogen supply and discharge unit 71 discharges hydrogen gas from the fourth section LS4. The hydrogen supply and discharge unit 71 includes a hydrogen gas tank 71A, a flow path 71B, and a hydrogen valve 71C. The structure and function of these members are similar to those of members of the hydrogen supply and discharge unit 70.
The nitrogen supply unit 80 communicates with the second section LS2 of the flow path LS. In particular, the nitrogen supply unit 80 directly communicates with the second section LS2 without going through the first section LS1, and supplies nitrogen gas to the flow path LS. The nitrogen supply unit 80 includes a nitrogen gas tank 80A, a flow path 80B, and a nitrogen valve 80C. The nitrogen gas tank 80A stores nitrogen gas. The flow path 80B communicates the nitrogen gas tank 80A with the second section LS2. The nitrogen valve 80C opens and closes the flow path 80B.
The nitrogen discharge unit 81 communicates with the third section LS3 of the flow path LS, and discharges nitrogen gas from the flow path LS. The nitrogen discharge unit 81 includes a nitrogen gas tank 81A, a flow path 81B, and a nitrogen valve 81C. The nitrogen gas tank 81A stores nitrogen gas. The flow path 81B communicates the nitrogen gas tank 81A with the third section LS3. The nitrogen valve 81C opens and closes the flow path 81B.
The attachment and detachment mechanism 1 further includes a pressure gauge 61, a thermometer 62, a pressure gauge 63, and a thermometer 64. The pressure gauge 61 detects the pressure in the first section LS1, whereas the thermometer 62 detects the temperature in the first section LS1. Similarly, the pressure gauge 63 detects the pressure in the fourth section LS4, whereas the thermometer 64 detects the temperature in the fourth section LS4.
The attachment and detachment mechanism 1 further includes a first joint part LT1 and a second joint part LT. By the first joint part LT1 and the second joint part LT2, the pump 50 can be attached to and detached from the flow path LS. In the present embodiment, the first joint part LT1 and the second joint part LT2 have a bayonet joint structure. Note that arbitrary joint structure, such as a flange joint, can be adopted for the first joint part LT1 and the second joint part LT2.
Next, the procedure for detaching the pump 50 from the flow path LS of the liquefied hydrogen system 1S and performing maintenance on the pump 50 will be described with reference to
As shown in
When separating the pump 50 from the flow path LS for maintenance of the pump 50, with the flow path LS filled with liquefied hydrogen, as shown in step S02 of
Next, in a state where the hydrogen gas has flown into the first section LS1, the second section LS2, the third section LS3, and the fourth section LS4, as shown in step S03 of
In this way, with the second section LS2 and the third section LS3 filled with the nitrogen gas, as shown in step S04 of
Note that when the maintenance of the pump 50 is completed, the operator reconnects the pump 50 to the flow path LS at the first joint part LT1 and the second joint part LT2. Thereafter, the operator performs the steps in the reverse order of the above detachment process.
Specifically, the operator fills the pump 50, the second valve 92, and the third valve 93 with the nitrogen gas to prevent the air and the hydrogen gas from mixing. In more detail, with the second valve 92 and the third valve 93 closed, the operator opens the nitrogen valve 80C and the nitrogen valve 81C, causes the nitrogen gas to flow into the pump 50, the second section LS2, and the third section LS3, and replaces the air with the nitrogen gas. Thereafter, the operator opens the second valve 92 and the third valve 93, thereby causing the hydrogen gas to flow again into the second section LS2 and the third section LS3. Next, the operator opens the first valve 91 and the fourth valve 94, thereby causing the liquefied hydrogen to flow into the first section LS1, the second section LS2, the third section LS3, and the fourth section LS4. As a result, the pump 50 can be operated again. Note that the opening and closing of each valve during the detachment and attachment of the pump 50 may be performed automatically.
As described above, in the present embodiment, along the direction in which the liquefied hydrogen flows from the liquefied hydrogen tank 100 to the hydrogen utilization facility 101 in the flow path LS, the first valve 91, the second valve 92, the first joint part LT1, the pump 50, the second joint part LT2, the third valve 93, and the fourth valve 94 are disposed in this order. When separating the pump 50 from the flow path LS, with the flow path LS filled with the liquefied hydrogen, the operator causes the hydrogen gas to flow into the first section LS1, the second section LS2, the third section LS3, and the fourth section LS4, discharging the liquefied hydrogen. Next, with the hydrogen gas flowing into the first section LS1, the second section LS2, the third section LS3, and the fourth section LS4, the operator causes the nitrogen gas to flow into the second section LS2 and the third section LS3, discharging the hydrogen gas. Furthermore, with the nitrogen gas flowing into the second section LS2 and the third section LS3, the operator decouples and seals the flow path LS with the first joint part LT1 and the second joint part LT2, separating the pump 50.
By such a method, the pump 50 can be safely detached from the flow path LS with the pump 50 filled with the nitrogen gas. The melting point of nitrogen gas is −210° C., making the nitrogen gas easier to solidify when exposed to the cold energy of the liquefied hydrogen at −253° C. However, in the present embodiment, even with the liquefied hydrogen filled on the liquefied hydrogen tank 100 side of the first valve 91 and on the hydrogen utilization facility 101 side of the fourth valve 94, the first section LS1 and the fourth section LS4 are filled with hydrogen gas, making it possible to prevent the cold energy of the liquefied hydrogen at approximately −253° C. from being transmitted to the nitrogen gas in the second section LS2 and the third section LS3. That is, the first section LS1 and the fourth section LS4 can each function as a temperature buffer. As a result, it is possible to prevent damage to the valves and flow paths caused by the nitrogen gas solidifying in the valves and flow paths due to the cold energy of the liquefied hydrogen being transferred to the nitrogen gas. Therefore, the pump 50 can be detached from the flow path LS for maintenance or other purposes by using the nitrogen gas, which is cheaper than helium, which is generally used as an inert gas. Therefore, maintenance of the pump 50 can be performed without being affected by the supply amount of helium gas. As a result, the maintenance cost of the liquefied hydrogen system IS can also be reduced. After the maintenance, the operation of the pump 50 can be quickly resumed by flowing the liquefied hydrogen again into the limited area from the first valve 91 to the fourth valve 94.
In the present embodiment, when filling the hydrogen gas between the first valve 91 and the fourth valve 94 of the flow path LS, the operator closes the first valve 91 and the fourth valve 94 and introduces the hydrogen gas between the first valve 91 and the fourth valve 94, thereby discharging the liquefied hydrogen. Therefore, the hydrogen gas filling operation and the liquefied hydrogen discharge operation can be performed efficiently while the liquefied hydrogen is pushed out by the hydrogen gas. Similarly, when filling the nitrogen gas between the second valve 92 and the third valve 93 of the flow path LS, the operator closes the second valve 92 and the third valve 93 and introduces the nitrogen gas between the second valve 92 and the third valve 93, thereby discharging the hydrogen gas. In this case as well, the nitrogen gas filling operation and the hydrogen gas discharge operation can be performed efficiently while the hydrogen gas is pushed out by the nitrogen gas.
Furthermore, in the present embodiment, the nitrogen supply unit 80 for supplying the nitrogen gas to the second section LS2 and the third section LS3 communicates directly with the second section LS2 of the flow path LS. Therefore, compared with the case where the nitrogen gas is supplied to the second section LS2 and the third section LS3 via the first section LS1 and the fourth section LS4, the nitrogen gas does not remain in the first section LS1 and the fourth section LS4, preventing the remaining nitrogen gas from solidifying. With such a configuration, it is also possible to prevent the hydrogen gas from leaking from the first section LS1 and the fourth section LS4 serving as temperature buffers into the atmosphere and to prevent air from entering the temperature buffers.
Note that in
The above adjustment operation will be specifically described using the first section LS1 in
Meanwhile, when the temperature of the first section LS1 drops significantly, there is a possibility that nitrogen may liquefy or solidify between the second valve 92 and the first joint part LT1. If the nitrogen gas liquefies in this way, there is a possibility that the occurrence of negative pressure may cause the hydrogen gas to leak from the first section LS1 to the second section LS2. When the hydrogen gas leaking into the second section LS2 vaporizes again due to heat input from the atmosphere, there is a possibility that this pressure may increase and the hydrogen gas may leak further into the atmosphere. In the present embodiment, when the temperature in the first section LS1 drops, the operator can operate the hydrogen supply and discharge unit 70 to raise the temperature of the first section LS1 by repeatedly supplying and discharging the hydrogen gas. As one example, by increasing the supply amount of the hydrogen gas to the first section LS1, the operator raises the temperature of the first section LS1. When the pressure increases accordingly, a small amount of hydrogen gas is discharged from the first section LS1, thereby allowing the pressure in the first section LS1 to be adjusted. Note that the measurement instruments such as the pressure gauge 61 and the thermometer 62 are not essential in the present disclosure. The above adjustment operation may be performed automatically.
In the present embodiment, as shown in
Similarly, in the present embodiment, as shown in
Note that when the pump 50 is separated from the flow path LS as equipment that handles liquefied hydrogen as in the present embodiment, the maintenance may take several days. Even in such a case, in the present embodiment, since the pumps 50 are disposed in parallel as shown in
The equipment maintenance method according to the present disclosure has been described above, but the present disclosure is in no way limited to the above-described embodiment. For example, the above-described equipment maintenance method can have the following modified embodiment.
The above embodiment has been described according to an aspect in which the valves are disposed in order along the direction in which the liquefied hydrogen flows from the liquefied hydrogen tank 100 to the hydrogen utilization facility 101. However, the direction in which the liquefied hydrogen flows may be the direction from the hydrogen utilization facility 101 to the liquefied hydrogen tank 100. In this case, the first valve 91, the second valve 92, the first joint part LT1, the pump 50, the second joint part LT2, the third valve 93, and the fourth valve 94 need to be disposed in order from the hydrogen utilization facility 101 to the liquefied hydrogen tank 100.
The above embodiment has been described according to an aspect in which each of the hydrogen gas and the nitrogen gas flows through the pump 50 from the second valve 92 side to the third valve 93 side, but the present disclosure is not limited to this aspect. The attachment and detachment mechanism 1 may include its own supply and discharge passages for the hydrogen gas and the nitrogen gas on both sides of the pump 50.
The liquefied hydrogen system IS includes a seal gas flow path 51 and a valve 52, instead of the nitrogen supply unit 80 and the nitrogen discharge unit 81 according to the above embodiment. The seal gas flow path 51 supplies a seal gas including nitrogen to a gap within the pump 50 to prevent leakage of the liquefied hydrogen within the pump 50. The operator can supply the above-described nitrogen gas to the flow path LS by switching the opening and closing of the valve 52.
In this modified embodiment, as in the above embodiment, with the hydrogen gas filled between the first valve 91 and the fourth valve 94, when the operator closes the second valve 92 and the third valve 93 and opens the valve 52, the nitrogen gas flows from the pump 50 into the flow path between the second valve 92 and the third valve 93. At this time, the hydrogen gas is discharged from a discharge flow path (not shown). Thereafter, as in the above embodiment, the operator can separate the flow path LS at the first joint part LT1 and the second joint part LT2, and detach the pump 50. With such a configuration as well, the pump 50 can be safely detached from the flow path LS while preventing the nitrogen gas from solidifying. In this way, the supply source of the nitrogen gas in the present disclosure may also be the pump 50.
Specifically, the attachment and detachment mechanism 1 includes a hydrogen supply unit 75 and an adjustment hydrogen discharge unit 76. The hydrogen supply unit 75 has a function of supplying the hydrogen gas to the section from the first valve 91 to the fourth valve 94. The hydrogen supply unit 75 has a function of adjusting the amount of hydrogen gas filled in the first section LS1 by supplying the hydrogen gas to the first section LS1 after the second valve 92 is closed. The adjustment hydrogen discharge unit 76 has a function of adjusting the amount of hydrogen gas filled in the first section LS1 by discharging the hydrogen gas from the first section LS1 after the second valve 92 is closed.
Similarly, the attachment and detachment mechanism 1 includes an adjustment hydrogen supply unit 85 and a hydrogen discharge unit 86. The hydrogen discharge unit 86 has a function of accepting the liquefied hydrogen and the hydrogen gas from the section from the first valve 91 to the fourth valve 94. The hydrogen discharge unit 86 has a function of adjusting the amount of hydrogen filled in the fourth section LS4 by accepting the hydrogen gas from the fourth section LS4 after the third valve 93 is closed. The adjustment hydrogen supply unit 85 has a function of adjusting the amount of hydrogen gas filled in the fourth section LS4 by supplying the hydrogen gas to the fourth section LS4 after the third valve 93 is closed.
In the above configuration as well, the operator can adjust the supply amount of hydrogen gas supplied from the hydrogen supply unit 75 and the discharge amount of hydrogen gas discharged from the adjustment hydrogen discharge unit 76 according to the detection results of the pressure gauge 61 and the thermometer 62. The operator can adjust the supply amount of hydrogen gas supplied from the adjustment hydrogen supply unit 85 and the discharge amount of hydrogen gas discharged from the hydrogen discharge unit 86 according to the detection results of the pressure gauge 63 and the thermometer 64. In particular, when the pressure gauge 61 or the thermometer 62 detects that the pressure or temperature of the hydrogen gas has dropped, the operator preferably increases the supply amount of hydrogen gas supplied from the hydrogen supply unit 75. The same applies to the adjustment hydrogen supply unit 85.
The specific embodiment described above includes the disclosure having the following configuration.
An equipment maintenance method according to one aspect of the present disclosure is an equipment maintenance method in a flow path having a first valve, a second valve, equipment, a third valve, and a fourth valve disposed in order along a direction in which liquefied hydrogen flows, and includes: filling hydrogen gas between the first valve and the fourth valve in the flow path; filling nitrogen gas between the second valve and the third valve in the flow path from a state where the hydrogen gas is filled between the first valve and the fourth valve in the flow path; and decoupling and sealing the flow path between the second valve and the equipment and between the third valve and the equipment, and separating the equipment from the flow path with the nitrogen gas filled between the second valve and the third valve in the flow path.
By this method, from the state where the liquefied hydrogen is filled on the flow path, after the hydrogen gas is filled between the first valve and the fourth valve, with the nitrogen gas filled between the second valve and the third valve, by decoupling the flow path between the second valve and the equipment in the flow path and between the third valve and the equipment, the equipment maintenance can be safely performed. As a result, after the maintenance, the operation of the equipment can be quickly resumed by flowing the liquefied hydrogen again into the limited area from the first valve to the fourth valve. The hydrogen gas filled between the first valve and the second valve and between the third valve and the fourth valve functions as a temperature buffer, thereby preventing the cold energy of the liquefied hydrogen from being transmitted to the nitrogen gas during the equipment maintenance and the nitrogen gas from solidifying.
The above method may further include closing the first valve and the fourth valve when filling the hydrogen gas between the first valve and the fourth valve in the flow path, and discharging the liquefied hydrogen by introducing the hydrogen gas between the first valve and the fourth valve.
By this method, the filling operation of the hydrogen gas and the discharging operation of the liquefied hydrogen can be performed efficiently.
The above method may further include closing the second valve and the third valve when filling the nitrogen gas between the second valve and the third valve in the flow path, and discharging the hydrogen gas by introducing the nitrogen gas between the second valve and the third valve.
By this method, the filling operation of nitrogen gas and the discharge operation of hydrogen gas can be performed efficiently.
The above method may further include introducing the hydrogen gas between the first valve and the second valve when filling the hydrogen gas between the first valve and the fourth valve in the flow path, and discharging the liquefied hydrogen from between the third valve and the fourth valve.
By this method, the hydrogen gas can be efficiently filled between the first valve and the fourth valve by using the equipment as the flow path for the hydrogen gas.
The above method may further include introducing the nitrogen gas between the second valve and the equipment when filling the nitrogen gas between the second valve and the third valve in the flow path, and discharging the hydrogen gas from between the equipment and the third valve.
By this method, the nitrogen gas can be efficiently filled in the section from the second valve to the third valve by using the equipment as the flow path for the nitrogen gas. Through this operation, the interior of the equipment can be filled with the nitrogen gas, allowing the equipment to be safely detached.
The above method may further include detecting temperature and pressure between the first valve and the second valve or between the third valve and the fourth valve with the equipment separated from the flow path, and adjusting an amount of the hydrogen gas filled according to a detection result of at least one of the temperature and the pressure.
By this method, even if the temperature or pressure of the filled hydrogen gas fluctuates during the equipment maintenance, by adjusting the amount of hydrogen gas filled, the temperature balance of the liquefied hydrogen, the hydrogen gas, and the nitrogen gas can be maintained stably.
The above method may further include increasing the amount of hydrogen gas filled when a drop in the temperature or the pressure between the first valve and the second valve or between the third valve and the fourth valve is detected.
By this method, even if the temperature or pressure of the filled hydrogen gas drops during the equipment maintenance, by increasing the amount of hydrogen gas filled, the temperature balance of the liquefied hydrogen, the hydrogen gas, and the nitrogen gas can be maintained further stably.
Number | Date | Country | Kind |
---|---|---|---|
2022-051696 | Mar 2022 | JP | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/JP2023/011248 | 3/22/2023 | WO |