Hydrogen liquefaction system

Abstract

To provide a hydrogen liquefaction system capable of being miniaturized with a simple structure and improving liquefaction efficiency of hydrogen.SOLUTION: There are provided a magnetic field confinement region 18 in which nuclear fusion reaction occurs, a superconducting coil 11 that generates a magnetic field in the magnetic field confinement region 18, a radiation shield 12 that is cooled by liquid nitrogen and shields radiation to the superconducting coil 11, a hydrogen generator 4 that generates hydrogen gas by using heat generated in the magnetic field confinement region 18, a first heat exchanger 14 that precools the hydrogen gas generated by the hydrogen generator 4 by nitrogen gas discharged from the radiation shield 12, and a refrigeration device 15 that liquefies the hydrogen gas precooled by the first heat exchanger 14.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a hydrogen liquefaction system. [Background technology]

[0002] Conventionally, hydrogen liquefaction systems have been known that include a hydrogen generator that generates hydrogen gas and a liquefaction device that has a refrigeration facility that cools the hydrogen gas generated by the hydrogen generator and liquefies the hydrogen gas. Because liquid hydrogen has a volume that is 1 / 800 of that of gaseous hydrogen, liquefying hydrogen gas is effective from the perspective of transportation efficiency, etc. The hydrogen generator generates hydrogen gas by, for example, reacting hydrocarbons with steam at high temperatures using a reforming catalyst.

[0003] Here, in order to cool hydrogen gas to a liquefied state using a liquefaction device, it is necessary to cool the hydrogen gas to an extremely low temperature. As a result, a large refrigeration capacity is required, and the refrigeration equipment also becomes large. For this reason, a technology equipped with a nitrogen liquefaction device has been disclosed as an example of refrigeration equipment (see, for example, Patent Document 1). According to this technology, the hydrogen gas is pre-cooled using liquid nitrogen before being cooled. The nitrogen liquefaction device is provided to continuously pre-cool the hydrogen gas using liquid nitrogen. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-169872 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-described embodiment, a nitrogen liquefaction device is required in addition to a refrigeration system to liquefy hydrogen gas, which makes the entire hydrogen liquefaction system complex and large, and also makes it difficult to improve the efficiency of hydrogen liquefaction.

[0006] Therefore, the present invention provides a hydrogen liquefaction system that can be made compact with a simple structure and can improve the efficiency of liquefying hydrogen. [Means for solving the problem]

[0007] In order to solve the above problems, the hydrogen liquefaction system of the present invention comprises a magnetic field confinement region in which a nuclear fusion reaction occurs, a superconducting coil that generates a magnetic field in the magnetic field confinement region, a radiation shield that is cooled by liquid nitrogen and shields the superconducting coil from radiation, a hydrogen generation device that generates hydrogen gas using heat generated in the magnetic field confinement region, a pre-cooling unit that pre-cools the hydrogen gas generated by the hydrogen generation device with nitrogen gas discharged from the radiation shield, and a refrigeration device that liquefies the hydrogen gas pre-cooled in the pre-cooling unit.

[0008] The hydrogen liquefaction system is used in conjunction with a nuclear fusion device. By configuring it in this way, hydrogen gas is first produced using the heat generated by the nuclear fusion device, allowing for efficient production of hydrogen gas. Fusion devices contain superconducting coils that use magnetic fields to confine high-temperature, high-density plasma for long periods of time. To generate a superconducting state in the superconducting coils and keep it stable, it is necessary to cool the superconducting coils to a temperature below their critical temperature. Fusion devices are equipped with a radiation shield that covers the superconducting coils and is cooled to a low temperature by liquid nitrogen to prevent the temperature of the superconducting coils from rising due to radiant heat. The low temperature of the radiation shield reduces the radiant heat transferred to the superconducting coils.

[0009] Therefore, the cold energy of the nitrogen discharged from the radiation shield was used to pre-cool the hydrogen gas. This eliminated the need for a nitrogen liquefaction device to liquefy hydrogen gas, allowing for a simpler hydrogen liquefaction system. This not only allowed for a simpler and more compact hydrogen liquefaction system, but also improved the efficiency of hydrogen liquefaction by the hydrogen liquefaction system.

[0010] In the above configuration, the nitrogen gas discharged from the radiation shield cools the heat exhaust portion of the refrigeration device.

[0011] This configuration reduces the energy consumption of the refrigeration device, thereby reducing the operating costs of the hydrogen liquefaction system.

[0012] In the above configuration, a container is provided that seals the hydrogen generation device and the pre-cooling unit, and the nitrogen gas used to pre-cool the hydrogen gas is discharged into the container.

[0013] This configuration provides an explosion-proof structure, and an explosion-proof hydrogen liquefaction system can be provided that also uses nitrogen as a radiation shield.

[0014] In the above configuration, a discharge device is provided that discharges the gas inside the container to the outside of the container while maintaining a positive pressure inside the container relative to the outside of the container.

[0015] This configuration prevents air (particularly oxygen) from entering the container, making it possible to further ensure explosion-proof properties.

[0016] In the above configuration, a detector for detecting the hydrogen concentration in the container is provided.

[0017] This configuration makes it possible to detect a hydrogen leak fault, stop hydrogen production to prevent an increase in hydrogen concentration, and facilitate recovery from the fault. In this way, it is possible to increase the variety of hydrogen liquefaction systems to meet user needs. [Effects of the Invention]

[0018] According to the present invention, the hydrogen liquefaction system can be made compact with a simple structure, and the efficiency of liquefying hydrogen by the hydrogen liquefaction system can be improved. [Brief explanation of the drawings]

[0019] [Figure 1]1 is a schematic configuration diagram of a hydrogen liquefaction system according to an embodiment of the present invention. [Figure 2] FIG. 1 is a schematic configuration diagram of a hydrogen liquefaction system according to a first modified example of an embodiment of the present invention. [Figure 3] FIG. 10 is a schematic configuration diagram of a hydrogen liquefaction system according to a second modified example of an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Next, an embodiment of the present invention will be described with reference to the drawings.

[0021] <Hydrogen liquefaction system> FIG. 1 is a schematic diagram of a hydrogen liquefaction system 1. As shown in FIG. As shown in FIG. 1, the hydrogen liquefaction system 1 includes a nuclear fusion device 2, a hydrogen generation device 4 connected to the nuclear fusion device 2 via a heat transfer medium flow path 3, a liquefaction device 6 connected to the hydrogen generation device 4 via a hydrogen flow path 5, a storage tank 7, a pump 8, and an on-off valve 9.

[0022] <Nuclear fusion device> The nuclear fusion device 2 comprises a vacuum vessel 10, a superconducting coil 11 housed within the vacuum vessel 10, and a radiation shield 12 provided within the vacuum vessel 10 and surrounding the superconducting coil 11. The superconducting coil 11 generates a magnetic field that confines high-temperature, high-density plasma for a long period of time, causing a nuclear fusion reaction in the confined plasma, generating heat. The nuclear fusion device 2 has a magnetic field confinement region 18 where the nuclear fusion reaction occurs. In order to generate a superconducting state in the superconducting coil 11 and to keep it stable, it is necessary to cool the superconducting coil 11 to a temperature below the critical temperature. The superconducting coil 11 is constantly cooled by a cooling device (not shown).

[0023] The radiation shield 12 is maintained at an extremely low temperature by liquid nitrogen and covers the superconducting coil. As a result, all of the radiant heat transferred to the superconducting coil comes from the radiation shield 12, and the lower the temperature of the object generating the radiation, the less radiant heat is transferred. This reduces the amount of radiant heat transferred to the superconducting coil 11. A nitrogen flow path 13 is connected to the radiation shield 12. Nitrogen flows through the nitrogen flow path 13 to cool the radiation shield 12. Hereinafter, the nitrogen flow path 13 may be referred to as the downstream side based on the direction of nitrogen flow.

[0024] The nitrogen flow path 13 has a nitrogen supply path 13a through which nitrogen is supplied to the radiation shield 12, and a nitrogen discharge path 13b through which nitrogen is discharged from the radiation shield 12. The downstream side of the nitrogen discharge path 13b is connected to the liquefaction device 6. Liquefied nitrogen (liquid nitrogen; LN2) is supplied to the radiation shield 12 via the nitrogen supply path 13a. The supplied liquid nitrogen undergoes heat exchange in the radiation shield 12 and is discharged in a vaporized state (GN2).

[0025] <Hydrogen generator> The hydrogen generator 4 generates hydrogen gas (GH2) by thermally decomposing raw material water at a high temperature of approximately 600°C to 900°C through a combination of multiple chemical reactions (for example, the IS process). However, the present invention is not limited to this, and the hydrogen generator 4 may also generate hydrogen gas through other thermochemical reactions such as the copper-chlorine cycle or hydrocarbon reforming.

[0026] The high temperature of approximately 600°C to 900°C is prepared by utilizing heat from plasma undergoing a nuclear fusion reaction in the magnetic confinement region 18 via the heat medium flow path 3. That is, a heat transfer medium flows within the heat medium flow path 3, and is circulated between the nuclear fusion device 2 and the hydrogen generator 4 via the heat medium flow path 3. Therefore, the heat of the nuclear fusion reaction in the nuclear fusion device 2 is transferred to the hydrogen generator 4 by the heat transfer medium. As the heat transfer medium, for example, a fluid such as oil is used. However, the heat transfer medium is not limited to this, and any heat transfer medium can be used as long as it can transfer the heat of the nuclear fusion reaction in the nuclear fusion device 2 to the hydrogen generator 4.

[0027] The hydrogen gas generated by the hydrogen generator 4 flows through a hydrogen flow path 5 connected to the hydrogen generator 4. Hereinafter, the hydrogen flow path 5 may be referred to as the upstream side and downstream side based on the flow direction of hydrogen.

[0028] <Liquefaction equipment> The liquefaction device 6 is connected to the hydrogen flow path 5 downstream of the hydrogen generator 4. The liquefaction device 6 is equipped with a first heat exchanger 14 that exchanges heat with the hydrogen flow path 5 and functions as a pre-cooling unit that pre-cools the hydrogen gas, and a refrigeration device 15 that is connected to the hydrogen flow path 5 downstream of the first heat exchanger 14 and liquefies the hydrogen gas. A nitrogen discharge path 13b is connected to the first heat exchanger 14.

[0029] The refrigeration device 15 includes a second heat exchanger 16 that exchanges heat with the hydrogen flow path 5, and a refrigerator 17 connected to the second heat exchanger 16. The refrigerator 17 is, for example, a so-called gas refrigerator. Examples of the refrigerant used in the refrigerator 17 include a helium refrigerant and a hydrogen refrigerant.

[0030] <Hydrogen liquefaction system operation> Next, the operation of the hydrogen liquefaction system 1 will be described. When the heat medium flow path 3, which has been heated by the heat of the nuclear fusion device 2, is supplied to the hydrogen generator 4, the high temperature causes a thermochemical reaction that causes thermal decomposition of water, producing hydrogen gas. The produced hydrogen gas flows into the liquefaction device 6 via the hydrogen flow path 5.

[0031] In the liquefaction device 6, first, heat is exchanged between the nitrogen discharged from the radiation shield 12 and the hydrogen gas via the first heat exchanger 14. In other words, the hydrogen gas is cooled (pre-cooled) by the nitrogen discharged from the radiation shield 12 via the first heat exchanger 14. Next, the hydrogen gas is further cooled by the refrigeration device 15. As a result, the hydrogen gas is liquefied when it passes through the refrigeration device 15. The liquefied hydrogen (LH2; hereinafter referred to as liquid hydrogen) is stored in the storage tank 7. The liquid hydrogen stored in the storage tank 7 is pumped up by the pump 8 and supplied to an external device (not shown) by opening the on-off valve 9.

[0032] As described above, the hydrogen liquefaction system 1 comprises the nuclear fusion device 2, the hydrogen generation device 4, and the liquefaction device 6. In the liquefaction device 6, hydrogen gas is pre-cooled by the nitrogen used in the radiation shield 12 of the nuclear fusion device 2. In the hydrogen liquefaction system 1, hydrogen gas is generated using the heat generated in the nuclear fusion device 2, so hydrogen gas can be generated efficiently. Furthermore, because the nitrogen used in the radiation shield 12 is used to pre-cool the hydrogen gas in the liquefaction device 6, the liquefaction device 6 can be made simple in structure. Therefore, the hydrogen liquefaction system 1 can be made compact with a simple structure, and the efficiency of hydrogen liquefaction by the hydrogen liquefaction system 1 can be improved.

[0033] The liquefaction device 6 includes a first heat exchanger 14 to which the nitrogen used in the radiation shield 12 is supplied, and a refrigeration device 15 provided downstream of the first heat exchanger 14. The refrigeration device 15 includes a second heat exchanger 16 and a refrigerator 17. Since the configuration of the liquefaction device 6 can be simplified in this way, the hydrogen liquefaction system 1 can be reliably made smaller.

[0034] [First Modification] In the above embodiment, the liquefaction device 6 is described as including the first heat exchanger 14 and the refrigeration device 15. The refrigeration device 15 is described as including the second heat exchanger 16 and one refrigerator 17. However, this is not limited to this, and the liquefaction device 6 may be provided with a plurality of refrigeration devices. This will be explained in detail below.

[0035] FIG. 2 is a schematic configuration diagram of a hydrogen liquefaction system 1 according to a first modified example of the embodiment. As shown in Figure 2, the liquefaction device 6 includes an additional refrigeration device 20 separate from the refrigeration device 15. The additional refrigeration device 20 is connected downstream of the refrigeration device 15 in the hydrogen flow path 5. The additional refrigeration device 20 includes a cooling section 21 that exchanges heat with the hydrogen flow path 5, and a heat exhaust section 22 that exchanges heat with the nitrogen gas from the radiation shield 12.

[0036] The additional refrigeration device 20 may be, for example, a so-called magnetic refrigerator. Magnetic refrigeration is a refrigerator that utilizes the phenomenon (magneto-caloric effect) in which a magnetic material generates heat when a magnetic field is applied to it, and its temperature drops when the magnetic field is removed. A magnetic refrigerator uses a solid magnetic material instead of a refrigerant. In the first modified example, the nitrogen used in the radiation shield 12 is supplied to the additional refrigeration unit 20 in addition to the first heat exchanger 14. With this configuration, the nitrogen discharged from the radiation shield 12 cools the heat exhaust section 22 of the additional refrigeration unit 20. The additional refrigeration unit 20 exchanges heat with hydrogen gas in the cooling section 21 and exhausts it to nitrogen gas in the heat exhaust section 22, and the smaller the temperature difference between the hydrogen gas to be cooled and the nitrogen gas to be exhausted, the less energy is required for cooling.

[0037] Therefore, according to the first modification described above, in addition to the same effects as the above embodiment, it is possible to reliably cool hydrogen gas while allocating the cooling capacity to each of the refrigeration units 15, 20. In particular, if the nitrogen used in the radiation shield 12 is used to cool the heat exhaust unit 22 of the additional refrigeration unit 20, the temperature of the heat exhaust unit 22 can be lowered and the temperature difference between the cooled and heat exhausted portions can be reduced, thereby reducing the energy consumption of the additional refrigeration unit 20. This allows the operating costs of the hydrogen liquefaction system 1 to be reduced.

[0038] In the above embodiment, the refrigerator 17 is, for example, a gas refrigerator. In the above first modified example, the case where one additional refrigeration unit 20 is provided is described. The case where the additional refrigeration unit 20 is, for example, a magnetic refrigerator is described. However, this is not limited to this, and various refrigerators can be used for the refrigerator 17 and the additional refrigeration unit 20. A magnetic refrigerator can be used as the refrigerator 17, and a gas refrigerator can be used as the additional refrigeration unit 20. Furthermore, the number of additional refrigeration devices 20 is not limited to one, but two or more may be provided.

[0039] [Second Modification] FIG. 3 is a schematic configuration diagram of a hydrogen liquefaction system 1 according to a second modified example of the embodiment. 3, it is also possible to use the nitrogen in the radiation shield 12 in combination with the hydrogen liquefaction system 1 having explosion-proof specifications. More specifically, the hydrogen liquefaction system 1 in the second modified example includes a hydrogen generation device 4, a refrigeration device 15, a storage tank 7, a pump 8, and a container 31 that seals the on-off valve 9, and an exhaust device 33 that exhausts gas from the container 31 to the outside.

[0040] Nitrogen supplied to the first heat exchanger 14 is discharged into the container 31. As a result, the container 31 is filled with nitrogen. To prevent the pressure inside the container 31 from becoming too high due to the discharged nitrogen gas, the nitrogen gas is discharged to the outside of the container 31 by the discharge device 33. However, the discharge device 33 maintains the pressure inside the container 31 to be positive (higher) than the pressure outside the container 31. This prevents air (particularly oxygen) from entering the container 31 and reacting with hydrogen even if hydrogen leaks from the container 31 due to damage or the like.

[0041] The discharge device 33 includes a detector 32 that detects the hydrogen concentration inside the container 31. In the above-described environment, the detector 32 makes it possible to detect the hydrogen concentration inside the container 31 with high accuracy. When the detector 32 detects that the hydrogen concentration in the container 31 exceeds a predetermined value, it determines that hydrogen has leaked from any of the hydrogen flow path 5, the hydrogen generator 4, the refrigeration device 15, the storage tank 7, the pump 8, and the on-off valve 9. In this case, hydrogen generation in the hydrogen generator 4 is stopped to prevent the hydrogen concentration in the container 31 from increasing. This makes it possible to start repair work for the malfunction while the hydrogen concentration of the gas in the container 31 is low. Therefore, the risk of repair work such as replacing the gas in the container 31 can be reduced.

[0042] Therefore, according to the second modification described above, it is possible to provide an explosion-proof hydrogen liquefaction system 1 that can detect hydrogen leaks in any of the hydrogen flow path 5, the hydrogen generator 4, the refrigeration device 15, the storage tank 7, the pump 8, and the on-off valve 9, and that also uses nitrogen as a radiation shield. In this way, it is possible to increase the variety of hydrogen liquefaction systems 1 that meet the needs of users.

[0043] In the above-described second modified example, the container 31 is described as sealing the hydrogen generator 4, refrigeration device 15, storage tank 7, pump 8, and on-off valve 9 in one space. However, this is not limited to this, and the container 31 does not need to seal all devices such as the hydrogen generator 4 and liquefaction device 6 in one space, and may be configured such that the sealed space is divided into multiple sections so as to seal only desired devices (for example, the hydrogen generator 4 and refrigeration device 15, etc.). This allows explosion-proof devices to be appropriately arranged.

[0044] In the second modified example described above, when it is determined from the detection result by detector 32 that the hydrogen concentration inside container 31 has exceeded a predetermined value, hydrogen is discharged to the outside of container 31 via an on-off valve (not shown). However, this is not limited to this, and a configuration may also be adopted in which an alarm (not shown) is sounded in addition to discharging hydrogen.

[0045] The present invention is not limited to the above-described embodiment, and includes various modifications to the above-described embodiment without departing from the spirit of the present invention.

[0046] For example, in the above embodiment, the liquefaction device 6 is described as including the first heat exchanger 14 that exchanges heat with the hydrogen flow path 5, and the refrigeration devices 15, 20 that are connected downstream of the first heat exchanger 14 in the hydrogen flow path 5. However, this is not limited thereto, and the liquefaction device 6 may be any device that can cool and liquefy hydrogen gas. For example, instead of using the refrigeration device 15, hydrogen gas may be liquefied using a decompression method.

[0047] In the above embodiment, the liquid hydrogen stored in the storage tank 7 is supplied to an external device (not shown). However, this is not limiting, and the liquid hydrogen stored in the storage tank 7 can also be used to cool the superconducting coil 11. [Explanation of symbols]

[0048] 1...Hydrogen liquefaction system 2…Nuclear fusion device 4...Hydrogen generator 6…Liquefaction device 11...Superconducting coil 12...Radiation shield 14...First heat exchanger (precooling section) 15... Refrigeration equipment 18...Magnetic field confinement region 20...Additional refrigeration unit (refrigeration unit) 31…Container 32...Detector 33…Discharge device

Claims

1. a magnetic confinement region where a nuclear fusion reaction occurs; a superconducting coil for generating a magnetic field in the magnetic confinement region; a radiation shield cooled by liquid nitrogen to shield the superconducting coil from radiation; a hydrogen generator that generates hydrogen gas by utilizing heat generated in the magnetic confinement region; a pre-cooling unit that pre-cools the hydrogen gas generated by the hydrogen generation device with nitrogen gas discharged from the radiation shield; a refrigeration device that liquefies the hydrogen gas pre-cooled in the pre-cooling unit; Equipped with A hydrogen liquefaction system characterized by:

2. cooling a heat exhaust portion of the refrigeration device with the nitrogen gas discharged from the radiation shield; 2. The hydrogen liquefaction system according to claim 1.

3. a container that seals the hydrogen generation device and the pre-cooling unit; The nitrogen gas used to pre-cool the hydrogen gas is discharged into the container.

3. The hydrogen liquefaction system according to claim 1 or 2.

4. a discharge device that discharges gas from the container to the outside while maintaining a positive pressure inside the container relative to the outside of the container; 4. The hydrogen liquefaction system according to claim 3.

5. a detector for detecting a hydrogen concentration in the container; 4. The hydrogen liquefaction system according to claim 3.

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