Hydrogen fuel supply system and hydrogen liquefaction method

Abstract

A hydrogen fuel supply system according to one embodiment of the present disclosure is provided with: a liquefied hydrogen tank for storing liquefied hydrogen; a supply line that connects the liquefied hydrogen tank and a hydrogen fuel engine and supplies hydrogen gas to the hydrogen fuel engine; a pressure pump which is located in the supply line and which pressurizes the liquefied hydrogen to a pressure equal to or higher than a critical pressure; a return line that connects the liquefied hydrogen tank to a portion of the supply line downstream of the pressure pump; a pressure-reducing / temperature-increasing valve located in the return line and configured to reduce the pressure of the high-pressure hydrogen pressurized by the pressure pump to a pressure near an inversion temperature curve and increase the temperature of the high-pressure hydrogen; a catalyst reactor located in the return line and bringing the hydrogen heated by the pressure-reducing and temperature-increasing valve into contact with a secondary-positive conversion catalyst; and a reduced-pressure liquefaction valve located in the return line, the reduced-pressure liquefaction valve reducing the pressure of the hydrogen passing through the catalyst reactor and converting the hydrogen into liquefied hydrogen.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a hydrogen fuel supply system and a hydrogen liquefaction method. BACKGROUND

[0002] In the following Patent Literature 1, disclosed is an apparatus that pressurizes boil-off gas naturally generated in an LNG tank, cools a portion of the pressurized boil-off gas using supercooled LNG to condense it, and returns it to the LNG tank.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent No. 7119063 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In recent years, hydrogen fuel has attracted attention from the viewpoint of environmental protection. In a hydrogen fuel engine, when hydrogen gas obtained by pressurizing liquefied hydrogen is returned to a tank again, it can be liquefied using a refrigerant, but a new power is required for this. Without the additional power, it is theoretically impossible to completely liquefy, and even if high-pressure hydrogen is depressurized to the original pressure, a portion thereof becomes hydrogen gas. This is because, due to heat emitted from a pressurizing pump and the like, a system with 100% efficiency cannot be realized. If liquefied hydrogen stored in a liquefied hydrogen tank becomes hydrogen gas and is returned to the liquefied hydrogen tank, the internal pressure of the liquefied hydrogen tank rises, which is not preferable.

[0008] An object of the present disclosure is to provide a hydrogen fuel supply system capable of changing hydrogen to liquefied hydrogen at a high proportion when hydrogen pressurized to a pressure above a critical pressure is depressurized and returned to a liquefied hydrogen tank.

[0009] MEANS FOR SOLVING THE PROBLEMS

[0010] A hydrogen fuel supply system of one embodiment of the present disclosure includes a liquefied hydrogen tank that stores liquefied hydrogen; a supply line that connects the liquefied hydrogen tank and a hydrogen fuel engine, and supplies hydrogen gas to the hydrogen fuel engine; a pressurizing pump that is positioned in the supply line, and pressurizes liquefied hydrogen to a pressure above a critical pressure; a return line that connects a portion of the supply line downstream of the pressurizing pump and the liquefied hydrogen tank; a depressurizing and warming valve that is positioned in the return line, and depressurizes high-pressure hydrogen pressurized by the pressurizing pump to a pressure around a reverse temperature curve to warm it; a catalyst reactor that is positioned in the return line, and contacts hydrogen warmed by the depressurizing and warming valve with a para-to-normal conversion catalyst; and a depressurizing and liquefying valve that is positioned in the return line, and changes hydrogen that has passed through the catalyst reactor to liquefied hydrogen by depressurizing it.

[0011] Inventive Effects

[0012] The hydrogen fuel supply system according to one embodiment of the present disclosure is capable of changing liquefied hydrogen at a high rate when hydrogen pressurized to above the critical pressure is depressurized and returned to the liquefied hydrogen tank. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a block diagram of a hydrogen fuel supply system. DETAILED DESCRIPTION

[0014] Hereinafter, an embodiment will be described. Figure 1 is a block diagram of a hydrogen fuel supply system 100 according to the embodiment. As shown in the figure, the hydrogen fuel supply system 100 according to the embodiment has a liquefied hydrogen tank 11, a supply line 12, a pressurizing pump 13, a heater 14, a return line 15, a depressurizing and temperature-increasing valve 16, a catalyst reactor 17, and a depressurizing and liquefying valve 18. Hereinafter, these constituent elements will be described in order. Figure 1

[0015] The liquefied hydrogen tank 11 is a tank that stores liquefied hydrogen. The liquefied hydrogen tank 11 includes a liquid phase portion 21 filled with liquefied hydrogen and a gas phase portion 22 filled with hydrogen gas. In the liquefied hydrogen tank 11, when the internal pressure rises above an allowable value, a portion of the hydrogen gas is discharged from the gas phase portion 22. Normally, the hydrogen gas discharged from the liquefied hydrogen tank 11 is released to the atmosphere or treated by incineration or the like. Therefore, in order not to waste the hydrogen fuel, it is also preferable to suppress the internal pressure of the liquefied hydrogen tank 11.

[0016] The supply line 12 is a pipe that connects the liquefied hydrogen tank 11 and a hydrogen fuel engine 101. The hydrogen fuel engine 101 is an apparatus that uses hydrogen gas as fuel, such as a gas engine and a boiler. The supply line 12 takes liquefied hydrogen from the liquid phase portion 21 of the liquefied hydrogen tank 11, changes the taken liquefied hydrogen to hydrogen gas, and supplies the changed hydrogen gas to the hydrogen fuel engine 101 as fuel.

[0017] The pressurizing pump 13 is a pump that pressurizes liquefied hydrogen, and is located in the supply line 12. The pressurizing pump 13 pressurizes the liquefied hydrogen taken from the liquefied hydrogen tank 11 to above the critical pressure. The pressurizing pump 13 can be constituted by a plurality of pumps, or can be constituted by only one pump. For example, the pressurizing pump 13 can include a low-pressure pump and a high-pressure pump that further pressurizes the liquefied hydrogen pressurized by the low-pressure pump.

[0018] The heater 14 is an apparatus that heats hydrogen, and is located in the supply line 12. The heater 14 according to the embodiment is located in a portion of the supply line 12 that is more downstream than the pressurizing pump 13. Therefore, the heater 14 heats hydrogen pressurized by the pressurizing pump 13. The critical hydrogen heated by the heater 14 is supplied to the hydrogen fuel engine 101.

[0019] ​The return line 15 is a line that connects the supply line 12 and the liquefied hydrogen tank 11. The return line 15 of the present embodiment is connected to a portion of the supply line 12 that is downstream of the pressure increasing pump 13 and upstream of the heater 14. The return line 15 takes, from the supply line 12, hydrogen that is left over from the hydrogen that is supplied to the hydrogen fuel engine 101 after being pressurized by the pressure increasing pump 13, changes the taken hydrogen to liquefied hydrogen, and returns the hydrogen to the liquefied hydrogen tank 11. If most of the hydrogen that is returned to the liquefied hydrogen tank 11 is changed to liquefied hydrogen, the internal pressure of the liquefied hydrogen tank 11 can be suppressed, and further, the useless consumption of hydrogen fuel can be suppressed. In addition, the hydrogen that is taken by the return line 15 from the supply line 12 is at a temperature that is higher than that of the liquefied hydrogen and the liquefied gas inside the liquefied hydrogen tank 11, but is at an extremely low temperature (for example, -200°C or lower) and at a high pressure (for example, 20 MPaG or higher).

[0020] The pressure reducing and temperature increasing valve 16 is located in the return line 15 and is a valve that depressurizes the hydrogen that is taken from the supply line 12. The pressure reducing and temperature increasing valve 16 can be configured by one valve or can be configured by a plurality of valves. Here, the process in which a high-pressure fluid is depressurized and expanded by a valve is isenthalpic expansion, which is called Joule-Thomson expansion. In Joule-Thomson expansion, if the pressure is higher than the inversion temperature curve, the temperature rises due to the depressurization. Hydrogen has a characteristic in which the inversion temperature curve is in a low-temperature region compared to other gases such as natural gas, and thus the following characteristic is utilized: by depressurizing high-pressure, extremely low-temperature hydrogen, the temperature is increased before the inversion temperature curve is reached, and at a pressure that is lower than the inversion temperature curve, the temperature can be decreased to a liquefaction temperature. In the present embodiment, the high-pressure, extremely low-temperature hydrogen at the inlet of the pressure reducing and temperature increasing valve 16 is temporarily increased in temperature by being depressurized to just before the inversion temperature curve is reached.

[0021] The catalyst reactor 17 is a device that brings hydrogen into contact with a para-ortho conversion catalyst. The catalyst reactor 17 is located in a portion of the return line 15 that is downstream of the pressure reducing and temperature increasing valve 16. Here, hydrogen includes ortho-hydrogen in which the spin directions of protons are the same and para-hydrogen in which the spin directions of protons are different. When the temperature of hydrogen rises, para-hydrogen is converted to ortho-hydrogen, and the proportion of ortho-hydrogen increases. The conversion from para-hydrogen to ortho-hydrogen is an endothermic reaction, and thus the temperature of hydrogen decreases when the conversion occurs. However, the conversion from para-hydrogen to ortho-hydrogen takes several days or so to reach an equilibrium state, and thus even if the temperature of hydrogen rises due to the pressure reducing and temperature increasing valve 16, the endothermic reaction does not immediately occur.

[0022] Therefore, the hydrogen fuel supply system 100 of the present embodiment brings hydrogen that is increased in temperature by the pressure reducing and temperature increasing valve 16 into contact with a para-ortho conversion catalyst by the catalyst reactor 17. The hydrogen that is brought into contact with the para-ortho conversion catalyst is promoted to convert from para-hydrogen to ortho-hydrogen. Therefore, the proportion of ortho-hydrogen included in the hydrogen rises to a value that corresponds to the temperature of the hydrogen, that is, a value in an equilibrium state. Due to this, the endothermic reaction occurs when the conversion occurs, and the temperature of the hydrogen decreases. In addition, as the para-ortho conversion catalyst, for example, iron hydroxide or the like can be utilized.

[0023] The decompression liquefaction valve 18 is a valve that decompresses and liquefies hydrogen that has passed through the catalyst reactor 17. The decompression liquefaction valve 18 is located in a portion of the return line 15 that is downstream of the catalyst reactor 17. The decompression liquefaction valve 18 can be composed of one valve or a plurality of valves. In the present embodiment, by further decompressing from a state in which the temperature has decreased due to the endothermic reaction to a tank pressure, the temperature can be decreased to a liquefaction temperature. In addition, in a case in which the pressure of hydrogen at the inlet of the decompression liquefaction valve 18 is higher than the inversion temperature curve, the hydrogen is temporarily warmed by decompressing the hydrogen, but the hydrogen can be cooled by further decompression.

[0024] By decompressing and cooling the hydrogen with the decompression liquefaction valve 18, the temperature of the hydrogen is lower than the boiling point and the hydrogen changes to liquefied hydrogen. Also, as described above, the temperature of the hydrogen that has passed through the catalyst reactor 17 is decreased, and from this state, the hydrogen is decompressed with the decompression liquefaction valve 18, and thus the proportion of liquefaction increases. Therefore, with the hydrogen fuel supply system 100 of the present embodiment, high-pressure hydrogen can be changed to liquefied hydrogen at a high proportion. As a result, the internal pressure of the liquefied hydrogen tank 11 can be suppressed, and the wasteful consumption of hydrogen fuel can also be suppressed.

[0025] <Summary>

[0026] A first aspect disclosed in the present specification is a hydrogen fuel supply system that includes: a liquefied hydrogen tank that stores liquefied hydrogen; a supply line that connects the liquefied hydrogen tank to a hydrogen fuel engine and supplies hydrogen gas to the hydrogen fuel engine; a pressurizing pump that is located in the supply line and pressurizes liquefied hydrogen to a pressure that is higher than a critical pressure; a return line that connects a portion of the supply line that is downstream of the pressurizing pump to the liquefied hydrogen tank; a decompression warming valve that is located in the return line and decompresses and warms high-pressure hydrogen that has been pressurized by the pressurizing pump to a pressure in the vicinity of an inversion temperature curve; a catalyst reactor that is located in the return line and contacts hydrogen that has been warmed by the decompression warming valve with a para-to-normal conversion catalyst; and a decompression liquefaction valve that is located in the return line and decompresses and changes hydrogen that has passed through the catalyst reactor to liquefied hydrogen.

[0027] With this structure, when pressurized hydrogen is decompressed and returned to the liquefied hydrogen tank, it can be changed to liquefied hydrogen at a high proportion.

[0028] A second aspect disclosed in the present specification is a method of liquefying hydrogen, in which pressurized high-pressure hydrogen is decompressed to a pressure in the vicinity of an inversion temperature curve and warmed, the warmed hydrogen is contacted with a para-to-normal conversion catalyst, and the hydrogen that has been contacted with the para-to-normal conversion catalyst is further decompressed and changed to liquefied hydrogen.

[0029] According to the method, the pressurized hydrogen can be changed into liquefied hydrogen at a high proportion when the pressurized hydrogen is depressurized.

Claims

1. A hydrogen fuel supply system, comprising: A liquefied hydrogen tank, used to store liquefied hydrogen; A supply pipeline connects the liquefied hydrogen tank to the hydrogen fuel engine and supplies hydrogen to the hydrogen fuel engine; A booster pump, located in the supply line, pressurizes the liquefied hydrogen to a pressure above the critical pressure. The return line connects the downstream portion of the supply line from the pressurization pump to the liquefied hydrogen tank. A pressure-reducing and temperature-increasing valve, located in the return pipeline, reduces the pressure of the high-pressure hydrogen after it has been pressurized by the pressurizing pump to a pressure near the inverted temperature curve, thereby increasing its temperature. A catalyst reactor, located on the return line, contacts hydrogen heated by the pressure-reducing and heating valve with the neutrophil-conversion catalyst; and A pressure-reducing liquefaction valve, located on the return line, depressurizes the hydrogen passing through the catalyst reactor and converts it into liquefied hydrogen.

2. A method for liquefying hydrogen, wherein, The high-pressure hydrogen is depressurized to near the reversal temperature curve and then heated. The heated hydrogen comes into contact with the intermediate-to-normal conversion catalyst, and the hydrogen in contact with the intermediate-to-normal conversion catalyst is further depressurized and transformed into liquefied hydrogen.

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