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 pressurizing pump which is located in the supply line and pressurizes the liquefied hydrogen to a critical pressure or higher; a return line that connects the liquefied hydrogen tank to a portion of the supply line downstream of the pressure pump; a pressure-reducing and temperature-increasing valve located in the return line, the pressure of the return hydrogen flowing into the return line being reduced to a pressure near an inversion temperature curve, and the temperature of the return hydrogen being increased by the pressure-reducing and temperature-increasing valve; a heat exchanger which is located at a position spanning the supply line and the return line, and which cools the return hydrogen heated by the pressure-reducing and temperature-increasing valve using, as a refrigerant, the supply hydrogen supplied to the hydrogen fuel engine among the hydrogen pressurized by the pressure pump; and a reduced-pressure liquefaction valve located in the return line, the reduced-pressure liquefaction valve reducing the pressure of the return hydrogen passing through the heat exchanger and converting the reduced-pressure hydrogen into liquefied hydrogen.

Description

Technical Field

[0001] This disclosure relates to hydrogen fuel supply systems and methods for liquefying hydrogen. Background Technology

[0002] Patent document 1 discloses a control device that, when receiving liquefied gas from a cargo tank to a storage tank, delivers the liquefied gas to the storage tank while the gas is cooled to a subcooled state by a refrigeration unit.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2022 / 209850 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In recent years, hydrogen fuel has received attention from an environmental protection perspective. In hydrogen fuel supply systems that supply hydrogen to hydrogen fuel cells, surplus hydrogen can be liquefied by cooling it using a refrigeration unit, in addition to returning it to the liquefied hydrogen tank. However, using a large-capacity refrigeration unit increases the weight, manufacturing cost, operating cost, and size of the hydrogen fuel supply system, making it less desirable.

[0008] The purpose of this disclosure is to provide a hydrogen fuel supply system that can omit or miniaturize the refrigeration unit used to liquefy hydrogen back to the liquefied hydrogen tank.

[0009] Methods for solving problems

[0010] One aspect of the hydrogen fuel supply system disclosed herein includes: a liquefied hydrogen tank for storing liquefied hydrogen; a supply line connecting the liquefied hydrogen tank to a hydrogen fuel cell engine for supplying hydrogen to the engine; a pressurization pump located on the supply line for pressurizing the liquefied hydrogen to a pressure above a critical pressure; a return line connecting a downstream portion of the supply line (below the pressurization pump) to the liquefied hydrogen tank; a pressure-reducing and temperature-increasing valve located on the return line for reducing the pressure of the return hydrogen flowing into the return line from the pressurized hydrogen by the pressurization pump to a pressure near a reversal temperature curve, thereby increasing its temperature; a heat exchanger located across the supply line and the return line for using the supply hydrogen from the pressurized hydrogen by the pressurization pump, supplied to the hydrogen fuel cell engine, as a refrigerant to cool the return hydrogen heated by the pressure-reducing and temperature-increasing valve; and a pressure-reducing and liquefaction valve located on the return line for reducing the pressure of the return hydrogen passing through the heat exchanger and converting it into liquefied hydrogen.

[0011] Invention Effects

[0012] According to one aspect of the hydrogen fuel supply system disclosed herein, the refrigeration unit used to liquefy hydrogen back to the liquefied hydrogen tank can be omitted or miniaturized. Attached Figure Description

[0013] Figure 1 This is a block diagram of a hydrogen fuel supply system. Detailed Implementation

[0014] The implementation method will be described below. Figure 1 This is a block diagram of the hydrogen fuel supply system 100 according to an embodiment. (As shown) Figure 1 As shown, the hydrogen fuel supply system 100 of this embodiment includes a liquefied hydrogen tank 11, a supply line 12, a pressurization pump 13, a heater 14, a return line 15, a pressure reducing and heating valve 16, a heat exchanger 17, and a pressure reducing and liquefaction valve 18. These components will be described in turn below.

[0015] The liquefied hydrogen tank 11 is a tank for storing liquefied hydrogen. The liquefied hydrogen tank 11 includes a liquid phase section 21 filled with liquefied hydrogen and a gas phase section 22 filled with hydrogen gas. In the liquefied hydrogen tank 11, when the internal pressure rises and exceeds a permissible value, a portion of the hydrogen gas is discharged from the gas phase section 22. Normally, the hydrogen gas discharged from the liquefied hydrogen tank 11 is released into the atmosphere or disposed of by combustion or other methods. Therefore, in order to consume hydrogen fuel without waste, it is preferable to suppress the internal pressure of the liquefied hydrogen tank 11.

[0016] Supply line 12 is a piping that connects liquefied hydrogen tank 11 to hydrogen fuel cell engine 101. Hydrogen fuel cell engine 101 is a device that uses hydrogen as fuel, such as a gas engine or boiler. Supply line 12 obtains liquefied hydrogen from the liquid phase section 21 of liquefied hydrogen tank 11, converts the obtained liquefied hydrogen into hydrogen gas, and supplies it to hydrogen fuel cell engine 101 as fuel.

[0017] The pressurization pump 13, located on the supply line 12, is a pump that pressurizes liquefied hydrogen. The pressurization pump 13 pressurizes the liquefied hydrogen obtained from the liquefied hydrogen tank 11 to a pressure above the critical pressure. The pressurization pump 13 can consist of multiple pumps or a single pump. For example, the pressurization pump 13 may also include a low-pressure pump and a high-pressure pump that further pressurizes the liquefied hydrogen pressurized by the low-pressure pump.

[0018] Heater 14, located on supply line 12, is a device for heating hydrogen. In this embodiment, heater 14 is located downstream of pressurization pump 13 on supply line 12. Therefore, heater 14 heats the hydrogen pressurized by pressurization pump 13. The hydrogen heated by heater 14 is then supplied to hydrogen fuel cell engine 101.

[0019] The return line 15 is a line connecting the supply line 12 and the liquefied hydrogen tank 11. In this embodiment, the return line 15 is connected to the portion of the supply line 12 that is downstream of the pressurization pump 13 and upstream of the heater 14. The return line 15 takes the remaining hydrogen from the hydrogen pressurized by the pressurization pump 13 that was not supplied to the hydrogen fuel cell engine 101 from the supply line 12, converts the obtained hydrogen into liquefied hydrogen, and returns it to the liquefied hydrogen tank 11.

[0020] Hereinafter, the hydrogen that flows back to the liquefied hydrogen tank 11 from the hydrogen pressurized by the pressurization pump 13 via the return line 15 will be referred to as "return hydrogen," and the hydrogen supplied to the hydrogen fuel cell engine 101 will be referred to as "supply hydrogen." That is, the hydrogen pressurized by the pressurization pump 13 is divided into return hydrogen and supply hydrogen. In addition, if most of the return hydrogen can be converted into liquefied hydrogen, the internal pressure of the liquefied hydrogen tank 11 can be suppressed, thereby suppressing the wasteful consumption of hydrogen fuel. Furthermore, although the temperature of the return hydrogen flowing into the return line 15 is higher than that of the liquefied hydrogen and liquefied gas in the liquefied hydrogen tank 11, it is at extremely low temperature (e.g., below -200°C) and high pressure (e.g., above 20 MPaG).

[0021] The pressure-reducing and temperature-raising valve 16, located on the return line 15, is a valve for reducing the pressure of the return hydrogen obtained from the supply line 12. The pressure-reducing and temperature-raising valve 16 can be a single valve or multiple valves. Here, the process of the high-pressure gas expanding due to pressure reduction by the valve is isenthalpic expansion, known as Joule-Thomson expansion. In Joule-Thomson expansion, if the pressure is higher than the inversion temperature curve, the temperature rises due to pressure reduction. Hydrogen has the characteristic that its inversion temperature curve is in a low-temperature region compared to other gases such as natural gas; therefore, it is possible to utilize the following property: by reducing the pressure of the high-pressure, extremely low-temperature hydrogen, it can be heated before reaching the inversion temperature curve, and at a pressure lower than the inversion temperature curve, it can be cooled to its liquefaction temperature. The pressure-reducing and temperature-raising valve 16 can raise the temperature of the return hydrogen by reducing the pressure to near the inversion temperature curve.

[0022] The heat exchanger 17 is a device for cooling the returned hydrogen. The heat exchanger 17 is located downstream of the portion of the supply line 12 connected to the return line 15 and upstream of the heater 14, and downstream of the pressure-reducing and heating valve 16 on the return line 15. Furthermore, the heat exchanger 17 cools the returned hydrogen by exchanging heat between the returned hydrogen and the supply hydrogen. That is, the supply hydrogen is used as a refrigerant to cool the returned hydrogen. Additionally, since the returned hydrogen is heated by the pressure-reducing and heating valve 16, the temperature of the returned hydrogen at the inlet of the heat exchanger 17 is higher than the temperature of the supply hydrogen.

[0023] The pressure-reducing liquefaction valve 18 is a valve that liquefies the returned hydrogen that has passed through the heat exchanger 17 by reducing its pressure. The pressure-reducing liquefaction valve 18 is located downstream of the heat exchanger 17 in the return line 15. The pressure-reducing liquefaction valve 18 can be a single valve or multiple valves. In this embodiment, the pressure of the returned hydrogen at the inlet of the pressure-reducing liquefaction valve 18 is near or lower than the pressure of the inverted temperature curve, and the pressure-reducing liquefaction valve 18 can cool the returned hydrogen by reducing its pressure. Furthermore, if the pressure of the returned hydrogen at the inlet of the pressure-reducing liquefaction valve 18 is higher than the pressure of the inverted temperature curve, the returned hydrogen temporarily heats up by reducing its pressure, but can be cooled down by further reducing its pressure.

[0024] The return hydrogen is depressurized and cooled by the pressure-reducing liquefaction valve 18, thereby liquefying it into liquefied hydrogen. Furthermore, the return hydrogen, having passed through the heat exchanger 17, is supplied with hydrogen for cooling, thus increasing the proportion of return hydrogen liquefied through pressure reduction based on the pressure-reducing liquefaction valve 18. As a result, the hydrogen fuel supply system 100 according to this embodiment can liquefy return hydrogen even without using a refrigeration unit. However, the hydrogen fuel supply system 100 may also include a refrigeration unit for cooling the return hydrogen. Even in this case, the return hydrogen is supplied with hydrogen for cooling, so a large-capacity refrigeration unit for liquefying the return hydrogen is not required. Therefore, the hydrogen fuel supply system 100 according to this embodiment can omit or miniaturize the refrigeration unit.

[0025] <Summary>

[0026] The first item disclosed in this specification is a hydrogen fuel supply system comprising: a liquefied hydrogen tank for storing liquefied hydrogen; a supply line connecting the liquefied hydrogen tank to a hydrogen fuel cell engine for supplying hydrogen to the engine; a pressurization pump located on the supply line for pressurizing the liquefied hydrogen to a pressure above a critical pressure; a return line connecting a downstream portion of the supply line (below the pressurization pump) to the liquefied hydrogen tank; a pressure-reducing and temperature-increasing valve located on the return line for reducing the pressure of the return hydrogen flowing into the return line from the pressurized hydrogen by the pressurization pump to a pressure near a reversal temperature curve, thereby increasing its temperature; a heat exchanger located across the supply line and the return line for using the supply hydrogen supplied to the hydrogen fuel cell engine from the pressurized hydrogen by the pressurization pump as a refrigerant to cool the return hydrogen heated by the pressure-reducing and temperature-increasing valve; and a pressure-reducing and liquefaction valve located on the return line for reducing the pressure of the return hydrogen passing through the heat exchanger and converting it into liquefied hydrogen.

[0027] According to this structure, the refrigeration unit used to liquefy hydrogen and return it to the liquefied hydrogen tank can be omitted or miniaturized.

[0028] The second item disclosed in this specification is a method for liquefying hydrogen, wherein pressurized hydrogen is branched into first hydrogen and second hydrogen, the first hydrogen is depressurized to a pressure near the inversion temperature curve and heated, the first hydrogen is cooled by exchanging heat between the heated first hydrogen and the second hydrogen, and the cooled first hydrogen is further depressurized to change into liquefied hydrogen.

[0029] Furthermore, in the implementation method, "return hydrogen" and "supply hydrogen" are equivalent to "first hydrogen" and "second hydrogen" in the second item, respectively. According to the above method, the refrigerator used to liquefy the first hydrogen can be omitted or miniaturized.

Claims

1. A hydrogen fuel supply system having: a liquefied hydrogen tank that stores liquefied hydrogen; a supply line that connects the liquefied hydrogen tank with a hydrogen fuel engine to supply hydrogen gas to the hydrogen fuel engine; a pressurizing pump that is located in the supply line to pressurize the liquefied hydrogen to above a critical pressure; a return line that connects a portion of the supply line that is downstream of the pressurizing pump with the liquefied hydrogen tank; a depressurizing and warming valve that is located in the return line to depressurize return hydrogen that flows into the return line from the hydrogen pressurized by the pressurizing pump to a pressure in the vicinity of an inversion temperature curve to warm the return hydrogen; a heat exchanger that is located at a position that straddles the supply line and the return line to cool the return hydrogen warmed by the depressurizing and warming valve using supply hydrogen that is supplied to the hydrogen fuel engine from the hydrogen pressurized by the pressurizing pump as a refrigerant; and a depressurizing liquefying valve that is located in the return line to depressurize the return hydrogen that has passed through the heat exchanger to change the return hydrogen to liquefied hydrogen.

2. A hydrogen liquefaction method in which: pressurized hydrogen is branched into first hydrogen and second hydrogen, the first hydrogen is depressurized to a pressure in the vicinity of an inversion temperature curve to warm the first hydrogen, the first hydrogen that has been warmed is cooled by causing the first hydrogen to exchange heat with the second hydrogen, and the first hydrogen that has been cooled is further depressurized to change the first hydrogen to liquefied hydrogen. ​ ​ ​ ​ ​ ​ ​ ​ ​

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