Hydrogen fuel supply system and hydrogen liquefying method

Abstract

To provide a hydrogen fuel supply system for enabling the elimination or downsizing of a refrigeration machine for liquefying hydrogen to be returned into a liquefied hydrogen tank.SOLUTION: A hydrogen fuel supply system includes: a liquefied hydrogen tank; a supply line for linking the liquefied hydrogen tank and a hydrogen fuel engine to supply hydrogen gas to the hydrogen fuel engine; a pressurizing pump located in the supply line for pressurizing the liquefied hydrogen up to a critical pressure or higher; a return line linking a portion downstream of the pressurizing pump in the supply line and the liquefied hydrogen tank; a depressurizing temperature raising valve located in the return line for depressurizing the returned hydrogen flowing into the return line of the hydrogen pressurized by the pressurizing pump, down to a pressure near a reverse temperature curve to raise the temperature; a heat exchanger located across the supply line and the return line for cooling the returned hydrogen raised in temperature by the depressurizing temperature raising valve using supply hydrogen to be supplied to the hydrogen fuel engine of the hydrogen pressurized by the pressurizing pump, as refrigerant; and a depressurization liquefying valve located in the return line for depressurizing returned hydrogen passing through the heat exchanger to change it into liquefied hydrogen.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a hydrogen fuel supply system and a method for liquefying hydrogen. [Background technology]

[0002] The following Patent Document 1 discloses a control device that, when receiving liquefied gas from a cargo tank into a storage tank, sends the liquefied gas to the storage tank in a state in which the liquefied gas has been cooled to a subcooled state by a refrigerator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2022 / 209850 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, hydrogen fuel has been attracting attention from the viewpoint of environmental protection. In a hydrogen fuel supply system that supplies hydrogen gas to a hydrogen fuel engine, when the excess hydrogen is returned to a liquefied hydrogen tank, a refrigerator can be used to cool and liquefy the excess hydrogen. However, using a refrigerator with a large capacity is not preferable because it increases the weight, manufacturing costs, operating costs, and size of the hydrogen fuel supply system.

[0005] An object of the present disclosure is to provide a hydrogen fuel supply system that eliminates the need for a refrigerator for liquefying hydrogen to be returned to a liquefied hydrogen tank, or that can be made smaller. [Means for solving the problem]

[0006] A hydrogen fuel supply system according to one aspect of the present disclosure includes a liquefied hydrogen tank for storing liquefied hydrogen, a supply line connecting the liquefied hydrogen tank and a hydrogen fuel engine and supplying hydrogen gas to the hydrogen fuel engine, a pressure reduction and heating valve located on the supply line and reducing the pressure of return hydrogen that has flowed into the return line from among the hydrogen pressurized by the pressure reduction pump to a pressure near an inversion temperature curve, and heating the return hydrogen, a heat exchanger located astride the supply line and the return line and using supply hydrogen that is supplied to the hydrogen fuel engine from among the hydrogen pressurized by the pressure reduction pump as a refrigerant, and a pressure reduction and liquefaction valve located on the return line and reducing the pressure of the return hydrogen that has passed through the heat exchanger to convert it into liquefied hydrogen. Effect of the Invention

[0007] According to the hydrogen fuel supply system according to one aspect of the present disclosure, it is possible to omit or reduce the size of a refrigerator for liquefying hydrogen to be returned to the liquefied hydrogen tank. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram of a hydrogen fuel supply system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An embodiment will be described below. Fig. 1 is a block diagram of a hydrogen fuel supply system 100 according to an embodiment. As shown in Fig. 1, the hydrogen fuel supply system 100 according to this embodiment includes a liquefied hydrogen tank 11, a supply line 12, a pressure pump 13, a heater 14, a return line 15, a pressure reducing heating valve 16, a heat exchanger 17, and a pressure reducing liquefaction valve 18. Below, these components will be described in order.

[0010] The liquefied hydrogen tank 11 is a tank that stores 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. When the internal pressure of the liquefied hydrogen tank 11 rises and exceeds an allowable value, a portion of the hydrogen gas is discharged from the gas phase section 22. Typically, the hydrogen gas discharged from the liquefied hydrogen tank 11 is disposed of by being released into the atmosphere or incinerated. Therefore, in order to avoid wasteful consumption of hydrogen fuel, it is desirable to suppress the internal pressure of the liquefied hydrogen tank 11.

[0011] The supply line 12 is a pipe that connects the liquefied hydrogen tank 11 and the hydrogen fuel engine 101. The hydrogen fuel engine 101 is equipment that uses hydrogen gas as fuel, such as a gas engine or a boiler. The supply line 12 obtains liquefied hydrogen from the liquid phase portion 21 of the liquefied hydrogen tank 11, converts the obtained liquefied hydrogen into hydrogen gas, and supplies it to the hydrogen fuel engine 101 as fuel.

[0012] The pressurizing pump 13 is located in the supply line 12 and is a pump that pressurizes the liquefied hydrogen. The pressurizing pump 13 pressurizes the liquefied hydrogen obtained from the liquefied hydrogen tank 11 to a pressure equal to or higher than the critical pressure. The pressurizing pump 13 may be composed of a plurality of pumps, or may be composed of only one pump. For example, the pressurizing pump 13 may include a low-pressure pump and a high-pressure pump that further pressurizes the liquefied hydrogen pressurized by the low-pressure pump.

[0013] The heater 14 is located in the supply line 12 and is a device that heats hydrogen. The heater 14 in this embodiment is located in a portion of the supply line 12 downstream of the pressure pump 13. Therefore, the heater 14 heats the hydrogen pressurized by the pressure pump 13. The hydrogen heated by the heater 14 is supplied to the hydrogen fuel engine 101.

[0014] The return line 15 is a line that connects the supply line 12 and the liquefied hydrogen tank 11. In this embodiment, the return line 15 is connected to a portion of the supply line 12 downstream of the pressure pump 13 and upstream of the heater 14. The return line 15 obtains, from the supply line 12, surplus hydrogen that is not supplied to the hydrogen fuel engine 101 among the hydrogen pressurized by the pressure pump 13, converts the obtained hydrogen into liquefied hydrogen, and returns it to the liquefied hydrogen tank 11.

[0015] Hereinafter, the hydrogen pressurized by the pressurizing pump 13 that flows into the return line 15 and is returned to the liquefied hydrogen tank 11 will be referred to as "return hydrogen", and the hydrogen supplied to the hydrogen fuel engine 101 will be referred to as "supplied hydrogen". In other words, the hydrogen pressurized by the pressurizing pump 13 is branched into return hydrogen and supplied hydrogen. If most of the return hydrogen could be converted to liquefied hydrogen, the internal pressure of the liquefied hydrogen tank 11 could be suppressed, and thus unnecessary consumption of hydrogen fuel could be suppressed. Furthermore, the return hydrogen that flows into the return line 15 is at a higher temperature than the liquefied hydrogen and liquefied gas in the liquefied hydrogen tank 11, but is at an extremely low temperature (e.g., -200°C or lower) and high pressure (e.g., 20 MPaG or higher).

[0016] The pressure reducing and heating valve 16 is located in the return line 15 and is a valve that reduces the pressure of the return hydrogen obtained from the supply line 12. The pressure reducing and heating valve 16 may be composed of one valve or multiple valves. Here, the process in which high-pressure gas is reduced in pressure and expanded by the valve is isenthalpic expansion, and is called Joule-Thomson expansion. In Joule-Thomson expansion, if the pressure is higher than the inversion temperature curve, the temperature increases due to pressure reduction. Since hydrogen has a characteristic that the inversion temperature curve is in a lower temperature range than other gases such as natural gas, it is possible to utilize the fact that the pressure of high-pressure, cryogenic hydrogen can be increased in temperature until it reaches the inversion temperature curve, and can be decreased to the liquefaction temperature at a pressure lower than the inversion temperature curve. The pressure reducing and heating valve 16 can increase the temperature of the return hydrogen by reducing the pressure to a pressure near the inversion temperature curve.

[0017] The heat exchanger 17 is a device that cools the return hydrogen. The heat exchanger 17 is located across a portion of the supply line 12 downstream of the portion to which the return line 15 is connected and upstream of the heater 14, and a portion of the return line 15 downstream of the pressure reducing and heating valve 16. The heat exchanger 17 cools the return hydrogen by exchanging heat between the return hydrogen and the supply hydrogen. That is, the return hydrogen is cooled using the supply hydrogen as a refrigerant. Note that since the return hydrogen has been heated by the pressure reducing and heating valve 16, the temperature of the return hydrogen at the inlet of the heat exchanger 17 is higher than the temperature of the supply hydrogen.

[0018] The pressure reduction liquefaction valve 18 is a valve that reduces the pressure of the return hydrogen that has passed through the heat exchanger 17 to liquefy it. The pressure reduction liquefaction valve 18 is located downstream of the heat exchanger 17 in the return line 15. The pressure reduction liquefaction valve 18 may be composed of one valve or may be composed of multiple valves. In this embodiment, the pressure of the return hydrogen at the inlet of the pressure reduction liquefaction valve 18 is close to or lower than the pressure of the inversion temperature curve, and the pressure reduction liquefaction valve 18 can reduce the temperature of the return hydrogen by reducing the pressure. Note that when the pressure of the return hydrogen at the inlet of the pressure reduction liquefaction valve 18 is higher than the pressure of the inversion temperature curve, the return hydrogen is temporarily heated by reducing the pressure of the return hydrogen, but the temperature of the return hydrogen can be reduced by further reducing the pressure.

[0019] The return hydrogen is decompressed and cooled by the pressure reducing liquefaction valve 18, so that the return hydrogen is liquefied and changes into liquefied hydrogen. Since the return hydrogen that has passed through the heat exchanger 17 is cooled by the supplied hydrogen, the proportion of the return hydrogen that is liquefied by the pressure reducing liquefaction valve 18 increases. As a result, the hydrogen fuel supply system 100 according to this embodiment can liquefy the return hydrogen without using a refrigerator. However, the hydrogen fuel supply system 100 may be provided with a refrigerator that cools the return hydrogen. Even in this case, since the return hydrogen is cooled by the supplied hydrogen, a refrigerator with a large capacity is not required to liquefy the return hydrogen. Therefore, the hydrogen fuel supply system 100 according to this embodiment can omit the refrigerator or reduce the size of the refrigerator.

[0020] <Summary> A 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 and a hydrogen fuel engine and supplying hydrogen gas to the hydrogen fuel engine; a pressure reduction and heating valve located on the supply line for reducing the pressure of return hydrogen that has flowed into the return line from among the hydrogen pressurized by the pressure reduction pump to a pressure near the inversion temperature curve, thereby raising the temperature; a heat exchanger located astride the supply line and the return line for cooling the return hydrogen that has been heated by the pressure reduction and heating valve using as a refrigerant supply hydrogen that is supplied to the hydrogen fuel engine from among the hydrogen pressurized by the pressure reduction pump; and a pressure reduction and liquefaction valve located on the return line for reducing the pressure of the return hydrogen that has passed through the heat exchanger, thereby changing it into liquefied hydrogen.

[0021] According to this configuration, it is possible to omit or reduce the size of a refrigerator for liquefying hydrogen to be returned to the liquefied hydrogen tank.

[0022] A second item disclosed in this specification is a method for liquefying hydrogen, which comprises splitting pressurized hydrogen into first hydrogen and second hydrogen, reducing the pressure of the first hydrogen to a pressure near the inversion temperature curve and raising the temperature of the first hydrogen, cooling the heated first hydrogen by heat exchange with the second hydrogen, and further reducing the pressure of the cooled first hydrogen to convert it into liquefied hydrogen.

[0023] In the embodiment, the "return hydrogen" and the "supplied hydrogen" correspond to the "first hydrogen" and the "second hydrogen" in the second item, respectively. According to the above method, it is possible to omit or downsize a refrigerator for liquefying the first hydrogen. [Explanation of symbols]

[0024] 11 Liquefied hydrogen tank 12 Supply Line 13 Pressure pump 14 Heater 15 Return Line 16 Pressure reducing and heating valve 17 Heat exchanger 18 Pressure reducing liquefaction valve 21 Liquid phase 22 Gas phase section 100 Hydrogen Fuel Supply System 101 Hydrogen fuel engine

Claims

1. a liquefied hydrogen tank for storing liquefied hydrogen; a supply line connecting the liquefied hydrogen tank and a hydrogen fuel engine and supplying hydrogen gas to the hydrogen fuel engine; a pressure pump located in the supply line and configured to pressurize the liquefied hydrogen to a critical pressure or higher; a return line connecting a portion of the supply line downstream of the pressure pump and the liquefied hydrogen tank; a pressure reducing and heating valve located in the return line for reducing the pressure of the return hydrogen that has flowed into the return line among the hydrogen pressurized by the pressure pump to a pressure near an inversion temperature curve, thereby heating the return hydrogen; a heat exchanger located between the supply line and the return line, for cooling the return hydrogen heated by the pressure reducing and heating valve using hydrogen pressurized by the pressure increasing pump and supplied to the hydrogen fuel engine as a refrigerant; a pressure reduction and liquefaction valve located in the return line for reducing the pressure of the return hydrogen that has passed through the heat exchanger to convert it into liquefied hydrogen.

2. A method for liquefying hydrogen, comprising: dividing pressurized hydrogen into first hydrogen and second hydrogen; reducing the pressure of the first hydrogen to a pressure near an inversion temperature curve pressure to raise its temperature; cooling the heated first hydrogen by heat exchange with the second hydrogen; and further reducing the pressure of the cooled first hydrogen to convert it into liquefied hydrogen.

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