EQUIPMENT FOR MANUFACTURING LIQUID HYDROGEN

Abstract

An equipment for manufacturing liquid hydrogen according to the present disclosure, which is configured to perform the first isothermal process, the first isobaric process, the isenthalpic process, the second isothermal process, and the second isobaric process in the diagram of temperature T and enthalphy S for liquefying gaseous hydrogen, comprises: a compressor located on a hydrogen flow path to perform the first isothermal process; a precooler and a heat exchanger which are connected to the compressor, on the hydrogen flow path, in this order to perform the first isobaric process; a Joule-Thomson valve connected to the heat exchanger, on the hydrogen flow path, to perform the isenthalpic process; a first cryocooler and second cryocoolers connected to the Joule-Thomson valve sequentially, on the hydrogen flow path, to perform the third isobaric process between the isenthalpic process and the second isothermal process; and a storage tank which is connected to the first cryocooler and the second cryocoolers to perform the second isothermal process on the hydrogen flow path.

Description

This application claims priorities to Korean Patent Applications No. 10-2019-0137821, filed on Oct. 31, 2019 and 10-2020-0139883, filed on Oct. 27, 2020, all the benefits accruing therefrom under 35 U.S.C. § 119, the disclosures of which are incorporated herein in its entirety by reference.

TECHNICAL FIELD

The present disclosure relates to an equipment for manufacturing liquid hydrogen, which repeatedly performs the precoolable Linde-Hampson cycle on a hydrogen flow path with supplying gaseous hydrogen periodically from the outside to the hydrogen flow path.

BACKGROUND

Generally, hydrogen is made from raw materials (i.e., petroleum, coal, natural gas, LPG, bio or nuclear power, etc.) for producing the same at the production site and then is transported to the place of use (i.e., filling stations, buildings, power plants, households, etc.). Here, gaseous hydrogen is stored at high pressure of 200 bar or more, but liquid hydrogen is stored at atmospheric pressure, so liquid hydrogen is more advantageous than gaseous hydrogen in terms of safety.

Since the volume of liquid hydrogen is reduced to about 1/800 when it is formed from gaseous hydrogen, liquid hydrogen has a volume energy density of 800 times compared to gaseous hydrogen at the same pressure. Therefore, the technology for liquefying gaseous hydrogen has recently attracted attention. Gaseous hydrogen is liquefied at about −253° C. (absolute temperature of 20K) under atmospheric pressure. The liquefaction of the gaseous hydrogen is performed through a liquefaction tool which repeatedly performs the precoolable Linde-Hampson cycle.

The precoolable Linde-Hampson cycle, as viewed from a diagram of temperature T and enthalpy S, is a cycle made up of a pseudo quadratic comprising the first isothermal process, the first isobaric process, the isenthalpic process, the second isothermal process and the second isobaric process in order.

The liquefaction tool is configured to cool raw gaseous hydrogen, which is supplied periodically, by a precooler in the precoolable Linde-Hampson cycle to get liquid hydrogen and residual gaseous hydrogen, to heat the residual gaseous hydrogen by the precooler to mix the residual gaseous hydrogen with the raw gaseous hydrogen, and to cool the mixed gaseous hydrogen again.

The term ‘precooling’ refers to a method for cooling the raw or the mixed gaseous hydrogen by a precooler between a compressor and a heat exchanger in the precoolable Linde-Hampson cycle. The pre-cooler uses liquefied natural gas to cool or heat the raw or the mixed gaseous hydrogen for heat exchanging between the raw or the mixed gaseous hydrogen and the liquefied natural gas.

However, the liquefied natural gas has a boiling point of −162° C. under atmospheric pressure, and the precoolable Linde-Hampson cycle has a limitation in sufficiently cooling the raw or the mixed gaseous hydrogen for the liquefaction of the raw or the mixed gaseous hydrogen since the gaseous hydrogen is liquefied at −253° C. under atmospheric pressure conditions.

The heat exchanger is used with the precooler to cool the raw or the mixed gaseous hydrogen, but the temperature for liquefying the gaseous hydrogen is too low to develop a liquefaction atmosphere for the raw or the mixed gaseous hydrogen. In addition, the heat exchanger is connected to a Joule-Thomson valve as seen in the Linde-Hampson cycle, and the Joule-Thomson valve is connected to a storage tank as seen in the Linde-Hampson cycle.

The Joule-Thomson valve manufactures liquid hydrogen and the residual gaseous hydrogen in the precoolable Linde-Hampson cycle and supplies the liquid hydrogen and the residual gaseous hydrogen to the storage tank. The internal atmospheric temperature of the storage tank comes from the temperature of the liquid hydrogen and the residual gaseous hydrogen. Since the internal atmospheric temperature of the storage tank is not involved in the liquefaction of residual gaseous hydrogen, the liquefaction tool requires a lot of time to obtain liquid hydrogen for domestic or industrial use from the raw or the mixed gaseous hydrogen through the precoolable Linde-Hampson cycle.

The liquefaction tool is disclosed as a prior art in Korean Laid-Open Patent Publication No. 10-2020-0109054.

SUMMARY

It is an object of the present disclosure to solve the conventional problems, and to provide a suitable equipment for manufacturing liquid hydrogen in which the precoolable Linde-Hampson cycle is carried out repeatedly when viewed from the hydrogen flow path, the cooling limitation of the precooler and the heat exchanger for gaseous hydrogen after the compressor is overcome, and the liquefaction of gaseous hydrogen is partially performed in the storage tank, thereby maximizing the amount of liquified gaseous hydrogen every cycle.

An equipment for manufacturing liquid hydrogen according to the present disclosure, which is configured to perform the first isothermal process, the first isobaric process, the isenthalpic process, the second isothermal process, and the second isobaric process in the diagram of temperature T and enthalphy S for liquefying gaseous hydrogen, comprises: a compressor located on a hydrogen flow path to perform the first isothermal process; a precooler and a heat exchanger which are connected to the compressor, on the hydrogen flow path, in this order to perform the first isobaric process; a Joule-Thomson valve connected to the heat exchanger, on the hydrogen flow path, to perform the isenthalpic process; a first cryocooler and second cryocoolers, which are connected to the Joule-Thomson valve, on the hydrogen flow path in this order, to perform the third isobaric process between the isenthalpic process and the second isothermal process; and a storage tank which is connected to the first cryocooler and the second cryocoolers to perform the second isothermal process, on the hydrogen flow path, wherein the third isobaric process connects the isenthalpic process and the second isothermal process therebetween in the diagram of temperature T and enthalphy S.

Preferably, the compressor mixes and compresses internal gaseous hydrogen and external gaseous hydrogen to produce circulating gaseous hydrogen while maintaining the highest temperature in the diagram when the first isothermal process is performed, the internal gaseous hydrogen having absolute temperature of 300K and pressure range of 2 bar to 4 bar is supplied from the precooler, and the external gaseous hydrogen having absolute temperature of 300K and pressure of 60 bar is periodically supplied to the compressor from the outside.

Preferably, the circulating gaseous hydrogen has absolute temperature of 300K and pressure range of 40 bar to 80 bar at the output end of the compressor.

Preferably, the precooler and the heat exchanger gradually lower the temperature of the circulating gaseous hydrogen from the compressor in this order to produce the 1^st and the 2^nd low-temperature gaseous hydrogens when the first isobaric process is performed.

Preferably, the precooler operates at the initial stage of the first isobaric process to receive the circulating gaseous hydrogen from the compressor and let the circulating gaseous hydrogen and the liquefied natural gas be heat-exchanged to produce the 1^st low-temperature gaseous hydrogen from the circulating gaseous hydrogen.

Preferably, the 1^st low-temperature gaseous hydrogen has absolute temperature range of 77K to 80K and pressure range of 40 bar to 80 bar at the output end of the precooler.

Preferably, the heat exchanger operates at the final stage of the first isobaric process to receive the 1^st low-temperature gaseous hydrogen from the pre-cooler and cools the 1^st low-temperature gaseous hydrogen to produce the 2^nd low-temperature gaseous hydrogen.

Preferably, the 2^nd low-temperature gaseous hydrogen has absolute temperature range of 60K to 76K and pressure range of 40 bar to 80 bar at the output end of the heat exchanger.

Preferably, the Joule-Thomson valve, when performing the isenthalpic process, receives the 2^nd low-temperature gaseous hydrogen from the heat exchanger, expands the volume of the 2^nd low-temperature gaseous hydrogen and cools the 2^nd low-temperature gaseous hydrogen to produce the 3^rd low-temperature gaseous hydrogen, and the 3^rd low-temperature gaseous hydrogen is maintained below the maximum inversion temperature at which gaseous state of the 3^rd low-temperature gaseous hydrogen is converted into liquid state.

Preferably, the 3^rd low-temperature gaseous hydrogen has absolute temperature range of 40K to 60K and pressure range of 2 bar to 4 bar at the output end of the Joule-Thomson valve.

Preferably, the first cryocooler, when performing the third isobaric process, receives the 3^rd low-temperature gaseous hydrogen from the Joule-Thomson valve, cools the 3^rd low-temperature gaseous hydrogen to produce gaseous hydrogen for storing and liquid hydrogen for storing, and supplies them to the storage tank. The gaseous hydrogen for storing can be made to have a bigger mass ratio than that of the liquid hydrogen for storing from the 3^rd low-temperature gaseous hydrogen coming from the Joule-Thomson valve.

Preferably, the gaseous hydrogen for storing and the liquid hydrogen for storing have absolute temperature range of 20K to 30K and pressure range of 2 bar to 4 bar at the output end of the first cryocooler.

Preferably, the second cryocoolers connected to the first cryocooler via the storage tank on the hydrogen flow path, receives the gaseous hydrogen for storing from the storage tank, when performing the third isobaric process, cools the gaseous hydrogen for storing to produce the 1st low-temperature gaseous hydrogen for storing, and supplies the 1^st low-temperature gaseous hydrogen for storing to the storage tank.

Preferably, the 1^st low-temperature gaseous hydrogen for storing has absolute temperature range of 10K to 20K and pressure range of 2 bar to 4 bar at the output terminals of the second cryocoolers to keep the temperature of the internal atmosphere inside the storage tank constant and is partially liquefied with a portion of the gaseous hydrogen for storing in the storage tank.

Preferably, the second isothermal process is performed such that the storage tank receives and stores the gaseous hydrogen for storing and the liquid hydrogen for storing from the first cryocooler, that the gaseous hydrogen for storing contacts with the 1^st low-temperature gaseous hydrogen for storing from the second cryocooler inside the storage tank to produce a 2^nd low-temperature gaseous hydrogen for storing on the hydrogen flow path, and that the 1^st low-temperature gaseous hydrogen for storing and the 2^nd low-temperature gaseous hydrogen for storing are mixed up to produce low-temperature gaseous hydrogen for storing at the lowest temperature along the diagram during the flow of the low-temperature gaseous hydrogen for storing from the inside toward the outside the storage tank.

Preferably, the second isobaric process is performed such that, when viewed along the hydrogen flow path, the temperature of the low-temperature gaseous hydrogen for storing from the storage tank is gradually increased by heating the low-temperature gaseous hydrogen for storing with the heat exchanger and the precooler in this order to produce gaseous hydrogen for raising the temperature and the internal gaseous hydrogen.

Preferably, the gaseous hydrogen for raising the temperature is formed by heating the low-temperature gaseous hydrogen for storing with the heat exchanger and has absolute temperature range of 140K to 150K and pressure range of 2 bar to 4 bar at the output end of the heat exchanger.

Preferably, the internal gaseous hydrogen is formed by heating the gaseous hydrogen for raising the temperature with the liquefied natural gas at the precooler and has absolute temperature of 300K and pressure range of 2 bar to 4 bar at the output end of the precooler.

In the equipment for manufacturing liquid hydrogen according to the present disclosure, in order to carry on the precoolable Linde-Hampson cycle, the precooler, the heat exchanger and the Joule-Thomson valve are sequentially arranged between the compressor and the first cryocooler, after passing the precooler, heat exchanger and the Joule-Thomson valve, the temperature of gaseous hydrogen at the output end of the Joule-Thomson is lowered below the maximum inversion temperature, thereby gaseous hydrogen in the first cryocooler is in gaseous state as well as in liquid state.

In order to carry on the precoolable Linde-Hampson cycle, a plurality of second cryocoolers connected to the storage tank after the first cryocooler are arranged to keep the internal temperature of the storage tank lower than that of the output end temperature of the first cryocooler, the Joule-Thomson valve used between the compressor and the first cryocooler make the precooler and the heat exchanger to overcome the cooling limit for gaseous hydrogen, and the second cryocoolers are used for partial liquefying gaseous hydrogen from the storage tank, which maximize the amount of liquid hydrogen.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certain preferable embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic layout diagram showing the internal structure of an equipment for manufacturing liquid hydrogen according to the present disclosure.

FIG. 2 is a block diagram schematically showing an operating order of the equipment for manufacturing liquid hydrogen of FIG. 1.

FIG. 3 is the temperature T and enthalpy S diagram showing the precoolable Linde-Thomson cycle on a hydrogen flow path in the equipment for manufacturing liquid hydrogen of FIG. 1.

DETAILED DESCRIPTION

Referring FIGS. 1 to 3, the equipment for manufacturing liquid hydrogen 100 according to the present disclosure is configured to perform the first isothermal process, the first isobaric process, the isenthalpic process, the second isothermal process, and the second isobaric process in the temperature T and enthalphy S diagram of FIG. 3 to liquefy gaseous hydrogen.

In a schematic view, the hydrogen liquefaction apparatus 100, as shown in FIG. 1 or FIG. 2, comprises a compressor 10, a precooler 30, a heat exchanger 40, a Joule-Thomson valve 50, a first cryocooler 60, a storage tank 70, and second cryocoolers 80, 90 on a hydrogen flow path.

The compressor 10 is located on the hydrogen flow path to perform the first isothermal process (a-b in FIG. 1 or FIG. 3). The precooler 30 and the heat exchanger 40 are connected to the compressor 10 on the hydrogen flow path in this order to perform the first isobaric process (b-c and c-d in FIG. 1 or FIG. 3; hereinafter referred to as ‘b-d’).

The Joule-Thomson valve 50 is connected to the heat exchanger 40 on the hydrogen flow path to perform the isenthalpic process (d-e in FIG. 1 or FIG. 3). A first cryocooler 60 and second cryocoolers 80, 90 are connected to the Joule-Thomson valve 50, on the hydrogen flow path in this order, to perform the third isobaric process (e-f and f-h in FIG. 1 or FIG. 3; hereinafter referred to as ‘e-h’) between the isenthalpic process (d-e) and the second isothermal process (h-g3 in FIG. 1 or FIG. 3).

The storage tank 70 is connected to the first cryocooler 60 and the second cryocoolers 80, 90 to perform the second isothermal process (h-g3), on the hydrogen flow path. Here, the third isobaric process (e-h) connects the isenthalpic process (d-e) and the second isothermal process (h-g3) therebetween in the diagram of FIG. 3.

In more detail, referring FIGS. 1 to 3, the compressor 10 mixes and compresses the internal gaseous hydrogen (not shown in the drawings) and external gaseous hydrogen (g1 in FIG. 1) to produce circulating gaseous hydrogen (not shown in the drawings) while maintaining the highest temperature in the diagram when the first isothermal process (a-b) is performed.

The internal gaseous hydrogen having absolute temperature of 300K and pressure range of 2 bar to 4 bar is supplied from the precooler 30. The external gaseous hydrogen g1 having absolute temperature of 300K and pressure of 60 bar is periodically supplied to the compressor 10 from the outside. The circulating gaseous hydrogen has absolute temperature of 300K and pressure range of 40 bar to 80 bar at the output end of the compressor 10.

Referring FIGS. 1 to 3, the precooler 30 and the heat exchanger 40, in this order, gradually lower the temperature of the circulating gaseous hydrogen from the compressor 10 to produce the 1^st and the 2^nd low-temperature gaseous hydrogens (not shown in the drawings) when the first isobaric process (b-d) is performed.

Here, referring FIGS. 1 to 3, the precooler 30 operates at the initial stage (b-c) of the first isobaric process (b-d) to receive the circulating gaseous hydrogen from the compressor 10 and let the circulating gaseous hydrogen and the liquefied natural gas (20 in FIG. 1) be heat-exchanged to produce the 1^st low-temperature gaseous hydrogen from the circulating gaseous hydrogen. The liquefied natural gas 20 may obtain heat from the circulating gaseous hydrogen.

The 1^st low-temperature gaseous hydrogen has absolute temperature range of 77K to 80K and pressure range of 40 bar to 80 bar at the output end of the precooler 30. Referring FIG. 1 to FIG. 3, the heat exchanger 40 operates at the final stage (c-d) of the first isobaric process (b-d) to receive the 1^st low-temperature gaseous hydrogen from the pre-cooler 30 and cools the 1^st low-temperature gaseous hydrogen to produce the 2^nd low-temperature gaseous hydrogen.

The 2^nd low-temperature gaseous hydrogen has absolute temperature range of 60K to 76K and pressure range of 40 bar to 80 bar at the output end of the heat exchanger 40. The Joule-Thomson valve 50, referring FIG. 1 to FIG. 3, operates at the isenthalpic process (d-e) to receive the 2^nd low-temperature gaseous hydrogen from the heat exchanger 40, expands the volume of the 2^nd low-temperature gaseous hydrogen and cools the 2^nd low-temperature gaseous hydrogen to produce the 3^rd low-temperature gaseous hydrogen (not shown in the drawings).

The 3^rd low-temperature gaseous hydrogen is maintained below the maximum inversion temperature at which gaseous state of the 3^rd low-temperature gaseous hydrogen is converted into liquid state. The 3^rd low-temperature gaseous hydrogen has absolute temperature range of 40K to 60K and pressure range of 2 bar to 4 bar at the output end of the Joule-Thomson valve 50.

Referring FIG. 1 to FIG. 3, the first cryocooler 60, when performing the initial stage (e-f) of the third isobaric process (e-h), receives the 3^rd low-temperature gaseous hydrogen from the Joule-Thomson valve (50), cools the 3^rd low-temperature gaseous hydrogen to produce gaseous hydrogen for storing (g2 in FIG. 1) and liquid hydrogen for storing (LH2 in FIG. 1), and supplies them to the storage tank 70. The gaseous hydrogen for storing (g2) can be made to have a bigger mass ratio than that of the liquid hydrogen for storing (LH2) from the 3^rd low-temperature gaseous hydrogen coming from the Joule-Thomson valve 50.

The gaseous hydrogen for storing g2 and the liquid hydrogen for storing LH2 have absolute temperature range of 20K to 30K and pressure range of 2 bar to 4 bar at the output end of the first cryocooler 60. Referring FIG. 1 to FIG. 3, the second cryocoolers 80 and 90 are connected to the first cryocooler 60 via the storage tank 70, when performing the final stage (f-h) of the third isobaric process (e-h), receive the gaseous hydrogen for storing g2 from the storage tank 70, cool the gaseous hydrogen for storing g2 to produce a 1^st low-temperature gaseous hydrogen for storing (not shown in the drawing), and supply the 1^st low-temperature gaseous hydrogen for storing to the storage tank 70.

The 1^st low-temperature gaseous hydrogen for storing has absolute temperature range of 10K to 20K and pressure range of 2 bar to 4 bar at the output terminals of the second cryocoolers 80 and 90 to keep the temperature of the internal atmosphere inside the storage tank 70 constant and is partially liquefied with a portion of the gaseous hydrogen for storing g2 in the storage tank.

Referring FIG. 1 to FIG. 3, the second isothermal process (h-g3) is performed such that the storage tank 70 receives and stores the gaseous hydrogen for storing g2 and the liquid hydrogen for storing LH2 from the first cryocooler 60, that the gaseous hydrogen for storing g2 contacts with the 1^st low-temperature gaseous hydrogen for storing from the second cryocoolers 80, 90 inside the storage tank 70 to produce a 2^nd low-temperature gaseous hydrogen for storing on the hydrogen flow path, and that the 1^st low-temperature gaseous hydrogen for storing and the 2^nd low-temperature gaseous hydrogen for storing are mixed up to produce low-temperature gaseous hydrogen for storing g3.

Referring the diagram, the second isothermal process (h-g3) is performed at the lowest temperature along the hydrogen flow path during the flow of the low-temperature gaseous hydrogen for storing g3 from the inside toward the outside the storage tank 70.

Referring FIG. 1 to FIG. 3, the second isobaric process (g3-i and i-a) is performed such that, when viewed along the hydrogen flow path, the temperature of the low-temperature gaseous hydrogen for storing g3 from the storage tank 70 is gradually increased by heating the low-temperature gaseous hydrogen for storing g3 with the heat exchanger 40 and the precooler 30 in this order to produce gaseous hydrogen for raising the temperature (not shown in the drawings) and the internal gaseous hydrogen (not shown in the drawings).

The gaseous hydrogen for raising the temperature is formed by heating the low-temperature gaseous hydrogen for storing g3 with the heat exchanger 40 and has absolute temperature range of 140K to 150K and pressure range of 2 bar to 4 bar at the output end of the heat exchanger 40. The internal gaseous hydrogen is formed by heating the gaseous hydrogen for raising the temperature with the liquefied natural gas 20 at the precooler 30 and has absolute temperature of 300K and pressure range of 2 bar to 4 bar at the output end of the precooler 30.

Claims

1. An equipment for manufacturing liquid hydrogen, which is configured to perform the first isothermal process, the first isobaric process, the isenthalpic process, the second isothermal process, and the second isobaric process in the diagram of temperature T and enthalphy S for liquefying gaseous hydrogen, comprising:

a compressor located on a hydrogen flow path to perform the first isothermal process;

a precooler and a heat exchanger which are connected to the compressor, on the hydrogen flow path, sequentially to perform the first isobaric process;

a Joule-Thomson valve connected to the heat exchanger, on the hydrogen flow path, to perform the isenthalpic process;

a first cryocooler and second cryocoolers connected to the Joule-Thomson valve, on the hydrogen flow path sequentially, to perform the third isobaric process between the isenthalpic process and the second isothermal process; and

a storage tank which is connected to the first cryocooler and the second cryocoolers to perform the second isothermal process on the hydrogen flow path,

wherein the third isobaric process connects the isenthalpic process and the second isothermal process therebetween in the diagram of temperature T and enthalphy S.

2. The equipment for manufacturing liquid hydrogen according to claim 1,

wherein the compressor mixes and compresses internal gaseous hydrogen and external gaseous hydrogen to produce circulating gaseous hydrogen while maintaining the highest temperature in the diagram when the first isothermal process is performed,

wherein the internal gaseous hydrogen which is supplied from the precooler has absolute temperature of 300K and pressure range of 2 bar to 4 bar, and

wherein the external gaseous hydrogen which is supplied to the compressor from the outside has absolute temperature of 300K and pressure of 60 bar.

3. The equipment for manufacturing liquid hydrogen according to claim 2,

wherein the circulating gaseous hydrogen has absolute temperature of 300K and pressure range of 40 bar to 80 bar at the output end of the compressor.

4. The equipment for manufacturing liquid hydrogen according to claim 1,

wherein the precooler and the heat exchanger gradually lower the temperature of the circulating gaseous hydrogen from the compressor in this order to produce the 1st and the 2nd low-temperature gaseous hydrogens when the first isobaric process is performed.

5. The equipment for manufacturing liquid hydrogen according to claim 4,

wherein the precooler operates at the initial stage of the first isobaric process to receive the circulating gaseous hydrogen from the compressor and let the circulating gaseous hydrogen and liquefied natural gas be heat-exchanged to produce the 1st low-temperature gaseous hydrogen from the circulating gaseous hydrogen.

6. The equipment for manufacturing liquid hydrogen according to claim 5,

wherein the 1st low-temperature gaseous hydrogen has absolute temperature range of 77K to 80K and pressure range of 40 bar to 80 bar at the output end of the precooler.

7. The equipment for manufacturing liquid hydrogen according to claim 4,

wherein the heat exchanger operates at the final stage of the first isobaric process to receive the 1st low-temperature gaseous hydrogen from the precooler and cools the 1st low-temperature gaseous hydrogen to produce the 2nd low-temperature gaseous hydrogen.

8. The equipment for manufacturing liquid hydrogen according to claim 7,

wherein the 2nd low-temperature gaseous hydrogen has absolute temperature range of 60K to 76K and pressure range of 40 bar to 80 bar at the output end of the heat exchanger.

9. The equipment for manufacturing liquid hydrogen according to claim 1,

wherein the Joule-Thomson valve, when performing the isenthalpic process, receives the 2nd low-temperature gaseous hydrogen from the heat exchanger, expands the volume of the 2nd low-temperature gaseous hydrogen, and cools the 2nd low-temperature gaseous hydrogen to produce the 3rd low-temperature gaseous hydrogen,

wherein the 3rd low-temperature gaseous hydrogen is maintained below the maximum inversion temperature at which gaseous state of the 3rd low-temperature gaseous hydrogen is converted into liquid state.

10. The equipment for manufacturing liquid hydrogen according to claim 9,

wherein the 3rd low-temperature gaseous hydrogen has absolute temperature range of 40K to 60K and pressure range of 2 bar to 4 bar at the output end of the Joule-Thomson valve.

11. The equipment for manufacturing liquid hydrogen according to claim 1,

wherein the first cryocooler, when performing the third isobaric process, receives the 3rd low-temperature gaseous hydrogen from the Joule-Thomson valve, cools the 3rd low-temperature gaseous hydrogen to produce gaseous hydrogen for storing and liquid hydrogen for storing, and supplies them to the storage tank, and

wherein the gaseous hydrogen for storing can be made to have a bigger mass ratio than that of the liquid hydrogen for storing from the 3rd low-temperature gaseous hydrogen coming from the Joule-Thomson valve.

12. The equipment for manufacturing liquid hydrogen according to claim 11,

wherein the gaseous hydrogen for storing and the liquid hydrogen for storing have absolute temperature range of 20K to 30K and pressure range of 2 bar to 4 bar at the output end of the first cryocooler.

13. The equipment for manufacturing liquid hydrogen according to claim 1,

wherein the second cryocoolers are connected to the first cryocooler via the storage tank on the hydrogen flow path, receives the gaseous hydrogen for storing from the storage tank, when performing the third isobaric process, cools the gaseous hydrogen for storing to produce the 1st low-temperature gaseous hydrogen for storing, and supplies the 1st low-temperature gaseous hydrogen for storing to the storage tank.

14. The equipment for manufacturing liquid hydrogen according to claim 13,

wherein the 1st low-temperature gaseous hydrogen for storing has absolute temperature range of 10K to 20K and pressure range of 2 bar to 4 bar at the output terminals of the second cryocoolers to keep the temperature of the internal atmosphere inside the storage tank constant and is partially liquefied with a portion of the gaseous hydrogen for storing in the storage tank.

15. The equipment for manufacturing liquid hydrogen according to claim 1,

wherein the second isothermal process is performed such that the storage tank receives and stores the gaseous hydrogen for storing and the liquid hydrogen for storing from the first cryocooler, that the gaseous hydrogen for storing contacts with the 1st low-temperature gaseous hydrogen for storing from the second cryocoolers inside the storage tank to produce a 2nd low-temperature gaseous hydrogen for storing on the hydrogen flow path, and that the 1st low-temperature gaseous hydrogen for storing and the 2nd low-temperature gaseous hydrogen for storing are mixed up to produce low-temperature gaseous hydrogen for storing at the lowest temperature on the diagram during the flow of the low-temperature gaseous hydrogen for storing from the inside the storage tank toward the outside the storage tank.

16. The equipment for manufacturing liquid hydrogen according to claim 1,

wherein the second isobaric process is performed such that, when viewed along the hydrogen flow path, the temperature of the low-temperature gaseous hydrogen for storing from the storage tank is gradually increased by heating the low-temperature gaseous hydrogen for storing with the heat exchanger and the precooler in this order to produce gaseous hydrogen for raising the temperature and the internal gaseous hydrogen.

17. The equipment for manufacturing liquid hydrogen according to claim 16,

wherein the gaseous hydrogen for raising the temperature is formed by heating the low-temperature gaseous hydrogen for storing with the heat exchanger and has absolute temperature range of 140K to 150K and pressure range of 2 bar to 4 bar at the output end of the heat exchanger.

18. The equipment for manufacturing liquid hydrogen according to claim 16,

wherein the internal gaseous hydrogen is formed by heating the gaseous hydrogen for raising the temperature with the liquefied natural gas at the precooler and has absolute temperature of 300K and pressure range of 2 bar to 4 bar at the output end of the precooler.