JP2025513220A - Method for producing liquefied hydrogen - Google Patents

Abstract

1. A method for liquefying hydrogen gas, comprising:
providing an initial cooling of the hydrogen by indirect heat exchange with an external refrigerant, commonly referred to as pre-cooling;
further cooling and liquefying the cooled hydrogen by heat exchange with hydrogen or helium or a mixture thereof with neon;
housing the heat exchangers necessary for said pre-cooling in a first insulated container, usually called a cold box;
housing the heat exchangers necessary for further cooling and liquefaction in a second insulated vessel or cold box;
housing the second insulated container or cold box within the volume of the first insulated container;
Includes.
[Selected figure] Figure 2

Description

The present invention relates to a method for liquefying hydrogen gas, and in particular to a method for arranging the necessary heat exchangers.

The hydrogen liquefaction process typically involves a first step, which is the pre-cooling part of the process, where the hydrogen is cooled to a temperature of about -150 to -200°C by heat exchange with an external refrigerant such as nitrogen, and a second step where the hydrogen is further cooled and liquefied by heat exchange with hydrogen or helium, both optionally mixed with neon.

To minimize heat ingress, in current practice, the heat exchangers and associated equipment required for the aforementioned second step of the process, i.e., further cooling and liquefaction, are typically housed in a vacuum insulated container, shown diagrammatically in FIG. 1 with equipment designations and stream numbering. A hydrogen stream at room temperature [1] flows into the hot passage of a first heat exchanger [A], the outlet stream [2] of which typically has a temperature of −190° C. The cooling required in the heat exchanger [A] is provided by a first refrigerant stream or streams, such as nitrogen [3], which flows through the cold passage of the heat exchanger [A] and emerges as a heated stream or streams [4]. The cooled stream [2] flows into the hot passage of a second heat exchanger [B], the outlet vapor of which [5] comprises liquefied nitrogen and has a temperature below −240° C. The necessary cooling in the second heat exchanger [B] is provided by a second refrigerant stream or streams, such as hydrogen or helium [6], which flow through the cold passages of the second heat exchanger [B] and emerge as a heated stream or streams [7].

The heat exchanger [A] is housed in a vessel or cold box [C], typically containing granular insulation such as perlite. A stream of dry inert gas [8] is introduced into vessel [C] to exclude air and moisture and is discharged to the atmosphere as stream [9]. The heat exchanger [B] is housed in a vacuum insulated vessel [D].

Due to practical difficulties in providing large vacuum insulated vessels, the type of construction shown in Figure 1 can only be used for hydrogen liquefaction capacities of about 50 tons per day. For the much larger hydrogen liquefaction plants currently under consideration, with serial capacities of up to 500 tons per day, multiple vacuum insulated heat exchangers will be required.

The present invention relates to the final stage of the hydrogen liquefaction process, particularly the process part where the fluid temperature is below -150°C.

The applicant notes that in a typical hydrogen liquefaction facility, the heat exchanger capacity, commonly referred to as UA, required for the above-mentioned first step of pre-cooling to a temperature of -150°C to -200°C is approximately five times the corresponding heat exchanger capacity for the second step of further cooling and liquefying the hydrogen. Thus, the total heat exchanger capacity required for the first step is expected to be greater than the total heat exchanger capacity required for the second step.

The invention consists of placing the heat exchangers required for the second step in an insulated containment or cold box that is placed within a larger insulated containment or cold box that also contains the heat exchangers required for the first step.

With this arrangement, the temperature difference between the ambient temperature of the second step containment, which is about -150°C, and the temperature of the liquid hydrogen product, which is -250°C, is about 100°C. This temperature difference is much smaller than the temperature difference of about 280°C between the ambient temperature and the liquid hydrogen if the second step containment were installed separately from the first step containment. As a result, the potential heat leakage into the second step containment is reduced compared to the heat leakage into the separate second step containment. The need for vacuum insulation construction of the second step containment becomes less critical, allowing the use of a conventional cold box construction.

This avoids the capacity limitations of the vacuum insulation structure that would be required to install multiple vacuum insulated heat exchangers in the coldest parts of the liquefaction process in high power plants.

The smaller inner cold box is filled with slightly higher pressure hydrogen or helium to prevent nitrogen from leaking from the surrounding larger cold box and freezing on the surfaces of the heat exchangers required in the second step.

Thus, in accordance with the main aspects of the invention (see FIG. 2 and the equipment numbers and flow numbers shown therein), there is provided a process and apparatus for liquefying hydrogen as follows, the invention comprising:
providing a first flow of hydrogen gas [11] at room temperature;
cooling the stream [11] in the hot passage of a first heat exchanger [A] having an exit steam [12] having a temperature between -150°C and -200°C;
providing a first refrigerant stream or streams [13], such as nitrogen;
passing the stream [11] through a cold passage of a first heat exchanger [A] having an outlet stream [14] at a temperature lower than that of the stream [11];
passing stream [12] through the hot passage of a second heat exchanger [B] having an outlet stream [15] comprising liquid hydrogen having a temperature below -240°C;
providing a second refrigerant stream or streams [16], such as hydrogen or helium;
passing the stream [16] through a cold passage of a second heat exchanger [B] having an outlet [17] at a lower temperature than that of stream [12];
providing a first insulated container [C] housing a first heat exchanger [A];
providing a second insulated enclosure [D] housing a second heat exchanger [B];
A step of housing the second insulating container [D] within a volume of the first insulating container [C];
providing a nitrogen gas flow [18];
passing stream [18] through the volume of said first insulated vessel [C] to sweep out air and moisture in the outlet stream [19];
providing a flow of hydrogen or helium gas [20];
passing stream [20] through the volume of said second insulated vessel [D] to sweep out the nitrogen in outlet stream [21];
providing a valve [E] having an inlet flow [21] and an outlet flow [22];
adjusting valve [E] to maintain the pressure of stream [21] at a level higher than the pressure of stream [19];
Includes.

The insulated containers [C] and [D] typically contain a granular insulating material such as perlite.

Optionally, the state of the stream [15] may be a gas state with a temperature below -200°C.

Claims (6)

1. A method for liquefying hydrogen gas, comprising:
providing a flow of room temperature hydrogen gas [11];
cooling the stream [11] in the hot passage of a first heat exchanger [A] having an exit steam [12] having a temperature between -150°C and -200°C;
providing a first refrigerant flow [13], such as nitrogen;
passing stream [13] through a cold passage of a first heat exchanger [A] having an outlet stream [14] at a lower temperature than that of stream [11];
passing stream [12] through the hot passage of a second heat exchanger [B] having an outlet stream [15] comprising liquid hydrogen having a temperature below -240°C;
providing a second refrigerant flow [16], such as hydrogen or helium;
passing stream [16] through a cold passage of said heat exchanger [B] having an outlet stream [17] at a temperature lower than that of stream [12];
providing a first insulated container [C] housing a first heat exchanger [A];
providing a second insulated enclosure [D] housing a second heat exchanger [B];
A step of housing the second insulating container [D] within a volume of the first insulating container [C];
The method according to claim 1, further comprising: 10. The method of claim 1 ,
providing a nitrogen gas flow [18];
passing said stream [18] through the volume of the first insulated vessel [C] to sweep out air and moisture in the outlet stream [19];
The method according to claim 1, further comprising: The method according to claim 1 or 2,
providing a flow of hydrogen or helium gas [20];
passing said stream [20] through the volume of said second insulated vessel [D] to sweep out the nitrogen in outlet stream [21];
The method according to claim 1, further comprising: 4. The method of claim 3,
providing a valve [E] having an inlet flow [21] and an outlet flow [22];
adjusting valve [E] to maintain the pressure of stream [21] at a level higher than the pressure of stream [19];
The method according to claim 1, further comprising: The method according to any one of claims 1 to 4,
4. The process of claim 3, wherein the hydrogen of stream [15] is in gaseous state and at a temperature below −200° C. The method according to any one of claims 1 to 5,
The method according to claim 1, wherein either or both of said insulating containers [C], [D] comprise a particulate insulating material such as perlite.

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