Fluid liquefaction method and apparatus

Abstract

The present invention is an apparatus for liquefying a fluid such as hydrogen, and includes at least a part (6) of a set of heat exchangers configured to lower the temperature of the fluid to be cooled to a first temperature and a precooling system (20) in heat exchange relation therewith, and a cooling system (21) in heat exchange relation with at least a part of the set of heat exchangers (6, 7, 8, 9, 10). The cooling system (21) and the precooling system each include a refrigeration cycle refrigerator (21, 20) for a cycle gas including a compression mechanism (15, 150) and an expansion mechanism (17, 170) in a cycle circuit (14, 140). The compression mechanism includes a set of centrifugal compressors (15, 150) attached to a shaft (19, 190) rotationally driven by a set of motors (18, 180), and the expansion mechanism includes at least one turbine (17, 170) coupled to the same shaft (19) as at least one compression stage (15). The present invention relates to the apparatus.

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for liquefying a fluid such as hydrogen and / or helium.

[0002] More specifically, the present invention is an apparatus for liquefying a fluid such as hydrogen and / or helium, having an upstream end intended to be connected to a source of gaseous fluid and a downstream end intended to be connected to a member for collecting the liquefied fluid, and including a circuit for cooling the fluid. The apparatus includes a set of heat exchangers in heat exchange relationship with the circuit (3) for cooling the fluid. The apparatus includes a precooling system configured to lower the temperature of the fluid to be cooled to a first temperature, for example, included between 30 and 110 K, which is in heat exchange relationship with at least a part of the set of heat exchangers. The apparatus further includes a cooling system configured to lower the temperature of the fluid to be cooled from the first temperature to a second temperature, for example, included between 15 and 25 K, which is in heat exchange relationship with at least a part of the set of heat exchangers. The cooling system includes a first refrigerator having a refrigeration cycle operating with a first cycle gas containing helium and / or hydrogen. The first refrigerator includes a compression mechanism for compressing the cycle gas, at least one cooling member for cooling the cycle gas, an expansion mechanism for expanding the cycle gas, and at least one heating member for heating the expanded cycle gas, which are arranged in series in the cycle circuit. The compression mechanism includes a plurality of compression stages in series, which are constituted by a set of centrifugal compressors. The compression stages are attached to a shaft rotationally driven by a set of motors. The expansion mechanism includes a plurality of expansion stages constituted by a set of centripetal turbines. The present invention relates to the apparatus.

Background Art

[0003] An apparatus for liquefying cryogenic fluids, particularly hydrogen, generally includes a precooling system that uses a cryogenic source such as a liquid nitrogen storage unit or a closed or semi-closed cycle refrigerator operating with nitrogen.

[0004] The minimum pressure of the precooling cycle determines the minimum temperature (cut-off temperature) that the precooling cycle gas reaches. Thus, this low pressure of the precooling cycle is set to the lowest possible value in order to lower the cut-off temperature at the low temperature end of this precooling cycle, and thus to effectively precool the flow of the gas to be liquefied before it exchanges heat with the cycle gas of the refrigerator in which the gas to be liquefied lowers its temperature to the liquefaction temperature.

[0005] In this structure, a multistage compression station is used that includes a gearwheel or other device for improving the speed between the rotational speed supplied by a generally 50 Hz or 60 Hz electric motor and the rotational shaft that supports a plurality of compression stages that require a higher shaft rotational speed for reasons of energy efficiency. In this structure, as described below, the liquefaction process cannot be given great flexibility.

[0006] One of the known solutions is to use the so-called movable "IGV" (inlet guide vane) technology, which makes it possible to vary the gas flow rate on the intake side, typically in the first compression stage of the cycle that includes this IGV. Generally, this technology is installed only at the inlet of the first compression stage of the refrigeration cycle for cost reasons and to limit the number of moving parts that can cause failures in the entire facility. This solution is only partially satisfactory. In particular, the overall efficiency and output of the facility are not satisfactory. In particular, with this solution, the facility cannot cope with an intermittent energy supply, or if it can, the output is somewhat unsatisfactory.

[0007] Another solution is to use a refrigeration cycle operating on a mixed refrigerant ("MR"). However, with these solutions, the cut-off temperature becomes higher (a mixture of hydrocarbon and nitrogen species components results in a cut-off temperature 20 to 50 degrees higher than a pre-cooling cycle operating on pure nitrogen when mixed), and higher thermodynamic requirements are imposed on the final cooling cycle. Furthermore, if a leak occurs, the mixture that the operator has to replenish is complex for the operator to reconstitute (as it is necessary to determine the most leaked component and gradually readjust the mixture). Lowering the cut-off temperature of this cycle (typically by adding a higher proportion of nitrogen to the mixture) significantly reduces the output of this method (it decreases by about 10% when the cut-off temperature is lowered by 5K). The object of the present invention is to improve all or part of the above-mentioned drawbacks of the prior art.

Summary of the Invention

Means for Solving the Problems

[0008] For this purpose, the device according to the present invention, in other respects according to its general definition given in the above premise, essentially has at least one turbine coupled to the same shaft as at least one compression stage so as to supply the mechanical action generated during expansion to the compression stage, and the pre-cooling system includes a second refrigerator having a refrigeration cycle operating with a second cycle gas, the second refrigerator including a compression mechanism for compressing the cycle gas, which is arranged in series in the cycle circuit, at least one cooling member for cooling the cycle gas, an expansion mechanism for expanding the cycle gas, and at least one heating member for heating the expanded cycle gas, the compression mechanism including a plurality of compression stages in series, which are constituted by a set of centrifugal compressors, the compression stages being attached to a shaft rotationally driven by a set of motors, the expansion mechanism including one or more expansion stages constituted by a set of centripetal turbines, at least one of which is coupled to the same shaft as at least one compression stage so as to supply the mechanical action generated during expansion to the compression stage.

[0009] Furthermore, some embodiments of the present invention may include one or more of the following features: - The cycle gas of the second refrigerator includes at least one of nitrogen, neon, helium, hydrogen, oxygen, argon, or carbon dioxide. - The first refrigerator and the second refrigerator include respective motors of the same type and / or respective compressors of the same type, and / or respective turbines of the same type. - The first refrigerator and the second refrigerator include at least one common motor, the shaft of which is coupled to one or more of the compressors of the first refrigerator and / or one or more of the turbines, and is also coupled to one or more of the compressors of the second refrigerator and / or one or more of the turbines of the second refrigerator. - The set of motors of the first refrigerator and / or the second refrigerator includes at least one variable-speed electric motor that is controlled by an electrical signal, for example, by changing the frequency of the electrical signal. - The set of motors of the second refrigerator includes at least one variable-speed electric motor that is controlled by an electrical signal, for example, by changing the frequency of the electrical signal. The low-temperature power supplied by the second refrigerator determines a first temperature and depends on the rotational speed of the at least one motor. - The set of motors of the first refrigerator includes at least one variable-speed electric motor that is controlled by an electrical signal, for example, by changing the frequency of the electrical signal. The low-temperature power supplied by the first refrigerator determines a second temperature and depends on the rotational speed of the at least one motor. - The device includes an electronic control member for controlling at least one motor of the first refrigerator and at least one motor of the second refrigerator. The control member is configured to control the speed set values of the motors of the first and second refrigerators together. - The control member is configured to increase or decrease the speed set values of the motors of the first and second refrigerators by the same percentage.

[0010] The present invention also relates to a method for liquefying a fluid such as hydrogen and / or helium using an apparatus having any one of the above or below features, the method comprising the steps of cooling the fluid to be cooled to a first temperature, for example, included between 30 and 110 K, using a second refrigerator, and a subsequent step of cooling the fluid to be cooled from the first temperature to a second temperature, for example, included between 15 and 25 K.

[0011] According to other possible specific features: - The method includes the step of controlling the value of the first temperature by controlling at least one rotational speed of the motors of the set of motors of the second refrigerator. - The cycle circuit of the first refrigerator and the cycle circuit of the second refrigerator contain the same cycle gas and are interconnected via at least one valve.

[0012] The present invention may also relate to an alternative apparatus or method including any combination of the above or below features within the scope of the claims.

[0013] Further specific features and advantages will become apparent by reading the following description provided with reference to the drawings.

[0014] The present invention will be understood more deeply by reading the following description. The following description is provided merely by way of example and with reference to the drawings.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0016] Throughout the figures, the same reference numerals refer to the same elements.

[0017] In this detailed description, the following embodiments are examples. The "mode for carrying out the invention" refers to one or more embodiments, but this does not mean that their features are applicable only to a single embodiment. The individual features of different embodiments can be combined and / or exchanged to provide other embodiments.

[0018] The apparatus 1 shown in [Figure 1] for liquefying a fluid such as hydrogen and / or helium includes a circuit 3 for cooling the fluid, having an upstream end intended to be connected to a source 2 of gaseous fluid and a downstream end 23 intended to be connected to a member 4 for collecting the liquefied fluid.

[0019] The source 2 may include a unit (network) for distributing a gas (e.g., hydrogen) and / or a unit for producing a gas (e.g., hydrogen). The source 2 may in particular include an electrolysis device or a steam reforming unit.

[0020] The collecting member 4 may include, for example, at least one cryogenic liquid storage unit. Upstream of the storage unit 4, the circuit 3 for cooling the fluid may preferably include valves, such as an expansion valve 12 and / or an expansion turbine.

[0021] The liquefaction device 1 includes a set of heat exchangers 6, 7, 8, 9, 10 arranged in series and / or in parallel in a heat exchange relationship with the circuit 3 for cooling the fluid, and a pre-cooling system 20 in a heat exchange relationship with at least a part 6 of the set of heat exchangers.

[0022] This pre-cooling system is generally configured to lower the temperature of the fluid to be cooled to a first temperature, for example, a temperature included between 30 and 110 K, for example, up to 80 K.

[0023] The liquefaction device 1 further includes a cooling system 21 that is in a heat exchange relationship with at least a part of a set of heat exchangers 6, 7, 8, 9, 10.

[0024] This cooling system is configured to further lower the temperature of the fluid to be cooled from a first temperature to a second temperature, for example, a temperature included between 15 and 25 K, for example, 20 K, so as to be able to liquefy the fluid.

[0025] As shown, the cooling system includes a first refrigerator 21 having a refrigeration cycle that operates using a first cycle gas containing helium and / or hydrogen. This first refrigerator 21 includes a compression mechanism 15 for compressing the cycle gas, at least one cooling member for cooling the cycle gas, an expansion mechanism 17 for expanding the cycle gas, and at least one heating member for heating the expanded cycle gas, which are arranged in series within the cycle circuit 14.

[0026] That is, the first refrigerator 21 subjects the cycle gas to a thermodynamic cycle. In the thermodynamic cycle, the cycle gas at the cooling end reaches a considerably low temperature (cryogenic temperature), constitutes cryogenic power, and the cryogenic power is placed in a heat exchange relationship with the fluid to be liquefied.

[0027] The fluid to be liquefied (for example, hydrogen) is preferably a fluid different from the fluid of the cycle gas (for example, helium that may contain one or more other components in some cases).

[0028] Therefore, preferably, these two circuits are separate.

[0029] As shown, the set of heat exchangers for cooling the fluid to be liquefied preferably includes one or more countercurrent heat exchangers 6, 7, 8, 9 arranged in series, and two separate parts of the cycle circuit 14 perform circulation simultaneously in a countercurrent operation (respectively cooling and heating separate flows of the cycle gas).

[0030] That is, these plurality of countercurrent heat exchangers form both a member for cooling the cycle gas (e.g., after compression and after one or more expansion stages) and a member for heating the cycle gas (after expansion and before returning to the compression mechanism).

[0031] The compression mechanism includes a plurality of compression stages 15 in series composed of a set of centrifugal compressors 15. For example, the compression mechanism includes at least four compression stages 15 composed of a set of centrifugal compressors arranged in series (and optionally in parallel).

[0032] The compression stage 15 may be composed of an impeller wheel of a motor-driven centrifugal compressor.

[0033] The compression stage 15 (i.e., the impeller wheel of the compressor) is attached to a shaft 19 that is rotationally driven by a set of motors 18 (at least one motor).

[0034] Preferably, all compressors 15 are centrifugal.

[0035] The expansion mechanism preferably includes a plurality of expansion stages composed of a set of centripetal turbines 17, and at least one of the turbines 17 is coupled to the same shaft 19 as at least one compression stage 15 so as to supply the mechanical action generated during expansion to the compression stage 15. For example, the expansion mechanism includes three or more expansion stages formed by centripetal turbines 17 arranged at least partially in series.

[0036] Preferably, the number of compression stages (e.g., the number of compression impeller wheels) is greater than the number of expansion stages (e.g., the number of expansion turbine wheels). Preferably, all turbines 17 are centripetal and are arranged mainly in series.

[0037] The device 1 may include cooling members 8, 9 for cooling the cycle gas, which are configured to cool the cycle gas at at least one outlet of the turbine 17. That is, after expansion in the turbine 17, the cycle gas can be cooled to a value typically included between 2K and 30K.

[0038] Furthermore, at least one of the turbines 17 is coupled to the same shaft 19 as the compression stage 15 of the compressor in order to supply the mechanical action generated during expansion to the compressor.

[0039] This structure makes it possible to uncouple (isolate) the method of using the heat transfer fluid (e.g., a helium-based cycle gas) with respect to the delivery temperature of the fluid to be liquefied (e.g., hydrogen). In particular, this makes it possible to increase the value of the low-pressure level of the cycle gas in the cycle circuit 14 to a higher pressure than in known devices. This is possible even if the overall compression ratio of the cycle gas is relatively low. This centrifugal compression technique has not generally been recommended for hydrogen liquefaction in the prior art due to limitations in the compression ratio per stage.

[0040] As a result, the device 1 may include one or more motor-driven turbo compressors as part of the compression station. The motor-driven turbo compressor is an assembly including a motor whose shaft directly drives a set of compression stages (impeller wheels) and a set of expansion stages (turbines). This directly uses the mechanical expansion action in one or more compressors 15 of the cycle gas.

[0041] The precooling system 21 includes a second refrigerator 20 with a refrigeration cycle operating using a second cycle gas. This second refrigerator 20 similarly includes a compression mechanism 150 for compressing the cycle gas, at least one cooling member 160 for cooling the cycle gas, an expansion mechanism 170 for expanding the cycle gas, and at least one heating member 6 for heating the expanded cycle gas, which are arranged in series in the cycle circuit 140.

[0042] The compression mechanism includes a plurality of compression stages 150 in series, which are composed of a set of centrifugal compressors 150. The compression stage 150 is attached to a shaft 190 that is rotationally driven by a set of motors 180.

[0043] The expansion mechanism includes one or more expansion stages composed of a set of centripetal turbines 170.

[0044] Similar to the first refrigerator, at least one of the turbines 170 is coupled to the same shaft 190 as at least one of the compression stages 150 so as to supply the mechanical action generated during expansion to the compression stage 150.

[0045] That is, the first refrigerator 21 and the second refrigerator 20 preferably have the same overall structure and technology.

[0046] Due to the structure of this pre-cooling system 20, it is possible to lower the cut-off temperature of the pre-cooling system 20 compared with known devices, and the flexibility is improved.

[0047] The cycle gas of the second refrigerator 20 may include at least one of nitrogen, neon, helium, hydrogen, oxygen, argon, or carbon dioxide. Preferably, the cycle gas for this second refrigerator for performing pre-cooling is composed of, for example, a mixture of helium and neon, or helium and nitrogen. Preferably, this device uses only noble gases and / or inert gases during the cycle.

[0048] This makes it possible to reach a lower temperature (usually less than 80K) in the pre-cooling system without adversely affecting the overall output and without the risk of causing condensation or freezing of components that may dramatically affect the turbomachinery and heat exchangers in the circuit.

[0049] As shown, at least one heat exchanger 6 can be common to the following streams: circuit 3 for cooling the fluid, circuit 14 of the first refrigerator (in particular two streams: before and after compression), and circuit 140 of the second refrigerator (for example two streams: before and after expansion).

[0050] As described above, the first refrigerator 21 and the second refrigerator 20 preferably have the same overall structure and the same technology. In particular, these two refrigerators 20, 21 preferably include components that are of the same type or identical. What "identical" or "of the same type" means are components that employ the same technology (motor, turbine wheel, compressor impeller wheel, bearings, housing, etc.), but they do not necessarily have to be exactly identical. For example, components of the same type may have different sizes.

[0051] Thus, the first refrigerator 21 and the second refrigerator 20 include, for example, respective motors of the same type, and / or respective compressors of the same type, and / or respective turbines of the same type, and / or bearings (magnetic or gas) of the same type.

[0052] The two cycles 14, 140 include, for example, a centripetal turbine and a centrifugal compressor coupled to the same shaft. These components of the same type enable the sharing of components or sub-components: for example, the same electric motor, the same electric technology system for motor-compressors and motor-turbo compressors, the same wheels, the same dimensions, the same design, etc. This enables the procurement of shared parts and, in particular, reduces the number of parts of the components or members of the apparatus 1 (for example, the motor, bearings, etc. of the entire liquefaction unit).

[0053] This enables a single type of machine to be used in a single same apparatus 1 (a single same facility) for both precooling (for example from 300K to 80K) and cooling (for example between 80K and 20K). For example, only the turbines may be different.

[0054] The cryogenic components can be housed in separate thermally insulated (preferably vacuum) cryogenic boxes or in one and the same cryogenic box (e.g., having or not having independent separate volumes).

[0055] Furthermore, as schematically shown in [Figure 2], the first refrigerator 21 and the second refrigerator 20 can include a common motor 18, 180 with respect to the rotating shafts 19, 190 to which the wheels of the two refrigerators 20, 21 are coupled. For example, the shafts 19, 190 of the motors 18, 180 are coupled to at least one impeller wheel of the compressor 15 and / or the turbine wheel of the turbine 17 of the first refrigerator 21, and are also coupled to at least one impeller wheel of the compressor 150 and / or the turbine wheel of the turbine 170 of the second refrigerator 20.

[0056] Similarly, the motors of the two refrigerators 20, 21 can share common components, such as the same power supply circuit and / or the same variable speed electronics ("VFD").

[0057] Preferably, at least a part of the set of motors 18, 180 of the first and / or second refrigerators 21, 20 is a variable speed electric motor controlled by an electrical signal, for example by a frequency variation of the electrical signal.

[0058] Furthermore, the cryogenic power supplied by each refrigerator 20, 21 preferably depends on the rotational speed of one or more motors. For example, the supplied cold power is proportional to the rotational speed of the motor.

[0059] In particular, the rotational speed of one or more motors 180 of the second refrigerator 20 determines the lowest temperature (cut-off temperature) supplied by the second refrigerator 20. Thereby, the second temperature in the process for cooling and liquefying the fluid to be liquefied is determined.

[0060] As schematically shown in [[Fig. 3]], the apparatus 1 preferably includes an electronic control member 11 for controlling at least one of motors 18, 180. The electronic control device 11 includes, for example, a microprocessor or a computer or any other suitable system.

[0061] As shown, the electronic member 11 can control at least one of the motors 18 of the first refrigerator 21 and at least one of the motors 180 of the second refrigerator 20. In particular, this control member 11 can be configured to control the rotational speed set values of the motors of the first and second refrigerators 20, 21 together. That is, the control of one of the refrigerators 20 or 21 determines (depends on) the control of the other refrigerator 21 or 20.

[0062] For example, the control member 11 can be configured to increase or decrease the rotational speed set values of the motors 18, 180 of the first refrigerator 21 and the second refrigerator 20 by the same percentage.

[0063] For example, the temperature condition of the fluid to be liquefied can be controlled via the rotational speeds of the motors 18, 180. Thus, for example, if it is necessary to reduce (or increase) the rotational speed of the motor of the first refrigerator 21 by 30%, the rotational speed of the motor 20 of the second refrigerator can also be reduced (or increased) by 30%. This can be achieved by a single control set value instruction (identical or single signal).

[0064] Preferably, the precooling cycle is a closed cycle, and the cooling cycle is also a closed cycle in the same way.

[0065] In one possible variation, the two cycles can be connected via an equalizing valve (and a control system for operating the valve). This makes it possible to evenly divide the low-temperature power generated by the two refrigerators 20, 21 without changing the rotational speed of the corresponding motor.

[0066] The apparatus 1 provides considerable flexibility in the control of the low-temperature power of the precooling system 20 and the cooling system 21.

[0067] Therefore, it is possible to control and set the temperature at the junction between the two refrigerators of circuit 3 for liquefying the fluid.

[0068] Device 1 also makes it possible to increase the low-temperature generation capacity in the cooling system while maintaining the same structure, i.e., maintaining liquefied gas at a temperature lower than the nominal operating point. Specifically, it is possible to lower the cut-off temperature of the precooling system on a case-by-case basis. As a result, the heat load on the cooling system is reduced, and thus the liquefied fluid is further supercooled when it exits the liquefaction device. The cut-off temperature can be adjusted over a wider temperature range.

Claims

1. An apparatus for liquefying a fluid such as hydrogen and / or helium, comprising a circuit (3) for cooling the fluid, having an upstream end intended to be connected to a source (2) of a gaseous fluid and a downstream end (23) intended to be connected to a member (4) for collecting the liquefied fluid, the apparatus (1) comprising a set of heat exchangers (6, 7, 8, 9, 10) in heat exchange relation with the circuit (3) for cooling the fluid, the apparatus (1) comprising a precooling system (20) configured to lower the temperature of the fluid to be cooled to a first temperature included, for example, between 30 and 110 K, in heat exchange relation with at least a part (6) of the set of heat exchangers, the apparatus (1) further comprising a cooling system (21) in heat exchange relation with at least a part of the set of heat exchangers (6, 7, 8, 9, 10) and configured to lower the temperature of the fluid to be cooled from the first temperature to a second temperature included, for example, between 15 and 25 K, the cooling system (21) comprising a first refrigerator (21) having a refrigeration cycle operating with a first cycle gas containing helium and / or hydrogen, the first refrigerator (21) comprising a compression mechanism (15) for compressing the cycle gas, arranged in series in a cycle circuit (14), at least one cooling member (6, 7, 8, 9) for cooling the cycle gas, an expansion mechanism (17) for expanding the cycle gas, and at least one heating member (10, 9, 8, 7, 6) for heating the expanded cycle gas, the compression mechanism comprising a plurality of compression stages (15) in series, which are constituted by a set of centrifugal compressors (15), the compression stages (15) being attached to a shaft (19) rotationally driven by a set of motors (18), the expansion mechanism comprising a plurality of expansion stages constituted by a set of centripetal turbines (17), at least one of the turbines (17) being coupled to the same shaft (19) as at least one compression stage (15) so as to supply a mechanical action generated during expansion to the compression stage (15), the precooling system (21) comprising a second refrigerator (20) having a refrigeration cycle operating with a second cycle gas, the second refrigerator (20) comprising a compression mechanism (150) for compressing the cycle gas, arranged in series in a cycle circuit (140), andAt least one cooling member (160, 6) for cooling the cycle gas, an expansion mechanism (170) for expanding the cycle gas, and at least one heating member (6) for heating the expanded cycle gas, wherein the compression mechanism includes a plurality of compression stages (150) in series, which are constituted by a set of centrifugal compressors (150), the compression stage (150) is attached to a shaft (190) rotationally driven by a set of motors (180), the expansion mechanism includes one or more expansion stages constituted by a set of centripetal turbines (170), and at least one of them is coupled to the same shaft (190) as at least one compression stage (150) so as to supply the mechanical action generated during expansion to the compression stage (150). In the device, the set of motors (18) of the first refrigerator (21) includes at least one variable-speed electric motor controlled by an electric signal by changing the frequency of the electric signal, the low-temperature power supplied by the first refrigerator determines the second temperature and depends on the rotational speed of the at least one motor (18), the set of motors (180) of the second refrigerator (20) includes at least one variable-speed electric motor controlled by an electric signal by changing the frequency of the electric signal, the low-temperature power supplied by the second refrigerator determines the first temperature and depends on the rotational speed of the at least one motor (180). Device, characterized by the above.

2. The liquefaction device according to claim 1, wherein the cycle gas of the second refrigerator (20) contains at least one of nitrogen, neon, helium, hydrogen, oxygen, argon, or carbon dioxide.

3. The liquefaction device according to claim 1 or 2, wherein the first refrigerator (21) and the second refrigerator (20) include respective motors of the same type and / or respective compressors of the same type, and / or respective turbines of the same type.

4. The liquefaction device according to any one of claims 1 and 3, wherein the first refrigerator (21) and the second refrigerator (20) include at least one common motor (18, 180), and its shaft (19, 190) is coupled to one or more of the compressors (15) of the first refrigerator (21) and / or one or more of the turbines, and is also coupled to one or more of the compressors (150) of the second refrigerator (20) and / or one or more of the turbines (170) of the second refrigerator (20).

5. The liquefaction device according to any one of claims 1 to 4, wherein the device includes an electronic control member (11) for controlling at least one of the motors (18) of the first refrigerator (21) and at least one of the motors of the second refrigerator (20), and the control member (11) is configured to control the speed set values of the motors of the first and second refrigerators (20, 21) together.

6. The liquefaction device according to claim 5, wherein the control member (11) is configured to increase or decrease the speed set values of the motors of the first and second refrigerators (20, 21) by the same percentage.

7. A method for liquefying a fluid such as hydrogen and / or helium using the device according to any one of claims 1 to 6, the method comprising: cooling the fluid to be cooled to the first temperature included, for example, between 30 and 110 K using the second refrigerator (20); and a subsequent step of cooling the fluid to be cooled from the first temperature to the second temperature included, for example, between 15 and 25 K.

8. The liquefaction method according to claim 7, characterized in that the method includes a step of controlling the value of the first temperature by controlling at least one rotational speed of the motor of the set of motors of the second refrigerator (20).

9. The liquefaction method according to any one of claims 1 to 8, characterized in that the cycle circuits (14, 140) of the first refrigerator (21) and the second refrigerator (20) contain the same cycle gas and are interconnected via at least one valve.

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