Fluid liquefaction method and apparatus
The lack of efficiency and flexibility of existing equipment is solved by adopting a turbine-compression cascaded refrigeration cycle system and a second refrigerator in liquefied hydrogen and helium equipment, achieving lower cutoff temperatures and larger Flexibility improves the efficiency and adaptability of the liquefaction process.
Patent Information
- Application Number
- CN202380049754.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-07-08
- Filing Date
- 2023-06-20
- Publication Date
- 2025-02-14
AI Technical Summary
Existing LHG and Helium equipment has shortcomings in efficiency and flexibility, especially in poor performance during intermittent energy supply and efficient liquefaction.
The refrigeration circulation system is adopted that is connected to the turbine and compression cascade, and the refrigeration cycle is run using the second circulating gas through the second refrigerator, reducing the temperature of the fluid to be cooled, and jointly controlling the motor speed of the first and second refrigerators through the electronic control member. To improve cooling efficiency and flexibility.
Lower cutoff temperatures and greater flexibility are achieved, efficiency and adaptability of the liquefaction process are improved, and cutoff temperatures can be modified over a wider temperature range.
Smart Images
Figure CN119452224A_ABST
Abstract
Description
[0001] The present invention relates to an apparatus and a method for liquefying a fluid such as hydrogen and / or helium.
[0002] The invention relates more particularly to a device for liquefying a fluid such as hydrogen and / or helium, the device comprising a circuit for the fluid to be cooled, the circuit 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; the device comprising a set of heat exchangers, the set of heat exchangers being in heat exchange relationship with the circuit (3) for the fluid to be cooled; the device comprising a precooling system, the precooling system being in heat exchange relationship with at least a portion of the set of heat exchangers and being configured to reduce the temperature of the fluid to be cooled to a first temperature, for example, the first temperature being between 30K and 110K; the device further comprising a cooling system, the cooling system being in heat exchange relationship with at least a portion of the set of heat exchangers and being configured to reduce the temperature of the fluid to be cooled to a first temperature, for example, the first temperature being between 30K and 110K; the device further comprising a cooling system, the cooling system being in heat exchange relationship with at least a portion of the set of heat exchangers and being configured to reduce the temperature of the fluid to be cooled to a first temperature, for example, the first temperature being between 30K and 110K The temperature of the cooled fluid is reduced from a first temperature to a second temperature, for example, the second temperature is between 15K and 25K, wherein the cooling system includes a first refrigerator, which uses a first circulating gas containing helium and / or hydrogen to run a refrigeration cycle, and the first refrigerator includes: a compression mechanism for compressing the circulating gas, at least one cooling component for cooling the circulating gas, an expansion mechanism for expanding the circulating gas, and at least one heating component for heating the expanded circulating gas, which are arranged in series in a circulation loop, wherein the compression mechanism includes several compression stages in series, which are composed of a group of centrifugal compressors, which are installed on shafts driven by a group of motors, and the expansion mechanism includes several expansion stages composed of a group of centripetal turbines.
[0003] Plants for liquefying cryogenic fluids, and in particular for liquefying hydrogen, generally include a pre-cooling system using a cold source, such as a liquid nitrogen reservoir or a closed-loop or semi-closed-loop refrigerator operating on nitrogen.
[0004] The lowest pressure in the precooling cycle determines the lowest temperature (cut-off temperature) reached by the precooling cycle gas. Therefore, the low pressure of the precooling cycle is set to the lowest possible value to reduce the cut-off temperature at the cold end of the precooling cycle and thus effectively precool the gas stream to be liquefied before the gas to be liquefied exchanges heat with the circulating gas of the refrigerator, which reduces the temperature to the liquefaction temperature.
[0005] Such architectures typically employ multi-stage compression stations that include gears or other devices for increasing the speed between the speed provided by the electric motors, typically 50 Hz or 60 Hz, and the speed provided by the rotating shaft carrying the multiple compression stages, which for reasons of energy efficiency require much higher shaft rotation speeds. Such architectures do not allow for much flexibility in the liquefaction process as described below.
[0006] A known solution is to use the so-called mobile "IGV" (inlet guide vane) technology, which makes it possible to vary the gas flow rate on the inlet side, typically of the first compression stage of the cycle comprising these IGVs. Usually, for cost reasons and in order to limit the number of moving parts that could potentially cause the failure of the entire facility, this technical equipment is installed only at the inlet of the first compression stage of the relevant refrigeration cycle. This solution is only partially satisfactory. In particular, the overall efficiency and output of the facility are not satisfactory. In particular, this solution does not allow the facility to cope with intermittent energy supplies, or, if it can, with a somewhat unsatisfactory output.
[0007] Another solution is to use refrigeration cycles operating on mixed refrigerants (MR). However, these solutions provide higher cut-off temperatures (mixtures of hydrocarbon and nitrogen components, when mixed, produce cut-off temperatures 20 to 50 degrees higher than pre-cooling cycles operating on pure nitrogen), which places higher thermodynamic demands on the final cooling cycle. Moreover, in the event of a leak, the mixture that the operator has to replenish is difficult for the operator to re-formulate (since it must be determined which component or components have leaked the most and the mixture must be readjusted step by step). If the cut-off temperature of the cycle is lowered (typically by adding a higher proportion of nitrogen to the mixture), the output of the method drops significantly (on the order of 10% if the cut-off temperature is lowered by 5 K). The object of the present invention is to alleviate all or some of the above-mentioned disadvantages of the prior art.
[0008] To this end, the device according to the invention is, among other aspects, based on its general definition given in the above preamble, characterized in that at least one of the turbines is connected to the same shaft as at least one compression stage so as to supply the compression stage with the mechanical work generated during the expansion, and characterized in that the precooling system comprises a second refrigerator that runs a refrigeration cycle using a second circulating gas, the second refrigerator comprising: a compression mechanism for compressing the circulating gas, at least one cooling member for cooling the circulating gas, an expansion mechanism for expanding the circulating gas, and at least one heating member for heating the expanded circulating gas, arranged in series in a circulation loop, wherein the compression mechanism comprises several compression stages in series, which are composed of a group of centrifugal compressors, which are mounted on shafts driven in rotation by a group of motors, and the expansion mechanism comprises one or more expansion stages composed of a group of centrifugal turbines, at least one of which is connected to the same shaft as at least one compression stage so as to supply the compression stage with the mechanical work generated during the expansion.
[0009] Additionally, some embodiments of the present invention may include one or more of the following features:
[0010] - the circulating gas of the second refrigerator comprises at least one of the following: nitrogen, neon, helium, hydrogen, oxygen, argon or carbon dioxide,
[0011] - the first refrigerator and the second refrigerator comprise respective motors of the same type, and / or respective compressors of the same type, and / or respective turbines of the same type,
[0012] the first refrigerator and the second refrigerator comprise at least one common electric motor, the shaft of which is coupled to one or more of the compressors and / or one or more of the turbines of the first refrigerator and is also coupled to one or more of the compressors and / or one or more of the turbines of the second refrigerator,
[0013] the set of motors of the first refrigerator and / or the second refrigerator comprises at least one variable speed electric motor controlled by an electric signal, for example by varying the frequency of the electric signal,
[0014] the set of motors of the second refrigerator comprises at least one variable speed electric motor controlled by an electric signal, for example by varying the frequency of the electric signal, and is characterized in that the cooling power supplied by the second refrigerator determines the first temperature and depends on the rotation speed of the at least one electric motor,
[0015] the set of motors of the first refrigerator comprises at least one variable speed electric motor controlled by an electric signal, for example by varying the frequency of the electric signal, and is characterized in that the cooling power supplied by the first refrigerator determines the second temperature and depends on the rotation speed of the at least one electric motor,
[0016] the device comprises electronic control means for controlling at least one of the motors of the first refrigerator and at least one motor of the second refrigerator, the control means being configured to jointly control speed set points of the motors of the first refrigerator and the second refrigerator,
[0017] The control member is configured to increase or decrease the speed set points of the motors of the first refrigerator and the second refrigerator by the same percentage.
[0018] The present invention also relates to a method for liquefying a fluid such as hydrogen and / or helium using an apparatus having any of the features described above or below, the method comprising the step of cooling the fluid to be cooled to a first temperature, for example, between 30K and 110K, using a second refrigerator, and then cooling the fluid to be cooled from the first temperature to a second temperature, for example, between 15K and 25K.
[0019] According to other possible specific characteristics:
[0020] - the method comprises the step of controlling the value of the first temperature by controlling the speed of at least one motor of the set of motors of the second refrigerator,
[0021] The circulation circuits of the first refrigerator and the second refrigerator contain the same circulation gas and are interconnected via at least one valve.
[0022] The invention may also relate to any alternative device or method comprising any combination of the above or below features falling within the scope of the claims.
[0023] Additional unique features and advantages will become apparent from a reading of the following description provided with reference to the accompanying drawings, in which: BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The invention will be better understood from reading the following description which is given by way of example only and with reference to the accompanying drawings, in which:
[0025] [ Figure 1 ] is a partial schematic diagram showing an example of the structure and operation of an example of a liquefaction device according to the present invention,
[0026] [ Figure 2 ] is a partial schematic diagram of a detail of such a device in a variant embodiment,
[0027] [ Figure 3 ] is a partial schematic diagram of another detail of this device in another embodiment variant. DETAILED DESCRIPTION
[0028] The same reference numerals refer to the same elements throughout the drawings.
[0029] In this detailed description, the following embodiments are examples. Although the description relates to one or more embodiments, this does not mean that these features only apply to a single embodiment. The various features of different embodiments may also be combined and / or interchanged to provide other embodiments.
[0030] For liquefying fluids such as hydrogen and / or helium and in [ Figure 1 ] comprises a circuit 3 for a fluid to be cooled, 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.
[0031] The source 2 may comprise a unit (network) for distribution and / or a unit for producing a gas, such as hydrogen. The source 2 mainly comprises in particular an electrolyser or a steam reforming unit.
[0032] The connection member 4 may, for example, comprise at least one cryogenic liquid storage unit.Upstream of the storage unit 4, the circuit 3 for the fluid to be cooled preferably comprises a valve, for example an expansion valve 12 and / or an expansion turbine.
[0033] The liquefaction device 1 comprises: a group of heat exchangers 6, 7, 8, 9, 10 arranged in series and / or parallel, which are in heat exchange relationship with the circuit 3 for the fluid to be cooled; and a precooling system 20, which is in heat exchange relationship with at least a part of the group of heat exchangers 6.
[0034] The pre-cooling system is typically configured to reduce the temperature of the fluid to be cooled to a first temperature, for example between 30K and 110K, for example 80K.
[0035] The liquefaction plant 1 further comprises a cooling system 21 which is in heat exchange relationship with at least a part of the set of heat exchangers 6 , 7 , 8 , 9 , 10 .
[0036] The cooling system itself is configured to further reduce the temperature of the fluid to be cooled from the first temperature to a second temperature, for example between 15 K and 25 K, for example 20 K, to allow liquefaction of said fluid.
[0037] As shown, the cooling system includes a first refrigerator 21 having a refrigeration cycle, which operates using a first circulating gas containing helium and / or hydrogen. The first refrigerator 21 includes: a compression mechanism 15 for compressing the circulating gas, at least one cooling member for cooling the circulating gas, an expansion mechanism 17 for expanding the circulating gas, and at least one heating member for heating the expanded circulating gas, which are arranged in series in a circulating loop 14.
[0038] This means that the first refrigerator 21 subjects the circulating gas to a thermodynamic cycle in which the circulating gas at the cold end reaches a very low (cryogenic) temperature to constitute cold power which is then placed in heat exchange relationship with the fluid to be liquefied.
[0039] The fluid to be liquefied (eg hydrogen) is preferably a different fluid from the cycle gas (eg helium, possibly with one or more other components).
[0040] Preferably, the two circuits are therefore separated.
[0041] As shown, the group of one or more heat exchangers for cooling the fluid to be liquefied preferably includes one or more countercurrent heat exchangers 6, 7, 8, 9, which are arranged in series and in which two separate parts of the circulation loop 14 are circulated simultaneously in countercurrent operation (for cooling and heating separate circulating gas flows, respectively).
[0042] That is, the plurality of counter-flow heat exchangers form both a means for cooling the cycle gas (eg, after compression and after one or more expansion stages) and a means for heating the cycle gas (after expansion and before return to the compression mechanism).
[0043] The compression mechanism comprises a plurality of compression stages 15 connected in series, constituted by a set of centrifugal compressors 15. For example, the compression mechanism comprises at least four compression stages 15, constituted by a set of centrifugal compressors arranged in series (and possibly in parallel).
[0044] The compression stage 15 may be constituted by the impeller of a motorized centrifugal compressor.
[0045] The compression stage 15 (that is to say the compressor wheel) is mounted on shafts 19 which are driven in rotation by a set of electric motors 18 (at least one electric motor).
[0046] Preferably, all compressors 15 are of the centrifugal type.
[0047] The expansion mechanism preferably comprises several expansion stages formed by a set of centripetal turbines 17, wherein 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 work produced during expansion to the compression stage 15. For example, the expansion mechanism comprises three or more expansion stages formed by centripetal turbines 17 arranged at least partially in series.
[0048] Preferably, the number of compression stages (eg the number of compression impellers) is greater than the number of expansion stages (eg the number of expansion turbine impellers). Preferably, all turbines 17 are of the centripetal type and are mainly arranged in series.
[0049] The apparatus 1 may comprise cooling means 8, 9 for cooling the cycle gas and configured to cool the cycle gas at the outlet of the at least one turbine 17. That is, after expansion in the turbine 17, the cycle gas may be cooled to a value typically between 2K and 30K.
[0050] 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 compressor with the mechanical work produced during the expansion.
[0051] This architecture enables the method using a heat transfer fluid (e.g. a helium-based circulating gas) to be decoupled from (made independent of) the delivery temperature of the fluid to be liquefied (e.g. hydrogen). This makes it possible in particular to increase the value of the low pressure level of the circulating gas in the circulating loop 14 to a higher pressure than in known devices. This is possible despite a relatively low overall circulating gas compression ratio. Due to the limitations of the compression ratio per stage, this centrifugal compression technology is generally not recommended for the liquefaction of hydrogen in the prior art.
[0052] Thus, the apparatus 1 may comprise one or more motor-driven turbocompressors in a part of a compression station. A motor-driven turbocompressor is an assembly comprising a motor, the shaft of which directly drives a set of compression stages (impellers) and a set of expansion stages (turbines). This exploits mechanical expansion work directly at one or more of the compressors 15 of the circulating gas.
[0053] The pre-cooling system 21 includes a second refrigerator 20, which uses the second circulating gas to run a refrigeration cycle. The second refrigerator 20 also includes: a compression mechanism 150 for compressing the circulating gas, at least one cooling member 160 for cooling the circulating gas, an expansion mechanism 170 for expanding the circulating gas, and at least one heating member 6 for heating the expanded circulating gas, which are arranged in series in the circulating loop 140.
[0054] The compression mechanism includes a plurality of compression stages 150 connected in series, which are formed by a group of centrifugal compressors 150. The compression stages 150 are mounted on shafts 190, which are rotationally driven by a group of motors 180.
[0055] The expansion mechanism includes one or more expansion stages consisting of a set of centripetal turbines 170.
[0056] As in the case of the first refrigerator, at least one of the turbines 170 is coupled to the same shaft 190 as at least one compression stage 150 in order to supply the compression stage 150 with the mechanical work produced during expansion.
[0057] This means that the first refrigerator 21 and the second refrigerator 20 preferably have the same overall structure and technology.
[0058] This architecture of the precooling system 20 enables the cut-off temperature of the precooling system 20 to be reduced and provides greater flexibility compared to known devices.
[0059] The circulating gas of the second refrigerator 20 may include at least one of the following: nitrogen, neon, helium, hydrogen, oxygen, argon or carbon dioxide. Preferably, the circulating gas of the second refrigerator for performing precooling is composed of, for example, a mixture of helium and neon or a mixture of helium and nitrogen. Preferably, the device uses only rare gases and / or inert gases in the cycle.
[0060] This makes it possible to obtain lower temperatures (typically below 80 K) in the precooling system without adversely affecting the overall output and without causing the risk of condensation or even freezing of the components, which would have significant effects on the turbines and exchangers of the circuit.
[0061] As illustrated, at least one exchanger 6 can be common to the following flows: the circuit 3 for the fluid to be cooled, the circuit 14 of the first refrigerator (in particular two flows: after compression and before compression), and the circuit 140 of the second refrigerator (for example two flows: before expansion and after expansion).
[0062] As mentioned above, the first refrigerator 21 and the second refrigerator 20 preferably have the same overall structure and the same technology. In particular, the two refrigerators 20, 21 preferably include the same type or the same components. "The same" or "the same type" refers to components (motor, turbine impeller, compressor impeller, bearing, housing, etc.) that use the same technology but are not necessarily strictly the same. For example, components of the same type can have different sizes.
[0063] Thus, the first refrigerator 21 and the second refrigerator 20 comprise, 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 of the same type (magnetic or gas).
[0064] The two cycles 14, 140 comprise, for example, a centripetal turbine and a centrifugal compressor coupled to the same shaft. These components of the same type allow the sharing of components or subcomponents: for example, the same electric motor, the same electrical system for the motor compressor and the motor turbo compressor, the same impeller, the same size, the same design, etc. This allows the sharing of resources and makes it possible in particular to reduce the number of parts of the components or members of the device 1 (for example: motors, bearings in the entire liquefaction unit, etc.).
[0065] This allows the same device 1 (same facility) to use a single type of machine both for pre-cooling (eg from 300 K to 80 K) and for cooling (eg between 80 K and 20 K). For example, only the turbine would be different.
[0066] The cryogenic components may be housed in a separate insulated (preferably vacuum) cold box or in the same cold box (eg, with or without a separate individual volume).
[0067] In addition, and as [ Figure 2 ], the first refrigerator 21 and the second refrigerator 20 may include a common motor 18, 180, and the impellers of the two refrigerators 20, 21 are connected to the rotating shafts 19, 190 of the motor. For example, the shafts 19, 190 of the motors 18, 180 are connected to at least one impeller of the compressor 15 of the first refrigerator 21 and / or the turbine impeller of the turbine 17, and are also connected to at least one impeller of the compressor 150 of the second refrigerator 20 and / or the turbine impeller of the turbine 170.
[0068] Likewise, the motors of the two chillers 20, 21 may share common components, such as the same power circuitry and / or the same variable speed electronics ("VFD").
[0069] Preferably, at least a part of the set of motors 18, 180 of the first refrigerator 21 and / or the second refrigerator 20 is a variable speed motor controlled by an electrical signal, for example by changing the frequency of the electrical signal.
[0070] Furthermore, the cooling power supplied by each refrigerator 20, 21 is preferably dependent on the rotational speed of the motor or motors, the supplied cooling power being, for example, proportional to the rotational speed of the motors.
[0071] In particular, the rotation speed of the motor or motors 180 of the second refrigerator 20 determines the lowest temperature (cut-off temperature) supplied by the second refrigerator 20. This determines the second temperature used in the process of cooling and liquefying the fluid to be liquefied.
[0072] like[ Figure 3 ], the device 1 preferably comprises electronic control means 11 for controlling at least one motor 18, 180. The electronic controller 11 comprises, for example, a microprocessor or a computer or any other suitable system.
[0073] As shown, the electronic component 11 can control at least one of the motors 18 of the first refrigerator 21 and at least one motor 180 of the second refrigerator 20. The control component 11 can be particularly configured to jointly control the speed set points of the motors of the first refrigerator and the second refrigerator 20, 21. That is, the control of one of the refrigerators 20 or 21 determines (depends on) the control of the other refrigerator 21 or 20.
[0074] For example, the control member 11 may be configured to increase or decrease the speed set points of the motor 18 of the first refrigerator 21 and the motor 180 of the second refrigerator 20 by the same percentage.
[0075] For example, the temperature condition of the liquefied fluid can be controlled by the speed of the motor 18, 180. Thus, for example, if the speed of the motor of the first refrigerator 21 must be reduced (or increased) by 30%, the speed of the motor 20 of the second refrigerator is also reduced (or increased) by 30%. This can be achieved via a single control set point command (same or single signal).
[0076] Preferably, the pre-cooling cycle is a closed-loop cycle, and the cooling cycle is also a closed-loop cycle.
[0077] In one possible variant, the two cycles can be connected via a balancing valve (and a control system for operating the valve). This allows the cold power generated by the two refrigerators 20, 21 to be distributed without changing the speed of the corresponding motors.
[0078] The device 1 provides great flexibility in controlling the cooling power of the pre-cooling system 20 and the cooling system 21 .
[0079] Thus, the temperature at the connection between the two refrigerators in the circuit 3 can be controlled and set for the fluid to be liquefied.
[0080] The device 1 also makes it possible to increase the capacity to generate cold in the cooling system while maintaining the same architecture, i.e. the temperature of the liquefied gas is below the nominal operating point. In particular, the cut-off temperature of the pre-cooling system can be reduced on an ad hoc basis. This makes it possible to reduce the heat load on the cooling system and thus make the liquefied fluid even more subcooled when it leaves the liquefier. The cut-off temperature can be modified over a wider temperature range.
Claims
1. A device for liquefying a fluid such as hydrogen and / or helium, the device comprising a circuit (3) for the fluid to be cooled, the circuit having an upstream end intended to be connected to a source of gaseous fluid (2) and a downstream end (23) intended to be connected to a member (4) for collecting the liquefied fluid; the device (1) comprising a set of heat exchangers (6, 7, 8, 9, 10) in heat exchange relationship with the circuit (3) for the fluid to be cooled; the device (1) comprising a precooling system (20) The device (1) further comprises a cooling system (21), which is in a heat exchange relationship with at least a part of the group of heat exchangers (6) and is configured to reduce the temperature of the fluid to be cooled to a first temperature, for example, the first temperature is between 30K and 110K; the device (1) further comprises a cooling system (21), which is in a heat exchange relationship with at least a part of the group of heat exchangers (6, 7, 8, 9, 10) and is configured to reduce the temperature of the fluid to be cooled from the first temperature to a second temperature, for example, the second temperature is between 15K and 25K, wherein The cooling system (21) comprises a first refrigerator (21) which runs a refrigeration cycle using a first circulating gas containing helium and / or hydrogen, wherein the first refrigerator (21) comprises: a compression mechanism (15) for compressing the circulating gas, at least one cooling member (6, 7, 8, 9) for cooling the circulating gas, an expansion mechanism (17) for expanding the circulating gas, and at least one heating member (10, 9, 8, 7, 6) for heating the expanded circulating gas, which are arranged in series in a circulating loop (14), wherein the compression mechanism comprises a plurality of compression stages (15) connected in series, wherein the compression stages are composed of a group of centrifugal compressors (15), and the compression stages are connected in series. The precooling system (21) is characterized in that the compression stage (15) is mounted on a shaft (19) driven in rotation by a set of motors (18), the expansion mechanism includes a plurality of expansion stages consisting of a set of centripetal turbines (17), wherein at least one of the turbines (17) is connected to the same shaft (19) as at least one compression stage (15) so as to supply the compression stage (15) with the mechanical work generated during the expansion, and is characterized in that the precooling system (21) includes a second refrigerator (20) which runs a refrigeration cycle using a second circulating gas, and the second refrigerator (20) includes: a compression mechanism (150) for compressing the circulating gas, a cooling mechanism (150) for cooling the circulating gas, and a cooling mechanism (150) for cooling the circulating gas. At least one cooling member (160, 6) for circulating gas, an expansion mechanism (170) for expanding the circulating gas, and at least one heating member (6) for heating the expanded circulating gas, wherein the compression mechanism comprises a plurality of compression stages (150) connected in series, the compression stages being composed of a group of centrifugal compressors (150), the compression stages (150) being mounted on a shaft (190) driven in rotation by a group of motors (180), and the expansion mechanism comprising one or more expansion stages being composed of a group of centripetal turbines (170), at least one of the turbines being coupled to the same shaft (190) as at least one compression stage (150) so as to supply the compression stage (150) with heat. The mechanical work generated during the expansion is characterized in that the group of motors (18) of the first refrigerator (21) includes at least one variable speed motor, which is controlled by the electrical signal by changing the frequency of the electrical signal, and characterized in that the cooling power supplied by the first refrigerator determines the second temperature and depends on the rotation speed of the at least one motor (18), and the group of motors (180) of the second refrigerator (20) includes at least one variable speed motor controlled by the electrical signal by changing the frequency of the electrical signal, and characterized in that the cooling power supplied by the second refrigerator determines the first temperature and depends on the rotation speed of the at least one motor (180).
2. The liquefaction equipment according to claim 1, characterized in that: The circulating gas of the second refrigerator (20) includes at least one of the following: nitrogen, neon, helium, hydrogen, oxygen, argon or carbon dioxide.
3. The liquefaction equipment according to claim 1 or 2, characterized in that: 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 equipment according to any one of claims 1 and 3, characterized in that The first refrigerator (21) and the second refrigerator (20) include at least one common motor (18, 180), the shaft (19, 190) of the at least one motor being connected to one or more of the compressors (15) and / or one or more of the turbines of the first refrigerator (21), and also connected to one or more of the compressors (150) and / or one or more of the turbines (170) of the second refrigerator (20).
5. The liquefaction equipment according to any one of claims 1 to 4, characterized in that: The liquefaction device comprises an electronic control member (11) for controlling at least one of the motors (18) of the first refrigerator (21) and at least one motor of the second refrigerator (20), the control member (11) being configured to jointly control the speed set points of the motors of the first refrigerator and the second refrigerator (20, 21).
6. The liquefaction equipment according to claim 5, wherein: The control member (11) is configured to increase or decrease the speed set points of the motors of the first refrigerator and the second refrigerator (20, 21) by the same percentage.
7. A method for liquefying a fluid such as hydrogen and / or helium using an apparatus as described in any one of claims 1 to 6, the method comprising the step of cooling the fluid to be cooled to a first temperature, for example, between 30K and 110K, using the second refrigerator (20), and then cooling the fluid to be cooled from the first temperature to a second temperature, for example, between 15K and 25K.
8. The liquefaction method according to claim 7, characterized in that: The liquefaction method includes the step of controlling the value of the first temperature by controlling the speed of at least one motor in the set of motors (180) of the second refrigerator (20).
9. The liquefaction method according to any one of claims 1 to 8, characterized in that: The circulation circuits (14, 140) of the first refrigerator (21) and the second refrigerator (20) contain the same circulation gas and are interconnected via at least one valve.