Facility and method for liquefying a fluid

Abstract

The invention relates to a facility and method for liquefying a fluid, in particular hydrogen, helium or neon. The facility (1) comprises a circuit (2) of fluid to be liquefied, a first refrigerator (4), and a separate cryogenic fluid source (51). A first pre-cooling circuit (5) is connected to the source (51). A first heat exchange system (6, 61, 62) brings the main circuit (4), the circuit (2) of fluid to be liquefied, and the first pre-cooling circuit (5) into thermal contact with one another. A second heat exchange system (7) allows heat to be exchanged between the fluid circuit (2) and the first refrigerator (4). A second pre-cooling circuit (8) is connected to the source (51), with a system (81) for lowering the temperature of the fluid. A third heat exchange system (9) allows heat to be exchanged between the circuit (2) of fluid to be liquefied and the second pre-cooling circuit (8).

Description

Installation and process for liquefying a fluid

[0001] The present invention relates to an installation and a method for liquefying a fluid. The proposed solution is advantageously applicable, in particular, to the liquefaction of fluids such as hydrogen, helium, or neon.

[0002] A fluid circulating in a liquefiable fluid circuit can be liquefied by cooling it from ambient temperature to its liquefaction temperature through heat exchange between the fluid circuit and one or more cryogenic refrigeration cycles. Typically, the cooling takes place in several stages, including one or more pre-cooling stages and a final (or main) cooling or liquefaction stage.

[0003] When the fluid to be liquefied is hydrogen or helium, it is known, for example from US4530744, to include an initial pre-cooling stage by heat exchange with liquid nitrogen. Such pre-cooling is implemented, for example, using a liquid nitrogen storage tank or a dedicated refrigeration cycle. In this case, the temperature of the fluid to be liquefied after the pre-cooling stage is typically between 75 K and 85 K. The cooling power required to cool the fluid to its liquefaction temperature must be supplied by the main, less energy-efficient refrigeration cycle.

[0004] As an alternative to, or in addition to, liquid nitrogen pre-cooling, a pre-cooling cycle using a mixed refrigerant containing a hydrocarbon mixture, also known as a mixed refrigerant (MR) cycle, is still used. This type of cycle can achieve temperatures between 90 K and 120 K, which still relies on the main refrigeration or liquefaction cycle to provide the necessary cooling power for the final temperature reduction. Again, the main cycle is less thermally efficient. Furthermore, the refrigerants used in MR cycles are highly flammable, even explosive, which creates industrial hazards and necessitates the implementation of explosive atmosphere prevention measures (ATEX).

[0005] In these known solutions, and in particular when the fluid to be liquefied is hydrogen (liquefaction temperature of about 20 K) or helium (liquefaction temperature of about 4 K), the main cycle must therefore guarantee the necessary cooling power to obtain a temperature difference of several tens of K at temperatures below 80 K.

[0006] This type of device can reach consumption levels of several tens of megawatts, and its energy efficiency is difficult to optimize due to inefficiencies in the main refrigeration or liquefaction cycle.

[0007] To increase the production of liquid hydrogen, it is necessary to improve the efficiency of liquefaction processes. The present invention aims to effectively overcome these drawbacks.

[0008] According to a first aspect, the invention relates to a liquefaction installation for a fluid, in particular hydrogen, helium or neon, comprising a circuit for the fluid to be liquefied, with a first end intended to be connected to a source of the fluid to be liquefied and a second end connected to a liquefied fluid collection device, and a first refrigerator comprising a first cycle circuit and configured to subject a first cycle fluid to a thermodynamic work cycle.

[0009] The installation also includes a cryogenic fluid source, separate from the first refrigerator, such as a source of nitrogen, argon, oxygen, helium, and / or neon at cryogenic temperature.

[0010] The installation includes a first pre-cooling circuit comprising a first end connected to the cryogenic fluid source, a first heat exchange system, configured to exchange heat between the first cycle circuit, the liquefied fluid circuit and the first pre-cooling circuit; and a second heat exchange system disposed, in the liquefied fluid circuit, downstream of the first heat exchange system and configured to exchange heat between the liquefied fluid circuit and the first cycle circuit.

[0011] The installation further includes a second pre-cooling circuit with a first end connected, directly or indirectly, to the cryogenic fluid source and comprising a system for lowering the temperature of the cryogenic fluid supplied by the cryogenic fluid source, and a third heat exchange system.

[0012] The third heat exchange system is located, in the circuit of the fluid to be liquefied, between the first and second heat exchange systems.

[0013] The third heat exchange system is located in the second pre-cooling circuit, downstream of the temperature lowering system, and is configured to exchange heat between the liquefied fluid circuit and the second pre-cooling circuit.

[0014] Compared to known solutions, the invention allows for a lower temperature at which the fluid to be liquefied enters the second heat exchange system. This reduces the load on the first refrigerator and improves the system's efficiency. Indeed, greater cooling capacity is provided by the first and second pre-cooling cycles, which exhibit higher efficiencies, meaning they consume less energy for the same cooling output.

[0015] Another advantage obtained through the invention is the ability to reduce the size of the equipment and / or machines that are part of the first cycle circuit.

[0016] According to one embodiment, the cryogenic fluid source is configured to supply the cryogenic fluid at a second temperature greater than or equal to the saturation temperature of the fluid at ambient pressure, and the temperature lowering system is configured to bring the cryogenic fluid to a third temperature, lower than the saturation temperature of the cryogenic fluid at ambient pressure.

[0017] According to one embodiment, the temperature lowering system comprises, arranged in series in the second pre-cooling circuit, and connected by a set of pipes equipped with a set of valves: a first phase separator with a liquid part, intended to receive a liquid phase of the cryogenic liquid, and a gaseous part, intended to receive a gaseous phase of the cryogenic liquid, and a compression element.

[0018] The second pre-cooling circuit includes a bypass line with one end connected to the liquid part of the first phase separator and a second end connected to the gaseous part of the first phase separator.

[0019] The third heat exchange system is configured to exchange heat between the fluid circuit to be liquefied and the bypass line.

[0020] This arrangement allows, for example by using an inert gas such as nitrogen in the second pre-cooling cycle, the first phase separator to be maintained at a pressure below atmospheric pressure during operation. This improves the safety of the installation and eliminates the risks associated with explosive atmospheres.

[0021] According to one embodiment, the temperature lowering system includes an expansion device, for example a valve or a turbine, disposed, in the second pre-cooling circuit, upstream of the first phase separator.

[0022] According to one embodiment, the temperature lowering system includes a first heat exchanger comprising a first passage disposed, in the second pre-cooling circuit, upstream of the expansion member, and a second passage disposed, in the second pre-cooling circuit, between the first phase separator and the compression member.

[0023] This allows us to recover and utilize the cold from the gaseous part of the first phase separator.

[0024] According to one embodiment, the first heat exchange system is configured to exchange heat between the fluid circuit to be liquefied and the second pre-cooling circuit downstream of the compression unit.

[0025] According to one embodiment, the first heat exchange system includes a second exchanger and a third exchanger arranged in series in the cycle circuit of the first refrigerator.

[0026] The first pre-cooling circuit includes: a second phase separator connected to the source of cryogenic fluid or liquid and comprising a liquid part and a gaseous part; a liquid sampling line with a first end connected to the liquid part of the second phase separator; and a gas sampling line with a first end connected to the gaseous part of the second phase separator.

[0027] The second exchanger is in heat exchange with the gas sampling line, and the third heat exchanger is in heat exchange with the liquid sampling line.

[0028] According to one design, the liquid sampling line is in heat exchange with the second exchanger.

[0029] According to one implementation, the second end of the liquid sampling line is connected to the gas sampling line, upstream of the second exchanger.

[0030] According to one design, the first refrigerator is a Turbo-Brayton type refrigerator.

[0031] According to one design, the first refrigerator is a refrigerator of the type implementing a Claude cycle, a Linde cycle or a Brayton cycle.

[0032] According to one implementation, the cryogenic liquid source is a fixed or mobile storage of cryogenic liquid, in particular liquid nitrogen.

[0033] In one embodiment, the cryogenic fluid or liquid source is a liquefier comprising a second cycle circuit, configured to liquefy a gaseous stream and produce a cryogenic liquid stream at the second temperature. For example, this liquefier liquefies a nitrogen stream and produces a liquid nitrogen stream.

[0034] According to one embodiment, the installation includes a first ortho-para converter disposed in the circuit of fluid to be liquefied, the first heat exchange system being configured to put the circuit of fluid to be cooled in heat exchange with the first pre-cooling circuit upstream and downstream of the first ortho-para converter.

[0035] According to one embodiment, the fluid circuit to be cooled is in heat exchange with the liquid sampling line upstream and downstream of the first ortho-para converter.

[0036] According to one embodiment, the installation includes a second ortho-para converter disposed in the circuit of fluid to be liquefied, the third heat exchange system being configured to put the circuit of fluid to be cooled in heat exchange with the second pre-cooling circuit upstream and downstream of the second ortho-para converter.

[0037] According to one embodiment, the fluid circuit to be cooled is in heat exchange with the bypass pipe upstream and downstream of the ortho-para converter.

[0038] According to one embodiment, the compression element is configured to receive an inlet fluid at a temperature between 66 K and 200 K, in particular between 66 K and 90 K, for example 85 K. That is to say, the compression element is a cryogenic compression element.

[0039] This helps to improve the overall efficiency of the installation.

[0040] According to one embodiment, the compression unit is configured to receive an inlet fluid at a temperature between 270 K and 310 K, in particular 300 K.

[0041] According to one embodiment, the second pre-cooling circuit includes a second end which is connected to a vent, or to the cryogenic fluid source, or to the first pre-cooling circuit upstream of at least part of the first heat exchange system.

[0042] According to one embodiment, the second pre-cooling circuit includes a second end which is connected to the first pre-cooling circuit upstream of the second heat exchanger.

[0043] According to one embodiment, the first end of the second pre-cooling circuit is connected to the liquid part of the second phase separator.

[0044] According to a second aspect, the invention relates to a process for liquefying a fluid to be liquefied, in particular hydrogen or helium or neon.

[0045] The process uses a first refrigerator subjecting a first cycle fluid to a thermodynamic work cycle to bring the first cycle fluid to a first temperature, and a cryogenic fluid source separate from the first refrigerator and supplying the cryogenic fluid at a second temperature, higher than the first temperature.

[0046] In particular, the first temperature can be substantially equal to the liquefaction temperature of the fluid to be liquefied. Typically, the first temperature is within a range of ±5 K around the liquefaction temperature of the fluid to be liquefied, and preferably within a range of ±0.5 K around that same temperature.

[0047] The process includes the following steps.

[0048] A first step a) of cooling the fluid to be liquefied by heat exchange with a first portion of cryogenic fluid at the second temperature.

[0049] A step b) of cooling a second portion of cryogenic fluid to a third temperature, lower than the second temperature and higher than the first temperature.

[0050] A second step c) of cooling the fluid to be liquefied by heat exchange with the second portion of cryogenic fluid at the third temperature.

[0051] A third step d) of cooling the fluid to be liquefied by heat exchange with the first cycle fluid at the first temperature.

[0052] According to one implementation, the cryogenic fluid source is a cryogenic liquid source, and step b) of cooling the second portion of cryogenic fluid includes the following substeps.

[0053] A substep b1) of supplying the second portion of cryogenic fluid to a first phase separator in which a liquid phase and a vapor phase of the cryogenic fluid are formed.

[0054] A substep b2) of pumping the vapor phase of the cryogenic fluid to lower and / or maintain the vapor phase pressure at a pressure lower than the pressure at which the source supplies the cryogenic fluid, and the liquid phase temperature at the third temperature.

[0055] According to one implementation, during substep b2) the vapor phase pressure of the cryogenic fluid is lowered and / or maintained at a value below atmospheric pressure.

[0056] According to one implementation, the pressure of the second portion of cryogenic fluid is reduced a first time before substep b1) of supplying the second portion of cryogenic fluid to the first phase separator.

[0057] According to one implementation, the vapor phase of the second portion of cryogenic fluid is taken from the first phase separator and put into heat exchange with the second portion of cryogenic fluid in order to cool the second portion of cryogenic fluid.

[0058] According to one implementation, the fluid to be liquefied is hydrogen or helium, the cryogenic fluid source is a liquid nitrogen source, the second portion of cryogenic fluid is a stream of liquid nitrogen supplied by the source at a pressure between 1 and 30 bara, in particular 20 to 25 bara, and the second temperature is between 77 K and 123 K, in particular between 80 K and 85 K.

[0059] According to one implementation, the third temperature is between 64 K and 84 K, specifically between 65 K and 68 K.

[0060] According to one implementation, the fluid to be liquefied is hydrogen, and the second step c) of cooling the fluid to be liquefied includes the following substeps.

[0061] A substep c1) of cooling the fluid to be liquefied to the third temperature and obtaining a hydrogen stream having an ortho-hydrogen content of between 40% and 50%, in particular 45%.

[0062] A substep c2) of ortho-para conversion of at least a part of the hydrogen stream obtained in substep c1) and of obtaining a hydrogen stream at a fourth temperature, higher than the third temperature, and having an ortho-hydrogen content of between 20 and 40%, in particular 30%.

[0063] A substep c3) of cooling the hydrogen stream obtained in substep c2) to the third temperature.

[0064] According to one implementation, the fluid to be liquefied is hydrogen, and the first step a) of cooling the fluid to be liquefied includes the following substeps.

[0065] A substep a1) of cooling the fluid to be liquefied to the second temperature and obtaining a hydrogen stream having an ortho-hydrogen content between 50% and 75%, in particular 55%.

[0066] A substep a2) of ortho-para conversion of at least a part of the hydrogen stream obtained in substep a1) and of obtaining a hydrogen stream at a fifth temperature, higher than the second temperature, and having an ortho-hydrogen content of between 40% and 50%, in particular 45%.

[0067] A substep a3) of cooling the hydrogen stream obtained in substep a2) to the second temperature.

[0068] According to one implementation, the fifth temperature is higher than the second temperature, and lower than the second temperature plus 10 K, in particular lower than the second temperature plus 5 K, preferably lower than the second temperature plus 1 K.

[0069] According to one implementation, the fourth temperature is higher than the third temperature, and lower than the third temperature plus 10 K, in particular lower than the third temperature plus 5 K, preferably lower than the third temperature plus 1 K.

[0070] According to one implementation, the pressure reached within the first phase separator following step b2) is between 150 mbara and 900 mbara, in particular 200 mbara.

[0071] The invention may also relate to any alternative device or method comprising any combination of the above or below features, particularly within the scope of the claims.

[0072] The invention will be better understood upon reading the following description and examining the accompanying figures. These figures are given for illustrative purposes only and are in no way intended to limit the invention.

[0073] is a schematic and partial representation of an installation according to the invention.

[0074] is a schematic and partial representation of a first embodiment of the invention.

[0075] is a schematic and partial representation of a second embodiment of the invention.

[0076] is a schematic and partial representation of a third embodiment of the invention.

[0077] is a schematic and partial representation of a fourth embodiment of the invention.

[0078] According to a first aspect, and with reference to the, the invention proposes a fluid liquefaction installation 1 comprising a fluid circuit to be liquefied 2, with a first end intended to be connected to a source of fluid to be liquefied and a second end connected to a liquefied fluid collection device 3.

[0079] The fluid to be liquefied can, for example, be hydrogen, helium, or neon.

[0080] Installation 1 further includes a first refrigerator 4 comprising a first cycle circuit and configured to subject a first cycle fluid to a thermodynamic work cycle. As shown in the figures, the first refrigerator may include, in series in the cycle circuit 4, a compression section 41, a cooling section 6, 7, an expansion section 42 and a heating section 7, 6.

[0081] A cryogenic fluid source 51, separate from the first refrigerator 4, is also part of the installation 1. The source 51 can, for example, be a cryogenic liquid reservoir, or a separate installation that provides a stream of cryogenic fluid.

[0082] Typically, source 51 provides one of: liquid nitrogen, liquid argon, liquid oxygen, cryogenic temperature helium, cryogenic temperature neon, or a mixture of at least two of these fluids.

[0083] Installation 1 includes a first pre-cooling circuit 5 comprising a first end connected to the cryogenic fluid source 51. A first heat exchange system 6, 61, 62, is provided and configured to exchange heat between the first cycle circuit 4, the liquefied fluid circuit 2 and the first pre-cooling circuit 5.

[0084] A second heat exchange system 7 is provided and disposed, in the liquefied fluid circuit, downstream of the first heat exchange system 6, 61, 62 and configured to put the liquefied fluid circuit 2 and the first cycle circuit 4 into heat exchange.

[0085] Installation 1 further includes a second pre-cooling circuit 8 with a first end connected to the cryogenic fluid source 51.

[0086] The first end of the second pre-cooling circuit can be connected directly to the source 51, i.e. the cryogenic fluid supplied by the source 51 arrives at the first end of the second pre-cooling circuit 8 in substantially the same thermodynamic conditions in which it left the source 51.

[0087] The first end of the second pre-cooling circuit 8 can also be connected to the source 51 via the first pre-cooling circuit 5, i.e. the first end of the second pre-cooling circuit 8 can be connected to a pipe or element forming part of the first pre-cooling circuit, and the cryogenic fluid supplied by the source 51 reaches the first end of the second pre-cooling circuit 8 after passing through the first pre-cooling circuit 5.

[0088] In both cases the cryogenic fluid source 51 is configured to supply the cryogenic fluid at the same level of temperature and pressure, regardless of whether the cryogenic fluid is intended to circulate in the first pre-cooling circuit 5 or in the second pre-cooling circuit 8.

[0089] The second pre-cooling circuit 8 also includes a temperature reduction system 81 for the cryogenic fluid supplied by the cryogenic fluid source 51, and a third heat exchange system 9 located in the liquefied fluid circuit 2, between the first 6, 61, 62 and the second 7 heat exchange system. The third heat exchange system 9 is located in the second pre-cooling circuit 8, downstream of the temperature reduction system 81, and is configured to facilitate heat exchange between the liquefied fluid circuit 2 and the second pre-cooling circuit 8.

[0090] Thanks to this configuration, the second pre-cooling circuit allows, from the same source of cryogenic fluid 51, the fluid to be liquefied to a temperature lower than that of the source 51.

[0091] The temperature at which the fluid to be liquefied enters the second heat exchange system 7 is lowered. This reduces the load on the first refrigerator 4 and improves the efficiency of the installation 1.

[0092] Consequently, a larger portion of the cooling power required for liquefaction is supplied by the first and second pre-cooling cycles. These cycles consume less energy for the same cooling power generated.

[0093] The invention retains the advantages of proven pre-cooling solutions using inert gases such as nitrogen, which are very easy to produce or supply. However, the invention extends the operating temperature range of known pre-cooling solutions to lower temperature ranges, thereby reducing the load on the main refrigeration or liquefaction cycle and thus optimizing the system's efficiency.

[0094] In one embodiment, the cryogenic fluid source 51 is configured to supply the cryogenic fluid at a second temperature greater than or equal to the saturation temperature of the fluid at ambient pressure, and the temperature lowering system 81 is configured to bring the cryogenic fluid to a third temperature, lower than the saturation temperature of the cryogenic fluid at ambient pressure.

[0095] It is preferable for the second temperature to be close to the saturation temperature of the cryogenic fluid at ambient pressure. For example, the second temperature could be between the saturation temperature and the saturation temperature plus 10 K.

[0096] In one embodiment, the cryogenic fluid source 51 can be a cryogenic liquid source.

[0097] In one embodiment, illustrated for example in, the temperature lowering system 81 comprises, arranged in series in the second pre-cooling circuit 8, and connected by a set of pipes fitted with a set of valves, a first phase separator 82 and a compression element 83. The first phase separator 82 comprises a liquid part, intended to receive a liquid phase of the cryogenic liquid, and a gaseous part, intended to receive a gaseous phase of the cryogenic liquid.

[0098] The second pre-cooling circuit 8 includes a bypass line 84 with a first end connected to the liquid part of the first phase separator 82 and a second end connected to the gaseous part of the first phase separator 82. The third heat exchange system 9 is configured to exchange heat between the fluid circuit to be liquefied 2 and the bypass line 84.

[0099] This installation is particularly well-suited to the use of an inert gas, such as nitrogen or the other examples mentioned above, for the second pre-cooling cycle. This increases the installation's safety. The first phase separator can operate at a pressure lower than atmospheric pressure, thus avoiding the risks associated with explosive atmospheres.

[0100] The compression unit 83 can therefore be configured to maintain the first phase separator 82 at a pressure lower than atmospheric pressure.

[0101] In one embodiment, the temperature lowering system 81 includes an expansion device 86 disposed, in the second pre-cooling circuit 8, upstream of the first phase separator 82. The expansion device 86 may in particular include or be constituted by a Joule-Thomson type valve, a turbine or a two-phase turbine.

[0102] In one embodiment, the temperature lowering system 81 includes a first heat exchanger 85 comprising a first passage disposed, in the second pre-cooling circuit 8, upstream of the expansion member 86, and a second passage disposed, in the second pre-cooling circuit 8, between the first phase separator 82 and the compression member 83.

[0103] The cryogenic fluid from the source 51 to the first phase separator 82 can thus be put in heat exchange with the cryogenic fluid leaving the first phase separator 82 towards the compression element 83. The sensible heat of the cryogenic fluid at the outlet of the first phase separator 82 is thus utilized.

[0104] In one embodiment, the first heat exchange system 61 is configured to exchange heat between the fluid circuit to be liquefied 2 and the second pre-cooling circuit 8 downstream of the compression unit 83.

[0105] In one embodiment, the first heat exchange system 6 comprises a second heat exchanger 61 and a third heat exchanger 62 arranged in series in the cycle circuit 4 of the first refrigerator. The first pre-cooling circuit 5 comprises a second phase separator 52, connected to the cryogenic liquid source 51 and comprising a liquid portion and a gaseous portion.

[0106] The first pre-cooling circuit 5 also includes a liquid sampling line 53 with a first end connected to the liquid part of the second phase separator 52, and a gas sampling line 54 with a first end connected to the gaseous part of the second phase separator 52. The second heat exchanger 61 is in heat exchange with the gas sampling line 54, and the third heat exchanger 62 is in heat exchange with the liquid sampling line 53.

[0107] When the second phase separator 52 is present, as shown for example in the figure, the first end of the second pre-cooling circuit 8 can be connected to the source 51 via the second phase separator 52. In particular, the first end of the second pre-cooling circuit 8 can be connected to the liquid section of the second phase separator 52. The second pre-cooling circuit 8 is then supplied with cryogenic liquid that is under the temperature and pressure conditions of the second phase separator 52.

[0108] When the second phase separator 52 is present, the compression member 83 can be configured so that its suction pressure is lower than the pressure prevailing in the second phase separator 52. This can, for example, be a sub-atmospheric pressure.

[0109] In one embodiment, the liquid sampling line 53 is in heat exchange with the second exchanger 61.

[0110] In one embodiment, the second end of the liquid sampling line 53 is connected to the gas sampling line 54, upstream of the second exchanger 61.

[0111] During the operation of installation 1, the cryogenic fluid circulating in the liquid sampling line 53 is in a vapor state at the outlet of the third heat exchanger 62. It can then be mixed with the gas circulating in the gas sampling line 54.

[0112] Installation 1 can be sized so that, during this mixing, the two fluids are at approximately the same temperature.

[0113] In one embodiment, the first refrigerator 4 is a Turbo-Brayton type refrigerator, in which the compression section 41 comprises at least two centrifugal compression stages and the expansion section comprises at least one centripetal expansion stage. The compression and expansion stages are driven in rotation by at least one high-speed motor. At least one of the motors is coupled to a shaft, one end of which carries a compressor wheel and the other end a turbine wheel.

[0114] The use of this type of refrigerator is particularly advantageous when the fluid to be liquefied has a liquefaction temperature of 70 K or less. This is the case, for example, for neon, hydrogen, and helium.

[0115] The actual improvement in energy efficiency will depend on the primary refrigeration cycle. This improvement is particularly significant for Turbo Brayton type cycles.

[0116] In one implementation, the first refrigerator 4 is a refrigerator implementing a Claude cycle, a Linde cycle or a Brayton cycle.

[0117] In one embodiment, the cryogenic liquid source 51 is a fixed or mobile storage of cryogenic liquid, in particular liquid nitrogen.

[0118] In one embodiment, the cryogenic liquid source 51 is a liquefier, not shown in the figures, comprising a second cycle circuit, configured to liquefy a gaseous stream and produce a cryogenic liquid stream, in particular to liquefy a nitrogen stream and produce a liquid nitrogen stream.

[0119] The second cycle circuit can be thermally integrated into the installation 1, i.e. the first heat exchange system 6, 61, 62 can be configured to put the second cycle circuit in heat exchange with the fluid circuit to be liquefied and optionally with the first cycle circuit.

[0120] Alternatively, the cryogenic liquid source 51 can be a refrigerator or a liquefier configured to subject a second cycle gas to a thermodynamic work cycle in order to cool an intermediate fluid. This intermediate fluid constitutes the cryogenic liquid supplied by the source 51.

[0121] In one embodiment, installation 1 is a hydrogen liquefaction installation, and it includes a first ortho-para converter, not shown in the figures, disposed in the liquefied fluid circuit 2. An ortho-para converter is understood to be a device designed and configured to facilitate the transition of at least part of the hydrogen molecules from the ortho-hydrogen isomer to the para-hydrogen isomer.

[0122] The first heat exchange system is configured to put the liquefied fluid circuit 2 in heat exchange with the first pre-cooling circuit 5 upstream and downstream of the first ortho-para converter. That is to say, in operation, the fluid to be liquefied is cooled twice by heat exchange with the first pre-cooling circuit 5: once before passing through the first ortho-para converter and a second time after passing through the first ortho-para converter.

[0123] In one embodiment, the liquefied fluid circuit 2 is in heat exchange with the liquid sampling line 53 upstream and downstream of the first ortho-para converter. That is to say, in operation, the fluid to be liquefied is cooled twice by heat exchange with the liquid sampling line 53: once before passing through the first ortho-para converter and a second time after passing through the first ortho-para converter.

[0124] In one embodiment, installation 1 includes a second ortho-para converter, not shown in the figures, located in the liquefied fluid circuit 2. The third heat exchange system is configured to connect the liquefied fluid circuit 2 to the second pre-cooling circuit 8, both upstream and downstream of the second ortho-para converter. This means that, during operation, the liquefied fluid is cooled twice by heat exchange with the second pre-cooling circuit 8: once before passing through the second ortho-para converter and a second time after passing through it.

[0125] In one embodiment, the liquefied fluid circuit 2 is in heat exchange with the bypass line 84 upstream and downstream of the ortho-para converter. That is to say, in operation, the liquefied fluid is cooled twice by heat exchange with the bypass line 84: once before passing through the second ortho-para converter and a second time after passing through the second ortho-para converter.

[0126] In one embodiment, represented for example by enet, the compression element 83 is configured to receive an inlet fluid at a temperature between 66 K and 200 K, specifically between 66 K and 90 K, for example 85 K. That is to say, the compression element is a cryogenic compression element. This improves the overall efficiency of the installation 1.

[0127] In one embodiment, represented for example in the figure, the compression element 83 is configured to receive an inlet fluid at a temperature between 270 K and 310 K, specifically 300 K. That is to say, the compression element is an ambient temperature compression element. This simplifies the installation.

[0128] In one embodiment, as represented for example in, the second pre-cooling circuit 8 includes a second end which is connected to a vent, or to the cryogenic fluid source 51, or to the first pre-cooling circuit 5 upstream of at least part of the first heat exchange system 6, 61.

[0129] In one embodiment, represented for example in, the second end of the second pre-cooling circuit 8 is connected to the first pre-cooling circuit 5 upstream of the second heat exchanger 61.

[0130] According to a second aspect, the invention proposes a method for liquefying a fluid to be liquefied 2, in particular hydrogen, helium, or neon. The method uses a first refrigerator 4 subjecting a first cycle fluid to a thermodynamic work cycle to bring the first cycle fluid to a temperature, and a cryogenic fluid source 51 separate from the first refrigerator 4 and supplying the cryogenic fluid at a second temperature, higher than the first temperature.

[0131] The first temperature is preferably approximately equal to the liquefaction temperature of the fluid to be liquefied. Typically, the first temperature is within a range of plus or minus 5 K around the liquefaction temperature of the fluid to be liquefied, and preferably within a range of plus or minus 0.5 K.

[0132] When the fluid to be liquefied is hydrogen, the first temperature is typically between the liquefaction temperature of hydrogen and that temperature plus 5 K, preferably between the liquefaction temperature of hydrogen and that temperature plus 0.5 K.

[0133] The method according to the invention comprises the following steps.

[0134] A first step a) of cooling the fluid to be liquefied 2 by heat exchange with a first portion of cryogenic fluid 51 at the second temperature.

[0135] A step b) of cooling a second portion of cryogenic fluid 51 to a third temperature, lower than the second temperature and higher than the first temperature.

[0136] A second step c) of cooling the fluid to be liquefied 2 cooled in step a) by heat exchange with the second portion of cryogenic fluid 51 at the third temperature.

[0137] A third step d) of cooling the fluid to be liquefied 2 cooled in step c) by heat exchange with the first cycle fluid at the first temperature.

[0138] In one implementation, the second temperature is greater than or equal to the saturation temperature of the cryogenic fluid at ambient pressure, and the third temperature is less than the saturation temperature of the cryogenic fluid at ambient pressure.

[0139] The second temperature can, for example, be between the saturation temperature and the saturation temperature plus 10 K. The first and / or second portion of cryogenic fluid 51 can be supplied in the liquid state.

[0140] The first and second portions of cryogenic fluid 51 can be two distinct portions of cryogenic fluid supplied by the source 51 under the same thermodynamic conditions. That is to say, the first and second portions of cryogenic fluid 51 can be at the same temperature and pressure when supplied by the source 51.

[0141] Alternatively, the second portion of cryogenic fluid can be formed from a portion of the first portion. For example, the first portion can be supplied in a gaseous state at a temperature close to its saturation temperature and then at least partially liquefied. A portion of the liquefied first portion can then form the second portion. In this example, the first portion is supplied in a gaseous state, and the second portion is supplied in a liquid state.

[0142] In all cases, there is no need for source 51 to supply the cryogenic fluid at a plurality of temperature and / or pressure levels.

[0143] In an implementation, step b) includes the following substeps.

[0144] A substep b1) of supplying the second portion of cryogenic fluid to a first phase separator 82 in which a liquid phase and a vapor phase of the cryogenic fluid are formed.

[0145] A substep b2) of pumping the vapor phase of the cryogenic fluid into the first phase separator 82 to lower and / or maintain the vapor phase pressure at a pressure lower than the pressure at which the source 51 supplies the cryogenic fluid, and the liquid phase temperature at the third temperature.

[0146] When a second phase separator 52 is present, substep b2) aims to lower and / or maintain the vapor phase pressure at a pressure lower than the pressure prevailing in the second phase separator 52.

[0147] The pressure reached within the first phase separator 82 following step b2) may in particular be a sub-atmospheric pressure.

[0148] In one implementation, the pressure of the second portion of cryogenic fluid is reduced once before substep b1.

[0149] In one implementation, the vapor phase of the second portion of cryogenic fluid is taken from the first phase separator 82 and put into heat exchange with the second portion of cryogenic fluid in order to cool the second portion of cryogenic fluid, before introducing the second portion of cryogenic fluid into the first phase separator 82.

[0150] In one implementation, the fluid to be liquefied 2 is hydrogen or helium, the cryogenic fluid source 51 is a liquid nitrogen source, the second portion of cryogenic fluid is a stream of liquid nitrogen supplied by the source 51 at a pressure between 1 and 30 bara, in particular 20 to 25 bar, and the second temperature is between 77 K and 123 K, in particular between 80 K and 85 K.

[0151] The initial temperature is typically between 18 K and 22 K, specifically 20.4 K, if the fluid to be liquefied is hydrogen. The initial temperature is typically between 3 K and 5 K, specifically 4.2 K, if the fluid to be liquefied is helium.

[0152] In one implementation, the third temperature is between 64 K and 84 K, specifically between 65 K and 68 K.

[0153] The first refrigerator 4 can thus, in a very favorable case, be limited to providing cooling power corresponding to cooling from 64 K to the liquefaction temperature. This corresponds to a gain of approximately 20 K, for which the cooling power is supplied by the cryogenic fluid source 51 and by the second pre-cooling circuit 8, with a significantly improved energy efficiency.

[0154] In one implementation, the fluid to be liquefied is hydrogen, and step c) includes the following substeps.

[0155] A substep c1) of cooling the hydrogen to be liquefied to the third temperature and obtaining a hydrogen stream having an ortho-hydrogen content of between 40 and 50%, in particular 45%.

[0156] A substep c2) of ortho-para conversion of at least a part of the hydrogen stream obtained in substep c1) and of obtaining a hydrogen stream at a fourth temperature, higher than the third temperature, and having an ortho-hydrogen content of between 20 and 40%, in particular 30%.

[0157] A substep c3) of cooling the hydrogen stream obtained in substep c2) to the third temperature.

[0158] In one implementation, the fluid to be liquefied is hydrogen, and step a) includes the following substeps.

[0159] A substep a1) of cooling the hydrogen to be liquefied to the second temperature and obtaining a hydrogen stream having an ortho-hydrogen content between 50 and 75%, in particular 55%.

[0160] A substep a2) of ortho-para conversion of at least a part of the hydrogen stream obtained in substep a1) and of obtaining a hydrogen stream at a fifth temperature, higher than the second temperature, and having an ortho-hydrogen content of between 40% and 50%, in particular 45%.

[0161] A substep a3) of cooling the hydrogen stream obtained in substep a2) to the second temperature.

[0162] In one implementation, the fifth temperature is above the second temperature and below the second temperature plus 10 K, in particular below the second temperature plus 5 K, preferably below the second temperature plus 1 K.

[0163] In one implementation, the fourth temperature is above the third temperature and below the third temperature plus 10 K, in particular below the third temperature plus 5 K, preferably below the third temperature plus 1 K.

[0164] In one implementation, the pressure reached within the first phase separator 82 following step b2) is between 150 mbar and 900 mbar, specifically 200 mbar. That is to say, the phase separator is operated at a sub-atmospheric pressure.

Claims

Installation (1) for liquefying a fluid, in particular hydrogen or helium, comprising a circuit of the fluid to be liquefied (2), with a first end intended to be connected to a source of the fluid to be liquefied and a second end connected to a liquefied fluid collection unit (3), a first refrigerator (4) comprising a first cycle circuit and configured to subject a first cycle fluid to a thermodynamic work cycle, a source of cryogenic fluid (51), separate from the first refrigerator, a first pre-cooling circuit (5) comprising a first end connected to the source of cryogenic fluid (51), a first heat exchange system (6, 61, 62), configured to exchange heat between the first cycle circuit, the circuit of the fluid to be liquefied (2) and the first pre-cooling circuit (5), a second heat exchange system (7) disposed, in the circuit of the fluid to be liquefied,downstream of the first heat exchange system (6, 61, 62) and configured to exchange heat between the liquefied fluid circuit (2) and the first cycle circuit (4), characterized in that it further comprises a second pre-cooling circuit (8) with a first end connected to the cryogenic fluid source (51) and comprising a temperature reduction system (81) for the cryogenic fluid supplied by the cryogenic fluid source (51), and a third heat exchange system (9) disposed, in the liquefied fluid circuit (2), between the first (6, 61, 62) and the second (7) heat exchange system, the third heat exchange system (9) being disposed, in the second pre-cooling circuit (8), downstream of the temperature reduction system (81) and being configured to exchange heat between the liquefied fluid circuit (2) and the second cycle circuit (4). pre-cooling (8). Installation according to claim 1, wherein the cryogenic fluid source (51) is configured to supply the cryogenic fluid at a second temperature greater than or equal to the saturation temperature of the fluid at ambient pressure, and the temperature lowering system (81) is configured to bring the cryogenic fluid to a third temperature, lower than the saturation temperature of the cryogenic fluid at ambient pressure. An installation according to any one of claims 1 or 2, wherein the temperature lowering system (81) comprises, arranged in series in the second pre-cooling circuit (8), and connected by a set of pipes equipped with a set of valves, a first phase separator (82) with a liquid part, intended to receive a liquid phase of the cryogenic liquid, and a gaseous part, intended to receive a gaseous phase of the cryogenic liquid, and a compression member (83), the second pre-cooling circuit (8) comprising a bypass line (84) with a first end connected to the liquid part of the first phase separator (82) and a second end connected to the gaseous part of the first phase separator (82), and the third heat exchange system (9) being configured to exchange heat between the circuit of fluid to be liquefied (2) and the bypass line (84). Installation according to claim 3, wherein the compression member (83) is configured to maintain the first phase separator (82) at a pressure lower than atmospheric pressure. Installation according to any one of claims 3 or 4, wherein the temperature lowering system (81) includes an expansion device (86) disposed, in the second pre-cooling circuit (8), upstream of the first phase separator (82). Installation according to claim 5, wherein the temperature lowering system (81) comprises a first heat exchanger (85) comprising a first passage disposed, in the second pre-cooling circuit (8), upstream of the expansion member (86), and a second passage disposed, in the second pre-cooling circuit (8), between the first phase separator (82) and the compression member (83). Installation according to any one of claims 3 to 6, wherein the first heat exchange system (61) is configured to heat exchange the fluid circuit to be liquefied (2) with the second pre-cooling circuit (8) downstream of the compression unit (83). A process for liquefying a fluid to be liquefied (2), in particular hydrogen or helium, the process using a first refrigerator (4) subjecting a first cycle fluid to a thermodynamic work cycle to bring the first cycle fluid to a first temperature, and a cryogenic fluid source (51) separate from the first refrigerator (4) and supplying the cryogenic fluid at a second temperature, higher than the first temperature, the process comprising the following steps: a) a first cooling of the fluid to be liquefied (2) by heat exchange with a first portion of cryogenic fluid (51) to the second temperature; b) cooling of a second portion of cryogenic fluid (51) to a third temperature, lower than the second temperature and higher than the first temperature;c) a second cooling of the fluid to be liquefied (2) cooled in step a) by heat exchange with the second portion of cryogenic fluid (51) at the third temperature; d) a third cooling of the fluid to be liquefied (2) cooled in step c) by heat exchange with the first cycle fluid at the first temperature. A method according to claim 8, wherein the second temperature is greater than or equal to the saturation temperature of the cryogenic fluid at ambient pressure, and the third temperature is less than the saturation temperature of the cryogenic fluid at ambient pressure. A method according to any one of claims 8 or 9, wherein step b) comprises the following substeps: b1) supplying the second portion of cryogenic fluid to a first phase separator (82) in which a liquid phase and a vapor phase of the cryogenic fluid are formed; b2) pumping the vapor phase of the cryogenic fluid to lower and / or maintain the pressure of the vapor phase at a pressure lower than the pressure at which the source (51) supplies the cryogenic fluid, in particular at a pressure lower than atmospheric pressure, and the temperature of the liquid phase at the third temperature. A method according to claim 10, wherein, during substep b2) the vapor phase pressure of the cryogenic fluid is lowered and / or maintained at a value below atmospheric pressure. A method according to any one of claims 10 or 11, wherein the pressure of the second portion of cryogenic fluid is reduced a first time before substep b1). A method according to any one of claims 10 to 12, wherein the vapor phase of the second portion of cryogenic fluid is taken from the phase separator and put into heat exchange with the second portion of cryogenic fluid in order to cool the second portion of cryogenic fluid. A method according to any one of claims 9 to 13, wherein the fluid to be liquefied is hydrogen or helium, the cryogenic fluid source is a liquid nitrogen source, the second portion of cryogenic fluid is a stream of liquid nitrogen supplied by the source at a pressure between 1 bara and 30 bara, the second temperature is between 77 K and 123 K, in particular between 80 K and 85 K, and the third temperature is between 64 K and 84 K, in particular between 65 K and 68 K. A process according to any one of claims 9 to 14, wherein the fluid to be liquefied is hydrogen, and step c) comprises the following substeps: c1) cooling the fluid to be liquefied to the third temperature and obtaining a hydrogen stream having an ortho-hydrogen content of between 40 and 50%, in particular 45%; c2) ortho-para conversion of at least a portion of the hydrogen stream obtained in substep c1) and obtaining a hydrogen stream at a fourth temperature, higher than the third temperature, and having an ortho-hydrogen content of between 20 and 40%, in particular 30%; c3) cooling the hydrogen stream obtained in substep c2) to the third temperature.

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