Installation and method for refrigerating a fluid at cryogenic temperature

Abstract

The invention relates to a liquefied gas production plant comprising a feed gas supply circuit (2), a set of heat exchanger(s) (3, 4, 5, 6), a refrigerator for cooling all or part of the set of heat exchanger(s) (3, 4, 5, 6), the supply circuit (2) comprising, between the set of heat exchanger(s) (3, 4, 5, 6) and its downstream end (22), a final expansion turbine (14) for expanding the feed gas to a liquid state, the supply circuit (2) comprising a bypass line (17) from the final expansion turbine (14) equipped with a first expansion valve (15), a second expansion valve (16) arranged in series upstream or downstream of the first expansion valve (15) and the final expansion turbine (14), and a heat exchange line (61). additional configured to ensure heat exchange with a heat exchanger (6) of the assembly of exchanger(s) (3, 4, 5,6) of heat when the feed gas is expanded by the first expansion valve (15) via the bypass line (17), the additional heat exchange line (61) ensuring this heat exchange with said heat exchanger (6) between the expansion carried out by the first expansion valve (15) and the expansion carried out by the second expansion valve (16), the additional heat exchange line (61) being located upstream or, respectively, downstream of the expansion carried out by the first expansion valve (15). Abbreviated figure: Fig. 1,

Description

Title of the invention: Installation and method for refrigerating a fluid to cryogenic temperature

[0001] The invention relates to an installation and a method for refrigerating a fluid at cryogenic temperature.

[0002] The invention relates more particularly to an installation for producing cryogenic liquefied gas, for example liquefied hydrogen, comprising a supply circuit for supplying supply gas to be cooled, the supply circuit comprising an upstream end intended to be connected to a gas source and a downstream end intended to be connected to at least one cryogenic storage configured to collect and store liquefied gas, the installation comprising a set of heat exchanger(s) in heat exchange with the supply circuit, the installation comprising at least one cooling device in heat exchange with all or part of the set of heat exchanger(s), the at least one cooling device comprising a cryogenic refrigerator with a cycle gas comprising at least one of: helium, hydrogen, neon, nitrogen, oxygen or methane, the downstream end of the supply circuit comprising,between the set of heat exchanger(s) and the second end intended to be connected to the storage, a final expansion turbine configured to expand the feed gas which is in the liquid state at the inlet of said turbine, the feed circuit further comprising a bypass line of the final expansion turbine provided with a first expansion valve, preferably of the Joule Thomson type, the feed circuit comprising a second expansion valve, preferably of the Joule Thomson type arranged in series upstream or, respectively, downstream of the first expansion valve and the final expansion turbine, the feed circuit comprising an additional heat exchange line configured to ensure heat exchange with a heat exchanger of the set of heat exchanger(s) when the feed gas is expanded by the first expansion valve via the bypass line.

[0003] Producing a sub-cooled liquefied fluid makes it possible to effectively combat thermal inputs and the generation of gas resulting from the vaporization of saturated liquid ("boil-off") throughout a distribution chain. Indeed, a sub-cooled liquid subjected to parasitic thermal inputs first heats up while remaining in the liquid phase before vaporizing once the boiling point is reached.

[0004] The invention thus relates in particular to a liquefier delivering a sub-cooled liquid which may be, for example, hydrogen, helium, carbon dioxide, air, nitrogen, oxygen and / or a mixture comprising some of these. molecules. Subcooling a fluid such as liquid hydrogen is more energy-intensive than a liquefier delivering liquid at saturation because subcooling induces a temperature lower than the saturation temperature (efficiency compared to an ideal Carnot machine).

[0005] The invention relates in particular to applications such as liquefaction units where subcooled production is required. The invention relates in particular to installations for liquefying components with a liquefaction temperature below -200°C because the list of usable molecules is limited (typically for the liquefaction of hydrogen or helium).

[0006] Liquefaction units, particularly hydrogen liquefiers, generally liquefy the gas through a two-step process: 1) Cooling and / or liquefying the product through one or more closed-loop cooling cycles and 2) final expansion of the product through an expansion system to a pressure close to atmospheric pressure (typically 15 to 30 or 40 bara before expansion to 1.5 to 3 bara after expansion).

[0007] The composition of the cooling cycle gas of stage 1 is generally either close to the product itself (generally hydrogen, typically at a content of at least 90 mol%), or a lighter chemical element (generally more than 20 mol% helium). In the first case, the product obtained after expansion is generally a saturated liquid while in the second case this allows the production of subcooled liquid.

[0008] It is generally preferred to produce subcooled liquid without requiring the use of a "light" final cooling cycle as described above (because it is generally more expensive and more difficult to implement).

[0009] Liquefaction units (e.g., units producing liquefied nitrogen, liquefied hydrogen, or helium) are powered by at least one closed-loop cycle of a fluid generally composed of the component of the product to be liquefied (with a purity of up to 90 mol% or greater than 99 mol%). The refrigeration cycle is composed of compressor(s), (turbo)expander(s), and expander(s) such as valve(s) and / or turbine(s).

[0010] The final stage of the cooling cycle is generally provided by an expansion valve (Joule Thomson) producing a saturated liquid at low pressure (close to ambient pressure, typically between 0.05 and 0.2 MPaG). This sets the low temperature point of the process.

[0011] The feed gas to be cooled / liquefied is cooled by the cooling cycle through a heat exchanger to a minimum temperature above the aforementioned low temperature point due to the temperature differential between the inlet and outlet of a heat exchanger providing heat exchange between two fluids. (typically between 0.5°C and 3°C difference).

[0012] The feed gas is then expanded through a Joule-Thomson valve to a pressure close to atmospheric pressure (typically close to or equal to the low pressure of the cooling cycle). The expanded product is saturated and its vapor phase is separated in a tank. The saturated liquid is made available and the saturated gas is recycled into the process.

[0013] Various solutions exist for this final expansion: Joule Thomson type valve and / or turbine to expand the product to the liquid state.

[0014] See for example the article “Integrated Design for Demonstration of Efficient Liquefaction of Hydrogen (IDEALHY)” (authors K. Stolzenburg and R. Mubbala (Hydrogen Liquefaction Report D3.16). See also US2010272634A or CN107014151.

[0015] The production of saturated liquid brings several limitations to the use of the product. "Flash" vaporization gas can form in the distribution pipes due to the pressure drop and the heat input. This induces a two-phase flow whose physical properties complicate the design of the circuits (increased risk of vibrations).

[0016] In the case of a high hydrostatic pressure difference between the liquid production point and the top of the liquid storage tank, additional flash gas of the product may be produced, increasing the loss of liquid product.

[0017] A final expansion turbine for the liquefied feed gas provides sufficient subcooling to avoid or limit flash gas or reduced unit operation.

[0018] However, when this turbine is unavailable (maintenance for example) its replacement by an emergency expansion valve does not make it easy to achieve the thermodynamic conditions required at the outlet of the liquefier.

[0019] An aim of the present invention is to overcome all or part of the drawbacks of the prior art noted above.

[0020] To this end, the installation according to the invention, moreover in accordance with the generic definition given in the preamble above, is essentially characterized in that the additional heat exchange line is configured to ensure this heat exchange with said heat exchanger between the expansion carried out by the first expansion valve and the expansion carried out by the second expansion valve, the additional heat exchange line being located upstream or, respectively, downstream of the expansion carried out by the first expansion valve.

[0021] Furthermore, embodiments of the invention may include one or more of the following features: - the heat exchanger in heat exchange with the additional heat exchange line is the end exchanger of the assembly heat exchanger(s) in series, one outlet of which is connected to the inlet of the final expansion turbine, the supply circuit makes two successive separate passages in the end exchanger of the set of exchangers, the additional heat exchange line constituting one of the two passages, the supply circuit comprises, arranged in series in this order from upstream to downstream: a first of the two passages in the end exchanger, the second expansion valve, the second of the two passages in the end exchanger, the final expansion turbine with its bypass line provided with the first expansion valve, and the second end, the supply circuit comprises, arranged in series in this order from upstream to downstream: a first of the two passages in the end exchanger, the final expansion turbine with its bypass line equipped with the first expansion valve, the second of the two passages in the end exchanger, the second expansion valve and the second end, the feed circuit comprises, between on the one hand, the final expansion turbine and its bypass line and, on the other hand, the second of the two passages in the end exchanger, a bypass line configured to recover fluid at the outlet of the final expansion turbine without passing through the second of the two passages in the end exchanger, the installation is configured to produce liquefied hydrogen, the feed circuit comprising at least one catalysis section configured to convert ortho hydrogen into para hydrogen, the catalysis section being located in at least one of the two passages in the end exchanger, for example in the first passage and / or outside the end exchanger, at the outlet of one of the two passages in the end exchanger, the feed circuit comprises a third expansion valve, preferably of the Joule Thomson type, arranged in series with the first and second expansion valves, the third expansion valve is arranged downstream or upstream of the first expansion valve, the installation comprises a regulating member arranged at the inlet of the final expansion turbine and configured to regulate the pressure and / or flow rate in the supply circuit and / or the rotation speed of said turbine, the bypass line of the expansion turbine also bypassing this regulating member, the installation comprises a control system configured to enable the installation to be switched into a first operating mode in which the bypass line is closed and liquefied cryogenic fluid is produced via an expansion in the final expansion turbine, and in a second operating mode in which the bypass line is open and the final expansion turbine is stopped and liquefied cryogenic fluid is produced via a double expansion via the first expansion valve and second expansion valve and via a passage in the additional heat exchange line.

[0022] The invention also relates to a method for liquefying cryogenic gas, for example liquefied hydrogen, using a production installation comprising a feed gas supply circuit comprising an upstream end connected to a gas source and a downstream end connected to at least one cryogenic storage, the installation comprising a set of heat exchanger(s) in heat exchange with the supply circuit and at least one cooling device in heat exchange with all or part of the set of heat exchanger(s), the at least one cooling device comprising a cryogenic refrigerator with a cycle gas comprising at least one of: helium, hydrogen, neon, nitrogen, oxygen or methane, the downstream end of the supply circuit comprising, between the set of heat exchanger(s) and the second end, a final expansion turbine for the liquefied gas,the method comprising: a step of cooling a feed gas flow circulating in the feed circuit by heat exchange with the set of heat exchanger(s) cooled by the at least one cooling device to a temperature below the critical temperature of the feed gas or below the bubble temperature of the feed gas, and a step of main expansion of this cooled and liquefied feed gas flow in the final expansion turbine to produce a liquid flow having a pressure higher than the saturation or bubble pressure of said feed gas to preferably produce only an entirely liquid phase, or a step of emergency expansion of this cooled feed gas flow in the first expansion valve and in the second expansion valve by-passing the final expansion turbine,and cooling by heat exchange with a heat exchanger the set of heat exchanger(s) between the expansions in the first expansion valve and the second expansion valve.,

[0023] According to other possible particularities: - in the main expansion stage, the fluid pressure ratio between upstream and downstream of the final expansion turbine is between five and twenty, preferably between five and ten, - in the emergency expansion stage, the cooled feed gas stream is expanded in the first expansion valve or in the second expansion valve with a pressure ratio of between five and twenty and preferably between five and ten to produce a fluid in liquid state at the outlet of said valve, - the process comprises two successive passages of the feed gas flow through the same heat exchanger of the set of heat exchangers which is located upstream of the final expansion turbine, - the method comprises a step of switching between the main expansion step and the emergency expansion step, for example depending on the on or off state of the final expansion turbine, - the method comprises a step of switching from the main expansion step to the emergency expansion step during which the feed gas flow gradually bypasses the final expansion turbine and the supply of cooled feed gas to the final expansion turbine is interrupted and a pressure drop is generated by the second expansion valve, - the feed gas is hydrogen and / or helium, the cooling device comprising a cycle gas refrigerator comprising hydrogen and / or helium, - the feed gas is hydrogen, the process comprising a step of converting ortho hydrogen into para hydrogen in and / or downstream of a passage in a heat exchanger of the set of exchangers, - the process comprises an additional isenthalpic expansion step of the feed gas downstream of the final expansion turbine with a pressure ratio between 1.05 and five, preferably in the range between 1.3 and 2.7.

[0024] The invention may also relate to any alternative device or method comprising any combination of the above or below features within the scope of the claims.

[0025] Other features and advantages will appear on reading the description below, given with reference to the figures in which: Brief description of the figures

[0026] The invention will be better understood on reading the following description given solely by way of example and with reference to the appended drawings in which:

[0027] [Fig-1] is a schematic and simplified view illustrating the structure and function operation of a cryogenic liquefied gas production facility according to a first embodiment,

[0028] [Fig.2] is a schematic and partial view illustrating the structure and operation of a cryogenic liquefied gas production facility according to a second embodiment,

[0029] [Fig.3] is a schematic and partial view illustrating the structure and operation of a cryogenic liquefied gas production installation according to a third embodiment. Detailed description

[0030] In all the figures, the same references refer to the same elements.

[0031] In this detailed description, the following embodiments are examples. Well that the description refers to one or more embodiments, this does not mean that the features apply only to a single embodiment. Single features of different embodiments may also be combined and / or interchanged to provide other embodiments.

[0032] The installation 1 for producing cryogenic liquefied gas shown in [Fig.l] comprises a circuit 2 for supplying feed gas to be cooled (for example hydrogen or helium). This supply circuit 2 comprises an upstream end 21 intended to be connected to a source 123 of gas (for example an electrolyser or any other suitable source) and a downstream end 22 intended to be connected to at least one cryogenic storage 18 configured to collect and store the liquefied gas.

[0033] The installation 1 comprises a set of heat exchanger(s) 3, 4, 5, 6 in heat exchange with the supply circuit 2 and at least one cooling device in heat exchange with all or part of the set of heat exchanger(s).

[0034] The at least one cooling device is configured to produce a cold power which is used to cool the gas of the supply circuit 2 indirectly via the heat exchanger(s).

[0035] The at least one cooling device preferably comprises a cryogenic refrigerator 9 with cycle gas comprising at least one of: helium, hydrogen, neon, nitrogen, oxygen or methane.

[0036] The cooling device 9 preferably comprises a cycle gas refrigerator comprising hydrogen and / or helium. The cycle gas may be conventionally subjected to a thermodynamic cycle 8 comprising compression in a compression mechanism (compressor(s)) 7, cooling of the compressed gas (heat exchanger(s) 3, 4, 5, 6), expansion of the cooled compressed gas (turbine(s) 10 and / or valve(s)) 11 and heating of the held gas (heat exchanger(s) 6, 5, 4, 3). As illustrated schematically, the cycle circuit 8 may comprise at least one phase separator pot 12 and / or a thermosiphon type system.

[0037] As illustrated, the installation 1 may further comprise an additional cooling device 13 configured to ensure pre-cooling of the gas in the supply circuit 2 to an intermediate temperature. The refrigerator 9 The aforementioned cryogenic system can thus ensure cooling from the intermediate temperature to the final liquefaction temperature.

[0038] The additional cooling device 13 (pre-cooling) may comprise a cold fluid loop (nitrogen) or a cycle circuit refrigerator whose cycle gas is nitrogen, or a mixture of refrigerant gases ("MR") for example. The installation 1 may comprise more than two cooling devices.

[0039] As illustrated, the downstream end 22 of the supply circuit 2 comprises, between the set of heat exchangers 3, 4, 5, 6 and the second end 22 intended to be connected to the storage 18, a final expansion turbine 14 configured to expand the cooled supply gas to the liquid state. That is to say, at the inlet of the final expansion turbine 14, the supply gas has been brought in liquid form (pressure lower than the critical pressure and temperature lower than the saturation temperature, the saturation temperature defining the boundary temperature between the liquid state and the gaseous state) or is brought to the inlet of the final expansion turbine 14 in dense supercritical form (pressure higher than the critical pressure and temperature lower than the critical temperature).

[0040] At the outlet of the turbine 14, the expanded fluid is at least partly in liquid form.

[0041] This final expansion turbine 14 is thus arranged downstream of the last heat exchanger 6 of the set of exchangers in series from upstream to downstream.

[0042] The supply circuit 2 further comprises a line 17 for bypassing the final expansion turbine 14 provided with a first expansion valve 15, preferably of the Joule Thomson type.

[0043] As illustrated, the supply line 2 may comprise a regulating member 23 arranged at the inlet of the final expansion turbine 14 and configured to regulate the pressure and / or flow rate in the circuit 2 and / or the rotation speed of said turbine 14. This regulating member 23 comprises or consists for example of a valve. The bypass line 17 of the expansion turbine 14 preferably also bypasses this pressure and / or flow rate regulating member 23.

[0044] In addition, the supply circuit 2 comprises a second expansion valve 16, preferably of the Joule Thomson type, arranged in series upstream of the first expansion valve 15 and the final expansion turbine 14. The supply circuit 2 also comprises an additional heat exchange line 61 configured to provide heat exchange with a heat exchanger 6 of the set of heat exchanger(s) after passing through the second expansion valve 16 and before passing into the final expansion turbine 14 or the first expansion valve 15. That is to say, the additional heat exchange line 61 is configured to provide this heat exchange with said heat exchanger 6 between the expansion carried out by the second expansion valve 16 and the expansion carried out by the first expansion valve 15.

[0045] The additional heat exchange line 61 is in this example located upstream of the expansion carried out by the first expansion valve 15.

[0046] Thus, according to this architecture, when the final expansion turbine 14 is operational, this turbine can expand the previously liquefied gas to produce subcooled liquid.

[0047] For example, during a main expansion, the cooled feed gas stream (typically hydrogen) is expanded in the final expansion turbine 14 to produce a liquid stream having a pressure greater than the saturation pressure of said feed gas to preferably produce only an entirely liquid phase. In this main expansion, the fluid pressure ratio between the upstream and downstream of the final expansion turbine 14 is preferably between five and twenty, preferably between five and ten.

[0048] When the final expansion turbine 14 is not available (maintenance for example), the liquid in the supply circuit 2, after its expansion in the second expansion valve 16 and passage in the additional heat exchange line 61, is expanded in the first expansion valve 15 of the bypass line. This produces a subcooled liquid limiting the flash downstream.

[0049] Thus, when the final expansion turbine 14 is bypassed, the pressure and / or the flow rate can be controlled by the second expansion valve 16 between the passages 60, 61 in the end exchanger 6 (case of [Fig.1] and [Fig.2]) or by the valve 15 (case of [Fig.3]).

[0050] For example, during this emergency expansion, the flow of feed gas cooled and expanded in the second expansion valve 16 then undergoes cooling by heat exchange 61 with the heat exchanger 6 and is then expanded in the first expansion valve 15 by bypassing the final expansion turbine 14.

[0051] This makes it possible to operate the installation without the final expansion turbine 14 while maintaining thermodynamic conditions of the liquid produced limiting the risk of vaporization (flash).

[0052] In this emergency expansion, the cooled feed gas flow is expanded in the first expansion valve 15 (and / or in the second expansion valve 16) with a pressure ratio preferably between five and twenty and preferably between five and ten to produce a fluid in the liquid state at the outlet.

[0053] As illustrated, the heat exchanger 6 in heat exchange with the additional heat exchange line 6 may be the downstream end exchanger 6 of the set of heat exchangers 3, 4, 5, 6 in series, one outlet of which is connected to the inlet of the final expansion turbine 14.

[0054] Furthermore, as illustrated, the supply circuit 2 can make two successive separate passages 60, 61 in the same end exchanger 6 (two exchange lines separate), the additional heat exchange line constituting one 61 of the two passages. That is to say that the supply circuit 2 can comprise, arranged in series in this order from upstream to downstream: a first 60 of the two passages in the end exchanger 6, the second expansion valve 16, the second 61 of the two passages in the end exchanger 6, the final expansion turbine 17 with its bypass line 17 provided with the first expansion valve 15 and the second end.

[0055] The feed circuit 2 preferably comprises at least one catalysis section 20 configured to convert ortho hydrogen into para hydrogen. For example, the catalysis section(s) 20 are configured to convert the majority of the hydrogen into Para hydrogen (Ortho to Para conversion), for example above 80% or above 85% or above 95% for example 99% of Para at the outlet of the catalysis section 20.

[0056] This catalysis section 20 may be located in at least one of the two passages 60, 61 in the end exchanger 6, for example in the first 60 passage.

[0057] Furthermore, the feed circuit 2 may comprise a third expansion valve 24, preferably of the Joule Thomson type, arranged in series with the first 15 and second 16 expansion valves. In this example, this third expansion valve 24 is located downstream of the final expansion turbine 17 and the bypass line 17. This third expansion valve 24 allows additional isenthalpic expansion of the feed gas downstream of the final expansion turbine 14 with a pressure ratio preferably between 1.05 and five, preferably in the range between 1.3 and 2.7.

[0058] As shown schematically in [Fig.l], the installation 1 may comprise a control system 25 configured to allow the installation 1 to be switched into a first operating mode in which the bypass line 17 is closed and liquefied cryogenic fluid is produced via an expansion in the final expansion turbine 14 or into a second operating mode in which the bypass line 17 is open and the final expansion turbine 14 is stopped and liquefied cryogenic fluid is produced via a double expansion via the second expansion valve 16 and first expansion valve 15 and via a passage in the additional heat exchange line 61. The control system 25 may comprise, for example, an electronic control member comprising a microprocessor and configured to control all or part of the valves and in particular a valve making it possible to bypass the final expansion turbine 14 in favor of the first expansion valve 15.This switching can be manual or in response to a signal representative of the operating state of the final expansion turbine 14. Of course, the control system 25 could be at least partly manual.

[0059] The switching can be activated for example manually, for example during transient phases such as starts or stops of the installation and / or automatically if the temperature of the fluid at a given point in the installation is too high. For example, if the temperature at the outlet of the first passage 60 (measured or estimated or deduced by another measurement reflecting this temperature: for example a pressure, a level and / or a temperature at another point in the refrigeration cycle) goes above a given threshold.

[0060] For example, in the first mode, most of the expansion of the fluid can be carried out in the final expansion turbine 14 and the rest of the expansion can be carried out downstream of said turbine 14 (via the third expansion valve 24 cf. [Fig. 1] and [Fig. 2] or via the second expansion valve 16 cf. [Fig. 3]). These expansions are configured to produce a 100% liquid flow at the outlet of the final expansion turbine 14. In the mode of [Fig. 3], most of the expansion can be carried out between the two passages 60 and 61

[0061] Preferably, when switching from a main expansion to an emergency expansion, the first expansion valve 15 is controlled to gradually bypass the final expansion turbine 14 before interrupting the supply of cooled feed gas to the final expansion turbine 14. For example, a pressure drop is generated by the second expansion valve 16. The switching is preferably carried out in less than 10 min.

[0062] For example, when the final expansion turbine 14 is stopped, the installation 1 can first control the opening of the bypass line 17 of the turbine 14 and can close the valve 23 located at the inlet of the turbine 14. Then, then progressively the first expansion valve 15 is opened and the pressure drop is controlled (created) by the valve 24 for example.

[0063] The embodiment of [Fig. 2] differs from the previously described embodiment only in that the catalysis section 20 is located at the outlet of the first passage 60 in the end heat exchanger 6 (in a tank upstream of the second expansion valve 16). The conversion then takes place outside the exchanger in a tank 20 in which the catalyst is placed. This adiabatic conversion is also exothermic (like the continuous conversion). The fluid is therefore heated in the tank 20 and passes back into the end heat exchanger 6 to be cooled (in the second passage 61).

[0064] In the embodiment of [Fig. 3] the supply circuit 2 comprises, arranged in series in this order from upstream to downstream: a first 60 of the two passages in the end heat exchanger 6, the third expansion valve 24, the final expansion turbine 14 with its bypass line 17 provided with the first expansion valve 15, the second 61 of the two passages in the end exchanger 6 then the second expansion valve 16 and the second end 22. In this embodiment, the third expansion valve 24 can also be omitted and its function can in this case to be ensured by the first expansion valve 15.

[0065] In this configuration, the fluid of the feed circuit 2 1 can be cooled and liquefied (or densified if it is at a pressure higher than the critical pressure of the component) by indirect heat exchange with the refrigerator 9 in the heat exchanger 6 during the first pass 60. This cold feed stream in liquid or supercritical dense phase 3 is then expanded through the final expansion turbine 14 to a pressure high enough to prevent the production of a vapor phase in the outlet stream 4. The fluid expanded 4 by the turbine 14 is entirely liquid. Preferably upstream of the final expansion turbine 14, a valve 23 (for example a throttle valve) can be used to control the rotation speed of the final expansion turbine 17.

[0066] As illustrated, the supply circuit 2 may comprise, between on the one hand, the outlet of the final expansion turbine 14 and its bypass line 17 and, on the other hand, the second 61 of the two passages in the end exchanger 6, a diversion line 19 configured to allow fluid to be recovered directly at the outlet of the final expansion turbine 14 (or the bypass), that is to say without passing through the second 61 of the two passages in the end exchanger 6 (see [Fig. 3].

[0067] The flow produced at the outlet of the final expansion turbine 14 (or the bypass) can either be directly made available via the bypass line 19, or returned to a heat exchanger 16 (generally the same heat exchanger as illustrated) to be further cooled and stored (after the expansion 16 in the second expansion valve 16). For example, a portion of the fluid produced at the outlet of the final expansion turbine 14 is sent into this bypass line 19, the remainder of the flow being sent into the second passage 61.

[0068] The pressure of the flow at the outlet of the final expansion turbine 14 (or of the bypass line 17) can be configured at a pressure high enough to prevent the production of a vapor phase in the flow 4 which must re-enter the heat exchanger 6 for the second pass.

[0069] The expansion rates of the first 15 and second 16 expansion valves (i.e. the intermediate pressure upstream of the second expansion valve 16) can be adjusted to prevent (or limit) the production of a vapor phase in the flow which makes the second passage 61 in the heat exchanger 6. This simplifies the design of the injection of this flow into the heat exchanger 6 (no need for a phase separator vessel and / or a two-phase injection system).

[0070] The final cooling by indirect heat exchange of the flow during the second passage 61 makes it possible to always control the temperature of the final liquid product. The downstream valve 16, 24 makes it possible to expand the fluid to a pressure close (taking into account the pressure drop along the pipes and the equipment) to the operating pressure. operation of the liquid storage which will receive the liquid.

[0071] The first expansion valve 15 thus allows emergency operation without the final expansion turbine 14 while controlling the discharge temperature thanks to the final cooling step 61 of the flow. This solution allows the use of a final expansion turbine 14 without risking jeopardizing the availability of the installation 1 in the event of a possible malfunction or unavailability of the turbine 14. The last heat exchange (second passage 61) can be carried out at least in part with the same refrigerant as the cooling of the main process gas flow.

[0072] The thermodynamic conditions (temperature and pressure) of the liquid produced via the final expansion turbine 14 or via the bypass line 17 may be similar.

[0073] The pressure at the outlet of the final expansion turbine 14 can be adjusted by the dedicated expansion valve 16, 24 upstream or downstream to protect the turbine from any production of vapor phase.

[0074] In particular, the third expansion valve 24 ([Fig.l] and [Fig.2] or valve 16 in [Fig.3]) can be controlled to ensure a back pressure downstream of the turbine 14 to avoid vaporizations (flash) in particular during the bypass of the final expansion turbine 14. This valve 24 can be configured to ensure a minimum acceptable pressure at the outlet of the turbine 14.

[0075] The pressure of the fluid at the outlet of the final expansion turbine 14 can, for example, be maintained at a pressure level 0.1 to a few bars higher than the saturation pressure of the fluid.

[0076] The installation may comprise a sensor for measuring the discharge pressure at the outlet of the final expansion turbine 14 and the installation may be configured to regulate the pressure of the fluid at the outlet of the final expansion turbine 14 as a function of the measured pressure. The installation may comprise a sensor for measuring the temperature of the fluid at the outlet and / or at the inlet of the final expansion turbine, the regulation of the discharge pressure being carried out as a function of the measured temperature.

[0077] The temperature of the fluid at the outlet of the final expansion turbine 14 may be between 15 and 30K, preferably between 20 and 25K.

[0078] By Joule Thomson type expansion valve is meant, for example, an isenthalpic expansion element whose passage section can be enlarged or narrowed. That is to say that the fluid can heat up or cool down in this valve depending on its inlet temperature and pressure conditions and the characteristics of the gas (in particular its temperature inversion curve, in the case of hydrogen in particular).

Claims

Claims

1. Installation for producing cryogenic liquefied gas, for example liquefied hydrogen, comprising a circuit (2) for supplying supply gas to be cooled, the supply circuit (2) comprising an upstream end (21) intended to be connected to a gas source (123) and a downstream end (22) intended to be connected to at least one cryogenic storage (18) configured to collect and store liquefied gas, the installation (1) comprising a set of heat exchanger(s) (3, 4, 5, 6) in heat exchange with the supply circuit (2), the installation (1) comprising at least one cooling device (9, 13) in heat exchange with all or part of the set of heat exchanger(s) (3, 4, 5, 6), the at least one cooling device (9, 13) comprising a cryogenic refrigerator (9) with cycle gas comprising at least one of: helium, hydrogen, neon, nitrogen, oxygen or methane,the downstream end (22) of the supply circuit (2) comprising, between the set of heat exchanger(s) (3, 4, 5, 6) and the second end (22) intended to be connected to the storage (18), a final expansion turbine (14) configured to expand the supply gas which is in the liquid state at the inlet of said turbine (14), the supply circuit (2) further comprising a bypass line (17) of the final expansion turbine (14) provided with a first expansion valve (15), preferably of the Joule Thomson type, the supply circuit (2) comprising a second expansion valve (16), preferably of the Joule Thomson type, arranged in series upstream or, respectively, downstream of the first expansion valve (15) and of the final expansion turbine (14), the supply circuit (2) comprising an additional heat exchange line (61) configured to ensure heat exchange with a heat exchanger (6) of the set of exchanger(s) (3, 4, 5,6) heat when the feed gas is expanded by the first expansion valve (15) via the bypass line (17), characterized in that the additional heat exchange line (61) is configured to ensure this heat exchange with said heat exchanger (6) between the expansion carried out by the first expansion valve (15) and the expansion carried out by the second expansion valve (16), the additional heat exchange line (61) being located upstream or, respectively, downstream of the expansion carried out by the first expansion valve (15).,

2. Installation according to claim 1, characterized in that the heat exchanger (6) in heat exchange with the additional heat exchange line (61) is the end exchanger (6) of the set of heat exchanger(s) (3, 4, 5, 6) in series, one outlet of which is connected to the inlet of the final expansion turbine (14).

3. Installation according to claim 2, characterized in that the supply circuit (2) makes two successive separate passages (60, 61) in the end exchanger (6) of the set of exchanger(s) (3, 4, 5, 6), the additional heat exchange line constituting one (61) of the two passages.

4. Installation according to claim 3, characterized in that the supply circuit (2) comprises, arranged in series in this order from upstream to downstream: a first (60) of the two passages in the end exchanger (6), the second expansion valve (16), the second (61) of the two passages in the end exchanger (6), the final expansion turbine (14) with its bypass line (17) provided with the first expansion valve (15), and the second end (22).

5. Installation according to claim 3, characterized in that the supply circuit (2) comprises, arranged in series in this order from upstream to downstream: a first (60) of the two passages in the end exchanger (6), the final expansion turbine (14) with its bypass line (17) provided with the first expansion valve (15), the second (61) of the two passages in the end exchanger (6), the second expansion valve (16) and the second end (22).

6. Installation according to claim 5, characterized in that the supply circuit (2) comprises, between on the one hand, the final expansion turbine (14) and its bypass line (17) and, on the other hand, the second (61) of the two passages in the end exchanger (6), a diversion line (19) configured to recover fluid at the outlet of the final expansion turbine (14) without passing through the second (61) of the two passages in the end exchanger (6).

7. Plant according to any one of claims 3 to 6, configured to produce liquefied hydrogen, characterized in that the supply circuit (2) comprises at least one catalysis section (20) configured to convert ortho hydrogen into para hydrogen, the catalysis section (20) being located in at least one (60) of the two passages (60, 61) in the end exchanger (6), for example in the first (60) passage and / or outside the end exchanger (6), at the outlet of one of the two passages (60, 61) in the end exchanger (6).

8. Installation according to any one of claims 1 to 7, characterized in that the supply circuit (2) comprises a third expansion valve (24), preferably of the Joule Thomson type, arranged in series with the first (15) and second (16) expansion valves.

9. Installation according to claim 8, characterized in that the third expansion valve (24) is arranged downstream or upstream of the first expansion valve (15).

10. Installation according to any one of claims 1 to 9, characterized in that it comprises a regulating member (23) arranged at the inlet of the final expansion turbine (14) and configured to regulate the pressure and / or the flow rate in the supply circuit (2) and / or the rotation speed of said turbine (14), the bypass line (17) of the expansion turbine (14) also bypassing this regulating member (23).

11. Installation according to any one of claims 1 to 10, characterized in that it comprises a control system (25) configured to allow switching the installation (1) into a first operating mode in which the bypass line (17) is closed and liquefied cryogenic fluid is produced via an expansion in the final expansion turbine (14), and into a second operating mode in which the bypass line (17) is open and the final expansion turbine (14) is stopped and liquefied cryogenic fluid is produced via a double expansion via the first expansion valve (15) and second expansion valve (16) and via a passage in the additional heat exchange line (60).

12. A method of liquefying cryogenic gas, for example liquefied hydrogen, using a production facility comprising a feed gas supply circuit (2) comprising an upstream end (21) connected to a gas source (123) and a downstream end (22) connected to at least one cryogenic storage (18), the facility (1) comprising a set of heat exchanger(s) (3, 4, 5, 6) in heat exchange with the supply circuit (2) and at least one cooling device (9, 13) in heat exchange with all or part of the set of heat exchanger(s) (3, 4, 5, 6), the at least one cooling device (9, 13) comprising a cryogenic refrigerator (9) with a cycle gas comprising at least one of: helium, hydrogen, neon, nitrogen, oxygen or methane, the downstream end (22) of the supply circuit (2) comprising, between the set of heat exchanger(s) (3, 4, 5, 6) and the second end (22) a turbine (14) for final expansion of the liquefied gas, the method comprising: - a step of cooling a feed gas flow circulating in the feed circuit (2) by heat exchange with the set of heat exchanger(s) (3, 4, 5, 6) cooled by the at least one cooling device (9, 13) to a temperature below the critical temperature of the feed gas or below the bubble temperature of the feed gas, and - a step of main expansion of this cooled and liquefied feed gas flow in the final expansion turbine (14) to produce a liquid flow having a pressure higher than the saturation or bubble pressure of said feed gas to preferably produce only an entirely liquid phase,or - an emergency expansion step of this cooled feed gas flow in the first expansion valve (15) and in the second expansion valve (16) by-passing the final expansion turbine (14), and cooling by heat exchange with a heat exchanger (6) of the set of heat exchanger(s) (3, 4, 5, 6) between the expansions in the first expansion valve (15) and the second expansion valve (16).,

13. Liquefaction method according to claim 12, characterized in that, in the main expansion step, the fluid pressure ratio between the upstream and downstream of the final expansion turbine (14) is between five and twenty, preferably between five and ten.

14. Liquefaction method according to claim 12 or 13, characterized in that, in the emergency expansion step, the cooled feed gas flow is expanded in the first expansion valve (15) or in the second expansion valve (16) with a pressure ratio of between five and twenty and preferably between five and ten to produce a fluid in the liquid state at the outlet of said valve.

15. Liquefaction method according to any one of claims 12 to 14, characterized in that it comprises two successive passages (60, 61) of the feed gas flow in the same heat exchanger (6) of the set of heat exchanger(s) (3, 4, 5, 6) which is located upstream of the final expansion turbine (14).

16. Method according to any one of claims 12 to 15, characterized in that it comprises a step of switching between the expansion step main and the emergency expansion stage, for example depending on the on or off state of the final expansion turbine (14).

17. Method according to claim 16, characterized in that it comprises a step of switching from the main expansion step to the emergency expansion step during which the flow of feed gas gradually bypasses (15) the final expansion turbine (14) and the supply of cooled feed gas to the final expansion turbine (14) is interrupted (23) and a pressure drop is generated by the second expansion valve (16).

18. A method according to any one of claims 12 to 17, characterized in that the feed gas is hydrogen and / or helium, the cooling device (9, 13) comprising a cycle gas refrigerator comprising hydrogen and / or helium.

19. Method according to any one of claims 12 to 18, characterized in that the feed gas is hydrogen, the method comprising a step of converting ortho hydrogen into para hydrogen in and / or downstream of a passage in a heat exchanger (6) of the set of exchangers.

20. Method according to any one of claims 12 to 19, characterized in that it comprises an additional isenthalpic expansion step (24) of the feed gas downstream of the final expansion turbine (14) with a pressure ratio of between 1.05 and five, preferably in the range between 1.3 and 2.7.

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