Installation and method for refrigerating a fluid at cryogenic temperature
The additional heat exchange line between expansion valves in liquefaction units addresses the inefficiencies of producing subcooled liquids, ensuring stable and simplified liquid production by controlling thermodynamic conditions, even without a final expansion turbine.
Patent Information
- Application Number
- FR2023005892
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-06-12
- Publication Date
- 2025-10-31
- Estimated Expiration
- 2043-06-12
AI Technical Summary
Existing liquefaction units face challenges in producing subcooled liquids efficiently, leading to flash vaporization and increased design complexity due to two-phase flows and pressure drops, particularly when a final expansion turbine is unavailable.
Incorporating an additional heat exchange line between the expansions by the first and second expansion valves, allowing for double expansion and maintaining thermodynamic conditions to produce subcooled liquids, even when the final expansion turbine is not operational.
Ensures stable production of subcooled liquids, reducing the risk of flash vaporization and simplifying the design of distribution circuits by controlling thermodynamic conditions, even in the absence of a final expansion turbine.
Smart Images
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Abstract
Description
Title of the invention: Installation and method for refrigerating a fluid at 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 a cryogenic liquefied gas production installation, for example liquefied hydrogen, comprising a feed gas supply circuit 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 unit 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 cycle gas refrigerator comprising at least one of: helium, hydrogen, neon, nitrogen, oxygen or methane, the downstream end of the supply circuit comprising,between the heat exchanger assembly(ies) and the second end intended to be connected to the storage, a final expansion turbine configured to expand the feed gas which is in a liquid state at the inlet of said turbine, the feed circuit further comprising a bypass line from the final expansion turbine equipped 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 heat exchanger assembly(ies) when the feed gas is expanded by the first expansion valve via the bypass line.
[0003] Producing a subcooled liquefied fluid makes it possible to effectively combat heat inputs and the generation of gases resulting from the vaporization of saturated liquids ("boil-off") throughout a distribution chain. Indeed, a subcooled liquid subjected to unwanted heat 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 subcooled 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 using a liquefier to deliver saturated liquid because subcooling induces a temperature lower than the saturation temperature (efficiency compared to an ideal Carnot engine).
[0005] The invention relates in particular to applications such as liquefaction units where subcooled production is required. The invention also relates 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, in particular hydrogen liquefiers, generally liquefy the gas by a two-stage process: 1) Cooling and / or liquefaction of the product by means of 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 from 15 to 30 or 40 bara before expansion down to 1.5 to 3 bara after expansion).
[0007] The composition of the cooling cycle gas in step 1 is generally either close to the product itself (usually hydrogen, typically at a concentration of at least 90 mole percent) or a lighter chemical element (usually more than 20 mole percent helium). In the first case, the product obtained after expansion is generally a saturated liquid, while in the second case, it allows the production of a subcooled liquid.
[0008] It is generally preferred to produce subcooled liquid without requiring the use of a final "light" cooling cycle as described above (because it is generally more expensive and more difficult to implement).
[0009] Liquefaction units (for example, units producing liquefied nitrogen, liquefied hydrogen, or helium) are supplied by at least one closed-loop fluid circuit, generally composed of the component of the product to be liquefied (with a purity of up to 90% by mole or greater than 99% by mole). The refrigeration cycle consists of compressor(s), (turbo)expander(s), and expansion valve(s) such as valve(s) and / or turbine(s).
[0010] The final stage of the cooling cycle is generally ensured 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 lowest 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 higher than the aforementioned low temperature point due to the temperature differential between the inlet and the outlet of a heat exchanger ensuring 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 back into the process.
[0013] Various solutions exist for this final expansion: Joule Thomson type valve and / or turbine to expand the product in 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 introduces several limitations to the use of the product. "Flash" vaporization gas can form in the distribution pipes due to pressure drop and 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 of the liquefied feed gas allows sufficient subcooling to avoid or limit flash gas or reduced operating unit.
[0018] However, when this turbine is unavailable (maintenance for example) its replacement by an emergency expansion valve does not allow the required thermodynamic conditions to be easily reached at the outlet of the liquefier.
[0019] One object of the present invention is to overcome all or part of the disadvantages of the prior art noted above.
[0020] To this end, the installation according to the invention, which also conforms to 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 achieved by the first expansion valve and the expansion achieved by the second expansion valve, the additional heat exchange line being located upstream or, respectively, downstream of the expansion achieved 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 series of heat exchanger(s) whose outlet is connected to the inlet of the final expansion turbine. The supply circuit makes two distinct successive passes through the end exchanger of the exchanger assembly(ies), the additional heat exchange line constituting one of the two passes, The supply circuit comprises, arranged in series in this order from upstream to downstream: the first of the two passages through the end exchanger, the second pressure-reducing valve, the second of the two passages through the end exchanger, the final pressure-reducing turbine with its bypass line equipped with the first pressure-reducing valve, and the second end. The supply circuit comprises, arranged in series in this order from upstream to downstream: the first of the two passes through the end exchanger, the final expansion turbine with its bypass line equipped with the first expansion valve, the second of the two passes through the end exchanger, the second expansion valve and the second end, The supply 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 supply circuit includes a third pressure-reducing valve, preferably of the Joule-Thomson type, arranged in series with the first and second pressure-reducing valves. The third pressure relief valve is located downstream or upstream of the first pressure relief valve. The installation includes a regulating device located 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 rotational speed of said turbine, the bypass line of the expansion turbine also bypassing this regulating device, - the installation includes a control system configured to allow switching the installation into a first operating mode in which the bypass line is closed and liquefied cryogenic fluid is produced via expansion in the final expansion turbine, and into 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 double expansion through 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 process for liquefying cryogenic gas, for example liquefied hydrogen, using a production plant comprising a feed gas circuit having an upstream end connected to a gas source and a downstream end connected to at least one cryogenic storage unit, the plant comprising a set of heat exchanger(s) in heat exchange with the feed 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 cycle gas refrigerator comprising at least one of: helium, hydrogen, neon, nitrogen, oxygen or methane, the downstream end of the feed circuit comprising, between the set of heat exchanger(s) and the second end, a final expansion turbine for the liquefied gas,the process comprising: a step of cooling a feed gas stream circulating in the feed circuit by heat exchange with the assembly of heat exchanger(s) cooled by 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 main expansion step of this cooled and liquefied feed gas stream in the final expansion turbine to produce a liquid stream having a pressure above the saturation or bubble pressure of said feed gas to preferably produce only a completely liquid phase, or alternatively an emergency expansion step of this cooled feed gas stream in the first expansion valve and in the second expansion valve by bypassing the final expansion turbine,and cooling by heat exchange with a heat exchanger, the assembly of heat exchanger(s) between the expansions in the first expansion valve and the second expansion valve.
[0023] According to other possible features: - in the main expansion stage, the fluid pressure ratio between the upstream and downstream sides of the final expansion turbine is between five and twenty, preferably between five and ten, - in the emergency expansion stage, the cooled feed gas flow is expanded in the first expansion valve or in the second expansion valve with a pressure ratio between five and twenty and preferably between five and ten to produce a fluid in a liquid state at the outlet of said valve, - the process comprises two successive passes of the feed gas flow through the same heat exchanger of the heat exchanger assembly(ies) which is located upstream of the final expansion turbine, - the process includes a switching step between the main expansion stage and the backup expansion stage, for example depending on whether the final expansion turbine is running or stopped, - the process includes a switching step from the main expansion stage to the backup expansion stage 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 includes a cycle gas refrigerator containing hydrogen and / or helium, - the feed gas is hydrogen, the process including a step of converting ortho hydrogen to para hydrogen in and / or downstream of a passage through a heat exchanger of the set of exchangers, - the process includes 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 become apparent from the following description, made with reference to the figures in which: Brief description of the figures
[0026] The invention will be better understood upon reading the following description, given solely by way of example and made with reference to the accompanying drawings in which:
[0027] [Fig. 1] is a schematic and simplified view illustrating the structure and operation of a cryogenic liquefied gas production plant 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 plant 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 plant according to a third embodiment. Detailed description
[0030] In all figures, the same references refer to the same elements.
[0031] In this detailed description, the following embodiments are examples. The fact that the description refers to one or more embodiments does not mean that the features apply only to a single embodiment. Simple features from different embodiments can also be combined and / or interchanged to provide other embodiments.
[0032] The cryogenic liquefied gas production installation 1 shown in [Fig. 1] includes a feed gas circuit 2 for the cooled gas (e.g., hydrogen or helium). This feed circuit 2 includes an upstream end 21 for connection to a gas source 123 (e.g., an electrolyzer or any other suitable source) and a downstream end 22 for connection to at least one cryogenic storage unit 18 configured to collect and store the liquefied gas.
[0033] Installation 1 includes 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] At least one cooling device is configured to produce a cooling power which is used to indirectly cool the gas in the supply circuit 2 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 can conventionally be 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 a heating of the held gas (heat exchanger(s) 6,5,4,3)- As schematically illustrated, the cycle circuit 8 may include at least one phase separator pot 12 and / or a thermosiphon type system.
[0037] As illustrated, the installation 1 may further include an additional cooling device 13 configured to pre-cool the gas in the supply circuit 2 to an intermediate temperature. The aforementioned cryogenic refrigerator 9 can thus ensure cooling from the intermediate temperature to the final liquefaction temperature.
[0038] The additional cooling (pre-cooling) device 13 may include a cold fluid (nitrogen) loop or a cycled refrigerator whose cycle gas is nitrogen, or a mixture of refrigerant gases (“MR”) for example. The installation 1 may include more than two cooling devices.
[0039] As illustrated, the downstream end 22 of the feed 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 feed gas into a liquid state. That is to say, at the inlet of the final expansion turbine 14, the feed gas has been supplied in liquid form (pressure below the critical pressure and temperature below the saturation temperature, the saturation temperature defining the limiting temperature between the liquid and gaseous states) or is supplied to the inlet of the final expansion turbine 14 in a dense supercritical form (pressure above the critical pressure and temperature below the critical temperature).
[0040] At the outlet of 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 includes a bypass line 17 from the final expansion turbine 14 equipped with a first expansion valve 15, preferably of the Joule Thomson type.
[0043] As illustrated, the supply line 2 may include a control device 23 located 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 rotational speed of said turbine 14. This control device 23 includes, or is constituted, for example, by a valve. The bypass line 17 of the final expansion turbine 14 preferably also bypasses this pressure and / or flow control device 23.
[0044] Furthermore, the supply circuit 2 includes 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 includes an additional heat exchange line 61 configured to ensure in heat exchange with a heat exchanger 6 of the heat exchanger assembly(ies) after passing through the second expansion valve 16 and before passing through the final expansion turbine 14 or the first expansion valve 15. That is to say, 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 second expansion valve 16 and the expansion carried out by the first expansion valve 15.
[0045] In this example, the additional heat exchange line 61 is located upstream of the expansion achieved 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 higher than the saturation pressure of said feed gas, preferably producing only a completely liquid phase. In this main expansion, the fluid pressure ratio between the upstream and downstream sides of the final expansion turbine 14 is preferably between five and twenty, and more preferably between five and ten.
[0048] When the final expansion turbine 14 is not available (for example, for maintenance), the liquid in the supply circuit 2, after expansion in the second expansion valve 16 and passing through the additional heat exchange line 61, is expanded in the first expansion valve 15 of the bypass line. This produces a subcooled liquid, limiting flash downstream.
[0049] Thus, when the final expansion turbine 14 is bypassed, the pressure and / or flow 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 cooled and expanded supply gas flow 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 allows the installation to operate without the final expansion turbine 14 while maintaining thermodynamic conditions of the produced liquid limiting the risk of vaporization (flash).
[0052] In this emergency expansion, the cooled supply 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 exchanger line 6 can be the downstream end heat 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 distinct passes 60, 61 in the same end exchanger 6 (two separate exchange lines), the additional heat exchange line constituting one 61 of the two passes. That is to say, the supply circuit 2 can comprise, arranged in series in this order from upstream to downstream: a first 60 of the two passes in the end exchanger 6, the second expansion valve 16, the second 61 of the two passes in the end exchanger 6, the final expansion turbine 17 with its bypass line 17 equipped with the first expansion valve 15 and the second end.
[0055] The supply circuit 2 preferably includes 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 mostly hydrogen into para hydrogen (ortho to para conversion), for example above 80% or above 85% or above 95%, for example 99% para at the outlet of the catalysis section 20.
[0056] This catalytic section 20 can 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 supply circuit 2 may include a third pressure-reducing valve 24, preferably of the Joule-Thomson type, arranged in series with the first 15 and second 16 pressure-reducing valves. In this example, this third pressure-reducing valve 24 is located downstream of the final expansion turbine 17 and the bypass line 17. This third pressure-reducing valve 24 allows for an additional isenthalpic expansion 24 of the feed gas downstream of the final expansion turbine 14 with a pressure ratio preferably between 1.05 and 5, preferably in the range between 1.3 and 2.7.
[0058] As schematically illustrated in [Fig. 1], the installation 1 may include 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 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 double expansion through the second expansion valve 16 and the first expansion valve 15, and via a passage through the additional heat exchange line 61. The control system 25 may, for example, include an electronic control unit comprising a microprocessor and configured to control all or part of the valves, and in particular a valve allowing the final expansion turbine 14 to be bypassed in favor of the first expansion valve 15. This switching can be manual or in response to a signal representing the operating status of the final expansion turbine 14. Of course, the control system 25 could be at least partially manual.
[0059] The switching can be activated, for example, manually, for example during transient phases such as system start-ups or shutdowns, and / or automatically if the fluid temperature at a specific point in the system is too high. For example, if the temperature at the outlet of the first pass 60 (measured, estimated, or deduced from another measurement reflecting this temperature: for example, a pressure, a level, and / or a temperature at another point in the refrigeration cycle) exceeds a specified threshold.
[0060] For example, in the first mode, most of the fluid expansion can be carried out in the final expansion turbine 14, and the remainder of the expansion can be carried out downstream of said turbine 14 (via the third expansion valve 24, see [Fig. 1] and [Fig. 2], or via the second expansion valve 16, see [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 a backup expansion, the first expansion valve 15 is controlled to progressively 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 switchover is preferably carried out in less than 10 minutes.
[0062] For example, when the final expansion turbine 14 is stopped, the installation 1 can first command 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, gradually the first expansion valve 15 is opened and the pressure loss 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 catalytic section 20 is located at the outlet of the first pass 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 pass 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 equipped with the first expansion valve 15, the second 61 of the two passages in the end heat 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 be ensured by the first expansion valve 15.
[0065] In this configuration, the fluid in the feed circuit 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 the dense liquid or supercritical phase 3 is then expanded through the final expansion turbine 14 to a pressure high enough to prevent the formation 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 throttling valve) can be used to control the rotational speed of the final expansion turbine 17.
[0066] As illustrated, the supply circuit 2 may include, 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 bypass line 19 configured to allow fluid to be recovered directly at the outlet of the final expansion turbine 14 (or the bypass), i.e. without passing through the second 61 of the two passages in the end exchanger 6 (cf. [Fig.3].
[0067] The flow produced at the outlet of the final expansion turbine 14 (or the bypass) can either be made available directly via the bypass line 19, or returned to a heat exchanger 16 (generally the same heat exchanger as illustrated) for further cooling and storage (after the expansion 16 in the second expansion valve 16). For example, part of the fluid produced at the outlet of the final expansion turbine 14 is sent to this bypass line 19, the remainder of the flow being sent to 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 16 expansion valve) can be adjusted to prevent (or limit) the production of a vapor phase in the flow which carries out the second pass 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 pass 61 ensures continuous control of the final liquid product temperature. The downstream valve 16, 24 allows the fluid to be reduced to a pressure close (taking into account the pressure drop along the pipes and the equipment) to the operating pressure of the liquid storage tank that will receive the liquid.
[0071] The first expansion valve 15 thus allows backup operation without the final expansion turbine 14 while controlling the discharge temperature thanks to the final cooling stage 61 of the flow. This solution allows the use of a final expansion turbine 14 without risking the availability of the installation 1 in the event of a possible malfunction or unavailability of the turbine 14. The last heat exchange (second pass 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 phase vapor.
[0074] In particular, the third expansion valve 24 ([Fig. 1] and [Fig. 2] or valve 16 in [Fig. 3]) can be controlled to provide back pressure downstream of the turbine 14 to prevent vaporization (flash), especially 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 fluid pressure 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 fluid saturation pressure.
[0076] The installation may include 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 fluid pressure at the outlet of the final expansion turbine 14 according to the measured pressure. The installation may also include a sensor for measuring the fluid temperature at the outlet and / or inlet of the final expansion turbine, with the discharge pressure being regulated according to the measured temperature.
[0077] The temperature of the fluid at the outlet of the final expansion turbine 14 can be between 15 and 30K, preferably between 20 and 25K.
[0078] A Joule-Thomson type expansion valve is understood, for example, to be an isenthalpic expansion element whose passage area can be enlarged or reduced. That is to say, the fluid can be heated or cooled in this valve depending on its inlet temperature and pressure conditions and the characteristics of the gas (in particular its temperature inversion curve, especially in the case of hydrogen).
Claims
1. Demands A cryogenic liquefied gas production installation, configured to produce liquefied hydrogen, comprising a feed gas supply circuit (2) for cooling, 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 unit (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 feed 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 cycle gas refrigerator (9) comprising at least one of: helium, hydrogen, neon, nitrogen, oxygen, or methane,the downstream end (22) of the feed circuit (2) comprising, between the heat exchanger assembly (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 feed gas which is in a liquid state at the inlet of said turbine (14), the feed circuit (2) further comprising a bypass line (17) from the final expansion turbine (14) equipped with a first expansion valve (15), preferably of the Joule-Thomson type, the feed 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 the final expansion turbine (14), the feed circuit (2) comprising an additional heat exchange line (61) configured to provide heat exchange with a heat exchanger (6) of heat from 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), 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 exchange line (61), additional heat being located upstream or, respectively, downstream of the expansion achieved by the first expansion valve (15), and in that the heat exchanger (6) in heat exchange with the additional heat exchange line (61) is the end heat exchanger (6) of the series heat exchanger(s) (3, 4, 5, 6) assembly, one outlet of which is connected to the inlet of the final expansion turbine (14), and in that the supply circuit (2) makes two successive distinct passes (60, 61) in the end heat exchanger (6) of the heat exchanger assembly (3, 4, 5, 6), the additional heat exchange line constituting one (61) of the two passes, and in which the supply circuit (2) includes a third expansion valve (24), preferably of the Joule-Thomson type, arranged in series with the first (15) and second (16) valves of relaxation.
2. Installation according to claim 1, 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) equipped with the first expansion valve (15), and the second end (22).
3. Installation according to claim 1, characterized in that the supply circuit (2) comprises, arranged in series in this order from upstream to downstream: a first (60) of the two passes in the end exchanger (6), the final expansion turbine (14) with its bypass line (17) equipped with the first expansion valve (15), the second (61) of the two passes in the end exchanger (6), the second expansion valve (16) and the second end (22).
4. Installation according to claim 3, 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 bypass 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).
5. An installation according to any one of claims 2 to 4, configured to produce liquefied hydrogen, characterized in that the feed circuit (2) comprises at least one catalysis section (20) configured to convert orthohydrogen in 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).
6. Installation according to any one of claims 1 to 5, characterized in that the third pressure relief valve (24) is disposed downstream or upstream of the first pressure relief valve (15).
7. Installation according to any one of claims 1 to 6, characterized in that it comprises a control element (23) disposed at the inlet of the final expansion turbine (14) and configured to regulate the pressure and / or flow in the supply circuit (2) and / or the rotational speed of said turbine (14), the bypass line (17) of the expansion turbine (14) also bypassing this control element (23).
8. Installation according to any one of claims 1 to 7, 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 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 double expansion through the first expansion valve (15) and second expansion valve (16) and via a passage in the additional heat exchange line (60).
9. A hydrogen liquefaction process, using a production plant comprising a feed gas circuit (2) having an upstream end (21) connected to a gas source (123) and a downstream end (22) connected to at least one cryogenic storage unit (18), the plant (1) comprising a set of heat exchanger(s) (3, 4, 5, 6) in heat exchange with the feed 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 cycle gas refrigerator (9) comprising at least one of: of helium, hydrogen, neon, nitrogen, oxygen or methane, the downstream end (22) of the feed circuit (2) comprising, between the heat exchanger assembly (3, 4, 5, 6) and the second end (22) a final expansion turbine (14) of the liquefied gas, the process comprising: -a step of cooling a feed gas stream circulating in the feed circuit (2) by heat exchange with the heat exchanger assembly (3, 4, 5, 6) cooled by 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 main expansion stage of this cooled and liquefied feed gas stream in the final expansion turbine (14) to produce a liquid stream having a pressure greater than the saturation or bubble pressure of said feed gas to preferably produce only a completely liquid phase, or - an emergency expansion stage of this cooled feed gas stream in a first expansion valve (15) and in the second expansion valve (16) by bypassing the final expansion turbine (14), and cooling by heat exchange with a heat exchanger (6) of the heat exchanger assembly (3, 4, 5, 6) between the expansions in the first expansion valve (15) and the second expansion valve (16), the process comprising two successive passes (60, 61) of the feed gas stream through the same heat exchanger (6) of the heat exchanger assembly (3, 4, 5,6) of heat which is located upstream of the final expansion turbine (14),
10. Liquefaction process according to claim 9, characterized in that, in the main expansion stage, the fluid pressure ratio between upstream and downstream of the final expansion turbine (14) is between five and twenty, preferably between five and ten.
11. Liquefaction process according to claim 9 or 10, 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 between five and twenty and preferably between five and ten to produce a fluid in the liquid state at the outlet of said valve.
12. A method according to any one of claims 9 to 11, characterized in that it comprises a switching step between the step of main expansion and the emergency expansion stage, for example depending on the operating or stopped state of the final expansion turbine (14).
13. The method according to claim 12, characterized in that it comprises a switching step from the main expansion stage to the backup expansion stage during which the feed gas flow bypasses (15) progressively 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).
14. A method according to any one of claims 9 to 13, 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.
15. A process according to any one of claims 9 to 14, characterized in that the feed gas is hydrogen, the process comprising a step of converting ortho hydrogen to para hydrogen in and / or downstream of a passage through a heat exchanger (6) of the heat exchanger assembly.
16. A method according to any one of claims 9 to 15, 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 between 1.05 and five, preferably in the range between 1.3 and 2.7.