Installation and process for liquefying a fluid

Abstract

The invention relates to an installation for liquefying a fluid such as hydrogen comprising a circuit (3) of fluid to be cooled having a downstream end (23) intended to be connected to a member (4) for collecting the liquefied fluid, a set of heat exchanger(s) (5) in heat exchange with the circuit (3) of fluid to be cooled, at least one refrigerator (2) in heat exchange with at least part of the set of heat exchanger(s) (5), the refrigerator having a cycle circuit (12) comprising: a cycle gas compression mechanism (20), at least one cycle gas cooling member (21, 5), a cycle gas expansion mechanism (22) and at least one expanded cycle gas heating member (5), the cycle gas compression mechanism comprising at least two compression stages (20) arranged in series, the expansion mechanism comprising at least two expansion turbines (22), the fluid circuit (3) to be cooled cool possessing,at its upstream end, at least one feed gas compression stage (13), one of the turbines (22) being mechanically coupled (122) to the feed gas compression stage (13) to provide mechanical work produced during expansion. Abstract figure: Fig. 1,

Description

Title of the invention: Installation and method for liquefying a fluid

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

[0002] The invention relates more particularly to an installation for liquefying a fluid such as hydrogen and / or helium comprising a circuit of fluid to be cooled having an upstream end intended to be connected to a source of gaseous fluid and a downstream end intended to be connected to a member for collecting the liquefied fluid, the installation comprising a set of heat exchanger(s) in heat exchange with the circuit of fluid to be cooled, the installation comprising at least one refrigerator in heat exchange with at least part of the set of heat exchanger(s), the refrigerator being a refrigerator with a refrigeration cycle of a cycle gas comprising mainly hydrogen and / or helium, the refrigerator having a cycle circuit comprising: a mechanism for compressing the cycle gas, at least one member for cooling the cycle gas,a cycle gas expansion mechanism and at least one member for reheating the expanded cycle gas, the cycle gas compression mechanism comprising at least two compression stages arranged in series, the expansion mechanism comprising at least two expansion turbines, the fluid circuit to be cooled having, at its upstream end, at least one supply gas compression stage.

[0003] The pressure of the feed gas influences the amount of energy required to be extracted to liquefy this feed gas stream. A feed gas stream at a relatively high pressure is not necessarily always available or may be energy-intensive to produce. Thus, for example, it is known to provide compressors, typically using volumetric technology, to increase the pressure of the feed gas before it is liquefied. This solution is, however, costly in terms of equipment, maintenance and energy consumption.

[0004] In the case of hydrogen, according to other solutions, the feed gas source (electrolyzer or steam reforming device) is configured to supply hydrogen at high pressure. However, this requires significantly increasing the cost of the production equipment, its durability and its energy consumption.

[0005] An aim of the present invention is to overcome all or part of the drawbacks of the prior art noted above.

[0006] To this end, the installation according to the invention, moreover conforming to the definition generic as given in the preamble above, is essentially characterized in that one of the turbines is mechanically coupled to the compression stage of the feed gas to provide mechanical work produced during expansion.

[0007] Furthermore, embodiments of the invention may include one or more of the following features: - the feed gas compression stage is of the centrifugal compressor type, - the fluid circuit to be cooled has, at its upstream end, several feed gas compression stages arranged in series, and in that turbines of the cycle circuit are mechanically coupled respectively to the feed gas compression stages in series, - the expansion mechanism comprises several expansion turbines arranged in series from upstream to downstream, the turbines in series are coupled respectively with compression stages in series taken in the reverse order of their arrangement in series, that is to say that at least one turbine is coupled with a compression stage located upstream of a compression stage coupled to another turbine which precedes it, - the fluid in the fluid circuit to be cooled passing through the compression stages is of a different nature or composition from the fluid circulating in the respectively coupled turbines, for example respectively hydrogen having different Ortho / Para proportions, - only some of the expansion turbines are coupled with feed gas compression stages, - the cycle gas compression mechanism comprises at least two centrifugal type compression stages, at least one expansion turbine being coupled with one of these compression stages of the cycle gas compression mechanism, - the installation is configured so that, in operation, the inlet pressures of the turbines are distinct, the at least one expansion turbine coupled with one of these compression stages of the cycle gas compression mechanism has an inlet pressure which is relatively higher than the inlet pressure of the at least one turbine coupled to a feed gas compression stage, - the at least one expansion turbine is of the centripetal type and / or the compression stage(s) of the feed gas with rotating wheel compressor is of the centrifugal type, - several compression stages are coupled to the same turbine, - the installation includes a pre-cooling system in exchange thermal with at least part of the heat exchanger(s) assembly, said pre-cooling system comprising a heat transfer fluid circuit such as liquid nitrogen and / or a cycle circuit refrigerator of a mixture of refrigerants, the pre-cooling system being configured to cool the fluid circuit to be cooled to an intermediate temperature between the temperature of the fluid at the upstream end of the circuit and the temperature of the fluid at the downstream end of the circuit.

[0008] The invention also relates to a method for producing cryogenic liquefied gas, for example liquid hydrogen, using an installation according to any one of the characteristics above or below, the method comprising a step of compressing a feed gas flow in the at least one feed gas compression stage, a step of cooling the compressed feed gas in the set of heat exchanger(s), in which at least part of the work of compressing the feed gas is provided by at least one turbine of the cycle circuit. The invention may also relate to any alternative device or method comprising any combination of the characteristics above or below within the scope of the claims.

[0009] Other features and advantages will appear on reading the description below, given with reference to the figures in which: Brief description of the figures

[0010] 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:

[0011] [Fig. 1] is a schematic and simplified view illustrating an example of structure and operation of an installation according to a first possible embodiment of the invention,

[0012] [Fig.2] is a schematic and simplified view illustrating an example of structure and operation of an installation according to a second possible embodiment of the invention. Detailed description

[0013] In all the figures, the same references refer to the same elements.

[0014] In this detailed description, the following embodiments are examples. Although 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.

[0015] The installation 1 for liquefying a fluid such as hydrogen and / or helium illustrated in [Fig.l] comprises a circuit 3 of fluid to be cooled having one end upstream intended to be connected to a source of gaseous fluid and a downstream end 23 intended to be connected to a member 4 for collecting the liquefied fluid.

[0016] The source may comprise, for example, an electrolyser or a steam reforming system. The source provides, for example, hydrogen at a first temperature (for example ambient) and at a first pressure, for example between 2 and 25 bar.

[0017] The installation 1 comprises a set of heat exchanger(s) 5 in heat exchange with the circuit 3 of fluid to be cooled. In the schematic example illustrated, a single heat exchanger 5 is shown but several heat exchangers in series can be provided.

[0018] The installation 1 comprises at least one refrigerator 2 in heat exchange with at least part of the set of heat exchanger(s) 5 and configured to supply cold power to the exchanger(s) 5.

[0019] The refrigerator 2 is a refrigerator with a refrigeration cycle of a cycle gas preferably comprising mainly hydrogen and / or helium.

[0020] The refrigerator has a cycle circuit 12 comprising: a mechanism 20 for compressing the cycle gas (preferably several compressors), at least one member 21, 5 for cooling the cycle gas (one or more heat exchangers), a mechanism 22 for expanding the cycle gas (expansion turbines and possibly valve(s)) and at least one member 5 for reheating the expanded cycle gas (one or more heat exchangers).

[0021] The cycle gas compression mechanism comprises at least two compression stages 20 arranged in series, for example centrifugal compressors.

[0022] The expansion mechanism comprises at least two expansion turbines 22, for example centripetal turbines.

[0023] The expansion mechanism may further comprise at least one Joule Thomson type expansion valve 25 arranged for example in series downstream of the turbines 22.

[0024] As illustrated, the installation 1 may comprise a pre-cooling system 6 in heat exchange with at least part of the set of heat exchanger(s) 5. This pre-cooling system 6 may be provided to pre-cool the circuit 3 of fluid to be cooled to an intermediate temperature between the first temperature and the colder temperature obtained at the downstream end 23 (for example liquefaction temperature obtained at the downstream end).

[0025] The pre-cooling system 6 may comprise a circuit 7 of heat transfer fluid such as liquid nitrogen and / or a refrigerator with a circuit 7 of a cycle of a mixture of refrigerants.

[0026] The circuit 3 of fluid to be cooled has, at its upstream end, at least one stage 13 for compressing the feed gas with a compressor, preferably of the type radial centrifugal.

[0027] According to an advantageous feature, at least one of the turbines 22 is mechanically coupled 122 to the feed gas compression stage 13 to provide the compression stage 13 with mechanical work produced during expansion. The coupling is for example achieved by coupling the two wheels (turbine and compressor) to the same rotating shaft 122 to form a “turbocharger”).

[0028] That is to say, the expansion work of the cycle circuit is used at least partially to increase the pressure of the feed gas at room temperature which is going to be liquefied.

[0029] This increase in the pressure of the feed gas makes it possible to reduce the energy to be extracted from the fluid that one seeks to liquefy, while expending less energy than according to the prior art.

[0030] The expansion turbines 22 thus process a gas flow rate significantly higher than the feed gas flow rate to be liquefied. The mechanical power extracted from the turbine side (which is supplied to the compressor) is therefore substantial and makes it possible to generate a significant compression ratio on the feed circuit to be liquefied. This mechanical power is in fact assimilated to the product of the mass flow rate by the enthalpy variation (delta H) at the terminals of the machine considered (turbine or compressor). If the mass flow rate is lower in the compression of the feed circuit 3 than in the turbines of the cycle circuit, the enthalpy variation in the compression of the feed circuit 3 will therefore be significantly higher and therefore the compression ratio at its terminals as well.

[0031] As illustrated, the circuit 3 of fluid to be cooled may have, at its upstream end, several stages 13 for compressing the feed gas with a radial volumetric type compressor, typically centrifugal, arranged in series. All or part of these compressors 13 may be mechanically coupled 122 respectively to respective turbines. Similarly, several compression stages may be coupled to the same turbine 22 (on a common shaft).

[0032] As illustrated, the expansion mechanism may comprise several expansion turbines 22 arranged in series from upstream to downstream.

[0033] As illustrated, preferably, the turbines 22 in series are coupled respectively with compression stages 13 in series taken in the reverse order of their arrangement in series. That is to say, at least one turbine 22 is coupled with a compression stage 13 located upstream of a compression stage 13 coupled to another turbine 22 which precedes it.

[0034] Unlike the example illustrated, only a portion of the expansion turbines 22 can be coupled with one or more compression stages 13 of the feed gas.

[0035] In addition, one or more turbines 12 may be coupled with one or more compressors 20 of the cycle circuit 12. For example, the cycle gas compression mechanism comprises at least two centrifugal type compression stages 20 and at least one expansion turbine 22 is coupled with one of these compression stages 20 of the cycle gas compression mechanism.

[0036] Preferably, the refrigerator 1 is configured so that, in operation, the inlet pressures of the turbines 22 are distinct and the at least one expansion turbine 22 is coupled with one of these compression stages 20 of the cycle gas compression mechanism at an inlet pressure which is relatively higher than the inlet pressure of the at least one turbine 22 coupled 122 to a feed gas compression stage 13.

[0037] This makes it possible to limit the resultant of the axial forces applied to the terminals of each turbomachine.

[0038] Alternatively or in combination, it is possible to recover the expansion work in a hybrid manner. That is to say, for example, the turbines 12 operating at the highest pressures provide their work to pistons (or other), for example in the cycle circuit while the turbines 12 operating at lower pressures provide their work to the compressor(s) of the feed gas.

[0039] This work recovery improves the efficiency of the installation, in particular over the entire temperature range from 300K to 20K.

[0040] [Fig. 2] illustrates a possible alternative embodiment. Elements identical to those described previously are designated by the same numerical references and are not described a second time.

[0041] This variant differs from that of [Fig.l] essentially in that turbines 22 are also coupled to compressors 20 of the cycle circuit 12. That is to say that mechanical expansion work (at least one turbine 22) is provided both to compress 13 the feed gas (to at least one compressor 13) and to compress the cycle gas (at least one compressor 20).

[0042] In the non-limiting example illustrated, two expansion turbines 22 in series are coupled respectively to a compressor 20 (among three compressors 13) of the cycle circuit 12 and to a compressor 13 of the feed gas. In this example, the first turbine 22 in series is coupled with the last compressor 20 of the cycle circuit 12.

[0043] Of course, any other different arrangement can be envisaged to provide mechanical work to n (whole number) compressors 13 of the feed gas and to m (whole number) compressors 22 of the cycle gas. The number of turbines is then n+m (unless several compressors are coupled to the same turbine).

[0044] Depending on the pressure of the cycle gas or the feed gas, the couplings with the turbines can be adapted. This can be adapted to control the axial loads experienced by the turbo-expanders thus formed.

[0045] For example, when there are several turbines 22 coupled to several compressors 20 of the cycle circuit 12, the first turbines 22 are preferably coupled from upstream to downstream, with the compressors 20 of the cycle circuit 12 located downstream of the compressors in series. This makes it possible to couple turbines 12 and compressors 20 at the same relatively higher pressure level (for example between 50 and 60 bar).

[0046] On the other hand, the following turbine(s) 22 are coupled respectively with the compressor(s) of the supply circuit 3 which are at the same relatively lower pressure level (for example between 10 and 20 bar). This pairing of the turbines and compressors by pressure level makes it possible to reduce the axial loads induced in the common drive shafts concerned.

[0047] Thus, the turbine(s) 22 which draw in a relatively higher pressure are coupled to compressors installed on circuits of equivalent pressure while the turbine(s) 22 which draw in a relatively lower pressure are coupled to the compressors installed on a lower pressure circuit (supply circuit 3 in particular).

Claims

Claims

1. Installation for liquefying a fluid such as hydrogen and / or helium comprising a circuit (3) of fluid to be cooled having an upstream end intended to be connected to a source of gaseous fluid and a downstream end (23) intended to be connected to a member (4) for collecting the liquefied fluid, the installation (1) comprising a set of heat exchanger(s) (5) in heat exchange with the circuit (3) of fluid to be cooled, the installation (1) comprising at least one refrigerator (2) in heat exchange with at least part of the set of heat exchanger(s) (5), the refrigerator (2) being a refrigerator with a refrigeration cycle of a cycle gas mainly comprising hydrogen and / or helium, the refrigerator having a cycle circuit (12) comprising: a mechanism (20) for compressing the cycle gas, at least one member (21, 5) for cooling the cycle gas,a cycle gas expansion mechanism (22) and at least one member (5) for reheating the expanded cycle gas, the cycle gas compression mechanism comprising at least two compression stages (20) arranged in series, the expansion mechanism comprising at least two expansion turbines (22), the circuit (3) of fluid to be cooled having, at its upstream end, at least one stage (13) for compressing the feed gas, characterized in that the circuit (3) of fluid to be cooled has, at its upstream end, several stages (13) for compressing the feed gas arranged in series, and in that turbines (22) of the cycle circuit (12) are mechanically coupled (122) respectively to the stages (13) for compressing the feed gas in series to provide mechanical work produced during expansion, the expansion mechanism comprising several expansion turbines (22) arranged in series from upstream to downstream and in that,the turbines (22) in series are coupled respectively with compression stages (13) in series taken in the reverse order of their arrangement in series, that is to say that at least one turbine (22) is coupled with a compression stage (13) located upstream of a compression stage (13) coupled to another turbine (22) which precedes it,

2. Installation according to claim 1, characterized in that the stage (13) for compressing the feed gas is of the centrifugal compressor type.

3. Installation according to any one of claims 1 to 2, characterized in that the fluid of the circuit (3) of fluid to be cooled passing through the compression stages (13) is of a different nature or composition from the fluid circulating in the turbines (22) respectively coupled, for example respectively hydrogen having different Ortho / Para proportions.

4. Installation according to any one of claims 1 to 3, characterized in that only a part of the expansion turbines (22) are coupled with compression stages (13) of the feed gas.

5. Installation according to claim 4, characterized in that the cycle gas compression mechanism comprises at least two centrifugal type compression stages (20), at least one expansion turbine (22) being coupled with one of these compression stages (20) of the cycle gas compression mechanism.

6. Installation according to claim 5, characterized in that it is configured so that, in operation, the inlet pressures of the turbines (22) are distinct, and in that the at least one expansion turbine (22) coupled with one of these compression stages (20) of the cycle gas compression mechanism has an inlet pressure which is relatively higher than the inlet pressure of the at least one turbine (22) coupled (122) to a feed gas compression stage (13).

7. Installation according to any one of claims 1 to 6, characterized in that the at least one expansion turbine (22) is of the centripetal type and / or the stage(s) (13) for compressing the feed gas with a rotating wheel compressor is of the centrifugal type.

8. Installation according to any one of claims 1 to 7, characterized in that several compression stages are coupled to the same turbine (22).

9. Installation according to any one of claims 1 to 8, characterized in that it comprises a pre-cooling system (6) in heat exchange with at least part of the set of heat exchanger(s) (5), said pre-cooling system (6) comprising a circuit (7) of heat transfer fluid such as liquid nitrogen and / or a circuit refrigerator (7) of a cycle of a mixture of refrigerants, the pre-cooling system (6) being configured to cool the fluid circuit (3) of fluid to be cooled to an intermediate temperature between the temperature of the fluid at the upstream end of the circuit (3) and the temperature of the fluid at the downstream end of the circuit (3).

10. A method of producing cryogenic liquefied gas, for example liquid hydrogen, using a plant according to any one of the preceding claims, the method comprising a step of compressing a feed gas flow in the at least one feed gas compression stage (13), a step (5) of cooling the compressed feed gas in the set of heat exchanger(s) (5), wherein at least part of the work of compressing the feed gas is provided by at least one turbine (22) of the cycle circuit.

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