Method for liquefying a feed fluid at a cryogenic temperature

Abstract

The invention relates to a plant for liquefying a feed fluid at a cryogenic temperature, comprising: a feed circuit (2); a set of heat exchanger(s) (3, 4) exchanging heat with the feed circuit; a device (6) for cooling the set of heat exchanger(s) and comprising a refrigerator which employs cycle gas comprising hydrogen and / or helium and at least one additional constituent having a molar mass greater than 15 g / mol, the cycle circuit (60) comprising at least one unit (7) for purifying the cycle gas by adsorption arranged downstream of a compressor of the compression system (16) and upstream of an expansion unit of the expansion system (26), the plant (1) comprising at least one regeneration pipe (8) for the cycle-gas purifying unit (7), the regeneration pipe being configured to inject a stream of regeneration gas into the cycle-gas purifying unit (7) during a regeneration phase, the at least one regeneration pipe (8) having an upstream end connected to the feed circuit (2) and / or to the cycle circuit (60) and a downstream end connected to an inlet of the cycle-gas purifying unit (7).

Description

Title: METHOD FOR LIQUEFYING A FEED FLUID AT A CRYOGENIC TEMPERATURE

[0001] The invention relates to an installation and a process for liquefying a feed fluid at a cryogenic temperature.

[0002] The invention relates in particular to the liquefaction of hydrogen.

[0003] The invention relates more particularly to an installation for liquefying a feed fluid at a cryogenic temperature, for example hydrogen, comprising a feed circuit for the feed fluid, a heat exchanger(s) assembly in heat exchange with the feed circuit, a cooling device in heat exchange with at least a part of the heat exchanger(s) assembly configured to cool the feed fluid to a determined target temperature, the cooling device comprising a cycle gas refrigerator comprising, in a cycle circuit, a compression system, a cooling system and an expansion system to subject the cycle gas to a thermodynamic cycle to produce cold, wherein the cycle gas comprises hydrogen and / or helium and at least one additional component having a molar mass greater than 15g / mol, the cycle circuit comprising at least one cycle gas purification member by adsorption, the cycle gas purification member being disposed downstream of a compressor of the compression system and upstream of an expansion member of the expansion system, the installation comprising at least one regeneration line of the cycle gas purification member configured to inject a regeneration gas stream into the cycle gas purification member during a regeneration phase.

[0004] Document FR2723183A describes a liquefaction process that uses hydrogen supplemented by a mixture of hydrocarbons as cycle gas. The hydrogen is compressed with the hydrocarbons which are used for a pre-cooling. The cooling down to the liquefaction temperature of hydrogen is obtained with the hydrogen purified of the hydrocarbons via a separation obtained by successive expansions. These successive expansions which allow a condensation of the heaviest compounds then the last compounds are eliminated via a separation column to allow an expansion at very low temperature without risking solidifying impurities.

[0005] This solution nevertheless presents risks of solidifications of compounds in the cycle.

[0006] Other documents provide for carrying out the separation of the hydrocarbons after precooling by adsorption. However, these solutions require providing sources of pure gas at ambient temperature (hydrogen) for the regeneration of the adsorbents. This is not always possible.

[0007] An aim of the present invention is to overcome all or part of the disadvantages of the prior art noted above.

[0008] To this end, the installation according to the invention, moreover conforming to the generic definition given in the preamble above, is essentially characterized in that the at least one regeneration line comprises an upstream end connected to feed circuit and / or to cycle circuit and a downstream end connected to an inlet of the cycle gas purification member.

[0009] Furthermore, embodiments of the invention may comprise one or more of the following features: - the installation comprises a pre-cooling device in heat exchange with at least a part of the heat exchanger(s) assembly, the pre-cooling device being configured to cool the feed fluid to a pre-cooling temperature higher than the target temperature, - the feed circuit comprises a feed gas adsorption purification member, the at least one regeneration line of the cycle gas purification member comprising an upstream end connected to the feed circuit at an outlet of a feed gas adsorption purification member, - the upstream end of the regeneration line of the cycle gas purification member is connected to the feed circuit downstream of its cooling by the pre-cooling device, the regeneration line of the cycle gas purification member comprising a heating member configured to heat the concerned gas stream before its supply to the cycle gas purification member to a determined regeneration temperature, for example to ambient temperature, - the upstream end of the regeneration line of the cycle gas purification member is connected to the cycle circuit downstream of the cycle gas purification member, at a portion of the cycle circuit which, in operating configuration, is at a cryogenic temperature, for example around 80K, the regeneration line comprising a heating member configured to heat the concerned gas stream to a determined regeneration temperature, for example ambient temperature, - the upstream end of the regeneration line is connected to the cycle circuit downstream of an expansion member of the expansion system at a portion of the cycle circuit which, in operating configuration, is at a temperature equal to or close to the target temperature, - the heating member of the regeneration line comprises at least one among: at least one heating passage in at least one of the heat exchanger(s) assembly, a heater distinct from the heat exchanger(s) assembly, for example an electric heater, - the installation comprising a regeneration system of the feed gas adsorption purification member, the regeneration system comprising a circuitry and a heating member configured to sweep the adsorption purification member with a regeneration gas stream at a determined regeneration temperature, the heating member of the regeneration system of the feed gas adsorption purification member (9) comprising or consisting of the heating member of the regeneration line, - the installation comprising at least one expansion turbine supported by a gas-type bearing, for example a cycle gas turbine, the bearing of said turbine being supplied with support gas by at least one supply line, the supply line being connected to the regeneration line, - the at least one supply line is a bypass of the regeneration line.

[0010] The invention also relates to a process for liquefying a feed fluid at a cryogenic temperature, for example hydrogen, the process using an installation provided with a feed circuit for the feed fluid, a heat exchanger(s) assembly in heat exchange with the feed circuit, a cooling device in heat exchange with at least a part of the heat exchanger(s) assembly, the cooling device comprising a cycle gas refrigerator comprising, in a cycle circuit, a compression system, a cooling system and an expansion system to subject the cycle gas to a thermodynamic cycle to produce cold, wherein the cycle gas comprises hydrogen and / or helium and at least one additional component having a molar mass greater than 15g / mol, the cycle circuit comprising at least one cycle gas purification member by adsorption, the cycle gas purification member being disposed downstream of a compressor of the compression system and upstream of an expansion member of the expansion system, the process comprising a step of regenerating the cycle gas purification member by sweeping with a regeneration gas stream, the regeneration gas stream being supplied by the feed circuit and / or the cycle circuit.

[0011] According to other possible particularities, the regeneration gas stream is withdrawn from the feed circuit and / or from the cycle circuit downstream of a purification at a temperature comprised between 100 and 70K and a determined purity, said stream being heated before its supply to the cycle gas purification member to a determined regeneration temperature, for example to ambient temperature.

[0012] The invention may also relate to any alternative device or process comprising any combination of the features above or below within the scope of the claims.

[0013] Other particularities and advantages will appear upon reading the following description, made with reference to the figures in which: Brief description of the figures

[0014] The invention will be better understood upon reading the following description given solely by way of example and made with reference to the appended drawings in which:

[0015] [Fig. 1] is a schematic and partial view illustrating the structure and the operation of a first exemplary embodiment of an installation according to the invention,

[0016] [Fig. 2] is a schematic and partial view illustrating the structure and the operation of a second exemplary embodiment of an installation according to the invention,

[0017] [Fig. 3] is a schematic and partial view illustrating the structure and the operation of a third exemplary embodiment of an installation according to the invention. Detailed description

[0018] In all the figures, the same references relate to the same elements.

[0019] 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. Simple features of different embodiments may also be combined and / or interchanged to provide other embodiments.

[0020] The installation 1 for liquefying a feed fluid at a cryogenic temperature illustrated in [Fig. 1] can in particular liquefy hydrogen.

[0021] The installation 1 comprises a feed circuit 2 for the feed fluid (typically a more or less pure hydrogen stream), a heat exchanger(s) assembly 3, 4 in heat exchange with the feed circuit.

[0022] The installation 1 further comprises a cooling device 6 in heat exchange with at least part of the heat exchanger(s) assembly configured to cool the feed fluid to a determined target temperature, for example 20K or a neighboring temperature, with a view to its liquefaction.

[0023] As shown schematically, the installation 1 may comprise at least one pre-cooling device 5 configured to pre-cool the feed gas stream between the initial temperature (ambient temperature for example) and an intermediate pre-cooling temperature (for example 80K).

[0024] The pre-cooling device 5 may comprise a cycle refrigerator (for example nitrogen) comprising for example a compression 15 and an expansion 25 to produce cold. Any other precooling device may be considered.

[0025] The cooling device 6 comprises a cycle gas refrigerator comprising, in a cycle circuit 60, a compression system 16, a cooling system and an expansion system 26 to subject the cycle gas to a thermodynamic cycle to produce cold. The cycle gas comprises hydrogen and at least one additional component having a molar mass greater than 15g / mol, for example at least one hydrocarbon, for example a mixture of refrigerants.

[0026] After purification and pre-cooling of the cycle gas, the cycle circuit 60 comprises at least one cycle gas purification member 7 by adsorption (for example of the TSA type). This cycle gas purification member 7 is disposed downstream of a compressor of the compression system 16 and upstream of an expansion member of the expansion system 26 to remove the heavy components before expansion and cooling to temperatures below 80K.

[0027] This purification member 7 is configured in particular to produce a regeneration gas with a determined degree of purity, in particular free of compound(s) having a molar mass greater than 2g / mol from a mixture of hydrogen and / or helium and of CnHm type compounds (for example at least one CnHm type compound different from CH4 and for example without nitrogen). For example, upstream of the purification member 7, the hydrogen cycle gas contains a few ppm of C2H6 and of C3H8.

[0028] The gas purification member 7 may in particular comprise several separation vessels disposed in parallel and alternating purification phases (adsorption of impurities) and regeneration phases (evacuation of impurities). The purification member 7 may be of the molecular sieve type (zeolite of the 13X type for example).

[0029] To this end, the installation 1 comprises at least one regeneration line 8 of the cycle gas purification member 7 configured to periodically inject a regeneration gas stream into the cycle gas purification member 7 during a regeneration phase.

[0030] According to an advantageous particularity, the at least one regeneration line 8 comprises an upstream end connected to feed circuit 2 and / or to cycle circuit 60 and a downstream end connected to an inlet of the cycle gas purification member 7. That is to say that feed gas (pure hydrogen) and / or cycle gas (pure hydrogen) is used as regeneration gas.

[0031] As illustrated, the feed circuit 2 may comprise, for example downstream of a portion pre-cooled to the pre-cooling temperature, a feed gas adsorption purification member 9 (for example of the TSA type).

[0032] The regeneration line 8 of the cycle gas purification member 7 may comprise an upstream end connected to feed circuit 2 at an outlet of the feed gas adsorption purification member 9. The feed gas is for example purified to a determined level of purity, for example so as to be free of compounds having a molar mass greater than 2g / mol.

[0033] To this end, the regeneration line 8 of the cycle gas purification member 7 may comprise a heating member 10 configured to heat the concerned gas stream before its supply to the cycle gas purification member 7 to a determined regeneration temperature, for example to ambient temperature.

[0034] That is to say that purified and cold feed gas (for example 80K) can be heated before being used for the regeneration of the cycle gas purification member 7.

[0035] The heating member 10 may comprise a heating passage in at least one of the heat exchanger(s) assembly 3, 4. That is to say that this gas stream is heated by yielding cold to the installation to cool the feed circuit and / or the cycle circuit.

[0036] The heating member 10 may also comprise a heater distinct from the heat exchanger(s) assembly 3, 4, for example an electric heater.

[0037] As illustrated, this heating member 10 can ensure both the heating of the regeneration gas of the feed gas purification member 9 and the heating of the regeneration gas of the cycle gas purification member 7.

[0038] Thus the withdrawal of this regeneration gas (withdrawal from the feed circuit 2) and its heating can be shared for these two purification members 7, 9 of the two circuits 2, 60. These common equipments can be used in particular successively for these two functions and / or simultaneously.

[0039] As illustrated, after sweeping of the purification member 7, the regeneration gas loaded with impurities can be returned, via a recycling line 18, into the cycle circuit 60, for example into the compression system 16 notably at an intermediate pressure level between two compression stages. As illustrated, a heating member 12 may be provided in this return line 18 to bring the recycled gas back to ambient temperature for example.

[0040] The embodiment of [Fig. 2] differs from that of [Fig. 1] in that the regeneration gas used for the regeneration of the cycle gas purification member 7 is withdrawn from the cycle circuit 60.

[0041] For example, the upstream end of the regeneration line 8 is connected to the cycle circuit 60 downstream of the cycle gas purification member 7, at a portion of the cycle circuit which, in operating configuration, is at a cryogenic temperature, for example around or below 80K.

[0042] As illustrated, the upstream end of the regeneration line 8 may be connected to the cycle circuit 60 downstream of a cycle gas member 26, of the cycle gas purification member 7 to withdraw a pure cycle gas stream at an intermediate pressure (for example between 5 and 20 bar) and which returns to a temperature for example of 40K or lower. The regeneration line 8 comprising in the same way a heating member 10 to heat the concerned gas stream to a determined regeneration temperature, for example ambient temperature.

[0043] As illustrated schematically with dotted lines in [Fig. 1] and [Fig. 2], at least one turbine 15 of the pre-refrigeration cycle may be coupled to a compressor 25 of the same cycle to form a turbo-compressor. The same applies to the refrigeration cycle 60.

[0044] As shown schematically in [Fig. 3], the cycle circuit may in particular comprise at least one expansion turbine 26 supported by a gas-type bearing, for example a cycle gas turbine. As illustrated, the turbine 26 may be coupled to a compressor 16 of the cycle circuit 60 on a same axis. It should be noted that optionally this turbo-compressor arrangement (turbine coupled to a compressor) may also apply to one or more compressors of the feed circuit if applicable.

[0045] The bearing of said turbine 26 may be supplied with support gas by at least one supply line 11. This supply line 11 may be connected to the regeneration line 8. That is to say that the pure gas used for the regeneration of a purification member can also be used to supply a bearing.

[0046] For example, the at least one supply line 11 is a bypass of the regeneration line 8 (or vice versa).

[0047] In the non-limiting example of [Fig. 3], purified gas with a view to regeneration can be withdrawn at the outlet of a cycle gas purification member 7. This cycle gas is heated, for example in a part 3 of the heat exchanger assembly. A first fraction of this heated gas can be distributed (after an optional valve 17) via a first supply line 11 to support the bearing of at least one compressor 16. The regeneration gas is sent via the line 8 into the purification member(s) 7 to be regenerated. A second fraction of this gas can be distributed via a second supply line 11 to support the bearing of at least one turbine 26. As illustrated, a gas stream can also be sent (line 80) for the regeneration of a feed gas purification member 9.

[0048] The distribution of the different pure gas streams can be ensured by a set of valves 17.

[0049] In the illustrated example, after sweeping of the purification member 7, the regeneration gas loaded with impurity can be returned into the cycle circuit 60, for example at the inlet of the compression 16.

[0050] The invention makes it possible to ensure, when necessary, the regeneration of the adsorbents with a purified gas stream of the installation. Despite the heating of a cold gas to have a regeneration gas at a non-cryogenic temperature, the impact on the energy efficiency of the installation is minor and in particular more advantageous overall than the known solutions.

[0051] In particular, the installation uses a feed gas stream at a pressure comprised for example between 10 and 60 bara and / or a cycle gas stream at a pressure comprised between 1 and 70 bara (for example a low-pressure portion comprised between 1 and 3 bar, a mediumpressure part between 5 and 10 bara and a high-pressure part between 50 and 70 bara). The regeneration can be carried out with a stream at one of these pressures, preferably at the medium pressure. These pure gas streams under pressure allow a regeneration of the adsorbents and can be shared and can even be recycled in the installation after use.

[0052] The gas stream for the bearing(s) (if applicable) is for its part preferably at a pressure comprised between 20 and 50 bara.

[0053] The regenerations of the feed gas and cycle gas purification members can be synchronized or not.

Claims

1. Installation for liquefying a feed fluid at a cryogenic temperature, forexample hydrogen, comprising a feed circuit (2) for the feed fluid, a heat exchanger(s) assembly (3, 4) in heat exchange with the feed circuit, a cooling device (6) in heat exchange with at least a part of the heat exchanger(s) assembly configured to cool the feed fluid to a determined target temperature, the cooling device (6) comprising a cycle gas refrigerator comprising, in a cycle circuit (60), a compression system (16), a cooling system and an expansion system (26) to subject the cycle gas to a thermodynamic cycle to produce cold, wherein the cycle gas comprises hydrogen and / or helium and at least one additional component having a molar mass greater than 15g / mol, the cycle circuit (60) comprising at least one cycle gas purification member (7) by adsorption, the cycle gas purification member (7) being disposed downstream of a compressor of the compression system (16) and upstream of an expansion member of the expansion system (26), the installation (1) comprising at least one regeneration line (8) of the cycle gas purification member (7) configured to inject a regeneration gas stream into the cycle gas purification member (7) during a regeneration phase, characterized in that the at least one regeneration line (8) comprises an upstream end connected to feed circuit (2) and / or to cycle circuit (60) and a downstream end connected to an inlet of the cycle gas purification member (7) and in that it comprises at least one expansion turbine (26) supported by a gas-type bearing, for example a cycle gas turbine, the bearing of said turbine (26) being supplied with support gas by at least one supply line (11), the supply line (11) being connected to the regeneration line (8).

2. Installation according to claim 1, characterized in that at least oneexpansion turbine (26) is coupled to a compressor (26) forming a turbo-compressor, the common axis of the turbine and of the coupled compressor being supported by a gas-type bearing supplied with support gas by the supply line (11)

3. Installation according to claim 1 or 2, characterized in that the at leastone supply line (11) is a bypass of the regeneration line (8).

4. Installation according to any of claims 1 to 3, characterized in that itcomprises a pre-cooling device (5) in heat exchange with at least a part of the heat exchanger(s) assembly (3, 4), the pre-cooling device (5) being configured to cool the feed fluid to a pre-cooling temperature higher than the target temperature.

5. Installation according to any one of claims 1 to 4, characterized in thatthe feed circuit (2) comprises a feed gas adsorption purification member (9), the at least one regeneration line (8) of the cycle gas purification member (7) comprising an upstream end connected to the feed circuit (2) at an outlet of a feed gas adsorption purification member (9).

6. Installation according to claims 4 and 5, characterized in that theupstream end of the regeneration line (8) of the cycle gas purification member (7) is connected to the feed circuit (2) downstream of its cooling by the pre-cooling device (5), the regeneration line (8) of the cycle gas purification member (7) comprising a heating member (10) configured to heat the concerned gas stream before its supply to the cycle gas purification member (7) to a determined regeneration temperature, for example to ambient temperature.

7. Installation according to any one of claims 1 to 6, characterized in thatthe upstream end of the regeneration line (8) of the cycle gas purification member (7) is connected to the cycle circuit (60) downstream of the cycle gas purification member (7), at a portion of the cycle circuit which, in operating configuration, is at a cryogenic temperature, for example around 80K, the regeneration line (8) comprising a heating member (10) configured to heat the concerned gas stream to a determined regeneration temperature, for example ambient temperature.

8. Installation according to claim 7, characterized in that the upstream endof the regeneration line (8) is connected to the cycle circuit (60) downstream of an expansion member of the expansion system (26) at a portion of the cycle circuit which, in operating configuration, is at a temperature equal to or close to the target temperature.

9. Installation according to any one of claims 6 to 8, characterized in thatthe heating member (10) of the regeneration line (8) comprises at least one among: at least one heating passage in at least one of the heat exchanger(s) assembly (3, 4), a heater distinct from the heat exchanger(s) assembly (3, 4), for example an electric heater.

10. Installation according to claim 6 combined with any one of claims 7 to9, comprising a regeneration system of the feed gas adsorption purification member (9), the regeneration system comprising a circuitry and a heating member configured to sweep the adsorption purification member (9) with a regeneration gas stream at a determined regeneration temperature, characterized in that the heating member of the regeneration system of the feed gas adsorption purification member (9) comprises or consists of the heatingmember (10) of the regeneration line (8).

11. Process for liquefying a feed fluid at a cryogenic temperature, forexample hydrogen, the process using an installation provided with a feed circuit (2) for the feed fluid, a heat exchanger(s) assembly (3, 4) in heat exchange with the feed circuit, a cooling device (6) in heat exchange with at least a part of the heat exchanger(s) assembly (3, 4), the cooling device (6) comprising a cycle gas refrigerator comprising, in a cycle circuit (60), a compression system (16), a cooling system and an expansion system (26) to subject the cycle gas to a thermodynamic cycle to produce cold, wherein the cycle gas comprises hydrogen and / or helium and at least one additional component having a molar mass greater than 15g / mol, the cycle circuit (60) comprising at least one cycle gas purification member (7) by adsorption, the cycle gas purification member (7) being disposed downstream of a compressor of the compression system (16) and upstream of an expansion member of the expansion system (26), the process comprising a step of regenerating the cycle gas purification member (7) by sweeping with a regeneration gas stream, the regeneration gas stream being supplied by the feed circuit (2) and / or the cycle circuit (60) and in that regeneration gas is used to supply a gas-type bearing supporting an expansion turbine (26) of the installation and / or a gas-type bearing supporting a common axis of a coupled turbine and compressor forming a turbo-compressor of the installation.

12. Process according to claim 11, characterized in that the regeneration gasstream is withdrawn from the feed circuit (2) and / or from the cycle circuit (60) downstream of a purification at a temperature comprised between 100 and 70K and a determined purity, said stream being heated before its supply to the cycle gas purification member (7) to a determined regeneration temperature, for example to ambient temperature.

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