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

Process for liquefying a feed fluid at a cryogenic temperature

[0001] The invention relates to an installation and a method 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 set of heat exchanger(s) in heat exchange with the feed circuit, a cooling device in heat exchange with at least part of the set of heat exchanger(s) 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 for subjecting the cycle gas to a thermodynamic cycle to produce cold, in which 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 arranged 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 pipe of the cycle gas purification member configured to inject a flow of regeneration gas into the cycle gas purification member during a regeneration phase.

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

[0005] This solution still presents risks of solidification of compounds in the cycle.

[0006] Other documents provide for the separation of hydrocarbons after pre-cooling by adsorption. However, these solutions require the provision of sources of pure gas at room temperature (hydrogen) for the regeneration of adsorbents. This is not always possible.

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

[0008] To this end, the installation according to the invention, moreover in accordance with the generic definition given in the preamble above, is essentially characterized in that the at least one regeneration pipe comprises an upstream end connected to the supply circuit and / or to the 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 portion of the heat exchanger 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 pipe of the cycle gas purification member comprising an upstream end connected to the feed circuit at an outlet a feed gas adsorption purification member, the upstream end of the regeneration pipe 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 gas flow concerned 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 the operating configuration, is at a cryogenic temperature, for example around 80K, the regeneration line comprising a heating member configured to heat the gas flow concerned to a determined regeneration temperature, for example to 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 the operating configuration, is at a temperature equal to or close to the target temperature, the regeneration pipe heating member comprises at least one of: at least one reheating passage in at least one of the set of heat exchangers, a heater separate from the set of heat exchangers, for example an electric heater, the installation comprising a system for regenerating the feed gas adsorption purification member, the regeneration system comprising circuitry and a reheating member configured to sweep the adsorption purification member with a flow of regeneration gas at a determined regeneration temperature, the reheating member of the regeneration system of the feed gas adsorption purification member (9) comprising or consisting of the regeneration pipe heating member,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 lift gas by at least one supply line, the supply line being connected to the regeneration line, the at least one supply line is a branch of the regeneration line.,

[0010] The invention also relates to a method for liquefying a feed fluid at a cryogenic temperature, for example hydrogen, the method using an installation provided with a feed circuit for the feed fluid, a set of heat exchanger(s) in heat exchange with the feed circuit, a cooling device in heat exchange with at least part of the set of heat exchanger(s), the cooling device comprising a cycle gas refrigerator comprising, in a cycle circuit, a compression system, a cooling system and an expansion system for subjecting the cycle gas to a thermodynamic cycle to produce cold, in which 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 member for purifying the cycle gas by adsorption,the cycle gas purification member being arranged downstream of a compressor of the compression system and upstream of an expansion member of the expansion system, the method comprising a step of regenerating the cycle gas purification member by scavenging with a regeneration gas flow, the regeneration gas flow being supplied by the supply circuit and / or the cycle circuit.,

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

[0012] 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.

[0013] Other features and advantages will appear on reading the description below, made with reference to the figures in which: Brief description of the figures

[0014] 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:

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

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

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

[0018] In all figures, the same references refer 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. Single 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 the can in particular liquefy hydrogen.

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

[0022] The installation 1 further comprises a heat exchange cooling device 6 with at least part of the heat exchanger assembly configured to cool the feed fluid to a determined target temperature, for example 20K or a similar 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 flow 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 pre-cooling device may be envisaged.

[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 for subjecting 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 member 7 for purifying the cycle gas by adsorption (for example of the TSA type). This member 7 for purifying the cycle gas is arranged 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 compounds of the CnHm type (for example at least one compound of the CnHm type 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 C3H8.

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

[0029] For this purpose, the installation 1 comprises at least one pipe 8 for regenerating the cycle gas purification member 7 configured to periodically inject a flow of regeneration gas into the cycle gas purification member 7 during a regeneration phase.

[0030] According to an advantageous feature, the at least one regeneration pipe 8 comprises an upstream end connected to the supply circuit 2 and / or to the cycle circuit 60 and a downstream end connected to an inlet of the cycle gas purification member 7. That is to say that supply 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 member 9 for purifying the feed gas by adsorption (for example of the TSA type).

[0032] The regeneration pipe 8 of the cycle gas purification member 7 may comprise an upstream end connected to the supply 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] For this purpose, the regeneration pipe 8 of the cycle gas purification member 7 may comprise a reheating member 10 configured to reheat the gas flow concerned before its supply to the cycle gas purification member 7 at a determined regeneration temperature, for example at ambient temperature.

[0034] That is, cold purified feed gas (e.g. 80K) can be reheated before being used for regeneration by the cycle gas purification member 7.

[0035] The heating member 10 may comprise a heating passage in at least one of the set of heat exchangers 3, 4. That is to say that this gas flow is heated by giving off cold to the installation to cool the supply circuit and / or the cycle circuit.

[0036] The heating member 10 may also comprise a heater separate from the set of heat exchanger(s) 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 (taken from supply circuit 2) and its reheating can be shared for these two purification devices 7, 9 of the two circuits 2, 60. This common equipment can be used in particular successively for these two functions and / or simultaneously.

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

[0040] The embodiment of the is distinguished from that of the in that the regeneration gas used for the regeneration of the cycle gas purification member 7 is taken from the cycle circuit 60.

[0041] For example, the upstream end of the regeneration pipe 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 the operating configuration, is at a cryogenic temperature, for example around or below 80K.

[0042] As illustrated, the upstream end of the regeneration pipe 8 can be connected to the cycle circuit 60 downstream of a cycle gas member 26, of the cycle gas purification member 7 to take a flow of pure cycle gas 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 pipe 8 similarly comprises a reheating member 10 to reheat the flow of gas concerned to a determined regeneration temperature, for example ambient temperature.

[0043] As illustrated schematically with dotted lines, at least one turbine 15 of the pre-refrigeration cycle can 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 the, 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 the same axis. Note that possibly this turbo-compressor arrangement (turbine coupled to a compressor) may also apply to one or more compressors of the supply circuit if necessary.

[0045] The bearing of said turbine 26 can be supplied with lift gas by at least one supply line 11. This supply line 11 can 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 branch of the regeneration line 8 (or vice versa).

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

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

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

[0050] The invention makes it possible to ensure, when necessary, the regeneration of adsorbents with a flow of purified gas from the installation. Despite the reheating 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 known solutions.

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

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

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

Claims

A plant for liquefying a feed fluid at a cryogenic temperature, for example hydrogen, comprising a feed circuit (2) for the feed fluid, a set of heat exchanger(s) (3, 4) in heat exchange with the feed circuit, a cooling device (6) in heat exchange with at least part of the set of heat exchanger(s) 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) for subjecting 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 member (7) for purifying the cycle gas by adsorption, the member (7) for purifying the cycle gas being arranged 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 pipe (8) for the member (7) for purifying the cycle gas configured to inject a flow of regeneration gas into the member (7) for purifying the cycle gas during a regeneration phase, characterized in that the at least one regeneration pipe (8) comprises an upstream end connected to the supply circuit (2) and / or to the cycle circuit (60) and a downstream end connected to an inlet of the member (7) for purifying the cycle gas 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 lift gas by at least one supply line (11), the supply line (11) being connected to the regeneration line (8) and / or the installation comprising at least one expansion turbine (26) coupled to a compressor (26) forming a turbo-compressor, the common axis of the turbine and the coupled compressor being supported by a gas-type bearing supplied with lift gas by the supply line (11)., Installation according to claim 1, characterized in that the at least one supply pipe (11) is a branch of the regeneration pipe (8). Installation according to claim 1 or 2, characterized in that it comprises a pre-cooling device (5) in heat exchange with at least part of the set of heat exchanger(s) (3, 4), the pre-cooling device (5) being configured to cool the supply fluid to a pre-cooling temperature higher than the target temperature. Installation according to any one of claims 1 to 3, characterized in that the supply circuit (2) comprises a member (9) for purifying the supply gas by adsorption, the at least one pipe (8) for regenerating the member (7) for purifying the cycle gas comprising an upstream end connected to the supply circuit (2) at an outlet of a member (9) for purifying the supply gas by adsorption. Installation according to claims 3 and 4, characterized in that the upstream end of the regeneration pipe (8) of the cycle gas purification member (7) is connected to the supply circuit (2) downstream of its cooling by the pre-cooling device (5), the regeneration pipe (8) of the cycle gas purification member (7) comprising a heating member (10) configured to heat the gas flow concerned before its supply to the cycle gas purification member (7) to a determined regeneration temperature, for example to ambient temperature. Installation according to any one of claims 1 to 5, characterized in that the upstream end of the regeneration pipe (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 the operating configuration, is at a cryogenic temperature, for example around 80K, the regeneration pipe (8) comprising a heating member (10) configured to heat the gas flow concerned to a determined regeneration temperature, for example ambient temperature. Installation according to claim 6, characterized in that the upstream end of the regeneration pipe (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 the operating configuration, is at a temperature equal to or close to the target temperature. Installation according to any one of claims 5 to 7, characterized in that the member (10) for heating the regeneration pipe (8) comprises at least one of: at least one heating passage in at least one of the set of heat exchanger(s) (3, 4), a heater separate from the set of heat exchanger(s) (3, 4), for example an electric heater. Installation according to claim 5 combined with any one of claims 6 to 8, comprising a system for regenerating the member (9) for purifying the feed gas by adsorption, the regeneration system comprising a circuit and a heating member configured to sweep the member (9) for purifying by adsorption with a flow of regeneration gas at a determined regeneration temperature, characterized in that the heating member of the system for regenerating the member (9) for purifying the feed gas by adsorption comprises or consists of the member (10) for heating the regeneration pipe (8). A method of liquefying a feed fluid at a cryogenic temperature, for example hydrogen, the method using an installation provided with a feed circuit (2) for the feed fluid, a set of heat exchanger(s) (3, 4) in heat exchange with the feed circuit, a cooling device (6) in heat exchange with at least part of the set of heat exchanger(s) (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) for subjecting 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 member (7) for purifying the cycle gas by adsorption, the member (7) for purifying the cycle gas being arranged downstream of a compressor of the compression system (16) and upstream of an expansion member of the expansion system (26), the method comprising a step of regenerating the member (7) for purifying the cycle gas by scavenging with a flow of regeneration gas, the flow of regeneration gas being supplied by the supply 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., Method according to claim 10, characterized in that the regeneration gas flow is taken from the supply circuit (2) and / or from the cycle circuit (60) downstream of a purification at a temperature between 100 and 70K and a determined purity, said flow being reheated before its supply to the cycle gas purification member (7) at a determined regeneration temperature, for example at ambient temperature.

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