Refrigerator, liquefaction plant and process.

Abstract

The invention relates to a cycle gas refrigerator, an installation and a method comprising, in a cycle circuit (60), a cycle gas comprising a first light component consisting of hydrogen and / or helium and at least one heavy component having a molar mass greater than 15g / mol, the cycle circuit (60) comprising a turbine (26) coupled to a compressor (16) on a common shaft (20), the refrigerator comprising a casing (19) housing a first chamber (150) in which the compressor (16) is mounted, a second chamber (24) in which the turbine (26) is mounted, a third intermediate chamber (18) in which the shaft (20) is mounted, the first chamber (150) being connected to a first circuit containing unpurified cycle gas at a first pressure, the second chamber (24) being connected to a second circuit of purified cycle gas at a second pressure and at a cryogenic temperature,the third chamber (24) being connected to a third circuit of unpurified cycle gas at a third pressure, the first pressure being higher than the second pressure, the third pressure being lower than the second pressure, the refrigerator (6) comprising a barrier cavity (11) situated between the third chamber and the second chamber (24) and connected to a fourth supply circuit (111) containing purified cycle gas, the fourth supply circuit (111) being configured to supply purified cycle gas at ambient temperature at a fourth regulated pressure to promote the migration of the barrier gas to the second chamber (24) or to the third chamber. (Shorthand figure: Fig. 1)

Description

Title of the invention: Refrigerator, liquefaction installation and process.

[0001] The invention relates to a refrigerator, a liquefaction installation and a method of implementation.

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

[0003] The invention relates more particularly to 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 a first light component consisting of hydrogen and / or helium and at least one additional heavy component having a molar mass greater than 15g / mol, the cycle circuit comprising at least one cycle gas purification device for the heavy component(s), the cycle gas purification device being disposed downstream of a compressor of the compression system and upstream of a turbine of the expansion system, the turbine being coupled to a compressor on a common shaft forming a turbo-compressor, the refrigerator comprising a casing housing a first chamber in which the compressor is mounted for rotation,a second chamber in which the turbine is mounted for rotation, a third intermediate chamber in which the shaft is mounted for rotation on a set of bearing(s), the first chamber being connected to a first circuit of the refrigerator containing unpurified cycle gas at a first pressure, i.e. gas comprising the light component and one or more heavy component(s), the second chamber being connected to a second pressurized gas circuit of the refrigerator containing purified cycle gas at a second pressure and at a cryogenic temperature, i.e. gas comprising the light component at a temperature below 120K and free of all or most of the heavy component(s), the third chamber being connected to a third gas circuit of the refrigerator containing unpurified cycle gas at a third pressure, i.e. gas comprising the light component and one or more heavy component(s),the first pressure being higher than the second pressure, the third pressure being lower than the second pressure, the refrigerator comprising a dam cavity located between the third chamber and the second chamber, the dam cavity being connected to a fourth refrigerator supply circuit containing purified cycle gas.

[0004] Document FR2723183A describes a liquefaction process that uses hydrogen supplemented with a mixture of hydrocarbons as the cycle gas. Hydrogen is compressed with hydrocarbons which are used for pre-cooling. Cooling to the hydrogen liquefaction temperature is achieved using hydrogen purified from hydrocarbons via a separation process involving successive expansions. These successive expansions allow for the condensation of the heaviest compounds, and the remaining compounds are then removed via a separation column to enable expansion at very low temperatures without the risk of solidifying impurities.

[0005] The turbine(s) of the cycle circuit can be coupled to a compressor of the cycle circuit to recover work.

[0006] The cryogenic turbine must process a cycle gas purified of heavy compounds to prevent them from freezing. The turbine and compressor ends therefore process gas streams of different natures (compositions).

[0007] It is therefore necessary to ensure that there is no migration of the relatively hot unpurified gas into the relatively cold purified gas circuits.

[0008] It is known for this purpose to provide for the injection of a barrier gas to separate the parts at risk at the level of the shaft.

[0009] The known solutions are not satisfactory or applicable to the aforementioned case.

[0010] One object of the present invention is to overcome all or part of the disadvantages of the prior art noted above.

[0011] To this end, the installation according to the invention, which otherwise conforms to the generic definition given in the preamble above, is essentially characterized in that the fourth supply circuit is configured to supply purified cycle gas at ambient temperature at a fourth regulated pressure to promote the migration of the barrier gas towards the second chamber or towards the third chamber.

[0012] According to other possible features: - the fourth supply circuit includes a pressure regulating device, for example a valve, configured to supply purified cycle gas at the fourth pressure which is equal to the second pressure or which is lower than the second pressure but higher than the third pressure, - the dam cavity is delimited longitudinally along the shaft (20) by two labyrinth-type joints, - the fourth supply circuit includes a pressure and / or flow regulating valve, - the fourth supply circuit is connected to the cycle circuit downstream of the purification unit, - the fourth supply circuit includes a heating element configured to heat the cycle gas supplied to the dam cavity, - The shaft is supported at the turbine by a first bearing and at the compressor by a second bearing. - the first bearing is a magnetic bearing or a gas bearing supplied with levitation gas, for example supplied with levitation gas from the first pressurized gas circuit, - the second bearing is a magnetic bearing or a gas bearing supplied with lifting gas, for example supplied with lifting gas from the third pressurized gas circuit and / or the fourth supply circuit. - The invention also relates to a liquefaction installation for 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 refrigerator according to any one of the above or below characteristics.

[0013] According to other possible features: - the installation includes a pre-cooling device in heat exchange with at least part of the heat exchanger assembly(ies), the pre-cooling device being configured to cool the feed fluid to a pre-cooling temperature higher than the target temperature, - the feed circuit includes a purification unit by adsorption of the feed gas, the fourth feed circuit being connected to the feed circuit downstream of the purification unit, - the compressor coupled to the turbine is a compressor of the supply circuit or a compressor of the compression system of the cycle circuit.

[0014] The invention also relates to a refrigeration process using a refrigerator according to any one of the above or below characteristics or an installation according to any one of the above or below characteristics, comprising a stage of expansion, in the turbine coupled to the compressor, of a purified cycle gas stream at a temperature between 100K and 20K and simultaneously a compression, in the compressor, of an unpurified cycle gas, the process comprising a stage of injection, into the dam cavity, of a dam gas consisting of purified cycle gas and at a temperature between 275K and 310K.

[0015] According to a possible feature, the barrier gas injected during the injection step is at a controlled pressure to promote the migration of the barrier gas towards the second chamber or towards the third chamber.

[0016] 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.

[0017] Other features and advantages will become apparent from the following description, given with reference to the figures in which: Brief description of the figures

[0018] 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:

[0019] [Fig. 1] 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,

[0020] [Fig.2] is a schematic longitudinal sectional view of a detail of the refrigerator turbo-machine of the installation illustrating the arrangement of the wheels (turbine and compressor) on a refrigerator shaft and its operation according to one possible embodiment. Detailed description

[0021] In all figures, the same references refer to the same elements.

[0022] 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 from different embodiments can also be combined and / or interchanged to provide other embodiments.

[0023] The installation 1 for liquefying a feed fluid at a cryogenic temperature illustrated in [Fig.1] can in particular liquefy hydrogen.

[0024] The installation 1 includes a supply circuit 2 for the supply fluid (typically a more or less pure hydrogen stream), a set of heat exchanger(s) 3, 4 in heat exchange with the supply circuit 2.

[0025] Installation 1 further includes a heat exchange cooling device 6 with at least part of the heat exchanger assembly(ies) configured to cool the feed fluid to a predetermined target temperature, for example 20K or a temperature close to it, for the purpose of its liquefaction.

[0026] As schematically shown, the installation 1 may include 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).

[0027] The pre-cooling device 5 may include a cycle refrigerator (e.g., nitrogen) comprising, for example, a compression 15 and an expansion 25 for producing cold. Any other pre-cooling device may be considered.

[0028] The cooling device 6 comprises a cycle gas refrigerator including, 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 15 g / mol, for example, at least one hydrocarbon, for example, a mixture of nitrogen-type refrigerants and a mixture of hydrocarbons.

[0029] The refrigerator can in particular be configured to cool the feed gas flow between the intermediate pre-cooling temperature and a target temperature (for example around 20K).

[0030] After purification and pre-cooling of the cycle gas, the cycle circuit 60 includes at least one cycle gas purification device 7 by adsorption (for example, of the TSA type). This cycle gas purification device 7 is located downstream of a compressor of the compression system 16 and upstream of an expansion device of the expansion system 26 to remove heavy components before expansion and cooling to temperatures below 80K.

[0031] This purification stage 7 is configured in particular to produce a regeneration gas with a determined degree of purity, specifically free from compound(s) having a molar mass greater than 2 g / mol, from a mixture of hydrogen and / or helium and CnHm-type compounds (for example, at least one CnHm-type compound other than CH4 and, for example, without nitrogen). For example, upstream of the purification stage 7, the hydrogen cycle gas contains a few ppm of C2H6 and C3H8.

[0032] The gas purification unit 7 may, in particular, comprise several separation vessels arranged in parallel and alternating between purification phases (adsorption of impurities) and regeneration phases (removal of impurities). The purification unit 7 may be of the molecular sieve type (13X zeolite, for example).

[0033] As illustrated, the supply circuit 2 may include, for example downstream of a portion pre-cooled to the pre-cooling temperature, a purification element 9 for the adsorption of the feed gas (for example of the TSA type).

[0034] As schematically illustrated with dashed lines, at least one turbine 26 of the cycle circuit can be coupled to a compressor 16 of the same cycle to form a turbo-compressor. The same applies to the pre-cooling cycle 5, which can include a turbo-compressor.

[0035] As seen in [Fig.2], the turbine 2 is coupled to a compressor 16 on a common shaft 20 forming a turbo-compressor.

[0036] The refrigerator 6 includes a casing 19 housing a first chamber 150 in which the compressor 16 is mounted in rotation, a second chamber 24 in which the turbine 26 is mounted in rotation and a third intermediate chamber 18 in which the shaft 20 is mounted in rotation on a set of bearings 21.

[0037] For example, the shaft 20 is supported by at least two bearings 21 (one on the turbine side 26 and one on the compressor side 16). The bearings 21 can be of the gas type (for example static) or magnetic type.

[0038] The first chamber 150 is connected to a first circuit of the refrigerator containing unpurified cycle gas at a first pressure, i.e., gas comprising the light component and one or more heavy component(s). The first chamber 150 is supplied, for example, with cycle gas at the inlet or outlet of a compression stage of the cycle circuit 60 at a non-cryogenic temperature, for example, ambient temperature.

[0039] The second chamber 24 is connected to a second pressurized gas circuit of the refrigerator containing purified cycle gas at a second pressure and cryogenic temperature.

[0040] That is to say, the turbine 26 is supplied with cycle gas comprising the light component at a temperature below 120K, for example 80K and free of all or most of the heavy component(s).

[0041] The third chamber 18 is connected to or supplied with unpurified cycle gas at a third pressure. As before, this unpurified gas comprises the light component and one or more heavy component(s).

[0042] The refrigerator is configured to maintain pressures in the circuits such that the first pressure (for example 30 bara) is greater than the second pressure (for example 10 bara) and the third pressure (for example 7 bara) is less than the second pressure.

[0043] To prevent the migration of components that can freeze to the second chamber which is at cryogenic temperature, the refrigerator 6 includes a barrier cavity 11 located between the third chamber 18 and the second chamber 24.

[0044] The dam cavity 11 can be delimited longitudinally along the shaft 20 by two labyrinth-type joints 17.

[0045] The barrier cavity 11 is connected to a fourth refrigerator supply circuit 111 containing purified cycle gas. This fourth supply circuit 11 is configured to provide purified cycle gas at ambient temperature (for example, between 275 and 310 K) at a fourth regulated pressure to promote the migration of the barrier gas to the second chamber 24 or to the third chamber 18.

[0046] As illustrated, the fourth supply circuit 111 preferably includes a pressure regulating device 110 (for example a pressure and / or flow regulating valve 110), configured to supply purified cycle gas at the fourth pressure which is equal to the second pressure (of the second chamber 24) or which is lower than the second pressure but higher than the third pressure (of the third chamber 18).

[0047] The fourth supply circuit 111 is for example connected to the cycle circuit 6 downstream of the purification organ 7.

[0048] This purified cycle gas is at cryogenic temperature. To bring it to ambient temperature, the fourth supply circuit 111 may include for this purpose a heating element 112 configured to heat the cycle gas supplied to the dam cavity 11.

[0049] This heating element 112 may include, for example, a passage through a heat exchanger of the refrigerator 6. This allows the cold to be utilized in the refrigerator, for example in a heat exchanger 3 of the installation.

[0050] According to this arrangement, the hot end (compressor side 16 and central section equipped with bearings 21) operates with unpurified gas, while the cryogenic cold end (turbine side 26) operates with purified gas, i.e., gas compatible with use at cryogenic temperatures, typically around 80 K or less. To prevent the migration of impure fluid from the hot end to the cryogenic end, a purified barrier gas at ambient temperature is injected near the bearing 21 on the turbine side 26.

[0051] This barrier gas is injected with a determined pressure level. Its injection pressure in the labyrinth seal, instead of said barrier, is preferably equal to the pressure at the turbine 26. In this case, this barrier gas can migrate towards the central part of the shaft 20.

[0052] However, the pressure of this injected barrier gas may be higher than the pressure at the turbine. In this case, the barrier gas may migrate towards the turbine 26. Injecting a relatively hot gas towards the cryogenic turbine is not recommended, but this does prevent the migration of heavy components.

[0053] Note that the bearings 21 supporting the shaft 20 can be of the magnetic bearing or gas-bearing type. In the case of gas bearings, the lifting gas in the bearings can be supplied by all or part of the aforementioned pressurized fluid circuits. For example, on the compressor 16 side, the lifting gas can be taken from the unpurified gas flow (for example, taken from the compression outlet in the cyclel circuit 60 which produces, for example, pressure levels between 1 and 6 bara, between 6 and 20 bara, and between 20 and 60 bara).

[0054] The simplified arrangement in [Fig. 1] is not limiting in any way. The number and arrangement of the compressors 16 and turbines 26 may differ. In particular, the installation may include several turbines in series, at least some of which are coupled to one or more compressors.

[0055] The compressor(s) 16 coupled to at least one turbine can be located in a compression stage at relatively low, high or medium pressure.

[0056] Similarly, it could be considered that the compressor coupled to the turbine is a compressor of the supply circuit 2.

[0057] Note that the dam gas could be taken from the supply circuit 2 (downstream of the purification unit 9).

[0058] The distribution of the different pure gas flows can be ensured by a set of valves.

[0059] The regenerations of the feed gas and cycle gas purification organs may or may not be synchronized.

[0060] Note that in the schematic representation of [Fig. 1], one end of the first chamber 150 is delimited by a labyrinth-type joint 17. This type of arrangement is optional and more applicable to a "closed wheel" type architecture.

[0061] Furthermore, the examples of embodiments described are in no way limiting, the shape and / or location of the labyrinth-type joint(s) 17 may be modified.

Claims

1. Demands 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 a first light component consisting of hydrogen and / or helium and at least one additional heavy component having a molar mass greater than 15g / mol, the cycle circuit (60) comprising at least one cycle gas purification device (7) for removing the heavy component(s), the cycle gas purification device (7) being disposed downstream of a compressor of the compression system (16) and upstream of a turbine (26) of the expansion system (26), the turbine (26) being coupled to a compressor (16) on a common shaft (20) forming a turbo-compressor, the refrigerator comprising a casing (19) housing a first chamber (150) in which the compressor (16) is mounted for rotation,a second chamber (24) in which the turbine (26) is mounted for rotation, a third intermediate chamber (18) in which the shaft (20) is mounted for rotation on a set of bearing(s) (21), the first chamber (150) being connected to a first circuit of the refrigerator containing unpurified cycle gas at a first pressure, i.e. gas comprising the light component and one or more heavy component(s), the second chamber (24) being connected to a second pressurized gas circuit of the refrigerator containing purified cycle gas at a second pressure and at a cryogenic temperature, i.e. gas comprising the light component at a temperature below 120K and free of all or most of the heavy component(s), the third chamber (24) being connected to a third gas circuit of the refrigerator containing unpurified cycle gas at a third pressure,that is to say, gas comprising the light component and one or more heavy component(s), the first pressure being greater than the second pressure, the third pressure being less than the second pressure, the refrigerator (6) comprising a dam cavity (11) situated between the third chamber and the second chamber (24), the dam cavity (11) being connected to a fourth supply circuit (111), of the refrigerator containing purified cycle gas, the fourth supply circuit (111) being configured to supply purified cycle gas at room temperature at a fourth regulated pressure to promote the migration of the barrier gas to the second chamber (24) or to the third chamber.

2. Refrigerator according to the preceding claim characterized in that the fourth supply circuit (111) includes a pressure regulating device (110), for example a valve, configured to supply purified cycle gas at the fourth pressure which is equal to the second pressure or which is less than the second pressure but greater than the third pressure.

3. Refrigerator according to any one of the preceding claims, characterized in that the barrier cavity (11) is delimited longitudinally along the shaft (20) by two labyrinth-type seals (17).

4. Refrigerator according to any one of the preceding claims, characterized in that the fourth supply circuit (111) includes a pressure and / or flow regulating valve (110).

5. Refrigerator according to any one of the preceding claims, characterized in that the fourth supply circuit (111) is connected to the cycle circuit (6) downstream of the purification unit (7).

6. Refrigerator according to the preceding claim, characterized in that the fourth supply circuit (111) includes a heating element (112) configured to heat the cycle gas supplied to the dam cavity (11).

7. Refrigerator according to any one of the preceding claims, characterized in that the shaft (20) is supported at the turbine (26) by a first bearing (21) and supported at the compressor (16) by a second bearing (21).

8. Refrigerator according to the preceding claim, characterized in that the first bearing (21) is a magnetic bearing or a gas bearing supplied with levitation gas, for example supplied with levitation gas from the first pressurized gas circuit.

9. Refrigerator according to claim 7 or 8, characterized in that the second bearing (21) is a magnetic bearing or a gas bearing supplied with levitation gas, for example supplied with levitation gas from the third pressurized gas circuit and / or the fourth supply circuit (111).

10. Installation 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 a 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 refrigerator according to any one of the preceding claims.

11. Installation according to the preceding claim, characterized in that it comprises a pre-cooling device (5) in heat exchange with at least part of the heat exchanger 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.

12. Installation according to claim 10 or 11, characterized in that the supply circuit (2) includes a feeding gas adsorption purification element (9), the fourth supply circuit (111) being connected to the supply circuit (2) downstream of the purification element (9).

13. Installation according to any one of claims 10 to 12, characterized in that the compressor (16) coupled to the turbine is a compressor of the supply circuit (2) or a compressor (16) of the compression system of the cycle circuit.

14. A refrigeration method using a refrigerator according to any one of claims 1 to 9 or an installation according to any one of claims 10 to 13, comprising a step of expansion, in the turbine (26) coupled to the compressor (16), of a purified cycle gas stream at a temperature between 100K and 20K and simultaneously a compression, in the compressor (16), of an unpurified cycle gas, the method comprising a step of injection, into the dam cavity (11), of a dam gas consisting of purified cycle gas and at a temperature between 275K and 310K.

15. A method according to claim 14, characterized in that the barrier gas injected during the injection step is at a controlled pressure to promote the migration of dam gas towards the second chamber (24) or towards the third chamber (18).

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