Turbomachine assembly, use thereof, and method for liquefying hydrogen

Abstract

The invention relates to a turbomachine assembly (10), with a plurality of compressor sections (11a, 11b) for increasing the pressure of a work medium such as a process gas, wherein the respective compressor section (11a, 11b) has a compressor shaft (13a, 13b), with an electric machine (16) which has a shaft (17), wherein the respective compressor shaft (13a, 13b) runs coaxially with the shaft (17) of the electric machine (16) and is coupled to the shaft (17) of the electric machine (16), wherein the electric machine (16) and the respective compressor section (11a, 11b) are located in a common, hermetically sealed, single-part or multi-part housing (18) and are mounted in the housing (18) via active magnetic bearings (19) in such a way that the work medium flows around or through the respective compressor section (11a, 11b), the electric machine (16) and the bearings (19), with a feed line (14), via which uncompressed work medium at the input pressure level of the turbomachine assembly (10) can be fed to the turbomachine assembly (10), with a discharge line (15), via which work medium compressed by the turbomachine assembly (10) can be discharged at an output pressure level of the turbomachine assembly (10), with a branching line (26), via which work medium at a fourth pressure level which is greater than the second pressure level and lower than the output pressure level or corresponds to the output pressure level can be branched off from a compressor section (11b) and can be fed to the electric machine (16) in order to cool the electric machine (16).

Description

[0001] Turbomachine arrangement, use thereof and method for liquefying hydrogen

[0002] The invention relates to a turbomachine arrangement. Furthermore, the invention relates to the use of the turbomachine arrangement and a method for liquefying hydrogen using a refrigerant.

[0003] WO 2013 / 139568 A1 discloses a turbomachine arrangement with a multi-stage compressor section and an electric machine, wherein the electric machine drives the compressor section to increase the pressure of a working medium. A compressor shaft of the compressor section runs coaxially with a shaft of the electric machine and is coupled to the shaft of the electric machine. The electric machine and the compressor section are arranged in a common housing and supported in the housing via bearings. Compressed working medium can be extracted from one stage of the compressor section as a cooling gas, which can be used to cool the electric machine.

[0004] A turbomachine arrangement with at least one single-stage or multi-stage compressor section and an electric machine driving the or each compressor section is also referred to as an integrated motor-compressor.

[0005] EP 1 074 746 B1 discloses a turbo compressor with multiple compressor sections. The compressor sections and the electric motor that drives the compressor sections are arranged in a gas-tight housing and supported by bearings within the housing. The shaft of each compressor section and the shaft of the electric motor run coaxially to each other and are coupled without any gear ratio. A compressed working fluid, which is branched off from a compressor section, is used to cool the electric motor. Hydrogen plays a crucial role in the decarbonization of the energy industry. Hydrogen can store and transport renewable energy, in particular. In order to transport hydrogen efficiently, for example by ship, the liquefaction of hydrogen is important.To liquefy hydrogen, a refrigerant is compressed to a defined process pressure using a turbomachine arrangement and then expanded to provide the cooling energy required to liquefy the hydrogen. Previously known turbomachine arrangements are only partially suitable for compressing the refrigerant for liquefying hydrogen, as refrigerant can escape into the environment through leaks. This can be a relatively small leak during normal operation, i.e., outside of a fault situation, or a relatively large leak during a fault situation.

[0006] There is a need for a novel turbomachine arrangement that is particularly suitable for efficiently compressing refrigerant for the liquefaction of hydrogen while avoiding the risk of refrigerant leakage during regular operation. Based on this, the present invention is based on the object of creating a novel turbomachine arrangement, as well as the use thereof and a novel method for liquefying hydrogen.

[0007] This object is achieved by a turbomachine arrangement according to claim 1, by the use of the turbomachine arrangement according to claim 14 and by the method according to claim 15.

[0008] The turbomachine arrangement according to the invention has a plurality of single-stage or multi-stage compressor sections for increasing the pressure of a working medium such as a process gas, wherein the respective compressor section has a compressor shaft, namely at least with a first compressor section for compressing the working medium starting from an inlet pressure of the turbomachine arrangement to a first pressure level, and a second compressor section for compressing the working medium following the first compressor section starting from a second pressure level to a third pressure level which is greater than the first pressure level.The turbomachine arrangement according to the invention has an electric machine which has a shaft, wherein the respective compressor shaft runs coaxially to the shaft of the electric machine, wherein the respective compressor shaft is coupled to the shaft of the electric machine preferably without any translation, and wherein the electric machine and the respective compressor section are arranged in a common, hermetically sealed, single-part or multi-part housing and are mounted in the housing via active magnetic bearings, such that at least the respective compressor section and the electric machine and preferably also the active magnetic bearings are surrounded or flushed by the working medium.

[0009] The turbomachine arrangement according to the invention has a supply line and a discharge line, wherein uncompressed working medium can be supplied to the turbomachine arrangement via the supply line at the inlet pressure level of the turbomachine arrangement, and wherein compressed working medium can be discharged from the turbomachine arrangement via the discharge line at an outlet pressure level of the turbomachine arrangement.

[0010] The turbomachine arrangement according to the invention has a branch line via which working medium at a fourth pressure level, which is greater than the second pressure level and less than the initial pressure level or corresponds to the initial pressure level, can be branched off from a compressor section and can be supplied to the electrical machine and preferably also to the active magnetic bearings for cooling at least the electrical machine.

[0011] The turbomachine arrangement according to the invention allows, in particular, efficient compression of a refrigerant used in the liquefaction of hydrogen while avoiding the risk of leakage of the working medium or refrigerant during normal operation. In the event of a fault, a potential leak can be kept to a minimum. To cool at least the electric machine of the turbomachine arrangement, which is arranged together with the compressor sections driven by the electric machine in a common, hermetically sealed housing, the compressed working medium branched off from one of the compressor sections via the branch line is used. This working medium is drawn off at the fourth pressure level, which is greater than the second pressure level. The working medium used to cool at least the electric machine is therefore branched off via the branch line from a compressor section arranged downstream of the first compressor section.

[0012] The working medium branched off for cooling has a pressure level that is higher than the second pressure level and thus the suction pressure level of the second compressor section. As a result, the working medium used for cooling has a relatively high density, which enables efficient cooling because, due to the higher density, only a relatively small volume flow of the working medium is branched off and passed through the electric machine for cooling. This also reduces any potential pressure loss as a result of cooling. The electric machine can be operated at higher power. This is particularly advantageous when the turbomachine arrangement is used to compress a refrigerant to liquefy hydrogen, because in this case, due to the low inlet pressure of the turbomachine arrangement and the low first pressure level, high volume flows would have to be branched off from the first compressor section for cooling.This is avoided with the invention.

[0013] Avoiding the risk of leakage of the working medium or refrigerant during normal operation is important in order to prevent the working medium or refrigerant from escaping into the environment during normal operation. Furthermore, if leakage of the working medium or refrigerant is avoided, there is no need to replace working medium or refrigerant lost due to a leak. This is particularly advantageous if the working medium or refrigerant is a mixture of different elements whose composition must be maintained for proper operation. In this context, it is important that the housing of the turbomachine arrangement according to the invention is hermetically sealed. Seals such as dry gas seals, which are required in conventional turbomachine arrangements to seal the turbomachine arrangement from the environment, can be dispensed with.

[0014] It is also important that the bearings of the turbomachine assembly according to the invention are active magnetic bearings. Therefore, no oil supply to the bearings via an oil supply system is required. The turbomachine assembly according to the invention does not require a sealing system in the bearing area. There is no risk of oil being introduced into or entrained by the working medium or coolant.

[0015] The turbomachine arrangement according to the invention is low-maintenance, particularly since maintenance of seals such as dry gas seals and no maintenance of an oil supply system is required. Maintenance intervals are on the order of 15 years.

[0016] In particular, the turbomachine arrangement according to the invention has a third compressor section for compressing the working medium, following the second compressor section, from a fifth pressure level to a sixth pressure level, which is greater than the third pressure level and preferably corresponds to the initial pressure level of the turbomachine arrangement. This also serves to compress the working medium while avoiding the risk of leakage of the working medium during regular operation, which is used in particular in the liquefaction of hydrogen as a refrigerant. In the event of a fault, a potential leak can be kept to a minimum.

[0017] The turbomachine arrangement according to the invention preferably has a return line, wherein the working fluid, which is fed through the electric machine for cooling the electric machine, can be returned to the second compressor section via the return line. This allows the efficiency of the compression of the working fluid to be increased. The working fluid fed through the electric machine is thus returned at a pressure level that is greater than the inlet pressure level of the turbomachine arrangement.

[0018] The turbomachine arrangement according to the invention preferably has a first heat exchanger for cooling the working medium downstream of the first compressor section and upstream of the second compressor section. This allows the efficiency of compression of the working medium to be further increased. The working medium used to cool the electric machine is thus cooled via the first heat exchanger before being recompressed in the second compressor section. This is important for further increasing the efficiency of compression of the working medium.

[0019] Preferably, a second heat exchanger is also provided to cool the working medium compressed to the initial pressure level.

[0020] The turbomachine arrangement according to the invention preferably has at least one separator for separating condensate from the working medium. Depending on the working medium, the turbomachine arrangement according to the invention has at least one separator for separating and discharging any condensate that may occur.

[0021] Preferred developments of the invention will become apparent from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail, without being limited thereto, with reference to the drawings. Herein:

[0022] Fig. 1 is a highly schematic representation of a first turbomachine arrangement according to the invention;

[0023] Fig. 2 is a highly schematic representation of a second turbomachine arrangement according to the invention; Fig. 3 is a highly schematic representation of a third turbomachine arrangement according to the invention;

[0024] Fig. 4 shows a detail of the turbomachine arrangements of Figs. 1 to 3;

[0025] Fig. 5 is a highly schematic representation of a fourth turbomachine arrangement according to the invention;

[0026] Fig. 6 is a highly schematic representation of a fifth turbomachine arrangement according to the invention;

[0027] Fig. 7 is a highly schematic representation of a sixth turbomachine arrangement according to the invention;

[0028] Fig. 8 shows a detail of the turbomachine arrangements of Figs. 5 to 7; and

[0029] Fig. 9 is a diagram of a hydrogen liquefaction system.

[0030] The present invention relates to a turbomachine arrangement 10, which is designed in particular as an integrated motor-compressor.

[0031] Fig. 1 shows a first embodiment of a turbomachine arrangement 10 according to the invention, designed as an integrated motor-compressor, which has two compressor sections 11a, 11b for increasing the pressure of a working medium, preferably for compressing a process gas.

[0032] Process gas is preferably a refrigerant used to liquefy hydrogen.

[0033] Each compressor section 11a, 11b in Fig. 1 has several compressor stages 12a, 12b and a compressor shaft 13a, 13b, wherein the first compressor section 11a and thus the turbomachine arrangement 10 are supplied with uncompressed working medium via a supply line 14 of the turbomachine arrangement 10 at an inlet pressure level p E can be supplied, and wherein the working medium compressed by the compressor section 11b and thus by the turbomachine arrangement 10 is at an initial pressure level p Acan be discharged via a discharge line 15 of the turbomachine arrangement 10.

[0034] The turbomachine assembly 10 of Fig. 1, designed as an integrated motor-compressor, further comprises an electric machine 16 with a shaft 17, wherein the electric machine 16 serves to drive the compressor sections 11a, 11b. The compressor shafts 13a, 13b and the shaft 17 of the electric machine 16 extend coaxially to one another. Furthermore, the compressor shafts 13a, 13b and the shaft 17 of the electric machine 16 are preferably coupled directly and without any gear ratio or without any gear ratio.

[0035] The electric machine 16 and the compressor section 11a, 11b are arranged in a common, hermetically sealed and thus gas-tight housing 18 and are rotatably mounted in the housing 18 via active magnetic bearings 19 (see Fig. 4).

[0036] The compressor sections 11a, 11b are preferably separated on the pressure side by separating elements 50, in particular from a section of the housing 18 accommodating the electric machine 16. The separating elements 50 can be designed as so-called load pistons 50a or as so-called restrictions 50b such as throttle bushings (see Fig. 4 and Fig. 8). These separating elements 50 serve only to internally separate the compressor sections 11a, 11b and not to seal the turbomachine assembly 10 from the environment.

[0037] The gas-tight housing 18 can be constructed in one or more parts. Preferably, the compressor section 11a, 11b, the electric machine 16, and preferably also the active magnetic bearings 19 are all surrounded or flushed by the working medium, in particular the process gas.

[0038] The compressor shafts 13a, 13b are coupled to the shaft 17 of the electric machine 16 via couplings 20a, 20b (see Fig. 4). If, as shown in Fig. 1, the compressor sections 11a, 11b are arranged on different sides of the motor 16 in the common housing 18, each of the shafts 13a, 13b of the two compressor sections 11a, 11b is directly coupled to the shaft 17 of the electric machine 16 via a respective coupling 20a, 20b.

[0039] If, in contrast to the exemplary embodiment shown, both compressor sections 11a, 11b are positioned on the same side of the electric machine 16, one shaft of a compressor section is coupled directly to the shaft 17 of the electric machine 16 via the respective coupling, whereas the other compressor section is indirectly coupled to the shaft 17 of the electric machine 16 via the shaft of this compressor section.

[0040] The first compressor section 11a serves to compress the working medium starting from the inlet pressure level p E of the turbomachine arrangement 10 to a first pressure level p1. The second compressor section 11b serves for the subsequent compression of the working medium, starting from a second pressure level p2 to a third pressure level p3. In Fig. 1, the third pressure level p3 corresponds to the initial pressure level p A . The second pressure level p2 is lower than the first pressure level p1 due to pressure losses between the two compressor sections 12a, 12b. The third pressure level p3, to which the second compressor section 11b compresses the working medium, is higher than the first pressure level p1, to which the first compressor section 11a compresses the working medium.

[0041] The pressure loss between the two compressor sections 11a, 11b results in Fig. 1 in that the working medium compressed by the first compressor section 11a is guided downstream of the first compressor section 11a and upstream of the second compressor section 11b via a first heat exchanger 21, which serves to cool the working medium between the two compressor sections 11a, 11b.

[0042] A further pressure loss arises in Fig. 1 because, downstream of the first heat exchanger 21, the working medium is passed through a separator 22 to separate condensate from the working medium compressed by the first compressor section 11a and cooled by the first heat exchanger 21 and to discharge it in the direction of arrow 23. The condensate may occur as a result of the compression of the working medium and its cooling between the compressor sections 11a, 11b.

[0043] The gaseous phase of the working medium compressed by the first compressor section 11a and cooled by the first heat exchanger 21 is fed to the second compressor section 12b for further compression at the second pressure level p2 in Fig. 1. Arrows 24 and 25 illustrate that compressed working medium can be discharged and supplied downstream of the separator 22.

[0044] The discharge and supply of the working medium in the direction of arrows 24, 25 can also take place directly upstream or directly downstream of the first heat exchanger 21. Particularly preferably, the discharge of the working medium in the direction of arrow 24 takes place directly downstream of the separator 22 and thus upstream of the second compressor section 12b, and the supply of the working medium in the direction of arrow 25 takes place directly upstream of the first heat exchanger 21.

[0045] The turbomachine arrangement 10 according to the invention has a branch line 26, via which the working medium is supplied to a fourth pressure level p4, which is greater than the second pressure level p2 and less than the initial pressure level p A or the initial pressure level p A corresponds, can be branched off from the compressor section 12b and fed to at least the electrical machine 16 for cooling.

[0046] The working fluid branched off from the second compressor section 11b via the branch line 26 in Fig. 1 is fed via the electric machine 16 and preferably also via the active magnetic bearings 19 for cooling the same. This working fluid is taken off in Fig. 1 at the fourth pressure level p4, which is greater than the second pressure level p2 and less than the third pressure level or the output pressure level p A The fourth pressure level p4 can also be the third pressure level p3 or the initial pressure level p AThe second pressure level p2 corresponds to the inlet pressure level of the second compressor section 11b and the third pressure level p3 corresponds in Fig. 1 to the outlet pressure level p A the turbomachine arrangement 10.

[0047] The working fluid branched off from the compressor section 12b via the branch line 26 for cooling the electric machine 16 and preferably the active magnetic bearings 19 is, after the working fluid has been passed through the electric machine 10 and preferably through the bearings 19, returned toward the second compressor section 11b by means of a return line 27. In Fig. 1, the return line 27 has a separate heat exchanger 28 for cooling the working fluid used to cool the electric machine 16 and the bearings 19 upstream of the second compressor section 11b. Upstream of the heat exchanger 28, a switchable valve 39 is integrated into the return line 27.

[0048] A particle filter can be arranged in the branch line 26. Such a particle filter can prevent particles from entering the area of ​​the electrical machine, such as metallic particles that can become detached from cables.

[0049] A droplet filter may be arranged downstream of the separator 22. The separator 22 may include a demisting device.

[0050] Fig. 2 shows a modification of the turbomachine arrangement 10 of Fig. 1, in which the working medium discharged via the return line 27, which was guided via the electric machine 16 and preferably the active magnetic bearings 19 for cooling, is guided via the first heat exchanger 21 and thus also via the separator 22. In Fig. 2, a heat exchanger 30 and a valve 40 are assigned to the branch line 26. The valve 40 serves to adjust the volume flow of the working medium branched off via the branch line 26 and guided at least via the electric machine 16 for cooling the same. The position of the valve 40 can be regulated depending on a measured temperature of the electric machine 16. If the temperature of the electric machine 16 is too high, the valve 40 is opened further. If the temperature of the electric machine 16 is too low, the valve 40 is closed further.This can further increase the efficiency of the turbomachine arrangement 10.

[0051] With regard to all other details, the embodiment of Fig. 2 corresponds to the embodiment of Fig. 1, so that the same reference numbers are used for the same components to avoid unnecessary repetition.

[0052] The turbomachine arrangement 10 of Fig. 1 , 2 further comprises a second heat exchanger 29, which serves to cool the working medium to the outlet pressure level p A the turbomachine arrangement 10, i.e. in Fig. 1, 2 the cooling of the working medium downstream of the second compressor section 11 b.

[0053] Fig. 3 shows a modification of the turbomachine assembly 10 of Fig. 2. Again, to avoid unnecessary repetition, identical reference numerals are used for identical components. The following only discusses those details by which the embodiment of Fig. 3 differs from the embodiment of Fig. 2 and thus also from the embodiment of Fig. 1.

[0054] In Fig. 3, both the heat exchanger 30 and a separator 31 are integrated into the branch line 26. The heat exchanger 30 serves to cool the working medium branched off from the second compressor stage 12 via the branch line 26, and the separator 31 serves to separate condensate. Condensate can be discharged from the separator 31 in the direction of arrow 51. A further heat exchanger 32 couples the branch line 26 to the return line 27 in order to heat the working medium to be conducted via the electric machine 16 and the active magnetic bearings 19 in a defined manner in order to transfer the working medium to a superheated state and thus counteract the risk of condensate formation in the area of ​​the electric machine 16 and the bearings 19. In Fig. 3, the switchable valve 39 is assigned to the return line 27.The valve 39, like the valve 40, serves to adjust the volume flow of the working medium branched off via the branch line 26 and guided at least via the electric machine 16 for cooling the same.

[0055] The position of valve 39, in turn, can be controlled depending on a measured temperature of the electrical machine 16. If the temperature of the electrical machine 16 is too high, valve 39 is opened further. If the temperature of the electrical machine 16 is too low, valve 39 is closed further. In Fig. 3, valve 39, like valve 40 in Fig. 2, can be assigned to the branch line 26. In Fig. 2, valve 40, like valve 39 in Fig. 3, can be assigned to the return line 27.

[0056] Fig. 5 shows a further development of the turbomachine arrangement 10 of Fig. 2, wherein again, to avoid unnecessary repetition, the same reference numerals are used for the same components and only those details are discussed below by which the turbomachine arrangement of Fig. 5 differs from the turbomachine arrangement of Fig. 2 and thus also from the turbomachine arrangement of Fig. 1. With regard to all other details, reference can again be made to the explanations regarding the turbomachine arrangement of Figs. 1, 2.

[0057] The turbomachine arrangement 10 of Fig. 5 has, in addition to the first compressor section 11a and the second compressor section 11b, a third compressor section 11c. This third compressor section 11c serves to compress the working medium downstream of the second compressor section 11b, starting from a fifth pressure level p5 to a sixth pressure level p6, which in the embodiment of Fig. 5 corresponds to the initial pressure level p Acorresponds to the turbomachine arrangement 10. In Fig. 5, the working medium leaves the second compressor section 11b at the third pressure level p3, which is higher than the fourth pressure level p4, the pressure loss between the two compressor sections 11b, 11c being caused by the working medium being guided through a heat exchanger 33 and a separator 34. The heat exchanger is used to cool the working medium between the second and third compressor sections 11b and 11c, the separator 34 serves to separate condensate in order to supply the third compressor section 11c exclusively with the gaseous phase in the direction of arrow 35, but to separate the liquid phase, i.e. the condensate, from the gaseous phase, which is then discharged in the direction of arrow 36.

[0058] Between the separator 34 and the third compressor section 11c, compressed working medium can again be discharged in the direction of arrow 37 and supplied in the direction of arrow 38.

[0059] Separators are used in the turbomachine arrangements 10 shown in Figs. 1, 2, 3, and 5. Such separators are required when the working fluid used tends to condense under the prevailing pressure and temperature conditions. If, for example, helium, neon, or hydrogen is used as the working fluid for the turbomachine arrangement 10, which does not tend to condense under the prevailing pressure and temperature conditions, the separators shown in Figs. 1, 2, 3, and 5 can be omitted.

[0060] Thus, Fig. 6 shows a modification of the turbomachine arrangement 10 of Fig. 5, in which no separators are present. Accordingly, the turbomachine arrangement 10 of Fig. 6 is particularly suitable for compressing hydrogen, helium, or even neon. Also, no heat exchanger is assigned to the branch line 26 in Fig. 6. However, with regard to all other details, the turbomachine arrangement 10 of Fig. 6 corresponds to the turbomachine arrangement 10 of Fig. 5, so that the same reference numerals are used for the same components.

[0061] Fig. 7 shows a modification of the turbomachine arrangement 10 of Fig. 5, which differs from the turbomachine arrangement 5 of Fig. 7 only in that the working medium, which serves to cool the electric machine 16 and the active magnetic bearings 19, is branched off via the branch line 26 not in the region of the second compressor section 11b, but in the region of the third compressor section 11c, so that accordingly the fourth pressure level p4, at which the working medium is branched off via the branch line 26, is greater than the fifth pressure level p5 and smaller than the sixth pressure level p6 and thus smaller than the initial pressure level p A .

[0062] Furthermore, in Fig. 7, in contrast to Fig. 5, the working medium which was guided for cooling via the electric machine 16 and the active magnetic bearings 19 is guided via the return line 27 downstream of the second compressor section 11b directly in the direction of the third compressor section 11c, namely via the heat exchanger 33 and the separator 34.

[0063] Fig. 8 shows that no clutch is connected between the shafts 13b, 13c of the compressor sections 11b, 11c.

[0064] Furthermore, Fig. 8 shows that the coupling 20a is a rigid coupling and the coupling 20b is a flexible coupling. In Fig. 8, the compressor shaft of one of the compressor sections, namely the compressor shaft 13a of the first compressor section 11a, is coupled to the shaft 17 of the electric machine 16 via the rigid coupling, wherein the compressor shafts 13b, 13c of the compressor sections 11b, 11c are coupled to the shaft 17 of the electric machine 16 via the flexible coupling. The use of a flexible coupling is advantageous in turbomachine arrangements 10 with at least three compressor sections 11a, 11b, 11c (see Figs. 5, 6, 7) and thus a resulting long shaft composed of the shafts 13b, 13c, and 17. The flexible coupling 20b flexibly couples the shafts 13b, 13c of the compressor sections 11b, 11c to the shaft 17 of the electric machine 16, whereby, as shown in Fig.8 shows that an additional radial bearing 19 is required in the area of ​​the coupling 20b compared to the coupling 20a.

[0065] Typically, the shafts 13a, 13b, 13c, 17 of the compressor stages 11a, 11b, 11c and of the electric machine 16 are made of a metallic material. The impellers of the compressor stages 12a, 12b, 12c are also typically made of a metallic material. Preferably, the metallic material of the impellers of the compressor stages 12a, 12b, 12c has a low density and a high strength-to-mass ratio. In particular, the metallic material of the impellers of the compressor stages 12a, 12b, 12c is an aluminum alloy material or a titanium alloy material. This is particularly preferred when the compressor stages are designed as tie-bolt rotors, as known from US Pat. No. 3,749,516 or US Pat. No. 3,184,153.This is advantageous for enabling higher peripheral speeds for the respective compressor stages 12a, 12b, 12c, thereby increasing the pressure increase achievable during compression in the respective compressor stages 12a, 12b, 12c. This is particularly important for the compression of a refrigerant used to liquefy hydrogen. The number of compressor sections 11a, 11b, 11c required for compression can thus be reduced.

[0066] It is also possible to use a composite material, such as a CFRP or GFRP material, for the impellers of at least one compressor stage 12a, 12b, 12c, at least in sections, in particular at least in the area of ​​the radially outer sections of the impellers. This is also advantageous in order to enable higher circumferential speeds for the respective compressor stage 12a, 12b, 12c and thus to increase the pressure increase achievable during compression in the respective compressor stage 12a, 12b, 12c. The impellers and thus rotor blades of the respective compressor stage 12a, 12b, 12c can be made radially outwardly from a CFRP or GFRP material and radially inwardly from a metallic material. The compressor shafts 13a, 13b, 13c and the shaft 17 of the electric machine 16 are then preferably made of a metallic material.This is particularly advantageous when compressing hydrogen or helium as the working medium, i.e., a working medium with a low density. The number of compressor sections 11a, 11b, and 11c required for compression can thus be reduced.

[0067] Composite material can also be used for the shafts 13a, 13b, 13c, and 17. The compressor stages 12a, 12b, and 12c can be designed as open compressor stages or closed compressor stages. As described above, the compressor stages can be designed as tie-bolt rotors. Tie-bolt rotors are known from US Pat. No. 3,749,516 or US Pat. No. 3,184,153.

[0068] The invention allows a particularly effective or efficient compression of a working medium, such as a process gas, namely a refrigerant which is used as a refrigerant in the liquefaction of hydrogen.

[0069] Thus, as already described in detail above, it is possible to compress both a refrigerant that tends to condense under the pressure and temperature conditions prevailing in the compressor sections 11a, 11b, 11c, in particular on the suction side, and a refrigerant that does not tend to condense under the pressure and temperature conditions prevailing in the compressor sections 11a, 11b, 11c, in particular on the suction side, for the liquefaction of hydrogen.

[0070] The invention therefore relates not only to the turbomachine assembly 10 as such, but also to its use for compressing a working medium used to liquefy hydrogen as a refrigerant, while avoiding the risk of leakage of the working medium during normal operation. In the event of a fault, potential leakage can be minimized.

[0071] Furthermore, the invention relates to a method for liquefying hydrogen using a refrigerant, wherein the refrigerant is compressed using at least one turbomachine arrangement 10 according to the invention. Following compression of the refrigerant with the at least one turbomachine arrangement 10 according to the invention, the compressed refrigerant is expanded to provide the cooling energy required to liquefy the hydrogen.

[0072] Fig. 9 shows a highly simplified schematic of a system 41 for liquefying hydrogen. Gaseous hydrogen to be liquefied is supplied to system 41 via a supply line 42. The gaseous hydrogen to be liquefied is passed through heat exchanger stages 43, 44 for gradual cooling as shown in Fig. 2. Gaseous hydrogen is still present downstream of heat exchanger stage 43, and liquefied hydrogen is collected in a container 45 downstream of heat exchanger stage 44 and an expansion valve 46.

[0073] Immediately downstream of the heat exchanger stage 44, liquefied hydrogen is present, which is partially expanded in the area of ​​the expansion valve 46. This causes the hydrogen to cool even further, so that the liquid hydrogen in the container 45 has an even lower temperature than the liquid hydrogen upstream of the expansion valve 46. Part of the liquefied hydrogen evaporates, and the resulting cooling energy further cools the remaining liquid hydrogen.

[0074] Any remaining gaseous hydrogen phase can be branched off from the tank 45 in the direction of arrow 53 and passed downstream of the heat exchanger stages 43, 44 via a compressor 47 and returned to the supply line 42. Liquid hydrogen can be withdrawn from the tank 45 in the direction of arrow 52.

[0075] The refrigerant required for cooling and liquefying the hydrogen is compressed individually for each heat exchanger stage 43, 44 via a turbomachine arrangement 10 according to the invention, wherein the refrigerant required by the turbomachine arrangements 10 is expanded in expansion devices 48, 49 to provide the required cooling energy.

[0076] In the refrigeration circuit comprising the expansion device 48, the refrigerant used is preferably a refrigerant that condenses under the prevailing pressure and temperature conditions, such as methane, ethane, propane, butane, pentane, nitrogen, or another hydrocarbon, or a refrigerant mixture of at least two of these refrigerants, which is compressed and expanded. In the refrigeration circuit comprising the expansion device 49, the refrigerant used is preferably a refrigerant that does not condense under the prevailing pressure and temperature conditions, such as hydrogen, helium, or neon, or a refrigerant mixture of at least two of these refrigerants.

[0077] List of reference symbols

[0078] 10 Turbomachine arrangement

[0079] 11a Compressor section

[0080] 11 b Compressor section

[0081] 11c Compressor section

[0082] 12a Compressor stage

[0083] 12b Compressor stage

[0084] 12c compressor stage

[0085] 13a Compressor shaft

[0086] 13b Compressor shaft

[0087] 13c Compressor shaft

[0088] 14 Supply line

[0089] 15 Discharge line

[0090] 16 electric machine

[0091] 17 Wave

[0092] 18 housings

[0093] 19 camps

[0094] 20a coupling

[0095] 20b Coupling

[0096] 21 heat exchangers

[0097] 22 separators

[0098] 23 Condensate drainage

[0099] 24 Working medium discharge

[0100] 25 Working medium supply

[0101] 26 branch line

[0102] 27 Return line

[0103] 28 heat exchangers

[0104] 29 heat exchangers

[0105] 30 heat exchangers

[0106] 31 separators

[0107] 32 heat exchangers

[0108] 33 heat exchangers

[0109] 34 separator working medium supply

[0110] Condensate drainage

[0111] Working medium discharge

[0112] Working medium supply

[0113] valve

[0114] valve

[0115] Hydrogen liquefaction system

[0116] supply line

[0117] Heat exchanger stage

[0118] Heat exchanger stage

[0119] container

[0120] Expansion valve

[0121] compressor

[0122] Relaxation facility

[0123] Relaxation facility

[0124] Separating elements a Load piston b Restriction

[0125] Condensate drainage

[0126] Liquid hydrogen extraction

[0127] Hydrogen gas removal

Claims

AMENDED CLAIMS received by the International Bureau on 28 March 2025 (25.03.2025) 1. Turbomachine arrangement (10), with several single- or multi-stage compressor sections (11a, 11b, 11c) for increasing the pressure of a working medium such as a process gas, wherein the respective compressor section (11a, 11b, 11c) has a compressor shaft (13a, 13b, 13c), namely at least with a first compressor section (11a) to compress the working medium starting from an inlet pressure of the turbomachine arrangement (10) to a first pressure level, and a second compressor section (11b) to compress the working medium following the first compressor section (11c) starting from a second pressure level to a third pressure level which is greater than the first pressure level, with an electric machine (16) having a shaft (17), wherein the respective compressor shaft (13a, 13b, 13c) is coaxial with the shaft (17) of the electric machine (16) and is coupled to the shaft (17) of the electric machine (16),wherein the electric machine (16) and the respective compressor section (11a, 11b, 11c) are arranged in a common, hermetically sealed, single-part or multi-part housing (18) and are mounted in the housing (18) via active magnetic bearings (19), such that at least the respective compressor section (11a, 11b, 11c) and the electric machine (16) are surrounded or flushed by the working medium, with a supply line (14) via which uncompressed working medium can be supplied to the turbomachine arrangement (10) at the inlet pressure level of the turbomachine arrangement (10), with a discharge line (15) via which working medium compressed by the turbomachine arrangement (10) can be discharged at an outlet pressure level of the turbomachine arrangement (10), with a branch line (26) via which the working medium can be supplied at a fourth pressure level, which is greater than the second pressure level and less than the outlet pressure level or the Output pressure level,can be branched off from a compressor section (11b, 11c) and fed to the electrical machine (16) for cooling the electrical machine (16), AMENDED SHEET (ARTICLE 19) characterized by a first heat exchanger (21) for cooling the working medium downstream of the first compressor section (11a) and upstream of the second compressor section (1b),

7. a return line (27) via which the working medium guided via the electric machine (16) for cooling the electric machine (16) can be returned in a first alternative in the direction of the second compressor section (11b) [claim 6; Fig. 1, 2, 3, 5, 6] and in a second alternative in the direction of a third compressor section (11c) [page 15, lines 5-9; Fig. 7], wherein the return line (27) guides the working medium guided via the electric machine (16) for cooling the electric machine (16) via the first heat exchanger (21) or via a separate heat exchanger (28, 33) [claim 8; page 15, lines 5-9].

2. Turbomachine arrangement (10) according to claim 1, characterized in that the third pressure level corresponds to the output pressure level of the turbomachine arrangement (10).

3. Turbomachine arrangement (10) according to claim 1, characterized in that the third compressor section (11c) is designed to compress the working medium following the second compressor section (11b) from a fifth pressure level to a sixth pressure level which is greater than the third pressure level and preferably corresponds to the output pressure level of the turbomachine arrangement (10).

4. Turbomachine arrangement (10) according to one of claims 1 to 3, characterized in that the branch line (26), via which the working medium can be supplied to the electric machine (16) at the fourth pressure level, branches off the working medium from the second compressor section (11 b). AMENDED SHEET (ARTICLE 19) 5. Turbomachine arrangement (10) according to one of Claims 3, characterized in that the branch line (26), via which the working medium can be supplied to the electric machine (16) at the fourth pressure level, branches off the working medium from the second compressor section (11 b) or from the third compressor section (11 c).

6. Turbomachine arrangement according to one of claims 1 to 5, characterized by a second heat exchanger (29) for cooling the working medium compressed to the initial pressure level.

7. Turbomachine arrangement according to one of claims 1 to 6, characterized by at least one separator (22, 34, 31) for separating condensate from the working medium.

8. Turbomachine arrangement according to one of claims 1 to 7, characterized in that the compressor shaft of one of the compressor sections, in particular the compressor shaft (13a) of the first compressor section (11a), is coupled to the shaft (17) of the electric machine (16) via a rigid coupling, and in that the compressor shaft of at least one other compressor section, in particular at least the compressor shaft (13b) of the second compressor section (11b), is coupled to the shaft (17) of the electric machine (16) via a flexible coupling.

9. Turbomachine arrangement according to one of claims 1 to 8, characterized in that the compressor shafts (13a, 13b, 13c), the shaft (17) of the electric machine (16) and impellers of the compressor stages (12a, 12b, 12c) are each made of a metallic material, wherein the metallic material of the impellers of the compressor stages (12a, 12b, 12c) has a higher AMENDED SHEET (ARTICLE 19) strength-to-mass ratio than the metallic material of the compressor shafts (13a, 13b, 13c) and the shaft (17) of the electric machine (16), wherein the metallic material of the impellers of the compressor stages (12a, 12b, 12c) is preferably an aluminium alloy material or a titanium alloy material or a magnesium alloy material.

10. Turbomachine arrangement according to one of claims 1 to 9, characterized in that the compressor shafts (13a, 13b, 13c) and the shaft (17) of the electric machine (16) are each made of a metallic material, and in that the impellers of the compressor stages (12a, 12b, 12c) are at least partially made of a CFRP material or GFRP material.

11. Use of a turbomachine arrangement (10) according to one of claims 1 to 10 for compressing a working medium used for the liquefaction of hydrogen as a refrigerant.

12. A method for liquefying hydrogen with the aid of a refrigerant, wherein at least one turbomachine arrangement (10) according to one of claims 1 to 10 compresses the refrigerant as the working medium of the turbomachine arrangement (10) and subsequently the compressed refrigerant provided by the turbomachine arrangement (10) is expanded in order to provide the cooling energy required for liquefying the hydrogen. AMENDED SHEET (ARTICLE 19)

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