Turbomachine arrangement, use thereof and method for liquefying hydrogen

Abstract

Turbomachine arrangement (10), with several compressor sections (11a, 11b) for increasing the pressure of a working 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 to 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 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 the respective compressor section (11a, 11b), the electric machine (16) and the bearings (19) are are flushed or flushed through, 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 working medium can be branched off from a compressor section (11b) at a fourth pressure level, which is greater than the second pressure level and less than the outlet pressure level or corresponds to the outlet pressure level, and can be supplied to the electrical machine (16) for cooling the electrical machine (16).

Description

The invention relates to a turbomachine arrangement. The invention further relates to the use of the turbomachine arrangement and to a method for liquefying hydrogen with the aid of a refrigerant.WO 2013 / 139568 A1 discloses a turbomachine arrangement having a multistage compressor section and an electric machine, wherein the electric machine drives the compressor section for increasing the pressure of a working medium. A compressor shaft of the compressor section is coaxial 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 are mounted in the housing via bearings. Compressed working medium can be removed from one stage of the compressor section as cooling gas, which working medium can be used for cooling the electric machine.A turbomachine arrangement having at least one single-stage or multistage compressor section and an electric machine driving the or each compressor section is also referred to as an integrated motor-compressor.EP 1 074 746 B1 discloses a turbocompressor having a plurality of compressor sections. The compressor sections and the electric machine which drives the compressor sections are arranged in a gas-tight housing and are mounted in the housing via bearings. The shaft of the respective compressor section and the shaft of the electric machine run coaxially with respect to one another and are coupled in a transmission-free manner. Compressed working medium is used for cooling the electric machine, which working medium is branched off from a compressor section.In decarbonization of energy management, hydrogen plays a decisive role. Hydrogen can store and transport renewable energy in particular. In order to be able to transport hydrogen efficiently, for example, by means of ships, the liquefaction of the hydrogen is of importance. A refrigerant is used for liquefying hydrogen, which is compressed to a defined process pressure with the aid of a turbomachine arrangement and is subsequently expanded to provide the cold energy required for liquefying the hydrogen. Previously known turbomachine arrangements are suitable only to a limited extent for compressing the refrigerant for liquefying hydrogen, since refrigerant reaches the environment via a leakage, namely both during regular operation, i.e. outside a fault case, a relatively small leakage and also in the event of a fault case a relatively large leakage.There is a need for a novel turbomachine arrangement which is suitable in particular for the efficient compression of refrigerant for the liquefaction of hydrogen while avoiding the risk of leakage of the refrigerant during regular operation. Proceeding from this, the object of the present invention is to create a novel turbomachine arrangement, and also the use thereof and a novel method for liquefying hydrogen.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.The turbomachine arrangement according to the invention has a plurality of single-stage or multistage 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 having a first compressor section in order to compress the working medium from an input pressure of the turbomachine arrangement to a first pressure level, and having a second compressor section in order to compress the working medium subsequently to the first compressor section 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 with the shaft of the electric machine, wherein the respective compressor shaft is preferably coupled to the shaft of the electric machine in a transmission-free manner, and wherein the electric machine and the respective compressor section are arranged in a common, hermetically sealed, one-part or multi-part housing and are mounted in the housing via active magnetic bearings in such a way that at least the respective compressor section and the electric machine and preferably also the active magnetic bearings are flushed or flushed by the working medium.The turbomachine arrangement according to the invention has a feed line and a discharge line, wherein non-compressed working medium at the inlet pressure level of the turbomachine arrangement can be supplied via the feed line of the turbomachine arrangement, and wherein working medium compressed from the turbomachine arrangement can be discharged via the discharge line at an outlet pressure level of the turbomachine arrangement.The turbomachine arrangement according to the invention has a branch line, via which working medium can be branched off from a compressor section at a fourth pressure level, which is greater than the second pressure level and less than the output pressure level or corresponds to the output pressure level, and can be supplied to the electric machine and preferably also to the active magnetic bearings for cooling at least the electric machine.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 a leakage of the working medium or refrigerant during regular operation. In the event of a fault, a possible leakage can be limited to a minimum.For cooling 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, which is branched off from one of the compressor sections via the branch line and is taken off at the fourth pressure level, which is greater than the second pressure level, is used. The working medium used for cooling at least the electric machine is accordingly branched off via the branch line from a compressor section which is arranged downstream of the first compressor section.The working medium branched off for cooling has a pressure level which 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, as a result of which efficient cooling is possible, since only a relatively low volume flow of the working medium is branched off as a result of the higher density and is conducted via the electric machine for cooling. This also reduces a possible pressure loss as a result of the cooling. The electric machine can be operated at higher power. This is particularly advantageous in particular if the turbomachine arrangement is used for compressing a refrigerant for liquefying hydrogen, since in this case high volume flows would have to be branched off from the first compressor section as a result of the low inlet pressure of the turbomachine arrangement and the low first pressure level for cooling. This is avoided with the invention.Avoiding the risk of a leakage of the working medium or refrigerant during regular operation is important in order to prevent working medium or refrigerant from entering the environment during regular operation. Further, when leakage of the working medium or refrigerant is avoided, there is no need to replace working medium or refrigerant lost by leakage. This is of great advantage in particular when the working medium or refrigerant is a mixture of different elements, the composition of which 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. It is possible to dispense with seals, such as dry gas seals, which are required in conventional turbomachine arrangements for sealing the turbomachine arrangement from the environment.It is furthermore important that the bearings of the turbomachine arrangement according to the invention are active magnetic bearings. Accordingly, no oil supply to the bearings via an oil supply system is required. The turbomachine arrangement according to the invention does not require a sealing system in the region of the bearings. There is no risk that oil is introduced or introduced into the working medium or refrigerant.The turbomachine arrangement according to the invention is not very maintenance-intensive, and in particular it is necessary to maintain seals such as dry gas seals and not to maintain an oil supply system. Maintenance periods are on the order of 15 years.In particular, the turbomachine arrangement according to the invention has a third compressor section in order to compress the working medium, following the second compressor section, starting 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. This likewise serves for compressing the working medium while avoiding the risk of a leakage of the working medium during regular operation, which is used as refrigerant in particular during the liquefaction of hydrogen. In the event of a fault, a possible leakage can be limited to a minimum.The turbomachine arrangement according to the invention preferably has a return line, it being possible for the working medium, which is conducted via the electric machine for cooling the electric machine, to be conducted back in the direction of the second compressor section via the return line. This allows the efficiency of the compression of the working medium to be increased.The working medium conducted via the electric machine is accordingly returned to a pressure level which is greater than the inlet pressure level of the turbomachine arrangement.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. The efficiency of the compression of the working medium can thereby be further increased. The working medium used for cooling the electric machine is thus cooled via the first heat exchanger before renewed compression in the second compressor section. This is important for further increasing the efficiency of the compression of the working medium.Preferably, a second heat exchanger is also provided for cooling the working medium compressed to the output pressure level.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 the at least one separator in order to separate out and discharge condensate which arises.Preferred developments of the invention are evident from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawings, without being restricted thereto. The following shows: FIG. 1 is a highly schematic illustration of a first turbomachine arrangement according to the invention; FIG. 2 is a highly schematic illustration of a second turbomachine arrangement according to the invention; FIG. 3 is a highly schematic illustration of a third turbomachine arrangement according to the invention; FIG. 4 shows a detail of the turbomachine arrangements of FIGS. 1 to 3 ; FIG. 5 is a highly schematic illustration of a fourth turbomachine arrangement according to the invention; FIG. 6 is a highly schematic illustration of a fifth turbomachine arrangement according to the invention; FIG. 7 is a highly schematic illustration of a sixth turbomachine arrangement according to the invention; FIG. 8 shows a detail of the turbomachine arrangements of FIGS. 5 to 7 ; and FIG. 9 is a schematic of a system for liquefying hydrogen.The present invention relates to a turbomachine arrangement 10, which is designed in particular as an integrated motor compressor.FIG. 1 shows a first exemplary embodiment of a turbomachine arrangement 10 according to the invention, which is designed as an integrated motor compressor and has two compressor sections 11 a, 11 bfor increasing the pressure of a working medium, preferably for compressing a process gas.Process gas is preferably a refrigerant which is used for liquefying hydrogen.Each compressor section 11 a, 11 bhas in FIG. 1 a plurality of compressor stages 12 a, 12 band a compressor shaft 13 a, 13 b, wherein non-compressed working medium can be supplied to the first compressor section 11 aand thus to the turbomachine arrangement 10 via a supply line 14 of the turbomachine arrangement 10 at an input pressure level p E and wherein working medium compressed by the compressor section 11 band thus by the turbomachine arrangement 10 can be discharged at an input pressure level p A via a discharge line 15 of the turbomachine arrangement 10.The turbomachine arrangement 10 of FIG. 1, which is designed as an integrated motor-compressor, furthermore has an electric machine 16 having a shaft 17, the electric machine 16 serving for driving the compressor sections 11 a, 11 b. The compressor shafts 13 a, 13 band the shaft 17 of the electric machine 16 run coaxially with respect to one another. Furthermore, the compressor shafts 13 a, 13 band the shaft 17 of the electric machine 16 are preferably coupled directly and without transmission or without transmission.The electric machine 16 and the compressor section 11 a, 11 bare arranged in a common, hermetically sealed and thus gas-tight housing 18 and rotatably mounted in the housing 18 via active magnetic bearings 19 (see FIG. 4 ).The compressor sections 11 a, 11 bare preferably separated by separating elements 50 on the pressure side, in particular from a section of the housing 18 receiving the electric machine 16. The separating elements 50 can be designed as so-called load pistons 50 aor as so-called restrictions 50 bsuch as throttle bushes (see FIGS. 4 and 8 ). These separating elements 50 serve only for the internal separation of the compressor sections 11 a, 11 band not for the sealing of the turbomachine arrangement 10 with respect to the enclosure.The gas-tight housing 18 can be formed in one part or in multiple parts. The compressor section 11 a, 11 b, the electric machine 16 and preferably also the active magnetic bearings 19 are preferably all surrounded by or surrounded by the working medium, in particular the process gas.The coupling of the compressor shafts 13 a, 13 bto the shaft 17 of the electric machine 16 takes place via clutches 20 a, 20 b(see FIG. 4 ).Then, as shown in FIG. 1, when the compressor sections 11 a, 11 bare arranged on different sides of the engine 16 in the common housing 18, each of the shafts 13 a, 13 bof the two compressor sections 11 a, 11 bis directly coupled to the shaft 17 of the electric machine 16 via a clutch 20 a, 20 b, respectively.If, in contrast to the exemplary embodiment shown, both compressor sections 11 a, 11 bare positioned on the same side of the electric machine 16, one shaft of one compressor section is directly coupled to the shaft 17 of the electric machine 16 via the respective clutch, whereas the other compressor section is indirectly coupled to the shaft 17 of the electric machine 16 via the shaft of this compressor section.The first compressor section 11 afunctions to compress the working medium from the input pressure level p E of the turbomachine arrangement 10 to a first pressure level p 1. The second compressor section 11 bserves for the subsequent compression of the working medium, starting from a second pressure level p 2 to a third pressure level p 3. In FIG. 1, the third pressure level p 3 corresponds to the output pressure level p A. The second pressure level p 2 is lower than the first pressure level p 1. due to pressure losses between the two compressor sections 12 a, 12 b. The third pressure level p 3, to which the second compressor section 11 bcompresses the working medium, is greater than the first pressure level p 1, to which the first compressor section 11 acompresses the working medium.The pressure loss between the two compressor sections 11 a, 11 bresults in FIG. 1 in that the working medium compressed by the first compressor section 11 ais guided downstream of the first compressor section 11 aand upstream of the second compressor section 11 bvia a first heat exchanger 21, which serves for cooling the working medium between the two compressor sections 11 a, 11 b.A further pressure loss results in FIG. 1 in that the working medium is subsequently conducted to the first heat exchanger 21 via a separator 22 in order to separate condensate from the working medium compressed by the first compressor section 11 aand cooled by the first heat exchanger 21 and to discharge it in the direction of the arrow 23. The condensate can be produced as a result of the compression of the working medium and the cooling thereof between the compressor section 11 a, 11 b.The gaseous phase of the working medium compressed by the first compressor section 11 aand cooled by the first heat exchanger 21 is supplied in FIG. 1 at the second pressure level p 2 to the second compressor section 12 bfor further compression. The arrows 24 and 25 illustrate that compressed working medium can be discharged and supplied downstream of the separator 22.The discharge and supply of the working medium in the sense of the 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 takes place in the direction of the arrow 24 directly downstream of the separator 22 and thus upstream of the second compressor section 12 band the supply of the working medium in the direction of the arrow 25 directly upstream of the first heat exchanger 21.The turbomachine arrangement 10 according to the invention has a branch line 26, via which working medium at a fourth pressure level p 4, which is greater than the second pressure level p 2 and less than the output pressure level p A or corresponds to the output pressure level p A can be branched off from the compressor section 12 band fed to at least the electric machine 16 for cooling purposes.The working medium branched off from the second compressor section 11 bin FIG. 1 via the branch line 26 is conducted via the electric machine 16 and preferably also via the active magnetic bearings 19 for cooling the same. This working medium is taken from FIG. 1 at the fourth pressure level p 4 which is greater than the second pressure level p 2 and less than the third pressure level or the output pressure level p A respectively. The fourth pressure level p 4 can also correspond to the third pressure level p 3 or the output pressure level p A respectively. The second pressure level p 2 corresponds to the input pressure level of the second compressor section 11 band the third pressure level p 3 corresponds in FIG. 1 to the output pressure level p A of the turbomachine arrangement 10.The working medium branched off from the compressor section 12 bvia the branch line 26 for cooling the electric machine 16 and preferably the active magnetic bearings 19 is, after the working medium has been conducted via the electric machine 10 and preferably via the bearings 19, fed back in the direction of the second compressor section 11 bby means of a return line 27, wherein in FIG. 1 the return line 27 has a separate heat exchanger 28 for cooling the working medium used for cooling the electric machine 16 and the bearings 19 upstream of the second compressor section 11 b. Upstream of the heat exchanger 28, a switchable valve 39 is integrated into the return line 27.A particulate filter may be disposed in the branch line 26. Such a particle filter can be used to prevent particles from entering the area of the electric machine, for example metallic particles that can become detached from lines, for example.A droplet filter may be disposed downstream of the separator 22. The separator 22 may include a defogger.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 has been 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 in the branch line 26. The valve 40 serves for setting the volumetric flow of the working medium branched off via the branch line 26 and conducted at least via the electric machine 16 for cooling the same. The position of the valve 40 can be regulated as a function of 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. As a result, the efficiency of the turbomachine arrangement 10 can be further increased.With regard to all other details, the exemplary embodiment of FIG. 2 corresponds to the exemplary embodiment of FIG. 1, so that the same reference numerals are used for the same assemblies in order to avoid unnecessary repetitions.The turbomachine arrangement 10 of FIGS. 1, 2 also has a second heat exchanger 29, which serves for cooling the working medium to the output pressure level p A of the turbomachine arrangement 10, that is to say in FIGS. 1, 2 for cooling the working medium downstream of the second compressor section 11 b.FIG. 3 shows a modification of the turbomachine arrangement 10 of FIG. 2, wherein the same reference numerals are used for the same assemblies in turn in order to avoid unnecessary repetitions. Only those details will be discussed below by means of which the exemplary embodiment of FIG. 3 differs from the exemplary embodiment of FIG. 2 and thus also from the exemplary embodiment of FIG. 1.In FIG. 3, both the heat exchanger 30 and a separator 31 are integrated into the branch line 26. The heat exchanger 30 serves for cooling the working medium branched off from the second compressor stage 12 via the branch line 26, and the separator 31 serves for separating condensate. Condensate can be discharged from the separator 31 in the direction of the 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 same into an overheated state and thus counteract the risk of condensate formation in the region 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 serves, like the valve 40, for setting the volumetric 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 39 can in turn be regulated as a function of a measured temperature of the electric machine 16. If the temperature of the electric machine 16 is too high, the valve 39 is opened further. If the temperature of the electric machine 16 is too low, the valve 39 is closed further. In FIG. 3, the valve 39 can be assigned to the branch line 26, as can the valve 40 in FIG. 2. In FIG. 2, the valve 40, as in FIG. 3, the valve 39 can be assigned to the return line 27.FIG. 5 shows a development of the turbomachine arrangement 10 of FIG. 2, wherein, in turn, the same reference numerals are used for the same assemblies in order to avoid unnecessary repetitions, and only those details are discussed below, by means of 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 relating to the turbomachine arrangement of FIGS. 1, 2.The turbomachine arrangement 10 of FIG. 5 has a third compressor section 11 cin addition to the first compressor section 11 aand the second compressor section 11 b. This third compressor section 11 cis used for compressing the working medium downstream of the second compressor section 11 b, starting from a fifth pressure level p 5 to a sixth pressure level p 6, which in the exemplary embodiment of FIG. 5 corresponds to the output pressure level p A of the turbomachine arrangement 10. In FIG. 5, the working medium leaves the second compressor section 11 bat the third pressure level p 3, which is higher than the fourth pressure level p 4, wherein the pressure loss between the two compressor sections 11 b, 11 cis due to the guidance of the working medium via a heat exchanger 33 and a separator 34. The heat exchanger 33 serves for cooling the working medium between the second and third compressor sections 11 band 11 c, the separator 34 serves for separating condensate in order to feed the gaseous phase exclusively in the direction of the arrow 35 to the third compressor section 11 c, but to separate the liquid phase, i.e. the condensate, from the gaseous phase, which is then discharged in the direction of the arrow 36.Compressed working medium can again be discharged between the separator 34 and the third compressor section 11 cin the direction of the arrow 37 and supplied in the direction of the arrow 38.Separators are used in each case in the turbomachine arrangements 10 of FIGS. 1, 2, 3 and 5. Such separators are required when the working medium used tends to condense under the prevailing pressure and temperature conditions. If, for example, helium, neon or hydrogen is used as the working medium for the turbomachine arrangement 10, which is not prone to condensation under the prevailing pressure and temperature conditions in each case, the separators in FIGS. 1, 2, 3 and 5 can be dispensed with.Thus, FIG. 6 shows a modification of the turbomachine arrangement 10 from FIG. 5, in which no separators are present. Accordingly, the turbomachine arrangement 10 of FIG. 6 is suitable in particular for compressing hydrogen, helium or even neon. In FIG. 6, no heat exchanger is also assigned to the branch line 26. With regard to all other details, however, the turbomachine arrangement 10 of FIG. 6 corresponds to the turbomachine arrangement 10 of FIG. 5, so that the same reference numerals are again used for the same assemblies.FIG. 7 shows a modification of the turbomachine arrangement 10 of FIG. 5, which differs from the turbomachine arrangement 5 of FIG. 7 merely in that the working medium, which serves for cooling the electric machine 16 and the active magnetic bearings 19, is not branched off in the region of the second compressor section 11 b, but rather in the region of the third compressor section 11 c, with the result that the fourth pressure level p 4, at which the working medium is branched off via the branch line 26, is accordingly greater than the fifth pressure level p 5 and less than the sixth pressure level p 6 and therefore less than the output pressure level p A.Furthermore, in contrast to FIG. 5, in FIG. 7 the working medium which has been conducted via the electric machine 16 and the active magnetic bearings 19 for cooling is conducted downstream of the second compressor section 11 bdirectly in the direction of the third compressor section 11 c, namely via the heat exchanger 33 and the separator 34.FIG. 8 shows that no clutch is connected between the shafts 13 b, 13 cof the compressor sections 11 b, 11 c.Furthermore, FIG. 8 shows that the clutch 20 ais a rigid clutch and the clutch 20 bis a flex clutch. In FIG. 8, the compressor shaft of one of the compressor sections, namely the compressor shaft 13 aof the first compressor section 11 a, is coupled to the shaft 17 of the electric machine 16 via the rigid clutch, and the compressor shafts 13 b, 13 cof the compressor sections 11 b, 11 care coupled to the shaft 17 of the electric machine 16 via the flex clutch. The use of a flex coupling is advantageous in turbomachine arrangements 10 having at least three compressor sections 11 a, 11 b, 11 c(see FIGS. 5, 6, 7 ) and therefore a long shaft resulting therefrom, which is composed of the shafts 13 b, 13 cand 17. The flex clutch 20 bflexibly couples the shafts 13 b, 13 cof the compressor sections 11 b, 11 cto the shaft 17 of the electric machine 16, whereby, as shown in FIG. 8, an additional radial bearing 19 is required in the region of the clutch 20 bin comparison with the clutch 20 a.The shafts 13 a, 13 b, 13 c, 17 of the compressor stages 11 a, 11 b, 11 cand of the electric machine 16 are typically manufactured from a metallic material. The impellers of the compressor stages 12 a, 12 b, 12 care also typically manufactured from a metallic material. Preferably, the metallic material of the impellers of the compressor stages 12 a, 12 b, 12 chas a low density and a higher ratio of strength to mass. In particular, the metallic material of the impellers of the compressor stages 12 a, 12 b, 12 cis an aluminum alloy material or a titanium alloy material. This is preferred in particular when the compressor stages, as known from U.S. Pat. No. 3,749,516 A or U.S. Pat. No. 3,184,153 A, are designed as draw bolt rotors. This is advantageous in order to enable higher peripheral speeds for the respective compressor stage 12 a, 12 b, 12 c,as a result of which the pressure increase which can be achieved during the compression in the respective compressor stage 12 a, 12 b, 12 acan be increased. This is of importance in particular for the compression of a refrigerant serving for the liquefaction of hydrogen. The number of compressor sections 11 a, 11 b, 11 cnecessary for compression can thus be reduced.It is also possible to use a composite material, such as a CFRP or GRP material, for the impellers of at least one compressor stage 12 a, 12 b, 12 cat least in sections, in particular at least in the region of radially outer sections of the impellers. This is also advantageous in order to enable higher peripheral speeds for the respective compressor stage 12 a, 12 b, 12 cand thus to increase the pressure increase which can be achieved during the compression in the respective compressor stage 12 a, 12 b, 12 c. The impellers and thus rotor blades of the respective compressor stage 12 a, 12 b, 12 cmay be manufactured radially on the outside from a CFRP or GRP material and radially on the inside from a metallic material. The compressor shafts 13 a, 13 b, 13 cand the shaft 17 of the electric machine 16 are then preferably manufactured from a metallic material. This is advantageous in particular when hydrogen or helium is compressed as working medium, i.e. a working medium with low density. The number of compressor sections 11 a, 11 b, 11 cnecessary for compression can thus be reduced.Composite material can also be used for the shafts 13 a, 13 b, 13 c, 17. The compressor stages 12 a, 12 b, 12 cmay be embodied as open compressor stages or closed compressor stages.The compressor stages can be designed as draw bolt rotors, as explained above. Draw bolt rotors are known from U.S. Pat. No. 3,749,516 A or U.S. Pat. No. 3,184,153 A.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 refrigerant in the liquefaction of hydrogen.Thus, as already described above in detail, it is possible to compress both a refrigerant which tends to condense in the pressure and temperature conditions prevailing in each case in the compressor sections 11 a, 11 b, 11 cand a refrigerant which does not tend to condense in the pressure and temperature conditions prevailing in each case in the compressor sections 11 a, 11 b, 11 cand also a refrigerant which does not tend to condense in the refrigerant which acts in the pressure and temperature conditions prevailing in each case in the suction side and which do not tend to condense for the liquefaction of hydrogen.The invention therefore relates not only to the turbomachine arrangement 10 as such, but also to the use thereof for compressing a working medium serving for liquefying hydrogen as refrigerant, specifically while avoiding the risk of the working medium leaking during regular operation. In a possibly occurring fault event, a possible leakage can be limited to a minimum.The invention further relates to a method for liquefying hydrogen with the aid of a refrigerant, wherein the refrigerant is compressed with the aid of at least one turbomachine arrangement 10 according to the invention. Following the compression of the refrigerant with the at least one turbomachine arrangement 10 according to the invention, the compressed refrigerant is expanded in order to provide the cooling energy required for liquefying the hydrogen.Figure 9 shows a greatly simplified schematic of a system 41 for liquefying hydrogen. Gaseous hydrogen to be liquefied is supplied to the system 41 via a feed line 42. The gaseous hydrogen to be liquefied is conducted for gradual cooling according to FIG. 2 via heat exchanger stages 43, 44, wherein gaseous hydrogen is still present downstream of the heat exchanger stage 43 and liquefied hydrogen is present downstream of the heat exchanger stage 44 and an expansion valve 46, which is collected in a container 45.Immediately downstream of the heat exchanger stage 44, liquefied hydrogen is present, which is partially expanded in the region of the expansion valve 46. As a result, the hydrogen cools down 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. a portion of the liquefied hydrogen evaporates, thereby resulting cooling energy further cooling down the remaining liquid hydrogen.A gaseous hydrogen phase which may still be present can be branched off from the container 45 in the direction of the arrow 53 and be guided downstream of the heat exchanger stages 43, 44 via a compressor 47 and fed back into the feed line 42. Liquid hydrogen can be removed from the container 45 in the direction of the arrow 52.The refrigerant required for cooling and liquefying the hydrogen is individually compressed 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 in order to provide the required cooling energy.In the expansion device 48 comprising refrigeration circuit, the refrigerant is preferably a refrigerant condensing 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, compressed and expanded.In the expansion device 49 comprising refrigeration circuits, the refrigerant is preferably a refrigerant which 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, compressed and expanded.List of reference characters10 Turbomachine arrangement 11 a Kompressor section 11 b Kompressor section 11 c Kompressor section 12 a Kompressor stage 12 b Kompressor stage 12 c Kompressor stage 13 a Kompressor shaft 13 b Kompressor shaft 13 c Kompressor shaft 14 Feed line 15 Discharge line 16 Electric machine 17 Shaft 18 Housing 19 Bearing 20 a Kupplung 20 b Kupplung 21 Heat exchanger 22 Separator 23 Condensate discharge 24 Working medium discharge 25 Working medium feed 26 Branch line 27 Return line 28 Heat exchanger 29 Heat exchanger 30 Heat exchanger 31 Separator 32 Heat exchanger 33 Heat exchanger 34 Separator 35 Working medium feed 36 Condensate discharge 37 Working medium discharge 38 Working medium feed 39 Valve 40 Valve 41 System for liquefying hydrogen 42 Feed line 43 Heat exchanger stage 44 Heat exchanger stage 45 Container 46 Expansion valve 47 Compressor 48 Expansion device 49 expansion device 50 separation elements 50a load pistons 50b restriction 51 condensate discharge 52 liquid hydrogen discharge 53 hydrogen gas dischargeReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedWO 2013 / 139568 A1

[0002] EP 1 074 746 B1

[0004] U.S. Pat. No. 3,749,516 A [0062, 0065]U.S. Pat. No. 3,184,153 A [0062, 0065]

Claims

Turbomachine arrangement (10), having a plurality of single-stage or multistage 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 having a first compressor section (11a) for compressing the working medium to a first pressure level starting from an input pressure of the turbomachine arrangement (10), and having a second compressor section (11b) for compressing the working medium subsequently to the first compressor section (11c) starting from a second pressure level to a third pressure level which is greater than the first pressure level, having an electric machine (16) which has a shaft (17), wherein the respective compressor shaft (13a, 13b, 13c) extends coaxially to 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, one- or multi-part housing (18) and are mounted in the housing (18) via active magnetic bearings (19) in such a way that at least the respective compressor section (11a, 11b, 11c) and the electric machine (16) are flushed or flushed by the working medium, with a feed line (14), via which non-compressed working medium at the input pressure level of the turbomachine arrangement (10) can be fed to the turbomachine arrangement (10), with a discharge line (15), via which working medium compressed by the turbomachine arrangement (10) can be discharged at an output pressure level of the turbomachine arrangement (10), having a branch line (26), via which working medium can be branched off from a compressor section (11b, 11c) at a fourth pressure level, which is greater than the second pressure level and less than the output pressure level or corresponds to the output pressure level, and can be supplied to the electric machine (16) for cooling the electric machine (16).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).Turbomachine arrangement (10) according to Claim 1, characterized bya third compressor section (11c) in order to compress the working medium, following the second compressor section (11b), starting 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).Turbomachine arrangement (10) according to one of Claims 1 to 3, characterized in that the branch line (26), via which the working medium at the fourth pressure level can be fed to the electric machine (16), branches off the working medium from the second compressor section (11b).Turbomachine arrangement (10) according to one of Claim 3, characterized in that the branch line (26), via which the working medium at the fourth pressure level can be supplied to the electric machine (16), branches off the working medium from the second compressor section (11b) or from the third compressor section (11c).Turbomachine arrangement (10) according to one of Claims 1 to 5, characterized bya return line (27), via which the working medium which is guided via the electric machine (16) for cooling the electric machine (16) can be guided back in the direction of the second compressor section (11b).Turbomachine arrangement according to one of Claims 1 to 6, characterized bya first heat exchanger (21) for cooling the working medium downstream of the first compressor section (11a) and upstream of the second compressor section (11b).Turbomachine arrangement according to one of Claim 7, characterized in that the return line (27) conducts the working medium, which is conducted via the electric machine (16) for cooling the electric machine (16), via the first heat exchanger (21) or via a separate heat exchanger (28).Turbomachine arrangement according to one of Claims 1 to 8, characterized bya second heat exchanger (29) for cooling the working medium compressed to the output pressure level.Turbomachine arrangement according to one of Claims 1 to 9, characterized byat least one separator (22, 34, 31) for separating condensate from the working medium.Turbomachine arrangement according to one of Claims 1 to 10, 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 clutch, 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 clutch.Turbomachine arrangement according to one of Claims 1 to 11, 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 produced from a metallic material, the metallic material of the impellers of the compressor stages (12a, 12b, 12c) having a higher ratio of strength to mass than the metallic material of the compressor shafts (13a, 13b, 13c) and of the shaft (17) of the electric machine (16), the metallic material of the impellers of the compressor stages (12a, 12b, 12c) preferably being an aluminum alloy material or a titanium alloy material or a magnesium alloy material.Turbomachine arrangement according to one of Claims 1 to 11, characterized in that the compressor shafts (13a, 13b, 13c) and the shaft (17) of the electric machine (16) are each produced from a metallic material, and in that the impellers of the compressor stages (12a, 12b, 12c) are produced at least partially on a CFRP material or GRP material.Use of a turbomachine arrangement (10) according to one of Claims 1 to 13 for compressing a working medium serving for liquefying hydrogen as refrigerant.Method for liquefying hydrogen with the aid of a refrigerant, wherein at least one turbomachine arrangement (10) according to one of Claims 1 to 13 compresses the refrigerant as 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.

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