Cryogenic expansion turbine with magnetic bearing

Abstract

A cryogenic expansion turbine system (10) includes a turboexpander (12) configured to receive and expand a cryogenic gas feed stream (24). A rotating shaft (16) operably connects the turboexpander and a resistance device, such as a compressor (14) or brake. The bearing housing (18) has a bearing cooling fluid inlet port and a bearing cooling fluid outlet port. An electromagnetic bearing (22) is located within the bearing housing and rotatably supports the rotating shaft. A bearing cooling circuit (72) directs a flow of bearing cooling fluid (62) through the bearing cooling fluid inlet port into the bearing housing such that the electromagnetic bearing is cooled and resulting heated bearing cooling fluid (68) exits the bearing housing via the cooling fluid outlet port.

Description

[0001] Priority claim

[0002] This application claims priority to U.S. Provisional Application No. 63 / 330,005, filed on April 12, 2022, the contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates generally to cryogenic fluid expansion devices and, more particularly, to a cryogenic expansion turbine having magnetic bearings that provide cooling of the bearings. Background Art

[0004] A turboexpander or turboexpander is used to expand a cryogenic gas in an industrial process, such as the liquefaction of hydrogen or natural gas, thereby providing refrigeration therefor. The work done by the cryogenic gas in turning the expander impeller of the turboexpander cools the gas in the expander. The centrifugal or axial flow of the cryogenic gas through the turbine while expanding is typically used to drive a compressor, generator or other actuator to extract work from the expanding gas. Partial liquefaction of the expanding gas may occur.

[0005] When a turboexpander is used to drive a compressor or generator, the expander impeller is usually located at one end of a rotating shaft and the compressor impeller or generator is located at the opposite end of the rotating shaft. The rotating shaft runs at very high speeds (usually 25,000 revolutions per minute or more) and must therefore be supported by suitable bearings.

[0006] Magnetic bearings are already used in cryogenic turboexpanders because they support the rotating shaft within a bearing housing without physical contact. As a result, the bearings have low friction and are not subject to wear or speed limitations. Most magnetic bearings are active magnetic bearings and therefore use electromagnets, which require continuous electrical power. As a result, heat builds up in the electrical coils of the electromagnets and thus in the bearing housing, which therefore requires cooling.

[0007] Additionally, seals around the rotating shaft must be positioned between the bearing housing and the turboexpander because the bearings operate at temperatures much higher than cryogenic turboexpanders, which operate at low temperatures. As the bearings heat up, pressure builds up within the bearing housing, forcing gas to leak through the seals into the turboexpander. To avoid damage to the seals, proper management of the bearing temperature is required. Damaged seals can cause the cold gas within the turboexpander to be contaminated by hot fluid leaking from the bearings and damage the bearings by cold fluid leaking from the turboexpander. While high-temperature superconducting (HTS) magnetic bearings use the temperature of the refrigerant gas to eliminate electrical resistance in the bearings, fluid isolation within the HTS magnetic bearing housing and the turboexpander housing may still be required in some cases, such as where the compressor brake is driven by the turboexpander under steady-state conditions. Summary of the invention

[0008] Aspects of the present subject matter may be implemented individually or together in the methods, devices, and systems described and claimed below. These aspects may be used alone or in combination with other aspects of the subject matter described herein, and the description of these aspects is not intended to exclude the individual use of these aspects or the individual claims of these aspects or the different combinations set forth in the appended claims.

[0009] In one aspect, a cryogenic expansion turbine includes a turboexpander configured to receive and expand a cryogenic gas feed stream, a resistance device, and a rotating shaft operably connected to the turboexpander and the resistance device. A bearing housing has a bearing cooling fluid inlet port and a bearing cooling fluid outlet port. A plurality of electromagnetic bearings are located in the bearing housing and rotatably support the rotating shaft. A bearing cooling circuit directs a bearing cooling fluid flow into the bearing housing via the bearing cooling fluid inlet port, thereby cooling the plurality of electromagnetic bearings. The generated heated bearing cooling fluid leaves the bearing housing via the cooling fluid outlet port.

[0010] In another aspect, a method of cooling an electromagnetic bearing in a cryogenic expansion device having a turboexpander operably connected to a drag load via a rotating shaft supported by an electromagnetic bearing in a bearing housing includes the steps of directing a bearing cooling fluid to the bearing housing, cooling the electromagnetic bearing using the bearing cooling fluid to produce heated bearing cooling fluid, and withdrawing the heated bearing cooling fluid from the bearing housing.

[0011] In yet another aspect, a cryogenic expansion turbine includes a turboexpander configured to receive and expand a cryogenic gas feed stream, a resistance device, and a rotating shaft operably connecting the turboexpander and the resistance device. The bearing housing has a bearing cooling fluid inlet port and a bearing cooling fluid outlet port. A plurality of electromagnetic bearings are located in the bearing housing and rotatably support the rotating shaft. A cooling jacket at least partially surrounds the bearing housing. The bearing cooling circuit is configured to direct the bearing cooling fluid flow into the cooling jacket, whereby the plurality of electromagnetic bearings are cooled, and the generated heated bearing cooling fluid leaves the cooling jacket. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a schematic diagram of a first embodiment of a cryogenic expansion turbine of the present disclosure.

[0013] Figure 2 is a schematic diagram of a second embodiment of a cryogenic expansion turbine of the present disclosure.

[0014] Figure 3 is a schematic diagram of a third embodiment of the cryogenic expansion turbine of the present disclosure.

[0015] Figure 4is a schematic diagram of a fourth embodiment of the cryogenic expansion turbine of the present disclosure.

[0016] Figure 5 is a schematic diagram of a fifth embodiment of the cryogenic expansion turbine of the present disclosure.

[0017] Figure 6 is a schematic diagram of a sixth embodiment of the cryogenic expansion turbine of the present disclosure. DETAILED DESCRIPTION

[0018] A more detailed description of the systems and methods according to the present disclosure is set forth below. It should be understood that the following description of specific systems and methods is exemplary and does not exhaust all possible variations or applications. Therefore, the scope of the present disclosure is not restrictive and should be understood to include variations or embodiments that can be thought of by ordinary technicians.

[0019] It should be noted herein that lines, conduits, ducts, channels and similar structures and corresponding flows are sometimes indicated by the same element numerals as shown in the figures.

[0020] Reference numerals introduced in the specification in conjunction with the drawings may be repeated in one or more subsequent drawings for shared elements or features without additional description in the specification, in order to provide context for the other features.

[0021] In the claims, letters are used to identify claimed steps (e.g., a, b, and c). These letters are used to aid in referring to method steps and are not intended to indicate the order in which the claimed steps should be performed, unless and only to the extent such an order is specifically recited in the claims.

[0022] Although the embodiments described below use hydrogen as the cryogenic gas feed stream expanded in the turboexpander, the technology disclosed herein can be used to expand other cryogenic fluids. In addition, although hydrogen is used as a recirculation and bearing cooling fluid in the embodiments described below, alternative fluids known in the art can also be used.

[0023] A first embodiment of the cryogenic expansion turbine of the present invention is Figure 1The whole is indicated by 10. The cryogenic expansion turbine 10 includes a turboexpander 12 and a resistance device (which is a compressor 14 in this embodiment) connected by a rotating shaft 16. The rotating shaft 16 is rotatably mounted in a bearing housing 18 by active or electromagnetic bearings 22a-22d. As is known in the prior art, seals are provided around the rotating shaft at two locations where the shaft leaves the bearing housing 18. Suitable active or electromagnetic bearings can be obtained from the SKF Group in Gothenburg, Sweden or the Waukesha Bearing Company in Waukesha, Wisconsin, USA. Examples of suitable active magnetic bearings are introduced in U.S. Patent No. 4,652,780 to Murakami et al., U.S. Patent No. 4,720,649 to Habermann et al., U.S. Patent No. 9,845,829 to Hay et al., and U.S. Patent No. 10,030,703 to Bauce et al., the contents of each of which are incorporated herein by reference. Examples of high temperature superconducting (HTS) magnetic bearings suitable for use in the embodiments described below are disclosed in European Patent Application No. EP1835188 to Nexans and US Patent No. 5,789,837 to Shin et al., the contents of each of which are incorporated herein by reference.

[0024] As is known in the art, the turboexpander 12 includes an inlet, an outlet, and an expander impeller, so that the gas entering the turboexpander expands and the resulting cooling fluid leaves the turboexpander. The compressor 14 includes an inlet, an outlet, and a compressor impeller, which is rotated by the rotating expander impeller via a rotating shaft 16, so that the turboexpander 12 and the compressor 14 are operably connected by the rotating shaft 16.

[0025] A hydrogen cryogenic gas feed stream 24 enters the turboexpander 14 and expands as it performs work. The resulting cooled hydrogen fluid feed stream exits as stream 26. The turboexpander may be located within a cold box 28 where the cooled hydrogen fluid stream continues the liquefaction process.

[0026] The compressor 14 is provided with a recirculating fluid circuit. Figure 130 in the figure. A hydrogen recirculation stream 32 enters the compressor 14 and is compressed. As a result, the turboexpander 12 performs work while turning the compressor 14. The resulting heated recirculation stream leaves the compressor as stream 34 and is cooled in an aftercooler 36. By way of example only, the aftercooler may be a heat exchanger that uses ambient air or a refrigerant as a cooling stream. The recirculation fluid circuit includes a recirculation fluid removal line 38 having a corresponding removal valve 42. When the removal valve 42 is open, cooling fluid 44 from the aftercooler 36 may be directed out of the recirculation fluid circuit via line 38. Alternatively, when valve 42 is closed (which is the normal operating mode), fluid 44 is directed through an expansion valve 46 to provide a flow pressure resistance such that the turboexpander 12 is forced to perform work while turning the compressor 14. As a result, an expansion and cooling stream 32 is formed (when the supply valve 48 is closed).

[0027] When the supply valve 48 is open, additional hydrogen recirculation fluid may be provided to the recirculation loop via the supply line 52. As previously described, the removal valve 42 may be opened to remove fluid from the recirculation fluid loop 30. The supply valve 48 and the removal valve 42 may be automatic and feedback control may be provided via the pressure controller 54 so that the proper amount of fluid may be maintained within the recirculation loop. A speed controller 55 may also be provided for the expansion valve 46, which may also be automatic. By way of example only, the speed controller may be an outer loop (i.e., a cascade control scheme) supplying a pressure controller. Similar valve control schemes may be used for the following described Figure 2 and Figure 3 in the system.

[0028] Figure 1 The system is provided with a bearing cooling circuit, generally indicated at 72. A bearing cooling fluid, such as hydrogen, from a pressurized source is in fluid communication with a cooling fluid line 62 of the bearing circuit provided with a control valve 64. By way of example only, the cooling fluid may be pressurized to about 20 psi above the pressure at the outer diameter of the expander impeller of the turboexpander 12. When the control valve 64 is opened, as indicated by arrows 66a, 66b and 66c, hydrogen cooling gas is provided to the interior of the bearing housing via the cooling fluid inlet port. Although in Figure 1 , but the housing may alternatively have only one inlet port or more than three inlet ports. The coils of the active magnetic bearings 22a-22d are cooled by the hydrogen cooling fluid, and the heated cooling fluid exits the bearing housing 18 via the cooling fluid outlet ports and the piping of the bearing cooling circuit, as shown by arrows 68. Figure 1 One cooling fluid outlet port is shown in FIG, but the housing may alternatively have more than one outlet port.

[0029] The heated hydrogen cooling fluid 68 exiting the bearing housing 18 may be directed to the liquefaction system compressor or other destination. Figure 1 The system has an open-loop bearing cooling circuit.

[0030] The second embodiment of the system of the present disclosure is Figure 2 200 and includes a closed-loop bearing cooling circuit 272. In addition to the configuration of the bearing cooling circuit, Figure 2 The configuration and operation of the system 200 is Figure 1 same.

[0031] exist Figure 2 In the system of FIG. 1 , the cooling fluid line 202 branches off from the line 204 of the recirculation fluid circuit, generally indicated at 230. As a result, a portion of the hydrogen in the recirculation circuit flows through the line 202 and enters the interior of the bearing housing 208 via the cooling fluid inlet port, as indicated by arrow 206. Figure 2 One cooling fluid inlet port is shown, but the housing may alternatively have more than one inlet port. The coils of the active magnetic bearings 222a-222d are cooled by the hydrogen cooling fluid, and the heated cooling fluid exits the bearing housing 208 via the cooling fluid outlet port and line 216. Figure 2 One cooling fluid outlet port is shown in FIG, but the housing may alternatively have more than one outlet port.

[0032] The heated hydrogen cooling fluid in line 216 exiting the bearing housing 208 flows back into the recirculating fluid circuit and enters the circuit through connecting line 218. As a result, Figure 2 The system has a closed-loop bearing cooling circuit.

[0033] The cooling fluid supply line 220 is provided with a valve 224 and communicates with a pressurized supply of hydrogen gas. As a result, when the valve 224 is open, the cooling fluid circuit and the recirculation fluid circuit can be supplemented with hydrogen gas if necessary.

[0034] Figure 2 Embodiments of provide the advantage of generally not requiring additional removal of hydrogen from the bearing cooling fluid circuit, as well as the efficiencies provided by compressor 214 (powered by turboexpander 212) providing a hydrogen cooling flow to the bearings.

[0035] In addition to the components described above, Figure 2 The rest of the system has the same structure and function as the previous embodiment.

[0036] if Figure 2 If the system requires additional braking, causing the turbo expander to perform additional work, or requires additional compression of the recirculation and brake fluid circuit, then Figure 3 As shown, additional resistance means in the form of a second compressor may be added Figure 2 More specifically, referring to Figure 3 , the recirculation fluid circuit, generally indicated at 330, may include first and second compressor stages 314a and 314b. The first and second compressor stages 314a and 314b are both powered by the turboexpander 312 and may be separate compressors or separate stages of a single compressor.

[0037] like Figure 3 As shown, the heated cooling fluid exits the bearing housing 308 via the cooling fluid outlet port of the bearing cooling circuit 372 and the line 316 and is directed to the inlet of the first compressor stage 314a. In addition, the stream 332 formed when the cooling fluid 344 from the aftercooler 336 is directed through the expansion valve 346 as in the previous embodiment is directed into the first compressor stage 314a. The heated recirculation flow exits the second compressor stage 314b as stream 334 and is cooled in the aftercooler 336.

[0038] In addition to the above components, Figure 3 The rest of the system has the same structure and function as the previous embodiment.

[0039] A fourth embodiment of the system of the present disclosure is Figure 4 The whole is indicated at 400. In this embodiment, high temperature superconducting (HTS) magnets are used in HTS magnetic bearings 422a-422d. HTS magnetic bearings also require cooling to compensate for heat losses, but without resistance, the magnets will not generate heat when operating. Figure 4 The system includes a bearing cooling circuit 472 in which a cooling fluid line 402 branches off from a hydrogen cryogenic gas feed line 424 entering the turboexpander 414. As a result, when the inlet control valve 404 is open, a portion of the hydrogen feed stream from line 424 flows through the bearing cooling fluid inlet line 402 and enters the interior of the bearing housing 408 via the cooling fluid inlet port. By way of example only, the hydrogen in line 402 may be approximately 60°K. Although Figure 4 One cooling fluid inlet port is shown, but the housing may alternatively have more than one inlet port. The HTS magnetic bearings 422a-422d are cooled by a hydrogen cooling fluid so that the superconducting material is cooled to the necessary cryogenic temperature (e.g., <70°K), thereby avoiding or minimizing electrical resistance and heat generated by the current flow. The heated cooling fluid exits the bearing housing 408 via the cooling fluid outlet port and the bearing cooling fluid outlet line 416 under the control of the outlet control valve 418, and may be returned to the main system compressor within the loop through which the hydrogen feed flow in line 424 flows. In some alternative embodiments, the expander gas may exit through the compression loop. Although in Figure 4 One cooling fluid outlet port is shown in FIG, but the housing may alternatively have more than one outlet port.

[0040] The heated hydrogen cooling fluid exiting the bearing housing 408 through line 416 and valve 418 may be directed to a liquefaction system compressor or other destination. Valve 418 may be automatic and provided with feedback control including a temperature controller 428 to appropriately regulate the flow of fluid through line 416 to ensure adequate cooling of the high temperature superconducting magnetic bearings 422a-422d.

[0041] like Figure 4 As shown at 432 in FIG. 4 , a portion of the hydrogen introduced into the bearing housing 408 may be returned to the turboexpander 412 where it joins the stream 426 exiting the turboexpander 412 after expansion and cooling.

[0042] As in Figure 3 In the embodiment, Figure 4 The system includes a recirculating fluid circuit, which may be a closed loop cycle, generally indicated at 430, which includes two compressor stages 414a and 414b to provide sufficient cooling within the turboexpander 412. In some alternative embodiments, a single compressor may be sufficient.

[0043] In addition to the components described above, Figure 4 The rest of the system has the same structure and function as the previous embodiment.

[0044] Figure 4 The magnetic field of the HTS magnetic bearing of the embodiment may be much stronger than that of the conventional magnetic bearing. In addition, the motor and generator based on HTS (related to the embodiment described below) can be reduced to 1 / 3 of the original size. With a stronger magnetic field and a smaller size, higher speeds and higher efficiency can be achieved. Similar situations also apply to high temperature superconducting generator brakes.

[0045] A fifth embodiment of the system of the present disclosure is Figure 5 The whole is indicated by 500 and is replaced by a generator / eddy current brake 502 Figure 4 The compressors 414a and 414b act as drag devices for the turbo expander 512. Such a generator can optionally be provided as an HTS generator, since the cryogenic gas is already nearby for its use. As a result, the generator 502 acts as an eddy current brake. Figure 5 The rest of the system has Figure 4 The system has the same structure and function.

[0046] It should be understood that Figure 5 The generator / eddy current brake 502 can be replaced Figure 1-4 Any compressor that acts as a resistance device. In addition, Figure 1-4 Any compressor can be Figure 5The generator / eddy current brake 502 is supplemented so that in each embodiment the rotating shaft rotated by the turbo expander rotates the compressor and the generator / eddy current brake as a resistance device.

[0047] In a sixth embodiment of the system of the present disclosure, a cooling jacket 606 at least partially surrounds a bearing housing 608 as an alternative to directing cooling gas into the bearing housing to cool the magnetic bearings. As shown by arrow 605, the cooling jacket has an inlet port and receives water. As a result, the side walls outside the bearing housing 608 are surrounded by cooling water to provide cooling for the bearings 622a-622d inside. As shown by arrow 607, the jacket has an outlet port through which heated water or evaporated gas leaves the jacket when cooler water enters through the inlet port of 605. Thus, cooling water circulates through the jacket. In an embodiment where the bearings 622a-622d are HTS magnetic bearings, the side walls outside the bearing housing 608 may be surrounded by liquid nitrogen to provide cooling for the bearings inside.

[0048] Figure 6 The rest of the system has Figure 5 The system has the same structure and function.

[0049] While preferred embodiments of the present disclosure have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made thereto without departing from the spirit of the present disclosure, the scope of which is defined by the appended claims.

Claims

1. A cryogenic expansion turbine, comprising: a turboexpander configured to receive and expand a cryogenic gas feed stream; b. Resistance device; c. a rotating shaft operatively connected to the turboexpander and the resistance device; d. a bearing housing having a bearing cooling fluid inlet port and a bearing cooling fluid outlet port; e. a plurality of electromagnetic bearings, which are located in the bearing housing and rotatably support the rotating shaft; f. A bearing cooling circuit configured to direct a flow of bearing cooling fluid into the bearing housing via a bearing cooling fluid inlet port, whereby the plurality of electromagnetic bearings are cooled, and the resulting heated bearing cooling fluid exits the bearing housing via a cooling fluid outlet port.

2. The cryogenic expansion turbine according to claim 1, wherein: The resistance device includes a compressor.

3. The cryogenic expansion turbine of claim 2, further comprising a recirculating fluid circuit including an aftercooler configured to receive compressed fluid from the compressor, an expansion valve configured to receive cooling fluid from the aftercooler and direct the expanded fluid to the compressor.

4. The cryogenic expansion turbine according to claim 3, wherein: The recirculation fluid circuit also includes a recirculation fluid removal line having a removal valve configured to remove recirculation fluid from the recirculation fluid circuit when the removal valve is open, and a recirculation fluid supply line having a supply valve configured to add recirculation fluid to the recirculation fluid circuit when the supply valve is open.

5. The cryogenic expansion turbine of claim 3, further comprising a hydrogen recirculation fluid.

6. The cryogenic expansion turbine according to claim 3, wherein: The bearing cooling circuit is configured to receive bearing cooling fluid from the recirculation fluid circuit and return bearing cooling fluid from the recirculation fluid circuit.

7. The cryogenic expansion turbine according to claim 6, wherein: The bearing recirculation circuit provides bearing cooling fluid downstream of the aftercooler and returns the bearing cooling fluid to the recirculation downstream of the expansion valve.

8. The cryogenic expansion turbine of claim 6, further comprising a hydrogen recirculation fluid and a hydrogen bearing cooling fluid.

9. The cryogenic expansion turbine according to claim 6, wherein: The bearing cooling circuit also includes a bearing cooling fluid supply line and a bearing cooling fluid supply valve, the bearing cooling fluid supply valve being configured to provide bearing cooling fluid to the bearing cooling circuit when opened.

10. The cryogenic expansion turbine according to claim 6, wherein: The resistance device includes a first compressor stage and a second compressor stage, wherein the aftercooler is configured to receive compressed fluid from the second compressor stage and the expansion valve is configured to direct the expanded fluid to the first compressor.

11. The cryogenic expansion turbine according to claim 10, wherein: The first and second compressor stages are first and second stages of a single compressor.

12. The cryogenic expansion turbine according to claim 10, wherein: The first compressor stage includes a first compressor and the second compressor stage includes a second compressor.

13. The cryogenic expansion turbine according to claim 2, wherein: The resistance device includes a first compressor stage and a second compressor stage.

14. The cryogenic expansion turbine according to claim 13, wherein: The first and second compressor stages are first and second stages of a single compressor.

15. The cryogenic expansion turbine according to claim 13, wherein: The first compressor stage includes a first compressor and the second compressor stage includes a second compressor.

16. The cryogenic expansion turbine of claim 1, further comprising a gas feed line configured to deliver a cryogenic gas feed stream to the turboexpander, and wherein, The bearing cooling circuit comprises: g. a bearing cooling fluid inlet line configured to receive a bearing cooling fluid from the gas feed line and direct the bearing cooling fluid to the bearing cooling fluid inlet port; h. A bearing cooling fluid outlet line configured to receive heated bearing cooling fluid from a bearing cooling fluid outlet port of the bearing housing.

17. The cryogenic expansion turbine according to claim 16, wherein: The bearing cooling fluid inlet line includes an inlet control valve, and the bearing cooling fluid outlet line includes an outlet control valve.

18. The cryogenic expansion turbine of claim 16 further comprising a hydrogen cryogenic feed gas and a hydrogen bearing cooling fluid.

19. The cryogenic expansion turbine according to claim 16, wherein: The resistance device includes a first compressor stage and a second compressor stage, and further includes a recirculation fluid circuit including an aftercooler configured to receive compressed fluid from the second compressor stage, an expansion valve configured to receive cooling fluid from the aftercooler and direct expansion fluid to the first compressor stage.

20. The cryogenic expansion turbine according to claim 16, wherein: The resistance device includes an eddy current brake.

21. The cryogenic expansion turbine of claim 1 further comprising a hydrogen bearing cooling fluid.

22. The cryogenic expansion turbine according to claim 1, wherein: The resistance device includes an eddy current brake.

23. The cryogenic expansion turbine according to claim 1, wherein: The resistance device includes a compressor and an eddy current brake.

24. The cryogenic expansion turbine according to claim 1, wherein: The plurality of electromagnetic bearings are high temperature superconducting magnetic bearings.

25. A method of cooling an electromagnetic bearing in a cryogenic expansion device having a turboexpander operatively connected to a drag load via a rotating shaft supported by the electromagnetic bearing in a bearing housing, the method comprising the steps of: a. directing the bearing cooling fluid to the bearing housing; b. cooling the electromagnetic bearing using the bearing cooling fluid, thereby generating a heated bearing cooling fluid; c. Pump heated bearing cooling fluid from the bearing housing.

26. The method according to claim 25, wherein: The bearing cooling fluid includes hydrogen.

27. The method according to claim 26, wherein: The bearing cooling fluid comprises hydrogen at approximately 60°K.

28. The method according to claim 25, wherein: The drag load includes a compressor, and further includes the step of compressing a recirculation fluid using the compressor, and wherein step a includes directing a portion of the recirculation fluid to the bearing housing as the bearing cooling fluid.

29. The method according to claim 28, wherein: The recirculation fluid and the bearing cooling fluid include hydrogen.

30. The method of claim 25, further comprising the step of directing a cryogenic gas feed stream to the turboexpander, and wherein step a. comprises directing a portion of the cryogenic gas feed stream to the bearing housing as the bearing cooling fluid.

31. The method according to claim 30, wherein: The cryogenic gas feed stream and the bearing cooling fluid include hydrogen.

32. The method of claim 25, wherein: The plurality of electromagnetic bearings are high temperature superconducting magnetic bearings.

33. A cryogenic expansion turbine comprising: a turboexpander configured to receive and expand a cryogenic gas feed stream; b. Resistance device; c. a rotating shaft operatively connected to the turboexpander and the resistance device; d. a bearing housing having a bearing cooling fluid inlet port and a bearing cooling fluid outlet port; e. a plurality of electromagnetic bearings, which are located in the bearing housing and rotatably support the rotating shaft; f. a cooling jacket at least partially surrounding the bearing housing; g. A bearing cooling circuit configured to direct a flow of bearing cooling fluid into a cooling jacket, thereby cooling the plurality of electromagnetic bearings, and resulting heated bearing cooling fluid exiting the cooling jacket.

34. The cryogenic expansion turbine according to claim 32, further comprising water as the bearing cooling fluid.

35. The cryogenic expansion turbine according to claim 32, wherein: The resistance device includes an eddy current brake.

36. The cryogenic expansion turbine according to claim 32, wherein: The resistance device includes a compressor.

37. The cryogenic expansion turbine according to claim 33, wherein: The plurality of electromagnetic bearings are high temperature superconducting magnetic bearings.

38. The cryogenic expansion turbine of claim 37, further comprising nitrogen as the bearing cooling fluid.

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