Circulating gas refrigerator and apparatus for liquefying a feed fluid at cryogenic temperatures

Abstract

The present utility model relates to a cycle gas refrigerator and an apparatus for liquefying a feed fluid at low temperature. The cycle gas refrigerator comprises a compression system, a cooling system and an expansion system, the expansion system comprising at least one expansion turbine coupled to a compressor, the expansion turbine and the compressor each being coupled to one end of a common shaft, the expansion turbine, the compressor and the shaft being housed in a housing, the housing accommodating a first chamber for the compressor, an intermediate second chamber for the shaft and a third chamber for the turbine, the refrigerator comprising a set of pressurized fluid circuits in communication with at least two cavities located in the second chamber for supplying a pressurized gas flow to attenuate or counteract the axial forces acting on the shaft, the shaft comprising at least one disc-shaped flange located between the turbine and the compressor, the flange extending transversely to its axis of rotation, the flange being associated with at least one labyrinth seal for longitudinally separating two cavities intended to be subjected to different pressures on either side of the flange.

Description

Technical Field

[0001] This utility model relates to a circulating gas chiller and a device for liquefying feed fluid at low temperatures.

[0002] More specifically, this invention relates to a circulating gas refrigerator comprising a compression system, a cooling system, and an expansion system in a circulation loop for thermodynamically circulating the circulating gas to generate cooling. The expansion system includes at least one expansion turbine coupled to a compressor of the refrigerator and, for example, a compressor of a system for compressing the circulating gas. The expansion turbine and the compressor are each coupled to one end of a common shaft. The expansion turbine, the compressor, and the shaft are housed in a housing containing a first chamber in which the compressor is rotatably mounted, an intermediate second chamber in which the shaft is rotatably mounted on a bearing assembly including one or more bearings, and a third chamber in which the turbine is rotatably mounted. The refrigerator includes a pressurized fluid circuit communicating with at least two chambers located in the second chamber. The pressurized fluid circuit is configured to supply a predetermined flow rate of pressurized gas to the chambers to attenuate or counteract the axial force on the shaft caused by the pressure difference between the dominant pressures in the first and third chambers. Background Technology

[0003] In refrigeration cycles that utilize turbines, energy recovery from the cryogenic turbine is crucial for improving energy efficiency.

[0004] This is especially important for high-power hydrogen liquefaction plants that use such refrigeration units (e.g., 60 to 300 tons per day).

[0005] One solution is to recover power via a compressor connected to the cryogenic turbine shaft to increase the compression discharge or intake pressure of the main compressor station.

[0006] Given the limitations in terms of the volumetric flow rate to be processed, these connected compressors are installed at the outlet of the compression station, where the pressure is highest (greater than 20 bar). On the cryogenic turbine side, the optimal arrangement is for the turbines to be connected in series in order from the highest pressure (e.g., 30 to 50 bara, absolute pressure) to the lowest pressure (e.g., 1 to 10 bara).

[0007] The pressure difference between the connected turbine and compressor components becomes significant. This pressure difference generates an axial load, which must be partially compensated by selected bearings supporting the shaft and by properly distributing the pressure across the rotor surfaces involved via the turbine sealing system.

[0008] In turbines, the load-carrying capacity of bearings is roughly proportional to the size of the machine. Specifically, the larger the turbine, the larger the surface area exposed to pressure. Due to the pressure difference between the two ends of the shaft, the axial load is greater than or very close to the maximum load-carrying capacity of the bearing (magnetic, gas, rolling, or other).

[0009] One known solution is to use a thrust balancing mechanism (TEM).

[0010] Another solution is to install a balance piston on the centrifugal compressor.

[0011] Another solution is to install impeller balancing holes, which involves creating a cavity at the rear of the impeller to maintain "moderate" pressure, or to counteract the residual axial force caused by the pressure difference on the impeller blades. However, this does not counteract the piston effect within the diameter range of the labyrinth seal on the shaft.

[0012] The purpose of this utility model is to overcome all or part of the above-mentioned shortcomings of the prior art. Utility Model Content

[0013] Therefore, the main feature of the refrigeration machine according to this utility model (which in other respects is consistent with the general definition given for it in the preamble above) is that, between the turbine and the compressor, the shaft includes at least one disc-shaped flange extending transversely to its axis of rotation, which is associated with at least one labyrinth seal for longitudinally separating two chambers designed to withstand different pressures on both sides of the flange.

[0014] Furthermore, embodiments of this utility model may have one or more of the following features:

[0015] - The refrigeration unit includes a labyrinth seal located at the top of the flange.

[0016] - The refrigeration unit includes two labyrinth seals located at the base of the flange on both sides.

[0017] The refrigeration unit includes a first chamber connected to a circuit of high-pressure fluid from a compressor. The first chamber communicates with the front side of the compressor—that is, the side of the compressor opposite to the side of the compressor with blades located in the compression chamber—to generate a balancing force on the compressor that is opposite to the force generated by compression within the compression chamber. The first chamber is defined toward the turbine by a labyrinth seal.

[0018] A second cavity is defined between the first cavity and the flange.

[0019] - A third chamber is defined between the second chamber and the turbine, and the third chamber is defined at its turbine-side end by at least one labyrinth seal.

[0020] A fourth chamber is defined between the third chamber and the turbine, and the two ends of the fourth chamber are defined by labyrinth seals.

[0021] - The fourth chamber is connected to a pressurized gas source configured to maintain a lower pressure in the fourth chamber than in the third chamber, thereby facilitating the migration of leaked gas from the third chamber to the fourth chamber.

[0022] -A fifth cavity is formed within a volume communicating with the front side of the turbine—that is, the side of the turbine opposite to the side where the turbine blades are located.

[0023] - The flange is located in the central part of the shaft.

[0024] - The flange associated with the labyrinth seal ensures separation between the third cavity and the second cavity.

[0025] - The third chamber is connected to a pressurized gas source with a pressure higher than that in the second chamber.

[0026] -Flange adjacent to turbine

[0027] - The flange is located near the compressor.

[0028] - The second chamber is connected to a pressurized gas source with a lower pressure than the first chamber.

[0029] - The refrigerator has a sixth chamber located between the third and fourth chambers.

[0030] - The flange is magnetized, or has a magnetized portion that mates with an adjacent magnetized portion located in the housing, thereby forming a magnetic bearing for supporting the shaft.

[0031] According to the present invention, the device can generate cooling power during which an expansion turbine expands the circulating gas by creating a pressure difference between the dominant pressures in the first and third chambers, and a compressor compresses the gas. This pressure difference generates a longitudinal force along the shaft, and a pressure regulation step is performed in the chamber to generate a reverse longitudinal reaction force of the same or substantially equal strength, thereby limiting the combined axial force acting on the shaft.

[0032] This invention may also relate to any alternative means that include any combination of the above or following features within the scope of the claims.

[0033] Other specific features and advantages will become apparent from the following description provided with reference to the accompanying drawings. Attached Figure Description

[0034] A better understanding of this invention will be achieved by reading the following description, which is given by way of example only, and by referring to the accompanying drawings, in which:

[0035] Figure 1 This is a partial schematic diagram illustrating an example of the structure and operation of a device including a refrigeration unit according to a possible exemplary embodiment of the present invention.

[0036] Figure 2 This is a detailed longitudinal sectional schematic diagram of the arrangement of the impellers (turbine and compressor) on the shaft of the refrigeration unit according to the first possible embodiment.

[0037] Figure 3 This is a detailed longitudinal sectional schematic diagram of the arrangement of the impellers (turbine and compressor) on the shaft of the refrigeration unit according to the second possible embodiment.

[0038] Figure 4 This is a detailed longitudinal sectional schematic diagram of the arrangement of the impellers (turbine and compressor) on the shaft of the refrigeration machine according to the third possible embodiment.

[0039] Figure 5 It is a detailed longitudinal sectional view of the arrangement of the refrigeration unit's shaft, used to schematically depict the balance of axial forces. Detailed Implementation

[0040] In all the accompanying drawings, the same reference numerals refer to the same elements.

[0041] In this detailed description, the following embodiments are merely examples. Although the description relates to one or more embodiments, this does not mean that these features are applicable only to a single embodiment. Various features in different embodiments may also be combined and / or interchanged to provide other embodiments.

[0042] Figure 1 The device 1 shown by way of example is a liquefier for a cryogenic feed fluid (e.g., hydrogen). The device 1 includes a feed circuit 2 for the feed fluid and a heat exchanger assembly comprising one or more heat exchangers 3, 4, which exchange heat with the feed circuit. A cooling device 6 exchanges heat with at least some of the heat exchangers in the heat exchanger assembly, and the cooling device is configured to cool the feed fluid to a predetermined target temperature, for example, for liquefaction. As shown, the device optionally includes a pre-cooling device 23, which exchanges heat with at least some of the heat exchangers in the assembly.

[0043] Cooling device 6 includes a circulating refrigeration unit.

[0044] The circulating gas chiller 6 includes a compression system 16, a cooling system 3 and 4, and an expansion system 26 in a circulation loop 60, which are used to thermodynamically circulate the circulating gas to generate cooling.

[0045] The expansion system includes at least one expansion turbine 26, which is connected to the compressor 16 of the refrigeration unit.

[0046] The heat exchangers 3 and 4 in this group can have at least one counter-current exchanger that simultaneously heats and cools the circulating fluid at two points in the cycle (cooling after compression and returning to pre-compression heating after expansion).

[0047] In this example, the expansion turbine 26 is connected to the compressor of the system 16 used to compress the circulating gas.

[0048] The expander turbine 26 and the compressor 16 are each connected to one end of the common shaft 20. For example... Figure 2 As shown, the expansion turbine 26, compressor and shaft 20 can be housed in a housing 19, which defines a first chamber 15 (or volume) in which the compressor 16 is rotatably mounted, an intermediate second chamber in which the shaft 20 is rotatably mounted on a bearing assembly including one or more bearings 21, and a third chamber 24 in which the turbine 26 is rotatably mounted.

[0049] The turbo compressor of the refrigeration unit 6 includes a pressurized fluid circuit connected to at least two chambers 14, 18, 17, 11 located in the second chamber.

[0050] For simplicity, the fixed portion of the stator around the axis is not shown.

[0051] As described in more detail below, the pressurized fluid circuit is configured to supply a predetermined flow rate of pressurized gas into the chamber to reduce or counteract the axial force on shaft 20 caused by the pressure difference between the dominant pressures in the first chamber 15 and the third chamber 24. It should be noted that the pressure is not necessarily radially constant at the location where pressure is applied.

[0052] The common shaft 20 includes at least one disc-shaped flange 10 between the turbine 26 and the compressor 16, which extends transversely to its axis of rotation. The flange 10 is associated with at least one labyrinth seal 9, which serves to longitudinally separate two chambers 18 and 17 that are intended to be subjected to different pressures on both sides of the flange 10.

[0053] Therefore, the flange 10 forms a force-balancing "piston" on the shaft 20, and one or more labyrinth seals located on and / or at the base of the flange limit gas leakage due to the pressure difference across the flange 10.

[0054] exist Figure 2 In one embodiment, the labyrinth seal 9, which rotates with the shaft 20, is located at the top of the flange 10 and engages with its complementary portion fixed to the fixed portion of the device 1.

[0055] exist Figure 3 In the embodiment (described in more detail below), two additional labyrinth seals 9 are provided at the base of the flange 10 and on both sides of the flange 10.

[0056] In the illustrated embodiment, the device includes a first chamber 14 connected to a high-pressure fluid circuit communicating with the front of the compressor 16 (i.e., the side of the compressor 16 opposite to the side where the compressor blades are located in the compression chamber). For example, the first chamber 14 is supplied with pressurized gas compressed by the compressor 16 (at a second pressure higher than a first pressure at the compressor inlet). This generates an axial (longitudinal) balancing force F1 on the compressor 16, opposite to the force F0 generated by compression within the compression chamber.

[0057] like Figure 2 As shown, the first cavity 14 may be annular and may be defined toward the turbine 26 by a labyrinth seal 9.

[0058] Following the labyrinth seal 9, a second cavity 18 is defined between the first cavity 14 and the flange 10. As shown, this second cavity 18 can accommodate the first bearing 21. This second cavity 18 can be connected to the circuit 13 and maintained at a third pressure below the first pressure (e.g., via a set of valves). This second cavity 18 can recover leaks originating from the first cavity and migrating through the labyrinth seal 9. In this example, the flange 10 is located at the central portion of the shaft 20.

[0059] like Figure 2 As shown, on the other side of flange 10, labyrinth seal 9 defines a third chamber 17. This third chamber accommodates a second bearing 21 located on the turbine 26 side. This third chamber 17 can maintain a fourth pressure higher than the third pressure via pressurized gas circuit 12, for example, by drawing a high-pressure flow from the first chamber. The fourth pressure can be regulated by a valve in circuit 12. The pressure difference between the third and fourth chambers generates a longitudinal force F2 on the flange toward compressor 16.

[0060] A fourth chamber 11 is then defined between the third chamber 17 and the turbine 26. The two ends of this fourth chamber 11 are defined by labyrinth seals 9. For example, the fourth chamber 11 forms a gap between two seals 9. The fourth chamber 11 is connected to a pressurized gas source configured to maintain a fifth pressure in the fourth chamber that is lower than the pressure in the third chamber 17. For example, the fourth chamber 11 is connected to a relatively low-pressure chamber of the turbine 26. This arrangement facilitates the migration of gas leakage from the third chamber 17 to the fourth chamber 11, which is evacuated, for example, via a circuit equipped with a valve or back pressure regulator, allowing the dominant pressure value in the chamber upstream of the valve or back pressure regulator to be actively or passively adjusted.

[0061] This arrangement reverses leakage management compared to known arrangements.

[0062] After defining the labyrinth seal 9 of the fourth chamber 11 on the turbine 26 side, the fifth chamber 25 communicates with the front side of the turbine 26 (i.e., the side of the turbine 26 opposite to the side where the blades are located in the third chamber 24). This arrangement generates a longitudinal force F3 on the turbine impeller 26 that is opposite to the forces F4 and F5 generated by the gas pressure acting on the blades and directed towards the compressor 16.

[0063] Pressure regulation in various chambers allows for the generation of opposing longitudinal reaction forces of equal or nearly equal strength, thereby limiting the resultant axial force acting on the shaft to a value significantly lower than the load-bearing capacity of the selected bearing. This prevents significant leakage and avoids contamination of the relatively cooler circuit (turbine side) by the relatively hot flow (compressor side). Figure 3 Implementation examples and Figure 2 The main difference in the embodiments is that the flange 10 associated with the labyrinth seal 9 is adjacent to the turbine 26.

[0064] Identical components are represented by the same reference numerals.

[0065] The second cavity 18 extends across most of the shaft and surrounds the two bearings 21.

[0066] like Figure 3 As shown, another flange 100 without the labyrinth seal 9 can be provided on the shaft (e.g., in the central portion) in the second cavity 18.

[0067] As before, the pressure regulation within each cavity allows for the limitation or counteraction of axial forces on shaft 20.

[0068] Figure 4 Implementation examples and Figure 3 The main difference in this embodiment is that the flange 10 associated with the labyrinth seal 9 is adjacent to the compressor 16. Additionally, another flange 100 located in the central portion without the labyrinth seal 9 is replaced by an inverted double-cone-shaped protrusion on the shaft, which, for example, allows the bearing to remain in place while limiting the impact on the rotor dynamics of the shaft. Furthermore, the bearing 21 is omitted for simplicity.

[0069] The second chamber 18 and the third chamber 17 are formed on both sides of the flange 10, and are at a relatively low pressure on the compressor side and a relatively high pressure on the turbine side.

[0070] In this embodiment, a central cavity 22 (e.g., referred to as a sixth cavity) is located between the third cavity 17 and the fourth cavity 11. The central cavity 22 extends over most of the shaft 20 and is preferably under a relatively low pressure, lower than the pressure in the third cavity 17.

[0071] The protrusion in the central portion of shaft 20 creates a pressure gradient at different radial points of the rotor in the central cavity 22.

[0072] The second chamber 18 is connected to a pressurized gas source at a pressure lower than that in the first chamber 14. This low-pressure source could be a low-pressure gas source located at the expansion turbine 26. The relatively higher pressure in the third chamber 17 can be tapped off at the compressor 16, for example, at its outlet.

[0073] The flange 10 can be magnetized, or it can have a magnetized portion that cooperates with an adjacent magnetized portion located in the housing 19 to form a magnetic bearing for supporting the shaft 20. In this case, the flange 10 performs a dual function. This, of course, also applies to other embodiments, particularly... Figure 2 Examples of implementations.

[0074] It should be noted that the aforementioned bearing 21 can be a magnetic bearing or a gas bearing. In the case of a gas bearing, the lift gas inside the bearing 21 can be supplied by all or part of the corresponding pressurized fluid circuit described above.

[0075] This arrangement has many advantages.

[0076] This allows for the handling of specific volumetric flow rates and speeds adapted to the compressor. Axial loads are thus limited and matched to the load-carrying capacity of bearing 21. Internal leakage is also limited. In particular, leakage flow is reduced by two-thirds compared to known conventional solutions.

[0077] Figure 5 A shaft 20 with section A is shown schematically, having a flange 10 with section B and a labyrinth seal 9. P1 represents the high pressure on the compressor side (located on the right side in this example, but not shown). For example, P1 is equal to 55 bar.

[0078] Following the labyrinth seal 9, the cavity on one side of the flange 10 can be at a pressure P2 lower than P1 (e.g., P2 equals 25 bar). On the other side of the flange 10, another cavity can be at an intermediate pressure P3 between P1 and P2 (e.g., P3 equals 30 bar). Subsequently, the cavity between the two labyrinth seals 9 can be maintained at a pressure P4 lower than P2 (e.g., P4 equals 17 bar). Finally, at the low-pressure end, the pressure on the turbine side (left side in this example, but not shown) can also be equal to P4.

[0079] Using these pressure values, the sum of the axial forces (with a negative sign to the right) can be given by the following relationship: 55A + 25B - 30B - 17A.

[0080] To achieve axial balance, 38A = 5B is necessary. Therefore, the dimensions of flange 10 can be designed for this purpose.

Claims

1. A circulating gas refrigerator comprising a compression system, a cooling system, and an expansion system in a circulation loop (60) for thermodynamically circulating a circulating gas to generate cooling capacity, the expansion system comprising at least one expansion turbine (26) coupled to a compressor (16) of the circulating gas refrigerator, the expansion turbine (26) and the compressor (16) each coupled to one end of a common shaft (20), the expansion turbine (26), the compressor and the shaft (20) being housed in a housing (19), the housing (19) accommodating a first chamber in which the compressor (16) is rotatably mounted. The circulating gas chiller (6) comprises a second intermediate chamber (15) in which the shaft (20) is rotatably mounted on a bearing assembly including one or more bearings (21), and a third chamber (24) in which the expansion turbine (26) is rotatably mounted. The circulating gas chiller (6) includes a set of pressurized fluid circuits communicating with at least two chambers located in the second chamber, the pressurized fluid circuits being configured to supply pressurized gas at predetermined flow rates to each chamber to reduce or counteract the axial force on the shaft (20) caused by the pressure difference between the dominant pressures in the first chamber (15) and the third chamber (24), wherein... The shaft (20) includes at least one disc-shaped flange (10) between the expansion turbine (26) and the compressor (16), the flange extending transversely to its axis of rotation, the flange (10) being associated with at least one labyrinth seal (9) for longitudinally separating two cavities (18, 17) designed to withstand different pressures on either side of the flange (10), characterized in that the circulating gas refrigeration unit includes a first cavity (14) connected to a circuit of high-pressure fluid from the compressor (16), the first cavity communicating with the front of the compressor (16) to generate a balancing force on the compressor (16) opposite to the force generated by compression within the compression chamber, the front of the compressor (16) being... For the side of the compressor (16) opposite to the side of the compressor with blades in the compression chamber, the first cavity (14) is defined by a labyrinth seal (9) toward the expansion turbine (26), and a second cavity (18) is defined between the first cavity (14) and the flange (10), and a third cavity (17) is defined between the second cavity (18) and the expansion turbine (26), the third cavity (17) being defined at its end on the side of the expansion turbine (26) by at least one labyrinth seal (9), and a fourth cavity (11) is defined between the third cavity (17) and the expansion turbine (26), the two ends of the fourth cavity (11) being defined by labyrinth seals (9).

2. The circulating gas refrigerator according to claim 1, characterized in that, The expansion turbine is connected to the compressor (16) of the circulating gas refrigerator and the compressor of the system for compressing the circulating gas.

3. The circulating gas refrigerator according to claim 1 or 2, characterized in that, The circulating gas refrigerator includes a labyrinth seal (9) located on top of the flange (10).

4. The circulating gas refrigerator according to claim 1 or 2, characterized in that, The circulating gas refrigerator includes two labyrinth seals (9) located at the base of the flange (10) and on both sides of the flange (10).

5. The circulating gas refrigerator according to claim 1 or 2, characterized in that, The fourth chamber (11) is connected to a pressurized gas source configured to maintain a pressure in the fourth chamber lower than that in the third chamber (17) to facilitate the migration of gas leaks from the third chamber (17) to the fourth chamber (11).

6. The circulating gas refrigerator according to claim 1 or 2, characterized in that, A fifth cavity (25) is formed in a volume that communicates with the front of the expansion turbine (26), the front of which is the side of the expansion turbine (26) opposite to the side of the expansion turbine on which the blades are provided.

7. The circulating gas chiller according to claim 5, characterized in that, The flange (10) is located in the central portion of the shaft (20).

8. The circulating gas chiller according to claim 6, characterized in that, The flange (10) is located in the central portion of the shaft (20).

9. The circulating gas refrigerator according to claim 1 or 2, characterized in that, The flange (10) associated with the labyrinth seal (9) ensures separation between the third cavity (17) and the second cavity (18).

10. The circulating gas refrigerator according to claim 9, characterized in that, The third chamber (17) is connected to a pressurized gas source with a pressure higher than that in the second chamber (18).

11. The circulating gas refrigerator according to claim 9, characterized in that, The flange (10) is adjacent to the expansion turbine (26).

12. The circulating gas refrigerator according to claim 1 or 2, characterized in that, The flange (10) is adjacent to the compressor (16).

13. The circulating gas refrigerator according to claim 12, characterized in that, The second chamber (18) is connected to a pressurized gas source with a pressure lower than that in the first chamber (14).

14. The circulating gas refrigerator according to claim 12, characterized in that, The circulating gas refrigerator has a sixth chamber (22) located between the third chamber (17) and the fourth chamber (11).

15. The circulating gas refrigerator according to claim 1 or 2, characterized in that, The flange (10) is magnetized or has a magnetized portion, which cooperates with an adjacent magnetized portion located in the housing (19) to form a magnetic bearing for supporting the shaft (20).

16. An apparatus for liquefying a feed fluid at cryogenic temperatures, the apparatus comprising a feed circuit (2) for the feed fluid, a heat exchanger assembly comprising one or more heat exchangers (3, 4) exchanging heat with the feed circuit, and a cooling device exchanging heat with at least a portion of the heat exchangers in the heat exchanger assembly comprising one or more heat exchangers, the cooling device being configured to cool the feed fluid to a predetermined target temperature, the cooling device comprising a circulating gas chiller according to any one of claims 1 to 15.

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