Refrigeration equipment

Abstract

The present invention relates to a cryogenic type refrigeration and / or liquefaction device, which comprises a working circuit (2) containing a working fluid, and the working circuit (2) includes in series: a mechanism (5) for cooling the working fluid, a mechanism (7) for expanding the working fluid, and a mechanism (6) for heating the working fluid, wherein the expansion mechanism comprises two expansion turbines (7) of a centripetal type, the two expansion turbines are respectively mounted at two ends of a single shaft (8), and the two turbines (7) have blades (9) oriented in opposite directions along the direction of the shaft (8).

Description

Technical Field

[0001] The present invention relates to a refrigeration and / or liquefaction device of the cryogenic type.

[0002] More particularly, the present invention relates to a refrigeration and / or liquefaction device of the cryogenic type, which includes a working circuit containing a working fluid, and the working circuit includes in series: a mechanism for cooling the working fluid, a mechanism for expanding the working fluid, and a mechanism for heating the working fluid. Background Art

[0003] Refrigeration and / or liquefaction devices of the cryogenic type generally have one or more turbines for expanding a working gas.

[0004] Generally, these gas turbines are mounted on the same shaft as a compressor wheel to transfer useful mechanical torque to the shaft, or these gas turbines are mounted on a shaft including a brake wheel, and the brake wheel is located at the end of the shaft opposite to the turbine.

[0005] Such a brake wheel brakes the rotation of the rotating shaft on which the turbine is mounted. This brake wheel is generally located in a closed circuit of a braking gas, the braking gas is compressed in the wheel, then cooled by a cold source in a heat exchanger that remains cold, and then expanded (for example in an expansion valve). Preferably, the gas circulating in the braking circuit can be the same as the working fluid on the expansion turbine side.

[0006] This solution increases the volume and cost of the facility. This is because it is necessary to provide hot components (braking circuit for the brake wheel) as close as possible to the components (working circuit) at low temperature and manage the constant supply of a cold source (preferably close to ambient temperature) on the braking circuit side. Summary of the Invention

[0007] The object of the present invention is to solve all or part of the defects of the prior art mentioned above.

[0008] To this end, according to the present invention, on the other hand, the device according to its upper definition given in the foregoing part is mainly characterized in that the expansion mechanism includes two centripetal expansion turbines, which are respectively mounted at two ends of a single shaft, and the blades of the two turbines are oriented in opposite ways along the direction of the shaft.

[0009] In addition, embodiments of the present invention may have one or more of the following features:

[0010] - The working circuit includes a mechanism for compressing the working fluid, and the mechanism for compressing the working fluid is arranged in series with the cooling mechanism and upstream of the cooling mechanism;

[0011] - The working fluid is allowed to enter the two turbines in a direction transverse to the shaft carrying the turbines, and the gas flow expanding in the turbines is discharged from each turbine in opposite directions that are substantially parallel to the shaft;

[0012] - The two turbines are arranged directly in series in the working circuit, i.e., there is no intermediate heat exchange system for cooling or heating the working fluid between the two turbines;

[0013] - The two turbines are arranged in series in the working circuit and there is an intermediate heat exchange system for cooling and / or heating the working fluid between the two turbines;

[0014] - The two turbines are arranged in parallel in the working circuit;

[0015] - The device includes a system for braking the rotation of the shaft carrying the two turbines;

[0016] - The braking system is an induction braking system and includes coils that interact with the shaft by generating induced current;

[0017] - The braking system is located in the central part of the shaft, i.e., between the two turbines;

[0018] - The braking system includes an alternator of the type that operates at ambient temperature or at low temperature;

[0019] - The rotating shaft is supported by a system having bearings of the rolling bearing type or in particular magnetic levitation bearings, gas bearings or oil-impregnated bearing type;

[0020] - The device has a circuit for a fluid to be cooled in heat exchange with the working fluid circulating in the working circuit.

[0021] The present invention also relates to any alternative device or method falling within the scope of the present invention and including any combination of the above or below-described features. Description of the Drawings

[0022] After reading the following description with reference to the accompanying drawings, other specific features and advantages will become apparent, wherein:

[0023] Figure 1 is a partial schematic view showing the structure and operation of a possible example of a refrigeration and / or liquefaction device capable of implementing the present invention;

[0024] Figure 2 is a partial schematic view showing the details of such a device and in particular the arrangement of two turbines on a single shaft. Detailed Description

[0025] The refrigeration device 1 (or liquefaction device), shown by way of non-limiting example, is a device of the refrigeration type. This means that the refrigeration device cools a working gas having a low temperature, in particular a low temperature between -100 °C and -273 °C.

[0026] The working circuit 2 contains a working fluid, in particular at least one of the following, for example: hydrogen, helium, nitrogen, oxygen, carbon monoxide, carbon dioxide, and methane.

[0027] The refrigeration device 1 can be used to extract heat from at least one component or fluid 3 by (direct or indirect) heat exchange with the working fluid circulating in the working circuit 2.

[0028] The working circuit 2 can be open (meaning that the working fluid is supplied to the circuit 2 and the working fluid is extracted outside the circuit 2) or closed (the working fluid in a closed cycle). In the example shown, the working circuit 2 is of the closed type and includes the following structures arranged in series: a compression mechanism 4 for compressing the working fluid, a mechanism for cooling the working fluid, an expansion mechanism 7 for expanding the working fluid, and a mechanism for heating the working fluid to restart the cycle (compression, cooling, expansion, etc.).

[0029] The compression mechanism is optional because the working fluid can be obtained or provided in the form of a pressurized or compressed working fluid.

[0030] The compression mechanism 4 includes, for example, one or more compression stages provided, for example, by one or more volume compression stages and / or by a compressor wheel, for example, of the centrifugal type. In the example shown, two compressors are arranged in series. In addition, a cooling exchanger 5 can be arranged at the outlet of one or each compressor. For example, the compression of the working fluid is preferably isentropic or substantially isentropic (or isothermal).

[0031] The compressed and cooled gas can then expand in a plurality of turbines 7 arranged in series and / or in parallel. For example, the expansion is preferably isentropic (or isothermal). Thus, between two expansion stages, depending on the preferred architecture of the process, the working fluid is heated or cooled by one or more exchangers 6 that exchange heat countercurrently with the working fluid returning to the compression mechanism. The heating or cooling between the expansion stages is preferably isobaric or substantially isobaric.

[0032] Specifically, the cold working fluid can then be heated in these exchangers 6 and then returned to the compression mechanism to restart the cycle.

[0033] The gas to be cooled (and / or the gas to be liquefied) can be arranged to exchange heat with the cooling exchanger 5 in the circuit 12 until the gas reaches the target temperature and can, for example, be liquefied and collected in a reservoir 11.

[0034] As a variant or in combination therewith, the working fluid may itself be liquefied and stored in a container to provide cooling for the device and / or to supply liquefied gas to the user.

[0035] According to the invention, the expansion mechanism includes two centripetal expansion turbines 7, which are respectively mounted at two ends of a single shaft 8. These two expansion turbines 7 have blades, and these blades are oriented in opposite ways along the direction of the shaft 8.

[0036] Conventionally, the shaft 8 is mounted or supported on a bearing 10, which is in particular a magnetic levitation bearing, a gas bearing, an oil-impregnated bearing or other types of bearings.

[0037] This means that the expansion mechanism includes at least two expansion turbines 7, which are mounted at two ends of a single shaft 8 and each expansion turbine ensures the expansion of at least a part of the working gas.

[0038] This arrangement enables one braking wheel to be replaced by an additional expansion turbine 7, which improves the efficiency of the facility by increasing the number of turbines in a single facility. The facility increases its production capacity without increasing its volume.

[0039] The refrigeration device 1 may have a plurality of pairs of expansion turbines 7 mounted on two ends of respective shafts 8.

[0040] Therefore, compared with the traditional framework, the invention enables additional expansion turbines 7 to be added. In the shown example, for example, the expansion turbine 7 surrounded by a dashed line may be an additional turbine allowed by this novel architecture.

[0041] The two expansion turbines 7 carried by a single shaft 8 may be arranged in series in the working circuit 2, which means that the two expansion turbines 7 in series ensure the successive expansion of a single gas flow. In this arrangement, the energy efficiency of a production plant incorporating such a device is improved with little change in the investment cost. The two turbine impellers may be arranged to incorporate intermediate heating in order to obtain a temperature equal to the temperature at the suction inlets of the two expansion stages and thus to make the sizes of the impellers consistent.

[0042] As an alternative or in combination therewith, the two expansion turbines 7 carried by a single shaft 8 may be arranged in parallel in the working circuit 2, which means that the two expansion turbines 7 arranged in parallel ensure the expansion of two different parts of the working gas flow (see, for example, the branches of the working circuit 2). In this arrangement, the sizes of the respective expansion turbines 7 can be reduced because the impellers of the two expansion turbines 7 are each allocated a part (e.g., 50%) of the total fluid flow to be processed in this case.

[0043] Therefore, the axial and radial forces of the shaft 8 provided with two turbines can be compensated due to the symmetric configuration of the two turbines with respect to the midpoint of the shaft 8.

[0044] This arrangement enables improving the feasibility of the thermodynamic process, especially for units with very high production volumes.

[0045] Of course, the refrigeration device 1 may have other expansion turbines 7 arranged conventionally (arranged on the same shaft as a compressor wheel or as a brake wheel on the same shaft).

[0046] As Figure 2 shown, the two expansion turbines 7 are centripetal turbines. As indicated by the arrows, the working gas to be expanded is allowed to enter each expansion turbine 7 at the outer periphery of the expansion turbine 7 by means of a guiding member (such as movable or fixed vanes). The working gas can be allowed to enter the turbine especially in a direction transverse to the shaft 8 carrying the turbine (i.e., radially). The gas expanded in each expansion turbine 7 can be sucked in the central part of the expansion turbine 7 and towards the outside of the shaft 8. This means that the expanded gas flow is sucked in the opposite direction, substantially parallel to the shaft 8.

[0047] The vanes (i.e., the vanes guiding the gas flow) of the two expansion turbines 7 are advantageously inclined in opposite directions (sucking the expanded gas in opposite directions) to allow for an almost isentropic expansion for each impeller and to ensure a force balance without generating parasitic forces, which would have to be compensated by the selected bearing system. For example, the two expansion turbines 7 can have the same or similar geometries, but are arranged in a manner antisymmetric with respect to the median plane transverse to the shaft 8.

[0048] The device preferably includes a braking system 9 for braking the rotation of the shaft 8 carrying the two expansion turbines 7. The braking system can be inductive, having coils mounted around the shaft and enabling braking of the shaft 8 by generating an induced current. The braking can be controlled especially by controlling the current supplied to the induction coil (or induction coils). The rotation of the shaft (made of a suitable metal or other material) generates an induced current, which tends to brake the shaft.

[0049] Such a braking system can advantageously be located in the central part of the shaft 8, i.e., between the two expansion turbines 7.

[0050] For example, the braking system can include or consist of an alternator, which is arranged in the central part of the shaft, for example, and operates at ambient temperature / room temperature or at low temperature.

[0051] In the latter case, the entire shaft 8 can operate at low temperature, as can its stationary components (the stator with the electromagnet). In this case, there are no relatively hot parts or components in the vicinity of the elements at low temperature.

[0052] Thus, the entire environment in the vicinity of these turbines is also at low temperature. This limits or eliminates possible radiation and / or conduction from the hot areas to the cold areas. The actual efficiency of the turbines is thus increased due to the reduction or elimination of parasitic heat losses.

[0053] Of course, the present invention is not limited to the above exemplary embodiments.

[0054] Thus, in one embodiment, the shaft can drive more than two turbine impellers. The stationary components for converting kinetic energy into pressure potential energy can be configured in a suitable manner at the outlet of each impeller.

[0055] For example, a long diffuser can be configured at the outlet of each turbine impeller to obtain this function. For example, machined mechanical components can be provided which enable the same function (gradual increase of the flow cross-section) and also enable the flow to reach the next distributor of the next turbine arranged in series.

Claims

1. A refrigeration device of the cryogenic type, which includes a working circuit (2) containing a working fluid, and the working circuit (2) is in series including: a cooling mechanism for cooling the working fluid, an expansion mechanism for expanding the working fluid, and a heating mechanism for heating the working fluid. Among them, the expansion mechanism includes two centripetal expansion turbines (7), and the two expansion turbines are respectively installed at two ends of a single shaft (8). The two expansion turbines (7) have blades oriented in opposite ways along the direction of the shaft (8). The refrigeration device includes a plurality of pairs of expansion turbines (7) installed on two ends of their respective shafts (8). The two expansion turbines (7) carried by a single shaft (8) are arranged in series in the working circuit (2), which means that the two expansion turbines in series ensure the successive expansion of a single gas flow, and intermediate heating is combined between the two expansion turbines arranged in series to obtain a temperature equal to the temperature at the suction ports of the two expansion stages.

2. The refrigeration device according to claim 1, characterized in that, the working circuit (2) includes a compression mechanism (4) for compressing the working fluid, and the compression mechanism is arranged in series with the cooling mechanism (5) and arranged upstream of the cooling mechanism (5).

3. The refrigeration device according to claim 1 or 2, characterized in that, the working gas enters the two expansion turbines (7) in a direction transverse to the shaft (8) carrying the two expansion turbines (7), and the gas flow expanding in the expansion turbines (7) is discharged from each expansion turbine (7) in opposite directions that are substantially parallel to the shaft (8).

4. The refrigeration device according to claim 1, characterized in that, the refrigeration device includes a braking system (9) for braking the rotation of the shaft (8) carrying the two expansion turbines (7).

5. The refrigeration device according to claim 4, characterized in that, the braking system (9) is inductive and includes a coil that interacts with the shaft (8) by generating an induced current.

6. The refrigeration device according to claim 4 or 5, characterized in that, the braking system (9) is located in the central part of the shaft (8), that is, between the two expansion turbines (7).

7. The refrigeration device according to claim 4 or 5, characterized in that, the braking system (9) includes an alternator of the type operating at ambient temperature or at low temperature.

8. The refrigeration device according to claim 1 or 2, characterized in that, the rotating shaft (8) is supported by a system with rolling bearings.

9. The refrigeration device according to claim 1 or 2, characterized in that, the rotating shaft (8) is supported by a system with bearings (10) of the type of magnetic suspension bearings, gas bearings or oil-impregnated bearings.

10. The refrigeration device according to claim 1 or 2, characterized in that, the refrigeration device has a circuit (12) of a fluid to be cooled in the heat exchange with the working fluid circulating in the working circuit (2).

11. The refrigeration device according to claim 1, Characterized in that, The refrigeration device is a liquefaction device.

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