Cycle gas refrigerator and liquefaction facility

Abstract

The invention relates to a cryogenic refrigerator (2) with a cycle circuit comprising a compression mechanism having at least three rotary compressors (4) arranged in parallel and mounted, respectively, on three rotary shafts, at least two of the rotary shafts being coupled respectively to turbines (10), at least one motor (12) for driving at least one of the rotary shafts (11), at least the two compressors (4) in parallel coupled to a turbine (10) are each associated with a respective member (9) for measuring the flow rate passing through the compressor (4) in question and with a respective member (14) for regulating the flow rate admitted into the compressor (4), the coupled turbines (10) each comprising a respective sensor (17) for measuring the speed of rotation of the turbine (10) and a respective system (15, 16) for controlling the speed of rotation of the turbine (10), the refrigerator (1) comprising a control member (20) comprising a microprocessor and configured to receive measurements from the flow measurement members (9) and from the sensors (17) for measuring the speed and controlling the flow control members (14).

Description

Cycle gas refrigerator and liquefaction plant.

[0001] The invention relates to a cycle gas refrigerator and a liquefaction plant.

[0002] The invention relates more particularly to a cycle gas refrigerator, comprising a cycle circuit containing a cycle gas comprising at least one of: nitrogen, helium, hydrogen, the cycle circuit being configured to subject the cycle fluid to a thermodynamic cycle to bring the cycle fluid to a determined cryogenic temperature at at least one end of the cycle circuit, the cycle circuit comprising a cycle fluid compression mechanism, a cycle fluid cooling mechanism, a cycle fluid expansion mechanism, wherein the cycle fluid expansion mechanism comprises at least two turbines rotatably mounted on respective rotating shafts, the compression mechanism comprising at least three rotary compressors arranged in parallel in the cycle circuit and respectively mounted on three rotating shafts, at least two of the rotating shafts being coupled respectively,to the turbines to recover the work of expanding the cycle fluid for compressing the cycle fluid.,

[0003] An important aspect in hydrogen and / or helium refrigerators / liquefiers is to minimize energy consumption. One way to reduce this consumption is to recover energy from the expansion of the cycle gas for the compression of this cycle gas via a machine called a "turbo-booster" (i.e. "turbo-compressor", i.e. coupling of a turbine and a compressor). See for example US2015168057A or WO2009130466A. Turbo-compressors make it possible both to reduce the consumption of electrical energy supplied to the cycle and to reduce the size of the cycle compressor.

[0004] Turbo compressors can be placed upstream or downstream of a cycle compressor depending on the process conditions. This arrangement is most commonly found in cycles. Indeed, this arrangement is the simplest for process control because each compressor is independent of the others. This series configuration is made possible by operating conditions favorable to good compression efficiency and adequate working fluids.

[0005] Turbocharging requires matching the parameters of the expanded fluid to the compressed fluid so that both functions are performed with maximum efficiency. Turbochargers must also be able to operate in all configurations encountered by the refrigerator / liquefier. Turbocharger operating parameters can constrain the possible turbine arrangements, making the process less efficient or more complex.

[0006] In the case of turbochargers arranged in parallel, these compressors will achieve the same compression ratio. The variation in power of one turbine will then have a direct impact on the other turbochargers and therefore an impact on the efficiency and operability of the entire refrigerator.

[0007] An aim of the present invention is to overcome all or part of the drawbacks of the prior art noted above.

[0008] To this end, the refrigerator according to the invention, moreover in accordance with the generic definition given in the preamble above, is essentially characterized in that it comprises at least one motor for driving at least one of the rotating shafts carrying a turbine and a compressor and in that at least the two compressors in parallel coupled to a turbine are each associated with a respective member for measuring the flow rate passing through the compressor concerned and with a respective member for regulating the flow rate admitted into the compressor, for example one or more mobile steering members upstream or downstream such as an "IGV", the at least two turbines coupled to the compressors each comprising a respective sensor for measuring the rotation speed of the turbine and a respective system for controlling the rotation speed of the turbine,the refrigerator comprising an electronic control and command device comprising a microprocessor and configured to receive measurements from the flow measuring devices and the speed measuring sensors and to control the flow regulating devices.,

[0009] According to the proposed solution, the refrigerator uses at least one motor-turbo-compressor (instead of the turbo-compressor previously described) in order to carry out this active control between compressors coupled in parallel via an adjustment of the electrical powers injected into the motor. This control could be carried out by a rotation frequency variator of the said electric motor(s).

[0010] Although the addition of motor(s) increases the hardware investment of the refrigerator, this allows the rotation frequency of the motor to be controlled to improve the expansion efficiency of the turbines and / or parallel compression and the compression power. That is to say, compared to the prior art it is thus possible to increase the output pressure compared to a conventional turbo-booster, or it is possible to reduce the size of the cycle compressor.

[0011] Providing at least one motor makes it possible to control the rotation speed of the corresponding wheels (compressor and turbine) and to stabilize the operation of the coupled compressor and turbine assemblies, especially if several are installed in parallel. Indeed, in the case of a parallel arrangement, the slightest disturbance can destabilize the assembly and make operation suboptimal. This can even lead to operating one of the compressors in an unsafe operating area such as the pumping zone. This disadvantage is eliminated or reduced thanks to the motor(s). This also makes it possible to optimize the operating point of the machines (compressors / turbines).

[0012] Furthermore, embodiments of the invention may include one or more of the following features: the compressors in parallel are identical, the electronic control and command member being configured to apply a flow rate setpoint admitted into the compressors which is identical for all the compressors in parallel, the electronic control and command member is configured to apply an identical rotation speed setpoint for the turbines coupled to the compressors, the flow rate regulation member admitted into the compressor comprises at least one of: one or more mobile steering members, an inlet guide valve “IGV” arranged upstream, a variable vane diffuser downstream of the compressor wheel, a compressor bypass system, the refrigerator comprises a flow rate regulation member admitted into the compressor common to at least several of the compressors in parallel,the turbine rotation speed control system comprises at least one of: an inlet guide valve "IGV", a throttle valve, a turbine bypass system, the refrigerator comprises three or more drive motors configured to respectively drive the three rotating shafts of the three rotary compressors arranged in parallel in the cycle circuit, the electronic control and command unit is configured to control the speeds of the motor(s), the motor(s) are of the electric type and the electronic control and command unit is configured to control the rotation speed of the motor(s) to achieve the same compression ratio in each compressor.,

[0013] The invention also relates to a plant for liquefying a feed gas stream comprising a feed pipe configured to be connected to a source of feed gas to be liquefied, for example hydrogen, a set of heat exchangers in heat exchange with the feed gas stream carried by the feed pipe, the plant comprising a refrigerator in heat exchange with the set of heat exchangers and configured to cool the feed gas stream, the refrigerator conforms to any one of the characteristics above or below.

[0014] The invention may also relate to any alternative device or method comprising any combination of the above or below features within the scope of the claims.

[0015] Other features and advantages will appear on reading the description below, made with reference to the figures in which: Brief description of the figures

[0016] The invention will be better understood on reading the following description, given solely by way of example and with reference to the appended drawings in which:

[0017] is a schematic and partial view of an example of structure and operation of a liquefaction installation comprising an example refrigerator according to the invention.

[0018] is a schematic and partial view illustrating an example of operation of an electronic control and command device of the refrigerator. Detailed description

[0019] In all figures, the same references refer to the same elements.

[0020] In this detailed description, the following embodiments are examples. Although the description refers to one or more embodiments, this does not mean that the features apply only to a single embodiment. Single features of different embodiments may also be combined and / or interchanged to provide other embodiments.

[0021] The illustrated cycle gas refrigerator 2 comprising a cycle circuit 3 containing a cycle gas comprising at least one of: nitrogen, helium, hydrogen.

[0022] The cycle circuit 3 is configured to subject the cycle fluid to a thermodynamic cycle to bring the cycle fluid to a determined cryogenic temperature at at least one end of the cycle circuit 3. As illustrated in, this produced cold power can be used to cool a feed gas stream 18 such as hydrogen for example via a set of heat exchangers 19. The feed gas stream can be supplied to a first end of a feed pipe 18 by a source 19. A second end of the feed pipe can be connected to a storage for recovering the cooled (liquefied) feed gas.

[0023] In another variant not shown, the cold power produced can be used to liquefy the cycle gas itself which can be recovered.

[0024] The cycle circuit 3 comprises, preferably arranged in series in the cycle circuit 3, a cycle fluid compression mechanism 4, a cycle fluid cooling system 5, 6, 7, 8, a cycle fluid expansion mechanism 10 and a cycle fluid heating system.

[0025] The cycle fluid expansion mechanism 10 comprises at least two turbines 10 mounted in rotation on respective rotating shafts 11, preferably arranged in series in the cycle circuit 3.

[0026] The compression mechanism comprises at least three rotary compressors 4 arranged in parallel in the cycle circuit 3 and mounted respectively on three rotating shafts. At least two of the rotating shafts of the compressors 4 are coupled respectively to the turbines 10 to recover the expansion work of the cycle fluid for the compression of the cycle fluid. The cooling system and the cycle gas reheating system may comprise one or more heat exchangers, in particular one or more countercurrent heat exchangers ensuring a heat exchange between relatively cold and hot flows of the cycle.

[0027] In addition, the refrigerator 2 comprises at least one motor 12 for driving at least one of the rotating shafts 11 carrying a turbine 10 and a compressor 4. That is to say that at least one of the compressor pairs coupled to a turbine (turbo-compressor) is a motor-turbo-compressor.

[0028] In addition, at least the two compressors 4 in parallel coupled to a turbine 11 are each associated with a respective member 9 for measuring the flow rate passing through the compressor 4 concerned (for example a flow meter) and with a respective member 14 for regulating the flow rate admitted into the compressor 4.

[0029] The respective flow regulation member 14 admitted into the compressor 4 is for example one or more mobile guide members arranged upstream and / or downstream such as an “IGV” (Inlet Guide Vane). Alternatively or in combination, the respective flow regulation member 14 admitted into the compressor 4 may be a bypass (controlled diversion of the flow supplying the compressor or compression stage concerned).

[0030] In addition, the turbines 10 coupled to the compressors 4 each preferably comprise a respective sensor 17 for measuring the rotation speed of the turbine 10 and a respective system 15, 16 for controlling the rotation speed of the turbine 10.

[0031] The refrigerator 1 comprising an electronic control and command member 20 comprising a microprocessor and configured to receive measurements from the flow rate measuring members 9 and the speed measuring sensors 17 and to control the flow rate regulating members 14, 16 and / or motor(s) 12. Cf.

[0032] This allows the cycle gas flow rate to be controlled in the 4 compressors in parallel. It is thus possible to apply a flow rate setpoint for one of the 4 compressors and to copy the same setpoint for the other 4 compressors in parallel (all compression stages can be composed of compressors connected in parallel).

[0033] Flow control can be achieved using an external actuator, for example an “IGV” arranged upstream of the compressor, an “IGV” arranged downstream of the compressor, a diffuser with controlled vanes, a compressor bypass line and valve 4.

[0034] An admitted flow regulation member 14 may be common to several of the compressors in parallel.

[0035] The system 15, 16 for controlling the rotation speed of the turbine 10 may comprise, for example: an “IGV” which may be variable at the input and / or a throttling valve and / or a turbine bypass valve. This speed control system may regulate a rotation speed which is preferably the same target for each machine.

[0036] This allows speed adjustment parameters to be defined for each turbocharger assembly. This allows, for example, the turbocharger speeds to be offset from a setpoint if inappropriate behavior is observed (e.g. pressure oscillation, unstable hydraulic behavior, compressor surge, etc.).

[0037] The use of at least one motor to drive a compressor coupled to a turbine of the parallel sets makes it possible to control the rotation speed of the compressor(s) / turbine(s) set, whatever the operating conditions around the turbine and the compressor. The motor power can be adapted according to the power of the turbine and that required by the compressor. This makes it possible to stabilize the operation of the rotating machines (compressors / turbines). This is particularly interesting compared to an arrangement of turbo-compressors in parallel (without motors), which can quickly become destabilized. The proposed arrangement also makes it possible to adjust the rotation speed so as to optimize the operation of the machines. In addition, the motor(s) make it possible to increase the power of the compressor concerned with respect to that of the associated turbine. This provides better operation (depending on the cycle configuration).

[0038] The gas flow rate through each turbine can be determined by its distributor geometry, unless a control system (e.g. IGV / Expansion Valve type upstream of the equipment) can adjust it to some extent.

[0039] The total cycle flow rate can be determined by the turbine flow rate (with possibly also a possible flow sent to a cold end of the cycle). This total flow rate is compressed in the compression mechanism. The distribution of this total flow rate between parallel compressors can be achieved either passively (typically via a very similar hydraulic circuit) or "actively" (for example via an IGV, throttle valve, etc.). In the end, the entire cycle gas flow rate is compressed.

[0040] Preferably, the fluid circuit leading to each compressor is configured to have the same characteristics in terms of pressure loss in particular (reproduction of obstacles for the gas: same number of elbows / developed lengths of pipes, etc.).

[0041] This configuration is particularly advantageous or efficient when the compressor / turbine speeds and compressor mechanical powers are identical for each compressor.

[0042] The mechanical power of the compressor which is for example either:

[0043] - that of the coupled turbine in the case of a turbo-compressor,

[0044] - that of the turbine supplemented by / added to that of the engine in the case of a motor-turbo-compressor.

[0045] Because the engine power is equal to the compressor power minus the turbine power, if all compressors and turbines have the same power, the engines will deliver the same power. The configuration can also be advantageous when the compressors are driven with different speeds but compressor diameters (wheel diameter) adjusted to provide the optimal compression ratio. In the example illustrated, the cycle circuit comprises three drive motors 12 configured to drive respectively three rotating shafts 11 of three rotating compressors 4 arranged in parallel in the cycle circuit 3. The three compressors 4 in parallel are coupled respectively to three turbines 11.

[0046] Of course, this configuration is not limiting. Thus it is possible to envisage any other configuration, for example: more than two compressors, turbines in series and / or in parallel (the architecture being adapted to balance the powers of the turbines on each of the shafts which connect them to the compressors). For example, at least one wheel (compressor / turbine) is arranged at each end of the motor drive shaft. The number of motors driving the compressors is preferably greater than two. The 4 compressors arranged in parallel have identical pressure differentials (between their inlet and outlet). However, the flow rates within these 4 compressors in parallel can fluctuate and be different. This can generate problems and instabilities when the 4 compressors in parallel are identical.

[0047] The control described above makes it possible to correct this problem. The control also makes it possible to regulate the rotation speed of the coupled turbines 10 at a determined operating point, in particular the optimum operating point of the turbine, i.e. at its maximum efficiency.

[0048] The electronic control and command unit 20 can be configured to further control the speeds of the motor(s) 12 of the motor-turbo-compressors in parallel, for example via a frequency converter (electric motor). This motor speed makes it possible to set the optimal operating point of the turbines and compressors.

[0049] The electronic control and command unit 20 can be configured to apply an identical rotation speed setpoint for the turbines 10 coupled to the compressors 4.

Claims

A cycle gas refrigerator (2), comprising a cycle circuit (3) containing a cycle gas comprising at least one of: nitrogen, helium, hydrogen, the cycle circuit (3) being configured to subject the cycle fluid to a thermodynamic cycle to bring the cycle fluid to a determined cryogenic temperature at at least one end of the cycle circuit (3), the cycle circuit (3) comprising a cycle fluid compression mechanism (4), a cycle fluid cooling mechanism (5, 6, 7, 8), a cycle fluid expansion mechanism (10), wherein the cycle fluid expansion mechanism (10) comprises at least two turbines (10) rotatably mounted on respective rotating shafts (11), the compression mechanism comprising at least three rotary compressors (4) arranged in parallel in the cycle circuit (3) and mounted respectively on three rotating shafts,at least two of the rotating shafts being coupled respectively to the turbines (10) to recover the expansion work of the cycle fluid for the compression of the cycle fluid, characterized in that it comprises at least one motor (12) for driving at least one of the rotating shafts (11) carrying a turbine (10) and a compressor (4) and in that at least the two compressors (4) in parallel coupled to a turbine (10) are each associated with a respective member (9) for measuring the flow rate passing through the compressor (4) concerned and with a respective member (14) for regulating the flow rate admitted into the compressor (4), for example one or more mobile steering members upstream or downstream such as an "IGV", the at least two turbines (10) coupled to the compressors (4) each comprising a respective sensor (17) for measuring the rotational speed of the turbine (10) and a respective system (15, 16) for controlling the speed of rotation of the turbine (10),the refrigerator (1) comprising an electronic control and command member (20) comprising a microprocessor and configured to receive measurements from the flow rate measuring members (9) and the speed measuring sensors (17) and to control the flow rate regulating members (14) and in that the compressors in parallel are identical, the electronic control and command member (20) being configured to apply a flow rate setpoint admitted into the compressors (4) which is identical for all the compressors (4) in parallel., Refrigerator according to claim 1, characterized in that the electronic control and command member (20) is configured to apply an identical rotation speed setpoint for the turbines (10) coupled to the compressors (4). Refrigerator according to any one of claims 1 to 2, characterized in that the flow regulation member (14) admitted into the compressor (4) comprises at least one of: one or more mobile steering members, an inlet guide valve “IGV” arranged upstream, a variable vane diffuser downstream of the compressor wheel, a compressor bypass system. Refrigerator according to any one of claims 1 to 3, characterized in that it comprises a member (14) for regulating the flow admitted into the compressor (4) common to at least several of the compressors in parallel. Refrigerator according to any one of claims 1 to 4, characterized in that the system (15, 16) for controlling the rotation speed of the turbine (10) comprises at least one of: an inlet guide valve "IGV", a throttle valve, a turbine bypass system. Refrigerator according to any one of claims 1 to 5, characterized in that it comprises three or more drive motors (12) configured to respectively drive the three rotating shafts (11) of the three rotating compressors (4) arranged in parallel in the cycle circuit (3). Refrigerator according to claim 1 characterized in that the electronic control and command member (20) is configured to control the speeds of the motor(s) (12). Refrigerator according to claim 7 characterized in that the motor(s) (12) are of the electric type and the electronic control and command member (20) is configured to control the rotation speed of the motor(s) (12) to achieve the same compression ratio in each compressor. Installation for liquefying a feed gas flow comprising a feed pipe (18) configured to be connected to a source (19) of feed gas to be liquefied, for example hydrogen, a set of heat exchangers (19) in heat exchange with the feed gas flow conveyed by the feed pipe (18), the installation (2) comprising a refrigerator (2) in heat exchange with the set of heat exchangers (19) and configured to cool the feed gas flow, characterized in that the refrigerator (2) conforms to any one of claims 1 to 8.

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