Fluid liquefaction method and device

A device for liquefying a fluid, the device comprising:

• a circuit for fluid to be cooled, having an upstream end configured to be connected to a source of gaseous fluid, and a downstream end configured to be connected to a member for collecting the liquefied fluid;
• a set of heat exchanger(s) in a heat-exchange relationship with the circuit for fluid to be cooled;
• a pre-cooling system in a heat-exchange relationship with at least part of the set of heat exchanger(s) and configured to lower the temperature of the fluid to be cooled to a first temperature between 30 K and 110 K;
• a cooling system in a heat-exchange relationship with at least part of the set of heat exchanger(s) and configured to lower the temperature of the fluid to be cooled from the first temperature to a second temperature between 15 and 25 K,
• wherein the cooling system comprises a first refrigerator with a refrigeration cycle operating using a first cycle gas containing helium and/or hydrogen, said first refrigerator comprising, arranged in series in a cycle circuit:
• a compression mechanism configured to compress the cycle gas, at least one cooling member configured to cool the cycle gas, an expansion mechanism configured to expand the cycle gas, and at least one heating member configured to heat the expanded cycle gas,
• wherein the compression mechanism comprises a plurality of compression stages in series, said plurality of compression stages being comprised of a set of centrifugal compressor(s),
• wherein the plurality of compression stages are mounted on shafts rotationally driven by a set of motor(s),
• wherein the expansion mechanism comprises several expansion stages comprised of a set of centripetal turbines, wherein at least one of the centripetal turbines is coupled to a same shaft as at least one compression stage so as to supply to the compression stage mechanical work produced during the expansion,
• wherein the pre-cooling system comprises a second refrigerator with a refrigeration cycle operating using a second cycle gas, said second refrigerator comprising, arranged in series in a second cycle circuit:
• a second compression mechanism configured to compress the second cycle gas, at least one cooling member configured to cool the second cycle gas, a second expansion mechanism configured to expand the second cycle gas, and at least one heating member configured to heat the expanded second cycle gas,
• wherein the second compression mechanism comprises a second plurality of compression stages in series, said plurality of compression stages being comprised of a second set of centrifugal compressor(s),
• wherein the second plurality of compression stages are mounted on shafts rotationally driven by a second set of motor(s),
• wherein the second expansion mechanism comprises one or more expansion stages comprising a second set of centripetal turbine(s), at least one of which is coupled to a same shaft as at least one second compression stage so as to supply to the second compression stage mechanical work produced during the expansion,
• wherein the set of motor(s) of the first refrigerator comprises at least one variable-speed electric motor controlled by an electrical signal by varying the frequency of the electrical signal, and
• wherein the cold power supplied by the first refrigerator determines the second temperature and is dependent on a rotational speed of at least one motor in the set of motors of the first refrigerator(18),
• wherein the second set of motor(s) of the second refrigerator comprises at least one variable-speed electric motor controlled by an electrical signal by varying the frequency of the electrical signal,
• wherein the cold power supplied by the second refrigerator determines the first temperature and is dependent on a rotational speed of said at least one motor in the second set of motors of the second refrigerator),
• the device further comprising:
• an electronic control member configured to control at least one of the motor(s) of the first refrigerator and at least one motor of the second refrigerator, the electronic control member being configured to control jointly a speed setpoint for the motors of the first and second refrigerators, such that the control of one of the refrigerators determines, or is dependent on, the control of the other refrigerator.