Closed-loop refrigeration cycles for liquid oxygen densification are disclosed. The disclosed refrigeration cycles may be turbine-based refrigeration cycles or a Joule-Thompson (JT) expansion valve based refrigeration cycles and include a refrigerant or working fluid comprising a mixture of neon or helium together with nitrogen and/or oxygen.

Closed-loop refrigeration cycles for liquid oxygen densification are disclosed. The disclosed refrigeration cycles may be turbine-based refrigeration cycles or a Joule-Thompson (JT) expansion valve based refrigeration cycles and include a refrigerant or working fluid comprising a mixture of neon or helium together with nitrogen and/or oxygen.

Described herein is a method of removing refrigerant from a natural gas liquefaction system in which vaporized mixed refrigerant is withdrawn from the closed-loop refrigeration circuit and introduced into a distillation column so as to be separated into an overhead vapor enriched in methane and a bottoms liquid enriched in heavier components. Overhead vapor is withdrawn from the distillation column to form a methane enriched stream that is removed from the liquefaction system, and bottoms liquid is reintroduced from the distillation column into the closed-loop refrigeration circuit. Also described are methods of altering the rate of production in a natural gas liquefaction system in which refrigerant is removed as described above, and a natural gas liquefaction systems in which such methods can be carried out.

Provided are an apparatus and method for liquefying natural gas. The apparatus for liquefying natural gas includes a gas compressor configured to receive and compress the natural gas from a natural gas feed stream, a heat exchanging unit configured to cool a high-pressure natural gas passing through the gas compressor through heat exchange, an expansion valve configured to expand the cooled natural gas passing through the heat exchanging unit, a hold-up drum configured to phase-separate a gas-liquid mixture produced by passing through the expansion valve and divide the gas-liquid mixture into a liquefied natural gas and a cryogenic recycle gas having nitrogen content greater than that of the liquefied natural gas so as to discharge the liquefied natural gas and the cryogenic recycle gas, and a bypass line configured to provide the recycle gas discharged from the hold-up drum to the heat exchanging unit.

A cooling system includes a compressor configured to pressurize carbon dioxide to form pressurized carbon dioxide, a mixer configured to generate mixed refrigerant in which the pressurized carbon dioxide and solvent in a liquid state, a depressurization apparatus provided downstream from the mixer and configured to depressurize the mixed refrigerant, a separator configured to separate carbon dioxide in a gas state from the mixed refrigerant, a heat exchanger configured to exchange heat between the mixed refrigerant cooled through depressurization and a fluid to be cooled, and a second heat exchanger configured to cool the carbon dioxide or the mixed refrigerant using vaporized carbon dioxide or the mixed refrigerant.

Methods and systems for liquefying natural gas using environmentally-friendly low combustibility refrigerants are provided. Methods of liquefaction include cooling a fluid in an LNG facility via indirect heat exchange with an environmentally-friendly low combustibility refrigerant selected from the group consisting of: a fluorinated olefin, xenon, any derivative thereof, and any combination thereof.

A liquefaction system and method for producing liquefied natural gas (LNG) is provided. The liquefaction system may include a heat exchanger to cool natural gas to LNG, a first compressor to compress and combine first and second portions of a single mixed refrigerant from the heat exchanger, a first cooler to cool the single mixed refrigerant from the first compressor to a first liquid phase and a gaseous phase, and a first liquid separator to separate the first liquid phase from the gaseous phase. The liquefaction system may also include a second compressor to compress the gaseous phase, a second cooler to cool the compressed gaseous phase to a second liquid phase and the second portion of the single mixed refrigerant, a second liquid separator to separate the second liquid phase from the second portion of the single mixed refrigerant, and a pump to pressurize the first liquid phase.

Disclosed is a device for refrigerating or liquefying a fluid such as natural gas or hydrogen, comprising a fluid circuit that is to be cooled and has an upstream end for connection to a source of gaseous fluid as well as a downstream end for connection to a member for collecting the cooled or liquefied fluid, the device comprising a heat exchanger assembly in heat exchange with the fluid circuit to be cooled, the device comprising a refrigerator in heat exchange with at least a portion of the exchanger assembly, the refrigerator being of the type that has a cycle for refrigerating a cycle gas containing at least one of: helium, hydrogen, nitrogen or neon; said refrigerator comprising in series in a cycle circuit: a mechanism for compressing the cycle gas, at least one member for cooling the cycle gas, a mechanism for expanding the cycle gas, and at least one member for reheating the expanded cycle gas, wherein the compression mechanism comprises a plurality of compression stages in series composed of a centrifugal compressor assembly, the compression stages being mounted on a set of shafts that are rotationally driven by a motor assembly, the at least one member for cooling the cycle gas comprising at least one heat exchanger at the outlet of at least one compression stage in heat exchange with the cycle circuit, said heat exchanger being cooled by a heat transfer fluid, characterized in that the compression mechanism comprises at least two compression stages that are arranged successively in series and do not include any member for cooling the cycle gas such as a heat exchanger therebetween.

Disclosed is a device for refrigerating or liquefying a fluid such as natural gas or hydrogen, comprising a circuit for fluid that is to be cooled and has an upstream end for connection to a source of gaseous fluid and a downstream end for connection to a member for collecting the cooled or liquefied fluid, the device comprising a heat exchanger assembly in heat exchange with the circuit of fluid to be cooled, the device comprising a refrigerator in heat exchange with at least a portion of the heat exchanger assembly, the refrigerator being of the type that has a cycle for refrigerating a cycle gas containing at least one of: helium, hydrogen, nitrogen or neon; said refrigerator comprising, arranged in series in a cycle circuit: a mechanism for compressing the cycle gas, at least one member for coding the cycle gas, a mechanism for expanding the cycle gas, and at least one member for reheating the expanded cycle gas, wherein the compression mechanism comprises a plurality of compression stages in series composed of a centrifugal compressor assembly, the compression stages being mounted on a set of shafts rotated by an assembly of one or more motors, the at least one member for cooling the cycle gas comprising at least one heat exchanger arranged at the outlet of at least one compression stage in heat exchange with the cycle circuit, said heat exchanger being cooled by a heat-transfer fluid, characterized in that the compression mechanism comprises at least two compression stages that are arranged successively in series and do not include any member for cooling the cycle gas such as a heat exchanger therebetween.

Disclosed is a device for refrigerating or liquefying a fluid such as natural gas or hydrogen, comprising a fluid circuit that is to be cooled and has an upstream end for connection to a source of gaseous fluid as well as a downstream end for connection to a member for collecting the cooled or liquefied fluid, the device comprising a heat exchanger assembly in heat exchange with the fluid circuit to be cooled, the device comprising a refrigerator in heat exchange with at least a portion of the exchanger assembly, the refrigerator being of the type that has a cycle for refrigerating a cycle gas containing at least one of: helium, hydrogen, nitrogen or neon; said refrigerator comprising in series in a cycle circuit: a mechanism for compressing the cycle gas, at least one member for cooling the cycle gas, a mechanism for expanding the cycle gas, and at least one member for reheating the expanded cycle gas, wherein the compression mechanism comprises a plurality of compression stages in series composed of a centrifugal compressor assembly, the compression stages being mounted on a set of shafts that are rotationally driven by a motor assembly, the at least one member for cooling the cycle gas comprising at least one heat exchanger at the outlet of at least one compression stage in heat exchange with the cycle circuit, said heat exchanger being cooled by a heat transfer fluid, characterized in that the compression mechanism comprises at least two compression stages that are arranged successively in series and do not include any member for cooling the cycle gas such as a heat exchanger therebetween.