Device and method for pre-cooling a stream of a target fluid to a temperature less than or equal to 90 k

A device for pre-cooling a flow of a target gas to a temperature less than or equal to 90 K, comprising:

• a group of at least two heat exchangers for exchanging heat between the target gas flow, a flow of a first cooling fluid and at least one flow among a flow of a second cooling fluid and a flow of a third cooling fluid,
• the target gas downstream of the group of exchangers remaining in gas form,
• a closed circulation circuit for a flow of a second cooling fluid, said fluid comprising at least methane, said circuit comprising:
• at least one stage of compressing the flow of the second fluid,
• at least one stage of liquid-gas separation of the flow of the second fluid to form a liquid part and a gas part, at least one of the two parts being provided to at least one said heat exchanger and
• at least one stage of expanding the flow of the second fluid and
• a circulation circuit for a flow of the third cooling fluid through at least one of said heat exchangers, said circuit not comprising an expansion turbine, said third fluid having a circulation temperature in said exchanger of less than 90K, said circulation circuits of each cooling fluid being separate.