Alternative pre-cooling arrangement

A method for liquefying natural gas, the method comprising the steps of:

• providing a natural gas feed stream;
• providing a first refrigerant stream;
• precooling in a first precooling refrigeration system at least the natural gas feed stream;
• precooling in a second precooling refrigeration system at least the first refrigerant stream;
• and
• vaporizing the precooled first refrigerant stream in a cryogenic heat exchanger to cool the precooled natural gas feed stream through indirect heat exchange,
• wherein the second precooling refrigeration system precools only stream(s) having a composition different from the stream(s) precooled by the first precooling refrigeration system.

A natural gas liquefaction system for large capacity liquefaction plants, the system comprising:

• a first precooling refrigeration system that accepts one stream selected from the group consisting of:
• a natural gas feed stream, and
• an at least one refrigerant stream;
• a second precooling refrigeration system that accepts any remaining stream(s) not accepted by the first precooling refrigeration system and from the group consisting of:
• the natural gas feed stream, and
• the at least one refrigerant stream;
• and
• a cryogenic heat exchanger fluidly connected to the first precooling refrigeration system and the second precooling refrigeration system and adapted to accept the natural gas feed stream and the at least one refrigerant stream from the first precooling refrigeration system and the second precooling refrigeration system, wherein the at least one refrigerant stream is used to liquefy the natural gas feed stream,
• wherein the second precooling refrigeration system accepts only stream(s) having a composition different from the stream(s) accepted by the first precooling refrigeration system.