Compression train including one centrifugal compressor and LNG plant

A compression train for a natural gas liquefaction process, the compressor train comprising:

• a driver machine;
• a single centrifugal compressor machine driven in rotation by the driver machine, the compressor machine comprising a single casing, at least two sections of compression housed inside the single casing, a main inlet passage configured to receive a refrigerant gas to be compressed by one of the at least two sections of compression, an auxiliary outlet configured to discharge the refrigerant gas compressed by the one of the at least two sections of compression from the compressor machine, an auxiliary inlet configured to receive the refrigerant gas, having been compressed by the one of the at least two sections of compression and subsequently externally cooled, to be further compressed by another of the at least two sections of compression, and a main outlet configured to discharge the refrigerant gas having been further compressed by the another of the at least two sections of compression from the compressor machine,
• wherein the compressor machine is configured to compress a refrigerant gas with a molecular weight less than 30 g/mol from a suction pressure to a discharge pressure, the ratio between discharge pressure at the main outlet and suction pressures at the main inlet is higher than 10, and each section of the at least two sections of compression comprises a respective two or more compression stages.