Patent ID: 8197227

Claim:
A multi-stage compressor system for compressing gas, comprising: a plurality of compressor elements ( 2 - 5 - 28 ) discharging compressed and heated gas during operation located in series one after the other, said compressed gas circulating between said compressor elements; one of said compressor elements ( 5 - 28 ) being driven by a motor ( 9 ), and at least another one of said compressor elements ( 2 ) being driven separately without a mechanical link with said motor ( 9 ); wherein the one compressor element ( 5 - 28 ) which is driven by the motor ( 9 ) is of the screw type, and the other compressor element ( 2 ) which is driven separately is of the centrifugal type; an expander ( 18 ) included in a closed power cycle ( 12 ) using a circulating medium inside the power cycle and drivingly connected to said other compressor element; a heater arranged to receive and heat said circulating medium; said heater arranged to receive at least part of the compressed and heated gas discharged from a compressor element and to heat the circulating medium in said heater using said compressed and heated gas.