Abstract: A compression method, a multistage compression system and an air separation method and plant in which a gas is compressed in a series of compression stages to produce a compressed gas and each of the compression stages incorporate a variable speed compressor. In such compression method and system, the compressed air is produced at a pressure that remains stable during both normal operational conditions and during turn down conditions during which the flow rate of the gas is reduced. This reduction is accomplished by reducing the speed of the compressor in an initial compression stage such that the compressor operates at a point along its peak efficiency operating line at which the pressure ratio is directly proportional to the flow rate and such that the lower turn down flow rate is obtained at a reduced pressure which is made up in successive compression stages.

Abstract: A compression method, a multistage compression system incorporating such method and an air separation method and plant utilizing such compression method and system in which a gas is compressed in a series of compression stages to produce a compressed gas and each of the compression stages incorporate a variable speed compressor. In such compression method and system, the compressed air is produced at a pressure that remains stable during both normal operational conditions and during turn down conditions during which the flow rate of the gas is reduced. This reduction is accomplished by reducing the speed of the compressor in an initial compression stage such that the compressor operates along a peak efficiency operating line at which the pressure ratio is directly proportional to the flow rate and such that the lower turn down flow rate is obtained at a reduced pressure which is made up in successive compression stages.