Abstract: A centrifugal compressor assembly, especially one having two or more stages, comprises a first compressor casing having. A fluid inlet and a fluid outlet and a first impeller rotatable within the first compressor casing. The assembly further comprises a second compressor casing having a fluid inlet and a fluid outlet and a second impeller rotatable within the second compressor casing. Drive for the compressors is provided by an electric motor, preferably a permanent magnet motor, disposed between the first and second compressor casings and comprising a stator and a rotor rotatable within the stator. A drive shaft is provided, wherein the first impeller, second impeller and the rotor are mounted on the drive shaft and rotatable therewith.

Abstract: A method and apparatus for compressing and drying a gas, typically air, are provided in which a multistage compressor is employed to produce interstage and final stage compressed gas. Regenerative adsorbent is employed to dry the final stage compressed gas. Interstage gas is used to regenerate the saturated adsorbent. Preferably, two beds of regenerable adsorbent are provided, each operable in a drying mode and a regeneration mode. In the drying mode, final stage compressed gas is passed through the bed of adsorbent in order to be dried, until the adsorbent is saturated. In the regeneration mode, moisture is removed from the saturated adsorbent by a stream of interstage compressed gas. The two beds are preferably alternately operated in the drying mode and the regeneration mode, in order to provide a continuous process.