A method for separating air by cryogenic distillation wherein, during a first run, a first flow rate of air is compressed in at least one compressor, cooled and separated in a system of columns, a first flow rate of a first distillation product is produced, voltage electricity requirements of the compressor or compressors of the method are met from an electricity grid, during a second run, a second flow rate of air lower than the first flow rate of air is compressed in the compressor, the second flow rate is cooled and separated in the system of columns, a second flow rate of a first distillation product is produced, lower than the first flow rate of the first product, voltage electricity requirements of the compressor being lower than during the first run and, during an intermediate run taking place after the first run and before the second run.

The present disclosure relates to systems and methods useful for power production. In particular, a power production cycle utilizing CO.sub.2 as a working fluid may be combined with a second cycle wherein a compressed CO.sub.2 stream from the power production cycle can be heated and expanded to produce additional power and to provide additional heating to the power production cycle.

An apparatus for separating air by cryogenic distillation comprises N air compressors (C1, C2, C3) connected so as to receive air at ambient pressure and designed to produce air at a first pressure above 12 bar absolute, N being at least 3, each of the compressors being driven by a single asynchronous motor (M1, M2, M3), the total power of the compressors being at least 10 MW.

An air separation plant is provided that includes a plurality of air compressors, a plurality of air purification units, and one or more cold boxes. In a first mode of operation, a first air compressor is configured to compress air to a higher pressure than a second air compressor. In a second mode of operation, the second air compressor is configured to compress air to a higher pressure than during the first mode of operation.