Multiple reboiler, double column, elevated pressure air separation cycles and their integration with gas turbines

In a process for the cryogenic distillation of air to separate out and produce at least one of its constituent components, wherein the cryogenic distillation is carried out in a distillation column system having at least two distillation columns operating at different pressures;

• a feed air stream is compressed to a pressure in the range between 70 and 300 psia (500 and 2,000 kPa) and essentially freed of impurities which freeze out at cryogenic temperatures;
• at least a portion of the compressed, essentially impurities-free feed air is cooled and fed to and rectified in the first of the two distillation columns thereby producing a higher pressure nitrogen overhead and a crude liquid oxygen bottoms;
• the crude oxygen bottoms is reduced in pressure and fed to the second of the two distillation columns for distillation thereby producing a lower pressure nitrogen overhead and a liquid oxygen bottoms;
• a fraction of the cooled, compressed, essentially impurities-free feed air portion is at least partially condensed by heat exchange against the liquid oxygen bottoms in a first reboiler/condenser and fed to at least one of the two distillation columns;
• at least a portion of the higher pressure nitrogen overhead is condensed by heat exchange against liquid descending the second distillation column in a second reboiler/condenser located in the low pressure column between the bottom of the second distillation column and the feed point of the crude liquid oxygen bottoms;
• the condensed higher pressure nitrogen is fed to at least one of the two distillation columns as reflux;
• and a gaseous nitrogen product is produced;
• the improvement to allow effective operation of the process at elevated pressures comprises:
• (a) heat exchanging a portion of the liquid oxygen bottoms of the second column against a nitrogen vapor stream, wherein prior to such heat exchange the pressure of at least one of the two streams being heat exchanged against each other undergoes a change in an operation that achieves a temperature difference between the liquid oxygen bottoms and the nitrogen vapor stream so that upon heat exchange the nitrogen vapor is totally condensed and the liquid oxygen bottoms portion is at least partially vaporized;
• (b) utilizing the condensed nitrogen as reflux in at least one of the two distillation columns;
• and
• (c) warming the vaporized oxygen to recover refrigeration.