Efficient single column air separation cycle and its integration with gas turbines

Abstract

The present invention is an improvement to a process for the cryogenic distillation of air to produce both nitrogen and oxygen products carried out in a single distillation column system wherein a feed air stream is distilled thereby producing a nitrogen overhead and a liquid oxygen bottoms. The improvement is characterized in that: (a) operating the single distillation column at a pressure between 70 and 300 psia [480 and 2,070 kPa.sub.(absolute) ]; (b) withdrawing a portion of the liquid oxygen bottoms having an oxygen concentration greater than 80% oxygen and preferably between 85% and 97% oxygen from the bottom of the single distillation column and reducing the pressure of and vaporizing the withdrawn liquid oxygen by heat exchange against a condensing nitrogen stream removed from a top section of the single distillation column; (c) feeding the condensed, nitrogen stream to a top section of the single distillation column as reflux; and (d) recovering the vaporized oxygen as at least a substantial portion of the oxygen product. The improvement can be further characterized by providing boilup by boiling at least another portion of the liquid oxygen bottoms by heat exchange against a condensing vapor stream, wherein the vapor stream to be condensed in an air stream at a higher pressure than the feed air stream or a recycle nitrogen stream at a pressure greater than the operating pressure of the single distillation column, or by recycling a portion of the oxygen product at a pressure of at least the operating pressure of the single distillation column to the bottom of the distillation column and/or by providing intermediate boilup to the stripping section of the single distillation column system by vaporizing a portion of descending column liquid by heat exchange against another condensing vapor stream, wherein the other vapor stream to be condensed is either an air stream at a higher pressure than the feed air stream or a recycle nitrogen stream at a pressure greater than the operating pressure of the single distillation column.

Dependencies are inferred from the claim text.