Cryogenic air separation system with dual feed air side condensers

Claim 1

Method for the separation of air by cryogenic distillation to produce product gas comprising: (A) condensing at least some of a first portion of cooled compressed feed air and introducing resulting liquid into a first column of an air separation plant, said first column operating at a pressure generally within the range of from 60 to 100 psia; (B) turboexpanding a second portion of the cooled, compressed feed air and introducing a first part of the resulting turboexpanded feed air into said first column; (C) condensing at least some of a second part of the turboexpanded feed air and introducing the resulting fluid into said first column; (D) separating the fluids introduced into said first column into nitrogen-enriched and oxygen-enriched fluids and passing said fluids into a second column of said air separation plant, said second column operating at a pressure less than that of said first column; (E) separating the fluids passed into the second column into nitrogen-rich vapor and oxygen-rich liquid; (F) withdrawing oxygen-rich liquid from the second column and vaporizing a first portion of the withdrawn oxygen-rich liquid by indirect heat exchange with the second part of the turboexpanded feed air to carry out the condensation of step (C); (G) increasing the pressure of a second portion of the withdrawn oxygen-rich liquid and vaporizing the resulting liquid by indirect heat exchange with the first portion of the feed air to carry out the condensation of step (A); and (H) recovering vapor resulting from the heat exchange of steps (F) and (G) as product oxygen gas.