| abstract |
At least a portion of a waste stream (785) from an elevated pressure airnseparation cryogenic process, in which compressed feed air (711,719) is cooled toncryogenic temperature in a main heat exchanger (713) having a cold end and a warmnend and separated in a distillation column system having at least two distillation columnsn(717,735) into at least a nitrogen-enriched product (757,771), an oxygen-enrichednproduct (793) and said gaseous waste stream (785) is isentropically expanded (787) tonprovide at least a portion of the work required to compress (721) a process stream othernthan the gaseous waste stream at a temperature warmer than the temperature of thencold end of said main heat exchanger (713). The alternative process streams to bencompressed can be: at least a portion (719) of the feed air, at least a portion of thenoxygen-enriched product (793) or at least a portion of the nitrogen-enriched productn(757,771). |