Medium-pressure nitrogen production with high oxygen recovery

摘要

Oxygen (186) and nitrogen (168) are obtained by a cryogenic air separation process using a distillation system having at least a higher pressure column (124) and a lower pressure column (150). A nitrogen-enriched liquid stream (164) is recovered from the higher pressure column (124) and is at least partially vaporized by indirect heat exchange (192) at a pressure intermediate that of the higher pressure column (124) and the lower pressure column (150). A vapor stream (190) is withdrawn from an intermediate location of the stripping section of the lower pressure column (150) and is at least partially condensed by indirect heat exchange (192) with the nitrogen-enriched liquid stream (164). At least some of the nitrogen product (168) is recovered from the vapor (166) that results from the at least partial vaporization (192) of the nitrogen-enriched liquid (164). The process is appropriate for the production of nitrogen in quantities up to 40 mole % of the incoming air flow (100).