Triple column distillation system for oxygen and pressurized nitrogen production

摘要

Air is cryogenically separated to produce an oxygen product with purity less than 98% and a nitrogen product in a distillation column system with a low pressure column (24), a medium pressure column (22) and a high pressure column (20). Oxygen-enriched streams, (140, 162) from the high and medium pressure columns (20, 22) are fed to the medium and low pressure columns (22, 24) respectively and at least a portion (146) of the high pressure nitrogen overhead (144) is condensed by heat exchange (28) against a liquid stream in the medium pressure column (22) or the high pressure column bottoms (142). The condensed high pressure nitrogen overhead (160) is used to provide reflux to the high pressure column (20). Gaseous oxygen (186) of less than 98% purity is obtained from the low pressure column (24) and nitrogen (172) in an amount of at least 35% of feed air flow is obtained from the high pressure column (20) and/or the medium pressure column (22).