CRYOGENIC METHOD OF AIR FLOW SEPARATION

摘要

The efficiency of producing liquid products from a cryogenic air separation process using a distillation column system having at least a high pressure distillation column (902) and a low pressure distillation column (904) in thermal communication with each other and in which system the low pressure column (904) operates at a pressure of 60 to 520 kPag (9 to 75 psig) and at least 50% of the feed air is removed as a nitrogen product (130) from the low pressure column (904), said product having a nitrogen concentration of at least 95% and is a pressure of at least 60 kPag (9 psig), is improved by partially warming the nitrogen product by heat exchange (918), isentropically expanding the warmed product (920,922) and use of the inherent refrigeration of the expanded nitrogen. The refrigeration can be recovered by heat exchange (916) against a liquid stream (5) from the high pressure column (902) and/or by heat exchange (900) against the feed air (101).