Companded total condensation loxboil air distillation

Claim 1

A dual pressure cryogenic distillation process for producing gaseous oxygen from a supply of compressed and cleaned air comprising: a. cooling a major fraction of said compressed and cleaned air: b. rectifying said major fraction in a high pressure rectifier to liquid nitrogen overhead product and kettle liquid bottom product; c. distilling the kettle liquid in a low pressure column to liquid oxygen bottom product and gaseous nitrogen overhead product; d. working expanding a compensating vapor comprised of at least 77% N 2 thereby producing refrigeration; e. further compressing the remaining minor fraction comprising no more than about 30% of said compressed, cleaned warm air in a compressor powered by said expansion work; f. pressurizing said liquid oxygen to at least about 0.2 ATA above LP column bottom pressure; g. cooling the minor air fraction to near its dewpoint; h. condensing substantially all the minor air fraction by exchanging latent heat with said pressurized liquid oxygen; i. withdrawing evaporated oxygen as product; j. dividing the condensed air into two streams, each comprising at least 15% of said minor fraction; k. injecting one of said streams into an intermediate height of the HP rectifier and injecting the second stream into an intermediate height of the LP column; and l. separately reboiling said LP column bottoms by exchanging latent heat with at least one of: (i) HP rectifier overhead vapor and (ii) partially condensing major fraction of said supply air.