Tonnage nitrogen air separation with side reboiler condenser

Claim 1

A process for producing large quantities of nitrogen at relatively high pressure by the cryogenic separation of air in a two stage distillation column comprising the steps of: (a) compressing a feed air stream to an elevated pressure and removing water and carbon dioxide from the compressed air; (b) cooling the compressed air against rewarming process streams by indirect heat exchange; (c) introducing at least a portion of the cooled air stream into the high pressure stage of said distillation column; (d) removing a bottom stream from the high pressure stage of the distillation column, reducing its pressure and introducing it into the low pressure stage of the distillation column; (e) removing a gaseous nitrogen stream from the top of the high pressure stage of the distillation column and condensing a portion of it against oxygen-enriched liquid in the bottom of the low pressure stage of the distillation column to produce a first liquid nitrogen stream; (f) removing oxygen-enriched liquid from the bottom of the low pressure stage of the distillation column and reducing its pressure; (g) condensing another portion of the gaseous nitrogen stream from the high pressure stage of step (e) against the oxygen-enriched liquid of step (f) to provide a gaseous oxygen-enriched stream and a second liquid nitrogen stream; (h) returning a first portion of the first and/or second liquid nitrogen streams to the high pressure stage of the distillation column as reflux; (i) reducing in pressure and introducing a second portion of the first and second liquid nitrogen streams to the low pressure stage of the distillation column as reflux; (j) removing a gaseous nitrogen product from the low pressure stage of the distillation column, and (k) rewarming the gaseous oxygen-enriched stream of step (g) and expanding it through an expansion turbine to produce refrigeration for the process by heat exchanging the expanded oxygen-enriched stream against process streams.