PROCESS AND APPARATUS FOR THE SEPARATION OF AIR BY CRYOGENIC DISTILLATION

摘要

A process for the cryogenic separation of air using a multiple column distillation system comprising at least a higher pressure column ("HP column") and a lower pressure column ("LP column"), comprising: feeding cooled feed air to the high pressure column for separation into high pressure nitrogen-enriched overhead vapor and crude liquid oxygen; feeding at least one low pressure column feed stream comprising nitrogen and oxygen to the low pressure column for separation into nitrogen-rich overhead vapor and liquid oxygen; refluxing the low pressure column with a liquid stream from or derived from the high pressure column; feeding expanded air to an auxiliary separation column for separation into auxiliary column nitrogen-rich overhead vapor and oxygen-rich liquid and removing the nitrogen rich overhead vapour as a product stream; feeding bottom liquid from the auxiliary column to an intermediate location of the low pressure column;and refluxing the auxiliary column with a nitrogen rich liquid stream from or derived from the HP column.