Device and process for air separation by cryogenic distillation

摘要

An air separation plant has a mixing column and at least one double column with a low pressure connected to a mid-pressure column via a vaporizer-condenser. A second vaporizer-condenser vaporizes a liquid containing 22 - 70 mol% oxygen received from the low pressure column and partly condenses air to be supplied to the double column. An Independent claim is included for the following: (a) Air separation as above. Preferred Features: Untreated air is supplied direct to the bottom of the low pressure column. A nitrogen rich gas leaves the top of the mid-pressure column. Liquid from the bottom of the mid-pressure column goes partly to the second vaporizer-condenser and partly to a first level in the mid-pressure column. The vaporized liquid from the second vaporizer-condenser goes to a relatively lower level in the mid-pressure column.