Patent ID: 6339938
Filing Date: 2002-01-22
Classification: F25J

Abstract:
Air separation apparatus comprising a column system comprising at least one double column comprising a medium-pressure column (104) and a low-pressure column (105) which are thermally linked to each other by a first reboiler/condenser (111) where the gas at the top of the medium-pressure column condenses, means for sending compressed and purified air to a heat exchanger (100) where it cools, means (2) for sending cooled air to the medium-pressure column in gas form, means for sending an oxygen-enriched fluid from the medium-pressure column to the low-pressure column where it is separated by cryogenic distillation, means for sending a nitrogen-enriched fluid from the medium-pressure column to the low-pressure column, means for withdrawing a nitrogen-rich fluid and an oxygen-rich fluid from the low-pressure column, a second reboiler/condenser (109), means (86) for sending air to the second reboiler/condenser where it condenses at least partially, and means for sending the at least partially condensed air to the low-pressure column, means (18) for sending a liquid from the low-pressure column or from the medium-pressure column or from another column (107) of the column system to the second reboiler/condenser, characterized in that the liquid (18) sent to the second reboiler/condenser contains between 22 and 70 mol % of oxygen and in that the at least partially condensed air sent to the column system comprises the only stream of liquefied air sent to the column system.