Air separation procedure to produce argon uses cryogenic distillation with additional liquid flow containing 18-30 mol percent oxygen fed to low pressure column

摘要

The procedure uses at least three distillation columns: the head of a medium pressure column (13) in thermal communication with a low pressure column (15), and an auxiliary column (29) that produces an argon-rich fluid and has part (7) of its air feed sent in the form of a gas to the medium pressure column. A second liquid flow (21) containing 18-30% of oxygen is fed to the low pressure column at a second level. The first and/or second flow is of air. The procedure uses a system with at least three distillation columns: the head of a medium pressure column (13) in thermal communication with a low pressure column (15), and an auxiliary column (29) that produces an argon-rich fluid and has part (7) of its air feed sent in the form of a gas to the medium pressure column. A gas rich in argon (25) is fed from the low pressure column to the auxiliary column, which produces a fluid richer in argon than the gas. A first liquid flow (19) containing 18-30 mol percent of oxygen is fed to the low pressure column at a first level, and a nitrogen-rich flow is drawn from the low pressure column. The procedure differs in that a second liquid flow (21) containing 18-30 per cent mol of oxygen is fed to the low pressure column at a second level, and that the first and/or second flow is of air. In addition, a nitrogen-rich liquid flow (23) is sent from the medium pressure column to the low pressure column at a point above the first and/or second level.