Importance

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Abstract

Air is separated by cryogenic distillation comprising the steps of feeding compressed, cooled and purified air to a high pressure column where it is separated into a first nitrogen enriched stream at the top and a first oxygen enriched stream at the bottom. At least a portion of the first oxygen enriched stream is fed to an intermediate pressure column to yield a second nitrogen enriched stream at the top and a second oxygen enriched stream at the bottom. At least a portion of the second nitrogen enriched stream is sent to a low pressure column or to a top condenser of an argon column, and at least a portion of the second oxygen enriched stream is sent to the low pressure column. A third oxygen enriched stream is separated at the bottom and a third nitrogen enriched stream is separated at the top of the low pressure column. A heating gas is sent to a bottom reboiler of the low pressure column, and at least a portion of the third oxygen enriched stream is removed at a removal point. A first argon enriched stream containing between 3 and 20% argon is removed from the low pressure column, and the first argon enriched stream is sent to the argon column having a top condenser. A second argon enriched stream, richer in argon than the first argon enriched stream, is recovered at the top of the argon column and a fourth oxygen enriched stream is removed at the bottom of the argon column. The argon column operates at a pressure at least 0.5 bar lower than the pressure of the low pressure column.

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First Claim