Patent ID: 6397631
Filing Date: 2002-06-04
Classification: F25J

Abstract:
A process for separating a multi-component fluid comprising oxygen and nitrogen to produce nitrogen, said process using a distillation column system having at least three distillation columns, including a higher-pressure column operating at a first pressure, a lower-pressure column operating at a second pressure lower than the first pressure, and a supplemental column operating at a third pressure greater than or equal to the second pressure, wherein the higher-pressure column and the lower-pressure column are thermally linked through a first heat exchanger and each distillation column has a top, a bottom, and a plurality of locations between the top and the bottom, comprising the steps of:feeding a first stream of the multi-component fluid to the higher-pressure column; feeding a second stream of the multi-component fluid or another multi-component fluid compromising oxygen and nitrogen to the supplemental column; withdrawing a first nitrogen-rich vapor stream from the higher-pressure column or the lower-pressure column; withdrawing a first oxygen-rich liquid stream from the lower-pressure column; heat exchanging at least a portion of the first oxygen-rich liquid stream indirectly against at least a portion of the first nitrogen-rich vapor stream in the first heat exchanger or a second heat exchanger, thereby at least partially vaporizing the first oxygen-rich liquid stream and at least partially condensing the first nitrogen-rich vapor stream; eventually changing the pressure of at least a portion of the condensed first nitrogen-rich vapor stream; eventually feeding at least a portion of the condensed first nitrogen-rich vapor stream to the supplemental column; withdrawing a second oxygen-rich liquid stream from the supplemental column; feeding at least a portion of the second oxygen-rich liquid stream to the lower-pressure column or the higher-pressure column; and withdrawing a first stream of nitrogen product from the supplemental column.