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US 4,439,220 AGranted
Dual column high pressure nitrogen process
AssigneeUnion Carbide Corporation
InventorsWalter J. Olszewski, Ravindra F. Pahade, John H. Ziemer
Life of this patent
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Abstract
A process to efficiently produce large quantities of elevated pressure nitrogen at a high recovery by the cryogenic separation of air employing two separate columns each of which is equipped with a top condenser and wherein the second column processes a feed stream obtained from the first column.
Claims17
A process for the production of nitrogen gas at greater than atmospheric pressure by the separation of air by rectification comprising:
- (A) introducing cleaned, cooled feed air at greater than atmospheric pressure into a high pressure column having a top condenser, and operating at a pressure of from about 80 to 300 psia;
- (B) separating said feed air by rectification in said high pressure column into a first nitrogen-rich vapor fraction and a first oxygen-enriched liquid fraction;
- (C) recovering from about 20 to 60 percent of said first nitrogen-rich vapor fraction as high pressure nitrogen gas at a pressure of from about 80 to 300 psia and a purity of at least 99 mole percent;
- (D) condensing a portion of said first nitrogen-rich vapor fraction by indirect heat exchange with said first oxygen-enriched liquid fraction thereby producing a first nitrogen-rich liquid portion and a first oxygen-enriched vapor fraction;
- (E) employing said first nitrogen-rich liquid portion as liquid reflux for said high pressure column;
- (F) introducing said first oxygen-enriched vapor fraction into a medium pressure column having a top condenser, and operating at a pressure, lower than that of said high pressure column pressure, of from about 40 to 150 psia;
- (G) separating said first oxygen-enriched vapor fraction by rectification in said medium pressure column into a second nitrogen-rich vapor fraction and a second oxygen-enriched liquid fraction;
- (H) recovering from about 20 to 60 percent of said second nitrogen-rich vapor fraction as medium pressure nitrogen gas at a pressure of from about 40 to 150 psia and a purity of at least 99 mole percent;
- (I) condensing a portion of said second nitrogen-rich vapor fraction by indirect heat exchange with said second oxygen-enriched liquid fraction thereby producing a second nitrogen-rich liquid portion and a second oxygen-enriched vapor fraction;
- (J) employing said second nitrogen-rich liquid portion as liquid reflux for said medium pressure column;
- and
- (K) removing from the process said second oxygen-enriched vapor fraction.
9 more elements
Dependencies are inferred from the claim text.