Refrigeration – Processes – Circulating external gas
Patent
1990-12-26
1992-08-11
Capossela, Ronald C.
Refrigeration
Processes
Circulating external gas
62 44, F25J 302
Patent
active
051375591
ABSTRACT:
This invention relates to a cryogenic process for the separation of air utilizing an integrated multi-column distillation system wherein an ultra high purity nitrogen rich, oxygen rich and optionally an argon rich product are generated. In the cryogenic distillation separation of air, air is initially compressed, pretreated and cooled for separation into its components. Ultra high purity, e.g., nitrogen having less than 0.1 ppm of volatile impurities is generated with enhanced nitrogen product recovery by withdrawing liquid nitrogen from the higher pressure column at an intermediate point and charging that fraction as reflux to the lower pressure column, withdrawing a nitrogen stream which is rich in volatile contaminants from the top of the high pressure column, partially condensing the nitrogen stream and removing the uncondensed portion as a purge stream, and, withdrawing an ultra high purity nitrogen product at a point below a nitrogen vapor withdrawal point at the top of the lower pressure column. Alternatively, no purge need be taken and the volatile impurities allowed to pass to the low pressure column. In that case, a nitrogen fraction rich in volatile impurities is removed from an upper portion of the low pressure column, condensed and at least a portion of the uncondensed fraction removed as a purge and the condensed portion returned to the low pressure column.
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Air Products and Chemicals Inc.
Brewer Russell L.
Capossela Ronald C.
Marsh William F.
Simmons James C.
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