Refrigeration – Processes – Circulating external gas
Patent
1991-10-30
1992-07-14
Bennet, Henry A.
Refrigeration
Processes
Circulating external gas
62 25, 62 27, 62 31, 62 34, F25J 304, F25J 302
Patent
active
051299321
ABSTRACT:
This invention relates to a cryogenic process for the separation of air utilizing an integrated multi-column distillation system wherein a nitrogen rich, oxygen rich and argon rich product are generated. In the cryogenic distillation separation of air, air is initially compressed, pretreated and cooled for separation into its components. Moderate pressure, e.g., 25-80 psia nitrogen is generated with enhanced nitrogen product purity and greater recovery of both nitrogen and argon by effecting a high boil-up rate in the bottom of the lower pressure column, thereby creating a reduced liquid flow/vapor flow ratio (L/V) and utilizing a higher than customary nitrogen reflux to the top of the lower pressure column, where the concentration of oxygen in nitrogen is less than about 10 ppm by volume or the nitrogen purity is at least about 99.5% by volume.
Refrigeration to drive the system is obtained by recovering the energy from the waste nitrogen stream and oxygen vapor from the lower pressure column.
A second method for obtaining refrigeration is to withdraw oxygen as a bottoms liquid from the lower pressure column, expanding that liquid to a lower pressure and using it to condense the nitrogen vapor generated in a higher pressure column which has been expanded in a turbo-expander to provide the refrigeration.
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Agrawal Rakesh
Woodward Donald W.
Air Products and Chemicals Inc.
Bennet Henry A.
Brewer Russell L.
Kilner Christopher B.
Marsh William F.
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