US 11,933,538 B2
System and method for recovery of nitrogen, argon, and oxygen in moderate pressure cryogenic air separation unit
Brian R. Kromer, Buffalo, NY (US); and Neil M. Prosser, Lockport, NY (US)
Assigned to Praxair Technology, Inc., Danbury, CT (US)
Filed by Brian R. Kromer, Buffalo, NY (US); and Neil M. Prosser, Lockport, NY (US)
Filed on Apr. 14, 2021, as Appl. No. 17/229,919.
Claims priority of provisional application 63/022,611, filed on May 11, 2020.
Prior Publication US 2021/0348842 A1, Nov. 11, 2021
Int. Cl. F25J 3/04 (2006.01); F25J 3/02 (2006.01)
CPC F25J 3/04054 (2013.01) [F25J 3/0295 (2013.01); F25J 3/0406 (2013.01); F25J 3/04066 (2013.01); F25J 3/04072 (2013.01); F25J 3/04127 (2013.01); F25J 3/04212 (2013.01); F25J 3/04242 (2013.01); F25J 3/04454 (2013.01); F25J 2235/50 (2013.01); F25J 2260/20 (2013.01)] 8 Claims
OG exemplary drawing
 
1. A nitrogen and argon producing cryogenic air separation unit comprising:
a main air compression system configured to receive an incoming feed air stream and produce a compressed air stream;
an adsorption based pre-purifier unit configured for removing water vapor, carbon dioxide, nitrous oxide, and hydrocarbons from the compressed air stream and produce a compressed and purified air stream, wherein the compressed and purified air stream is split into at least a first part of the compressed and purified air stream and a second part of the compressed and purified air stream;
a main heat exchange system configured to cool the first part of the compressed and purified air stream and to partially cool the second part of the compressed and purified air stream;
a turboexpander arrangement configured to expand the partially cooled second part of the compressed and purified air stream to form an exhaust stream; and
a distillation column system having a higher pressure column and a lower pressure column linked in a heat transfer relationship via a condenser-reboiler and configured to separate the cooled first part of the compressed and purified air stream and a first portion of the exhaust stream and produce an oxygen enriched stream from the base of the lower pressure column and a nitrogen product stream from the overhead of the lower pressure column;
the distillation column system further includes an argon column arrangement operatively coupled with the lower pressure column, the argon column arrangement having at least one argon column and an argon condenser, and wherein the argon column arrangement is configured to receive an argon-oxygen enriched stream from the lower pressure column and to produce an oxygen enriched bottoms stream that is returned to or released into the lower pressure column and an argon-enriched overhead that is directed to the argon condenser;
wherein the argon condenser is configured to condense the argon-enriched overhead against all or a portion of the oxygen enriched stream from the lower pressure column to produce a crude argon stream or a product argon stream, an argon reflux stream and an oxygen enriched waste stream; and
a turbine air stream column bypass circuit configured for combining a second portion of the exhaust stream with the oxygen enriched waste stream such that the second portion of the exhaust stream bypasses the distillation column system.