US 12,352,496 B2
Air separation unit and method for cryogenic separation of air using a distillation column system including an intermediate pressure kettle column
Neil M. Prosser, Lockport, NY (US)
Assigned to Praxair Technology, Inc., Danbury, CT (US)
Filed by Neil M. Prosser, Lockport, NY (US)
Filed on Jul. 28, 2022, as Appl. No. 17/875,687.
Prior Publication US 2024/0035740 A1, Feb. 1, 2024
Int. Cl. F25J 3/00 (2006.01); F25J 3/04 (2006.01)
CPC F25J 3/0409 (2013.01) [F25J 3/04212 (2013.01); F25J 3/0423 (2013.01); F25J 3/04412 (2013.01); F25J 3/04672 (2013.01); F25J 3/04727 (2013.01); F25J 3/0486 (2013.01); F25J 2200/20 (2013.01); F25J 2230/40 (2013.01)] 21 Claims
OG exemplary drawing
 
1. An air separation unit for production of product streams from a source of purified, compressed feed air, the air separation unit comprising:
a higher pressure column configured to receive one or more streams of compressed, purified air and a first reflux stream and yield a nitrogen-rich overhead and a kettle liquid;
a lower pressure column configured to receive a diverted liquid air stream and a second reflux stream and yield a low pressure product grade nitrogen overhead, an oxygen liquid at the bottom of the column, and an argon-oxygen contain side stream;
a main condenser-reboiler disposed in the lower pressure column and configured for thermally coupling the higher pressure column and the lower pressure column by liquefying at least a portion of the nitrogen-rich overhead from the higher pressure column against the oxygen liquid at the bottom of the lower pressure column to yield the first reflux stream and the second reflux stream;
an intermediate pressure kettle column configured to receive the kettle liquid from the higher pressure column and yield an oxygen-rich bottoms and a nitrogen rich overhead;
a once-through kettle column reboiler disposed in the intermediate pressure kettle column and configured to boil a portion of the descending liquid in the intermediate pressure kettle column against a first part of the argon-oxygen side stream to yield an ascending vapor stream in the intermediate pressure kettle column and an argon-oxygen liquid stream that is returned to an intermediate location of the lower pressure column;
a once-through kettle column condenser configured to condense all or a portion of the nitrogen rich overhead of the kettle column against a portion of the oxygen-rich bottoms of the intermediate pressure kettle column; and
an argon column arrangement comprising one or more argon columns and a once-through argon condenser;
wherein at least one of the one or more argon columns is configured to receive a second part of the argon-oxygen side stream from the lower pressure column and yield an argon-rich overhead and an oxygen-rich bottoms that is returned to the intermediate location of the lower pressure column;
wherein the once-through argon condenser is disposed within the lower pressure column at a location above the intermediate location of the lower pressure column and the argon-rich overhead is condensed against a portion of the descending liquid in the lower pressure column and/or a diverted portion of the liquid air stream to produce a crude argon stream; and
wherein the oxygen-rich kettle column bottoms of the intermediate pressure kettle column is not directly returned to the lower pressure column or the argon condenser.