Patent ID: 11933541
Assignee: PRAXAIR TECHNOLOGY, INC.
Field: Chemical engineering (Chemistry)
Classification: CPC F | IPC F

Claim 10:
11. A method for operating a nitrogen and argon producing air separation unit, the air separation unit configured to receive an incoming feed air stream and produce two or more nitrogen product streams, and a crude argon stream, the air separation unit having a main air compression system, a waste expansion refrigeration circuit, a main heat exchanger, and a distillation column system having a higher pressure column and a lower pressure column linked in a heat transfer arrangement via a main condenser-reboiler, an argon column configured for receiving an argon-oxygen containing stream from the lower pressure column and an argon condenser configured for condensing an argon-rich vapor stream from the argon column against an oxygen containing condensing medium, the method comprising the steps of:
(a) directing a first portion of a boil-off stream from an argon condenser to the waste expansion refrigeration circuit;
(b) mixing or blending the first portion of the boil-off stream from the argon condenser with a liquid oxygen stream from the lower pressure column to produce an oxygen-rich feed stream and control the oxygen content of the oxygen-rich feed stream feed stream;
(c) directing the oxygen-rich feed stream to the waste expansion refrigeration circuit;
(d) recycling a second portion of the boil-off stream from the argon condenser to the main air compression system;
(e) mixing or blending the second portion of the boil-off stream from the argon condenser with the incoming feed air stream; and
wherein the argon column has less than about 200 stages of separation and the argon recovery from the air separation unit is 75% or more of the argon contained in the incoming feed air stream.