Refrigeration – Cryogenic treatment of gas or gas mixture – Separation of gas mixture
Reexamination Certificate
2000-02-16
2001-04-10
McDermott, Corrine (Department: 3744)
Refrigeration
Cryogenic treatment of gas or gas mixture
Separation of gas mixture
Reexamination Certificate
active
06212906
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to air separation for the production of lower purity products wherein a column is not employed.
BACKGROUND ART
Oxygen-enriched air is widely used in a number of applications such as in furnace operations and chemical oxidation processes. While lower purity oxygen may be produced with a system using distillation columns, such systems are generally not economical for producing oxygen-enriched air. Oxygen-enriched air may be produced with a system employing reflux condensers, and it is desirable to produce oxygen-enriched air with a reflux condenser system with improved efficiency over known such systems.
Accordingly, it is an object of this invention to provide a reflux condenser system for producing oxygen-enriched air which operates with improved efficiency compared to conventional reflux condenser systems.
Often it is desirable to also produce lower purity nitrogen in addition to oxygen-enriched air in the production facility so as to use the lower purity nitrogen for inerting, drying or blanketing at the same location where the oxygen-enriched air is used.
Accordingly, it is a further object of this invention to provide a reflux condenser system for producing oxygen-enriched air which operates with improved efficiency compared to conventional reflux condenser systems and which can also effectively produce lower purity nitrogen.
SUMMARY OF THE INVENTION
The above and other objects, which will become apparent to those skilled in the art upon a reading of this disclosure, are attained by the present invention, one aspect of which is:
A method for producing oxygen-enriched air comprising:
(A) dividing feed air into a first portion comprising from 25 to 45 percent of the feed air and into a second portion comprising from 55 to 75 percent of the feed air;
(B) passing the first portion of the feed air through a first regenerator wherein said first portion is cooled and cleaned of high boiling impurities, and passing the second portion of the feed air through a second regenerator wherein said second portion is cooled and cleaned of high boiling impurities;
(C) passing the cooled and cleaned first and second portions of the feed air into and up the condensing side of a reflux condenser having a condensing side and a vaporizing side and condensing a portion of said upwardly flowing feed air to form a first vapor portion and a first liquid portion;
(D) passing the first liquid portion into and down the vaporizing side of the reflux condenser and vaporizing a portion of said downwardly flowing first liquid portion to form a second vapor portion and a second liquid portion; and
(E) vaporizing said second liquid portion and recovering the resulting vaporized second liquid portion as product oxygen-enriched air.
Another aspect of the invention is:
Apparatus for producing oxygen-enriched air comprising:
(A) at least two first regenerators, at least two second regenerators, means for providing feed air to the first regenerators, and means for providing feed air to the second regenerators;
(B) a primary heat exchanger, means for passing feed air from the first regenerators to the primary heat exchanger, and means for passing feed air from the second regenerators to the primary heat exchanger;
(C) a reflux condenser having a vaporizing side and a condensing side, means for passing feed air from the primary heat exchanger into the condensing side of the reflux condenser, and means for passing fluid from the condensing side of the reflux condenser into the vaporizing side of the reflux condenser;
(D) means for passing fluid from the condensing side of the reflux condenser to the primary heat exchanger and from the primary heat exchanger to the second regenerators; and
(E) means for passing fluid from the vaporizing side of the reflux condenser to the primary heat exchanger and from the primary heat exchanger to the first regenerators, and means for recovering product oxygen-enriched air from the first regenerators.
As used herein, the term “feed air” means a mixture comprising primarily nitrogen and oxygen, such as ambient air.
As used herein, the terms “turboexpansion” and “turboexpander” mean respectively method and apparatus for the flow of high pressure gas through a turbine to reduce the pressure and the temperature of the gas.
As used herein, the term “indirect heat exchange” means the bringing of two fluids into heat exchange relation without any physical contact or intermixing of the fluids with each other.
As used herein, the term “regenerator” means a reversible periodic heat exchanger through which gases flow in an alternating fashion and in which heat in transit is temporarily stored in a packing material of high thermal capacity.
As used herein, the term “reflux condenser” means a heat exchange device containing a plurality of vertically oriented finned tubes or passages for the flow of vapor from the bottom to the top of the tubes or passages, collectively termed the condensing side of the reflux condenser, and a plurality of vertically oriented finned tubes or passages for the flow of liquid from the top to the bottom of the tubes or passages, collectively termed the vaporizing side of the reflux condenser. Each condensing tube or passage is in heat exchange relationship with at least one vaporizing tube or passage such that the vapor rising through the condensing tubes or passages is partially condensed by indirect heat exchange with the liquid flowing down the vaporizing tubes or passages which is partially vaporized.
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Bergman, Jr. Thomas John
Billingham John Fredric
Lau Andrew Chun-Pong
Nguyen Tu Cam
Drake Malik N.
Ktorides Stanley
McDermott Corrine
Praxair Technology Inc.
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