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Cryogenic rectification process and apparatus for vaporizing a pumped liquid product

  • US 5,379,598 A
  • Filed: 08/23/1993
  • Issued: 01/10/1995
  • Est. Priority Date: 08/23/1993
  • Status: Expired due to Term
First Claim
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1. A process for separating air and thereby producing a gaseous oxygen product at a delivery pressure, said process comprising:

  • compressing the air, removing heat of compression from the air, and purifying the air;

    cooling the air in a main heat exchanger;

    prior to the cooling of the air, further compressing at least a portion of the air to be cooled to form a further compressed air stream and removing heat of compression from the further compressed air stream;

    removing at least part of the further compressed air stream from the main heat exchanger at a location of the main heat exchanger at which said further compressed stream has a temperature in the vicinity of a theoretical pinch point temperature determined for the main heat exchanger, still further compressing at least a portion of said at least part of the further compressed air stream removed from the main heat exchanger to form a first subsidiary air stream, and introducing said first subsidiary air stream back into the main heat exchanger at a level thereof having a warmer temperature than said theoretical pinch point temperature;

    after reintroduction into the main heat exchanger, fully cooling said first subsidiary air stream to a temperature suitable for its rectification;

    removing part of the air to be cooled from the main heat exchanger to form a second subsidiary air stream and cooling said subsidiary air stream to a temperature suitable for its rectification without the use of the main heat exchanger;

    the second subsidiary air stream being cooled by expanding said second subsidiary air stream with the performance of expansion work;

    applying at least part of the work of expansion to the further compression of said at least portion of the at least part of the further compressed air stream removed from the main heat exchanger;

    rectifying the air in the first and second subsidiary air streams within an air separation unit configured such that liquid oxygen is produced;

    supplying refrigeration to the process to maintain energy balance of the process; and

    removing a liquid oxygen stream from the air separation unit composed essentially of the liquid oxygen, pumping the liquid oxygen stream to the delivery pressure, vaporizing said liquid oxygen stream in the main heat exchanger such that it is fully warmed to ambient temperature, and extracting said liquid oxygen stream from the main heat exchanger as the gaseous oxygen product.

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