Air separation with argon recovery
AssigneeLinde Aktiengesellschaft
InventorDietrich Rottmann
Life of this patent
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Abstract
An air separation system is provided comprising a double rectification column associated with a raw argon column, the latter being operated at a pressure substantially lower than the low-pressure part of the double column. A coupled turbine-compressor system is used: (a) to lower the pressure of the argon-containing gas entering a raw argon column from the low-pressure column; and (b) to compress evaporated liquid stemming from the high-pressure column which has been used to indirectly condense raw argon product at the top of the raw argon column. Also, a pump is employed to remove liquid from the bottom of the raw argon column and recycle it to the low-pressure column.
Claims28
In a process of air separation by rectification, wherein air is compressed, prepurified, cooled and preseparated in a high-pressure stage of a two-stage rectification into a nitrogen-rich fraction and an oxygen-rich liquid, both fractions are fed at least partially to a low-pressure stage of said two-stage rectification and separated into oxygen and nitrogen, and an argon-containing oxygen stream is removed from said low-pressure stage and fed to a raw argon rectification stage wherein said argon-containing oxygen stream is subjected to rectification, the improvement which comprises conducting said raw argon rectification stage at a pressure lower than the pressure of said low-pressure stage and said argon-containing oxygen stream is work-expanded before being introduced into said raw argon rectification stage.
Apparatus suitable for separating air into oxygen, nitrogen and argon, comprising:
- a double rectification column comprising a high-pressure stage and a low-pressure stage;
- a raw argon rectification column
- first and second conduit means communicating said low-pressure stage with said raw argon rectification column;
- and
- work expansion means incorporated in said first conduit means.
In a process of air separation by rectification, wherein air is compressed, prepurified, cooled and preseparated in a high-pressure stage of a two-stage rectification into a nitrogen-rich fraction and an oxygen-rich liquid, both fractions are fed at least partially to a low-pressure stage of said two-stage rectification and separated into oxygen and nitrogen, and an argon-containing oxygen stream is removed from said low-pressure stage and fed to a raw argon rectification stage wherein said argon-containing oxygen stream is subjected to rectification, the improvement which comprises:
- conducting said raw argon rectification stage at a pressure lower than the pressure of the low-pressure stage;
- subjecting at least a portion of said oxygen-rich liquid from said high-pressure stage to indirect heat exchange with a gaseous head fraction from the head of said raw argon rectification column, whereby said oxygen-rich liquid is at least partially evaporated to form a liquid fraction and an evaporated gaseous fraction;
- and
- compressing said evaporated gaseous fraction before introduction thereof into said low-pressure stage.
In a process of air separation by rectification, wherein air is compressed, prepurified, cooled and preseparated in a high-pressure stage of a two-stage rectification into a nitrogen-rich fraction and an oxygen-rich liquid, both fractions are fed at least partially to a low-pressure stage of said two-stage rectification and separated into oxygen and nitrogen, and an argon-containing oxygen stream is removed from said low-pressure stage and fed to a raw argon rectification stage wherein said argon-containing oxygen stream is subjected to rectification, the improvement which comprises:
- conducting said raw argon rectification stage at a pressure lower than the pressure of said low-pressure stage;
- and
- removing a residual liquid fraction from the bottom of said raw argon rectification stage, increasing the pressure of said residual liquid fraction to the pressure of said low-pressure stage, and introducing said residual liquid fraction into said low-pressure stage.
In a process of air separation by rectification, wherein air is compressed, prepurified, cooled and preseparated in a high-pressure stage of a two-stage rectification into a nitrogen-rich fraction and an oxygen-rich liquid, both fractions are fed at least partially to a low-pressure stage of said two-stage rectification and separated into oxygen and nitrogen, and an argon-containing oxygen stream is removed from said low-pressure stage and fed to a raw argon rectification stage wherein said argon-containing oxygen stream is subjected to rectification, the improvement which comprises:
- conducting said raw argon rectification stage at a pressure lower than the pressure of said low-pressure stage;
- subjecting at least a portion of said oxygen-rich liquid to indirect heat exchange with a gaseous head fraction from said raw argon rectification stage to form a liquid fraction and an evaporated gaseous fraction;
- subjecting said argon-containing oxygen stream to work expansion before being introduced into said raw argon rectification stage;
- and
- compressing said evaporated gaseous fraction, wherein at least a portion of the energy used for compression of said evaporated gaseous fraction is obtained by said work expansion of said argon-containing oxygen stream.
In a process of air separation by rectification, wherein air is compressed, prepurified, cooled and preseparated in a high-pressure stage of a two-stage rectification into a nitrogen-rich fraction and an oxygen-rich liquid, both fractions are fed at least partially to a low-pressure stage of said two-stage rectification and separated into oxygen and nitrogen, and an argon-containing oxygen stream is removed from said low-pressure stage and fed to a raw argon rectification stage wherein said argon-containing oxygen stream is subjected to rectification, the improvement which comprises:
- conducting said raw argon rectification stage at a pressure which is at least 0.5 bar lower than the pressure of said low-pressure stage, and
- recovering a crude argon product stream from said raw argon rectification stage.
Dependencies are inferred from the claim text.