US PATENT SUBCLASS 62 / 644
.~.~.~.~ Upstream operation

Current as of: June, 1999
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62 /   HD   REFRIGERATION

600  DF  CRYOGENIC TREATMENT OF GAS OR GAS MIXTURE {4}
617  DF  .~ Separation of gas mixture {3}
640  DF  .~.~ Air {3}
643  DF  .~.~.~ Distillation {4}
644.~.~.~.~ Upstream operation {2}
645  DF  .~.~.~.~.~> Flowline expansion engine {1}
647  DF  .~.~.~.~.~> Spaced initial charging

DEFINITION

Classification: 62/644

Upstream operation:

(under subclass 643) Subject matter wherein the feed air stream is operated on by some process prior to entering a distillation column.