Cryogenic triple-pressure air separation with LP-to-MP latent-heat-exchange
OwnerDonald C. Ericksoninventor
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Abstract
This invention makes possible a substantial improvement in the distillation column efficiencies of a cryogenic air separation process while still retaining high reboil rates through the argon stripping section of the low pressure column. Those advantages result in a lower energy requirement for separating air while still yielding medium to high oxygen purity. In a triple pressure column arrangement, the medium pressure column efficiency is increased by reboiling it at two or more locations by latent heat exchange with both the high pressure and low pressure columns. The LP column vapor which reboils the MP column is taken from above at least part of the argon stripper, to maintain a high reboil rate through the stripper.
Claims21
A process for producing oxygen of at least about 96% purity comprising
- (a) feeding at least part of a supply of moisture and CO.sub.2 free air to a high pressure (HP) rectification column;
- (b) feeding at least part of the oxygen enriched liquid bottom product from the HP column to a medium pressure (MP) column;
- (c) feeding substantially all of the further oxygen enriched liquid bottom product from the MP column to a low pressure (LP) column comprised of an argon stripping section and at least one rectification section;
- (d) reboiling both the MP and LP columns by latent heat exchange with HP column vapor;
- (e) exchanging latent heat between vapor from an intermediate height of the LP column and liquid from an intermediate height of the MP column, and returning reflux to the LP column and reboil to the MP column;
- (f) withdrawing gaseous N.sub.2 from the MP column overhead
- (g) withdrawing oxygen of said purity from the bottom of said LP column.
An apparatus comprising:
- means designed for separating from air, oxygen of at least 96% purity by cryogenic distillation including a high pressure rectification column;
- a medium pressure distillation column which is reboiled in part by the HP column;
- a low pressure distillation column comprising rectifier and argon stripper which is reboiled by the HP column;
- a reboiler/reflux condenser which exchanges latent heat between LP column intermediate height vapor and MP column intermediate height liquid;
- and means for withdrawing oxygen of said purity from the bottom of said LP column And a conduit for withdrawal of gaseous N.sub.2 from the MP column overhead.
In a process for producing oxygen of at least 96% purity in a triple pressure distillation apparatus comprised of a high pressure column, medium pressure column, and low pressure column comprised of an argon stripping section and at least one rectification section, the improvement comprising:
- providing intermediate reflux to the LP column and intermediate reboil to the MP column by indirect exchange of latent heat from LP column intermediate height vapor to MP column intermediate height liquid;
- reboiling both the MP and LP columns by latent heat exchange with HP column vapor;
- transporting substantially all the MP column bottom liquid to the LP column for further purification;
- withdrawing gaseous overhead nitrogen from the MP column;
- and withdrawing oxygen of said purity from the bottom of said LP column.
Dependencies are inferred from the claim text.