Cryogenic air separation with cold argon recycle
OwnerDonald C. Ericksoninventor
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Abstract
The invention provides an efficient means of increasing oxygen purity and recovery and also argon recovery in cryogenic distillative air separation plants. In addition, the invention makes it possible to increase the oxygen delivery pressure from high efficiency triple pressure configurations without using an oxygen vacuum compressor. These advantages are obtained by incorporating an argon recycle compressor within the cold box, which compresses argon from an argon rectifier, causes it to condense against boiling liquid oxygen from the argon stripper, and uses the condensed argon to reflux the argon rectifier. Pressurized high purity oxygen can then be obtained using a LOX pump, plus a split supply pressure configuration in which an elevated pressure rectifier gasifies the LOX.
Claims20
In a process for separating air by cryogenic distillation comprising stripping argon from a liquid oxygen stream in an argon stripper and reducing the oxygen content of a gaseous argon stream in an argon rectifier, the improvement comprising increasing the reboil rate through the argon stripper and rectifier using a compressor internal to the cold box by:
- (a) compressing gaseous argon from the argon rectifier;
- (b) condensing at least part of the compressed argon by latent heat exchange with boiling oxygen from the argon stripper;
- (c) reboiling the argon stripper with at least part of the evaporated oxygen from step (b);
- (d) refluxing the argon rectifier with at least part of the condensed argon from step (b).
In a cryogenic air separation apparatus for producing medium to high purity oxygen comprising a low pressure distillation column comprising at least an argon stripper and an argon rectifier, the improvement comprising means designed, sized, and arranged for increasing the reboil rate through the stripper and rectifier while minimizing the energy requirements, including:
- (a) an argon compressor which is internal to the cold box;
- (b) a vapor conduit from the rectifier to the compressor;
- (c) a means for vaporizing argon stripper bottom liquid by latent heat exchange with a condensing gas;
- (d) a vapor conduit from the compressor to the heat exchange means;
- (e) a liquid conduit to transport condensed argon from the heat exchange means to the argon rectifier reflux inlet.
A triple pressure distillation apparatus for air separation comprising
- a high pressure (HP) rectifier which receives at least part of the supply air;
- a medium pressure (MP) distillation column which received and further distills liquid bottom product from the HP rectifier, and which is refluxed by direct injection of liquid nitrogen;
- a conduit for removing nitrogen vapor from the MP column overhead;
- a low pressure (LP) distillation column which receives and further purifies liquid bottom product from the MP column;
- at least one means for latent heat transfer from the HP rectifier to the MP column;
- a means for latent heat transfer from the Hp rectifier to the LP column;
- a means for latent heat transfer from the Lp column to the MP column;
- means designed, sized, and arranged for increasing the reboil rate through the LP column while minimizing the energy requirement, including an argon compressor internal to the cold box.
Dependencies are inferred from the claim text.