Triple distillation column nitrogen generator with plural reboiler/condensers
AssigneeAir Products and Chemicals, Inc.
InventorRakesh Agrawal
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Abstract
The present invention is a cryogenic process for the production of nitrogen by distilling air in a double column distillation system comprising a high pressure column and a low pressure column associated functionally with an extra high pressure (EHP) distillation column for added nitrogen production. The critical step of the invention is the dual pathway condensation of nitrogen streams in two reboiler/condensers located in the stripping section of the low pressure column to provide condensed high pressure and EHP nitrogen streams that provides liquid reflux to the high pressure columns.
Claims10
A cryogenic process for the production of nitrogen by distilling air in a triple column distillation system consisting essentially of an associated discrete extra pressure column, a high pressure column and a low pressure column, comprising:
- a) dividing a compressed feed air stream into a first and second air substreams;
- b) cooling the first air substream to near its dew point and rectifying the cooled, first substream in the high pressure column, thereby producing a high pressure nitrogen overhead stream and a crude oxygen bottoms liquid;
- c) further compressing and cooling the second air substream to near its dewpoint and feeding the further compressed, cooled, second substream to the bottom section of the extra high pressure distillation column, thereby producing an extra high pressure (EHP) overhead nitrogen stream and an oxygen-rich bottoms liquid stream;
- d) condensing the EHP overhead nitrogen stream in a lowermost reboiler/condenser located in the lower portion of the stripping section of the low pressure distillation column;
- e) feeding at least a portion of the condensed EHP nitrogen stream to the top section of the extra high pressure column as liquid reflux;
- f) feeding the oxygen-rich bottom stream from the high pressure column to the middle section of the low pressure column for distillation;
- g) condensing a portion of the high pressure overhead nitrogen stream in an upper reboiler/condenser located in the middle portion of the stripping section of the low pressure column, and returning said condensed portion to the top of the high pressure column to provide liquid reflux to the high pressure column;
- h) removing the balance of the high pressure overhead nitrogen stream from the top of the high pressure column, warming this high pressure stream to recover refrigeration and recovering the warmed high pressure stream from the process as a high pressure first nitrogen product, and
- i) removing a low pressure nitrogen stream from the top of the low pressure column, warming the removed nitrogen stream to recover refrigeration and recovering the warm, low pressure stream from the process as a low pressure second nitrogen product.
A cryogenic process for the production of nitrogen by distilling air in a triple column distillation system consisting essentially of a discrete extra pressure column, a high pressure column and a low pressure column, comprising:
- a) dividing a compressed air feed stream into a first and second substream;
- b) cooling the first substream to near its dew point and dividing the cooled, first substream into a cooled third and fourth substreams;
- c) rectifying at least a portion of the cooled third substream in the high pressure distillation column, thereby producing a high pressure nitrogen overhead stream and a crude oxygen bottoms liquid;
- d) further compressing and cooling to near its dewpoint the second substream and feeding same to the bottom section of the extra high pressure distillation column, thereby producing an extra high pressure (EHP) overhead nitrogen stream and an oxygen-rich liquid bottoms stream;
- e) condensing the overhead EHP nitrogen stream in an intermediate reboiler/condenser located in the lower part of the stripping section of the low pressure column;
- f) feeding at least a portion of this condensed nitrogen stream to the top portion of the extra high pressure column;
- g) condensing the portion of the cooled fourth air substream in the bottom most reboiler/condenser located in the lower portion of the LP column;
- h) splitting the fully condensed air feed stream produced in step (g) to provide an impure reflux stream for both the high pressure and low pressure columns;
- i) removing a low pressure nitrogen stream from the top of the low pressure column, warming the removed nitrogen stream to recover refrigeration, and recovering the warmed low pressure stream from the process as a low pressure first nitrogen product;
- j) condensing a portion of the high pressure nitrogen stream from the top of the high pressure column in an uppermost reboiler/condenser located in the lower portion of the low pressure column, to produce a condensed nitrogen stream which is used to provide a liquid reflux to the top of the high pressure column;
- and
- k) removing the balance of the high pressure nitrogen stream from the top of the high pressure column, warming the high pressure nitrogen stream balance to recover refrigeration and recovering the warmed high pressure stream from the process as a high pressure second nitrogen product.
Dependencies are inferred from the claim text.