Triple distillation column nitrogen generator with plural reboiler/condensers

Claim 2

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.

Claim 3

The process of claim 1 which further comprises removing an oxygen-enriched bottoms liquid from the bottom of the low pressure column; vaporizing the removed, oxygen-enriched bottoms liquid in a reboiler/condenser located in the top of the low pressure column against condensing low pressure nitrogen overhead, thereby creating an oxygen-waste stream, and warming the oxygen-waste stream to recover refrigeration.

Claim 4

The process of claim 2 which further comprises expanding the warmed, oxygen-waste stream to produce work, and further warming the expanded oxygen-waste stream to recover any remaining refrigeration.

Claim 5

The process of claim 1 which further comprises feeding at least another portion of the condensed EHP nitrogen stream generated in step (d) to the top of the high pressure distillation column to provide additional liquid reflux.

Claim 6

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.

Claim 7

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.

Claim 8

The process of claim 5 which further comprises removing a portion of the cooled, first compressed feed air stream and expanding the removed portion to generate work.

Claim 9

The process of claim 6 which further comprises further cooling the expanded portion and feeding the further cooled expanded portion to an intermediate location of the low pressure column for distillation.

Claim 10

The process of claim 6 which further comprises warming the expanded portion to recover refrigeration and venting the warmed, expanded portion.

Claim 11

The process of claim 5 which further comprises removing an oxygen-enriched bottoms liquid from the bottom of the low pressure column; vaporizing the removed, oxygen-enriched bottoms liquid in a reboiler/condenser located in the top of the low pressure column against condensing low pressure nitrogen overhead, thereby creating an oxygen-waste stream, and warming the oxygen-waste stream to recover refrigeration.

Claim 12

The process of claim 9 which further comprises expanding the partially warmed, oxygen-waste stream to produce work, and further warming the expanded oxygen-waste stream to recover any remaining refrigeration.