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US 4,464,188 AGranted
Process and apparatus for the separation of air
AssigneeAir Products and Chemicals, Inc.
InventorsRakesh Agrawal, Thomas E. Cormier
Life of this patent
Estimating the term…
Abstract
A process and apparatus is set forth for the separation of air by cryogenic distillation in a rectification column using two nitrogen recycle streams and a sidestream of the feed air stream to reboil the column. One of the nitrogen recycle streams is expanded to provide refrigeration and to provide power to compress the feed air sidestream.
Claims15
A process for the separation of air by cryogenic distillation of the air in a distillation column comprising the steps of:
- (a) compressing a feed air stream to an elevated pressure and aftercooling the pressurized air stream;
- (b) removing water and carbon dioxide from the cooled pressurized air stream;
- (c) splitting the feed air stream into a sidestream and a remaining stream;
- (d) cooling the remaining stream in heat exchange against other process streams before introducing it into a distillation column;
- (e) compressing the sidestream and cooling it in heat exchange against process streams;
- (f) reboiling the distillation column with the compressed sidestream before reducing the pressure of the sidestream and introducing it into the column;
- (g) separating a nitrogen product stream and an oxygen-enriched stream from said distillation column;
- (h) condensing a portion of the nitrogen product stream against the oxygen-enriched stream and returning it to the column as reflux;
- (i) rewarming the remaining nitrogen product stream by heat exchange against process streams and compressing at least a portion of the product stream to an intermediate elevated pressure;
- (j) splitting a first nitrogen recycle stream from the compressed nitrogen product stream and cooling it against process streams;
- (k) further compressing at least a portion of the nitrogen product stream and splitting a second nitrogen recycle stream from the nitrogen product stream before expanding said second recycle stream in an expander to a lower temperature and pressure and introducing it into the first recycle stream to form a combined recycle stream;
- (l) reboiling the distillation column with said combined recycle stream before reducing it in pressure and introducing it into the column as reflux.
9 more elements
An apparatus comprising elements designed, sized and arranged for the separation of air by cryogenic distillation, including;
- (a) a compressor for compressing a feed air stream to an elevated pressure;
- (b) a drier for removing moisture and carbon dioxide from the compressed feed air stream;
- (c) heat exchange means for cooling the feed air stream against process streams;
- (d) a distillation column for rectifying the feed air stream into a nitrogen product stream and an oxygen-enriched stream;
- (e) means for separately conveying a sidestream and a remaining feed air stream through said heat exchange means and to said distillation column;
- (f) a supplemental compressor for increasing the pressure of the sidestream;
- (g) an air reboiler for reboiling the distillation column with the sidestream by heat exchange before introducing the latter into the distillation column as feed to said column;
- (h) means for removing a nitrogen product stream from said column and rewarming it by heat exchange against process streams;
- (i) a first nitrogen product compressor for increasing the pressure of at least a portion of the nitrogen product stream to an intermediate level;
- (j) means for separating and recycling a first nitrogen recycle stream to said distillation column including a recycle reboiler in which the nitrogen recycle stream reboils the column by heat exchange before being introduced into the column as reflux;
- (k) a second nitrogen product compressor for increasing the pressure of at least a portion of the nitrogen product stream to a high level;
- (l) means for separating and recycling a second nitrogen recycle stream from said nitrogen product stream to said column including an expander for reducing the temperature and pressure of said second nitrogen recycle stream.
9 more elements
A process for the separation of air by cryogenic distillation of the air in a distillation column comprising the steps of:
- (a) compressing a feed air stream to an elevated pressure and aftercooling the pressurized air stream;
- (b) removing water and carbon dioxide from the cooled pressurized air stream;
- (c) splitting the feed air stream into a sidestream and a remaining stream;
- (d) cooling the remaining stream in heat exchange against other process streams before introducing it into a distillation column;
- (e) compressing the sidestream and cooling it in heat exchange against process streams;
- (f) reboiling the distillation column with the compressed sidestream before reducing the pressure of the sidestream and introducing it into the column;
- (g) separating a nitrogen product stream and an oxygen-enriched stream from said distillation column;
- (h) condensing a portion of the nitrogen product stream against the oxygen-enriched stream and returning it to the column as reflux;
- (i) rewarming the remaining nitrogen product stream by heat exchange against process streams and compressing at least a portion of the product stream to an intermediate elevated pressure;
- (j) splitting a first nitrogen recycle stream from the compressed nitrogen product stream and cooling it against process streams;
- (k) reboiling the distillation column with said first nitrogen recycle stream before reducing it in pressure and introducing it into the column as reflux;
- (l) further compressing at least a portion of the nitrogen product stream and splitting a second nitrogen recycle from the nitrogen product stream;
- (m) expanding the second nitrogen recycle stream in an expander to lower temperature and pressure;
- (n) reboiling the distillation column with said second nitrogen recycle stream separately from said first nitrogen recycle stream before reducing it in pressure and introducing it into the column as reflux.
11 more elements
Dependencies are inferred from the claim text.