Separation of air: improved heylandt cycle

Claim 1

A method of separating air, comprising: compressing and purifying the air; forming a first stream composed of the compressed and purified at a temperature suitable for its separation by fractional distillation; introducing the first stream into a higher pressure distillation column, the top of which is in heat exchange relationship with the bottom of a lower pressure distillation column; separating the air in the higher pressure column into oxygen-rich liquid and gaseous nitrogen fractions; condensing the gaseous nitrogen fraction and using it, at least in part, to provide reflux for the higher pressure column; withdrawing a stream of the oxygen-rich liquid fraction from the bottom of the higher pressure column and introducing it into the lower pressure column at an intermediate level thereof; separating the oxygen-rich liquid fraction into oxygen and nitrogen fractions within the lower pressure column; withdrawing product oxygen and liquid oxygen from the lower pressure column; forming a second stream composed of the compressed and purified air; pre-cooling the second stream and subjecting the pre-cooled second stream to a first Joule-Thomson expansion to form a liquid-vapor mixture at a pressure of essentially that of the higher pressure column; separating the liquid-vapor mixture into a liquid phase and a vapor phase; introducing a stream of the vapor phase into the higher-pressure column at a level above that at which the first stream enters the higher pressure column; and taking the entire liquid phase and forming it into a stream; sub-cooling the stream composed of the liquid phase and subjecting it to a second Joule-Thomson expansion and then introducing it into the lower pressure column.

Claim 2

A method of separating air, comprising: compressing and purifying the air; forming a first stream composed of the compressed and purified at a temperature suitable for its separation by fractional distillation; introducing the first stream into a higher pressure distillation column, the top of which is in heat exchange relationship with the bottom of a lower pressure distillation column; separating the air in the higher pressure column into oxygen-rich liquid and gaseous nitrogen fractions; condensing the gaseous nitrogen fraction and using it, at least in part, to provide reflux for the higher pressure column; withdrawing a stream of the oxygen-rich liquid fraction from the bottom of the higher pressure column and introducing it into the lower pressure column at an intermediate level thereof; separating the oxygen-rich liquid fraction into oxygen and nitrogen fractions within the lower pressure column; withdrawing product oxygen and liquid oxygen from the lower pressure column; forming a second stream composed of the compressed and purified air; pre-cooling the second stream and subjecting the pre-cooled second stream to a first Joule-Thomson expansion to form a liquid-vapor mixture at a pressure of essentially that of the higher pressure column; separating the liquid-vapor mixture into a liquid phase and a vapor phase; introducing a stream of the vapor phase into the higher-pressure column at a level above that at which the first stream enters the higher pressure column; and taking the entire liquid phase and forming it into a stream; sub-cooling the stream composed of the liquid phase and subjecting it to a second Joule-Thomson expansion and then introducing it into the lower pressure column.

Claim 7

An apparatus for separating air, comprising: (a) means for compressing air; (b) means for purifying the compressed air; (c) means for forming a first stream of the compressed and purified air at a temperature suitable for its separation by fractional distillation; (d) a higher pressure distillation column for separating air into oxygen-enriched liquid and gaseous nitrogen fraction; (e) the high pressure distillation column having an inlet for said first stream of compressed and purified air; (f) a lower pressure distillation column for separating the oxygen-enriched liquid, the bottom of which is in heat exchange relationship with the top of the higher pressure distillation column; (g) a condenser for condensing the said gaseous nitrogen fraction and for providing a first part of the condensed nitrogen as reflux for the higher pressure distillation column; (h) means for conducting a second part of the condensed nitrogen the lower pressure distillation column as reflux; (i) means for conducting a stream of the oxygen-rich liquid fraction from the bottom of the higher pressure distillation column and introducing it into the lower pressure distillation column at an intermediate level thereof; (j) the lower pressure distillation column having a first outlet for product gaseous oxygen and a second outlet for liquid oxygen; (k) means for forming a second stream of the compressed and purified air; (l) means for pre-cooling the second stream of the compressed and purified air; (m) a first Joule-Thomson expansion valve for reducing the pressure of the pre-cooled stream and thereby to form a liquid-vapour mixture at a pressure essentially the same as that of the operating pressure of the higher pressure column; (n) a phase separator for separating the liquid-vapour mixture into a liquid phase and a vapour phase; (o) means for introducing a stream of the vapour phase into the higher pressure distillation column at a level above that of the inlet for the said first stream of compressed and purified air to the higher pressure distillation column; (p) means for taking the entire said liquid phase as a stream and sub-cooling it; (q) a second Joule-Thomson expansion valve for reducing the pressure of said sub-cooled stream of liquid phase; and (r) means for introducing the reduced pressured stream of the sub-cooled liquid phase into the lower pressure distillation column.

Claim 8

An apparatus for separating air, comprising: (a) means for compressing air; (b) means for purifying the compressed air; (c) means for forming a first stream of the compressed and purified air at a temperature suitable for its separation by fractional distillation; (d) a higher pressure distillation column for separating air into oxygen-enriched liquid and gaseous nitrogen fraction; (e) the high pressure distillation column having an inlet for said first stream of compressed and purified air; (f) a lower pressure distillation column for separating the oxygen-enriched liquid, the bottom of which is in heat exchange relationship with the top of the higher pressure distillation column; (g) a condenser for condensing the said gaseous nitrogen fraction and for providing a first part of the condensed nitrogen as reflux for the higher pressure distillation column; (h) means for conducting a second part of the condensed nitrogen the lower pressure distillation column as reflux; (i) means for conducting a stream of the oxygen-rich liquid fraction from the bottom of the higher pressure distillation column and introducing it into the lower pressure distillation column at an intermediate level thereof; (j) the lower pressure distillation column having a first outlet for product gaseous oxygen and a second outlet for liquid oxygen; (k) means for forming a second stream of the compressed and purified air; (l) means for pre-cooling the second stream of the compressed and purified air; (m) a first Joule-Thomson expansion valve for reducing the pressure of the pre-cooled stream and thereby to form a liquid-vapour mixture at a pressure essentially the same as that of the operating pressure of the higher pressure column; (n) a phase separator for separating the liquid-vapour mixture into a liquid phase and a vapour phase; (o) means for introducing a stream of the vapour phase into the higher pressure distillation column at a level above that of the inlet for the said first stream of compressed and purified air to the higher pressure distillation column; (p) means for taking the entire said liquid phase as a stream and sub-cooling it; (q) a second Joule-Thomson expansion valve for reducing the pressure of said sub-cooled stream of liquid phase; and (r) means for introducing the reduced pressured stream of the sub-cooled liquid phase into the lower pressure distillation column.