Optimized intermediate height reflux for multipressure air distillation
OwnerDonald C. Ericksoninventor
Life of this patent
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Abstract
The invention discloses process and apparatus for separating high purity oxygen and crude argon from air by fractional distillation. The improvement, which applies to both dual pressure and triple pressure configurations, entails maximizing the distillation efficiency of both the HP rectifier (2 of FIG. 1) and the LP N.sub.2 rectifier (1a and 1b) by feeding precisely correct quantities of liquid air reflux to each via respective valves (6) and (8). In order to efficiently produce the required amount of liquid air, liquid oxygen at least 0.2 ATA above LP column pressure is evaporated by two air condensers: a total condenser (22) and a partial condenser (23).
Claims22
A process for the fractional distillation of a supply of compressed and cleaned air to high purity oxygen and crude argon comprising:
- (a) distilling an oxygen-argon mixture to liquid oxygen bottom product and crude argon overhead product in an argon-oxygen distillation column comprised of an argon stripper and an argon rectifier;
- (b) pressurizing said liquid oxygen bottom product to at least about 0.2 ATA above argon stripper bottom pressure;
- (c) evaporating at least part of said pressurized liquid oxygen by exchanging latent heat in a first oxygen evaporator with a major fraction of said supply air which is partially condensed thereby;
- (d) withdrawing at least part of said evaporated oxygen as product;
- (e) supplying at least the uncondensed fraction of the air from said first oxygen evaporator to a high pressure (HP) rectifier, and rectifying it therein to N.sub.2 overhead product and oxygen-enriched bottom product;
- (f) refluxing the overhead of said HP rectifier and reboiling the bottom of said argon stripper by exchanging latent heat;
- (g) refluxing the overhead of a nitrogen (N.sub.2) removal column for distilling said HP rectifier bottom product to oxygen-argon mixture, at least part of which is supplied to said distilling step a), by supplying it with depressurized liquid N.sub.2 from the overhead of said HP rectifier;
- (h) evaporating additional liquid oxygen in a second oxygen evaporator by exchanging latent heat with about 10 to 20% of said supply air and thereby producing liquid air;
- and
- (i) splitting said liquid air into respective intermediate height reflux streams for both said HP rectifier and said N.sub.2 removal column.
A process for the cryogenic distillative separation of a supply of compressed and cleaned air into at least high purity oxygen comprising:
- (a) stripping argon from a liquid oxygen-argon mixture in at least one argon stripper operating near atmospheric pressure;
- (b) evaporating the liquid oxygen bottom product from said at least one argon stripper by exchanging latent heat with three different condensing gases:
- (i) about 10 to 20 percent of the supply air which is essentially totally condensed thereby;
- (ii) at least the majority of the remaining supply air which is partially condensed thereby;
- and
- (iii) nitrogen from the overhead of a high pressure rectifier;
- (c) supplying at least the uncondensed portion of said partially condensed supply air to said HP rectifier, and rectifying it into said overhead nitrogen and a oxygen-enriched bottom liquid;
- (d) distilling said bottom liquid into said oxygen-argon mixture and low pressure nitrogen in a low pressure nitrogen removal column;
- and
- (e) supplying approximately half of the liquid air from step (b)(i) to an intermediate reflux height of said HP rectifier and essentially all of the remainder to an intermediate reflux height of said low pressure nitrogen removal column.
Apparatus designed, adapted, and dimensioned for cryogenic distillative separation of cleaned and compressed supply air into at least high purity oxygen comprising:
- (a) a high pressure rectifier;
- (b) a nitrogen removal column which incorporates an argon-oxygen stripper at the bottom;
- (c) a first latent heat exchanger for evaporating liquid oxygen, said first latent heat exchanger designed to receive and essentially totally condense between about 10 to 20% of said supply air;
- (d) a means for splitting the liquid air from said first latent heat exchanger into two streams for respective supply to intermediate reflux heights of said HP rectifier and said N.sub.2 removal column;
- (e) a second latent heat exchanger for evaporating liquid oxygen obtained at least partly from said argon stripper by exchanging latent heat with a major fraction of said supply air which is partially condensed thereby;
- (f) a means for routing at least the uncondensed portion of the air leaving said second latent heat exchanger to said HP rectifier;
- and
- (g) a means for supplying depressurized liquid nitrogen separation product from said HP rectifier to said N.sub.2 removal column as overhead reflux therefor.
Process for distillative separation of a supply of compressed and cleaned air into high purity oxygen and crude argon comprising:
- (a) rectifying at least the uncondensed portion of at least a major fraction of said supply air to N.sub.2 overhead product and bottom liquid;
- (b) reboiling an argon-oxygen stripper which is connected to an argon-oxygen rectifier by exchanging latent heat with HP rectifier overhead N.sub.2 ;
- (c) refluxing the overhead of said argon-oxygen rectifier by exchanging latent heat with at least part of the depressurized HP rectifier bottom liquid;
- (d) refluxing an intermediate height of said argon-oxygen rectifier by exchanging latent heat with an unevaporated portion of the liquid withdrawn from said overhead refluxing step;
- and
- (e) separately feeding at least the vapor components produced by said overhead and intermediate reflux condensers to different heights of a N.sub.2 removal column.
Apparatus for fractional distillation of a supply of compressed and cleaned air to high purity oxygen and crude argon comprising:
- (a) a high pressure rectifier;
- (b) an argon distillation column comprised of an argon stripper and an argon rectifier;
- (c) a reboiler/reflux condenser for exchanging latent heat between said HP rectifier overhead N.sub.2 and argon stripper bottom liquid oxygen;
- (d) an overhead reflux condenser for said argon rectifier which is supplied depressurized HP rectifier bottom liquid for partial evaporation therein;
- and
- (e) an intermediate height reflux condenser for said argon rectifier which is supplied at least part of the unevaporated liquid from said overhead reflux condenser.
Dependencies are inferred from the claim text.