Rectifier liquid generated intermediate reflux for subambient cascades
OwnerDonald C. Ericksoninventor
Life of this patent
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Abstract
The invention discloses process and apparatus for increasing the efficiency of subambient cascaded .fractional distillations such as air separation, ethane-ethylene separation, or nitrogen rejection from natural gas. The improvement provides an advantageous means of generating the optimal amount of intermediate reflux liquid for both rectifications in the cascade. Referring to FIG. 4, a latent heat exchanger (415) is provided in which a liquid from the HP rectifying section (403) of the cascade exchanges latent heat with a minor fraction of the feed gas. The condensed feed is then split by two valves (409 and 410) into respective intermediate reflux streams for both parts of the cascade (402 and 403).
Claims40
In a process for the subambient temperature fractional distillation of a fluid mixture comprising rectifying at least part of the feed at high pressure, distilling the rectified feed at a lower pressure, reboiling said distilling step by exchanging latent heat with vapor from said rectifiying step, and refluxing said distilling step with depressurized liquid from said latent heat exchanging step, the improvement comprising:
- (a) essentially totally condensing a minor fraction of the feed, which is preferably at a pressure at least as high as the pressure of said rectifying step, by exchanging latent heat with a liquid from said rectifying step;
- (b) splitting the condensed feed into at least two streams;
- and
- (c) intermediate refluxing said high pressure rectifying step with one of said streams and said low pressure distilling step with another.
In an apparatus for the subambient temperature fractional distillation of a fluid feed mixture comprising a high pressure (HP) rectifying section, and a low pressure (LP) distillation column including a reboiler for exchanging latent heat with HP rectifying section overhead vapor and for providing overhead reflux liquid to both said HP rectifying section and said LP distillation column, the improvement comprising:
- (a) a means for essentially totally condensing a minor fraction of said feed mixture by exchanging latent heat with a liquid from said HP rectifying section;
- (b) a means for splitting the condensed feed into at least two streams;
- and
- (c) a means for routing one of said strams to an intermediate reflux height of said HP rectifying section, and another to an intermediate reflux height of said LP distillation column.
A process for fractionally distilling a supply of compressed and cleaned air to product oxygen and co-product nitrogen comprising:
- (a) rectifying a major fraction of said supply air to liquid nitrogen (LIN) overhead product and oxygen-enriched liquid bottom product in a high pressure rectifier;
- (b) evaporating part of said LIN by exchanging latent heat with a minor fraction of said supply air, which is essentially totally condensed thereby;
- (c) distilling said bottom product in a N.sub.2 removal column;
- and
- (d) refluxing intermediate heights of said HP rectifier and said N.sub.2 removal column with the liquid air from step (b).
An apparatus for producing oxygen and nitrogen by fractional distillation of a supply of compressed and cleaed air comprising:
- (a) a high pressure (HP) rectifier;
- (b) a low pressure column including a reboiler/reflux condenser for exchanging latent heat between HP rectifier vapor and LP column liquid;
- (c) an evaporator for evaporating part of the overhead product liquid nitrogen (LIN) from said HP rectifier by exchanging latent heat with a minor fraction of said supply air;
- and
- (d) a means for withdrawing liquid air from said evaporator and splitting it into separate intermediate height reflux streams for said HP rectifier and said LP column.
A process for the subambient fractional distillation of a supply of pressurized feed gas mixture comprising:
- (a) providing at least one high pressure (HP) fractionating column comprised of at least one rectifying section, at least one stripping section, a reboiler, and at least one reflux condenser;
- (b) providing at least one low pressure (LP) distillation column which receives enriched feed mixture from said HP column;
- (c) increasing the pressure of a minor fraction of the supply mixture;
- (d) essentially totally condensing said increased-pressure fraction in said reboiler;
- and
- (e) splitting the condensed feed into at least two intermediate reflux streams, one for said HP column and another for said LP column.
Dependencies are inferred from the claim text.