US 5,289,688 AGranted

Inter-column heat integration for multi-column distillation system

AssigneeAir Products and Chemicals, Inc.

InventorRakesh Agrawal

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Abstract

This invention relates to an improvement in a process for the separation of a multi-component stream by distillation. A multi-component feed is introduced to a multicolumn distillation system comprising a main column and a side column wherein at least a light component A is separated from a heavier component C in the main column, the lighter component A being removed as an overhead fraction and the heavier component C being removed as a bottoms fraction. The improvement for enhanced recovery of a component in the side column comprises withdrawing a liquid fraction from the main column at a point intermediate the overhead and bottoms and introducing that liquid fraction to an upper portion of the side column. Lighter components are withdrawn from the side column and returned to an optimal location in the distillation system, typically the main column. Reboiling in the side column is effected by removing a portion of the liquid typically from the bottom of this column and vaporizing this fraction against a vapor fraction obtained from the main column. At least a portion of the vapor fraction from the main column is condensed and liquid is returned to an optimal point in the main column distillation system. The vapor fraction withdrawn from the main column and used to vaporize the bottoms of the side column is withdrawn at a point below the liquid removal point for the liquid feed to the side column.

Claims9

Dependent claims

In a process for separation of a multi-component stream comprising at least one volatile component A and at least one component of lower volatility C, said multi-component stream contaminated with impurities I having a volatility greater than component A wherein said multi-component stream is introduced to a multi-column distillation system incorporating a side column having a reboiler associated therewith, said side column effecting separation and recovery of at least one component in said multi-component stream, the improvement which comprises:

(a) introducing said multi-component stream to a first column wherein a first column overhead fraction enriched in component A and a first column bottoms fraction enriched in component C is obtained;
(b) withdrawing a first column liquid fraction containing A contaminated with impurities I from said first column at a point intermediate said first column overhead fraction and an introduction point of said multi-component stream to said first column;
(c) introducing said first column liquid fraction to an upper portion of said side column and recovering component A contaminated with impurities I as a first side column overhead fraction and recovering A of high purity as a first side column bottoms fraction;
(d) withdrawing from said side column a first side column liquid fraction for vaporizing at least a portion thereof in a boiler/condenser;
(e) withdrawing a first column vapor fraction from said first column at a point intermediate the introduction point of said multicomponent stream to said first column and a withdrawal point of said first column liquid fraction and condensing at least a portion of said first column vapor fraction against said first side column liquid fraction in said boiler/condenser as set forth in step (d);
(f) recovering and returning at least a portion of resulting vaporized first side column liquid fraction to said side column;
and
(g) recovering and utilizing at least a portion of resulting condensed first column vapor fraction obtained in step (e) as reflux in said multi-column distillation system.

5 more elements

In a process for separation of a multi-component stream comprising at least one volatile component A and at least one component of lower volatility C and a component B having a volatility intermediate that of A and C wherein said multi-component stream is introduced to a multi-column distillation system incorporating a side column having a reboiler associated therewith, said side column effecting separation and recovery of at least one component in said multi-component stream, in improvement which comprises:

(a) introducing said multi-component stream to a first column wherein a first column overhead fraction enriched in component A and a first column bottoms fraction enriched in component C is obtained;
(b) withdrawing a first column liquid fraction from said first column containing components A and B at a point intermediate said first column overhead fraction and an introduction point of said multi-component stream to said first column;
(c) introducing said first column liquid fraction to an upper portion of said side column, removing A as a first side column overhead fraction and recovering B as a first side column bottoms fraction;
(d) withdrawing a first side column liquid fraction from said side column for vaporizing at least a portion thereof in a boiler/condenser;
(e) withdrawing a first column vapor fraction from said first column at a point intermediate the introduction point of said multicomponent stream to said first column and a withdrawal point of said first column liquid fraction and condensing at least a portion of said first column vapor fraction against said first side column liquid fraction in said boiler/condenser as set forth in step (d);
(f) removing and returning at least a portion of a resulting vaporized first side column liquid fraction to said side column;
and,
(g) recovering and utilizing at least a portion of a resulting condensed first column vapor fraction obtained in step (e) for reflux in said multi-column distillation system.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/793,032Filed 15 Nov 1991
Granted: 1 Mar 1994
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

B01D 3/146
By two or more of a fractionation, separation or rectification step: multiple effect distillation
F25J 3/04309
Using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched streams: of nitrogen
F25J 3/04412
Using a dual pressure main column system: in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the…
F25J 2200/34
Processes or apparatus using separation by rectification: using a side column fed by a stream from the low pressure column