Selective olefin extraction

Patent metadata

Field	Value
Publication number	US-9409838-B2
Application number	US-201314058607-A
Country	US
Kind code	B2
Filing date	Oct 21, 2013
Priority date	Nov 7, 2012
Publication date	Aug 9, 2016
Grant date	Aug 9, 2016

Abstract

A process and system for separating butenes and butanes by extractive distillation using a polar solvent is disclosed. The process may include: contacting a hydrocarbon mixture including butanes and butenes with a lean solvent mixture in an extractive distillation column to form an enriched solvent fraction comprising butenes; recovering an overheads fraction comprising butanes and a bottoms fraction from the extractive distillation column; feeding the bottoms fraction to a stripper including a stripping section and a wash section; recovering the lean solvent mixture as a bottoms fraction and a stripper overheads fraction comprising butenes and water from the stripper; condensing the overheads fraction to form a water fraction and a product butenes fraction; feeding water as reflux to a top of the stripper wash section; feeding at least a portion of the condensed water fraction intermediate the top and bottom of the stripper wash section as a second reflux.

First claim

What is claimed:

1. A process for separating butenes and butanes by extractive distillation using a polar solvent, the process comprising:
contacting a hydrocarbon mixture comprising butanes and butenes with a lean solvent mixture comprising water and one or more polar solvents in an extractive distillation column to form an enriched solvent fraction comprising the butenes and solvent(s);
recovering an overheads fraction comprising butanes from the extractive distillation column;
recovering the enriched solvent fraction as a bottoms fraction from the extractive distillation column;
feeding the bottoms fraction to a stripper above a stripping section and below a wash section of the stripper to separate the butenes from the enriched solvent fraction;
recovering the lean solvent mixture as a bottoms fraction from the stripper;
recovering a stripper overheads fraction comprising butenes and water from the stripper;
condensing the stripper overheads fraction to form a condensed water fraction and a product butenes fraction;
feeding water as a reflux to a top of the stripper wash section;
feeding at least a portion of the condensed water fraction intermediate the top and bottom of the stripper wash section as a second reflux.

2. The process of claim 1 , wherein the hydrocarbon mixture is a vapor fraction recovered from a butadiene recovery process.

3. The process of claim 1 , further comprising vaporizing the hydrocarbon mixture in a feed vaporization system prior to the contacting.

4. The process of claim 1 , wherein the condensed water fraction used as the second reflux is a single liquid phase.

5. The process of claim 1 , wherein the condensing the stripper overheads fraction comprises condensing the stripper overheads fraction in a two-stage condensation process comprising:
partially condensing the stripper overheads fraction to condense and recover the water as the condensed water fraction and to recover a vapor fraction comprising the butenes;
condensing the vapor fraction comprising the butenes to form the product butene fraction.

6. The process of claim 1 , wherein the stripper overheads fraction comprises less than 10 ppm solvent, by weight.

7. The process of claim 1 , wherein the stripper overheads fraction comprises 5 ppm or less solvent, by weight.

8. The process of claim 1 , wherein the product butene fraction comprises less than 1 ppm solvent, by weight.

9. The process of claim 1 , further comprising:
withdrawing a liquid side draw from the stripper;
at least partially vaporizing the liquid side draw by indirect heat exchange in a first heat exchanger with the lean solvent mixture recovered as a bottoms fraction from the stripper;
returning the at least partially vaporized side draw to the stripper.

10. The process of claim 9 , further comprising:
recovering a partially cooled lean solvent mixture from the first heat exchanger;
contacting at least one of (a) the enriched solvent fraction as a bottoms fraction from the extractive distillation column and (b) one or more liquid side draws from the extractive distillation column via indirect heat exchange in a second heat exchanger with the partially cooled lean solvent mixture.

11. The process of claim 10 , wherein at least one of the first heat exchanger and the second heat exchanger is a once-thru vaporization type exchanger.

12. The process of claim 10 , further comprising contacting a partially cooled lean solvent mixture recovered from at least one of the first heat exchanger and the second heat exchanger via indirect heat exchange with the hydrocarbon mixture to at least partially vaporize the hydrocarbon mixture prior to the contacting.

Assignees

• Lummus Technology Inc

Inventors

• Schwint Kevin John
• Brummer Robert J

Classifications

• C10G21/00

  Refining of hydrocarbon oils, in the absence of hydrogen, by extraction with selective solvents (C10G17/00, C10G19/00 take precedence) · CPC title

• B01D3/40 Primary

  Extractive distillation · CPC title

• C07C9/10

  with four carbon atoms · CPC title

• B01D3/143

  by two or more of a fractionation, separation or rectification step · CPC title

• B01D3/34

  with one or more auxiliary substances · CPC title