Separating carbon dioxide and ethane from a mixed stream

Patent metadata

Field	Value
Publication number	US-9964352-B2
Application number	US-201314376359-A
Country	US
Kind code	B2
Filing date	Mar 8, 2013
Priority date	Mar 21, 2012
Publication date	May 8, 2018
Grant date	May 8, 2018

Abstract

Embodiments described herein provide methods and systems for separating a mixed ethane and CO 2 . A method described includes generating a liquid stream including ethane and CO 2 . The liquid stream is flashed to form an ethane vapor stream and solid CO 2 . The solid CO 2 is accumulated in an accumulation vessel and the gas is removed from the top of the accumulation vessel.

First claim

What is claimed is:

1. A method for separating a mixed stream comprising ethane and CO 2 , comprising:
providing a mixed stream comprising ethane and CO 2 ;
generating a liquid stream comprising an azeotropic mixture of ethane and CO 2 from the mixed stream;
passing the liquid stream through a flash valve into a first accumulation vessel, forming a gas that is enhanced in ethane and forming solid CO 2 ;
accumulating the solid CO 2 in the first accumulation vessel;
heating the first accumulation vessel;
allowing the temperature and pressure to rise in the first accumulation vessel until the CO 2 melts and forms liquid CO 2 ;
removing the gas from the top of the first accumulation vessel;
condensing the gas that was removed from the top of the accumulation vessel to form a condensed gas;
stripping the condensed gas to remove a contaminated ethane stream that comprises ethane, methane, and CO 2 ;
separating methane from the contaminated ethane stream to form a remainder stream that comprises ethane and CO 2 ; and
combining the remainder stream with the liquid stream.

2. The method of claim 1 , wherein the mixed stream is provided by separating the mixed stream from a natural gas feed stream.

3. The method of claim 1 , further comprising switching to a second accumulation vessel when the first accumulation vessel is filled with solid CO 2 .

4. The method of claim 1 , wherein heating the solid CO 2 in the first accumulation vessel causes sublimation of at least a fraction of the CO 2 , removing at least a portion of hydrocarbons trapped in the solid CO 2 .

5. The method of claim 1 , further comprising
closing an inlet valve to the first accumulation vessel prior to heating of the first accumulation vessel; and
closing an outlet valve to the first accumulation vessel prior to allowing the temperature and pressure to rise in the first accumulation.

6. The method of claim 5 , comprising:
opening the outlet valve to the first accumulation vessel and draining the liquid CO 2 from the first accumulation vessel; and
providing the liquid CO 2 as a product stream.

7. The method of claim 1 , further comprising sending the methane to a separate purification unit.

8. The method of claim 1 , comprising fractionating the mixed stream to remove CO 2 and generate the azeotropic mixture comprising ethane and CO 2 .

9. The method of claim 1 , comprising fractionating the mixed ethane and CO2 stream to remove ethane and generate the azeotropic mixture comprising ethane and CO2.

10. The method of claim 1 , wherein the azeotropic mixture comprises 70% CO 2 and 30% ethane at about 600 psia.

Assignees

• Oelfke Russell H
• Exxonmobil Upstream Res Co

Inventors

• Oelfke Russell H

Classifications

• F25J3/0233

  separation of CnHm with 1 carbon atom or more · CPC title

• F25J2270/90

  External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration · CPC title

• F25J2205/20

  using solidification of components · CPC title

• F25J2280/40

  Control of freezing of components · CPC title

• B01D3/36 Primary

  Azeotropic distillation · CPC title