Methods of selectively separating CO2 from a multicomponent gaseous stream using CO2 hydrate promoters

• US 6,352,576 B1
• Filed: 03/30/2000
• Issued: 03/05/2002
• Est. Priority Date: 03/30/2000
• Status: Expired due to Fees

• Current Assignee: Los Alamos National Security LLC (Government of the United States of America)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Spencer, Dwain F., Currier, Robert P.
• Primary Examiner(s): Smith, Duane
• Assistant Examiner(s): Greene, Jason M.
• Application Number:
  US09/538,704
• Time in Patent Office: 705 Days
• Field of Search: 951/49, 952/36, 952/37, 951/53, 962/43, 423/220, 423/437.1, 62/531, 588/250, 585/15, 481/983, 481/273, 481/275, 481/97.FM
• US Class Current: 95/236
• CPC Class Codes: B01D 53/1475 Removing carbon dioxide
• CPC Class Codes: C10K 1/101 with water only
• CPC Class Codes: Y02C 20/40 of CO2
• CPC Class Codes: Y02P 20/151 Reduction of greenhouse gas [GHG] emissions, e.g. CO2

Abstract

Methods are provided for the selective removal of CO₂ from a multicomponent gaseous stream to provide a CO₂ depleted gaseous stream having at least a reduction, e.g. 30 to 90%, in the concentration of CO₂ relative to the untreated multicomponent gaseous stream. In practicing the subject methods, the multicomponent gaseous stream is contacted with an aqueous fluid, e.g. CO₂ nucleated water, under conditions of selective CO₂ clathrate formation to produce a CO₂ clathrate slurry and CO₂ depleted gaseous stream. A feature of the subject invention is that a CO₂ hydrate promoter is employed, where the CO₂ hydrate promoter is included in the multicomponent gaseous stream and/or the aqueous fluid. The CO₂ hydrate promoter serves to reduce the minimum CO₂ partial pressure required for hydrate formation as compared to a control. The subject methods find use in a variety of applications where it is desired to selectively remove CO₂ from a multicomponent gaseous stream.

Claims

1. A method for removing CO₂ from a multicomponent gaseous stream to produce a CO₂ depleted gaseous stream, said method comprising:

(a) providing a multicomponent gaseous stream;

(b) contacting said multicomponent gaseous stream with an aqueous fluid under conditions sufficient to produce CO₂ hydrates, whereby CO₂ is removed from said gaseous stream by said aqueous fluid and concomitantly fixed as CO₂ clathrates upon said contacting to produce a CO₂ depleted gaseous stream and a CO₂ clathrate slurry; and

(c) separating said CO₂ depleted gaseous stream from said CO₂ clathrate slurry;

with the proviso that said method further comprises reducing the CO₂ partial pressure requirement of hydrate formation as compared to a control by providing a sufficient amount of a CO₂ hydrate promoter in at least one of said multicomponent gaseous stream and said aqueous fluid;

whereby CO₂ is removed from a multicomponent gaseous stream.

2. The method according to claim 1, wherein said conditions sufficient to produce CO₂ hydrates comprise a temperature of about −

1.5 to 10°

C.

3. The method according to claim 1, wherein said aqueous fluid is CO₂ nucleated water.

4. The method according to claim 1, wherein a CO₂ hydrate promoter is present in both said multicomponent gaseous stream and said aqueous fluid.

5. A method for removing CO₂ from a multicomponent gaseous stream to produce a CO₂ depleted gaseous stream, said method comprising:

(a) providing a multicomponent gaseous stream;

(b) contacting said multicomponent gaseous stream with CO₂ nucleated water under conditions sufficient to produce CO₂ hydrates, whereby CO₂ is removed from said gaseous stream and concomitantly fixed as CO₂ clathrates upon said contacting to produce a CO₂ depleted gaseous stream and a CO₂ clathrate slurry; and

(c) separating said CO₂ depleted gaseous stream from said CO₂ clathrate slurry;

with the proviso that said method further comprises reducing the CO₂ partial pressure requirement of hydrate formation as compared to a control by providing a sufficient amount of a CO₂ hydrate promoter in at least one of said gaseous stream and said nucleated water, wherein said CO₂ hydrate promoter is present in an amount sufficient to reduce the CO₂ partial pressure requirement of hydrate formation at 0°

C. as compared to a control;

whereby CO₂ is removed from a multicomponent gaseous stream.

6. The method according to claim 5, wherein said CO₂ partial pressure requirement of hydrate formation in the presence of said CO₂ hydrate promoter does not exceed about 9 atm.

7. The method according to claim 5, wherein said CO₂ hydrate promoter is a low molecular weight compound not exceeding about 350 daltons.

8. The method according to claim 7, wherein said low molecular weight compound is a halogenated hydrocarbon.

9. The method according to claim 7, wherein said low molecular weight compound is a sulfur containing compound.

10. The method according to claim 7, wherein said low molecular weight compound is an organic salt.

11. The method according to claim 5, wherein said contacting occurs at a temperature ranging from about 0.5 to 3°

C.

12. The method according to claim 5, wherein said contacting occurs at a system pressure ranging from about 3 to 200 atm.

13. A method for removing CO₂ from a multicomponent gaseous stream to produce a CO₂ depleted gaseous stream, said method comprising:

(a) providing a multicomponent gaseous stream comprising a gaseous CO₂ hydrate promoter that reduces the CO₂ partial pressure requirement of hydrate formation as compared to a control, wherein said gaseous CO₂ hydrate promoter is a compound that has a vapor pressure ranging from about 0.1 to 1 atm at its hydrate formation temperature, wherein said CO₂ hydrate promoter is present in an amount sufficient to provide for CO₂ hydrate formation at a CO₂ partial pressure of less than about 9 atm at about 0°

C.;

(b) contacting said multicomponent gaseous stream with CO₂ nucleated water under conditions sufficient to produce CO₂ hydrates, whereby CO₂ is removed from said gaseous stream and concomitantly fixed as CO₂ clathrates upon said contacting to produce a CO₂ depleted gaseous stream and a CO₂ clathrate slurry, wherein said CO₂ nucleated water optionally contains a CO₂ hydrate promoter; and

(c) separating said CO₂ depleted gaseous stream from said CO₂ clathrate slurry;

whereby CO₂ is removed from a multicomponent gaseous stream.

14. The method according to claim 13, wherein said CO₂ hydrate promoter in said multicomponent gaseous stream is a low molecular weight compound not exceeding about 350 daltons.

15. The method according to claim 14, wherein said low molecular weight compound is a sulfur containing compound.

16. The method according to claim 15, wherein said sulfur containing compound is selected from the group consisting of H₂S, SO₂ and CS₂.

17. The method according to claim 15 wherein said contacting occurs at a temperature ranging from about 0.5 to 3°

C.

18. The method according to claim 13, wherein said contacting occurs at a system pressure ranging from about 3 to 200 atm.

19. The method according to claim 13, wherein said method has a single-pass CO₂ separation ratio of at least about 50%.