Process for the recovery of carbon dioxide from a gas stream

• US 7,601,315 B2
• Filed: 12/28/2006
• Issued: 10/13/2009
• Est. Priority Date: 12/28/2006
• Status: Active Grant

• Current Assignee: Shell Oil Company (Shell Plc)
• Original Assignee: Cansolv Technologies Inc. (Shell Plc)
• Inventors: Ouimet, Michel A.
• Primary Examiner(s): Vanoy; Timothy C
• Application Number:
  US11/616,992
• Publication Number:
  US 20080159937A1
• Time in Patent Office: 1,020 Days
• Field of Search: 423/228
• US Class Current: 423/228
• CPC Class Codes: B01D 2252/2041 Diamines
• CPC Class Codes: B01D 2252/20415 Tri- or polyamines
• CPC Class Codes: B01D 2252/20447 containing a piperazine-ring
• CPC Class Codes: B01D 2252/20484 with one hydroxyl group
• CPC Class Codes: B01D 2252/20489 with two or more hydroxyl groups
• CPC Class Codes: B01D 2252/604 Stabilisers or agents inhibiting degradation
• CPC Class Codes: B01D 2257/302 Sulfur oxides
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 53/1475 Removing carbon dioxide
• CPC Class Codes: B01D 53/1493 Selection of liquid materials for use as absorbents
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

A process for removing acid gas from a gas stream utilizes a low viscosity absorbent comprising a solution of at least one selected amine. The absorbent may include (1) at least one polyamine in the absence of an effective amount of tertiary amine functionalities having a pKa sufficient to neutralize carbamic acid, wherein the polyamine has at least one primary amine functionality having a pKa of <10.0 at 25° C. and wherein the feed gas stream has an SO2 concentration less than 5 ppm vol.; or (2) a polyamine in the absence of an effective amount of tertiary amine functionalities having a pKa sufficient to neutralize carbamic acid, wherein the polyamine has at least one secondary amine functionality having a pKa for each sorbing nitrogen of <10.0 at 25° C. The polyamines may include diethylenetriamine (DETA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA) or mixtures thereof.

Claims

1. A process for recovering CO₂ from a feed gas stream comprising:

a. treating the feed gas stream with a regenerated absorbent having a viscosity less than 15 centistokes that is selected from one the of the following groups;

i. at least one polyamine in the absence of an effective amount of tertiary amine functionalities having a pKa sufficient to neutralize carbamic acid, the polyamine having at least one primary amine functionality having a pKa of <

10.0 at 25°

C. wherein and the feed gas stream has an SO₂ concentration less than 5 ppm vol.; and

,

ii. a polyamine in the absence of an effective amount of tertiary amine functionalities having a pKa sufficient to neutralize carbamic acid, the polyamine having at least one secondary amine functionality having a pKa for each sorbing nitrogen of <

10.0 at 25°

C.

 

to obtain a spent absorbent and a CO₂ lean gas stream;

b. conveying the CO₂ rich amine absorbent to a regeneration zone; and

,

c. regenerating the absorbent by steam stripping, wherein the steam stripping is conducted using from 1.0 to 2.0 pounds of steam per pound of CO₂ absorbed.

2. The process of claim 1 wherein the absorbent is selected from group (i) and the feed gas stream is treated with a SO₂ absorbent prior to being treated with the regenerated absorbent.

3. The process of claim 1 wherein the absorbent is selected from group (i) and the regenerated absorbent comprises an aqueous solution having a concentration of less than 0.001 molar of compounds having electrophilic functional groups.

4. The process of claim 3 wherein the electrophilic functionalities comprise alkylhydroxy groups.

5. The process of claim 3 wherein the compounds having electrophilic functional groups comprise alkanolamines, sulfur dioxide sulfite, bisulfite and carbonyl compounds.

6. The process of claim 1 wherein the regenerated and spent absorbents have a difference in CO₂ loading per mole of absorbent of 0.4 to 1.0 mole CO₂/mole of amine, when treating a feed gas comprising greater than 4 % vol. of CO₂.

7. The process of claim 1 wherein the CO₂ lean gas stream contains less than 1 % vol. CO₂.

8. The process of claim 1 wherein the CO₂ lean gas stream contains less than 10% of the CO₂ in the feed gas stream.

9. The process of claim 1 wherein the CO₂ lean gas stream contains less than 50% of the CO₂ in the feed gas stream.

10. The process of claim 1 wherein the amine reacts with the CO₂ to form an amine salt.

11. The process of claim 1 wherein the absorbent is selected from group (i) and the process further comprises selecting at least one of diethylenetriamine (DETA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA) or mixtures thereof as the absorbent.

12. The process of claim 1 wherein the regenerated absorbent has an absence of any tertiary amine functionality having a pKa for the sorbing nitrogen of >

6.0 at 25°

C.

13. The process of claim 1 wherein the absorbent has an absence of any tertiary amine functionality that has a pKa greater than 7 at 25°

C.

14. The process of claim 1 wherein the absorbent has at least one amine that is a primary or a secondary amine and has at least one tertiary amine functionality wherein each tertiary amine functionality has a pKa less than 7 at 25°

C.

15. The process of claim 14 wherein each tertiary amine functionality has a pKa less than 6 at 25°

C.

16. The process of claim 1 wherein the absorbent comprises N-(2-hydroxyethyl)piperazine.

17. The process of claim 1 wherein the absorbent consists essentially of N-(2-hydroxyethyl)piperazine.

18. A process for recovering CO₂ from a feed gas stream comprising:

a. treating the feed gas stream with a regenerated absorbent having a viscosity less than 15 centistokes that is selected from one the of the following groups;

i. at least one polyamine in the absence of an effective amount of tertiary amine functionalities having a pKa sufficient to neutralize carbamic acid, the polyamine having at least one primary amine functionality having a pKa of <

10.0 at 25°

C. wherein and the feed gas stream has an SO₂ concentration less than 5 ppm vol.; and

,

ii. a polyamine in the absence of an effective amount of tertiary amine functionalities having a pKa sufficient to neutralize carbamic acid, the polyamine having at least one secondary amine functionality having a pKa for each sorbing nitrogen of <

10.0 at 25°

C.

 

to obtain a spent absorbent and a CO₂ lean gas stream;

b. conveying the CO₂ rich amine absorbent to a regeneration zone; and

,

c. regenerating the absorbent;

wherein the regenerated and spent absorbents have a difference in CO₂ loading per mole of absorbent of 0.4 to 1.0 mole CO₂/mole of amine, when treating a feed gas comprising greater than 4 % vol. of CO₂.