Self-Concentrating Absorbent for Acid Gas Separation

• US 20090263302A1
• Filed: 04/28/2009
• Published: 10/22/2009
• Est. Priority Date: 04/07/2006
• Status: Active Grant

• Current Assignee: Liang Hu
• Original Assignee: Liang Hu
• Inventors: Hu, Liang
• Granted Patent: US 7,846,407 B2
• Time in Patent Office: Days
• US Class Current: 423/228
• CPC Class Codes: B01D 2252/202 Alcohols or their derivatives
• CPC Class Codes: B01D 2252/2023 Glycols, diols or their derivatives
• CPC Class Codes: B01D 2252/20405 Monoamines
• CPC Class Codes: B01D 2252/20484 with one hydroxyl group
• CPC Class Codes: B01D 2252/20494 Amino acids, their salts or derivatives
• CPC Class Codes: B01D 2252/504 Mixtures of two or more absorbents
• CPC Class Codes: B01D 53/1425 Regeneration of liquid absorbents
• CPC Class Codes: B01D 53/1456 Removing acid components
• CPC Class Codes: B01D 53/1493 Selection of liquid materials for use as absorbents
• CPC Class Codes: B01D 53/62 Carbon oxides
• CPC Class Codes: B01D 53/96 Regeneration, reactivation or recycling of reactants
• CPC Class Codes: C10L 3/10 Working-up natural gas or synthetic natural gas
• CPC Class Codes: C10L 3/102 of acid contaminants
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

An process for efficiently deacidizing a gaseous mixture is described. The process utilizes a self-concentrating absorbent that absorbs an acid gas at reduced overall energy costs for the deacidizing operation.

Claims

1. A method for deacidizing a gaseous mixture comprising an acid gas, comprising:

contacting the gaseous mixture with an absorbent in an absorption unit, wherein the absorbent comprises an amine dissolved in a solvent at a first concentration;

allowing the absorbent to absorb the acid gas to form a concentrated-amine phase, wherein the concentrated-amine phase is mechanically separable from the remaining of the absorbent and comprises a concentrated amine at a concentration higher than the first concentration and an absorbed acid gas, wherein the concentrated amine comprises the amine or the amine having a chemical modification, and the absorbed acid gas comprises the acid gas or the acid gas having a chemical modification;

separating the concentrated-amine phase from the remaining of the absorbent;

cycling the remaining of the absorbent back into the absorption unit;

providing the concentrated-amine phase to a regeneration unit, so as to obtain the acid gas and the concentrated amine; and

cycling the regenerated concentrated amine back into the absorption unit.

2. The method of claim 1, wherein the acid gas is selected from the group consisting of carbon dioxide (CO₂), sulfur dioxide (SO₂), sulfur trioxide (SO₃), hydrogen sulfide (H₂S), carbon oxysulfide (COS), carbon disulfide (CS₂), mercaptans (RSH), nitric oxide (NO), nitric dioxide (NO₂), fluorides, HCl, HF and a combination thereof.

3. The method of claim 1, wherein the amine is selected from the group consisting of monoethanolamine, diethanolamine, triethanolamine, ethanolamines, isopropanolamines, ethyleneamines, alkyl alkanolamines, methyldiethanolamine, piperidine, dibutylamine, diisopropylamine, and a combination thereof.

4. The method of claim 1, wherein the solvent comprises one or more components selected from the group consisting of alcohols, glycols, alkanes, unsaturated hydrocarbon, ethers, esters, aldehydes, ketones, glycol ethers, alkylene carbonates, dialkyl carbonates, sulfolane, ionic liquids, polymers, water, an aqueous solution containing one or more salts selected from alkaline salts, ammonium salts, alkanolamine salts, or alkaline-earth salts, and derivatives thereof.

5. The method of claim 4, wherein the solvent comprises a C₈ to C₁₂ alcohol.

6. The method of claim 1, wherein the absorbent comprises at least one amine selected from the group consisting of monoethanolamine, diethanolamine, piperidine, dibutylamine, or diisopropylamine, triethanolamine, ethanolamines, isopropanolamines, ethyleneamines, alkyl alkanolamines and methyldiethanolamine, and the amine is dissolved in a solvent comprising at least one of a C₈-C₁₂ alcohol, glycol and glycol ether.

7. The method of claim 1, wherein the absorption unit is an absorber, a membrane contractor, and any equipment that provides gas liquid contact.

8. The method of claim 1, wherein the solvent increases the absorption of the acid gas into the absorbent as compared to the absorption of the acid gas by the amine alone.

9. The method of claim 1, wherein after the absorbent absorbs the acid gas to form a gas-rich absorbent, the gas-rich absorbent moves downward from the absorption unit to the separation unit by gravity.

10. The method of claim 1, wherein after the step of separation, the concentrated-amine phase moves downward from the separation unit to the regeneration unit by gravity.

11. A system for deacidizing a gaseous mixture comprising an acid gas, comprising:

an absorption unit adapted to allow contact between the gaseous mixture and an absorbent comprising an amine dissolved in a solvent at a first concentration, wherein the absorbent absorbs the acid gas to form a concentrated-amine phase, wherein the concentrated-amine phase is mechanically separable from the remaining of the absorbent, and the concentrated-amine phase comprises a concentrated amine at a concentration higher than the first concentration and an absorbed acid gas, wherein the concentrated amine comprises the amine or the amine having a chemical modification, and the absorbed acid gas comprises the acid gas or the acid gas having a chemical modification

a separation unit adapted to allow separation of the concentrated-amine phase from the remaining of the absorbent; and

a regeneration unit adapted to allow regeneration of the concentrated-amine phase, so as to obtain the acid gas and the concentrated amine.

12. The system of claim 11, wherein the separation unit is placed in a position lower than the absorption unit, so that after the absorbent absorbs the acid gas to form a gas-rich absorbent, the gas-rich absorbent moves downward from the absorption unit to the separation unit by gravity.

13. The system of claim 12, wherein the absorption unit, the separation unit and the regeneration unit are placed in a single tower, wherein the separation unit is placed in a position lower than the absorption unit and the regeneration unit is placed in a position lower than the separation unit, so that after the absorbent absorbs the acid gas, the gas-rich absorbent moves downward from the absorption unit to the separation unit by gravity, and after the step of separation, the concentrated-amine phase moves downward from the separation unit to the regeneration unit by gravity.

14. The system of claim 11, wherein the regeneration unit is placed in a position lower than the separation unit, so that after the step of separation, the concentrated-amine phase moves downward from the separation unit to the regeneration unit by gravity.

15. A method for deacidizing a gaseous mixture comprising an acid gas, comprising:

contacting the gaseous mixture with an absorbent in an absorption unit, wherein the absorbent comprises an agent dissolved in a solvent at a first concentration, wherein the agent is selected from the group consisting of amino-acid salts, amides, alkaline salts, alkaline-earth salts, ammonium salts, ureas, alkaline metal phosphates, carbonates, borates, acid phosphites, phosphites, phosphonite, phosphinate, phosphonate, acid phosphates, pyrophosphites, bicarbonates, metaborates, diborates, tetraborates, pentaborates, and combinations thereof;

allowing the absorbent to absorb the acid gas to form a concentrated-agent phase, wherein the concentrated-agent phase is mechanically separable from the remaining of the absorbent and comprises a concentrated agent at a concentration higher than the first concentration and an absorbed acid gas, wherein the concentrated agent comprises the agent or the agent having a chemical modification, and the absorbed acid gas comprises the acid gas or the acid gas having a chemical modification;

separating the concentrated-agent phase from the remaining of the absorbent;

cycling the remaining of the absorbent back into the absorption unit;

providing the concentrated-agent phase to a regeneration unit, so as to obtain the acid gas and the concentrated agent; and

cycling the regenerated concentrated agent back into the absorption unit.

16. The method of claim 15, wherein the solvent comprises water, an aqueous solution containing one or more salts selected from alkaline salts, ammonium salts, alkanolamine salts, alkaline-earth salts, phosphates, acid phosphites, phosphites, phosphonite, phosphinate, phosphonate, acid phosphates, pyrophosphites, carbonates, bicarbonates, borates, metaborates, diborates, tetraborates, or pentaborates.

17. A system for deacidizing a gaseous mixture comprising an acid gas, comprising:

an absorption unit adapted to allow contact between the gaseous mixture and an absorbent comprising an agent dissolved in a solvent at a first concentration,

wherein the agent is selected from the group consisting of amino-acid salts, amides, alkaline salts, alkaline-earth salts, ammonium salts, ureas, alkaline metal phosphates, carbonates, borates, acid phosphites, phosphites, phosphonite, phosphinate, phosphonate, acid phosphates, pyrophosphites, bicarbonates, metaborates, diborates, tetraborates, pentaborates, and combinations thereof;

wherein the absorbent absorbs the acid gas to form a concentrated-agent phase, the concentrated-agent phase is mechanically separable from the remaining of the absorbent, and the concentrated-agent phase comprises a concentrated agent at a concentration higher than the first concentration and an absorbed acid gas,

wherein the concentrated agent comprises the agent or the agent having a chemical modification, and the absorbed acid gas comprises the acid gas or the acid gas having a chemical modification;

a separation unit adapted to allow separation of the concentrated-agent phase from the remaining of the absorbent; and

a regeneration unit adapted to allow regeneration of the concentrated-agent phase, so as to obtain the acid gas and the concentrated agent.

18. The system of claim 17, wherein the solvent comprises water, an aqueous solution containing one or more salts selected from alkaline salts, ammonium salts, alkanolamine salts, alkaline-earth salts, phosphates, acid phosphites, phosphites, phosphonite, phosphinate, phosphonate, acid phosphates, pyrophosphites, carbonates, bicarbonates, borates, metaborates, diborates, tetraborates, or pentaborates.