METHOD FOR REMOVING HEAT STABLE BASE SALTS FROM A CONTAMINATED BASIC SOLUTION, AND USE THEREOF IN A PROCESS FOR RECOVERING ACID GAS FROM AN ACID GAS STREAM

• US 20130309155A1
• Filed: 01/24/2012
• Published: 11/21/2013
• Est. Priority Date: 01/24/2011
• Status: Active Grant

• Current Assignee: Electrosep Technologies Inc.
• Original Assignee: Electrosep Technologies Inc.
• Inventors: Parisi, Paul
• Granted Patent: US 9,908,085 B2
• Time in Patent Office: Days
• US Class Current: 423/229
• CPC Class Codes: B01D 2252/103 Water
• CPC Class Codes: B01D 2252/204 Amines
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 53/1425 Regeneration of liquid absorbents
• CPC Class Codes: B01D 53/1456 Removing acid components
• CPC Class Codes: B01D 53/62 Carbon oxides
• CPC Class Codes: B01D 53/96 Regeneration, reactivation or recycling of reactants

Abstract

A method for removing heat stable base salts, such as amine salts, is disclosed. The method of the present invention can be used to reduce the level of heat stable salts in a solvent gas stream in an acid gas removal process. A solvent in which the lean acid gas loading is high is first stripped to achieve an acceptable lean gas loading. The lean solution is then reclaimed using one or more methods. The purified base or amine solution can be used again to remove acid gases from a gas stream. A process for recovering acid gas from an acid gas stream is also disclosed. The process also comprises a reduction of the level of heat stable salts in the solvent gas stream.

Claims

1. ) A method for removing heat-stable base salts from a contaminated aqueous basic solution, said solution comprising at least one base in salt form having heat stable anions associated therewith, said method comprising:

a) passing a feedstream comprising said contaminated aqueous basic solution to a regeneration zone for obtaining a regenerated lean solvent stream comprising said heat-stable base salts, the feedstream before the regeneration zone having a base acid gas loading of greater than 1,000 ppm, and

b) passing all or a portion of said regenerated lean solvent stream to a reclamation unit for producing a product stream comprising at least in part a base in free base form in which the level of said heat-stable base salts has been lowered by said reclamation unit;

wherein said feedstream in step (a) comprises at least one portion of a rich or lean base stream in an acid gas recovery process, said rich or lean base stream comprising at least in part primary and/or secondary amine forming carbamates in contact with the acid gas, said carbamates being also removed by the method from the contaminated aqueous basic solution.

2. ) The method of claim 1, wherein in step a) a tail gas stream comprising acid gases is also obtained.

3. ) The method of claim 1, wherein the product stream produced in step b) is used as an absorbent in said base acid gas recovery process.

4. ) The method of claim 1, wherein in step (a), said at least one base of the feedstream comprises amines, amides, other organic and/or inorganic bases allowing regenerable absorption and desorption of acid gases, or mixture thereof.

5. ) The method of claim 4, wherein said amines are monoethanolamine, methyldiethanolamine, diethanolamine, aminoethoxyethanol, piperazine, diisopropyl amine or mixture thereof.

6. ) The method of claim 1, wherein the feedstream also comprises water and amine(s) in free base form.

7. ) The method of claim 1, wherein the regeneration zone is a stripping column.

8. ) The method of any claim 1, wherein the reclamation unit is an electrodialysis unit, a distillation unit or an ion exchange unit.

9. ) The method of claim 1, wherein the lean solvent stream after the regeneration zone and being fed to the reclamation unit, has a base acid gas loading of less than 1,000 ppm.

10. ) The method of claim 1, wherein the feedstream before the regeneration zone has a base acid gas loading of greater than 10,000 ppm.

11. ) The method of claim 1, wherein the lean solvent stream being fed to the reclamation unit after the regeneration zone has a base acid gas loading of less than 10,000 ppm.

12. (canceled)

13. ) A process for recovering acid gas from an acid gas stream, the process comprising the steps of:

a) passing an acid gas stream to an absorption zone wherein the acid gas stream is in contact with a lean solvent comprising at least one base which is an absorbent of acid gases, said absorbent comprising at least in part primary and/or secondary amine(s) forming carbamates in contact with the acid gas;

b) withdrawing from the absorption zone a product gas stream depleted in acid gases relatively to the gas stream;

c) withdrawing from the absorption zone a rich solvent stream comprising the absorbent and absorbed acid gases;

d) passing the rich solvent stream to a first regeneration zone wherein;

said absorbed acid gases and said carbamates are desorbed from the rich solvent stream to provide a first tail gas stream comprising acid gases, and

a first lean solvent stream is formed, said first lean solvent stream comprising base(s) in salt form having heat stable anions associated therewith and having a base acid gas loading of greater than 1,000 ppm;

e) passing the first lean solvent stream withdrawn from the regeneration zone to the absorption zone of step (a) for further treatment in a loop process;

f) partially withdrawing an amount of the first lean solvent stream before the absorption zone;

g) passing said amount of the first lean solvent stream to a second regeneration zone wherein;

all or a portion of remaining absorbed acid gases and carbamates that were not desorbed in step (d) are desorbed from said amount of the first lean solvent stream to provide a second tail gas stream comprising acid gases, and

a second lean solvent stream is formed, said second lean solvent stream also comprising base(s) in salt form having heat stable anions associated therewith;

h) passing said second lean solvent stream to a reclamation unit for producing a base stream comprising at least in part a base in free base form in which the level of said heat-stable base salts has been lowered by said reclamation unit; and

i) passing said base stream to the absorption zone used in step (a) for reacting with the process acid gas stream in a loop process.

14. ) The process of claim 13, wherein said at least one base comprises amine(s), amide(s), other organic and/or inorganic base(s) allowing regenerable absorption and desorption of acid gases, or mixture thereof.

15. ) The process of claim 14, wherein said amines are monoethanolamine, methyldiethanolamine, diethanolamine, aminoethoxyethanol, piperazine, diisopropyl amine or mixture thereof.

16. The process of claim 13, wherein the first and second lean solvent streams also comprise water and amine(s) in free base form.

17. The process of claim 13, wherein the first and second regeneration zones are stripping columns.

18. The process of claim 13, wherein the reclamation unit is an electrodialysis unit, a distillation unit or an ion exchange unit.