Configurations and methods of acid gas removal

• US 20050172807A1
• Filed: 12/11/2003
• Published: 08/11/2005
• Est. Priority Date: 12/12/2002
• Status: Active Grant

• Current Assignee: Fluor Enterprises Incorporated (Fluor Corporation)
• Original Assignee: Fluor Corporation
• Inventors: Mak, John
• Granted Patent: US 7,637,987 B2
• Time in Patent Office: Days
• US Class Current: 95/235
• CPC Class Codes: B01D 53/1425 Regeneration of liquid absorbents
• CPC Class Codes: B01D 53/1456 Removing acid components
• CPC Class Codes: B01D 53/1462 Removing mixtures of hydrogen sulfide and 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 plant includes a vacuum stripper (118) that receives a lean hydrogen sulfide-containing physical solvent (32) and in which substantially hydrogen sulfide-free stripping gas (51,52) is provided by at least one of a high-pressure flash vessel (110) and a medium pressure flash vessel (112). Contemplated configurations advantageously extend the range of use for physical solvents to treat sour gas comprising carbon dioxide and hydrogen sulfide, and can be used to meet most pipeline specification of 4 ppm hydrogen sulfide.

Claims

1. A plant comprising:

a vacuum stripper that is configured to produce an ultra-lean physical solvent from a lean hydrogen sulfide-containing physical solvent; and

at least one of a high-pressure flash vessel and a medium pressure flash vessel coupled to the vacuum stripper, wherein the at least one of the high-pressure flash vessel and the medium pressure flash vessel provide a substantially hydrogen sulfide-free stripping gas to the vacuum stripper.

2. The plant of claim 1 further comprising an absorber that receives the ultra-lean physical solvent and that is configured to operate with an isothermal gradient or with a decreasing top-to-bottom thermal gradient.

3. The plant of claim 2 wherein the absorber receives a feed gas that comprises at least 10 mol % carbon dioxide and at least 500 ppm hydrogen sulfide.

4. The plant of claim 3 wherein the feed gas has a pressure of at least 1000 psig.

5. The plant of claim 4 wherein the feed gas is at least partially dehydrated, and wherein the at least partially dehydrated feed gas is further cooled by a rich solvent.

6. The plant of claim 1 wherein the lean hydrogen sulfide-containing physical solvent comprises at least 100 ppm hydrogen sulfide, and wherein the ultra-lean physical solvent comprises less than 100 ppm hydrogen sulfide.

7. The plant of claim 6 wherein the ultra-lean solvent comprises less than 10 ppm hydrogen sulfide.

8. The plant of claim 1 wherein the lean hydrogen sulfide-containing physical solvent is selected from the group consisting of propylene carbonate, n-methyl pyrolidone, dimethyl ether of polyethylene glycol, and tributyl phosphate.

9. The plant of claim 1 wherein the substantially hydrogen sulfide-free stripping gas comprises at least 95 mol % carbon dioxide.

10. The plant of claim 1 further comprising a separator in which acid gas is separated from a rich solvent, thereby producing the lean hydrogen sulfide-containing physical solvent, and wherein part of the acid gas is compressed and injected into a formation.

11. The plant of claim 10 wherein the vacuum stripper further produces a second acid gas that is combined with the acid gas from the separator.

12. A method of producing an ultra-lean physical solvent, comprising:

separating in at least one of a high-pressure flash vessel and a medium pressure flash vessel a substantially hydrogen sulfide-free stripping gas from a physical solvent; and

stripping hydrogen sulfide from a lean hydrogen sulfide-containing physical solvent in a vacuum stripper to form the ultra-lean physical solvent.

13. The method of claim 12 further comprising a step of feeding the ultra-lean physical solvent to an absorber, and operating the absorber with an isothermal gradient or with a decreasing top-to-bottom thermal gradient.

14. The method of claim 13 further comprising a step of feeding a feed gas to the absorber at a pressure of at least 1000 psig, wherein the feed gas comprises at least 10 mol % carbon dioxide and at least 500 ppm hydrogen sulfide.

15. The method of claim 12 wherein the lean hydrogen sulfide-containing physical solvent is selected from the group consisting of propylene carbonate, n-methyl pyrolidone, dimethyl ether of polyethylene glycol, and tributyl phosphate.

16. The method of claim 12 wherein the substantially hydrogen sulfide-free stripping gas comprises at least 95 mol % carbon dioxide.