Configurations And Methods For High Pressure Acid Gas Removal

• US 20120073441A1
• Filed: 03/24/2010
• Published: 03/29/2012
• Est. Priority Date: 03/25/2009
• Status: Active Grant

• Current Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Original Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Inventors: Mak, John
• Granted Patent: US 9,114,351 B2
• Time in Patent Office: Days
• US Class Current: 95/246
• CPC Class Codes: B01D 2256/24 Hydrocarbons
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 53/1425 Regeneration of liquid absorbents
• CPC Class Codes: B01D 53/1462 Removing mixtures of hydrogen sulfide and carbon dioxide
• CPC Class Codes: B01D 53/62 Carbon oxides
• CPC Class Codes: B01D 53/78 with gas-liquid contact
• CPC Class Codes: C10L 3/102 of acid contaminants
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

Physical solvent is regenerated using flashing and stripping processes to produce an ultra-lean solvent. In especially preferred aspects, flashed C1-C3 hydrocarbons are recycled to the absorber, while C4+ hydrocarbons are recovered from the CO2 that is removed from the solvent. It is further preferred that depressurization of the rich solvent provides most of the refrigeration duty.

Claims

1. A method of acid gas removal from a feed gas, comprising:

contacting the feed gas in an absorber with an ultra-lean physical solvent to form a rich solvent and a treated feed gas;

sequentially depressurizing the rich solvent to remove C1-C3 hydrocarbons from the rich solvent to form a depressurized solvent, and recycling the C1-C3 hydrocarbons to the absorber;

flashing and stripping the depressurized solvent to produce an ultra-lean solvent and a flashed gas that predominantly comprises CO2 and C4+ components;

wherein the step of stripping is performed with a portion of the treated feed gas to form stripped vapors, and wherein the stripped vapors are recycled to the absorber; and

separating the flashed gas in a separator to produce a CO2 stream having less than 5% C4+ components and a C4+ product.

2. The method of claim 1 wherein refrigeration content of the depressurized solvent is employed for cooling of at least one of the ultra-lean solvent and the feed gas.

3. The method of claim 1 wherein the depressurized solvent is heated to a temperature of at least 50°

F. using heat content of the feed gas.

4. The method of claim 1 wherein the portion of the treated feed gas is heated and then expanded to stripper pressure in a turbo expander to thereby generate power.

5. The method of claim 1 wherein the feed gas entering the absorber has a pressure of at least 1000 psia, comprises at least 10 mol % CO2, and is cooled prior to entering the absorber to a temperature that is effective to condense heavy hydrocarbons.

6. The method of claim 1 wherein the step of sequentially depressurizing the rich solvent comprises depressurization using a hydraulic turbine.

7. The method of claim 1 wherein the step of flashing is performed using a first flashing step to about atmospheric pressure and a second step to below atmospheric pressure.

8. The method of claim 1 wherein the flashed gas is dehydrated in a dehydration unit prior to the step of separating the flashed gas in the separator.

9. The method of claim 1 wherein the CO2 stream from the separator is partially condensed to produce a reflux stream and a CO2 vapor.

10. A method of regenerating a physical solvent, comprising:

providing a rich physical solvent at a pressure of at least 1000 psig, wherein the rich solvent comprises C1-C3 hydrocarbons, C4+ components, and CO2;

sequentially depressurizing the rich solvent to a pressure effective to the remove C1-C3 hydrocarbons from the rich solvent while maintaining substantially all of the CO2 to thereby form a depressurized solvent, and recycling the C1-C3 hydrocarbons to an absorber;

flashing the depressurized solvent to a pressure sufficient to release substantially all of the CO2 and C4+ components to thereby form a flashed solvent;

separating the C4+ components from the CO2 to thereby produce a CO2 stream having less than 5% C4+ components and a C4+ product; and

stripping the flashed solvent with a portion of a treated feed gas to so form an ultra-lean solvent and stripped vapors, and recycling the stripped vapors to the absorber.

11. The method of claim 10 wherein the step of sequentially depressurizing is performed using a hydraulic turbine, and wherein the depressurized rich solvent is used to cool at least one of a feed gas and the ultra-lean solvent.

12. The method of claim 10 wherein the depressurized solvent is heated to a temperature of at least 50°

F. using heat content of a feed gas to an absorber.

13. The method of claim 10 wherein the step of flashing is performed using a first flashing step to about atmospheric pressure and a second step to below atmospheric pressure.

14. The method of claim 10 wherein the step of stripping the flashed solvent is performed with a treated feed gas.

15. The method of claim 14 further comprising a step of heating the portion of the treated feed gas and expanding the heated portion of the treated feed gas in a turbo expander to thereby generate power.

16. The method of claim 10 further comprising a step of dehydrating the flashed gas in a dehydration unit prior to the step of separating the C4+ components from the CO2.

17. A gas treatment plant comprising:

an absorber configured to absorb C1-C3 hydrocarbons, C4+ components, and CO2 from a feed gas using an ultra-lean solvent at a pressure of at least 1000 psig to thereby allow formation of a treated feed gas and a rich solvent;

a plurality of flash vessels configured to receive and sequentially flash the rich solvent to produce a depressurized solvent and C1-C3 hydrocarbons;

a low-pressure flash stage fluidly coupled to the plurality of flash vessels and configured to flash the depressurized solvent to thereby produce a flashed gas comprising CO2 and C4+ components and a flashed solvent;

a stripping column that is fluidly coupled to the low-pressure flash stage and configured to allow stripping of the flashed solvent with a portion of the treated feed gas to so produce the ultra-lean solvent and stripped vapors;

a fractionator that is fluidly coupled to the low-pressure flash stage and configured to separate C4+ components from the CO2 to thereby produce a CO2 stream having less than 5% C4+ components and a C4+ product;

a first recycle conduit fluidly coupled to the plurality of flash vessels and the absorber for recycling the C1-C3 hydrocarbons to the absorber; and

a second recycle conduit fluidly coupled to the stripping column and the absorber for recycling the stripped vapors to the absorber.

18. The gas treatment plant of claim 17 further comprising a heat exchanger configured to allow heating the depressurized solvent using heat from the feed gas.

19. The gas treatment plant of claim 17 wherein the low-pressure flash stage is configured to allow flashing of the depressurized solvent to sub-atmospheric pressure.

20. The gas treatment plant of claim 17 further comprising a separator fluidly coupled to the absorber and configured to allow separation of condensed heavy hydrocarbons from the feed gas.