CONFIGURATIONS AND METHODS FOR HIGH PRESSURE ACID GAS REMOVAL IN THE PRODUCTION OF ULTRA-LOW SULFUR GAS

• US 20130055729A1
• Filed: 02/17/2010
• Published: 03/07/2013
• Est. Priority Date: 02/17/2010
• Status: Active Grant

• Current Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Original Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Inventors: Mak, John
• Granted Patent: US 9,295,940 B2
• Time in Patent Office: Days
• US Class Current: 62/56
• CPC Class Codes: B01D 2252/202 Alcohols or their derivatives
• CPC Class Codes: B01D 2252/2021 Methanol
• CPC Class Codes: B01D 2252/2023 Glycols, diols or their derivatives
• CPC Class Codes: B01D 2252/2025 Ethers or esters of alkylene glycols, e.g. ethylene or propylene carbonate
• CPC Class Codes: B01D 2252/20431 Tertiary amines
• 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 53/18 Absorbing units; Liquid distributors therefor B01D3/16, B01D3/26, B01D3/30 take precedence; packing elements B01J19/30, B01J19/32
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

Acid gas is removed from a high pressure feed gas that contains significant quantities of CO2 and H2S. In especially preferred configurations and methods, feed gas is contacted in an absorber with a lean and an ultra-lean solvent that are formed by flashing rich solvent and stripping a portion of the lean solvent, respectively. Most preferably, the flash vapors and the stripping overhead vapors are recycled to the feed gas/absorber, and the treated feed gas has a CO2 concentration of less than 2 mol % and a H2S concentration of less than 10 ppmv, and more typically less than 4 ppmv.

Claims

1. A method of removing acid gas from a feed gas having a CO2 content of at least 10 mol % and an H2S content of at least 0.01 mol %, comprising:

feeding a lean physical solvent and an ultra-lean physical solvent at different locations into an absorber to counter-currently contact the feed gas to produce a rich physical solvent and a treated gas;

wherein the absorber is operated at a pressure of at least 500 psig;

regenerating the lean physical solvent in a flash regeneration section and feeding a first portion of the lean physical solvent to the absorber; and

feeding a second portion of the lean physical solvent to a stripping column to so produce the ultra-lean physical solvent;

2. The method of claim 1 further comprising a step of producing a hydrocarbon-containing recycle gas in the flash regeneration section and feeding the recycle gas to the feed gas or absorber.

3. The method of claim 1 wherein the stripping column produces an overhead product that is combined with the recycle gas.

4. The method of claim 1 further comprising a step of using a portion of the treated gas as a stripping gas in the stripping column.

5. The method of claim 4 wherein refrigeration content from expansion of the portion of the treated gas is used for cooling the ultra-lean physical solvent.

6. The method of claim 1 wherein heat content of the feed gas is used in the flash regeneration section to produce a CO2-containing flash vapor.

7. The method of claim 1 further comprising a step of compressing the feed gas and chilling the compressed feed gas to a temperature that is sufficient to condense C5+ hydrocarbons.

8. The method of claim 1 wherein the feed gas has a CO2 content of at least 20 mol % and an H2S content of at least 0.1 mol %, and wherein the treated gas has an H2S content of equal or less than 4 ppmv.

17. The plant of claim 1 wherein the flash regeneration section comprises a plurality of flash vessels, and a plurality of respective conduits that allow feeding vapors from the flash vessels to the absorber or feed gas.

18. The plant of claim 1 wherein the flash regeneration section comprises a plurality of hydraulic turbines.

19. The plant of claim 1 further comprising a third conduit coupled to the stripping column and configured to provide a stripping column overhead product to the absorber.

20. The plant of claim 1 further comprising a chiller and separator coupled to the absorber and configured to allow chilling of the feed gas to a temperature that is sufficient to condense and separate C5+ hydrocarbons from the feed gas.

9. A method of treating a rich physical solvent, comprising:

flashing the rich solvent in multiple successive stages from a first pressure to a second pressure to generate a hydrocarbon-containing flash gas and a flashed solvent;

heating and further flashing the flashed solvent from the second pressure to a third pressure to generate a CO2-containing flash gas and a lean solvent; and

stripping a portion of the lean solvent in a stripping column to produce a stripping column overhead product and an ultra-lean solvent.

10. The method of claim 9 further comprising a step of combining the hydrocarbon-containing flash gas and the stripping column overhead product.

11. The method of claim 9 wherein the step of heating the flashed solvent comprises using heat content of at least one of an absorber feed gas and the lean solvent to heat the flashed solvent.

12. The method of claim 9 wherein the first pressure is at least 1000 psig, the second pressure is at least 75 psig, and the third pressure is equal or less 40 psig.

13. The method of claim 9 wherein the step of stripping the portion the lean solvent is performed using treated feed gas from an absorber as a stripping gas.

14. The method of claim 9 wherein the portion of the lean solvent is between 20% and 50% of the lean solvent.

15. The method of claim 9 further comprising a step of feeding the lean solvent and the ultra-lean solvent into an absorber at different positions, wherein the absorber is operated at a pressure of at least 500 psig.

16. A plant for acid gas removal from a feed gas, comprising:

an absorber configured to receive a feed gas and to produce a treated gas at a pressure of at least 500 psig, wherein the absorber is further configured to separately receive a lean physical solvent and an ultra-lean physical solvent and to produce a rich physical solvent;

a flash regeneration section fluidly coupled to the absorber and configured to receive the rich physical solvent and to produce the lean physical solvent from the rich physical solvent;

a stripping column fluidly coupled to the flash regeneration section and configured to receive a first portion of the lean physical solvent and to produce the ultra-lean physical solvent from the lean physical solvent;

a first conduit coupled to the flash regeneration section and configured to provide a second portion of the lean physical solvent to the absorber; and

a second conduit coupled to the stripping column and configured to provide the ultra-lean physical solvent to the absorber.