Configurations and methods of flexible CO2 removal

• US 10,000,713 B2
• Filed: 12/12/2014
• Issued: 06/19/2018
• Est. Priority Date: 12/12/2013
• Status: Active Grant

• Current Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Original Assignee: Fluor Technologies Corporation (Fluor Corporation)
• Inventors: Mak, John
• Primary Examiner(s): HOLECEK, CABRENA L
• Application Number:
  US14/569,268
• Publication Number:
  US 20150166915A1
• Time in Patent Office: 1,285 Days
• CPC Class Codes: B01D 2252/20 Organic absorbents
• CPC Class Codes: B01D 2252/2025 Ethers or esters of alkylene glycols, e.g. ethylene or propylene carbonate
• CPC Class Codes: B01D 2252/2026 Polyethylene glycol, ethers or esters thereof, e.g. Selexol
• CPC Class Codes: B01D 2252/20468 containing a pyrrolidone-ring
• CPC Class Codes: B01D 2256/24 Hydrocarbons
• CPC Class Codes: B01D 2257/304 Hydrogen sulfide
• CPC Class Codes: B01D 53/1406 Multiple stage absorption
• CPC Class Codes: B01D 53/1425 Regeneration of liquid absorbents
• CPC Class Codes: B01D 53/1431 Pretreatment by other processes
• CPC Class Codes: B01D 53/1475 Removing carbon dioxide
• CPC Class Codes: B01D 53/1493 Selection of liquid materials for use as absorbents
• CPC Class Codes: C10L 2290/06 Heat exchange, direct or indirect
• CPC Class Codes: C10L 2290/08 Drying or removing water
• CPC Class Codes: C10L 2290/48 Expanders, e.g. throttles or flash tanks
• CPC Class Codes: C10L 2290/541 Absorption of impurities during preparation or upgrading of a fuel
• CPC Class Codes: C10L 2290/545 Washing, scrubbing, stripping, scavenging for separating fractions, components or impurities during preparation or upgrading of a fuel
• CPC Class Codes: C10L 3/103 Sulfur containing contaminants
• CPC Class Codes: C10L 3/104 Carbon dioxide
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

A plant includes a pretreatment unit for H2S removal and air dehydration, and at least two absorbers that receive a feed gas at a pressure of at least 300 psig with variable CO2 content (e.g., between 5 to 60 mol %), wherein the feed gas is scrubbed in the absorbers with an ultralean and a semi-lean physical solvent, respectively, at low temperatures to at least partially remove the CO2 from the feed gas. Such configurations produces a low CO2 dry treated gas and a H2S-free CO2 for sequestration while advantageously providing cooling by expansion of the rich solvent that cools the semi-lean solvent and the feed gas, wherein an ultralean solvent is produced by stripping using dry air.

Claims

1. A method of treating a hydrocarbonaceous feed gas that contains H2S and CO2, the method comprising the steps of:

selectively removing H2S from the feed gas to produce an H2S depleted feed gas;

using a first absorber and a second absorber to remove CO2 from the H2S depleted feed gas using a semi-lean and an ultralean solvent, respectively, thereby producing a product gas and a rich solvent;

reducing pressure of the rich solvent to generate work, a cooled flashed solvent, a CO2 stream, and refrigeration;

using the cooled flashed solvent to cool the H2S depleted feed gas and the semi-lean solvent;

stripping the cooled flashed solvent with dried air to thereby produce the ultralean solvent; and

combining a portion of the ultralean solvent with the H2S depleted feed gas upstream of the first absorber and the second absorber and upstream of the using the cooled flashed solvent to cool the H2S depleted feed gas.

2. The method of claim 1 wherein the hydrocarbonaceous feed gas has a pressure of at least 300 psig and comprises at least 5 mol % CO2.

3. The method of claim 1 wherein the first and second absorbers are configured into a single column having a first and second absorber section.

4. The method of claim 1 wherein the solvent is a physical solvent selected from the group consisting of propylene carbonate, tributyl phosphate, normal methyl pyrrolidone, a dimethyl ether of polyethylene glycol, and a polyethylene glycol dialkyl ether.

5. The method of claim 1 wherein the step of selectively removing H2S comprises a step of solvent absorption with an H2S selective solvent or a step of adsorption of H2S to a solid adsorbent.

6. The method of claim 1 wherein the product gas has a CO2 content of 500 ppmv to 0.5 mol % CO2.

7. The method of claim 1 wherein the dried air has a water dew point of equal or less than −

40°

F.

8. The method of claim 1 wherein the semi-lean solvent is produced from the second absorber and cooled to a temperature between 10°

F. to −

20°

F.

9. The method of claim 1 wherein the rich solvent is flashed to two separators operating in series, and wherein at least one or two recycle streams are produced by the separators that are then compressed and recycled back to the first absorber, the second absorber, or the H2S depleted feed gas.

10. The method of claim 1 wherein at least 85% of the CO2 content in the rich solvent is removed from the solvent at atmospheric pressure.

11. The method of claim 1 wherein the step of striping the flashed solvent with dried air is performed at about atmospheric pressure.

12. The method of claim 1 wherein the first absorber is operated to have a temperature of about 30°

F. to about −

10°

F. at a bottom section.

13. The method of claim 1, wherein the ultralean solvent and the semi-lean solvent have a temperature ranging from −

25°

F. to 105°

F.

14. A method of treating a hydrocarbonaceous feed gas that contains H₂S and CO₂, the method comprising the steps of:

removing H₂S from the feed gas to produce an H₂S depleted feed gas;

combining a first portion of an ultralean solvent with the H₂S depleted feed gas;

cooling the H₂S depleted feed gas having the first portion of the ultralean solvent using a cooled flashed solvent to produce a cooled H₂S depleted feed gas;

using a first absorber and a second absorber to remove CO₂ from the cooled H₂S depleted feed gas using a semi-lean solvent and a second portion of the ultralean solvent, respectively, thereby producing a product gas and a rich solvent;

reducing a pressure of the rich solvent to generate work, the cooled flashed solvent, a CO₂ stream, and refrigeration; and

stripping the cooled flashed solvent with dried air to thereby produce the ultralean solvent.

15. The method of claim 14 wherein the first and second absorbers are configured into a single column having a first and second absorber section.

16. The method of claim 14 wherein the solvent is a physical solvent selected from the group consisting of propylene carbonate, tributyl phosphate, normal methyl pyrrolidone, a dimethyl ether of polyethylene glycol, and a polyethylene glycol diallyl ether.

17. The method of claim 14 wherein the dried air has a water dew point of equal or less than −

40°

F.

18. The method of claim 14 wherein the rich solvent is flashed to two separators operating in series, and wherein at least one or two recycle streams are produced by the separators that are then compressed and recycled back to the first absorber, the second absorber, or the H2S depleted feed gas.

19. The method of claim 14 wherein at least 85% of the CO₂ content in the rich solvent is removed from the solvent at atmospheric pressure.

20. The method of claim 14 wherein the step of stripping the flashed solvent with dried air is performed at about atmospheric pressure.