Configurations and methods of flexible CO2 removal

Patent metadata

Field	Value
Publication number	US-10000713-B2
Application number	US-201414569268-A
Country	US
Kind code	B2
Filing date	Dec 12, 2014
Priority date	Dec 12, 2013
Publication date	Jun 19, 2018
Grant date	Jun 19, 2018

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.

First claim

What is claimed is:

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 H 2 S and CO 2 , the method comprising the steps of:
removing H 2 S from the feed gas to produce an H 2 S depleted feed gas;
combining a first portion of an ultralean solvent with the H 2 S depleted feed gas;
cooling the H 2 S depleted feed gas having the first portion of the ultralean solvent using a cooled flashed solvent to produce a cooled H 2 S depleted feed gas;
using a first absorber and a second absorber to remove CO 2 from the cooled H 2 S 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 CO 2 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 CO 2 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.

Assignees

• Fluor Tech Corp

Inventors

• Mak John

Classifications

• C10L2290/08

  Drying or removing water · CPC title

• B01D2252/20

  Organic absorbents · CPC title

• C10L3/104 Primary

  Carbon dioxide · CPC title

• C10L3/103

  Sulfur containing contaminants · CPC title

• B01D2252/2025

  Ethers or esters of alkylene glycols, e.g. ethylene or propylene carbonate · CPC title