Configurations and methods for high pressure acid gas removal in the production of ultra-low sulfur gas

• US 9,295,940 B2
• Filed: 02/17/2010
• Issued: 03/29/2016
• 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
• Primary Examiner(s): Smith, Duane
• Assistant Examiner(s): SHAO, PHILLIP Y
• Application Number:
  US13/579,506
• Publication Number:
  US 20130055729A1
• Time in Patent Office: 2,232 Days
• Field of Search: None
• US Class Current: 1/1
• 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 using a flash regeneration section and feeding a first portion of the flashed lean physical solvent to the absorber; and

feeding a second portion of the flashed lean physical solvent to a stripping column and using a portion of the treated gas as a stripping gas 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 wherein the portion of the treated gas used as a stripping gas in the stripping column is between 2 to 5% of the treated gas.

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.