Process for treating a gas stream to selectively separate acid gases therefrom

• US 5,820,837 A
• Filed: 08/07/1997
• Issued: 10/13/1998
• Est. Priority Date: 05/20/1996
• Status: Expired due to Term

• Current Assignee: Mobil Oil Corporation (Exxon Mobil Corporation)
• Original Assignee: Mobil Oil Corporation (Exxon Mobil Corporation)
• Inventors: Marjanovich, Barry S., Stang, Don A.
• Primary Examiner(s): LANGEL, WAYNE A
• Application Number:
  US08/906,657
• Time in Patent Office: 432 Days
• Field of Search: 423/220, 423/226, 423/227, 423/228, 423/229, 95/161, 95/173, 95/174
• US Class Current: 423/220
• CPC Class Codes: B01D 19/0015 in contact columns containing plates, grids or other filling elements
• CPC Class Codes: B01D 3/06 Flash distillation
• CPC Class Codes: B01D 53/1418 Recovery of products
• CPC Class Codes: B01D 53/1425 Regeneration of liquid absorbents
• CPC Class Codes: B01D 53/1456 Removing acid components
• CPC Class Codes: C01B 17/0408 Pretreatment of the hydrogen sulfide containing gases
• CPC Class Codes: C01B 32/50 Carbon dioxide
• CPC Class Codes: Y02C 20/40 of CO2
• CPC Class Codes: Y02P 20/151 Reduction of greenhouse gas [GHG] emissions, e.g. CO2
• CPC Class Codes: Y02P 70/10 Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working

Abstract

A treatment method for removing acid gases by contacting a sour gas stream with a solvent (e.g. an organic amine) which absorbs H₂ S in preference to CO₂ and hydrocarbons. The rich solvent is then regenerated by selectively separating the absorbed hydrocarbons in a first flash, a large portion of the CO₂ in a high-temperature, low-pressure second flash tank, and the substantially all of the remaining acid gases in a high-temperature, low-pressure stripper. The regenerated solvent is recycled and the recovered acid gases are processed to recover sulphur from the H₂ S. The CO₂ recovered from the second tank is contacted with a second solvent to provide high-quality CO₂.

Claims

1. A method for treating a sour hydrocarbon gas stream containing hydrogen sulfide (H₂ S) and carbon dioxide (CO₂), said method comprising:

passing said sour hydrocarbon gas stream into a high-pressure contactor vessel;

contacting said sour hydrocarbon gas stream with a solvent within said contactor vessel to absorb H₂ S and CO₂ from said sour gas stream to produce a rich solvent;

passing said rich solvent through a regeneration cycle to regenerate said rich solvent by removing substantial amounts of said H₂ S and CO₂ and any hydrocarbons absorbed by said solvent from said sour gas, said regenerating comprising;

passing said rich solvent through a first flash tank having an operating temperature of from about 135°

to about 160°

F. wherein the pressure of said rich solvent is reduced to less than about 100 psig to separate only substantially all of the hydrocarbons from said rich solvent;

recovering said separated substantially all of said hydrocarbons from said first flash tank and removing said separated hydrocarbons from said regeneration cycle for individual handling;

heating said rich solvent from said first flash tank to a temperature of from about 215°

to about 240°

F. before passing it through a second flash tank where the pressure of the solvent is further reduced to less than about 25 psig to thereby selectively separate a substantial portion of said CO₂ from said rich solvent;

recovering said separated substantial portion of said CO₂ from said second flash tank and removing said separated portion of said CO₂ from said regeneration cycle;

passing said separated CO₂ from said second flash tank to a CO₂ contactor vessel; and

contacting said CO₂ with a second solvent to absorb substantially all of any H₂ S present in said CO₂ to produce a second rich solvent;

passing said rich solvent from said second flash tank to a stripper to separate substantially all of said H₂ S remaining in said rich solvent to thereby regenerate said solvent;

removing said separated, substantially all of said remaining H₂ S from said stripper and removing said separated H₂ S from said regeneration cycle for separate handling; and

recycling said regenerated solvent to contact said sour gas stream.

2. The method of claim 1 wherein said solvent is comprised of an organic amine which absorbs H₂ S in preference to both CO₂ and hydrocarbons.

3. The method of claim 2 wherein said organic amine is at least about 50% methyldiethanolamine.

4. The method of claim 2 wherein said second solvent is comprised of said regenerated solvent.

5. The method of claim 2 wherein said second rich solvent is combined with said rich solvent from said second flash tank before said solvents are passed to said stripper.

6. The method of claim 4 wherein said CO₂ from said second flash tank is cooled before it is passed through said CO₂ contactor vessel.

7. The method of claim 2 wherein:

said CO₂ contactor vessel has an operating temperature of less than about 110°

F. and an operating pressure of from about 5 to about 15 psig.