Scrubbing CO2 from methane-containing gases using an aqueous stream

• US 6,667,347 B2
• Filed: 09/14/2001
• Issued: 12/23/2003
• Est. Priority Date: 09/14/2001
• Status: Active Grant

• Current Assignee: Chevron USA Incorporated (Chevron Corp.)
• Original Assignee: Chevron USA Incorporated (Chevron Corp.)
• Inventors: Munson, Curtis, OʼRear, Dennis J.
• Primary Examiner(s): PARSA, JAFAR F
• Application Number:
  US09/951,551
• Publication Number:
  US 20030055116A1
• Time in Patent Office: 830 Days
• Field of Search: 518/700, 518/702, 951/50, 166/267
• US Class Current: 518/700
• CPC Class Codes: B01D 53/1475 Removing carbon dioxide
• CPC Class Codes: C07C 7/11 by absorption, i.e. purification or separation of gaseous hydrocarbons with the aid of liquids
• CPC Class Codes: C07C 9/04 Methane production by treatment of sewage C02F11/04; natural gas, synthetic natural gas C10L3/06
• CPC Class Codes: C10G 2/32 with the use of catalysts
• CPC Class Codes: Y02C 20/20 of methane
• 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 20/582 Recycling of unreacted starting or intermediate materials

Abstract

A method for removing CO₂ from a gas stream, including methane and CO₂. The method includes contacting a gas stream with an aqueous stream, so that at least a portion of the CO₂ in the gas stream is dissolved into the aqueous stream, thereby creating a CO₂-depleted gas stream, having an enriched methane concentration, and a CO₂-enriched aqueous stream. The CO₂-enriched aqueous stream is separated from the gas stream. Finally, the CO₂-enriched aqueous stream is disposed of in at least one of a marine environment, a terrestrial formation or combination thereof.

Claims

1. A method for removing CO₂ from a gas stream, the method comprising:

a. contacting a gas stream, comprising methane and CO₂, with an aqueous stream so that at least a portion of the CO₂ in the gas stream is dissolved into the aqueous stream, creating a CO₂-depleted gas stream having an enriched methane concentration and a CO₂-enriched aqueous stream, wherein the aqueous stream is at a pressure greater than about atmospheric pressure and less than a pressure of a source of the gas stream and wherein the aqueous stream has a pH of at least about 7.0;

b. separating the CO₂-enriched aqueous stream from the gas stream; and

c. disposing of the CO₂-enriched aqueous stream in at least one of a marine environment, a terrestrial formation or combination thereof, wherein disposal of the CO₂-enriched aqueous stream is done at conditions sufficient to ensure that at least about 75% of the CO₂ removed from the gas stream remains dissolved in the aqueous stream.

2. The method of claim 1, wherein the aqueous stream is obtained from at least one of sea water, reaction water formed in a Fischer-Tropsch GTL process, spent cooling water from a Fischer-Tropsch GTL process, river water, non-potable water, water recovered from hydrocarbon production and combinations thereof.

3. The method of claim 1, wherein the terrestrial formation is selected from the group consisting essentially of a hydrocarbonaceous formation, a non-hydrocarbonaceous formation and combinations thereof.

15. The process of claim 1, further comprising adjusting the pH of the aqueous stream with a basic material prior to contacting the aqueous stream with the gas stream.

16. The process of claim 15, further comprising, de-aerating the aqueous stream prior to contacting the aqueous stream with the gas stream.

4. A process for converting methane-containing gas in a Fischer-Tropsch GTL facility into liquid hydrocarbons, the process comprising:

a) contacting a methane-containing gas being supplied to a Fischer-Tropsch GTL facility, with an aqueous stream so that at least a portion of CO₂ in the methane-containing gas is dissolved into the aqueous stream creating a CO₂-depleted methane-containing gas and a CO₂-enriched aqueous stream, wherein upon contact with the methane-containing gas, the aqueous stream is at a pressure greater than about atmospheric pressure and less than a pressure of a source supplying the methane-containing gas and wherein before contact with the methane-containing gas, the aqueous stream has a pH of at least about 7.0;

b) separating the CO₂-enriched aqueous stream from the gas stream;

c) disposing of the CO₂-enriched aqueous stream in at least one of a marine environment, a terrestrial formation or combinations thereof wherein disposal of the CO₂-enriched aqueous stream is done at conditions sufficient to ensure that at least about 75% of the CO₂ removed from the gas stream remains dissolved in the aqueous stream; and

d) processing the CO₂-depleted methane-containing gas in the Fischer-Tropsch GTL facility to obtain liquid hydrocarbons.

5. The process of claim 4, wherein the aqueous stream is selected from the group consisting essentially of sea water, reaction water formed in a Fischer-Tropsch GTL process, spent cooling water from a Fischer-Tropsch GTL process, river water, non-potable water, water recovered from hydrocarbon production and combinations thereof.

6. The process of claim 4, wherein the terrestrial formation is selected from the group consisting essentially of a hydrocarbonaceous formation, a non-hydrocarbonaceous formation and combinations thereof.

7. A method for removing CO₂ from a gas the method comprising:

a) contacting a gas, comprising methane and CO₂, with a CO₂-selective adsorbent, at a pressure greater than about atmospheric pressure and less than a pressure of a source supplying the gas stream creating a CO₂-enriched adsorbent and a CO₂-depleted gas having an enriched methane concentration;

b) treating the CO₂-enriched adsorbent, regenerating the adsorbent for recycling for reuse in step (a) and forming a CO₂ stream;

c) contacting the CO₂ stream with an aqueous stream, so that at least a portion of the CO₂ is dissolved into the aqueous stream providing a CO₂-enriched aqueous stream, wherein the aqueous stream is at a pressure greater than about atmospheric pressure and less than a pressure of a source of the CO₂ stream and wherein prior to contact with the CO₂ stream, the aqueous stream has a pH of at least about 7.0; and

d) disposing of the CO₂-enriched aqueous stream in at least one of a marine environment, a terrestrial formation or combination thereof wherein the disposal of the CO₂-enriched aqueous stream is done at a pressure sufficient to ensure that at least about 75% of the CO₂ removed from the CO₂ stream remains dissolved in the aqueous stream.

8. The method of claim 7, wherein the aqueous stream is obtained from at least one of sea water, reaction water formed in a Fischer-Tropsch GTL process, spent cooling water from a Fischer-Tropsch GTL process, river water, water, water recovered from hydrocarbon production and combinations thereof.

9. The process of claim 7, wherein the pressure is sufficient to ensure that at least about 90% of the CO₂ removed from the CO₂ stream remains dissolved in the aqueous stream.

10. The process of claim 7, wherein the terrestrial formation is selected from the group consisting essentially of a hydrocarbonaceous formation, a non-hydrocarbonaceous formation and combinations thereof.

11. A method for removing CO₂ from a gas stream, the method comprising:

a) contacting a gas stream comprising methane and CO₂ with an aqueous stream selected from the group consisting of reaction water formed in a Fischer Tropsch GTL process, spent cooling water from a Fischer Tropsch GTL process, water recovered from hydrocarbon production, and mixtures thereof, at a pressure greater than about atmospheric pressure and less than a pressure of a source of the gas stream, so that at least a portion of the CO₂ in the gas stream is dissolved into the aqueous stream creating a CO₂-depleted gas stream, having an enriched methane concentration and a CO₂-enriched aqueous stream;

b) separating the CO₂-enriched aqueous stream from the gas stream; and

c) disposing of the CO₂-enriched aqueous stream in at least one of a marine environment, a terrestrial formation or combination thereof at a temperature, pressure and pH such that at least about 75% of the CO₂ removed from the gas stream remains dissolved in the aqueous stream.

12. An integrated process for converting methane-containing gas in a Fischer-Tropsch GTL facility into liquid hydrocarbons, the process comprising:

a) contacting a methane-containing gas, being supplied to a Fischer-Tropsch GTL facility, with an aqueous stream comprising reaction water formed in the Fischer Tropsch GTL process, spent cooling water from the Fischer Tropsch GTL process, and mixtures thereof, at a pressure greater than about atmospheric pressure and less than a pressure of a source of the methane-containing gas, so that at least a portion of CO₂ in the methane-containing gas is dissolved into the aqueous stream, creating a CO₂-depleted methane-containing gas and a CO₂-enriched aqueous stream;

b) separating the CO₂-enriched aqueous stream from the gas stream;

c) disposing of the CO₂-enriched aqueous stream in at least one of a marine environment, a terrestrial formation or combination thereof at a temperature, pressure and pH such that at least about 75% of the CO₂ removed from the gas stream remains dissolved in the aqueous stream;

d) processing the CO₂-depleted methane-containing gas in the Fischer-Tropsch GTL facility to obtain liquid hydrocarbons;

e) isolating a least a portion of the reaction water formed in the Fischer Tropsch process, the spent cooling water from the Fischer Tropsch process, or mixtures thereof to provide an aqueous stream; and

f) recycling the aqueous stream to contact the methane-containing gas.

13. The process of claim 12, wherein prior to contact with the methane containing gas, the aqueous stream has a pH of greater than 7.0.

14. The process of claim 13, wherein the pH of the aqueous stream is increased by adding an alkali material, adding ammonia, adding a base, or combinations thereof.

17. The process of claim 12, further comprising adjusting the pH of the aqueous stream with a basic material prior to contacting the aqueous stream with the gas stream.

18. The process of claim 17, further comprising, de-aerating the aqueous stream prior to contacting the aqueous stream with the gas stream.