Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
  • B01D53/1456—Removing acid components
  • B01D53/1475—Removing carbon dioxide
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
  • Y02C20/00—Capture or disposal of greenhouse gases
  • Y02C20/40—Capture or disposal of greenhouse gases of CO2
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E20/00—Combustion technologies with mitigation potential
  • Y02E20/32—Direct CO2 mitigation

Definitions

• the present invention is directed to producing CO 2 -depleted hydrocarbons from CO 2 -rich hydrocarbon resources.
• the present invention is directed to underwater scrubbing of CO 2 -containing hydrocarbon resources with an aqueous stream to produce a CO 2 -depleted hydrocarbon resource and a CO 2 -enriched aqueous stream.
• CO 2 is a well known environmental pollutant that contributes to atmospheric warming via the Greenhouse effect.
• CO 2 is a common contaminant in hydrocarbon resources such as, for example, natural gas.
• hydrocarbon resources such as, for example, natural gas.
• disposal of the CO 2 is problematic.
• U.S. Patent No. 6,170,264 to Viteri describes a low or no pollution engine for delivering power to vehicles or for other power applications.
• fuel and oxygen are combusted within a gas generator, generating water and CO 2 with carbon-containing fuels.
• the combustion products, steam, carbon-containing fuels and CO 2 are then passed through a condenser where the steam is condensed and the CO 2 is collected or discharged.
• the CO 2 is compressed and cooled so that it is in a liquid phase or super critical state.
• the dense phase CO 2 is then further pressurized to a pressure matching a pressure, less hydrostatic head, .existing deep within a porous geological formation, a deep aquifer, a deep ocean location or a terrestrial formation from which return of the CO 2 into the atmosphere is inhibited.
• Viteri describes disposing of CO 2 from a power generation plant into the ocean or a terrestrial formation, wherein CO 2 gas is first compressed and cooled to form a liquid phase which is then further compressed to match the hydrostatic head.
• the present invention satisfies the above objectives by providing a process that not only economically removes CO 2 from hydrocarbon resources, but also disposes of the removed CO 2 in a manner that isolates the CO 2 from the environment.
• the process of the present invention removes CO 2 from hydrocarbon resources by contacting a hydrocarbon resource with an aqueous stream, preferably at an elevated pressure. More specifically, processes of the present invention separate CO 2 from a hydrocarbon resource by scrubbing the resource with an aqueous stream at elevated pressure, producing a CO 2 -containing aqueous stream that can be disposed of, for example, in at least one of a marine environment, a terrestrial formation or combination thereof.
• one important advantage of the present invention is that it can remove CO 2 from hydrocarbon resources without having to use costly compression and/or condensation processes.
• An additional advantage is that the present invention can dispose of removed CO 2 in an aqueous stream in, for example, a marine environment, a terrestrial formation or combination thereof, thereby effectively isolating the CO 2 from the environment.
• a process, according to the present invention, for removing CO 2 from a CO 2 -containing hydrocarbon asset can include contacting the hydrocarbon asset with an aqueous stream at an underwater location so that at least a portion of the CO 2 in the hydrocarbon asset is dissolved into the aqueous stream, creating a CO 2 -depleted hydrocarbon asset and a CO 2 -enriched aqueous stream.
• the CO 2 -enriched aqueous stream is then separated from the hydrocarbon asset.
• the CO 2 -enriched aqueous stream is disposed of in at least one of a marine environment, a terrestrial formation or combination thereof.
• a method, according to the present invention, for producing a CO 2 -depleted hydrocarbon gas from a hydrocarbon/CO 2 gas mixture can include contacting a hydrocarbon CO 2 gas mixture underwater with an aqueous stream, so that at least a portion of the CO 2 in the gas mixture is dissolved into the aqueous stream, creating a CO 2 -depleted hydrocarbon gas-and a CO 2 -enriched aqueous stream. Next, the CO 2 -enriched aqueous stream is separated from the gas stream. Finally, a CO 2 -depleted hydrocarbon gas is produced.
• Fig. 1 is a schematic view of a preferred embodiment of a process for producing CO 2 -de ⁇ leted hydrocarbons, according to the present invention.
• Fig. 2 is a schematic view of another preferred embodiment of a process for producing CO 2 -depleted hydrocarbons, according to the present invention.
• At least a portion of CO 2 present in a CO 2 - containing hydrocarbon is removed by contacting the CO 2 -containing hydrocarbon with an aqueous stream, preferably at an elevated pressure. Once the CO 2 has been removed, a CO 2 -enriched aqueous stream is generated and is disposed of, for example, in at least one of a marine environment, a terrestrial formation or combination thereof, so that the CO 2 is sufficiently isolated from the environment.
• CO 2 in a hydrocarbon resource such as, for example, a natural gas
• a hydrocarbon resource such as, for example, a natural gas
• an aqueous stream such as sea water
• CO 2 -depleted hydrocarbon resource can be removed and then isolated from the environment by scrubbing using an aqueous stream, such as sea water, in an underwater location to produce a CO 2 -depleted hydrocarbon resource and a CO 2 - enriched aqueous stream.
• aqueous stream such as sea water
• Another advantage of the present invention is that because the process is conducted underwater, scrubbing can be inexpensively conducted at a pressure greater than about atmospheric pressure, thereby enhancing CO 2 dissolution.
• An additional advantage of the present invention is that because the process is conducted underwater, the process can substantially minimize and/or eliminate the need for costly gas compressors and/or liquid pumps to increase the pressure of an adsorbent used to separate CO 2 from a hydrocarbon resource.
• Yet another advantage of the present invention is that by disposing of the CO 2 -enriched aqueous stream in at least one of a marine environment, a terrestrial formation or combination thereof, the present invention disposes of removed CO 2 in a manner that isolates the CO 2 from the environment.
• Scrubbing of CO 2 from gases using aqueous liquids, according to the present invention should be conducted at non-extreme pressures to avoid formation of methane, CO 2 and other hydrates. The dissolution of CO 2 in water is enhanced at elevated pressures.
• temperature and salinity can also be important during processing. For instance, ' at relatively high temperatures, hydrate formation can occur. Also, at relatively low temperatures, a higher solubility of gas into water and a higher selectivity for removal of CO 2 over methane and other valuable hydrocarbons can be achieved. Salinity can also affect the solubility of hydrocarbons in water. For instance, a greater "salting-out" effect can occur on non-ionic hydrocarbons like methane.
• temperature and salinity of the aqueous stream can be varied to maximize selectivity for CO 2 removal. Further, in instances where sea water is used as the aqueous stream, salt in the sea water can exhibit a slight tendency to reduce the temperature at which hydrates form. [0017] It is known in the art that the maximum pressure that can be tolerated to avoid hydrate formation at various temperatures for methane and CO 2 are as follows:
• Sloan also provides numerous examples of gas mixtures and resulting temperatures/pressures at which hydrates form. Suitable operating temperature/pressure combinations are determined on a case by case basis for each gas composition. Sloan describes methods for estimating suitable operating conditions. For instance, for a typical light gas, hydrate formation can be avoided by operating at about 300 psig and about 10°C.
• a pressure less than maximum must be used.
• hydrate formation can also be controlled via kinetics and/or heat transfer.
• pressure near or above a maximum limit can be used as long as residence time is minimized.
• FIG. 1 A preferred embodiment of a process, according to the present invention, for producing CO 2 -depleted hydrocarbons from CO 2 -containing hydrocarbons by underwater scrubbing is depicted in Figure 1.
• a CO 2 -containing hydrocarbon asset stream 11 is provided from a CO 2 -containing hydrocarbon asset source 10. If necessary, the pressure of the CO 2 -containing hydrocarbon asset stream 11 is reduced in a pressure reducer 12. The CO 2 -containing hydrocarbon asset stream 11 then enters a scrubber 13. A stream of sea water 14 enters the scrubber 13. Scrubbing is conducted, producing a CO 2 -depleted hydrocarbon stream 15 and a CO 2 -containing sea water stream 18.
• the CO 2 -depleted hydrocarbon stream 15 travels above the surface of the water 16 where it is either stored or used for applications including, but not limited to, electric power generation, fuel, syngas generation.
• the CO 2 -containing sea water stream 18 is disposed of by being injected into at least one of a marine environment or a CO 2 disposal reservoir 20 under the sea bed 17 in a disposal stream 19.
• An important advantage of this embodiment is that both the sea water used for scrubbing and the hydrocarbon gas asset are at elevated pressures, facilitating dissolution of CO 2 into the sea water.
• the CO 2 - depleted hydrocarbon asset can be further processed.
• the resulting CO 2 -depleted hydrocarbon asset can be processed using at least one suitable processing step including, but not limited to, compression, condensation, separation of liquids, sulfur removal, dehydration, mercury removal, radon removal, blending with other gas streams, heating, valve adjustment, combinations thereof and the like.
• the CO 2 -depleted hydrocarbon asset can be transported to market for use in various applications.
• suitable applications for CO 2 -depleted hydrocarbon assets produced by the present invention include, but are not limited to, electric power generation, furnace fuel, syngas generation, GTL feed stock, methanol feed stock, combinations thereof and the like.
• the scrubber can be at any location under the water including, but not limited to, immediately under the sea level at the production platform, between the production platform and the sea bed, on the sea bed, or even under the sea bed.
• the hydrocarbon gas asset stream is at a pressure greater than the hydrostatic head at the location of the scrubber, the pressure of the hydrocarbon asset can be reduced to the hydrostatic pressure of the scrubber.
• the scrubber is preferably positioned on the sea bed and is associated with other production equipment located at this position.
• the scrubber located at a position above the sea bed where the pressure of the asset matches or exceeds the hydrostatic pressure, rather than being positioned on the sea bed.
• the present invention can avoid having to compress the hydrocarbon asset stream to achieve the hydrostatic pressure.
• the scrubber is preferably positioned immediately under the sea level at the production platform and is associated with other production equipment located in this position.
• contacting of the aqueous liquid stream and the hydrocarbon asset is performed at a depth where hydrostatic water pressure is less than or equal to a pressure of a source of the hydrocarbon asset.
• the temperature of the scrubber is left uncontrolled and remains at ambient conditions. However, under certain situations, it may be preferable to either. heat or cool the scrubber to facilitate CO 2 removal from the hydrocarbon gas asset stream. For example, if the hydrocarbon gas asset stream includes a viscous liquid, heating may be desirable. In addition, if larger amounts of CO 2 are intended to be removed from the hydrocarbon gas asset stream, cooling may be desirable.
• the source of the sea water, or alternative aqueous liquid, in processes of the present invention can either be adjacent to the scrubber or can be positioned some distance away from the scrubber.
• the cold sea water may be delivered, for example, though a pipe to the scrubber.
• the source of the sea water, or alternative aqueous liquid is in close proximity to the scrubber.
• the aqueous liquid source is within about 1 kilometer of the scrubber and more preferably is within about 100 meters of the scrubber.
• liquid hydrocarbons present in the CO 2 - containing hydrocarbon asset stream are preferably separated prior to scrubbing.
• the separation of liquid hydrocarbons from the CO 2 -containing hydrocarbon asset stream can also be conducted underwater.
• the pressure required for injection may be greater than the pressure of the CO 2 -containing stream exiting the scrubber.
• pressure can be inexpensively increased using liquid phase pumps.
• a pump used to inject a CO 2 -enriched aqueous stream into a terrestrial formation is positioned at a depth greater than or equal to a depth of a separator separating the CO 2 -enriched aqueous stream from a hydrocarbon asset.
• the CO 2 -containing stream is injected at a pressure and temperature sufficient to ensure that the CO 2 does not vaporize, but remains dissolved in the aqueous liquid.
• suitable terrestrial formations include, but are not limited to, hydrocarbonaceous formations, non-hydrocarbonaceous formations, combinations thereof and the like.
• suitable terrestrial formations include, but are not limited to, underground natural liquid and gaseous formations, coal beds, methane hydrates, combinations thereof and the like.
• suitable marine environments include, but are not limited to, oceans, seas, lakes, springs, reservoirs, pools, ponds, rivers, combinations thereof and the like.
• a marine disposal site for a CO 2 -enriched aqueous stream need not be near the scrubber, but can be some distance away from the scrubber.
• the hydrocarbon production facility is located in shallow water, it may be desirable to dispose of the CO 2 -enriched aqueous stream in a deep water disposal site some distance away from the production facility.
• the marine disposal site is within about 10 kilometers of the scrubber, more preferably it is within about 1 kilometer of the scrubber and most preferably is within about 100 meters of the scrubber.
• FIG 1 is shown as being positioned underwater, the CO 2 -containing hydrocarbon asset source does not have to be underwater.
• the hydrocarbon asset source can be positioned near a shore line with CO 2 -containing hydrocarbon assets being pipelined to an offshore location where underwater scrubbing of CO 2 is performed.
• sea water for scrubbing in processes of the present invention, there are several suitable alternative aqueous liquids that can be used instead of, or in combination with, sea water to scrub CO 2 from CO 2 -containing hydrocarbon assets.
• Suitable alternative aqueous liquids include, but are not limited to, reaction water formed in a Fischer-Tropsch Gas-To-Liquid (GTL) process, spent cooling water from a Fischer-Tropsch GTL facility, river water or other non potable water and water recovered from crude or gas production.
• GTL Gas-To-Liquid
• the aqueous stream preferably sea water, used to scrub
• CO from the CO 2 -containing hydrocarbon asset has a pH that is as high as possible.
• the pH of the aqueous stream is greater than about 7.0 in order to facilitate scrubbing of CO 2 .
• Numerous suitable techniques may be employed to increase the pH of the aqueous stream used to scrub CO 2 .
• One suitable way to increase the pH is to add an alkali and/or other basic materials including, but not limited to, ammonia.
• alkali and/or other basic materials including, but not limited to, ammonia.
• preferred aqueous sources include, but are not limited to, sea water, river water and other non potable water sources.
• Fischer-Tropsch GTL process water may be an especially suitable aqueous liquid for CO 2 -scrubbing because GTL process water is abundantly produced during Fischer-Tropsch GTL processing.
• nCO + 2nH 2 - nH 2 O + nCH 2 a hydrocarbon product from a Fischer-Tropsch process
• nCH 2 represents a hydrocarbon product from a Fischer-Tropsch process
• GTL process water may contain acidic contaminants such as, for example, acetic acid. Acidic contaminants can lower the pH of the process water, thereby reducing CO 2 solubility.
• acidic contaminants can lower the pH of the process water, thereby reducing CO 2 solubility.
• GTL process water is used to scrub CO 2 from CO 2 -containing hydrocarbon assets, it is preferable to remove acidic contaminants from the GTL process water prior to using it as a scrubbing stream.
• Various suitable methods exist for removing acidic contaminants from GTL process water including, but not limited to distillation, adsorption onto alumina or a basic material and oxidation.
• the scrubbing liquid used is not sea water, and contains air, the scrubbing liquid is preferably de-aerated prior to scrubbing.
• De-aeration of the scrubbing liquid increases a liquid's capacity to adsorb CO 2 and minimizes the introduction of air into the CO 2 -containing hydrocarbon gas stream.
• Processes for de-aeration of aqueous streams are well known and are used, for example, in desalination plants and for preparation of boiler feed water. Such processes are described in detail, for example, in John H. Perry's Chemical Engineering Handbook, Fourth Edition, pages 9-51, McGraw Hill Book Company, 1963, the entire disclosure of which is incorporated herein by reference. [0037] In certain situations it may be preferable to dispose of the CO 2 - enriched aqueous stream in the same formation used to supply the CO 2 -enriched hydrocarbon asset.
• CO 2 - enriched aqueous stream it may be preferable to dispose of the CO 2 - enriched aqueous stream in the same formation from which the hydrocarbon asset is supplied to maintain and/or augment the pressure of the formation.
• pressure maintenance it may be beneficial to, at least partially, vaporize the CO 2 during injection rather than before or during pumping.
• CO 2 vaporization can be achieved by reducing the pH of the aqueous stream.
• a suitable way to reduce the pH of the aqueous stream is to inject an acid.
• acid may be conveniently obtained from acidic waste water produced by a GTL facility.
• a CO 2 -enriched aqueous stream is injected into a formation not only to dispose of the CO 2 removed from the hydrocarbon asset stream, but also to maintain the pressure in the formation.
• an acidic stream can be injected into the formation to induce CO 2 vaporization by reducing the pH of the aqueous stream.
• Mixing of the acidic stream and the CO 2 -enriched aqueous stream can be conducted at various 1 suitable locations. However, to minimize problems that may be associated with compression, it is preferable to mix the acidic solution and the CO 2 -enriched aqueous stream after they have been separately compressed. Mixing can take place in the formation, for example, by using either separate wells or by alternating injection of the streams. Mixing can also be conducted above ground after the liquids have been pressurized.
• the injection of an aqueous stream, possibly with an added surfactant, into a terrestrial formation can facilitate hydrocarbon asset recovery and/or production.
• the aqueous stream may not be highly selective to scrubbing CO .
• Technology for selective scrubbing of CO 2 is well known in the art and typically uses amines.
• operating conditions may vary, in preferred embodiments operating conditions are adjusted to ensure that the hydrocarbon asset is in a gas phase during contact with the aqueous liquid stream. That is, in preferred embodiments, temperature, pressure, pH and contacting duration should be sufficient to ensure that at least about 75%, more preferably at least about 85% and most preferably at least about 90% by weight of the hydrocarbon asset is in a gas phase.
• disposal of a CO 2 -enriched aqueous stream should be conducted at a depth, pressure, temperature and pH sufficient to ensure that at least about 75 % , more preferably at least about 85 % and most preferably at least about 90% of the CO 2 removed from a hydrocarbon asset remains dissolved in the aqueous stream.
• scrubbers that are capable of operating underwater are preferred.
• scrubbers that minimize the use of complex equipment, such as pumps and control valves, may be especially preferred.
• a CO 2 -containing hydrocarbon asset stream 22 is provided from a CO 2 -containing hydrocarbon asset source 21.
• the CO 2 -containing hydrocarbon asset stream 22 passes through a pressure reducer 23, that, if necessary, reduces the pressure of the hydrocarbon asset stream 22.
• the hydrocarbon asset stream 22 then enters a scrubber 24.
• the scrubber 24 is a long tube filled with slowly downward moving sea water that enters the scrubber 24 in a sea water stream 26.
• the hydrocarbon asset stream 22, preferably in the form of a gas, is injected into a bottom section of the tube above a discharge point for a CO 2 -containing sea water exit stream 30.
• the pressure of the hydrocarbon asset gas 25 at the top of the tube is maintained at above about atomospheric pressure in order to keep the level of sea water in the tube slightly below the surrounding sea level.
• the sea water stream 26 is pumped into the tube at a rate sufficient to remove a desired amount of CO 2 .
• the pumping rate is adjusted to reach a desired level of CO 2 removal.
• the diameter of the tube is selected so that at a desired sea water pumping rate and hydrocarbon production rate, a downward flow of sea water will not exceed an upward gas bubble velocity.
• a CO 2 -depleted hydrocarbon stream 27 exits the process above the sea level 28.
• a C ⁇ 2 -containing sea water stream 30 exits the scrubber 24 for at least one of marine disposal and disposal in an underground reservoir 32. If disposed of in an underground reservoir 32, the CO 2 -containing sea water is directed under the sea bed 29 to the underground CO 2 disposal reservoir 32.
• Example 1 A CO 2 -rich source of natural gas from an undersea source is obtained with the following molar composition: about 80% CH 4 , about 20% CO 2 and a trace amount of H 2 S.
• the gas is scrubbed in a counter-current contactor with de-aerated sea water at about 0°C or about 30°C and about 300 psig to remove approximately 90% of the CO 2 and to produce a gas with only about 2% CO 2 .
• a pressure of about 300 psig is equivalent to a water depth of about 700 feet.
• the minimum amount of water need per mole of gas along with gas composition and selectivity is as follows:
• the above table provides data for both equilibrium and practical water requirements.
• the equilibrium value is calculated with equilibrium constants.
• some water such as, for example, about 20%, is required to overcome slow transfer that can occur as adsorption approaches equilibrium, and to compensate for slight effects caused by dissolved air if non-de-aerated water is used as the scrubbing fluid.

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• 2001
  • 2001-09-14 US US09/951,552 patent/US6620091B1/en not_active Expired - Lifetime
• 2002
  • 2002-08-29 JP JP2003528294A patent/JP2005502461A/ja active Pending
  • 2002-08-29 AU AU2002335691A patent/AU2002335691A1/en not_active Abandoned
  • 2002-08-29 BR BRPI0212463-7A patent/BR0212463A/pt not_active Application Discontinuation
  • 2002-08-29 WO PCT/US2002/027922 patent/WO2003024605A2/en not_active Ceased
  • 2002-08-30 ZA ZA200206993A patent/ZA200206993B/xx unknown
  • 2002-09-04 AU AU2002300871A patent/AU2002300871B2/en not_active Ceased
  • 2002-09-13 NL NL1021452A patent/NL1021452C2/nl not_active IP Right Cessation
  • 2002-09-16 GB GB0221456A patent/GB2387796B/en not_active Expired - Fee Related

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