WO2014047685A1 - Power production from ucg product gas with carbon capture - Google Patents

Power production from ucg product gas with carbon capture Download PDF

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Publication number
WO2014047685A1
WO2014047685A1 PCT/AU2013/001099 AU2013001099W WO2014047685A1 WO 2014047685 A1 WO2014047685 A1 WO 2014047685A1 AU 2013001099 W AU2013001099 W AU 2013001099W WO 2014047685 A1 WO2014047685 A1 WO 2014047685A1
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Prior art keywords
carbon dioxide
underground coal
coal seam
product gas
steam
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PCT/AU2013/001099
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French (fr)
Inventor
Denis DOUCET
Original Assignee
Linc Energy Ltd
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Publication date
Priority claimed from AU2012904206A external-priority patent/AU2012904206A0/en
Application filed by Linc Energy Ltd filed Critical Linc Energy Ltd
Publication of WO2014047685A1 publication Critical patent/WO2014047685A1/en
Priority to AU2015100328A priority Critical patent/AU2015100328A4/en

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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/295—Gasification of minerals, e.g. for producing mixtures of combustible gases
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10K—PURIFYING OR MODIFYING THE CHEMICAL COMPOSITION OF COMBUSTIBLE GASES CONTAINING CARBON MONOXIDE
    • C10K1/00—Purifying combustible gases containing carbon monoxide
    • C10K1/002—Removal of contaminants
    • C10K1/003—Removal of contaminants of acid contaminants, e.g. acid gas removal
    • C10K1/004—Sulfur containing contaminants, e.g. hydrogen sulfide
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10K—PURIFYING OR MODIFYING THE CHEMICAL COMPOSITION OF COMBUSTIBLE GASES CONTAINING CARBON MONOXIDE
    • C10K1/00—Purifying combustible gases containing carbon monoxide
    • C10K1/02—Dust removal
    • C10K1/024—Dust removal by filtration
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10K—PURIFYING OR MODIFYING THE CHEMICAL COMPOSITION OF COMBUSTIBLE GASES CONTAINING CARBON MONOXIDE
    • C10K1/00—Purifying combustible gases containing carbon monoxide
    • C10K1/08—Purifying combustible gases containing carbon monoxide by washing with liquids; Reviving the used wash liquors
    • C10K1/10—Purifying combustible gases containing carbon monoxide by washing with liquids; Reviving the used wash liquors with aqueous liquids
    • C10K1/101—Purifying combustible gases containing carbon monoxide by washing with liquids; Reviving the used wash liquors with aqueous liquids with water only
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B41/00—Equipment or details not covered by groups E21B15/00 - E21B40/00
    • E21B41/005—Waste disposal systems
    • E21B41/0057—Disposal of a fluid by injection into a subterranean formation
    • E21B41/0064—Carbon dioxide sequestration
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/006—Production of coal-bed methane
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
    • E21B43/164—Injecting CO2 or carbonated water
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K21/00—Steam engine plants not otherwise provided for
    • F01K21/04—Steam engine plants not otherwise provided for using mixtures of steam and gas; Plants generating or heating steam by bringing water or steam into direct contact with hot gas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K7/00—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating
    • F01K7/16—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being only of turbine type
    • F01K7/22—Steam engine plants characterised by the use of specific types of engine; Plants or engines characterised by their use of special steam systems, cycles or processes; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating the engines being only of turbine type the turbines having inter-stage steam heating
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B1/00—Methods of steam generation characterised by form of heating method
    • F22B1/02—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers
    • F22B1/18—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines
    • F22B1/1853—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines coming in direct contact with water in bulk or in sprays
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • C01B2203/0465—Composition of the impurity
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • C01B2203/0465—Composition of the impurity
    • C01B2203/048—Composition of the impurity the impurity being an organic compound
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
    • C01B2203/0465—Composition of the impurity
    • C01B2203/0485—Composition of the impurity the impurity being a sulfur compound
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J2300/00—Details of gasification processes
    • C10J2300/16—Integration of gasification processes with another plant or parts within the plant
    • C10J2300/1603—Integration of gasification processes with another plant or parts within the plant with gas treatment
    • C10J2300/1606—Combustion processes
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J2300/00—Details of gasification processes
    • C10J2300/16—Integration of gasification processes with another plant or parts within the plant
    • C10J2300/1603—Integration of gasification processes with another plant or parts within the plant with gas treatment
    • C10J2300/1612—CO2-separation and sequestration, i.e. long time storage
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J2300/00—Details of gasification processes
    • C10J2300/16—Integration of gasification processes with another plant or parts within the plant
    • C10J2300/164—Integration of gasification processes with another plant or parts within the plant with conversion of synthesis gas
    • C10J2300/1643—Conversion of synthesis gas to energy
    • C10J2300/165—Conversion of synthesis gas to energy integrated with a gas turbine or gas motor
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J2300/00—Details of gasification processes
    • C10J2300/16—Integration of gasification processes with another plant or parts within the plant
    • C10J2300/164—Integration of gasification processes with another plant or parts within the plant with conversion of synthesis gas
    • C10J2300/1643—Conversion of synthesis gas to energy
    • C10J2300/1653—Conversion of synthesis gas to energy integrated in a gasification combined cycle [IGCC]
    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10J—PRODUCTION OF PRODUCER GAS, WATER-GAS, SYNTHESIS GAS FROM SOLID CARBONACEOUS MATERIAL, OR MIXTURES CONTAINING THESE GASES; CARBURETTING AIR OR OTHER GASES
    • C10J2300/00—Details of gasification processes
    • C10J2300/16—Integration of gasification processes with another plant or parts within the plant
    • C10J2300/1671—Integration of gasification processes with another plant or parts within the plant with the production of electricity
    • 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
    • Y02E20/16—Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]
    • Y02E20/18—Integrated gasification combined cycle [IGCC], e.g. combined with carbon capture and storage [CCS]
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/10—Process efficiency
    • Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P30/00—Technologies relating to oil refining and petrochemical industry
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
    • Y02P90/70—Combining sequestration of CO2 and exploitation of hydrocarbons by injecting CO2 or carbonated water in oil wells

Definitions

  • the present invention pertains to methods of electric power generation that utilise underground coal gasification (UCG) product gas as a fuel source for producing combustion reactions, with low carbon dioxide emissions.
  • UCG underground coal gasification
  • Underground coal gasification is a process by which product gas is produced from a coal seam by combusting and gasifying the coal in situ in the presence of an oxidant.
  • the product gas is typically referred to as synthesis gas or syngas and can be used as a feedstock for various applications, including clean fuels production, chemical production, and electricity generation.
  • Wells are drilled into the coal seam to allow for oxidant injection and product gas extraction.
  • the wells are linked or extended to form an in-seam well channel to facilitate oxidant injection, cavity development, and product gas flow.
  • the well allowing the injection of oxidant is called an injection well.
  • the well from which product gas emerges is called a production well.
  • Both horizontal and vertical well regions can be used for injection and production.
  • Underground coal gasification may also utilise one or more vertical wells (service wells) located between the injection and production wells.
  • a coal seam having an in-seam well channel is typically referred to as a coal gasifier.
  • the gasifier will have a combustion zone within which coal is
  • UCG product gas will contain: (1 ) main syngas components (e.g., CO, H 2 , CO 2 , N 2 , and CH 4 ); (2) solid particles/particulates (e.g., soot, ash and coal particles); (3) water; (4) minor components such as C2-C 6 hydrocarbons, oxygen, argon, sulphur containing components (e.g., H2S, COS, CS 2 , mercaptans, and thiophenes), nitrogen based components (e.g., NH 3 and HCN), hydrocarbon components (e.g., coal condensate, BTEX (benzene, toluene, ethylbenzene and xylenes) and PAHs (polycyclic aromatic hydrocarbons)); and (5) trace components such as heavy metals (arsenic and mercury) and chlorides.
  • main syngas components e.g., CO, H 2 , CO 2 , N 2 , and CH 4
  • Rankine cycle power generation systems have long been in use as a source of electric power.
  • a typical steam power plant includes a boiler, which heats a pressurised working fluid (typically water) to form high temperature/pressure steam.
  • the high temperature/pressure steam is then fed into a turbine where it is expanded to a lower pressure and reduced to a lower temperature.
  • the turbine outputs power from the power plant. Thereafter, the steam is typically condensed back to a liquid for recirculation in the system.
  • Coal is a preferred fuel source for Rankine cycle power generation systems due its low cost.
  • coal combustion based Rankine cycle power generation systems generate significant amounts of carbon dioxide.
  • An object of the present invention is to provide a coal-based Rankine cycle power generation system and method for power generation with low carbon dioxide emissions (i.e., capture of carbon dioxide produced).
  • the invention provides a method of generating electric power from an underground coal seam with carbon dioxide capture, including the steps of: (i) gasifying the underground coal seam in situ, (ii) collecting UCG product gas from the underground coal seam, (iii) passing the product gas through a water wash, (iv) removing sulphur from the product gas, (v) combusting the product gas with substantially pure oxygen in the presence of water in a gas generator to produce a high temperature steam/carbon dioxide mixture, (vi) expanding the high
  • gasifying the underground coal seam in situ includes injecting substantially pure oxygen and carbon dioxide into the underground coal seam.
  • the invention provides a method of generating electric power from an underground coal seam with carbon dioxide capture, including the steps of: (i) gasifying the underground coal seam in situ, (ii) collecting UCG product gas from the underground coal seam, (iii) removing particulates from the product gas, (iv) combusting the product gas with substantially pure oxygen in the presence of water in a gas generator to produce a high temperature steam/carbon dioxide mixture, (v) expanding the high temperature steam/carbon dioxide mixture through a plurality of turbines to generate electric power, (vi) condensing the steam to recover the carbon dioxide, (vii) dehydrating the recovered carbon dioxide, (viii) compressing the recovered carbon dioxide, and (ix) removing SO x and/or NO x from the recovered carbon dioxide, wherein gasifying the underground coal seam in situ includes injecting substantially pure oxygen and carbon dioxide into the underground coal seam.
  • the carbon dioxide injected into the underground coal seam is recovered carbon dioxide (i.e., recovered from combustion of the UCG product gas and substantially pure oxygen in the gas generator).
  • the plurality of turbines include a high-pressure turbine, an intermediate-pressure turbine, and a low-pressure turbine.
  • the high temperature steam/carbon dioxide mixture is passed through a reheater after leaving the high-pressure turbine and prior to entering the intermediate-pressure turbine to increase the temperature of the mixture.
  • the reheater combusts UCG product gas with substantially pure oxygen.
  • the invention provides a method of generating electric power from an underground coal seam with carbon dioxide capture, including the steps of: (i) gasifying the underground coal seam in situ, (ii) collecting UCG product gas from the underground coal seam, (iii) passing the product gas through a water wash, (iv) removing sulphur from the product gas, (v) combusting the product gas with substantially pure oxygen in the presence of water in a gas generator to produce a high temperature steam/carbon dioxide mixture, (vi) using the high temperature steam/carbon dioxide mixture to generate steam in a pressurised boiler,
  • the invention provides a method of generating electric power from an underground coal seam with carbon dioxide capture, including the steps of: (i) gasifying the underground coal seam in situ, (ii) collecting UCG product gas from the underground coal seam, (iii) removing particulates from the product gas, (iv) combusting the product gas with substantially pure oxygen in the presence of water in a gas generator to produce a high temperature steam/carbon dioxide mixture, (v) using the high temperature steam/carbon dioxide mixture to generate steam in a pressurised boiler, (vi) expanding the generated steam through a turbine to generate electric power, (vii) condensing the steam in the steam/carbon dioxide mixture to recover the carbon dioxide, (viii) dehydrating the recovered carbon dioxide, (ix) compressing the recovered carbon dioxide, and (x) removing SO x and/or NO x from the recovered carbon dioxide, wherein gasifying the underground coal seam in situ includes injecting substantially pure oxygen and carbon dioxide into the underground coal seam.
  • the carbon dioxide injected into the underground coal seam is recovered carbon dioxide.
  • Figure 1 is a flow diagram of a method for generating electric power from an underground coal seam with carbon dioxide capture, according to an embodiment of the present invention.
  • Figure 2 is a flow diagram of another method for generating electric power from an underground coal seam with carbon dioxide capture, according to an embodiment of the present invention.
  • Figure 3 is a flow diagram of yet another method for generating electric power from an underground coal seam with carbon dioxide capture, according to an embodiment of the present invention.
  • Figure 4 is a flow diagram of a further method for generating electric power from an underground coal seam with carbon dioxide capture, according to an embodiment of the present invention.
  • Figure 1 a flow diagram of a direct method for generating electric power from an underground coal seam with carbon dioxide capture.
  • This direct method utilises a "cold clean-up" (i.e., water wash) process to remove entrained particulates, water soluble contaminants, and coal condensate from the raw UCG product gas.
  • a "cold clean-up" i.e., water wash
  • Raw UCG product gas 10 produced by an underground coal gasifier 12 is passed through a water wash process 15 for removal of entrained particulates, water soluble contaminants, and coal condensate 17, and a sulphur removal process 20 for removal of sulphur 22, to provide clean syngas 25.
  • Clean syngas 25 is fed into a gas generator 27 for combustion with substantially pure oxygen 30 in the presence of water 32, which is injected into the gas generator 27, to produce a high temperature steam/CO 2 mixture 35.
  • the high temperature steam/C0 2 mixture 35 is expanded through a high- pressure turbine 37 to generate electric power 40.
  • the high temperature steam/CO2 mixture 35 is further expanded through an intermediate-pressure turbine 42 and a low-pressure turbine 45 to generate electric power 40.
  • the high temperature steam/CO 2 mixture 35 is passed through an optional reheater 47 after leaving the high-pressure turbine 37 and prior to entering the intermediate-pressure turbine 42.
  • the reheater 47 improves overall cycle efficiency by increasing the temperature of the steam/CO 2 mixture 35 before it enters the intermediate-pressure turbine 42.
  • the reheater 47 combusts clean syngas 25 with substantially pure oxygen 30.
  • a lower temperature steam/CO2 mixture 50 exits the one or more turbines and is fed into a de-saturator or condenser 52 where the steam is condensed to water 55 to recover carbon dioxide 57.
  • de-saturator is meant a water wash that recirculates and cools the condensed fluid (i.e., water). The cooled, condensed fluid is directly mixed with the incoming stream to cool it.
  • typical condensers include shell and tube heat exchangers, with the steam on the shell side and cooling water on the tube side. Small amounts of non-condensable gases can be removed by air extraction pumps.
  • shell and tube condensers are utilised for low
  • the recovered carbon dioxide 57 is dried, purified, and compressed 60 to provide liquefied carbon dioxide 62 (i.e., captured carbon dioxide).
  • Captured carbon dioxide 62 is suitable for use in chemical production (e.g., urea and methanol), enhanced oil recovery, enhanced coal bed methane production, and geo-sequestration.
  • chemical production e.g., urea and methanol
  • enhanced oil recovery e.g., enhanced oil recovery
  • enhanced coal bed methane production e.g., enhanced coal bed methane production
  • geo-sequestration e.g., urea and methanol
  • a portion of the recovered carbon dioxide 57 is recirculated to the underground coal gasifier 12 for use as a diluent of the substantially pure oxygen 30, both of which are injected into the underground coal gasifier 12 to support combustion and gasification of the underground coal seam.
  • Dilution of the injected oxygen with carbon dioxide provides multiple benefits, including allowing the use of low cost materials for injection piping, avoiding nitrogen entering the system (which will reduce the purity of the recovered C0 2 ), and increasing overall thermal efficiency compared to injection of steam, or water (which first needs to be evaporated before reacting in the gasifier, contributing unwanted hydrogen to the UCG product gas).
  • Water 55 from the de-saturator or condenser 52 is passed through a water treatment process 65 for clean-up, to produce clean water 67.
  • Contaminated water 70 from the water wash process 15 is also passed through the water treatment process 65 for clean-up.
  • water 55 from the de-saturator or condenser 52 is recirculated to the gas generator 27 via the water treatment process 65, as injected water 32.
  • Substantially pure oxygen 30 is provided by an air separation unit 72.
  • FIG. 2 a flow diagram of another direct method for generating electric power from an underground coal seam with carbon dioxide capture is shown.
  • This direct method utilises a "hot clean-up" (i.e., filtration) process to remove entrained particulates from the raw UCG product gas.
  • Raw UCG product gas 10 produced by an underground coal gasifier 12 is passed through a filtration process 16 for removal of entrained particulates, to provide hot syngas 26.
  • any suitable type of filtration process for removal of entrained particulates can be employed.
  • particulate removal can be done in two stages; the first stage for removal of larger particles, and the second stage for removal of very fine particulates that remain in the hot syngas 26 after the first stage.
  • suitable particulate removal systems include hot candle filters (for removal of particulates as a dry solid), water scrubbers (for removal of particulates as a slurry), electrostatic precipitators, and separators, such as cyclone separators and cyclone separators employing water scrubbers.
  • the filtration process will reduce the particulate content of the hot syngas 26 to a level below about 1 mg/Nm 3 , but the actual required level will depend on downstream equipment requirements, and can be ascertained by one of ordinary skill in the art.
  • Hot syngas 26 is fed into a gas generator 27 for combustion with substantially pure oxygen 30 in the presence of water 32, which is injected into the gas generator 27, to produce a high temperature steam/C02 mixture 35.
  • the high temperature steam/C0 2 mixture 35 is expanded through a high- pressure turbine 37 to generate electric power 40.
  • the high temperature steam/CO 2 mixture 35 is further expanded through an intermediate-pressure turbine 42 and a low-pressure turbine 45 to generate electric power 40.
  • the high temperature steam/CO 2 mixture 35 is passed through an optional reheater 47 after leaving the high-pressure turbine 37 and prior to entering the intermediate-pressure turbine 42.
  • the reheater 47 improves overall cycle efficiency by increasing the temperature of the steam/CO 2 mixture 35 before it enters the intermediate-pressure turbine 42.
  • the reheater 47 combusts hot syngas 26 with substantially pure oxygen 30.
  • a lower temperature steam/CO 2 mixture 50 exits the one or more turbines and is fed into a de-saturator or condenser 52 where the steam is condensed to water 55 to recover carbon dioxide 57.
  • the recovered carbon dioxide 57 is passed through a drying
  • suitable SOx/NOx clean-up processes include low temperature, high pressure water scrubbing plus a lead chamber process, and separation by liquefaction/distillation. Both processes may be required depending on required CO 2 purity.
  • a portion of the recovered carbon dioxide 57 is recirculated to the underground coal gasifier 12 for use as a diluent of the substantially pure oxygen 30, both of which are injected into the underground coal gasifier 12 to support combustion and gasification of the underground coal seam.
  • Water 55 from the de-saturator or condenser 52 is passed through a water treatment process 65 for clean-up, to produce clean water 67.
  • water 55 from the de-saturator or condenser 52 is recirculated to the gas generator 27 via the water treatment process 65, as injected water 32.
  • Substantially pure oxygen 30 is provided by an air separation unit 72.
  • FIG. 3 a flow diagram of an indirect method for generating electric power from an underground coal seam with carbon dioxide capture is shown.
  • This indirect method utilises a "cold clean-up" (i.e., water wash) process to remove entrained particulates, water soluble contaminants, and coal condensate from the raw UCG product gas.
  • a "cold clean-up" i.e., water wash
  • Raw UCG product gas 10 produced by an underground coal gasifier 12 is passed through a water wash process 15 for removal of entrained particulates, water soluble contaminants, and coal condensate 17, and a sulphur removal process 20 for removal of sulphur 22, to provide clean syngas 25.
  • Clean syngas 25 is fed into a gas generator 27 for combustion with substantially pure oxygen 30 in the presence of water 32, which is injected into the gas generator 27, to produce a high temperature steam/C0 2 mixture 35.
  • the high temperature steam/C02 mixture 35 is used to generate steam 75 in a pressurised boiler 77, and the steam 75 is expanded through a turbine 80 to generate electric power 40.
  • a lower temperature steam/C0 2 mixture 50 exits the pressurised boiler 77 and is fed into a de-saturator or condenser 52 where the steam is condensed to water 55 to recover carbon dioxide 57.
  • the recovered carbon dioxide 57 is dried, purified, and compressed 60 to provide liquefied carbon dioxide 62.
  • a portion of the recovered carbon dioxide 57 is recirculated to the underground coal gasifier 12 for use as a diluent of the substantially pure oxygen 30, both of which are injected into the underground coal gasifier 12 to support combustion and gasification of the underground coal seam.
  • Water 55 from the de-saturator or condenser 52 is passed through a water treatment process 65 for clean-up, to produce clean water 67.
  • Contaminated water 70 from the water wash process 15 is also passed through the water treatment process 65 for clean-up.
  • water 55 from the de-saturator or condenser 52 is recirculated to the gas generator 27 via the water treatment process 65, as injected water 32.
  • Substantially pure oxygen 30 is provided by an air separation unit 72.
  • FIG. 4 a flow diagram of another indirect method for generating electric power from an underground coal seam with carbon dioxide capture is shown.
  • This indirect method utilises a "hot clean-up" (i.e., filtration) process to remove entrained particulates from the raw UCG product gas.
  • a hot clean-up i.e., filtration
  • Raw UCG product gas 10 produced by an underground coal gasifier 12 is passed through a filtration process 16 for removal of entrained particulates, to provide hot syngas 26.
  • the filtration process will reduce the particulate content of the hot syngas 26 to a level below about 1 mg/Nm 3 , but the actual required level will depend on downstream equipment requirements, and can be ascertained by one of ordinary skill in the art.
  • Hot syngas 26 is fed into a gas generator 27 for combustion with substantially pure oxygen 30 in the presence of water 32, which is injected into the gas generator 27, to produce a high temperature steam/C02 mixture 35.
  • the high temperature steam/C0 2 mixture 35 is used to generate steam 75 in a pressurised boiler 77, and the steam 75 is expanded through a turbine 80 to generate electric power 40.
  • a lower temperature steam/CO2 mixture 50 exits the pressurised boiler 77 and is fed into a de-saturator or condenser 52 where the steam is condensed to water 55 to recover carbon dioxide 57.
  • the recovered carbon dioxide 57 is passed through a drying
  • a portion of the recovered carbon dioxide 57 is recirculated to the underground coal gasifier 2 for use as a diluent of the substantially pure oxygen 30, both of which are injected into the underground coal gasifier 12 to support combustion and gasification of the underground coal seam.
  • Water 55 from the de-saturator or condenser 52 is passed through a water treatment process 65 for clean-up, to produce clean water 67.
  • water 55 from the de-saturator or condenser 52 is recirculated to the gas generator 27 via the water treatment process 65, as injected water 32.
  • Substantially pure oxygen 30 is provided by an air separation unit 72.

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Abstract

The invention provides methods of generating electric power from underground coal seams with capture of carbon dioxide.

Description

POWER PRODUCTION FROM UCG PRODUCT GAS WITH CARBON CAPTURE
TECHNICAL FIELD
[0001] The present invention pertains to methods of electric power generation that utilise underground coal gasification (UCG) product gas as a fuel source for producing combustion reactions, with low carbon dioxide emissions.
BACKGROUND ART
[0002] Underground coal gasification is a process by which product gas is produced from a coal seam by combusting and gasifying the coal in situ in the presence of an oxidant. The product gas is typically referred to as synthesis gas or syngas and can be used as a feedstock for various applications, including clean fuels production, chemical production, and electricity generation.
[0003] Wells are drilled into the coal seam to allow for oxidant injection and product gas extraction. The wells are linked or extended to form an in-seam well channel to facilitate oxidant injection, cavity development, and product gas flow.
[0004] The well allowing the injection of oxidant is called an injection well. The well from which product gas emerges is called a production well. Both horizontal and vertical well regions can be used for injection and production. Underground coal gasification may also utilise one or more vertical wells (service wells) located between the injection and production wells.
[0005] A coal seam having an in-seam well channel is typically referred to as a coal gasifier. The gasifier will have a combustion zone within which coal is
combusted in the presence of an oxidant, a gasification zone located downstream of the combustion zone in which coal is gasified and partially oxidized to produce product gas, and a downstream pyrolysis zone in which pyrolysis of coal occurs. Hot product gas flows downstream from the gasification zone and exits the ground from a well head of the production well. As coal is consumed or gasified, a gasifier
(gasification) cavity within the coal seam develops and grows in size. [0006] Typically, UCG product gas will contain: (1 ) main syngas components (e.g., CO, H2, CO2, N2, and CH4); (2) solid particles/particulates (e.g., soot, ash and coal particles); (3) water; (4) minor components such as C2-C6 hydrocarbons, oxygen, argon, sulphur containing components (e.g., H2S, COS, CS2, mercaptans, and thiophenes), nitrogen based components (e.g., NH3 and HCN), hydrocarbon components (e.g., coal condensate, BTEX (benzene, toluene, ethylbenzene and xylenes) and PAHs (polycyclic aromatic hydrocarbons)); and (5) trace components such as heavy metals (arsenic and mercury) and chlorides.
[0007] Rankine cycle power generation systems (e.g., steam power plants) have long been in use as a source of electric power. A typical steam power plant includes a boiler, which heats a pressurised working fluid (typically water) to form high temperature/pressure steam. The high temperature/pressure steam is then fed into a turbine where it is expanded to a lower pressure and reduced to a lower temperature. The turbine outputs power from the power plant. Thereafter, the steam is typically condensed back to a liquid for recirculation in the system.
[0008] Coal is a preferred fuel source for Rankine cycle power generation systems due its low cost. However, coal combustion based Rankine cycle power generation systems generate significant amounts of carbon dioxide.
[0009] While Rankine cycle power generation systems fuelled by coal are highly effective in producing electric energy, there is a need for systems that capture carbon dioxide from coal combustion, thus enabling coal-based Rankine cycle power generation systems with low carbon dioxide emissions.
SUMMARY OF INVENTION
[0010] An object of the present invention is to provide a coal-based Rankine cycle power generation system and method for power generation with low carbon dioxide emissions (i.e., capture of carbon dioxide produced).
[0011] In one aspect, the invention provides a method of generating electric power from an underground coal seam with carbon dioxide capture, including the steps of: (i) gasifying the underground coal seam in situ, (ii) collecting UCG product gas from the underground coal seam, (iii) passing the product gas through a water wash, (iv) removing sulphur from the product gas, (v) combusting the product gas with substantially pure oxygen in the presence of water in a gas generator to produce a high temperature steam/carbon dioxide mixture, (vi) expanding the high
temperature steam/carbon dioxide mixture through a plurality of turbines to generate electric power, (vii) condensing the steam to recover the carbon dioxide, (viii) dehydrating the recovered carbon dioxide, and (ix) compressing the recovered carbon dioxide, wherein gasifying the underground coal seam in situ includes injecting substantially pure oxygen and carbon dioxide into the underground coal seam.
[0012] In another aspect, the invention provides a method of generating electric power from an underground coal seam with carbon dioxide capture, including the steps of: (i) gasifying the underground coal seam in situ, (ii) collecting UCG product gas from the underground coal seam, (iii) removing particulates from the product gas, (iv) combusting the product gas with substantially pure oxygen in the presence of water in a gas generator to produce a high temperature steam/carbon dioxide mixture, (v) expanding the high temperature steam/carbon dioxide mixture through a plurality of turbines to generate electric power, (vi) condensing the steam to recover the carbon dioxide, (vii) dehydrating the recovered carbon dioxide, (viii) compressing the recovered carbon dioxide, and (ix) removing SOx and/or NOx from the recovered carbon dioxide, wherein gasifying the underground coal seam in situ includes injecting substantially pure oxygen and carbon dioxide into the underground coal seam.
[0013] In one embodiment, the carbon dioxide injected into the underground coal seam is recovered carbon dioxide (i.e., recovered from combustion of the UCG product gas and substantially pure oxygen in the gas generator).
[0014] In another embodiment, the plurality of turbines include a high-pressure turbine, an intermediate-pressure turbine, and a low-pressure turbine. [0015] In a further embodiment, the high temperature steam/carbon dioxide mixture is passed through a reheater after leaving the high-pressure turbine and prior to entering the intermediate-pressure turbine to increase the temperature of the mixture.
[0016] Suitably, the reheater combusts UCG product gas with substantially pure oxygen.
[0017] In yet another aspect, the invention provides a method of generating electric power from an underground coal seam with carbon dioxide capture, including the steps of: (i) gasifying the underground coal seam in situ, (ii) collecting UCG product gas from the underground coal seam, (iii) passing the product gas through a water wash, (iv) removing sulphur from the product gas, (v) combusting the product gas with substantially pure oxygen in the presence of water in a gas generator to produce a high temperature steam/carbon dioxide mixture, (vi) using the high temperature steam/carbon dioxide mixture to generate steam in a pressurised boiler,
(vii) expanding the generated steam through a turbine to generate electric power,
(viii) condensing the steam in the steam/carbon dioxide mixture to recover the carbon dioxide, (ix) dehydrating the recovered carbon dioxide, and (x) compressing the recovered carbon dioxide, wherein gasifying the underground coal seam in situ includes injecting substantially pure oxygen and carbon dioxide into the underground coal seam.
[0018] In a further aspect, the invention provides a method of generating electric power from an underground coal seam with carbon dioxide capture, including the steps of: (i) gasifying the underground coal seam in situ, (ii) collecting UCG product gas from the underground coal seam, (iii) removing particulates from the product gas, (iv) combusting the product gas with substantially pure oxygen in the presence of water in a gas generator to produce a high temperature steam/carbon dioxide mixture, (v) using the high temperature steam/carbon dioxide mixture to generate steam in a pressurised boiler, (vi) expanding the generated steam through a turbine to generate electric power, (vii) condensing the steam in the steam/carbon dioxide mixture to recover the carbon dioxide, (viii) dehydrating the recovered carbon dioxide, (ix) compressing the recovered carbon dioxide, and (x) removing SOx and/or NOx from the recovered carbon dioxide, wherein gasifying the underground coal seam in situ includes injecting substantially pure oxygen and carbon dioxide into the underground coal seam.
[0019] In one embodiment, the carbon dioxide injected into the underground coal seam is recovered carbon dioxide.
BRIEF DESCRIPTION OF DRAWINGS
[0020] Figure 1 is a flow diagram of a method for generating electric power from an underground coal seam with carbon dioxide capture, according to an embodiment of the present invention.
[0021] Figure 2 is a flow diagram of another method for generating electric power from an underground coal seam with carbon dioxide capture, according to an embodiment of the present invention.
[0022] Figure 3 is a flow diagram of yet another method for generating electric power from an underground coal seam with carbon dioxide capture, according to an embodiment of the present invention.
[0023] Figure 4 is a flow diagram of a further method for generating electric power from an underground coal seam with carbon dioxide capture, according to an embodiment of the present invention.
DESCRIPTION OF EMBODIMENTS
[0024] Throughout this specification, unless the context requires otherwise, the words "comprise", "comprises" and "comprising" will be understood to mean the inclusion of a stated integer, group of integers, step, or steps, but not the exclusion of any other integer, group of integers, step, or steps.
[0025] In the figures, like reference numerals refer to like features. [0026] Referring to the drawings, there is shown in Figure 1 a flow diagram of a direct method for generating electric power from an underground coal seam with carbon dioxide capture. This direct method utilises a "cold clean-up" (i.e., water wash) process to remove entrained particulates, water soluble contaminants, and coal condensate from the raw UCG product gas.
[0027] Raw UCG product gas 10 produced by an underground coal gasifier 12 is passed through a water wash process 15 for removal of entrained particulates, water soluble contaminants, and coal condensate 17, and a sulphur removal process 20 for removal of sulphur 22, to provide clean syngas 25.
[0028] Clean syngas 25 is fed into a gas generator 27 for combustion with substantially pure oxygen 30 in the presence of water 32, which is injected into the gas generator 27, to produce a high temperature steam/CO2 mixture 35.
[0029] The high temperature steam/C02 mixture 35 is expanded through a high- pressure turbine 37 to generate electric power 40. Optionally, the high temperature steam/CO2 mixture 35 is further expanded through an intermediate-pressure turbine 42 and a low-pressure turbine 45 to generate electric power 40.
[0030] Optionally, the high temperature steam/CO2 mixture 35 is passed through an optional reheater 47 after leaving the high-pressure turbine 37 and prior to entering the intermediate-pressure turbine 42. The reheater 47 improves overall cycle efficiency by increasing the temperature of the steam/CO2 mixture 35 before it enters the intermediate-pressure turbine 42.
[0031] The reheater 47 combusts clean syngas 25 with substantially pure oxygen 30.
[0032] A lower temperature steam/CO2 mixture 50 exits the one or more turbines and is fed into a de-saturator or condenser 52 where the steam is condensed to water 55 to recover carbon dioxide 57. [0033] By "de-saturator" is meant a water wash that recirculates and cools the condensed fluid (i.e., water). The cooled, condensed fluid is directly mixed with the incoming stream to cool it.
[0034] As will be understood by one of ordinary skill in the art, typical condensers include shell and tube heat exchangers, with the steam on the shell side and cooling water on the tube side. Small amounts of non-condensable gases can be removed by air extraction pumps.
[0035] Suitably, shell and tube condensers are utilised for low
pressure/temperature designs, and de-saturators for high pressure/temperature designs.
[0036] The recovered carbon dioxide 57 is dried, purified, and compressed 60 to provide liquefied carbon dioxide 62 (i.e., captured carbon dioxide).
[0037] Captured carbon dioxide 62 is suitable for use in chemical production (e.g., urea and methanol), enhanced oil recovery, enhanced coal bed methane production, and geo-sequestration.
[0038] According to an important aspect of the present invention, a portion of the recovered carbon dioxide 57 is recirculated to the underground coal gasifier 12 for use as a diluent of the substantially pure oxygen 30, both of which are injected into the underground coal gasifier 12 to support combustion and gasification of the underground coal seam. Dilution of the injected oxygen with carbon dioxide provides multiple benefits, including allowing the use of low cost materials for injection piping, avoiding nitrogen entering the system (which will reduce the purity of the recovered C02), and increasing overall thermal efficiency compared to injection of steam, or water (which first needs to be evaporated before reacting in the gasifier, contributing unwanted hydrogen to the UCG product gas).
[0039] Water 55 from the de-saturator or condenser 52 is passed through a water treatment process 65 for clean-up, to produce clean water 67. Contaminated water 70 from the water wash process 15 is also passed through the water treatment process 65 for clean-up.
[0040] According to an important aspect of the present invention, water 55 from the de-saturator or condenser 52 is recirculated to the gas generator 27 via the water treatment process 65, as injected water 32.
[0041] Substantially pure oxygen 30 is provided by an air separation unit 72.
[0042] Referring to Figure 2, a flow diagram of another direct method for generating electric power from an underground coal seam with carbon dioxide capture is shown. This direct method utilises a "hot clean-up" (i.e., filtration) process to remove entrained particulates from the raw UCG product gas.
[0043] Raw UCG product gas 10 produced by an underground coal gasifier 12 is passed through a filtration process 16 for removal of entrained particulates, to provide hot syngas 26.
[0044] Any suitable type of filtration process for removal of entrained particulates can be employed. For example, particulate removal can be done in two stages; the first stage for removal of larger particles, and the second stage for removal of very fine particulates that remain in the hot syngas 26 after the first stage.
[0045] As will be known by one of ordinary skill in the art, suitable particulate removal systems include hot candle filters (for removal of particulates as a dry solid), water scrubbers (for removal of particulates as a slurry), electrostatic precipitators, and separators, such as cyclone separators and cyclone separators employing water scrubbers. Preferably, the filtration process will reduce the particulate content of the hot syngas 26 to a level below about 1 mg/Nm3, but the actual required level will depend on downstream equipment requirements, and can be ascertained by one of ordinary skill in the art. [0046] Hot syngas 26 is fed into a gas generator 27 for combustion with substantially pure oxygen 30 in the presence of water 32, which is injected into the gas generator 27, to produce a high temperature steam/C02 mixture 35.
[0047] The high temperature steam/C02 mixture 35 is expanded through a high- pressure turbine 37 to generate electric power 40. Optionally, the high temperature steam/CO2 mixture 35 is further expanded through an intermediate-pressure turbine 42 and a low-pressure turbine 45 to generate electric power 40.
[0048] Optionally, the high temperature steam/CO2 mixture 35 is passed through an optional reheater 47 after leaving the high-pressure turbine 37 and prior to entering the intermediate-pressure turbine 42. The reheater 47 improves overall cycle efficiency by increasing the temperature of the steam/CO2 mixture 35 before it enters the intermediate-pressure turbine 42.
[0049] The reheater 47 combusts hot syngas 26 with substantially pure oxygen 30.
[0050] A lower temperature steam/CO2 mixture 50 exits the one or more turbines and is fed into a de-saturator or condenser 52 where the steam is condensed to water 55 to recover carbon dioxide 57.
[0051] The recovered carbon dioxide 57 is passed through a drying,
compressing, and contaminant removal process 61 to provide purified and liquefied carbon dioxide 62. The process of contaminant removal removes SOx NOx contaminants 64.
[0052] As will be known by one of ordinary skill in the art, suitable SOx/NOx clean-up processes include low temperature, high pressure water scrubbing plus a lead chamber process, and separation by liquefaction/distillation. Both processes may be required depending on required CO2 purity.
[0053] According to an important aspect of the present invention, a portion of the recovered carbon dioxide 57 is recirculated to the underground coal gasifier 12 for use as a diluent of the substantially pure oxygen 30, both of which are injected into the underground coal gasifier 12 to support combustion and gasification of the underground coal seam.
[0054] Water 55 from the de-saturator or condenser 52 is passed through a water treatment process 65 for clean-up, to produce clean water 67.
[0055] According to an important aspect of the present invention, water 55 from the de-saturator or condenser 52 is recirculated to the gas generator 27 via the water treatment process 65, as injected water 32.
[0056] Substantially pure oxygen 30 is provided by an air separation unit 72.
[0057] Referring to Figure 3, a flow diagram of an indirect method for generating electric power from an underground coal seam with carbon dioxide capture is shown. This indirect method utilises a "cold clean-up" (i.e., water wash) process to remove entrained particulates, water soluble contaminants, and coal condensate from the raw UCG product gas.
[0058] Raw UCG product gas 10 produced by an underground coal gasifier 12 is passed through a water wash process 15 for removal of entrained particulates, water soluble contaminants, and coal condensate 17, and a sulphur removal process 20 for removal of sulphur 22, to provide clean syngas 25.
[0059] Clean syngas 25 is fed into a gas generator 27 for combustion with substantially pure oxygen 30 in the presence of water 32, which is injected into the gas generator 27, to produce a high temperature steam/C02 mixture 35.
[0060] The high temperature steam/C02 mixture 35 is used to generate steam 75 in a pressurised boiler 77, and the steam 75 is expanded through a turbine 80 to generate electric power 40. [0061] A lower temperature steam/C02 mixture 50 exits the pressurised boiler 77 and is fed into a de-saturator or condenser 52 where the steam is condensed to water 55 to recover carbon dioxide 57.
[0062] The recovered carbon dioxide 57 is dried, purified, and compressed 60 to provide liquefied carbon dioxide 62.
[0063] According to an important aspect of the present invention, a portion of the recovered carbon dioxide 57 is recirculated to the underground coal gasifier 12 for use as a diluent of the substantially pure oxygen 30, both of which are injected into the underground coal gasifier 12 to support combustion and gasification of the underground coal seam.
[0064] Water 55 from the de-saturator or condenser 52 is passed through a water treatment process 65 for clean-up, to produce clean water 67. Contaminated water 70 from the water wash process 15 is also passed through the water treatment process 65 for clean-up.
[0065] According to an important aspect of the present invention, water 55 from the de-saturator or condenser 52 is recirculated to the gas generator 27 via the water treatment process 65, as injected water 32.
[0066] Substantially pure oxygen 30 is provided by an air separation unit 72.
[0067] Referring to Figure 4, a flow diagram of another indirect method for generating electric power from an underground coal seam with carbon dioxide capture is shown. This indirect method utilises a "hot clean-up" (i.e., filtration) process to remove entrained particulates from the raw UCG product gas.
[0068] Raw UCG product gas 10 produced by an underground coal gasifier 12 is passed through a filtration process 16 for removal of entrained particulates, to provide hot syngas 26. [0069] Preferably, the filtration process will reduce the particulate content of the hot syngas 26 to a level below about 1 mg/Nm3, but the actual required level will depend on downstream equipment requirements, and can be ascertained by one of ordinary skill in the art.
[0070] Hot syngas 26 is fed into a gas generator 27 for combustion with substantially pure oxygen 30 in the presence of water 32, which is injected into the gas generator 27, to produce a high temperature steam/C02 mixture 35.
[0071] The high temperature steam/C02 mixture 35 is used to generate steam 75 in a pressurised boiler 77, and the steam 75 is expanded through a turbine 80 to generate electric power 40.
[0072] A lower temperature steam/CO2 mixture 50 exits the pressurised boiler 77 and is fed into a de-saturator or condenser 52 where the steam is condensed to water 55 to recover carbon dioxide 57.
[0073] The recovered carbon dioxide 57 is passed through a drying,
compressing, and contaminant removal process 61 to provide purified and liquefied carbon dioxide 62. The process of contaminant removal removes SOx/NOx contaminants 64.
[0074] According to an important aspect of the present invention, a portion of the recovered carbon dioxide 57 is recirculated to the underground coal gasifier 2 for use as a diluent of the substantially pure oxygen 30, both of which are injected into the underground coal gasifier 12 to support combustion and gasification of the underground coal seam.
[0075] Water 55 from the de-saturator or condenser 52 is passed through a water treatment process 65 for clean-up, to produce clean water 67.
[0076] According to an important aspect of the present invention, water 55 from the de-saturator or condenser 52 is recirculated to the gas generator 27 via the water treatment process 65, as injected water 32. [0077] Substantially pure oxygen 30 is provided by an air separation unit 72.
[0078] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics can be combined in any suitable manner in one or more
combinations.
[0079] Throughout the specification the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one embodiment or specific collection of features. It will therefore be appreciated by those of skill in the art that, in light of the instant disclosure, various modifications and changes can be made in the particular embodiments exemplified without departing from the scope of the present invention.

Claims

1. A method of generating electric power from an underground coal seam with carbon dioxide capture, comprising the steps of:
a. gasifying the underground coal seam in situ;
b. collecting UCG product gas from the underground coal seam;
c. passing the product gas through a water wash;
d. removing sulphur from the product gas;
e. combusting the product gas with substantially pure oxygen in the presence of water in a gas generator to produce a high temperature steam/carbon dioxide mixture;
f. expanding the high temperature steam/carbon dioxide mixture through a plurality of turbines to generate electric power;
g. condensing the steam to recover the carbon dioxide;
h. dehydrating the recovered carbon dioxide; and
i. compressing the recovered carbon dioxide,
wherein gasifying the underground coal seam in situ comprises injecting substantially pure oxygen and carbon dioxide into the underground coal seam.
2. The method of claim 1 , wherein the carbon dioxide injected into the underground coal seam is recovered carbon dioxide.
3. The method of claim 1 or claim 2, wherein the plurality of turbines comprise a high-pressure turbine, an intermediate-pressure turbine, and a low-pressure turbine.
4. The method of claim 3, wherein the high temperature steam/carbon dioxide mixture is passed through a reheater after leaving the high-pressure turbine and prior to entering the intermediate-pressure turbine to increase the temperature of the mixture.
5. The method of claim 4, wherein the reheater combusts UCG product gas with substantially pure oxygen.
6. A method of generating electric power from an underground coal seam with carbon dioxide capture, comprising the steps of:
a. gasifying the underground coal seam in situ;
b. collecting UCG product gas from the underground coal seam;
c. removing particulates from the product gas;
d. combusting the product gas with substantially pure oxygen in the presence of water in a gas generator to produce a high temperature steam/carbon dioxide mixture;
e. expanding the high temperature steam/carbon dioxide mixture through a plurality of turbines to generate electric power;
f. condensing the steam to recover the carbon dioxide;
g. dehydrating the recovered carbon dioxide;
h. compressing the recovered carbon dioxide; and
i. removing SOx and/or NOx from the recovered carbon dioxide,
wherein gasifying the underground coal seam in situ comprises injecting substantially pure oxygen and carbon dioxide into the underground coal seam.
7. The method of claim 6, wherein the carbon dioxide injected into the underground coal seam is recovered carbon dioxide.
8. The method of claim 6 or claim 7, wherein the plurality of turbines comprise a high-pressure turbine, an intermediate-pressure turbine, and a low-pressure turbine.
9. The method of claim 8, wherein the high temperature steam/carbon dioxide mixture is passed through a reheater after leaving the high-pressure turbine and prior to entering the intermediate-pressure turbine to increase the temperature of the mixture.
10. The method of claim 9, wherein the reheater combusts UCG product gas with substantially pure oxygen.
11. A method of generating electric power from an underground coal seam with carbon dioxide capture, comprising the steps of: a. gasifying the underground coal seam in situ;
b. collecting UCG product gas from the underground coal seam;
c. passing the product gas through a water wash;
d. removing sulphur from the product gas;
e. combusting the product gas with substantially pure oxygen in the presence of water in a gas generator to produce a high temperature steam/carbon dioxide mixture;
f. using the high temperature steam/carbon dioxide mixture to generate steam in a pressurised boiler;
g. expanding the generated steam through a turbine to generate electric power;
h. condensing the steam in the steam/carbon dioxide mixture to recover the carbon dioxide;
i. dehydrating the recovered carbon dioxide; and
j. compressing the recovered carbon dioxide,
wherein gasifying the underground coal seam in situ comprises injecting substantially pure oxygen and carbon dioxide into the underground coal seam.
12. The method of claim 11 , wherein the carbon dioxide injected into the underground coal seam is recovered carbon dioxide.
13. A method of generating electric power from an underground coal seam with carbon dioxide capture, comprising the steps of:
a. gasifying the underground coal seam in situ;
b. collecting UCG product gas from the underground coal seam;
c. removing particulates from the product gas;
d. combusting the product gas with substantially pure oxygen in the presence of water in a gas generator to produce a high temperature steam/carbon dioxide mixture;
e. using the high temperature steam/carbon dioxide mixture to generate steam in a pressurised boiler;
f. expanding the generated steam through a turbine to generate electric power; g. condensing the steam in the steam/carbon dioxide mixture to recover the carbon dioxide;
h. dehydrating the recovered carbon dioxide;
i. compressing the recovered carbon dioxide; and
j. removing SOx and/or NOx from the recovered carbon dioxide,
wherein gasifying the underground coal seam in situ comprises injecting substantially pure oxygen and carbon dioxide into the underground coal seam.
14. The method of claim 13, wherein the carbon dioxide injected into the underground coal seam is recovered carbon dioxide.
PCT/AU2013/001099 2012-09-26 2013-09-25 Power production from ucg product gas with carbon capture WO2014047685A1 (en)

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WO2018145982A1 (en) * 2017-02-08 2018-08-16 Thyssenkrupp Industrial Solutions Ag Method for treating a synthesis gas stream
CN109138952A (en) * 2018-10-29 2019-01-04 邓晓亮 A kind of system and method for overcritical underground coal gasification(UCG) output power generation
CN112127868A (en) * 2020-09-27 2020-12-25 中国地质大学（北京） Test device for simulating underground coal gasification and oil shale co-production and test method thereof
CN114320447A (en) * 2022-01-07 2022-04-12 北京科技大学 Efficient utilization and secondary sequestration method for carbon resources of deep coal seam difficult to mine

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CN104695933A (en) * 2015-02-13 2015-06-10 新奥气化采煤有限公司 Gasification method and gasification furnace of coal seams based on branch wells
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CN109138952A (en) * 2018-10-29 2019-01-04 邓晓亮 A kind of system and method for overcritical underground coal gasification(UCG) output power generation
CN109138952B (en) * 2018-10-29 2024-04-19 邓晓亮 System and method for generating power by underground gasification of supercritical coal
CN112127868A (en) * 2020-09-27 2020-12-25 中国地质大学（北京） Test device for simulating underground coal gasification and oil shale co-production and test method thereof
CN114320447A (en) * 2022-01-07 2022-04-12 北京科技大学 Efficient utilization and secondary sequestration method for carbon resources of deep coal seam difficult to mine

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