Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
  • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
  • F02C3/00—Gas-turbine plants characterised by the use of combustion products as the working fluid
  • F02C3/34—Gas-turbine plants characterised by the use of combustion products as the working fluid with recycling of part of the working fluid, i.e. semi-closed cycles with combustion products in the closed part of the cycle
• • 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
  • F01K23/00—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids
  • F01K23/02—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled
  • F01K23/06—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle
  • F01K23/10—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle with exhaust fluid of one cycle heating the fluid in another cycle
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/50—Carbon oxides
  • B01D2257/504—Carbon dioxide
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2230/00—Manufacture
  • F05D2230/50—Building or constructing in particular ways
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2230/00—Manufacture
  • F05D2230/80—Repairing, retrofitting or upgrading methods
• • 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]
• • 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 relates to the field of climate protection technology, and in particular to reduced complexity and increased efficiency of carbon capture in combined cycle power plants, in which waste heat from a gas turbine engine is used to raise steam for a steam turbine.
• our prior patent application PCT/EP2007/057434 uses vortex nozzles in an improved process for separating CO2 from a gas flow, such as the exhaust from a gas turbine engine burning a fossil fuel.
• the process comprises: compressing the gas flow to a pressure of about 2 - 3 bar, cooling it down to about - 40 0 C to - 50 0 C, supersonically expanding it through vortex nozzles so that solid CO2 centrifugally precipitates from the rest of the gas flow, and discharging the CO2 from the outer wall of the vortex nozzle for further treatment, such as preparation for sequestration.
• Figure 1 diagrammatically illustrates a known type of sequential arrangement of plant components for a CO2 capture process specifically adapted for use in conjunction with a combined cycle power plant.
• a gas turbine engine 10 compresses intake air 11 in a compressor 12, burns fuel in the compressed air 13 in a combustor 14, and obtains work from the combustion gases 15 in a turbine 16, which drives the compressor 12 via a common shaft 17.
• the major part of the mechanical power developed in turbine 16 is used to drive the electrical generator G.
• the exhaust gases 18 are typically at about atmospheric pressure and contain about 3-4 volume % CO2.
• the hot exhaust or flue gases 18 exit from the exhaust duct of turbine 16 and are passed through a heat recovery steam generator (HRSG) 19 which raises steam 20 for expansion through a steam turbine 21 to generate further power from a generator G, driven through a shaft on which steam turbine 21 is mounted.
• HRSG heat recovery steam generator
• the wet steam 22 is passed through a condenser 23, and the condensed water 24 is then recycled to the HRSG 19 by pump P.
• the flue gases 25 remain at about atmospheric pressure, but have been reduced to a temperature of about 80-120 0 C.
• Gases 25 are then cooled down to approximately ambient temperature (typically the temperature of available cooling water + 10 K) in a heat exchanger 26.
• the cooling water used in the heat exchanger 26 may, for example, be re-cooled in one or more cooling towers, or environmental water from a river, lake or sea, could be used to cool the flue gases 25.
• carbon dioxide separation in a vortex nozzle requires the gases to be pressurised in the range 2 to 3 bars, at least.
• the cooled flue gas 27 is therefore compressed in a gas compressor 28, driven by a motor M1 , which may be powered by electricity generated by the gas turbine 10 and the steam turbine 21.
• the gas compressor 28 maybe directly coupled to the shafts of either the gas or the steam turbine.
• the compressed flue gases 29 must then be cooled down to a temperature of -40 to -50 0 C before the CO2 can be cryogenically separated in a set of vortex nozzles 38 whose inlets are arranged to receive flue gases in parallel with each other (only one nozzle is shown). This is achieved by a flue gas cooling system operating in a three-stage process.
• each heat pump 33/36 comprises an evaporator 331/361 , a compressor 332/362 driven by a motor M2, a condenser 333/363, and a metering valve 334/364.
• flue gas 31 from the first cooling stage passes through the evaporator 331 of active cooling cycle 33.
• Flue gas 34 leaves evaporator 331 at a temperature which is 2 to 5 K above the freezing point of water, the evaporator being equipped with a suitable known means of separating condensed water from the flue gas.
• flue gas 34 from the second stage is further cooled down to the required temperature of -40 0 C to -50 0 C by an evaporator 361 of the second active cooling cycle 36.
• Evaporator 361 must be equipped with a suitable means of removing ice deposited on the heat exchanger surfaces during cooling of the flue gas.
• compressed cooled flue gas 37 enters the vortex nozzles 38, where it is cooled by expansion and centhfugally separated into a CO2 stream 39 and a residual flue gas stream 43.
• the CO2 stream 39 is cleaned, compressed by gas compressor 40 and fed into a pipeline 41 for storage, while the residual flue gas 44 is discharged into the atmosphere through a flue, stack (S), or the like, after undergoing further environmental cleaning procedures, if necessary.
• the condenser 363 for refrigerant in the second active cooling cycle is placed downstream of the vortex nozzles 38 so that the cold, CO2-depleted flue gas 43 exhausted from the vortex nozzle 38 can be used as a heat sink.
• a low carbon emissions combined cycle power plant utilises vortex nozzles to separate out carbon dioxide from flue gases at cryogenic temperatures, and the plant's complexity is minimised by: operating a gas turbine engine part of the plant with a turbine exhaust pressure and pressure of the downstream parts of the plant located between the gas turbine engine and the vortex nozzles at a pressure, which is high enough to assure an inlet pressure to the vortex nozzle of at least 2 bar.
• the turbine exhaust pressure is the required inlet pressure of the vortex nozzle plus the pressure losses of all components and duct between the turbine exit and the inlet of the vortex nozzle.
• Such downstream parts of the plant preferably comprise a heat recovery steam generator (HRSG) and a gas cooling system.
• the gas cooling system preferably comprises a heat exchange arrangement operable to cool flue gases received from the HRSG down to a temperature approximating normal ambient temperature and active cooling apparatus operable to further cool the flue gases down to a temperature range of roughly -40 0 C to -50 0 C.
• a low carbon emissions combined cycle power plant comprises: a gas turbine engine fuelled by carbon-containing fuel and operable to exhaust carbon dioxide-containing flue gases from a turbine exhaust duct; a heat recovery steam generator (HRSG) operable to raise steam by cooling flue gases received from the turbine exhaust duct; a steam turbine operable to produce shaft power from steam received from the HRSG; a heat exchanger arrangement operable to cool flue gases received from the HRSG down to a temperature approximating normal ambient temperature; active cooling apparatus operable to further cool the flue gases down to a temperature range of roughly -40 0 C to -50 0 C; and a plurality of vortex nozzles, each vortex nozzle having an inlet to receive flue gases from the active cooling apparatus and being operable to separate out carbon dioxide cryogenically from the received flue gases and to emit carbon dioxide depleted flue gases; wherein, in use, the gas turbine engine exhaust duct, the HRSG, the heat exchanger arrangement, and the active cooling apparatus operate at a pressure, which is high
• the plant further comprises: a gas compressor operable to compress separated carbon dioxide received from the vortex nozzles and pass it to a pipeline for conveyance to storage; and a flue gas discharge stack or the like to receive the carbon dioxide depleted flue gases and discharge them to atmosphere, optionally after removal of further pollutants from the flue gases.
• a gas compressor operable to compress separated carbon dioxide received from the vortex nozzles and pass it to a pipeline for conveyance to storage
• a flue gas discharge stack or the like to receive the carbon dioxide depleted flue gases and discharge them to atmosphere, optionally after removal of further pollutants from the flue gases.
• the plant may be provided with a flow diverter located between the HRSG and the heat exchange arrangement and operative to recirculate a proportion (e.g., 10%, 20%, 30%, 40% or up to 50%) of the gases that pass through the HRSG by injecting them into a compressor of the gas turbine engine (GT compressor) at a location whose pressure is substantially the same as the pressure of the recirculated gases.
• a proportion e.g., 10%, 20%, 30%, 40% or up to 50%
• the plant may be adapted by the designer to inject the recirculated gases into the GT compressor at a desired temperature chosen in accordance with the thermodynamic cycle it is desired to adopt.
• the temperatures of the recirculated injected gases and the GT compressor air at the injection location should be substantially the same as each other.
• thermodynamic cycle improvements can be achieved analogous to those attributable to compressor intercooling. Such cooling of the recirculated flue gases could provide increased engine power output and cycle thermal efficiency without exceeding the temperature limits of the GT compressor and combustor.
• the HRSG could cool the flue gases part of the way down to the desired temperature and a gas cooler between the flow diverter and the GT compressor could cool the gases the remainder of the way down to the desired temperature.
• the HRSG incorporates a flow diverter so that a desired proportion of the flue gases are diverted to the GT compressor before the gases have passed completely through the HRSG. If the part of the HRSG between its inlet and the flow diverter is not capable of cooling the flue gases all the way down to a desired temperature for injection of the flue gases to the GT compressor, there could be a gas cooler between the flow diverter in the HRSG and the GT compressor to further cool the diverted flue gases to the desired temperature.
• the gas turbine engine used in the plant may be a modified version of a pre- existing engine having a plurality of turbine stages and operative with a pressure in the turbine exhaust duct of approximately 1 bar, the modified version having at least one turbine stage less than the pre-existing engine, whereby the modified version is operative with a pressure in the turbine exhaust that is the above-mentioned required inlet pressure of the vortex nozzle plus the pressure losses of the downstream parts of the plant located between the gas turbine engine and the vortex nozzles .
• the invention also embraces a process for obtaining low carbon emissions from a combined cycle power plant that includes a gas turbine engine fuelled by carbon-containing fuel such that the engine exhausts carbon dioxide- containing flue gases, the process further comprising: a first cooling step in which the flue gases are cooled by using them to raise steam to drive a steam turbine to produce shaft power; a second cooling step in which the flue gases are further cooled to a temperature approximating normal ambient temperature; a third cooling step in which the flue gases are further cooled to a temperature range of approximately -40 0 C to -50 0 C; a cryogenic separation step comprising separating carbon dioxide from the flue gases and emitting carbon dioxide depleted flue gases; wherein exhaustion of the flue gases from the gas turbine engine and cooling of the flue gases occurs at a pressure, which is high enough to assure entry to the cryogenic separation step of at least roughly 2 bar.
• Figure 1 is a flow diagram illustrating a known type of combined cycle plant with an added CO 2 capture facility
• Figure 2 is a flow diagram illustrating a simplified version of the plant of Figure 1 according to a first embodiment of the invention
• Figure 3 is a flow diagram illustrating a known type of combined cycle plant with flue gas recirculation and an added CO 2 capture facility; and Figures 4A to 4C are flow diagrams illustrating simplified versions of the plant of Figure 3 according to second, third and fourth embodiments of the invention.
• turbine 16A having fewer turbine stages than is normal for a gas turbine engine in a combined cycle power plant, in that it may allow turbine 16A to be designed for increased mass flow and power. This possibility arises because the greater length and weight of the turbine rotor blades in the final stages of the turbine 16 causes the blades and the rotors on which they are mounted to be the most highly stressed components in the turbine. They are therefore limiting factors in terms of the turbine's mechanical integrity.
• HRSG 19A of Figure 2 must be constructed to withstand the higher pressure and temperature of the flue gases 18A issuing from the turbine exhaust. Because HRSG 19A will operate at increased temperature and pressure compared to HRSG 19, it will have an increased heat flow rate and may have a better heat exchange efficiency. Nevertheless, to enable elimination of the gas cooler 26 ( Figure 1 ), it may be necessary to provide HRSG 19A with a significantly larger heat exchange area than HRSG 19. Whatever the construction of HRSG 19A, heat exchanger 30 should be constructed to be capable of cooling the flue gas 25A that exits from HRSG 19A to approximately ambient temperature (typically the temperature of available cooling water + 10 K).
• Figures 2 to 4C indicate only one vortex nozzle 38, there will in fact be an array of vortex nozzles receiving the flue gases in parallel with each other.
• Figure 3 diagrammatically illustrates a known type of sequential arrangement of plant components for a CO 2 capture process specifically adapted for use in conjunction with a combined cycle power plant having exhaust gas recirculation. It comprises a modified form of the plant in Figure 1 , in which it is assumed that the following plant parameters are the same in both Figure 1 and Figure 3:
• the flue gas 25 that exits the HRSG 19 in Figure 3 is further cooled in the gas cooler 26.
• the flue gas 27 is at or near ambient pressure and temperature (i.e., the temperature of the available cooling water + 10 K).
• it is split into two streams by a diverter 45, one stream 46 being returned to the inlet of the compressor 12 of the gas turbine engine 10 and the other stream 48 being forwarded to the gas compressor 28 and the cooling units 30, 331 , 361 in preparation for entry to the vortex nozzles 38.
• the recirculated flue gas stream 46 is mixed with a stream of ambient air 1 1A in a gas mixer 47. It is assumed here that about 50% of the flue gas 27 is recirculated, though lesser proportions of flue gas recirculation, e.g., in the range 10% to 50%, would also be worthwhile.
• a purpose of exhaust gas recirculation is to increase the CO2 concentration in the turbine exhaust gas 18B, thus facilitating more efficient separation of the
• the mass flow rate of the non-recirculated flue gas stream 48 in Figure 3 will be only half that of flue gas stream 27 in Figure 1 , meaning that the compressor 28 will impose only half the power drain on the plant compared with compressor 28 in Figure 1. Furthermore, the power that is required to run the active cooling cycles 33 and 36 is also reduced to one half. Proportions of recirculated flue gases 46 that are less than 50% will of course result in lower power savings in compressor 28 and active cooling cycles 33 and 36.
• the recirculated gas should be injected into the gas turbine engine's compressor at a location where the pressure of the recirculated gas is substantially the same as the pressure in the compressor.
• the recirculated gases 46 are injected into the intake of the compressor 12, but in Figure 4A, recirculated gases 46A are injected at an inter-stage location L part-way through the compressor.
• thermodynamic cycle the temperature of the recirculated gases when injected into the compressor of the gas turbine engine will depend on the thermodynamic cycle adopted by the designer.
• the temperature of the recirculated flue gases 46A substantially matches the compressor air temperature at the injection location L. This strategy minimises mixing losses in the compressor.
• thermodynamic cycle improvements in a manner analogous to that achieved by compressor intercooling, i.e., it provides increased engine output power and thermal efficiency without exceeding the temperature limits of the engine's compressor and combustor.
• the required temperatures of the recirculated flue gases could be achieved by appropriate construction (e.g., amount of heat exchange area) of the HRSG 19A.
• Figure 4B proposes that the temperature of the recirculated gases 46A be further reduced after diversion and prior to injection by means of a gas cooler 50 inserted between the diverter 45 and the compressor 12A.
• Figure 4C A further variation of the invention is shown in Figure 4C.
• HRSG 19B incorporates a diverter (not shown) that functions similarly to diverter 45 in Figures 3 to 4B to divert a proportion 52 of the flue gases to the location L in the compressor 12A.
• the first part of the HRSG 19B between the inlet for flue gases 18B and the HRSG's diverter, may be designed to cool the flue gases 18B to a temperature at least approaching (or perhaps even lower than), the temperature of the compressor air at the location L. However, if it is deemed necessary to attain a flue gas injection temperature that is lower than that attainable by cooling in the first part of the HRSG 19B, the flue gases may be further cooled after diversion by a gas cooler 54 (shown in broken lines) inserted between the diverter in the HRSG and the location L in the compressor 12A.
• the second part of the HRSG 19B, between the HRSG's diverter and the exit for flue gases 25A is designed to cool the remaining flue gases 25B to a temperature low enough to enable gas cooler 30 to cool them to a temperature at least approaching ambient.
• location L will comprise a single axial location within the compressor 12A, but will extend around its circumference so that the inflow of recirculated gases is at least approximately evenly distributed around that circumference.
• Figures 1 to 4C diagrammatically illustrate a standard type of non- reheated gas turbine engine as part of the combined cycle plant
• the invention would of course also be applicable to combined cycle plants that include reheated gas turbine engines.
• Such engines have two sequentially arranged combustion stages for greater thermodynamic efficiency, a high pressure turbine being arranged to take some of the energy out of the gases from the first combustion stage before passing the gases to the second combustion stage for reheat.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Engine Equipment That Uses Special Cycles (AREA)
• Chimneys And Flues (AREA)

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• 2008
  • 2008-02-04 EP EP08101260A patent/EP2085587A1/en not_active Withdrawn
• 2009
  • 2009-01-22 WO PCT/EP2009/050727 patent/WO2009098128A1/en not_active Ceased
  • 2009-01-22 JP JP2010545425A patent/JP5383708B2/ja not_active Expired - Fee Related
  • 2009-01-22 EP EP09707777.0A patent/EP2240675B1/en not_active Not-in-force
• 2010
  • 2010-08-02 US US12/848,311 patent/US8327647B2/en not_active Expired - Fee Related

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