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
  • F02C6/00—Plural gas-turbine plants; Combinations of gas-turbine plants with other apparatus; Adaptations of gas-turbine plants for special use
  • F02C6/18—Plural gas-turbine plants; Combinations of gas-turbine plants with other apparatus; Adaptations of gas-turbine plants for special use using the waste heat of gas-turbine plants outside the plants themselves, e.g. gas-turbine power heat plants
• • 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
  • F01K23/103—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 with afterburner in exhaust boiler
  • F01K23/105—Regulating means specially adapted therefor
• • 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
• • 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
  • Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

Definitions

• the invention relates to combined cycle power plants with integrated C02 capture and supplementary firing as well as to their operation.
• CCS carbon capture and storage
• CCS carbon capture and storage
• Capture is defined as a process, in which CO2 is removed either from the flue gases after combustion of a carbon based fuel or the removal of and processing of carbon before combustion. Regeneration of any absorbents, adsorbents or other means to remove CO2 from a flue gas or fuel gas flow is considered to be part of the capture process.
• Backend CO2 capture also called post- combustion capture
• CCPP combined cycle power plants
• post-combustion capture the CO2 is removed from a flue gas. The remaining flue gas is released to the atmosphere and the CO2 is compressed for transportation, and storage.
• technologies known to remove CO2 from a flue gas such as absorption, adsorption, membrane separation, and cryogenic separation. Power plants with post combustion capture are the subject of this invention.
• the CO2 concentration in the CCPP flue gas depends on the fuel composition, the gas turbine type and load and may vary substantially depending on the operating conditions of the gas turbine. This variation in CO2 concentration can be detrimental to the performance, efficiency, and operatability of the CO2 capture system.
• the main objective of the present invention is to provide a combined cycle power plant (CCPP) comprising at least one gas turbine, one heat recovery steam generator (HRSG), one steam turbine, and carbon dioxide (CO2) capture system with enhanced operational flexibility, and to reduce capacity penalties for CO2 capture as well as an operating method for such a CCPP.
• CCPP combined cycle power plant
• the impact of CO2 capture on the capacity of a CCPP is to be minimized, i.e. the electric power delivered to the power grid by the plant including the CO2 capture system is to be maximized.
• the essence of the invention is an operating method for a CCPP with flue gas recirculation, which allows operation of a supplementary firing burner in flue gases of a CCPP with flue gas recirculation, which at least partially compensates for the power requirements of the CO2 capture system.
• the supplementary firing burner can be installed in the HRSG of the CCPP or as a duct firing in the flue duct from the gas turbine to the HRSG.
• the flue gas flow of a gas turbine is split into at least two partial flows downstream of the HRSG.
• a first partial flow is returned to the inlet of the gas turbine via a flue gas recirculation line, and a second partial flow is directed via the CO2 capture system to the stack for release to the environment.
• a bypass around the CO2 capture system for direct release of flue gases to the environment can be provided to increase the operational flexibility. This allows any combination of recirculation rate, of flue gas flow to CO2 capture unit, and direct flue gas flow to the stack without CO2 capture.
• Flue gas recirculation is applied to minimize the CO2 capture system's size, its costs, and its power requirements.
• the recirculation rate is defined as the ratio of flue gas mass flow from the gas turbine, which is recirculated to the compressor inlet, to the total flue gas mass flow of the gas turbine.
• the oxygen concentration in the flue gas would ideally be 0%. Due to cooling air, which bypasses the gas turbine's combustion chamber, and excess oxygen needed to assure complete combustion, recirculation is limited and some residual oxygen remains in the exhaust gas even with recirculation.
• Typical recirculation rates determined by the operational requirements of the gas turbine are in the order of 30% to 50% for base load operation.
• a low excess air supplementary firing burner is a burner, which can be operated in a gas flow with less than 10% oxygen concentration with a low stoichiometric ratio.
• the stoichiometric ratio for this kind of a low excess air supplementary firing burner should be below 2, preferably below 1.5 or even below 1.2. Ideally this kind of burner can operate with a stoichiometric ratio as close as possible to 1.
• a conventional duct burner or interstage burner could be used with additional air supply at a high excess air ratio. However, this would dilute the CO2 concentration in the flue gas and increase the flue gas flow. It is therefore not an adequate solution for this application.
• the oxygen content can also be used in the context of this invention.
• the recirculation rate can be controlled by at least one control organ.
• This can for example be a controllable damper or a fixed splitter with a control organ like a flap or valve in one or both of the flue gas lines downstream of the splitter.
• Stable complete combustion in this context means, that CO and unburned hydrocarbon emissions stay below the required level, which is in the order of ppm or single digit ppms and that the combustion pulsations stay within the normal design values. Emission levels are typically prescribed by guarantee values. Design values for pulsation depend on the gas turbine, operating point, and combustor design, as well as on the pulsation frequency. They should remain well below 10% of the combustor pressure. Typically they stay below 1 or 2 % of the combustor pressure.
• the recirculation rate can for example also be used to control the oxygen concentration of the compressor inlet gases after mixing ambient air with the recirculation flow.
• the target oxygen concentration of the inlet gasses can for example be a fixed value, which is sufficient to assure stable, complete combustion in the gas turbine under all operating conditions.
• the target oxygen concentration of the flue gases is a function of relative load of the supplementary firing. It can be minimized according to the requirements of the gas turbine as long as the supplementary firing is switched off. Once supplementary firing is switched on, the requirements of the gas turbine and of the supplementary firing have to be considered. The larger one of the two requirements determines the target residual oxygen concentration of the flue gas.
• the required residual oxygen concentration for the supplementary firing itself can be a fixed value or a function of the burner load of the supplementary firing.
• the recirculation rate can be a fixed rate or determined independently of the supplementary firing.
• the additional airflow, and/ or oxygen enriched airflow, and/or oxygen flow is controlled.
• the additional airflow, and/ or oxygen enriched airflow, and/or oxygen flow can be a fixed flow.
• excess air or oxygen should be avoided in the flue gases in order to keep the efficiency of the CO2 capture high. Therefore a control of the additional air, and/ or oxygen enriched air, and/or oxygen flow is proposed.
• the additional airflow, and/ or oxygen enriched airflow, and/or oxygen flow is controlled as a function of the flue gas recirculation rate.
• the additional airflow, and/ or oxygen enriched airflow, and/or oxygen flow is controlled as a function of residual oxygen concentration of the flue gases of the gas turbine.
• the additional airflow, and/ or oxygen enriched airflow, and/or oxygen flow is controlled as a function of the relative load of the supplementary firing.
• control parameters and targets are possible.
• good operation conditions for the supplementary firing can be obtained with a combination of control as function of residual oxygen concentration of the flue gases and of load of supplementary firing.
• the additional ambient air flow, and/ or oxygen enriched airflow, and/ or oxygen flow is preheated by low-grade heat from a water steam cycle of the combined cycle power plant, and/ or the CO2 capture system, and/ or the flue gases.
• CCPP combined cycle power plant
• the CCPP comprises at least one gas turbine, one HRSG, one steam turbine, CO2 capture system and a supplementary firing. Further, it comprises one recirculation line and one flue gas line to the CO2 capture system. According to one embodiment a low excess air supplementary firing is provided in the HRSG of the combined cycle power plant.
• ambient air, and/ or oxygen enriched air, and/ or oxygen supply lines to the low excess supplementary firing is provided.
• an oxygen enrichment plant and/ or an air separation unit can be provided.
• At least one oxygen measurement or CO2 measurement device can be installed to measure the oxygen concentration or CO2 concentration of the inlet gases of the compressor inlet gas and/ or to measure the residual oxygen concentration of the hot flue gases of the gas turbine and/ or to measure the residual oxygen concentration of the flue gases from the HRSG.
• the supplementary firing can also be used to increase the plant flexibility and to provide power to compensate the influence of variations in the ambient conditions or to cover periods of peak power demand.
• the recirculated flue gas has to be further cooled after the HRSG by a re-cooler before mixing it with ambient air for reintroduction into the compressor of the gas turbine.
• the control organ for controlling the recirculation rate is installed downstream of this re-cooler to reduce thermal load on this control organ.
• Fig. 1 schematically shows a CCPP with backend CO2 absorption including flue gas recirculation and low excess air ratio supplementary firing.
• Fig. 2 schematically shows a low excess air ratio supplementary firing burner for application in a HRSG of a CCPP with flue gas recirculation.
• Fig. 3 schematically shows the normalized residual oxygen concentration of the gas turbine flue gas GT O 2 required for supplementary firing as a function of the relative load of the supplementary firing SF
• Fig. 4 schematically shows the normalized residual oxygen concentration of the gas turbine flue gas GT02 required for supplementary firing as a function of relative load of the supplementary firing SF
• a power plant for execution of the proposed method consists a conventional CCPP, equipment for flue gas recirculation, a supplementary firing 10, plus a CO2 capture system 18.
• FIG. 1 A typical arrangement with post combustion capture, flue gas recirculation, and supplementary firing 10 is shown in Fig. 1.
• a gas turbine 6, which drives a first generator 25, is supplied with compressor inlet gas 3, and fuel 5.
• the compressor inlet gas 3 is a mixture of ambient air 2, and a first partial flow 21 of the flue gases, which is recirculated via a flue gas recirculation line.
• the inlet gas is compressed in the compressor 1.
• the compressed gas is used for combustion of fuel 5 in a combustor 4, and pressurized hot gasses expand in a turbine 7. Its main outputs are electric power, and hot flue gasses 8.
• the gas turbine's hot flue gasses 8 pass through a HRSG 9, which generates steam 30 for a steam turbine 13.
• HRSG 9 or the flue gas duct from the gas turbine 6 to the HRSG 9 supplementary firing 10 is integrated.
• the supplementary firing is supplied with fuel gas 12 and ambient air/ oxygen 11.
• the steam turbine 13 either is arranged in a single shaft configuration with the gas turbine 6 and the first generator 25, or is arranged in a multi shaft configuration to drive a second generator 26. Further, steam is extracted from the steam turbine 13 and supplied via a steam line 15 to a CO2 capture system 18. The steam is returned to the steam cycle as a condensate via a return line 17 and is reintroduced into the steam cycle.
• the steam cycle is simplified and shown schematically without different steam pressure levels, feed water pumps, etc., as these are not subject of the invention.
• a first partial flow 21 of the flue gases from the HRSG 19 is recirculated to the inlet of the compressor 1 of the gas turbine 6 where it is mixed with ambient air 2.
• the fist partial flow 21 is cooled in the recirculation flue gas cooler 27 before mixing with the ambient air 2.
• a second partial flow 20 of the flue gases from the HRSG 19 is directed to the CO2 capture system 18 by a damper 29.
• a CO2 capture system 18 typically consists of a CO2 absorption unit, in which CO2 is removed from the flue gas by an absorbent, and a regeneration unit, in which the CO2 is released from the absorbent.
• a flue gas cooler 23 might also be required.
• the CO2 depleted flue gas 22 is released from the CO2 capture system 18 to a stack 32.
• the flue gases from the HRSG can be bypassed or partly bypassed via the flue gas bypass 24.
• the captured CO2 31 will be compressed in a CO2 compressor and the compressed CO2 will be forwarded for storage or further treatment.
• Measurement devices to measure the oxygen concentration and/ or CO2 concentration are proposed in order to better control the residual oxygen concentration.
• an inlet air CO2 and/or 02 measurement device 36 can be applied for better control of inlet gas composition for the gas turbine 6.
• a gas turbine flue gas CO2 and/or 02 measurement device 37 can for example be applied.
• a HRSG flue gas CO2 and/or 02 measurement device 38 can for example be applied.
• FIG. 2 An example of a supplementary firing 10 for burning fuel gas 12 with ambient air at low excess air ratio and with oxygen /oxygen enriched air 11 in an HRSG 9 is shown in Fig. 2.
• burner boxes 28 for supplementary firing are arranged traversal, spaced apart in arrays in a cross section of the HRSG inlet 33 or inside the HRSG.
• Gas turbine flue gas 8 passes past the burner boxes 28 through the passages between the boxes while the flame of the supplementary firing is stabilized in them.
• Additional ambient air or oxygen 11 as well as fuel gas 12 are supplied to the burner boxes and injected via the fuel gas injection orifices 34 and the oxidizer injection orifices 35.
• oxygen is not injected directly into burner boxes 28 but diluted with some carrier gas like ambient air or recirculated flue gas before it comes into contact with the fuel gas 12.
• the oxygen concentration of the flue gases of the gas turbine 8 is not controlled and independent of the operation of supplementary firing.
• the supplementary firing typically is simply switched on, after the gas turbine reaches base load and operated independently of the gas turbine 8.
• Base load is typically the operating condition with the lowest residual oxygen concentration in the flue gases.
• the oxygen concentration stays practically constant at this level and only slight changes due to changes in the ambient conditions occur.
• this approach is not feasible with flue gas recirculation and minimized residual oxygen concentration in the hot flue gases from the gas turbine 8, as conventional supplementary firing does not work properly under these conditions.
• the residual oxygen concentration after gas turbine GT 02 Js controlled as a function of the relative load of the supplementary firing as shown in Fig. 3. It is normalized with the minimum residual oxygen concentration of the flue gas from the gas turbine 8, which would be reached if the gas turbine 6 were operated at the recirculation limit of the gas turbines.
• the residual oxygen concentration after gas turbine GT02 is higher than the minimum residual oxygen concentration of the flue gas required for the gas turbine operation. Therefore the recirculation rate is restricted to allow supplementary firing.
• the required residual oxygen concentration varies as a function of load.
• a required oxygen concentration which is proportional to the load, is possible.
• the load range might be restricted to higher loads, e.g. 40% to 100% load.
• a variation of the residual oxygen concentration of the flue gases from the GT 8 is needed. This increases the complexity of the control integration, and can lead to combustion instabilities in the GT. Further, it leads to variation in the second partial flow 20 of the flue gases, which flows to the CO2 capture system 18, as a function of the relative load of the supplementary firing.
• the required residual oxygen concentration for the supplementary firing can limit the recirculation ration and result in an increased maximum second partial flow 20.
• supplementary firing with additional ambient air, oxygen enriched air or oxygen flow F a , r is applied.
• Oad can be kept constant independently of relative load of the supplementary firing. Therefore no complex control interface or logic between the gas turbine and supplementary firing is needed.
• the fuel gas is burned in the supplementary firing burner with an additional ambient airflow, oxygen enriched airflow or oxygen flow Fair-
• the supplementary firing burner can thereby work independently from gas turbine flue gas oxygen concentration and produces flue gas at low 02 and high CO2 concentrations.
• the flue gas recirculation rate could and shall be designed at its maximum allowed value to keep the minimal oxygen concentration i.e. the highest CO2 concentration in the gas turbine flue gases while sending the minimum amount of flue gas from CCPP to the CO2 capture plant.
• the normalized additional ambient air, oxygen enriched air or oxygen flow Fair required to assure stable and complete combustion is also shown in Fig. 4. It is normalized with the additional ambient air or oxygen flow required at 100% load.
• the temperature is low and a relatively high ambient airflow, oxygen enriched airflow or oxygen flow F a , r is required to assure complete combustion. It is typically well above stoichiometric and results in high residual oxygen concentration SF O2 after the supplementary firing.
• oxygen enriched airflow or oxygen flow F a ⁇ r only increases at a low rate.
• the fuel specific additional ambient airflow, oxygen enriched airflow or oxygen flow F a ⁇ r can be reduced.
• the resulting normalized residual oxygen concentration after supplementary firing SFo2 is also shown in this Figure. It is normalized with the oxygen concentration after supplementary firing SF O 2 at 100% load. For this example it reaches a minimum at 100% load. At 100% load the combustion temperature is highest, which facilitates a fast complete combustion down to very low residual oxygen concentration and corresponding high CO2 concentration.
• the CO2 concentration is inverse proportional to the residual oxygen concentration, and low oxygen concentration corresponds to a high CO2 concentration.
• the CO2 and the residual oxygen concentration at different locations of the thermodynamic process of a CCPP can be determined using main process parameters. Based on the inlet mass flow, the recirculation rate, the fuel mass flows, mass flow of ambient airflow, oxygen enriched airflow or oxygen flow F a ⁇ r injected, and the combustion efficiency, the oxygen concentration and CO2 concentration in the inlet gas, after the gas turbine, and after the supplementary firing can be estimated. These estimated values are used in one embodiment of the invention.
• CO2 can for example easily be measured using Nondispersive Infrared (NDIR) CO2 Sensors, or Chemical CO2 Sensors.
• Oxygen concentration can, among others, be measured using zirconia, electrochemical or Galvanic, infrared, ultrasonic sensors, and laser technology. Fast online sensors can be applied for optimized operation.
• blowers might be advantageous for first partial flow 21 of the flue gases, which is recirculation or for the second partial flow 20 of the flue gases, which flows to the CO2 capture system 18. Without blowers the pipes and equipment size needed to allow sufficient flow with existing pressure differences might become prohibitive.
• oxygen enriched airflow or oxygen flow F a i r when used for the supplementary firing this flow can be preheated by low grade heat from the water steam cycle, and/ or the CO2 capture system 18, and/ or the flue gases. Return condensate from intermediate pressure feed water can for example be utilized for this.
• dampers or other control organs which inherently lead to a pressure drop
• controlled blowers could for example be variable speed blowers or blowers with controllable blade or guide vane angles.
• Second partial flow (Flue gas CO2 capture system)
• First partial flow (Flue gas recirculation)

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Engine Equipment That Uses Special Cycles (AREA)
• Treating Waste Gases (AREA)

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• 2008
  • 2008-12-24 EP EP08172880A patent/EP2246532A1/en not_active Withdrawn
• 2009
  • 2009-12-21 JP JP2011542806A patent/JP5627598B2/ja not_active Expired - Fee Related
  • 2009-12-21 CA CA2747643A patent/CA2747643A1/en not_active Abandoned
  • 2009-12-21 EP EP09801974A patent/EP2368023A2/en not_active Withdrawn
  • 2009-12-21 WO PCT/EP2009/067674 patent/WO2010072729A2/en not_active Ceased
  • 2009-12-21 CN CN200980153140.XA patent/CN102265005B/zh not_active Expired - Fee Related
• 2011
  • 2011-06-10 US US13/157,897 patent/US8365537B2/en not_active Expired - Fee Related
• 2013
  • 2013-01-11 US US13/739,806 patent/US20130118179A1/en not_active Abandoned

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