Defining CCS Ready: An Approach to An International Definition

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Appendix B: Technology Design Options for a Capture Ready PlantRetrofitting a pulverized coal boiler for oxy-fuel firing can be quite complex. The mainchanges at the time of retrofit are:• Addition of an air separation unit (ASU) and associated equipment at retrofit;• Installation of a flue gas (CO 2 -steam) recycle system to reduce flame temperatures andtransport coal into the boiler (provisions could be made for this recycle system in aCapture Ready design).• Replacement of air-fired burners with burners capable of burning with the oxygen/fluegasrecycle mixture;• Installation of flue gas condenser;• Modified heat integration to use newly available sources of low-temperature heat (e.g.,from the flue gas recirculation cooler and CO 2 compressor intercooler), such that thesteam bleed, which is normally be used to preheat boiler feedwater, is no longerrequired and can be expanded in the low-pressure steam turbine (a Capture Ready plantcould have an overcapacity in the low-pressure steam turbine as well as in the electricitygenerator);• The air ingress should be minimized to 3 to 5% 136 in a PC boiler for oxy-firing. (Inleakageof air—sometimes as high as 20%—into the boiler and its ancillaries, a normalpractice in a standard PC boiler, will cause the CO 2 product to be diluted with air andpartly destroying the effect of burning the coal with pure oxygen; hence the need forminimizing the air ingress);• Ensure handling of the gas flows both before and after the retrofit, as the gas flows inthe flue-gas desulphurisation unit (FGD) will be different after retrofit of oxy-firing.B.2.2 Capture Ready Design Concepts for Oxy-fuel CombustionThe characteristics of a reference power plant and three different options for an Oxy-fuelcombustion plant, based on the IEA GHG 2007/4 report, are described below.Reference Plant: The reference plant under the Oxy-fuel approach is the same referenceplant used in the amine scrubbing approach described above. The plant represents a BAUcase with no anticipation of future CO 2 capture controls. The plant is a nominal 600 MWsupercritical PC. Emission control options include flue gas desulfurization, selective catalyticreduction, and activated carbon injection. The plant is assumed to have four steam turbinestages: one high, one intermediate, and two low-pressure stages.Option 1 (Essentials case): The first Capture Ready option represents a low-costapproach. Along with the minimum essential Capture Ready steps, such as ensuring enoughland and building space, the only major expense to this option is the FEED work to plan forretrofitting to oxy-fuel combustion. In the FEED design work, provisions would be made inducting for the recirculation of flue gas back into the boiler. Further provisions would be forthe interconnection and integration of the air separation unit and the CO 2 compressionplant. In this approach, no additional equipment is purchased.136 International Energy Agency Greenhouse Gas R&D Programme (IEA GHG). (2007a). CO2 capture ready plants (Reportno. 2007/4). Cheltenham, UK: Author.23 February 2010 84
Appendix B: Technology Design Options for a Capture Ready PlantOption 2 (Oversize Generator case): The second option represents a more costlyapproach than Option 1, with the benefits of lowering total capture costs (on a $/kWbasis) and improved heat rate performance. FEED work will be similar to Option 1, withthe exception of design and incorporation of an oversize turbo-generator to captureadditional steam.In the water-steam-condensate cycle of a steam turbine power generation station, somesteam is bled off from power generation purposes to reheat condensate and feedwater toimprove overall cycle efficiency. However some of this bleed-off could be made up from lowgrade heat recovery made available by the oxy-fuel combustion approach. Low grade heatrecovery is available from three sources with this retrofit: (1) flue gas recirculation circuit,(2) ASU, and (3) CO 2 compression equipment. An additional 2% to 3% of gross capacitycould be reclaimed with an oversized turbo-generator.Option 3 (Oversize Turbine/Generator case): This option represents an incrementalpre-investment to Option 2. In addition to the generator upgrade, oversizing the steamturbine and cooling towers would also be required. Estimates of up to 5% of additionalcapacity could be recovered if all low-grade recoverable heat is captured. In Option 2, fullrecovery is constrained by steam turbine size and limited cooling tower capability.B.2.3 Economics of Oxy-Fuel Capture Ready OptionsExhibit B-6 presents a line-item breakdown of the capital costs for the PC reference plant,in the United States in 2007 dollars, the same reference plant used in the amine scrubbingcase. The overnight total plant costs are approximately $866 million or $1,575 per kW.Exhibit B-6: Capital Cost Breakdown for PC Reference Plantand Oxy-fuel Combustion Options in US dollarsIncremental CostsReference Capture Ready Capture Ready Capture ReadySystem NamePlant $000 Option 1 $000 Option 2 $000 Option 3 $000Coal Handling 53,456Feedwater & Misc. BOP System 74,795PC Boiler 280,708Flue Gas Cleanup 126,202Ducting 35,801Steam Turbine Generator 112,230 1,025 5,125Cooling Tower and Water Circulation 37,285 1,025 3,075Ash + Waste Handling 12,070Wiring and Cabling 47,183Instrumentation & Control 20,284Improvements to Site + Buildings 66,377Incremental Front End Engineering and Design 4,100 5,125 6,150Total Plant Cost ($000) 866,391 4,100 7.175 14,350Total Plant Cost ($/kW) 1,575 7 13 323 February 2010 85
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Defining CCS Ready: AnApproach to A
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PrefacePrefaceThe Global CCS Instit
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Acknowledgements and CitationsThe c
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Executive SummaryThe components spe
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Chapter 1: IntroductionJustificatio
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CO2 Transport Ready PlantExhibit 1-
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