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Development of High Efficiency CFB Technology to Provide FlexibleAir/Oxy Operation for Power Plant with CCS
FLEXI BURN CFB
WP5: Power plant integration, optimizationWP5: Power plant integration, optimizationand economics for a commercial scale plant
2nd Project Workshop, 6th February 2013, Ponferrada
WP5: Power plant integration, optimization andeconomics for a commercial scale plant
Development of
Feasibility and readiness for the utilization of
the technology within different regions in EU
WP2
WP6
WP7: Coordination and dissemination
2
Comparison of air-
and oxy-firing
Development of
design tools
Boiler design
and performance
Power plant integration,optimization and
economics
WP1 WP4 WP5
Technology demonstration andbackground for the commercialscale design process
Supporting R&Dwork
Viable boiler design Viable power plant
Demonstration testsat large pilot unitand commercial
scale air fired unit
WP3
WP5: MAIN OBJECTIVES
1. To produce an optimized design for a commercial scale FLEXI BURN CFB plant, bystudying different concepts.
2. To develop optimized concepts for ASU and CPU systems for the case of the FlexiBurn CFB plants.
3. To analyze possible integration of the different main systems of the plant in order tooptimize the concept.optimize the concept.
4. To identify and assess health and safety issues related to new operating conditions
5. To develop a dynamic process model in order to estimate the concept response timesto different changes, and to analyze the flexibility of the plant.
6. To determine basic operation procedures for the integrated plant and detect thepossible limitations of the concept.
7. To estimate economics for the new concept and evaluate their feasibility on acommercial scale range
Basis of the FLEXI BURN plant
• Steam parameters:
600 ºCReheated steam temperature
57 barReheated steam pressure
270 barMain steam pressure
598 ºCMain steam temperature
600 ºCReheated steam temperature
57 barReheated steam pressure
270 barMain steam pressure
598 ºCMain steam temperature
• Main plant characteristics:
• ~330 MWe gross.
• Design coal: Spanish anthracite+petcoke(70/30%)
• Cooling tower.
4
• CO2 compressed to transport bypipeline.
CONCENTRATION
H2O < 500 ppm
CO < 2000 ppm
O2 + N2 + Ar < 4 vol%
SOx < 100 ppm
NOx < 100 ppm
CO2 >95.5 %
• Other oxycombustion criteria:
• Air inleakage: Base case 1% (sensitivity analysis up to 3%).
• O2/CO2 ratio: close to air concentration (24% O2 wet).
• Oxygen purity:
Oxygen purity 96,6 % volPressure 1,2 barTemperature 20 ºC
Final configuration of the integrated plant. Basecase
5
Utilities
Utilities
Final configuration of the integrated plant. Basecase
• Definition of other main PFDs of the FLEXI BURN CFB plant:
6
CPU Conceptual design
Oxy-Combustion
Flue Gas
Flue Gas Condenserw/Heat Recovery
Multi-Stage FeedCompressionSystem
CarbonBed
CO2
ColdBox
CO2 toSequestration
AdvancedSOx/NOx
Treatment
RegenVent
CO2
VPSAWater
Water
DryerBeds
High PressureScrubbing Tower
ProcessCondensate
ProductCompressors
Optimised concept:
• Very high CO2 recovery rate. (Near zero Emissions plant)• Lower SOX and NOX in purified CO2.
7
ASPEN Plant Model. Optimisation
Boiler
Oxidant Flue gas
CPUASU
SteamCycle
IntegrationIntegration
Power Utilities Power Utilities
8
Application of the model for:
• Evaluation of operation in air/oxy modes, for different loads andoperating conditions.
• Analysis of the influence of selected parameters (e.g., O2 purity, recirc.ratio…)
• Evaluation of different integration alternatives for process optimisation
ASPEN Plant Model. Optimisation
• Evaluation of different integration alternatives for process optimisation
Boilermodel
9
Base case without heat integration:
ASPEN Plant Model. Optimisation
Load (plant, %MCR) 90%
Fuel kg/s 27,95
Steam Turbine Output MW 279,79
Gross efficiency (Boiler+cycle) % 43,41
Auxiliary Power MW 24,76
Air mode:
Net power MW 255,03
Net efficiency % 39,57
Load (plant, %MCR) 100%
Fuel kg/s 30,61
Steam Turbine Output MW 332,5
Gross efficiency (Boiler+Cycle) % 47,11
Auxiliary Power MW 27,26
Net Power (Boiler+Cycle) MW 305,24
ASU + CPU Power MW 79,13
Net Power (plant) MW 226,11
Net efficiency % 32,03
OXY mode:
CO2 purity in product stream %v 96,8
Pure CO2 captured % 98,5
With ASU and CPU heat integration:
ASPEN Plant Model. Optimisation
AC.2:
•net power output: +5 MW
•net efficiency: +0.7% (abs)
Base AC.2
Fuel kg/s 30,61 30,61
Steam Turbine Output MW 332,49 337,16
Net Power (plant) MW 226,1 231,03
Net efficiency % 32,03 32,73•net efficiency: +0.7% (abs)
•Reduction of CW: -37%
•Additional heat exchangers: +14.
Operational procedures morecomplex.
Net efficiency % 32,03 32,73
CW in ASU kg/s 1216 782
No. coolers CW 12 12
No. coolers BFW 0 4
CW in CPU kg/s 2264 1421
No. coolers CW 18 17
No. coolers BFW 0 11
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Dynamic process model for power plant
• A dynamic model of the process integrate that covers the process units ASU (Airseparation unit), CFB (Circulating fluidized bed boiler), and CPU (CO2 compressionand purification unit) was constructed
• The model includes the main process units and streams of the process to providethe characteristic dynamic features of the system
• The control loops and supporting calculations that were essentially required tooperate the system are included.
• The simulation studies include typical operation transients, such as load changes• The simulation studies include typical operation transients, such as load changesand changes between oxy-firing and air-firing
• The simulation model was built using the Apros simulation software . Aspensimulation products have also been applied to support the modelling especiallyregarding the sub-processes ASU and CPU.
• Simulator can be used for upper level control development and testing. Thetechnical link between the simulator and the controller was developed and testedduring the modelling task.
• The primary target is to provide information on dynamic behaviour of theintegrated system
This information is essential for verifying the feasibility of the processconcept and its control strategies from low level to upper level controllers
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APROS
A dynamic tool combining Apros and AspenDynamics simulators
• Neither tool alone was able to simulate the entire ASU + CFB + CPU process in detailcombine the two
ASPEN PLUS DYNAMICS
Air Separation Unit Carbon compression and PurificationUnit
CFB boiler unit
Turbine and water cycle
SIMULINK
Cases which were calculated in Flexi burn
Boiler load change 40 -> 100% and 100 -> 40%, air firing
Boiler load change 40 -> 100% and 100 -> 40%, oxy firing
Swicthing from air firing over to oxy firing
Fuel feed trip, air- and oxy firing
Feed water pump trip, air- and oxy firing
Boiler load change 100 -> 40 -> 100%, oxy firing. Integrated use ofApros and Aspen Dynamics.
CO2-compressor trip, oxy firing
10% step changes into fuel feed (40%->50%->…->100%), oxymode.
Boiler at different loads 40%/60%/80%/100%, oxy mode. Governorvalve dynamic response studied by 10% position step changes. 14
Load change from 100%-70%-100% in oxy-mode. Integrateduse of Aspen Dynamics and Apros which were linked togetherby Simulink.
The variables which were sent from Aspen to Apros: Oxygen flow (gaseous and liquid)
Simulation example: Load change 100% to 70%and back, integrated use ASU + CFB + CPU
Oxygen flow (gaseous and liquid)
Oxygen concentration (mass fraction, gaseous and liquid))
Oxygen temperature (gaseous and liquid)
Nitrogen concentration (mass fraction, gaseous and liquid)
The variables which were sent from Apros to Aspen:
Oxygen demand from the boiler according to boiler load
Oxygen flow control to the boiler was carried out by using oxygen liquid andgaseous buffer tanks. ASU-unit main variables (O2 –concentration, O2 –production) were controlled by using different kind of proportion-, pressure-,level- and flow-controllers.
15
APROS
Simulation example: Load change 100% to 70%and back, integrated use ASU + CFB + CPU
ASPEN PLUS DYNAMICS
Air Separation Unit Carbon compression and PurificationUnit
CFB boiler unit
Turbine and watercycle
SIMULINK
16
Operational procedures
• Definition of the operational limitations (regulation, equipment limits, load profiles...
• Based on previous limitations, experiences in CIUDEN TDP and dynamic modelling start-up, shut down and transition main sequences have been defined for each of the main.
• Example: Start-up overall philosophy:
– ASU start-up (if hot or warm)
– Boiler start-up in air mode. (ASU start-up in parallel if plant is cold.)– Boiler start-up in air mode. (ASU start-up in parallel if plant is cold.)
– Syncro to grid.
– Change to oxycombustion mode
– CPU start-up. Gas scrubbers system start-up.
– CO2 dry line in operation, opening of the CO2 sealing lines.
– CPU start-up continuation.
– Opening of the transport line valve.
– Increase of load up to nominal value.17
Safety issues
• FLEXI BURN CFB must face new safety issues due to the integration of new unitsin a power plant, ASU and CPU.
Associated risks for new gases in the plant:
Gas Associated Risks
O2 gas Enhanced combustion with O2
O2 liquid Enhanced combustion with O2.O2 liquid Enhanced combustion with O2.
Cryogenic risks.
High concentrated CO2 Asphyxiant atmosphere.
Toxicity.
Cryogenic risks.
Nitrogen gas
Nitrogen liquid
Asphyxiant atmosphere.
Cryogenic risks
18
Safety issues
• Works developed in this area in the FLEXI BURN CFB project:
Revision and definition of malfunctions and risks
Identification of safeguards for each risk.
Definition of general operating procedures and design guidelines. Identification ofstandards than can be considered in the design of the equipments.standards than can be considered in the design of the equipments.
Definition of main rules for FLEXI BURN CFB gas vents design
Safety supervision during the operation. Inspections
Contingency and emergency procedures. Definition of potential emergencyconditions
19
Design modifications for new FLEXI BURN CFBconcept compared to conventional power plant
Design of power plant auxiliary equipment for dual operation
• Fans (higher temperatures, materials, erosion-corrosion combined effects, CO2 sealing).
• Dampers (control, tighness).
• Bagfilter (tight joints, CO2 sealing in the ashes discharge, Acid resistant material high range ofretention efficiency specially in smallest particle sizes, cleaning system adapted to use dry recycledCO2 or air).CO2 or air).
• Limestone and fuel feeding system (wider range of capacity, CO2 as transport media, pressureseals, corrosion and agglomeration).
• Flue gas ducts: (tightness for air inleakages and gas leakages, expansion joints, reduction offlanges, additional line of dry CO2 for sealing purpouses)
• Steam cycle for dual operation: (duplicates lines, new heat exchangers and by-passes, start-upconstrains)
• Electrical equipment: (higher voltage level for ASU and CPU feeding, static starters, increment ofthe UPS size, additional back-up diesel engine)
• Specific instrumentation needed for dual operation
20
Design modifications for new FLEXI BURN CFBconcept compared to conventional power plant
Study to reduce air inleakage:
Three main activities have been carried out:
• Definition of critical areas where air inleakage can be a problem. (flanges, joints,dampers, manholes, measuring ports, HRA area, dust removal system, ID fan.....)
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• Available methods to reduce the air inleakage in each area. (CO2 sealing, fibermembranes, CO2 cleaning system, special design of some equipment...)
• Detection of air inleakage.
• Local detection (O2 and CO2 measurements, measuring ports, localpressurization, local corrosion, IR Thermography, Ultrasonic Acoustics...)
• Monitoring of air inleakage level during the operation.
Other differences for new FLEXI BURN CFBconcept compared to conventional power plant
Project construction schedule. Definition of construction planning:
Total duration of the construction for the plant will increase from 42 months that could bea typical value for a air combustion plant to 60 months, what means an increase ofmore than 40%.
Minimum site requirements:
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• Identification of site requirements. Identified extra area and utilities required.
• Analyzed different plot-plant configurations.
Economics
Economical boundary conditions:
Based on EBTF guidelines (European best practice guidelines for assessment ofCO2 capture technologies).
Sensitivity analysis for main key parameters.
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Sensitivity analysis
DCF ± 50 %
CO2 emission credit ± 100 %
Limestone ± 30 %
Fuel ± 50 %
Capacity Factor Max +5 %
Capacity Factor Min -30 %
Efficiency Loss (%point) -5 %
EPC ± 30 %
Study on-going
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