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

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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.

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• 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

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Utilities

Utilities

Final configuration of the integrated plant. Basecase

• Definition of other main PFDs of the FLEXI BURN CFB plant:

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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.

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ASPEN Plant Model. Optimisation

Boiler

Oxidant Flue gas

CPUASU

SteamCycle

IntegrationIntegration

Power Utilities Power Utilities

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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

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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.

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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

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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

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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

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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

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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