WP1: Oxygen-firing knowledge –Comparison of air- and oxygen-
firing (RTD)
2nd FLEXI BURN CFB Workshop6th February 2013, Ponferrada, Spain
WP1: Oxygen-firing knowledge – Comparison of air- and oxygen-firing
Comparison of air-and oxy-firing
Development ofdesign tools
Boiler designand performance
Power plant integration, optimization
and economics
Feasibility and readiness for the utilization of the technology within different regions in EU
WP1
WP2
WP4 WP5
WP6
Technology demonstration and background for the commercial scale design process
Supporting R&D work
Viable boiler design Viable power plant
WP7: Coordination and dissemination
Demonstration tests at large pilot unit and commercial
scale air fired unit
WP3
Content
• Objective
• A compact summary of the work carried out
• Main results achieved in WP1
• Exploitation of the results
• Deliverables and publications
Main objectives
The purpose is to extend the knowledge of oxygen-firingin a circulating fluidized bed (CFB) boiler that is in a CO2- H2O rich atmosphere differing considerably from that ofnormal combustion with air
1. Laboratory scale combustion tests under air- and oxygen-firing conditions with different fuels and blends (VTT)
2. Effect of flue gas composition (air-firing versus oxygen-firing) on heat transfer (UNIZAR-LITEC)
3. Effect of flue gas composition (air-firing versus oxygen-firing) and process scale-up on hydrodynamics (CzUT)
4. Submodels for combustion and emission formation (VTT, LUT)
Totally seven different fuels were selected for the combustion testsThe selected project fuels cover the whole range of coals from anthracite to ligniteStraw pellet represents a typical agrobiomass which is easily available whereas wood represents a typical good quality forest-based biomass which is also available in many locations of the Europe
Small pilot scale CFB experiments (0.1MW) under air- and oxygen-firing conditions
Fuels Mixture ratio on energy basis (LHV wet)
Mixture ratio on mass basis (wet)
Anthracite + Pet-coke 55/45 70/30Anthracite 100 100Bituminous coal (Polish) 100 100Lignite (Spanish) + South African coal 55/45 70/30Anthracite + wood 90/10 85/15Bituminous coal (Polish) + straw pellet 80/20 75/25
Variation in the selected fuelsAsh 0.6 – 35.6 w-%Volatiles 10.2 – 83.2 w-%Suphur 0.02 – 6.3 w-%
Fuel flexibility
Combustion air/oxy
800
820
840
860
880
900
0 2 4 6 8
Tem
pera
ture
[o C]
Distance from the air grid [m]
AirOxy
0
2
4
6
8
10
12
0 5 10
O2
(vol
-%)
Distance from the grid [m]
Air
Oxy
05
10152025303540
0 5 10
H 2O
(vol
-%)
Distance from the grid [m]
AirOxy
0
20
40
60
80
100
0 5 10
CO2
(vol
-%)
Distance from the grid [m]
AirOxy
Ash characteristics: air/oxyBottom ash
Bottom ash
Oxygen-firing test with high temperature
Air-firing test
Measured calcium compounds in bottom ash 0
1
2
3
4
800 850 900 950Tota
l UBC
in a
sh st
ream
s (%
of H
HV)
Bed temperature (oC)
OxyAir
Combustion process dynamics air/oxy
• Combustion process dynamics in oxygen-firing is different compared to air-firing• Fuel reactivity is somewhat similar in air- and oxygen-firing
Impulse changes
Time
Var
iabl
eStep changes
Var
iabl
eTime
Combustion submodeldevelopment and validation
Char combustion and char inventory in fluidized bed combustion was studied under air- and oxygen-firing modes
No significant effect, when N2 is replaced with CO2 was found
– the lower diffusivity of O2 in CO2compensates the increased gasification rate
Methods to calculate the char burning, char inventory and the particle size distribution in bed were developed including the effect of internal gasification of the particles and boundary layer combustion of CO close to particles
The developed submodel was validated based the pilot scale data
Measured and calculated residence times (or char inventories ) in the bed for Spanish anthracite in air ( ) and oxyfuel ( ) combustion.
0
10
20
30
40
750 800 850 900 950
Calc
ium
util
izat
ion
(%)
Bed temperature (oC)
OxyAir
Sulphur capture and NO (air/oxy)Calcium utilisation SCa
RET/
RET, sulphur retention [%]
• Sulfur capture increases with temperature in oxygen-firing conditions• NO emissions are typically lower in the oxygen-firing compared to air-firing
which is most probably related to flue gas recirculation and heterogeneous reactions in the bed area
0
20
40
60
80
100
750 800 850 900 950NO in
flue
gas (
mg/
MJ)
Bed temperature (oC)
Air
Oxy
NOx model development and validation
NO and N2O emission according to NOx-sub-model simulation (coherent line) and according to pilot scale measurement (dots) in air combustion.
NO and N2O emission according to NOx-sub-model simulation (coherent line) and according to pilot scale measurement (dots) in oxyfuel combustion.
Heterogeneous char nitrogen reactions were added to the existing 1-dimensional time dependent NOx-sub-modelThe nitrogen sub-model developed in air-firing conditions describes the NO formation in oxygen-firing well and N2O formation relatively well.
Process scale-up and hydrodynamics
• CFB technology is scaling up with the latest high-efficiency SC-OTU-references Lagisza (460 MWe). The Lagisza power plant (460 MWe), located in the southern Poland, is the world's largest CFB boiler, which is also the world's first supercritical CFB once-through unit (OTU)
CFB800 agisza Turow 4-6 JEA Turow 1-3 Furnace - Width m 40 27.6 22.0 26.0 21.2 - Depth m 12 10.6 10.1 6.7 9.9 - Height m 50.0 48.0 42.0 35.1 43.5
Unit Capacity (MWe)
0
100
200
300
400
500
600
1970 1975 1980 1985 1990 1995 2000 2005 2010Start-Up Year
Pilot Plant Oriental Chem
Lagisza
JEA
Turow 1
VaskiluodonNova ScotiaTri-State
General Motors
800 800 MWeUnit Capacity (MWe)
0
100
200
300
400
500
600
1970 1975 1980 1985 1990 1995 2000 2005 2010Start-Up Year
Pilot Plant Oriental Chem
Lagisza
JEA
Turow 1
VaskiluodonNova ScotiaTri-State
General Motors
800 800 MWe
Reference plant for the project
• Aim was to develop a dynamic similarity formula that will enable the analysis of boiler hydrodynamics in a laboratory scale based on the operation parameters
• The analysis will be performed on a 3D stand, with the geometric similarity being preserved
• Due to symmetry of combustion chamber the test stand is a half of the original Lagisza boiler in lateral direction
• The cold model was built with using a strong transparent plexiglass to get best possible visibility from every direction to the whole circulation process.
• Effect of process scale-up on hydrodynamics has been studied with experiments in cold flow pilots
Process scale-up and hydrodynamics
Process scale-up and hydrodynamics• Use of scale models allows the hydrodynamics of
the Lagisza 460MWe supercritical CFB boiler to be satisfactorily reflected on a scaling model with a scale factor of k=1/20
• Determination the hydrodynamic parameters for oxygen-firing conditions was carried out by numerical modelling
CFD models of the back pass develop and validated for two scales:
Lagisza 460 MW(e) // CIUDEN 30 MW(t)And for varying flue gas compositions, eg
Air firing //Oxy firing
Heat transfer to heat exchangers in back pass (convection and radiation)
Validation: FWE design vs calculations
Shell-sidevelocity magnitude
The modelling tools have been developed to support the development of the concept
The new 3D model frame is a major achievement and allows more detailed and realistic simulations of large CFB furnaces
The new developed 3D sorbent model allows simulation of various phenomena, which could not be done with the old 3D model, such as modelling of carbonation, direct sulfation and desulfation and flow modelling of each particle size fraction
The new features improve the prediction capability significantly
Based on the 3D modelling study, the sorbent reactions in oxygen-firing conditions may have a large impact on the furnace process. These reactions can have a large impact on local gas atmosphere, velocities and temperatures
Development of submodels and modelling tools for 3D modelling
Oxygen concentration of Flexi-Burn CFBin air fired (left) and oxygen fired (right) mode.
Main results achieved in WP1
• Small pilot scale CFB experiments (0.1MW) under air- and oxygen-firingconditions have been completed with totally 33 experiments
• >50 Bench scale tests have been carried out under air-and oxygen-firingconditions to study combustion, emission formation and recarbonationphenomena in detail
• Transition between air- and oxygen firing conditions could be carried outsmoothly and safely with the renovated automation system which includedan automated transition mode between air- and oxygen-firing
• Combustion process could be operated in the both modes without anymajor drawbacks. However, recarbonation must be taken into to account inoxygen-firing especially in loop seal
• Based on the dynamic tests and simulation studies the reliable control ofoxidant oxygen concentration is very important from the safe operation andprocess controllability point of view
• If flue gas emissions are expressed in milligrams per megajoules the emission levels between air- and oxygen-firing have no remarkable differences (except NO)
• NO emissions are typically lower in the oxygen-firing compared to air-firing (flue gas recirculation and heterogeneous reactions)
• As has been demonstrated by the laboratory tests carried out, the use of two scaling models developed in the work allows the hydrodynamics of the Lagisza 460MWe supercritical CFB boiler to be satisfactorily reflected (also quantitatively) on a scaling model with a scale factor of k=1/20.
• The new 3D model frame was developed including emission submodelsfor 3D furnace code to simulate oxygen-firing conditions. – The new model is currently the only 3D CFB model, which includes emission
models
Main results achieved in WP1
BEN CH SCALE REACTOR (BFB/CFB)
Air
O2, C O2, CO, N2 , SO2, NO
Secon dary air
Con tin uou sfu el fee d
Fuel ba tch fee d
Co oler/hea ter
C ooler
Prima ry g as hea tin gPC con trol and d ata lo gging system
Cyclone
FilterTo Sta ck
BEN CH SCALE REACTOR (BFB/CFB)
Air
O2, C O2, CO, N2 , SO2, NO
Secon dary air
Con tin uou sfu el fee d
Fuel ba tch fee d
Co oler/hea ter
C ooler
Prima ry g as hea tin gPC con trol and d ata lo gging system
Cyclone
FilterTo Sta ck
A ir
O2, C O2, CO, N2 , SO2, NO
Secon dary air
Con tin uou sfu el fee d
Fuel ba tch fee d
Co oler/hea ter
C ooler
Prima ry g as hea tin gPC con trol and d ata lo gging system
Cyclone
FilterTo Sta ck
VTT0.3kW
VTT0.1MW
CANMET1MW
CIUDEN30MW
Dem
onst
ratio
n sc
ales
Time
Concept for 300 MWe
2009 2012
Exploitation of the results
WP1 R&D SupportDevelopment of submodel for
combustion and emissions WP2 Design tools
WP4 Boiler design
WP5 Power plant concept
Laboratory scale combustion tests provided a base for development and validation of the design tools needed in the concept development
DeliverablesD3 :Selection of project fuels and definition of test matrix for small scale CFB experimentsD5: Small pilot scale CFB experiments under air-and oxygen-firing conditionsD9: Validation results of sub-models for combustion, emission performance, heat transfer and CFB boiler scale-up
Deliverables and publications in WP1
Publications1. Tourunen, A., Leino, L., Pikkarainen, T., Nevalainen, H. and Kuivalainen, R. Small pilot scale
CFB experiments under air- and oxygen-firing conditions. 2nd IEAGHG International OxyfuelCombustion Conference, September 12th-16th 2011, Australia http://www.ieaghg.org/index.php?/20100518210/2nd-oxyfuel-combustion-conference.html
2. Saastamoinen, J. and Tourunen, A. 2012. Model for char combustion particle size distribution and inventory in air- and oxy-fuel combustion in fluidized beds. Energy & Fuels, vol. 26, 1, ss. 407-416
3. Saastamoinen, H., Leino, T. and Tourunen A. 2012. Comparison of emission formation during pyrolysis and char combustion in air and oxyfuel conditions in fluidized bed. Proceedings of 21st International Conference on Fluidized BedCombustion, Naples, Italy, 3 - 6 June 2012., ss. 463 - 470
Deliverables and publications in WP1
4. Mirek P., 2012, Air flow optimization and gas-solid flow similitude in circulating fluidized bed boilers,Wydawnictwo Politechniki Cz stochowskiej, No. 240, ISSN 0860-5017, ISBN 978-83-7193-548-0
5. Mirek P., 2011, A simplified methodology for scaling hydrodynamic data from Lagisza 460MWe supercriticalCFB boiler, Chemical and Process Engineering, 32 (4/1), pp. 245-253, DOI: 10.2478/v10176-011-0019-1.
6. Mirek P., Ziaja J., 2011, The influence of sampling point on solids suspension density applied in scaling of thehydrodynamics of a supercritical CFB boiler, Chemical and Process Engineering, 32 (4), pp. 391-399, DOI:10.2478/v10176-011-0031-5.
7. Mirek P., 2012, Scaling of Lagisza 460MW supercritical CFB boiler hydrodynamics, Rynek Energii, Nr 2 (99)2012, pp. 162-166.
8. Mirek P., Ziaja J., Nowak W., June, 3-6, 2012, Verification of the scaling relationships for Lagisza 460MWesupercritical CFB boiler, 21st International Conference on Fluidized Bed Combustion, Naples (Italy).
9. Mirek P., Ziaja J., Nowak W., June, 3-6, 2012, The influence of the inert material sampling location on thescaling of flow phenomena in a circulating fluidized bed boiler, 21st International Conference on FluidizedBed Combustion, Naples (Italy).
10. Saastamoinen, J., Tourunen A. and Leino T. Modeling of particle size distribution of limestone in air- and oxy-fuel combustion in fluidized beds. Will be submitted to Powder Technology.