Oxyfuel-CFB boiler scale-up based on integrated experimental and modeling workg p g

The 1st International Oxyfuel Combustion ConferenceSeptember 9th, 2009

Reijo Kuivalainen (FW), Toni Pikkarainen (VTT), Timo Leino (VTT), Antti Tourunen (VTT),

Kari Myöhänen (LUT), Sirpa Takkinen (LUT), Timo Hyppänen (LUT)

Presentation outline

• IntroductionE i t l k• Experimental work

• One-dimensional modeling• Three dimensional modeling• Three-dimensional modeling• Single particle model for sulfur sorbent• Scale-up approachScale up approach• Conclusions

2/17

IntroductionFoster Wheeler´s CFB Experience

• Foster Wheeler Fluidized Bed Technology Basis: Over 30 Years and 22 GWe

Flexi-BurnTM CFB Development•Foster Wheeler has been developing oxy-fuel CFB combustion since 2003:Basis: Over 30 Years and 22 GWe

• Foster Wheeler Energia Oy in Finland is the Technology Center for Fluidized Bed Boilers in Foster Wheeler Global Power Group

CFB combustion since 2003: •Knowledge and design tool development•Test activities (VTT bench scale & small pilot CFB)•Conceptual and feasibility studies to develop the boiler design (Oxy-fuel, oxy-readiness and

350 CIRCULATING FLUID BED (CFB) BOILERS

• Total 24 000 MWe CFB sold

retrofitting cases have been studied)

•Pilot test activities at larger scale facilities • ~0.1 MWth (current) → ~1 MWth (2009) → 30 MWth (2010 11)• 309 in operation for variety fuels:

coal, lignite, petroleum coke, biomass, RDF, etc.

• 32 under construction• The world largest and first SC OTU CFB

30 MWth (2010-11)

•The Spanish government has decided on investment for the CIUDEN 30 MWth class pilot CFB f ilit hi h id f ll i t lg

with the capacity of 460 MWe at PKE’s Lagisza plant in Poland is in operation.

CFB facility, which provides a full experimental CCS platform for the demonstration and validation of oxy/air-fuel combustion in sufficient scale to allow continuation to commercial scale.

•FW has developed and is offering the CFB technology in 600-800 MWe scale with 600 °C

3/17

steam temperature."Flexi-BurnTM" is trademark of Foster Wheeler AG

Bench Scale and Pilot Scale CFB Combustors at VTTCFB Combustors at VTT

Pilot Scale CFB Combustor (30-100 kW)Bench Scale BFB/CFB Test Rig

• Applicable for oxygen and air combustion research • The height of the riser is 8.0 m and the inner diameter is 167 mm• Process conditions (e.g. load, temperature, O2 level) can be controlled

almost independently

• Height of the riser tube is 610 mm and inner diameter 32.8 mm.• Pre-heated primary gas is fed into the combustion chamber through a

perforated grid and also secondary gas feed point could be used.• Different kind of gas mixtures can be used e.g. O2, CO2, SO2, CO and H2O in

addition to air and nitrogen.

4/17

almost independently• Extensive process measurements and sampling possibilities

• Temperature and pressure profiles along the riser are measured.• Temperature is controlled with surrounding electric heaters.

ExperimentalPilot scale CFB combustorPilot scale CFB combustor

Test Fuel power Tbed Tfreeboard Ca/S, total FG RC* Feed gas O2

number kW °C °C molar ratio %, wet %, wet1 31.8 815 797 1.5 0 20.8 Low load

Notes

3 8 8 5 9 5 0 0 8 o oad2 51.4 866 865 2.1 0 20.8 Full load (base test)3 52.6 868 870 2.1 0 20.8 Fouling at temp.T2

3b 51.4 854 866 2.1 0 20.8 Air staging4 52.2 874 877 1.3 0 20.8 Low Ca/S5 48.0 893 895 2.2 0 20.8 High temp.6 51.4 893 895 1.3 0 20.8 High temp., low Ca/S

Air

g p ,7 32.5 799 805 1.7 7 19.7 FG RC, low load8 69.4 784 811 1.9 70 24.1 Low temp.9 74.8 858 870 2.1 63 29.2 Medium temp.

10 89.6 913 926 2.0 64 28.8 High temp.11 89.7 909 921 1.2 64 28.0 High temp., low Ca/S12 75.0 864 874 1.2 65 27.7 Medium temp., low Ca/S

Oxyg

• 7 air- and 7 oxygen- combustion tests runs were carried out with Polish bituminous coal (used also in Lagisza 460 MW OTU SC CFB)

12 75.0 864 874 1.2 65 27.7 Medium temp., low Ca/S13 73.9 867 876 2.6 64 28.4 Medium temp., high Ca/S

13b 73.3 866 875 2.1 64 28.3 Medium temp. (repetition)14 72.7 868 873 2.1 0 27.3 Bottled CO2 feed

gen

bituminous coal (used also in Lagisza 460 MWe OTU SC CFB). • The varied parameters in the tests were load, temperature level,

limestone calcium to fuel sulphur ratio (Ca/S) and air staging. • One of the air-firing tests was carried out with 7% flue gas recycling and

one oxygen firing test with bottled O /CO feed (no flue gas recycling)

5/17

one oxygen-firing test with bottled O2/CO2 feed (no flue gas recycling).

Modeling work: 1D modelModeling work: 1D model

CFB-pilot 1D CFB model• The 1D CFB furnace model, which has been

implemented in the CFB boiler thermal performance calculation tool, and is used at

n n+1

n-1

n n+1

n-1

n n+1

n-1

n n+1

n-1

n n+1

n-1

n n+1

n-1

n n+1

n-1

n n+1

n-1

n n+1

n-1

n n+1

n-1

n n+1

n-1

n n+1

n-1

n n+1

n-1

n n+1

n-1

n n+1

n-1

Foster Wheeler for dimensioning of CFB boilers.

• The 1D model is semi-empirical tool consisting of se eral s b models for e g comb stion and n-2n-2n-2n-2n-2n-2n-2n-2n-2n-2n-2n-2n-2n-2n-2of several sub-models for e.g. combustion and emission formation/reduction.

• The empirical correlations used in the sub-models are validated with extensive amount ofmodels are validated with extensive amount of small- and full-scale measurements.

• Sub-models are being modified to enable phenomenal simulation and scaling up of oxy

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3combustion conditions.

• The air- and oxygen-firing tests were analyzed with the current version of the 1D CFB model using parameters fitted for air combustion and

6/17

using parameters fitted for air combustion and VTT’s CFB-pilot configuration.

Air combustion test 2 –vertical gas & temp. profilesg p p

CO2-profiles

16

18

20

Cyc

lone

O2-profiles

20

25ModelMeasurement

Cyc

lone

6

8

10

12

14

16

CO

2 (dr

y, m

ol-%

)

C

10

15

20

O2 (

dry,

mol

-%)

0

2

4

0 1 2 3 4 5 6 7 8 9 10 11

Height (m)

ModelMeasurement

CO-profiles T-profiles

0

5

0 1 2 3 4 5 6 7 8 9 10 11

Height (m)

8000

10000

12000

14000

ppm

)

ModelMeasurement

Cyc

lone

860

870

880

890

900

C)

Cyc

lone

0

2000

4000

6000

CO

(dry

,

800

810

820

830

840

850

T (o C

ModelMeasurement

7/17

00 1 2 3 4 5 6 7 8 9 10 11

Height (m)

8000 1 2 3 4 5 6 7 8 9 10 11

Height (m)

Oxygen combustion test 9 –vertical gas & temp profilesvertical gas & temp. profiles

CO2-profiles

80

90

100

O2-profiles

30

35ModelMeasurement

Cyc

lone

30

40

50

60

70

CO

2 (dr

y, m

ol-%

)

Model

Cyc

lone

10

15

20

25

O2 (

dry,

mol

-%)

T-profilesCO-profiles

0

10

20

0 1 2 3 4 5 6 7 8 9 10 11

Height (m)

ModelMeasurement

0

5

0 1 2 3 4 5 6 7 8 9 10 11

Height (m)

860

870

880

890

900

C)

Cyc

lone

20000

25000

30000

ppm

)

ModelMeasurement C

yclo

ne

800

810

820

830

840

850T

(o C

ModelMeasurement

0

5000

10000

15000

CO

(dry

,

8/17

8000 1 2 3 4 5 6 7 8 9 10 11

Height (m)

00 1 2 3 4 5 6 7 8 9 10 11

Height (m)

Modeling work: 3D model

Modeling examplesLarge scale CFB unit

Oxygen concentration Carbon monoxide profiles

9/17

Three-dimensional CFB furnace model

Model frame

Reaction paths

10/17

3D-modeling of oxycombustion

• Retrofit studies– Reference plant: Lagisza CFB, Poland– Conversion to oxycombustion using existing furnace but making changes to internal heat

transfer surfaces– Low-end oxy combustion, inlet O2 = 24 – 30%.– Different operating conditions resulting to different sulfur capture mechanisms– Different operating conditions resulting to different sulfur capture mechanisms

• Case studies with high input oxygen share– Imaginary CFB power plant with 600 MWt thermal capacity.– Conventional air-fired unit as a reference.– Oxy Design: Unit design for high-end oxycombustion, inlet O2 = 48 – 59%.– Operation with different boiler loads.

• Main conclusions:Wi h l i l h h l d i f CFB b il b i il i fi d i Th– With low inlet oxygen, the thermal design of a CFB boiler can be similar to air-fired units. The sulfur capture mechanisms can be affected by controlling the furnace temperature.

– High inlet oxygen results in higher combustion heat per volume and higher local temperatures and the thermal design, e.g. the placement of the heat transfer surfaces is more challenging.

11/17

Three-dimensional modeling is necessary for supporting the design.

Retrofit studies

Temperature profilesFurnace conditions vs. calcination curve

Heat flux profilesHeat flux profilesOxygen concentration

12/17

Single particle model for limestone

• Particle model describes reactions in a single particle as a function of time in a changing environment.• A spherical particle is divided to one-dimensional nested control volumes.p p• Differential mass and energy balance equations are written, which solve the gas flow by diffusion and

convection, gas and solid reactions and energy flow by conduction.

Control volume CaCO3 CaO

CaSO4

(1) Calcination CaCO CaO + CO

Outside environment:- temperature- gas composition

(1) Calcination CaCO3 → CaO + CO2(2) Carbonation CaO + CO2 → CaCO3(3) Sulfation CaO + SO2 + 0.5O2 → CaSO4(4) Direct sulfation CaCO3 + SO2 + 0.5O2 → CaSO4 + CO2(5) Desulfation CaSO4 → CaO + SO2 + 0.5O2

13/17

g p ( ) 4 2 2

Lagrangian mixing model

• A Lagrangian mixing model is applied to simulate the dispersion of limestone particles inside a CFB furnace.

• The steady-state flow field of bed is solved by a semi-empiricalmodel or by separate CFD studies.

• Particle tracks are solved by a random walk model.• The mean velocity is equal to steady-state velocity of bedThe mean velocity is equal to steady state velocity of bed.• The fluctuating velocity simulates turbulent mixing of particles.

Eulerian flow fieldof bedof bed

Mean velocityLimestone particle

Mean particle track'uuu iii

iu

'iu

Total velocity

p

St h ti ti l t k

14/17

FluctuationStochastic particle tracks

Gaining design and operation experiencep

• Air combustion:– Vast experimental and modeling

experience from air combustion (bench-scale Pilots >300 operating units; max. 460 MWe)operating units; max. 460 MWe)

– Verified design models and engineering tools

• Oxy-fuel combustion:O y ue co bust o– Bench-scale at VTT– 30-100 kWth pilot scale at VTT– 1 MWth pilot scale at CANMET1 MWth pilot scale at CANMET– 30 MWth demonstration unit at

CIUDEN– 300 MWe ENDESA Generación Flexi-

15/17

eBurn CFB demonstration project

Conclusions

• Development approach based on theoretical studies, experiments at different scales, compilation of the acquired knowhow in design tools / process models used in designing boilersof the acquired knowhow in design tools / process models used in designing boilers

• The Lagisza 460 MWe CFB boiler has been used as a reference in oxy combustion case studies (retrofit & greenfield Flexi-Burn CFB)

• Prediction tools show studied oxyfuel boiler configurations viable.• Experimental results from bench and pilot scale test units show good emission performance.• Adapting an existing CFB boiler design for oxy combustion appears technically feasible without

major changes in the boiler structures and heat surfaces.• Uncertainties in prediction of large scale performance will be eliminated:• Uncertainties in prediction of large scale performance will be eliminated:

– Models are being modified and testing continued to consider oxy combustion characteristics– Demonstration in 30 MW scale scheduled to start in 2010– Capability to offer Foster Wheeler Flexi-Burn CFB design by 2011

• Utilizing the proven scale-up methodology, the commercialization and scaling up the Flexi-BurnCFB technology is expected to be achieved in much bigger steps than the realized scale-up of air-fired CFB boilers

16/17

Acknowledgements

The experiments and modeling work described in this presentation have been performed by VTT and LUT for Foster Wheeler with support from Tekes p y pp(the Finnish Funding Agency for Technology and Innovation) and Finnish Academy.

Thank you for your attention!for your attention!

reijo.kuivalainen@fwfin.fwc.com

17/17