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)

Laboratory scale test rigs

0.1 MW CFB pilot test rig 0.3 kW CFB/BFB bench scale test rig

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.