3. mixed fuel firing
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1/3/10
3. Mixed Fuel Firing
1/3/10
Chemical Aspects of Industrial Utilization of Biofuels
1. Introduction2. Fuel Burning Characteristics3. Combustion Equilibria4. Melting Equilibria and Ash Behavior5. High Temperature Corrosion6. Flue Gas Emission Chemistry7. Mixed Fuel Firing
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Challenges in Multi-Fuel Firing in FBC
Emission Limits Fouling of Heat Surfaces Superheater Corrosion Bed Sintering Ash Utilization
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Fuels in the Latest Major FBC Projects
Wood fuels 16/23Peat 10/23Coal 8/23Sludges 8/23Pet Coke 4/23
Multi-Fuel vs Single Fuel 20 vs 3
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Number of Publications on “Co-combustion" or “Co-firing" ScienceFinder, January 2003, after (Leckner 2003).
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Challenges in Multi-Fuel Firing in FBC
How Can Fundamental Research Contribute?
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Fuel Interaction in FBC
FoulingSintering
Emissions
Fuel A 50% Fuel B
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Fuel Interaction in FBC
FoulingSintering
Emissions linear
Fuel A 50% Fuel B
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Gaseous Emissions SO2 and NOx
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Chalmers CFBC Tests with Coal, Wood, Sludge
(Leckner, Åmand)
12 MW CFBC with external coolingConstant conditions (temp., air distribution)Results for fundamental analysis and modelling
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SO2 Emission with Wood-Coal (Leckner et al.)
Sulphurdioxide
ppm(6% O2)
Wood 50%(Energy)
Coal0
100
200
300
400
500
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SO2 Emission with Wood-Coal(Leckner et al.)
Sulphurdioxide
ppm(6% O2)
0
100
200
300
400
500
Wood 50%(Energy)
Coal
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NO Profiles in CFBC(Leckner et al.)
0 2 4 6 8 10 12
Reactor height, m
0
100
200
300
400
500Secondary air
Wood
Coal
NO
x pp
m
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Nitrogen Oxides with Coal and Wood(Leckner et al.)
Coal Wood
Volatile, % db 40 80N(fuel), % db 1.6 0.14
CFBC NO, ppm 50 60
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NO Emission with Wood-Coal(Leckner et al.)
Nitricoxideppm
(6% O2)
0
50
100
150
Wood 50%(Energy)
Coal
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NO Emission with Wood-Coal(Leckner et al.)
Nitricoxideppm
(6% O2)
0
50
100
150
Wood 50%(Energy)
Coal
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NO Emission with W&C (Leckner et al.)
Nitricoxideppm
(6% O2)
0
50
100
150
Wood 50%(Energy)
Coal
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Superheater Foulingin BFBC
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BFBC for Biomass Fuels
Rice huskEucalyptus bark
Fuel
Fly ash
Fouling
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Ash Forming Elements in Rice Husk and Eucalyptus BarkRICE HUSK
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
Si Al Fe Ti Mn Ca Mg P Na K S Cl
mg/
(kg
dry
solid
s)
Unreactive, calculatedReactiveTotal in
EUCALYPTUS BARK
0
10000
20000
30000
40000
50000
60000
70000
80000
90000
Si Al Fe Ti Mn Ca Mg P Na K S Cl
mg/
(kg
dry
solid
s)
Unreactive, calculatedReactiveTotal in
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Rice Husk & Rice Husk Ash
Rice husk, untreated
Rice husk ash (laboratory ash)200 µm
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Rice Husk: Boiler Fly Ash vs. Laboratory Ash
2nd pass ash from the boiler Rice husk laboratory ash
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Eucalyptus Bark & Eucalyptus Bark Ash
Eucalyptus bark ash (laboratory ash)
Eucalyptus bark, untreated
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Fly Ash of Rice Husk and Eucalyptus Bark
Rice husk ash
Silica (SiO2)
Not Molten
Large Particles
Eucalyptus bark ash
Chlorides and Sulphates of K, Na, and Ca
Partially Molten > 700ºC
Vapours, Small Particles
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Fly Ash Particles Approaching Tube Surfaces
Rice husk ash Bark ash
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Fouling Test Facility (University of Toronto)
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100% Rice Husk
After 40 minutes
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100% Bark
After 40 minutes
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Fly Ash Particles Approaching Tube Surfaces
Rice husk ash Bark ash
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Probe Deposits: Rice Husk - Bark
Depositionrate
mg/m2-sec
Rice husk 50%(Dry Mass)
Bark0
5
10
15
20
25
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Fly Ash Particles Approaching Tube Surfaces
Rice husk ash
Rice husk & bark ash
Bark ash
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36% Bark - 64% Rice Husk
After 40 minutes
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Test Tube Surfaces after Exposure (40 min)
100% Rice husk, Deposit Mass = 10 mg
Rice/Eucalyptus 64/36 % Deposit Mass = 13 mg
100% Eucalyptus bark,Deposit Mass = 195 mg
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Rice husk 50% Bark
Probe Deposits: Rice Husk - Bark
Depositionrate
mg/m2-sec
0
5
10
15
20
25
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Rice husk 50% Bark
Probe Deposits: Rice Husk - Bark
Depositionrate
mg/m2-sec
0
5
10
15
20
25
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Rice husk 50% Bark
Probe Deposits: Rice Husk - Bark
Depositionrate
mg/m2-sec
0
5
10
15
20
25
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Probe Deposits: Peat - Straw
Mass ofelementsas oxides
(mg)
0
50
100
150
300
350
Peat 50% Straw
250
200
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Probe Deposits: Peat - Straw
Mass ofelementsas oxides
(mg)
0
50
100
150
300
350
Peat 50% Straw
250
200
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Mass of Element Oxides in Deposits
Mass ofelementsas oxides
(mg)
0
50
100
150
250
300
Peat 50% Bark
200
ClSO3K2ONa2OMgOCaOMnOCr2O3Fe2O3SiO2Al2O3
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Conclusions (i)
Mixed-Fuel Firing Great Potential for FBCMajor Challenge to Boiler Manufacturers & Operators:
Emission ControlBed Sintering and Fouling ControlCorrosion Control
Fuel Interaction May Cause Surprises (Non-Linear Relationships)
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Conclusions (ii)- How Can Fundamental Research Contribute?
- We Need Fundametal Studies on- Emission Chemistry Interactions- Ash Interactions- Fuel Characterization for Mixed-Fuel Firing- Modelling of Mixed Fuel Systems
...to Interprete Pilot and Full Scale Experiences
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