Current status of biomass cofiring
ExCo55, Copenhagen, May 25, 2005
Jaap Koppejan, Project Manager Bioenergy
1 Presentation overview
• Concepts applied • Global status of application • R&D issues
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2 Biomass Cofiring: Concepts and Technologies
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3 Global coal utilization (Mton/y)
240 257 66
962 1.254 150 327
160 131
• 5%e cofiring globally ˜ 40 GW ˜ -300 Mton CO2/year
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4 Biomass Cofiring: Examples
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5 Why co-firing biomass with coal?
• Strong reduction in emissions of greenhouse gases and other pollutants
• It stongly supports the formation of a biomass commodity market
• Large opportunities, short term
(5%e cofiring globally ˜ 40 GW ˜ -300 Mton CO2/year)
• Cheap option for renewable energy
• Highly efficient
• Job creation
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6 Biomass co-firing: Best use of resources
1 Cofired Units (demonstration and optimized) 0,9 Dedicated Unit Increasing Size 0,8
0,7
0,6 Efficiency/Coal Efficiency
0,5
0,4 10 MWe 60 MWe
Source: Baxter, 2004
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7 Generation costs of cofiring are low
Typical biomass Cost (US$ per ton)
Source: Antares Group Inc
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8 Biomass co-firing concepts
• Direct co-combustion in coal fired Coal burners power plants
• Indirect co-combustion with pre- gasification or other thermal pretreatment
Biomass feeding Biomass feeding • Indirect co-combustion in gas-fired power plants
• Parallel co-combustion (steam side integration) Wet slag remover grate
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9 Direct co-firing of biomass
Delta Electricity, Australia
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10 Direct co-firing of biomass (cont.)
EMISSION
Flue gas COAL Grinding BURNERS BOILER treatment
Steam turbine
Physical SECONDARY pre-treatment FUEL(S) pulverising / drying pelletising / mixing
The key issue is the behaviour of the blended fuel in the coal mills (brittle fracture, heat balance,..)
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11 Biomass co-firing via pre-gasification
• Option for waste-derived fuels • Amer (NL), Lahti (Finland)
• Investment costs: 300-1100 euro/kW e
ash fouling utilisation bed gas cooling/ agglomeration purification LCV gas
CFB gasifier SCR
ESP FGD coal biomass
stack
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12 Amer-9 wood gasifier
CFB gasifier • waste wood • 83 MWth input
• 170 kton CO2 red
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14 Indirect co-firing for gas fired boilers
Pyrolysis Biomass Boiler Liquefaction
Bio Bio oil oil Gas/coal
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15 Parallel co-combustion (steam-side coupling)
SCR
ESP FGD coal
stack steam
ESP biomass
stack
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16 Parallel co-combustion (steam-side coupling) Enstedvaerket power plant – Abenraa, Denmark • Straw • Highly corrosive nature of straw at high temperatures • Contamination of the coal ash.
• Biomass boiler: 40 MWe and coal-fired unit: 660 MWe
Vasteras CHP plant – Vasteras city, Sweden • CHP plant has four units using coal and oil with an overall capacity of 500 MWe and 900 MW for district heating. • CFB boiler for biomass 200 t/ steam)
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17 Status of application
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18 Status as of 2004
• approx. 40 pulverised coal fired power plants worldwide that cofired biomass on a commercial basis • on average 3% energy input, • some 3.5 Mton of coal substituted
• around 10 Mton of CO2 reduction.
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19 Global activities on biomass co-firing
Australia: About 5 PC power plants cofire up to 5 mass% of wood (demolition wood, fresh wood)
USA: Approx 40 PC plants have demonstrated cofiring capabilities, hardly any commercial operation
EU: National goals of 5 – 12% of power production using biomass, near term goals are mostly being accomplished through co-firing
Scandinavia: 150 fluidized bed boilers use secondary fuels such as sawdust, wood chips, forest residues which are co-fired with peat, wood or coal
Germany: PC plants (lignite and coal) cofire sewage sludge commercially, trials with straw and wood
The Netherlands: Already applied in all available Dutch coal-fired plants at up to 20%m (about 10%e)
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20 Coal Covenant in the Netherlands
• Agreed May 2002, to be accomplished in 2008
• 3.3 Mton CO2 reduction by co-firing biomass in coal fired power stations
• equals 475 MWe installed capacity • 12 % replacement of coal (heat) input • requiring ~ 2.2 Mton of biomass/waste per year
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21 Global overview of biomass/coal cofiring initiatives
• Recently done by IEA Bioenergy Task 32
• Internet database produced at www.ieabcc.nl
• 135 plants identified that co-fire biomass in plants that originally fire coal as main fuel
• 105 direct, 1 direct + parallel, 5 indirect, 24 yet unknown
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22 IEA Bioenergy Task 32 database (1)
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23 IEA Bioenergy Task 32 database (2)
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24 Countries where cofiring has been done:
Australia; 8 Austria; 5
Belgium; 1 USA; 41 Denmark; 5
Finland; 18
UK; 2 The Netherlands; 5 Thailand; 1 Germany; 27 Taiwan; 1 Indonesia; 2 Sweden; 15 Spain; 2 Italy; 1 Norway; 1
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25 Database details
yet unknown; 31 Number of plants
PF; 56 that co-fire this Fuel fuel Wood 41
CFB; 29 Sludge 30 Peat 20 BFB; 11 Grate; 8 Straw 16 Oil 12 Bark 10 RDF 7
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26 Research and demonstration issues
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27 Ash deposition may widely vary
Red Oak Wood Pittsburgh #8 coal
Danish Wheat Straw 15% Imperial Straw / 85% Pittsburgh #8 Coal
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28 Ash deposition may widely vary (2)
100
10
1
0.1 Deposition Rate (gm deposit/kg fuel) 0.01 Straw Wheat Straw Wood Switchgrass Pittsburgh #8 Eastern Kentucky
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29 Corrosion rates can sometimes be predicted with (sometimes complex) chemical mechanisms
Corrosion Potential 2.5 High Low
2.0
1.5
1.0 Stoichiometric Sulfur:Alkali Vapor 0.5 Deposit Chlorine (% dry mass) 0.0 6 8 2 4 6 8 2 4 6 8 1 10 100 2*Fuel Sulfur/Max (Available Alkali, Chloride)
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30 Striated Flows: particle path trajectories
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31 Insufficient mixing in a boiler may lead to unexpected and problematic combustion conditions
Oxygen Contours Temperature variations
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32 Striated flows: Ash deposition [ g/m2/h]
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33 Striated Flows: Model vs. experiments
160000 140000 O2 CO model prediction 140000 2 120000 model prediction 120000 100000 100000 80000 80000 ppm ppm 60000 60000
40000 40000
20000 20000
0 0 0 20 40 60 80 100 120 140 0 20 40 60 80 100 120 140 distance from back (in) distance from back (in)
110000 measured2003-10-14 COA-F 2 110000 measured O2 2003-10-14 A-F 2003-10-14 R-U 105000 105000 2003-10-14 R-U
100000 100000
95000 95000 ppm ppm 90000 90000 85000 85000 80000 80000 0 50 100 0 50 100 distance from back (in) distance from back (in)
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34 Task 32 project: SCR deactivation through biomass cofiring
Furnace duct wall
Flue gas
Pressure transducer P (feedback to eductor air control)
Ammonia mass flow controller (feedback from NO x measurement) 2–3 feet Static Mixer Anhydrous ammonia
Pre-catalyst Multiport gas sampling selector valve
Soot Gas blowing pump
6” 4” Analyzers Post-catalyst gas sampling (x6)
P Pressure transducers (x6) P P (feedback to eductor air) Reactor P exhaust P P Hoppers Eductor air mass flow controllers (steered by pressure drop) Eductors
Eductor air
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35 SCR deactivation
1.4 CaO 1.2 S SO3 1 Na2O 0.8 V2O3 0.6 0.4 0.2 Normalized Concentration 0 Limit Fresh(1) Fresh(2) Detection
Source: Larry Baxter, BYU, 2004 Exposed(1) Exposed(2)
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36 Project: SCR deactivation
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37 Technical challenges for cofiring
• Cost effective methods for getting more and and wider varieties of fuels into the boiler
• Occurance of insufficienct gas mixing / stratified flows in the boiler
• Fouling and corrosion of the boiler (alkali metals, chlorine)
• Continuation of fly ash utilization (unburned carbon, contamination, behaviour in cement)
• Impact on performance of flue gas cleaning (SCR DeNOx, performance of FGD unit)
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38 Non-technical barriers
• Economic aspects • lack of financial incentives • uncertain fuel prices/availability
• Legislative aspects (utilization of fly ash in cement, determining green share of electricity produced, unclear emission legislation)
• Public perception of co-firing of biomass/waste
• Getting the permits through
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39 Concluding remarks
• Co-firing represents a cost effective, short term option at a large scale
• Although more needs to be done, there is already a wealth of practical experience under different conditions
• IEA Bioenergy Task 32 wants to contribute to the problems the cofiring community is facing
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40 Task 32 workshops 2004-2006 Topic Organising Country Planning
Co-firing Netherlands Rome, May 2004
Public perception of Canada + USA Victoria, Aug- Sept. biomass cofiring 2004 Aerosols Austria Austria, March 2005 Small scale systems Netherlands Paris, Oct 2005
Fuel Flexibility Sweden ?, Spring 2006
Cofiring (tentative) NL (with Task 33) Netherlands, 2006
Corrosion and deposit UK Glasgow, autumn 2006 formation
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41 Thank you for your attention
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