Biofuel and Biomass firing technologies

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DALKIA’s experience: More than 600,000t of biomass p.a. (More than 80 plants) North Europe Zone Europe duzone Nord

Estonia : 5 heating plants 25 MW (th) 60,000 t of wood

North Atlantic ZoneZone

Lithuania : 8 heating plants 100 MW (th) 250,000 t of wood

Atlantique Nord

Germany Leinefelde CHP : 2.1 MWe 60,000 t of wood Czech Republic (cofiring) Zone Olomouc CHP :Pecos 41 MWe Krnoc CHP : 6.3 MWe 50,000 t of wood

France : 60 heating plants 150 MW (th) 180,000 t of wood

Chile (project) : Masisa CHP : 6,5 MWe 180,000 t of wood

South Zone Zone sud

Pecos Zone

Spain (project) : San pere : 6 MWe 65,000 t of wood

Brazil (project) : UTE : 3 x 12 MWe 3 x 160,000 t of wood

Direction du d é veloppement Development Zone

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Part 1

Biomass as Fuel

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Types of biomass ƒ Some examples of bio-fuels (2 main categories): ƒ Wood and waste from wood industry ƒ Wood chips, Sawdust, Shavings, Barks, Pellets, Logs ƒ Etc… ƒ Agricultural products and waste ƒ Straw ƒ Seeds ƒ Hemp ƒ Fast-growing trees (willows, poplars) ƒ Grasses ƒ Etc… ƒ Co-fired fuels: ƒ Peat, coal, sludge, etc... ƒ But also: Straw + wood, etc.. Significant variety and possible combination which generate for each of them there own technical challenge

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The full chain of biomass Fuel receiving/preparation/storage block diagram

Straw Bark Sawdust Other wood Industry residue Forest exploitation residues Recycled wood

Logs Rejected fuel

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Continuous availability of the primary energy. One example: Straw ƒ Different kinds: Wheat, barley, rye, rape, etc.. ƒ Rape: High Calcium rate => Limited quantity (ash melting point) ƒ Yield per ha: 4.5 to 12 t/ha depending on kind. ƒ Ratio grain/straw: 0.5 to 1.1 => Various straw yields ƒ Quantity availability: +/-5% depending on weather ƒ Logistics: ƒ Distance of the resources (max 100km), roads, size of bales, density (100 to 300kg/m3),storage (short harvesting) , loading lorries, access to field, etc.. ƒ Other markets for the fuel Critical to anticipate the variability of the resource and to have a local understanding of it

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Additional information required about the primary energy ƒ Physical and chemical characteristics (Using representative samples): ƒ CV range ƒ Potential uneven combustion ƒ Moisture (And CV) ƒ Overweight fuel handling ƒ Reduced boiler capacity (=> burn more expensive fuel) ƒ Reduced efficiency ƒ Excessive flue gas on flue gas treatment ƒ Ash content ƒ Overweight ash removal systems ƒ Increased costs and wear 7

Additional information required about the primary energy ƒ Physical and chemical characteristics (Using representative samples): ƒ Temperature of ash fusibility (K, P, Mg) and alkaline components (K, Na, Ca) ƒ Bed /gate impact ƒ Fouling impact ƒ ESP impact

ƒ Impact of fertiliser, pesticides, salts (Cl, S)... ƒ High temperature corrosion ƒ Corrosion if low temperature feedwater/DHN water (design, fuel quality, prefer chain conveyors Accelerated wear (Chute,..)=> fuel quality, design Chain conveyor feeding the boiler => light design, wet fuel screw/conveyor for ash => foreign bodies, high ash content Vitrification =>low ash melting point, high furnace temp. Etc..

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Energy metering for the fuel ƒ Weight ƒ LCV ƒ Ash ƒ (removed dry/wet, sand input- from bed or fuel, fly ash, bottom ash, etc…)

ƒ Moisture content ƒ (conductivity, sampling…)

ƒ ƒ ƒ ƒ

Size screening Undesirable element (Metal, ice, snow, stones, etc…) Etc.. Can be difficult if: ƒ Mainly if fuel quality is inconsistent and/or various kind of fuels are used ƒ More than one supplier (depending on invoicing method) ƒ Large plant meaning many samples ƒ Method of invoicing ( inlet/outlet boiler )? 13

Part 2

Technologies and compatibility with Biomass

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Classification of solid fuels: Biomass is a challenging fuel 35

CONSUMER PDF MIXED PLASTICS

PETROLEUM COKE

BITUMINOUS COALS

COLORED OR PRINTED CONSUMER PDF MIXED WOOD AND PLASTICS PLASTICS RF PELLETS

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PDF INDUSTRIAL

LHV, MJ/kg

Biofuels

POLYOLEFIN COLORED PLASTICS OR PRINTED PLASTICS, (PE, PP, PC...) CLEAN

PDF PLYCOMMERCIAL WOOD

CHIPBOARD

BROWN COALS, LIGNITE 10

WOOD BIOMASS

DEMOLITION WOOD RDF

FIBER RESIDUE

PEAT

PVC PVC

BARK

CONSUMER PDF MSW PAPER AND WOOD

5 0

STANDARD DESIGN

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2

NO CHALLENGE

SOME CHALLENGES

Boiler Designs

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10

MULTIPLE CHALLENGES

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Challenging fuels ƒ

ƒ

ƒ

ƒ

Too dusty fuel (sawdust, straw, …) ƒ Fouling in boiler-house and around fuel handling station; ATEX regulation; ƒ Risk of fire and explosion (in boiler, ducts and flue gas treatment) ƒ Incomplete combustion in the furnace (for grates) and of combustion in the second pass ƒ colder bed if BFB, CFB Too wet fuel ƒ Tendency to freeze, bridging ƒ Overload in fuel receiving station, conveyors ƒ Reduced boiler capacity (fuel volume limited, excessive flue gas temperature, need top up with expensive fuel..) ƒ Reduced efficiency (Incomplete combustion with grate or spreader stocker if not homogenous) Too dry fuel ƒ Hazard of overheatind and damaging grate ƒ Ash melting /Vitrification: ƒ Bed and refractory agglomeration ƒ Sand agglomeration if BFB, CFB ƒ Recirculation may be needed (to control the oxygen level and regulate the combustion –BFB) Ash content 16 ƒ Overload fuel removing system ƒ Foreign bodies

Boiler sizing ƒ

Must run for a minimum of 8000 hours a year ƒ For economical reasons (high investment)

ƒ

Sized on summer needs (DHN) or base load for industry ƒ Prefer CHP to condensation ƒ Take into account technical minimum of other boiler(s) ƒ Availability of the biomass ressource

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Flexibility ƒ No peak lopping or fast response time capability ƒ High inertia ( up to 30% for grate, spreader stoker boilers) ƒ Time needed for start and stop depend on size and technology (esp. if sand bed)

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Minimum load ƒ Depends on boiler size, technology and fuel. (Varies from 30 to 60%) ƒ But Steam parameters may change below a certain point (e.g:70%)

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Can be multi-fuel boiler ƒ To secure the fuel supply ƒ Fossil fuel needed for BFB /CFB

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Compatibility with fuel ƒ The smaller boilers are adapted for higher fuel quality (dry wood logs, pellets, wood chips)

ƒ

Heat or power generation

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Combustion technology

ƒ ƒ ƒ ƒ ƒ

Fixed or moving grate Spreader stoker Fluidised bed (BFB, CFB) (> 15/20MW) Cigar burners (10 /30 MW) Gasification.

ƒ

Mix (examples): ƒ Straw with cigar + grate for wood (up to 100%) ƒ Straw for grate + spreader for wood (up to 50%) ƒ Sludge injection in chute of grate boiler ƒ Etc..

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Combustion technology : Grate/ BFB -CFB /Cigar Moving/fixed grates

Rotating grate with Volcan furnace

Cigar burner and grate with straw disintegrator

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Combustion technologies Comparison of existing systems BFB or CFB

Mobile grid Burner with placed feed

Spreader stoker

Fuel flexibility Fuel granulometry

+++ o

++ ++

+ +

Efficiency

++

o

+

Auxiliary electrical consumption -

+

+

Ash & residues

+

-

o

Reactives / Sand

+/-

-/+

-/+

Emissions (CO / NOx)

-/+

o/-

+/o

Load follow-up

++

-

++

Price

-

+

+

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Boilers 40-400 kWth. Wood logs boilers Wood logs boilers

Upside down flame (“gasifier effect ”)

Mobile grate

Pellets or chips boilers

Under feed stoker

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400 kWth biomass boiler-house

Gas extraction boiler

Screw conveyor

Multicyclone

Feed hopper Flying ash collector

Bottom ash removal

Screw feeder to boiler’s combustion chamber 22

Combustion technology : Size of boilers Range of use

Capacity

Type of boilers

Domestic boilers

15-40 kW th

ƒThermal-fireplaces ƒWood thermal-stoves ƒWood boilers ƒPellets boilers ƒUpside down flame (gasified effect)

Boilers for big houses

40-400 kW th

ƒUpside down flame (gasified effect) ƒFixed grate ƒUnder feed stoker fireplace (hearth) ƒPellets boilers

District heating boilers

0,4 – 20 MW th

ƒMoving grate ƒSpreader stoker ƒBubbling fluidised bed (>15MW) ƒCigar (>10MW)

Industrial boilers for power and/or heat production

1-80 MW th

ƒMoving grate ƒSpreader stoker ƒCigar ( About -1% efficiency) Technology and manufacturer Method of calculation (through fuel or losses) Scope (deaerator, blowdown, etc…)

ƒ

Power consumption: ƒ For grate, spreader stokers technologies: 15-25 kWe/MWth (pumps, FD, ID, ESP, fuel handling ) ƒ For BFB, CFB technologies: 25-35 kWe/MWth (air booster, flue gas recycling etc. ƒ NB: Traditional gas boiler house: About 10 kWe/MWth 24

Heat and Power generation ƒ Hot water and process Steam ƒ Pressure depends on the application (DHN, etc..) ƒ No specific problem with P&T

ƒ Steam parameters for power generation ƒ according to the turbine characteristics and the outlet levels for the customer process ƒ To risk of fouling (ash melting point) ƒ To risk of corrosion ƒ Typical parameters: ƒ Plant < 16 MWt P = 24-45 bara; T=350-440°C ƒ Plant between 15 and 70 MW P = 40/65 bara ; T = 420- 540 °C ƒ Plant > 70 MW : P = 90 bara ; T : 540 °C ƒ With Straw, parameters can reach 90bar/540C or 200bar/560C ƒ CHP or condensation mode ƒ Stability of parameters for ST 25

Greenfield or retrofit ?

ƒ A retrofit can half the investment cost ƒ ƒ ƒ ƒ ƒ

Risk of the lifecycle of the remaining parts Difficult interface with existing plant during construction There may not be enough space From coal or other boilers Requires experienced boiler manufacturer

ƒ A Greenfield ƒ Guarantees latest technology for all plant ƒ Dedicated plant

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Fuel drying

ƒ Drum dryer or Mat dryer ƒ Often quite problematic=>Not recommended in general ƒ Operational issues ƒ Space required with flue gas temperature >170C ƒ Displace useful heat (>140C required) if steam or hot water is used. ƒ NB: Technologies in appendix

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Availability ƒ BFB or CFB: ƒ 8200 hours p.a.

ƒ Grate ƒ 8050 hours p.a

ƒ NB: ƒ Depends on reliability, easy access for maintenance,.. ƒ Reduced availability on the first year ƒ 12 or 24 months availability guaranteed

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Investment and O&M ƒ Investment: ƒ ƒ ƒ ƒ ƒ

Technologies Steam parameters Level of manning and automation Turnkey or EPCM Market (Appetite of suppliers, steel,..)

ƒ Operation ƒ Design and technologies

Depends a lot on fuel, technology and contractual risk organisation

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Ash: A critical issue ƒ Typical ash content (On dry) ƒ 3% wood, 8% bark, etc…

ƒ Technologies: ƒ Multi-cyclone (