Properties of solid biofuels and comparison to fossil...
Transcript of Properties of solid biofuels and comparison to fossil...
© Eija Alakangas, VTT
Properties of solid biofuels and comparisonto fossil fuels
Eija Alakangas, VTT
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© Eija Alakangas, VTT
Energy units
REMEMBER THIS1 toe = 11.63 MWh 1 MWh= 3 600 MJ = 3.6 GJtoe = equivalent oil tonne 1 MW= MJ/s
k kilo 103 T tera 1012
M mega 106 P peta 1015
G giga 109 E eksa 1018
14.18681.1630.1Gcal
0.238810.27780.02388GJ
0.863.610.086MWh
1041.86811.631toe
GcalGJMWhtoe
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Classification of biomass fuels
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Characterisation of solid biofuels – boiler
20
35Net calorific value, MJ/kg
FUEL RANK
PEAT
BARK
MULTIPLE CHALLENGES SOME CHALLENGES NO CHALLENGE0 0,1 0,5 1
WOOD BIOMASSDEMOLITION
WOOD
FIBER RESIDUE
PDFINDUSTRIAL
PDF COMMERCIAL
CHIP-BOARD
POLYOLEFINPLASTICS(PE, PP, PC...)
COLOREDOR PRINTEDPLASTICS,CLEAN
COLORED OR PRINTEDMIXEDPLASTICS
RFPELLETS
PLY-WOOD
5
10
PVC
RDF
MSW
PVC
CONSUMER PDFWOOD AND PLASTICS
CONSUMER PDFMIXED PLASTICS
CONSUMER PDFPAPER AND WOOD
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BITUMINOUS COALS
BROWN COALS,LIGNITE
STANDARDDESIGN
PETROLEUM COKE
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Characterisation of solid biofuels – C, H, Q
Net calorific value of dry matter
404.0 4.5 90 85
80
75
70
6065
55
C=50 %
H=3.5 %
5.0 5.5 6.0 6.5
30
20
0 10 20 30 40 50 60 70 80 90 100
MJ/kgQ
Volatile matter, %
Ant
raci
te
Cok
e
Bro
wn
coai
Pea
t
Woo
d
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Classification based on raw material
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Classification of wood fuels
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Wood fuel properties and comparison to other fuels
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Chemical properties
Elementary analysis− Carbon (C), hydrogen (H) and nitrogen (N)− Sulphur (S), chlorine (Cl), fluorine (F) and bromium (Br) − Ultimate analysis includes analysis of ash content, moisture,
volatiles and char
Properties like sulphur, chlorine and heavy metals are important to know for environmental reasonsHigh alkali content like potassium (K), sodium (Na) and chlorine (Cl) can cause corrosion and slagging problems in steam boilersMajor and minor elements (mg/kg dry matter)− Major elements; (Al, Ca, Fe, Mg, P, K, Si, Na and Ti)− Minor elements; (As, Cd, Co, Cr, Cu, Hg, Mn, Mo, Ni, Pb, Sb, Se,
Sn, V and Zn)
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Composition of wood
Chlorine content (Cl) for virgin wood < 0,05w-% of dry matter.Usually mineral content less than 1w-% of dry matter. Most important are: potassium (K), magnesium (Mg), manganese (Mn), calcium (Ca), sulphur (S), chlorine (Cl), phosphorus (P), iron (Fe), aluminium (Al) and zinc (Zn).
MoistureDry matter
* proportion in dry matter (d), %
CHAR (C)11,4 - 15,6%*
VOLATILES84 - 88%*
Ash0,4-2,0%*
Carbon Hydrogen (H) 6,0 - 6,2%Oxygen (O) 38 - 42 % Nitrogen (N) 0,1 - 0,4 % Sulphur (S) 0,01
*
* *
-
(C) 49 - 51%*
BARKI 60 %SAW DUST 55 %FRESH WOOD 50 - 60 %
STEM CHIPS 25 - 40 %FIREWOOD 20 25 %
LOGGING RESIDUE 35 - 50 %
-WOOD PELLET 8 - 10 %
Eija Alakangas
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© Eija Alakangas, VTT
Composition of wood
Lignin includes lot of carbon and hydrogen – energy producingLignin content is higher for coniferous (soft wood) than deciduous (hard wood) trees
WOOD
Energy producing part
Hydrogen
OxygenCarbon
MOISTURE
Nitrogen
Ash
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Properties of wood fuels
0.02 – 0.150.001 – 0.0020.01– 0.030.3 – 0.5<0.055.4 – 6.048 – 52Whole treechips
0.1 – 0.40.075 – 0.0300.01– 0.040.3 – 0.5<0.056.0 – 6.248 – 52Loggingresidue chips
0.02 – 0.150.001 – 0.0020.01– 0.030.3 – 0.5<0.065.4 – 6.048 – 52Stem chips
0.02 – 0.150.001 – 0.0020.01– 0.030.3 – 0.5< 0.056.0 – 6.548 – 52Firewood (oven-readylog)
0.02 – 0.150.001 – 0.0020.01– 0.03< 0.16<0.0076.0 – 6.149 - 50Wood pellet
0.70.25 – 0.50< 0.050.1 – 0.5<0.056.2 – 6.448 – 52Ply wood
0.1 – 0.50.007 – 0.0200.01– 0.050.3 – 0.5<0.056.2 – 6.848 – 52Bark
0.02 – 0.150.001 – 0.0050.01– 0.030.3 – 0.4<0.056.2 – 6.448 – 52Sawdust
KNaClNS H2 CFuel
Properties are stated in value w-% of dry matter
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Comparison of solid biofuels
0.02 – 0.40.001–0.020.01– 0.030.3–0.5<0.055,4-6.848 – 52Wood, general
30(ash)00.1 (ash)0.5–1.50.07-0.17 5.5–6.548 – 50Olive residues
0.70.460.055.548Miscanthuschopped
0.69–1.300.01–0.60.14–0.970.4–0.60.10–0.205.8 – 6.045 - 47Straw pellets
0.69–1.300.01–0.60.14–0.970.4–0.60.10–0.205.8–6.045 - 47Straw
0.4–1.00.002–0.0050.042.00.146.545Energy grain
1.2–2.3< 0.0010.40.7–1.10.06–0.255.6–5.944.6–46.7Reed canarygrass,autumnharvested.
0.3–0.5<0.030.04–0.090.65-1.10.04–0.135.3–5.845–49Reed canary grass, springharvested
KNaClNS H2 CFUEL
Properties are stated in value w-% of dry matter
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Comparison to fossil fuels
KNaClNS H2 CFUEL
0.02 – 0.40.001–0.02
0.01–0.030.3–0.5<0.055,4-6.848 – 52Woodgeneral
---0.01-0.030.113.786.2Light fuel oil
-<0.0004-0.3-0.40.8-0.9510.188.4Heavy fuel oil
0.020.0070.02-0.061.0-3.00.005–0.35.0 – 6.552 – 56Fuel peat
0.0030.0120.100.8 – 1.5< 0.53.5 – 5.068 – 78Coal
Properties are stated in value w-% of dry matter
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Physical and mechanical properties (1)
Moisture (M)−Wood fuels are usually wet except wood pellets or briquettes− Moisture effect into calorific value− Healthy issues (mould, decay, fungi)− Moist fuel is difficult to transport (flow properties)
Ash content (A)− Important for combustion and ash handling− Nordic wood species has low ash content, but southern
European wood species have higher ash content. − Impurities like sand, soil and chemicals include ash content− Problems in large boiler when ash content is more than 3w-
% and in small-scale boilers when ash content is more than 0.5w-%
− Also the ash composition affect to combustion and re-use
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Ash content: Relevance
0 2 4 6 8Ash content (A) in fuel
0
100
200
300
400
500
700
% (d.b.)
mg/Nm3
(13 % O2)
Regression for wood fuels:
y = 13,3 + 22,7 AR² = 0,67 (N = 79) D
ust
emis
sions
Wood chips and pelletsHerbaceous and grain fuels
Influence of the ash content on dust emissions(49 kW wood chip boiler)
Source: Hans Hartman, TZF
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Physical and mechanical properties (2)
Ash melting behaviour− Important for combustion; slagging and fouling− For herbaceous biomass ash melting temperatures are lower
than for woody biomass− Some wood species has lower ash melting temperatures e.g.
eucalyptus, poplarParticle size (P)− Important for handling and combustion− Also geometry of the piece is important (long sticks or
cylindar form− Aim is to produce homogenous particle size distribution− Long sticks and fine particles cause problems
© Eija Alakangas, VTT
Particle density/bulk density
0 20 40 60 800
0,2
0,4
0,6
0,8
1
1,2
Specific mass demand
Spec
ific
volu
me
dem
and
Heating oilRapeseed oil
Hard coalEthanol Methanol
Straw-pellets
Deciduous wood chipsConiferous wood chips
Cereals - big square balesCereals - chopped
Straw - big square balesCereals - round bales
Straw - round balesStraw - small square bales
Straw - chopped
Hardwood logsSoftwood logs
Wood-pellets
m³/GJ
kg/GJ
Effects of fuel density
Energy densityTransport and storagevolume demandLogistical planningCombustion properties(specific heat conductivity, rate of gasification)(Hardness of compactedmaterial: Particle density)
Source: Hans Hartman, TZF
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Space requirement for 10 MWh, m3
Needed Storage Volume for 10 MWh [m³]
1,0 1,12,0
8,0
11,0
3,24,2
8,4
11,4 11,512,5
15,0
21,0
16,118,0
21,7
0,0
5,0
10,0
15,0
20,0
25,0
Light fue
l oil
Bio-oil
Coal
Sod pe
atMille
d peat
Wood p
ellet
Straw pelle
t
Shredded b
ark, dry
(birch
Loggin
g resid
ue ch
ips, dry
(spru
ce)
Logg
ing re
sidue c
hips,
dry (pi
ne)
Loggin
g res
idue ch
ips, fr
esh (
spruc
e)
Loggin
g res
idues b
undle
, fres
h (sp
ruce)
Shredd
ed bark
, fres
h (pin
e)
Square bi
g stra
w bale,
whea
t & ba
rley
Round
reed
cana
ry gras
s bale
Round s
traw bale
, whe
at & barl
eym³
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Bulk density (BD)−Bulk density is important property for
transportation, conveyors and for fuel feeding − In small plants trade is based on measurement
of bulk density and moisture contentParticle density (DE) informs the mechanical durability of briquettesMechanical durability (DU)− Important property for pellets
Net calorific value (Q)− Informs the energy content of the fuel− In medium and large scale trade is based on
measuring weight, moisture content and net calorific value
Analysis of bulk density at 2 MW heating plant.
Physical and mechanical properties (3)
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Summary of physical/mechanical properties
Durability(of pellets)
Bulk density
Moisture content
Particle density
Size distribution
Bridgingproperties
Calorificvalue (as received) Ash content
Ash softeningbehaviour
Impurities
Interdependency among physical/mechanical properties
Source: Hans Hartman, TZF
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© Eija Alakangas, VTT
Net calorific value, dry matter, MJ/kg*
05
1015202530354045
CoalHeav
y fuel o
ilLight
fuel
oilMille
d peat
Sod peat
Peat p
ellets
Sawdust
Bark, birc
hBark,
pine
Ply wood, h
og fuel
Wood pellet
Stem w
ood ch
ips
Logging resid
ue chips
Whole tre
e chips
Reed can
ary gras
s, sp
ring
Energy g
rain
Straw, c
hopped
Solid re
cove
red fu
el, SRF
MJ/kg
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Net calorific value as received - calculation
Net calorific value as received (Q)Minimum value to be stated (calculation by taking into account the selected moisture category and the typical variation of the net calorific value of dry matter at constant pressure)
qp,net,ar net calorific value as received, (MJ/kg)qp,net,d net calorific value (constant pressure) dry basis
(MJ/kg)Mar total moisture (w-%)0,02443 is the correction factor of the enthalpy of vaporization (constant
pressure) for water (moisture) at 25 °C [MJ/kg per 1 w-% of moisture]
Calculation formula is available in EN 14961-1
arar
dnet,arnet, MMqq p ×−−
×= 02443,0)100
100(,p,
Calorimetric bomb prEN 14918, Photo: ENAS Oy
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Net calorific value as received, MJ/kgar*
*Typical average moisture content has been used.
05
1015202530354045
Coal
Right fu
el oil
Light
fuel o
ilMille
d pea
tSod
peat
Peat p
ellets
Sawdu
stBark
, birc
h
Bark, c
onife
rous
Ply woo
d, ho
g fue
l
Woo
d pell
et
Stem w
ood c
hips
Logg
ing re
sidue
s chip
s
Who
le tre
e chip
s
Reed c
anary
gras
s, sp
ring
Energy
grain
Straw, c
hopp
ed
Solid r
ecov
ered f
uel, S
RF
MJ/kg
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Net calorific value as received - wood
Net calorificheating value as received MJ/kg
20
15
10
5
20 40 60 80
Moisture content, %
Net calorific heating valueper total mass
Net calorific heating valueper dry mass
Gross calorific heating valueper dry mass
Freshforest chips
Dry forestchips
Wetbark
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Kattilahyötysuhde polttoaineen kosteuspitoisuuden funktiona
88,5
89
89,5
90
90,5
91
91,5
92
92,5
93
93,5
30 35 40 45 50 55 60 65 70 75Kosteus [%]
Hyö
tysu
hde
[%]
1% efficiency change inboiler efficiency
in 400 MWth boiler
~ 40 GWh more fuel needed
(= 500 000 € in year)
Moisture content at plant - blending
Source: Janne Kärki, VTTMoisture, w-%
Boiler efficiency, %
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© Eija Alakangas, VTT
Ash content versus net calorific value
0 5 10 15 20 25Ash content in dry matter
13
14
15
16
17
18
19
21
13
14
15
16
17
18
19
21
%
Herbaceous biomass
Wood fuels
042ha010.ppt
Source: TFZ
Net calorific value in dry matter, MJ/kg
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Bark – moisture and energy density
July September October November March April
10 20 30 40 50
Moisture content
Energy density
70
60
50
40
30
20
10
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
Moisture content, % Energy density MWh/m3 loose
Consecutive number of load measured Source: Risto Impola, VTT
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© Eija Alakangas, VTT
Moisture content of logging residues
Source: Risto Impola, VTT
10
20
30
40
50
60
1 2 3 4 5 6 7 8 9 10 11 12
100
200
300
400
500
1 2 3 4 5 6 7 8 9 10 11 12
1020
30
40
50
Month / 2001
Moisture %
Waterkg/m3
Moisture content, %Large power plants, average 48.3 %
Small heating plants, average 38.4 %
Large power plants, average 392 kg/m3
Small heating plants, average 262 kg/m3
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Energy density of logging residues chips
Source: Risto Impola, VTT
1 2 3 4 5 6 7 8 9 10 11 12
Month / 2001
Large power plants, average 0.77 kWh/m 3
0.6
0.7
0.8
0.9Energy density MWh/m3 loose
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Properties of used wood and comparison to virgin wood
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© Eija Alakangas, VTT
Used wood versus virgin wood – 1/3
<0,0005 – 0,002< 0,002w-% dry matterFl
<0,01 – 0,050,02 – 0,12w-% dry matterCl
<0,01 – 0,20<0,02 – 0,08w-% dry matterS
<0,1 – 1,10,25 – 1,00w-% dry matterN
5,6 – 7,05,9 – 6,4w-% dry matterH
47 - 5449,1 – 52,3w-% dry matterC
17,1 – 20,618,6 – 18,9MJ/kg dry matterNet calorific value
0,2 – 10,00,7 – 4,0w-% dry matterAsh, A
Virgin woodprEN14961-1
Used woodFinland
UnitProperty
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© Eija Alakangas, VTT
500 – 2 000490mg/kg dryFe
200 – 5 000630 – 910mg/kg dryK
100 – 3 000N.A.mg/kg dryMg
9 - 84072 – 115mg/kg dryMn
10 – 2 000200 – 630mg/kg dryNa
50 – 1 30049mg/kg dryP
2 – 20 000N.A.mg/kg drySi
500 – 20 000mg/kg dryCa
10 – 3 000130 – 600mg/kg dryAl
Virgin woodprEN 14961-1
Used woodFinland
UnitProperty
Used wood versus virgin wood – 2/3
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© Eija Alakangas, VTT
Used wood versus virgin wood – 3/3
5 – 20079 – 300mg/kg dryZn
0,7 – 3,00,5 – 2,2mg/kg dryV
< 0,5 – 50,05,4 – 76,0mg/kg dryPd
< 0,1 – 80,03,2 – 10,0mg/kg dryNi
< 0,02 – 2,0< 0,01 – 2,0mg/kg dryHg
0,5 – 200,05,5 – 80,0mg/kg dryCu
0,2 – 40,05,2 – 60,0mg/kg dryCr
< 0,05 – 5,0*0,12 – 0,50mg/kg dryCd
<0,1 – 6,0< 2 – 34mg/kg dryAs
1 – 50 Ei tietoamg/kg dryTi
Virgin woodprEN 14961
Used wood Finland
UnitProperty
* willow
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© Eija Alakangas, VTT
Classification of used wood
A – Chemically untreated wood residues and by-productsB – Chemically treated wood residues and by-products− Chemically treated wood do not include heavy metals more than
virgin wood or halogenated compounds as a result of treatment with wood preservatives or coating
Classes A and B no waste incineration directive (WID) to beapplied, properties according to solid biofuel standardEN14961-1
C – Solid recovered fuel− include heavy metals or halogenated compounds as a result of
treatment with wood preservatives or coating− Do not include impregrated wood− Demolition wood, if ”cleaness” can be proved by analysis
For class C waste incineration directive (WID) is applied and solid recoved fuel standard applied (prEN15359).
D – Hazarous waste− Includes impregnated wood
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© Eija Alakangas, VTT
Chemical and mechanical impurity
Mechanical impurity
Coating, glueing, painting = chemicalimpurity
Chemical impurity can not be removed.
Class A can not include chemical impurity.
Mechanical impurities are separate part of fuel can part of themcan be removed (metal separation) and some more difficultto remove (plastic, construction material: concrete, insulationmaterial).
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© Eija Alakangas, VTT
Multi-fuel use – possibility to biomass
Forest industry
E. Alakangas
Electricity
Peat
Agrobiomass
Logging residues
Forest chips for energy
GPS
Round wood forraw material
Processheat
Flexible useof different biofuels
Bark andother residues
Forest woodPeat land
CHP plant
Districtheat
Low CO -emissions2
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© Eija Alakangas, VTT
Influence of properties to large scalecombustion
Alkalis e.g. sodium (Na) and potassium(K) together with chlorine
form alkali chlorines, which stick to heat surfaceshot corrosion, when material temperature is more 450–480oClower steam values when chlorine content is higher than 0.05 p-%
Analysis of reactive K+Na content in dry matterproblems, when K+Na is more than 3 000 mg/kg (0.3 w-%)if ply wood K+Na is higher than 0.5w-%, cofiring with other fuels
Cofiring with sulphur content fuelIf peat or coal is used alkali chlorides react with sulphur oxides from peat and coal combustion and form alkali sulphates or with aluminium silicate form alkali silicates.
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© Eija Alakangas, VTT
Effect of chlorine-sulphur chemistry to deposit formation in boilers
Source: Martti Aho, VTT
Heat transfersurface
Condensation and fixing
Lack of protecting
compounds
Low ash content
RI
SKY COMPOUNDSALKALICHLORIDES
Cl releases corrosionä
BARK/FOREST RESIDUE
FOREST RESIDUE COAL
Cocombustion
PR
OTECTING REACTIONSALKALISILICATES,
SULPHATES
RISKY COMPOUNS
SULPHUR DIOXIDE, Al-SILICATES
PROTECTIVES
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© Eija Alakangas, VTT
Effects to combustion - 2
Sodium in ply wood reacts with quartz in fluidisation bed material (sand)
agglomerate with potassium, calcium or manganeseuse of quartz-free bed material
Use of ply wood residues can increase bed temperaturesuse with wet fuelspecial boiler design
High ash content (> 3w-%)with chlorine can cause problems in boiler. Metallic aluminium (folio packages) in demolition wood, wood packages or wood residues from window or door industry
melting of ash in low temperature or stick into cold surfaces
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© Eija Alakangas, VTT
Deposite formation of boiler tubes
Slagging of bedmaterial
Hot corrosion of boiler tubes
Problems in fluidised bed boilers when using biomass fuels
Increase operation and maintenance costs, decrease of boiler efficiency and effects to lifetime of boiler
Source: Janne Kärki, VTT
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© Eija Alakangas, VTT
Recommendation for used wood
Combustion technology (e.g. hightemperature, combustion time)Cofiring in boilers > 20 MWth
Recommendations for boilertechnology
< 120 mg/kg dry woodZn
< 10 mg/kg dry woodPb
< 2 000 mg/kg dry wood(< 0.2 w-%)
Metallic aluminium
< 3 000 mg/kg dry wood(0.3 w-%)
Reactive Na+K (SFS-ISO 11885-1:1998 mod)
< 0.1w-% dry matterCl
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© Eija Alakangas, VTT
Threshold values for used wood –class B
Bark, coniferous< 4 mg/kg dryAr
Bark, coniferous< 1 mg/kg dryCd
Bark, coniferous< 0,1 mg/kg dryHg
Bark, coniferous< 50 mg/kg dryPb
Bark, coniferous< 200 mg/kg dryZn
Bark, coniferous**< 0,1w-% dryCl
Bark, coniferous< 40 mg/kg dryCr
Bark, coniferous< 30 mg/kg dryCu
Virgin wood, in whichvalue is based
Threshold valueProperty
** virgin wood <0.05 w-% of dry matter
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© Eija Alakangas, VTT
Recommendations for cofiring
If fluidised bed boiler is designed for combustion of peat or/and wood processing residues:− 50% wood can be used of total fuel amount and half of that can be
forest residues
Cofiring of peat or coal− Peat keeps boiler clean
− Peat can secure fuel quality and supply
− Ash from biomass fuel binds sulphur from peat and reduces emissions
Less than 10w-% of reed canary grass can be safely cofired withpeat and other solid biofuels.
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© Eija Alakangas, VTT
CO2 –factors
266,6874,1Blend, 70% peat and 20% wood
7,2 (0,76-15,1)2 ( 0,21 – 4,2)Glued or coated wood
61,217,0Demolition wood
114,4831,8Solid recovered fuel
198,055,0Natural gas
266,7674,1Light fuel oil
283,6878,8Heavy fuel oil
340,5694,6Coal
349,297,0Peat pellets
367,2102Sod peat
381,24105,9Milled peat
0 *(394,56)0 *(109,6)Wood
kgCO2/MWhgCO2/MJFUEL
1 gCO2/MJ = 3.6 kgCO2/MWh * CO2 factor for wood is zero in GHG calculations.
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© Eija Alakangas, VTT
Additional information
Alakangas, E. Properties of wood fuels used in Finland, Technical Research Centre of Finland, VTT , Project report PRO2/P2030/05 (Project C5SU00800), Jyväskylä 2005, 90 p. + app. 10 p. (www.bio-south.com)
Wiik, C. et al. Used wood in the EU – Part 1Classification, properties and practices, DIV.6 – Part 2. 86 p.(www.bionorm2.eu).Alakangas, E. et. Al. Used wood in the EU – Part 2A catalogue of used wood examples, DIV.6 – Part 3. 86 p.(www.bionorm2.eu). 32 p.
Biodat international database of solid biofuel properties (underpreparation) (www.phydades.info)