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Bioenergy utilization in Sweden
Claes TullinSP Swedish National Testing and
Research Institute
Outline• Introduction to biomass in Sweden• Waste wood combustion• Increasing market for refined fuels (pellets)
Energy sourcesGlobal (100 000 TWh)
Biofuels 10%
Coal 25%
Hydro 2%Nuclear 7%
Gas 21%
Oil 35%
Sweden (484 TWh)
Biofuels 18%
Hydro 15%
Nuclear 15%Other 5%
Oil 42%
Coal 5%
Supply of district heating
0
10
20
30
40
50
60
1970 1975 1980 1985 1990 1995 2000
TWh
Waste heatHeat pumpsElectric boilersBiofuels, peat etc,blast furnace gasCoal, includingNatural gas, including LPGOil
Driving mechanisms (1)
• Emissions of fossil CO2 do enhance the green-house effect = a political truth!! => CO2 reductions important!• Tax on CO2 from fossil fuels
• Ban on landfilling of combustible wastes (from jan. 2002)
• Closing of nuclear reactors• Power shortage
Increasing use of Bioenergy
1970 – 2000: + 2 TWh/year1980 – 2000: + 2.5 TWh/year1990 – 2000: + 3.1 TWh/year2000 – 2010: + ?? TWh/year
District heating
• Forest residues• Briquettes, pellets• Sorted wastes
- Waste wood- RDF- Sludge
• MSW
2. Dedicated waste wood combustion
• Contaminants due to treatments- CCA (Cu, Cr, As)- Paints (Zn, Pb, Cd, ..)- Boards (N, Cl, S)
• Increased fouling/corrosion• Emissions (EU incineration directive)
- Metals and HCl
Waste wood project Swedish Thermal Engineering
Research Institute
• Literature data ash chemistry• Detailed fuel analysis• Detailed field measurements• Numerical simulation• Laboratory studies on Zn/Pb chemistry
Two case studies: - Grate combustion (vibrating grate; 117 MWth)- Fluid bed (BFB; 98 MWth)
• Characterisation of fuel fractions- Painted, boards, plastics, metals
• Size distribution• Chemical analyses
Detailed fuel analysis
Laboratory sieve => 5 fractions
Sieving result
0
10
20
30
40
50
60
70
v-%
0-3 mm 3-6,5 mm 6,5-45 mm > 45 mm
Sållets hålstorlek
Sållningsresultat enligt sållningsmetod SCAN CM40
RT, H S RT, H I RT, I S RT, I I Skog, H I Skog, I S
Figur 1
dust-
fine-
middle-
course-
Sieving result
Fines + dust = 30 w-%• 60 % of the deposit related compounds (Zn,
Pb, Na, K)• 40 % for Cl
Dust = 7 w-%• 40 % of deposit related compounds (Zn, Pb,
Na, K) • 10 % för Cl
0
10
20
30
40
50
60
70
80
90
100
0
200
400
600
800
1000
1200
1400
1600
Zink i beläggning [vikt-%]Klor i beläggning [vikt-%]Medel HCl i rökgas [ppm](K, Na)Cl (IACM) [ppm]BeläggningstillväxtZink i bränsle [mg/kg]Klor i bränsle [mg/kg]
RTHI RTHS Skog HS
Fuel quality – deposit formation
Cl in fuel
Zn in fuel
Deposit
Zn in deposit
Deposit probe test50% biomix/50% recycled wood, 12 h exposure, tring 500 °C
Without ChlorOut;
chloride conc ~25%
grow rate 21 g/m2/h
With ChlorOut;
chloride conc <0.2%
grow rate 6 g/m2/h
Eld
Överhettare II
On-line kaliumkloridanalysator
Kondensat
ChlorOut
lösning
Sprayplym
ChlorOut installation Idbäcken
A high energy ion hits the surface and gives rise to a cascade of secondary ions from the outermost 1-2 atomic layers of the sample surface. The secondary ions are detected by a mass spectrometer.
TOF-SIMS - Time-of-Flight Secondary Ion Mass Spectrometry
Schematic picture of the SIMS process.
TOF-SIMS analysis of SH-deposit
1,E+00
1,E+01
1,E+02
1,E+03
1,E+04
1,E+05
1,E+06
1,E+07
1,E+08
0,01 0,1 1 10 100dN/d
log(
Dp)
(Ant
al p
artik
lar/c
m3
norm
erat
på
7% O
2)
0
25
50
75
100
125
150
175
200
dm/d
log(
Dp)
(mg/
m3
norm
erat
på
7%
O2
torr
gas
)
Partikelkonc; Skog H I Partikelkonc; RT H I Masskonc; Skog H I Masskonc; RT H I
Aerosol characteristics (grate)
Aerosol characteristics (BFB)
Chem analysis of PM fractions
0%
20%
40%
60%
80%
100%
H2:1 H2:3 H2:5 H2:7 H2:9 H2:11 H2:13 H5:1 H5:3 H5:5 H5:7 H5:9 H5:11
Sam
man
sättn
ing
(mol
proc
ent)
0
1
2
3
4
5
6
7
8
9
ZnFeCaKClSPSiAlMgNaDiameter H5Diameter H2
RT-Händelö, import Skogsflis Baltikum
Conclusions: deposit formation
• In comparison with forest residues, combustionof waste wood =>- Higher rate of deposit formation- More Zn, Pb, K, Cl in the deposits- Increased corrosion
• Less Zn in FB deposits
ZnO thermally stable….
… but Zn still found in deposits and submicron particles:
Transport mechanisms from fuel bed to heat exchangers:
• ZnO pigment particles as such• ZnO reduced to Zn which evaporates• ZnO + HCl => ZnCl2 which evaporates
Experimental set-up
ELPI-Instrument
Partikelfri Luft
HCl
N2
UGN
Luftfördelare
Fluidbädd
Glasull
ZnO(s) + HCl(g)
⇒ZnCl2 (s)
⇒ZnCl2 (g)
⇒Cooling
⇒ZnCl2(s) with dp < 1 µm
Vacuum pump
Corona charger
electrometers
Combustion tests with (1) waste fuel samples and (2)doped reference fuels
Cyklon samt stoftfilter
Sekundär Luft
Primärluft och eventuell HCl och SO2
UGN
Luftfördelare
Fluidbädd
Glasull
Gasanlays instrument
Bränsleinmatning med en karusellmatare
Bränsleschakt
Results - 1ZnO + 500 ppm HCl
1,E+001,E+011,E+021,E+031,E+041,E+051,E+061,E+071,E+081,E+09
0 1000 2000 3000 4000 5000 6000
Tid (s)
Nto
t (A
ntal
par
tikla
r/cm
3)
050100150200250300350400450
Tem
pera
tur (
oC)
F14: Ntot (Antal/cm3) Temperatur
100 300 500 700 900 11000.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0.045
0.050
File: M:\4640KVF\HSC MBg\KWN\1_4.OGI
C
mol-%
Temperature
H2O(g)
ZnCl2(g)Cl2(g)
HCl(g)
Zn(g)
Thermodynamic predictions
Results: Formation of Zn • Thermodynamic calculation predict Zn(g)
formation but….• this cannot be confirmed in experiments
(CO, T = 850-1050 oC)=> kinetic limitations!?
100 300 500 700 900 11000.000
0.005
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0.045
0.050
File: M:\4640KVF\HSC MBg\KWN\1_1.OGI
C
mol-%
Temperature
CO2(g)Zn(g)
HCl(g)
H2O(g)
ZnCl2(g)
Continuous combustion of painted wood -Additives reduce evaporation
• Addition of SO2 and Kaolin reduce the vaporation of Zn• Large difference between fluid bed and grate
combustion conditions
3. Domestic heating in Sweden
Biofuel24%
Electricity34%
District heating
8%
Oil34%
Emissions from different domestic combustion equipment per net kWh
Type of combustion Tar, mg VOC, mg NOx, mg Particles,
Trad. wood boiler 2 500 10 000 350 1 800Modern wood boiler 30 300 520 80Modern wood stove 50 700 n.a. 80Pellet boiler 20 160 <270 160Pellet stove 20 120 <270 160
Installed Pellet Burners
05000
10000150002000025000300003500040000
1997 1998 1999 2000 2001 2002
Pellet burners
Delivered pellets (Sweden)
Source: PIR
0
100000
200000
300000
400000
500000
600000
700000
80000019
92
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
ton
pelle
ts >2 MW 50 kW- 2 MW< 50 kWTotal
Issues in Pellet Combustion• Environmental problems?
- NOx- Particulates
• If replacing oil burners/electricity• Technical issues
- Pellet quality- Maintenance- Operator independent- Installation
• Economy/Market- Supply
• Safety
Fuel-N conversion to NOx is high in pellet burners/stoves
0
0,2
0,4
0,6
0,8
1
1,2
0 0,05 0,1 0,15 0,2 0,25Fuel-N (w eight-%)
Con
vers
ion
of F
uel-N
=> N
Ox
0
100
200
300
400
500
NO
2 (m
g/nm
3; 1
0%O
2)
100% Conversion
Oil => Pellets Higher NOx- emissions
NOx-emissions for 25 000 kWh
0
5
10
15
20
25
Pellets (low N)
Pellets(high N)
Oil
NO
2 (k
g/ye
ar)
Grate Boiler, 2,5 MW, Wood Briquettes
0
10
20
30
40
50
60
70
80
0.01 0.1 1 10Dp (µm)
Mass size distribution
Number size distributiondN/dlog(Dp)(10^6 st/Ncm3)
dm/dlog(Dp)(mg/Nm3)
Di = 0.1 µm
Di = 0.3 µm
KCl7%
NaCl1%
Na2SO45%
Na2CO31%
K2CO324%
K2SO462%
KCl29%
NaCl2%
Na2SO42%
Na2CO31%
K2CO311%
K2SO455%
TOF-SIMS Results - Pellet Stove
General conclusions
• Steady increase in the use of Bioenergy• Increasing use of ”waste” fuels• Waste wood
- Problems with deposit formation/corrosion- Fuel quality (Cl, Zn, Pb)- Primary/secondary combustion actions
• Increasing use of pellets (small scale)- NOx- Particles