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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

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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

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10

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100

0

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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

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0,2

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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

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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

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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