Bioenergy Utilization in Sweden

Bioenergy utilization in Sweden

Claes Tullin SP Swedish National Testing and Research Institute Outline • Introduction to biomass in Sweden • Waste wood combustion • Increasing market for refined fuels (pellets) Energy sources

Global (100 000 TWh) Sweden (484 TWh) Nuclear 7% Hydro 2% Other 5% Gas 21% Biofuels 10% Nuclear 15%

Oil 42% Hydro 15%

Coal 25%

Oil 35% Biofuels 18%

Coal 5% Supply of district heating

Waste heat 40 Heat pumps Electric boilers 30 Biofuels, peat etc,

TWh blast furnace gas 20 Coal, including Natural gas, including LPG 10 Oil

1970 1975 1980 1985 1990 1995 2000 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/year 1980 – 2000: + 2.5 TWh/year 1990 – 2000: + 3.1 TWh/year 2000 – 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 ¾ Two case studies:

- Grate combustion (vibrating grate; 117 MWth)

- Fluid bed (BFB; 98 MWth) Detailed fuel analysis

• Characterisation of fuel fractions - Painted, boards, plastics, metals • Size distribution • Chemical analyses Laboratory sieve => 5 fractions Sieving result

Sållningsresultat enligt sållningsmetod SCAN CM40

RT, H S RT, H I RT, I S RT, I I Skog, H I Skog, I S middle-

50 fine-

40 v-% 30 dust- course- 20

0 0-3 mm 3-6,5 mm 6,5-45 mm > 45 mm Sållets hålstorlek Figur 1 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 Fuel quality – deposit formation

100 1600

90 1400

1200 70 Cl in 1000 60 fuel Zink i beläggning [vikt-%] Klor i beläggning [vikt-%] Medel HCl i rökgas [ppm] 50 800 (K, Na)Cl (IACM) [ppm] Zn in Zn in Beläggningstillväxt Zink i bränsle [mg/kg] 40 fuel deposit 600 Klor i bränsle [mg/kg]

400

200 10 Deposit

0 0 RTHI RTHS Skog HS Deposit probe test 50% biomix/50% recycled wood,

12 h exposure, tring 500 °C

Without ChlorOut; With ChlorOut; chloride conc ~25% chloride conc <0.2% grow rate 21 g/m2/h grow rate 6 g/m2/h ChlorOut installation Idbäcken Kondensat

Sprayplym Överhettare II

On-line kaliumklorid analysator

Eld ChlorOut lösning TOF-SIMS - Time-of-Flight Secondary Ion Mass Spectrometry 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. Schematic picture of the SIMS process. TOF-SIMS analysis of SH-deposit

Aerosol characteristics (grate)

1,E+08 200

1,E+07 175

1,E+06 150

1,E+05 125

1,E+04 100

1,E+03 75 på 7% O2 torr gas) 1,E+02 50 dm/dlog(Dp) (mg/m3 normerat 1,E+01 25

1,E+00 0 dN/dlog(Dp) (Antal partiklar/cm3 normerat på 7% O2) dN/dlog(Dp) (Antal partiklar/cm3 0,01 0,1 1 10 100

Partikelkonc; Skog H I Partikelkonc; RT H I Masskonc; Skog H I Masskonc; RT H I Aerosol characteristics (BFB) Chem analysis of PM fractions RT-Händelö, import Skogsflis Baltikum

100% 9

80% 7 Zn Fe 6 Ca 60% K 5 Cl S 4 P 40% Si Al 3 Mg

Sammansättning (molprocent) Na 2 20% Diameter H5 Diameter H2 1

0% 0 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 Conclusions: deposit formation

• In comparison with forest residues, combustion of 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

Partikelfri Luft ZnO(s) + HCl(g) ELPI- Instrument Glasull ⇒ZnCl2 (s) Corona charger ⇒ZnCl2 (g)

electrometers ⇒Cooling UGN ⇒ZnCl2(s) with dp < 1 µm Vacuum pump Fluidbädd

Luftfördelare

N2 HCl Combustion tests with (1) waste fuel samples and (2) doped reference fuels

Gasanlays instrument Sekundär Luft Bränsleinmatning med en Cyklon samt karusellmatare stoftfilter Glasull

Bränsleschakt

UGN

Fluidbädd

Luftfördelare

Primärluft och eventuell HCl och SO2 Results - 1

ZnO + 500 ppm HCl Thermodynamic predictions

) 1,E+09 450 mol-% File: M:\4640KVF\HSC MBg\KWN\1_4.OGI 1,E+08 400 0.050 1,E+07 350 0.045 1,E+06 300 1,E+05 250 0.040 1,E+04 200 1,E+03 150 0.035 1,E+02 100 Temperatur (oC) Temperatur 0.030 1,E+01 50 H2O(g) Ntot (Antal partiklar/cm3 1,E+00 0 0.025 ZnCl2(g) 0 1000 2000 3000 4000 5000 6000 Cl2(g) 0.020 Tid (s) 0.015 HCl(g) F14: Ntot (Antal/cm3) Temperatur 0.010

0.005 Zn(g) Temperature 0.000 C 100 300 500 700 900 1100

Results: Formation of Zn • Thermodynamic calculation predict Zn(g) formation but…. • this cannot be confirmed in experiments (CO, T = 850-1050 oC) => kinetic limitations!?

mol-% File: M:\4640KVF\HSC MBg\KWN\1_1.OGI 0.050 CO2(g) 0.045 Zn(g) HCl(g) 0.040

0.035

0.030 H2O(g) 0.025 ZnCl2(g) 0.020

0.015

0.010

0.005

Temperature 0.000 100 300 500 700 900 1100 C

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 District heating 8% Biofuel 24%

Oil 34%

Electricity 34% 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 1 800 Modern wood boiler 30 300 520 80 Modern wood stove 50 700 n.a. 80 Pellet boiler 20 160 <270 160 Pellet stove 20 120 <270 160 Pellet burners

Installed Pellet Burners

40000 35000 30000 25000 20000 15000 10000 5000 0 1997 1998 1999 2000 2001 2002 Delivered pellets (Sweden)

800000 700000 600000 >2 MW 500000 50 kW- 2 MW 400000 < 50 kW 300000 ton pellets ton Total 200000 100000 0 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002

Source: PIR 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

1,2 500

1 100% Conversion 400

0,8 300 0,6 200 0,4

100 NO2 (mg/nm3; 10%O2) 0,2 Conversion of Fuel-N=> NOx Fuel-N=> of Conversion 0 0 0 0,05 0,1 0,15 0,2 0,25 Fuel-N (weight-%) Oil => Pellets Higher NOx- emissions

25 NOx-emissions for 25 000 kWh 20 15 10 5

NO2 (kg/year)NO2 0 Pellets Pellets Oil (low N) (high N) Grate Boiler, 2,5 MW, Wood Briquettes

80 70 Mass size distribution 60 dN/dlog(Dp) Number size distribution (10^6 st/Ncm3) 50 40 30 20 dm/dlog(Dp) (mg/Nm3) 10 0 0.01 0.1 1 10 Dp (µm) TOF-SIMS Results - Pellet Stove

NaCl KCl Na2CO3 NaCl 1% 7% 1% 2%

Na2SO4 KCl 5% 29%

K2CO3 24% Na2CO3 K2SO4 1% 55% K2SO4 Na2SO4 62% 2% K2CO3 11%

Di = 0.1 µm Di = 0.3 µm

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