properties of solid biofuels and comparison to fossil...

© Eija Alakangas, VTT

Properties of solid biofuels and comparisonto fossil fuels

Eija Alakangas, VTT

2


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

3


Classification of biomass fuels

4


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

10

BITUMINOUS COALS

BROWN COALS,LIGNITE

STANDARDDESIGN

PETROLEUM COKE

5


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

6


Classification based on raw material

7


Classification of wood fuels

8


Wood fuel properties and comparison to other fuels

9


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)

10


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

11


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

12


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

13


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


14


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


15


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

16


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

17



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


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)


19


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

20


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.


21


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


22


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

23


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

24


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

25


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

26


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, %

27


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

28


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

29


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

30


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

31


Properties of used wood and comparison to virgin wood

32


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

33


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


34



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

35


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

36


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).

37


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

38


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.

39


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

40


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

41


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

42


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

43


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

44


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.

45


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.

46


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)

properties of solid biofuels and comparison to fossil...

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