chemical physical properties of bio-coalusers.jyu.fi/~daagar/necc2012.pdfdefining the thermal regime...
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Defining the thermal regime known as torrefaction
Chemical Physical Properties of Bio-coal
David Agar1 Margareta Wihersaari2
1 Department of Chemistry
2 Department of Biological and Environmental Science
University of Jyväskylä
Nordic Environmental Chemistry Conference, Kakskerta, Turku, 4-7 June, 2012
Presentation Outline Introduction What is Bio-coal? Why Bio-coal?
Torrefaction Process overview The torrefaction regime Solid fuel properties of torrefied wood Torrefaction versus carbonisation
Bio-coal production Active players in Europe Three key properties of bio-coal from experiment data Conclusions
What is Bio-coal? Solid fuel made from biomass (renewable) Fossil coal substitute High heating value (MJ/kg, compared to untreated biomass) High bulk energy density (MJ/m3) Handling properties like fossil coal (easy to grind)
Fuel for coal-fired power plants (large-scale production)
Bio-coal as briquette Bio-coal as pellets
What Bio-coal is NOT Not (grilling) charcoal Not bio-char (soil additive) Not bio-carbon (high-end technical carbon product) Note: Especially confusing in Finnish
Biohiili Bio-coal Bio-char Bio-carbon
The Finnish language may have many different words for snow but this is not the case for high-carbon products
Why Bio-coal? EU Climate & Energy Package Reduce GHG emissions by 2020 Secure inland energy sources (inland biomass)
Untreated biomass not feasible (i.e. wood pellets) Enabling technology: co-combustion using bio-coal would be
a fast method of cutting CO2 emissions significantly because…
Coal-fire power plants (black dots)
Helsingin Sanomat 28.10.2010
Torrefaction (roasting or incomplete pyrolysis) at the heart of bio-coal production
Torrefaction T = 220-300 C
(inert atmosphere)
Raw Biomass
Torrefied Biomass
Torrefaction gases
Energy 1.0 Mass 1.0
Energy 0.9 Mass 0.7
Energy 0.1 Mass 0.3
Heating value increase = 0.9/0.7 = 1.29 29% increase
The Composition of Woody Biomass Component Chemical Formula Hardwood
mass (%) Softwood mass (%)
Cellulose (C6H10O5)n 43 43
Hemicellulose (C5H8O4)n 34 28
Lignin [(C9H10O3)(CH3O)0.9-1.7]n 23 29
Rate of thermal degradation of the three components of woody biomass
Yang H et al., Characteristics of hemicellulose, cellulose and lignin pyrolysis, Fuel 2007
cellulose
Torrefaction Regime 220-300 C
Volatile matter and fixed carbon content of fuels
10
15
20
25
30
35
0
10
20
30
40
50
60
70
80
90
100
wood sod peat torrefied wood coal wood charcoal
Volatile matter (%)
Fixed carbon (%)
Ash content (%)
Higher heating value (MJ/kg)
com
posi
tion
(%)
higher heating value (MJ/kg)
Pine wood (T = 285 C, t = ?) Bourgeois & Doat (1984)
Typical Polish coal used in Finland
Elemental compositional changes
Composition of beech wood and torrefeed beech wood (T= 220-280C) in van Kravelen diagram
Prins et al. More efficient biomass gasification via torrefaction (2006)
Torrefaction versus carbonisation Heating value, as received = 10 MJ
9 MJ
6 MJ
Extent of pyrolysis
Pelletointiraja (ligniini ei riittää)
g
0
100
200
300
400
500
600
700
800
900
1000
hake torrefioitu puu puuhiili
tuhka
N
O
H
C
H20
Limit of pelletisation (lignin decomposition)
Mass balance – 1 kg of wood
Wood charcoal Torrefied wood Wood chips
Bio-coal production is an optimisation problem
Minimise Maximise
Reaction time Reactor size Process complexity Investment expenses
Raw material particle size Ability to pelletise/briquette Heat transfer Use of torrefaction gas Grindability of product
Bio-coal versus conventional wood pellets
∆E = 10%
Bio-coal
Wood pellets
Torrefaction technology developers in Europe
Kiel J, Torrefaction for upgrading biomass into commodity fuel, 2011.
Are the expectations of bio-coal realistic = based on scientific findings?
Key Property Popular Claim Experimental Data*
Mass/Energy Balance 70/90% 29% heating value increase
61-82/73-92% 7-21% (woody) 7-15% (agro)
Grindability Same as fossil coal 7-36 kWh/t
Improved, grinding energy reduced 68-89% (reactivity?) 52-150 kWh/t
Equilibrium Moisture Content (ECM)
Hydrophobic or 3-6% max. 2.2% (RH 11.3%) 8.7% (RH 83.6%) Measured at 30 degrees C
*Experimental data from peer-reviewed scientific journal publications. Agar D, Wihersaari M. Bio-coal, torrefied lignocellulosic resources – key properties for its use in co-firing with fossil coal – their status, Biomass & Bioenergy (2012).
Conclusions Bio-coal is a fossil coal substitute for coal-fired power plants Potential to cut CO2 emissions significantly from energy sector Torrefaction is a distinct thermal regime in which mostly
hemicellulose undergoes degradation (220-300 C) Bio-coal production is an optimisation problem and is not trivial Three key properties of bio-coal are available from recent peer-
reviewed literature for modelling of economics and GHG-emission balance.
Thank You For your attention
David Agar1 Margareta Wihersaari2
1 Department of Chemistry
2 Department of Biological and Environmental Science
University of Jyväskylä
Nordic Environmental Chemistry Conference, Kakskerta, Turku, 4-7 June, 2012