Torri Faction
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Transcript of Torri Faction
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Energy upgrading of biomass by
Torrefaction Technology.
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Biomass
Biomass is one of the better energy source (Kulkarni and Dalai
2006). In theory it has a potential to contribute over 800 EJ in
comparison to current energy use i.e. 400EJ, without affecting
the worlds food supply (Rosillo-Calle and Woods 2012).
It is considered as the fourth largest energy source after coal,oil and natural gas (Ladanai and Vinterbck 2009), providing 35
per cent of the energy needs of the three- quarters of the
worlds population.
. Biomass energy is readily obtained from wood, twigs, straw,
dung, agriculture residues, and e.t.c. Biomass is burnt either
directly for heat, or to generate electricity, or converted into
other energy products such as biofuels (Kurchania 2012)
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Densified Fuel
The stored energy (Solar energy) of trees can be made
available in the form of densified fuel, which is easily
transported and combusted to produce heat. Densified fuel is available in the form of large fuel logs,
briquettes, and pellets.
Briquettes and pellets are also used commercially and
industrially in central heating systems and gassifiers. Briquettes are made of agro and forest residues such as
Mustard husk, Wheat husk, Cotton husk, Cotton stalk, Saw
dust, ground nut shell, Castor seed husk, Pine needle, coffee
husk e.t.c. Biomass are processed in automatic modern plants where
first biomass is dried up to 10% moisture then cut pulverized
to fine powder then finally pressed in high power press to give
it pellet/briquette shape.
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Torrifaction
Torrefaction of biomass can be described as a mild
form of thermal conversion at temperatures
typically ranging between 200-300 C in the absenceof oxygen.
During torrefaction the biomass properties are
changed to obtain a much better fuel quality(increased heating value). Low calorific components
are transferred to the gas phase.
The torrefaction objective is to improve the energy
properties of biomass within a defined residencetime and temperature less than 300 C.
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Torrefaction Color changes
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Added value of torrefaction
Torrifaction (+ densification) enables energy-efficient (>90%)
upgrading of biomass into commodity solid biofuels withfavorable properties in view of logistics and end use
Favorable properties include high energy density, better water
resistance, slower biodegradation, improved grind ability,
good flow ability, homogenized material properties Therefore, cost savings in handling and transport, advanced
trading schemes(futures) possible, higher co-firing
percentages and enabling technology for gasification-based
biofuels and bio-chemicals production Applicable to a wide range of lignocelluloses biomass
feedstock, even mixed waste streams
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Composition of Biomass
"The polymeric structure of woody and herbaceous biomass
comprises mainly cellulose, hemicellulose and lignin.
Hemicellulose is a complex, branched and heterogeneous polymeric
network, based on pentoses such as xylose and arabinose, hexoses
such as glucose, mannose and galactose, and sugar acids. It has a
lower molecular weight than cellulose and its role is to connect
lignin and cellulose fibers
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Cellulose is a long chain polysaccharide formed by Dglucose units,
linked by 1,4 glycosidic bonds: its structure has crystalline parts
and amorphous ones.
Lignin is an amorphous polymer made by different phenolic
compounds and is the main component of cell walls.
Lignin holds together cellulose and hemicellulose fibers and gives
support, resistance and impermeability to the plant.
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Schematic role of Pretreatment of
Biomass to Biofuel
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How Torrifaction leads to increase heating value
Pretreatment can open up the fiber. The composite structure of thebiomass cell wall is destroyed during torrifaction and the individual
components are released. Pretreatment releases hemicelluloses from the biomass cell walls and
makes them accessible to chemical and biochemical degradation.
The polymer chains is cleaved and C5 sugars, mainly xylose isreleased and further degraded into furfural.
The major role of hemicelluloses in wood is to impart viscoelasticproperties. The degradation of hemicellulose makes wood morebrittle and rigid.
The removal of OH groups (dehydration reactions) results in a more
hydrophobic surface. The brittleness (better grindability) and higher moisture resistance
are important properties that are used as an argument for the use ofpretreated biomass for the production of fuel pellets to substitutecoal in heat and power plants.
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Torrefaction Process
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Characteristics of Biomass
Moisture Content analysis- Moisture content can
be calculated based on weight loss after oven
drying the material for 8 hr at 105 C.
Calorific Value- It can be calculated by Bomb
Calorimeter.
Weight LossIt can be simply calculated by weight
of biomass before and after torrifaction.
Lignocellulose content- It can be eastimated by FTIR
analyzer.
Estimation of Carbohydrate- It can be done by
TGA(Thermogravimetric analyzer ).
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Torrifaction Bioreactor Design
Batch reactor is used for torrifaction. A metal box
with a volume of about 2 L and two opening (5mm
in diameter) for nitrogen inlet and gas outlet . Box
can be installed in prgrammable muffle furnace and
connected to nitrogen cylinder with pressure and
flow regulator, water seal valve and fitting and pipesfor gas inlet, outlet and temperature sensors. A
temperature sensor is used in centre of the metal
reactor and connected to a thermometer andcomputer system controlling the heating of the
oven . The material torrifaction can be done at 220,
240, 260, and 280 C for 2 hr.
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Result
Fibre analysis of coconut shell are degrading during
torrifaction.
Combined torrifaction and briquetting are used to increase
the fuel value of biomass by increasing its energy density
and improving its handling and combustion properties.
GraphsBiomass wt Vs temperature
CV Vs temperature
Strength of pellets/Briquette
Lignin, Hemicellulose, and Cellulose Degrading
Temperature of initial biomass and torrified biomass.
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