Torri Faction

8/13/2019 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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Documents

Torri Faction