Pilot Scale Testing of Biomass

Torrefaction Technology

Sudhagar ManiAssistant Professor, Biological & Agricultural Engineering

Faculty of Engineering, University of Georgia, Athens, GAFaculty of Engineering, University of Georgia, Athens, GA

Ph: (706) 542Ph: (706) 542--2358; Email: 2358; Email: smani@engr.uga.edusmani@engr.uga.edu

IntroductionIntroductionIssues with biomass feedstock

• Wide range of moisture content (60-15% wb)

• Low bulk density (4 – 8 lbs/ft3)

• Low energy density (4,500-7,500 Btu/lb)

• Uneven particle sizes (no flow)

• Difficult to handle, store and transport

• High transport and storage cost

• Self heating and emission of off gases during storage

IntroductionIntroductionIssues with thermoIssues with thermo--chemical conversion chemical conversion technologiestechnologies

•• Combustion/coCombustion/co--firing:firing:

Difficult to coDifficult to co--fire with coalfire with coal

Low energy densityLow energy density

High energy demand for grinding biomassHigh energy demand for grinding biomass

•• GasificationGasification

Tar formation

Low C/H ratio for liquid fuel production

•• Pyrolysis: Pyrolysis:

BioBio--oil instability & coke formationoil instability & coke formation

Biomass Gasification ProcessBiomass Gasification Process

Three step processThree step process1.1. Drying Drying -- evaporated moisture (<200evaporated moisture (<200ooC)C)

2.2. Pyrolysis Pyrolysis –– release of volatiles and char (~450release of volatiles and char (~450ooC)C)

3.3. Partial oxidation of volatiles and char (~800Partial oxidation of volatiles and char (~800ooC)C)

Complex, partial oxidation reactionComplex, partial oxidation reaction

ФФ –– Equivalence Ratio (ER) =Equivalence Ratio (ER) =

For gasification, For gasification, ΦΦ = 0.25 = 0.25 –– 0.50.5

[ ] tarashCHCOHCOOOCH 422heat

26.04.1 +++++⎯⎯→⎯φ+

( )( ) .Stoic

actual

F/AF/A

Biomass vs. CoalBiomass vs. Coal

Torrefied Biomass

What is Torrefaction? What is Torrefaction? Solid-state thermal hydrolysis of biomass in an inert of biomass in an inert atmosphere (e.g.,Natmosphere (e.g.,N22))Temperature range Temperature range –– 180 to 300180 to 300ooCCHemicelluloseHemicellulose is hydrolyzed is hydrolyzed via release of acetic acid via release of acetic acid and subsequent hydrolysis reaction productsand subsequent hydrolysis reaction productsMoisture reduction, oxygen content reducedMoisture reduction, oxygen content reducedSome extractives volatilized, but 70Some extractives volatilized, but 70--80% solids 80% solids recoveredrecoveredMost familiar example Most familiar example –– roasting coffeeroasting coffee

Green chip Torrefied chip

Mass & Energy Balance

Torrefaction Process

Biomass

Volatile off gases

Torrefiedbiomass

1 m

0.3 m

0.7 m

1 E

~0.2 E

0.9 E

External heat supplyTemp: 180-280oCHeating rate: <50oC/minResidence time: > mins

Condensable:WaterOrganic acids, alcoholsFurans, ketonesTerpenes, phenolsWaxes, tannins, lipids

Non-condensable:H2, CO, CO2, CH4,Toluene, benzene

~0.1 E

Rotary drum reactor Rotary drum reactor –– UGAUGA(indirect heating)(indirect heating)

Capacity = 400 lbs/run

Torrefaction Torrefaction -- Pilot scale testingPilot scale testing

Clean pine chips with less than 1% fines (< ¼inch)

Uniform initial moisture content of 10% (wb)

Temperature conditions – T200, T225, T250, T275 & T300oC

Residence time – 20 & 40 min

Inert gas flow rate was kept constant

Steady state operation

Pilot Unit Pilot Unit –– Torrefied Biomass YieldTorrefied Biomass Yield

Torrefied biomass Torrefied biomass –– Moisture ContentMoisture Content

Torrefied Biomass Torrefied Biomass -- Compositional changesCompositional changes

Biomass  Ash (%) C H N S O/C Ratio

HHV

(MJ/kg)

CT‐PC 0.27 47.9 7.4 0.3 0.14 0.91 18.46

TPC‐200 0.27 50.8 7.3 0.3 0.1 0.82 20.22

TPC‐225 0.27 51.7 7.2 0.3 0.08 0.78 20.83

TPC‐250 0.25 57.8 6.8 0.26 0.08 0.61 23.71

TPC‐275 0.35 67.9 6.5 0.3 0.07 0.38 27.0

TPC­300 0.43 74.3 5.78 0.33 0.05 0.25 30.61

Coal 6.3 77.9 6.7 1.95 2.02 0.16 33.11

Torrefaction of Pine ChipsTorrefaction of Pine Chips

Torrefaction Process

Torrefied Biomass Characteristics

Coal like brown biomass

Higher energy density –

(20 to 23 GJ/tonne)

Hydrophobic in nature due to removal of hydroxyl groups – easy storage

Brittle biomass – Less energy required for grinding

Torrefied biomass Torrefied biomass –– Bulk densityBulk density

Improved Improved PelletingPelleting ProcessProcess

Raw material Drying process Drying

Torrefaction Pelletization Products

Raw material Torrefaction

Grinding PelletizationHigh quality Pellets

Results Results –– Grinding EnergyGrinding Energy

Results: Bulk Flow PropertiesResults: Bulk Flow Properties

Biomass grindsa

SPHT(Dimensionless)

Bulk density (kg m-3)

Particle density

(Mg m-3)

Specific grinding energy

consumption (kW h t-1)

Untreated-PC 0.48 381.0 1.40 239.7TPC-225 oC 0.52 342.4 1.41 107.9TPC-250 oC 0.51 331.8 1.40 70.0TPC-275 oC 0.60 376.1 1.37 54.7TPC-300 oC 0.62 400.2 1.34 35.0

Results Results –– Particle Size DistributionParticle Size Distribution

Results Results –– Torrefied Powder Particle SizeTorrefied Powder Particle Size

Effect of Torrefaction on Pellet Density

225

275275

225

ConclusionsConclusionsTorrefaction is a promising (platform) pretreatment technology for conversion of biomass into fuels & chemicals

During torrefaction, hemi-cellulose was almost hydrolyzed and resulted in higher energy density product with a heating value of more than 23 MJ/kg or 10,000 Btu/lb.

Torrefaction process significantly reduced the specific grinding energy of biomass with up to 10 fold reduction.

Particle size and size distributions were skewed down or narrowed down as torrefaction temp. increases.

Pelleting of torrefied biomass pose some challenges in maintaining the pellet quality

AcknowledgementResearch Team• Dr. Sudhagar Mani, Team Leader • Dr. KC Das, Director, Biorefinery Program• Dr. J. Kastner, Catalyst Expert• Mr. Ryan Adolphson, Engg. Outreach Director• Brian Bibens, M.Sc. Student • Manunya Phanphanich, M.S. Student• Eric Gobert, Research Technician

Financial Support

Traditional Industries Program of Georgia

The Southern Company Services

Biorefinery grant by Department of Energy

Thank you

Biomass Torrefaction Technology

Direct Combustion or co-firing

Gasification & Fast Pyrolysis

Biochemical conversion

Densification

Value added products –Nano-fibers