Pyrolysis of Biomass to Produce Bio-oil, Biochar and Combustible Gas

John EdwardsSchool of Engineering and Advanced Technology

Massey University

Energy Postgraduate Conference 2008

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What is Pyrolysis?

“Pyrolysis is thermal cracking in the absence of oxygen.” Cedric Briens

“Pyrolysis is the thermal decomposition of organic material at elevated temperatures, in the absence of gases such as air or oxygen.” Greenpeace

Heat introduced, O2 excluded

An endothermic reaction

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What is Biomass?

• “Biomass is all non-fossil organic materials that have an intrinsic chemical energy content.” Ralph Sims

• Distillers’ Grains, Coffee Grounds, Grape Seeds and Skins, Sugarcane Bagasse, Sawdust and Tobacco Leaves.

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What Pyrolysis of Biomass Is Not

1. New

2. The Holy Grail of Renewable Energy.

Pyrolysis dates back to at least ancient Egyptian times.

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Pyrolysis of Biomass

HEAT

Combusti

ble Gas

BiocharBiomass

Bio-OilVapour

Condensation

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The Organic Chemistry

3C6H10O5 HEAT

Pyrolytic reaction using cellulose:

Liquid Bio-Oil

Combustible Gas

Biochar

C6H8O +8H2O +CH4+2CO+2CO2+ 7C

Water of Pyrolysis

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Some Advantages of Pyrolysis of Biomass

• Carbon neutrality• Utilises otherwise waste biomass• Potential to be self-sustaining energy-wise• Increases bulk and energy density of

biomass• Source of valuable chemicals• Biomass source can be decoupled from the

energy utilisation

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Fast Pyrolysis of BiomassObjective to maximize liquid yield

The three main variables in the pyrolysis process are:

• Reaction temperature.• Biomass heating rate.• Vapour residence time.

Moderate temperatures ≈ 500°C and short vapourresidence time are required to maximize liquid yield.

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Fast Pyrolysis of BiomassProduct yields (dry feed basis) for pyrolysis of wood.

A.V.Bridgwater

Mode Conditions Liquid Char Gas

Fast pyrolysisModerate temperature,

short residence time 75% 12% 13%

Slow PyrolysisLow temperature, very long residence time

30% 35% 35%

GasificationHigh temperature, long residence time.

5% 10% 85%

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Bubbling fluidised bed method

A.V. Bridgwater et al

Biomass feed

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0

10

20

30

40

50

60

250 300 350 400 450 500 550 600 650

Reaction Temperature °C

Yie

lds

We

igh

t%

Yields vs Reaction Temperature for Grape Seeds and Skins 5 seconds residence time

Gas

Liquid

Char

Maximum liquid yield

0

5

10

15

20

25

30

35

40

Yie

ld %

2.5 secs 5 secs 20 secs

Vapour Residence Time

Liquid

Gas

Solid

Grape Skin Pyrolysis Yields vs Residence Time Reaction Temperature 500°C

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Heat of pyrolysis vs heating value of product gas for grape skins

0.0

0.5

1.0

1.5

2.0

2.5

3.0

250 300 350 400 450 500 550 600 650

Reaction Temperature °C

Heat

kJ/g

Gra

pe S

kin

Feed

Heat of pyrolysis

Heating value of product gas

Self sustaining

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Production of Ethanol from Corn

I nstitute for Chemicals and Fuels from Alternative ResourcesInstitute for Chemicals and Fuels from Alternative Resources

Mike Jacobson

1litre of ethanol = 800grams of distillers’ grains

Distillers’ grain has a heating value of 6 to 20 MJ/kgBulk density ≈ 400kg m-3

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Options for Distillers’ Grains

PyrolysisDistillers’ Grains

Sequestration of Biochar

Heat of Pyrolysis provided by combustible gas

CO2

Ethanol Production

Pure Ethanol

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Bulk and Energy Densities

Density Energy Density

Kg m-3 MJ kg-1 GJ m-3

Green whole wood chips 350 9.6 3.4

Pyrolysis Bio-Oil 1200 18.0 21.6

Ratio 1:3.4 1:1.9 1:6.4

Comparisons of Bulk and Energy Densities for Biomass and Bio-Oil

Phillip C. Badger, Peter Fransham

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Mobile Pyrolysis Unit

400 kg/h Demo Unit

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Comparison of Bio-oil with Heavy Fuel oilPhysical property Pyrolysis Bio-oil Heavy Fuel Oil

Water, wt% 15-30 0.1

Specific Gravity 1.2 0.94

Heating Value (MJ/kg) 13-19 40

Solids, wt% 0.2-0.1 0.2-1.0

Viscosity, (at 50°C) (cP) 40-100 180

pH 2.5

Oxygen, wt% 35-60 0.6-1.0

Dinesh Mohan et al

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The Challenges For upgrading of bio-oil to transport fuels

• Low volatility

• Low heating value.

• High viscosity

• Corrosiveness

• Coking

Every biomass is different!

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Alternatives to upgrading

• Gasification of bio-oil to syngas

• Combination of bio-oil with diesel

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Opportunities

• New Zealand has a plethora of biomass from forest and agricultural waste, for example

• Bio-oil and biochar co-production can be economically, environmentally and climate friendly

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ConclusionsPyrolysis of Biomass

• Rapidly developing technology

• Added Value Economy

• Carbon negative solution Environment

• Increased bulk and energy density EconomyEnvironment

• More work needs to be done for upgrading

to transport fuels

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Distillers’ Grains Biomass

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Distillers’ Grain Biochar

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Distillers’ Grain Bio-oil

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Acknowledgements

• Massey University

• Ann-Marie Jackson

• Professor Don Cleland

• Professor Clive Davies

• The University of Western Ontario• Professor Franco Berruti• Professor Cedric Briens• Dr. Lorenzo Ferrante• Mohammad Latifi• Ran Xu• Rohan Bedmutha• Mike Jacobson

Queen Elizabeth II Technicians’ Study Awards

Shirley and Lukey

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Thank you

Questions?

John Edwards

School of Engineering and Advanced Technology

Massey University

Palmerston North

email: J.Edwards@massey.ac.nz