Study on gas release during torrefaction of woody biomass and its constituents

(1)

torrefaction of woody biomass

and its constituents

Timothée NOCQUET, Capucine DUPONT, Jean-Michel COMMANDRE,

Céline BOACHON, Yannick SOUDAIS, Sylvain SALVADOR

(2)

~200 µm “spherical” particles required for injection in entrained flow gasifier

The process: from biomass to fuel

Syngas (H₂, CO)

Biomass

Pretreatment Gasification

Post-treatment Synthesis Collection Liquid fuel (Diesel Fischer-Tropsch, methanol/DME)

Drying

Milling

Thermal pretreatment: torrefaction

inert atmosphere 250- 300°C

atmospheric pressure

Enhances grindability

Technically difficult and expensive

(3)

Torrefaction issues

Solid mass loss

Gas and condensables

formation

Process

Fundamental

How to keep mass loss as low

as possible?

How to deal with harmful gas

and condensables?

How does the biomass polymer

decompose?

(4)

Objective and working plan

• Objective: To develop a model able to describe kinetics of

• Approach: sum of decomposition of the biomass main constituents

• First step: Experiments in TGA-FTIR and lab-scale device

1. To check additive law

2. To close mass balance with released gas and condensables

3. To study the gas and condensables formation

Solid mass loss

Gas and condensables

formation

(5)

TGA facility

TGA

(Setaram 92)

Gas analyzer : FTIR

(Perkin-Elmer System 2000)

(230°C)

t (min) T (°C) 20 0 20°C.min-1 10 min T_reaction 60 min 250;280;300 °C Temperature atmospheric Pressure N₂ Atmosphere 30 mL.min-1 Gas flowrate 22,7 % 28,5 % 48,9 % cellulose hemicellulose lignin

Study in chemical

regime

Beech

Lignin (extracted from beech) Cellulose

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Results at 250°C

• Lignin: smooth and continuous mass loss

• Xylan: significant mass loss

• Cellulose: nearly no mass loss

• Additive law: OK

0

20

40

60

80

100

0 1000

2000

3000

4000

Time (s)

M

a

s

l

o

s

(

%

)

beech

lignin

cellulose

xylan

sum

(7)

Results at 280°C

0 20 40 60 80 100 0 1000 2000 3000 4000

Time (s)

M

a

s

l

o

s

(

%

)

beech

lignin

xylan

cellulose

sum

• Lignin: smooth and continuous mass loss

• Xylan: fast and sharp mass loss

• Cellulose: slow but significant mass loss

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Results at 300°C

• Lignin: smooth and continuous mass loss

• Xylan: fast and very sharp mass loss

• Cellulose: slow but the highest mass loss after long duration

• Additive law: not valid

0

20

40

60

80

100

0 1000

2000

3000

4000

Time (s)

M

a

s

l

o

s

(

%

)

cellulose

lignin

xylan

beech

sum

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0 20 40 60 80 100 0 1000 2000 3000 4000 Time (s) M a s s l o s s ( % ) cellulose lignin xylan beech sum

Synthesis of the results

0 20 40 60 80 100 0 1000 2000 3000 4000 Time (s) M a s s l o s s ( % ) beech lignin xylan cellulose sum _T=280°C 0 20 40 60 80 100 0 1000 2000 3000 4000 Time (s) M a s s l o s s ( % ) beech lignin cellulose xylan sum T=250°C T=300°C

Additive law:

• Valid at 250°C and 280°C for typical process

duration

• Not valid at 300°C

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Long duration test at 300°C

• Additive law valid for very long durations (3h)

OK for prediction of “final” solid yield

Confirmation: gap due to

slower decomposition of cellulose in beech

• Interaction between constituents?

• Structure of cellulose?

0

20

40

60

80

100

0 2500

5000

7500

10000

Time (s)

M

a

s

l

o

s

(

%

)

cellulose

lignin

xylan

beech

sum

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The lab-scale device ALIGATOR

beech Biomass 280°C Temperature 1.5 g Sample mass atmospheric Pressure N₂ Atmosphere 30 mL.min-1 Gas flowrate

t

T (°C)

20 0

5°C.min

-1 10 min

280 1h

Study in chemical

regime

N2 M N2 26mm GC analyzer

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Global mass balance

• Main products: H

₂

O, CO

₂

, acetic acid

• Significant yields of other species

H2O CO2 CO Acetic acid Formic acid Formaldehyde Furfural Methanol solid

Torrefaction of beech

(280°C, 1h)

0,00 0,02 0,04 0,06 0,08 m a s s p ro d u c e d (m g /m g r a w b io m a s s ) H2O CO 2 CO Ace tic a cid Form ic a cid Form alde hyde Fur fura l Met hano l 0.08 0.06 0.04 0.02 0 0,00 0,02 0,04 0,06 0,08 m a s s p ro d u c e d (m g /m g r a w b io m a s s ) H2O CO 2 CO Ace tic a cid Form ic a cid Form alde hyde Fur fura l Met hano l 0.08 0.06 0.04 0.02 0

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TGA-FTIR device

TGA

(Setaram 92)

Gas analyzer : FTIR

(Perkin-Elmer System 2000)

(230°C)

t (min) T (°C) 20 0 20 20 20

20°°°°C.minC.minC.minC.min----1111

10 min

T T T

T_reaction_reaction_reaction_reaction 60 min60 min60 min60 min

T:\300-Projets_Transverses\300.118-PEGASE\IRTF\Timothé\spectres extraits\Hêtre 300°C\Spectrum at 919. 5 Secs (Hêtre 30-300°C n°2 - diff - super.spp).0 2010/8/11 1000 1500 2000 2500 3000 3500 4000 Wavenumber 0 .0 0 0 .0 2 0 .0 4 0 .0 6 0 .0 8 0 .1 0 0 .1 2 0 .1 4 A b s Wave number (cm-1₎ A b so rb a n ce ( -) Beech

Lignin (extracted from beech) Cellulose

FTIR Spectrum

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Beech: Gas species mean value vs temperature

Increase of temperature

Increase of each gas yield

0 0,002 0,004 0,006 0,008 A ( -) 250°C 280°C 300°C methanol 0 0,01 0,02 0,03 0,04 0,05 0,06 A ( -) 250°C 280°C 300°C CO 0 0,4 0,8 1,2 1,6 A ( -) 250°C 280°C 300°C CO2 0 0,025 0,05 0,075 0,1 0,125 0,15 A ( -) 250°C 280°C 300°C acetic acid 0 0,002 0,004 0,006 A ( -) 250°C 280°C 300°C furfural 0 0,004 0,008 0,012 A ( -) 250°C 280°C 300°C formic acid 0 0,001 0,002 0,003 0,004 A ( -) 250°C 280°C 300°C formaldehyde 0 0,0025 0,005 0,0075 0,01 0,0125 A ( -) 250°C 280°C 300°C H2O

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Beech: CO

₂

and formic acid vs time

• Increase of temperature

Increase of each gas yield

• For both products: peak of concentration at the same time for all temperatures

• Long duration time:

– CO

₂

still released

– No more formation of formic acid

formic acid 0 0,01 0,02 0,03 0,04 0,05 0 1000 2000

Time (s)

A

(

-)

beech 250°C beech 280°C beech 300°C CO2 0 1 2 3 4 5 0 1000 2000

Time (s)

A

(

-)

beech 250°C beech 280°C beech 300°C Formic acid CO₂

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Beech, lignin and cellulose: comparison at 300°C

CO

₂

and CO produced both

by lignin and cellulose

0 0,01 0,02 0,03 0,04 0,05 0,06 A ( -) Bee ch Lign in Cel lulo se CO 0 0,4 0,8 1,2 1,6 A ( -) Bee ch Lign in Cel lulo se CO2 0 0,001 0,002 0,003 0,004 A ( -) Bee ch Lign in Cel lulo se formaldehyde 0 0,002 0,004 0,006 0,008 A ( -) Bee ch Lign in Cel lulo se methanol 0 0,004 0,008 0,012 A ( -) Bee ch Lign in Cel lulo se formic acid 0 0,025 0,05 0,075 0,1 0,125 0,15 A ( -) Bee ch Lign in Cel lulo se acetic acid