Stu tudy of f self lf-heating phenomenon of f torrefied wood in - - PowerPoint PPT Presentation

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

Stu tudy of f self lf-heating phenomenon of f torrefied wood in in contact wit ith

• xygen
• PhD. th

thes esis is started

• ct
• ctobre 1st

st 2014

2014

Jean-louis Dirion Patricia Arlabosse Sylvain Salvador Olivier Bonnefoy Alexandre Govin

Brieuc Evangelista

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

1.

• 1. Introduction 2.
• 2. Bib

ibliography 3.

• 3. Exp

Experimental al res esults 4.

• 4. Conclusi

sion & pe persp spectives

• a. Social cont

ntext

• a. Prot
• toc
• col
• l pres

esent entation

• n
• b. Sciien

entific cont ntext

• b. Calor
• rimet

etry, TGA GA & DSC

• How to

to ach achie ieve th the energetic ic tr transi sition ?

• From fossil to renewable energy sources

2

Increase biomasses energetic valorization

Biochemical route Th Ther ermochemic ical rou

• ute

(Hydrolysis, fermentation, distillation...) (Combustion, co-combustion, gazeification, pyrolysis...)

Wea eak fu fuel el properties es

• High water content
• Low energy density
• Poor grindability
• Poor decay resistancy

Hig Higher gr grade fu fuel el

• Lower water content
• Higher energy density
• Better grindability
• Better decay resistancy

Pretreatments

• Grinding
• AFEX
• Torr
• rrefactio

ion

• …

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

1.

• 1. Introduction 2.
• 2. Bib

ibliography 3.

• 3. Exp

Experimental al res esults 4.

• 4. Conclusi

sion & pe persp spectives

• a. Social cont

ntext

• a. Prot
• toc
• col
• l pres

esent entation

• n
• b. Sciien

entific cont ntext

• b. Calor
• rimet

etry, TGA GA & DSC

• Development of
• f large scale torrefaction market expected to

to the decade to to come (Th Thrän et et al

• al. 2016

2016)

• Safety issue
• Science beyond self-heating phenomenon:

3

He Heat gen eneration

Exothermic reaction(s)

He Heat diss dissipation

Highly size dependent

Self Self-heating Self Self-ig ignit ition Not

• thing

Thermal runaway

Temperature Time

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

1.

• 1. Introduction 2.
• 2. Bib

ibliography 3.

• 3. Exp

Experimental al res esults 4.

• 4. Conclusi

sion & pe persp spectives

• a. Social cont

ntext

• a. Prot
• toc
• col
• l pres

esent entation

• n
• b. Sciien

entific cont ntext

• b. Calor
• rimet

etry, TGA GA & DSC

• Ind

Industria ial sa safety ty iss ssue

• The larger the system the more sensitive to self-heating and self-

ignition (Franck-Kamenetskii 1969)

• Phenomenon observed with torrefied wood (Verhoeff et al. 2012)

4

(Esbjerg, Danemark, 1998) 70 000 tonnes de pellets de bois

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

1.

• 1. Introduction 2.
• 2. Bib

ibliography 3.

• 3. Exp

Experimental al res esults 4.

• 4. Conclusi

sion & pe persp spectives

• a. Social cont

ntext

• a. Prot
• toc
• col
• l pres

esent entation

• n
• b. Sciien

entific cont ntext

• b. Calor
• rimet

etry, TGA GA & DSC

• Th

Thesis is sci scientific ap approach

• The larger the system

 Industrial issues  Understanding and control of physicochemical phenomenon

involved

• Multi-scale approach

5

mg Powder Reaction only g Particle Diffusion + reaction kg Fixed bed particules Advection + diffusion + reaction

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

1.

• 1. Introduction 2.
• 2. Bib

ibliography 3.

• 3. Exp

Experimental al res esults 4.

• 4. Conclusi

sion & pe persp spectives

• a. Social cont

ntext

• a. Prot
• toc
• col
• l pres

esent entation

• n
• b. Sciien

entific cont ntext

• b. Calor
• rimet

etry, TGA GA & DSC

• Th

Thesis is sci scientific ap approach

• The larger the system

 Industrial issues  Understanding and control of physicochemical phenomenon

involved

• Multi-scale approach

6

mg Powder Reaction only g Particle Diffusion + reaction kg Fixed bed particules Advection + diffusion + reaction

Today’s program: how to desc scrib ibe th the reaction kin kinetic between oxygen an and tor

• rrefied wood?

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

1.

• 1. Introduction 2.
• 2. Bib

ibliography 3.

• 3. Exp

Experimental al res esults 4.

• 4. Conclusi

sion & pe persp spectives

• a. Social cont

ntext

• a. Prot
• toc
• col
• l pres

esent entation

• n
• b. Sciien

entific cont ntext

• b. Calor
• rimet

etry, TGA GA & DSC

1.

• 1. In

Introduction

• a. Social context
• b. Scientific context

2.

• 2. Bib

iblio liographic resu sults

3.

• 3. Experimental par

arts

• a. Protocol presentation
• b. Calorimetry, TGA and DSC results

4.

• 4. Con
• nclusion & perspectives

7

Presentation overv rview

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

1.

• 1. Introduction 2.
• 2. Bib

ibliography 3.

• 3. Exp

Experimental al res esults 4.

• 4. Conclusi

sion & pe persp spectives

• a. Social cont

ntext

• a. Prot
• toc
• col
• l pres

esent entation

• n
• b. Sciien

entific cont ntext

• b. Calor
• rimet

etry, TGA GA & DSC

• What doe
• es th

the lit literature teach us us ?

• Coal industry: long time issue

Reaction called « low – temperature oxidation » Related to mining and handling hazards

• General findings

8

Chemisorption of O2 creation of surface oxides

(Vastola et al. 1964)

Thermal decomposition

• f surface oxides

(Marinov 1977)

CO and CO2 are the main gaseous product

(Gethner 1985)

Complex reaction mecanism simplifies

(Wang et al. 2003)

Reactive sites: carbon atoms limiting reagent (Teng & Hsieh 1999)

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

1.

• 1. Introduction 2.
• 2. Bib

ibliography 3.

• 3. Exp

Experimental al res esults 4.

• 4. Conclusi

sion & pe persp spectives

• a. Social cont

ntext

• a. Prot
• toc
• col
• l pres

esent entation

• n
• b. Sciien

entific cont ntext

• b. Calor
• rimet

etry, TGA GA & DSC

• Clas

lassical protocol*

• Raw material: beech wood powder (<80 µm)
• Two severities of torrefaction

Mild (240°C, 20 min), yield 86 +/- 1% Severe (290°C, 3 min), yield 68 +/- 2%

• Oxidative step temperature range [°C] & experimental devices

9

40 70 100 140 150 225

Calorimeter TGA* TGA* DSC*

Inert atmosphere: nitrogen Temperature Torrefaction Oxidative step Oxidative atmosphere: O2 + N2 Drying Time 0

𝑍𝑗𝑓𝑚𝑒 = 𝑛𝑢𝑝𝑠𝑠𝑓𝑔𝑗𝑓𝑒 𝑛𝑒𝑠𝑧

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

1.

• 1. Introduction 2.
• 2. Bib

ibliography 3.

• 3. Exp

Experimental al res esults 4.

• 4. Conclusi

sion & pe persp spectives

• a. Social cont

ntext

• a. Prot
• toc
• col
• l pres

esent entation

• n
• b. Sciien

entific cont ntext

• b. Calor
• rimet

etry, TGA GA & DSC

• Cal

alorim imetric ic resu esult lts, [40 40 ; 70 70] °C

• Specificity of the protocol

 Torrefaction ex situ  Heat flow stabilized 10 hours under nitrogen flush then 12 hours under air flush

Maximum heat flow followed by an exponential decay

• Highest number of free reactive site at time 0 and consumption

Increase with torrefaction severity

• Higher propensity to self-heat and self-ignite

10 10

Severely torrefied Mildly torrefied

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

1.

• 1. Introduction 2.
• 2. Bib

ibliography 3.

• 3. Exp

Experimental al res esults 4.

• 4. Conclusi

sion & pe persp spectives

• a. Social cont

ntext

• a. Prot
• toc
• col
• l pres

esent entation

• n
• b. Sciien

entific cont ntext

• b. Calor
• rimet

etry, TGA GA & DSC

• Why doe
• es th

the heat flo flow not

• t go

go bac ack to to zero ?

• Diffusion ?

 Effective diffusion coefficient:

• Experimental artefact ?
• Equilibrium between pyrolysis reactions and oxygen adsorption

(Kaji et al. 1987)

• Small

ll heat of

• f physis

isorption in involv lved

11 11

𝐸𝑃2𝑓𝑔𝑔~ 𝑀𝑑² 𝜐𝑑 = (5 µ𝑛)2 10ℎ = 10−16 𝑛2. 𝑡−1

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

1.

• 1. Introduction 2.
• 2. Bib

ibliography 3.

• 3. Exp

Experimental al res esults 4.

• 4. Conclusi

sion & pe persp spectives

• a. Social cont

ntext

• a. Prot
• toc
• col
• l pres

esent entation

• n
• b. Sciien

entific cont ntext

• b. Calor
• rimet

etry, TGA GA & DSC

• TGA resu

sults, [100 100 ; 140 140] °C

Small amount of oxygen adsorbed on the wood surface Increase with severity of torrefaction

• Higher number of free reactive sites

→ Increase of carbon content with torrefaction severity

12 12

Severely torrefied Mildly torrefied

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

1.

• 1. Introduction 2.
• 2. Bib

ibliography 3.

• 3. Exp

Experimental al res esults 4.

• 4. Conclusi

sion & pe persp spectives

• a. Social cont

ntext

• a. Prot
• toc
• col
• l pres

esent entation

• n
• b. Sciien

entific cont ntext

• b. Calor
• rimet

etry, TGA GA & DSC

• TGA resu

sults, [150 150 ; 225 225] °C

At temperature ≈ 175°C pyrolysis > adsorption

• Above 200°C, non-negligeable mass loss involved

Thermal degradation decreases with torrefaction severity

• Wood volatile matters decrease with torrefaction severity

13 13

Severely torrefied Mildly torrefied Time [h]

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

1.

• 1. Introduction 2.
• 2. Bib

ibliography 3.

• 3. Exp

Experimental al res esults 4.

• 4. Conclusi

sion & pe persp spectives

• a. Social cont

ntext

• a. Prot
• toc
• col
• l pres

esent entation

• n
• b. Sciien

entific cont ntext

• b. Calor
• rimet

etry, TGA GA & DSC

• TGA resu

sults: in influ fluence of

• f oxygen con
• ncentration

Thermal degradation enhanced by oxygen

• Pyrolysis reactions of surface oxides: thermal decomposition
• Pyrolysis reactions of torrefied wood: thermal cracking

14 14

Severely torrefied Mildly torrefied

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

1.

• 1. Introduction 2.
• 2. Bib

ibliography 3.

• 3. Exp

Experimental al res esults 4.

• 4. Conclusi

sion & pe persp spectives

• a. Social cont

ntext

• a. Prot
• toc
• col
• l pres

esent entation

• n
• b. Sciien

entific cont ntext

• b. Calor
• rimet

etry, TGA GA & DSC

• DS

DSC resu sults, [150 150 ; 225 225] °C

Exothermic overall heat flow but thermal degradation (TGA)

• Pyrolysis reactions govern the mass
• Adsorption reactions govern the heat flow

The heat flow goes back to zero

• Endothermic pyrolysis reactions enhanced

15 15

Severely torrefied Mildly torrefied Specific heat flow [mW/mg] Specific heat flow [mW/mg]

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

1.

• 1. Introduction 2.
• 2. Bib

ibliography 3.

• 3. Exp

Experimental al res esults 4.

• 4. Conclusi

sion & pe persp spectives

• a. Social cont

ntext

• a. Prot
• toc
• col
• l pres

esent entation

• n
• b. Sciien

entific cont ntext

• b. Calor
• rimet

etry, TGA GA & DSC

• Co

Conclu lusio ion

• How to describe the low-temperature oxidation of torrefied

wood ?

Similarities between low-temperature oxidation of torrefied

wood and coal:

• Chimisorption describes well the heat involved
• Pyrolysis reactions of surface oxides

Difference

• Pyrolysis reactions of torrefied wood at lower temperature

Reactions

16 16

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

1.

• 1. Introduction 2.
• 2. Bib

ibliography 3.

• 3. Exp

Experimental al res esults 4.

• 4. Conclusi

sion & pe persp spectives

• a. Social cont

ntext

• a. Prot
• toc
• col
• l pres

esent entation

• n
• b. Sciien

entific cont ntext

• b. Calor
• rimet

etry, TGA GA & DSC 17 17

40 70 100 140 150 225

• On

On goin

• ing work: kin

kinetic mod

• dellin

ling

Temperature range [°C]

• 1. Modelling adsorption at very low termperature

Based on calorimetric results Pyrolysis reactions neglected

• 2. Modelling thermal cracking

Based on TGA and DSC results without oxygen

• 3. Modelling thermal decomposition

Based on TGA and DSC results with oxygen

• 4. Verify the reaction kinetics

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

Th Thank you for r your attentio ion Questio ions are welc lcome

18 18

Institut Mines-Télécom

13 july 2017

Institut Mines-Télécom

1.

• 1. Intr

troducti tion

• n 2.
• 2. Biblio

liography y 3.

• 3. Ex

Experim imental l result lts 4.

• 4. Con
• nclu

lusio ion & & pe perspectiv ives

• a. Social co

cont ntext a. Calor

• rimet

etry b.

• b. Sci

ciien entific c co cont ntex ext b.

• b. TGA

GA c.

• c. DSC
• References:

19 19

• Ahmed, S., Back, M.H. & Roscoe, J.M., 1987. A Kinetic Model for the Low Temperature Oxidation of Carbon : I. Combustion

and Flame, 70, pp.1–16.

• Campbell, P.A. & Mitchell, R.E., 2008. The impact of the distributions of surface oxides and their migration on characterization
• f the heterogeneous carbon – oxygen reaction. Combustion and Flame, 154, pp.47–66.
• Franck-Kamenetskii, D.., 1969. Diffusion and heat transfer in chemical kinetics (2nd edition). Plenum Press.
• Gethner, J.S., 1985. Thermal and oxidation chemisrty of coal at low temperature. Fuel, 64, pp.1443–1446.
• Haynes, B.S. & Newbury, T.G., 2000. Oxyreactivity of Carbon Surface Oxides. Combustion of Solid Fuels, 28, pp.2197–2203.
• Kaji, R., Hishinuma, Y. & Nakamura, Y., 1987. Low temperature oxidation of coals-a calorimetric study. Fuel, 66, pp.154–157.
• Marinov, V.N., 1977. Self-ignition and mechanisms of interaction of coal with oxygen at low temperatures . 1 . Changes in the

composition of coal heated at constant rate to 250 ° C in air. Fuel, 56, pp.153–157.

• Teng, H. & Hsieh, C.-T., 1999. Activation Energy for Oxygen Chemisorption on Carbon at Low Temperatures. Industrial &

Engineering Chemistry Research, 38, pp.292–297.

• Thrän, D. et al., 2016. Moving torrefaction towards market introduction – Technical improvements and economic-

environmental assessment along the overall torrefaction supply chain through the SECTOR project. Biomass and Bioenergy, pp.1–17. Available at: http://linkinghub.elsevier.com/retrieve/pii/S0961953416300538.

• Vastola, F.J., Hart, P.J. & Walker, P.L., 1964. A study of carbon-oxygen surface complexes using O18 as a tracer. Carbon, 2,

pp.65–71.

• Verhoeff, F., Kiel, J. & Zwart, R., 2012. ECN’s moving bed torrefaction technology in light of desired product qualities. , p.27.
• Wang, H., Dlugogorski, B.Z. & Kennedy, E.M., 2003. Coal oxidation at low temperatures: Oxygen consumption, oxidation

products, reaction mechanism and kinetic modelling. Progress in Energy and Combustion Science, 29(6), pp.487–513.