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Graz, 23.01.2020

Reliability of TGA data for

characterization of alternative

biomass feedstocks

Stefan Retschitzegger, Norbert Kienzl, Andrés Anca-Couce, Christos Tsekos, Scott Banks, Tzouliana Kraia, Francesco Zimbardi, Axel Funke, Paula Marques

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Content

• Introduction

• Methodology

• Results

– TGA test

– Data evaluation

• Summary

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Introduction – BRISK 2

• 15 European partners

• Development of methods

and research infrastructure

– thermochemical and

biochemical conversion

– enhanced measurement

techniques

– new biorefining approaches

– simulation tools

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Introduction – TGA round robin

Potential for future

• Biomass can play a more relevant role in the production of

power, liquid fuels or chemicals

Thermo-chemical processes using ligno-cellulosic biomass

Biomass characterisation

• mass loss behaviour is commonly determined by TGA

• TGA results in literature have strong deviations

– mainly attributed to biomass inhomogeneity

– impact of institution, operator, equipment, … not known

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Introduction – TGA round robin

0

50

100

150

200

250

300

Cellulose Hemicellulose Lignin

Ac

tiva

tio

n E

ne

rgy (

kJ/m

ol)

[16] Quan et al. 2016 (FWO)

[17] Yeo et al. 2019 (Friedman)

[17] Yeo et al. 2019 (Combined kinetic method)

[18] Kim et al. 2016 (n.a.)

[19] Kim et al. 2017 (OFW)

[20] Kok et al. 2017 (KAS)

[20] Kok et al. 2017 (OFW)

[21] Wang et al. 2017 (OFW)

[22] Sungsuk et al. 2016 (1 step decomposition)

[23] Abdelouahed et al. 2017 (Kissinger)

[23] Abdelouahed et al. 2017 (KAS)

[23] Abdelouahed et al. 2017 (Friedman)

[24] Adenson et al. 2018 (1 step decomposition)

[25] Burra et al. 2019 (2 steps model - step 1)

[26] Fan et al. 2017 (1 step decompostion)

[27] Wang et al. 2018 (First order reaction)

[28] Wang et al. 2016 (Avrami-Erofeev model)

• Variation of data in literature

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Scope – TGA round robin

• Investigate the

reproducibility of TGA

biomass pyrolysis

• 7 European partners

• Eliminate influence of

biomass inhomogeneity via

homogenized feedstock

• Eliminate error from data

evaluation all results

evaluated by one partner

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Methodology – TGA round robin

• Fuels

– Avicel® PH-101 cellulose

– Beech wood

• low initial mass sample

(ideally of 3 mg)

• Pyrolysis from 150 – 500 °C

• Detailed handling protocols

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Methodology – TGA

• Scheme of TGA

0

2

4

6

8

10

12

14

16

150 200 250 300 350 400 450 500

Temperature [°C]

-dm

/dt

[%/m

in]

0

20

40

60

80

100

Mass [

%]

DTG [%/min]

TG [%]

m500°C

Tonset

Tsh

Tpeak

Toffset

(dm/dt)peak

(dm/dt)sh

• m vs. t and dm/dt vs. t

Source: Quelle: Netzsch-Gerätebau GmbH

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Cellulose pyrolysis –

Conversion α

• shape of the curves almost similar for all cases

• max reaction rate at 328.3 ± 9.2 °C; literature1: 327 ± 5 °C

1 Gronli et al. A round-robin study of cellulose pyrolysis kinetics by thermogravimetry. 1999

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Cellulose pyrolysis –

Modelling (single reaction)

• averaged error in the fitting: 2.9 ± 1.2 % low error

• Error: mainly at temperatures around 350°C due to the tail of

the DTG curve especially pronounced in case #3

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Beech wood pyrolysis

Conversion α

• Beech wood: 1 peak, 1 shoulder Cellulose: one peak only

results from hemicellulose

• obtained deviations between participants are of a similar order as for cellulose

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Beech wood pyrolysis

Comparison of activation energies

• Activation energy Ea calculated by Isoconversional KAS method

• Standard deviations 20 – 25 kJ/mol - within acceptable range

• One case significantly lower

100

120

140

160

180

200

220

240

0 0.2 0.4 0.6 0.8 1

Ea (

kJ/m

ol)

Conversion (-)

No outliers#1 #2 #3 #4

#5 #6 #7

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Beech wood pyrolysis – modelling

• Beech is modelled simulating 3 components:

– hemi-cellulose, cellulose, lignin

• Fluctuations in signals of some partners (e.g. #7)

cellulose hemi-cellulose lignin

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Summary and Outlook

• TGA is widely used, but mass loss kinetics for biomass

pyrolysis is still a non resolved topic.

• Round robin of TGA pyrolysis experiments with 7 partners

– Pure Cellulose: satisfactory reproduction of pyrolysis

experiments from literature (Gronli et al. 1999)

– Beech Wood: deviations with different devices are of a similar

order as for cellulose

– BUT certain deviations are obtained in DTG curves for all cases

– Detailed documentation of protocols necessary

– Evaluation of protocols for elucidation of remaining variation

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Acknowledgment

• Funding received from European Union’s Horizon 2020

Research and Innovation Programme under grant agreement

number 731101 (BRISK II) is gratefully acknowledged.

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Norbert Kienzl

norbert.kienzl@best-research.eu

www.best-research.eu

Thank you for your attention!