A Peak Temperature Method (PTM)for the Kinetic Analysis of Biomass

Pyrolysis and Biomass Composition

Teresa Martí-RossellóJun Li

Leo Lue

Department of Chemical and Process EngineeringUniversity of Strathclyde

Glasgow, UK

Peak Temperature Method

Biomass and Biomass Pyrolysis

Scaling-up challenges

Kinetic mechanisms

Transport phenomena

Biomass characerizationGenerizability to biomass compositionand operating conditions

Intraparticle

Reactor scale

Peak Temperature Method

Biomass and Biomass Pyrolysis

Scaling-up challenges

Kinetic mechanisms

Transport phenomena

Biomass characerizationGenerizability to biomass compositionand operating conditions

Intraparticle

Reactor scale

conversion efficiency

Peak Temperature Method

Thermogravimetric Analysis (TA) and Model Fitting

Pyrolysis of a wood sample at 10 K/min (Várhegyi, 2007);blue: TG curve, green: DTG curve

Peak Temperature Method

Thermogravimetric Analysis (TA) and Model Fitting

dα

dt=−k (T ) f (α)

k=A e−E /RT

f (α)=(1−α)

Rate of reaction:

Arrhenius equation:

Reaction model:

Pyrolysis of a wood sample at 10 K/min (Várhegyi, 2007);blue: TG curve, green: DTG curve

α : fraction of reacted biomassE: activation energy kJ mol-1

A: pre-exponential factor s-1

R: universal gas constant kJ K−1mol−1

Peak Temperature Method

PTM rate of reactionComparison of Gauss (dashed line)and Arrhenius curves (solid line)

Peak Temperature Method

PTM rate of reactionComparison of Gauss (dashed line)and Arrhenius curves (solid line)

Gauss parameters:center and

Arrhenius parameters: A and E

σ

Peak Temperature Method

PTM rate of reactionComparison of Gauss (dashed line)and Arrhenius curves (solid line)

Gauss parameters:center and

Arrhenius parameters: A and E

σ

Peak temperature and σT p

Peak Temperature Method

PTM rate of reaction

Observable features of a DTG curveComparison of Gauss (dashed line)and Arrhenius curves (solid line)

Peak Temperature Method

PTM rate of reaction

dα

dT=exp [T p

σ −T p

2

σT−(T p

σ )2

eT p

σ p(T )]σ−1dα

dT=

Aβ

exp [−ERT

−A EβR

p (T )]

p (T )=∫T0

T

k (T )

AdT

Parameters: A, E Parameters: , T p

Observable features of a DTG curveComparison of Gauss (dashed line)and Arrhenius curves (solid line)

2.355 σ=FWHM

: heating rateβH: height

Tp: peak temperature

: width of the peak as in σ

σ

Peak Temperature Method

Kinetic parameters and composition from the DTG features

Experimental data: beech wood pyrolysis at 5 K/min(Gronli, 2002)

Peak Temperature Method

Kinetic parameters and composition from the DTG features

Ei=RT p , i

2

σ iAi=

βσ i

eT p , iσi

Experimental data: beech wood pyrolysis at 5 K/min(Gronli, 2002)

xi: component fraction i : biomass components (cellulose, hemicellulose, lignin)

Peak Temperature Method

Kinetic parameters and composition from the DTG features

x i=H p ,i σ i

βexp [−(T p , iσ i )

2

eT p , i

σ i p(T p , i)]

Ei=RT p , i

2

σ iAi=

βσ i

eT p , iσi

Experimental data: beech wood pyrolysis at 5 K/min(Gronli, 2002)

xi: component fraction i : biomass components (cellulose, hemicellulose, lignin)

Peak Temperature Method

Kinetic parameters and composition from the DTG features

x i=H p ,i σ i

βexp [−(T p , iσ i )

2

eT p , i

σ i p(T p , i)]

Ei=RT p , i

2

σ iAi=

βσ i

eT p , iσi

Width of the peakValue of kinetic parameters

Peak temperatureValue of kinetic parameters

Experimental data: beech wood pyrolysis at 5 K/min(Gronli, 2002)

xi: component fraction

Height*Width of the peakComponent fraction

i : biomass components (cellulose, hemicellulose, lignin)

Peak Temperature Method

Example of multi-component fitting

Experimental data: beech wood pyrolysis at 5 K/min(Gronli, 2002)

Peak Temperature Method

Example of multi-component fitting

dαdT

=−exp [T pσ −

T p2

σT−(T p

σ )2

eT pσ p( y )]σ−1

O.F .=∑j=1

n

[( dα

dT )calc

−( d α

dT )exp ]

2

Deconvolution of a DTG curve

( dα

dT )calc

=∑i=1

3

xidα

dT

Parameters to adjust: T p ,i ,σ i , xi

Peak Temperature Method

Example of multi-component fitting

dαdT

=−exp [T pσ −

T p2

σT−(T p

σ )2

eT pσ p( y )]σ−1

O.F .=∑j=1

n

[( dα

dT )calc

−( d α

dT )exp ]

2

Deconvolution of a DTG curve

( dα

dT )calc

=∑i=1

3

xidα

dT

Parameters to adjust: T p ,i ,σ i , xi

Intial guess and contraints directly from the plot

Peak Temperature Method

Example of multi-component fitting

dαdT

=−exp [T pσ −

T p2

σT−(T p

σ )2

eT pσ p( y )]σ−1

O.F .=∑j=1

n

[( dα

dT )calc

−( d α

dT )exp ]

2

Deconvolution of a DTG curve

( dα

dT )calc

=∑i=1

3

xidα

dT

Parameters to adjust: T p ,i ,σ i , xi

Intial guess and contraints directly from the plot

Sigma can be constrained in terms of temperature

Peak Temperature Method

How peak temperature and width change with heating rate

−lnβ

β∗=

T p∗

σ∗ (T p

∗

T p

−1)+2 lnT p

∗

T p

σ

σ∗=(

T p

T p∗ )

2

DTG curves derived for E= 100 kJ/mol at different heating rates

Lines: activation energy curves.Dots: experimental data from cellulose pyrolysis.

Asterisk indicates features belonging to a reference curve.

Peak Temperature Method

How peak temperature and width change with heating rate

−lnβ

β∗=

T p∗

σ∗ (T p

∗

T p

−1)+2 lnT p

∗

T p

σ

σ∗=(

T p

T p∗ )

2

DTG curves derived for E= 100 kJ/mol at different heating rates

Lines: activation energy curves.Dots: experimental data from cellulose pyrolysis.

Asterisk indicates features belonging to a reference curve.

Peak Temperature Method

How peak temperature and width change with heating rate

−lnβ

β∗=

T p∗

σ∗ (T p

∗

T p

−1)+2 lnT p

∗

T p

σ

σ∗=(

T p

T p∗ )

2

DTG curves derived for E= 100 kJ/mol at different heating rates

Lines: activation energy curves.Dots: experimental data from cellulose pyrolysis.

Asterisk indicates features belonging to a reference curve.

Peak Temperature Method

How peak temperature and width change with heating rate

−lnβ

β∗=

T p∗

σ∗ (T p

∗

T p

−1)+2 lnT p

∗

T p

σ

σ∗=(

T p

T p∗ )

2

DTG curves derived for E= 100 kJ/mol at different heating rates

Lines: activation energy curves.Dots: experimental data from cellulose pyrolysis.

Asterisk indicates features belonging to a reference curve.

Peak Temperature Method

How peak temperature and width change with heating rate

−lnβ

β∗=

T p∗

σ∗ (T p

∗

T p

−1)+2 lnT p

∗

T p

σ

σ∗=(

T p

T p∗ )

2

DTG curves derived for E= 100 kJ/mol at different heating rates

Lines: activation energy curves.Dots: experimental data from cellulose pyrolysis.

Asterisk indicates features belonging to a reference curve.

Peak Temperature Method

How peak temperature and width change with heating rate

−lnβ

β∗=

T p∗

σ∗ (T p

∗

T p

−1)+2 lnT p

∗

T p

σ

σ∗=(

T p

T p∗ )

2

DTG curves derived for E= 100 kJ/mol at different heating rates

Lines: activation energy curves.Dots: experimental data from cellulose pyrolysis.

Asterisk indicates features belonging to a reference curve.

Peak Temperature Method

How peak temperature and width change with heating rate

−lnβ

β∗=

T p∗

σ∗ (T p

∗

T p

−1)+2 lnT p

∗

T p

σ

σ∗=(

T p

T p∗ )

2

DTG curves derived for E= 100 kJ/mol at different heating rates

Lines: Activation energy curves.Dots: experimental data from cellulose pyrolysis.

Asterisk indicates features belonging to a reference curve.

Peak Temperature Method

Example of simultaneous fitting

Experimental data: macadamia nut shell pyrolysis (Xavier, 2016)

Peak Temperature Method

Example of simultaneous fitting

Experimental data: macadamia nut shell pyrolysis (Xavier, 2016)

T p ,i∗ σi

∗ H i∗

Peak Temperature Method

Example of simultaneous fitting

Experimental data: macadamia nut shell pyrolysis (Xavier, 2016)

T p ,i∗ σi

∗ H i∗

O.F .=∑j=1

n

[( dα

dT )calc

−( dα

dT )exp ]

2

( dα

dT )calc

=∑k=1

4

∑i=1

3

xid α

dT

Peak Temperature Method

Conclusions

● Quick method to determine the kinetic parameters and biomass composition based on the shape of the DTG curve.

● Suitable for single or parallel reactions of multi-component mechanisms.

● It can be applied to other processes studied with thermogravimetric analysis.

Peak Temperature Method

Thank you for your attention!