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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!
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