A Peak Temperature Method (PTM) for the Kinetic Analysis ... · dt =−k(T)f (α) k=Ae−E/RT f...
Transcript of A Peak Temperature Method (PTM) for the Kinetic Analysis ... · dt =−k(T)f (α) k=Ae−E/RT f...
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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
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Peak Temperature Method
Biomass and Biomass Pyrolysis
Scaling-up challenges
Kinetic mechanisms
Transport phenomena
Biomass characerizationGenerizability to biomass compositionand operating conditions
Intraparticle
Reactor scale
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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
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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
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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
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Peak Temperature Method
PTM rate of reactionComparison of Gauss (dashed line)and Arrhenius curves (solid line)
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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
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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
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Peak Temperature Method
PTM rate of reaction
Observable features of a DTG curveComparison of Gauss (dashed line)and Arrhenius curves (solid line)
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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
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Peak Temperature Method
Kinetic parameters and composition from the DTG features
Experimental data: beech wood pyrolysis at 5 K/min(Gronli, 2002)
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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)
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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)
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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)
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Peak Temperature Method
Example of multi-component fitting
Experimental data: beech wood pyrolysis at 5 K/min(Gronli, 2002)
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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
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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
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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
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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.
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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.
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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.
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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.
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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.
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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.
![Page 25: A Peak Temperature Method (PTM) for the Kinetic Analysis ... · dt =−k(T)f (α) k=Ae−E/RT f (α)=(1−α) Rate of reaction: Arrhenius equation: Reaction model: Pyrolysis of a](https://reader034.fdocuments.us/reader034/viewer/2022052101/603b50c2ad9d4359012c9b50/html5/thumbnails/25.jpg)
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.
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Peak Temperature Method
Example of simultaneous fitting
Experimental data: macadamia nut shell pyrolysis (Xavier, 2016)
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Peak Temperature Method
Example of simultaneous fitting
Experimental data: macadamia nut shell pyrolysis (Xavier, 2016)
T p ,i∗ σi
∗ H i∗
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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
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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.
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Peak Temperature Method
Thank you for your attention!