Updating CRE: Applicationsweb.abo.fi/fak/tkf/tek/Files/cacre2014/MicroKin-PC-5.pdf · 2014. 5....
Transcript of Updating CRE: Applicationsweb.abo.fi/fak/tkf/tek/Files/cacre2014/MicroKin-PC-5.pdf · 2014. 5....
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Updating CRE: Applications
Prof. Paolo Canu
University of Padova - Italy
Computer-Aided Chemical Reaction Engineering Course
Graduate School in Chemical Engineering (GSCE) Åbo Akademi - POKE Researchers network
May 2014
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Contents 3. Kinetics
3.1 Power law 3.2 LHHW
3.3 Detailed 4. Kinetic studies
5. Applications
A.1 Tuning of Sh(z) in a monolith (2.3 + 3.1) A.2 CH4 combustion on Pt in a monolith (2.3 + 3.1) A.3 CO combustion in an annular reactor (2.2 + 3.3) A.4 CH4 partial oxidation on Rh foam (2.2 + 3.3) A.5 CH4 partial oxidation on Pt monolith (2.3 + 3.3) A.6 Herogeneous reaction simulation by CFD (2.3 + 3.1) A.7 H2 oxidation on pure Pt in stagnation flow (2.3 + 3.3)
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A1) Tuning of Sh(z) in a monolith CFD+simple kinetics
Correlations for Mass Transfer
in Reacting and Developing Laminar Flow with Arbitrary Kinetics
Fundamental calculation (CFD)
of developing mass- and velocity- boundary layers
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A1) Tuning of Sh(z) in a monolith Reaction and diffusion in series Wall mass flux is affected by the rate of consumption
0 Rdr
NAA B
r
A
AA
dCN Ddr
= − ⋅
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A1) Tuning of Sh(z) in a monolith Simple solutions (effective K):
• Infinitely fast reaction
• First order reaction
• Second order reaction
00,, 0
A A
A
r C Cr R C= =
= =0 0A A eff A
DN C K CR
′= − ⋅ = − ⋅
00,
,
A A
AA
r C CNr R Ck
= =
= =0 0
11 1A A eff AN C K C
kβ
′′= − ⋅ = − ⋅+
00,
,
A A
AA
r C C
Nr R Ck
= =
= =
2
0 042A A eff AN C K Ckk
β β β
′′′= ± + ⋅ = − ⋅
β
?
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A1) Tuning of Sh(z) in a monolith ‘effective/apparent’ K’s
It is a concept that holds only for 1st order kinetics
Arbitrary kinetics requires accounting for both MT and reaction at the same time
It remains a series process (MT → reaction)
but MT is influenced by surface reaction
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A1) Tuning of Sh(z) in a monolith local Sh from CFD
From T(r) , Y(r ) profiles, a local, wall Nu and Sh numbers can be calculated
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A1) Tuning of Sh(z) in a monolith hm correlations through Sh : HT analogies
• Bräuer and Fetting (’66) (linear correlation)
• i.e. with a first order kinetic Sh lies between constant (=null) wall concentration and constant wall flux (=reaction), with a quadratic function:
(0) ( )(0)(
2)
'2 '
DaIISh ShS ShDaII Sh
hSh
S h −⋅
∞⋅
−+
∞=
1 1 1
effK kβ= +
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A1) Tuning of Sh(z) in a monolith CFD – First Order Kinetic
• Perfect agreement with asymptotic theoretical value (as expected)
• Experimental correlations for entrance region (very short, semilogx ) not very precise
10-4
10-3
10-2
4
6
8
10
12
14
z (m)
Sh
Variation of Sh number through the reactor channel
Sh FemLabShCShW
Sh(Da)
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A1) Tuning of Sh(z) in a monolith CFD – Second Order Kinetic
Actual Sh number • doesn’t match
Bräuer’s correlation! • is no more into the
ShC-ShW region
10-4
10-3
10-2
4
6
8
10
12
14
z (m)
Sh
Variation of Sh number through the reactor channel
Sh FemLabShCShW
Sh(Da)
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A1) Tuning of Sh(z) in a monolith Conclusions
CFD gives precise correlations for local Sh and Nu
→ use in pseudo 2D models
it make sense to use more detailed kinetics, whereas CFD cannot manage
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A2) CH4 combustion on Pt in a monolith CFD + power law kinetics 1. Investigating the role of transport processes 2. Use of CFD for kinetic studies (as a subroutine)
• Experimental data from literature (10 cm monolith sectioned in 4 segments)
• CFD: CFX4.2 • Optimization: Levenberg-Marquardt open source fortran routine
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Catalytic wall
inlet outlet
Simmetry axis
A2) CH4 combustion on Pt in a monolith 2D Model - density
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Catalytic wall
inlet outlet
Simmetry axis
A2) CH4 combustion on Pt in a monolith 2D Model - Axial velocity
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A2) CH4 combustion on Pt in a monolith 2D Model - CH4 concentration
Catalytic wall
inlet outlet
Simmetry axis
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Catalytic wall
inlet outlet
Simmetry axis
A2) CH4 combustion on Pt in a monolith 2D Model - Temperature
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
2D Model - literature kinetics
solid = literature kinetics, different A’s dotted = D CH4 / 10
Literature kinetics predicts a sudden ignition MT overestimated
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
2D Model – kinetics tuned
Higher Tin (leading to clear ignition) is difficult to predict – poor mechanism
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
2D Model – gas/surface reactions
Homogeneous reactions are negligible
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
3D Model
Large T gradients along the walls
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
3D Model – segmentation
Perfect mixing between elements is assumed
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
3D Model – segmentation
Larger transients in the corners (the most active) Approaches the continuous channel model
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
3D Model – local CH4 concentration
Corners are active The center supplies CH4 to the walls
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
3D Model – sensitivity analysis
Sensitivity (final XCH4): D >> A
Evidence of mass transfer control
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
3D Model – kinetic study
Inhibition by H2O provides a chemical explanation of the data
(unlikely, if MT prevails)
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A3) CO combustion in an annular reactor PFR + detailed gas & surface chemistry 1. Goal: validation of literature mechanism 2. Own experimental data
(KTH, syngas from biomass gassification)
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A3) CO combustion in an annular reactor CO chemistry 1. The lack of hydrogen simplifies the kinetics 2. Surface mechanism extracted from Deutschmann’s CH4 3. gas phase mechanism from GRI 4. CO inlet composition: 0.5, 1 and 2% in air
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A3) CO combustion in an annular reactor The annular reactor • Annular reactor is supposed isothermal (Beretta & al.) • Actually < 10° longitudinal temperature increase on catalyst • The tubular model (CHEMKIN) used for the annular geometry
preserving the same residence time and catalytic area
Quartz, 0.006 m ID
1% Pt- γAl2O3 washcoated
Thermocouple
Mullite, 0.004 m OD
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A3) CO combustion in an annular reactor Isothermal simulations • Disagreement with the experiments • Opposite effect of increasing % COin
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
200 250 300 350 400 450 500 550
Catalyst temperature [°C]
Con
vers
ion
of C
O
% Oin
% COin
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A3) CO combustion in an annular reactor Sensitivity analysis Reducing rate of adsorption of O2 (!)
Better agreement and correct trend for %Coin!
% COin
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
200 250 300 350 400 450 500
Catalyst temperature [°C]
Con
vers
ion
of C
O
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A3) CO combustion in an annular reactor Isothermal assumption check
Tcat = in the inner pipe, at xcat
• adiabatic temperature increase: 90 K/1%CO • adiabatic reactor Match the measured ΔT • reactor is NOT isothermal!
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A3) CO combustion in an annular reactor Conclusions
• Detailed mechanisms are required for a predictive intrinsic kinetics
• Mass transfer must be included in the reactor model
• Eventually shown that a too simplified (PFR) model can lead to wrong assumptions on kinetic parameters: be aware of this in deducing mechanisms
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A4) Kinetics of TOM & POM over Pt in a structured catalyst
• The same in Padua with Pt and KTH with Pt, Rh and Ru • Structured catalyst
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Typical experimental setup
OVEN
cat PT
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Experimental Design
• Temperature ramps • Varying C/O GHSV Heating Rate
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Equilibrium Analysis – C/O=2
• CH4 exp. concentration vs. equilibrium (■)
0
0,2
0,4
0,6
0,8
1
1,2
0 200 400 600 800 1000
temperatura (°C)
conc
etra
zion
e %
concentrazioneCH4 equilibriotermodinamico
GSHV (H-1)24200,concentrazioneCH4GSHV (h-1)49100,concentrazioneCH4GSHV (h-1)73800,concentrazioneCH4
GHSV
24200 h-1
GHSV
49100 h-1
GHSV
73800 h-1
EQUIL
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
0 200 400 600 800 1000
temperatura ( °C )
conc
entra
zion
e %
concentrazioneH2 equilibriotermodinamico
GSHV (H-1)24200,concentrazioneH2
GSHV (h-1)49100,concentrazioneH2
GSHV (h-1)73800,concentrazioneH2
Equilibrium Analysis – C/O=2
• H2 exp. concentration vs. equilibrium (■)
GHSV
24200 h-1
GHSV
49100 h-1
GHSV
73800 h-1
EQUIL
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
0
0,2
0,4
0,6
0,8
1
1,2
0 200 400 600 800 1000temperatura ( °C )
conc
entra
zion
e %
concentrazioneH2O equilibriotermodinamico
GSHV (H-1)24200,concentrazioneH2O
GSHV (h-1)49100,concentrazioneH2O
GSHV (h-1)73800,concentrazioneH2O
Equilibrium Analysis – C/O=2
• H2O exp. concentration vs. equilibrium (■)
GHSV
24200 h-1
GHSV
49100 h-1
GHSV
73800 h-1
EQUIL
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0 200 400 600 800 1000
temperatura (°C)
conc
entra
zion
e %
concentrazioneCO2 equilibriotermodinamico
GSHV (H-1)24200,concentrazioneCO2
GSHV (h-1)49100,concentrazioneCO2
GSHV (h-1)73800,concentrazioneCO2
Equilibrium Analysis – C/O=2
• CO2 exp. concentration vs. equilibrium (■)
GHSV
24200 h-1
GHSV
49100 h-1
GHSV
73800 h-1
EQUIL
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
0 200 400 600 800 1000
temperatura ( °C )
conc
entra
zion
e %
concentrazioneCO equilibriotermodinamico
GSHV (H-1)24200,concentrazioneCO
GSHV (h-1)49100,concentrazioneCO
GSHV (h-1)73800,concentrazioneCO
Equilibrium Analysis – C/O=2
• CO exp. concentration vs. equilibrium (■)
GHSV
24200 h-1
GHSV
49100 h-1
GHSV
73800 h-1
EQUIL
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
0
0,2
0,4
0,6
0,8
1
1,2
0 200 400 600 800 1000temperatura (°C)
conc
entra
zione
%
concentrazioneCH4 equilibriotermodinamico
GSHV (H-1)25100,concentrazioneCH4
GSHV (h-1)49100,concentrazioneCH4
GSHV (h-1)73800,concentrazioneCH4
Equilibrium Analysis – C/O=1
• CH4 exp. concentration vs. equilibrium (■)
GHSV
24200 h-1
GHSV
49100 h-1
GHSV
73800 h-1
EQUIL
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
0
0,5
1
1,5
2
2,5
0 200 400 600 800temperatura (°C)
conc
entra
zion
e %
concentrazione H2 equilibriotermodinamico
GSHV (H-1)25100,concentrazioneH2
GSHV (h-1)49100,concentrazioneH2
GSHV (h-1)73800,concentrazioneH2
Equilibrium Analysis – C/O=1
• H2 exp. concentration vs. equilibrium (■)
GHSV
24200 h-1
GHSV
49100 h-1
GHSV
73800 h-1
EQUIL
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
0
0,1
0,2
0,3
0,4
0,5
0,6
0 200 400 600 800 1000temperatura (°C)
conc
entra
zion
e %
concentrazione H2O equilibriotermodinamico
GSHV (H-1)25100,concentrazioneH2OGSHV (h-1)49100,concentrazioneH2OGSHV (h-1)73800,concentrazioneH2O
Equilibrium Analysis – C/O=1
• H2O exp. concentration vs. equilibrium (■)
GHSV
24200 h-1
GHSV
49100 h-1
GHSV
73800 h-1
EQUIL
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
0
0,05
0,1
0,15
0,2
0,25
0,3
0,35
0,4
0 200 400 600 800 1000temperatura (°C)
conc
entra
zion
e %
concentrazione CO2equilibriotermodinamico
GSHV (H-1)25100,concetrazioneCO2
GSHV (h-1)49100,concetrazioneCO2
GSHV (h-1)73800,concentrazione CO2
Equilibrium Analysis – C/O=1
• CO2 exp. concentration vs. equilibrium (■)
GHSV
24200 h-1
GHSV
49100 h-1
GHSV
73800 h-1
EQUIL
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
0
0,2
0,4
0,6
0,8
1
1,2
0 200 400 600 800 1000temperatura (°C)
conc
entra
zion
e %
concentrazioneCO equilibriotermodinamico
GSHV (H-1)25100,concentrazioneCO
GSHV (h-1)49100,concentrazioneCO
GSHV (h-1)73800,concentrazioneCO
Equilibrium Analysis – C/O=1
• CO exp. concentration vs. equilibrium (■)
GHSV
24200 h-1
GHSV
49100 h-1
GHSV
73800 h-1
EQUIL
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Analysis of the global reaction
ii
i i
j j jj
dC RCd
dC CR
d
υυτυ
υτ
= ⋅ ∆ = ∆= ⋅
Global reaction:
CH4 + aO2 = bH2 + cH2O + dCO + eCO2
A way to look into the data: identify the global reaction occurring into the reactor
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
0 200 400 600 800-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
T [°C]
gam
ma:
[-1
1]
Global reaction,C/O=2(- equil, . exp)
vH2vH2OvCOvCO2vCH4vO2
Global reaction stoichiometry - C/O=2
At higher T exp data approach equilibrium Effective reaction: CH4+O2 = 1.25H2+0.75H2O+0.75CO+0.25CO2
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Global reaction stoichiometry - C/O=1
Exp stoich. Quite far from equilibrium: Equilibrium reaction: CH4+0.5O2=2H2+CO Effective reaction: CH4+0.77O2= 1.65H2+0.47H2O+1.03CO+0.06CO2
0 200 400 600 800-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
T [°C]
gam
ma:
[-1
1]
Global reaction,C/O=1(- equil, . exp)
vH2vH2OvCOvCO2vCH4vO2 CO – CO2 reach equil.
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Mechanism recognizing
0 100 200 300 400 500 600 700 800 900-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
T [°C]
gam
ma:
[-1
1]
Contribution of different reactions,C/O=2(- equil, : exp)
CH4+2O2=CO2+2H2OCH4+H2O=CO+3H2CO+H2O=CO2+H2
0 100 200 300 400 500 600 700 800 900-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
T [°C]
gam
ma:
[-1
1]
Contribution of different reactions,C/O=1(- equil, : exp)
CH4+2O2=CO2+2H2OCH4+H2O=CO+3H2CO+H2O=CO2+H2
• Sensitive at the hypotheses on the mechanism • WGS equil. is late in comparison with other reactions
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
scan progressively shorted residence time, to spot the instantaneous stoichiometry
Mechanism recognizing
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Data simulation Pseudo 2D model with simplified kinetics Species mass balance
Energy balance
( )v 1...7d a idz
= − ⋅ − =Bc B S
c K c c
( ) 1...7Cata iρ⋅ − = − ⋅ =c B SK c c ν R
( )v cp Bt B S
dT a K T Tdz
ρ⋅ ⋅ = − ⋅ −
( ) ( )t B S Cata K T T ρ⋅ − = − ⋅RR ΔH
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Pseudo 2D simplified kinetics • Groppi kinetic mechanism
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Transport coefficients Monolith
i ic t
cell cell
Sh D NuK Kd d
λ⋅ ⋅= =
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Comparison between 1D MODELs
1D MODELS: PFR vs. Sh,Nu
0
20
40
60
80
100
300 350 400 450 500 550 600 650 700 750 800
T(°C)
XC
H4
%
GROPPI + Sh,NuEXPGROPPI + PFR
• Bad agreement of the kinetics in the ignition region • PFR over predicts the conversion at high T • Sh, Nu model matches the data at high T
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Temperature profiles • Peak in the surface temperature, Tin=750°C • Maximum in gas temperature is shifted downstream • First exothermic, then endothermic surf. reactions
Temperature profiles in the reactor
1023
1043
1063
1083
1103
1123
1143
1163
1183
0 0.002 0.004 0.006 0.008 0.01
z (m)
T(K
) T gas
T sup
Exp, out
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
• Adiabatic reactor
• Channel □ → ○ keeping Scat and τ • Every channel behaves similarly to the others • Calculations made with CHEMKIN PLUG • Deutschmann2001 mechanism
Data simulation PFR model with detailed kinetics
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Lower flow rate - conversion
meccanismo DEUTSCHMANN-Pt
0,0
0,2
0,4
0,6
0,8
1,0
0,8 1 1,2 1,4 1,6
T/Tinn
XC
H4
Calcolati con PLUG Sperimentali Sperimentali2
• Channel non-adiab. → rescaled T/Tign • At higher T the regime is mostly diffusive
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Higher flow rate - conversion
meccanismo DEUTSCHMANN-Pt
0
0,2
0,4
0,6
0,8
1
0,8 1 1,2 1,4 1,6T/Tinn
XC
H4
Calcolati con PLUG Sperimentali Sperimentali2 Sperimentali3
• Transport phenomena are increased, determining a better agreement even at higher T
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Conclusion
• Deutschmann2001 mechanism fits quite well our data, suggesting two chemical regimes
meccanismo DEUTSCHMANN-Pt
0
0,2
0,4
0,6
0,8
1
0,8 1 1,2 1,4 1,6T/Tinn
XC
H4
Calcolati con PLUG Sperimentali Sperimentali2 Sperimentali3
Total Oxidation
Partial Oxidation - Reforming
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Conclusion
• Pseudo 2D models: for kinetics other than first order, Sh number should be calculated numerically
• 1D model: Extend Chemkin PLUG, to account for both detailed kinetics and transport phenomena (pseudo-2D)
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A4) CH4 partial oxidation on Rh foam pseudo2D + detailed surface kinetics
• Spatially resolved (x) T and x data
(Horn & Schmidt, MN)
• Validation of literature mechanism (CH4 on Rh)
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A4) CH4 partial oxidation on Rh foam Chemistry
Global reactions expected:
Total Oxidation: CH4 + 2O2 = 2H2O + CO2 DH= –803 kJ·mol-1 Partial Oxidation to H2O and syngas: CH4 + O2 = H2 + CO + H2O DH = –278 kJ·mol-1 Partial Oxidation to Syngas: CH4 + 1/2O2 = 2H2 + CO DH = –36 kJ·mol-1
After O2 consumption:
Steam Reforming (SR): CH4 + H2O = 3H2 + CO DH = +206 kJ·mol-1 Water Gas Shift (WGS): H2O + CO = H2 + CO2 DH = –41 kJ·mol-1 Dry Reforming (DR): CH4 + CO2 = 2H2+ 2CO DH = +247 kJ·mol-1
P. Canu – CFD + µΚΙΝ Liège, Sept. 2011
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A4) CH4 partial oxidation on Rh foam Chemistry CPO Mech
R. Schwiedernoch, S. Tischer, C. Correa, O. Deutschmann, Chem. Eng. Sci. 58 (2003) 633.
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Autothermal Reactor – Rh/Al2O3 Foam Catalyst
FRONT HEAT
SHIELD
BACK HEAT
SHIELD CATALYST
INSULATION
CH4/O2=0.5
Tin = room T
A4) CH4 partial oxidation on Rh foam Catalyst arrangement
65
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A4) CH4 partial oxidation on Rh foam Reactor setup Reactor assembly, axial T, C measurements and computational domain
66
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A4) CH4 partial oxidation on Rh foam Measurements T, C spatially resolved
67
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A4) CH4 partial oxidation on Rh foam Eqs.
68
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A4) CH4 partial oxidation on Rh foam Bulk simulations Axially resolved results Vs. measurements
69
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A4) CH4 partial oxidation on Rh foam Simulations - Pure PFR model Axially resolved results Vs. measurements
Exit compositions very close to the experimental → end-of-the-tube data can be misleading
(poorly informative) 70
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A4) CH4 partial oxidation on Rh foam Simulations - surface
Axially resolved results at the surface
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P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A4) CH4 partial oxidation on Rh foam Simulations - Coverages Axially resolved results Coverages
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P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A4) CH4 partial oxidation on Rh foam Analysis of mass-transport limitations
Difference between bulk and superficial mole fractions (∆X), transport coefficient (KC) and production rate ( ˙s) for each species, all scaled with respect to the values of CH4
Marked limitations for both
• species of low diffusivity • species with high net production rates. caution in using the Chilton–Colburn analogy for fast reacting species
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P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A5) Herogeneous reaction simulation by CFD Hands-on illustration of CFD calculation through Multiphysics:
1. Arbitrary geometry
2. Generic chemistry
3. velocity distribution (simple and variable geometry)
4. homogeneous reaction
5. (simplified) surface reaction
Applications feasible with ordinary hardware and limited time
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P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A6) CH4 partial oxidation on Pt monolith CFP+µkin
Direct illustration of coupling mKIN to CFD through Multiphysics:
1. Cantera provides , given C at the surface
2. MP→ Matlab → Cantera
Applications quite manageable
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P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A6) CH4 partial oxidation on Pt monolith CFP+µkin CH4 combustion on Pt Honeycomb with inlet
CH4 (1%) O2 (1%)
T=500°C
Pt
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A6) CH4 partial oxidation on Pt monolith CFP+µkin CFD (Comsol MP) uses:
• Navier-Stokes eq. for Momentum • Stefan-Maxwell eq. for Species • Convection and Conduction for T gas • Conduction for T solid • Idel Gas Law for density
Detailed surface mechanism* (as BCs, through Cantera, via Matlab interface)
30 steps including: 7 molecular species 11 adsorbed species adsorption/desorption/ surface reaction
(see rsurf.m)
* R. Quiceno, J. Perez-Ramyrez, J. Warnatz, O. Deutschmann. Appl. Catal. A: General (2006)
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Methane catalytic partial oxidation Detailed chemistry
R. Quiceno, J. Perez-Ramyrez, J. Warnatz, O. Deutschmann , Appl. Catal. A: General (2006)
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
cata
lyst
com
puta
tion
al d
omai
n
z= –10 mm
z=10 mm
z=0
TG CH4 , O2 H2O , CO2 H2 , CO
max
max
max TS
A6) CH4 partial oxidation on Pt monolith CFP+µkin
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P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
Catalyst (1cm)
computational domain (3 cm)
max
2D model Carrier Ar, vIN = 0.25 m/s TIN = 500°C
Gas T
Solid T
Very localized heating 81
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
-10 -5 0 5 100
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0.008
0.009
0.01
z [mm]
mol
e fra
ctio
n
CO
H2
O2
CH4
CO2
H2O
Upstream flow
Experimental
CATALYST
Impressive axial diffusion (He =carrier) Agreement with experimental exit composition
At TIN=500°C, syngas negligible
A6) CH4 partial oxidation on Pt monolith CFP+µkin
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P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
-0.01 -0.008 -0.006 -0.004 -0.002 0 0.002 0.004 0.006 0.008 0.01770
780
790
800
810
820
830
z [m]
mea
n ga
s te
mpe
ratu
re [K
]
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01
827.2
827.4
827.6
827.8
828
828.2
828.4
828.6
828.8
z [m]
Tem
pera
ture
[K]
Surface T
mean gas T
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A6) CH4 partial oxidation on Pt monolith CFP+µkin
Upstream heat diffusion (He)
P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A6) CH4 partial oxidation on Pt monolith CFP+µkin
Surface coverages
Besides the first 0.1 mm, the surface is almost free Pt(S) sites CO(S) is the main coverage after O2 is consumed
0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.0110
-4
10-3
10-2
10-1
100
z [m]
fract
iona
l cov
erag
es
PT(S)H(S)H2O(S)OH(S)CO(S)C(S)O(S)
Pt(S)
O(S)
ABOVE 1%
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P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A6) CH4 partial oxidation on Pt monolith CFP+µkin - Conclusions
1. Coupling CFD and detailed chemistry is feasible 2. Surprising effects of interactions
between M/HT and chemistry are spotted
3. Still limited on homogeneous chemistry
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P. Canu – CRE with µKin CACRE, Åbo Akademi, 2014
A7) H2 oxidation on pure Pt in stagnation flow CFP+µkin
Just demonstration by Multiphysics
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