Nicole Reed

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COMSOL Modeling of Liquid Flow Through a
Fixed-Bed Packed Reactor for Adsorptive
Desulfurization
Nicole Reed Department of Energy and Mineral
Engineering EGEE 520 Penn State University April
29, 2008
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Desulfurization approaches require severe
conditions and are not suitable for fuel cell
applications

• Hydrodesulfurization (HDS)
• High Temp (300-350 C)
• High Pressure of H2 (30-40 bar)

Selective Adsorption (SARS) is achieved at
ambient pressure and temperature without hydrogen
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A fixed-bed continuous flow system measures the
performance of adsorbents for various fuels
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3
0.2513 g
Fuel samples collected at regular intervals
Samples weighed
Fixed-bed reactor
Amount of Treated Fuel
HPLCPump
Fuel
(X ppm S)
C C0
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This study focuses on liquid fuel flow through a
packed bed
Packed Bed Activated Carbon Porosity(e) 0.6
(experimental) Permeability(?) 1.88x10-11 m2
Fixed-bed reactor Volume 2.49 mL Length 0.15
m Width 0.0025 m
Fuel
Diesel Fuel Density 800 kg/m3 Flow Rate
0.05 ml/min ? 0.0005 m/s
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Darcys Law describes flow through porous medium
in terms of head gradients

• Darcys Law

Term Meaning Units
q Darcy Flux m/s
Q Discharge m3/s
K Hydraulic conductivity m/s
k Permeability m2
µ Absolute viscosity Ns/m2
? Density kg/m3
h head m
? Kinematic viscosity m2/s
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Boundary Conditions
2-D Axial Symmetry
r 0.0025 m
Quantity Value Unit Description
? 0.8 kg/m3 Density
? 1.88x10-11 m2 Permeability
µ .0024 Pas Dynamic Viscosity
f 0 kg/(m3s) Source Term
Insulation BC h 0.15 m
Inflow/Outflow 0.005 m/s
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Solution
Outflow 0.0005 m/s ?P 0.975 atm
Inflow 0.0005 m/s ?P 1.069 atm
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Validation
Darcys Law
Column Length
From COMSOL Solution
Maximum Pressure - Minimum Pressure Pressure
Drop 1.069 0.974 0.095 atm
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Parametric Study

• How does particle size and fuel flow rate affect
  the pressure drop?

Particle Size ? Permeability
50, 5, and 0.5 microns
Fuel flow rate ? Velocity
0.05, 0.20, and 1.0 ml/min
Case Flow Rate Velocity Particle Size Permeability Max Min P DROP
1 0.05 0.0005 5E-05 1.875E-11 1.069 0.974 0.095
2 0.20 0.002 5E-05 1.875E-11 1.278 0.9 0.378
3 1.00 0.04 5E-05 1.875E-11 6.56 -0.999 7.559
4 0.05 0.0005 5E-06 1.875E-13 8.095 -1.34 9.435
5 0.20 0.002 5E-06 1.875E-13 29 -8.4 37.4
6 1.00 0.04 5E-06 1.875E-13 569 -187 756
7 0.05 0.0005 5E-07 1.875E-15 770 -174 944
8 0.20 0.002 5E-07 1.875E-15 2736 -1042 3778
9 1.00 0.04 5E-07 1.875E-15 5470 -20890 26360
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Summary

• COMSOL can effectively model packed bed reactors
• with the following parameters
• Adsorbent porosity, particle size, density
• Fuel flow rate, density

Particle size and fuel flow rate affect pressure
drop across small reactors
COMSOL can be used to find limits for scale-up
models and other reactor designs
THANK YOU!