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1 Nicole Reed Department of Energy and Mineral Engineering EGEE 520 Penn State University April 29, 2008 COMSOL Modeling of Liquid Flow Through a Fixed-Bed Packed Reactor for Adsorptive Desulfurization
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Desulfurization approaches require severe conditions and are not suitable for fuel cell applications Selective Adsorption (SARS) is achieved at ambient pressure and temperature without hydrogen Hydrodesulfurization (HDS) –High Temp (300-350 °C) –High Pressure of H 2 (30-40 bar)
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A fixed-bed continuous flow system measures the performance of adsorbents for various fuels Fuel HPLC Pump (X ppm S) Fixed-bed reactor 23 Fuel samples collected at regular intervals 1 0.2513 g Samples weighed 1 Amount of Treated Fuel C = C 0
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This study focuses on liquid fuel flow through a packed bed Fuel Diesel Fuel Density = 800 kg/m 3 Flow Rate = 0.05 ml/min 0.0005 m/s Fixed-bed reactor Volume = 2.49 mL Length = 0.15 m Width = 0.0025 m Packed Bed: Activated Carbon Porosity(ε) = 0.6 (experimental) Permeability(κ) = 1.88x10 -11 m 2
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5 Darcy’s Law describes flow through porous medium in terms of head gradients Darcy’s Law: TermMeaningUnits qDarcy Fluxm/s QDischargem 3 /s KHydraulic conductivitym/s kPermeabilitym2m2 µAbsolute viscosityNs/m 2 ρDensitykg/m 3 hheadm νKinematic viscositym 2 /s
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6 Boundary Conditions r = 0.0025 m Insulation BC h = 0.15 m 2-D Axial Symmetry Inflow/Outflow = 0.005 m/s QuantityValueUnitDescription ρ0.8kg/m 3 Density κ1.88x10 -11 m2m2 Permeability µ.0024Pa·sDynamic Viscosity f0kg/(m 3 ·s)Source Term
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7 Solution Inflow = 0.0005 m/s ΔP = 1.069 atm Outflow = 0.0005 m/s ΔP = 0.975 atm
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8 Validation Darcy’s Law Column Length From COMSOL Solution: Maximum Pressure - Minimum Pressure = Pressure Drop 1.069 – 0.974 = 0.095 atm
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9 Parametric Study How does particle size and fuel flow rate affect the pressure drop? Particle Size Permeability Fuel flow rate Velocity CaseFlow RateVelocityParticle SizePermeabilityMaxMinP DROP 10.050.00055E-051.875E-111.0690.9740.095 20.200.0025E-051.875E-111.2780.90.378 31.000.045E-051.875E-116.56-0.9997.559 40.050.00055E-061.875E-138.095-1.349.435 50.200.0025E-061.875E-1329-8.437.4 61.000.045E-061.875E-13569-187756 70.050.00055E-071.875E-15770-174944 80.200.0025E-071.875E-152736-10423778 91.000.045E-071.875E-155470-2089026360 0.05, 0.20, and 1.0 ml/min 50, 5, and 0.5 microns
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10 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!
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