View
230
Download
0
Category
Preview:
Citation preview
8/6/2019 5019 Allain Presentation
1/15
Modeling of Transport and Reaction
in a Catalytic Bed Using a CatalystParticle Model.Florent Allain (speaker), Anthony G. Dixon
Worcester Polytechnic Institute - Chemical
Eng. Dpt. , Worcester, MA, USA
COMSOL Conference 2010 BostonPresented at the
http://www.comsol.com/conf_cd_2011_us8/6/2019 5019 Allain Presentation
2/15
Packed bed reactors: COconversion, MSR reaction, Benzeneconversion to cyclohexane
Characterized by N=ratio betweenbed and particle diameter,
Usual model: pseudo-
heterogeneous, effectiveness factorHigh N
Our model: pseudo-heterogeneous,diffusion in the solid particles.
Background
8/6/2019 5019 Allain Presentation
3/15
Our model (1)
Fluid equations:
Solid equations:
8/6/2019 5019 Allain Presentation
4/15
Boundary conditions:
Fluid phase:
Convective fluxes for C and T
Axis symmetry for C and T
Our model (2)
8/6/2019 5019 Allain Presentation
5/15
Boundary conditions:
Solid phase:
Axis symmetry
Our model (3)
8/6/2019 5019 Allain Presentation
6/15
Chemical eng. module
Fluid equations: 2D Convection
conduction/diffusion Solid equations: 3D
Conduction/diffusion
Extrusion coupling variablesfrom one geometry to the other.
Implementation in COMSOL 3.5
8/6/2019 5019 Allain Presentation
7/15
First case: CO conversion over copper-chromitecatalyst. N=11.
CO inlet concentration of 0.5 mol/m3,
O2 considered constant (30.6 mol/m3) in the
fluid and solid, Constant wall temperature of 385K.
Test case - Statement
8/6/2019 5019 Allain Presentation
8/15
Temperature profile Fluid (K) Temperature profile Solid (K)
Test case Results (1)
8/6/2019 5019 Allain Presentation
9/15
CO concentration profile Fluid(mol/m3)
CO concentration profile Solid(mol/m3)
Test case Results (2)
8/6/2019 5019 Allain Presentation
10/15
Machac et al. 2006 Present study
Hot spot in the center, at z= 2
Hot spot temperature: 475 K
Temperature differencesolid/fluid, r=0.5: 20K
Effective inlet concentration:
around 0.45mol/m3
Hot spot in the center, at z=
2.5 Hot spot temperature: 440 K
Temperature differencesolid/fluid, r=0.5: 43K
Effective inlet concentration:
0.414 mol/m3
Test case - Comparison
Similar profiles for both concentration and temperature in the fluid phase.
Need to get better coefficient for conduction/diffusion in the solid.
8/6/2019 5019 Allain Presentation
11/15
MSR reactions. N=6
Reaction rates from Hou et Hughes. The kineticsof methane steam reforming over a Ni/[alpha]-
Al2O catalyst. Chemical Engineering Journal(2001)
Data from simulations by Johnson Matthey.
Study case - Statement
8/6/2019 5019 Allain Presentation
12/15
Temperature profile Fluid (K) Temperature profile Solid (K)
Test case Results (1)
8/6/2019 5019 Allain Presentation
13/15
H2 concentration profile Fluid(mol/m3)
H2 concentration profile Solid(mol/m3)
Test case Results (2)
8/6/2019 5019 Allain Presentation
14/15
Good agreement in the test case with literature,
Model applicable to more complex reactions,
Need to reevaluate the heat and mass transfer
coefficient for MSR reaction, for both fluid andsolid phase.
Conclusion
8/6/2019 5019 Allain Presentation
15/15
The Donors of the American Chemical SocietyPetroleum Research Fund
COMSOL
Acknowledgments
Recommended