THREE DIMENTIONAL BGK APPROACH IN SIMULATION OF
STRUCTURED PACKINGS
M.R.Kamali, J.R. van Ommen, H.EA.van den Akker
Delft University of Technology, Prins Bernhardlaan 6, 2628 BW, Delft, The Netherlands
M.R.Kamali@tudelft.nl
Abstract
Application of structured packings can improve the performance of the multi-tubular catalytic
reactors in the Fischer-Tropsch (FT) synthesis. However, due to exothermic behavior and
kinetic of the FT reaction proper radial heat and mass transfer are strongly important in
achieving good selectivity in this kind of reactor. Heat and mass transfer are dependent to the
type and design of the structured packing and their orientation inside the multi-tubular reactor.
Process intensification in multi-tubular reactors is achievable by optimizing the design and
orientation of the structured packings. Ability of using bigger units without suffering the
selectivity, having less pressure drop in the column, reducing the by-products by limiting the
back mixing or improving the penetration inside the catalytic bed are some important issues in
this respect.
The aim of the current work is to combine Direct Numerical Simulation (DNS) with
experiments in order to get better insight about the hydrodynamics and heat and mass transfer
in the structured packings. These will end up to optimized design for the structured packings
and reactor. For the CFD part Lattice-Boltzmann (LB) approach based on three dimensional
BGK (Bhatnagar-Gross-Krook) model was applied. Selection of the LB is due to its
advantages for the current particular problem compared to other conventional CFD
approaches. In fact, complexity of the structured packings and much of the physics involved
in the FT reaction demand fast and accurate solvers. Besides complexity of the geometry, one
of the challenges in simulation of Fischer-Tropsch reactions in the structured packings is
involvement of interfacial dynamics and phase transition with presence of porous solid
particles. In LB simulation it is possible to consider thermodynamics of the phases and add
equation of states of interfaces to the simulation. However, the high density ratio between gas
and liquid in FT, and formation of liquid due to chemical reaction on porous solid particles
are some issues which need special treatment.
So far, we have succeeded in building a three dimensional model for the simulation of FT
reaction in the CCFS (Closed Cross Flow Structure) packing. An important advantage of
developed model is its fast and accurate calculation compared to other Finite Volume (FV)
based method. The model is under development to finally reach to the goal of optimizing the
structured packings for FT reactions.