Currently im working on the simulation (theoretical at this stage) of a fluidized bed (tubular) reactor working at high temperature under the influence of high solar radiative flux.
We are puting a lot of effort in modelling the interacion of radiation absorption-emission, chemical kinetics (temperature dependence, and so on) and for the mean time, we are NOT modelling the hydrodynamics.
To bypass hydrodynamics, we assume a pseudo-homogeneous model with axial convection-dispersion and radial dispersion on the mass and energy balance equations. However, im currently struggling to get correlations for (axial and radial) Dispersion coefficients correlations for fine powder fluidized beds. Anyone knows authors/books you could recommend me?
Thanks in advance,
Patricio V.
Dear Patricio Javier,
In this study, solids dispersion coefficients in fluidized beds of fine Group A particles were derived by modelling the data obtained in steady-state gas tracer experiments with a two-phase gas mixing model .Both baffle-free and baffled fluidized beds of FCC particles were tested in a two-dimensional cold model column with broad operating conditions covering both bubbling and turbulent flow regimes. As superficial gas velocity increases, the axial solids dispersion coefficients change in a similar trend as the axial gas dispersion coefficients in both baffle-free and baffled fluidized beds. The effects of different baffles on solids mixing are also similar to those on gas mixing. This demonstrates the close relationship between gas mixing and solids mixing in fluidized bed of fine particles. Gas mixing behaviour was investigated in a residence time distribution experiment in a bubbling fluidized bed of 0.07 m ID and 0.80 m high. Linear low density polyethylene (LLDPE) particles having a mean diameter of 772 Μm and a particle size range of 200-1,500 Μm were employed as the bed material. The stimulus-response technique with CO2 as a tracer gas was performed for the RTD study. The effects of gas velocity, aspect ratio (H0/D) and scale-up on the axial gas dispersion were determined from the unsteady-state dispersion model, and the residence time distributions of gas in the fluidized bed were compared with the ideal reactors. Fluidized beds are increasingly being used for catalytic polymerization because of a significant reduction in the operating and fixed costs. However, compared with a fluidized bed of FCC particles, the hydrodynamic studies of fluidized bed with polymeric particles are rather limited. An issue yet to be resolved in the modeling of the fluidized bed is whether or not the bed should be treated as a CSTR.
Regards,
Prem Baboo
Article Axial Gas Dispersion in a Fluidized Bed of Polyethylene Particles
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