Abstract
There are several configurations of fluidized beds commonly used in wastewater treatment units. Often their hydrodynamics is challenging to be evaluated experimentally, or too complex to be predicted accurately with empirical correlations only. In the present study, the computational fluid dynamics technique was applied to evaluate the hydrodynamic behavior of a liquid–solid fluidized bed in tapered bioreactors. The simulations were run with OpenFOAM, and they were based on a 3D, transient, Eulerian–Eulerian two-phase approach coupled with a turbulence model. Different tapered bioreactor angles were considered in the study, and the results showed a decrease in flow velocity along with the height of the device. Moreover, the distribution of the bioparticles within the fluidized bed was not found to be uniform, and it changed with the angle. It was also observed that bioparticle collisions caused large velocity fluctuations. Even though the bioreactor presented a square cross section, results also proved that the presence of the dead zone was negligible.
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Abbreviations
- C :
-
Coefficient (–)
- e :
-
Coefficient of restitution (–)
- f(α):
-
Particles population effect
- g :
-
Gravity acceleration (m/s²)
- k :
-
Turbulent kinetic energy (m²/s²)
- M :
-
Momentum transfer term (kg/(m² s²))
- p :
-
Pressure (Pa)
- P :
-
Turb. kinetic energy production (m²/s³)
- Re :
-
Reynolds number (–)
- Sr :
-
Strain rate (–)
- t :
-
Time (s)
- U :
-
Velocity (m/s)
- α :
-
Volume fraction (–)
- δ :
-
Biofilm thickness (µm)
- ϵ :
-
Turb. kinetic energy dissipation (m²/s³)
- γ :
-
Gran. temperature dissipation (m²/s³)
- λ :
-
Bulk viscosity (kg/(m s))
- μ :
-
Dynamic viscosity (kg/(m s))
- ϕ :
-
Tapered bioreactor angle (°)
- ρ :
-
Density (kg/m³)
- σ :
-
Turbulence model constant (–)
- Θ :
-
Granular temperature (m²/s²)
- D :
-
Drag
- L :
-
Lift
- r :
-
Relative
- l :
-
Liquid phase
- p :
-
Particulate phase
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Acknowledgements
This work was supported by the National Council for Scientific and Technological Development (CNPq), through Project Number 830795/1999-5. The authors also thank Dr. Tommaso Oggian for his insights reviewing this paper.
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Koerich, D.M., Lopes, G.C. & Rosa, L.M. Numerical study on the hydrodynamics of a fluidized-bed of bioparticles in tapered bioreactors with square shape cross-section. Braz. J. Chem. Eng. 37, 101–115 (2020). https://doi.org/10.1007/s43153-020-00010-4
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DOI: https://doi.org/10.1007/s43153-020-00010-4