Analysis of hydrodynamic effects on biofilm thickness in fluidized-bed tapered bioreactors

Fluidized beds in tapered geometries provide advantages such as a broad range of optimum operating conditions. However, the dynamics of the flow inside these bioreactors is significantly more complex, as they promote non-uniform bioparticles distribution. To this end, the CFD technique can give a detailed description of the flow in the bioreator. Hence, the aim of this work is to assess the influence of the hydrodynamic on the steady-state biofilm thickness through numerical simulations of liquid-solid fluidized bed. Two geometries of tapered bioreactors in the operating conditions used to develop biofilms. Simulations were run to solve the two-phase RANS equations using the open-source software OpenFOAM in transient-state. The SST k - omega model was used to estimate the turbulent features of the flow. Velocity and bioparticles distribution inside the reactor were analyzed for different inlet velocities, while bioparticles collision frequency and shear stresses were evaluated for various operating conditions. The comparison between the turbulent kinetic energy and the granular temperature indicated that the fluid flow is more turbulent than the bioparticles movement. The hydrodynamics influence on the steady-state biofilm thickness was assessed, and results led to the conclusion that biofilm is more sensitive to hydrodynamic shear stress than bioparticles collisions. (c) 2021 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.