Countercurrent multistage fluidized bed reactor for immobilized biocatalysts: III. Hydrodynamic aspects
In Parts I and II of this series we described the modelling, design, and operation of a multistage fluidized bed reactor (MFBR) for immobilized biocatalysts. This article deals with those aspects of the MFBR which are different from single‐stage fluidized beds which are operated in batch mode with respect to the solids. The semicontinuous transport of the particles requires perfect mixing of the particles in the reactor compartments, because particles are mainly transported from the bottom of these compartments. A large spread in the physical properties of the biocatalyst particles, especially of both size and density, may cause the particles to segregate into layers with different diameter and/or density. This affects the efficient use of the biocatalyst. The properties of the particles are dependent on the immobilization method. The suitability of different methods for possible future application in the MFBR is therefore compared. Because of segregation, successful use of a biofilm catalyst with a nonuniform thickness of the biofilm is doubtful. Experiments in a small scale reactor (± 0.1 m diameter) demonstrated that perfect particle mixing is possible using commercially available biocatalyst particles of uniform density. Co‐immobilization of the biocatalyst with glass powder in a gel is a simple and effective method of increasing gel density. High density particles allow high liquid flow rates, and thus an improved external mass transfer can be achieved.
Mixing and segregation in binary-solid liquid fluidised beds
Abstract Force balance considerations enable 'solid concentration relationships' to be evaluated for binary-solid particulate fluidisation which define the set of solid component volumetric concentrations that can coexist at axial locations in the fluidised state; these relationships are verified experimentally and applied to the analysis of mixing and segregation in water fluidised beds.
The influence of gravity on the stability of fluidized beds
Consequences d'un changement de force du champ gravitationnel sur la stabilite de suspensions fluidisees, a la lumiere d'un modele recent de fluidisation. Comparaison avec des resultats experimentaux publies