Hydrodynamic considerations on optimal design of a three‐phase airlift bioreactor with high solids loading

Abstract

The hydrodynamic study of a three-phase airlift (TPAL) bioreactor with an enlarged gas-liquid dual separator was carried out. Different lengths and diameters of the draft tube were tested to show how the design of the separator zone affects the hydrodynamic performance of the TPAL reactor. Ca-alginate beads with entrapped yeast biomass at different loadings (0, 7, 14 and 21% v/v) were used in order to mimic the solid phase of conventional high cell density systems, such as those with cells immobilized on carriers or flocculating cells. Important information on multiphase flow and distribution of gas and solid phases in the internal-loop airlift reactor (ALR) with high solids loading was obtained, which can be used for suggesting optimal hydrodynamic conditions in a TPAL bioreactor with high solids loading. It is finally suggested that the ALR with a dual separator and a downcomer to riser cross-sectional area ratio (A D /A R ) ranging from 1.2 to 2.0 can be successfully applied to batch/continuous high cell density systems, where the uniform distribution of solid phase, its efficient separation of particles from the liquid phase, and an improved residence time of air bubbles inside the reactor are desirable.

Characteristics of three-phase internal loop airlift bioreactors with complete gas recirculation for non-Newtonian fluids

“…However, from Figure 4, it can be found that varepslon SR decreases bute SD increases with increasing J G . These results are similar to those reported by Klein et al [28].…”

Multiphase flow characteristics of a novel internal-loop airlift reactor

“…During the modeling, the bridge effect that addition of solids leads to a decrease in the flow channel has been taken into account. The similar effect was reported by Klein et al [15]. In order to balance the energy inputted and consumed in the circulation, a modified diameter of the separator tubes is introduced as:…”

“…Because of the flow resis- tance increase with increasing solid holdup [14], the energy consumed by the flow increases and the liquid velocity decreases with increasing solid holdup. Klein et al [15] also found that the liquid velocity decreases with increasing solid holdup.…”

Customization of an optical probe device and validation of a signal processing procedure to study gas–liquid–solid flows. Application to a three-phase internal-loop gas-lift Bioreactor

“…This is better seen at 250 mL/min than at 400 mL/min. In general the gas holdup in the riser of iGLR decreases in the presence of solids, being more significant at gas superficial velocities above 10 cm/s (Freitas and Teixeira, 1998;Klein et al, 2003). It is important to note that in three-phase iGLR there are a lot of different mechanisms that may influence gas holdup (design, type of solids and operational conditions) and the impact of each one of them is not yet clear (Chisti, 1989).…”