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

摘要

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