(624b) CFD Simulation of Large-Scale Bioreactor with Side-Entry Agitator

    The scale-up and design of commercial scale stirred bioreactors from lab data is still a big challenge. The performance of a bioreactor largely depends on the efficient and homogeneous dispersion of gas-liquid and suspension of solid particles. It is difficult for engineers to rely on rules-of-thumb alone to deal with the uncertainties encountered in the design, scale-up and optimization of this complex three phase system. Mathematical modeling has been suggested to be a useful tool in the scale-up process.

    In the present work, a detailed computational fluid dynamics (CFD) simulation was conducted to predict the flow pattern in a large-scale bioreactor (3400 m³) with side-entry agitators. The CFD analysis was firstly carried out in a single-phase reactor. With 4 side agitators installed in the reactor, the horizontal continuous circular flow was indentified, which would facilitate the mixing of solid particles. Subsequently, the CFD simulation was extended to solid-liquid two-phase. The uniformity of solid suspension and the power input were used as the objectives to assess the effects of the shaft angle, stirring speed as well as the agitator quantity and an optimum installation mode was obtained. Finally, the bubbles generation and distribution in gas-liquid two-phase flow were examined by using Population Balance Model (PBM). The modeling results suggest that the formation and escape of different size bubbles could change the flow distribution at the upper tank, which would benefit the suspension of solid particles.