Scale-up of aerobic bioreactors by Eulerian and Lagrangian approaches – TRABOULE

TRAjectory Based Optimal UpscaLing of biorEactors

This project aims to improve the scale-up tools for industrial aerobic bioreactors. The reduction of greenhouse gases emissions is based, among other solutions, on the decarbonation of industries, and especially of the production of chemicals and fuels (including SAF). In this regard, biotechnologies make it possible to replace some fossil-based chemicals and fuels with bio-based alternatives produced by selective and energy-efficient fermentation processes. However, the scale-up of bioreactors is a non-trivial task, for which CFD has been identified for years as a promising extrapolation tool, replacing empirical correlations that are too imprecise. But its use remains limited by the difficulty of predicting the properties of gas-liquid systems such as the size of bubbles, their velocity, and their trajectories, especially in complex fermentation environments.
The proposed strategy is based on 2 major originalities. From an experimental point of view, it is proposed to investigate the properties of the gas phase of some aerated stirred tanks over a wide range of scales, i.e., from 20L to 15m3, taking advantage of existing experimental setups at IFPEN and TU Hamburg. From a numerical point of view, Lattice-Boltzmann modelling will be used to follow the evolution of a realistic large number of bubbles (up to several millions) in a Lagrangian framework. This rigorous digital twin will allow us to analyse bubble trajectories in pilot-scale stirred tanks, which in turn will serve as a basis for validating or improving the closure laws employed in Euler/Euler RANS CFD models. Such Euler/Euler approaches are less spatially resolved but capable of simulating bioreactors at industrial scale. The validation of the improved Euler/Euler approach will be carried out in the 15m3 setup available in TU Hamburg.