THESIS OF Luca Gemello*

Bubble flows are widely used in the chemical and biotech industries, since they are an easy way to introduce gas reactants into a liquid medium. In all these
industrial cases, knowing the bubble size is essential to the dimensioning of reactors since it is this that governs hydrodynamics and transfer of reactants.

Predicting the size and distribution of bubbles in reactors and fermenters is traditionally based on empirical correlations that, by nature, cannot be transposed from one geometry or system to another.

To overcome this, a multi-physical and multi-scale modeling approach was developped, incorporating physical bubble breakup and coalescence models
into a population balance modeling. The combined use of CFDa and a QMOMbmethod, results in reduced calculation times(1), a major issue in the industrial context.

The complete model was validated on a variety of flow geometries and operating conditions(2). It represents a major advance for the prediction of bubble size in large-capacity industrial reactors and fermenters.

Figure L. Gemello
Prediction via the calculation of bubble diameters and
comparison with experimental data (Ø 400 mm bubble
columns, water-air system).

It is currently being extended to non-Newtonian rheology systems, such as fermentation broth, involved in biofuel production.

a - Computational Fluid Dynamics.
b - Quadrature Method Of Moments.

*Thesis entitled "Hydrodynamic modeling of bubble columns using an approach combining two-fluid models and a population assessment"

(1) L. Gemello, V. Cappello, F. Augier, D. Marchisio, C. Plais, Chemical Engineering Research and Design, 2018, 136, 846-858.

(2) L. Gemello, C. Plais, F. Augier, D. Marchisio, Chemical Engineering Journal, 372, 2019, 590-604.

Scientific contacts: cecile.plais@ifpen.fr - Frédéric Augier