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Modeling of the fermentation in an internal loop airlift reactor

The airlift reactors have potential application in biotechnology industries due to their simple construction and less shear stress imposed on shear sensitive cells compared with the mechanically stirred tanks. This work was focused on mathematical modeling of the fermentation process in an internal loop airlift reactor (IALR). Simulation results were verified on the fermentation of the gluconic acid by the strain Aspergillus niger which has been chosen as a model system. The fermentation was carried out in three laboratory IALRs (each one with different scale: 12, 40 and 200 dm, respectively) and performed in growth or non-growth conditions. Model of the ILALR incorporated the material balance of each compound taking part in reaction. In the reactor there are recognized four main parts: bottom, riser, separator and downcomer. Each zone of that reactor was modeled separately due to the different flow pattern and the mixing behavior. Parameters of the model, such as mass transfer coefficient of oxygen, gas holdups, and circulation velocities, were predicted using experimentally determined correlations. The results of the simulations and experiments are in sufficient agreement.