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1989
Book
Titel
Influence of hydrodynamics and kinetics on performance of lactic acid concentration by electrodialysis
Abstract
One of the urgent problems in performing a continuous fermentation is the separation of inhibitive metabolites. Electrodialysis offers a possible solution for the continuous separation of ionic substances, as organic acids. To make such a coupled process feasible, the operating parameters must be known and described by a model. To set up a mathematical model, the influences of hydrodynamics and kinetics on the electrodialytic process is investigated with sodium lactate as a model substance. The hydrodynamics in the stack and the critical flow condition are determined by an electrochemical method and found to be dependent on temperatures and the dimensions of the flow channel. The mass transfer coefficient, expressed as a modified Nusselts number, is weakly influenced by the Reynolds number in the laminar region, while the influence of Schmidt number is approximately similar in both laminar and turbulent regions. Mass transfer studies are carried out at critical conditions of mass trans fer. Kinetics of the concentration is studied by batch experiments. The change in the transfer rate from the feed decreases as the concentration in the concentrate increases. The kinetics of the lactic acid concentration is found to be quadratic. It is independent of Reynolds number and inversely related with Schmidt number.