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Influence of hydrodynamics and kinetics on the performance of lactic acid concentration by electrodialysis

Einfluß von Kinetik und Hydrodynamik auf die Aufkonzentrierung von Milchsäure mit Hilfe der Elektrodialyse
: Bauer, W.; Murdia, L.K.; Rehmann, D.

Spiess, W.E.L.; Schubert, H.:
Engineering and Food. Proceedings of the Fifth International Congress. Vol.3: Advanced processes
London: Elsevier Applied Science, 1990
ISBN: 1-85166-467-X
S.253-262 : Abb.,Lit.
International Congress on Engineering and Food <5, 1989, Köln>
Fraunhofer ILV ( IVV) ()
Aufkonzentrierung; concentration; electrodialysis; Elektrodialyse; hydrodynamics; Hydrodynamik; lactic acid; mass transfer; Maximalkonzentration; maximum concentration; Mehrelektrodenprozeß; Milchsäure; multi-electrode-system; Stofftransport

One of the urgent problems in performing a continuous fermentation is the separation of inhibitive metabolites. Electrodialysis offers a possible solution for the separation and inhibitive metabolites. Electrodialysis offers a possible solution for the separation and concentration 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 model, the influence 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 conditions are determined by an electrochemical method and found to be dependent on temperature and on the dimension of the channel. The mass transfer coefficient, expressed as a modified Nusselts number, is wealdy influenced by the Reynolds number in the laminar region, but strongly in the turbulent, while the inluence of Schmidt number is approximately similar in both. Kinetics of the concentration is studied by batch experiments. The change in 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.