Experimental Determination of Axial Mixing Effects in An RDC Column for the Evaluation of Scale-up Parameters

Thursday, November 11, 2010: 10:10 AM
253 A Room (Salt Palace Convention Center)
Bernhard Preisack, Thomas Gurker and Matthäus Siebenhofer, Department of Chemical Engineering and Environmental Technology, Graz University of Technology, Graz, Austria

Implementation of Computational Fluid Dynamics (CFD) in prediction of hydrodynamic parameters of a 150[mm] Rotating Disc Contactor (RDC) led to the need of validating the simulated findings with experimentally determined residence time distribution data. For that purpose an RDC-column of 150 mm diameter and 2.9 m active height was designed and set up. The residence time distribution (RTD) of the continuous phase was determined with a four sensor conductivity setup installed along the active height. Residence time measurements were carried out with and without dispersed phase at different total flow rate, constant phase ratio and different rotor speed. Analysis of the RTD data was done by nonlinear regression of the fit parameters according to the dispersion model. To increase flexibility and accuracy of analysis, the convolution integration was applied on the signal. Calculation and analysis of the axial dispersion coefficient of the continuous phase was compared with several established correlations [1], unexpectedly indicating significant deviation of the experimentally obtained data from correlations in the recommended operation range. Several correlations did fit well with experiments below and close to the lower limits of operation but failed within the operation range. Hence a new correlation for prediction of dispersion, covering the complete operational field, was deduced. Future prospect of the program is investigation of the RTD correlation as well as the CFD simulation code for RDC columns of different diameter between 80 mm and 400 mm.

[1] Kumar, A.; Hartland, S.: Prediction of axial mixing coefficients in rotating disc and asymmetric rotating disc extraction columns.; The Canadian Journal of Chemical Engineering 70 (1992), Nr. 1, 77-87.

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