(8c) Scale-out Concept for Falling Film Micro Reactors

Over the past years the standard falling film microreactor (FFMR) developed by our institute [1] was successfully used for numerous gas-liquid reactions in the laboratory scale [2-5]. In the context of the German public funded research project µ.Pro.Chem [6] two types of enlarged falling film microreactors were developed following different scale-out concepts for the pilot and production scale. These concepts differ in the principles of construction and in the extent of the internal numbering-up. The new developed falling film microreactors were investigated using the same test reaction as used for the IMM standard FFMR, an oxidation reaction. Comparable yields could be reached even at a tenfold higher flow rate when the flow rate was related to the structured area. In addition executed experiments resulted both in a good liquid equal distribution (mean deviation 7%) and also in a good gas equal distribution, since in a decoloration reaction experiment no bleached areas were visible. This could be reached by an advanced distribution system. In one set of experiments the oxidation of an organic compound was performed with a maximum conversion of 80%. This reaction is in analogy to a real-case industrial process undergone in parallel. The predictability of scale-out by increase in channels dimensions was tested using the Nusselt and the more advanced Kapitza and Feind correlations for calculating the film thickness. It was aimed to compensate the channel dimensional increase by adjusting the flow rate and number of channel in a way that according to theory the same film thickness results. However, experiments show varying conversion, which probably is due to varying film thickness. The latter is corroborated by experimental determination of the film thickness done by confocal microscopy recently [7]. In addition to investigations in our institute first tests with a pilot scale FFMR, reaching liquid throughputs up to 1 l/h, were successfully carried out in industry based on the results obtained with the Standard FFMR. The aim of the scale-out concept is to transfer the industrial used gas-liquid reaction from the lab scale to the production scale. In future these more experimental works will be supplemented by modeling and by correlations obtained from dimensional analysis.

References:

1. Wille, Ch., Dissertation, TU Clausthal, 2000 2. Jähnisch, K., Baerns, M., Hessel, V., Ehrfeld, W., Haverkamp, V., Löwe, H., Wille, C., Guber, A.,. Direct fluorination of toluene using elemental fluorine in gas/liquid microreactors. Journal of Fluorine Chemistry 2000, 105, 117?128. 3. Löb, P., Löwe, H., Hessel, V., Fluorinations, Chlorinations and Brominations of Organic compounds in Micro Reactors, Journal of Fluorine Chemistry 2004, 125 (11) 1677-1694 4. Zanfir, M., Gavriilidis, Wille, Ch., Hessel, V., Carbon Dioxide Absorption in a Falling Film Microstructured Reactor: Experiments and Modelling, Industrial Engineering Chem. Res. 2005, 44 1742-1752. 5. Jähnisch, K. et al., IMRET-9, 2006, Abstracts: ?Ozonation of Olefins in Micro-structured Reactors? and ?Multistep process for synthesis of pharmaceutical intermediates by ozonation and hydrogenation using micro chemical engineering with integrated fiber-optical diamond ATR sensor?. 6. BMBF project µ.Pro.Chem ?http://www.mstonline.de/foerderung/projektliste/detail_html?vb_nr=V3MVT021" 7. Yeong, K-K., Gavrillidis, A., Zapf, R., Kost, H-J., Hessel, V., Boyde, A., Characterisation of liquid film in a microstructed falling film reactor using laser scanning confocal microscopy, Experimental Thermal and fluid science 30(2006) 463-472.