Fine Bubbles for Biocatalytic Processes

The rising demand in process engineering for aeration with high mass transfer performance with low pressure drop, low shear stress and avoidance of foaming opens an interesting field for new technologies. One possibility to achieve these goals is the aeration with fine bubbles whose diameter is less than 100 micrometers. In Japan, many applications of fine bubbles can be found and several companies have been established that are offering fine bubble generators (FBG) and analyzing devices for fine bubbles. In 2013, the technical committee for Fine Bubble Technologies (FBT) was established and approved by the Organization for Standardization (ISO). In Germany fine bubbles are known at the most in connection with flotation processes but their potential for mass transfer in two phase flows has not been addressed so far. Especially the question of physical properties and effectiveness has not been answered satisfactorily. Several authors are reporting a lifetime of fine bubbles in the range of several weeks and months, which is much longer than the predicted one. This effect is discussed very contradictorily and attributed to contaminations or surface charging. Nevertheless, the introduction of small-sized bubbles leads to large volume-specific interfacial areas and therefore to high mass transfer rates. The strong collaboration between Germany and Japan in the field of Multiscale Multiphase Process Engineering (MMPE joint conferences 2011 and 2014, supported by the DFG) provides a unique possibility to intensively exchange knowledge about fine bubbles and its applications between Germany and Japan and enables efficient research in this emerging field of technology. This project is intended to investigate the potential of fine bubbles for biocatalytic processes. High mass transfer performance, negligible two-phase pressure drop and shear stress as well as the avoidance of foaming and reactant evaporation are the most promising advantages of fine bubble aeration in comparison to conventional systems. While the measurement methods of the Institute of Multiphase Flows will provide a deep insight into hydrodynamics and mass transfer processes in fine bubble two-phase flows with high temporal and spatial resolution, the reaction engineering expertise and knowledge in biocatalysis of the Institute of Technical Biocatalysis will enable the detailed investigation of the effect of fine bubbles on biocatalytic reactions in stirred tanks as well as packed bed reactors. For the transfer of knowledge, Prof. Koichi Terasaka from Keio University, Japan is intended to join the project as Mercator Fellow. Furthermore, an intensive scientific exchange of students, PhD students and professors between Keio University and TUHH will foster research between the Universities and the presentation of results at the next International Symposium of MMPE 2017 in Toyama, Japan, is intended to motivate further initiatives related to research on fine bubbles.

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