Institute of Multiphase Flows

Project within the Priority Project 1740

"Experimental Investigation of Reactive Bubbly Flows - Influence of Boundary Layer Dynamics on Mass Transfer and Chemical Reactions"

2nd funding period: From Nov. 2017

In chemical process engineering often a gaseous substance has to be mixed with a continuous liquid phase in order to perform a reaction with high yield and selectivity (e.g. oxidation or hydrogenation). For this purpose, the use of well mixed bubble flows is preferred, in which the gaseous phase is dispersed in the liquid phase. The timescales of mixing are especially determined by the transport processes in the boundary layer close to the phase boundary and by the bubble swarm-turbulence. Tuning the transport timescales and the timescales of the chemical reactions can lead to a considerable potential for optimization of the actual yield and selectivity. For example, the influence of mixing behind bubbles of wake and bulk phase, like seen exemplary in Fig.1 for Taylor bubbles, could lead to differences in selectivity for competitive consecutive or competitive parallel reactions. 

Finished Project in DFG Priority Project 1506 

"Experimental investigation and modeling of local mass transfer rates in pure and contaminated Taylor flows"

2nd funding period from August 2013 - Juli 2016

For a process optimization, a deep understanding of  local transport processes at the fluidic interphases is essential. In Priority Programme SPP1506 "transport processes at fluid interfaces" of the DFG, these transport processes are investigated under defined conditions at single Taylor Bubbles rising in vertical channels. Those Taylor bubbles show the unusual behavior of a volume independent rise velocity and can be kept in the observation area by a constant counter-current flow. This enables to investigate the global and local transport processes during the dissolution process of gas bubbles in channels with Highspeed Particle Image Velocimetry and Highspeed Laser Induced Fluroescence. Concentration fields of dissolved gases can be visualized and measured with Fluorescent dyes, which are sensitive to the dissolved gas species. The hydrodynamic condition at the interphase are investigated by measuring the deposition of fluorecence particles, which follow the streamlines of the fluid. These techniques give new insights into the coupling of hydrodynamic and mass transfer at gas/liquids interphases. Process additives or unwanted contamination of impurities are often surface active and can influence the transport processes across the interface locally in different ways. In dependence of the concentration and ad-/desorption kinetics of the surface active agents (Surfactants), molecule layers can occur at the bubble interfaces. These layers can change the slip condition at the interface, which reduce the internal gas circulation and the external liquid velocity at the interface and therefore the convective transport.  Nevertheless, a molecule layer of surfactants is an additional diffusion resistance for the gas specie, which reduces the local mass flux as well. In this Project, we focus on the influence of Surfactants on the local and global transport phenomena, which lead to new insights into the complex coupled transport processes in multiphase reactors.

 This project is supported by the German Research Foundation (DFG) within the priority program

 DFG SPP 1506

Publications:

Sven Kastens on ResearchGate

Paper:

[4] Tanaka, S.; Kastens, S.; Fujioka, S.; Schlüter, M.; Terasaka, K.: Mass transfer from freely rising microbubbles in aqueous solutions of surfactant or salt, Chemical Engineering Journal, 2019, accepted, article in press, DOI: 10.1016/j.cej.2019.03.122. 

[3] Kastens, S.; Timmermann, J.; Strassl, F.; Rampmaier, R. F.; Hoffmann, A.; Herres-Pawlis, S.; Schlüter, M.: Test system for the investigation of reactive Taylor bubbles. Chem. Eng. Tech., 2017, 40(8), pp. 1494-1501, DOI: 10.1002/ceat.201700047 

[2] Iwakiri, M., Koichi T., Fujioka, S., Schlüter, M., Kastens, S., Tanaka, S.: Mass Transfer from a Shrinking Single Microbubble Rising in Water.  Japanese Journal of Multiphase Flow, 2017, 30(5),pp. 529-535, DOI:10.3811/jjmf.30.529

[1] Kastens, S.; Hosoda, S.; Schlüter, M.; Tomiyama, A.: Mass Transfer from Single Taylor Bubbles in Mini Channels, Chemical Engineering & Technology, 2015, 38(11), pp. 1925-1932, DOI: 10.1002/ceat.201500065.

Chapter in Books:

Kastens, S.; Meyer, C.; Hoffmann, M.; Schlüter, M.: Experimental Investigation and Modelling of Local Mass Transfer Rates in Pure and Contaminated Taylor Flows, in Transport Processes at Fluidic Interfaces (ISBN 978-3-319-56602-3), Bothe, D.; Reusken, A. (Eds.), Advances in Mathematical Fluid Mechanics, 2017, DOI: 10.1007/978-3-319-56602-3_21

International Oral Presentations:

19^th International Symposium on Application of Laser and Imaging Techniques on Fluid Mechanics, 2018, Lisbon, Portugal: „Influence of Boundary Layer Deformations of Mass Transfer and Chemical Reactions"; Sven Kastens, Jens Timmermann, Marko Hoffmann, Michael Schlüter

8^th European-Japanese Two-Phase Flow Group Meeting, 2018, New York, USA: „Experimental Investigation of Reactive Bubbly Flows - Influence of Boundary Layer Deformations of Mass Transfer and Chemical Reactions"; Sven Kastens, Jens Timmermann, Marko Hoffmann, Michael Schlüter

3^rd  International Symposium on Multiscale Multiphase Process Engineering, 2017, Toyama, Japan: „Characterization of reactive bubbly flows by means of reactive Taylor bubbles", Sven Kastens, Jens Timmermann, Florian Strassl, Robert F. Rampmaier, Sonja Herres-Pawlis, Michael Schlüter

Symposium on Non-Invasive Measuring Tools and Numerical Methods for the Investigation of Non-Reactive and Reactive Gas-Liquid Flows, FERMaT-SPP1740 Symposium Toulouse 2016, France: "PIV and LIF measurements for the investigation of mass transfer in clean & contaminated Taylor Flows"

9^th International Conference on Multiphase Flows, 2016, Florence, Italy: „LOCAL MASS TRANSFER PHENOMENA AT SINGLE TAYLOR BUBBLES IN A VERTICAL MINI CHANNEL“, Sven Kastens, Jiro Aoki, Chiara Pesci, Holger Marschall, Kosuke Hayashi, Michael Schlueter, Dieter Bothe, Akio Tomiyama

6^th International Workshop on Bubble and Drop Interfaces, 2015, Potsdam-Golm, Germany: „Experimental investigations of global & local mass transfer phenomena at single CO₂-Taylor bubbles in vertical channels“, Sven Kastens

2^nd International Symposium on Multiscale Multiphase Process Engineering, 2014, Hamburg, Germany: „Mass transfer from single Taylor bubbles in a mini channel“, Shogo Hosoda, Sven Kastens, Michael Schlüter, Akio Tomiyama

52^nd European Two-Phase Flow Group Meeting, 2014, Dresden, Germany: „Mass transfer from single Taylor bubbles in a mini channel“, Sven Kastens, Shogo Hosoda, Michael Schlüter, Akio Tomiyama