In chemical- and bioprocess 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 reactions can lead to a considerable potential for optimization of the yield and selectivity. Thus, transport processes in the boundary layer and close to the interphase in bubble flows with a following reaction are experimentally determined and subsequently modelled from the micro- to the macro-scale. Especially the influence of dynamic interface deformation of the bubbles, due to shape dynamics (wobbling), the momentum exchange at the gas-liquid interface (swarm turbulence) and bubble collisions (bouncing) are considered. To accurately observe and model the local transport processes near the phase boundary and within the wakes, different measurement techniques are applied to detect local three-dimensional flow field as well as three-dimensional concentration fields with high temporal and spatial resolution from the micro- to the macro-scale.
Group leader: Felix Kexel, M.Sc.
Fine bubbles and ultrafine bubbles
Bubble size distributions
Pressurized multiphase systems
Identification and overcoming of mass transfer limitations
High-performance multiphase reactors
DFG Project SCHL 617/27-1 and LI 899/19-1: "Fine Bubbles for Biocatalytic Processes: Microscale Phenomena and Novel Applications"
DFG Project SCHL 617/29-1: "Mixing structures in bubble wakes of single bubbles and bubble swarms and their influence on gas-liquid mass transfer and chemical reaction"
DFG SPP 1740: "Experimental Investigation of Reactive Bubbly Flows - Influence of Boundary Layer Dynamics on Mass Transfer and Chemical Reactions"
Federal Ministry of Education and Research (BMBF), grant number 031B0405A: “Protein Pressure Stability Impact (Prot P.S.I.)”
SFB 1615 “SMART Reactors”
Industrial projects (confidential)