STPI: Contact, mixing and micro-structured technologies

Leader: Joelle Aubin-Cano

Visualization of the generation of Taylor bubbles in microchannel – effect of the input geometry (air-ethanol dispersion, QG = QL = 0,8ml/min)

Understanding hydrodynamics to propose models and help the design

The activities of the theme focused on the understanding and characterization of local hydrodynamics, mixing and transfer phenomena in innovative equipment, such as microreactors and microstructured contactors, as well as in conventional devices (agitated reactors , static mixers) dealing with multiphase and complex fluids. Various experimental, numerical and modeling tools are used to qualify and quantify the phenomena. Significant progress has been made on the implementation of online measurements, such as Raman and near infrared spectroscopy and the application of particle image micro velocimetry (μPIV) to two-phase flows.

Velocity fields (measured by microPIV) in the liquid phase between two Taylor bubbles in microchannel.

New models with high capacity for innovation

Science of two-phase micro-scale flows

The study of two-phase flows – liquid-liquid and gas-liquid – are at the core research activities of this theme. These activities were carried out in regional, national and international frameworks (FERMaT Federation, ANR MIGALI (2010-2013), CNRS / ASRT projects (2009-2010, 2011-2012)). These works, both experimental and numerical, made it possible to explore the effects on local hydrodynamics of the geometry of the device, of the properties of fluids and of the operating conditions together with  its coupling with mass transfer phenomena. Through extensive experimental campaigns, based on sophisticated experimental techniques, such as μPIV [1] and digital image processing, characteristic times and lengths of the flows can be obtained. The consolidation of these data, inside a strong collaboration with the IMFT lab  around numerical simulation, has enabled the development of models for the prediction of bubble / drop size and mass transfer performance. One of  strong our contributions in this field lies in  the transfer  of rather fundamental data towards models and correlations allowing the design and the implementation of intensified processes (Theme Intensification Methodologies and Process Safety).

Analysis of the mixing  by three dimensions of segregation

Initiated in 2006, this work is carried out in collaboration with the University of Alberta (Canada). This resulted in a new definition of mixing based on three dimensions of segregation – intensity of segregation, scale of segregation and exposure – thus integrating the scales of concentration, length and time of the mixing process. The transposition of these variables, developed in the fields of demography and ecology, to applications in process engineering underlines the innovation of this approach. The theoretical definition is also supported by equations which describe the physical phenomena and by experimental measurements which make it possible to quantify the quality of the mixing.

Dissolved oxygen concentration fields measured by colorimetric technique

Directly linked to the other themes of the department

Supercritical microfluidics – This research work was developed in collaboration with researchers from the Supercritical CO2 processes team and the RAPSODEE lab (Albi) and through national projects (ANR mFSC (2009-2012) dedicated to  microfluidic systems and tcharacterization of supercritical flows.

Design and characterization of innovative interns – The design of microstructured interns has a primordial role for absorption or distillation processes where the development of high gas-liquid interfacial area and generation of film-like flow determine the process performance. An experimental bench with a rapid camera visualization technique were set up allowing the characterization of liquid film trickling on plates, a configuration representative of thein a counter current contactor.