Date of Award
Doctor of Philosophy (PhD)
This dissertation examines the application of optical probe techniques in two predominant multiphase reactors used for contacting gas and liquid phases: bubble column reactors and gas-liquid stirred tank reactors. Multiphase reactors are ubiquitous in industry, and for most processes, successful operation depends on successful inter- and intra-phase contacting and mixing. Extensive modeling and experimental research efforts have been made for better reactor design, modeling, and scale-up, yet, much remains unknown about the gas phase.
Optical probes offer significant advantages for gas phase dynamics measurements. Consequently, they have been adapted by numerous researchers around the world for detailed fluid dynamic investigations and model verifications. However, optical probes do possess a key disadvantage, the invasiveness that causes the measured parameters to show directional sensitivity.
Considering this often-overlooked disadvantage, this dissertation first details the development of the Optical Probe Probabilistic Model (OPPM), which turns the directional sensitivity into an advantage. The model makes use of simple logical assumptions and is gives novel information about bubble history that can be used for many things, e.g., sparger design, baffle design, and reactor modeling.
The application of the OPPM in a lab-scale bubble column reactors is then shown. For the (largest) mid-column zone, the results reveal the highest degree of gas phase backmixing in the transition flow regime. A plug flow reactor (PFR) like behavior, with the smallest degree of backmixing, was observed in the same zone for the homogeneous and heterogeneous flow regimes. For the entrance and exit zones, the gas phase dynamics showed very complex behavior that required case-by-case treatment.
Lastly, the dissertation discusses the usefulness of time-series analysis methods for optical probe measurements. In particular, it examines their use in lab-scale gas-liquid stirred tank reactors (STR) equipped with either a Ruston turbine (RT) or half circular blades disk turbine (CDT). The analyses reveals a physical local gas phase distinction between different global hydrodynamic flow regimes. These findings show the potential of optical probes as an industrial validation and control tool.
Milorad P. Dudukovic
Pratim Biswas, Renato Feres, Marcus Foston, Palghat A. Ramachandran,