Award Number: 233708
Program(s): PARTICULATE &MULTIPHASE PROCESPROCESS & REACTION ENGINEERING
Start Date: 2/1/2003
Principal Investigator: Khinast, Johannes
PI Email Address: firstname.lastname@example.org
The PI's research during the last years showed that selectivity and yield of fast gas-liquid reactions strongly depend on the dynamics of single rising bubbles in a continuous phase, and not on the large-scale mixing patterns in a chemical reactor. High selectivity and yield are important for a chemical process, since it reduces byproduct formation, which is undesired. In order to study the effects of bubble dynamics and bubble swarm dynamics on chemical reactions, a computational simulation model will be developed. The model takes into account nonstationary bubble deformation, break-up, coalescence, heat effects and surfactant adsorption. The multi-fluid model is based on surface tracking techniques, augmented by an efficient CFD solver that was developed by the PI's group. Concentration and temperature fields are computed by solving mass and energy balances simultaneously with the hydrodynamic code. Variable surface tension is accounted for by a surfactant adsorption model and an accurate description of surface tension forces. In order to investigate the impact of bubble swarms dynamics on fast reaction systems, the PI will study specific reaction systems of industrial importance, i.e., (i) a simple two-step Bourne reaction (liquid -liquid), (ii) the stereo-selective iodohydroxylation step for the Merck HIV protease inhibitor Crixivan (liquid-liquid), and (iii) the liquid-phase oxidation of cyclohexane, which is a complex free radical reaction with multiple time scales (gas-liquid). All reactions are known to be fast and mixing-sensitive.
The work is of fundamental and practical interest, for instance in the areas of phase-transfer catalysis, gas-liquid reactions, reactive absorptions and extractions. Several national and international research groups study the hydrodynamics of bubbles and bubble swarms. However, there is no systematic work that addresses reacting bubble swarms, which will be the ultimate goal of this research. In summary, the PI will develop realistic two- and three-dimensional simulation models of reacting bubble swarms, which can be used to create the first micro-scale closures for fast reactions in multi-phase systems to be incorporated in the existing coarse-grid CFD packages. In addition, the simulations will provide an insight into complex processes that are not accessible through experimental techniques, e.g., for metallurgical reactions or opaque media.
The research will also have educational impact, including the training of one graduate students in a multi-disciplinary environment and the development of course modules for various undergraduate and graduate courses.