E-mail: gt0360e@prism.gatech.edu
Areas: Phase Equilibria and Supercritical Fluids
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Name: Gregory J. Griscik E-mail: gt0360e@prism.gatech.edu Areas: Phase Equilibria and Supercritical Fluids |
1993-present Candidate for Ph.D. in Chemical Engineering. Expected graduation in September 1996. Research on the thermodynamics and morphology of crystals produced from the rapid expansion of supercritical solutions. Advisors: Dr. Ronald W. Rousseau and Dr. Amyn S. Teja. Minor in experimental statistical analysis.
1991-1993 M.S. Degree in Chemical Engineering. Graduated December 1993. Title: The Effect of Rapid Expansion Conditions on The Morphology of a Model Wax (n-Octacosane). Advisors: Dr. Ronald W. Rousseau and Dr. Amyn S. Teja.
NORTHWESTERN UNIVERSITY
Evanston, Illinois
1987-1991 B.S. Degree in Chemical Engineering with specialization in Process Optimization and Control.
Progress toward achieving the research goal continued from my Masters degree with RESS experiments at new conditions. The same solute - solvent system was used (n-octacosane - carbon dioxide) and a 2^4 factor design was implemented for different conditions of pre-expansion pressure, pre-expansion temperature, concentration, and nozzle configuration. The particle samples collected from these experiments were analyzed morphologically. Shape morphology was studied by observation from scanning electron microscope (SEM) pictures. Size morphology was measured through image analysis techniques and studied with the aid of statistical analysis. The morphology results eluded to the importance of knowing the path of expansion through the phase diagram.
Mathematical modeling of the fluid expansion through the different nozzle geometries was conducted in order to provide information about the path the solution follows. Modeling was done in two different ways. First, a finite step solution of the transport equations combined with a cubic equation of state was solved. This method was very similar to those used by other researchers in the literature. Second, a computational fluid dynamic package (Phoenics v2.1) was used to model the solution expansion. Phoenics seems to provided better results because it does not make the simplifications used in the finite step method. The Phoenics solution takes into account more detailed fluid property effects and solves the system of equations simultaneously over the entire geometry. Currently, only one dimensional solutions have been calculated.
In order to relate the results from the expansion simulations to the results of the RESS work, the phase diagram of the solution must be known for the regions in which the expansion paths travel. From the previously completed work, it is believed that a liquid-solution phase separation may occur before the final solidification of the solute. Therefore, the phase diagram will not only have to include the solid - fluid equilibrium lines but also the n-octacosane melt lines and possibly the liquid - liquid phase lines. Currently, work is being completed on measuring the n-octacosane melt line (three-phase line) in order to quantify the key regions of the phase diagram.
Once the key regions of the phase diagram has been quantified, conclusions about how the path of the expansions dictate the particle morphologies can be formulated. Ultimately, this will relate to how the RESS parameters affect particle morphology and thus achieving the goal of this research.
Griscik, G. J., R. W. Rousseau, and A. S. Teja, "Crystallization of Waxes From Supercritical Fluids" The Third International Workshop On Crystal Growth Of Organic Materials, Washington, D.C., August 27 - 31, 1995.
Griscik, G. J., R. W. Rousseau, and A. S. Teja, "The Morphology Of Long Chain Hydrocarbons Produced By The Rapid Expansion Of Supercritical Solutions" AIChE 1995 Annual Meeting, Miami Beach, Florida, November 12-17, 1995, paper 88d.
