Congratulations to Woo Xing Yi, Winner of the 2005 AIChE Separations Division Graduate Student Award

We are pleased to announce that Ms. Woo Xing Yi, a student under the NUS-UIUC Joint PhD Program under the supervision of Prof Richard D. Braatz from UIUC and Assoc Prof Reginald B. H. Tan from NUS, is the winner of the 2005 AIChE Separations Division Graduate Student Award in the area of Crystallization and Evaporation. The manuscript submitted for the award is titled “Simulation of Mixing Effects in Antisolvent Crystallization using a Coupled CFD-Micromixing-PBE Approach”. This is a highly competitive award with a global request for nominations. The award is sponsored by Cargill and AIChE Separations Division. It comprises a $300 check and a plaque for the student as well as a recognition plaque for the student’s advisor. The award was presented at the Separations Division’s Dinner on Monday, October 31st, 2005 at The Hilton Netherland Plaza Hotel in Cincinnati, Ohio, USA.

The goal of Xing Yi’s research is to develop algorithms to gain first principles understanding of the interaction between hydrodynamics and crystallization. This will allow us to develop systematic strategies for the design and optimization of the crystallization process, which is an important downstream process in the pharmaceutical industry. The abstract of the manuscript is:

"Antisolvent crystallization is widely used in the production of pharmaceuticals. Although it has been observed experimentally that the crystal size distribution is strongly influenced by the imperfect mixing of the antisolvent with the solution, these effects have not been adequately quantified. In this work, a turbulent computational fluid dynamics (CFD) code was coupled with a multi-environment probability density function (PDF) model, which captures the micromixing in the subgrid scale, and the population balance equation, which models the evolution of the crystal size distribution. The population balance equation (PBE) was discretized along the internal coordinate using a high-resolution central scheme. The presence of solids was addressed by treating the suspension as a pseudo-homogeneous phase with a spatial variation in the effective viscosity. This coupled CFD-PDF-PBE algorithm was applied to an antisolvent crystallization process in an agitated semibatch vessel, where the rising liquid level was modeled by a dynamic mesh. The effects of agitation speed, addition mode, and scale-up on the local primary nucleation and size-dependent growth and dissolution rates, as well as the crystal size distribution were numerically investigated.