Nanoprecipitation in Turbulent Liquid-Phase Vortex Reactors: A Fundamental Investigation of Scale Up Using Experimentally Validated CFD Models

Iowa State University, Ames IA

Investigators

Abstract

0932978 Olsen The production of uniform-sized nanoparticles from hydrophobic organic compounds by an economical, scalable process is very challenging. One of the most advanced processes to produce functional nanoparticles of precisely controlled size is Flash NanoPrecipitation, which requires very fast mixing of two or more streams to create uniform supersaturation. Presently, Flash NanoPrecipitation has only been demonstrated in microscale reactors with small production runs. This limitation is only suitable for selected applications, such as the production of high-value pharmaceutical agents. Other applications, such as the manufacturing of nanoparticles used in pesticides and cosmetics, will require much larger production runs, making microscale reactors economically unrealistic. For this reason the fluid dynamics and scalar transport processes associated with scale up Flash NanoPrecipitation to macroscale reactors capable of generating large quantities of functional nanoparticles will be investigated using a combined experimental and modeling approach in this research project. A fundamental understanding of rapid precipitation requires a detailed knowledge of the roles of macro, meso- and micromixing on the development of supersaturation, and the scalability of the processing conditions needed for Flash NanoPrecipitation (e.g. millisecond micromixing) is an open question that will be addressed here. To answer this question, turbulent reactive mixing in a macroscale multi-inlet vortex mixer (MIVM) reactor will be studied using non-intrusive optically based measurement techniques, and the results from these experiments will be used to develop and validate computational fluid dynamics (CFD) models of the mixing and reaction processes. The experimental techniques will include time-correlated (high-speed) stereo particle image velocimetry (SPIV), passive scalar and reactive planar laser induced fluorescence (PLIF), and simultaneous PIV/PLIF. The CFD models will be based on large eddy simulations (LES) and transported probability density function (PDF) models solved using the direct quadrature method of moments (DQMOM). Once developed and validated, these CFD models can be used by the chemical process industry as engineering tools for optimizing reactor design and operating parameters to produce customized functional nanoparticles in plant-scale MIVM reactors. Intellectual Merit: The development of computational models of turbulent reacting flows, especially in complex swirling geometries such as in a vortex reactor, is an important technical and intellectual challenge. For example, none of the subgrid scale closures for the chemical source term in CFD models of turbulent reacting flows have been fully validated for complex liquid-phase reacting flows due to a lack of detailed experimental data for the local velocity and concentration fields in well-defined reactor geometries. Broader Impact: Flash NanoPrecipitation shows promise for producing uniform-sized functional nanoparticles of organic compounds. However, this process has only been demonstrated in microscale reactors capable of producing only very small production runs. Scaling up the Flash NanoPrecipitation process to a macroscale MIVM reactor could greatly increase the commercial viability of this process for manufacturing a wider range of valuable end products. This project will also train students in state-of-the art engineering tools for scale up and design of chemical reactors.