One of the important challenges in nanomaterials production is scaling up laboratory processes to the industrial scale. Mathematical modeling is an integral component of our research strategy, both for process scale-up and design and for process optimization and control, depicted schematically below for a flame aerosol reactor for the production of titanium dioxide.
Many commodity chemicals and materials such as titanium dioxide, carbon black, silica and zinc oxide are produced in the form of fine powers in aerosol flame reactors. They are used in a wide variety of industrial and domestic products ranging from tyres, printing inks, paints, plastics, optical fibers, catalysts, pharmaceutical powders and cosmetics. The process is characterized by high temperatures and extremely small reactor residence times. Optimal design and operation of aerosol flame reactors is essential for producing particles with a narrow size distribution and high specific surface area, besides desired chemical composition. The product particle size distribution (PSD) depends strongly on flame dynamics inside the reactor. In order to predict PSD as a function of reactor operating conditions, it is necessary to integrate a particle population balance model for PSD with a computational fluid dynamics (CFD) model for flame dynamics. We have developed a coupled flame dynamics – population balance model for nanoparticle synthesis in high temperature aerosol flame reactors.
Concurrently we are also exploring synthesis of nanoparticles through the low temperature microemulsions route. Our objective here is to develop strategies for scaling up the process to produce monodisperse and very small nanoparticles of temperature sensitive materials as well as materials that cannot be produced via the flame aerosol synthesis route. We have developed and validated population balance models for evolution of nanoparticle size distribution with time and have also initiated experimental studies for scale-up.
We are also exploring the feasibility of scaling up nanoparticle production through high energy milling using equipment such as stirred media mill and planetary mill. We have already produced nanoparticles of alumina, titania and zirconia in kilogram quantities through this route and identifying critical parameters for scale-up.