V.S. Buddhiraju, N.K.V. Nadimpalli, V. Runkana
TCS Research, Tata Research Development and Design Centre, A division of Tata Consultancy Services,
Keywords: nanoparticles, aerosol flame reactor, CFD, PBM, furnace reactor
Summary:Aerosol flame synthesis is one of the commonly used methods for producing nanoparticles on a large scale. Large volumes of ultra-fine materials such as titania, silica, carbon black and zinc oxide etc. are produced in industrial furnace reactors. Particle size distribution (PSD) is one of the important variables that determines the end use of product nanoparticles. For example, monodisperse titania nanoparticles with size less than 100 nm are required in pigments whereas polydisperse particles are frequently used in catalyst applications. The PSD strongly depends on flame dynamics inside the reactor, which in turn, is a function of input process variables such as reactant flow rate and concentration, flow rates of air, fuel, carrier gas and the burner geometry. A coupled flame dynamics-population balance model (PBM) for nanoparticle synthesis in an aerosol flame reactor is presented here. The flame dynamics was simulated using the commercial computational fluid dynamics software CFX to predict the gas phase temperature, velocity and species fields. These results are subsequently utilized by PBM to predict the particle size distribution. Design of the burner, configuration of the input streams and reactor operating conditions affect the flame dynamics and the physico-chemical phenomena inside the reactor, and hence the PSD. Various case studies for process design and scale up of a lab scale flame reactor and pilot scale furnace reactor for synthesis of titania, silica and carbon black will be presented. The model predictions were tested with published experimental data for flame temperature and particle size distributions. The model presented here will be useful for simulation of fine particle production in industrial furnace reactors and for studying design changes with respect to sizing of nozzles, location of heating elements and for identifying the correct location for introducing the coolant from the discharge end.