Three-Dimensional CFD-Population Balance Simulation of a Chemical Vapor Synthesis Reactor for Aluminum Nanopowder: Nucleation, Surface Growth, and Coagulation

A chemical vapor synthesis (CVS) process for synthesizing aluminum nanopowder as a reactant for various hydrogen-storage materials was simulated using a mathematical technique that combines computational fluid dynamics (CFD) with the population balance model. In this process, aluminum powder is produced by reacting aluminum chloride with magnesium in the vapor phase. The CFD model solves the three-dimensional (3-D) turbulent governing equations of fluid flow, heat and mass transfer, and chemical kinetics in a multiphase domain. The population balance model incorporates nucleation, surface growth, and coagulation. The nucleation rate is computed using an expression from the classical nucleation theory. The growth rate is obtained by the combined effect of vapor condensation and coagulation. A comparison of the model predictions with the available experimental data showed good agreement under different operating conditions without the need of adjustable parameters. According to the results, the final particle size is determined by particle coagulation in this particular CVS process. The new model proposed in this article can be applied to other similar systems with confidence even without the need of any experimental data and can be used for scale-up of the process.