CFD model of a spinning disk reactor for nanoparticle production

The use of a spinning disk reactor (SDR) was investigated for the continuous production of nanoparticles of hydroxyapatite. SDR is an effective apparatus for the production of nanoparticles by wet chemical synthesis. Rotation of the disc surface at high speed creates high centrifugal fields, which promote thin film flow with a thickness in the range 50-500 ?m. Films are highly sheared and have numerous unstable surface ripples, giving rise to intense mixing. SDR performances are strongly affected by the adopted operating conditions such as the influence of rotation speed that determines the attainment of micro-mixing and the feeding point location that has a great influence on the particle size distribution of the product. The experimental device consists of a cylindrical vessel with an inner disk, 8.5 cm in diameter, made by PVC coated by an acrylic layer. The rotational velocity of the disc is controlled and ranges from 0 to 147 rad/s. The reagent solutions are fed over the disk at a distance of 5 mm from the disc surface through tubes, 1 mm in diameter. A computational fluid dynamic model, validated in a previous work, was used to optimize the operative conditions of SDR. Through the CFD model it is possible to analyse the hydrodynamic of the thin liquid film formed on the disk at different speed rotations and to individuate the best mixing conditions between the reagents varying the feeding point positions. The production of hydroxyapatite was also investigated adding the reaction kinetic to model the product formation in the liquid phase and the population balance equation to predict particle size distribution. The simulation results were compared with available experimental data showing that the CFD model is fully capable to describe the process and qualifies as a suitable engineering tool to perform the SDR process design. Copyright © 2015, AIDIC Servizi S.r.l.