Influence of the particle size on the microstructure and mechanical properties of grains containing mixtures of nanoparticles and microparticles: Levitator tests and pilot-scaled validation

The spray drying process is used in many industrial applications. However, different grain properties can be desirable depending on the later use of the powders produced. In this work the influence of the particle size on the particle packing fraction and the mechanical strength of grains containing silica nanoparticles, microparticles and their mixtures, was analyzed. Single droplet tests were carried out in an acoustic levitator at 120 °C. The shell thickness was calculated using the fluidity limits obtained from the modelling of the viscosity data. Results obtained showed good agreement with the experimentally measured ones. The addition of nanoparticles and high pH values produce an increase in the mechanical strength of the grains. Finally, different suspensions were dried in a pilot-scaled spray dryer. The results obtained for the mechanical strength of the spray died powders confirm the results obtained in the levitator test.