Design and optimization of stirrer and mixer design for the correct mixing of pharmaceutical powders through DEM

Mixing of granular materials is an important process for pharmaceutical industries. In this study, a quantifiable calculation method was suggested to determine the final mixing degree of the mixture. Based on that, the effect of the stirrer design, rotational speed, powder density, cohesivity, material ratios, and particle movement in the chamber guided through different designs of deflectors on the final mixing quality is examined. The results show that increasing the stirring speed, generates better mixing quality. However, introducing a varying rotational speed mode improves the mixing degree specially for binary mixtures with high relative densities. The improvement of the mixing with the number of contacting blades is observed. Finally, the introduction of a simple deflector drastically enhances the mixing quality and enables the feeding into the chamber, which is key for continuous operation with cohesive powders, making the process more stable and efficient by using more of the mixing volume. • Development of a numerical method for quantifying the mixing quality was shown to be robust. • UV/Vis Spectroscopy was used to validate the numerical results. • Adding one deflector to the mixer can lead to a significant influence on the powder behavior. • Using different rotational speeds within the single mixing process can be more advantageous than using a unique speed scheme. • Correlations between the boundary conditions and material properties should be considered to get the best mixing degree.