The influence of particle interfacial energies and mixing energy on the mixture quality of the dry-coating process

We investigate the effect of particle interface energies and mixing energy input on the macroscopic behavior of the dry-coating process by using the discrete element method (DEM). It is observed that the quality of the coating process is governed by two dimensionless numbers: the Stokes number St (mixing energy/strength of agglomerates) and the reduced intermixing coefficient Λ (cohesion /adhesion strength). Three unfavorable and one favorable process regimes were identified, and represented in a regime map as a function of St and Λ. For low St and Λ, carriers are lumped and random mixing is fairly poor. For low St and high Λ, the agglomerates are merged together and remain intact. At high St, the fine-carrier adhesion breaks and creates abundance of debris. Between these regions process conditions are favorable as is supported by experimental evidences. Results of this study can be used to establish guidelines for efficient operation of the dry-coating process in a high-shear mixer.