Local analysis of the tablet coating process: Impact of operation conditions on film quality

Modelling spray coating using a combined CFD–DEM and spherical harmonic formulation

“…Aerosol agglomeration and break-up modelling is also a highly active research area, involving complex interfacial physics (Qian and Law, 1997;Ashgriz and Poo, 1990). Agglomeration was neglected here, as the spray droplets were modelled outside the break-up zone near the nozzle (Suzzi et al, 2010), and were assumed to have subsequent trajectories sufficiently far apart for interactions between them to be minimal. Coating material often contains a solvent which progressively evaporates after the droplet has been produced.…”

“…After a spray droplet impacts a particle, coating material flows as a thin film over the surface. A complex computational model is required for even a basic version of this film flow over a single particle (Suzzi et al, 2010). Due to the high computational cost of modelling film flow for all particles in the system, a spreading model was not used.…”

“…Pharmaceutical applications typically require coating the active ingredients of tablets with thin polymer coatings. The homogeneity of the coating affects the delivery rate of the active material in the tablet and is therefore critical for calculating correct values for oral dosage (Suzzi et al, 2010). Other, less crucial, requirements for coatings in pharmaceutical applications include the cosmetic appearance of the final product and the need to mask the taste of unpalatable active ingredients (Turton, 2008).…”

“…Simulations and the Monte-Carlo model showed that preferred rotation axes of the particles within the drum delayed the 1= ffiffiffiffi N p trend towards homogeneous coating. An extremely detailed study of coating for different particle shapes has been carried out by Suzzi et al (2010), in which a single particle directly underneath a downward spray was modelled. The droplets in the spray were simulated using a 'parcel' technique, in which clouds of droplets were modelled as individual parcels.…”

Detailed analysis of air flow and spray loss in a pharmaceutical coating process

“…So far, computational investigations of coating processes have mainly concentrated on two aspects: the statistics of the tablet movement 7,8 and the local film formation on the tablet surface. 9,10 To our knowledge, apart from a work on the influence of different parameters on the spray shapes in a lab coater, 11 no work has been published focusing on the description of the drying air stream inside the coater and its influence on the spray.…”