Optimization and tracking of coating processes of pellets with polyvinylpyrrolidone solutions in an acoustic levitator

The purpose is to present the application of the acoustic levitation as a model system for a coating process with non-spherical and light particles in the fluidized bed reactor. An acoustic levitator has been used to track a pellet in a contactless position by Raman spectroscopy, while it was coated with polyvinylpyrrolidone by an ultrasonic nozzle. The Raman data were evaluated by a principal component analysis and a multivariate curve resolution. The pellets had a maximum size of 1.0 mm. To develop an optimization model, a design of experiments was performed in the acoustic levitator. The obtained optimization model demonstrated that the mass fraction of polyvinylpyrrolidone in the coating solution, the temperature and the optional air stream affected the coating thickness. To validate the optimization model, the pellets were coated in the acoustic levitator and in a fluidized bed reactor under the same conditions. The coated pellets had similar morphologies.