(77c) Experimental Study of Coating in a Bottom-Spray Fluidized Bed

The fluidized-bed coating of bulk solids is a widely used method for different processes and industries. Fluidized-bed coating (layering process) can be defined as a process which a layer of binder (solution, melt, suspension or powder) varying from a few microns to millimeters is formed on the surface of particles due to the solidification of binder. Several investigations have been devoted towards understanding the coating process in fluidized beds. However, most of the studies focused on spraying liquid droplets over the bed, which is not the best method to have a good quality coating in a fluidized bed coater. The present work aims to understand and predict the effect of different operating conditions on coating quality in a jetting fluidized bed with a spray of liquid droplets into the bed. The results showed that increasing the fluidizing gas flow rate and jet gas flow rate have a positive effect to achieve a better coating in this system, but there is a limitation for the binder flow rate which is dependent on the bed size and jet gas flow rate. Also based on the experimental results an empirical function was derived to predict the coating efficiency in different operating conditions.