FLUIDIZED-BED STUDY GRANULATION AND FILM COATING A NEW METHOD FOR THEINVESTIGATION OF THE COATING PROCESS ON A SINGLE SPHERE

The coating and granulation of solid particles in a fluidized bed is a process which converts pumpable and atomizable liquids (solutions, sl urries, melts) into granular solids in one step through drying. Althou gh this process has been applied in industry for several years, there is still a lack of understanding the physical fundamentals and the mec hanisms by which spherical granules are formed. Hence a new method was developed which allows the direct observation of the subsequent parti cle-forming mechanisms such as droplet deposition, spreading, wetting and drying. The authors will present a laboratory scale apparatus in w hich a single freely suspended particle can be coated under well defin ed and constant coating and drying conditions. With this device, parti cle-growth-rate and the development of particle morphology were measur ed and investigated under various experimental conditions.