The formation mechanism of granules in spray drying process was investigated by DEM-CIP method simulation coupled with a new binder segregation model. To confirm the validity of proposed binder segregation model, experiment on drying of aqueous slurry containing fine particles and binder was performed. The experimental concentration distribution of binder in a dried powder bed agreed well with the simulated one and this result shows that the proposed segregation model is valid to represent segregation phenomenon in the dried granule. Spherical hollow granules were formed with increasing the binder concentration, and the granules were dimpled at a higher concentration of binder. When the binder concentration in the surface region of a slurry droplet increased during drying, a shell of granule was formed because particle migration was inhibited by high fluid viscosity. For the rigid shell, granules were hollow. When the shell was formed early in drying and its thickness was thin, granule surface partially collapsed inward, whereas the granule resulted in sinking granules.
