Dependence of slurry characteristics on shape forming process of spray-dried granules

This study deals with the shape forming mechanism of granules spray-dried from alumina slurries whose dispersing system has been systematically controlled by adding nitric acid. Both the micro structure of granules and the slurry characteristics have been attentioned, in order to identify the main parameter governing the formation mechanism of granules. It is shown that the structure of spray-dried granules strongly depends on the degree of flocculation in the prepared slurry. Granules prepared from dispersed slurry are irregularly shaped and the majority of them are dimpled, while flocculated slurry results in essentially spherical and homogeneous granules. It is also shown that the shape forming process can be reasonably explained with invoking a shrinkage process of sprayed droplets.