THE ROLE OF MOISTURE AND GAP AIR-PRESSURE IN THE FORMATION OF SPHERICAL GRANULES BY ROTARY PROCESSING

Spheroids are usually produced by a multi-step extrusion-spheronizatio n process. The single-step production of spheroids may be carried out in a rotoprocessor. The use of feed materials in powder form requires an adaptation of the spheronizer machinery. This study investigates th e formation and growth of spheroids and the changes in the spheroid mo isture content in a single-step agglomeration-spheronization method. T here was a rapid increase in size and formfactor values when spheroids started to form and grow from the powder mix. Although there was a co ntinual and considerable loss of moisture with time, this did not have an appreciable effect on spheroid size and shape after the spheroid f ormation stage as the spheroid structure had already been determined. Spheroid size increased with higher liquid spray rates. The use of hig her gap air pressures resulted in a greater rate of moisture loss and the production of smaller spheroids.