The Role of Moisture and Gap Air Pressure in the Formation of Spherical Granules by Rotary Processing

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Abstract
Spheroids are usually produced by a multi-step extrusion-spheronization 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 the formation and growth of spheroids and the changes in the spheroid moisture content in a single-step agglomeration-spheronization method. There was a rapid increase in size and formfactor values when spheroids started to form and grow from the powder mix. Although there was a continual and considerable loss of moisture with time, this did not have an appreciable effect on spheroid size and shape after the spheroid formation stage as the spheroid structure had already been determined. Spheroid size increased with higher liquid spray rates. The use of higher gap air pressures resulted in a greater rate of moisture loss and the production of smaller spheroids.