Granulation of superphosphate in a rotary drum

Abstract Using water as a binding agent, some of the factors affecting the preparation of superphosphate granules have been investigated. The amount of water added to the material completely dominates the other physical variables in determining the characteristics of the granules formed. An optimum water content was found for which the proportion of granules within a specified size range (–4 + 14 Tyler mesh) was at a maximum. Granulation with simultaneous drying showed that an increase in the drying rate results in a decrease in the rate of granule growth. The speed at which the granulator is rotated to obtain the correct “tumbling action” is influenced by the internal surface of the drum and the presence and design of internal flights. The mechanical strength of superphosphate granules depends on the quantity of binding agent used in the granulation process and the degree of agitation. The dry strength of the granules formed is considerably greater than the wet strength.