Scaleup of a pharmaceutical granulation in planetary mixers

The scaleup of a pharmaceutical granulation in a series of planetary mixers with increasing bowl capacity between 5 and 200 liters has been studied by applying the classical dimensionless numbers of Power, Reynolds, and Froude to define the power consumption profile of each mixer as a function of the processing conditions in dimensionless form. Experiments were performed using a formulation based on dicalcium phosphate dihydrate containing pregelatinized starch, with water being added at a fixed rate. Samples were taken at different power consumptions and assessed using mixer torque rheometry. Geometrically similar machines gave the same dimensionless relationship, but when similarity was compromised by the use of modified bowls and blades, different relationships occurred. The results show that, for geometrically similar machines, it is possible to calculate the power consumption at a predefined granulation endpoint at any given operating condition at any scale.