Modelling the breakage stage in spheronisation of cylindrical paste extrudates

Spheronisation of cylindrical extrudates on a rotating friction plate involves breakage and rounding. Little attention has been given to the breakage stage and quantitative modelling of this process is scarce. Two simple models are compared with experimental data obtained for the early stages of spheronisation of microcrystalline cellulose/water extrudates. Tests were conducted for different times (t), rotational speeds (ω), initial loadings and on pyramidal friction plates with different dimensions. The first model, describing the number of pellets, validated ω3t as a characteristic time scale for the breakage stage. The kinetic parameters obtained by fitting showed a systematic dependence on plate dimensions expressed as a scaled gap width. The second model, a simple population balance, described the evolution of the number and length of pellets. The pseudo rate constants provided insights into the kinetics: extrudates tended to break near the middle, while breakage of smaller pellets was slowed down by more pellet‐pellet collisions.