An investigation into the effects of binder viscosity on agglomeration behaviour

A study is reported of the effects of binder viscosity and size of the constituent particles on agglomeration behaviour using a high shear mixer. Silicone fluids having viscosities in the range 0.001-56 Pa s were used as the binder liquid and non-porous calcium carbonates having mean particle sizes in the range 8-230 mu m were used as the solid. Both the size of the constituent particles and the viscosity of the binder were found to affect the agglomeration process. The liquid to solid ratio was independent of binder viscosity up to a critical value (of the order of 1 Pa s). Above this value the maximum liquid to solid ratio was increased. To form granules, a minimum binder viscosity was required, which increased with size of the constituent particles from 1 mPa s with 8 mu m particles to 1 Pa s with 230 mu m particles. Existing theories on the effects of material properties on agglomeration are reviewed and shown to represent some aspects of the observed behaviour. The theories did not, however, adequately predict the effect of binder viscosity on granule formation. A new analysis is proposed which provides an order-of-magnitude prediction of the minimum binder viscosity required.