(81a) Isolating Rate Processes in Spherical Agglomeration: An Investigation of the Breakage Mechanism Using a Contracting Nozzle

Authors: 
Smith, R. - Presenter, The University of Sheffield
Mohd Yusoff, S. N., University of Sheffield
Pitt, K., University of Sheffield
Arjmandi-Tash, O., The University of Sheffield
Litster, J. D., The University of Sheffield
Spherical agglomeration is a size enlargement process in which crystals are agglomerated in-situ in a crystallizer through the addition of immiscible bridging liquid. This process has the potential to improve flowability, solubility and compactibility of crystalline drugs. It can be used for the production of tablets in pharmaceutical industry. However, research to date has been restricted to product specific investigation. We proposed a three-step process mechanism for spherical agglomeration: wetting and nucleation; growth and consolidation; attrition and breakage.

The aim of this study is to investigate the breakage mechanism in spherical agglomeration process by isolating the breakage rate process. Systems consisting of model particles and bridging liquids are used; plastic beads with kerosene as the bridging liquid and water as the liquid suspension. Bridging liquid drop size was controlled by using a microfluidic system. This enable a range of different drop/particle size ratio to be investigated.

Agglomerate breakage was studied by pumping a suspension of spherical agglomerate through a contracting nozzle placed in between two syringes. The particle sizes distribution was measured before and after the agglomerates were broken using Malvern Mastersizer 3000 laser diffraction. The effect of different velocity gradient on agglomerate breakage was studied by varying the diameter of nozzles and the applied flow rate.

Here we present the results from these novel experiments. Agglomerate size as a function of fluid velocity, constriction diameter, and number of passes is discussed.