Fluid bed agglomeration with a narrow droplet size distribution

Abstract

In the fluid bed agglomeration processes liquid distribution influences the agglomerate growth. We developed a new nozzle that produces uniform droplets, which allows droplets to be easily controlled in size independently of liquid- and airflow of the nozzle. It was found that the spray rate and the mixing in the spray zone determine the average granule size and that there is linear relation between the number of droplets of which a granule consists and its volume, at the early stage of the process. The nucleation ratio factor introduced in this paper depends on the material properties of binder liquid and powder particles and is a useful parameter to describe the binder liquid efficiency. The decline of the growth rate of granules during the agglomeration process was due to the less sufficient rewetting of granules resulting in less growth. A linear relation was found between tracer mass added to the binder liquid and the granule mass in an early stage of the process. Solubility of the tracer was found not to influence its distribution. The new nozzle proves to be a good tool to study the effect of wetting and growth of granules.