Heat Transfer and Granule Growth Rate in Fluidized Bed Granulation

In this study, the mechanism of heat transfer between gas and granule in fluidized bed granulation was investigated, and the granule growth rate was predicted using heat transfer and moisture balance measurements. First of all, the heat transfer coefficient between gas and granules in a fluidized bed was measured using granules of four different sizes, and the experimental data obtained over a wide range of granule Reynolds number were found to be expressed as Nup=2+0.6Re1/2pPr1/3, where Nup, Rep and Pr indicate granule Nusselt number, Reynolds number and Prandtl number, respectively. Secondly, a model in which the heat transfer and the moisture balance were taken into consideration was proposed to predict the moisture content and granule growth rate during granulation. It was also confirmed that the experimental results at various binder (water) flow rates and inlet air temperatures were in good agreement with those predicted from the thoery. As a result, the mechanism of the heat transfer was elucidated and the granule growth rate during granulation could be predicted with high accuracy.