GROWTH-MECHANISM AND THE DEPENDENCE OF GRANULE SIZE ON DROP SIZE IN FLUIDIZED-BED GRANULATION

Closely sized granules have been formed in a fluidized bed by adding a series of precisely sized drops of binder solution. Resulting size data together with that from previous binder distribution and spray drop-size measurements provide a wide ranging correlation between granule size and drop size of the form D(g) varies as D(d)n. For lactose and ballotini particles under specified conditions, values of n were 0.80 and 0.85, respectively. The correlation applied over a wide size range, granules from 150 to 5000-mu-m and drops from 35 to 3000-mu-m diameter. An explanation for the correlation has been sought in terms of partial liquid filling of pores in the initially formed wet granule. This model appears most appropriate for a granule formed by engulfment of particles by a single drop rather than by a succession of agglomeration events involving several drops.