A new approach to wet granulation process has been developed, where the liquid binder is delivered to the powder bed as an aqueous foam rather than as an atomized spray. This paper compares nucleation of powder between foamed and sprayed binder addition methods.

Nucleation behaviours of several grades of glass ballotini and lactose powder via HPC and HPMC foamed solutions were studied and compared with the nucleation via single drops of the same fluids. Specific penetration time (penetration time per unit mass of liquid drop or foam) and nucleation ratio (ratio of mass of nucleus to mass of liquid binder) for both foam and drop addition methods were compared. The effects of powder particle size and liquid binder concentration on both parameters were examined.

Some powder-fluid combinations showed faster specific penetration times for foam, while for others liquid drops were faster. Using a less viscous foamed liquid binder and/or a larger particle size of powder creates a larger final nucleus size. The study of nucleation ratio suggests that foam addition method provides better liquid distribution efficiency and uses less liquid binder to nucleate the same number of grams of powder.