The mechanics of particle interactions and the prevailing level of compressive stresses and shear strains are affected by the scale of operation, which in turn affects the granule structure, strength and functional properties. This may be the main reason why the current scaling relationships are ineffective from a viewpoint of product engineering.
In a research programme supported by the EPSRC and four industrial organizations, i.e. Borax Europe, Hosokawa Micron BV, Pfizer Global Research and Development, and Procter and Gamble, we have addressed the following topics:
Development of methodologies for quantifying the structure of granules in terms of internal voidage and composition distributions, strength, shape, size and density.
Identification of the parameters that affect the structure of granules by using fundamental theories of microscopic contact mechanics of particles using DEM, macroscopic granular flow dynamics and kinetics of wetting.
Experimental work across several length scales (1 L, 5 L, 50 L and 250 L) to aid the analysis of the process.
In this paper, an overview of findings and their implications for granulation practice is presented.