Dependencies between internal structure and mechanical properties of spray dried granules – Experimental study and DEM simulation
The mechanical properties of spray dried granules are decisive with regard to further applications and can be modified via internal granule structure. To obtain the correlations between structural and mechanical properties, necessary experiments are often time and resource consuming. The simulation of varied granule structures and their effect on resulting mechanical properties seems to be a promising approach.
In this paper, a model of the particulate internal structure of a spray dried granule was generated with the Discrete Element Method (DEM) based on real structure parameters. The model considers real primary particle number, particle size distribution and radial granule inhomogeneity, what results in the implementation of granule shell thickness and macro void. The internal structure of simulated granules showed significant influence on their mechanical properties. An increase of granule shell thickness and packing density of the primary particles within the shell results in fracture strength increase accompanied by decreasing fracture strain. The simulated reduction of the solid bridge bond size between the primary particles representing the decreasing binder amount leads to decreasing fracture strength and strain as previously determined experimentally (Eckhard et al., 2014). Consequently, the DEM is appropriate for evaluating the effect of changed real internal structure parameters on resulting mechanical granule properties.
Keywords: granule structure, spray drying, compression strength, porosity.