3 Dynamics of Spray Granulation in Continuously …
93
teristics are topologically related to and significantly influence other characteristics,
for example the compression strength of a granule.
The apparent density of granules was measured by helium pycnometry (Multivolume Micrometrics 1305). The porosity of selected granules was measured via
X-ray micro-computed tomography (CT-ALPHA, ProCon X-Ray GmbH) as
described in Refs. [48, 49].
The compression strength was analyzed by single particle compression tests using
a Texture Analyser TA.XT plus (Stable Micro Systems). For detailed information on
the test procedure and evaluation of force-displacement curves, see [50].
Figure 17 shows results for the three characteristics. The solids density and the
compression strength of the granules show an increasing trend with increasing drying
potential, while the porosity reveals the opposite trend.
Fig. 17 a Average solids density, b granule porosity and c compression strength of the granules
according to drying potential of the individual granulation process experiments [1] (Used with
permission by Elsevier)