6 Dynamic Process Models for Fine Grinding and Dispersing
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Fig. 1 Model approach for stirred media mills
experimentally (grinding tests and radiometric densitometer) and via simulations
(coupled CFD-DEM) for several operation and process parameters. On the other
hand, a method has to be developed to efficiently measure the material properties of
particles in the lower micrometer range.
For a continuous grinding process within a stirred media mill a dynamic model
needs to account for the particle transport and the axial grinding media distribution
due to the suspension flow. To do so, the horizontally orientated stirred media mill
can be simulated as a series of instantly mixed cells that are connected by mixing
streams. The cell volumes and positions are defined according to the stirrer discs
(compare Fig. 2). The magnitude of the suspension mixing streams is calibrated based
on residence time experiments. The grinding media transport is investigated with
radiometric densitometry. For both transport phenomena (suspension and grinding
media), the dependency of the mixing coefficients on various operational parameters
is presented.
Fig. 2 Schematic
representation of cells for a
transport model in stirred
media mills
ω
cell
r
cell
r+1
cell
r-1