Granular Flow - Application
Validation of a scale model SAG mill
Validation is a very important issue both for DEM simulations and for
mill modelling. In this study, DEM simulation results are compared with
photographs for a scale model SAG (Semi-Autogenous) mill with Noranda
lifters for a range of speeds at a fill level of 35% (by volume). The full
experimental particle size distribution is used in these simulations. The
experimental results have been made available by JKMRC
for the purposes of validation.
DEM simulations of the SAG mill were undertaken using 2D, 3D slice
and full 3D models. An example of a simulation result for the 2D DEM
model is shown in the figure below. The shape of the lifters
is clearly visible.
 |
|
mill diameter :
mill length :
lifter profile :
fill level :
mill speed :
charge :
particle diam. : |
592 mm
200 mm
C-Noranda
35%
65% critical
balsalt, s.g. = 2.84
2 mm to 22.4 mm |
| 2D DEM simulation of the SAG
mill, with particles coloured by size |
Photographs were taken with 1/25 s exposure lengths producing streaks for
each particle. To enable a meaningful comparison, particle streaks are
also produced for the simulations. This is achieved by storing the
locations of all the particles at two times separated by 0.04 s. These
points are joined by lines whose width is the same as the particle
diameter. The streaks are coloured different shades of grey. For the full
3D results the streaks are drawn only for particles close to the front of
the mill reflecting the very limited depth of view in the experimental
photographs.
DEM simulation results have been compared with the experimental data,
for each of the three above-mentioned DEM models. The figures below
illustrate the comparison for the full 3D model for different mill speeds.
Excellent agreement can be observed between the DEM simulation results and
the experimental data, with the locations of the shoulder, toe and vortex
centres matching closely for each mill speed. The shapes of the cascading
free surfaces are also very similar for each pair.
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