XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3759
As it was mentioned earlier, another way to check
whether the steady state has been reached is by comparing
the net flow rates through the grates with the discharge rates
at the trunnion end. Table 2 shows that the net transport
through the grates is very close to the discharge rates for
both solids and water which is an indication of the steady
state been achieved.
The plots presented in Figure 2 are very useful when
different discharge systems are compared in terms of their
efficiency or recirculation of the solids and water in the
pans. Any design changes performed on a discharge system,
such as: grates open area, aperture of the grates, arrange-
ments of the grates, pan lifter designs, pans height, angle of
the discharge cone, etc., will change the appearance of these
plots and will allow quantifying the effect of these changes
on the performance of the discharge end.
In the next section such a comparison is carried out
on seven different designs for the grates’ position. With
each design the grates holes are moved gradually towards
the center of the mill, but the open area of the grates stays
unchanged. The seven designs are simulated for two dif-
ferent discharge systems in terms of the lifter bars design,
namely: radial design and curved design.
EFFECT OF GRATES’ RADIAL POSITION
ON THE MILL’S PERFORMANCE
The effect of the seven different radial positions of the grates’
openings on the mill’s discharge rate has been investigated
using a slightly modified version of the AG mill previously
used during the calibration process. The rotational speed
for all cases has been set at 74% CS. The design changes
that have been considered to the mill used in the calibration
process are:
• A new grate design with only three opening of
89 mm (3.5in) aperture each
• A lower total open area of 2.36 m2 (3658 in2) which
corresponds to 3.2% open area
• The filling level of the mill was set at 34%
• The initial percentage of solids by weight in the mill
was set at 85%
• Each design has been built in two versions, one with
radial lifter bars and one with curved lifter bars.
It must be mentioned here that the curved design has
been changed compared to the radial design. These changes
are:
• The lifter bars are curved, but the number of pans is
kept the same at 36
• The slots are shifted to be centered inside the pans
but the radial position is unchanged
The seven designs for the radial lifter bars are shown in
Figure 3, showing just a quarter of the mill.
The Radial1 and Curved1 have the holes positioned
further away from the center of the mill while for Radial7
and Curved7 the holes are closer to the center of the mill.
In case of the curved design, the openings are placed at
the same radial distance from the mill’s center, the only dif-
ference being that the holes are shifted to the left due to the
curved lifter bars. By doing this, the curved design doesn’t
Figure 3. Radial position of the grates for the radial discharge design
As it was mentioned earlier, another way to check
whether the steady state has been reached is by comparing
the net flow rates through the grates with the discharge rates
at the trunnion end. Table 2 shows that the net transport
through the grates is very close to the discharge rates for
both solids and water which is an indication of the steady
state been achieved.
The plots presented in Figure 2 are very useful when
different discharge systems are compared in terms of their
efficiency or recirculation of the solids and water in the
pans. Any design changes performed on a discharge system,
such as: grates open area, aperture of the grates, arrange-
ments of the grates, pan lifter designs, pans height, angle of
the discharge cone, etc., will change the appearance of these
plots and will allow quantifying the effect of these changes
on the performance of the discharge end.
In the next section such a comparison is carried out
on seven different designs for the grates’ position. With
each design the grates holes are moved gradually towards
the center of the mill, but the open area of the grates stays
unchanged. The seven designs are simulated for two dif-
ferent discharge systems in terms of the lifter bars design,
namely: radial design and curved design.
EFFECT OF GRATES’ RADIAL POSITION
ON THE MILL’S PERFORMANCE
The effect of the seven different radial positions of the grates’
openings on the mill’s discharge rate has been investigated
using a slightly modified version of the AG mill previously
used during the calibration process. The rotational speed
for all cases has been set at 74% CS. The design changes
that have been considered to the mill used in the calibration
process are:
• A new grate design with only three opening of
89 mm (3.5in) aperture each
• A lower total open area of 2.36 m2 (3658 in2) which
corresponds to 3.2% open area
• The filling level of the mill was set at 34%
• The initial percentage of solids by weight in the mill
was set at 85%
• Each design has been built in two versions, one with
radial lifter bars and one with curved lifter bars.
It must be mentioned here that the curved design has
been changed compared to the radial design. These changes
are:
• The lifter bars are curved, but the number of pans is
kept the same at 36
• The slots are shifted to be centered inside the pans
but the radial position is unchanged
The seven designs for the radial lifter bars are shown in
Figure 3, showing just a quarter of the mill.
The Radial1 and Curved1 have the holes positioned
further away from the center of the mill while for Radial7
and Curved7 the holes are closer to the center of the mill.
In case of the curved design, the openings are placed at
the same radial distance from the mill’s center, the only dif-
ference being that the holes are shifted to the left due to the
curved lifter bars. By doing this, the curved design doesn’t
Figure 3. Radial position of the grates for the radial discharge design