4
on dry solids). However, later on we need a safety margin
when it comes to the process guarantee. This is why a mois-
ture of 22 %w/w is chosen as the design line and only a
maximum of 65 g/t flocculant dosage is used.
Nevertheless, this pushed the specific solids throughput
already from 110 kg/m2/h with 0 g/t flocculant dosage to
520 kg/m2/h with 65 g/t flocculant dosage as shown in fig-
ure 6. For a total solids throughput of 170 t/h this resulted
in a required filtration area of 327 m2 what requires only 2
modern vacuum disc filters with 176 m2 each. This is a very
significant reduction in number of filters.
Now the question was what could be be guaranteed?
For the moisture, the design flocculant dosage was already
limited to 65 g/t in order to reach a moistzure of 22 %w/w
and keep the 1 %w/w safety margin. The modern vacuum
disc filters are safely discharging cake thicknesses down to
7 mm. Figure 7 shows the specific solids throughput plot-
ted versus the square root of the rotation speed. The previ-
ous sizing was done on the 10 mm cake thickness. If the
filter will be speeded up to reach the 7 mm cake thickness
at a speed of about 1.3 rpm (sqrt =1.14), the specific solids
throughput increases to 680 kg/m2/h. This is 30 %more
than required for the 170 t/h total solids throughput.
Based on the above, a Process Guarantee could be given
for
• two modern vacuum disc filters
• reaching a moisture of 23%w/w or less
• at a solids throughput of 170 t/h (on dry basis)
However, this guarantee applied to a tailings sample char-
acterized by specific values of particle size distribution,
mineral composition, clay content, feed solids and feed
temperature.
Finally, it was important to size the auxiliary units vac-
uum pump and blower. The blow air requirement is depen-
dant on the filter design and the maximum speed only.
Therefore, this is independent from the sample. However,
the amount of air passing through the cake within the oper-
ation window of the filter is important to know.
Figure 8 shows the air requirement of each filter at
vacuum pump suction conditions plotted versus the square
root of the filter speed. The operation window of the fil-
ter is 0.4 … 2.0 rpm (sqrt =0.63 … 1.41). Therefore, a
vacuum pump with 13,000 m3/h was chosen for each filter
to ensure that there is enough pump capacity available over
the full speed range.
COMMISSIONING PHASE AND 10 YEARS
OF OPERATION
After the filters had been manufactured, the auxiliaries
were ordered and were sent to the mine site for installation.
Some months later the plant was ready for commissioning
as the following photo shows.
Figure 6. Specific solids throughput vs flocculant dosage
Figure 7. Specific solids throughput versus square root of
the rotation speed
Figure 8. Air requirement of each filter versus square root of
the filter speed at vacuum pump suction conditions
on dry solids). However, later on we need a safety margin
when it comes to the process guarantee. This is why a mois-
ture of 22 %w/w is chosen as the design line and only a
maximum of 65 g/t flocculant dosage is used.
Nevertheless, this pushed the specific solids throughput
already from 110 kg/m2/h with 0 g/t flocculant dosage to
520 kg/m2/h with 65 g/t flocculant dosage as shown in fig-
ure 6. For a total solids throughput of 170 t/h this resulted
in a required filtration area of 327 m2 what requires only 2
modern vacuum disc filters with 176 m2 each. This is a very
significant reduction in number of filters.
Now the question was what could be be guaranteed?
For the moisture, the design flocculant dosage was already
limited to 65 g/t in order to reach a moistzure of 22 %w/w
and keep the 1 %w/w safety margin. The modern vacuum
disc filters are safely discharging cake thicknesses down to
7 mm. Figure 7 shows the specific solids throughput plot-
ted versus the square root of the rotation speed. The previ-
ous sizing was done on the 10 mm cake thickness. If the
filter will be speeded up to reach the 7 mm cake thickness
at a speed of about 1.3 rpm (sqrt =1.14), the specific solids
throughput increases to 680 kg/m2/h. This is 30 %more
than required for the 170 t/h total solids throughput.
Based on the above, a Process Guarantee could be given
for
• two modern vacuum disc filters
• reaching a moisture of 23%w/w or less
• at a solids throughput of 170 t/h (on dry basis)
However, this guarantee applied to a tailings sample char-
acterized by specific values of particle size distribution,
mineral composition, clay content, feed solids and feed
temperature.
Finally, it was important to size the auxiliary units vac-
uum pump and blower. The blow air requirement is depen-
dant on the filter design and the maximum speed only.
Therefore, this is independent from the sample. However,
the amount of air passing through the cake within the oper-
ation window of the filter is important to know.
Figure 8 shows the air requirement of each filter at
vacuum pump suction conditions plotted versus the square
root of the filter speed. The operation window of the fil-
ter is 0.4 … 2.0 rpm (sqrt =0.63 … 1.41). Therefore, a
vacuum pump with 13,000 m3/h was chosen for each filter
to ensure that there is enough pump capacity available over
the full speed range.
COMMISSIONING PHASE AND 10 YEARS
OF OPERATION
After the filters had been manufactured, the auxiliaries
were ordered and were sent to the mine site for installation.
Some months later the plant was ready for commissioning
as the following photo shows.
Figure 6. Specific solids throughput vs flocculant dosage
Figure 7. Specific solids throughput versus square root of
the rotation speed
Figure 8. Air requirement of each filter versus square root of
the filter speed at vacuum pump suction conditions