742 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
recovery of water so that it can be reused in the plant
(Julien, 2023).
There are some very large mines in the copper sector of
the mining industry and these extract massive amounts of
ore. Typically, the largest are located in South America and
many of these are at high altitude in the Andes Mountain
range. After the separation and concentration of the of the
copper ore, the remaining unwanted extracted material is
in a slurry form and must be managed in a responsible way.
Instead of wet storage in dams, as was the default manage-
ment solution for most mineral tailings, now the preferred
method is tailings slurry filtration and storing the filter cake
in an engineered stack (commonly referred to as ‘dry stack-
ing’, even though there is still some moisture present in
the filter cake). The obvious benefit of filtration and dry
stacking of tailings is the elimination of the tailings dam.
A tailings dam in a location such as the Andes is a risky
proposition because of topographic and seismic reasons.
However, one of the most important drivers that favours
filtration and dry stacking is water recovery. Tailings slurry
filtration recovers water that is relatively free of suspended
solids which increases the amount of water available for
recycling. Because of the high altitude of many of these
mines, water can be very expensive and recycling as much
of it as possible saves money.
The large volume of tailings produced in these copper
mines needs filtration equipment that is appropriate for the
scale. Filter suppliers must face this challenge and come up
with machines that are capable of much bigger throughputs
than previously considered practical. For example, Diemme
Filtration, already well known for producing large machines,
has now produced several units of its new generation of fil-
ter presses, the GHT5000, which is capable of processing
approximately three times the amount of slurry as that of
the largest of its filter presses currently in operation. It can
be demonstrated that by reducing the number of equip-
ment trains (where each train comprises a filter, drip tray,
cake feeder, cloth washing system and feed pumps), the
installation footprint and capital cost can be reduced. For
a copper tailings filtration plant that can dewater 80,000
tonnes of dry solids per day 10 × GHT5000 units would
be required as opposed to 30 × GHT2500 (largest filter
available prior to the introduction of the GHT5000). The
approximate saving in capital cost of the total installation of
the filtration plant by using the much larger filter model is
35% .However, Capex savings are related to location. The
cost savings include reduced building footprint, a reduction
in piping and electrical wiring and a reduced number of
ancillaries (e.g., cake feeders).
WATER RECOVERY AND REUSE
Plate filter presses are the more common choice for mineral
tailings dewatering where low filter cake moisture targets
are set. These machines work well even when there are fine
particles in the slurry. By blowing compressed air through
the cake, low moisture contents can be easily reached.
For copper mine tailings the cake moisture content is
usually between 10% and 20% (w/w). Plate filter presses,
when configured and operated correctly, will achieve a
cake moisture content lower than the best result of all the
competing dewatering technologies. Of course, for tailings
dewatering, an important factor is maintaining the maxi-
mum throughput while achieving the cake moisture target.
A plate filter press plate pack can be configured in many
ways. The main choices to be made in the physical plate
pack configuration include (but are not limited to
• fixed or variable chamber volume,
• chamber thickness,
• maximum slurry feeding.
• membrane squeezing pressure capability,
• compressed air path for cake blowing, and
• filter cloth selection.
Until the last twenty years, pressure filtration of tailings was
only used where no other choice was available and the main
reason for that was that the largest filter presses available
were relatively small compared with the size of machines
installed in tailings applications today. As the maximum
size of filter presses increased, the economics of using this
technology for tailings applications became more attractive.
One of the steps in the tailings dewatering process
using a filter press is cake desaturation. Cake desaturation
in a filter press is essentially achieved by displacing the
interstitial liquor in the filter cake with compressed air, as
shown in Figure 1. This step is often referred to as “cake
blowing” and usually follows the feeding and compaction
steps. It is often applied together with membrane squeez-
ing, depending on the plate pack configuration. The cake
desaturation step reduces the moisture content of the filter
cake. This improves the geotechnical properties of the filter
cake enabling it to be stacked to a higher level. It has the
added advantage of recovering more water.
Cake blowing is used to reduce the moisture content of
the filter cake. It can be applied for a number of different
reasons:
• To avoid cake liquefaction where saturated cakes are
thixotropic. These cakes typically have a high void
ratio.
• To reach the cake moisture target set by geotechni-
cal engineers so that it can be stacked safely to the
recovery of water so that it can be reused in the plant
(Julien, 2023).
There are some very large mines in the copper sector of
the mining industry and these extract massive amounts of
ore. Typically, the largest are located in South America and
many of these are at high altitude in the Andes Mountain
range. After the separation and concentration of the of the
copper ore, the remaining unwanted extracted material is
in a slurry form and must be managed in a responsible way.
Instead of wet storage in dams, as was the default manage-
ment solution for most mineral tailings, now the preferred
method is tailings slurry filtration and storing the filter cake
in an engineered stack (commonly referred to as ‘dry stack-
ing’, even though there is still some moisture present in
the filter cake). The obvious benefit of filtration and dry
stacking of tailings is the elimination of the tailings dam.
A tailings dam in a location such as the Andes is a risky
proposition because of topographic and seismic reasons.
However, one of the most important drivers that favours
filtration and dry stacking is water recovery. Tailings slurry
filtration recovers water that is relatively free of suspended
solids which increases the amount of water available for
recycling. Because of the high altitude of many of these
mines, water can be very expensive and recycling as much
of it as possible saves money.
The large volume of tailings produced in these copper
mines needs filtration equipment that is appropriate for the
scale. Filter suppliers must face this challenge and come up
with machines that are capable of much bigger throughputs
than previously considered practical. For example, Diemme
Filtration, already well known for producing large machines,
has now produced several units of its new generation of fil-
ter presses, the GHT5000, which is capable of processing
approximately three times the amount of slurry as that of
the largest of its filter presses currently in operation. It can
be demonstrated that by reducing the number of equip-
ment trains (where each train comprises a filter, drip tray,
cake feeder, cloth washing system and feed pumps), the
installation footprint and capital cost can be reduced. For
a copper tailings filtration plant that can dewater 80,000
tonnes of dry solids per day 10 × GHT5000 units would
be required as opposed to 30 × GHT2500 (largest filter
available prior to the introduction of the GHT5000). The
approximate saving in capital cost of the total installation of
the filtration plant by using the much larger filter model is
35% .However, Capex savings are related to location. The
cost savings include reduced building footprint, a reduction
in piping and electrical wiring and a reduced number of
ancillaries (e.g., cake feeders).
WATER RECOVERY AND REUSE
Plate filter presses are the more common choice for mineral
tailings dewatering where low filter cake moisture targets
are set. These machines work well even when there are fine
particles in the slurry. By blowing compressed air through
the cake, low moisture contents can be easily reached.
For copper mine tailings the cake moisture content is
usually between 10% and 20% (w/w). Plate filter presses,
when configured and operated correctly, will achieve a
cake moisture content lower than the best result of all the
competing dewatering technologies. Of course, for tailings
dewatering, an important factor is maintaining the maxi-
mum throughput while achieving the cake moisture target.
A plate filter press plate pack can be configured in many
ways. The main choices to be made in the physical plate
pack configuration include (but are not limited to
• fixed or variable chamber volume,
• chamber thickness,
• maximum slurry feeding.
• membrane squeezing pressure capability,
• compressed air path for cake blowing, and
• filter cloth selection.
Until the last twenty years, pressure filtration of tailings was
only used where no other choice was available and the main
reason for that was that the largest filter presses available
were relatively small compared with the size of machines
installed in tailings applications today. As the maximum
size of filter presses increased, the economics of using this
technology for tailings applications became more attractive.
One of the steps in the tailings dewatering process
using a filter press is cake desaturation. Cake desaturation
in a filter press is essentially achieved by displacing the
interstitial liquor in the filter cake with compressed air, as
shown in Figure 1. This step is often referred to as “cake
blowing” and usually follows the feeding and compaction
steps. It is often applied together with membrane squeez-
ing, depending on the plate pack configuration. The cake
desaturation step reduces the moisture content of the filter
cake. This improves the geotechnical properties of the filter
cake enabling it to be stacked to a higher level. It has the
added advantage of recovering more water.
Cake blowing is used to reduce the moisture content of
the filter cake. It can be applied for a number of different
reasons:
• To avoid cake liquefaction where saturated cakes are
thixotropic. These cakes typically have a high void
ratio.
• To reach the cake moisture target set by geotechni-
cal engineers so that it can be stacked safely to the