XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 743
desired height, particularly when the target cannot
be reached without desaturation of the filter cake.
• To maximise the water recovery
FILTER PERFORMANCE AND SIZING
FOR VERY LARGE APPLICATIONS
The use of a filter press for tailings dewatering is cur-
rently the most popular technology, combining flexibil-
ity regarding the kind of product to be filtered with very
high throughput and dewatering performance achievable,
often higher than any other technology currently available
(Whittering et al., 2019 Stickland, 2023). The tailoring of
the machine to suit the product characteristics can allow
the achievement of high performance on a wide range of
different tailings. It’s important that the optimisation pro-
cess should be carried out carefully to avoid oversizing and
extra costs. This requires a multi-step approach, involving a
comprehensive characterisation of the material and a thor-
ough testing phase. The definition of the target in terms
of residual cake moisture and filter throughput, as well as
a precise sampling of the material for the test, taking in
account variabilities over the years of operation and worst-
case scenarios, are aspects of upmost importance.
The set-up of a filter press process involves many differ-
ent variables like:
• Plate type: recessed (i.e., fixed volume) or membrane
(i.e., variable volume, allowing cake consolidation by
pressure squeezing), chamber thickness.
• Feeding (and, in case, squeezing) pressure
• Application of air blowing phase to get cake desatu-
ration and optimization of air consumption.
• Filter cloth selection(Kaswalder et al., 2018)
Any of these items can have a strong impact on both oper-
ating expense (OPEX) and capital expense (CAPEX) of the
equipment. Use of membrane plates instead of fixed vol-
ume ones, for example, presents a significant higher cost
but can be necessary to get the required cake moisture use
of air blowing is also often necessary to prevent liquefac-
tion and get an extra dewatering level, but the compressor
and its energy demand can increase drastically the costs.
In Figure 2, a graph showing the typical moisture range
achievable with different filter configurations on copper
tailings (the same application as the case study later dis-
cussed) is reported. It clearly shows the importance of the
target definition for a proper process configuration.
The physical-chemical characteristics of the slurry have
also a strong impact on the performance achievable, both
in terms of throughput (by affecting the filtration time) and
cake moisture. Any parameter has its own contribution,
and this makes a full understanding of the system quite dif-
ficult. The particle size distribution plays an important role,
considering that the packing of the cake determines many
process outcomes including filtration time, the easiness to
desaturate the cake and its final residual moisture. Figure 2
shows clearly that the assumption “as coarser the material,
as dryer the cake” is often true.
Another important feature that can impact on the fil-
tration performances is the mineralogy, that determines
the particles shape and consequently their packing while
forming the cake. This is particularly important for the
fine fraction (below 4 microns) which often can be clays.
The presence of phyllosilicates, characterized by their platy
structure, can lead to a very high cake specific resistance,
which in turn, causes long filtration times and higher resid-
ual moistures (Grosso et al., 2021). The worst case occurs
when swelling clays (i.e., smectites) are present. Their
impact is substantial from the geotechnical behaviour to
the filterability of the material, leading to stricter moisture
targets and lower dewatering efficiencies (Hawkey et al.,
2024).
To cater to the copper mining sector, particularly in
Chile and Peru, one needs to significantly increase the scale
of filter presses again. Applying the filter press technology
to tailings dewatering at this huge scale means that testing,
plate pack configuration and precise filter sizing are criti-
cal. Filter presses can be configured and operated to easily
achieve the target moisture content specified by the geo-
technical engineers for the stack design. However, and this
Figure 1. Simplified illustration of the filtration and cake
desaturation process
desired height, particularly when the target cannot
be reached without desaturation of the filter cake.
• To maximise the water recovery
FILTER PERFORMANCE AND SIZING
FOR VERY LARGE APPLICATIONS
The use of a filter press for tailings dewatering is cur-
rently the most popular technology, combining flexibil-
ity regarding the kind of product to be filtered with very
high throughput and dewatering performance achievable,
often higher than any other technology currently available
(Whittering et al., 2019 Stickland, 2023). The tailoring of
the machine to suit the product characteristics can allow
the achievement of high performance on a wide range of
different tailings. It’s important that the optimisation pro-
cess should be carried out carefully to avoid oversizing and
extra costs. This requires a multi-step approach, involving a
comprehensive characterisation of the material and a thor-
ough testing phase. The definition of the target in terms
of residual cake moisture and filter throughput, as well as
a precise sampling of the material for the test, taking in
account variabilities over the years of operation and worst-
case scenarios, are aspects of upmost importance.
The set-up of a filter press process involves many differ-
ent variables like:
• Plate type: recessed (i.e., fixed volume) or membrane
(i.e., variable volume, allowing cake consolidation by
pressure squeezing), chamber thickness.
• Feeding (and, in case, squeezing) pressure
• Application of air blowing phase to get cake desatu-
ration and optimization of air consumption.
• Filter cloth selection(Kaswalder et al., 2018)
Any of these items can have a strong impact on both oper-
ating expense (OPEX) and capital expense (CAPEX) of the
equipment. Use of membrane plates instead of fixed vol-
ume ones, for example, presents a significant higher cost
but can be necessary to get the required cake moisture use
of air blowing is also often necessary to prevent liquefac-
tion and get an extra dewatering level, but the compressor
and its energy demand can increase drastically the costs.
In Figure 2, a graph showing the typical moisture range
achievable with different filter configurations on copper
tailings (the same application as the case study later dis-
cussed) is reported. It clearly shows the importance of the
target definition for a proper process configuration.
The physical-chemical characteristics of the slurry have
also a strong impact on the performance achievable, both
in terms of throughput (by affecting the filtration time) and
cake moisture. Any parameter has its own contribution,
and this makes a full understanding of the system quite dif-
ficult. The particle size distribution plays an important role,
considering that the packing of the cake determines many
process outcomes including filtration time, the easiness to
desaturate the cake and its final residual moisture. Figure 2
shows clearly that the assumption “as coarser the material,
as dryer the cake” is often true.
Another important feature that can impact on the fil-
tration performances is the mineralogy, that determines
the particles shape and consequently their packing while
forming the cake. This is particularly important for the
fine fraction (below 4 microns) which often can be clays.
The presence of phyllosilicates, characterized by their platy
structure, can lead to a very high cake specific resistance,
which in turn, causes long filtration times and higher resid-
ual moistures (Grosso et al., 2021). The worst case occurs
when swelling clays (i.e., smectites) are present. Their
impact is substantial from the geotechnical behaviour to
the filterability of the material, leading to stricter moisture
targets and lower dewatering efficiencies (Hawkey et al.,
2024).
To cater to the copper mining sector, particularly in
Chile and Peru, one needs to significantly increase the scale
of filter presses again. Applying the filter press technology
to tailings dewatering at this huge scale means that testing,
plate pack configuration and precise filter sizing are criti-
cal. Filter presses can be configured and operated to easily
achieve the target moisture content specified by the geo-
technical engineers for the stack design. However, and this
Figure 1. Simplified illustration of the filtration and cake
desaturation process