400 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
• Work to improve mechanical availability
• Speed and resolution of ejector valves
• Acceptable belt occupancy levels and
• Higher total installation throughput rates per site,
i.e., 1850tph.
Beyond the pure technical aspects of the flowsheets and
equipment, there have also been considerable develop-
ments in associated aspects such as the establishment (or
expansion) of test facilities and departments or institutes
dedicated to work closely relating to sorting.
The impact of mine scale heterogeneity has many
implications for preconcentration and front-end mining.
In essence the main question relates to if the heterogeneity
is at a scale that can be exploited in the mining process and
can the heterogeneity be retained as material is presented to
sorting systems.
Ballentyne et al. (2020) examined the use of drill core
data to determine the potential value of applying bulk ore
sorting for three given cases. The opportunity and value
proposition for the three cases varied, but the use of the
heterogeneity index fed into the block model, in associa-
tion with grade, allowed optimization of the cut-off grade
for each operation and definition of the most beneficial
type of sorting.
From the literature, many bulk sorting applications
have been centred on underground mines using block cav-
ing methods. New Afton and Cadia East are two operations
that have led to a number of papers and studies (Cetin et al.
2023, Nadolski et al. 2018). Given the operating method
of block caves, it is highly appropriate that some form of
bulk sorting should be considered, given that there is no
way of physically differentiating material arriving at the
drawpoints. In an open pit setting, standard grade control
within the mining method is already a form of bulk sorting,
hence the focus is slightly different. For open pits, apply-
ing bulk sorting after grade control, could be considered
as a cascading level of separation, analogous to rougher-
cleaning in flotation.
CONFIGURATION AND OPERABILITY OF
CIRCUITS WITH SORTING
The great challenge in implementing preconcentration unit
operations into either Brownfield or Greenfield operations,
is the extra complexity in the value chain through the addi-
tion of unit operations and reject streams. The benefit,
however, is that gangue can be rejected earlier in the mining
value chain which can have significant benefits in energy
reduction and cost savings.
Adair et al. (2020) compared the benefits of a con-
ventional flowsheet with a flowsheet containing additional
stages of in-pit and in-plant preconcentration unit opera-
tions. Despite this analysis demonstrating the benefits,
one of the less discussed aspects is that preconcentration
changes the presentation of material to the downstream
processes. In a Greenfield environment, the impact of
removing certain material can be incorporated into the
milling and beneficiation design, but in a brownfields situ-
ation, the ramifications can be significant.
Since bulk sorting relies on grade variability, it is sensi-
tive to both ore body heterogeneity variability and value
chain heterogeneity variability as the former is governed by
the variable geology of the orebody whilst the latter is gov-
erned by mixing and blending throughout the value chain.
These two variabilities need to be assessed in the feasibility
study phase so that a reasonably accurate mine plan can be
determined to decide which ore goes for bulk sorting and
which ore is sent directly to waste or the mill.
By contrast, particle sorting mass rejection perfor-
mance is sensitive to variation in orebody heterogeneity
over time, but relatively insensitive to variability down the
value chain because the grade of the particle being sensed is
determined by the mineralogy and associations of the par-
ticles and not how they are mixed. The geology determines
the mineralogy and the textures of the particles and mixing
doesn’t influence the particle grade so particle sorting can
be applied right across the value chain. Sensing technolo-
gies which rely on mineral associations or proxies such as
gold associations with particular host rocks are particularly
prone to ore body variations as the association is typically
variable across the ore body.
The uncertainty of the orebody-wide sorting response
due to heterogeneity, cannot be overstated. The authors have
seen numerous examples where strong sorting responses are
noted on ores from certain domains, but the response is not
uniform across the wider orebody and cannot be usefully
predicted based on known ore body knowledge parameters.
In such cases, this is often the reason why further study of
preconcentration is discontinued.
As part of the discussion about downstream process-
ing, it is important to consider that sorting, unlike com-
minution or beneficiation, is not modifying the particles
or concentrating minerals per se. It is simply removing low
value particles and concentrating the valuable particles,
within the feed mass. To deliver liberation, the same types
of downstream processing will be required, although at
reduced unit or stage capacities.
The water balance advantage associated with the intro-
duction of preconcentration is obviously driven by the
water per tonne of material treated and the reduction in
mass through the use of preconcentration. The gain in
• Work to improve mechanical availability
• Speed and resolution of ejector valves
• Acceptable belt occupancy levels and
• Higher total installation throughput rates per site,
i.e., 1850tph.
Beyond the pure technical aspects of the flowsheets and
equipment, there have also been considerable develop-
ments in associated aspects such as the establishment (or
expansion) of test facilities and departments or institutes
dedicated to work closely relating to sorting.
The impact of mine scale heterogeneity has many
implications for preconcentration and front-end mining.
In essence the main question relates to if the heterogeneity
is at a scale that can be exploited in the mining process and
can the heterogeneity be retained as material is presented to
sorting systems.
Ballentyne et al. (2020) examined the use of drill core
data to determine the potential value of applying bulk ore
sorting for three given cases. The opportunity and value
proposition for the three cases varied, but the use of the
heterogeneity index fed into the block model, in associa-
tion with grade, allowed optimization of the cut-off grade
for each operation and definition of the most beneficial
type of sorting.
From the literature, many bulk sorting applications
have been centred on underground mines using block cav-
ing methods. New Afton and Cadia East are two operations
that have led to a number of papers and studies (Cetin et al.
2023, Nadolski et al. 2018). Given the operating method
of block caves, it is highly appropriate that some form of
bulk sorting should be considered, given that there is no
way of physically differentiating material arriving at the
drawpoints. In an open pit setting, standard grade control
within the mining method is already a form of bulk sorting,
hence the focus is slightly different. For open pits, apply-
ing bulk sorting after grade control, could be considered
as a cascading level of separation, analogous to rougher-
cleaning in flotation.
CONFIGURATION AND OPERABILITY OF
CIRCUITS WITH SORTING
The great challenge in implementing preconcentration unit
operations into either Brownfield or Greenfield operations,
is the extra complexity in the value chain through the addi-
tion of unit operations and reject streams. The benefit,
however, is that gangue can be rejected earlier in the mining
value chain which can have significant benefits in energy
reduction and cost savings.
Adair et al. (2020) compared the benefits of a con-
ventional flowsheet with a flowsheet containing additional
stages of in-pit and in-plant preconcentration unit opera-
tions. Despite this analysis demonstrating the benefits,
one of the less discussed aspects is that preconcentration
changes the presentation of material to the downstream
processes. In a Greenfield environment, the impact of
removing certain material can be incorporated into the
milling and beneficiation design, but in a brownfields situ-
ation, the ramifications can be significant.
Since bulk sorting relies on grade variability, it is sensi-
tive to both ore body heterogeneity variability and value
chain heterogeneity variability as the former is governed by
the variable geology of the orebody whilst the latter is gov-
erned by mixing and blending throughout the value chain.
These two variabilities need to be assessed in the feasibility
study phase so that a reasonably accurate mine plan can be
determined to decide which ore goes for bulk sorting and
which ore is sent directly to waste or the mill.
By contrast, particle sorting mass rejection perfor-
mance is sensitive to variation in orebody heterogeneity
over time, but relatively insensitive to variability down the
value chain because the grade of the particle being sensed is
determined by the mineralogy and associations of the par-
ticles and not how they are mixed. The geology determines
the mineralogy and the textures of the particles and mixing
doesn’t influence the particle grade so particle sorting can
be applied right across the value chain. Sensing technolo-
gies which rely on mineral associations or proxies such as
gold associations with particular host rocks are particularly
prone to ore body variations as the association is typically
variable across the ore body.
The uncertainty of the orebody-wide sorting response
due to heterogeneity, cannot be overstated. The authors have
seen numerous examples where strong sorting responses are
noted on ores from certain domains, but the response is not
uniform across the wider orebody and cannot be usefully
predicted based on known ore body knowledge parameters.
In such cases, this is often the reason why further study of
preconcentration is discontinued.
As part of the discussion about downstream process-
ing, it is important to consider that sorting, unlike com-
minution or beneficiation, is not modifying the particles
or concentrating minerals per se. It is simply removing low
value particles and concentrating the valuable particles,
within the feed mass. To deliver liberation, the same types
of downstream processing will be required, although at
reduced unit or stage capacities.
The water balance advantage associated with the intro-
duction of preconcentration is obviously driven by the
water per tonne of material treated and the reduction in
mass through the use of preconcentration. The gain in