XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 401
water efficiency is, however, somewhat reduced, in the case
of particle based sorters and in some cases bulk sorting. Use
of the dry sorting techniques generates dust and to con-
trol emissions, water sprays are the standard solution. In
addition, there can also be a requirement to wash particles
ahead of sorters, should there be significant coating that
will impair the sensor and therefore sorting effectiveness.
The potential for preconcentration to reduce the mass
of treated ore and to work in association with other emerg-
ing techniques, i.e., compressive grinding, dry systems,
Coarse Particle Liberation (CPL), does however, support
options for reduction in tails generation, or a move to dry
stacked tails (Luukkanen et al., 2022)
In Pit and Pre-Plant Preconcentration.
Of the available approaches, bulk sorting can be suited to
in-pit preconcentration, as minimum handling helps pre-
serve ore heterogeneity and it can be adapted for shovels,
trucks and conveyors operating in the pit. Sensor tech-
nologies suitable for in-pit bulk sorting include XRF on
shovels and conveyor belts (Faraj et al, 2022, Keeney et al,
2020), Magnetic Resonance (MR) on trucks and conveyor
belts (Coghill et al. 2020), and PGNAA on conveyor belts
(Kurth and Balzan et al. 2020).
When dealing with the front end of the mining pro-
cess, shovel-based preconcentration can add significant
complexity in the management of the truck and shovel fleet
as the material destination of each truck is not known until
after the sensing of each individual shovel or truck payload.
This may require a larger truck fleet to absorb the extra
variability of the ore with multiple trucks required for each
shovel to sort the ore at the rock face. This not only adds
additional costs and decreases productivity of the mining
stage of the value chain, but can also result in significant
variations in mine to mill throughput.
Another complexity to consider is that often in-pit
real estate can be limited and adding additional unit oper-
ations such as bulk sorting into the pit can be challeng-
ing for the smooth operation of the pit. The challenges of
adopting In Pit Crush &Convey (IPCC) are analogous to
those of pit bulk ore sorting, being frequently studied but
rarely adopted for bulk mining projects. They are, however,
entirely complementary and could pose a viable option in
unison that would be infeasible individually. With regards
to costs, the creation of multiple streams can result in mul-
tiple handling events of the ore and waste which can lower
the value of the sorting benefits.
The transition zone between mining and processing,
or what the authors have described as “pre-plant” mostly
applies to material that has been primary crushed and is
therefore typically has a top size of 400 mm. In this area,
the conveyor belt situation offers improved presentation to
the sensors, both in terms of bed thickness and opportu-
nities to use automated rejection. Over-belt sensing using
PGNAA and MR have both been deployed in this duty
(singularly and in combination) and given the application
advantages, this appears to be one of the most prospective
areas for further development and deployment. In evalu-
ating MR applications, the range of minerals that can be
detected is a key consideration and although the technique
appears to offer several advantages, the match of the sensor
to the duty is critical. Details of the application of MR is
provided by NextOre (2024).
In some instances, screening (size-based preconcentra-
tion) of primary crushed material is also an option, provid-
ing there is the option to exploit clear-cut macro liberation
at the relatively large particle size.
In-Plant Preconcentration
Screening, particle based sorting and Dense Media
Separation (DMS) are the main methods for “coarse” par-
ticle in-plant concentration, as the heterogeneity being
exploited is the particle grade of the value mineral or its
proxy. This type of heterogeneity is not destroyed by mixing.
Particle sorting can therefore be performed on streams
which have been blended. In the case of sensor-based par-
ticle sorting, the main operational aspects to control are
sensor validation, stream preparation, on-going calibration,
safety related sensor considerations and costs.
The introduction of ore sorting to a multi-stage crush-
ing flowsheet has distinct advantages over a large milling
circuit. The multi-stage crushing process has, by definition,
a number of opportunities to intervene with ore sorting
or particular size fractions at certain points along the lib-
eration pathway. The plant is generally modular, where
the addition or mothballing of crushers or screens is likely
to be feasible, at least more feasible than trying to flex the
throughput requirements of a SAG-ball mill circuit.
Additional costs that need to be accounted for when
implementing sensor-based particle systems include those
associated with the stream preparation, incorporation of
the accept/reject system (typically compressed air) and
additional health and safety practices that may be required
related to sensor sources control dust and noise.
Operating costs associated with sorting were reported
by Wraith et al. (2021) for the Renison site. In 2021, the
total cost for crushing and sorting was $4.80/t RoM, with
$1.80/t attributed to the sorter, with the breakdown of the
ore sorter operating costs given in Figure 1.
water efficiency is, however, somewhat reduced, in the case
of particle based sorters and in some cases bulk sorting. Use
of the dry sorting techniques generates dust and to con-
trol emissions, water sprays are the standard solution. In
addition, there can also be a requirement to wash particles
ahead of sorters, should there be significant coating that
will impair the sensor and therefore sorting effectiveness.
The potential for preconcentration to reduce the mass
of treated ore and to work in association with other emerg-
ing techniques, i.e., compressive grinding, dry systems,
Coarse Particle Liberation (CPL), does however, support
options for reduction in tails generation, or a move to dry
stacked tails (Luukkanen et al., 2022)
In Pit and Pre-Plant Preconcentration.
Of the available approaches, bulk sorting can be suited to
in-pit preconcentration, as minimum handling helps pre-
serve ore heterogeneity and it can be adapted for shovels,
trucks and conveyors operating in the pit. Sensor tech-
nologies suitable for in-pit bulk sorting include XRF on
shovels and conveyor belts (Faraj et al, 2022, Keeney et al,
2020), Magnetic Resonance (MR) on trucks and conveyor
belts (Coghill et al. 2020), and PGNAA on conveyor belts
(Kurth and Balzan et al. 2020).
When dealing with the front end of the mining pro-
cess, shovel-based preconcentration can add significant
complexity in the management of the truck and shovel fleet
as the material destination of each truck is not known until
after the sensing of each individual shovel or truck payload.
This may require a larger truck fleet to absorb the extra
variability of the ore with multiple trucks required for each
shovel to sort the ore at the rock face. This not only adds
additional costs and decreases productivity of the mining
stage of the value chain, but can also result in significant
variations in mine to mill throughput.
Another complexity to consider is that often in-pit
real estate can be limited and adding additional unit oper-
ations such as bulk sorting into the pit can be challeng-
ing for the smooth operation of the pit. The challenges of
adopting In Pit Crush &Convey (IPCC) are analogous to
those of pit bulk ore sorting, being frequently studied but
rarely adopted for bulk mining projects. They are, however,
entirely complementary and could pose a viable option in
unison that would be infeasible individually. With regards
to costs, the creation of multiple streams can result in mul-
tiple handling events of the ore and waste which can lower
the value of the sorting benefits.
The transition zone between mining and processing,
or what the authors have described as “pre-plant” mostly
applies to material that has been primary crushed and is
therefore typically has a top size of 400 mm. In this area,
the conveyor belt situation offers improved presentation to
the sensors, both in terms of bed thickness and opportu-
nities to use automated rejection. Over-belt sensing using
PGNAA and MR have both been deployed in this duty
(singularly and in combination) and given the application
advantages, this appears to be one of the most prospective
areas for further development and deployment. In evalu-
ating MR applications, the range of minerals that can be
detected is a key consideration and although the technique
appears to offer several advantages, the match of the sensor
to the duty is critical. Details of the application of MR is
provided by NextOre (2024).
In some instances, screening (size-based preconcentra-
tion) of primary crushed material is also an option, provid-
ing there is the option to exploit clear-cut macro liberation
at the relatively large particle size.
In-Plant Preconcentration
Screening, particle based sorting and Dense Media
Separation (DMS) are the main methods for “coarse” par-
ticle in-plant concentration, as the heterogeneity being
exploited is the particle grade of the value mineral or its
proxy. This type of heterogeneity is not destroyed by mixing.
Particle sorting can therefore be performed on streams
which have been blended. In the case of sensor-based par-
ticle sorting, the main operational aspects to control are
sensor validation, stream preparation, on-going calibration,
safety related sensor considerations and costs.
The introduction of ore sorting to a multi-stage crush-
ing flowsheet has distinct advantages over a large milling
circuit. The multi-stage crushing process has, by definition,
a number of opportunities to intervene with ore sorting
or particular size fractions at certain points along the lib-
eration pathway. The plant is generally modular, where
the addition or mothballing of crushers or screens is likely
to be feasible, at least more feasible than trying to flex the
throughput requirements of a SAG-ball mill circuit.
Additional costs that need to be accounted for when
implementing sensor-based particle systems include those
associated with the stream preparation, incorporation of
the accept/reject system (typically compressed air) and
additional health and safety practices that may be required
related to sensor sources control dust and noise.
Operating costs associated with sorting were reported
by Wraith et al. (2021) for the Renison site. In 2021, the
total cost for crushing and sorting was $4.80/t RoM, with
$1.80/t attributed to the sorter, with the breakdown of the
ore sorter operating costs given in Figure 1.