XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3583
Dry High Intensity Magnetic Separation
Tripathy et al. (2017) investigated the separation of hema-
tite fines from a low-grade ore using dry high-intensity
magnetic separators. It was concluded that dry high-inten-
sity magnetic separation can serve as a pre-concentrator/
scavenger unit, effectively rejecting a significant amount
of gangue. This approach helps conserve energy, especially
in the context of fine grinding for ore liberation (Tripathy
et al, 2017). Tripathy et al (2014) also conducted a com-
prehensive laboratory testwork using a dry high intensity
induced roll magnetic separator for concentrating hema-
tite fines, employing response surface methodology. The
optimized levels of process variables led to the attainment
of a maximum grade of 51.2% Fe with about 50% recov-
ery (Tripathy et al, 2014). Vale SA, Brazil, has invested
in a demo scale plant on dry separation using rare earth
roll magnetic separators for the beneficiation of iron ore
upstream of flotation. A simplified flowsheet for the dry
beneficiation of iron ore as described by Donda et al, 2019
is shown in Figure 3.
Ore Sorting
Sensor-based ore sorting is one of the promising technolo-
gies with potential to separate iron-bearing minerals or
gangue-bearing minerals from bulk ore. Ore sorting is gain-
ing importance for dry coarse particle separation to pre-
concentrate the feed prior fine grinding and beneficiation.
However, the technology is still under development and
is not yet mature. The ore sorting technology was initially
introduced in the 1930s and 1940s but had limited appli-
cation in the mining industry due to low machine through-
puts and constraints in the capabilities of existing sorters.
Recent advancements in detector technology, coupled with
increased computing capacity (enhanced machine capac-
ity), have now made sorting feasible for mining applica-
tions (Lessard et al, 2016). The potential use of sensor-based
sorters in the mining industry addresses the need to cut
costs, particularly in the context of declining ore grades and
rising tonnages. Various sensors can be employed based on
the specific characteristics of the minerals to be sorted. Key
technologies include X-ray fluorescence, X-ray transmis-
sion, and radiometric sorting.
Zero Waste Processes
The concept of zero waste is a theme which addresses both
sustainability and the circular economy. Conventional
concentrators generate tailings, usually in the form of a
slurry which consists of finely ground mineral particles
and huge volumes of process water. The tailings stream is
usually dewatered using thickeners (e.g., high rate, paste,
lamella, etc.) and the thickener overflow is recycled back to
the concentrator while the underflow is pumped to tailings
dams. Selection of the dewatering technology, flocculent,
and optimisation of the dewatering circuit are critical to
produce a clear thickener overflow for recycling back to the
concentrator. Both process water and tailings management
are important to improve the environmental footprint of
iron processing plants in the USA.
Water Management
Minnesota hosts 10% of the world’s surface fresh water by
volume. Mining operations consume a lot of water, and
there is therefore a need for the design of zero effluent dis-
charge concentrators to conserve freshwater sources. Process
water recycling also reduces or eliminates the release of pro-
cess water into surface freshwater bodies. Most iron ore
concentrators in the USA recycle process water. However,
there is anecdotal evidence from plant personnel suggesting
that process water quality negatively affects unit operations
like fine screening. It is also reported that the hematite flo-
tation process, especially the selective flocculation delim-
ing process, is sensitive to process water quality (Iwasaki,
2020). Recycling of process water results in accumulation
of ions, residual reagents, and organics which may be det-
rimental or beneficial to the concentrator’s metallurgical
performance. Extensive research is therefore necessary to
design closed water concentrators as well as water manage-
ment/optimisation protocols and procedures for the iron
Figure 3. Process flow sheet for dry concentration of iron ore
(Donda, 2019)
Dry High Intensity Magnetic Separation
Tripathy et al. (2017) investigated the separation of hema-
tite fines from a low-grade ore using dry high-intensity
magnetic separators. It was concluded that dry high-inten-
sity magnetic separation can serve as a pre-concentrator/
scavenger unit, effectively rejecting a significant amount
of gangue. This approach helps conserve energy, especially
in the context of fine grinding for ore liberation (Tripathy
et al, 2017). Tripathy et al (2014) also conducted a com-
prehensive laboratory testwork using a dry high intensity
induced roll magnetic separator for concentrating hema-
tite fines, employing response surface methodology. The
optimized levels of process variables led to the attainment
of a maximum grade of 51.2% Fe with about 50% recov-
ery (Tripathy et al, 2014). Vale SA, Brazil, has invested
in a demo scale plant on dry separation using rare earth
roll magnetic separators for the beneficiation of iron ore
upstream of flotation. A simplified flowsheet for the dry
beneficiation of iron ore as described by Donda et al, 2019
is shown in Figure 3.
Ore Sorting
Sensor-based ore sorting is one of the promising technolo-
gies with potential to separate iron-bearing minerals or
gangue-bearing minerals from bulk ore. Ore sorting is gain-
ing importance for dry coarse particle separation to pre-
concentrate the feed prior fine grinding and beneficiation.
However, the technology is still under development and
is not yet mature. The ore sorting technology was initially
introduced in the 1930s and 1940s but had limited appli-
cation in the mining industry due to low machine through-
puts and constraints in the capabilities of existing sorters.
Recent advancements in detector technology, coupled with
increased computing capacity (enhanced machine capac-
ity), have now made sorting feasible for mining applica-
tions (Lessard et al, 2016). The potential use of sensor-based
sorters in the mining industry addresses the need to cut
costs, particularly in the context of declining ore grades and
rising tonnages. Various sensors can be employed based on
the specific characteristics of the minerals to be sorted. Key
technologies include X-ray fluorescence, X-ray transmis-
sion, and radiometric sorting.
Zero Waste Processes
The concept of zero waste is a theme which addresses both
sustainability and the circular economy. Conventional
concentrators generate tailings, usually in the form of a
slurry which consists of finely ground mineral particles
and huge volumes of process water. The tailings stream is
usually dewatered using thickeners (e.g., high rate, paste,
lamella, etc.) and the thickener overflow is recycled back to
the concentrator while the underflow is pumped to tailings
dams. Selection of the dewatering technology, flocculent,
and optimisation of the dewatering circuit are critical to
produce a clear thickener overflow for recycling back to the
concentrator. Both process water and tailings management
are important to improve the environmental footprint of
iron processing plants in the USA.
Water Management
Minnesota hosts 10% of the world’s surface fresh water by
volume. Mining operations consume a lot of water, and
there is therefore a need for the design of zero effluent dis-
charge concentrators to conserve freshwater sources. Process
water recycling also reduces or eliminates the release of pro-
cess water into surface freshwater bodies. Most iron ore
concentrators in the USA recycle process water. However,
there is anecdotal evidence from plant personnel suggesting
that process water quality negatively affects unit operations
like fine screening. It is also reported that the hematite flo-
tation process, especially the selective flocculation delim-
ing process, is sensitive to process water quality (Iwasaki,
2020). Recycling of process water results in accumulation
of ions, residual reagents, and organics which may be det-
rimental or beneficial to the concentrator’s metallurgical
performance. Extensive research is therefore necessary to
design closed water concentrators as well as water manage-
ment/optimisation protocols and procedures for the iron
Figure 3. Process flow sheet for dry concentration of iron ore
(Donda, 2019)