3
the flowsheet and parameters of the laboratory scale tests
with rougher magnetic separation (1,150 Gauss), followed
by regrind targeting a P80 of 40 microns and three cleaning
stages (750 Gauss each). This study was completed in two
stages: the first stage consisted of a multivariable optimi-
zation study for rougher and cleaner magnetic separation
stages, for relevant variables such as feed flowrate and feed
solids percentage, and the second stage consisted of using
defined optimum parameters for process validation the
results of the validation stage of the pilot testwork reported
an iron concentrate grade of 64.9% Fe (SGA, 2023)
at 15.7% mass recovery (Aminpro, 2021). Parameters
obtained were considered for iron concentration plant
design at the time.
In 2021 laboratory scale exploration testwork was
completed using a third stage cleaner concentrate sample
obtained from the magnetic separation pilot plant. The
study explored reverse flotation, screening and hydrosepara-
tion. Results indicated that reverse flotation has the poten-
tial to improve iron concentrate grade and reduce silica
content for the Santo Domingo ore. For the sample tested,
the iron concentrate grade improvement was from 65% Fe
to 67% Fe and SiO2 reduction was from 4.7% SiO2 to
3.0%SiO2 (Clariant, 2021). In addition, hydroseparation
testwork was conducted on reground rougher concentrate
resulting in an iron concentrate grade improvement from
52.9%Fe to 54.2%Fe (Polimin, 2021). Although reverse
flotation and hydroseparation were considered favorable,
potential challenges associated with water recirculation
quality were anticipated within the copper-iron concentra-
tor plant at full-scale and therefore only hydroseparation
was carried forward in the iron concentration plant design.
During 2022, additional testwork was completed using
a low intensity magnetic separator drum at laboratory scale
and a third stage cleaner concentrate sample obtained from
the magnetic separation pilot plant. The focus of this test-
work was to determine the number of magnetic separation
cleaning stages required to achieve Direct Reduction grade
iron product. As such, a total of eight magnetic separation
stages were considered and the results demonstrated that
iron concentrate grade could be improved incrementally
through each additional stage (Aminpro, 2022), leading
to a further update to the iron concentration plant design.
This study also explored using different magnetic strengths
in the cleaner circuit to determine the impact to iron
grade and recovery. Results indicated that higher selectiv-
ity could be achieved using lower magnetic strength (500
Gauss) within the cleaner stages at the expense of mass pull.
Other parameters were also tested during this program, but
results were less favorable and therefore not adopted into
the flowsheet.
In early 2023, a new copper flotation pilot plant was
conducted to demonstrate suitability of the copper circuit
flowsheet established at the time and to produce sufficient
rougher flotation tailings for a second iron concentration
pilot plant using the industrial diameter 48 in (1.2 m)
magnetic drum separator. The objectives of the second
iron concentration pilot plant were to produce sufficient
iron concentrate for downstream tests, confirm the design
parameters obtained from the multivariable optimization
study completed earlier (mainly feed flowrate and feed
percent solids) and confirm the benefits of the updated
flowsheet. This iron concentration pilot plant included
rougher magnetic separation (1,150 Gauss), followed by
Figure 3. Pilot low intensity magnetic separator drum of
industrial diameter (48 in) used for the Santo Domingo
project
the flowsheet and parameters of the laboratory scale tests
with rougher magnetic separation (1,150 Gauss), followed
by regrind targeting a P80 of 40 microns and three cleaning
stages (750 Gauss each). This study was completed in two
stages: the first stage consisted of a multivariable optimi-
zation study for rougher and cleaner magnetic separation
stages, for relevant variables such as feed flowrate and feed
solids percentage, and the second stage consisted of using
defined optimum parameters for process validation the
results of the validation stage of the pilot testwork reported
an iron concentrate grade of 64.9% Fe (SGA, 2023)
at 15.7% mass recovery (Aminpro, 2021). Parameters
obtained were considered for iron concentration plant
design at the time.
In 2021 laboratory scale exploration testwork was
completed using a third stage cleaner concentrate sample
obtained from the magnetic separation pilot plant. The
study explored reverse flotation, screening and hydrosepara-
tion. Results indicated that reverse flotation has the poten-
tial to improve iron concentrate grade and reduce silica
content for the Santo Domingo ore. For the sample tested,
the iron concentrate grade improvement was from 65% Fe
to 67% Fe and SiO2 reduction was from 4.7% SiO2 to
3.0%SiO2 (Clariant, 2021). In addition, hydroseparation
testwork was conducted on reground rougher concentrate
resulting in an iron concentrate grade improvement from
52.9%Fe to 54.2%Fe (Polimin, 2021). Although reverse
flotation and hydroseparation were considered favorable,
potential challenges associated with water recirculation
quality were anticipated within the copper-iron concentra-
tor plant at full-scale and therefore only hydroseparation
was carried forward in the iron concentration plant design.
During 2022, additional testwork was completed using
a low intensity magnetic separator drum at laboratory scale
and a third stage cleaner concentrate sample obtained from
the magnetic separation pilot plant. The focus of this test-
work was to determine the number of magnetic separation
cleaning stages required to achieve Direct Reduction grade
iron product. As such, a total of eight magnetic separation
stages were considered and the results demonstrated that
iron concentrate grade could be improved incrementally
through each additional stage (Aminpro, 2022), leading
to a further update to the iron concentration plant design.
This study also explored using different magnetic strengths
in the cleaner circuit to determine the impact to iron
grade and recovery. Results indicated that higher selectiv-
ity could be achieved using lower magnetic strength (500
Gauss) within the cleaner stages at the expense of mass pull.
Other parameters were also tested during this program, but
results were less favorable and therefore not adopted into
the flowsheet.
In early 2023, a new copper flotation pilot plant was
conducted to demonstrate suitability of the copper circuit
flowsheet established at the time and to produce sufficient
rougher flotation tailings for a second iron concentration
pilot plant using the industrial diameter 48 in (1.2 m)
magnetic drum separator. The objectives of the second
iron concentration pilot plant were to produce sufficient
iron concentrate for downstream tests, confirm the design
parameters obtained from the multivariable optimization
study completed earlier (mainly feed flowrate and feed
percent solids) and confirm the benefits of the updated
flowsheet. This iron concentration pilot plant included
rougher magnetic separation (1,150 Gauss), followed by
Figure 3. Pilot low intensity magnetic separator drum of
industrial diameter (48 in) used for the Santo Domingo
project