2436 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
The Circuit
Figure 1 outlines the basic flowsheet of the Eagle Mill.
Ore is ground to around 120 microns in the ball mills and
floated with sodium isopropyl xanthate (SIPX) and methyl
isobutyl carbinol (MIBC) as the frother. After the bulk
roughers, the concentrate is reground to 30 microns before
feeding a cleaner circuit, followed by a copper/nickel sepa-
ration circuit. The high copper and nickel content of the
concentrates produce thick froth.
The fundamentals of flotation kinetics tell us that con-
centrates collected from the first rougher of a flotation cir-
cuit are generally of high grade. In some circuits, it can be
final grade material depending on what mineral is beimg
collected and requires no extra processing. With such a
high copper recovery in the first rougher at Eagle, discus-
sion began about the possibility of applying the author’s
successful work on the zinc circuit at Nyrstar’s Myra Falls
Mine (unpublished report). Applying flotation kinetics the-
ory, the idea involved taking the first rougher off as a final
concentrate (grade was suitable for zinc with little amounts
of other minerals) instead of sending it with the rest of the
zinc concentrate to the regrind. When head grades were
very high (10%), the material volume was too much for
the cleaner circuit, causing significant launder overflows.
With a large portion of the zinc rerouted around the clean-
ers, they never overflowed again regardless of the incoming
feed grade.
COPPER SELECTIVE REAGENTS
According to the literature1, pentlandite is susceptible to
flotation by a variety of copper selective collectors. However,
Table 1. Assays from November 2022 Bulk Rougher Survey,
with conversions into mineral assays
Ni Cu Fe S
Metal Grades 3.00% 2.65% 24.6% 13.7%
Pn Ch Po Py
Mineral Grades 8.77% 7.65% 17.6% 1.95%
Table 2. Metal recoveries from the first bulk rougher cell
Ni Cu Fe S MgO
62.41% 76.41% 25.91% 41.96% 5.09%
Figure 1. Flowsheet of the Eagle Humboldt Mill
The Circuit
Figure 1 outlines the basic flowsheet of the Eagle Mill.
Ore is ground to around 120 microns in the ball mills and
floated with sodium isopropyl xanthate (SIPX) and methyl
isobutyl carbinol (MIBC) as the frother. After the bulk
roughers, the concentrate is reground to 30 microns before
feeding a cleaner circuit, followed by a copper/nickel sepa-
ration circuit. The high copper and nickel content of the
concentrates produce thick froth.
The fundamentals of flotation kinetics tell us that con-
centrates collected from the first rougher of a flotation cir-
cuit are generally of high grade. In some circuits, it can be
final grade material depending on what mineral is beimg
collected and requires no extra processing. With such a
high copper recovery in the first rougher at Eagle, discus-
sion began about the possibility of applying the author’s
successful work on the zinc circuit at Nyrstar’s Myra Falls
Mine (unpublished report). Applying flotation kinetics the-
ory, the idea involved taking the first rougher off as a final
concentrate (grade was suitable for zinc with little amounts
of other minerals) instead of sending it with the rest of the
zinc concentrate to the regrind. When head grades were
very high (10%), the material volume was too much for
the cleaner circuit, causing significant launder overflows.
With a large portion of the zinc rerouted around the clean-
ers, they never overflowed again regardless of the incoming
feed grade.
COPPER SELECTIVE REAGENTS
According to the literature1, pentlandite is susceptible to
flotation by a variety of copper selective collectors. However,
Table 1. Assays from November 2022 Bulk Rougher Survey,
with conversions into mineral assays
Ni Cu Fe S
Metal Grades 3.00% 2.65% 24.6% 13.7%
Pn Ch Po Py
Mineral Grades 8.77% 7.65% 17.6% 1.95%
Table 2. Metal recoveries from the first bulk rougher cell
Ni Cu Fe S MgO
62.41% 76.41% 25.91% 41.96% 5.09%
Figure 1. Flowsheet of the Eagle Humboldt Mill