2
METALLURGICAL TESTS
The study was carried out on a sample of ore representative
of the first 10 years of the mining plan to feed the process.
The first studies were focused on obtaining ore with 100%
particle size under 3 mm from a closed circuit with a screen
and HPGR pilot equipment (Metso’s HRC300). The
HPGR product 3 mm screen undersize (e.g., rougher cir-
cuit feed) chemical composition was assayed at 27.5% total
Fe, 19.3% Satmagan magnetic Fe, 35.4% SiO2, 0.107%
Cu, and 2.7% S (Figure 2).
The undersize of the screen with P80 2000 μm was
tested by means of several sets of metallurgical tests in differ-
ent conditions and circuit configurations in the CMRL lab-
oratory in order to achieve the best process flowsheet under
the objectives of achieving high quality in final concentrate,
low process costs and being efficient and sustainable.
The following sections describe the key tests that helped
define the final flowsheet. In addition, the associated ben-
efits and recommended process equipment are presented.
Magnetite Liberation
The graph shows the iron and silica grades in the Davis tube
test concentrates performed at each size of the sample par-
ticle size distribution as received –3mm of the HPGR prod-
uct. Through this, the liberation by each range of particle
sizes is showed, which indicates a large liberation of mag-
netite with a decrease in silica content between 48 mesh
and 270 mesh at values of approximately 12% SiO2. Then,
from 270 mesh to 500 mesh the curve is flatter, indicating
that the reduction in size does not improve magnetite lib-
eration considerably. This condition makes it necessary to
propose a specific process design for this mineral that will
be explained later (Figure 3).
Cobbing Performance in a Single Stage
The magnetic rougher separation (cobbing) tests were
developed at three levels of magnetic intensity (800, 1,000
and 1,350 Gauss). The results show that at the intensities
of 1,000 and 1,350 Gauss the recovery of magnetic iron is
about 97% and the rejecting of siliceous gangue is similar
(about 32 to 33% of mass). This rejection contains very lit-
tle magnetite (1.46 – 1.54% Sat. Mag. Fe), so this process is
very efficient in rejecting gangue early avoiding its process-
ing, downstream of the process, especially in the primary
ball milling area with significant cost savings (Table 1).
Influence of HPGR and Cobbing on BWI
The decrease in the bond work index (BWI) is influenced
by the microfractures generated by the high pressure exerted
on the ore in HPGR equipment. The material received at
3 mm was the product of HPGR and was tested by the
BWI test at 150 mesh Ty (105 μm), as well as the concen-
trate obtained from the open circuit of magnetic rougher
separation (cobbing). The results show that the application
of HPGR reduces the BWI by 10.1% (13.5–12.5 kWh/
mt) and it is inferred that it would be related to the gen-
eration of microfractures generated by the high pressure of
the rollers. On the other hand, the application of magnetic
cobbing separation reduced the BWI by about 6.4% (12.5
– 11.7 kWh/mt), mainly influenced by rejection of high
hardness siliceous gangue, making the concentrate softer
(Table 2).
Primary Grinding Circuit
The next stage of the study was aimed at set up the best
grinding circuit, classification with meshes and achieving
Figure 3. Davis tube concentrate assay by size on –3 mm
HPGR product
Figure 2. As-received – 3mm HPGR product sizing
comparison
METALLURGICAL TESTS
The study was carried out on a sample of ore representative
of the first 10 years of the mining plan to feed the process.
The first studies were focused on obtaining ore with 100%
particle size under 3 mm from a closed circuit with a screen
and HPGR pilot equipment (Metso’s HRC300). The
HPGR product 3 mm screen undersize (e.g., rougher cir-
cuit feed) chemical composition was assayed at 27.5% total
Fe, 19.3% Satmagan magnetic Fe, 35.4% SiO2, 0.107%
Cu, and 2.7% S (Figure 2).
The undersize of the screen with P80 2000 μm was
tested by means of several sets of metallurgical tests in differ-
ent conditions and circuit configurations in the CMRL lab-
oratory in order to achieve the best process flowsheet under
the objectives of achieving high quality in final concentrate,
low process costs and being efficient and sustainable.
The following sections describe the key tests that helped
define the final flowsheet. In addition, the associated ben-
efits and recommended process equipment are presented.
Magnetite Liberation
The graph shows the iron and silica grades in the Davis tube
test concentrates performed at each size of the sample par-
ticle size distribution as received –3mm of the HPGR prod-
uct. Through this, the liberation by each range of particle
sizes is showed, which indicates a large liberation of mag-
netite with a decrease in silica content between 48 mesh
and 270 mesh at values of approximately 12% SiO2. Then,
from 270 mesh to 500 mesh the curve is flatter, indicating
that the reduction in size does not improve magnetite lib-
eration considerably. This condition makes it necessary to
propose a specific process design for this mineral that will
be explained later (Figure 3).
Cobbing Performance in a Single Stage
The magnetic rougher separation (cobbing) tests were
developed at three levels of magnetic intensity (800, 1,000
and 1,350 Gauss). The results show that at the intensities
of 1,000 and 1,350 Gauss the recovery of magnetic iron is
about 97% and the rejecting of siliceous gangue is similar
(about 32 to 33% of mass). This rejection contains very lit-
tle magnetite (1.46 – 1.54% Sat. Mag. Fe), so this process is
very efficient in rejecting gangue early avoiding its process-
ing, downstream of the process, especially in the primary
ball milling area with significant cost savings (Table 1).
Influence of HPGR and Cobbing on BWI
The decrease in the bond work index (BWI) is influenced
by the microfractures generated by the high pressure exerted
on the ore in HPGR equipment. The material received at
3 mm was the product of HPGR and was tested by the
BWI test at 150 mesh Ty (105 μm), as well as the concen-
trate obtained from the open circuit of magnetic rougher
separation (cobbing). The results show that the application
of HPGR reduces the BWI by 10.1% (13.5–12.5 kWh/
mt) and it is inferred that it would be related to the gen-
eration of microfractures generated by the high pressure of
the rollers. On the other hand, the application of magnetic
cobbing separation reduced the BWI by about 6.4% (12.5
– 11.7 kWh/mt), mainly influenced by rejection of high
hardness siliceous gangue, making the concentrate softer
(Table 2).
Primary Grinding Circuit
The next stage of the study was aimed at set up the best
grinding circuit, classification with meshes and achieving
Figure 3. Davis tube concentrate assay by size on –3 mm
HPGR product
Figure 2. As-received – 3mm HPGR product sizing
comparison