3
the best performance in the concentration stages down-
stream of the process. The main objective was to achieve
around 100% circulating load to ensure the best conditions
for size separation. The type of circuit tested was the closed
type with direct feed to the ball mill. Studies showed that
the best performance is achieved at 300 μm mesh cut size.
The P80 of the 300 µm screen oversize and undersize
were 1,277 microns and 178 microns, respectively. The
estimated recirculating load relative to the screen feed was
104% (Figure 4).
The cobbing circuit 300 µm screen undersize (e.g., cob-
bing LIMS concentrate) chemical composition was found
to be 35.3% total Fe, 27.8% Satmagan magnetic Fe, 30.5%
SiO2, 0.057% Cu, and 2.38% S.
Secondary grinding circuit with intermediate magnetic
separation
Subsequently, the main objectives were set to address the
design of the following stages, which were: first, to reduce
the tonnage that went to the secondary grinding stage and
second, to achieve in the secondary grinding circuit the low-
est percentage of particles less than 25 microns in the under-
size product. The studies showed that the incorporation of
a double-pass intermediate magnetic separation stage of
1,350 Gauss between the secondary grinding circuit met
the objectives set by rejecting 32% of the mass entering the
circuit. In turn, the circulating load resulted in only 2% at
a cut size of 53 µm which delivered a P80 of 37 µm. On the
other hand, the undersize of the sieve reached an iron grade
of 47.13% and 23.80% SiO2, this material was tested in
Davis tube demonstrating that it is possible to reach silica
less than 5%. The Davis tube results on the oversize indi-
cate that its passage is necessary for intermediate magnetic
separation (Tables 3 and 4).
Desliming and Magnetic Separation Cleaner
Three different circuits were tested to determine the grade
vs. recovery of each circuit. The three flowsheets were
LIMS-only, elutriation-only, and a combination of elutria-
tion-and-LIMS. The best result was achieved with the com-
bination of elutriation desliming and a double-pass LIMS
stage at 800 Gauss (Table 5 and Figure 5).
Table 1. Cobbing lab-scale LIMS – Magnetic field intensity testing
Product Wt (%)
Total
Fe (%)
Sat Mag
Fe (%)
SiO
2 (%)
Total Fe
Dist (%)
Sat Mag Fe
Dist (%)
SiO
2 Dist (%)
1350 Gauss
Concentrate 67.7 35.67 28.26 34.33 86.1 97.6 58.6
Tailings 32.3 12.09 1.46 50.84 13.9 2.4 41.4
1000 Gauss
Concentrate 66.4 36.36 29.76 33.79 85.8 97.4 56.0
Tailings 33.6 11.93 1.54 52.48 14.2 2.6 44.0
800 Gauss
Concentrate 62.6 36.53 28.55 33.12 83.1 96.3 52.4
Tailings 37.4 12.49 1.84 50.51 16.9 3.7 47.6
Table 2. BWI and percentage decrease in each product.
Item
BWI 150# Ty Reduction
(%)(kWh/tm) (kWh/tc)
Mine plant (composite
1st 10 year)*
13,9
Feed to LIMS 1350 G
(HPGR –3 mm)
12,5 11,3 –10,1
Concentrate from
LIMS 1350 G
11,7 10,6 –6,4
*the value of the BWI from the mining plan was projected
through the block model from tests for each UGM belonging to
the hardness variability study.
Figure 4. Rougher circuit testing -Bulk product size balance
with 300 µm closing screen
the best performance in the concentration stages down-
stream of the process. The main objective was to achieve
around 100% circulating load to ensure the best conditions
for size separation. The type of circuit tested was the closed
type with direct feed to the ball mill. Studies showed that
the best performance is achieved at 300 μm mesh cut size.
The P80 of the 300 µm screen oversize and undersize
were 1,277 microns and 178 microns, respectively. The
estimated recirculating load relative to the screen feed was
104% (Figure 4).
The cobbing circuit 300 µm screen undersize (e.g., cob-
bing LIMS concentrate) chemical composition was found
to be 35.3% total Fe, 27.8% Satmagan magnetic Fe, 30.5%
SiO2, 0.057% Cu, and 2.38% S.
Secondary grinding circuit with intermediate magnetic
separation
Subsequently, the main objectives were set to address the
design of the following stages, which were: first, to reduce
the tonnage that went to the secondary grinding stage and
second, to achieve in the secondary grinding circuit the low-
est percentage of particles less than 25 microns in the under-
size product. The studies showed that the incorporation of
a double-pass intermediate magnetic separation stage of
1,350 Gauss between the secondary grinding circuit met
the objectives set by rejecting 32% of the mass entering the
circuit. In turn, the circulating load resulted in only 2% at
a cut size of 53 µm which delivered a P80 of 37 µm. On the
other hand, the undersize of the sieve reached an iron grade
of 47.13% and 23.80% SiO2, this material was tested in
Davis tube demonstrating that it is possible to reach silica
less than 5%. The Davis tube results on the oversize indi-
cate that its passage is necessary for intermediate magnetic
separation (Tables 3 and 4).
Desliming and Magnetic Separation Cleaner
Three different circuits were tested to determine the grade
vs. recovery of each circuit. The three flowsheets were
LIMS-only, elutriation-only, and a combination of elutria-
tion-and-LIMS. The best result was achieved with the com-
bination of elutriation desliming and a double-pass LIMS
stage at 800 Gauss (Table 5 and Figure 5).
Table 1. Cobbing lab-scale LIMS – Magnetic field intensity testing
Product Wt (%)
Total
Fe (%)
Sat Mag
Fe (%)
SiO
2 (%)
Total Fe
Dist (%)
Sat Mag Fe
Dist (%)
SiO
2 Dist (%)
1350 Gauss
Concentrate 67.7 35.67 28.26 34.33 86.1 97.6 58.6
Tailings 32.3 12.09 1.46 50.84 13.9 2.4 41.4
1000 Gauss
Concentrate 66.4 36.36 29.76 33.79 85.8 97.4 56.0
Tailings 33.6 11.93 1.54 52.48 14.2 2.6 44.0
800 Gauss
Concentrate 62.6 36.53 28.55 33.12 83.1 96.3 52.4
Tailings 37.4 12.49 1.84 50.51 16.9 3.7 47.6
Table 2. BWI and percentage decrease in each product.
Item
BWI 150# Ty Reduction
(%)(kWh/tm) (kWh/tc)
Mine plant (composite
1st 10 year)*
13,9
Feed to LIMS 1350 G
(HPGR –3 mm)
12,5 11,3 –10,1
Concentrate from
LIMS 1350 G
11,7 10,6 –6,4
*the value of the BWI from the mining plan was projected
through the block model from tests for each UGM belonging to
the hardness variability study.
Figure 4. Rougher circuit testing -Bulk product size balance
with 300 µm closing screen