XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2421
slurry volume, 64% packing efficiency, and 25 vol% solid
were used to calculate the water volume, sample mass, and
total grinding media mass required for grinding. The esti-
mated values were 216 mL water, 199.30 g sample, and
3,968 g of balls. Afterward, chrome steel balls of varying
diameters were selected to have a total ball mass of approxi-
mately 3.96 kg for the study (see Table 3).
As the diameter (DM) of the 2 L mill jar is approxi-
mately 13.0 cm, the critical speed required for the mill-
ing process can be calculated in Equation 5. However, the
optimum rotational speed should be between 65 to 75% of
the critical speed (Dökme et al., 2017). As such, a grinding
speed of 82.2 rpm was used, as 70% of the calculated criti-
cal speed (117.4 rpm). 200 g of the representative sample
was used for each run of the grind calibration experiments.
The investigated grind times were 0, 3, 5, 10, 15, 20, and
30 min. Each experiment run was conducted three times
with fresh samples.
.3
.130
.3 N
D
42
0
42 117.4 rpm
c
M
===(5)
FLOTATION EXPERIMENTS
A 1.5 L Denver flotation cell was used for the flotation
experiments. After the grind calibration study, a grinding
time of 5 min was selected as it produced a suitably coarse
particle size distribution for investigating coarse particle
flotation. The experimental procedure started with the
addition of 1,250 mL water and 200 g sample after the
5 min grind. Then, the pH of the slurry was measured and
adjusted to 9 using NaOH (1 M). Afterward, the studied
collector was added and allowed to condition for 3 min.
Then, the 80 ppm frother (MIBC) was added and condi-
tioned for 1 min. The same frother dosage (80 ppm) was
used for each flotation test. After conditioning with the col-
lector and frother, the air was turned on at an air flowrate
of 5 L/min and an impeller speed of 700 rpm. The concen-
trates were collected at 1, 2, and 4 min at 10 s collection
intervals. Subsequently, the concentrates were dried in the
oven. Then, their dry weights were measured, and elemental
Table 3. Chrome steel ball mass and size for grind calibration
study
Diameter, cm Number Total Mass, kg
3.8 4 0.91
2.5 9 0.59
2.0 21 0.69
1.5 116 1.77
Total 150 3.96
compositions were examined using XRF to determine the
copper grade and recovery.
The experiment was initiated and conducted with the
following collectors:
a. Three PAX dosages (60, 120, 180 g/t) to under-
stand coarse particle flotation with the conventional
collector.
b. Three kerosene dosages (2.5, 5, and 10 µL), equiva-
lent to the amount of kerosene in the emulsions
below.
c. Three kerosene-in-water emulsion dosages (10, 20,
and 40 µL see below for calculations on estimated
dosages).
The emulsion dosage required for the flotation was cal-
culated based on the assumption that one 10 μm kerosene
oil droplet (4.19 × 10−10g) covers a 100 μm coarse particle
(1.45 × 10−6g) and an estimation of the number of particles
based on the grind calibration study. Based on XRF and
MLA analysis, the feed sample contained approximately
1wt.% Cu and 4wt.% chalcopyrite. With a feed of 200 g,
the mass is equivalent to 8 g, and the mass of the oil droplets
(mo) needed for the 8 g particles is calculated in Equation 6.
.45
.00231 M 8 4.19 10
1 10
0 g
o #
#==
-6
-10 ^h (6)
This is equivalent to oil volume (Vo) (kerosene, ρo =0.8 g/
cm3) estimated in Equation 7.
.8
.00231 .00288 V 0
0 0 cm
o
3 ==(7)
The volume of these oil droplets is approximately 2.88 µL.
Therefore, the volume of the emulsion required is 11.55 µL.
It was decided to investigate 10 µL, 20 µL, and 40 µL of
emulsion for the flotation experiments. The reagent dosages
corresponding to the 10 mL emulsion dose in the experi-
ment are provided in Table 4.
Table 4. Reagents dosages for the flotation experiments
MIBC,
ppm PAX, g/t
Kerosene
Only, g/t
Reagents (g/t) in
10 µL Emulsion
Kerosene PAX
80 60–180 10–40 10 0.11
RESULTS AND DISCUSSION
Emulsion Characteristics and Stability
The droplet size distribution of the kerosene-in-water emul-
sion with PAX measured with the Mastersizer 3000 is pro-
vided in Figure 1. This is depicted in terms of the volume
density and cumulative volume density versus size classes.
slurry volume, 64% packing efficiency, and 25 vol% solid
were used to calculate the water volume, sample mass, and
total grinding media mass required for grinding. The esti-
mated values were 216 mL water, 199.30 g sample, and
3,968 g of balls. Afterward, chrome steel balls of varying
diameters were selected to have a total ball mass of approxi-
mately 3.96 kg for the study (see Table 3).
As the diameter (DM) of the 2 L mill jar is approxi-
mately 13.0 cm, the critical speed required for the mill-
ing process can be calculated in Equation 5. However, the
optimum rotational speed should be between 65 to 75% of
the critical speed (Dökme et al., 2017). As such, a grinding
speed of 82.2 rpm was used, as 70% of the calculated criti-
cal speed (117.4 rpm). 200 g of the representative sample
was used for each run of the grind calibration experiments.
The investigated grind times were 0, 3, 5, 10, 15, 20, and
30 min. Each experiment run was conducted three times
with fresh samples.
.3
.130
.3 N
D
42
0
42 117.4 rpm
c
M
===(5)
FLOTATION EXPERIMENTS
A 1.5 L Denver flotation cell was used for the flotation
experiments. After the grind calibration study, a grinding
time of 5 min was selected as it produced a suitably coarse
particle size distribution for investigating coarse particle
flotation. The experimental procedure started with the
addition of 1,250 mL water and 200 g sample after the
5 min grind. Then, the pH of the slurry was measured and
adjusted to 9 using NaOH (1 M). Afterward, the studied
collector was added and allowed to condition for 3 min.
Then, the 80 ppm frother (MIBC) was added and condi-
tioned for 1 min. The same frother dosage (80 ppm) was
used for each flotation test. After conditioning with the col-
lector and frother, the air was turned on at an air flowrate
of 5 L/min and an impeller speed of 700 rpm. The concen-
trates were collected at 1, 2, and 4 min at 10 s collection
intervals. Subsequently, the concentrates were dried in the
oven. Then, their dry weights were measured, and elemental
Table 3. Chrome steel ball mass and size for grind calibration
study
Diameter, cm Number Total Mass, kg
3.8 4 0.91
2.5 9 0.59
2.0 21 0.69
1.5 116 1.77
Total 150 3.96
compositions were examined using XRF to determine the
copper grade and recovery.
The experiment was initiated and conducted with the
following collectors:
a. Three PAX dosages (60, 120, 180 g/t) to under-
stand coarse particle flotation with the conventional
collector.
b. Three kerosene dosages (2.5, 5, and 10 µL), equiva-
lent to the amount of kerosene in the emulsions
below.
c. Three kerosene-in-water emulsion dosages (10, 20,
and 40 µL see below for calculations on estimated
dosages).
The emulsion dosage required for the flotation was cal-
culated based on the assumption that one 10 μm kerosene
oil droplet (4.19 × 10−10g) covers a 100 μm coarse particle
(1.45 × 10−6g) and an estimation of the number of particles
based on the grind calibration study. Based on XRF and
MLA analysis, the feed sample contained approximately
1wt.% Cu and 4wt.% chalcopyrite. With a feed of 200 g,
the mass is equivalent to 8 g, and the mass of the oil droplets
(mo) needed for the 8 g particles is calculated in Equation 6.
.45
.00231 M 8 4.19 10
1 10
0 g
o #
#==
-6
-10 ^h (6)
This is equivalent to oil volume (Vo) (kerosene, ρo =0.8 g/
cm3) estimated in Equation 7.
.8
.00231 .00288 V 0
0 0 cm
o
3 ==(7)
The volume of these oil droplets is approximately 2.88 µL.
Therefore, the volume of the emulsion required is 11.55 µL.
It was decided to investigate 10 µL, 20 µL, and 40 µL of
emulsion for the flotation experiments. The reagent dosages
corresponding to the 10 mL emulsion dose in the experi-
ment are provided in Table 4.
Table 4. Reagents dosages for the flotation experiments
MIBC,
ppm PAX, g/t
Kerosene
Only, g/t
Reagents (g/t) in
10 µL Emulsion
Kerosene PAX
80 60–180 10–40 10 0.11
RESULTS AND DISCUSSION
Emulsion Characteristics and Stability
The droplet size distribution of the kerosene-in-water emul-
sion with PAX measured with the Mastersizer 3000 is pro-
vided in Figure 1. This is depicted in terms of the volume
density and cumulative volume density versus size classes.