2188 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Combustion Engineering, Inc.). Fractions with particle size
ranges of –38 µm and +38–75 µm were collected.
Methodology
Gas Dispersion Measurement
The volume of the collection zone occupied by gas bub-
bles, referred as the gas holdup (ε), can be utilized as an
evaluation parameter of gas dispersion. This is because the
gas holdup is a function of both the gas flow rate and the
bubble size (Finch and Dobby, 1990). The bed expansion
method can be used for the evaluation of the gas holdup.
The procedure involves measuring the location (height) of
the liquid surface before and after air flows enter in the
column. The gas holdup is obtained utilizing the following
Equation 1.
H
H H
i
i 0 f =
-
(1)
where Hi and H0 are the heights (measured from the
sparger) of the free surface after and before aeration, respec-
tively (Finch and Dobby, 1990).
The experimental setup for the gas dispersion (gas
holdup) measurements and microflotation is displayed
in Figure 1. The microflotation column is composed of a
gas entry tube at the bottom on the side, a glass porous
frit with an aperture size of 10 µm for the generation
of bubbles and a flotation lauder on the top for the col-
lection of concentrates during the flotation process.
The used air flowmeter was in the range between 0 and
500 mL/min.
The gas holdup measurement was carried out with dif-
ferent frother concentrations (20, 30, and 40 ppm) at dif-
ferent air flowrates (100 (0.22 cm/s), 150, 200, 250, 300,
350, 400, 450 and 500 mL/min) in the microflotation
column. For each experimental condition, the gas holdup
measurements were repeated 3 times, and the mean was
calculated.
The increase of frother (MIBC) concentration from 0
(deionised water) to 40 ppm, the gas holdup is increased
gradually at each air flowrate tested. Compared with
deionised water, when MIBC concentration is 20 and/
or 30 ppm, the plots to illustrate the gas holdup overlaps
with each other at some air flowrates, which is also proved
in Figure 2 (b), the increment in gas holdup when MIBC
is the similar to each other when MIBC concentration is
40 ppm, the gas holdup increases significantly. Based on the
gas holdup measurements, the preferred MIBC concentra-
tion is 40 ppm. However, from the perspective of reducing
the chemical dosage and taking the column capacity into
consideration, a concentration of 30 ppm is selected.
When the air flowrate was below 350 mL/min, due to
the small aperture size (10 µm) of the glass porous frit, the
pores are not fully taken to produce bubbles which means
the air pressure is not high enough to produce enough
bubbles for the microflotation process. When the air flow-
rate is 350 mL/min and above, the glass porous frit is fully
occupied to generate bubbles. During the gas holdup mea-
surement and microflotation process, sometimes the air
flowrate is unstable, the air flowrate is maintained in the
range of 300–400 mL/min.
XRD Analysis
The collected mineral particles with a particle size range
of 38–75 µm are used for the XRD analysis. XRD pat-
terns of the fresh mineral samples were determined by an
OLYMPUS BTX-513 instrument using Cu-Kα (λ =1.54
Å) radiation. The scanning range was between 5 and 55°
and the scanning step was 0.05°. The crystal particle size of
the minerals can be obtained using the Scherrer’s formula
in Equation 2.
Figure 1. Schematic diagram of the experimental setup
Combustion Engineering, Inc.). Fractions with particle size
ranges of –38 µm and +38–75 µm were collected.
Methodology
Gas Dispersion Measurement
The volume of the collection zone occupied by gas bub-
bles, referred as the gas holdup (ε), can be utilized as an
evaluation parameter of gas dispersion. This is because the
gas holdup is a function of both the gas flow rate and the
bubble size (Finch and Dobby, 1990). The bed expansion
method can be used for the evaluation of the gas holdup.
The procedure involves measuring the location (height) of
the liquid surface before and after air flows enter in the
column. The gas holdup is obtained utilizing the following
Equation 1.
H
H H
i
i 0 f =
-
(1)
where Hi and H0 are the heights (measured from the
sparger) of the free surface after and before aeration, respec-
tively (Finch and Dobby, 1990).
The experimental setup for the gas dispersion (gas
holdup) measurements and microflotation is displayed
in Figure 1. The microflotation column is composed of a
gas entry tube at the bottom on the side, a glass porous
frit with an aperture size of 10 µm for the generation
of bubbles and a flotation lauder on the top for the col-
lection of concentrates during the flotation process.
The used air flowmeter was in the range between 0 and
500 mL/min.
The gas holdup measurement was carried out with dif-
ferent frother concentrations (20, 30, and 40 ppm) at dif-
ferent air flowrates (100 (0.22 cm/s), 150, 200, 250, 300,
350, 400, 450 and 500 mL/min) in the microflotation
column. For each experimental condition, the gas holdup
measurements were repeated 3 times, and the mean was
calculated.
The increase of frother (MIBC) concentration from 0
(deionised water) to 40 ppm, the gas holdup is increased
gradually at each air flowrate tested. Compared with
deionised water, when MIBC concentration is 20 and/
or 30 ppm, the plots to illustrate the gas holdup overlaps
with each other at some air flowrates, which is also proved
in Figure 2 (b), the increment in gas holdup when MIBC
is the similar to each other when MIBC concentration is
40 ppm, the gas holdup increases significantly. Based on the
gas holdup measurements, the preferred MIBC concentra-
tion is 40 ppm. However, from the perspective of reducing
the chemical dosage and taking the column capacity into
consideration, a concentration of 30 ppm is selected.
When the air flowrate was below 350 mL/min, due to
the small aperture size (10 µm) of the glass porous frit, the
pores are not fully taken to produce bubbles which means
the air pressure is not high enough to produce enough
bubbles for the microflotation process. When the air flow-
rate is 350 mL/min and above, the glass porous frit is fully
occupied to generate bubbles. During the gas holdup mea-
surement and microflotation process, sometimes the air
flowrate is unstable, the air flowrate is maintained in the
range of 300–400 mL/min.
XRD Analysis
The collected mineral particles with a particle size range
of 38–75 µm are used for the XRD analysis. XRD pat-
terns of the fresh mineral samples were determined by an
OLYMPUS BTX-513 instrument using Cu-Kα (λ =1.54
Å) radiation. The scanning range was between 5 and 55°
and the scanning step was 0.05°. The crystal particle size of
the minerals can be obtained using the Scherrer’s formula
in Equation 2.
Figure 1. Schematic diagram of the experimental setup