2352 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
surface from either the solid-gas or solid-liquid interface.
The methods are listed with brief descriptions below, fol-
lowed by a more detailed description of the apparatus used
for each dosing method.
• Conventional batch dosing (Batch method). This is
the conventional method of dosing collector to a flo-
tation system. Collector in aqueous solution is dosed
into the flotation pulp, and mechanically agitated for
a period of time as a conditioning step prior to flo-
tation. For this method, collector adsorption occurs
mainly at the solid-liquid interface.
• Aerosol collector dosing (Aero method). For this
method, collector is aerosolised and is dosed con-
tinuously to the air supplying the flotation system.
In this way, collector is present in high concentra-
tion when the air bubbles are formed in the flotation
cell, thereby placing collector on the bubble surfaces.
For this method, collector adsorption should occur
mostly at the solid-gas interface.
• Zero-conditioning dosing (Zero method). This
method is identical to the Aero method, except
instead of aerosolising the collector and dosing it
together with the air, the collector is dosed continu-
ously as an aqueous solution into the pulp. In prac-
tical terms, it is similar to the down-the-bank dos-
ing method practised on many industrial operations
where a portion of the collector is dosed up-front,
with one or more smaller additional points down
the flotation bank. For this dosing method, collec-
tor adsorption likely occurs at both the solid-gas and
solid-liquid interfaces.
The degree to which collector adsorption onto the mineral
surface occurs at the solid-gas or solid-liquid interface is a
major difference between these methods. However, another
key difference is how the collector concentration in the
pulp changes during the test. For the batch method, all the
collector is added up-front, so the initial concentration is
at its maximum, which then decreases over the course of
the test as collector adsorbed onto the mineral surfaces is
removed with the flotation concentrate. For the aero- and
zero methods, the collector is dosed continuously during
the test so that by the end of the test an equivalent quan-
tity of collector is dosed as would have been dosed using
the batch method. In this way, the collector concentration
begins at 0 ppm and ends with collector concentration at
maximum, as collector is transferred from the bubbles to
the pulp over the course of the test. This varying collector
concentration profile makes the zero- and aerosol methods
similar to the down-the-bank, or staged collector dosing,
which is established industry practice on many minerals
processing plants.
Down-the-bank collector dosing is recognised as an
effective means of boosting recovery and/or reducing col-
lector consumption (Wills and Finch, 2016). Bazin and
Proulx (2001) demonstrate using laboratory and plant
scale data that down-the-bank dosing has little effect on
the recovery of fine particles, but is effective in increasing
the recovery of coarser particles, while dosing less collector
overall. The proposed reasoning for this observation is that
fine particles require less collector to float, so are quickly
recovered at low collector doses, allowing coarser particles,
which require more collector to float effectively, to acquire
the necessary collector coverage with subsequent collector
additions.
The apparatus used for each of the dosing methods is
commercially available equipment. No specialised equip-
ment is required for the batch method. The required mass
of collector solution is placed in a beaker and added to the
flotation pulp at the beginning of the conditioning step as
shown in Figure 1A.
The aero method makes use of a nebuliser (Tekceleo
Micronice ® T45-M05) to aerosolise the collector. The
device operates by applying ultrasonic vibration to a micro-
perforated membrane. The surface tension of the liquid
causes it to disperse into a cloud of droplets on contact-
ing the vibrating membrane. This mechanism ensures that
the physical and chemical properties of the solution are
not significantly altered. A variable dosage rate is achieved
by varying the vibration duty cycle. Figure 1B shows the
nebuliser delivering aerosolised collector into the air line
supplying the flotation cell. Forbes et al. (2023) provides
detailed information regarding the use of the Micronice ®
T45 nebuliser in the application of reagent dosing to min-
eral flotation systems.
For the zero method, collector solution is continuously
delivered to the intensely mixed zone at the bottom of the
flotation cell by means of a variable speed positive displace-
ment pump (Watson-Marlow 100 series). This is illustrated
in Figure 1C. The pump speed is adjusted such that over
the duration of the test it will have delivered the mass of
solution required to achieve the dosage rate (g/t) specified
for that test.
Data Processing
Flotation products are assayed using X-ray fluorescence
(XRF). All samples are analysed on an unsized basis, and
the tailings and combined flotation concentrate samples
are analysed on a sized basis after being screened into
fine (–38µm), middling (–38µm to +75µm) and coarse
surface from either the solid-gas or solid-liquid interface.
The methods are listed with brief descriptions below, fol-
lowed by a more detailed description of the apparatus used
for each dosing method.
• Conventional batch dosing (Batch method). This is
the conventional method of dosing collector to a flo-
tation system. Collector in aqueous solution is dosed
into the flotation pulp, and mechanically agitated for
a period of time as a conditioning step prior to flo-
tation. For this method, collector adsorption occurs
mainly at the solid-liquid interface.
• Aerosol collector dosing (Aero method). For this
method, collector is aerosolised and is dosed con-
tinuously to the air supplying the flotation system.
In this way, collector is present in high concentra-
tion when the air bubbles are formed in the flotation
cell, thereby placing collector on the bubble surfaces.
For this method, collector adsorption should occur
mostly at the solid-gas interface.
• Zero-conditioning dosing (Zero method). This
method is identical to the Aero method, except
instead of aerosolising the collector and dosing it
together with the air, the collector is dosed continu-
ously as an aqueous solution into the pulp. In prac-
tical terms, it is similar to the down-the-bank dos-
ing method practised on many industrial operations
where a portion of the collector is dosed up-front,
with one or more smaller additional points down
the flotation bank. For this dosing method, collec-
tor adsorption likely occurs at both the solid-gas and
solid-liquid interfaces.
The degree to which collector adsorption onto the mineral
surface occurs at the solid-gas or solid-liquid interface is a
major difference between these methods. However, another
key difference is how the collector concentration in the
pulp changes during the test. For the batch method, all the
collector is added up-front, so the initial concentration is
at its maximum, which then decreases over the course of
the test as collector adsorbed onto the mineral surfaces is
removed with the flotation concentrate. For the aero- and
zero methods, the collector is dosed continuously during
the test so that by the end of the test an equivalent quan-
tity of collector is dosed as would have been dosed using
the batch method. In this way, the collector concentration
begins at 0 ppm and ends with collector concentration at
maximum, as collector is transferred from the bubbles to
the pulp over the course of the test. This varying collector
concentration profile makes the zero- and aerosol methods
similar to the down-the-bank, or staged collector dosing,
which is established industry practice on many minerals
processing plants.
Down-the-bank collector dosing is recognised as an
effective means of boosting recovery and/or reducing col-
lector consumption (Wills and Finch, 2016). Bazin and
Proulx (2001) demonstrate using laboratory and plant
scale data that down-the-bank dosing has little effect on
the recovery of fine particles, but is effective in increasing
the recovery of coarser particles, while dosing less collector
overall. The proposed reasoning for this observation is that
fine particles require less collector to float, so are quickly
recovered at low collector doses, allowing coarser particles,
which require more collector to float effectively, to acquire
the necessary collector coverage with subsequent collector
additions.
The apparatus used for each of the dosing methods is
commercially available equipment. No specialised equip-
ment is required for the batch method. The required mass
of collector solution is placed in a beaker and added to the
flotation pulp at the beginning of the conditioning step as
shown in Figure 1A.
The aero method makes use of a nebuliser (Tekceleo
Micronice ® T45-M05) to aerosolise the collector. The
device operates by applying ultrasonic vibration to a micro-
perforated membrane. The surface tension of the liquid
causes it to disperse into a cloud of droplets on contact-
ing the vibrating membrane. This mechanism ensures that
the physical and chemical properties of the solution are
not significantly altered. A variable dosage rate is achieved
by varying the vibration duty cycle. Figure 1B shows the
nebuliser delivering aerosolised collector into the air line
supplying the flotation cell. Forbes et al. (2023) provides
detailed information regarding the use of the Micronice ®
T45 nebuliser in the application of reagent dosing to min-
eral flotation systems.
For the zero method, collector solution is continuously
delivered to the intensely mixed zone at the bottom of the
flotation cell by means of a variable speed positive displace-
ment pump (Watson-Marlow 100 series). This is illustrated
in Figure 1C. The pump speed is adjusted such that over
the duration of the test it will have delivered the mass of
solution required to achieve the dosage rate (g/t) specified
for that test.
Data Processing
Flotation products are assayed using X-ray fluorescence
(XRF). All samples are analysed on an unsized basis, and
the tailings and combined flotation concentrate samples
are analysed on a sized basis after being screened into
fine (–38µm), middling (–38µm to +75µm) and coarse