3
Lake City, Utah. Samples were obtained from a single cell
both before (using the original FloatForce design) and after
the installation of the new FloatForce+ rotor, allowing for a
consistent basis for evaluating power draw and motor effi-
ciency. Sampling was conducted in the fourth cell (704) of
Rougher Bank 7, a five-cell series, and included samples
collected based on a two-factor experimental design, along
with mixing profile samples. Details of the sampling meth-
odologies and the experimental setup are provided in the
following sub-sections.
Sampling Condition
During sampling campaigns, the percent solids and feed
flow rate to the rougher bank were kept consistent. The
feed percent solids were maintained at 30% by adjusting
the makeup water added to the feed box. The feed flow
rate was set at 1100 tons per hour (t/h) and controlled by
adjusting the feed pump speed, which in turn adjusted the
flow to the other three rougher banks in the circuit. Froth
depth in the cell sampled was kept at 13 inches for the mix-
ing profile measurements and at 14 inches for the metal-
lurgical tests.
Mixing Profile Measurements
To evaluate the mixing characteristics of both rotors, sam-
ples were collected from various depths within the cell.
Three rotor speeds,50, 55, and 60 Hz, corresponding to tip
speeds of 5.3, 5.9 and 6.4 m/s—were tested for each rotor.
The air flow rate was set at 580 standard cubic feet per min-
ute (scfm) and held constant throughout all mixing profile
sampling for both test campaigns. This air flow rate was
selected based on the automated control system utilized by
Kennecott to regulate airflows. By using froth velocity mea-
surements from the FrothSense camera system, the air sup-
ply was automatically adjusted to achieve a specific froth
velocity target. Before initiating each survey campaign, the
air flow rate was observed to be steady, indicating consistent
froth characteristics across the sampling rounds.
Design of Experiments (DoE Samples)
To evaluate the metallurgical performance of both rotors it
was decided to plan a Central Composite Rotable Design
(CCRD) optimization program using Minitab statistical
software. The method was chosen as it is used to determine
the optimum conditions for the flotation cell within the
chosen parameters. Two factors, air and rotor tip speed,
were chosen to be included and level was kept constant.
Using only two factors results 14 runs and it was thought
that it would be reasonable number of sampling rounds
to be completed so that steady state conditions would be
maintained during the survey, which is important in sta-
tistical design experiments. The range for both factors were
selected so that flotation cell was performing visually well,
and the statistical software Minitab was used to define the
parameters for the survey. With both rotors same motor
speed range 50 to 60 Hz (tip speed 5.3 to 6.4 m/s) were
maintained but the air flow range varied.
Figure 1. CFD predicted turbulent kinetic energy of FloatForce+
Figure 2. Newly designed FloatForce®+ rotor
Lake City, Utah. Samples were obtained from a single cell
both before (using the original FloatForce design) and after
the installation of the new FloatForce+ rotor, allowing for a
consistent basis for evaluating power draw and motor effi-
ciency. Sampling was conducted in the fourth cell (704) of
Rougher Bank 7, a five-cell series, and included samples
collected based on a two-factor experimental design, along
with mixing profile samples. Details of the sampling meth-
odologies and the experimental setup are provided in the
following sub-sections.
Sampling Condition
During sampling campaigns, the percent solids and feed
flow rate to the rougher bank were kept consistent. The
feed percent solids were maintained at 30% by adjusting
the makeup water added to the feed box. The feed flow
rate was set at 1100 tons per hour (t/h) and controlled by
adjusting the feed pump speed, which in turn adjusted the
flow to the other three rougher banks in the circuit. Froth
depth in the cell sampled was kept at 13 inches for the mix-
ing profile measurements and at 14 inches for the metal-
lurgical tests.
Mixing Profile Measurements
To evaluate the mixing characteristics of both rotors, sam-
ples were collected from various depths within the cell.
Three rotor speeds,50, 55, and 60 Hz, corresponding to tip
speeds of 5.3, 5.9 and 6.4 m/s—were tested for each rotor.
The air flow rate was set at 580 standard cubic feet per min-
ute (scfm) and held constant throughout all mixing profile
sampling for both test campaigns. This air flow rate was
selected based on the automated control system utilized by
Kennecott to regulate airflows. By using froth velocity mea-
surements from the FrothSense camera system, the air sup-
ply was automatically adjusted to achieve a specific froth
velocity target. Before initiating each survey campaign, the
air flow rate was observed to be steady, indicating consistent
froth characteristics across the sampling rounds.
Design of Experiments (DoE Samples)
To evaluate the metallurgical performance of both rotors it
was decided to plan a Central Composite Rotable Design
(CCRD) optimization program using Minitab statistical
software. The method was chosen as it is used to determine
the optimum conditions for the flotation cell within the
chosen parameters. Two factors, air and rotor tip speed,
were chosen to be included and level was kept constant.
Using only two factors results 14 runs and it was thought
that it would be reasonable number of sampling rounds
to be completed so that steady state conditions would be
maintained during the survey, which is important in sta-
tistical design experiments. The range for both factors were
selected so that flotation cell was performing visually well,
and the statistical software Minitab was used to define the
parameters for the survey. With both rotors same motor
speed range 50 to 60 Hz (tip speed 5.3 to 6.4 m/s) were
maintained but the air flow range varied.
Figure 1. CFD predicted turbulent kinetic energy of FloatForce+
Figure 2. Newly designed FloatForce®+ rotor