2936 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
have been described elsewhere (Imhof, 1988 Imhof et al.,
2002 Imhof et al., 1993 Imhof and Brown, 2000 Imhof
et al., 2004 Imhof, 2005 Veliz et al., 2016).
Pyle et al. (2022) reported the application of the
Imhoflot ™ cell for a Russian gold concentrator at rougher
and scalper duties. It was shown that the cell could produce
a mass pull of 5–10% with an enrichment ratio of 10–20
at the rougher-scalper duty. For the cleaner stage, a mass
pull in the range of 50–60% with an enrichment ratio of
1.5–2.5 was obtained. These results showed the feasibil-
ity of using the Imhoflot ™ cell as a flash flotation unit for
rapid recovery of particles and increasing overall flotation
circuit throughput.
Kazzinc–Altyntau Kokshetau processing plant,
Kazakhstan processes annually eight million tons of gold-
bearing ore from the Vasilkovsky deposit. The ore contains
sulfide minerals (arsenopyrite, pyrite, chalcopyrite, pyrrho-
tite, bismuthinite, etc.), oxides (rutile, magnetite, goethite
and hematite) and other minerals mainly silicates (quartz,
mica, feldspar, carbonate, chlorite, etc.). The main mineral
bearing the gold in solid solution is arsenopyrite. However,
gold is also found as natural finely disseminated nuggets,
complex locked and intergrown within texture with ultra-
fine grains of about 0.3–2 µm.
The existing conventional tank cells are working well for
the intermediate particle sizes, however, they do not work
adequately for the fines and ultra-fines (less than 10–20
µm). Low gold concentrate grade is negatively influenc-
ing the ultrafine grinding capacity and leaching efficiency.
Also, the high recirculation load of fines and ultrafines in
the flotation circuit reduces concentrate quality and plant
capacity.
Furthermore, the plant operator aims to achieve a
higher gold content in the final concentrate and also reduce
the gold content in the tailings at 0.3 g/t. Unfortunately,
the final tailings still contain a high Au content of about
0.4–0.5 g/t during the pilot trial period. The optical micro-
scopic investigation indicated that the main gold loss is
from ultrafine gold grains (1–2 µm).
Following the promising pilot test result using two
Imhoflot G-14 cells in 2019/ 2020 on the cyclone II over-
flow (see Hoang et al. 2022).
This paper presents the pilot test onsite on three differ-
ent streamlines:
i. Scavenger froth concentrate to produce the final
gold concentrate without recirculating back into the
rougher circuit
ii. Final tailings to recover the ultra-fine that lost to the
tailings
iii. Cleaning test to produce a higher concentrate grade.
MATERIALS AND METHODS
Flowsheet and Tested Streams
The run of mine (ROM) ore contains about 2 g/t gold
(Au), after crushing (i.e., d75,3 is about 5 mm) it is fed to
the primary grinding and hydro cyclone I stage. The pro-
cessing plant is divided into two lines with a total through-
put of 1000–1200 t/h. The flotation section includes two
stages, first flotation stage is flash flotation (intermediate
size) after the first stage grinding and classification, i.e.,
hydro cyclone. The tailings of flash flotation goes through
the secondary grinding with cyclone II. The cyclone over-
flow with the d80,3 of about 71 µm and approximately
0.8 g/t Au is fed to the rougher flotation. The rougher tail-
ings is sent to the scavenger, the rougher concentrate is fur-
ther upgraded in two cleaner stages (Figure 1). The final
concentrate contains about 25–30 g/t of Au ground in the
ultrafine Stirred Media Detritor (SMD) mill then goes into
leaching processes.
Figure 1 shows the main flowsheet of the plant, includ-
ing milling, gravity separation and flotation, highlighting
the tested streams: pilot test 1) scavenger concentrate, 2)
final tailings and 3) cleaner feed.
Imhoflot Pilot Testworks
The main objectives of the pilot test are to demonstrate the
effectiveness of the Imhoflot ™ pneumatic Gcell for recov-
ering fine gold lost into the tailings and also to produce a
high concentrate grade of the scavenger concentrate and
cleaning, improving the gold grade and to improve over-
all recovery. The pilotplant flowsheet, shown in Figure 2,
consisted of two Imhoflot G-14 cells ((tangential feed to
the separator vessel with 1.4 m diameter)) in a series with
a throughput of 30–40 m3/h. A representative feed sample
was extracted from the existing flotation plant and pumped
to a feed sump—T 1 (cf. Figure 2). The pulpfroth level in
the flotation cell is controlled by an inner hidden weir and
the pinch valves. The design with recycling load can allow
to achieve high recoveries with only two cells. The main
variables that can be used to adjust performance are, feed
volume and pressure, aeration rate and froth depth.
Tested Streamlines—Feed to Pilot Plant
Scavenger Plant Concentrate
The average gold content of the existing scavenger mechan-
ical cell (feed to pilot plant) is 5.3 g/t (average value of
7 tests). Table 1 shows the particle size distribution and
gold distribution of the scavenger concentrate (sampling
point 1, Figure 1), it shows the feed grade (6.44 g/t) is a
bit higher than the average of 5.3 g/t. Note that the feed to
have been described elsewhere (Imhof, 1988 Imhof et al.,
2002 Imhof et al., 1993 Imhof and Brown, 2000 Imhof
et al., 2004 Imhof, 2005 Veliz et al., 2016).
Pyle et al. (2022) reported the application of the
Imhoflot ™ cell for a Russian gold concentrator at rougher
and scalper duties. It was shown that the cell could produce
a mass pull of 5–10% with an enrichment ratio of 10–20
at the rougher-scalper duty. For the cleaner stage, a mass
pull in the range of 50–60% with an enrichment ratio of
1.5–2.5 was obtained. These results showed the feasibil-
ity of using the Imhoflot ™ cell as a flash flotation unit for
rapid recovery of particles and increasing overall flotation
circuit throughput.
Kazzinc–Altyntau Kokshetau processing plant,
Kazakhstan processes annually eight million tons of gold-
bearing ore from the Vasilkovsky deposit. The ore contains
sulfide minerals (arsenopyrite, pyrite, chalcopyrite, pyrrho-
tite, bismuthinite, etc.), oxides (rutile, magnetite, goethite
and hematite) and other minerals mainly silicates (quartz,
mica, feldspar, carbonate, chlorite, etc.). The main mineral
bearing the gold in solid solution is arsenopyrite. However,
gold is also found as natural finely disseminated nuggets,
complex locked and intergrown within texture with ultra-
fine grains of about 0.3–2 µm.
The existing conventional tank cells are working well for
the intermediate particle sizes, however, they do not work
adequately for the fines and ultra-fines (less than 10–20
µm). Low gold concentrate grade is negatively influenc-
ing the ultrafine grinding capacity and leaching efficiency.
Also, the high recirculation load of fines and ultrafines in
the flotation circuit reduces concentrate quality and plant
capacity.
Furthermore, the plant operator aims to achieve a
higher gold content in the final concentrate and also reduce
the gold content in the tailings at 0.3 g/t. Unfortunately,
the final tailings still contain a high Au content of about
0.4–0.5 g/t during the pilot trial period. The optical micro-
scopic investigation indicated that the main gold loss is
from ultrafine gold grains (1–2 µm).
Following the promising pilot test result using two
Imhoflot G-14 cells in 2019/ 2020 on the cyclone II over-
flow (see Hoang et al. 2022).
This paper presents the pilot test onsite on three differ-
ent streamlines:
i. Scavenger froth concentrate to produce the final
gold concentrate without recirculating back into the
rougher circuit
ii. Final tailings to recover the ultra-fine that lost to the
tailings
iii. Cleaning test to produce a higher concentrate grade.
MATERIALS AND METHODS
Flowsheet and Tested Streams
The run of mine (ROM) ore contains about 2 g/t gold
(Au), after crushing (i.e., d75,3 is about 5 mm) it is fed to
the primary grinding and hydro cyclone I stage. The pro-
cessing plant is divided into two lines with a total through-
put of 1000–1200 t/h. The flotation section includes two
stages, first flotation stage is flash flotation (intermediate
size) after the first stage grinding and classification, i.e.,
hydro cyclone. The tailings of flash flotation goes through
the secondary grinding with cyclone II. The cyclone over-
flow with the d80,3 of about 71 µm and approximately
0.8 g/t Au is fed to the rougher flotation. The rougher tail-
ings is sent to the scavenger, the rougher concentrate is fur-
ther upgraded in two cleaner stages (Figure 1). The final
concentrate contains about 25–30 g/t of Au ground in the
ultrafine Stirred Media Detritor (SMD) mill then goes into
leaching processes.
Figure 1 shows the main flowsheet of the plant, includ-
ing milling, gravity separation and flotation, highlighting
the tested streams: pilot test 1) scavenger concentrate, 2)
final tailings and 3) cleaner feed.
Imhoflot Pilot Testworks
The main objectives of the pilot test are to demonstrate the
effectiveness of the Imhoflot ™ pneumatic Gcell for recov-
ering fine gold lost into the tailings and also to produce a
high concentrate grade of the scavenger concentrate and
cleaning, improving the gold grade and to improve over-
all recovery. The pilotplant flowsheet, shown in Figure 2,
consisted of two Imhoflot G-14 cells ((tangential feed to
the separator vessel with 1.4 m diameter)) in a series with
a throughput of 30–40 m3/h. A representative feed sample
was extracted from the existing flotation plant and pumped
to a feed sump—T 1 (cf. Figure 2). The pulpfroth level in
the flotation cell is controlled by an inner hidden weir and
the pinch valves. The design with recycling load can allow
to achieve high recoveries with only two cells. The main
variables that can be used to adjust performance are, feed
volume and pressure, aeration rate and froth depth.
Tested Streamlines—Feed to Pilot Plant
Scavenger Plant Concentrate
The average gold content of the existing scavenger mechan-
ical cell (feed to pilot plant) is 5.3 g/t (average value of
7 tests). Table 1 shows the particle size distribution and
gold distribution of the scavenger concentrate (sampling
point 1, Figure 1), it shows the feed grade (6.44 g/t) is a
bit higher than the average of 5.3 g/t. Note that the feed to