2248 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
for slags, such as utilization in civil engineering, fertilizer
production, road construction, and landfilling, contrib-
uting to environmentally responsible metal production
(Shamsuddin, 2021). Slags from copper refining contain
a relatively high amount of copper in metallic form, but
also as oxides and sulphides, with other non-ferrous metals
being likewise present.
The copper smelter in Pirdop, Bulgaria, operated by
Aurubis Bulgaria AD, valorizes the generated copper slags
using flotation as main process aiming at maximizing cop-
per recovery and utilization. Despite extensive research on
the influence of pulp chemistry during sulphide ores flota-
tion (Adam et al., 1984 Bruckward et al., 2011 Gonçalves
et al., 2003 Greet et al., 2004 Huang &Grano, 2005a and
b Grano, 2009 Ekmekçi et al., 2005), the role of tempera-
ture variation in flotation of copper slags remains poorly
documented.
Previous observations (Pashkevich, Li, &Waters,
2022) suggested that temperature fluctuations affect grade,
recovery and selectivity in flotation. However, there is a
lack of comprehensive documentation on the tempera-
ture effects when copper slag flotation is concerned. While
temperature fluctuations and their impact on the flotation
of pyrite have been intensively studied (O’Connor &al.,
1984 O’Connor &Mills, 1990), the broader scope of
driving mechanisms affecting flotation has not been ade-
quately explored. The main objective of the present work is
to investigate the influence of temperature variation on the
flotation of the copper slags generated at Pirdop smelter.
This study aims to fill the existing literature gap by pro-
viding an added support on the influence of temperature
variation during the flotation of copper slags, thus contrib-
uting with insights into the cross-border aspects of mineral
processing and metallurgy of non-ferrous metals.
AURUBIS BULGARIA COPPER SMELTER,
PIRDOP
The pyrometallurgical process at Aurubis plant in Bulgaria
commences with blending and drying copper concentrates
before entering the flash smelter, ultimately yielding copper
matte with around 64% Cu. This matte is transformed into
high-purity blister copper, further refined to 99.5% Cu
anodes. The off-gas system controls and manages the emis-
sions from the smelter and converter sections sulfur-con-
taining gasses are used to produce sulfuric acid. The copper
anodes undergo electrorefining inside a tank house oper-
ated under controlled conditions. The tank house belong-
ing to the cathode production line, is dedicated to copper
electrorefining bringing high-grade (99.99% Cu) cathodes.
Iron silicate slags, produced by flash smelting and
converting are sent after being cooled and blended to the
processing plant, where they undergone size reduction and
flotation. Chemical reagents involving collectors (xantho-
genate) and frother are added at the various stages to facili-
tate flotation. The flotation plant with an annual capacity
of approximately 900000 tons produces final copper con-
centrate, grading about 20–27% Cu. Further on, the cop-
per concentrate is recycled back into the furnace as a blend
with raw (mineral) copper concentrates. The overall process
enables production of high-purity copper products through
sequence of metallurgical process units and operations, as
shown in the flowsheet (Figure 1).
EXPERIMENTAL
Sampling
Approximately 150 kilograms of copper slags were sourced
for the current study at Pirdop plant site. The material
was sampled from the cyclone overflow stream after the
Autogenous Mill. The sampling campaign lasted 4 days,
during which samples were collected ten times per day in
buckets, with each bucket collected 20 minutes after the
previous one. After overnight drying at 105 °C, around 4 kg
of dry sample was left in each bucket out of the initial mass
of 12–12.5 kg. Mixing and quartering of the collected slags
took place at Aurubis R&D laboratory on site, resulting in
14 bags with lots of 10.5 kg each, plus a sample lot of 5 kg.
The 14 bags were then shipped to the University of Liege,
while the 5 kg sample remained at Pirdop for comparative
cross-check assays with the results obtained in Liege.
Batch Flotation Tests
Grinding
The grinding tests were done with a sample of 1.4 kg which
was obtained by sub-sampling of the feed using riffle split-
ters. The grinding/milling under lab conditions aimed to
generate granulometry and P80 of the ground slag similar
to the one coming out from the autogenous mill stage
at the plant. For this purpose, 1.4 kg of copper slag and
1400 mL of tap water were added to a laboratory ball mill
‘Magotteaux,” leading to a prepared slurry of 30% w/w sol-
ids. The grinding media consisted of approximately 20 kg
forged steel balls of 34 mm diameter. The ball mill calibra-
tion tests indicated that grinding duration of 16 minutes
was required to achieve the granulometric target of D80
38 μm.
Flotation
Flotation was performed using a bottom-driven laboratory
Magotteaux Floatcell ® fitted with a 5-L cell. Air injection is
for slags, such as utilization in civil engineering, fertilizer
production, road construction, and landfilling, contrib-
uting to environmentally responsible metal production
(Shamsuddin, 2021). Slags from copper refining contain
a relatively high amount of copper in metallic form, but
also as oxides and sulphides, with other non-ferrous metals
being likewise present.
The copper smelter in Pirdop, Bulgaria, operated by
Aurubis Bulgaria AD, valorizes the generated copper slags
using flotation as main process aiming at maximizing cop-
per recovery and utilization. Despite extensive research on
the influence of pulp chemistry during sulphide ores flota-
tion (Adam et al., 1984 Bruckward et al., 2011 Gonçalves
et al., 2003 Greet et al., 2004 Huang &Grano, 2005a and
b Grano, 2009 Ekmekçi et al., 2005), the role of tempera-
ture variation in flotation of copper slags remains poorly
documented.
Previous observations (Pashkevich, Li, &Waters,
2022) suggested that temperature fluctuations affect grade,
recovery and selectivity in flotation. However, there is a
lack of comprehensive documentation on the tempera-
ture effects when copper slag flotation is concerned. While
temperature fluctuations and their impact on the flotation
of pyrite have been intensively studied (O’Connor &al.,
1984 O’Connor &Mills, 1990), the broader scope of
driving mechanisms affecting flotation has not been ade-
quately explored. The main objective of the present work is
to investigate the influence of temperature variation on the
flotation of the copper slags generated at Pirdop smelter.
This study aims to fill the existing literature gap by pro-
viding an added support on the influence of temperature
variation during the flotation of copper slags, thus contrib-
uting with insights into the cross-border aspects of mineral
processing and metallurgy of non-ferrous metals.
AURUBIS BULGARIA COPPER SMELTER,
PIRDOP
The pyrometallurgical process at Aurubis plant in Bulgaria
commences with blending and drying copper concentrates
before entering the flash smelter, ultimately yielding copper
matte with around 64% Cu. This matte is transformed into
high-purity blister copper, further refined to 99.5% Cu
anodes. The off-gas system controls and manages the emis-
sions from the smelter and converter sections sulfur-con-
taining gasses are used to produce sulfuric acid. The copper
anodes undergo electrorefining inside a tank house oper-
ated under controlled conditions. The tank house belong-
ing to the cathode production line, is dedicated to copper
electrorefining bringing high-grade (99.99% Cu) cathodes.
Iron silicate slags, produced by flash smelting and
converting are sent after being cooled and blended to the
processing plant, where they undergone size reduction and
flotation. Chemical reagents involving collectors (xantho-
genate) and frother are added at the various stages to facili-
tate flotation. The flotation plant with an annual capacity
of approximately 900000 tons produces final copper con-
centrate, grading about 20–27% Cu. Further on, the cop-
per concentrate is recycled back into the furnace as a blend
with raw (mineral) copper concentrates. The overall process
enables production of high-purity copper products through
sequence of metallurgical process units and operations, as
shown in the flowsheet (Figure 1).
EXPERIMENTAL
Sampling
Approximately 150 kilograms of copper slags were sourced
for the current study at Pirdop plant site. The material
was sampled from the cyclone overflow stream after the
Autogenous Mill. The sampling campaign lasted 4 days,
during which samples were collected ten times per day in
buckets, with each bucket collected 20 minutes after the
previous one. After overnight drying at 105 °C, around 4 kg
of dry sample was left in each bucket out of the initial mass
of 12–12.5 kg. Mixing and quartering of the collected slags
took place at Aurubis R&D laboratory on site, resulting in
14 bags with lots of 10.5 kg each, plus a sample lot of 5 kg.
The 14 bags were then shipped to the University of Liege,
while the 5 kg sample remained at Pirdop for comparative
cross-check assays with the results obtained in Liege.
Batch Flotation Tests
Grinding
The grinding tests were done with a sample of 1.4 kg which
was obtained by sub-sampling of the feed using riffle split-
ters. The grinding/milling under lab conditions aimed to
generate granulometry and P80 of the ground slag similar
to the one coming out from the autogenous mill stage
at the plant. For this purpose, 1.4 kg of copper slag and
1400 mL of tap water were added to a laboratory ball mill
‘Magotteaux,” leading to a prepared slurry of 30% w/w sol-
ids. The grinding media consisted of approximately 20 kg
forged steel balls of 34 mm diameter. The ball mill calibra-
tion tests indicated that grinding duration of 16 minutes
was required to achieve the granulometric target of D80
38 μm.
Flotation
Flotation was performed using a bottom-driven laboratory
Magotteaux Floatcell ® fitted with a 5-L cell. Air injection is