1202 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
prior to flotation. This circuit would include a centrifugal
gravity unit as is standard in the majority of gold plants
operating today (Fullam et al., 2016).
Liberation is assumed to be the same for both circuits
and optimised for gold and sulphide minerals. In both
cases for the same primary grind, some coarse tellurides
may report to the gravity concentrate due to the relatively
high specific gravity of telluride minerals (eg calaverite SG
9.1—9.4 (Calaverite, 2024)).
Circuit 1: Separation of a Telluride Concentrate by
Sequential Flotation
A sequential flotation circuit produces a telluride flotation
concentrate prior to a sulphide flotation concentrate as
shown in Figure 2. Telluride minerals exhibit natural float-
ability (Shackleton et al., 2007 Yan &Hariyasa, 1997) and
this circuit is designed to utilise this property to maximise
tellurium recovery.
Telluride minerals would be floated in a collectorless
preflotation stage creating a low tonnage stream suitable for
tellurium extraction. Small amounts of frother would be
used to create a stable froth. Pyrite depressants such as the
use of lime and cyanide would be considered to improve
the grade of the telluride concentrate.
The operation of circuit 1 would enable the removal of
any naturally floating minerals to the telluride concentrate.
As a result, this circuit may present an opportunity to treat
ores containing carbonaceous material. The carbonaceous
material would be removed to the telluride concentrate
thereby reducing gold preg-robbing in latter stages. Other
naturally floating sulphides, such as chalcopyrite (Heyes
&Trahar, 1977), may also report to the preflotation con-
centrate thereby reducing the consumption of cyanide in
leaching stages due to the presence of copper.
Other potential benefits to telluride flotation from cir-
cuit 1 would be reduced surface contamination by grinding
media and process water, and minimisation of the deleteri-
ous effects of reagents. The flotation recovery of telluride
minerals was observed to worsen when xanthate was used as
a collector, a reagent often used for sulphide flotation (Yan
&Hariyasa, 1997). This circuit would maximise the prob-
ability of telluride particles being recovered prior to surface
contamination occurring.
In contrast, for circuit 1 potential telluride losses may
occur for any telluride minerals liberated by a regrind stage
in the sulphide flotation circuit. Liberated telluride min-
erals would likely report to the sulphide concentrate and
would not leach under standard sulphide leaching condi-
tions, potentially resulting in gold losses. It would be rec-
ommended to complete a full liberation assessment of the
flotation feed prior to implementing this circuit to deter-
mine the locking characteristics.
Circuit 1 would be best suited to a new operation. It
would be challenging to retrofit a telluride flotation circuit
to the start of an existing concentrator circuit as it would
be required to process the entire feed tonnage. This would
be a capital intensive option, require a large footprint and
potentially be disruptive to the existing operation during
commissioning stages.
A circuit similar to that shown in Figure 2 was suc-
cessfully operated at the Emperor Mine in Fiji from 1976
to 1980 (Colbert, 1980) confirming the operational viabil-
ity of the circuit. Lime was added to the grinding circuit
prior to flotation to depress pyrite and frother was added
to stabilise the froth. One stage of rougher flotation and
three stages of cleaning were utilised. The telluride tailings
were then conditioned with xanthate and sulphide minerals
floated.
Grinding Gravity
Telluride
flotation
Sulphide
flotation
Telluride
concentrate
Gold-Tellurium
Leach
Gold
Leach
Sulphide
concentrate
Figure 2. Processing circuit 1—sequential flotation (simplified)
prior to flotation. This circuit would include a centrifugal
gravity unit as is standard in the majority of gold plants
operating today (Fullam et al., 2016).
Liberation is assumed to be the same for both circuits
and optimised for gold and sulphide minerals. In both
cases for the same primary grind, some coarse tellurides
may report to the gravity concentrate due to the relatively
high specific gravity of telluride minerals (eg calaverite SG
9.1—9.4 (Calaverite, 2024)).
Circuit 1: Separation of a Telluride Concentrate by
Sequential Flotation
A sequential flotation circuit produces a telluride flotation
concentrate prior to a sulphide flotation concentrate as
shown in Figure 2. Telluride minerals exhibit natural float-
ability (Shackleton et al., 2007 Yan &Hariyasa, 1997) and
this circuit is designed to utilise this property to maximise
tellurium recovery.
Telluride minerals would be floated in a collectorless
preflotation stage creating a low tonnage stream suitable for
tellurium extraction. Small amounts of frother would be
used to create a stable froth. Pyrite depressants such as the
use of lime and cyanide would be considered to improve
the grade of the telluride concentrate.
The operation of circuit 1 would enable the removal of
any naturally floating minerals to the telluride concentrate.
As a result, this circuit may present an opportunity to treat
ores containing carbonaceous material. The carbonaceous
material would be removed to the telluride concentrate
thereby reducing gold preg-robbing in latter stages. Other
naturally floating sulphides, such as chalcopyrite (Heyes
&Trahar, 1977), may also report to the preflotation con-
centrate thereby reducing the consumption of cyanide in
leaching stages due to the presence of copper.
Other potential benefits to telluride flotation from cir-
cuit 1 would be reduced surface contamination by grinding
media and process water, and minimisation of the deleteri-
ous effects of reagents. The flotation recovery of telluride
minerals was observed to worsen when xanthate was used as
a collector, a reagent often used for sulphide flotation (Yan
&Hariyasa, 1997). This circuit would maximise the prob-
ability of telluride particles being recovered prior to surface
contamination occurring.
In contrast, for circuit 1 potential telluride losses may
occur for any telluride minerals liberated by a regrind stage
in the sulphide flotation circuit. Liberated telluride min-
erals would likely report to the sulphide concentrate and
would not leach under standard sulphide leaching condi-
tions, potentially resulting in gold losses. It would be rec-
ommended to complete a full liberation assessment of the
flotation feed prior to implementing this circuit to deter-
mine the locking characteristics.
Circuit 1 would be best suited to a new operation. It
would be challenging to retrofit a telluride flotation circuit
to the start of an existing concentrator circuit as it would
be required to process the entire feed tonnage. This would
be a capital intensive option, require a large footprint and
potentially be disruptive to the existing operation during
commissioning stages.
A circuit similar to that shown in Figure 2 was suc-
cessfully operated at the Emperor Mine in Fiji from 1976
to 1980 (Colbert, 1980) confirming the operational viabil-
ity of the circuit. Lime was added to the grinding circuit
prior to flotation to depress pyrite and frother was added
to stabilise the froth. One stage of rougher flotation and
three stages of cleaning were utilised. The telluride tailings
were then conditioned with xanthate and sulphide minerals
floated.
Grinding Gravity
Telluride
flotation
Sulphide
flotation
Telluride
concentrate
Gold-Tellurium
Leach
Gold
Leach
Sulphide
concentrate
Figure 2. Processing circuit 1—sequential flotation (simplified)