XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1203
The circuit in the 1970s and 1980s utilised Fagergren
and Agitair flotation cells (Colbert, 1980). Since then, cell
designs have changed significantly and high intensity cells
that produce fine bubbles may be more suited to fine tellu-
ride flotation. The use of these cells may result in higher fines
recovery and a reduction in cleaning stages (Farrokhpay et
al., 2021).
Circuit 2: Separation of a Telluride Concentrate by
Reverse Flotation
A reverse flotation circuit is shown in Figure 2. In this cir-
cuit a telluride concentrate is floated from the bulk con-
centrate leaving the sulphide (largely pyrite) concentrate as
the tailing. This separation stage would require the use of
sulphide depressants such as lime and/or cyanide. Other
sulphide depressant regimes would be considered.
A significant benefit for circuit 2 is the ability to ret-
rofit this circuit to an existing concentrator. As the process
would only be treating the low tonnage concentrate stream,
implementation would have a lower capital cost and a
smaller footprint.
Circuit 2 in Figure 3 relies on telluride minerals being
recovered to the bulk sulphide concentrate prior to a sep-
aration being made between the telluride and sulphide
minerals. As previously mentioned, telluride minerals may
be depressed by reagent used for bulk sulphide flotation
(e.g., xanthate). This would result in gold losses as in any
subsequent flotation tailings leach circuit as gold telluride
minerals are unlikely to leach under standard leach condi-
tions (pH12).
A further disadvantage would be the flotation of sul-
phide minerals to the telluride concentrate and the loss of
telluride minerals to the sulphide concentrate. The tellu-
ride-pyrite separation would require careful control to min-
imise pyrite contamination of the telluride concentrate and
telluride contamination of the sulphide concentrate. Fine
grinding of the bulk concentrate may be beneficial in this
stage not only by the potential liberation of telluride min-
erals, but as an opportunity to oxidise the sulphide miner-
als. Aeration and decreasing grind size has been found to
increase pyrite depression in pyritic copper-gold flotation
(Agorhom et al., 2015).
The flotation component of circuit 2 was attempted
at operations in the Kalgoorlie region during the 1960s
however it was not successfully implemented mainly due
to a decline in the tellurium price (Field, 1963). At North
Kalgurli operation a telluride concentrate consisting of 1
to 2% of the bulk concentrate weight, could be separated
from the bulk concentrate after conditioning with cyanide
and lime (Field, 1963). The telluride concentrate contained
most of the tellurium plus a significant proportion of the
gold. One major drawback with the circuit was the 10 day
telluride leaching time—the circuit was discontinued as
hundreds of ounces were held up in the telluride agitator
tank.
Grinding Gravity
Sulphide
concentrate
Telluride
concentrate
Gold-Tellurium
Leach
Gold Leach
Bulk
flotation
Bulk
concentrate
Figure 3. Processing circuit 2—reverse flotation (simplified)
The circuit in the 1970s and 1980s utilised Fagergren
and Agitair flotation cells (Colbert, 1980). Since then, cell
designs have changed significantly and high intensity cells
that produce fine bubbles may be more suited to fine tellu-
ride flotation. The use of these cells may result in higher fines
recovery and a reduction in cleaning stages (Farrokhpay et
al., 2021).
Circuit 2: Separation of a Telluride Concentrate by
Reverse Flotation
A reverse flotation circuit is shown in Figure 2. In this cir-
cuit a telluride concentrate is floated from the bulk con-
centrate leaving the sulphide (largely pyrite) concentrate as
the tailing. This separation stage would require the use of
sulphide depressants such as lime and/or cyanide. Other
sulphide depressant regimes would be considered.
A significant benefit for circuit 2 is the ability to ret-
rofit this circuit to an existing concentrator. As the process
would only be treating the low tonnage concentrate stream,
implementation would have a lower capital cost and a
smaller footprint.
Circuit 2 in Figure 3 relies on telluride minerals being
recovered to the bulk sulphide concentrate prior to a sep-
aration being made between the telluride and sulphide
minerals. As previously mentioned, telluride minerals may
be depressed by reagent used for bulk sulphide flotation
(e.g., xanthate). This would result in gold losses as in any
subsequent flotation tailings leach circuit as gold telluride
minerals are unlikely to leach under standard leach condi-
tions (pH12).
A further disadvantage would be the flotation of sul-
phide minerals to the telluride concentrate and the loss of
telluride minerals to the sulphide concentrate. The tellu-
ride-pyrite separation would require careful control to min-
imise pyrite contamination of the telluride concentrate and
telluride contamination of the sulphide concentrate. Fine
grinding of the bulk concentrate may be beneficial in this
stage not only by the potential liberation of telluride min-
erals, but as an opportunity to oxidise the sulphide miner-
als. Aeration and decreasing grind size has been found to
increase pyrite depression in pyritic copper-gold flotation
(Agorhom et al., 2015).
The flotation component of circuit 2 was attempted
at operations in the Kalgoorlie region during the 1960s
however it was not successfully implemented mainly due
to a decline in the tellurium price (Field, 1963). At North
Kalgurli operation a telluride concentrate consisting of 1
to 2% of the bulk concentrate weight, could be separated
from the bulk concentrate after conditioning with cyanide
and lime (Field, 1963). The telluride concentrate contained
most of the tellurium plus a significant proportion of the
gold. One major drawback with the circuit was the 10 day
telluride leaching time—the circuit was discontinued as
hundreds of ounces were held up in the telluride agitator
tank.
Grinding Gravity
Sulphide
concentrate
Telluride
concentrate
Gold-Tellurium
Leach
Gold Leach
Bulk
flotation
Bulk
concentrate
Figure 3. Processing circuit 2—reverse flotation (simplified)