2342 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
• Disruption of the froth on subsequent flotation sepa-
rations, due to any remaining floating organic car-
bon (froth stability can be impacted significantly).
• The co-flotation (or entrainment) of value metals
and minerals resulting in lower overall circuit recov-
ery of those metals and minerals.
The main elements impacting a successful flotation sepa-
ration were described by Fuerstenau (1999) as a balance
between mechanical, physical and chemical factors. Physical
factors include the circuit design and cell selection, while
operational parameters include variables such as particle
size, %solids and ore mineralogy/type. Chemical factors
include not only reagents (collectors, frothers or depres-
sants and dispersants), but also pH conditions, flotation
feed preparation conditions (grinding media selection—for
example high chrome media versus mild steel media) and
water chemistry. While physical and operational parameters
can typically be adjusted to a limited degree, there is greater
flexibility in making a chemistry adjustment in operations.
It is also important to recognize, that without applying the
appropriate chemistry, the flotation separation will not be
able to reach its true full potential.
The purpose of this paper is to describe the importance
of understanding not only the ore mineralogy but also
the value of evaluating the flotation chemistry in order to
achieve the most successful flotation separation outcome. A
recent operational example of floating complex polymetal-
lic ores in the presence of organic carbon will be provided
to illustrate the value of the approach in developing and
implementing a solution in practice.
DESCRIPTION OF POLYMETALLIC
FLOTATION FLOWSHEET
The example provided pertains to a polymetallic ore
being processed using flotation to recover both a galena
(lead) and sphalerite (zinc) concentrate. Both concentrates
also contain measurable quantities of precious metals (gold
and silver). The flotation circuit comprises of a number of
sequential flotation operations (Figure 1):
• Carbon Pre-Float
• Lead Flotation
• Zinc Flotation
• Pyrite Flotation
The flowsheet originally comprised of only the lead and
zinc flotation circuits. With the imminent change in ore
mineralogy (second mine pit) that contained organic car-
bon in sufficient quantities to cause consistent issues in flo-
tation, the decision was made to add the Carbon Pre-Float
circuit, along with the Pyrite Flotation and Leach circuit to
augment overall gold recovery. The Carbon Pre-Float cir-
cuit never worked well due to operating challenges, includ-
ing froth phase management, misplaced lead and zinc
values, and losses in gold recovery as the subsequent carbon
concentrate treatment was unsuccessful at mitigating gold
recovery losses. The residual organic carbon remaining post
Carbon Pre-Float circuit, was sufficient to create significant
problems with froth transport in both the lead roughing
and cleaner circuits. The only immediate option to man-
age these problems was to reduce the mill feed rate which
resulted in a significant decrease in throughput. A number
of likely reasons for the challenges experienced with the
Carbon Pre-float circuit include:
• Insufficient retention time (short circuiting due to
the selection of 2 carbon rougher cells per line in the
design).
• Entrainment of values (feed %solids likely not
optimal).
• Inadequate reagent dosing control.
Pb
Flotag415on
Zn
Flotag415on
Pyrite
Flotag415on
TCM
Pre-Flotag415on
TCM
Concentrate Pb Concentrate Zn Concentrate TCM/Au-Ag
Concentrate Regrind
Pre-Leach
Flotag415on
Tailings
TCM/Au-Ag
Separag415on
Pyrite
Leach
Au/Ag
Figure 1. High level flowsheet of polymetallic flotation operation
• Disruption of the froth on subsequent flotation sepa-
rations, due to any remaining floating organic car-
bon (froth stability can be impacted significantly).
• The co-flotation (or entrainment) of value metals
and minerals resulting in lower overall circuit recov-
ery of those metals and minerals.
The main elements impacting a successful flotation sepa-
ration were described by Fuerstenau (1999) as a balance
between mechanical, physical and chemical factors. Physical
factors include the circuit design and cell selection, while
operational parameters include variables such as particle
size, %solids and ore mineralogy/type. Chemical factors
include not only reagents (collectors, frothers or depres-
sants and dispersants), but also pH conditions, flotation
feed preparation conditions (grinding media selection—for
example high chrome media versus mild steel media) and
water chemistry. While physical and operational parameters
can typically be adjusted to a limited degree, there is greater
flexibility in making a chemistry adjustment in operations.
It is also important to recognize, that without applying the
appropriate chemistry, the flotation separation will not be
able to reach its true full potential.
The purpose of this paper is to describe the importance
of understanding not only the ore mineralogy but also
the value of evaluating the flotation chemistry in order to
achieve the most successful flotation separation outcome. A
recent operational example of floating complex polymetal-
lic ores in the presence of organic carbon will be provided
to illustrate the value of the approach in developing and
implementing a solution in practice.
DESCRIPTION OF POLYMETALLIC
FLOTATION FLOWSHEET
The example provided pertains to a polymetallic ore
being processed using flotation to recover both a galena
(lead) and sphalerite (zinc) concentrate. Both concentrates
also contain measurable quantities of precious metals (gold
and silver). The flotation circuit comprises of a number of
sequential flotation operations (Figure 1):
• Carbon Pre-Float
• Lead Flotation
• Zinc Flotation
• Pyrite Flotation
The flowsheet originally comprised of only the lead and
zinc flotation circuits. With the imminent change in ore
mineralogy (second mine pit) that contained organic car-
bon in sufficient quantities to cause consistent issues in flo-
tation, the decision was made to add the Carbon Pre-Float
circuit, along with the Pyrite Flotation and Leach circuit to
augment overall gold recovery. The Carbon Pre-Float cir-
cuit never worked well due to operating challenges, includ-
ing froth phase management, misplaced lead and zinc
values, and losses in gold recovery as the subsequent carbon
concentrate treatment was unsuccessful at mitigating gold
recovery losses. The residual organic carbon remaining post
Carbon Pre-Float circuit, was sufficient to create significant
problems with froth transport in both the lead roughing
and cleaner circuits. The only immediate option to man-
age these problems was to reduce the mill feed rate which
resulted in a significant decrease in throughput. A number
of likely reasons for the challenges experienced with the
Carbon Pre-float circuit include:
• Insufficient retention time (short circuiting due to
the selection of 2 carbon rougher cells per line in the
design).
• Entrainment of values (feed %solids likely not
optimal).
• Inadequate reagent dosing control.
Pb
Flotag415on
Zn
Flotag415on
Pyrite
Flotag415on
TCM
Pre-Flotag415on
TCM
Concentrate Pb Concentrate Zn Concentrate TCM/Au-Ag
Concentrate Regrind
Pre-Leach
Flotag415on
Tailings
TCM/Au-Ag
Separag415on
Pyrite
Leach
Au/Ag
Figure 1. High level flowsheet of polymetallic flotation operation