2348 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
normal low carbon ore throughputs. Metal recoveries were
reduced, and general operating conditions were difficult.
Concentrate quality was poor with elevated TCM (above
sales limits) and moistures, in excess of 10% were observed.
This concentrate could not be shipped without further
treatment (sun drying and then blending with lower car-
bon concentrate).
Test Condition—No CPP and with Depressant Added
to Rougher Feed
The depressant was added to the second line, and the feed
to this line bypassed the CPP. It took a couple of shifts for
operations to stabilize as the operating staff became accus-
tomed to a different operating regimen, but once depressant
dosage was settled the operation was no more challenging
than operating the concentrator with low TCM ores. There
was no throughput reduction. While there were some inci-
dents of overflows in the cleaner circuits, these were related
back to unexpected increases in TCM in the feed, and a
slow response from operating staff to increase the depres-
sant dosage.
Pb, Ag and Zn recovery were at normal levels, however
there was a reduction in gold recovery. Concentrate quality
was good, and moisture was at typical levels (6% to 8%)
and concentrate could be shipped as produced.
Mineralogical analysis of the gold deportment showed
that the elevated TCM ore had gold associated with the
carbon. This gold was unfortunately lost with the depressed
carbon, however these losses were less that that seen in the
line operating under conventional conditions (no carbon
depressant added).
The following were key outcomes from the plant trial:
• Improved stability of rougher and cleaner circuits
(Pb) (Figures 7 and 8).
• Higher throughput—+20% increase in throughput
could be managed with depressant addition as com-
pared to the CPP circuit.
• Concentrate grade benefit was achieved—(statis-
tically significant increase in Pb final concentrate
grade, +6 –7%—with no loss in Pb recovery).
• Future savings in operating/maintenance cost (car-
bon pre-float circuit no longer needed).
• Unintended benefit—a significant improvement in
concentrate filtration performance and targeted mois-
ture content was realized.
• While the reagent adds significant additional oper-
ating cost, the increased cost was justified with the
improvement realized in overall plant performance.
CONCLUSIONS
A study of a complex sulfide ore that considered both min-
eralogy and flotation chemistry, resulted in a solution that
was successfully tested and subsequently implemented in
operation. Key findings from this work showed:
The orebody contains a range of different types of
organic carbon, from very structured (and therefore met-
allurgically less active), to very disordered and metallurgi-
cally active and disruptive to subsequent recovery processes
(leach and flotation).
Further work will be required to be able to discern
the variability of carbon “types” in operation, as current
measurement techniques are limited to detailed laboratory
studies and procedures. It is anticipated that if a proxy indi-
cator can be identified, it will allow for further optimization
opportunities (such as optimization of reagent additions).
The value of a systematic laboratory study, consider-
ing a range of flotation chemistries to target separation of
Figure 7. Lead cleaner flotation circuit—without organic
carbon depression
Figure 8. Lead cleaner flotation circuit—with organic carbon
depression
normal low carbon ore throughputs. Metal recoveries were
reduced, and general operating conditions were difficult.
Concentrate quality was poor with elevated TCM (above
sales limits) and moistures, in excess of 10% were observed.
This concentrate could not be shipped without further
treatment (sun drying and then blending with lower car-
bon concentrate).
Test Condition—No CPP and with Depressant Added
to Rougher Feed
The depressant was added to the second line, and the feed
to this line bypassed the CPP. It took a couple of shifts for
operations to stabilize as the operating staff became accus-
tomed to a different operating regimen, but once depressant
dosage was settled the operation was no more challenging
than operating the concentrator with low TCM ores. There
was no throughput reduction. While there were some inci-
dents of overflows in the cleaner circuits, these were related
back to unexpected increases in TCM in the feed, and a
slow response from operating staff to increase the depres-
sant dosage.
Pb, Ag and Zn recovery were at normal levels, however
there was a reduction in gold recovery. Concentrate quality
was good, and moisture was at typical levels (6% to 8%)
and concentrate could be shipped as produced.
Mineralogical analysis of the gold deportment showed
that the elevated TCM ore had gold associated with the
carbon. This gold was unfortunately lost with the depressed
carbon, however these losses were less that that seen in the
line operating under conventional conditions (no carbon
depressant added).
The following were key outcomes from the plant trial:
• Improved stability of rougher and cleaner circuits
(Pb) (Figures 7 and 8).
• Higher throughput—+20% increase in throughput
could be managed with depressant addition as com-
pared to the CPP circuit.
• Concentrate grade benefit was achieved—(statis-
tically significant increase in Pb final concentrate
grade, +6 –7%—with no loss in Pb recovery).
• Future savings in operating/maintenance cost (car-
bon pre-float circuit no longer needed).
• Unintended benefit—a significant improvement in
concentrate filtration performance and targeted mois-
ture content was realized.
• While the reagent adds significant additional oper-
ating cost, the increased cost was justified with the
improvement realized in overall plant performance.
CONCLUSIONS
A study of a complex sulfide ore that considered both min-
eralogy and flotation chemistry, resulted in a solution that
was successfully tested and subsequently implemented in
operation. Key findings from this work showed:
The orebody contains a range of different types of
organic carbon, from very structured (and therefore met-
allurgically less active), to very disordered and metallurgi-
cally active and disruptive to subsequent recovery processes
(leach and flotation).
Further work will be required to be able to discern
the variability of carbon “types” in operation, as current
measurement techniques are limited to detailed laboratory
studies and procedures. It is anticipated that if a proxy indi-
cator can be identified, it will allow for further optimization
opportunities (such as optimization of reagent additions).
The value of a systematic laboratory study, consider-
ing a range of flotation chemistries to target separation of
Figure 7. Lead cleaner flotation circuit—without organic
carbon depression
Figure 8. Lead cleaner flotation circuit—with organic carbon
depression