XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 2347
the laboratory test work program, that a plant trial would
be required to ensure the impact is demonstrated at scale.
However, it was also anticipated that the impact of depres-
sion at plant scale would be enhanced, as the froth is gen-
erally better controlled in the laboratory than is typically
possible in operation.
APPLICATION IN OPERATION
In order to ensure that a robust and statistically significant
interpretation of the value being provided by the carbon
depressant could be provided, the plant trial considered a
parallel trial for the plant trial design. The operation has
two identical lines, each consisting of a SABC comminu-
tion circuit and three lines of sequential rougher Pb and
Zn float cells. Both Pb and Zn circuit lines have dedicated
cleaner circuits. The two lines can be kept separate all the
way to concentrate filtration which simplifies analysis.
The experimental design selected was a paired trial
experimental design. Based on a standard deviation of
±7.5% (previous plant performance when processing high
organic carbon ores), 23 pairs of data were targeted to con-
firm the original recovery hypothesis. Each shift was con-
sidered a data set, and the test condition was not switched
between the two lines, due to limited available ore feed, and
challenges in applying the switch in operation. A paired
t-test analysis conducted on recent plant data did not show
a statistically significant difference in the lead and zinc mass
recoveries contained for each line, and that there appeared
to be no statistically discernable differences in the feed
properties (particle size and feed grade content) of the ore
presented to each line.
A two week plant trial was scheduled targeting typi-
cal ore with TCM (total carbonaceous material) between
0.15% and 0.3% and typical Pb, Zn, Au and Ag grades
within normal within normal parameters for the mill. From
extended laboratory testing an initial target dosage of the
carbon depressant was identified.
Initial expectations from the trial was increased Pb, Au
and Ag recovery, at least equivalent Zn recovery (although
laboratory testing indicated the likelihood of a reduction in
recovery), improved concentrate quality (lower TCM in the
concentrates) and improved concentrate moisture.
Historical operations with elevated TCM indicated
that the Carbon Prefloat Plant (CPP) would be challenging
to stabilize and operate, and that overflows from the cleaner
circuit feed tanks and first cleaner concentrate launders
would be prevalent. Elevated TCM content in particularly
the Pb concentrate and excessive concentrate moistures
(in excess of 10%) for both products were also expected.
Elevated base and precious metal losses were also observed
from time to time.
Conventional Operating Procedure—CPP in
Operation and no Depressant
The line utilizing the CPP experienced these operating
challenges, and despite intensive focus from operating,
technical and supervisory staff, stability was never fully
achieved. The challenges in the Pb cleaner circuit required a
significant reduction in throughput, up to 20% lower than
Figure 6. Value distribution—with and without carbon-pre-float and with corg depressant
the laboratory test work program, that a plant trial would
be required to ensure the impact is demonstrated at scale.
However, it was also anticipated that the impact of depres-
sion at plant scale would be enhanced, as the froth is gen-
erally better controlled in the laboratory than is typically
possible in operation.
APPLICATION IN OPERATION
In order to ensure that a robust and statistically significant
interpretation of the value being provided by the carbon
depressant could be provided, the plant trial considered a
parallel trial for the plant trial design. The operation has
two identical lines, each consisting of a SABC comminu-
tion circuit and three lines of sequential rougher Pb and
Zn float cells. Both Pb and Zn circuit lines have dedicated
cleaner circuits. The two lines can be kept separate all the
way to concentrate filtration which simplifies analysis.
The experimental design selected was a paired trial
experimental design. Based on a standard deviation of
±7.5% (previous plant performance when processing high
organic carbon ores), 23 pairs of data were targeted to con-
firm the original recovery hypothesis. Each shift was con-
sidered a data set, and the test condition was not switched
between the two lines, due to limited available ore feed, and
challenges in applying the switch in operation. A paired
t-test analysis conducted on recent plant data did not show
a statistically significant difference in the lead and zinc mass
recoveries contained for each line, and that there appeared
to be no statistically discernable differences in the feed
properties (particle size and feed grade content) of the ore
presented to each line.
A two week plant trial was scheduled targeting typi-
cal ore with TCM (total carbonaceous material) between
0.15% and 0.3% and typical Pb, Zn, Au and Ag grades
within normal within normal parameters for the mill. From
extended laboratory testing an initial target dosage of the
carbon depressant was identified.
Initial expectations from the trial was increased Pb, Au
and Ag recovery, at least equivalent Zn recovery (although
laboratory testing indicated the likelihood of a reduction in
recovery), improved concentrate quality (lower TCM in the
concentrates) and improved concentrate moisture.
Historical operations with elevated TCM indicated
that the Carbon Prefloat Plant (CPP) would be challenging
to stabilize and operate, and that overflows from the cleaner
circuit feed tanks and first cleaner concentrate launders
would be prevalent. Elevated TCM content in particularly
the Pb concentrate and excessive concentrate moistures
(in excess of 10%) for both products were also expected.
Elevated base and precious metal losses were also observed
from time to time.
Conventional Operating Procedure—CPP in
Operation and no Depressant
The line utilizing the CPP experienced these operating
challenges, and despite intensive focus from operating,
technical and supervisory staff, stability was never fully
achieved. The challenges in the Pb cleaner circuit required a
significant reduction in throughput, up to 20% lower than
Figure 6. Value distribution—with and without carbon-pre-float and with corg depressant