1
25-040
Grinding Chemistry and Its Impact on Copper Flotation
C. J. Greet
Magotteaux Australia Pty Ltd, Wingfield, South Australia, Australia
ABSTRACT
Grinding with an electrochemically inert grinding media
(i.e., high chrome white iron) shifts the pulp potentials to
more oxidising conditions, increases the dissolved oxygen
content and reduces the EDTA extractable iron concentra-
tion when compared with milling with electrochemically
active grinding media (forged steel). These changes in pulp
chemistry produce cleaner particle surfaces, reduce reagent
consumption, and increase concentrate grades and recover-
ies. This paper presents a robust laboratory test program
that not only demonstrates the changes in the pulp chemis-
try, but also provide an indication of the magnitude of the
metallurgical improvements that are possible.
While laboratory studies are interesting, the proof is in
the pudding! So, the paper provides an overview of plant tri-
als conducted at several porphyry copper operations around
the world: Newmont’s Cadia and Red Chris Operations, as
well as Evolution Mining’s Northparkes Operation. These
successful plant trials clearly demonstrate that selection of
the right grinding media alloy will yield savings in grind-
ing media consumption and reagent consumption as well
as increases in revenue through improved copper and gold
recoveries.
However, many of the porphyry copper mines on
the Eastern Pacific are copper-molybdenum deposits. The
paper presents laboratory test results for typical copper-
molybdenum operations and extrapolate these numbers to
what might be expected should a plant trial occur.
INTRODUCTION
Porphyry copper ore bodies represent the largest source of
copper in the world, with a significant number of these
deposits concentrated along the “ring of fire” round the rim
of the Pacific Ocean. The porphyry copper deposits in the
western and northern edges of the Pacific Ocean tend to
contain elevated concentrations of gold, while those on the
eastern edge are more likely to have economic quantities of
copper and molybdenum. This paper will provide details of
both laboratory and plant results for copper-gold porphyry
copper operations and looks to extrapolate these results to
copper-molybdenum porphyry deposits.
The key to a successful separation in mineral process-
ing is the preparation of particles with adequate liberation
under the correct pulp chemical conditions.
While the importance of liberation on flotation separa-
tions is generally understood and well documented in the
literature1, 2, 3, 4 ,the importance of pulp chemistry is more
nebulous, particularly with regard to the impact of grind-
ing media. Extensive work examining the electrochemical
interactions between grinding media and sulphide minerals
has been completed5, 6, 7, 8 .Broadly, these studies indicate
that most sulphide minerals are more noble than the grind-
ing media used during comminution, therefore a galvanic
couple between the media and the sulphide mineral(s)
exists, which increases the corrosion rate of the grinding
media. The corrosion products of the grinding media, iron
oxy-hydroxide species, invariably precipitate on to the
surfaces of the sulphide minerals thereby affecting their
floatability9.
More recently Bruckard, Sparrow &Woodcock10 pub-
lished an excellent review of the effect the grinding envi-
ronment has on the flotation of copper sulfides indicating
that electrochemically active grinding media increases iron
levels, lowers dissolved oxygen concentration in the slurry
and results in the formation of iron hydroxides. These
changes can have a deleterious impact on copper flota-
tion. However, measuring these pulp chemistry changes
and determining their impact on copper flotation at indus-
trial scale has proven to be difficult. This paper presents a
brief review of the robust laboratory procedure applied to
25-040
Grinding Chemistry and Its Impact on Copper Flotation
C. J. Greet
Magotteaux Australia Pty Ltd, Wingfield, South Australia, Australia
ABSTRACT
Grinding with an electrochemically inert grinding media
(i.e., high chrome white iron) shifts the pulp potentials to
more oxidising conditions, increases the dissolved oxygen
content and reduces the EDTA extractable iron concentra-
tion when compared with milling with electrochemically
active grinding media (forged steel). These changes in pulp
chemistry produce cleaner particle surfaces, reduce reagent
consumption, and increase concentrate grades and recover-
ies. This paper presents a robust laboratory test program
that not only demonstrates the changes in the pulp chemis-
try, but also provide an indication of the magnitude of the
metallurgical improvements that are possible.
While laboratory studies are interesting, the proof is in
the pudding! So, the paper provides an overview of plant tri-
als conducted at several porphyry copper operations around
the world: Newmont’s Cadia and Red Chris Operations, as
well as Evolution Mining’s Northparkes Operation. These
successful plant trials clearly demonstrate that selection of
the right grinding media alloy will yield savings in grind-
ing media consumption and reagent consumption as well
as increases in revenue through improved copper and gold
recoveries.
However, many of the porphyry copper mines on
the Eastern Pacific are copper-molybdenum deposits. The
paper presents laboratory test results for typical copper-
molybdenum operations and extrapolate these numbers to
what might be expected should a plant trial occur.
INTRODUCTION
Porphyry copper ore bodies represent the largest source of
copper in the world, with a significant number of these
deposits concentrated along the “ring of fire” round the rim
of the Pacific Ocean. The porphyry copper deposits in the
western and northern edges of the Pacific Ocean tend to
contain elevated concentrations of gold, while those on the
eastern edge are more likely to have economic quantities of
copper and molybdenum. This paper will provide details of
both laboratory and plant results for copper-gold porphyry
copper operations and looks to extrapolate these results to
copper-molybdenum porphyry deposits.
The key to a successful separation in mineral process-
ing is the preparation of particles with adequate liberation
under the correct pulp chemical conditions.
While the importance of liberation on flotation separa-
tions is generally understood and well documented in the
literature1, 2, 3, 4 ,the importance of pulp chemistry is more
nebulous, particularly with regard to the impact of grind-
ing media. Extensive work examining the electrochemical
interactions between grinding media and sulphide minerals
has been completed5, 6, 7, 8 .Broadly, these studies indicate
that most sulphide minerals are more noble than the grind-
ing media used during comminution, therefore a galvanic
couple between the media and the sulphide mineral(s)
exists, which increases the corrosion rate of the grinding
media. The corrosion products of the grinding media, iron
oxy-hydroxide species, invariably precipitate on to the
surfaces of the sulphide minerals thereby affecting their
floatability9.
More recently Bruckard, Sparrow &Woodcock10 pub-
lished an excellent review of the effect the grinding envi-
ronment has on the flotation of copper sulfides indicating
that electrochemically active grinding media increases iron
levels, lowers dissolved oxygen concentration in the slurry
and results in the formation of iron hydroxides. These
changes can have a deleterious impact on copper flota-
tion. However, measuring these pulp chemistry changes
and determining their impact on copper flotation at indus-
trial scale has proven to be difficult. This paper presents a
brief review of the robust laboratory procedure applied to