MINING CHEMICALS
In recent years, the mine had experienced
challenging mineralogy due to the depletion of
oxidised mineral reserves and the onset of
complex minerals.
The Process Health Check methodology was
used to analyse the site’s historical data. Among
the relevant variables that were closely scrutinised
were cyanide measurement and its dosage. It was
determined there were inconsistencies in the free
cyanide measurements due to copper variations
and sulphide levels in the ore. This variability
initially generated an overestimation of free cyanide.
It was determined that investing in an enhanced
method and frequency of free cyanide
measurement would significantly improve cyanide
control and result in a more efficient leaching
system.
Orica proceeded to implement Cyantific and its
OCM5500 Leach Process analyser. The latter
helped increase the accuracy and frequency of
free cyanide measurement, together with the
implementation of a control loop that was
integrated with the Distributed Control System of
the plant and actuators, Orica said. This automatic
dosage system was developed with the flexibility
to adjust the free cyanide set points that were
optimised for each ore type.
The automated control system managed to
significantly reduce free cyanide variability,
compared with the manual dosage, eliminating
the periods of excessive and insufficient dosage.
This resulted in a much more consistent free
cyanide level, enabling a reduction in the
consumption of reagents necessary for cyanide
destruction, which is a critical requirement for
tailings disposal, Orica said.
Once the free cyanide set point requirements
for each ore type was defined, there was a need to
have greater accuracy in the free cyanide
measurement to implement a new process control
methodology, Orica explained.
“An increased testing frequency was required to
configure the process for different operating
scenarios, which led to the integration of the OCM
5500 analyser with the control room and the
establishment of a methodology to continuously
control the leaching process,” the company said.
Throughout the project, a baseline was
established for each relevant variable, including
free cyanide concentrations before and after the
project.
The improved cyanide dosage control
successfully reduced the variability of free cyanide
in the process, according to Orica.
By adopting the automated cyanide dosage
system, the customer achieved a 40% reduction in
cyanide consumption and a more than 70% drop
in hydrogen peroxide consumption. It was
validated that gold recovery increased by an
average of 2.5% from the baseline.
Orica said: “These significant gains can be
further improved by using Orica’s LeachIT to
determine the optimum cyanide levels for various
blends of ores with different levels of copper and
sulphide minerals.
“Consistent levels of cyanide, as well as better
accuracy of the results, produces a more accurate
simulation of the leaching system and optimum
leaching conditions resulting in further gains to
customers.”
Collector development
Arkema-ArrMaz, recognising a need to simplify the
flotation process and improve grades and
recoveries across the Turkey feldspar industry,
established a Joint Collector Development
program (JCDP) in partnership with a leading
feldspar producer in the country five years ago.
The JCDP took a similar approach to that of
sulphide and other industrial mineral applications,
where advanced specialty blend collectors
formulated to specific ore mineralogy have
replaced single chemical component “commodity
collectors” to efficiently and cost-effectively
provide the selectivity required, according to
Abdul Gorken, Senior Metallurgist, Arkema-
ArrMaz, and Todd Parker, Global Mining Marketing
Manager, Arkema-ArrMaz.
Gorken and Parker explained: “Arkema-
ArrMaz’s JCDP develops and evaluates potential
collector chemistries formulated for a specific ore
mineralogy with statistical mixture designs that
consider mixture stability, component
compatibility, cost and application benefits.
“Since its inception, this JCDP has successfully
completed six stages of development and
evaluation, including multiple rounds of custom-
blend collector formulation at Arkema-ArrMaz’s
lab in Mulberry, Florida, as well as confirmatory
tests and plant evaluations onsite in Turkey.
“The results of each stage are used to drive
improvements for the next in an iterative process.”
The Turkey feldspar sector was chosen as the
country’s deposits typically contain problematic
gangue minerals such as heavy
impurities (mostly rutile, titanate and
spinel), significant amounts of mica
(mostly biotite and lesser amounts of
muscovite), and varying amounts of
troublesome clays (including kaolin,
illit and more), according to Gorken
and Parker.
“Most of the heavy magnetic iron
impurities can be removed by dry and
wet, high- and low-intensity magnetic
separators,” they said. “However, the
remaining heavy impurities consisting
mainly of rutile, non-magnetic iron
and mica require special reverse
flotation techniques for removal before acceptable
feldspar concentrate grade can be achieved.”
In the early 1990s, some major local feldspar
producers introduced a reverse flotation technique
whereby heavy impurities were floated away with
fatty acids first, after which mica was floated away
with amines in acidic media.
Later, with the development of more efficient
fatty acid collectors, the same or better separation
was achieved in a neutral flotation circuit using
more environmentally friendly processes, Gorken
and Parker explained.
Then prina oil, a residue from local olive oil
production, became the standard fatty acid
replacement. In the mid-2000s, with the
development of more selective fatty acid types
and amines, further grade and recovery
improvements were realised.
“Today, however, with the rapid growth of
Turkish feldspar production and the gradual
decline of higher-grade deposits, better flotation
concentration methods are needed,” Gorken and
Parker said. “Feldspar producers and suppliers
alike are seeking flotation improvements in
selectivity, processing cost and simplicity with
specially formulated fatty acids and amines.”
When floating feldspar, de-sliming followed by
two stages of flotation with two different
collectors are usually required to produce
acceptable product quality, according to Gorken
and Parker. The typical feldspar beneficiation
process involves:
n Grinding, classification, screening, cycloning;
n Magnetic separation; and
n Froth flotation:
n Direct flotation of feldspar – practiced on
feldspar ores with high quartz content; or
n Reverse flotation of feldspar – practiced
on feldspar ores with small amounts of
quartz.
Anionic collectors (typically fatty acids and their
soaps) make up 80% of industrial mineral
collectors and are considered analogous to
xanthates in sulphide flotation, according to
Gorken and Parker. “These collectors are used in
direct flotation of minerals with positive surface
Arrkema-ArrMaz’s CustoFloat custom blend
collectors yielded substantial performance
improvements and a much simpler single-stage
process in feldspar operations in Turkey
MAY 2020 | International Mining 39