Post on 29-Dec-2015
Low pH Pyrite Flotation Collector Development Program 1
Cytec SolutionsFor Solvent Extraction, Mineral Processing and Alumina Processing
Low pH Pyrite Flotation Collector Development Program1
As we head into 2012, we are all facing another exciting year and it is
clear that the pace of change in our world is continuing to accelerate.
This requires us all to be more agile and flexible in our approach. At
Cytec, we have continued on our strategic path of market needs driven
technology innovation that allows us to “Deliver Technology Beyond
our Customers’ Imagination”. When reviewing the feedback from
our recent customer survey, I was pleased to see that we are meeting
and in many cases exceeding your expectations in bringing innovative
solutions. We remain convinced that the development and deployment
of technology solutions to long term industry challenges is a source of
value for both us and our customers.
The Flotation Matrix 100® and Minchem modeling tools are particularly relevant in the fast
changing environment as they minimize the need for test work through careful experimental
design and high quality data interpretation. In combination with our excellent capabilities in
chemical design and optimization, it is possible for Cytec to continue to bring timely innovation
to our customers even though the pace has quickened. Another key lever in cutting time to
market is collaboration and as many of you know from personal experience this is remains key in
our success.
Over the last 18 months we have brought to market ACORGA® NR, ACORGA® OR, ACORGA®
OPT® 5540, EZ reagents for Electrostatic Separation, and the XR series of collectors as full or
partial NaSH replacement and we are seeing strong interest in all of these products. We have also
made significant progress on several other new product innovations that will be launched in 2012
including a scale control product, ACORGA CB™ for metal extraction processes. We have also
extended our geographic reach by establishing commercial presence in Peru and Serbia.
To address the growing demand for our Phosphine based chemistries including AEROPHINE®
and CYANEX® technologies, we have recently announcement plans to significantly expand
capacity at our manufacturing plant in Canada. This is a sign of our continued commitment to
the mining industry and ensuring we meet future demands.
I trust that you will find the latest edition of Cytec Solutions interesting and a source of
inspiration. Whether your interest is in Mineral Processing, Alumina Chemicals or Metal
Extraction Products there is something here for you.
Thank you for your valued business,
Martin Court
Vice President, In Process Separation
Letter from the Vice President
Low pH Pyrite Flotation Collector Development Program 11
Copper Solvent Extraction: Behavior of Iron and Manganese in Electrowinning Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
The Impact of PLS Viscosity on Solvent Extraction . . . . . . . . . . . . . . . . . . . . . . . .
Low pH Pyrite Flotation Collector Development Program . . . . . . . . . . . . . . . . .
Use of AEROPHINE® 3418A Promoter for Sulfide Minerals Flotation . . . . . . . . .
New Flocculants for Improved Processing of High Silica Bauxite . . . . . . . . . . . .
The Inhibition of Vishnevite Scale in Chinese Refineries Using MAX HT® 550 Scale Inhibitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3
8
12
16
24
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Table of Contents
Solvent Extractions
Mineral Processing
Alumina Processing
Cytec Mining Chemicals Business Segments2
Solvent Extraction
Almost 40 years in the solvent extraction (SX)
business has translated into extensive experience
and successes in solving difficult problems and in
introducing many patented formulations.
Cytec offers two extraction product families:
hydroxyoxime extractants under the
trademark ACORGA® extraction reagents and
organophosphorus derivatives under the trademark
CYANEX® solvent extraction reagents.
Mineral Processing
Cytec's new reagent technologies are changing the
face of the mineral processing industry. Precision
targeting of chemistries yields increased recoveries,
productivity and safety. Using Cytec products,
customers have been able to attain an entirely new
level of profitability.
Recovering maximum value from mineral ore
is our primary goal. To that end, Cytec has
brought advanced tools to precious and base
metals operations for solving increasingly difficult
problems. Cytec employs specialty collectors and
reagents, dewatering aids and antiscalants. These
include highly selective reagents and modifiers
to provide plants with enhanced kinetics,
productivity and throughput. Other advanced
tools include modeling software and statistical
process analysis and design tools, as well as
proprietary laboratory and field tests - many of
which have become industry standards.
Alumina Processing
Cytec continues to provide the alumina industry
with value-adding, efficiency-enhancing
technology for all stages in Bayer Process alumina
production. Cytec's technological innovations
for alumina processing began with programs
for the solid-liquid separation processes and the
introduction of synthetic polyacrylate flocculants
to replace starch and have continued with a
constant stream of new products.
Subsequent development of copolymers for the
CCD circuit provided significant improvements
in refinery economics and red mud disposal.
Cytec pioneered the release of hydroxamic
acid flocculants, a quantum leap in flocculant
technology for the clarification circuit, providing
improved economics, liquor filtration rates and
reduced settler scaling.
The development of MAX HT® socialite scale
inhibitor, a revolutionary product that eliminates
sodalite scale from heat exchangers throughout
the Bayer Process, is another testament to Cytec’s
commitment to provide technologically advanced
chemistry that brings real value and contributes to
the sustainability of the alumina industry.
All of Cytec's initiatives in alumina are supported
by a global team of field engineers - and a
vertically integrated supply chain - to support
today's programs and technologies with an eye to
future industry needs.
www.cytec.com
3Copper Solvent Extraction: Behavior of Iron and Manganese in Electrowinning Solutions
Troy Bednarski, Matthew Soderstrom - Tempe, AZ
Introduction
An important part of the electrowinning process
is managing the iron and manganese in the
electrolyte solution. The primary benefits of
controlling these are better current efficiency
and cathode quality. An electrowinning study
utilizing a Hull Cell was conducted to identify
the behavior and affects of iron and manganese in
the electrolyte during electrowinning. The Hull
Cell is a test electrowinning cell commonly used
in the electroplating industry to test the affects
of various additives. The cell is a trapezoidal
container which positions a single cathode at an
angle to an anode so the plating occurs at different
current densities as a function of distance down
the cell. The cell may be fitted with a paddle
to vary the agitation in the bath. The plating is
achieved on a batch basis so it is not necessarily
representative of commercial cells but these tests
effectively simulate the relative behavior of iron
and manganese within the electrolyte.
Iron Behavior
Ferric iron in the electrolyte is reduced at the
cathode thus consuming energy; the resulting
ferrous iron is then oxidized back to ferric iron
at the anode in a constant cycle. This oxidation-
reduction cycle reduces the current efficiency as
some of the electrons are no longer available for
copper reduction.
The affect of ferric iron on current efficiency
was investigated at various iron concentrations
and various current densities. The solution
composition and Hull Cell test conditions are
given below:
Solution conditions:
Synthetic electrolyte: 45 gpl copper, 155 gpl
sulfuric acid
Ferric iron (0, 1, 2, 3, 5, and 10 gpl)
Hull Cell conditions:
40 Degrees C
Lead anode
Copper cathode blank
Current density (18.3, 27.4 and 36.3 amp/ft2)
Rectifier amps ( 1, 1.5 and 2 amps)
Plating time (3hrs 22 min, 2hrs 15 min, and
1hr 41 min)
Solution agitation provided with a paddle
Table 1 shows the ferrous ion concentration
and ORP (oxidation reduction potential) of the
electrolyte following the electrowinning process
(with a set agitation rate). Although the initial
electrolyte was made up with ferric sulfate, as
shown, a significant portion of the iron was
reduced at the cathode back to the ferrous state
resulting in a reduction in the ORP value.
4Copper Solvent Extraction: Behavior of Iron and Manganese in Electrowinning Solutionscontinued
Table 1
Percent Ferrous Iron and Oxidation-Reduction Potential
+3
01235
9.5
+2
04138413938
ORP (mV)
605506502502500498
ORP (mV)
560483489489488495
ORP (mV)
615506504500498501
+2
02933313438
+2
04243383940
ORP (mV)
570625645660675690
36.6 amp/ft227.4 amp/ft218.3 amp/ft2Initial solution
ORP measured using a Ag/AgCl reference electrode with 4 M KCl filling solution
Under the test conditions, approximately 30- 40% of the ferric iron was reduced to ferrous iron during
electrowinning. Since the reduction of ferric to ferrous consumes an electron which is no longer available
to reduce Cu+2. Any increase in the electrolyte ferric iron concentration will result in a decrease in current
efficiency. Under these conditions, the decrease in current efficiency was also dependent on the current
density as shown in Figure 1. As the current density was increased, the current efficiency also increased for
a given total iron concentration.
Figure 1
Iron Concentration vs. Current Efficiency
Iron concentration vs current efficiency
60
65
70
75
80
85
90
95
100
0 2 4 6 8 10
Initial Ferric Iron Concentration (gpl)
Cu
rren
t ef
fici
ency
%
18.3 amp/ft2
27.4 amp/ft2
36.6 amp/ft2
Amps/ft2 calculated based on total cathode area (not taking into account diagonal configuration)
5Copper Solvent Extraction: Behavior of Iron and Manganese in Electrowinning Solutions
continued
Iron/Manganese Behavior
Although iron is a consumer of energy, its
presence is beneficial to ensure that any
manganese, present as Mn+2 does not oxidize
to higher oxidative states (Mn+4 or Mn+7). The
oxidation of manganese to MnO happens at the
anode surface. The MnO can flake off of the
anode surface deteriorating the anode quality.
This leads to accumulation of lead on the bottom
of the cell or increases the likelihood of lead
becoming trapped within the cathode affecting
product quality. Further oxidation of Mn
(especially if the permanganate ion is formed)
will oxidize the organic in the stripping stage of
the solvent extraction process. The oxidation of
the organic will affect both physical and chemical
performance of the extractant thereby negatively
impacting the SX process.
The historic rule of thumb to control these issues
has been to maintain a total Fe to Mn ratio of
10/1 in the electrolyte to prevent the formation of
manganese in higher valence states. At this ratio it
is assumed ~ ½ of the iron will be present in the
ferrous state. The reduction half-reaction shows
that 5 ferrous ions are needed to reduce Mn+7 to
Mn+2 as shown in the following balanced half-
reaction equation:
5Fe +2 + MnO4
- + 8H + 5Fe +3 + Mn +2 + 4H2O
Although a 10:1 ratio of iron to manganese
is often recommended, there are a number of
operations which operate at significantly lower
ratios without generating a high ORP value. While
operations with ratios significantly over 10:1 may
still generate Mn at higher valence states if the
total iron concentration is not high enough.
Synthetic electrolyte solutions containing 45 gpl
copper, 165 gpl sulfuric acid were generated with
the following Fe/Mn ratios.
30/1 (0.3 gpl Fe and 0.01 gpl Mn)
10/1 (1 gpl Fe and 0.1 gpl Mn)
4/1 (1 gpl Fe and 0.25 gpl Mn)
These solutions were tested in the Hull Cell with
(Table 2) and without (Table 3) agitation at a
temperature of 40 degrees C at a current density
of 27.4 amp/ft2.
The results show that the permanganate ion was
formed with the 4.3/1 Fe/Mn ratio, even with
ferrous iron present in the starting rich solution.
The presence of ferrous iron in the electrolyte did
delay the formation of Mn+7 by the oxidation/
reduction reaction. When ferrous was present in
the starting solution it took 30 minutes to achieve
an ORP value greater that 1100 mV. At a Fe/Mn
ratio of 9.6/1 or greater no permanganate was
formed. There was very little ferrous iron present
in the ending solution when utilizing the 9.6/1
ratio. This indicates that the ferric iron was
reduced to ferrous iron then oxidized back to
ferric due to reduction of higher valence state Mn
that would have been generated at the anode. This
was not the case at a Fe/Mn ratio of 30/1. There
was ferrous iron present in the ending solutions in
the range of 30-40%, similar to the results of
Table 1 when manganese was not present in the
starting solution.
Copper Solvent Extraction: Behavior of Iron and Manganese in Electrowinning Solutionscontinued
6
Table 2
Electrowinning with Cell Agitation
(1) @ 5 min, (2) @ 30 min
Rich Electrolyte Solution Lean Electrolyte Solution
4.3
4.3
9.6
29
32
ORP
(mV)
648
458
648
615
422
+3
(gpl)
0.98
0.98
0.9
0.21
0.21
+2
(gpl)
–
–
0.06
0.08
0.11
+2
(%)
–
–
6.3
28
34
ORP
1115(1)
1118(2)
583
503
505
+2
(gpl)
0
0.53
0
0
0.32
+3
(gpl)
0.98
0.45
0.96
0.29
0
Table 3
Electrowinning without Cell Agitation
+3
(gpl)
0.96(1)
0.29
+2
(gpl)
0
0
+3
(gpl)
0.93
0.2
+2
(%)
3.1
31
ORP
(mV)
587
545
+2
(gpl)
0.03
0.09
ORP
(mV)
642
627
9.6
29
Rich Electrolyte Solution Lean Electrolyte Solution
7Copper Solvent Extraction: Behavior of Iron and Manganese in Electrowinning Solutions
continued
Permanganate ion was generated even at a
9.6/1 Fe/Mn ratio when the cell was operated
without agitation, ORP = 1155 at 5 min. During
this test the cell agitation was turned on and
the permanganate slowly started to reduce, as
evidenced by a reduction of the ORP value and a
diminishing of the electrolyte color from purple
back to the original blue. At a Fe/Mn ratio of
29/1 cell agitation did not appear to influence the
formation of the permanganate ion, apparently
sufficient iron was present in the ferrous state.
Conclusion
Iron and manganese are typically present
in copper PLS and can be transferred to the
electrolyte by physical means (entrainment) and
chemical transfer (ferric iron only). The transfer
of iron to the electrolyte will reduce the current
efficiency. This reduction will depend on the iron
concentration in the electrolyte, the cell agitation
dynamics, and the current density.
When manganese is present in the electrolyte
it is important to monitor the ORP and insure
the electrolyte returning to SX will not cause
oxidation. This is typically achieved by having
ferrous iron present in the tankhouse (rule
of thumb 10/1 total iron/manganese ratio)
to prevent the oxidation of Mn to higher
oxidation states. At high oxidation states Mn
can affect organic quality, cathode quality and
cause maintenance and anode stability issues.
Limiting the transfer of Mn to the electrolyte
by controlling physical (A in O) entrainment
is the key to minimizing potential issues.
The Impact of PLS Viscosity on Solvent Extraction8
Figure 1
Impurities Balance Scheme
Heap
PLS Pond
EW
SX RaffinatePond
Copper Cathode
H2SO4 with Impurities
Raffinate withImpurities
Cu and Impurities
ImpuritiesConcentrate
Until Equilibriumis Reached
Cu
H2SO4 Addition
Figure 1 shows the impurities balance scheme.
Eventually an equilibrium is reached when the
dissolving of impurities in the heap is in balance
with the precipitation of impurities.
Aluminum and magnesium are two of the common
impurities which tend to build-up within the PLS
contributing to higher viscosities.
Figure 2 shows aluminum and magnesium
concentrations in the PLS from Chilean operations.
Figure 2 Al, Mg in PLS for Chilean operations
Concentration of Aluminium and Magnesium in PLSChilean Plants
0
2
4
6
8
10
12
14
16
18
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
SX PlantsAl Mg
Con
cent
ratio
n (g
pl)
Alexis Soto
Introduction
In commercial scale solvent extraction, the impact
of impurities in a PLS (pregnant leach solution)
is frequently underestimated. Additionally, when
impurities are considered, the focus tends to be on
iron, chloride or nitrate depending on the origin
of the ore
However, the accumulation of some other
impurities like aluminum and magnesium
can increase the PLS viscosities. Under these
conditions poor physical behaviors may occur,
including increased entrainment and/or reduced
stage efficiency.
The typical PLS viscosity in Chilean solvent
extraction operations is between 1.0 and 3.0 cPs.
However approximately 20% of operations have
viscosities significantly higher than 3.0 cPs.
Studies were conducted to evaluate impact of PLS
viscosity on Cu extraction stage efficiency and
phase disengagement.
PLS Impurities and Viscosity Data
During the leaching process a number of elements
other than copper also leach. Depending on the
water balance and solubility limits, the build-up of
these impurities can vary greatly.
As shown, Al and Mg have the greatest impact
while iron addition had limited affect on viscosity.
Stage Efficiency
To assess the impact of PLS viscosity on mixer
efficiency kinetics curves were generated for
various aqueous solutions. Each aqueous solution
was prepared by diluting a real leach liquor sample
(one with a high content of impurities) with
water and then adjusting Cu and pH to the same
original values. These solutions were mixed with a
20 Vol % ACORGA® M5640 solution at a mixer
speed of 600 rpm, under organic continuity at
room temperature. The copper transfer rate data
was used to estimate stage efficiency assuming
three stage mixing, each with one minute
retention time. The results of this analysis are
shown in Table 1.
Table 1
Aqueous Viscosity and Calculated Stage Efficiency
Dilution, %0255075
Aqueous Viscosities, cP
7.84.22.81.7
Efficiency, %91.694.195.698.3
As shown, the stage efficiency would be expected
to vary from 91.6% to 98.3% dependent on the
aqueous viscosity.
9The Impact of PLS Viscosity
on Solvent Extractioncontinued
Figure 3 shows PLS viscosity data for a number of
the operations.
Figure 3
Viscosities in PLS for Chilean Operations
Chilean Plants
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
SX Plants
Visc
osity
, cP
Pregnant Leach Solution Viscosity
Synthetic solutions were prepared containing Cu,
Cu/Fe, Cu/Fe/Al, Cu/Fe/Mg and Cu/Fe/Al/Mg.
These solutions contained Cu=6 gpl, Fe=10 gpl,
Al=15 gpl and Mg=15 gpl. The pH of each solution
was adjusted with sulfuric acid to 2.35 and the
viscosity of each was measured and compared to
the solution containing all four metals.
Figure 4 shows the percentage contribution of
each element/combination to the total viscosity.
Figure 4 Impact of Cu, Fe, Al and Mg on Viscosity
0
10
20
30
40
50
60
70
80
90
100
Cu Cu/Fe Cu/Fe/Al Cu/Fe/Mg Cu/Fe/Al/Mg
Impact of Impurities on PLS ViscositySynthetic solution, Cu 6 gpl, Fe, 10 gpl, Al 15 gpl, Mg 15 gpl
Co
ntr
ibu
tio
n o
n v
isco
sity
, %
10
The impact of stage efficiency on copper recovery
was modeled for a 2E+1S circuit. The results are
shown in the Figure 5 below.
Figure 5
Stage Efficiency vs. Cu Recovery
70
75
80
85
90
95
100
70 75 80 85 90 95 100
Extract Stage Efficiency %
2E+1S M5640 20 Vol%, PLS=7 gpl Cu, pH 2, LE=38 gpl Cu, 190 gpl
Stage Efficiency vs. Copper Recovery
As shown the improvement in stage efficiency
from 91% to 98% could lead to a 5% higher
copper recovery under the conditions tested.
Phase Disengagement (PD)
Phase disengagement tests, under both organic
and aqueous continuity, were completed using
the adjusted PLS solutions. The results are shown
in Figure 6.
Figure 6
Phase Disengagement Times Versus PLS Viscosity
0
50
100
150
200
250
300
350
400
450
PLS 1 (7.81 cP) PLS 2 (4.21 cP) PLS 3 (2.80 cP) PLS 4 (1.69 cP)
Time (sec)
Org. Cont. Aq. Cont.
Phase Disengagement Time
The Impact of PLS Viscosity on Solvent Extraction continued
As shown PLS viscosity has a direct impact on
phase disengagement time, this effect is especially
apparent under aqueous continuity.
The physical behavior was studied more in depth
in a piloting run.
Piloting Studies
A pilot trial was run in a 2E+1S configuration
utilizing 100 ml/min flow rates. The PLS was
adjusted with 0%, 25% and 50% dilution (Cu
and pH adjusted to original values).
Table 2
Piloting Conditions
Circuit ConfigurationRun Time per Test
Mixer Retention Time
Viscosity of PLS 1Viscosity of PLS 2Viscosity of PLS 3
hourm3 2
sec20 Vol%
cPcPcP
2 + 116
1.541.75184
M56407.814.212.79
Figure 7 Pilot Plant Pictures
11The Impact of PLS Viscosity
on Solvent Extractioncontinued
Figure 8
Pilot Plant Pictures
Table 3 shows the piloting results for each aqueous
solution. The high PLS viscosity resulted in
significantly larger dispersion bands, and higher A
in O entrainment verses the diluted PLS feeds.
Table 3
Piloting Results
Test
Viscosity of PLS
Units
cP
°C
°C
sec
mm
ppm
Test 1
7.81
0.81
25.6
42.7
91
17.8
71.3
Test 2
4.21
0.86
24.9
43
84
2.8
24.2
Test 3
2.79
0.91
25.1
43
73
1
5.2
Conclusions and Recommendations
In the Latin American region, PLS viscosities
under 3 cPs are common, however there are
a number of operations with viscosity values
significantly higher due to the build-up of
impurities (primarily Al and Mg).
High aqueous solution viscosity may result in:
Increased dispersion band depths
Increased A in O entrainment
Longer phase disengagement times,
particularly under aqueous continuity
Reduced stage efficiency
Decreased copper transfer and recovery
Increased cost to operate
The viscosity of the PLS should be monitored
continuously due to potential impacts on SX
performance. This is especially important for plant
start-up and until a steady state is reached.
Experimental Test Procedures
Table 1
Flotation and Condition Times
Unit Operation
Conditioning 1
Conditioning 2
Time, (min)
2
6
2
6
Fresh plant pulp was taken every day from the
flotation circuit feed, and diluted to 30% using
plant process dilution water (pH 1-2) in a 20 liter
pail. The pail was agitated using a Denver flotation
machine so a 2.5 kg representative sample of
pulp could be cut for flotation testing. Flotation
was done using a Denver flotation machine
operating at 1200 RPM's, using a 2.2 liter Denver
flotation cell. Flotation times can be seen in
Table 1. Collector and frother were added to the
conditioning stages as required using a micro
syringe (neat) or a plastic syringe as a 1% solution.
The air valve was opened full during flotation. A
thirty second induction time was allotted in order
to build froth. Four scrapes (once around the
cell) were pulled from the flotation cell every 10
seconds. Both concentrates were collected in one
pan. The concentrate and tail were filtered, dried,
and assayed for copper, sulfur and iron.
Results
Test results are reported in groups by day since
plant pulp was used for testing. At least one
standard test using AERO 8045 promoter was run
each day in order to set a benchmark for the set.
Low pH Pyrite Flotation Collector Development Program
Peter Riccio
12
Introduction
At an established Cytec customer site, low pyrite
recovery has been an ongoing problem in the
flotation circuit since plant commissioning in late
2004. Sulfur recovery as an indirect measure of
pyrite was improved from 40% to 65% in mid-
2005 when on site laboratory work confirmed
that AERO® 8045 promoter was a more effective
collector than AERO 407 promoter. However,
sulfur recoveries above 65% could never be
achieved. The customer requested the Ian Wark
Research Institute[1] to complete a surface analysis
study using Scanning Electron Microscopy, X-ray
Photoelectron Spectroscopy, and Time-of-Flight
Secondary Ion Mass Spectroscopy to determine if
clay coated pyrite played a role. It was concluded
that the pyrite losses to the tail are made up of
a combination of coarse (+ 100um) liberated
particles and finer (-200um) particles that have
been coated by clay fines. The majority of the
losses appear to be due to the former. A series of
diagnostic tests performed in the Cytec Stamford,
CT research facility using synthetic plant water
showed that AERO 8045 was complexing with
metal ions in solution in the harsh, slimy, low
pH, environment. The complexed collector was
unable to make pyrite hydrophobic, and float. The
laboratory screening results showed that AERO
3302, AERO 9863, and AERO XD102 would not
complex with ferric, ferrous, or copper in solution,
and therefore recover more sulfur (as pyrite).
Theses chemistries were then sent to the customer’s
site for laboratory flotation testing.
Objective
The objective was to formulate a flotation collector
in the laboratory that will recover pyrite under
harsh operating conditions, and increase sulfur
recovery above 75%.
13Low pH Pyrite Flotation Collector
Development Program continued
Tests CY-1 to CY-4 Alternative Collector Testing
In the first block of tests, the objective was to
determine which collector chemistries could be an
effective replacement for AERO 8045, and also
to determine the effective dosage (see Table 2).
AERO 8045 was tested at a high dose (168g/t)
so as to achieve the highest sulfur recovery. A
typical sulfur recovery of almost 63% was achieved
using AERO 8045. AERO 3302 was tested at less
than half the dosage of AERO 8045 (53g/t) and
recovered 81% of the total sulfur. Almost 90%
sulfur recovery was achieved when 82g/t of AERO
3302 promoter was used. Increasing the dose to
124g/t did not increase sulfur recovery. AERO
3302 was identified as a potential formulation
component. A subsequent experimental design the
following day was developed and completed using
AERO 3302 as the formulation base.
CY-6 to CY-14 Baseline Development and Collector Blends
The objective of second experimental design was
to develop a statistically significant AERO 8045
baseline recovery using replicate testing. AERO
3302 formulations were also tested for comparison.
Table 2AERO 3302 Dosage Study, Sulfur Recoveries
Test No
CY-1
CY-4
CY-2
CY-3
Collector
AERO 8045
AERO 3302
AERO 3302
AERO 3302
Collector Dose, g/t
168
53
82
124
Recovery,% S
62.61
81.39
89.97
89.08
Grade, % S
22.50
30.00
28.10
27.30
Calc Head, % S
9.92
10.87
11.24
10.45
Several replicates of AERO 8045 under the same
conditions were randomly completed over the
course of the day to determine baseline data
and test reproducibility. All gave similar results,
recovering approximately 70% of the sulfur,
41% to 45% of the iron, and 65% to 67% of the
copper (see Table 3).
The optimum dosage for AERO 3302 promoter
is approximately 62g/t where 86% of the total
sulfur was recovered. Increasing the dose to
126g/t did not significantly increase recovery.
This is consistent with the previous day's work.
This trend was also reflected in both iron and
copper recoveries. All metal recoveries were
substantially higher as compared to the AERO
8045 standard. The best metallurgy was achieved
using 81g/t AERO MX3048 promoter, which
is a formulated collector containing AERO
3302 and AERO XD102. AERO XD102 was
identified in the screening phase, and being
robust in the harsh flotation environment.
AERO MX3048 recovering 90% of the total
sulfur, 62.7% iron. The performance of the other
formulations tested, AERO 9863 and Reagent
S-10291 were inferior to AERO MX3048. AERO
MX3048 was chosen for an industrial plant
trial and renamed AERO MX3048 promoter.
14Low pH Pyrite Flotation Collector Development Programcontinued
Industrial Plant Trial Using AERO
MX3048 Promoter
A plant trial quantity of AERO MX3048
promoter was purchased by the customer as
the product proved to be very effective under
controlled laboratory conditions.
The full plant trial ran for 7 days. Sulfur recovery
ranged from 43% sulfur to 73% sulfur. The
scavenger tail grade was lower than the previous
day and ranged between 2.4% sulfur to 2.9%
sulfur. Sulfur Head grade ranged from 3.5% sulfur
to 6.1% sulfur. The final concentrate grade was
not affected with the increase in recovery. Frother
was turned off the fourth day of the trial which
was a significant cost savings. The froth was richly
mineralized in both the rougher and cleaner
concentrate. The final concentrate storage tank
was full, (>92%) and the pyrite filter press needed
to be operated so that the extra pyrite could be
stored on a stock pile for use at a later date. This is
the first time since commissioning that circuit has
performed well, even though the sulfur feed grade
was relatively low (2% sulfur).
Test No
CY-7
CY-9
CY-13
CY-12
CY-8
CY-10
CY-14
CY-6
CY-11
Product
AERO 8045
AERO 8045
AERO 8045
AERO MX3048
AERO 9863
S-10291
AERO 3302
AERO 3302
AERO 3302
Collector Dose, g/t
141
138
143
81
83
84
62
86
126
Recovery, % S
70.31
70.84
69.22
90.14
67.51
80.79
86.60
87.43
86.27
Grade, % S
20.57
19.68
18.98
23.62
25.51
27.61
24.16
26.61
21.33
Calc Head, % S
8.74
9.04
9.07
10.14
8.93
9.93
9.17
9.63
9.50
Recovery, % Fe
41.40
42.39
45.42
62.67
35.27
49.65
55.75
54.05
60.29
Recovery, % Cu
67.05
66.74
65.83
79.72
55.90
71.98
75.47
74.42
76.22
Table 3
Dosage and Blend Study
Half hourly spot samples of the head, tail and final
concentrate were collected as a cross-check with
the plant samples. The sulfur grades in the final
tail were quite similar between the plant and spot
samples, reading between 2.2% to 3.2% sulfur.
Conclusions
The AERO MX3048 promoter trial proved that
the product was successful in reducing sulfur in
the final tails in a low pH, and high dissolved
metal ion pulp. The product also improved total
sulfur recovery without the loss of sulfur grade.
In addition, the frother requirements dropped
substantially.
There was a significant decline in the tail
profile from surveys with the use of AERO
MX3048. Previous tail profile shows minimal
change in tail grade across the rougher/
scavenger cells.
Minimal change in final grade was noticed
with the increase in recovery.
15
Further reduction in tail could be achieved
by operating at higher pulp levels in all the
rougher and scavenger cells.
The use of stage dosing across all rougher
and scavenger cells, except for the last cell,
especially with the new promoter proved to be
beneficial in reducing recovery.
There is a step change reduction in the tail
grade for sulfur from the addition of the
new promoter and also through operating
adjustments made to the float circuit.
The feed grade was low towards the end,
hovering at 6% sulfur. However that did not
affect the performance of the float plant as it
normally would. Both concentrate tank level
and density were high.
The final concentrate grade remained very
consistent at above 50% sulfur with various
head grade and recoveries.
AERO MX3048 promoter trial proved that
the promoter was successful in reducing the
tail grade step wise, thereby improving the
overall sulfur recovery.
Further trials involving stage dosing will be
beneficial in reducing further the tail grade
and improve sulfur recovery.
Further adjustments and fine tuning on the
operating conditions of the float circuit (i.e.
froth level, pull rates and density, and possibly
desliming) is likely to improve sulfur recovery.
Addition of frother was stopped after the
fourth day of the trial. AERO MX3048
appears to provide some frothing
characteristics.
Low pH Pyrite Flotation Collector Development Program
continued
References
1. Bassell, Chris, Kawashima, Nobuyuki, Lewis,
Andrew, Newell, Ray, Ian Wark Research
Institute"Surface Analysis and pyrite flotation"
Report to Lane
Xang Minerals (Laos), April 2006.
16Use of AEROPHINE® 3418A Promoterfor Sulfide Minerals Flotation
Phillip Mingione
AEROPHINE® 3418A is a unique sulfide mineral
promoter produced by Cytec, based on phosphine
(PH3) chemistry. It has proven effective as a
collector for the sulfide minerals of copper and
particularly lead (galena), as well as for secondary
gold and silver values. AEROPHINE 3418A has
widest application as a Cu and/or Pb collector
for complex ores of Cu-Zn and Pb-Zn, which
frequently have significant quantities of associated
precious metal values. Advantages shown in
the use of AEROPHINE 3418A are improved
selectivities against Zn- and Fe-sulfides, increased
precious metals recoveries, reduced total collector
consumptions for Cu and/or Pb flotation, and
increased flotation kinetics leading to higher
recoveries of these values. Operating plant, pilot
plant and laboratory test data from treating
different ores are presented, demonstrating the
advantages in use and preferred application of
AEROPHINE 3418A.
Introduction
Cytec operates the only phosphine and
phosphine derivatives plant in North America,
located in Niagara Falls, Ontario. Specialty
chemicals manufactured at this facility are used
in many diverse applications, including solvent
extraction reagents. A unique phosphine-based
sulfide mineral promoter, AEROPHINE 3418A,
is also produced in this facility.
The origins of AEROPHINE 3418A promoter
date back to the 1960's, when it was established
that sulfide mineral collectors based on
phosphine chemistry demonstrated efficacy. This
new collector chemistry was found to provide
flotation performance differing significantly
from those of more traditional thiol collector
chemistries such as xanthates, dithiophosphates,
mercaptobenzothiazoles, thionocarbamates
and those with xanthogen groups. Some of
the advantages ultimately demonstrated by
AEROPHINE 3418A promoter compared to these
traditional collectors include:
Improved selectivities and recoveries in base
metals flotation, particularly with complex
polymetallic ores.
Increased recoveries of precious metals
associated with base metal ores.
Greater selectivity against iron-sulfide gangue
minerals.
Rapid flotation kinetics.
Decreased collector consumption.
A further advantage observed in operating
plants, but difficult to quantify, is very stable
flotation circuit operation. This characteristic of
AEROPHINE 3418A facilitates the optimization
of circuit performance, particularly by computer
control, and enables treatment of variable feeds
with predictability.
Application Ore Types
AEROPHINE 3418A has found widest
application in flotation of copper- and lead-sulfide
minerals, particularly where these are found in
complex sulfide ores containing sphalerite zinc
mineralization, and ores with high levels of pyrite
and/or pyrrhotite. These ore types frequently
contain secondary gold and/or silver values,
the recovery of which can have a significant
economic impact on the profitability of an
operating plant whose primary products are base
metal concentrates. AEROPHINE 3418A has a
particular affinity toward silver and silver-sulfides.
It is also in use to treat porphyry copper ores
where copper is the only base metal recovered,
and has been used as collector for the recovery of
Ag-jarosites. Test work has given indications that
17Use of AEROPHINE® 3418A Promoter
for Sulfide Minerals Flotationcontinued
nickel-bearing sulfide minerals are also
amenable to treatment using AEROPHINE
3418A as collector.
Laboratory testing in the zinc flotation stage
with some ores has given indications that
AEROPHINE 3418A may be effective as an
activated sphalerite collector. The results when
using AEROPHINE 3418A promoter as an
activated sphalerite collector, generally have not
as frequently shown the advantages more typically
seen of its application to copper, lead and precious
metals flotation stages. The reasons for this are not
clear, but are thought in part to be related to the
stoichiometry of Fe within the sphalerite crystal
lattice. Nevertheless, use of AEROPHINE 3418A
in a zinc flotation circuit should not be discounted.
Application and Evaluation Techniques
There are two basic tenets to follow for proper
evaluation of the potential metallurgical benefits
AEROPHINE 3418A may provide: 1) use staged
additions of AEROPHINE 3418A for optimum
selectivity and control, and 2) use AEROPHINE
3418A as the sole collector. Adherence to these two
tenets is strongly recommended.
AEROPHINE 3418A can be a very powerful
collector. For initial evaluations on ore presently
being treated,the first addition of AEROPHINE
3418A promoter should be made at approximately
50% of the dosage of the current collector dosage
in use. The concentrate from this flotation stage
should be kept for assay, separate from any
subsequent concentrates produced. The preferred
first addition point for AEROPHINE 3418A is to
a 0.5-3 minute conditioning stage before flotation.
Determining the effects of AEROPHINE 3418A
addition to grinding can be reserved for later stages
of the investigation.
If a visual assessment of this first flotation stage
is favorable, a second addition of AEROPHINE
3418A should be made at about 25% of the
currently used collector dosage. The concentrate
from this second flotation stage should be kept
separate from the first. If a visual assessment
seems to indicate more collector is required, a
third flotation stage should be carried out in a
like manner to the second stage, keeping this
concentrate separate from the others.
If, on the other hand, the first flotation stage
appears to be non-selective and pulls too much
weight, another test should be made with an initial
AEROPHINE 3418A promoter dosage no more
than 20-25% that of the normal collector dosage.
Subsequent flotation stage collector additions can
then be made with AEROPHINE 3418A dosages
10-15% that of the standard collector dosage.
If AEROPHINE 3418A is suited to treating the
ore under evaluation, its flotation performance will
generally be characterized by a heavily mineralized
froth and fast flotation kinetics. If too much
AEROPHINE 3418A is added to the head of
flotation, the froth may be so heavily mineralized
that it will collapse on itself and be difficult to
remove from the flotation cell. If more frother
is used to help move the froth off the cell, it is
possible to encounter an overfrothing condition
further along the rougher/scavenger flotation
stages. Staged additions of AEROPHINE 3418A
alleviate these conditions.
AEROPHINE 3418A generally displays little
or no frothing properties. At times this has
required an increase in frother dosage when using
AEROPHINE 3418A as a collector, compared to
the frother dosage required with a collector having
frothing properties. This has proven advantageous
in some plants, as it tends to separate the function
of collector from that of the frother. Optimum
18Use of AEROPHINE® 3418A Promoterfor Sulfide Minerals Flotationcontinued
circuit frothing control can then be more readily
achieved by frother dosage alone, without
complications of additional frothing contributed
by the collector. Alcohol frothers, such as MIBC,
are generally preferred for best results, although
a number of plants using AEROPHINE 3418A
as a collector utilize a glycol-based frother. Staged
addition of frother, with AEROPHINE 3418A
as a collector, is widely practiced. This same
practice generally applies to laboratory testing.
Having assay results in hand from the flotation
experiments conducted, the metallurgical data
will require evaluation. Particularly when dealing
with Cu-Zn or Pb-Zn ores, very frequently
containing Au and/or Ag values, certain
evaluation techniques tend to best establish and
highlight the performance characteristics of
AEROPHINE 3418A.
Take as an example, a Pb-Ag-Zn ore where a
majority of recoverable Ag reports to the Pb
concentrate. Assume that AEROPHINE 3418A
is being evaluated as the Pb circuit collector for
comparison to some standard collector normally
used to treat this ore. The widely used technique
of graphing the cumulative concentrate grades
(%Pb) vs. cumulative Pb recoveries provided by
the different collector systems tested is always a
good basis for initial comparisons. Very often the
use of AEROPHINE 3418A will demonstrate an
advantage at this level of evaluation,compared to
other collectors.
Since the example ore contains three different
metals of economic importance, and since the
distribution of these metals within the concentrates
produced has an impact on the overall economic
return, evaluation of flotation test data should be
carried out further.
In this instance, it would be very informative to
plot Ag recovery to the Pb concentrate vs. Pb
recovery,and Zn recovery to the Pb concentrate vs.
Pb recovery. This will help provide a clear picture
of where Ag and Zn are reporting in relation to
some comparative unit recovery of the primary
metal being recovered. Under such evaluation,
the use of AEROPHINE 3418A promoter
frequently has demonstrated a greater recovery
of Ag and/or greater rejection of Zn at some
established level of Pb recovery, when compared
to the same level of Pb recovery provided by a
different collector system.
Of course, the mineralogical associations of the
metals in question will have a large influence on
the attainable metallurgical results, i.e., a selective
increase in Ag recovery or decrease in Zn recovery
at comparable Pb recoveries. If, for example,
additional Ag recovery can only be obtained as
Ag associated with sphalerite or pyrite, it will not
be possible to demonstrate a selective increase in
Ag recovery to the Pb concentrate through the
use of different collectors. Increased selectivities
against sphalerite or pyrite may actually result in a
decrease in Ag recovery to Pb concentrate; this in
spite of equal or improved Pb recoveries or grades
when using AEROPHINE 3418A promoter as
the Pb circuit collector. If this situation exists,
it is suggested that Ag recoveries be compared
to the sum of Pb plus Zn recoveries, plus Fe
recoveries if found to be significantly influential.
In this manner, a Pb collector which undesirably
recovers sphalerite and pyrite, thereby seeming to
produce higher Ag recoveries to Pb concentrate,
may be shown as not offering any real advantage
compared to the more elective collector. The
plant's metallurgical objectives would define what
constitutes an advantage.
Figure 1 demonstrates data evaluation from the
use of AEROPHINE 3418A as the Pb collector
applied to a Pb-Zn ore,compared to usage of
the standard sodium isopropyl xanthate (SIPX)
collector. In this example Zn recovery to the Pb
19Use of AEROPHINE® 3418A Promoter
for Sulfide Minerals Flotationcontinued
concentrate is compared to the Pb recovery. It
can be seen that the use of 35 g/t AEROPHINE
3418A could reject an additional 2% of the Zn,
compared to the usage of the standard 45 g/t
SIPX collector, when the data are evaluated at the
final Pb recovery produced by SIPX. This offers
the distinct advantage of sending more Zn to the
Zn circuit for recovery. At the same time, there is
indication that the use of AEROPHINE 3418A
can provide additional Pb recovery. When this data
was originally evaluated as % Pb concentrate grade
vs. Pb recovery, an advantage was noted for the
use of AEROPHINE 3418A, as well. The greater
metallurgical advantage of improved Zn rejection
was not, however, readily apparent until the data
were evaluated as described.
Figure 1
Polymetallic Ore Data Evaluation
94
92
90
88
86
84
82
80
78
Pb %
Rec
ove
ry
Zn % Recovery to Pb Conc.14 16 18 20 22 24 26 28
35g/t AEROPHINE 3418A45g/t SIPX
The second tenet to follow when evaluating the
performance of AEROPHINE 3418A is to test it
completely on its own. This advice is based upon
applying AEROPHINE 3418A to a wide variety
of ores principally for Cu and Pb flotation. If
AEROPHINE 3418A is suited to treating an ore,
the preponderance of data in hand indicates it
will perform best generally when used as the sole
collector in the circuit to which it is being applied.
The conjunctive use of AEROPHINE 3418A
promoter with differing collectors may have
undesirable effects on the flotation performance
provided by AEROPHINE 3418A.
Every "rule" has its exceptions, however, and there
are a number of plants presently treating Cu-Zn
ores, using AEROPHINE 3418A promoter and
a dithiophosphate in the Cu flotation circuit.
Generally there are significant precious metals
values and secondary copper mineralization
associated with chalcopyrite at these plants.
The use of a dithiophosphate as a secondary
collector with AEROPHINE 3418A promoter
in these Cu flotation circuits has been shown to
offer a metallurgical advantage. It has first been
necessary to establish the flotation performance
of AEROPHINE 3418A as the sole collector,
so as to eliminate any undesirable effects which
a secondary collector potentially may exert on
the flotation system. In these circumstances the
conjunctive use of AEROPHINE 3418A promoter
with a dithiophosphate collector has been shown
to be an acceptable collector combination, without
negative impact on the resulting metallurgy.
Other thiol type collectors may demonstrate
suitability as secondary collectors with
AEROPHINE 3418A, as well.
The conjunctive use of xanthates with
AEROPHINE 3418A promoter, for Cu or Pb
flotation, is very strongly discouraged. There
is overwhelming data to show that such joint
reagent usage diminishes the benefits provided
by the AEROPHINE 3418A. The resulting
metallurgy from the conjunctive use of xanthates
20Use of AEROPHINE® 3418A Promoterfor Sulfide Minerals Flotationcontinued
and AEROPHINE 3418A will trend toward that
provided by xanthates used alone or, in some cases,
inferior metallurgy. Particularly where xanthate is
already in use for Cu or Pb flotation, the urge to
initially evaluate AEROPHINE 3418A as a partial
replacement for the xanthate should be resisted.
In these circumstances, proper assessment of the
metallurgical benefits which AEROPHINE 3418A
is capable of providing can only be made when
AEROPHINE 3418A is tested as the sole collector.
An example of the antagonistic effect of xanthate,
used conjunctively with AEROPHINE 3418A,
is shown in Figure 2. This is an example of Pb
flotation on a Pb-Zn ore. Collector dosages used
were 60 g/t. From Figure 2 it can be seen that
AEROPHINE 3418A promoter used on its own
provided superior selectivity against Zn compared
to the use of xanthate. When a combined dosage
of 75% AEROPHINE 3418A and 25% xanthate
was used, the resulting selectivity against Zn was
about the same as with xanthate used alone. Note
also that total Pb recovery is lower than with
either AEROPHINE 3418A or xanthate used on
their own.
Another example of xanthate antagonism of the
performance of AEROPHINE 3418A is given in
Table 1. These are plant operating data from trial
periods of AEROPHINE 3418A in a plant treating
a porphyry copper ore. The standard plant collector
was sodium isopropyl xanthate (SIPX). The data
given are each one week averages under the reagent
conditions indicated.
At the initial introduction of AEROPHINE 3418A
promoter into the flotation circuit, a conservative
approach was taken where the AEROPHINE
3418A replaced 33% of the normal SIPX dosage.
From the data in Table 1 it can be seen this
collector combination performed no better than
when SIPX was used alone. Subsequently the SIPX
Figure 2
Xanthate Antagonism Pb/Zn Ore – Pb Flotation
94
92
90
88
86
84
82
80
78
76
74
72
Pb %
Rec
ove
ry
Zn % Recovery to Pb Conc.18 20 22 24 26 28 30 32 34 36 38 40 42
Xanthate75:25 AEROPHINE 3418A/Xanthate
AEROPHINE 3418A
Table 1
Xanthate Antagonism AEROPHINE 3418A
Performance
Assays-% CuRelative Dosage
1.84
2.17
1.94
2.07
SIPX
1.00
0.67
0.50
0
Conc.
2702
2408
28.7
27.1
AEROPHINE3418A
0
0.33
0.50
0.43
0.20
0.24
0.21
0.19
% Rec.
89.79
89.81
89.83
91.46
and AEROPHINE 3418A dosages were equalized,
without any significant benefit resulting. When the
use of SIPX was eliminated, and AEROPHINE
3418A promoter was used as the sole collector
at 43%of the normal SIPX dosage rate, a
significant improvement in metallurgy was noted.
AEROPHINE 3418A has since been adopted as
21Use of AEROPHINE® 3418A Promoter
for Sulfide Minerals Flotationcontinued
the collector at this plant, used without any other
collector type. The dosage of AEROPHINE 3418A
has ultimately been optimized at 10% of the
former xanthate consumption.
In plant applications it may be possible to use a
low xanthate dosage toward the end of Cu or Pb
flotation, where little or no xanthate would be
recycled to the head of rougher flotation. This
possibility can exist where it is desired to recover
principally iron-sulfide minerals, bearing precious
metals or small amounts of the primary metal,
into a low grade scavenger concentrate. The only
area of application where the use of xanthate with
AEROPHINE 3418A can be recommended is for
activated sphalerite flotation. AEROPHINE 3418A
generally has not demonstrated advantages in use
as the sole collector for sphalerite as frequently
as it has for the flotation of copper minerals and
galena. As mentioned previously, this is thought
to be due to the stoichiometry of Fe within the
sphalerite crystal lattice. Use of a xanthate with
AEROPHINE 3418A in Zn flotation has given
promising results with some ores.
A peculiar characteristic of AEROPHINE 3418A
promoter, seen only in laboratory flotation
investigations, is its tendency to sometimes
produce better selectivities with increasing dosages.
This phenomenon has been noted with a number
of ores by different investigators. The reasons for
the occurrence of this phenomenon in laboratory
flotation are not known, but it is noteworthy that
it has not been observed in actual plant application.
There has, in fact, been a general tendency for
effective plant dosages of AEROPHINE 3418A
promoter to be lower than what may have been
indicated in laboratory investigations.
Figure 3 demonstrates increased selectivity against
Zn with increased AEROPHINE 3418A dosage,
when applied to laboratory Pb flotation on a Pb-
Zn ore.
Figures 3, 4 & 5
Laboratory Dosage Selectivity Phenomenon
Pb/Zn Ore – Pb Flotation97
96
95
94
93
92
91
90
89
88
87
Cu
% R
eco
very
18 20 22 24 26 28 30 32
Zn % Recovery to Cu Conc.
60g/t AEROPHINE 3418A
42g/t AEROPHINE 3418A
Pyrrhotitic Cu Ore
35g/t AEROPHINE 3418A40g/t AEROPHINE 3418A
30g/t AEROPHINE 3418A
Cu
% R
eco
very
90
85
80
75
70
65
60
55
50
% Cu Conc. Grade8 10 12 14 16 18 20
Cu/Zn Ore – Cu Flotation97
96
95
94
93
92
91
90
89
88
87
Cu
% R
eco
very
10 12 14 16 18 20 22 24 26 28 30 32 34
Zn % Recovery to Cu Conc.
10g/t AEROPHINE 3418A
7.5g/t AEROPHINE 3418A
22Use of AEROPHINE® 3418A Promoterfor Sulfide Minerals Flotationcontinued
Figure 4 demonstrates increasing selectivities
with increasing AEROPHINE 3418A dosages
when used for laboratory copper flotation. In
this example, the ore is a massive sulfide with
pyrrhotitegangue. The improved grades at higher
AEROPHINE 3418A dosages are due to increased
selectivity against the pyrrhotite.
Figure 5 shows the phenomenon when
AEROPHINE 3418A was applied to laboratory
copper flotation on a Cu-Zn ore. The increased
selectivity against Zn is evident at the higher
AEROPHINE 3418A dosage.
As stated previously, this peculiar trait of
AEROPHINE 3418A promoter to sometimes
demonstrate better selectivity when used at higher
dosages seems limited to laboratory testing only.
The information is provided solely for the purpose
of preparing the flotation investigator, should he or
she encounter this phenomenon in a laboratory
test program.
Advantages in Use
The following example highlights the advantages
which the use of AEROPHINE 3418A can provide.
Example
A laboratory flotation investigation was carried
out on a massive sulfide ore containing 0.67%
Cu and 0.7 g/t Au. The principal gangue sulfide
mineral was pyrrhotite which carried about half
the Au values.
Using a coarse feed granulometry of 50% minus
200 mesh, comparative testing of a variety of
different collectors established AEROPHINE
3418A promoter as providing the best combination
Figure 6
Increased Au Recovery in Cu Flotation
Au
% R
eco
very
40
38
36
34
32
30
28
26
24
22
20
18
16
70 72 74 76 78 80 82 84 86 88 90 92
Cu % Recovery
30g/t AEROPHINE 3418A
50g/t AEROPHINE 3418A
Figure 7
Selectivity in Cu Flotation
4 5 6 7 8 9 10 11 12 13
Cu
% R
eco
very
% Cu Conc. Grade
92
90
88
86
84
82
80
78
76
74
72
70
30g/t AEROPHINE 3418A
50g/t SIPX
23Use of AEROPHINE® 3418A Promoter
for Sulfide Minerals Flotationcontinued
of Cu and Au recoveries, and selectivity against
pyrrhotite. These benefits are illustrated in Figures
6 and 7.
Figure 6 compares Cu vs. Au recoveries for a
test made using 30 g/t AEROPHINE 3418A
and another made using 50g/t SIPX, both
with a flotation pH 10.1. Both tests produced
Cu recoveries of 90-91%. The test made with
AEROPHINE 3418A, however, recovered
significantly more Au per unit of Cu recovery than
did the test with SIPX. The use of AEROPHINE
3418A promoter also demonstrated improved
concentrate grades, illustrated in Figure 7,
compared to those produced by SIPX. This
was principally due to better selectivity against
pyrrhotite.
Since a large portion of Au contained in the ore is
associated with the pyrrhotite, yet AEROPHINE
3418A promoter was shown to be more selective
against pyrrhotite than SIPX, the increased Au
recovery produced by AEROPHINE 3418A is
attributed to improved recovery of some portion of
Au existing in a liberated state.
Conclusions
AEROPHINE 3418A is a unique sulfide mineral
promoter, based on phosphine chemistry. It has
found widest application for flotation of copper-
sulfides and galena, particularly where these are
found in complex polymetallic ores containing
sphalerite, and ores with high levels of pyrite and/
or pyrrhotite. Use of AEROPHINE 3418A has
demonstrated improved recoveries of base metals
and associated precious metals, with excellent
selectivity characteristics against iron-sulfide
gangue minerals and depressed sphalerite. Other
advantages seen in use are rapid flotation kinetics,
and decreased collector consumption compared
to more traditional thiol type collectors. The
unique flotation performance characteristics of
AEROPHINE 3418A can best be realized when
AEROPHINE 3418A is evaluated according to
recommended application techniques.
24New Flocculants for Improved Processing of High Silica Bauxite
Qi Dai, Matt Davis Ruzi Zhang
Introduction
An important element in the production of
alumina from bauxite is an effective solid-liquid
separation in gravity thickeners to generate sodium
aluminate liquor containing low amounts of
suspended solids. This process relies heavily on
synthetic flocculants that are introduced to the
slurry feed to enhance the aggregation of red mud
particles and accelerate the settling of the red mud.
Over the years, new reagents have been developed
to improve this separation, which include the high
molecular weight polyacrylates and hydroxamated
polyacrylamides that are routinely used today[1, 2].
Despite their widespread utility, these flocculants
are not always able to deal with the settling
problems brought on by the decreasing quality
of bauxite. One such example is with increasing
reactive silica levels in the bauxite. In the Bayer
process, silica and silicate minerals (mainly
kaolinite) react with caustic liquor to form sodalite
or DSP (desilication products) particles having
the general formula 3(Na2 2
O3 2
0-2H2 2
X, where X is an anionic species
such as OH-, Cl-, CO2
3- or SO4
2- [3]. The 2-step
reaction is thought to proceed according to the
following chemical reactions[3, 4]:
3 Al2Si
2O
5(OH)
4 + 18 NaOH
6 Na2SiO
3 + 6 NaAl(OH)
4 + 3 H
2O (1)
6 Na2SiO
3 + 6 NaAl(OH)
4 + Na
2X
Na6[Al
6Si
6O
24 2X + 12 NaOH + 6 H
2O (2)
Additional species can accompany DSP in the
mud depending upon factors such as liquor
chemistry and impurity mineral phases present
in the bauxite. These phases include calcium
aluminosilicates, calcium silicates, titanium
dioxide and calcium titanate. The presence of fine
particles of DSP and these other phases can have
a negative impact on overflow clarity, overflow
filtration, mud settling and compaction[5, 6]
which cannot be overcome by using conventional
flocculants and often result in flow cuts. Therefore
Cytec Industries has responded to the need for
further improvements in flocculant technology
to meet the challenges put forth by the industry’s
increased utilization of low quality bauxite ores.
This paper highlights a new family of polymers
incorporating silane functionality that show
improved flocculation of suspended silicate
and titanate solids in the Bayer process[7].
The development of these reagents and the
corresponding performance on slurries generated
from processing high silica gibbsitic bauxite has
been discussed elsewhere[8]. This publication
represents an extension of this technology
to settler and washer applications at plants
processing high silica diasporic bauxite (with
and without sweetening with gibbsitic bauxite),
a subject particularly applicable to the alumina
industry in China. Data from laboratory settling
experiments demonstrating the performance
of these polymers on slurry from representative
Bayer refineries are presented.
Experimental
The performance of the new flocculant was tested
on red mud slurries collected on-site at a number
of alumina refineries. The data from static cylinder
tests were used to compare results obtained from
the use of the new silane-containing polymers to
those using only a polyacrylate flocculant.
On-site evaluation of new reagents at several
refineries was conducted by obtaining thickener
feed and transferring to 500 ml graduated
cylinders to conduct laboratory settling tests.
25New Flocculants for Improved
Processing of High Silica Bauxitecontinued
For experiments evaluating the performance in
the washers, appropriate ratios of overflow and
underflow were combined to yield representative
slurries. To account for variation between batches,
measurement of slurry solids and liquor analysis
were performed on at least two cylinders per batch.
In all experiments, the polyacrylate flocculant
was added to the slurry using a single addition,
followed by 5 gentle mixing strokes of a
perforated plunger. In experiments evaluating the
developmental product CYFLOC™ SA settling
aid (one of the new flocculants), the polymer
was dosed prior to the standard addition of the
polyacrylate as described above. A polyacrylate
flocculant dose was chosen to achieve settling
rates representative of the plant, which were
calculated by timing the descent of the mud
interface, and these experiments were treated as
the control. After flocculant addition and mixing
were complete, the cylinders were left in a water
bath for a fixed time, after which the supernatant
clarity was measured gravimetrically by filtering an
aliquot of the overflow liquor. When this was not
possible, overflow clarity was determined with a
turbidimeter.
Results and Discussion
The dose response of CYFLOC SA was
investigated on settler feed slurry at a Bayer
refinery that was processing diasporic bauxite with
an average reactive silica level of 13% and A/S
(alumina to silica) ratio = 5. The dosage of the new
polymer was varied between 0 and 408 g/T which
was added in combination with a fixed dosage of
polyacrylate flocculant (522 g/T). Mud solids were
measured to be 98 g/L. Because it was not possible
to measure supernatant solids gravimetrically, the
performance of the new polymer was assessed by
measuring the turbidity of the supernatant. The
settling rate results, along with the supernatant
turbidity on the secondary axis, are displayed
in Figure 1.
Figure 1
Settling Rate (diamonds) and Supernatant Turbidity
(triangles) Data As a Function of CYFLOC SA
Dose When Dosed to Slurry Obtained While
Processing Diasporic Bauxite. In all experiments, the
polyacrylate dose was held constant at 522 g/ton.
0
50
100
150
200
250
300
350
0
2
4
6
8
10
0 75 150 225 300 375 450
Sup
ernatan
t Turb
idity (N
TU)
Sett
ling
Rat
e (m
/hr)
CYFLOC SA Dose (g/ton)
Settling RateTurbidity
As seen in Figure 1, increasing the dose of
CYFLOC SA results in a doubling in settling
rate. This large improvement in settling rate is
not accompanied with a significant change in the
supernatant turbidity.
The dose response of the same reagent, CYFLOC
SA, was investigated on plant slurry collected
from another Bayer refinery that was processing
diasporic bauxite while sweetening with 10%
gibbsitic bauxite. The dosage of the polymer was
varied between 0 and 481 g/ton which was added
in combination with a fixed dosage of polyacrylate
(154 g/ton). The settling rate and supernatant
clarity results are displayed in Figure 2.
26New Flocculants for Improved Processing of High Silica Bauxitecontinued
Figure 2
Settling Rate (diamonds) and Supernatant Turbidity
(triangles) Data As a Function of CYFLOC SA
Dose When Dosed to Slurry Obtained While
Processing Diasporic Bauxite and Sweetening with
10% Gibbsitic Bauxite. In all experiments, the
polyacrylate dose was held constant at 154 g/ton.
0
1
2
3
4
5
0
4
8
12
16
0 100 200 300 400 500
O/F C
larity (g/L)
Sett
lin
g R
ate
(m/h
r)
CYFLOC SA Dose (g/ton)
Settling RateClarity
From the data in Figure 2, it is clear that addition
of the new polymer to red mud slurries results
in improved supernatant clarity compared to the
addition of conventional flocculants alone. This
improvement in clarity was also accompanied by
an improvement in settling rate, with observed
increases up to 80%. These results illustrate the
applicability of this reagent to improve the settling
performance of slurry when the plant is processing
high silica diasporic bauxite and practicing
sweetening with gibbsitic bauxite.
During the course of our evaluations at Bayer
refineries, we also observed that improved
performance in the mud washing circuit could
be realized by the addition of CYFLOC SA. The
dose response of the new polymer was established
on feed to the 2nd washer of a Bayer refinery
processing high silica diasporic bauxite. The
dosage of the polymer was varied between 0 and
111 g/ton which was added in combination with
a fixed dosage of polyacrylate (120 g/ton). The
settling rate and supernatant turbidity results are
displayed in Figure 3.
Figure 3
Settling Rate (diamonds) and Supernatant Turbidity
(triangles) Data As a Function of CYFLOC SA Dose
When Dosed to Slurry Feed from the 2nd Washer.
In all experiments, the polyacrylate dose was held
constant at 120 g/ton.
0
50
100
150
200
250
0
2
4
6
8
10
0 50 100 150
Sup
ernatan
t Turb
idity (N
TU)
Sett
lin
g R
ate
(m/h
r)
CYFLOC SA Dose (g/ton)
Settling RateTurbidity
From the settling test data in Figure 3, it is
apparent that CYFLOC SA can significantly
improve flocculation performance in washers,
resulting in faster settling rates and lower overflow
solids. The data from these experiments show
a settling rate more than double that which is
obtained by the addition of polyacrylate alone.
This is accompanied by a large reduction in the
supernatant turbidity.
In the mining industry, the dual polymer
program is widely used, in which a low molecular
weight polymer is added first followed by a
high molecular weight polymer. The role of the
low molecular weight polymer (often referred
to as coagulant) is to form small mud particle
aggregates which can subsequently be flocculated
by the high molecular weight flocculant more
efficiently than the case of single polymer
program. There is also a variety of choice of the
low molecular weight polymer; cationic, anionic,
inorganic and organic[9]. However, in the Bayer
process, flocculation of red mud is almost solely
achieved by high molecular weight polymers with
occasional cases involving lime and dextran as
27New Flocculants for Improved
Processing of High Silica Bauxitecontinued
flocculation aids. Attempts have been made in the
past to find or develop coagulant type of polymers
to aid red mud flocculation without much success.
This new polymer is the first of this kind that has
shown significant improvement in this area.
Conclusions
1. Laboratory results conducted with plant slurry
demonstrate the effectiveness of new silane-
containing polymers for improved flocculation
of muds generated from processing high silica
diasporic bauxite.
2. A 2-3 time improvement in settling rate was
observed on multiple substrates obtained
from different plants when CYFLOC SA was
added in combination with a conventional
polyacrylate flocculant.
3. In most cases, this settling rate improvement
was also accompanied by a significant
improvement in overflow clarity by capturing
particles that would normally report to the
settler overflow.
4. CYFLOC SA was also shown to be effective at
improving flocculation efficiency in the mud
washing circuit.
References
1. Rothenberg, A.S., Spitzer, D.P., Lewellyn,
M.E., and Heitner, H.I., New reagents for
alumina processing, Light Metals, (1989),
pp. 91-96
2. Ryles, R.G., and Avotins, P.V., "Superfloc®
HX*, a new technology for the alumina
industry" (4th International Alumina Quality
Workshop, Darwin, Northern Territory,
1996), pp. 206-216.
3. Whittington, B.I., Fletcher, B.L., and Talbot,
C., The effect of reaction conditions on the
composition of desilication product (DSP)
formed under simulated Bayer conditions,
Hydrometallurgy, Vol. 49, (1998), pp. 1-22.
4. Smith, P., The processing of high silica
bauxites -- Review of existing and potential
processes, Hydrometallurgy, Vol. 98, (2009),
pp. 162-176.
5. Peiwang, L., Zhijian, L., Yucai, L., Hailong,
C., Fengling, W., and Hong, W., The
influence of the predesilication temperature
of bauxite slurry on the sedimentation of red
mud and the utilization of which in alumina
production, Light Metals, (1994), pp. 133-
136.
6. Li, S.-M., Ge, L.-Y., and Zeng, X.-Q., The
simulation experiment about silica to the
settling of red mud separation process, Ziran
Kexueban, Vol. 36, No. 3 (2007), pp. 18-20.
7. Dai, Q., Spitzer, D., Heitner, H.I., and Chen,
H.-L.T., Use of silicon-containing polymers
to improve red mud flocculation in the Bayer
process, US Patent Application 2008/0257827
A1, (2008).
8. Davis, M., Dai, Q., Chen, H.-L.T., and
Taylor, M., New Polymers for Improved
Flocculation of High DSP-Containing Muds,
Light Metals, (2010), pp. 57-61.
9. Heitner, H.I., Foster, T., and Panzer, H.P.,
"Mining Applications" (Encyclopedia of
Polymer Science and Engineering, 2nd Ed.,
Vol. 9, 1987), p. 824.
The Inhibition of Vishnevite Scale in Chinese Refineries Using MAX HT® 550 Scale Inhibitor28
Qi Dai, John Carr, Frank Kula, Jerome O’Keefe
Introduction
Silica present in bauxite dissolves under Bayer
alumina digestion conditions and subsequently
precipitates as a sodium aluminosilicate,
“desilication product” (DSP). This precipitation
occurs as scaling on the inside of the heat exchange
tubes and causes significant loss of heat transfer.
The impact of scale and options for dealing with
the scaling problem is well documented[1,2]. The
current method to clean the heater tubes is a
combination of acid and mechanical cleaning that
is unsatisfactory from an economical, safety, and
efficiency perspective[3].
In 2004, Cytec developed the MAX HT®
technology to prevent the aluminosilicate
scale growth in refinery evaporators and heat
exchangers[4]. Since then MAX HT has successfully
eliminated the formation of sodalite scale under
various process conditions[2,3,5,6]. This technology
was originally limited to double stream refineries,
becoming ineffective at high solids (single stream)
and low solids conditions. A second generation
product, MAX HT® 550, was developed that was
shown to work more robustly at low solid levels
encountered in some double stream refineries[7, 8].
The effectiveness of MAX HT is influenced
by the type of scale (mineralogy) formed at a
particular refinery. Development work focused on
inhibiting sodalite scale that is prevalent in many
Bayer plants. When scale other than sodalite is
predominant, MAX HT technology may have
reduced effectiveness requiring increased dosages
to inhibit scale formation. The tendency and type
of aluminosilicate scale to form in a particular
refinery will depend on a wide variety of factors,
related primarily to the type of bauxite and process
conditions. Table 1 shows some characteristics of
the scales in various regions of the world. Chinese
refineries have been shown to form vishnevite type
scale instead of sodalite or cancrinite commonly
found in other regions. This difference originates
from the type of the bauxite and impurity minerals
associated with it. Most vishnevite scale is found
in Chinese refineries which process domestic
diasporic bauxite. Some Chinese refineries process
imported gibbsitic bauxite, and evaporator scale in
those refineries is exclusively sodalite (not shown
in Table 1).
Performance testing of MAX HT in China began
with the first generation product in diasporic and
gibbsitic bauxite refineries. Standard laboratory
tests showed that the product performed well in
both refineries, achieving complete inhibition
of sodium aluminsilicate at expected dosages
(typically 15-40 ppm). The test work continued
after the development of the second generation
MAX HT. More recently, we discovered that
the second generation product is not only
more solids tolerant but also more effective in
inhibiting vishnevite scale than the first generation
product. This paper presents the laboratory
results simulating the formation and inhibition of
vishnevite scale using both first generation MAX
HT and second generation (MAX HT 550) scale
inhibitors.
Vishnevite Scale
Chemically, sodium aluminosilicate scale is usually
either sodalite or cancrinite, with cancrinite the
predominant scale in higher temperature plants.
Vishnevite forms a solid solution series with
cancrinite in which the main substitution is
between CO3 and SO
4. K+ incorporation may
also occur.
29The Inhibition of Vishnevite Scale in Chinese
Refineries Using MAX HT® 550 Scale Inhibitorcontinued
Cancrinite (Na, Ca)7-8
(Al6Si
6O
24)
(CO3, SO
4, Cl)
1.2-2.0 1-5H
2O
Vishnevite (Na,Ca,K)6-7
(Al6Si
6O
24)
(SO4, CO
3, Cl)
1.0-1.5 1-5H
2O
Sodalite Na8(Al
6Si
6O
24) Cl
Structurally, sodalite has a roughly spherical unit
cell of ca. 9Å and is isometric (cubic). Vishnevite
and cancrinite have rod like structures and unit
cells of ca. 12.7 X 5.15 Å and are both hexagonal.
All have very open structures and, as a result, low
densities that probably contribute to their ability
to lower heat exchanger efficiency.
Vishnevite scale is a unique type of aluminosilicate
scale commonly found in evaporators in Chinese
refineries processing domestic bauxite. While
the chemistry of all evaporator scales is sodium
aluminosilicate, vishnevite scale contains markedly
more SO3 and K
2O than sodalite and cancrinite
scales (Table 1).
Domestic Chinese bauxite is predominantly
diasporic, and has high amounts of clay minerals
including kaolinite, illite and pyrophyllite[9,10]. The
preference of forming vishnevite scale over sodalite
and cancrinite is due to the impurity minerals in
Chinese bauxite, especially illite and pyrite. As
described above, vishnevite forms when K
substitutes some Na and SO4- is incorporated as
anions in the crystal. Illite is the source of K+, and
pyrite is the source of SO4-. The presence of SO
4-
can promote the formation of vishnevite[11].
Table 1
Scales from Various Bayer Refineries in Different Regions
Plant
A
B
C
D
E
G
H
Region/ Country
Europe
Scale from
--
Scale
Vishnevite
Vishnevite
Vishnevite
--
SO3
3.8
1.4
1.5
11
4.4
--
1.7
--
7.8
6
4
4.56
4.06
K2O
0.5
0.4
0.7
0.2
0.7
--
0.04
--
10
16
7
3.17
2.15
CaO
0.05
0.1
0.3
0.1
0.2
--
0.04
--
0.05
3.5
1
0.26
1.14
Wt% in scale
*Chinese refineries processing diasporic bauxite
30The Inhibition of Vishnevite Scale in Chinese Refineries Using MAX HT® 550 Scale Inhibitorcontinued
Figure 1 below shows initial synthetic attempts
at forming vishnevite scale in the laboratory by
altering various liquor/digestion conditions.
Figure 1
XRD Spectrum of an Initial Attempt at Making
Vishnevite Scale in the Laboratory
0
500
1000
1500
2000
2500
01-071-5356> Sodalite - Na8(Al6Si6O24)
01-070-8054> Quartz- - SiO2
01-086-1155> Anatase - Ti0.784O2
10 20 30 40 50 60 70
Two-Theta (deg)
I(C
ou
nts
)
[S20085-101C.raw] carbonate scale - 1ds1ss0.3mmrs
Figures 2 and 3 show the effect of incorporating
increasing amounts of potassium hydroxide in the
synthetic liquor. Vishnevite scale was successfully
formed followed by a phase that had higher degree
of potassium cation substitution.
Figure 2
X-ray Diffraction Spectrum of a Laboratory
Prepared Vishnevite Scale with 25% NaOH
Replaced with KOH in the Liquor
10 20 30 40 50 60 700
500
1000
1500
2000
2500
3000
3500
Inte
nsi
ty(C
ou
nts
)
[S20146-6-14raw.raw]
00-046-1333> Vishnevite - Na8Al6Si6O24(SO4)-2H2O
Two-Theta (deg)
Methodology
Details of the laboratory scale inhibition test
can be found in[1,2]. The same method is used in
both the Cytec R&D laboratories and in alumina
refinery laboratories. In the Cytec laboratories,
tests are performed primarily in synthetic
Bayer liquors containing 0.8 g/L SiO2, 45 g/L
Al2O
3, 160 g/L NaOH, 40 g/L Na
2CO
3 and
20 g/L Na2SO
4. The composition was designed
to promote reasonable amount of sodalite
precipitation in the liquor in 16 hours. To
generate vishnevite solids, the formulation was
modified by substituting 50% NaOH replacement
with KOH (on a molar basis). Increasing Na2SO
4
above 20 g/L did not seem to promote the
formation of vishnevite.
The test method allows for a large number of tests
to be done rapidly with results that have proven
to be predictive of performance. The amount
of precipitated solids in each test is used as a
measure of inhibition performance; the less the
precipitation, the better the performance.
Analytical Characterization
The major mineral phases associated with
synthetically prepared and Bayer plant scales were
determined by x-ray diffraction (XRD) using a
Rigaku Multiflex spectrometer. Elemental data
were obtained via x-ray fluorescence (XRF) using
a Rigaku ZSX Primus II wavelength dispersive
spectrometer. Vibrational spectroscopy was
conducted at an outside laboratory with a Kaiser
Holoprobe dispersive Raman spectrometer using
785nm laser excitation to confirm the presence of
vishnevite scale in synthetically prepared samples.
31The Inhibition of Vishnevite Scale in Chinese
Refineries Using MAX HT® 550 Scale Inhibitorcontinued
Figure 3
X-ray Diffraction Spectrum of a Laboratory
Prepared Vishnevite Scale with 50% NaOH
Replaced with KOH in the Liquor
10 20 30 40 50 60 70x103
5.0
10.0
15.0
20.0
25.0
30.0
Inte
nsi
ty(C
ou
nts
)
[S20146-65B.raw] scale from KOH - 1ds1ss0.3mmrs
01-078-2203> Vishnevite - K0.5Na0.76(SiAlO4)(SO4)0.13(H2O)0.33
Two-Theta (deg)
Raman analysis was also performed for the
synthetic sample to confirm the presence of
vishnevite scale. Although the sample produced
a high fluorescence background masking some of
the characteristic bands, the most intense band for
vishnevite is observable at 995 cm-1 (Figure 4).
Figure 4
Raman Spectrum for Synthetically Made Scale
Showing Main Vibration at 995 cm-1.
500000
450000
400000
995 45
9
350000
300000
250000
200000
150000
100000
50000
1150 1100 1050 1000 950 900 850 800 750 700
wavenumbers
650 600 550 500 450 400 350 300 250
0
Results
Synthetic Liquors
Figure 5 compares the rate of sodalite
precipitation to that of vishnevite without
MAX HT addition. Vishnevite is formed by
replacing 50% of the NaOH with KOH (on
a molar basis). Vishnevite precipitates out at a
much slower rate than sodalite during the first
eight hours. Data from all other tests show
that at the end of the test (16 hours), the final
amount of precipitation reaches the same level
of 0.22±0.01g/120 mL. This provides an equal
basis to evaluate MAX HT performance when
comparing sodalite and vishnevite inhibition.
Figure 5
Rate of Sodalite vs. Vishnevite Precipitation
without MAX HT
Dose (ppm)
Prec
ipit
atio
n (g
/120
mL)
0
0.00
0.05
0.10
0.15
0.20
2 4 6 8 10
Vishnevite (50% NaOH replacement)
Sodalite (0% NaOH replacement)
Performance of the first generation MAX HT at
various NaOH replacement levels are shown in
Figure 6. Results are plotted as percentage of DSP
precipitation vs. blanks, i.e., no inhibitor added;
100% would mean no effect of the inhibitor,
while 0% means complete scale inhibition. As
the inhibitor dose increases, the precipitation
decreases to zero. There is, however, a slight trend
of increasing precipitation as NaOH replacement
increases to 50%, a condition favoring vishnevite
32The Inhibition of Vishnevite Scale in Chinese Refineries Using MAX HT® 550 Scale Inhibitorcontinued
formation. In contrast, MAX HT 550 displays
the opposite trend (Figure 7) with significantly
improved inhibition at higher NaOH replacement
by KOH.
Figure 6
Performance of First Generation MAX HT
Dose (ppm)
Pre
cip
itati
on
(%
of
bla
nk)
0
0
20
40
60
80
100
5 10 15 20
25% NaOH replacement50% NaOH replacement
No NaOH replacement
Figure 7
Performance of First Generation MAX HT 550
Dose (ppm)
Pre
cip
ita
tio
n (
% o
f b
lan
k)
0
0
20
40
60
80
100
1 2 3 4 5 6
25% NaOH replacement
50% NaOH replacement
0% NaOH replacement
Figure 8 compares the two generations of MAX
HT in vishnevite inhibition tests using liquors
with 25% and 50% NaOH replacement by KOH.
The results show that MAX HT 550 is superior
to the first generation in terms of vishnevite
inhibition. It can also be observed from Figures
6 and 8 that the first generation MAX HT,
although effective on both types aluminosilicate
scales, requires higher dosages to inhibit vishnevite
formation than sodalite formation (No NaOH
replacement).
Figure 8
Comparison of First Generation MAX HT and
MAX HT 550
Dose (ppm)
Prec
ipit
atio
n (
% o
f b
lan
k)
0
0
20
40
60
80
100
5 10 15 20 25
MAX HT 550 25% NaOHreplacementMAX HT 50% NaOHreplacementMAX HT 550 50% NaOHreplacement
MAX HT 25% NaOHreplacement
Plant Liquors
MAX HT was also tested in laboratories at a
number of refineries where evaporator scales
are identified as vishnevite. Two comparative
examples are displayed in Figures 9 and 10.
One example was performed using feed liquor
to the 1st Effect of the evaporator at Refinery K
(Figure 9) and the other example was performed
using spent liquor of Refinery L (Figure 10).
Consistent with previous test work, MAX HT
550 demonstrates superior vishnevite inhibition
relative to the first generation product.
One should not expect that the difference in
dosages required of the two generation
products will be the same as those required in
a plant. The important point from the results
33The Inhibition of Vishnevite Scale in Chinese
Refineries Using MAX HT® 550 Scale Inhibitorcontinued
presented here is that it is possible to eliminate
sodalite and vishnevite precipitation with MAX
HT 550 at much lower doses than with the first
generation product.
Figure 9
MAX HT Performance in Laboratory Tests Using
Feed Liquor to the 1st Effect of the Evaporator at
Refinery K
Dose (ppm)
Pre
cip
itati
on
(%
of
bla
nk)
0
0
20
40
60
80
100
5 10 15 20 25 30
MAX HT 550
MAX HT Gen.1
Figures 10
MAX HT Performance in Tests Using Spent Liquor
at Refinery L
Dose (ppm)
Pre
cip
ita
tio
n (
% o
f b
lan
k)
0
0
20
40
60
80
100
5 10 15 20 25 30
MAX HT 550
MAX HT Gen.1
Commercial discussions surrounding the efficacy
of MAX HT 550 are currently underway
throughout China with multiple customers.
Conclusions
1. MAX HT 550, the second generation of
aluminosilicate scale inhibitor effectively
inhibits scale and is far superior in terms
of vishnevite scale inhibition to the first
generation product.
2. The performance advantage of the second
generation over the first generation has been
proven in both synthetic liquors and real
plant liquors.
3. Chinese bauxites are predominantly diasporic
and contain potassium bearing silicate
clays. The presence of potassium in Bayer
liquor causes the formation of ‘vishnevite’; a
potassium aluminosilicate scale in evaporators.
4. Sodalite is the common aluminosilicate scale
in low temperature double stream plants,
while vishnevite occurs principally in Chinese
high temperature plants that process domestic
Chinese diasporitic bauxite.
5. X-ray diffraction and Raman spectroscopy of
synthetic scale samples showed the successful
formation of vishnevite.
6. In the laboratory, synthetic liquor for sodalite
precipitation can be modified to form
vishnevite by replacing NaOH in the liquor
by KOH.
34The Inhibition of Vishnevite Scale in Chinese Refineries Using MAX HT® 550 Scale Inhibitorcontinued
References
1. Spitzer, D., Rothenberg, A., Heitner, H.,
Kula, F., Lewellyn, M., Chamberlain, O., Dai,
Q. and Franz, C., Reagents for the elimination
of sodalite scaling, Light Metals (2005), pp
183-188.
2. Spitzer, D., Rothenberg, A., Heitner, H.,
Kula, F., Lewellyn, M., Chamberlain, O.,
Dai, Q. and Franz, C., A real solution to
sodalite scaling problems, Proceedings of the
7th International Alumina Quality workshop
(2005), pp 153-157.
3. Oliveira, A., Dutra, J., Batista, J., Lima,
J., Diniz, R. and Repetto, E., Performance
appraisal of evaporation system with scale
inhibitor application in Alunorte plant, Light
Metals (2008), pp 133-136.
4. Spitzer, D., Rothenberg, A., Heitner, H. and
Kula, F., Method of preventing or reducing
aluminosilicate scale in a Bayer process, U.S.
patent 6,814,873 (2004).
5. Spitzer, D., Chamberlain, O., Franz, C.,
Lewellyn, M. and Dai, Q., MAX HT™
sodalite scale inhibitor: Plant experience and
impact on the process, Light Metals (2008),
pp 57-62.
6. Riffaud, J.P., James, P.D., Allen, E. and
Murray, J.P., Evaluation of sodalite scaling
inhibitor – A user’s perspective, International
Symposium on Alumimum: From Raw
Materials to Applications – Combining Light
Metals 2006 and the 17th International
ICSOBA Symposium, Montreal, Canada,
Oct. 1-4, 2006, Bauxite and Alumina Session,
paper 29.7.
7. Spitzer, D., Rothenberg, A., Heitner, H. and
Kula, F., Polymers for preventing or reducing
aluminosilicate scale in a bayer process, U.S.
patent 7,442,755 (2008).
8. Lewellyn, M., Patel, A., Spitzer, D., Franz,
C., Ballentine, F., Dai, Q., Chamberlain,
O., Kula, F. and Chen, H., MAX HT 500:
A second generation sodalite scale inhibitor,
Proceedings of the 8th International Alumina
Quality workshop (2008), pp 121-124.
9. Gu, S., Chinese bauxite and its influences on
alumina production in China, Light Metals
(2008), pp 79-83.
10. Li, W., Liu, J., Liu, Z. and Wang, Y., The
most important sustainable development
issues of Chinese alumina industry, Light
Metals (2008), pp 191-195.
11. Bi, S. (Ed.), Process of alumina production,
Chemical Industry Press, Beijing, China
(2007), p.69 (Chinese).
12. W. Deer, R. Howie, J. Zussman, Rock
Forming Minerals, Vol. 4, Longman, Green
and Co. LTD, Ppp 289-295,
310-315
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