accounting for the froth in batch flotation testsaccounting for the froth in batch flotation tests...
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Accounting for the froth in Accounting for the froth in batch flotation testsbatch flotation tests
Peter Harris5 June 2009
CENTRE FOR MINERALS RESEARCH
sulphide
REAGENT RESEARCH FACILITY
Froth stabilityA dynamic froth is a complicated physico-chemical system which cannot be explained by a simple theory suitable for all types of foams or froths. There is no sharp transition from a weakly frothing condition to a strongly frothing one.
By necessity, flotation froths are weakly stable froths which need to breakdown rapidly for further treatment.
As a result all reagents used in the recovery of valuable minerals by flotation can affect, either directly or indirectly, the stability of the froth.
Direct effect• Frother (being surface –active) affects the
stability of the froth by lowering the surface tension of the liquid phase and increasing the stability of the froth films.
• Frother can also alter the bubble-size which, in turn , will affect froth stability.
• Any reagent that possesses some surface activity (i.e. has frothing properties), such as some DTP collectors, will alter the froth stability directly.
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Indirect effect• All the other reagents such as collectors,
activators or depressants will influence the froth stability by altering the nature of the hydrophobic particles entering the froth. All particles that attach to the air/water interface can have a major influence on froth stability.
• Strongly hydrophobic particles can destabilise froths by bridging the froth films and collapsing bubbles
• Close-packed weakly hydrophobic particles can stabilise froths by attaching at both interfaces and preventing the thinning of the lamellae.
Indirect effect (cont.)• The stability of the froth is then usually
dependent on a combination of these two effects.
• Ignoring the effect of the froth stability on the solids recovery in a batch flotation test can lead to erroneous conclusions and inhibit the understanding of reagent interactions.
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Measure of froth stability• How can froth stability it be measured?
Equilibrium froth height.Dynamic froth index (DFI)Froth collapse rate/ drainage rate
Not applicable to 3-phase froths
• Simplest method – water recovered at a fixed froth height
Batch flotation tests
Including the changes in froth stability can improve the understanding of the performance and interaction of the reagents used in batch flotation tests.
Confined to Merensky ore flotation (1% sulphides).
Depressant Research Facility.
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EXPERIMENTAL DETAILS
Merensky ores milled to 60% passing 75 µm for batch flotation tests.
Synthetic plant water used throughout, natural pH 9
(80 ppm Ca, 70 ppm Mg, 1000 T.D.S).
2 cm froth height, 7 L / min air flow, 1200 rpm impeller
speed.
4 concentrates at 2, 6, 12 and 20 min flotation time.
Feeds, concentrates and tails assayed for Cu, Ni and S.
REAGENTS
• Frother: 40 g/t DOW 200
• Collectors: SEX,SNPX,SIBX,PAX,DTP added to mill
• Activator: Cu SO4
• Depressants:
Guars supplied by Chemquest
CMC’s supplied by Akzo Nobel Functional Chemicals
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Total mass and water recoveries3 cmc’s of differing DS - 100g/t. X 50g/t.
SIBX or SEX
0
50
100
150
200
250
300
SEX SIBX SEX SIBX SEX SIBX
Dep 186 Dep 267 Dep 158
Wat
er, g
0
5
10
15
20
25
30
35
40
Mas
s, g
Water Mass
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Total mass and water recoveries3 cmc’s of differing DS - 300g/t. X 50g/t
0
50
100
150
200
250
300
SEX SIBX SEX SIBX SEX SIBX
Dep 186 Dep 267 Dep 158
Wat
er, g
0
5
10
15
20
25
30
35
40
Mas
s, g
Water Mass
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Nickel recovery rate (time)
0
5
10
15
20
25
30
35
40
45
50
0 5 10 15 20 25Time, min
Ni r
ecov
ery,
%
SEX 100g/t depressant SEX 300g/t depressantSIBX 100g/t depressant SIBX 300g/t depressant
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Nickel recovery as a function of water recovery (g)
0
5
10
15
20
25
30
35
40
45
50
0 50 1 00 150 200 2 50 300Wate r, g
Ni r
ecov
ery,
%
SEX 100g/t depressant SIBX 100g/t depressantSEX 300g/t depressant SIBX 300g/t depressant
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Gangue recovery vs waterIncreasing depressant dosage
0
5
10
15
20
25
30
35
0 50 100 150 200 250 300W ater , g
Tota
l gan
gue,
g
D ep 186 -100g/t- SEX D e p 186-300g /t - SEX D ep 186-500g/t- SEX
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Entrainment
On the assumption that the complete depression of naturally floating gangue occurs at high depressant dosage, any gangue reporting to the concentrate does so by entrainment only. This entrainability factor (slope) can be used to decouple floatable gangue from entrained gangue.
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Gangue recovery vs water at high depressant dosage (500g/t) all X
0
2
4
6
8
10
12
14
0 100 200 300 400 500 600Water, g
Tota
l gan
gue,
g
SIBX SEX SNPX PAX
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Floating gangue vs water. 100g/t cmc(active- content). Different DS
0
2
4
6
8
10
12
14
16
18
20
0 50 100 150 200 250 300Water, g
Floa
t gan
gue,
g
Dep 186-100g/t- SEX Dep 267-100g/t- SEX Dep 158-100g/t- SEX
Dep 186-100g/t- SIBX Dep 267-100g/t-SIBX Dep 158-100g/t- SIBX
entrain
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Total mass and water4 purified cmc’s (100-300g/t) – similar DS
0
100
200
300
400
500
600
700
800
100 300 100 300 100 300 100 300
KU 11 KU 11 KU 47 KU 47 FF 150 FF 150 FF 10 FF 10Reagent and dosage, g/t
Wat
er, g
0
10
20
30
40
50
60
Water Mass
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Mass vs waterpurified cmc’s
0
10
20
30
40
50
60
0 100 200 300 400 500 600 700 800Cum water,g
Cum
mas
s,g
FF 10 100g/t FF 10 300g/t FF 150 100g/t FF 150 300g/tKU 47 100g/t KU 47 300g/t KU 11 100g/t KU 11 300g/t
100g/t
300g/t
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Effect of depressant type, dosage andCu activation on froth stability
0
100
200
300
400
500
600
700
800
100 200 300 100 200 300 100 200 300 100 200 300
Cu Cu Cu Cu Cu Cu
CMC guar
Reagents and dosage (g/t)
Wat
er, g
0
10
20
30
40
50
60
70
80
Mas
s, g
Water Mass
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Effect of increasing depressant dosage on floatable gangue
0
10
20
30
40
50
60
70
80
90
0 100 200 300 400 500 600 700 800Water, g
Floa
ting
gang
ue, g
100 CMC 200 CMC 300 CMC 0 Dep100 guar 200 guar 300 guar
100 g/t
No depressant
200 g/t
300 g/t
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Floatable gangue at fixed water recovery – effect of depressant dosage
0
10
20
30
40
50
60
70
0 50 100 150 200 250 300 350Dosage, g/t
Floa
t gan
gue
at 3
50 g
wat
er
CMC Cu CMC guar Cu guar
CMCguar
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Solution depressant concentration –increasing dosage
0
20
40
60
80
100
120
140
0 200 400 600 800 1000 1200Dosage, g/t
Poly
mer
sol
utio
n co
ncen
tratio
n, m
g/l
guar cmc
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Ni recovery - increasing depressant dosage
0
10
20
30
40
50
60
70
0 100 200 300 400 500 600 700 800Water, g
Ni r
ecov
ery,
%
100 CMC 200 CMC 300 CMC100 guar 200 guar 300 guar
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500g/t guar – Effect of increasing X dosage from 50g/t to 150g/t
0
1 0
2 0
3 0
4 0
5 0
6 0
0 5 0 100 15 0 200 250 30 0 350 400 45 0
Water, g
Reco
very
, %
SEX 150g /t SNPX 150g/t SIBX 150g /t PAX 150g /t SEX 50g/t SNPX 50g/t SIBX 50g/t PAX 50g/t
50 g/tSEXSNPXSIBXPAX
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Total mass and water recoveries –increasing frother dosage
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0
100
200
300
400
500
600
700
800
900
1000
40g/t 50g/t 60g/t 70g/t 40g/t 50g/t 60g/t 70g/t 40g/t 50g/t 60g/t 70g/t
no dep 250g/t guar 500g/t guarfrother dosage
Wat
er, g
0
20
40
60
80
100
120
Mas
s, g
Water Mass
Effect of frother dosage on floatable gangue recovery
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0
10
20
30
40
50
60
70
80
90
100
0 200 400 600 800 1000 1200Water, g
Floa
t gan
gue,
g
40g/t D200 50g/t D200 60g/t D200 70g/t D200
No depressant
250 g/t guar
500 g/t guar
Increasing frother concentrationCu, Ni recoveries vs water – 150g/t X
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0
10
20
30
40
50
60
70
80
90
100
0 200 400 600 800 1000 1200Water, g
Cu, N
i rec
over
y, %
40g/t no dep 50g/t no dep 60g/t no dep 70g/t no dep40g/t 250g/t guar 50g/t 250g/t guar 60g/t 250g/t guar 70g/t 250g/t guar
Cu
Ni
Summary
• The stability of the froth is influenced by the nature of the hydrophobic particles entering the froth.
• Using water as a measure of froth stability allows a better understanding of the role and interaction of the reagent suite.
• Allows a better determination of the comparative behaviour of the various reagents.
• Does not replace classical grade-recovery curves.
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The people who really count
Thanks to:Jenny Wiese Jules KitengeBernard OostendorpRene van der MerweSam Morar (videos)
Sponsors: Anglo Platinum, Impala, Lonmin