accounting for the froth in batch flotation testsaccounting for the froth in batch flotation tests...

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.

Pilot plant froth A


Pilot plant frothB


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.


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.


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.


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


Indirect Effect –depressant, collector, activator


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


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


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


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


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


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.


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


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


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


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


Floating gangue vs water recoveredMerensky ores – different source


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


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


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


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


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


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


Direct Effect - Frother Dosage


Total mass and water recoveries –increasing frother dosage


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


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


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.


The people who really count

Thanks to:Jenny Wiese Jules KitengeBernard OostendorpRene van der MerweSam Morar (videos)

Sponsors: Anglo Platinum, Impala, Lonmin

accounting for the froth in batch flotation testsaccounting for the froth in batch flotation tests...

Documents