Accounting for the froth in batch flotation tests

Transcription

1 REAGENT RESEARCH FACILITY Accounting for the froth in batch flotation tests sulphide Peter Harris 5 June 29

2 Froth stability A 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.

3 Pilot plant froth A

4 Pilot plant froth B

5 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.

6 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.

7 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.

8 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

9 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.

10 EXPERIMENTAL DETAILS Merensky ores milled to 6% passing 75 µm for batch flotation tests. Synthetic plant water used throughout, natural ph 9 (8 ppm Ca, 7 ppm Mg, 1 T.D.S). 2 cm froth height, 7 L / min air flow, 12 rpm impeller speed. 4 concentrates at 2, 6, 12 and 2 min flotation time. Feeds, concentrates and tails assayed for Cu, Ni and S.

11 REAGENTS Frother: 4 g/t DOW 2 Collectors: SEX,SNPX,SIBX,PAX,DTP added to mill Activator: Cu SO 4 Depressants: Guars supplied by Chemquest CMC s supplied by Akzo Nobel Functional Chemicals

12 Indirect Effect depressant, collector, activator

13 Total mass and water recoveries 3 cmc s of differing DS - 1g/t. X 5g/t. SIBX or SEX Water, g Mass, g SEX SIBX SEX SIBX SEX SIBX Dep 186 Dep 267 Dep 158 Water Mass

14 Total mass and water recoveries 3 cmc s of differing DS - 3g/t. X 5g/t Water, g Mass, g SEX SIBX SEX SIBX SEX SIBX Dep 186 Dep 267 Dep 158 Water Mass

15 Nickel recovery rate (time) Ni recovery,% Time, min SEX 1g/t depressant SIBX 1g/t depressant SEX 3g/t depressant SIBX 3g/t depressant

16 Nickel recovery as a function of water recovery (g) Ni recovery, % Water, g SEX 1g/t depressant SEX 3g/t depressant SIBX 1g/t depressant SIBX 3g/t depressant

17 Gangue recovery vs water Increasing depressant dosage Total gangue, g Water, g Dep 186-1g/t- SEX Dep 186-3g/t- SEX Dep 186-5g/t- SEX

18 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.

19 Gangue recovery vs water at high depressant dosage (5g/t) all X Total gangue, g Water, g SIBX SEX SNPX PAX

20 Floating gangue vs water. 1g/t cmc (active- content). Different DS Float gangue, g entrain Water, g Dep 186-1g/t- SEX Dep 267-1g/t- SEX Dep 158-1g/t- SEX Dep 186-1g/t- SIBX Dep 267-1g/t-SIBX Dep 158-1g/t- SIBX

21 Total mass and water 4 purified cmc s (1-3g/t) similar DS Water, g KU 11 KU 11 KU 47 KU 47 FF 15 FF 15 FF 1 FF 1 Reagent and dosage, g/t Water Mass

22 Mass vs water purified cmc s 6 1g/t 5 Cum mass,g g/t Cum water,g FF 1 1g/t FF 1 3g/t FF 15 1g/t FF 15 3g/t KU 47 1g/t KU 47 3g/t KU 11 1g/t KU 11 3g/t

23 Floating gangue vs water recovered Merensky ores different source

24 Effect of depressant type, dosage and Cu activation on froth stability Water, g Mass, g Cu Cu Cu Cu Cu Cu CMC Reagents and dosage (g/t) guar Water Mass

25 Effect of increasing depressant dosage on floatable gangue 9 8 Floating gangue, g No depressant 1 g/t g/t 3 g/t Water, g 1 CMC 2 CMC 3 CMC Dep 1 guar 2 guar 3 guar

26 Floatable gangue at fixed water recovery effect of depressant dosage 7 Float gangue at 35 g water CMC guar Dosage, g/t CMC Cu CMC guar Cu guar

27 Solution depressant concentration increasing dosage Polymer solution concentration, mg/l Dosage, g/t guar cmc

28 Ni recovery -increasing depressant dosage Ni recovery, % Water, g 1 CMC 2 CMC 3 CMC 1 guar 2 guar 3 guar

29 5g/t guar Effect of increasing X dosage from 5g/t to 15g/t 6 5 Recovery, % g/t SEX SNPX SIBX PAX Water, g SEX 15g/t SNPX 15g/t SIBX 15g/t PAX 15g/t SEX 5g/t SNPX 5g/t SIBX 5g/t PAX 5g/t

30 Direct Effect - Frother Dosage

31 Total mass and water recoveries increasing frother dosage Water, g Mass, g g/t 5g/t 6g/t 7g/t 4g/t 5g/t 6g/t 7g/t 4g/t 5g/t 6g/t 7g/t no dep 25g/t guar 5g/t guar frother dosage Water Mass

32 Effect of frother dosage on floatable gangue recovery No depressant Float gangue, g g/t guar 5 g/t guar Water, g 4g/t D2 5g/t D2 6g/t D2 7g/t D2

33 Increasing frother concentration Cu, Ni recoveries vs water 15g/t X Cu Cu, Ni recovery, % Ni Water, g 4g/t no dep 5g/t no dep 6g/t no dep 7g/t no dep 4g/t 25g/t guar 5g/t 25g/t guar 6g/t 25g/t guar 7g/t 25g/t guar

34 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.

35 The people who really count Thanks to: Jenny Wiese Jules Kitenge Bernard Oostendorp Rene van der Merwe Sam Morar (videos) Sponsors: Anglo Platinum, Impala, Lonmin

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