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Iron Ore Beneficiation Africa - Heavy Liquid Separation at High Densities Date: 17 March 2014 Author Heloise Thiele Designation Specialist Consultant: Physical Separation

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Page 1: Heloise Thiele, Mintek

Iron Ore Beneficiation Africa - Heavy Liquid Separation at High

Densities

Date: 17 March 2014 Author Heloise Thiele

Designation Specialist Consultant: Physical Separation

Page 2: Heloise Thiele, Mintek

Presentation Outline

•  Why is High Density HLS Required? •  The MDS – Minerals Density Separator •  Why could conventional HLS not be used? •  Alternative powders •  Evaluation method •  Results •  HLS versus MDS in practice •  Conclusions

Page 3: Heloise Thiele, Mintek

Why is High Density HLS Required? •  Characterising Fe ores at densities >4.0g/cm3 •  In the past techniques like:

– Batch Jigging/Mineral Density Separator(MDS)

– Stone-by-stone pycnometry was used •  But these techniques had limitations like:

– MDS, inherent inefficiencies due to particle size effects etc. Modelling required

– Stone-by-stone pycnometry extremely time consuming and exposed to operator error

Page 4: Heloise Thiele, Mintek

The MDS – Mineral Density Separator

Page 5: Heloise Thiele, Mintek

The MDS – Mineral Density Separator

Page 6: Heloise Thiele, Mintek

The MDS – Mineral Density Separator

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The MDS – Results

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The MDS – Modelled density distributions

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The MDS – Modelled Washability results

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Why could conventional HLS not be used? •  Typical HLS separation makes use of mixtures of

fine atomised FeSi and TBE.

•  At densities >3.8g/cm3, high viscosities prohibits efficient separation from taking place.

•  The density of the FeSi used, required high mass% FeSi to be mixed with TBE (SG= 2.96g/cm3).

Page 11: Heloise Thiele, Mintek

Alternative powders •  Tungsten and Tungsten Carbide Powders were then

considered – Readily available – Fine particle size distribution – High densities

• W= 19.25g/cm3 • WC = 16.8g/cm3 compared to • FeSi = 6.8g/cm3

Page 12: Heloise Thiele, Mintek

Evaluation method •  Settling Velocities: To create a stable media for

separation to occur in, settling velocities should be low. Thus finer material will be required than with FeSi

•  Viscosity: Separation efficiency is related to viscosity of the media

•  Separation Efficiency: How do we measure if the separation was in fact efficient? – Density tracers – only up to 4.0g/cm3

– Classified stones

Page 13: Heloise Thiele, Mintek

Method: Viscosity measurements

a) Physica Rheolab QC rheometer. b) Double-gap measuring system

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Method: HLS

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Method: HLS

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Hematite Stones: Efficiency of separation

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Results: Mixing Ratios

Mass [%] in TBE

SG FeSi WC W

3.2 10.7 9.3 9.0

3.6 31.4 21.9 20.9

3.8 39.1 27.2 25.7

4.0 46.1 32.0 30.5

4.2 52.5 36.4 34.8

4.4 40.3 38.6

4.6 44.0 42.1

4.8 47.2 45.2

Page 18: Heloise Thiele, Mintek

Results: Settling Velocities •  The terminal settling velocity was calculated using

the following formula: •  V = kd2(Ds-Df) •  k=g/18*η •  Where: V= terminal velocity •  k = ratio constant •  g = gravitational acceleration (9.8g/m2) •  η = viscosity of fluid (TBE = 0.1 P.sec) •  d = diameter of the particle •  Ds = density of solid •  (FeSi = 6.8g/cm3, WC = 15.8g/cm3, W = 19.25g/cm3) •  Df = density of fluid (TBE = 2.96g/cm3)

Page 19: Heloise Thiele, Mintek

Results: Settling Velocities (cont)

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Results: Viscosity

0.00  20.00  40.00  60.00  80.00  

100.00  120.00  140.00  160.00  180.00  200.00  220.00  240.00  

3.5  3.75   4   4.25  4.5  4.75   5   5.25  5.5  5.75   6   6.25  6.5  

Viscosity

 (mPa.s)  

Rela%ve  density  (g/cm3)  

Viscosity  as  a  func%on  of  medium  density  

WC  

W  

FeSi    

Page 21: Heloise Thiele, Mintek

Results: Efficiency of separation

0  

10  

20  

30  

40  

50  

60  

70  

80  

90  

100  

3.60   3.70   3.80   3.90   4.00   4.10   4.20   4.30   4.40   4.50   4.60   4.70   4.80   4.90   5.00  

Par%%on

 Coe

fficien

t    (%

)  

Average    Density  (g/cm3)  

Effeciency  in  Separa%on  as  func%on  of  density    

4.29  g/cm3    

4.79  g/cm3  

4.55  g/cm3  

D50=4.29g/cm3 Ep=0.016 D50=4.55g/cm3

Ep=0.053 D50=4.79g/cm3 Ep=0.016

Page 22: Heloise Thiele, Mintek

HLS versus MDS in practice •  High Density HLS results

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HLS versus MDS in practice •  HLS versus MDS (modelled HLS)

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Predictive DMS modelling •  Use an empirical Weibull function to represent

partition surface of gravity concentrators in terms of size-density attributes

•  Y = 100[1-exp(-(ln(1/1-Yp))(ρ/ρp)(pd^q)] –  Y Partition number, a function of particle size –  and density –  Yp Pivot partition number, representing fraction of by-pass in gravity concentrators –  p that captures viscosity effects –  q represents flow conditions of the separator

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Predictive DMS modelling

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Back to the Fe Ore example

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Conclusions •  The relationship between solid media density (FeSi,

W and WC) and viscosity was established •  A sharp increase in media viscosity prevents FeSi in

the presence of TBE to obtain efficient separation at densities >4.0g/cm3.

•  Since WC and W are at significantly higher particle densities than FeSi, finer particle size distributions, such as <12µm, should be considered for these powders.

•  Fine WC (84% <25µm) in the presence of TBE is successful, in obtaining media densities as high as 6.0g/cm3, at low viscosities.

Page 28: Heloise Thiele, Mintek

Conclusions •  Very efficient separation could be measured at

densities as high as 4.79g/cm3 in WC and TBE media.

•  Due to the low viscosities measured up to densities as high as 6.0g/cm3, it is expected that efficient separation could be achieved at these densities. Further testwork should be conducted to confirm this.

•  The effect of particle size on the efficiency of separation should be evaluated.

Page 29: Heloise Thiele, Mintek