Jan Nesset

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A Benchmarking Tool for Assessing

Flotation Cell Hydrodynamics

W. Zhang, McGill University

J.A. Finch, McGill University


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A Benchmarking Tool forA Benchmarking Tool forAssessing Flotation CellAssessing Flotation Cell

HydrodynamicsHydrodynamicsJ.E. Nesset

Procemin Conference, Santiago , Chile

December 2, 2011

W. Zhang

J.A. Finch

I

NDO

MIN

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CO

NF

ID

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The presentation covers

The test cell and variables investigated The concepts of CCC and CCC95 The effect of key variables on D32

e overa 32 equa on The notion of a Road map for processoptimization

Implications for process improvement Case study: Lac des Iles3


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Illustrating the importance of frother

and small bubbles in flotation (video)

View inside a Denver laboratory flotation machine:

water-air system: no air, air added, air with frother 4Metso CBT Flotation Module 2002 (originally BPT 1996)


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Frother functions are multiple:1. Stabilizing of small bubbles (0.5 2 mm)

in pulp phase by preventing coalescence2. Bubble size and shape affect gas hold-

u , interfacial surface area of as and

5

hence particle collection efficiency3. Froth formation and stability thus

influencing water drainage, hence gangue

rejection and concentrate grade

This presentation looks at predicting

bubble size in the pulp phase


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Motivation for the work:

No adequate model existedfor redictin bubble size in

flotation

Seen as a significantshortcoming

6


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Variables investigated

Frother type (5) and concentration Gas rate Jg (volumetric air flow/cell area)

ower npu

mpe er spee Altitude (gas density) Viscosity (water temperature)

Testing in 2-phase water- gas system

no solids 7


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Gas Dispersion Terminology

Sauter Mean Bubble Size (mm)

of the bubble size distribution

Superficial Gas Velocity (cm/s)

32 = 31 21

=

Bubble Surface Area Flux (1/s)

= 60 32 8 =

Flotation Rate Constant (1/s)


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Test CellMetso RCS 0.8 m3

9


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Test CellMetso RCS 0.8 m3

10

QuiescentZone

TurbulentZone

Measurement

Location


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Frother

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Frother types tested (5)Frother Description Supplier Molecular Weight

Pentanol Simple alcohol Fisher 88

MIBC Methyl isobutyl carbinol Dow 102

DowFroth 250 Polypropylene glycol alkyl ether Dow 235-265

F140 Blend of aldehydes and ketones Flottec Mixture C8-C22: typical 200-250

F150 Polypropylene glycol Flottec 410-440

Covers broad range ofcommonly used frothers plus

low MW Pentanol 12


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The CCC and CCCXconcepts (X=% of A)

3

4

)

D32

= Dlimiting

+ Aexp[-Bppm]

Measured

Exponential Model

CCC50

CCC85

0

1

2

0 10 20 30 40 50

D32(m

Frother Addition (ppm)

CCC99A

Dlimiting

CCC95 values closely approximate Laskowskis CCC

values but easier to establish mathematically 13

CCC = Critical

Coalescence

Concentration

= Dl


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4

D32 versus frother concentration Normalized by (PPM/CCC95)

5 frother types 2 gas rates (Jg)1

2

3

4

D32(mm)

Jg=0.5 cm/s

Jg=1 cm/s

Model All Data

Model Jg=0.5 cm/s

Model Jg=1 cm/s

0

1

2

3

0 1 2 3 4 5 6 7 8 9 10

D32(mm)

Frother Addition (ppm/CCC95)

Jg=0.5 cm/s

Jg=1 cm/s

Model All Data

Model Jg=0.5 cm/s

Model Jg=1 cm/s

]9509.3[exp26.2874.032 CCC

ppm

D+=

Frother can be

characterized by itsCCC95 (@ Jg=0.5 cm/s)

00 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Frother Addition (ppm/CCC95)

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The link between CCC95 and HLB/MW(Jg=0.5 cm/s)

SURFACTANT MW HLB HLB/MW CCC or CCC95

Nesset (2006)

DF250 (PG) 264.37 7.8 0.0295 10.06

F150 (PG) 425 7.83 0.0184 4.23

Pentanol (A) 88 6.52 0.0741 30.47

MIBC (A) 102 6.1 0.05981 12.37

Nesset et al (2010)

HLB

Hydrophile Li o hile

. . . .

F150 (PG) 425 7.83 0.0184 5.99Pentanol (A) 88 6.52 0.0741 23.72

MIBC (A) 102 6.1 0.05981 10.54

Grau & Laskowski (2006)

PO1 (PG) 90.12 8.3 0.0921 46.8

PO2 (PG) 148.12 8.15 0.0550 25.1

DF200 (PG) 206.29 8 0.0388 17.3

DF250 (PG) 264.37 7.8 0.0295 9.1

DF1012 (PG) 397.95 7.5 0.0188 6.6

MIBC (A) 102.18 6.1 0.0597 11.2

HEX (A) 102.20 6.00 0.0587 8.07

DEMPH (A) 248.4 6.6 0.0266 3.23

DEH (A) 190.3 6.7 0.0352 5.90

MPDEH (A) 248.4 6.6 0.0266 3.73

PG = Polyglycols, A = Alcohol Measurements at Jg = 0.5 cm/s

BalanceA measure of the

solubility of ahydrocarbon in

water. Calculatedempirically fromthe molecular

structure

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CCC95 - HLB/MW relationshipy = 566.33x - 5.7599

R = 0.9922

20

30

40

50

CCC95atJg=0.

5cm/s

PG & Alcohol Ness et (2006)

PG & Alcohol Ness et et a l (2010)

PG Grau and Laskowski (2006)

Alcohol Grau and Laskowski (2006)

Polyglycols

Nesset (2006)

Pentanol (not

used)

Nesset et al

Pentanol (2010)

CCC95 values can be predicted frommolecular structure of the frother

0

10

0 0.02 0.04 0.06 0.08 0.1

CCC

o

HLB/MW

Alcohols

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Gas Rate, Jg

Impeller Speed(Power Input)

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5.0

032 )100( gJaDD +=

D32 versus Jg and impeller speedGas Rate, Jg

No meaningful effect ofpower input on D32

Impeller Speed (Power)

10.00 PPM Model

MIBC

0

1

2

3

4

5

2 4 6 8 10

D32

(mm)

Impeller Tip Speed (m/s)

0 ppm Jg=1

2.5 ppm Jg=1

5 ppm Jg=1

10 ppm Jg=1

0 ppm Jg=0.5

2.5 ppm Jg=0.5

5 ppm Jg=0.5

10 ppm Jg=0.5

Typical O perating Range

Cell Operating Limit

18

0.1

1.0

0 0.5 1 1.5

D32(mm)

Jg (cm/s)

2.63 PPM Model

5.6 PPM Model

8.74 PPM Model

17.6 PPM Model

0 ppm

2.63 ppm

5.16 ppm

8.74 ppm

17.6 ppm

0.1

1.0

10.0

0 0.5 1 1.5

D32(mm)

Jg (cm/s)

Model 0 PPM

Model 2.41 PPM

Model 4.82 PPM

Model 8.01 PPM

Model 16.02 PPM

0 ppm

2.41 ppm

4.82 ppm

8.01 ppm

16.02 ppm

DF250


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Viscosity

(water temperature)

Gas Density

(altitude)

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D32 correction factors for

viscosity and gas densityfactor v (viscosity)

o

= 200.776

= 0.132

factor d (altitude)

20

20

1.0

1.5

2.0

2.5

3.0

0 10 20 30 40 50

D32(mm)

Temperature (Co)

95% Confidence Limits

D32-Viscos ity Model

Test 1

Test 2

Test 3

Test 5

o

1.0

1.1

1.2

1.3

1.4

1.5

1.6

0 0.2 0.4 0.6 0.8 1

D32(mm)

Gas Density Relative to Standard Conditions, g/o

Model

Test 1 Jg=0.25

Test 2 Jg=0.25

Test 3 Jg=0.3

Test 4 Jg=0.3

95% Conf Limits

D32 = 1.06(o/g)0.132

R2Adj = 0.835

Region of Interest


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Interaction Effects on D32

- g

21


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Increasing Jg increasesboth the CCC95, and the

limiting Dl

1

2

3

4

D32

(mm)

Jg=.05

Jg=0.25

Jg=0.5

Jg=0.75

Jg=1.0

Increasing Jg and CCC95

Interaction effects:

Jg, CCC95 and limiting bubble size, Dl

0

0 5 10 15 20

DowFroth 250 (ppm)

y = -0.0176x + 1.0144

RAdj = 0.9995

y = -0.0171x + 1.1518

RAdj = 0.9597

0.2

0.4

0.6

0.8

1.0

1.2

0 10 20 30 40 50

Dlimiting

(m

m)

CCC95 (ppm)

Jg = 0.5 cm/s

Jg = 1 cm/s Frothers with higher

CCC95 have lowerlimiting D

l

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Interaction effects:are normalized relative to CCC95

at Jg = 0.5 cm/s

Polyglycol frothers (DF250, F140, F150)

6528.06736.09595 JCCCCCC +=

Adjustment factor for the limiting bubble size ()

Alcohol frothers (MIBC, Pentanol)

.

)2723.08639.0(9595 5.0 gJg JCCCCCC += =

)9506.10(0176.0 5.0== Jgl CCCf

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Overall D32 Model

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Overall D32 model

Overall equation for determining D

32from the key flotation variables

factors v(viscosity),

d(altitude),

l(limiting D

l) as described earlier

,,32 ppmgdv =

25

Note that a model for D32 also becomes a model for predicting Sb since

=6

32


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Overall D32 model The function is given by

[ ]

+++++=

9509.3exp)100(0619.0)267.0(316.2)100(064.0267.0 5.05.0

CCC

ppmJfJf glgl

g

CCC0 curve(maximum limiting bubble size)

-

of frother concentration andtype on the CCC0 curve

g

type on the CCC 99 curve(minimum limiting bubble size)

26

0

1

2

3

4

5

0.0 0.5 1.0 1.5 2.0

D32

(mm)

Jg (cm/s)

0 PPM Frother

4 PPM DF250

8 PPM DF250

16 PPM DF250

32 PPM DF250

CCC0 - Maximum D32

CCC99 - Minimum D32


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Model goodness-of-fitD32 and Sb measured versus modeled

D32 Model - All Data

95% C.L. 0.30 mm

R2 = 0.96

N = 1991

2

3

4

ModelD32(mm)

DF250 PPM Tests

MIBC PPM Tests

F150 PPM Tests

F140 PPM Tests

DF250 Jg Tests

MIBC Jg Tests

0 PPM Jg Tests

Viscosity/Temp

Altitude/Density

0

0 1 2 3 4

Measured D32 (mm)

95% CL

0

20

40

60

80

100

0 20 40 60 80 100

ModelSb

(s-1)

Measured Sb (s-1)

All Data

95% CL

Sb Model - All Data (Sb=6Jg/D32)

95% C.L. 8.0 s-1 (avg)

95% C.L. 22% (avg Relative)

N = 199

Note: Sb increasingly sensitive asD

32becomes smaller

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Model Comparison with

Plant Data

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Model validation with plant data

- notion of a Process Road Map

Plant data (3-

phase) fitcompletely

within model

5 Operating Plants

CompanyNA

PalladiumWMC* Xstrata Ni Escondida

Impala

Platinum

Operating Plant Site Lac des Iles Leinster Raglan Los

ColoradosUG2

Cell Manufacturer Outotec TC Outotec 16U Outotec 28U Outotec TCBateman TC,

Metso TC

Cell Size (vol), m3 130 16 28 100 50, 30

(2-phase)

,

Site Location Ontario Australia Quebec Chile South Africa

Metal/mineral floated Palladium Nickel Nickel Copper Platinum

* Now BHP Billiton, R = rougher, S = scavenger, C=cleaner

Model curves are for DowFroth 250 equivalent frother concentration

0

20

40

60

80

100

0.0 0.5 1.0 1.5 2.0

Sb

(s-1)

Jg (cm/s)

Plant DataLimiting DF250 CCC

16 PPM DF250

8 PPM DF250

4 PPM DF250

0 PPM Frother

Lac des Iles

WMC-LNO

Raglan

Escondida Los Colorados

Impala

0.1

1.0

10.0

0.0 0.5 1.0 1.5 2.0

D32(mm)

Jg (cm/s)

Plant Data0 PPM Frother

4 PPM DF250

8 PPM DF250

16 PPM DF250

32 PPM DF250

Lac des Iles

WMC-LNO

Raglan

Escondida Los Colorados

Impala

max

min

max

min

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Model Predictions

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Examples of model prediction

0

1

2

3

4

0 5 10 15 20 25 30 35 40 45

D32(mm)

Frother Concentration (ppm)

DowFroth 250Jg=2 cm/s

Jg=1.5 cm/s

Jg=1 cm/s

Jg=0.5 cm/s

Jg=0.2 cm/s

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35 40 45

Sb(s-1)


DowFroth 250Jg=2 cm/s

Jg=1.5 cm/s

Jg=1 cm/s

Jg=0.5 cm/s

Jg=0.2 cm/s

The optimumfrother

concentration

increases withincreasing gasrate (Jg)

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35 40 45

Sb(s-1)


Jg = 1cm/s

Pentanol

DowFroth 250

F-150

0

1

2

3

4

0 5 10 15 20 25 30 35 40 45

D32(mm)


Jg = 1 cm/s

Pentanol

DowFroth 250

F-150

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As a result, thesefrothers provideopportunity for

increasing Sb andhence flotation

kinetics

g er

frothers yieldlower limitingbubble size


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Case Study:

Using Model to Benchmark

Plant Performance

(Ontario, Canada)

10% Difference in Pd recoverybetween plant and pilot testing

(testing in 2003 and 2005)32


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Large difference in plant andpilot plant/lab bubble size

Combined

final tails

Flotation

Feed

Scavenger cells

Scavenger

tails

Cleaner

tails

Rougher cells

Lab Tests Plant and Pilot Tests

Combined

final tails

Flotation

Feed

Scavenger cells

Scavenger

tails

Cleaner

tails

Rougher cells

Lab TestsLab Tests Plant and Pilot TestsPlant and Pilot Tests

0

20

40

60

80

100

1 2 3 4 5 6 7

%

minus

1mm

bubbles

Cell No

Plant Cells

Pilot PlantCells

Std LabFloat

Final

concentrate

Final

concentrate

Plant cellsPlant cellsPlant cellsPlant cells

Pilot /lab cellsPilot /lab cellsPilot /lab cellsPilot /lab cells

- m nus mm u es

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LDI - Comparison of 2003 and 2005D32 and Sb with road map model

6th

Scavenger cell

2005 test of blended frother to 6th scavenge cell

2

3

4

D32(mm)

Lac des Iles Case Study0 PPM Frother

5 PPM MIBC

10 PPM MIBC

Limiting MIBC CCC

LDI 2003 Original Study

LDI 2005 Re-Study

Note repeatability of 2003 and2005 data @ 5 ppm MIBC

additional frother moves D32to match2003 pilot plant values

Additional frotheradded to 6th cell

Hernandez-Aguilar et al (2006)

0

1

0.0 0.5 1.0 1.5 2.0

Jg (cm/s)

LDI 2003 Pilot Plant

LDI 2005 w/BlendedlFrother

0

20

40

60

80

100

0.0 0.5 1.0 1.5 2.0

Sb(s-1)

Jg (cm/s)

Lac des Iles Case StudyLimiting MIBC CCC

10 PPM MIBC

5 PPM MIBC

0 PPM Frother

LDI 2003 Original Study

LDI 2005 Re-Study

LDI 2003 Pilot Plant

LDI 2005 w/Blendedl

Frother

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LDI Pd recovery improvementresulting from decrease in bubble

size with increased frotherParticle Size Pd Recovery for D32 in Specified Bubble

rac on ze ange

(microns) < 1.2 mm 1.2 mm to1.6 mm

> 1.6 mm

+45 21.3 10.2 7.9

-45 +10 15.1 7.3 7.3

-10 69.1 24.6 29.9

Pd recovery across 6th cell with additional frother to increase %-1mm bubbles(Hernandez-Aguilar et al, 2006)

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Maneuvering on the D32-Sb-Jg Roadmap

- A benchmarking tool

40

60

80

100

Sb

(1/s)

CCC99

CCC90

CCC75

BC

Increasing Sb by Jgalone will achieve

only a limitedincrease and loosesmall bubbles

0

20

0 0.5 1 1.5 2

Jg (cm/s)

CCC50

CCC0

Frother Jg D32 Sb

A CCC75 0.75 1.71 26.3

B CCC75 1.5 2.08 43.3 - eliminated small bubblesC CCC99 0.75 0.82 54.9 - increased small bubbles

b

increasing frotherconcentration, CCCX,is far more effectivethan increasing Jg

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Do you know where your plant islocated on the D32-Sb-Jg road map?

60

80

100

(s-1)

32 PPM DF250

16 PPM DF250

CCC99 - Maximum Sb

3

4

5

m)

0 PPM Frother

4 PPM DF250

CCC0 - Maximum D32

37

0

20

40

0.0 0.5 1.0 1.5 2.0

Sb

Jg (cm/s)

4 PPM DF250

0 PPM FrotherCCC0 -Minimum Sb

0

1

2

0.0 0.5 1.0 1.5 2.0

D32(

Jg (cm/s)

16 PPM DF250

32 PPM DF250CCC99 - Minimum D32

Note: These curves are forDF250 equivalent concentrationsbased on the D32model equations. Curves for other frothers will

be somewhat different


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Conclusions1. A robust empirical bubble size, D32, model

for flotation has been developed in the air-water system

Frother concentration, viscosity and gas rate are the

Gas density (altitude) effects are secondary Impeller speed (power) has minimal effect across4 - 9 m/s range

2. The model has been validated with plantdata (i.e. for the air-water-solid system)

3. A powerful benchmarking and optimizationtool

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Acknowledgements

NSERC, Metso Minerals, AMIRA P9O Industrial Chair corporate sponsors

, , , -

Eagle, COREM, SGS Lakefield Research,Flottec, Barrick, Shell

Many talented and enthusiastic students,colleagues and collaborators at McGill andat various plant sites


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For a copy of the paper and

presentation contact:

[email protected]

40

Thank YouThank You

Jan Nesset

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