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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
O
CO
NF
ID
O
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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
11
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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)
14
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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
15
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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
16
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Gas Rate, Jg
Impeller Speed(Power Input)
17
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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)
19
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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
22
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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
23
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Overall D32 Model
24
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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
27
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Model Comparison with
Plant Data
28
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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
29
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Model Predictions
30
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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)
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
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)
Frother Concentration (ppm)
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)
Frother Concentration (ppm)
Jg = 1 cm/s
Pentanol
DowFroth 250
F-150
31
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
33
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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
34
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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)
35
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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
36
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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
38
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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:
40
Thank YouThank You