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Transcript of Cesar Gomez
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7/27/2019 Cesar Gomez
1/22
AN APPROACH TO CHARACTERISE FROTHER
ROLES IN FLOTATION
Cesar O. Gomez and James A. FinchMcGill UniversityDepartment of Mining and Materials Engineering
Daniela Muoz-Cartes
Minera Escondida
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INTRODUCTION
Frother roles in flotation
It is generally agreed that frothers play two major roles inflotation:
Reduction of bubble size by preserving bubble formation size; and
Froth stabilization by influencing water carrying and drainage in the froth.
Frother characterization efforts have been focussed: Measuring bubble formation and velocity (mostly for single bubbles); or
Bubble coalescence or water drainage during formation or collapsing of afroth layer.
It has been demonstrated that a significant interaction betweenzones exists; therefore, frother effects should be characterizedallowing this interaction to occur.
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INTRODUCTION
Previous workReduction of bubble size by preventing coalescence
3
4
5
ETER,mm
0
1
2
0 10 20 30 40 50 60
BUBBLEDIAM
FROTHER CONCENTRATION, ppm
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3
4
5
TER,mm
INTRODUCTION
Previous workCritical Coalescence Concentration (CCC)
0
1
2
0 10 20 30 40 50 60
BUBBLEDIAM
FROTHER CONCENTRATION, ppm
CCC (Critical Coalescence Concentration)
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INTRODUCTION
Previous workFrothers affect gas holdup (same gas flow rate)
15
20
P,%
F150
1-Octanol
MIBC
1-Pentanol
0
5
10
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
GASHOLD
FROTHER CONCENTRATION, mmol/L
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INTRODUCTION
Previous workWater carrying rate (same froth depth)
0.4
0.5
RATE,cm/s
F-150
1-Octanol
MIBC
1-Pentanol
0.0
0.1
0.2
.
0 10 20 30 40
WAT
EROVERFLO
GAS HOLDUP, %
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OBJECTIVES
Develop a laboratory technique to simultaneously characterizefrother roles in flotation.
The following features were considered necessary:
Simultaneous measurement of three arameters: critical
coalescence concentration (CCC), water carrying rate, and gasholdup in the collection zone;
Continuous interaction between the collection and froth zonesduring measurements;
Automated operation, particularly on-line automatic control of frothdepth and volumetric gas flow rate in the test section; and
Automated monitoring and registering of process variables.
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EXPERIMENTAL SETUP
Laboratory column flotation
PVC column; Assembled with
flanged sections;
Db
DP
Overflow
water
F
Testsection
.
Diameter: 0.1 m.
Peristalticpump
P2Feed tank
Underflowcontrol valve
T
Air
SS porous
sparger
P1
F
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Db
DP
F
EXPERIMENTAL SETUP
Measurement of bubble sizeMcGill bubble size analyzer (MBSA)
P2
T
Air
P1
F
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Sliding sparger to facilitateinstallation;
Dispersing component is anexchangeable SS porous cylinder;
Cylinders with different porosities
Db
DP
F
EXPERIMENTAL SETUP
Sparger details
are available.
P2
T
Air
P1
F
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Db
DP
F
EXPERIMENTAL SETUP
Sparger details
P2
T
Aire
P1
F
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RESULTS
Effect of air flow rate on bubble size(10 ppm of DF250)
30
40
UENCY,%
Jg = 0.5 cm/s
Jg = 1.0 cm/s
Jg = 1.5 cm/s
0
10
20
0 1 2 3 4 5
NUMBERFRE
Q
BUBBLE DIAMETER, mm
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RESULTS
Effect of sparger porosity on bubble size(DF250, Jg = 1 cm/s)
3
4
5
TER,mm
Sparger 1 (coarser)
Sparger 2 (finer)
0
1
2
0 20 40 60 80 100
BUBBLEDIAM
FROTHER CONCENTRATION, ppm
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RESULTS
Effect of air flow rate on CCC(DF250, Sparger 1)
3
4
5
TER,mm
Jg = 0.5 cm/s
Jg = 1.0 cm/s
Jg = 1.5 cm/s
0
1
2
0 20 40 60 80 100
BUBBLEDIAM
FROTHER CONCENTRATION, ppm
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RESULTS
Typical characterization measurements(DF250, sparger 1, Jg = 1 cm/s )
15
20
25
3
4
5
P,%
TER,mm
Bubble size
Gas holdup
0.15
0.20
0.25
RATE,cm/s
0
5
10
0
1
2
0 20 40 60 80 100
GASHOLD
BUBBLEDIAM
FROTHER CONCENTRATION, ppm
0.00
0.05
0.10
0 5 10 15 20 25
WA
TEROVERFLO
GAS HOLDUP, %
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RESULTS
Comparison of frother roles(MIBC vs. DF260)
3
4
5
TER,mm
MIBC
DF250
0.15
0.20
RATE,cm/s
MIBC
DF250
0
1
2
0 20 40 60 80 100
BUBBLEDIAM
FROTHER CONCENTRATION, ppm
0.00
0.05
0.10
0 5 10 15 20
WATEROVERFLO
GAS HOLDUP, %
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RESULTS
Measurement reproducibility(DF 250, bubble size)
3
4
TER,mm
Repeat 1
Repeat 2Repeat 3
Repeat 4
Repeat 5
0
1
2
0 25 50 75 100 125
BUBBLEDIAM
FROTHER CONCENTRATION, ppm
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RESULTS
Measurement reproducibility(DF250, collection zone gas holdup)
15
20
25
UP,%
0
5
10
0 25 50 75 100 125
GASHO
L
FROTHER CONCENTRATION, ppm
Repeat 1
Repeat 2
Repeat 3
Repeat 4Repeat 5
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EXPERIMENTAL SETUP
Laboratory column flotationDb
DP
Overflow
water
F
Testsection
Peristaltic
pump
P2Feed tank
Underflowcontrol valve
T
Air
SS porous
sparger
P1
F
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RESULTS
Measurement reproducibility(DF250, water overflow rate)
0.04
0.05
0.06
WR
ATE,cm
/s Repeat 1
Repeat 2
Repeat 3
Repeat 4
Repeat 5
0.00
0.01
0.02
0.03
0 5 10 15 20 25
WATEROVERFL
GAS HOLDUP, %
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RESULTS
Plant frother replacement(DF250)
0.15
0.20
WR
ATE,cm
/sDF250
Frother 1Frother 2
Frother 33
4
TER,mm
DF250
Frother 1Frother 2
Frother 3
0.00
0.05
0.10
0 10 20 30
WATEROVERFL
GAS HOLDUP, %
0
1
2
0 25 50 75 100 125
BUBBLEDIA
M
FROTHER CONCENTRATION, ppm
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CONCLUSIONS
The results obtained in this work demonstrated:
Frother effects on gas dispersion can be effectively used tocharacterize frother roles by determination of:
The CCC to characterize bubble size reduction; and
depth. The gas holdup in the collection zone correlates with water
overflowing the froth, which have the potential to describeinteractions between zones;
Frother strength in one role does not necessarily reproduce in adifferent role; and
Measurements in a laboratory column with no solids were useful todecide replacement of a frother in an industrial operation.