Cesar Gomez

7/27/2019 Cesar Gomez

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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


2/22

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.


3/22

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


4/22

3

4

5

TER,mm

INTRODUCTION

Previous workCritical Coalescence Concentration (CCC)

0

1

2

0 10 20 30 40 50 60

BUBBLEDIAM


CCC (Critical Coalescence Concentration)


5/22

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


6/22

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, %


7/22

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.


8/22

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


9/22

Db

DP

F

EXPERIMENTAL SETUP

Measurement of bubble sizeMcGill bubble size analyzer (MBSA)

P2

T

Air

P1

F


10/22

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


11/22

Db

DP

F

EXPERIMENTAL SETUP

Sparger details

P2

T

Aire

P1

F


12/22

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


13/22

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



14/22

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



15/22

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


0.00

0.05

0.10

0 5 10 15 20 25

WA

TEROVERFLO

GAS HOLDUP, %


16/22

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


0.00

0.05

0.10

0 5 10 15 20

WATEROVERFLO

GAS HOLDUP, %


17/22

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



18/22

RESULTS

Measurement reproducibility(DF250, collection zone gas holdup)

15

20

25

UP,%

0

5

10

0 25 50 75 100 125

GASHO

L


Repeat 1

Repeat 2

Repeat 3

Repeat 4Repeat 5


19/22

EXPERIMENTAL SETUP

Laboratory column flotationDb

DP

Overflow

water

F

Testsection

Peristaltic

pump

P2Feed tank

Underflowcontrol valve

T

Air

SS porous

sparger

P1

F


20/22

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, %


21/22

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



22/22

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.

Cesar Gomez

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