1. Prof. Dr. Zafir Ekmekçi Assoc. Prof. Dr. Özlem BIÇAK
Flotation
Prof. Dr. Zafir Ekmekçi
Assoc. Prof. Dr. Özlem BIÇAK
Add picture of the flotation machines. Update the metal prices.

2. REFERENCES
Kelly, E.G. and Sprottiswood, D.J., Introduction to Mineral Processing, John Wiley and Sons, 1982.
King, R.P. (Ed.), Principles of Flotation, South African Institude of Mining and Metallurgy, 1982.
Fuerstenau, M.C., Miller, J.D. and Khun, M.C., Chemistry of Flotation, AIME, 1985.
Fuerstenau, D.W. (Ed), Froth Flotation 50th Anniversary Volume, AIME, 1962.
Gaudin, A.M., Flotation, 1957.
Wills, B.A., Mineral Processing Technology, Pergamon Press.
Mular, A.L., Halbe, D.N., Barrat, D.J., Mineral Processing Plant Design, SME, 2002.

3. I MID TERM: 26 OCTOBER 2015 MONDAY
II MID TERM: 14 DECEMBER 2015 MONDAY
For the Lecture Notes & Presentations:

4. Flotation Course Outline
Introduction and Principles of Flotation
General Concepts of Flotation
Properties and Structures of Minerals
Surface chemistry
Physical Aspects of Flotation
Flotation Chemicals
Flotation of Sulphide minerals
Flotation of Non-sulphide minerals
Effects of Particle Size
Flotation machines

5. Overall Scope of Course (1)
Definition of flotation
Basic principles
Aim to present basic principles for practical application
Complexity of flotation
Importance of chemistry & physics
Industrial practice

6. Overall Scope of Course (2)
Chemistry determines if mineral will float
Hydrophobic or hydrophilic
Physics determines the process efficiency
Particle & bubble size, equipment design
The chemical and physical principles will be developed
Applications to industrial practice will be discussed

7. 1. Introduction to Flotation
Definition of flotation
Importance of flotation to industry
Brief history of process development
Flotation in mineral circuits
Liberation & concentration
Mineral texture
Complexity of flotation
Scale of operations
Equipment
Applications

8. The stages required turning a mineral into metal:
The goal of mineral processing is to separate the valuable minerals from each other and from gangue.
The stages required turning a mineral into metal:
Mining
Mineral Processing
Extraction
Refining
Manufacturing

9. Scope of Mineral Processing
Heterogenous mixtures of finely divided solid phases frequently require an efficient technique for separation of components.
Separation of solids can be achieved, for appropriate particle sizes denoted by diameter (d), by techniques exploiting the following physical and physicochemical characteristics:
Colour :In sorting of lump coal or other distinct minerals (d> 50 mm).
Specific Gravity :In wet or dry gravity concentration techniques (d>0.1 mm)
Shape and Size :In screening and classification (d>0.04 mm)
Electrical Charge :In electrostatic separation of well-dried materials
(0.05<d<5 mm)
Magnetic In wet or dry magnetic concentration devices Susceptibility : (0.1<d<5 mm)
Surface Properties: In froth flotation, spherical agglomeration, selective flocculation (d<0.2 mm).

10. Scope of Froth Flotation
Flotation is undoubtedly the most widely employed, the most important and versatile mineral processing technique.
Flotation utilises the differences in physicochemical surface properties of particles of various minerals.
By using some chemicals mineral surfaces are either made water repellent (HYDROPHOBIC) or water loving (HYDROPHILIC).
A hydrophobic surface always tends to stick (adhere) air bubbles as hydrophilic surface does not.
When a small air bubble sticks to a hydrophobic mineral surface in water, density of the mineral becomes much less than that of waters so, the couple (mineral+air bubble) floats.

11. Weight of galena = 0.008 mm3 * 7.5 mg/mm3 = 0.06 mg
To understand the physics of flotation let us consider a cubic galena particle having 0.2 mm (200 m) dimension and an air bubble of 1 mm3 sticking together.
1 mm3 Air
Galena
Water
Volume of galena = 0.2*0.2*0.2=0.008 mm3
Weight of galena = mm3 * 7.5 mg/mm3 = 0.06 mg
Volume of air = 1 mm3
Weight of air = mg (negligible)
Volume of galena+air = mm3
Weight of galena+air = 0.06 mg ( mg)
Density of galena+air = 0.06mg / mm3 = mg/m3
Density of water = 1 mg/mm3
Ratio = 1/ =  17
An air bubble and a galena particle couple are approximately 17 times lighter than water so, the couple naturally floats to the surface.

12. In pulps (mineral - water mixtures) air bubbles are generated by a machine called flotation machine.
Air (self-aeration or forced)
Mineral
Air
Minerals or
Pulp
Non-float (sink) product
Float (froth products)

14. Importance of Flotation (1)
Very important in industry
Pb, Zn, Ag all produced by flotation
Most Cu still floated (leaching also)
Other metals Mn, Cr, Ni, Co, etc, etc
Phosphate, fluorite, feldspar, mica, etc
Coal floated on large scale
Used widely outside minerals industry

15. Importance of Flotation (2)
Flotation shapes modern industry
Enables more difficult ores to be treated
1935 average Cu ore in USA was 1.57%
1960 dropped to 0.72 %
And price of copper fell!
Economic reserves in the world have been greatly increased by flotation

16. Brief History of Flotation (1)
Year
Contributor
Contribution
1860
Haynes
Bulk-oil process
1877
Bessel
Boiling process for graphite
1885
Chemical-generation gas process for graphite
1886
Everson
Acidulated pulps desirable
1902
Froment, Potter and Delprat
Gas as a buoyant medium for sulphide ores
1905
Schwarz
Na2S to recover oxidized base metal minerals
1913
Sulphur dioxide to depress sphalerite
1921
Perkins and Sayre
Specific organic collectors -
Alkaline circuits
1922
Sheridan, Griswold
Cyanides to depress sphalerite and pyrite
1924
Sulman and Edser
Soaps for flotation of oxides
1925
Keller
Xanthates as collectors
1929
Gaudin
pH control
Jeanprost
Flotation of highly soluble salines
1933
Nessler
Flotation of water-soluble chemical salt mixtures
1934
Chapman and Littleford
Agglomeration
Alkyl sulphates as collectors
1935
Cationic collectors

17. Brief History of Flotation (1)
First industrial use about 100 years ago
1860 – oil added to trap grains which then floated with oil
1877 – flotation process for graphite using oil and boiling mixture
1901 – first large scale development for Zn
6 million tonnes recovered from dumps
Dry feed to hot acid solution produced gas bubbles

18. Brief History of Flotation (2)
Intense industrial research followed aimed at improving the basic process
Bubble generation
A “vacuum” process tried for bubble generation
Air bubbles generated by violent agitation – true froth flotation as we know it
Sub aeration introduced 1913

19. Brief History of Flotation (3)
Selective flotation was an important step as there was galena in the zinc dumps
1912 galena floated in alkaline solution
1912 lead “depressed” with dichromate
1913 zinc depressed with sulphur dioxide
Zinc “activated” by copper sulphate

20. Brief History of Flotation (4)
A major advance was modern collectors
Soluble organics with tri-valent N or bi-valent S were substituted for oils
1925 – discovery and use of xanthate – this is still used as the basic sulphide collector
For non-sulphides – soaps, alcohols and amines were used, but good results needed effective depressants

21. Brief History of Flotation (5)
Selective flotation was difficult – easy to float all minerals, but hard to float just one from ores with several minerals
Alkalis used to depress pyrite and float sphalerite
Sodium cyanide proved very valuable
At high pH pyrite & sphalerite depressed, galena floats
Then activate sphalerite with CuSO4 to float sphalerite
Finally neutralise to float pyrite

22. Brief History of Flotation (6)
1924 – systematic study of frothers
Needed to maintain a stable froth zone and small bubbles
Provided a large bubble area for particle capture

23. Brief History of Flotation (7)
Basic cell geometry established early
Many patents claimed improved operation
Some with induced air – some air sparged
Incremental changes to agitation, bubble generation, froth removal, etc.
Massive changes in scale from a few m3 to a few hundred m3

24. Brief History of Flotation (8)
Control systems and on-line instrumentation developed
During 70s continuous assay measurements
At the same time computer control systems were introduced
These gave operators great assistance
Still mainly stabilising control, but steadily improving

25. Brief History of Flotation (9)
Recently new flotation devices introduced
Columns the major change
Other special application units, eg for fine particles
Also new collectors and frothers introduced

26. Float demonstration

27. Flotation in a Mineral Circuit (1)
Mineral processing involves
Size reduction (crushing, grinding)
Separation (flotation, gravity, magnetic, etc)
Flotation is part of overall circuit
Optimisation must be of the overall circuit
Feed preparation must suit flotation
Flotation must be optimised for best overall performance of the circuit

28. Flotation in a Mineral Circuit (2)
Feed ores are always complex mixtures of minerals
Size reduction breaks the grains apart so that they may be floated separately
If the feed preparation is not satisfactory then flotation cannot solve the problem

29. Liberation and Concentration (1)
Feed preparation for flotation involves
Liberation of the mineral grains
Adjusting particle size to suit flotation
May not be able to do both at the same time:
Pure mineral particles may be too large to float
Fine grinding to liberate fine grained ores may produce particles too small to float well

30. Liberation and Concentration (2)
Liberation is achieved by size reduction
Breakage is generally random – not along grain boundaries
Thus particles must be much smaller than the grain “size” for good liberation
Liberation refers to a particular mineral
Galena grains generally smaller than sphalerite
The lead mineral is the first to liberate
If possible liberate one mineral, separate, then grind again to liberate second mineral (save grinding energy and limit overgrinding)

31. Liberation and Concentration (3)
“Locked” particles are not fully liberated and contain more than one mineral phase
Flotation is basically a physical separation
“Locked particles must go to con or tail
They dilute the purity of concentrate
They contribute to losses in tails
Overall strategy determines best destination

32. Liberation and Concentration (4)
Liberation effects on flotation and leaching
Flotation:
Surface process so controlled by surface exposure of mineral
The more exposure the faster the flotation
Locked particles can float
Leaching:
Surface exposure also needed
Also the more exposure the faster the leaching
Connectivity of the mineral phase determines extraction

33. Fully liberated particle - can be floated or leached
Gangue
Mineral
Simple locked particle – can be fully leached but goes either to flotation concentrate (dilutes purity) or tailings (losses)
Rimmed particle (1) – can be fully leached but will float to concentrate and dilute the purity
Mineral is only partly recovered by leaching, flotation, etc.
Rimmed particle (2) – cannot be recovered by leaching or flotation

34. Mineral and Particle Texture
The “texture” of an ore is the geometric arrangement of the mineral phases, e.g.
Mineral proportions
Mineral grain sizes
Mineral associations
The “texture” determines how the minerals will liberate and the types of particles
The structure of the particles determines how efficiently flotation or other separation processes will operate

35. 30 microns

36. Complexity of Flotation (1)
Flotation is very complex
Many chemical engineering processes are only one or two phases
Flotation - gas, liquid & many solid phases
Particle shapes and structures are complex
Fluid flows in cells poorly defined
Interfacial phenomena

37. Complexity of Flotation (2)
Only a general understanding is possible
Predictions still difficult
Early developments mainly empirical
Research work has been to try and explain what is happening
It is amazing that so complex a process can operate so effectively on so large a scale

38. Complexity of Flotation (3)
Some of the physical complexities are:
Relative movement of the phases – geometry & phase properties
Dynamics of the movement – collision of bubbles & particles, froth drainage
Recycle of the streams and circuit arrangements

39. Complexity of Flotation (4)
Some of the chemical complexities are:
Hydrolysis reactions & pH effects in water
Oxidation/reduction reactions due to flotation with air
Water composition defined by solubilities of the mineral species, pH, Eh
Surface conditions – hydrophobicity
Added chemical reagents

40. Complexity of Flotation (5)
Aim of lectures is to give a framework
General understanding of major factors
Look at simplified systems
Single mineral behaviour
Simple flotation equipment
Eliminate some of the complexities to get basic principles

41. Pulp Zone

42. Scale of Operations (1)
One of the early challenges was the development of large scale equipment
Early circuits expanded by duplication in parallel “lines”
Partly capacity but also thought to give flexibility of operation
Now trend to single lines & large equipment
Maintenance & control expensive with replicated equipment

43. Scale of Operations (2) Now huge AG and SAG mills (10m diameter)
Flotation cells up to about 200m3 volume
This makes massive plant capacities possible
Escondida – about 1M tonnes/y Cu produced
Chuquicamata – 65 M tonnes/y ore
El Teniente – 35 M tonnes/y ore
Ok Tedi – 29 M tonnes/y ore

44. Equipment (1) Basic flotation cells are tanks with
An aeration system – induced or sparged
Feed and exit pulp flow arrangements
Launder to collect the froth
Control systems

45. Equipment (2) Cells are connected into banks
Promotes plug flow of pulp
Minimises short circuiting
Banks are connected into stages & circuits
Roughing
Cleaning
Scavenging

46. Equipment (3) Many attempts to design better equipment
Major advance in recent years is the flotation column
Follows chemical engineering practice of counter-current processing
Now used widely in cleaning circuits

47. Equipment (4) Other recent developments
Jameson cell – short column induced air
coal, metals, waste
Microcell – fine bubbles for small particles
Coal
TurboFloat – development aimed to optimise aeration, mixing, separation
coal

48. Non-Sulphide Minerals
Applications
Sulphide Minerals
Copper
Zinc
Lead
Silver
Non-Sulphide Minerals
Feldspar
Phosphates
Mica
Quartz

49. History of Metal Prices