Introduction to Mineral ProcessingMIME-320 Click to edit Master subtitle style Extraction of energy resources Winter 2013

Based on presentation of Introduction to mineral processing by Prof J. Finch

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Rock to Metal: Extraction MetallurgyROCK

Mining

Ore or Run of Mine (ROM)

Extraction

METAL

Manufacturin g

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MiningORE BODYMining

ORE

WASTE ROCK

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Extraction Metallurgy

Mineral Processi ng HydroMetallur gy PyroMetallur gy

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Mineral Processing

ORE

Mineral Processing

VALUABLE MINERAL

GANGUE

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Some technical termsMineral

processing takes place at the mine site on surface The mineral processing plant is called a concentrator, or a mill The valuable mineral product is the concentrate The gangue product is the tailings6

Mineral ProcessingOre or Run of Mine (ROM)Mineral Processing

CONCENTRATE

TAILINGS

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Stages

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To prepare ore for mineral separation By reducing particle size to free valuable minerals from

Size Reduction or Comminution

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The need to size reduce

Gangu e

Valuabl e Mineral

Minerals must first be freed or liberated

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CrushingDivided

into stages:

q q q

Primary Secondary Tertiary- Few application

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Primary CrushersTo

crush ore from very big size to less than around 10 cm Large, robust machines Principal types: q Jaw crushers q Gyratory crushers

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Jaw Crusher

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Two jaws, fixed and moving Cycle of breakage/descent/discharge

Jaw Crusher

Feed opening width gape determines top feed size Discharge opening width set determines product size

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Gyratory Same Crusherconcept but designed to crush and discharge continuously

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Gyratory Crusher

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Secondary Crushers:Crush

product of primary crushers They have lower capacity compared to primary crusher Principal types: q cone crusher q hammer mills

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Cone Crusher

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Cone crusher

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The Set

Closed set Like Gyratory andjaw crushers

Open set Like cone crusher

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How to control product sizeTo

control the product size from crushing, size classification is required Crushers and classifiers are combined to form a circuitOre or ROM CrusherOver-size

Under-size Size Classification Product

Circulating Load

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Size ClassificationProcess

of separating particles into two streams:

Over-size particles Under-size particles

Main

method in crushing circuit

screening

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ScreeningScreens classify particles based on probability to pass through holes of given size in a deck

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Screening

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Screening

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GrindingProduct

of crushing is too coarse for mineral separation, and grinding is used for further size reduction28

GrindingThis

additional size reduction will produce particles fine enough to liberate the valuable mineral from the gangue

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Breakage and liberation

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A Particle Before Grinding - Unliberated or Locked

breakage planes

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Particle is Broken Along Planes

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Some Liberated (Free) Particles Produced

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Particles Types1) liberated mineral particles

2) locked particles

3) liberated gangue particles

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Relating Grind Size to LiberationQuestion: How can we measure the liberation size? Solution: By doing mineralography study by some relevant microscope

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Particles and GrainsParticl e Grain s

Microscopic image of the thin section of rock

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ObservationLiberation increases as the particle size is reduced relative to the grain sizeGrain size is the size of grain of the valuable mineral Example:The grain size of white mineral is 60 micron

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GrindingGrinding

system: wet, dry Wet grinding requires addition of water Pulp or slurry = water + ore The main grinding machine is called a Tumbling Mill

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Tumbling Mill

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Grinding Media (Charge) TypeThe

Tumbling Mill is named after the grinding media used:40

Grinding Media (Charge) Type Rod

Mill Ball Mill Autogenous Mill (AG) no steel ball Semi Autogenous Mill (SAG) - some steel balls

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Rod & Ball Mills3-6m 2.5 cm 2-4.5m2-5.5m

0.5 cm

0.5 cm

2-5.5m

0.1

cm

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Rod & Ball Mills

Grinding Action

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Rod & Ball Mills

Media Filling: About 40%

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Brekage Mechanism

Mechanism: Impact, Nipping and Friction

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Tumbling Motion

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How to control product sizeTo

control the product size from crushing, size classification is required Crushers and classifiers are combined to form a circuitCrusher product MillOver-size

Under-size Size Classification Product

Circulating Load

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Size Classification

Classification in grinding is a wet process The common classifier is a cyclone (or hydro-cyclone) Because of the tangential feed, a cyclone generates a centrifugal force that separates the feed into two streams

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Cyclone

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Grinding Circuits Open & Closed Circuits:

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Grinding Circuits Open & Closed: Rod & Ball Mills

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Ideal separation

Ideally, the concentrate should contain 100%

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Actual separation

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Principle of separationSeparation exploits differences in mineral properties, e.g.

mineral property density magnetism wet ability

technique gravity magnetic flotation56

Magnetic SeparationFee d

The Magnet Drum

Magnetic Product Non Magnetic57

Gravity SeparationMechanism

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Gravity SeparationJigLights Heavies

Water

Mechanism: Pulsation/ stratification

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Jigmechanism

Gravity SeparationJigMechanism: Pulsation /stratification

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Gravity SeparationHeavy media separator

the light particle floats the heavy particle sinks The density of liquid could be increased by adding Ferrosilicon The density of media (liquid) should be between light and heavy mineral

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Mechanism: flowing film Due to lighter density, the lighter particles would enter to splitter

Gravity SeparationCone separator

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Gravity SeparationCone separator

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Gravity SeparationComparison

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Froth flotationDefinition:Separation of one type of

particle (mineral) from another by attachment to bubbles

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Froth flotationMixed Minerals

Air Bubble

Separated Minerals

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Froth flotation

Air Bubble

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Froth flotationQuestion: Why do some particles remain wetted (by water), while others attach to a bubble?

The science of wetting will help answer this question: How surface atoms interact with water molecules

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WettingHydrophilic (water loving) Air bubbl e Hydrophobic (water hating) Water

Contact

Mineral remains

miner al

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Example

Hydrophobic surface/ teflon

Hydrophilic surface

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Simulation

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Froth

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Wetting: InteractionsSurface O H No bond O H

C

M +

Oxide mineral hydrophilic

Graphite hydrophobi c

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Wetting: InteractionsSulphide minerals Step 1- Reaction with oxygen S Cu

+

O

=

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Wetting: InteractionsSulphide minerals Step 2- Reaction with water

+

=

Sulphide minerals: weakly hydrophilic

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Wetting: Making a mineral hydrophobicCollectors: Chemical reagents that react with a surface to convert it from hydrophilic to hydrophobic

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Wetting: CollectorsGeneral structure:

hydrocarbon chain reactive head group

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Wetting: CollectorsAn example:

hydrocarbon chain head groupethyl xanthate

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Wetting: Making a mineral hydrophobicReaction (adsorption)

mineral particle

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Wetting: Making a mineral hydrophobic For sulphideminerals

+

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Wetting: Making a mineral hydrophobicFor sulphide minerals The reaction (adsorption) partially coats the surface with a hydrocarbon and the mineral becomes hydrophobic

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Froth flotationFlotation is not a chemical process Flotation separation is based on surface properties of minerals

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Inside a froth flotation cell

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Motion of a particle in a flotation cell

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Froth flotation CellMechanical Cell FeedConc. (Coal)

Column CellConc. (Coal)

FeedTail. (Ash)Concentrate

Cell bank

Tailing

Tail. (Ash)

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DewateringFilteration mechanism

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Dewateringbelt filtration

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Dewateringbelt filtration

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DewateringThickening mechanism

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Dewatering- Thickening

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Recommended TextbookWillsMineralprocessingtechnology :a n introduction to the practical aspects of ore treatment andmineralrecovery

McGill Library TN500W54 2006

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RefferencesFinch,J., Introduction to mineral processing, MIME200 R.O.Burt, Gravity concentration technology, Elsevier, 1984 N.L.Weiss, SME Mineral processing handbook, SME,1985

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