CHE1430-1 Introduction.pdf

8/14/2019 CHE1430-1 Introduction.pdf

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Hydrometallurgy

Theory and PracticeIntroduction, Mining, Milling

Eberhard KrauseHydroMet Solutions Inc.

Adjunct Professor, University of Toronto

Fall 2013


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Course Objectives

Provide metal-mining industry overview Strengthen chemical engineering principles as applied tohydrometallurgy

Provide examples of hydrometallurgical processes usedfor the recovery of selected metals Provide examples of hydrometallurgical processequipment

Discuss challenges of the metal-mining industry


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History of Metals Use First metal use was mainly decorative, e.g. gold

jewellery Gold and copper are malleable and can readily be

formed

Alloying of metals, e.g. bronze (Cu / Sn) Metals used to produce household items, coinage,

weapons

Metals use expanded with onset of the Iron Age Because of hardness and workability when heated,

better tools and weapons were produced


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Development of Metals Uses


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Estimated Abundance of Elements in Earths Crust


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Ore Formation Processes

Internal processes (magmatic, vulcanogenic) Fractional crystallization from melts Meteorite impact

Hydrothermal processes Induced by hot waters containing sulfide and/or

CO2, e.g. hydrothermal vents

Sedimentary deposits formed under water inreducing environments


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Sudbury, Ontario Area Cu/Ni/PGM Mines

Vale


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Volcanic Features of Mid-ocean Ridge

Hydrothermal vents Heated subsurface seawater migrates through cracks in

ocean crust

Warm-water vents 350oC (black, due tometal sulfides; Fe, Ni, Zn)

Dissolved metals precipitate to form sulfide deposits Unusual biological communities

Able to survive without sunlight Archaeons and bacteria oxidize hydrogen sulfide gas to provide

food


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HydrothermalVents


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Finding Minerals of Commercial Value

Exploration know-how and toolsArial photographyArea geology Geophysical methods to find anomalies

Satellite images Airborne magnetometers Gravity anomalies Seismic tomography Ground-penetrating radar

Similarities to known ore bodies Exploration drilling

Produce core samples for analysis Borehole logging Resource estimation

Tight drill spacing to gain more confidence


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Exploration Drilling Core Samples


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Deposit Estimation Three-dimensional Models


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Expertise required by large Mining

Companies for developing New Projects

ExplorationAnalytical

R&D(Select Proc.)

MiningUpgrading

(Milling)

Processing(Metals

Recovery)Sales

Engineering*Risk AnalysisFinance, HR

Legal,!

Abandon Project ?

* Internal and External:Pre-feasibility Study

Bankable Feasibility Study

Detailed Engineering

Tailings

Contaminated Water

Environment, Health & SafetyDecommissioning

SlagsResidues

Precipitates

Waste


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Minerals used for Metals Production

Sphalerite (zincblende), ZnS

ChalcopyriteCuFeS2

Gold


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Chalcopyrite Oxidation

ChalcopyriteCuFeS2

Chalcocite Cu2SCovellite CuS

AzuriteMalachite

Cu(OH)2.CuCO3 Cu(OH)2

.2CuCO3

H2O, O2

H2O

O2, CO2,


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Massive Pentlandite Nickel Ore


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Mining


R&D(Select Proc.)

MiningUpgrading

(Milling)

Processing(Metals

Recovery)

Sales

EngineeringRisk AnalysisFinance, HR

Legal,!

Tailings SlagsResidues

Precipitates

Waste


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Mining Wikipedia Definition

Miningis the extraction of valuablemineralsor othergeologicalmaterials from the earth, from an orebody,veinor (coal) seam. The term also includes the removalof soil. Materials recovered by mining include

base metals, precious metals, iron, uranium, coal,diamonds, limestone, oil shale, rock saltand potash. Anymaterial that cannot be grown through agriculturalprocesses, or created artificiallyin a laboratoryorfactory, is usually mined. Mining in a wider sense

comprises extraction of any non-renewable resource(e.g., petroleum, natural gas, or even water).


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Mining History

Historically, minerals were only found when visible Simple equipment was used to open crevices (picks and

shovels)

Shallow depth mining Use of horses and development of larger equipment, e.g.

water mills, pumps

Black powder (KNO3+ S + charcoal) first used 1627 inmining (Slovakia)

Dynamite (nitroglycerine in absorbent) patented in 1867 Equipment sizes continue to increase, resulting in

steadily increasing productivity with respect to tonnes ofore mined bulk mining

Ore grades are decreasing (increasing impurities)


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World Mining Map


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Typical Location of Oxide and Sulfide OresSulfide Mining

LateriteOpen Pit Mining

4800 LEVEL

5600 LEVEL

2000 LEVEL

4000 LEVEL

6000 LEVEL

0 1000

Feet

Laterite Ore

Sulfide Ore Miningin Hard Rock

Weathered / Oxidized Ores

Sulfide Ores


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Open-pit Mining

Open-pit mining is surface mining inwhich huge portions of earth are dugfrom the surface to extract the desiredmineral within them. During the miningprocess, the land face is scraped awayby explosives and digging creating adeeper and deeper pit until the miningis complete. The final shape of the

open pit is decided before excavationbegins. To most profitable mining pitsare the ones where the entire miningarea is divided into 3-D blocks. Usinggeological information from drilledholes, the value of the desired mineralin each block is estimated. The cost ofmining each particular block is alsodetermined, therefore you candesignate a profit value for each blockin the mine.

from T. Paisana Open Pit Mining


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Codelcos Chuquicamata (Chile) Open-pit Mine


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Typical Open-Pit Mining Equipment

Bucket-wheel

Excavator

Drill-rig

Crushing and

Conveying

Shovels

Trucks

Kennecotts Bingham Canyon Mine Landslide


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Kennecotts Bingham Canyon Mine LandslideApril 10, 2013

Nobody was hurt in the collapse of Rio Tintos Bingham Canyon open-pit mine in Utah,

the worlds largest, since workers had been evacuated following warning signs that theground was going to shift!



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Typical Mining Costs

Open-Pit (1-3 US$ per t ore mined) First choice if orebody is not too deep Ore is often soft Efficient, large-scale operation, economical for low-

grade ores

Underground(>>10 US$ per t ore mined) Smaller scale much less efficient

Everything must pass through mine shaft or other narrowpassage

Mining for deeper, high-grade deposits, commonly inhard rock formations

Stringent requirement for safety equipment Structural, personal, ventilation, pumping, safe areas, etc.

Long development time - high expense


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Mining Costs vs. Total Operating Costs

TC/RC = Treatment & Refining Charges

~20%

~65%


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Metal Production Costs

Depend on: Scale of operation

Size of orebody Ore grade

Tonnage of ore to be mined and treated Location of orebody

Near surface, underground, under water Ore mineralogy and impurities

complexity of treatment process Safety and environmental risks Political, social risks

C P d i C


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Copper Production Costs

TCRC costs = Treatment Charges plus Refining Charges


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It Depends !

!the only correct answer toalmost every question!

S f G O


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Scale of Gold Mining Operations

Barricks

GoldstrikeOperations

Micro Operatorsthen!. and now!

Inflationary Trends in Primary Metals


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Inflationary Trends in Primary Metals

Production


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Ore Upgrading (Milling)


R&D

(Select Proc.)

MiningUpgrading

(Milling)

Processing(Metals

Recovery)

Sales


Legal,!


Precipitates

Waste

Ph t i h f S lfid O (S db )


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Photomicrographs of a Sulfide Ore (Sudbury)Ccp Chalcopyrite CuFeS2

Pn Pentlandite (FeNi)9S8

Po Pyrrhotite Fe7S8

Rk Rock

Mag Magnetite Fe3O4


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Ore Upgrading Methods

Depend on chemical properties (mineralogy) andphysical properties of ore: Selectivity during mining

High-grading of ores Separation by size (rejection of oversize and/or

undersize) Crushing (in stages) Grinding (in stages) Classification (screens, hydrocyclones, etc.)

Gravity Separation (e.g. gold ores, chromite) Magnetic Separation (e.g. pyrrhotite removal) Optical sorting (e.g. diamonds) Flotation (e.g. sulfides in flotation cells or columns)


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Nickel Sulfide Ore Mineralogy and Upgrading

Major nickel mineral: pentlandite (~35% Ni), (Ni,Fe)9S8 Pyrrhotite (~0.65% Ni), Fe(1-x)S, is the major sulfide

contaminant

If not rejected, pyrrhotite (Po) would cause high smelter slag andSO2generation during smelting

Can contain up to 20% of ores nickel Silicate gangue, popularly termed rock, and most of the

Po are rejected at the mill (flotation and magneticseparation), producing a Ni concentrate.

Concentrates from nickel sulfide ores commonly containeconomic quantities of copper (usually as chalcopyrite),cobalt and precious metals (Au, Ag, PGM)


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Comminution: Jaw Crushers


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Comminution: Roll Crushers


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Comminution: Cone Crushers

Dry Classification (larger Particles)


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Dry Classification (larger Particles)

Vibrating

Screen

Grizzly

Gyratory Screener

O G i d bilit


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Ore Grindability Depends on ore compressive strength, hardness (Mohs

scale), brittleness (ease of cleaving), elasticity

Bond method useful for determining optimal crusher andmill type and size for particles 50 !0.05 mm, e.g.:

WB = cB(1/"dE 1/"dA) EFW

B

= grinding work (kJ/kg)cB = Bond grinding coefficient (Work Index)dA = grain size (e.g. d80) of feed materialdE = product grain size (e.g. d80)EF = efficiency factor

Bond Work Index determined in laboratory ball mills

Similar work indexes exist for crushing, rod mills andsmaller particles

Mohs Hardness Scale and Bond Work


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Mohs Hardness Scale and Bond WorkIndexes for Different Materials

Eff t f Mi l


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Effect of Mineralogy on

Grinding Efficiency

Ores contain various minerals of differentgrindabilities, resulting in potential over-grinding of some minerals, while others

remain too coarse for further processing. Solutions:

Stage-wise (closed-circuit) grinding withclassification between stages

Fines (e.g. clay minerals) removal by washing


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Basic Modes of Grinding

1

3

2

SAG (Semi Autogeneous Grinding) Mill


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SAG (Semi Autogeneous Grinding) Mill

R d d B ll Mill


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Rod and Ball Mills

Wet grinding most common

Stirred Media (Fine-Grinding) Mills


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Stirred Media (Fine-Grinding) Mills

IsaMill

Metso Vertimill

P ti l S ti b Si


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Particle Separation by Size

and/or Density

Vibrating Screens (dry or wet) Cone Classifiers (dry or wet) Spiral Classifiers (wet) Hydrocyclones (wet)Air Classification (dry) rarely used in mining

Wet Classification Vibrating Screen


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Wet Classification Vibrating Screen

Cone Classifiers


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Cone Classifiers

(wet or dry)

Reichert Cone

Spiral and Rake Classifiers


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pWork on settling velocity differences

Move coarse particles upwards away from fines

TwinRake

Classifier

Centrifugal Classifiers Hydrocyclones


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Centrifugal Classifiers - Hydrocyclones

Cyclone Pack

T i l H d l


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Typical Hydrocyclone

Dimensions


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Typical Particle Size Distributions


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yp

Bimodal Distribution

Particle Shapes SEM Images


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p g

Naturally Shaped SandsGround Concentrate gypsum crystals

Image Analysis e.g. Qemscan


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g y gQuantitative Evaluation of Minerals by

SCANning electron microscopyUsing backscattered electron and secondary electron signals,

in combination with electron-induced secondary X-ray emission

Particle Mapping Qemscan SEM Images


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pp g Q g


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Other Ore UpgradingEquipment

Gravity Separation for Heavy Particles,


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y p y ,e.g. Au, Chromite

Shaking Table

Magnetic Separation


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Magnetic Separation

DryMagneticSeparators

Wet

Magnetic

Separator

Flotation - Principle


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Flotation Principle Separation of more hydrophobic from less hydrophobic

(or hydrophilic) materials

Separation of sulfides from gangue minerals Separation of different sulfide minerals Other, e.g. phosphate flotation

Differences in hydrophobicity are increased through useof collectors (surfactants - commonly xanthates) and

other chemicals, e.g. pH and redox modifiers (e.g. lime,H2SO4, sulfite), activators (e.g. Cu2+), suppressants, e.g.

dextrin, CMC (carboxy methyl cellulose), and/orcomplexing agents (e.g. TETA).

The surfactant-treated hydrophobic minerals, e.g.sulfides, attach themselves to air bubbles and are floatedto the top of reactors with the help of frothers, e.g. MIBC(methyl isobutyl carbinol) or pine oil

OH

Collector Action - Xanthate


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Collector Action - Xanthate

Potassium Amyl Xanthate (PAX) production:RamylOH + CS2+ KOH#RamylOCS2K + H2OR = amyl, ethyl, isobutyl

Xanthate attaches to selected mineral surfaces, e.g.sulfides, through S atoms

Dixanthogen can form onmineral surfaces upon oxidation

K H2O

Attachment of PAX-treated Sulfidest Ai B bbl


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to Air Bubbles

Mechanically agitated

Flotation Cell

Contact angle measurementon mineral surface

Typical Grade Recovery Curve


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Typical Grade Recovery Curve

T i l Fl t ti C ll A t


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Typical Flotation Cell Arrangement

Scavenger Cleaner Cells

Inter-stage grinding usually improves grades and/or recovery

Effect of Particle Size Distribution onFl t ti f S lfid O


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Flotation of Sulfide Ores

Flotation Example (Pb-Zn Sulfide Ores)


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Flotation Example (Pb-Zn Sulfide Ores)

PbS (galena) is naturally floatable, while ZnS(sphalerite) is not easily collected

Two-stage process (galena flotation beforesphalerite flotation):

ZnSO4

is added in grinding to depress sphalerite duringPb flotation at pH ~7

Sulfite and/or cyanide may be added to minimize flotationof iron sulfides

CuSO4is added to activate sphalerite during Zn flotation:ZnS + Cu2+ ! CuS + Zn2+ (on surface)

CuS is more readily floatable than ZnS pH raised to 10-12 to minimize flotation of iron sulfides

Photomicrographs of a Sulfide Ore (Sudbury)


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g p ( y)

Ccp Chalcopyrite CuFeS2

Pn Pentlandite (FeNi)9S8

Po Pyrrhotite Fe7S

8Rk Rock

Mag Magnetite Fe3O4

Ground Feed Vales Clarabelle Mill,Copper Cliff ON


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MAG-CLNR

SCAVENGER

PYRRHOTITETAILS

ROCK TAILS

MAG-RCLNR

SCAV-CLNR

R - BR - A

BULK CONC

B Cleaner

Cu RougherCu Scavenger

Cu CONC

Copper Cliff, ONFlotation rate: Ccp > Pn > Po

DETA (diethylene triamine) or TETA(triethylene tetramine) and sulfite areadded to B Cleaner and PoRejection circuits.

Flotation of Pyrrhotite


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Flotation of Pyrrhotite

Pyrrhotite oxidation may lead to formation ofelemental sulfur on the particle surfaces Elemental sulfur is naturally floatable

Minute quantities of Cu and Ni dissolved from theCu / Ni minerals can activate the pyrrhotite andmake it floatable, e.g.:

FeS + Cu2+ ! CuS + Fe2+ (on surface)

Addition of complexing agents minimizes pyrrhotiteactivation

Mechanism of Pyrrhotite Depression involves


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CH2 CH2

NH

CH2

CH2Cu

NH2H2O

H2N

CH2 CH2 CH2 CH2

NHH2N NH2

CH2 CH2

NH

CH2

CH2Cu

NHH2N

CH2 CH2

H2N

CH2 CH2 CH2 CH2

NHH2N NH

CH2 CH2

NH2

DETA TETA

CuDETA2+ CuTETA2+

Similar Ni-DETA and Ni-TETA complexes also exist

y pComplex Formation

Mechanically agitated Flotation Cells


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y g

Column Flotation


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Column Flotation

Ore

Jameson (Short) Column Cell


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( )

Roseby Copper Project


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Xstrata - Raglan Concentrator


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LaRonde Mineral Processing Flowsheet


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g


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Thickener Types


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Stokes Law of Sedimentation


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Free Settlingof spherical particles invery dilute slurries:

Gravity force Fgpulls particles down pastdisplaced liquidAt the settling velocity $, gravity force Fg

equals the drag force Fd

2 (%p %f) g r2

$= ------------------- for Re < 0.59

where $= settling velocity

%fand %p= densities of fluid and particlesg = acceleration due to gravityr = particle radius = dynamic viscosity of fluid

Empirical solutions required for industriallyimportant Hindered Settlingsituations

Hindered Settling


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Stokes law describes the behaviour of a singlespherical particle in an infinite fluid.

Model has limitations for practical application: Particles are usually not spherical Different particles in the same suspension have different

densities and particle sizes

Particle-particle interactions modify the settling behaviouras the suspension becomes thicker hindered settling.

Semi-analytical or empirical solutions are requiredfor meaningful hindered settling calculations basedon simple settling tests.

Thickener Sizing - Kynch Method


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A = tu/ hoco

A = thickener area (m2/ t/h)tu = settling time (h)

ho= original pulp height (m)

co= original pulp density (t/m3)

Settling tests for sizing

are best carried out by

equipment suppliers!

Flocculation


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Polyacrylamide flocculants are added at high dilution (


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Deep-Cone

SettlingPond Paste Thickener

Applications for Paste Thickening


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Mine (Paste) Backfill

Counter-current Decantation (CCD)In ground thickeners


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In-ground thickeners,Cascading overflow

!!" $%&'()*)+ ,*-


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!"#"$% '($)

*+,--.+($/

!()01.2 '($)

34056,7

8.92

:$;056,78.92

'


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:0


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!!" . C*4)+789 >B3D&*;


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B 8,>"?40 ;">2+(-090$/ 2.92 50C."50; ;.0 /,-,>"/AD E0


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Feed Well

Turbodil

Internal Feed Dilution

Hydraulic

Rake Lift

Mechanism


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Vacuum FiltrationR t D Filt Horizontal Belt Filter


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Rotary Drum Filter Horizontal Belt Filter

Pressure Filtration


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AutomatedHorizontalFilter Press

Recessed Chamber Filter Press


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Filter Cloth Yarns and Weaves


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Affects:cloth tightness,

cloth elasticity,solution flow rateease of filter cake releasemechanical strength

Other Common Filtration Equipment


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Pressure Leaf FilterSand Filter

Vacuum Disc Filter

Pre-coat Pressure Disc Filter



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Companies for developing New Projects


R&D

(Process Dev)

MiningUpgrading

(Milling)

Processing(Metals

Recovery)

Sales


Legal,!


Precipitates

Waste

Reagents

What is Hydrometallurgy?


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y gy

Wikipedia:Hydrometallurgyis part of the field of extractive

metallurgyinvolving the use of aqueouschemistry for the recovery of metals from ores,concentrates, and recycled or residualmaterials.

Generic Hydrometallurgical Process


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Final metal or compound

Leaching

Metals Recovery

Purification

Ore, concentrate orIntermediate + water

Reagents

Reagents

Effluent

Treatment

Residue +PrecipitateDisposal

Reagents

CHE1430-1 Introduction.pdf

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