University of SaskatchewanUniversity of Saskatchewan

Geological EngineeringGeological EngineeringGEOE 498.3GEOE 498.3

Introduction to Mineral EngineeringIntroduction to Mineral Engineering

Lecture 13 Lecture 13 –– Mineral Processing 6Mineral Processing 6

Mineral Processing OverviewMineral Processing Overview

Mineral Processing Terms, EconomicsMineral Processing Terms, EconomicsComminutionComminution and Classificationand ClassificationPhysical processing methodsPhysical processing methodsChemical processing methodsChemical processing methodsWaste products treatment and disposalWaste products treatment and disposal

Process plant flow sheets: uranium and Process plant flow sheets: uranium and potashpotash

Cameco Cameco -- Rabbit Lake Operation: Rabbit Lake Operation: Uranium Milling Uranium Milling

Lorne SchwartzChief MetallurgistMining Division Technical ServicesU of S Engineering

The Power of Rock!!!

OutlineOutlineLocation/Site MapEagle Point MineRabbit Lake Mill• Process description

• Grinding• Leaching• Counter Current Decantation (CCD)• Solvent Extraction (SX)• Precipitation• Packaging• Water Treatment

• Historical ProductionSafety• LTA’s• Radiation

The Future of Rabbit Lake

Saskatoon

Rabbit Lake Operation Location MapRabbit Lake Operation Location Map

Rabbit Lake

N

Rabbit Lake Operation Site MapRabbit Lake Operation Site Map

1995-96

1979D-zone

1984-91

1977

B-zone

1974-84

1968

Rabbit

1997

1971

A-zone

1992-?

1980

Eagle

Eagle Point Mine Eagle Point Mine LongholeLonghole StopingStoping

15 to 30 m

Cement PadSBM

Production Holes 3.5” or 5.5” PVC Cased

CRF

Remote Mucking

Rabbit Lake MillRabbit Lake Mill

World’s Second Largest Uranium Milling Facility

U3O8 Recoveries of 96% to 97%

Additional Mill Feed From Cigar Lake Mine in 2013

Tailings Deposited in Rabbit Lake Pit

Rabbit Lake Mill Rabbit Lake Mill –– Tonnage ThroughputTonnage Throughput

0

100

200

300

400

500

600

700

Tonn

es(T

hous

ands

)

1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003Year

Process OverviewProcess Overview

-Reduces 20” rock to less than ¾” pebbles

- Uses cascading action for rock-on-rock breakage

GrindingGrindingFeed chute

Autogenous mill

Ball mill-Reduces ¾” pebbles to fine sand

- Uses 3” steel balls to break down rock by abrasion

GrindingGrindingClassification by hydrocyclone- centrifugal force used to separate fine particles from coarse- Fines go inward and upward with most of the water to the overflow pipe, and coarse particles move outward and down to the underflow.- Overflow slurry is fed to leaching circuit, and underflow returns to the ball mill for further grinding (closed circuit)

Leaching circuitLeaching circuit

One hour residence time per tank, 6 hours total

LeachingLeachingThe chemistry of leaching

Sulphuric acid ionizes in solution to form sulfate, bisulfate, and hydrogen ions.

1. H2 SO4 ----> 2H+ + SO4-2

Sulphuric Hydrogen SulfateAcid Ions Ions

2. H2 SO4 ----> H+ + HSO4-

BisulfateIons

The hydrogen ions react with hexavalent uranium, which dissolves as follows:

3. UO3 + 2H+ ---> UO2+2 + H2 O

Uranium (VI) Uranyl WaterOxide Ions

The complex uranyl sulfate anions are produced as follows:

4. UO2+2 + SO4

-2 ----> UO2 SO4Sulfate UranylIons Sulfate

Counter Current Decantation (CCD)Counter Current Decantation (CCD)

Waste solids are washed 6 times before going to tailings neutralizationRecycle streams used as wash water to minimize fresh water usageUranium-bearing liquid pumped to clarification, then Solvent Extraction

How a thickener worksHow a thickener works

Centre Well

Rakes

ClarificationClarification

Sand beds capture entrained solidsEnsures no solids enter solvent extraction

Solvent Extraction (SX)Solvent Extraction (SX)

Step #1 – ExtractionU transfer to organicRejects impurities

Or E4 Launder

Strip Solution

93%Sulphuric

Acid

Step #2 – StrippingU transfer from

organic to acidConcentration x10

Multiple stages in each step, similar to CCD

Solvent Extraction (SX)Solvent Extraction (SX)

-Typical cell has mixer section for close contact

of aqueous and organic phases

- Settler section allows time to separate layers

-Phases collected in launders, and go opposite ways

[(R3 NH)4 UO2 (SO4 )3 ]org + 2H2 SO4 2[(R3NH)2•SO4]org + [UO2(SO4)34-]aq

Gypsum PrecipitationGypsum Precipitation

-Neutralizes strong acid from stripping

-Lime addition creates gypsum solids, CaSO4

-Gypsum separated from strip solution by

thickening and filtering

Uranium Precipitation and DryingUranium Precipitation and Drying

Formation of insoluble Uranium Peroxide Hydrate:UO4 •xH2 O = yellowcakeWash away barren strip with 2 stages of thickeningDry yellowcake to about 1% moistureLoad yellowcake into drums for shipment to refinery

PackagingPackaging

Semi-automated drum filling and conveying system

Waste DisposalWaste Disposal

Rabbit Lake Site water balanceRabbit Lake Site water balance

NeutralizationNeutralizationResidue Neutralization:- Lime addition to waste

rock slurry- Deposition in Rabbit

Lake pit

Solution Neutralization:- All water from entire

site is treated before release to environment

- Process solutions are neutralized with lime

Pachuca – air agitated tank

Mine Water and Effluent TreatmentMine Water and Effluent Treatment

Ferric sulphate – precipitates ArsenicBarium chloride – precipitates RadiumSettling ponds and sand filters trap precipitates

Energy EquivalentEnergy Equivalent

5.5M lbs U3 O8

42M Tonnes

135M Barrels=

SafetySafety

0

5

10

15

20

25

30

35

40

1977 1980 1983 1986 1989 1992 1995 1998 2001 2004

Lost

Tim

e A

ccid

ents

John T. Ryan Safety Awards

• National award 2000

• Regional award 2003

0

5

10

15

20Su

rfac

ePe

rson

nel

Offi

ce S

taff

Und

ergr

ound

Min

ers

Nur

ses

Und

ergr

ound

Supp

ort W

kr

Und

ergr

ound

Mai

nten

ance

Surf

ace

Supp

ort

Surf

ace

Mai

nten

ance

Visi

tors

Surf

ace

Min

ers

Mill

Mai

nten

ance

Mill

Wor

kers

Effe

ctiv

e D

ose(

mSv

)Radiation SafetyRadiation Safety

Cameco Corporation Limit 20mSvCNSC Limit 50mSv

35 Years and Still Glowing35 Years and Still Glowing

Safe Production

Highly Skilled

Workforce

Multiple Orebody

Discoveries

URANIUM: A RESOURCE FOR CLEAN ENERGYHow does uranium become a nuclear fuel?

Fuel Preparation:Mine – mill – refinery – conversion – fuel fabrication

Eagle – Rabbit – Blind River - Port Hope – Zircatec

UO2

UF6

UO3UOCU oreBRRMine PHCFMill

ISR CBRSR-H

Refinery - Blind RiverNitric acid solvent extraction

Digestion SX Evaporation DenitrationUranium

Concentrates, sampling

UO3

Recycle to Mills

DryingEvaporation Calcining

HNO3 Recovery

RaffinateRaffinate

Refining:Refining:

Tote bins filled by Tote bins filled by weight and shipped to weight and shipped to Port Hope Port Hope

Port Hope Conversion Facility

Conversion process – Port Hope

Refining

Dissolution(HNO3 )

Conversion(HF)

Reduction(H2 )

Fluid BedReduction

(H2 )

ADU Ppt’n(NH3 )

UO3

UO2

UO2 UF4 UF6

ADU

Conversion(F2 )

Milling

UOC

Ore

Uranium conversion products

Only five commercial converter facilities in the world

UO3 UO2 UF4

Conversion products:

Natural UO2compressed into pellets for CANDU reactors

UF6 sent to enrichment facility

Uranium Enrichment:For light water reactorsDepleted U used for armor plating and radiation shielding

1000 kg Natural U(0.7% 235U )

130 kg Enriched U(~3.5% 235U)

870 kg Depleted U(~0.3% 235U)

Zircatec:Fuel bundle assembly

Chemical Energy – Fission reaction

neutron

+

235U

γ

γ

neutrons

Fissionproducts

+ HEAT

Moderator

Calandria tube

Coolant tube

Fuel bundle

Reactor wallNuclei of moderator atomsPath of neutron

• Neutron comes off too fast – and not cause fission• Moderation needed to slow down neutrons • Can be light water H2O or heavy water D2O or carbon

Global Nuclear Reactor Fleet (2005)

Total

Pressurized Water Reactors (PWR) 252

Boiling Water Reactors (BWR) 94

Magnox / Advanced Gas Reactors (AGR) 35

CANDU (Pressurized Heavy Water Reactors) 34

RBMK (Russian) 20

Others 6

TOTAL (Commercially Operable) 441

Candu Reactor Bundle Loading

Power Generation from a Nuclear ReactorHeated fluid passes through heat exchangersSteam runs turbine generatorCondensed steam recycle

Nuclear power accounts for about 17% of worldwide power production.

The uranium industry is heavily regulated by Agencies:

International Atomic Energy Agency – IAEACanadian Nuclear Safety Commission – CNSCEnvironment CanadaOntario Ministry of Environment /

Saskatchewan EnvironmentHuman Resources Development CanadaOntario Ministry of Labour / Saskatchewan Mines BranchWorkplace Safety & Insurance Board

World Power Demand

Direct link between quality of life and electricity consumptionRapid growth in developing worldYear 2000: 10 terawattsYear 2100: 40 terawatts

Nuclear’s contribution today

Kyoto Protocol drivers:• High CO2 in the long term• CO2 climbing rapidly recently• Climate effects are decades away• Enormous potential consequences

600 million tonnes per year• Kyoto Protocol CO2 reduction target

2.5 billion tonnes per year• CO2 emissions avoided world-wide by using today’s

nuclear power stations instead of coal-fired power stations

Alternatives to coal, oil and gas:

• Solar• Wind• Biomass• Hydro• Nuclear

Coal thermal 975 Oil thermal 742LNG thermal 608Photovoltaic 53 Wind 29Hydro 11Nuclear 9

Life Cycle COLife Cycle CO22 EmissionsEmissions (gram CO(gram CO22 per kWh)per kWh)

Principles of Electricity

ChemicalEnergy

Heat Steam Mechanical Energy

Electrical Energy

work

Consumption requires work Electricity is perishableEnergy must be produced at the same time as consumption

Renewables

–

the downsidesNo practical way to store grid-scale power (yet)Solar:

• Clouds?• Night?• Site area?• Expensive

Wind:• Discontinuous• Site area?• Birds?• NIMBY

(Not In My Back Yard)• Counter to demand

Renewables

–

the downsidesNot enough available

Hydro:• The good spots are

already used• Weather dependent• NIMBY

Biomass:• Still makes carbon

dioxide• 10 Terawatts = 100% of

agricultural land

Nuclear 2.3

Onshore wind farm- With stand by capacity

3.75.4

Offshore wind farm- With standby capacity

5.57.2

Wave and marine 6.6

Nuclear 2.3

Gas-fired Turbine (with carbon tax)

2.23.4

Coal-fired pulverized-fuel(with carbon tax)

2.55.0

Coal-fired circulating fluid bed(with carbon tax)

2.65.1

Royal Academy of EngineeringRoyal Academy of Engineering Electricity Generating Costs (pence/kWh)Electricity Generating Costs (pence/kWh)

Full life cycle costs:

Nuclear vs. carbon

Nuclear vs. renewables

Is nuclear power safe?

With over 10,000 reactor-years, in 32 countries, only 2 significant accidents:

Three Mile Island, 1979: Equipment failure. Small radiation release, no deaths, no injuries, no health effects

Chernobyl, 25 April 1986:• Flawed reactor design• Inadequate training• Procedure violation• Steam explosion• Graphite fire• 5% of core released• 31 immediate deaths• ~10 deaths since

Nuclear Power Nuclear Power -- ConclusionsConclusionsMinimize green house gases?

Economic?

Safe?

Assignment / Tutorial # 13Assignment / Tutorial # 13

Assignment / TutorialAssignment / TutorialName the processName the processName the equipmentName the equipment