University of Saskatchewan University of Saskatchewan Geological Engineering Geological Engineering GEOE 498.3 GEOE 498.3 Introduction to Mineral Engineering Introduction to Mineral Engineering Lecture 13 Lecture 13 – – Mineral Processing 6 Mineral Processing 6
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University of Saskatchewan - U of S Engineering of S GEOE498.3...Location/Site Map ... Sulphuric acid ionizes in solution to form sulfate, bisulfate, and hydrogen ions. 1. H 2 SO 4
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University of SaskatchewanUniversity of Saskatchewan
- 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
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