The Role of Mineralogy in Process Engineering€¦ · The Role of Mineralogy in Process Engineering...
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The Role of Mineralogy in Process Engineering
Orway Mineral Consultants (WA) Pty Ltd
Overview
Uranium Mineralogy
Primary Uranium Minerals
Secondary Uranium Minerals
Liberation
Gangue Mineralogy
Case Study
Mineralogy
Comminution
Leach
Mass Balance
Conclusion
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Primary Uranium Minerals
Type Name Composition
Oxides Uraninite /
Pitchblende
UO2
Silicates Coffinite U(SiO4)1-x(OH)4x
Uranothorite UThSiO4
Nb-Ta-Ti
Complex Oxides
Brannerite (U,Ca,Ce)(Ti,Fe)2O6
Davidite (La,Ce,Ca)(Y,U)(Ti,Fe+3)20O38
Betafite (Ca,U)2(Nb,Ti)2O6OH
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Secondary Uranium Minerals
Type Name Composition
Silicates Sklodowskite (H3O2)Mg(UO2)2(SiO4)2.2H2O
Uranophane Ca(UO)2Si2O7.6H2O
Uraniferous Zircon Ca(UO)2Si2O7.6H2O
Phosphates Autunite Ca(UO2)2(PO4)2.10-12(H2O)
Torbenite Ca(UO2)2(PO4)2.10-12(H2O)
Saleeite Mg(UO2)2(PO4)2.12H2O
Vanadates Carnotite K2(UO2)2(VO4)2.1-3(H2O)
Tyuyamunite Ca(UO2)2(VO4)2.8H2O
Arsenates Zeunarite Cu(UO2)2(AsO4)2.10-12H2O
Carbonates Schroeckingerite NaCa3(UO)2(CO3)3(SO4)F.10H2O
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Liberation
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Gangue Minerals Chemistry
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Carbonates (Dolomite)
CaMg(CO3)2 (s) + 2H2SO4 (aq) → CaSO4 (aq) + MgSO4 (aq) + 2CO2 (g) + 2H2O (l)
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Sulfides (Pyrrhotite)
Fe7S8(s) + 7H2SO4(aq) → 7FeSO4(aq) + 7H2S(g) +S(s)(aq)
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Calcium Sulfate
CaSO4 (s) + Na2CO3 (aq) → Na2SO4 (aq) + CaCO3 (aq)
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Fluoride / Chloride and Phosphate (Apatite)
3Ca5(PO4)3Cl(s) + 3H2SO4(aq) → 4Ca3(PO4)2(s) + 3CaSO4(aq) + 3HCl(aq) + H3PO4(aq)
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Fluoride / Chloride and Phosphate (Apatite)
Effect of Cl on Solvent Extraction :
2HCl (aq) + (R3NH)2SO4(o) → 2R3NHCl(o) + H2SO4(aq)
Effect of Cl on Ion Exchange :
4HCl (aq) + ResN4(SO4)2 (r) → ResN4Cl4(r) + 2H2SO4(aq)
Effect of Phosphate:
Fe2(SO4)3 (aq) + 2H3PO4 (aq) → 2FePO4 (s) +3H2SO4 (aq)
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Carbonaceous Ores
-25.0
-20.0
-15.0
-10.0
-5.0
0.0
5.0
10.0
15.0
20.0
25.0
0 20 40 60 80 100
Ura
niu
m R
ec
ove
ry (
%)
Leach Time (Hours)
Aqueous Uranium Deportment – Weak Acid Leach
U Ext (Calcfrom LiquorAssay) %
Conditions
Temperature : Ambient
U Conc. in Initial Lixiviant : 269ppm U
SG : 19% Solids
Eh : ~500mV (Ag/AgCl)
Lixiviant Concentration : ~5g/L H2SO4
Acid Consumption : 13 -14 kg/t
P80 : 75μm
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Soluble Silica (Albite)
2NaAlSi3O8(s) + H2SO4(aq) → Na2SO4(aq) + Al2SiO5(s) + 5SiO2(s) + H2O(l)
SiO2(s) +2H2O(l) → H4SiO4(aq)
Colloidal
Silica in
SX
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Clay (Palygorskite)
Palygorskite mineralogy Secondary Uranium Minerals
Trapped in Palygorskite
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Case Study
• Hard rock (granite hosted)
• 400ppm U – All Primary
• Low level sulfides
• Acid leach
• Remote from road, power, water and
infrastructure
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Uranium Mineralogy
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Gangue Mineralogy
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Uranium by Size
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Ore Breakage Opportunities
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Micro Cracking in a Brannerite Crystal
QEMSCAN particle map
analysed at a 1µm resolution
showing that, even at this
highest resolution, the
coffinite +/- uraninite veins
have been defined as "Fine
Uranium Intergrowths" due to
their very fine-grained nature.
The micro-cracking is not
visible in the particle maps
since the maps are based on
chemical composition, not
texture.
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Micro Cracking in a Brannerite Crystal
The fine-grained nature of
the coffinite +/- uraninite
veins and the presence of
micro-cracking in the
brannerite particle. The
coffinite in the veins has been
partially leached.
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Ore Preparation Flowsheet
• Coarse grind P80 710μm
• Microfractures
• Minimise gangue acid consumption while not
sacrificing the uranium extraction
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Comminution Flowsheet
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Leach Flowsheet
• Degassing tank ahead of leach circuit.
Calcite: CaCO3 (s) + H2SO4 (aq) → CaSO4 (aq) + CO2 (g) + H2O (l)
Pyrrhotite: Fe7S8 (s) + 7H2SO4 (aq) → 7FeSO4 (aq) + 7H2S (g) + S (s)
• Leaching at high slurry density (70% solids)
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Leaching Flowsheet
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Mass Balance Development
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Input
Mineral Distribution (%w/w) Formula
Uraninite 0.027 UO2
Coffinite 0.019 U(SiO4)1-x(OH)4x
Brannerite 0.003 (U,Ca,Ce)(Ti,Fe)2O6
Thorite 0.02 ThSiO4
Sulfide (Pyrrhotite) 1.1 Fe7S8
Carbonate (Calcite) 6.4 CaCO3
Apatite (Fluoroapatite) 0.15 Ca5(PO4)3F
Feldspar (Albite) 44 Na(AlSi3O8)
Kaolinite 2.5 Al2Si2O5(OH)4
Quartz 46 SiO2
Total 100
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Feed Vs Residue – Uranium Mineralogy
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Feed Vs Residue – Uranium Mineralogy
Uranium Minerals Chemistry
Reaction
Extent
Unit Value
Uraninite
UO2(s) + Fe2(SO4)3(aq) + 2H2SO4(aq) → H4UO2(SO4)3(aq) + 2FeSO4(aq) % 99
Coffinite USiO4(s) + Fe2(SO4)3(aq) + 2H2SO4(aq) → H4UO2(SO4)3(aq) + 2FeSO4(aq) + SiO2 (s) % 95
Brannerite UTi2O6(s) + Fe2(SO4)3(aq) + 2H2SO4(aq) → H4UO2(SO4)3(aq) +2FeSO4(aq) + 2TiO2 ( s) % 1.5
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Feed Vs Residue – Gangue Mineralogy
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Gangue Chemistry
Gangue Minerals Chemistry
Reaction
Extent
Unit Value
Reaction in the First Tank
Calcite Leaching
CaCO3(s) + H2SO4(aq) → CaSO4(aq) + H2O(l) + CO2(g) % 21
CaSO4(aq) + 2H2O(l) → CaSO4.2H2O(s)
g/L
Ca 0.64
Sulfide (Pyrrhotite) Leaching
Fe7S8(s) + 7H2SO4(aq) → 7FeSO4(aq) + 7H2S(g) +S(s) % 1
Reaction in the Second and Subsequent Leach Tanks
Ferric Generation (with Reagents)
Fe2O3 (s) + 3H2SO4 (aq) → Fe2(SO4)3(aq) + 3H2O(l) % 100
MnO2(s) + 2FeSO4(aq) + 2H2SO4(aq) → Fe2(SO4)3(aq) + MnSO4(aq) + 2H2O(l) % 99
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Gangue Chemistry
Gangue Minerals Chemistry
Reaction
Extent
Unit Value
Reaction in All Leach Tanks
Albite Leaching
2NaAlSi3O8(s) + H2SO4(aq) → Na2SO4(aq) + Al2SiO5(s) + 5SiO2(s) + H2O(l) % 9
Al2SiO5(s) + 3H2SO4(aq) → Al2(SO4)3(aq) + SiO2(s) + 3H2O(l) % 1.65
SiO2(s) + 2H2O(l) → H4SiO4(aq)
∆g/L
Si 2.6
Fluoroapatite Leaching
6Ca5(PO4)3F(s) + 6H2SO4(aq) → 7Ca3(PO4)2(s) + 6CaSO4(aq) +3CaF2(s) +4H3PO4(aq) % 31
Kaolinite Leaching
Al2Si2O5(OH)4(s) + 3H2SO4(aq) → Al2(SO4)3(aq) + 2SiO2(s) + 5H2O(l) % 1
Thorite Leaching
ThSiO4(s) + 2H2SO4(aq) → Th(SO4)2(aq) + 2H2O(l) + SiO2 (s) % 64
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Mass Balance Output
Parameters Unit Value
Leach
Leach Recovery % 93
Leach Discharge TDS g/L 64
Leach Sulfates Concentration g/L 42
Residue Filtration
Overall Wash Recovery % 88
Interstitial Liquid TDS g/L 56
Leach Sulfates Concentration g/L 39
Uranium mg/L 75
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Leach Reagent Consumption Rates
Parameters Unit Value
Reagents
Sulfuric Acid (H2SO4) (kg /dry tonne ore) 27
Pyrolusite (MnO2) (kg /dry tonne ore) 1.4
Hematite (Fe2O3) (kg /dry tonne ore) 1.0
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Effluent – H2S and CO2 Off-gases
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Effluent “Dry Tailings”
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Conclusion
Mineralogy of the feed and residue with respect to uranium
and gangue mineralogy is required for:
• Basis for the design of the processing plant
• Selection of process equipment for the preparation of
the ore for the leach
• Optimising the leach process with respect to reagent
consumption and uranium yield
• Basis for the development of mass balances for
uranium recovery processes
• Providing an early understanding of what the liquid
and solid effluent could comprise.
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Thank You