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Orway Mineral Consultants (WA) Pty Ltd

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