HEAP LEACHING TECHNOLOGY Moving the frontier for treatment

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1 HEAP LEACHING TECHNOLOGY Moving the frontier for treatment Applications in Niger and Namibia Jacques THIRY Sergio BUSTOS Technical Direction AREVA MINES FRANCE IAEA, Vienna, June 2014 Titre présentation Intervenant/réf juin p.1

2 HEAP LEACHING OF URANIUM ORES Interest on heap leaching of uranium ores motivated by expected increased participation of low grade ore treatment in future uranium production Significant reduction in CAPEX and energy costs by avoiding grinding, agitation tank reactors and filters Large experience and best practices transfer from conventional copper heap leaching operations Recent advances in bio-leaching by using archea and other thermophile bacterial strains open opportunities for the treatment of black shale deposits Actual operation at Somair and the Imouraren Project in Niger, together with Trekkopje Project in Namibia show AREVA s confidence on this technology Present extremely low uranium price situation (< 30 US$/lb U) has temporarily slowed and delayed further development and application of this technology Learnings and experience from operational practice and from R&D activities should help in facing challenges associated to future market demands for safe, efficient and clean uranium production Titre présentation Intervenant/réf juin p.2

3 CONTENTS The heap leaching unit operation The heap reactor Agglomeration quality Solution flow through the ore bed The reaction system Leaching performance Integration of the heap in the uranium recovery process The acid heap leaching process The alkaline heap leaching process Final remarks Titre présentation Intervenant/réf juin p.3

4 THE HEAP LEACHING UNIT OPERATION Titre présentation Intervenant/réf juin p.4

THE HEAP REACTOR Non confined auto-supported packed bed reactor Non flodded bed solution flow pattern Bed packing : agglomerated ore particles Agglomeration is key to ensure: heap stability ore

5 THE HEAP REACTOR Non confined auto-supported packed bed reactor Non flodded bed solution flow pattern Bed packing : agglomerated ore particles Agglomeration is key to ensure: heap stability ore bed permeability under non flooded bed liquid flow condition enhanced initial reagent distribution all over heap height Areva / M Ascani Titre présentation Intervenant/réf juin p.5

6 THE AGGLOMERATION QUALITY The amount of water and possible reagents required to produce a good agglomerate depends on particle size distribution (PSD), particularly on the amount of fines (<150µm) The PSD is a characteristic response of the ore to blasting and crushing operations The PSD of spheres can be characterized by the mean diameter D mean and by the Uniformity Coefficient C U describing the spread or standard deviation The PSD defines the apparent density ( App ) and therefore, the porosity ( ) 120 Particle Size Distribution SOMAIR D mean = (D 16 + D 50 + D 84 ) / 3 C U = D 60 / D 10 = 1 App / S Passing, w % Particle size, µm MA Tamgak M3 Tamou M4 Arlette M1 Ariège F Typical Model 1 BUT,.. 0re particles are not spheres!! And they are randomly packed Typical refers to PSD encountered at copper heap leach operations Titre présentation Intervenant/réf juin p.6

7 SOLUTION FLOW THROUGH ORE BED Non flooded bed gravity flow leading to the so called Thin Layer (TL) Leaching concept (Rauld et al, SME-AIME, Louisiana, March 1986) Specific discharge flow v and hydraulic conductivity K related by: v [cm/sec] = K [( - *)/( s - *)] 3 = g /µ [( - *)/( s - *)] 3 The difference ( *) is the excess of liquid retained by the ore agglomerates referred to *, which is the liquid retained once the flow has been stopped (at the end of drainage). s is the liquid retention under flooded bed condition. P = 3 / (1- ) 2 0,1800 0,1600 0,1400 0,1200 0,1000 0,0800 0,0600 0,0400 0,0200 0,0000 M2 Tamgak / Permeability Factor P 0,00 0,10 0,20 0,30 0,40 0,50 0,60 Porosity 6m 2m 2,20 2,10 2,00 1,90 1,80 1,70 1,60 1,50 1,40 1,30 1,20 APP e^3/(1-e)^2 Ro App The intrinsic permeability depends on ore PSD and on ore packing characteristics within the ore bed: = D P2 [ 3 / (1- ) 2 ] Somair typical values are: H = 6 m K = cm/sec v = 3 L/hm 2 Titre présentation Intervenant/réf juin p.7

8 THE REACTION SYSTEM Ore mineralogy and solution chemistry UO HCO 3- + CO 3 2- = UO 2 (CO 3 ) H 2 O UO H SO 4 2- = UO 2 (SO 4 ) H 2 UO Fe SO 4 2- = UO 2 (SO 4 ) Fe +2 Impurity dissolution V 2 O OH - = 2 VO H 2 0 CaSO 4 + CO 3 2- = CaCO 3 + SO FeO.OH + 6 H + = 2 Fe H 2 O Al 2 O H + = 2 Al H 2 O CaCO H + = CaSO 4 + CO 2 + H 2 O Dissolution kinetics controlled by mass transport phenomena, but mainly by reagent supply to the ore solution reaction inter-phase Volume application rate is 3 orders of magnitude lower at heap leaching as compared to agitation leaching Reagents concentration profiles along heap height Operating condition Unit Heap Agitation Specific flow rate L/hm Volume application rate m3/td 0,011 12,7 Solid-liquid contact time h 900 0,79 Solution residence time h 389 4,8 Total leaching time h Titre présentation Intervenant/réf juin p.8

9 LEACHING PERFORMANCE Need to distinguish between extraction and recovery Multiple leach cycles lead to large and slow solution inventory changes Increased heap height helps in improving [U] PLS, but compromises leaching time Increased specific flow rate reduces time but also reduces [U] PLS Trekoppje / U Leaching Performance 3 leach cycles, 9 m heap height Trekoppje / U Leaching Performance 9 m heap height U Dissolution & U Extraction, % ,00 0,40 0,80 1,20 1,60 2,00-20 L/S, m3/t U Dissolution % U Extraction % U Dissolution, % ,00 0,40 0,80 1,20 1,60 2,00 L/S, m3/t U Dissolution 4,5 L/hm2 U Dissolution 6 L/hm2 Titre présentation Intervenant/réf juin p.9

number of columns Time for tests CAPEX and OPEX for these tests

10 TESTWORK PROGRAM DEMANDS Heap Leaching processes set up require many lab scale tests in columns and pilot tests Dedicated Equipments Large number of columns Time for tests CAPEX and OPEX for these tests Namibia equipments Titre présentation Intervenant/réf juin p.10

11 TESTWORK PROGRAM DEMANDS Niger equipments for Somaïr and Imouraren Projects Titre présentation Intervenant/réf juin p.11

12 INTEGRATION OF THE HEAP IN THE URANIUM RECOVERY PROCESS Titre présentation Intervenant/réf juin p.12

13 ACID HEAP LEACHING PROCESS Similar to Copper heap leaching operations Anionic amine as SX organic extractant reagent Typical impurity release with final residue. Solution bleeding depending on acid consumption and gangue mineralogy Possible regeneration of oxidant Fe +3 by bacterial activity EV1 RLS Agglomerated Ore 1st Cycle LR Drain Final Residue H2SO4 OFF1 H2O H2SO4 DS RLS Pond PLS Pond Heap Leaching / U Extraction PLS BS Back-End / U Recovery SX- CO2 SX- S SDU pp UO4 pp SDU pp bleeding UO4 pp R ACE Solution Bleeding SDU pp R BS Pond Na2CO3 + H2O NaOH H2O2 H2SO4 + H2O UO4 Titre présentation Intervenant/réf juin p.13

14 ALKALINE HEAP LEACHING PROCESS Need of ore washing to minimize [Cl - ] PLS and [SO 2-4 ] PLS Three leach cycles to increase [U] PLS and to reduce PLS flow to IX Need of residue rinsing to minimize reagent losses Water balance very much affected by elution efficiency H2O EV1 EV2 H2O EV3 Agglomerated Ore Wash WR 1st Cycle ILS 1R ILS 2nd & 3rd RLS LR Drain DR Rinse Final Residue H2O recycle OFF1 OFF2 / OFF3 RS RO DS ILS Ponds PLS Pond Heap Leaching / U Extraction RLS Pond Wash solution effluent PLS BS Na2CO3 / NaHCO3 Back-End / U Recovery IX-A SDU pp R IX-E SDU pp UO4 pp UO4 pp R ACE BS Pond NaOH BC + H2O H2O2 H2SO4 + H2O UO4 Titre présentation Intervenant/réf juin p.14

15 Titre présentation Intervenant/réf juin p.15 FINAL REMARKS

16 FINAL REMARKS Uranium is being successfully extracted from low grade ores by heap leaching operations The response of the reaction system both at acid or alkaline leaching conditions is well know Proper characterization of ore feed is required to anticipate agglomeration quality, heap permeability and stability, and uranium dissolution kinetics and final recovery Many laboratory, bench scale tests and pilot plant demonstration at proper scale are necessary to provide suitable design parameters and to fit modeling efforts to actual results Large space for optimization opportunities to reduce ore throughput, water and reagents consumption Proper effluent solution management and control as well as proper residue disposal are required for safe and clean operation Titre présentation Intervenant/réf juin p.16

HEAP LEACHING OF LOW GRADE URANIUM ORES AT SOMAIR

HEAP LEACHING OF LOW GRADE URANIUM ORES AT SOMAIR Jacques THIRY Nicolas DURUPT AREVA NC Business Group Mines SEPA - Service d Etude de Procédés et Analyses Heap Leaching Somaïr More than 40 000 t of uranium