UNLOCKING VALUE IN COPPER ARSENIC SULPHIDE RESOURCES WITH THE COPPER ARSENIC CESL TECHNOLOGY

Transcription

1 UNLOCKING VALUE IN COPPER ARSENIC SULPHIDE RESOURCES WITH THE COPPER ARSENIC CESL TECHNOLOGY Jennifer Defreyne, Teck Resources Ole Wagner, Aurubis AG

2 Outline Arsenic Challenge Teck-Aurubis Strategic Partnership Cu-As Technical Work Program (TWP) Final Comments 2

3 Arsenic Challenge Arsenic Challenge Teck-Aurubis Strategic Partnership Cu-As Technical Work Program (TWP) Final Comments 3

4 Demand/Production [Mt Cu] Copper Market Trends Global Refined Copper Demand Demand for mine production Base case mine production Over 6 Mt of Cu deficit in Year [-] Major new production required by 2020 Requires ~45 additional new projects at 150 ktpa to ~30 existing mines >150 ktpa A difficult challenge for complex deposits such as those high in arsenic Sourced from Brook Hunt data (2011) 4

5 As Trend in Copper Concentrates 0.161% 0.163% 0.22% 0.22% The global average As content in copper concentrates will increase by appr. 37% The As content in high As containing concentrates is increasing from 0.37% in 2008 to 0.61% in : Global average As concentration X : Arsenic in concentrates [kt] The largest increase of As in concentrates between 2010 and 2015 comes from the development of new projects* The second driver is an increase of As in operational projects* like: Batu Hijau, Collahuasi, Kadjaran, Los Bronces, Los Pelambres, Antamina, Rapu Rapu, Telfer, and Escondida (*Source: Brook Hunt) 5

6 Future Arsenic Processing Capacity Lack of capacity of 30 kt in 2015 Infeasible for smelters to handle expected future increase of arsenic in concentrates from 2015 on X X : Arsenic in concentrates [kt] : Arsenic smelting capacities [kt] (Assumption: Max. global average As in concentrate blend: 0.18 %) Expecting rising penalty ranges and lower arsenic limits at smelter Chinese import limit (0.5% As) Stricter environmental regulations Long-term contracts involving high- As concentrates unlikely The surplus of arsenic in 2015 corresponds to approximately 5 Mt of Cu (30 mines 150 ktpa) 6

7 Copper-Arsenic Opportunity Copper Challenged Arsenic-rich Resources Much of the world s copper resources have contained arsenic Current copper market trends suggest there will be increasing need to re-evaluate challenged resources to meet demand Many significant copper deposits have arsenic contents that prohibit production of clean saleable concentrates A new technical solution is required CESL technology is a viable alternative to conventional smelting-converting for treating As-rich copper concentrates 7

8 Strategic Partnership Arsenic Challenge Teck-Aurubis Strategic Partnership Cu-As Technical Work Program (TWP) Final Comments 8

9 Teck Profile Canada s largest diversified miner Copper, Coal, Zinc, and Energy World-class lead and zinc smelter PM and specialty metal recovery Robust technical capabilities CESL Applied Research and Technology Experienced in hydrometallurgy Zinc Pressure Leach, Solvent Extraction, Electrowinning Vale s CESL Plant 9 9

10 Who is CESL? Part of Teck s Technology Group Developed proprietary hydrometallurgical technology for treating copper and nickel sulphide concentrates. Uses existing commercial technologies such as pressure oxidation, solvent extraction and electrowinning Photos: Vale s 10K tpa copper cathode CESL refinery, Brazil 10 10

11 Vale s CESL Plant Vale s small industrial plant in Brazil Usina Hidrometalúrgica Carajás uses CESL Copper Process 10,000 tpy Cu cathode design 11 11

12 Aurubis Profile Business capabilities cover all stages of the copper value chain from raw materials processing to finished products 2nd largest producer of copper cathodes worldwide and the European leader Global leader in copper recycling 12 12

13 Teck-Aurubis Partnership Synergies Leaders in sustainable resource development Mining Large Scale Copper Refining Copper fabrication Hydrometallurgy Profound commitment to social responsibility Copper marketing 13

14 Processing Route Teck Aurubis Teck - Aurubis Mine Smelter Mine Mill Mill Fabrication CESL Refinery Concentrate Copper Products Copper Cathode Strategic joint investment to solve technical issues related to treating concentrates with high (>0.3%) levels of arsenic using hydrometallurgy Good technical, environmental and product stewardship alignment between the two companies 14

15 CESL Copper Process Copper minerals are oxidized and leached using recycled raffinate Autoclave residue is washed and filtered Leach liquor is processed through Solvent Extraction Copper is transferred to pure electrolyte stream and cathodes plated Partial neutralization of raffinate for acid balance control Copper Concentrate Pressure Oxidation and Leach Solid Liquid Separation Solvent Extraction Copper Electrowinning 15

16 CESL Gold Process Gold and silver are leached at elevated pressure with recycled cyanide solution Limited dissolution of sulphur because of short leach retention time Gold and silver recovery using standard carbon Adsorption-Desorption (ADR) and electrowinning technology Copper recovery from solution and regenerate cyanide in recycled solution (Acidification) Cyanide recovery from plant effluent stream (Volatilization Reneutralization) Copper Leach Residue Pressure Cyanide Leach Gold Recovery (ADR + EW) Cyanide Recovery (AVR) 16

17 Technical Work Program Arsenic Challenge Teck-Aurubis Strategic Partnership Cu-As Technical Work Program (TWP) Final Comments 17

18 Technical Questions CESL Cu Process was demonstrated at industrial scale, but prior to implementation for arsenic-bearing concentrates: Can we achieve similarly high extraction from enargite and tennantite? What form does the arsenic take? Is the arsenic stable and can we ensure complete deportment to the residue? Will the arsenic leach in cyanide solution? Are we ready to build a full-scale gold plant? 18

19 Technical Work Program Developed staged program to address the questions Confirm copper extraction at the bench scale Pilot plant testing to generate residues for analysis and track arsenic deportment in the copper and gold processes Develop protocol and complete residue stability program with Dr. George Demopoulos (Professor, McGill University, Montreal, Canada) Confirm engineering design criteria, materials of construction and de-risk the scale-up of the gold process by operating a demonstration plant 19

20 Technical Work Program Schedule Bench Testwork Copper Pilot Testing Gold Pilot Testing Residue Stability Program Gold Demonstration Operations Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Bench Autoclave Copper Pilot Plant Autoclave Gold Demonstration Plant 20

21 Summary of Bench Testwork Results Bench Feed Material Copper Iron Sulphur Arsenic % % % % % Enargite, 21% Pyrite, 8% Chalcopyrite, 1.0% Tennantite, 5% Gangue Repeatability Tests: P= 1400 kpag, T = 150 C, R.T. = 90 min Test % Cu % As in % Fe in As:Fe* Extraction Residue Residue Ratio * As:Fe ratio in Ferric Arsenate (FeAsO 4 2H 2 O) =

22 Summary of Bench Testwork Results Toxicity Characteristic Leaching Procedure (TCLP) Measures the potential for metals to seep or leach into groundwater if a waste is disposed Conducted TCLP test on 3 different autoclave residues generated at increasing temperatures Arsenic limit in leachate = 2.5 mg/l Autoclave Temperature TCLP As mg/l 150 C C C 0.95 Conclusions from Bench Testing Excellent copper extraction from enargite (most refractory mineral) Indication that residue contains ferric arsenate, as literature would suggest Indication of low leaching characteristic of arsenic from the residue 22

23 Copper and Gold Pilot Plant Objectives Confirm copper and gold extraction from concentrates with varying As grades and mineralogies Optimize residue stability by manipulating operating parameters (grind size, retention time, acidity, flotation) Develop stability protocol and subject residue samples to testing Track arsenic in all process streams Gather data for future Environmental Impact Assessment Identify areas of high risk with respect to worker health 23

24 CESL Pilot Plant Grinding Pressure Oxidation Residue Washing SX/EW Pressure Cyanidation CN Recovery Loaded Carbon 24

25 Pilot Plant Feed Material Mineral [%] Formula Conc. B Conc. C Conc. D Chalcopyrite CuFeS Enargite/Luzonite Cu 3 AsS Tennantite Cu 12 As 4 S Chalcocite Cu 2 S Bornite Cu 5 FeS Covellite CuS Pyrite FeS Gangue %Cu = 26-30; %As = ; g/t Au =

26 Pilot Plant Campaign Scope Continuously integrated pilot plant operations from concentrate to copper cathode and gold on carbon All streams recycled internally and multi-element tracking Measure Unit Value Availability % 91 Operating Days (Cu + Au) d Concentrate Processed kg 4,800 Cathode Produced kg 1,000 Gold on Carbon g 22 Leach Residue Produced kg 3,700 Gypsum Produced kg 2,300 Bleed Cake Produced kg

27 Copper Sulphide Oxidation Copper Sulphide Oxidation 25-27% Cu 29-30% Cu Copper sulphide oxidation ranged between 96% and 99% for 5-month campaign Increase is a result of optimization, as well as increase in grade 27

28 Pilot Plant Gold Extraction Gold extraction >95% from several concentrates Current pilot work focused on concentrate C (8 g/t Au) Gold extraction = 80-85% Mineralogical analysis indicates gold in concentrate C was combination of free and hosted by refractory tellurides Pilot extracting >95% of free gold Gold Mineralogy for Concentrate C 75-85% Free Gold Petzite* Calaverite* Sylvanite* *Tellurides 28

29 Arsenic Deportment Output stream [%] Conc. B Conc. C Conc. D Deportment to Residue Deportment to Bleed Solids Near quantitative deportment of arsenic to plant residue; only a few mg/l As in circulating solution Pilot plant results indicate no arsenic leaching in the CESL gold process; undetectable in cyanide solution What possible forms could As be taking? 29

30 Background: Solubility of Various Arsenic Compounds Mineral TCLP Solubility (mg/l) Formula Commercially Practiced 1 Scorodite Arsenic ferrihydrite Scorodite: <0.5 Type I: 5-85 Type II: <0.5 Fe:As = 9:1: <0.5 Fe:As = 2:3: 1-2 FeAsO 4.2H 2 O Fe 2 (HAsO 4 ) 3.XH 2 O Fe 4 (AsO 4 ) 3 SO 4 OH 10 FeO(OH)(H 2 O).AsO Calcium arsenate >5 Ca 3 (AsO 4 ) Harris, Review of Worldwide Practices. 30

31 Residue Stability Testing Embarked on program to outline design criteria for long term residue disposal options Literature suggests that arsenic is less stable at increasing alkaline conditions 1 Decreased potential is suspected to increase solubility in residues (As 3+ vs. As 5+ ) 2 Does the presence of elemental S affect arsenic mobilization? Results will lead into long-term project plan 1 Bluteau, M., Demopoulos, G., The incongruent dissolution of scorodite Solubility, kinetics and mechanism. Hydrometallurgy, Vol McCreadie, H., Blowes, D.W., Ptacek, C.J., Jambor, J.L. (2000) Influence of Reduction Reactions and Solid-Phase Composition on Porewater Concentrations of Arsenic. Environmental Science and Technology, Vol 34 31

32 Experimental Method Sample Preparation Dried at 40 C, homogenized and split 75 g dry solids in 1.5 L deionized water Test Control Samples mildly agitated on a gyratory shaker Samples were monitored and adjusted for ph and Eh Test Sampling Filtrate samples were taken for ICP analysis on a set schedule Day 1, day 7, week 2, week 4, and week 8 (duplicate). 32

33 Summary of Results We can assume the majority of arsenic precipitates as Basic Ferric Arsenate Sulphate (Type II) and the rest taken up by hematite The presence of hematite and its possible role in accommodating some adsorbed arsenic provides enhanced stability Arsenic in filtrate below detection limit (30 ppb) for residues produced from processing concentrates B and C (1.5% As) Small effect of ph and potential for residue D (6.3% As) Sharp decrease in concentration hematite adsorption phenomenon? Same results for Cu, Zn etc. in historical work 33

34 Effect of ph All 8 week samples were < 0.3 mg/l As in filtrate Arsenic solubility increased with increasing ph This follows well with published solubility data on various ferric arsenate phases The residues are most stable from ph 5 ph 7 Residue (6.3% As) All other residues were below detection limit Unadjusted Eh, room temperature 34

35 Effect of potential Slurry Potential (mv) Slurry potential of 50 mv test was decreased to target value after each measurement Lower potential test (50 mv) demonstrated increased arsenic solubility Ene 27-Ene 06-Feb 16-Feb 26-Feb 08-Mar 18-Mar 28-Mar Unadjusted 230 mv 50 mv 35

36 Technical Questions CESL Cu Process was demonstrated at industrial scale, but prior to implementation for arsenic-bearing concentrates: Can we achieve similarly high extraction from enargite and tennantite? What form does the arsenic take? Is the arsenic stable and can we ensure complete deportment to the residue? Will the arsenic leach in cyanide solution? Are we ready to build a full-scale gold plant? 36

37 Gold Demonstration Plant Objectives Demonstrate fully integrated gold plant flow sheet from pressure cyanidation to gold electrowinning Optimize pressure cyanidation at demo scale Demonstrate high cyanide recovery and low cyanide consumption use for confirmation of operating cost Understand the water balance and determine effluent treatment requirement Demonstrate process and equipment reliability Collect engineering data, including design criteria and materials of construction, for scale-up 37 37

38 Gold Demonstration Plant Pressure Cyanidation Cyanide Destruction Cyanide Regeneration Carbon Adsorption Electrowinning 38 38

39 Gold Demonstration Results to Date % of Design Plant Extraction Au= 90-95% and Ag= 85% Residue Au=0.9 g/t and Ag= 2.5 g/t Gold Recovery To carbon: Au > 98%, Ag> 95% EW sludge: Au 35%, Ag 50%, Cu 15% AVR Cyanide Recovery Overall recovery 93% Stripper efficiency 99% Absorber efficiency >99% Effluent Treatment - SO 2 /Air 94 m 3 discharged all < 1 mg/l CN Week of Operation Actual Ramp-up Target 39 39

40 Final Comments Arsenic Challenge Teck-Aurubis Strategic Partnership Cu-As Technical Work Program (TWP) Final Comments 40

41 Final Comments The processing of arsenic-bearing copper deposits presents an opportunity in addressing predicted copper supply shortfalls Teck-Aurubis have partnered to address this issue through application of the Copper-Arsenic CESL Process Metallurgical and residue stability results have been excellent Based on technical performance and attractive economics Teck- Aurubis partnership is actively seeking opportunities for the development of Cu-As deposits with the CESL technology 41

42 Thank you! We are open for questions Acknowledgements: P Barrios, R Bruce, A Heidel, K Mayhew, R Mean, V Omaynikova 42