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Improved (bio) processing methods for complex ore, Lubin black shale case study Anne-Gwénaëlle GUEZENNEC (BRGM) BRGM, Environment and Process Division, France IMN, Non-ferrous metals Research Institute, Poland
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Page 1: Improved (bio) processing methods for complex ore, Lubin ...promine.gtk.fi/documents_news/promine_final_conference/15_55_G… · Batch, 20%solids Continuous, 25% solids, less agitation

Improved (bio) processing methods for complex ore,

Lubin black shale case study

Anne-Gwénaëlle GUEZENNEC (BRGM)

BRGM, Environment and Process Division, France IMN, Non-ferrous metals Research Institute, Poland

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> 2

Context of the study > Cu and Ag concentrate

• Black Shale Ore deposit (KGHM, Lubin, Poland) • Carbonate-rich • Polymineral: chalcocite, bornite, covellite, chalcopyrite • Flotation indexes

– Always been poor – in last 5-6 years further degradation (Cu ↓ As ↑)

> Pyrometallurgical process currently applied

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> 3

Context of the study

> Bioleaching demonstrated to be a viable option • Testwork at 42°C in batch and continuous mode • Cu recovery > 95% in batch mode (10% solids) • Cu recovery limited in continuous mode to 92% (15% solids, 6.5 days

residence time) – Partial chalcopyrite oxidation

Potential economic feasibility (Spolaore et al. 2009)

Aim of this work: Improve profitability of the process and demonstrate the advantage of bioprocessing route

> Preliminary techno-economic study

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> 4

How to improve process economy? Process economy

improvement

revenues by improving

process efficiency

Eh (< 420 mV) better dissolution of

chalcopyrite

operating costs

Agitation / aeration

rates

capital costs = tank volume

solids feed content > 20%

residence time < 6.5 days Cordoba et al. 2008; Pinches et al. 2000;

Third et al 2002; Tshilombo et al 2002

Non-traditional operating conditions: • Bioleaching tests (BRGM) • Electrowinning tests (IMN)

Direct electrowinning high Cu

content

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> 5

Materials and methods : bioleaching tests

Conditions investigated: - ↓ agitation/aeration rates to ↓ Eh - ↑ solids concentration to 25%

Analytical techniques: pH, Eh, DO, OUR

[Cu - Fe], bacterial community structure (CE-SSCP) Continuous pilot-scale unit

Initial operating conditions: 42 C, residence time 4.5 days, pH < 2, non limiting oxygen transfer + 1% CO2

Nutritive medium 0Km/3

Cu concentrate (%)

Ag As Cmin Corg Cu Fe S= 0.09 0.1 1.9 8.2 14.6 7.5 15.9

H2SO4 (20% v/v) Bioshale-BRGM bacterial consortium

Leptospirillum, Acidithiobacillus and

Sulfobacillus

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> 6

Results: bioleaching tests

20% solids feed concentration Non limiting O2 transfer

63% Cu dissolution in 5.2 days

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0 1 2 3 4 5 6 7residence time (days)

copp

er d

isso

lutio

n (%

)

20% solids

Concentrate and nutrients H2SO4

(20% v/v)

50L 20L

20L pH 1.6

Eh (mV) 600 1.5

O2 (mg/L) 5.6 611 1.7

OUR (mg/L/h) 193 5.6 616

202 5.4

147

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> 7

pH 1.8

Eh (mV) 592 1.5

O2 (mg/L) 3.2 642 1.6

OUR (mg/L/h) 86 5.1 639

163 5.3

126

Results: bioleaching tests

20% solids + ↓ agitation/aeration rates in R1 • 800 to 100 L/h • 450 to 340 rpm

No Eh ↓ but Cu dissolution ↑ 74% Cu recovery in 4.7 days

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copp

er d

isso

lutio

n (%

)20% solids20% solids aeration/agitation R1

Concentrate and nutrients H2SO4

(20% v/v)

50L 20L

20L

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> 8

Results: bioleaching tests

25% solids + ↓ AAR in R2 and R3 • 400 to 50 L/h • 420 to 300 rpm

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0 1 2 3 4 5 6 7residence time (days)

copp

er d

isso

lutio

n (%

)

20% solids20% solids aeration/agitation R125% solids agitation/aeration R1/2/3

pH 1.3

Eh (mV) 601 1.6

O2 (mg/L) 1.9 472 1.9

OUR (mg/L/h) 115 0.6 480

101 0.5

79

Conentrate and nutrients H2SO4

(20% v/v)

50L 20L

20L

No technical pb High copper tolerance (> 40 g/L)

87% Cu recovery in 4.5 days

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> 9

Results: bioleaching tests

Structure of the bioleaching consortium • At the end of batch, Bioshale-BRGM species present • In continuous mode, gradual ↓ of diversity • Finally, 2 organisms: Sb. benefaciens and L. ferriphilum

0102030405060708090

100

0 4 9 16 21 29 35 43 46 52 60 67 72Days in continuous mode

Rat

io (%

)

Sb. benefaciens Sb. thermosulfidooxidans L. ferriphilum At. caldus

Batch,20%solids

Continuous, 25% solids,

less agitation aeration

Continuous, 20% solids Continuous, 20% solids,

less agitation aeration

All functions still present

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> 10

Materials and methods : direct electrowinning tests Pregnant Leach Solution

Ag As Cl Zn Cu Fe Fe2+ < 0,0002 0.24 0,46 2,99 44,9 5,76 0,27

Pre-treatment tests:

• Hydrolytic Fe(III) removal using calcium carbonate

• Fe(III) removal by jarosite precipitation • Fe(III) removal by jarosite precipitation

combined to Cl-removal

Continuous EW tests for Cu removal:

• Constant Cu2+ content (~ 30 g/L) • Temperature: 55 C • Cathode current density: 200 A/m2

• Residence time in the cell: 1h

Continuous monitoring of : • Current intensity, • bath voltage, • current efficiency • electrical energy consumption

Comparison with SX-EW tests

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> 11

Results: direct EW tests

Fe(III) removal tests

Initial solution

(g.dm-3)

Mass of precipitated

residue

(g)

Final solution

(g.dm-3)

Removal to residue

(%) Cu2+ Fe pH Cu2+ Fe Cu2+ Fe

Hydrolytic Fe(III) removal using calcium

carbonate

44,91 5,76 161,8 3,0 43,08 0,23 4,07 96,0

Fe(III) removal by jarosite

precipitation 44,91 5,76 51.9 1,24 43,58 1,67 2,93 71,0

Hydrolytic removal: 96% of Fe(III) removed but significant loss of copper due to difficulties in filtration of the precipitate Jarosite precipitation: 71% of Fe(III) removed but lower loss of copper (easier filtration of the precipitate)

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> 12

Results: direct EW tests

Initial solution

Mass of copper cathode

(g)

Current efficiency

(%)

Energy consumption

(kWh/t Cu)

no pre-treatment 133.8 70.35 2653

hydrolytic Fe(III) removal 106.3 95.72 1828 Fe(III) removal by jarosite precipitation 97.6 91.06 2055

Fe(III) removal by jarosite precipitation combined to Cl- removal 90.8 91.47 2012

Fe(III) removal: energy consumption Cl removal: dendritic accretions onto copper deposits

ppm Ag Pb Fe Zn As

Impurities in the cathode 11,3 1,2 <1 2,8 <0,1

Max 25 5 10 4 5

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> 13

Conclusions

0

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0 1 2 3 4 5 6 7residence time (days)

copp

er d

isso

lutio

n (%

)

PromineBioshale

87% Cu dissolution in 4.5 days BUT 25% instead of 15% in previous tests

> Initial objectives • Improve profitability of Cu

concentrate bioleaching • Test of non traditional operating

conditions

> Bioleaching step: • Technical 25% solids feasibility

demonstrated • Improvement of Cu dissolution

when ↓ agitation/aeration rates

> EW steps: • Direct EW works! • Cu cathode of proper quality (morphology and composition) at

industrial current densities • Good current efficiency (90 – 95 %) and power consumption

(~2000 kWh/tCu), even with high Mg, Zn, Ni, Co, As concentrations in the electrolytes

• Conditions: Fe(III) <2g/L, Cl <0.5 g/L

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> 14

Mg, Ca, Cl leaching

Gypsum flotation

Bioleaching

Jarosite precipitation

Electrowinning

Cu cathodes Cu liberation

Evaporation & crystallization

Mix-sulphates (Zn, Co, Ni, Cu, Fe, Mg) Gypsum precipitation

Gypsum to ETP

Lubin concentrate

Jarosite disposal

Residue-treatment

Gypsum disposal External H2SO4

Ag recovery (tested by IMN) Economic evaluation (handled

by CUPRUM)


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