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Testwork using the Aachen Reactor at Beatrix

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					Testwork using the Aachen Reactor at Beatrix
By Philippe Muteba 24 October 2008

CONTENTS 1. 2. 3. 4. 5. 6. Introduction Aachen Reactor PrePre-oxidation Leaching Cyanide Destruction Conclusion

1.

Introduction

Objectives Improve leach kinetics by using Aachen reactor Improve Cyanide Consumption through preoxidation Effect Cyanide Destruction

I will not get injured today

2.

Aachen Reactor

Excellent bubble generator: 300um Pressure chamber: Turbulence and mixing create Oxygen injection in the chamber ensures DO > 30mg/L Simple pipe reactor

Eliminate unsafe behavior

2.

Aachen Reactor

Strive for free injury performance
5

2.

Aachen Reactor

Strive for free injury performance
6

3.

PrePre-oxidation

Depletion of cyanide and oxygen by sulphides: FeS + ½ O2 + 7CN- + H2O → Fe(CN)64- + SCN- + 2OHIf FeS is pre-oxidised: 2FeS + 2½ O2 + 8OH- → 2Fe(OH)3 + 4SO42- + H2O The formation of Fe(OH)3 inhibits further cyanide depletion

Eliminate unsafe behavior
7

3.

PrePre-oxidation
Typical operating parameters
Time[min] 0 5 10 15 20 25 Number of passes 0 6 11 17 22 28 pH 10.44 10.14 9.90 9.70 9.65 9.28 Temp.[oC] D.O.[mg/L] 23.1 28.3 32.0 35.1 37.1 39.0 10.3 23.7 26.3 25.9 28.0 31.5

Eliminate unsafe behavior
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3.
98 96 94

PrePre-oxidation

Recovery[%]

92 90 88 86 84 82 80 Base Case (C free) Base Case (with C) Run 1 Run2

No.1 GP ( HG=2.72g/t)

No.2 GP (HG=3.53g/t)
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3.

PrePre-oxidation
Gold Price = R 140,000.00

Recovery Change

Additional Revenue/mth R 420,000.00

Additional Cost/month R 360,000.00

Conclusion

No.1 GP

+0.3%

No Go

No.2 GP

+0.6%

R 336,000.00

R 360,000.00

Residual Cyanide Change = -21 ppm Eliminate unsafe behavior
10

4.

Leaching

Heterogeneous reaction: 4Au + 8NaCN + O2 + H2O → 4NaAu(CN)2 + 4NaOH Requires: Sufficient reagent concentration Good agitation

Eliminate unsafe behavior
11

4.
100 95 90

Leaching

Recovery [%]

85 80 75 70 65 60 55 50 Base Case Run 1(20 min) Run2(35 min)

No.1 GP ( HG=2.72g/t)

No.2 GP (HG=3.53g/t)
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4.

Leaching
100 90 80 70 60 50 40 30 20 10 Time [hours] 0 0 1 2 3 4 5 6 7 8 24
No.2 G P

Recovery [%]

N0.1GP Base Case

No.2GP Base Case

No.1 GP Run1

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5.

Cyanide Destruction

Procedure: Run the Aachen reactor for a total of 40 minutes 30L of sample transferred to the reactor tank Take samples every 10 minutes No.1 GP Run Add 50 ppm CuSO4 after 30 minutes No.2 GP Run Add CuSO4 before staring the reactor. Test also with a mixture of CUSO4, ZnSO4 and FeSO4 Eliminate unsafe behavior
14

5.

Cyanide Destruction
45 40 35 30 25 20 15 10 5 0

CN[ppm]

No.1 GP WAD CN Before Free CN Before

No.2 GP WAD CN After Free CN After
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5.

Cyanide Destruction
50 40 CNO [ppm] 30 20 10 0 No.1 GP Cyanate Before No.2 GP Cyanate after

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5.

Cyanide Destruction
135 110 NO3 [ppm] 85 60 35 10 -15 No.1 GP Nitrate before No.2 GP Nitrate after

17

5.

Cyanide Destruction

1150 850 550 250 -50 No.1 GP Sulphate before No.2 GP Sulphate after

SO4 [ppm]

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6.

Conclusion

The pre-oxidation and the leaching using the Aachen reactor have not improved the overall recovery. However, a slight cyanide saving is noticed. A slight cyanide destruction is observed when using O2. The reaction is improved when CuSO4 is added. Further investigation into the cyanide destruction using different oxidising reagents should effected.
Eliminate unsafe behavior
19

Questions?

20


				
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