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OPEN PIT & STOCKPILE ORE CONTROL FOR CYANIDE HEAP LEACHING to PREVENT A SOUR PAD Presented by Thom Seal, Ph.D., PE. Co-Authors: C. L. Bolin SME – Salt.

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Presentation on theme: "OPEN PIT & STOCKPILE ORE CONTROL FOR CYANIDE HEAP LEACHING to PREVENT A SOUR PAD Presented by Thom Seal, Ph.D., PE. Co-Authors: C. L. Bolin SME – Salt."— Presentation transcript:

1 OPEN PIT & STOCKPILE ORE CONTROL FOR CYANIDE HEAP LEACHING to PREVENT A SOUR PAD Presented by Thom Seal, Ph.D., PE. Co-Authors: C. L. Bolin SME – Salt Lake City March 1, 2000 Knight Piesold – ARD Conference – Elko, NV. March 15, 2012

2 ORE CONTROL n Cyanide Leachable - Mill & Heap Leach n Refractory – Mill {Roaster - Autoclave - Flotation} Grade – Leach {Biooxidation - ATS} Grade n Waste – General (Non Acid Generating) – Acid Generating (PAG)

3 METALLURGICAL CHARACTERISTICS n Cyanide Gold Extraction – CN Shake Test - AA for [Au] = AUCN – Fire Assay – AA/FA - Theoretical CN Gold Extraction n Preg. Rob – Spike w/Au CN Shake Test – Determine [Au] Absorbed by Ore – PRV = (AUCN + 0.1) - AUPR n Fuel Value = 1.3 (OrgC) + SS - Target 2.5

4 MINERAL CHARACTERISTICS n Sulfides – Pyrite - FeS 2 GQ - 10 microns (um) + – Arsenopyrite - FeAsS GQ microns (um) n Carbonates – Calcite - CaCO 3 – Dolomite - CaMg(CO 3 ) 2 – Siderite - FeCO 3 n Carbonaceous Material

5 ANALYTICAL n LECO Total Sulfur & Carbon n Sulfur as a Percent – % Sulfate Sulfur = SRO – % Sulfide Sulfur - Roast {% SS} = STOT - SRO n Carbon as a Percent – % Organic Carbon = CAI = OrgC – % Carbonate Carbon - Leach HCl {% CC} – % CC = CTOT - CAI

6 AGP n Acid Generating Potential - AGP – Equal to * % SS n Sample Equation: – 2 FeS O H 2 O 2 FeSO H SO 4 2- n Leads to Acid Rock Drainage

7 ANP n Acid Neutralization Potential - ANP – Equal to 3.67 * % CC n Sample Equation: – CaCO H + + SO 4 2- CaSO 4 + H 2 O + CO 2

8 NCV n Net Carbonate Value - NCV – Equal to ANP + AGP – NCV = 3.67 * % CC * % SS

9 EQUATIONS n Cyanide Hydrolyses at pH < 10 – CN - + H 2 O HCN + OH - n Cyanide Reaction with Sulfides – 2 FeS + 12 CN O H 2 O 2 Fe(CN) SO OH - n Lime Hydrolyses – CaO + H 2 O Ca(OH) 2

10 LIME USE MODEL n Net Reaction – 4 FeS CaO + 15 O H 2 O 4 Fe(OH) CaSO 4 n Regression Model – Lime (pounds/ton) = * NCV – Multiply by Safety Factor: Using S.F. = 2 for NA Stockpiles

11 LIME USE AND COLUMN TESTS

12 CYANIDE USE MODEL

13 GOLD EXTRACTION AND NCV

14 BLAST HOLE INFORMATION

15 GOLD QUARRY PIT - POLYGON

16 LIME USE MODEL n Net Reaction – 4 FeS CaO + 15 O H 2 O 4 Fe(OH) CaSO 4 n Regression Model – Oxide Ore – Lime (pounds/ton) = * NCV – Multiply by Safety Factor: Using S.F. = 2 for NA Stockpiles

17 LIME USE MODEL n Regression Model – ARD Stockpile Ore Lime (pounds/ton) = 6.68 – 7.68 * CC * SRO 1.09 CC = % Carbonate Carbon SRO = % S as SO 4 (Sulfate Sulfur)

18 Lime Model for ARD Stockpiles

19 NAL Gold Production

20 NAL Solution Grade

21 Gold Quarry Results n 2.6 million stockpile tons n 2.5 million mines tons n 85,000 recovered Au oz. n Net Revenue n $ 18,000,000 n

22 CONCLUSIONS n Reagent Utilization is Ore Dependant n Run of Mine Ore to have + NCV Value n Biooxidation of Ores with NCV Values less than n Caustic Cost is 7.5 times higher than Lime n Cyanide Cost is 22 times higher than Lime n Ore Destination by Grade, AA/FA, Preg. Rob and NCV Value


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