Transcript open pit & stockpile ore control for cyanide heap

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
ORE CONTROL
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Cyanide Leachable - Mill & Heap Leach
Refractory
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Mill {Roaster - Autoclave - Flotation} Grade
Leach {Biooxidation - ATS} Grade
Waste
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General (Non Acid Generating)
Acid Generating (PAG)
METALLURGICAL
CHARACTERISTICS
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Cyanide Gold Extraction
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Preg. Rob
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CN Shake Test - AA for [Au] = AUCN
Fire Assay
AA/FA - Theoretical CN Gold Extraction
Spike w/Au CN Shake Test
Determine [Au] Absorbed by Ore
PRV = (AUCN + 0.1) - AUPR
Fuel Value = 1.3 (OrgC) + SS - Target 2.5
MINERAL
CHARACTERISTICS
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Sulfides
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GQ - 10 microns (um) +
GQ - 1-2 microns (um)
Carbonates
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Pyrite - FeS2
Arsenopyrite - FeAsS
Calcite - CaCO3
Dolomite - CaMg(CO3)2
Siderite - FeCO3
Carbonaceous Material
ANALYTICAL
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LECO Total Sulfur & Carbon
Sulfur as a Percent
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% Sulfate Sulfur = SRO
% Sulfide Sulfur - Roast {% SS} = STOT SRO
Carbon as a Percent
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% Organic Carbon = CAI = OrgC
% Carbonate Carbon - Leach HCl {% CC}
% CC = CTOT - CAI
AGP
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Acid Generating Potential - AGP
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Sample Equation:
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Equal to - 1.37 * % SS
2 FeS2 + 7 O2 + 2 H2O 
2 FeSO4 + 4 H+ + 2 SO42-
Leads to Acid Rock Drainage
ANP
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Acid Neutralization Potential - ANP
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Equal to 3.67 * % CC
Sample Equation:
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CaCO3 + 2 H+ + SO42- 
CaSO4 + H2O + CO2
NCV
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Net Carbonate Value - NCV
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Equal to ANP + AGP
NCV = 3.67 * % CC - 1.37 * % SS
EQUATIONS
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Cyanide Hydrolyses at pH < 10
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Cyanide Reaction with Sulfides
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CN- + H2O  HCN + OH2 FeS + 12 CN- + 5 O2 + 2 H2O 
2 Fe(CN)64- + 2 SO42- + 4 OH-
Lime Hydrolyses
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CaO + H2O  Ca(OH)2
LIME USE MODEL
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Net Reaction
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4 FeS2 + 8 CaO + 15 O2 + 6 H2O 
4 Fe(OH)3 + 8 CaSO4
Regression Model
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Lime (pounds/ton) = 5.066 - 2.6874 * NCV
Multiply by Safety Factor: Using S.F. = 2 for
NA Stockpiles
LIME USE AND
COLUMN TESTS
Lime Addition to Oxide CN Extractions vs. NCV
Column Model: CaO (lbs/ton) = 5.066 - 2.6874 * NCV
25
Lime lbs/ton
20
15
10
y = -2.6874x + 5.066
R2 = 0.5904
5
Column Tests
Linear (Column Tests)
0
-5
-4
-3
-2
-1
NCV
0
1
2
3
CYANIDE USE MODEL
Cyanide Addition to Oxide CN Extractions vs. NCV
Column Model: NaCN (lbs/ton) = 0.505 - 0.1534 * NCV
1.8
Column Tests
1.6
Linear (Column Tests)
NaCN lbs/ton
1.4
1.2
1
0.8
0.6
y = -0.1534x + 0.505
R2 = 0.477
0.4
0.2
0
-5
-4
-3
-2
-1
NCV
0
1
2
3
GOLD EXTRACTION
AND NCV
Percent of Total Gold Extracted
Percentage of Total Gold Extraction as a function of NCV
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
-5
-4
-3
-2
-1
Column Tests
0
NCV
1
2
3
4
BLAST HOLE
INFORMATION
Gold Quarry Blast Hole Information
Class
Drill Hole #
LGL
13645
99
Au Fire Assay [AuFA] 0.031
Ratio AuCN/AuFA 0.323
016 Pattern #
0.010 CN Extractable Au [AuAA]
0.006 Preg. Rob Value [AuPR]
Series #
Total Sulfur [STOT]
Sulfate S [SRO]
Sulfide S [SS]
Fuel Value [FV]
Low Recovery General Leach
1.32
0.43
0.89
0.96
0.06
0.05
0.02
-1.17
Total Carbon [CTOT]
Organic Carbon [OC]
Carbonate Carbon [CC]
Net Carbonate Value [NCV]
GOLD QUARRY PIT POLYGON
Gold Quarry Pit
Bench:
4550
Poly Num: C245
Mat'l Class: LGL
Tons:
10,397
AuFA:
0.04
AuAA:
0.02
AA/FA Ratio:
43%
Newmont Mining Co.
SS%:
1.06
OC%:
0.04
CC%:
0.02
NCV:
-1.37
Lime #/ton: 10.5
December 2,1999
Spacing:
18'
Drill Depth: 30'
Hole Dia:
7.9"
LIME USE MODEL
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Net Reaction
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4 FeS2 + 8 CaO + 15 O2 + 6 H2O 
4 Fe(OH)3 + 8 CaSO4
Regression Model – Oxide Ore
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Lime (pounds/ton) = 5.066 - 2.6874 * NCV
Multiply by Safety Factor: Using S.F. = 2 for
NA Stockpiles
LIME USE MODEL
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Regression Model – ARD Stockpile Ore
Lime (pounds/ton) =
6.68 – 7.68 * CC1.01 + 45.7 * SRO1.09
CC = % Carbonate Carbon
SRO = % S as SO4 (Sulfate Sulfur)
Lime Model for ARD Stockpiles
NA Stockpiles [Lab Lime vs Stk Lime Model-1]
Lab Lime #/ton
50
40
30
20
R2 = 0.7075
10
0
0
10
20
30
Stk Lime Model-1 #/ton
40
NAL Gold Production
NAL Gold Production - 3Q 2001
Au oz/ton Solution
800
700
600
500
400
300
6/18
7/8
7/28
8/17
Shifts
9/6
9/26
10/16
NAL Solution Grade
Au oz/ton Solution
NAL Preg Grade - 3Q 2001
0.018
0.017
0.016
0.015
0.014
0.013
0.012
0.011
0.01
6/18
INPreg
7/8
7/28
8/17
Shifts
9/6
9/26
10/16
Gold Quarry Results
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2.6 million stockpile tons
2.5 million mines tons
85,000 recovered Au oz.
Net Revenue
$ 18,000,000
1996 - 1999
CONCLUSIONS
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Reagent Utilization is Ore Dependant
Run of Mine Ore to have + NCV Value
Biooxidation of Ores with NCV Values less than 2.0
Caustic Cost is 7.5 times higher than Lime
Cyanide Cost is 22 times higher than Lime
Ore Destination by Grade, AA/FA, Preg. Rob and
NCV Value