7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
1/42
Use of Intensive Cyanidation to treatSilver Flotation Concentrates
Presenter: Nigel Grigg, General Manager, Gekko Systems SA
Nick Katsikaros, Product Improvement Manager, Gekko SystemsVictor Delgado, Manager, Metallurgical Processes, Hochschild Mining PLC
Tim Hughes, R & D Manager, Gekko Systems
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
2/42
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
3/42
Intensive Cyanidation leaching is carried out at elevatedlevels of sodium cyanide levels ranging between 5,000 50,000 ppm, in rich oxygen environment >15 ppm dO
High Metal Volume Leaching Rates ConcentratedRecovery
Compare CIL and IC producing ~500oz/day
Medium grade CIL producing ~500 oz/day @ 150 t/h at 4 ppm Au; 45% solids; 24h leach; 5800m 3Volumetric leaching rate = 0.1 gAu/m 3 /hr IC treating BCC concentrate ~500 oz/day @ 2 t/day conc at 7500 ppm Au; 1.5m 3 active volume; 15 hleachVolumetric leaching rate = 700 gAu/m 3 /hr
IC is 7,000 times more space efficient than CIP.
What is Intensive Cyanidation
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
4/42
What is the ILR?
ILR (Inline Leach Reactor) is Gekko Systems IC concentratetreatment system for gold and silver
Batch and continuous designs Suitable for high and low grade concentrates Based on a rolling drum system Fully automated
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
5/42
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
6/42
2. The Continuous Flowsheet
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
7/42
Partially Leached Gold Particle Showing Diffusion Layer Continuous removal of this layer significantly improves
leach kinetics The rolling action attritions this layer providing high shear
required for IC conditions
Mixing Drives IC Kinetics
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
8/42
1)The high shear mixing zoneremoves the attrition layer fromthe gold speeding up cyanideaccess to the gold surface
2) Solution mixing zone Solutionis drawn out and oxygen is drawn
in.
3) Pure oxygen Zone ensuring highdissolved oxygen levels aresustained.
4) High surface area forsolution/oxygen interface
5) Solution solid mixing zone forfast kinetics and an efficientchemical reaction
ILR Cross Section
ILR Cross Section
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
9/42
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
10/42
CASE STUDY - MINE BACKGROUND
HOCHSCHILD SELENE MINE Underground silver mine in Peru ~1,000 tonne/day plant (2006)
~13.5 tonne/day high grade Au concentrate Sold the flotation concentrate to smelters Started an Investigation into cheaper way to treat the
concentrates Contacted Gekko to look at a leach facility at the Ares plant
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
11/42
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
12/42
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
13/42
ILR10000 Module Ares Site
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
14/42
Site Specific - Modifications
Modifications - Fine Feed (
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
15/42
ARES - ILR COMMISSIONING
CommissioningTake 1
Only peroxideavailable
Buildingincomplete
Temp slightlylower thanpreviouslyconsidered asambient!
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
16/42
ARES - ILR COMMISSIONING
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50
R e c o v e r y
%
leaching time hr
Batch 1 Peroxide and Lead Nitrate
Au Recovery Ag Recovery d O2
Batch 1 Summary Lead Nitrate added twice
(6h and 24h) Effectively leaching was
completed in 18h DO at target after 10h Poor leaching
performance ? 60% recovery Panic? No not yet...
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
17/42
ILR COMMISSIONING
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60
R e c o v e r y
%
leaching time hr
Batch 2 Peroxide and Lead Nitrate
Au by solid Ag by solid sO2
Batch 2 Summary 82% Au Recovery 80% Ag Recovery Total leach time 57.5h Low DO until 16 hours Lower peroxide addition Suspected some form of
silver coating orcompound was forming
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
18/42
ILR COMMISSIONING
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50
R e c o v e r y
%
leaching time hr
Batch 3 Peroxide and Lead Nitrate
Au Recovery Ag Recovery d O2
Batch 3 - Summary 15kg/t lead nitrate;
peroxide before cyanide A Pre-oxidation process? Solution assays gave erratic
results 71% Au Recovery 91% Ag Recovery Some promise!
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
19/42
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
20/42
ILR COMMISSIONING
CommissioningTake 2
Installation 99%complete
Oxygen andperoxide available
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
21/42
ILR Commissioning
Reground conc. in processwater
Constant peroxide add
Leach time +50 hours96% Au Recovery87.8% Ag Recovery
Fast initial leaching but
then slowed. Recoveries measured by
solids assay
Batch 4 - Summary
0
10
20
30
40
50
6070
80
90
100
0 10 20 30 40 50
R e c o v e r y
%
leaching time hr
Batch 4 - Process Water Regrind and Peroxide
Au Recovery Ag Recovery d O2
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
22/42
ILR Commissioning
Batch 5 - Summary 65 hours
97.1% Au Recovery92.6% Ag Recovery
Slow rates initially
limited by oxygen flow Final leach rate faster
than Batch 4 DO increases as oxygen
demand drops Leach time is +60 h Leaching incomplete
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60
R e c o v e r y
%
leaching time hr
Batch 5 - Process Water Regrind and Oxygen
Au Recovery Ag Recovery d O2
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
23/42
ILR Commissioning
Peroxide additionreduced to keep dObelow 10ppm.
Fast initial rates andimproved final rates. 48 hours
97.5% Au Recovery94.3% Ag Recovery
Getting closer.. .
Batch 6 - Summary
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50
R e c o v e r y
%
leaching time hr
Batch 6 - Barren Solution Regrind and ControlledPeroxide Addition
Au Recovery Ag Recovery d O2
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
24/42
ILR Commissioning
Peroxide until dO < 6ppm;with oxygen
48 hours
97.7% Au Recovery96.4% Ag Recovery
End of Gekko
commissioning on site Optimization...
Batch 7 - Summary
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50
R e c o v e r y
%
leaching time hr
Batch 7 - Barren Solution Regrind and CombinedOxidant
Au Recovery Ag Recovery d O2
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
25/42
ILR Commissioning
Hypothesis was that high peroxide concentration was creating aslow leaching silver phase or causing a passivation coating.
Reducing peroxide to keep dO below 6ppm improved recovery.
Oxygen generator eventually returned as at high altitude itwas inefficient and expensive. Oxygen was not required.
Operational optimisation of other steps, including clarificationreduced total cycle times.
Batch 8 onwards ...
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
26/42
Conclusion
Hochschild now produce Silver dore from high grade flotationconcentrates at the Ares site.
Recoveries of + 98% for gold and silver using dO controlled
peroxide addition, achieved within the 48hrs Recoveries matched the testwork predictions. Able to produce dore or sell to the smelter dependant on
requirements.
5 more ILR5000 units purchased to increase production capacity
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
27/42
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
28/42
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
29/42
Leach Kinetics Grind Sensitive
P80 = 212 um 12hrs - 96% recovery Combined gravity and
flotation concentrates
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
30/42
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
31/42
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
32/42
PFD - Proposed
ILR18hrs Filtration Direct EWC Bleed to MC Detoxification Silver Dore
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
33/42
Electrowinning Modelling?
Electrowinning modelling Very high current effeciencies are achieved at high silver
grades Direct electrowinning a cost effective recovery option
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
34/42
Other Elements?
Other elements inleach into solution?
Need to consider a
zero discharge circuit
But locked cycle testshowed a drop in leachrecovery
Require Detoxification
of a bleed stream
Ag Silver 2677 Cu Copper 223
Al Aluminium
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
35/42
Detoxification -Cyanide Oxidation
Natural Degredation Alkaline Chlorination Ozone CAROs Acid
H2O2 SO2/AIR
The last 2 options peroxide and INCO process arethe most common.
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
36/42
Terminology Total, WAD, Free
Fe CNAu CN
Ni CN
Cu CNZn CNAg CN
CN-, HCN= CN F
CN WAD
CNTOT
stronglycomplexed
CNF = Free Cyanide CN WAD = Weak Acid DissociableCNTOT = Total Cyanide OCN - = Cyanate
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
37/42
After H 2O2 Test work ?
Detox able to get WAD cyanide levels down well under
international discharge to a TSF standards (50ppmWAD) Detox also precipitated out other metals and so we were able
to maintain leach recoveries.
Feed CNwad Peroxide:CNwad Ratio Final Solution CNwad\
16.2 gpl 10:1 2.93 ppm
16.2 gpl 5:1 7.16 ppm
1.62 gpl 10:1 1.16 ppm
1.62 gpl 5:1 2.81 ppm
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
38/42
ILR Models ILR45K for Silver Concentrates
ILR Models - increasing in size
6 x ILR5000 = 1 x Super ILR45K Design for High Volumes 56tpbatch Flotation concentrates 5tph @ 10hrs residence time
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
39/42
ILR Models ILR45K for Silver Concentrates
Super ILR45K
Design for High Volumes
i.e. Flotation concentrates
56tpbatch @ 24hrsresidence time
5tph @ 10hrs residencetime
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
40/42
Conclusion
Intensive Cyanidation of Silver Flotation concentratesis feasible
It offers many financial benefits to the company The ILR is a suitable IC unit Ensure locked cycle test work is performed and
modelling is performed with locked cycle testsolutions
Gekko are continuing to develop a range of technology and services to provide clients withsuitable options
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
41/42
7/27/2019 17.10 - NIGEL GRIGG - Silver Concentrate Leaching Presentation 2012 Final
42/42
Questions
Top Related