dry stacking operation at pogo mine, alaska
TRANSCRIPT
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Dry Stacking Operation
at Pogo Mine, Alaska June 12, 2014
Sumitomo Metal Mining Pogo LLC
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Contents
1. About Pogo Mine
• Geology
• Mining and paste backfill
• Process
2. Dry Stacking Operation
• About Dry Stack Tailings Facility (DSTF)
• Flotation tailings geotechnical characteristics
• Monitoring
3. Operational Challenges
• Filter plant issues
• DSTF construction design
• Lessons learnt
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Tokyo
Tokyo
Chiba
Kanagawa
Kagoshima
Toyo Smelter Ehime
Hyogo
SMM’s Core Facilities in Japan
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SMM’s Overseas Assets
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Tintina Gold Belt
N. W. T.
Y U K O N
B. C.
A L A S K A
DONLIN CK.
11.4 M oz
TRUE NORTH
1.3 M oz DUBLIN GULCH
3.1 M oz
POGO/LIESE ZONE
5 Moz Au
FORT KNOX
8.8 M oz
TINTINA GOLD BELT
SIGNIFICANT GOLD DEPOSIT
GOLD DEPOSIT or OCCURRENCE400 kilometers
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Geologic Map
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Orebodies
Looking NE
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Liese Zone
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Pogo Mine as of 1999
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Goodpaster River
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Pogo Mine as of 2005
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Drift & Fill Mining Method
15m
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Paste Plant Process Flow
Recycle Tailing Pond
(RTP)
Floatation tailing thickener
CIP tailing thickener Overflow
UnderflowUnderflow
Cement silo
Filter press
Filter cake stock pile
UndergroundHigh-Pressure Paste Pump
Paste
FCU/FCIP tailing
BFD waterCement
RTP water
tanktank
tank
tank
Flotation tailing thickener
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Paste Backfill in Stope
Stope void
Barricade Blast off
Plan view
Cross section
Paste pipe
Breathing pipe
Blast off point
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Paste Backfill - Barricade
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Paste
Backfill
Cut 1
Cut 2
Exposed Paste Backfill Wall
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Processing
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Pogo Process Flow
Surface Disposal
Flotation TailingCIP Tailing
Filtering
Paste Backfill
ILR
Regrind Leach/CIP/Stripping
EW
CN Destruct
Cyanide ContactGrinding
Gravity
Flotation
Non Cyanide Contact
90%10%
60%
40%
Concentrate
ILR: Intensive Leach Reactor
EW: Electrowinning
CIP: Carbon-in-Pulp
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Production
0.0
0.5
1.0
1.5
2.0
2.5
0
100
200
300
400
500
600
700
800
900
1000
2006 2007 2008 2009 2010 2011 2012 2013
Cu
mu
lati
ve A
u P
rod
uct
ion
(Mo
z)
Ore
Pro
cess
ed
(kt
pa)
Au Production - Cumulative (oz)
Ore Processed (ktpa)
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Dry Stack Tailings Facility (DSTF)
Why DSTF?
• Geographical and geotechnical restrictions for
conventional tailings dam:
• Narrow and steep valleys;
• Deep alluvial valley infillings;
• Permafrost.
• Lowest operational risks:
• Non-susceptible to liquefaction failures;
• Less impact on surface and ground water quality.
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DSTF – Plan & Cross Section
(as of Sep. 2013)
60m
Recycle
Tailings
Pond
Inlet 1
Inlet 2
Inlet 3 Inlet 4
New Diversion Ditch
New Haul Road
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Flow-through Drain
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Recycle Tailings Pond (RTP)
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Diversion Ditch Construction
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Inlet Construction
Insulation Board
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New South Flume
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Filtering Process Open Filter Plate Pack
Filter Press
• Filter Plates: 6m2 x 24/each
• Cycle Time: Approx. 15 min.
• Capacity: 9dt/batch
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Dry Stacking Process
①
②
③
④
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Flotation Tailings – Grain Size Distribution
• Permeability (saturated): 1.6~7.8×10-6 cm/sec
Grain Size (mm)
Pe
rce
nt
Fin
er
80%
75μm
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Geotechnical Properties of Flotation Tailings
Water Content (%)
Dry
Density (
pcf) 15.8%, 109.8 pcf
Standard Proctor Test
90%
95%
Direct Shear Test (Normal Stress: 24~120kPa)
100%
35
36
37
38
39
40
41
42
43
90% 95% 100%
Fric
tio
n A
ngl
e (
de
gre
e)
Compaction Effort
1.75 g/cm3
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1.3
1.4
1.5
1.6
1.7
1.8
4 6 8
Dry
De
nsi
ty (
g/cm
3)
No. of Passes
1 Day
2 Days
3 days
7 Days
Dry Stacking under Cold Weather
Air Temp. during Compaction Test: -23 ~ -7℃
90%
100%
Frozen Dewatered Tailings
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Stability Evaluation (18Mt Facility)
Material Name ColorUnit Weight
(g/cm3)
Sat. Unit
Weight
(g/cm3)
Cohesion
(kPa)
Internal
Friction Angle
(deg)
Compacted Tailings 1.68 2.05 0 34
Tailings@GPA 2.00 2.40 0 34
Rock Shell 2.00 2.40 0 38
Flow-through Drain 2.00 2.40 0 38
Starter and Toe Berm 2.00 2.40 0 32
Overburden 2.00 2.40 0 32
Bedrock 2.50 2.50 0 40
Pseudostatic analysis, considering:
• Vertical ground acceleration
(upward)
• Excess pore pressure
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Geotechnical Monitoring at Shells
Nuclear Densometer
Shell 2
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Water Quality Monitoring at DSTF
:Surface water sampling point
:Ground water monitoring wells
:Flumes with pressure transducer (Flow measurement)
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Piezometer Installation
SB-1 GP-1 RR-1
SB-1 GP-1
RR-1
2012 DSTF Extent
18Mt DSTF Extent
2012 DSTF Extent
18Mt DSTF Extent
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Piezometer Installation - Major Findings
• Permafrost exists within
DSTF;
• Phreatic surface exists near
the base of DSTF;
• Density and geotechnical
properties of in-situ samples
coincide well with past
laboratory test results;
• Potential of acid rock
drainage from DSTF is
minimal.
Vibrating Wire Piezometer
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Operational Challenges
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Filter Plant Issues
• Poor performance of filter
presses:
• Plan: 2,040tpd with two filters
• Actual: 1,360tpd
• Causes:
• Longer cycle time
• Lower mechanical availability:
• Excess wear of filter cloths
• Frequent mechanical failure
Pinhole on the cloth
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0
2
4
6
8
10
12
14
16
18
Plan Actual
Cyc
le T
ime
(m
in)
Cake Discharge
Air Blowing
Press
Filtration
Cycle Time for Dewatering
• More fine particles
(<20µm) than plant
test
• Higher dilution of
waste rock?
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0
500
1000
1500
2000
2500
3000
20
07
20
08
20
09
20
10
20
11
20
12
20
13
Cycles per cloth
Excess Wear of Filter Cloths
Causes
• Debris in slurry → Pinholes
• Folding of cloths
Solutions
• Trash removal screen and
strainers
Target
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60%
65%
70%
75%
80%
85%
90%
95%
100%
20
07
20
08
20
09
20
10
20
11
20
12
20
13
Mechanical Availability of
Filters (%)
Mechanical Availability of Filters
Causes
• Excess parts wear
Solutions
• Washing & Maintenance!
• Dayshift:
Two filters in operation,
one in maintenance
• Nightshift:
Three filters in operation
Target
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DSTF Construction Design Issues
60m
Extent of 2015
STARTER
BERM
FLOW THROUGH
DRAIN
GENERAL PLACEMENT
AREA SHELL DEPOSITION
AREA
ROCKFILL TOE
BERM
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DSTF Construction – Plan vs. Actual
Rock Shell
Shell Deposition Area General Placement Area
Plan
Actual
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DSTF Placement Tonnage - Plan vs. Actual
Plan Actual
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
11.0
12.0
13.0
Pre
-200
6
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
Cu
mu
lati
ve T
on
nag
e (
Mt)
Flotation TailingsWaste Rocks
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
11.0
12.0
13.0
Pre
-200
6
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
Cu
mu
lati
ve T
on
nag
e (
Mt)
Flotation TailingsWaste Rocks
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Lessons Learnt on Dry Stacking
• Dewatering:
• Expect more fine particles;
• Consider abrasiveness of
tailings;
• Remove debris from feed.
• DSTF Construction Design:
• General Placement Area with
Rock Shell;
• Haul road planning with the
raise of GPA;
• Conservative placement plan.
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Thank you for your attention!