Dry Stacking Operation at Pogo Mine, Alaska June 12, Sumitomo Metal Mining Pogo LLC

Transcription

1 Dry Stacking Operation at Pogo Mine, Alaska June 12, 2014 Sumitomo Metal Mining Pogo LLC

2 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

3 SMM s Core Facilities in Japan Tokyo Hyogo Tokyo Chiba Toyo Smelter Ehime Kanagawa Kagoshima

4 SMM s Overseas Assets

5 Tintina Gold Belt A L A S K A N. W. T. TRUE NORTH FORT KNOX 1.3 M oz 8.8 M oz DUBLIN GULCH 3.1 M oz Y U K O N DONLIN CK M oz POGO/LIESE ZONE 5 Moz Au B. C. 400 kilometers TINTINA GOLD BELT SIGNIFICANT GOLD DEPOSIT GOLD DEPOSIT or OCCURRENCE

6 Geologic Map

7 Orebodies Looking NE

8 Liese Zone

9 Pogo Mine as of 1999

10 Goodpaster River

11 Pogo Mine as of 2005

12 Drift & Fill Mining Method 15m

13 Paste Plant Process Flow Flotation Floatation tailing thickener CIP tailing thickener Overflow Underflow Underflow tank Cement silo tank Recycle Tailing Pond (RTP) Filter press tank tank Paste FC U/F CIP tailing BFD water Cement RTP water Filter cake stock pile High-Pressure Paste Pump Underground

14 Paste Backfill in Stope Plan view Barricade Blast off Stope void Cross section Paste pipe Breathing pipe Blast off point

15 Paste Backfill - Barricade

16 Exposed Paste Backfill Wall Cut 2 Cut 1 Paste Backfill

17 Processing

18 Pogo Process Flow Grinding Non Cyanide Contact Cyanide Contact Gravity ILR EW Flotation Regrind Concentrate Flotation Tailing 90% Filtering Surface Disposal 60% Leach/CIP/Stripping CN Destruct CIP Tailing Paste Backfill 40% 10% ILR: Intensive Leach Reactor EW: Electrowinning CIP: Carbon-in-Pulp

19 Ore Processed (ktpa) Cumulative Au Production (Moz) Production Au Production - Cumulative (oz) Ore Processed (ktpa)

20 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.

21 DSTF Plan & Cross Section (as of Sep. 2013) New Haul Road Inlet 1 Inlet 2 Recycle Tailings Pond New Diversion Ditch Inlet 4 Inlet 3 60m

22 Flow-through Drain

23 Recycle Tailings Pond (RTP)

24 Diversion Ditch Construction

25 Inlet Construction Insulation Board

26 New South Flume

27 Filtering Process Open Filter Plate Pack Filter Press Filter Plates: 6m 2 x 24/each Cycle Time: Approx. 15 min. Capacity: 9dt/batch

28 Dry Stacking Process

29 Percent Finer Flotation Tailings Grain Size Distribution 80% 75μm Grain Size (mm) Permeability (saturated): 1.6~ cm/sec

30 Dry Density (pcf) Friction Angle (degree) Geotechnical Properties of Flotation Tailings 100% 95% 90% 15.8%, g/cm pcf 3 Water Content (%) % 95% 100% Compaction Effort Standard Proctor Test Direct Shear Test (Normal Stress: 24~120kPa)

31 Dry Density (g/cm 3 ) Dry Stacking under Cold Weather % % No. of Passes 1 Day 2 Days 3 days 7 Days Air Temp. during Compaction Test: -23 ~ -7 Frozen Dewatered Tailings

32 Stability Evaluation (18Mt Facility) Pseudostatic analysis, considering: Vertical ground acceleration (upward) Excess pore pressure Material Name Color Unit Weight (g/cm 3 ) Sat. Unit Weight (g/cm 3 ) Cohesion (kpa) Internal Friction Angle (deg) Compacted Tailings Tailings@GPA Rock Shell Flow-through Drain Starter and Toe Berm Overburden Bedrock

33 Geotechnical Monitoring at Shells Nuclear Densometer Shell 2

34 Water Quality Monitoring at DSTF :Surface water sampling point :Ground water monitoring wells :Flumes with pressure transducer (Flow measurement)

35 Piezometer Installation 2012 DSTF Extent SB-1 GP-1 RR-1 18Mt DSTF Extent SB-1 GP-1 RR-1 18Mt DSTF Extent 2012 DSTF Extent

36 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

37 Operational Challenges

38 Pinhole on the cloth 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

39 Cycle Time (min) Cycle Time for Dewatering Cake Discharge More fine particles (<20µm) than plant test Higher dilution of waste rock? 8 Air Blowing 6 Press 4 Filtration 2 0 Plan Actual

40 Excess Wear of Filter Cloths Cycles per cloth Target Causes Debris in slurry Pinholes Folding of cloths Solutions Trash removal screen and strainers

41 Mechanical Availability of Filters 100% 95% 90% 85% 80% 75% 70% 65% Mechanical Availability of Filters (%) Target Causes Excess parts wear Solutions Washing & Maintenance! Dayshift: Two filters in operation, one in maintenance Nightshift: Three filters in operation 60%

42 DSTF Construction Design Issues Extent of 2015 SHELL DEPOSITION AREA GENERAL PLACEMENT AREA ROCKFILL TOE BERM STARTER BERM FLOW THROUGH DRAIN 60m

43 DSTF Construction Plan vs. Actual Plan Shell Deposition Area General Placement Area Actual Rock Shell

44 Pre Pre Cumulative Tonnage (Mt) Cumulative Tonnage (Mt) DSTF Placement Tonnage - Plan vs. Actual Plan Actual Flotation Tailings Waste Rocks Flotation Tailings Waste Rocks

45 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.

46 Thank you for your attention!