Tailings remediation with dredge mining technology Bart Hogeweg Andrina Drost

Who we are – Royal IHC

• Market leader in integrated vessels, advanced equipment and life-cycle services for the dredging, offshore construction and wet mining markets

• Headquarters in the Netherlands, with a global presence

Outline

• Introduction – why remediate tailings? • Dry vs Wet • Wet mining technology

– Hydro guns – Dredge mining – Combination

• Cost aspects • Summary

Introduction – Poor recoveries

• Example: Ergo Gold Mining in South Africa – Coarse grained sand dumps, high gold grade – Slimes dams, contain lower grades of gold

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Introduction – Secondary commodities

• Example: Palabora in South Africa – Magnetite recovered as by-product of copper

operations, separately stockpiled onsite

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Introduction – Tailings management

• Example: Syncrude in Canada – Oil sands tailings re-handling “Mildred Lake”

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Introduction – Tailings remediation

• Portman Bay in Spain – Galena and sphalerite tailings deposited in sea,

nowadays an environmental threat

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Wet vs. dry method

• Remediation should be profitable, hence low costs preferred

Dry mining Wet mining

Mining Shovels Dredger or hydro guns

Transportation Trucks Pipeline

Delivery to plant Dry material Wet (slurrified) material

Operational costs Relatively high, tailings transported by trucks, high energy costs

Relatively low, since tailings are pumped via pipelines, low energy consumption

Deposit types Tailings heaps, dams and beaches

Tailings heaps, dams, ponds and beaches

Wet method – Hydro guns

• Hydro guns: used at tailings heaps and dams – Example: Minera Valle Central SA., reprocessing

historical copper tailings of Codelco’s El Teniente mine in Chile.

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Wet method – Dredging

• Dredging: used at tailings dams, ponds and beaches – Example: Iron ore tailings rehandling at Carajas

mine, Vale S.A. in Brazil

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Wet method – Combination

• Combination of hydro gun and dredging – Hydro guns loosening tailings from dam/heap,

dredger slurrifies tailings in sump – Example: Stradbroke Island in Australia

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Cost comparison

• Dredge mining has capability for (very) large unit capacity – Hydro guns: 8,000 – 10,000t per day – Dredge mining: 5,000 – 120,000t per day

• Dredge mining integrates excavation and hydraulic transport (pumping) in single piece of equipment. Hydro guns require separate pump stations – Hydro guns: $750,000 per unit (exc pump station) – Mining dredger: $1,500,000 - $20,000,000 per dredger

Operational cost aspects of wet mining

1. Wear (soil properties) 2. Slurry transport distance 3. Diesel driven vs electric driven 4. Production 5. Dredging depth

• Dredge mining with low wear, short transport

distance, electric: ~$0.30-0.60/ton • Dredge mining with high wear, long transport

distance, diesel: ~$0.80-1.50/ton

MAREC

• MAREC Group formed to provide integrated sustainable solutions for tailings remediation projects – Royal Eijkelkamp – Witteveen+Bos Consulting

Engineers – IHC Mining

Summary

• Optimal re-handling technique depends on the project conditions and deposit characteristics

• Hydro guns: tailings heaps • Dredging: tailings dams, ponds and beaches • Combination: tailing dams/heaps with a

significant portion of the material above water table, as well as below

Thank you Royal IHC IHC Mining Advisory Services Bart Hogeweg b.hogeweg@ihcmerwede.com +31 6 1205 0345

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