Name and Location
Thunderbird mineral sands project, Australia.

Client
Sheffield Resources.

Project Description
A prefeasibility study (PFS) completed on the project has confirmed the technical viability, and economics of the Thunderbird project.

The study is based on a mineral resource of 3.2-billion tonnes, grading 6.8% heavy minerals for 19.3-million tonnes of zircon, 61.1-million tonnes of ilmenite and eight-million tonnes of leucoxene.

At a planned mining rate of 18-million tonnes a year after ramp-up, average annualised production over a 32-year mine life is estimated to be 114 000 t of zircon, 439 000 t of ilmenite and 30 000 t of HiTi84 leucoxene.

The proposed mining technique is a strip mining and backfill method typically used in dry mining operations in the mineral sands industry.

At the proposed run-of-mine feed rate of 2 340 t/h, six large dozers will deliver the ore to three 810 t/h skid-mounted dozer trap mining unit plants (MUPs). A fourth standby MUP is required to minimise downtime during mine-face relocation.

Ore mining will be supported by a fleet of three loaders and three 100 t trucks. Waste mining, oversize removal and dam wall construction and rehandle will be conducted using a fleet comprising loaders, trucks, excavators and scrapers. Low strip ratios in the early years will enable the ore mining fleet to also service the waste mining load.

The MUPs will screen coarse oversize ore, with undersize ore to be fed to a scrubber trommel. The undersize from the trommel will be slurried and pumped to the wet concentrator plant (WCP). Maximum pumping distance from the MUPs to the WCP is 2 100 m.

This will require the WCP to be relocated in production years 12, 20 and 28. The slurried ore from the MUPs will be combined at the WCP, screened at 2 mm and –2 mm fraction, then further slurried before being deslimed on dual cyclone clusters.

Cyclone underflow will be transferred to two identical gravity circuits comprising eight stages of spiral separators, which will separate sand from the heavy minerals. Cyclone overflow will be transferred to a deep cone thickener for the recovery of process water.

Thickened underflow (clay slimes) will be pumped initially into an off-path tails dam and later codisposed with sand tails into the mine void. Tailings codisposal testwork indicates polymer-treated tails will achieve high consolidation rates, with high water recovery from tailings expected.

The WCP will be a semipermanent, relocatable plant, built on skids.

Processing water for slurrying and the WCP will be supplied by a process water dam near the WCP.

The heavy minerals concentrate (HMC) will be slurried and pumped to the mineral separation plant (MSP). The HMC will be received at a concentrate upgrade plant at the MSP site, where it will be screened at 850 μ, with undersize material separated using magnetic and gravity separation techniques to produce magnetic (ilmenite-bearing) and nonmagnetic (HiTi 84 and zircon-bearing) concentrates and tails.

Magnetic concentrate will be pumped to an attritioner to remove surface coatings and then pumped to an ilmenite dry plant (IDP) for drying and further processing.

Nonmagnetic concentrate from the wet high-intensity magnetic separator will be processed through several stages of gravity concentration using spiral concentrators.

It will then be pumped to the hot acid leach plant (HAL) for dewatering and storage. Additional processing of magnetics streams from the primary zircon circuit, including batch feeding using a HAL stage, will produce secondary and special zircon products.

Conductors from the primary electrostatic circuit will be processed by a second stage of electrostatic separation to produce a HiTi84 (87.7% titanium dioxide) product, which will be bagged for export.

The magnetics received at the IDP will be dried, screened and then separated using one circuit of electrostatic separators to produce ilmenite product and rejects.

The MSP will be a fixed plant and will be located approximately 500 m from the initial WCP site for the first 12 years.

Overall zircon recovery, excluding semiprocessed and recirculated streams, is calculated at 67%.

Net Present Value/Internal Rate of Return
Not stated.

Value
The capital cost of the project is estimated at $394.1-million.

Duration
Commissioning work is expected in 2018 and the first full year of production is targeted for 2019.

Latest Developments
The PFS will be updated in the second half of 2015 to include positive infill drilling results yet to be incorporated and to focus on reducing costs and increasing margins.

A definitive feasibility study for the project is planned for 2016, followed by mine construction in 2017.

Key Contracts and Suppliers
None stated.

On Budget and on Time?
Not stated.

Contact Details for Project Information
Sheffield Resources, tel +61 8 6424 8440, fax +61 8 9321 1710 or email info@sheffieldresources.com.au.