Mount Woods Magnetite Project — 2013 Technical Report

This report details the proposed processing route for the Mount Woods Magnetite Project, based on testwork on Snaefell deposit samples, with four production rate options considered.

Report context

The July 2013 technical report for the Mount Woods Magnetite Project, owned by IMX Resources Limited, presents the results of testwork and process design for a proposed magnetite beneficiation plant located adjacent to the ROM pad and open pit in South Australia. The project considered nominal (wet) production rates of 1.8 Mtpa, 2.5 Mtpa, 4.7 Mtpa and 9.4 Mtpa. The process design was prepared on the basis of 24-hour continuous operation, 365 days per year, with two 12-hour shifts per day. Plant operating hours were 6,500 hours per year for primary crushing and 8,410 hours per year for fine crushing.

Processing route

Testwork and product specification

The testwork program completed for the Mount Woods Magnetite Project demonstrated that samples provided for the Snaefell deposit could be beneficiated by crushing, grinding, magnetic separation and filtration to produce a 68.5% Fe product with a mass yield in the order of 26% average over the life of mine.

Primary crushing

For the 1.8 Mtpa and 2.5 Mtpa options, jaw crushing was selected as the required feed rate of less than 1,500 tph permitted this technology. For the 4.7 Mtpa and 9.4 Mtpa options, primary gyratory crushers were chosen as the required feed rate exceeded 1,500 tph. The report noted that the ore has relatively low hardness and future studies should consider the possibility of using sizers for primary crushing.

Secondary size reduction

For the 1.8 Mtpa and 2.5 Mtpa options, cone crushers were determined to offer the most economical and lowest risk solution. For the 4.7 Mtpa and 9.4 Mtpa options, HPGR technology was selected as the physical number of cone crushers required became excessive, and HPGR offered a more compact and efficient operation. The crushed product size of 80% passing 5 mm was selected as suitable for treatment by dry LIMS units.

Screening

Banana screen technology was chosen for the project, using a multi-slope configuration to remove fine material quickly at the higher-sloped feed end and efficiently pass near-sized particles at the flatter discharge end. This was selected to maintain the smallest footprint and reduce capital cost.

Low intensity magnetic separation

Two LIMS technologies were used in the plant design. Dry LIMS followed crushing to remove a low-grade rejects stream (approximately one third of feed tonnage) before grinding. Wet LIMS followed milling as an efficient separator of fine magnetite mineralisation. Both technologies use a magnetic field in the range of 1,000 Gauss.

Milling circuit

A single ball mill in closed circuit with hydrocyclones was determined to be the most efficient configuration for each flowsheet option, based on the relative low hardness of the material. The milling circuit was designed to reduce particle size from P80 5 mm to P80 approximately 80 microns. For the 4.7 Mtpa option, three lines of 20-foot diameter ball mills were required; for the 9.4 Mtpa option, six lines were required.

Up current classification

Floatex density separators were selected for fine silica removal from the magnetite concentrate. In these units, solids in the slurry feed settle against an upwards flowing water stream, washing light fine silica particles to the overflow while heavier magnetite particles fall to the base as underflow.

Slurry transport

For the 1.8 Mtpa and 2.5 Mtpa options, a 47 km slurry pipeline was determined to be more economical than a railway. The report identified that keeping the slurry "dirty" (containing ultrafine solids) assists in maintaining suspension during pipeline transport, with classification to be performed at the rail head. For the 4.7 Mtpa and 9.4 Mtpa options, a railway to the plant site was determined to be more economical, with short slurry pipelines (approximately 3 km) to transfer concentrate to the dewatering section.

Process water and desalination

The initial water investigation determined that while sufficient water volume could be sourced, it had a reasonably high level of salinity. A comparison determined that processing in "saline water" followed by fresh water washing provided a better outcome than full desalination. The plant would operate using local borefield water, with a small amount desalinated by reverse osmosis for use as wash water to ensure residual salt in the filtered product did not exceed customer tolerated levels.

Filtration

Vacuum filtration was selected due to the need to wash the filter cake and the relatively coarse nature of the product. The report assumed it would take twice the residual volume of washing water to reduce the alkali content of the concentrate water to a suitable concentration.

Key reported parameters

Note: The table values represent the design basis for the plant and do not show LOM average figures for the entire project.

Technical qualifications

The process design criteria figures represent the design basis for the plant and do not show the LOM average figures for the entire project. The selection of belt filtration and the wash volumes will need to be confirmed through additional testwork and an understanding of the water salinity used in processing that will be carried out in the next phase of project evaluation and development. The report noted that for the 1.8 Mtpa and 2.5 Mtpa options, keeping the slurry "dirty" and performing the classification step at the rail head would reduce overall project risks, but further study work should be undertaken to balance economic pumping costs for pumping "clean slurry" after UCC treatment with pumping "dirty slurry" with final treatment at the remote rail siding. The study assumed water supply is suitable for process use but of insufficient quality for final product filter cake wash water without treatment, to be confirmed with further studies.

Source: Mount Woods Magnetite Project , July 2013 Technical Report, Sections 17.1-17.7.