This report presents the proposed recovery methods for the Iron Hills Project, detailing the designed process to beneficiate magnetite ore from the Barlow deposit into high-grade concentrate.
Report context
The Iron Hills Project Preliminary Economic Assessment, dated October 2025 (DRA Ref.: G9161-0000-PM-REP-0001-Rev. 0), describes a proposed iron ore processing facility for the Barlow deposit. The recovery methods section (Section 17) outlines the designed beneficiation process, which relies on conventional physical separation techniques including crushing, grinding, magnetic separation, and flotation. Both the crushing and concentrator plants were designed by DRA at a PEA level.
Processing route
Crushing circuit
The proposed crushing plant is designed to process approximately 11.00 Mdmtpa of crushed crude ore. With an allowance of twenty days per year for major repairs and maintenance, the crusher system is planned to operate 24 hours per day, 345 days per year (8,280 hours per year). Based on an operational utilization rate of 74.06%, the total effective operating hours available for crushing is 6,132 hours per year.
ROM ore with a nominal F100 of 1,000 mm and nominal F80 of 589 mm will be dumped into a dump hopper. Oversized material will be broken down using a hydraulic rock breaker. Material will be transferred from the dump hopper directly into a gyratory crusher with an open side setting of 175 mm. The primary crushed ore has a P100 of 366 mm and a P80 of 143 mm.
Discharge from the gyratory crusher is transferred via an apron feeder to two classification screens equipped with 50 mm apertures. Undersized material bypasses the secondary crushing circuit and is directed to the crushed ore stockpile, while oversized material is directed to a surge bin. The screens also receive recirculated product from the secondary cone crusher, completing the closed-loop configuration of the secondary crushing circuit.
The secondary cone crusher receives material from the primary surge bin and operates with a closed side setting of 45 mm. The crushed product is recirculated back to the secondary crushing screens. The secondary crushing circuit yields products with P100 at 50 mm and P80 at 40 mm.
HPGR grinding and dry cobbing
The primary HPGR grinding circuit and dry cobbing section is designed to process 11.00 Mdmtpa of crushed ore. The secondary HPGR grinding circuit is designed to process 8.8 Mdmtpa of concentrate produced in the dry cobbing section. The HPGR and dry cobbing plant will operate continuously, 24 hours per day, 350 days per year, totaling 8,400 hours annually. Based on an operational utilization rate of 93.86%, the total effective operating hours available are 7,884 hours per year. An allowance of fifteen days per year is allocated for major repairs and maintenance.
The primary HPGR grinding stage is designed to reduce coarse feed material to a product with P100 and P80 sizes of 6 mm and 4 mm, respectively. Material from the crushed ore stockpile is conveyed to the primary HPGR surge bin. A belt feeder extracts crushed ore and discharges it to a single HPGR unit with rolls of 2.2 m diameter by 2.0 m width, equipped with an installed power of 2 × 2,844 kW. The HPGR operates in closed-circuit configuration with two double-deck banana screens, each with an internal size of 3,000 mm × 7,300 mm. Oversized material is recirculated at a rate of 107%, while undersized material proceeds to the dry cobbing stage.
The proposed dry cobbing stage consists of a dry magnetic separation circuit designed to upgrade the ore by removing low-grade or non-magnetic waste material. This process employs dry magnetic separator drums to concentrate iron-bearing particles without water. The dry cobbing circuit achieves a mass recovery (yield) rate of approximately 80%. The annual production rate of iron ore concentrate from the dry cobbing circuit is estimated at 8.8 Mdmtpa. Non-magnetic material is directed to a coarse tailings stockpile, while magnetic material is conveyed to the secondary HPGR surge bin.
The secondary HPGR stage is designed to reduce material from the dry cobbing circuit to a product with P100 and P80 sizes of 850 µm and 510 µm, respectively. A belt feeder extracts material and discharges it to a single HPGR unit with rolls of 1.8 m diameter by 1.8 m width, equipped with an installed power of 2 × 2,054 kW. This stage operates in closed-circuit configuration with an air classifier and a dedusting system, which includes four dry cyclones and one baghouse. Coarser particles are recirculated back to the HPGR at a recirculation rate of 85%.
Beneficiation plant
The magnetite beneficiation plant is designed to process 8.80 Mdmtpa of ground dry cobbing concentrate and produce 2.46 Mdmtpa of final high-grade magnetite concentrate. The plant will operate continuously, 24 hours per day, 350 days per year, totaling 8,400 hours annually. Based on an operational utilization rate of 93.86%, the total effective operating hours available are 7,884 hours per year.
The secondary HPGR ground product, with an approximate P100 of 850 µm and P80 of 510 µm, will be collected and slurried with water in an agitated tank. The resulting slurry, with a solids concentration of 30% by weight, will be pumped to a rougher LIMS circuit. The rougher unit will operate with a stage weight recovery of 93.13%. The concentrate exiting the rougher stage will have an increased solids content of approximately 60%.
Concentrate from the rougher LIMS is directed to a cyclone pump box, diluted to 52% solids, and pumped to a hydrocyclone. The cyclone underflow gravitates to the primary regrind vertical mills, designed to operate at 60% solids in the feed, with a feed particle size F80 of 510 µm and a product size P80 of 45 µm. The regrind product is combined with cyclone overflow and diluted to 25% solids before being fed to the cleaner LIMS.
The secondary regrind and finisher magnetic separation will have the same configuration as the cleaner stage. Concentrate from the cleaner LIMS is diluted to 48% solids and pumped to a hydrocyclone. The cyclone underflow gravitates to the secondary regrind vertical mills, with a feed particle size F80 of 45 µm and a product size P80 of 20 µm. The regrind product is combined with cyclone overflow and diluted to 20% solids before being fed to the finisher LIMS.
Reverse silica flotation is employed to remove SiO2 impurities. Slurry enters the flotation circuit at a solid concentration of 30%. Reagents are added to depress the iron-bearing minerals while allowing silica-rich mineral to be selectively floated. This stage achieves a mass recovery of 84.8%.
Thickening and filtration
The flotation concentrate is pumped to the concentrate thickener feed tank. The thickener overflow is pumped to the process water tank, while underflow thickened concentrate at 55% solids by weight is pumped to a filter press. The resulting filter cake, with approximately 5% moisture by weight, is discharged onto a conveyor that transports the concentrate to the concentrate stockpile.
Different tailings streams from the rougher LIMS, cleaner LIMS, finisher LIMS, and reverse silica flotation are pumped to the tailings thickener feed tank. The thickener overflow is pumped to the process water tank, while underflow thickened tailings at 50% solids by weight is pumped to the TMF.
Key reported parameters
| Parameter | Unit | Value | Basis |
|---|---|---|---|
| ROM feed (Phase 1) | Mdmtpa | 11.0 | Design |
| ROM feed (Phase 2, additional) | Mdmtpa | 11.0 | Design |
| Total ROM feed (Phases 1 and 2) | Mdmtpa | 22.0 | Design |
| Concentrate production (per phase) | Mdmtpa | 2.46 | Design |
| ROM feed magnetite content | % | 22.6 | Design basis |
| ROM feed hematite content | % | 5.6 | Design basis |
| ROM feed magnetic Fe | % | 16.36 | Design basis |
| ROM feed total Fe | % | 20.28 | Design basis |
| Final concentrate magnetite purity | % | 91.78 | Design |
| Final concentrate total Fe grade | % | 67.76 | Design |
| Life-of-mine magnetic Fe recovery | % | 74.85 | Projected |
| Overall mass recovery | % | 22.4 | Design |
| Global magnetite recovery | % | 90.97 | Design |
| Global hematite recovery | % | 7.49 | Design |
| Global total Fe recovery | % | 74.85 | Design |
| Dry cobbing mass recovery | % | 80 | Design |
| Rougher LIMS mass recovery | % | 93.13 | Design |
| Cleaner LIMS mass recovery | % | 68.46 | Design |
| Finisher LIMS mass recovery | % | 51.76 | Design |
| Flotation mass recovery | % | 84.85 | Design |
| Concentrate moisture content | % w/w | 5.00 | Design |
| Primary crushing availability | % | 94.52 | Design |
| Primary crushing utilization | % | 74.06 | Design |
| HPGR/dry cobbing availability | % | 95.89 | Design |
| HPGR/dry cobbing utilization | % | 93.86 | Design |
| Secondary HPGR/beneficiation availability | % | 95.89 | Design |
| Secondary HPGR/beneficiation utilization | % | 93.86 | Design |
| Crushing Work Index (85th percentile) | kWh/t | 27.05 | Testwork basis |
| Rod Bond Work Index (85th percentile) | kWh/t | 16.09 | Testwork basis |
| Ball Bond Work Index (closing screen 200 Mesh,85th percentile) | kWh/t | 8.8 | Testwork basis |
| Ball Bond Work Index (closing screen400 Mesh,85th percentile) | kWh/t | 10 | Testwork basis |
| Ball Bond Work Index (closing screen 500 Mesh,85th percentile) | kWh/t | 10.6 | Testwork basis |
Project website: https://www.barlowmetal.ca/en/our-projects/project/iron-hills-project
Technical qualifications
The process design described in this report is based on a Preliminary Economic Assessment (PEA) level of study. Both the crushing and concentrator plants were designed by DRA at a PEA level. All reported capacities, recoveries, and grades are design criteria or projected values, not historical operating data. Testwork basis parameters such as Bond Work Indices are cited at the 85th percentile. The report notes that process flow diagrams are provided in Figures 17.1 through 17.3, but these figures are not reproduced in the text. No actual operating performance data are presented in the report.
Source: Iron Hills Project, Technical Report Preliminary Economic Assessment, October 2025, DRA Ref.: G9161-0000-PM-REP-0001-Rev.0, Section 17 Recovery Methods
