The 2015 feasibility study for Century's Joyce Lake direct shipping iron ore project chose dry crushing and screening to turn all mined ore into lump and fines, with no process rejects.
The Joyce Lake Direct Shipping Iron Ore (DSO) project lies in Labrador, about 20 km northeast of Schefferville, Québec, and can only be reached by air. It forms part of the Attikamagen Property, held 100% by Labec Century Iron Ore Inc. (LCIO), a joint venture 60% owned by Century Iron Mines Corporation through Century Iron Ore Holdings and 40% by WISCO Canada Attikamagen Resources Development & Investment Limited. The feasibility study by BBA, with an effective date of March 2, 2015, covers an iron ore development project with 17.72 Mt of mineral reserves to be mined by open pit over about seven years. Nominal output was 2.5 Mtpa of lump and sinter fines, trucked to a rail loop and railed to the IOC port at Sept-Îles. The report does not set a construction start date.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Mineral reserves | 17.72 | Mt | Processed over about 7 years |
| Nominal plant feed | 2,500,000 | tpa | Dry basis, per mine plan |
| Design plant feed | 3,000,000 | tpa | Dry basis, maximum capacity |
| Line capacity | 350 | tph | Each of two mobile lines |
| Average feed grade | About 62 | % Fe | High grade ore |
| High grade cut-off | 55 | % Fe | Low grade 52% to 55% Fe stockpiled |
| ROM moisture | 6 | % | Nominal |
| Operating days | 240 | days per year | No winter operation |
| Equipment utilization | 75 | % | Design criteria |
| Lump product size | 6.3 to 31.5 | mm | Higher value product |
| Fines product size | Less than 6.3 | mm | Penalty if over 15% below 100 µm |
| Crusher work index | 10.6 | kWh/t | Jaw and cone crushers |
| Plant power demand | 865 | kW | Estimated draw |
| Haul distance to rail loop | 43 | km | Bi-train side dump trucks |
| Initial capital cost | 259.6 | $ million | Including indirect costs and contingency |
Overview
Joyce Lake is a direct shipping ore project, so the plant only sizes the ore. Run-of-mine ore averaging about 62% Fe goes through two stages of dry crushing and screening to make a lump product and a fines product. All mined ore becomes saleable product. BBA notes that 62% Fe is the benchmark grade at which no iron premium or penalty applies. Lump should upgrade slightly during processing as finer silica reports to the fines.
Early in the study, BBA ran a trade-off between dry processing alone and adding a wet plant to upgrade 50% to 55% Fe material. The wet case assumed scrubbing and screening for lump at 57% Fe, plus wet high intensity magnetic separation and desliming for a fines concentrate, at 75% overall iron recovery. It lengthened the mine life and raised saleable tonnage. Higher operating costs, higher capital and lower average prices from grade penalties meant it did not improve the project's finances. The study found that the deposit holds too little 50% to 55% Fe material to justify a wet plant.
The study therefore kept the simple dry flowsheet. Material between 52% and 55% Fe goes to low grade stockpiles for processing at the end of mine life. Waste between 50% and 52% Fe can be stockpiled separately in case markets change, though the study treats it as waste.
Key Process Stages
Feed and scalping
Mine haul trucks deliver ore to a run-of-mine stockpile pad with room to segregate ore by grade for blending. A 16 t front-end loader manages the pad and feeds the plant, at about 50% utilization during the season. It tips ore into a feed hopper fitted with a static grizzly at 600 mm. There is no rock breaker. Oversize goes to a stockpile, and a contractor breaks it in batches once enough has built up.
Primary crushing
Material through the static grizzly reaches a vibrating grizzly feeder that splits at 130 mm. The +130 mm fraction goes to a jaw crusher with a top size of 225 mm. The jaw product and the grizzly undersize combine on a common collecting conveyor. Where the ore is highly fractured, much of it is expected to bypass the jaw crusher.
Screening and secondary crushing
A triple deck horizontal screen splits the combined stream three ways. The +31.5 mm material goes to a cone crusher, which crushes to a target top size of 32 mm and returns its product to the screen. Because the cone runs in closed circuit with the screen, nothing coarser than 31.5 mm reaches the lump product. The -31.5/+6.3 mm fraction becomes lump and the -6.3 mm fraction becomes fines. A double deck screen would normally do this job. BBA added the third deck to unload the 6 mm deck and avoid deep beds and poor screening between lump and fines.
Product stockpiles and loadout
Each product drops through a chute onto its own conveyor and stacker. The lump stockpile holds about 9,000 t and the fines stockpile about 4,000 t, both roughly 16 hours of output to cover planned maintenance. There is space for 24,000 t emergency stockpiles of each product. A second 16 t loader fills the product haul trucks and runs the stockpiles, at about 60% utilization. Processing ends when product is in the trucks.
Additional Interesting Data and Summary
Vendors were asked to propose their own equipment arrangements. BBA weighed mobile and semi mobile plants and one-line and two-line layouts, and picked two mobile half-capacity lines of 350 tph each. The choice offered lower cost and flexibility, including the option of running the lines at separate locations during construction.
Each line has a 35 t feed hopper, a 1.3 m by 6.0 m vibrating grizzly feeder of 30 kW, a 0.8 m by 1.4 m jaw crusher of 132 kW, a 2.1 m by 6.1 m triple deck screen of 37 kW and a cone crusher of 200 kW. The jaw plants draw 221 kW in total, screening 78 kW, cone crushing 393 kW and conveying 173 kW.
The plant is sized for 100% hard ore, with a relatively coarse design feed size so it keeps its capacity through long hard ore campaigns. The design size distribution has 60% passing 256 mm and 14% passing 32 mm. The plant does not run between mid-November and mid-March.
A separate trade-off found road haulage cheaper than a rail spur from the Schefferville line. Bi-train trucks with two 75 t side dump trailers carry 145 t per trip on the 43 km road to the rail loop. The fleet needs ten trucks, plus one spare. BBA recommended more targeted test work during detailed engineering to confirm the crusher selection and the lump and fines grades across a range of feed grades.
Key Processes
- Static grizzly scalping at 600 mm with contractor breaking of oversize
- Vibrating grizzly feeder split at 130 mm
- Jaw crushing of primary oversize
- Triple deck screening into oversize, lump and fines
- Cone crushing in closed circuit with the screen
- Separate lump and fines stockpiles with emergency storage
- Truck haulage of products to a rail loop
Source: NI 43-101 Technical Report – Feasibility Study, Joyce Lake Direct Shipping Iron Ore (DSO) Project, Attikamagen Property, Labrador, March 2, 2015.
Project website: Joyce Lake DSO Project
