The Joyce Lake DSO Project is a simple dry crushing and screening operation designed to produce lump and fines iron ore products from high-grade direct shipping ore.
Report context
The Joyce Lake DSO Project Feasibility Study, dated December 2022, presents a dry crushing and screening processing route for the production of lump and fines iron ore products. The project is designed to process run-of-mine (ROM) ore at a nominal 6% moisture content, with processing operations limited to approximately 214 days per year, typically from April through November. The feasibility study was prepared for Century Global Commodities Corporation and Joyce Direct Iron Inc. under National Instrument 43-101 guidelines.
Processing route
Process overview
The Joyce Lake DSO flowsheet consists of a two-stage dry crushing and screening process designed to produce lump and fines products. The processing battery limits start at the ROM ore stockpile and end with product loaded into product haul trucks.
ROM ore is delivered from the open pit mine to the ROM ore stockpile area using CAT 777 (or equivalent) trucks. Sufficient stockpiling space is provided to allow segregation of ore for blending feed materials ahead of the crushing plant to minimize product grade variability. A dedicated front-end loader of 16 tonnes capacity is used for maintaining the ROM stockpile and for feeding the plant.
The front-end loader transfers material from the ROM stockpile to a feed hopper fitted with a static grizzly screen to scalp off any oversized material (+600 mm). No rock breaker is provided; the +600 mm material is rejected to a stockpile to be processed later by a contractor once sufficient material has accumulated.
Crushing and screening circuit
The material passing the static grizzly is directed onto a vibrating grizzly feeder that separates material at 130 mm prior to the primary crushing stage. The oversize material (+130 mm) is fed to a jaw crusher where it is crushed to a top size of 225 mm. The undersize material from the static grizzly joins the jaw crusher product, and the combined materials are conveyed to a triple-deck horizontal screen.
The triple-deck screen separates the material into three products:
- Oversize +31.5 mm material conveyed from the top screen deck to a cone crusher for further size reduction to a targeted top size of 32 mm
- Lump product (-31.5/+6.3 mm)
- Fines product (-6.3 mm)
The material discharged from the cone crusher is returned to the triple-deck screen, operating in closed loop to ensure that no material coarser than 31.5 mm is sent with the final lump product. A third deck was added to the screen to relieve the load on the 6 mm screen, alleviating excessive bed depth issues and inefficient screening that might be encountered in separating the fines and lump products.
The proposed ROM particle size distribution used for design assumes a relatively coarse feed to ensure sufficient processing capacity during extended periods of harder ore processing. The design accounts for the possibility that, during periods of mining in areas where ore is highly fractured, a significant amount of ore will likely bypass the jaw crusher.
Product handling and stockpiling
Fines material is placed into stockpiles. The fines product stockpile has a design capacity to hold 16 hours of material to allow for scheduled plant maintenance shutdowns. Lump material is fed to a rotary dryer prior to being discharged onto a radial stacker, placing the dried lump into stockpiles. The lump stockpiles reach a maximum capacity of nearly 900,000 tonnes, representing the full year production of lump material. The stockpile is tarped progressively throughout the year to avoid re-wetting, and the pad is designed with drainage to avoid pooling of rainwater.
Process plant lump and fines products are loaded into haul trucks for transportation to the Astray rail load out area. Fines are loaded and hauled during the summer months and lump during the winter months. A 95-tonne capacity Kenworth side-dump chassis with an additional side dump trailer attached was selected for product transport.
A dedicated front-end loader with a nominal capacity of 16 tonnes is required to load the haul trucks and manage the product stockpiles, including emergency stockpiles. Cycle time analysis indicates this equipment would have a utilization rate of about 60% during the operating season. A Twin Shaft Sizer unit will be installed on-site as a feed breaker to reduce frozen chunks to manageable sizes as mitigation against material freezing in the lump stockpile.
Low-grade material management
Material grading between 52% and 55% Fe will be stockpiled in low-grade stockpiles for processing through the dry plant at the end of mine life. Waste material grading between 50% and 52% Fe will also be segregated from other waste and stockpiled for potential future processing.
A 2014 trade-off study compared the selected dry processing flowsheet against a scenario incorporating wet processing to upgrade material having Fe grade between 50% and 55% Fe. The wet processing scenario assumed an overall iron recovery of 75%, with wet scrubbing and screening sufficient to produce a lump product (-31.5/+6.3 mm) grading 57% Fe from low-grade material. The trade-off study concluded that the wet plant scenario would not improve the financial performance of the project due to higher operating costs, lower annual revenues from increased penalties, and substantially higher capital costs. The Joyce Lake deposit does not contain enough material in the 50-55% Fe range to justify the addition of a wet processing plant.
The qualified person recommends that ore sorting test work be developed and executed during operations targeting low and below cut-off grade material. The low-grade lump product created in the crushing circuit is within an ideal range for typical ore sorting applications. Material produced during the first years of operation could be passed through an on-site test unit to assess the potential for upgrading low-grade material.
Drying system
Lump material is dried to a target 2% moisture using a rotary dryer before stockpiling. The rotary dryer is run directly on diesel fuel, with an estimated yearly diesel consumption of 1.1 million litres. Product moisture expectations are 2% for lump and 7% for fines, both respecting typical shipping liquefaction limits for iron ore. The rotary dryer serving for lump drying could be used as a mitigation measure in the event of higher than acceptable moisture content in the fine material.
Operating season
The processing facility is designed to operate for a maximum of 214 days per year, with operations not intended during the colder winter months, typically between mid-November to mid-March. Inclement weather could shorten the production season to as little as 200 days. The crushing and screening circuit is designed to produce 2.5 Mtpa within a shortened (200 days) season. Annual product production and sales are based on the annual mine plan of 2.5 Mtpa of ore tonnes, while the plant design is based on an annual maximum production of 3.0 Mtpa of product.
Process design criteria
The plant is configured as a two-line mobile plant with each line designed to process 50% of the total process throughput, equivalent to 350 tonnes per hour. The two half-lines mobile plant design was retained for reasons of cost, flexibility, and reliability, including the possibility of using the two lines at separate locations during project construction if necessary.
Key process design criteria include:
| Criteria | Unit | Value |
|---|---|---|
| Annual plant feed (dry basis) – design | tpa | 3,000,000 |
| Annual plant feed (dry basis) – nominal | tpa | 2,500,000 |
| Operating time (days per year) | d | 200-240 |
| Operating time (nominal) | d | 214 |
| Operating time (hours per day) | h | 24 |
| Equipment utilization | % | 75 |
| Lump size | mm | 6.3 – 31.5 |
| Fines size | mm | 0 – 6.3 |
| Lump undersize tolerance (<8 mm) | % | 10 |
| Fines undersize tolerance (<100 µm) | % | 15 |
Project website: http://centuryglobal.ca/projects/joyce-lake-attikamagen/
Major mechanical equipment
| Equipment | Description | No. of Units | Size | Installed Power (kW) |
|---|---|---|---|---|
| Grizzly | Bar spacing – 600 mm x 600 mm | 2 | TBD | N/A |
| Feed hopper | Capacity = 35 t | 2 | TBD | N/A |
| Vibrating grizzly feeder | Bar spacing at discharge = 130 mm | 2 | 1.3 m x 6.0 m | 30 |
| Jaw crusher | Capacity = 240-780 t/h; Closed side setting = 50-175 mm | 2 | 0.8 m x 1.4 m | 132 |
| Secondary screen | Triple-deck horizontal screen | 2 | 2.1 m x 6.1 m | 37 |
| Cone crusher | Capacity = 150-470 t/h; Closed side setting: 13-51 mm | 2 | 3.2 m x 2.4 m x 2.7 m | 200 |
Particle size distribution
The particle size distributions do not account for any product degradation, neither on-site nor in transport. Due to the hard nature of the material, product degradation is assumed to be minimal. No penalties have been accounted for in the analysis for the production of very fine material (-100 µm) or the degradation of lump into fine material.
Simulated lump and fines particle size distributions:
| Screen size (µm) | Lump Cumulative Passing (%) | Fines Cumulative Passing (%) |
|---|---|---|
| 31,500 | 100 | 100 |
| 25,400 | 93.5 | 100 |
| 19,050 | 75.8 | 100 |
| 12,700 | 40.3 | 100 |
| 6,700 | 4.0 | 98.1 |
| 4,750 | 0.2 | 82.1 |
| 2,360 | 0 | 47.9 |
| 1,180 | 0 | 29.8 |
| 600 | 0 | 21.6 |
| 300 | 0 | 14.6 |
| 150 | 0 | 10.4 |
| 106 | 0 | 8.3 |
| 75 | 0 | 7.1 |
Key reported parameters
| Parameter | Unit | Value | Basis |
|---|---|---|---|
| Annual plant feed (dry basis) – design | tpa | 3,000,000 | Design |
| Annual plant feed (dry basis) – nominal | tpa | 2,500,000 | Nominal |
| Lump size | mm | -31.5/+6.3 | Design |
| Fines size | mm | -6.3 | Design |
| ROM nominal moisture | % | 6 | Design |
| Dried lump target moisture | % | 2 | Design |
| Fines product moisture | % | 7 | Expected |
| Jaw crusher work index | kWh/t | 10.6 | Testwork |
| Abrasion work index | g | 0.56 | Testwork |
| Lump stockpile capacity | t | 900,000 | Design |
| Fines stockpile capacity (16h) | t | 4,000 | Design |
| Emergency stockpile capacity | t | 24,000 | Design |
| Total process plant power demand | kW | 1,081 | Design |
| Rotary dryer diesel consumption | ML/year | 1.1 | Design |
| Product transportation | – | 95 t Kenworth side-dump with trailer | Design |
| Product loading equipment | – | 16 t front-end loader | Equipment utilization ~60% |
Technical qualifications
Specific limitations identified in the report include:
- The particle size distributions presented do not account for any product degradation, neither on-site nor in transport. Product degradation is assumed to be minimal due to the hard nature of the material, and no penalties have been accounted for in the analysis for the production of very fine material (-100 µm) or the degradation of lump into fine material.
- The crushing and screening circuit design criteria were first developed by BBA using simulation software with input test work results. As part of the request for budgetary proposals, vendors performed their own analysis and proposed equipment and arrangements to meet targeted throughput with ore characteristics provided from the client's test work.
- Further targeted test work is recommended prior to final design to confirm the selected crushing circuit design, as well as the iron grade content of lump and fines products, over a range of ROM iron content process feed grades.
- The annual production figures reference a Wisco specification dated September 2014 for certain elemental values (S, P, As) that were not developed for the mine plan. Values for these elements are averages from test work on bulk samples.
- The design accounts for the possibility that inclement weather could shorten the production season to as little as 200 days; the crushing and screening circuit has been designed to produce 2.5 Mtpa within a shortened season.
- The 2014 trade-off study assumed an overall iron recovery of 75% in wet processing, and some assumptions in that study were not supported by sufficient test work and would require significantly more test work for confirmation.
- There is a risk that portions of the lump stockpile could freeze into chunks not suitable for transportation; a Twin Shaft Sizer unit is included as mitigation. Stockpiles will be tarped progressively throughout the year to avoid re-wetting, and the pad is designed with drainage to avoid pooling of rainwater.
Source: Joyce Lake DSO Project , 2022 Technical Report, Feasibility Study for the Joyce Lake DSO Iron Ore Project, December 2022, Chapter 17: Recovery Methods, Sections 17.1, 17.2, 17.3, 17.4, 17.5, 17.6, 17.7, and 17.8.
