Preliminary Economic Assessment for the North American Lithium Expansion Project

This Preliminary Economic Assessment outlines the proposed expansion of the North American Lithium operation in Québec, Canada, from a current design capacity of 4,200 tpd to a new design rate of 6,500 tpd of concentrator feed.

Report context

This Preliminary Economic Assessment (PEA) for the North American Lithium Expansion Project, located in Québec, Canada, was prepared to evaluate the proposed expansion of the existing lithium processing facility. The expansion design is based on the existing plant configuration, historical operational data, metallurgical testwork as described in Chapter 13 of the report, and equipment information from suppliers. The study establishes the design basis for the plant, capital costs, and operating costs developed in this PEA. The report is dated as part of the technical documentation for the project, with the full document referencing the project location as Québec, Canada.

Processing route

Existing Plant Configuration

The North American Lithium operation is currently authorized at 4,500 tpd for the concentrator, with a plant design at 4,200 tpd and an authorized mining mineral feed rate of 4,700 tpd to produce spodumene concentrate. The existing operation consists of three distinct processing areas: crushing and ore sorting on the ROM ore to produce an upgraded plant feed for downstream processing; a spodumene concentrator producing a saleable spodumene concentrate using grinding, desliming, magnetic separation and flotation; and dewatering of the final spodumene concentrate and the concentrator tailing material.

Proposed Expansion Design

The NAL process plant expansion is designed to increase the overall plant capacity to a design rate of 6,500 tpd. This will be achieved through several key modifications:

1. Replacement of the crushing and ore sorting area with a new circuit capable of processing 6,800 tpd of ROM ore. Crushed ore is conveyed from the crushing and ore sorting area to a covered crushed ore stockpile with 15,000 tonnes live storage. The stockpile is equipped with 2 reclaim tunnels, each with 2 feeders and conveyors, providing feed to Concentrator 1 (existing) and Concentrator 2 (new).

2. The addition of a second concentrator (Concentrator 2) to be operated in parallel to the existing concentrator, enabling a combined concentrator process rate of 6,500 tpd of feed using grinding, desliming, magnetic separation and spodumene flotation.

3. Additional concentrate filters, and replacement of the existing tails dewatering area with a new tailings thickener receiving tail streams from both the existing Concentrator 1 and new Concentrator 2.

4. Redundancy in the existing WHIMS circuit is fulfilled by adding a third WHIMS.

5. A concentrate storage facility integrated into the existing plant building combining flows of Concentrator 1 and new Concentrator 2, improving on current plant concentrate rehandling.

Primary Crushing, Secondary Crushing and Ore Sorting

A ROM blend feeds the coarse ore to the Primary Crusher at a top size of 900 mm, and the crushed ore at a nominal Closed Size Setting (CSS) of 130 mm is transferred to the Oversize Grizzly via the Primary Conveyor which screens the ore at 90 mm. The +90 mm oversize from the Grizzly is fed to the Secondary Crusher and the resultant re-crushed ore at a nominal CSS of 90 mm is discharged onto the Primary Conveyor to join the material from the Primary Crusher and thus transferred to the Oversize Grizzly for rescreening.

The under-size material from the grizzly is transferred to Ore Sorting. Crushed material from Primary and Secondary Crushing is fed to the Sorter Screen where it is separated by size into four products:

1. Material from the top deck (-90 mm +75 mm) is transferred to the Primary Sorter Screen and wet screened. Washed oversize material is fed to the Primary Sorter, while wet screen undersize nominally -4 mm in size is transferred as a slurry to the existing Concentrator 1 rod mill.

2. Material from the second deck (-75 mm + 50 mm) is transferred to the Secondary Ore Sorter.

3. Material from the bottom deck (-50 mm + 25 mm) is transferred to the Tertiary Ore Sorter.

4. The screen undersize (-25 mm) reports to the Fine Ore Conveyor for transfer to the Covered Stockpile.

5. Rejects from all sorters are conveyed to the rejects stockpile to be loaded by front end loader onto trucks for disposal with the mine waste.

Tertiary Crushing and Fine Ore Storage

The sorter products are fed to the tertiary crushing circuit which consists of the Tertiary Crusher (nominal CSS of 18 mm) in closed circuit with the Tertiary Crusher Screen (cut size = 20 mm). The sorter stream is introduced to the circuit at the feed to the Tertiary Crusher Screen. Screen oversize is transferred to the Tertiary Crusher and the crushed material from the Tertiary Crusher returned to the screen.

The screen undersize at a nominal P80 of 8 mm reports to the Fine Ore Conveyor for transfer to the Covered Stockpile. The Covered Stockpile is a new weatherproof storage shed which stores the fine ore. Reclaim of the stockpile fine ore is by means of two sets of parallel reclaimers (4 in total), located in the reclaim tunnels under the Covered Stockpile, one set feeding the Existing Concentrator (Concentrator 1) and the second the Expansion Concentrator (Concentrator 2). Full plant feed can be supplied by a single feeder for each circuit, while the second feeder provides redundancy, reduces size segregation in the stockpile and maximises stockpile storage. This undercover storage eliminates environmental effects on the ore fed to the plant to provide a consistent feed moisture and all-weather availability.

Existing Concentrator (Concentrator 1)

Grinding and Desliming

The grinding circuit consists of primary open circuit rod mill followed by a ball mill working in a closed circuit with 6 x Stack Sizer Screens. The rod mill is fed at an average rate of 4,200 dtpd by the dedicated reclaimers on the Covered Stockpile and also receives the screen undersize slurry from the Primary Sorter Screen.

The Rod Mill product is pumped to the Ball Mill and the Ball Mill product is pumped to the Stack Sizer Screens. The oversize with a nominal P80 of 970 microns is returned to the ball mill. The undersize at a nominal P80 of 225 microns is deslimed by 17 x Primary Deslime Cyclones to remove slime material (nominal overflow cut size D50 = 10 µm). The slime material reports to the Tailings Thickener.

Magnetic Separation

The deslimed underflow from the above is diluted with process water and then pumped to a low-intensity magnetic separator (LIMS) followed by 2 x wet high-intensity magnetic separator (WHIMS) in series with a new parallel first stage standby WHIMS magnetic separator (2 Duty/1 Standby (new)). The magnetics extracted by both stages are combined and pumped to the Tailings Thickener.

The non-magnetic slurry from the above then reports to second stage deslime cyclones that returns the slime to the LIMS feed box. Second deslime stage cyclone underflow then undergoes high-intensity conditioning at 55% w/w solids with a fatty acid collector in the Rougher Conditioning Tanks, 2 x tanks in series. The conditioned slurry is fed to the feed box of the rougher flotation circuit via gravity.

Spodumene Flotation

The non-magnetic slurry from the above undergoes high-intensity conditioning with a fatty acid collector (FA-2) at 55% solids in the Rougher Conditioning Tanks, 2 x 26 m³ tanks in series. The conditioned slurry is diluted to 40% solids and overflows to the Rougher circuit, a bank of 3 x 30 m³ rougher flotation cells. The rougher tailing from the final cell is pumped to the Scavenger Deslime Cyclone. The cyclone overflow reports to the secondary deslime cyclone feed pumpbox and the underflow reports to the Scavenger Conditioning Tanks (2 tanks in series) which feed the Scavenger circuit, a bank of 3 x 30 m³ scavenger flotation cells. The Scavenger circuit provides additional flotation time to recover any remaining spodumene and the scavenger tailings are pumped to the Tailing Thickener for dewatering.

Rougher Concentrate and Scavenger Concentrates are combined and sent to Cleaner 1 Circuit, which also receives the Cleaner 2 tailings. The combined feed is processed through a bank of 18 x 8.5 m³ cleaner cells in two lines. Cleaner 1 tailing reports to the Tailings Thickener and Cleaner 1 concentrate is pumped to the Cleaner 2 Circuit.

Cleaner 2 circuit receives Cleaner 1 concentrate and Cleaner 3 tailings and processes it through a bank of 13 x 5.1 m³ cleaner cells in a single row. Cleaner 2 concentrate is recirculated back to the feed to Cleaner 1 Circuit and Cleaner 2 concentrate is sent to Cleaner 3 for final cleaning.

Cleaner 3 circuit receives Cleaner 2 concentrate and undertakes the final polishing of the spodumene concentrate to produce a saleable product using 19 x 2.8 m³ cleaner cells in a single row. Cleaner 3 tailings is recirculated back to the feed to Cleaner 2 circuit. Cleaner 3 concentrate is sent to the Concentrate Tank to commence dewatering.

Expansion Concentrator (Concentrator 2)

Grinding and Desliming

The circuit is fed via conveyor from the dedicated reclaim feeders drawing material from underneath the Covered Crushed Ore Stockpile at a design rate of 2,300 tpd. The grinding circuit consists of a single stage ball mill working in a closed circuit with 4 x Mill Cyclones targeting a grind size of P80 of 200 microns. Mill Cyclone underflow returns to the ball mill. Mill Cyclone overflow is deslimed by 12 x Primary Deslime Cyclones to remove slime material. The slime material reports to the Tailings Thickener.

Magnetic Separation

The deslimed Primary Deslime Cyclone Underflow from the above is diluted with process water and pumped to a low-intensity magnetic separator (LIMS) followed by 2 x wet high-intensity magnetic separator (WHIMS) in parallel (1 Duty/1 Standby). The magnetics extracted by both stages are combined and pumped to the Tailings Thickener.

Key reported parameters

*Note: all parameters are design rating unless noted otherwise.*

Technical qualifications

The upgraded design will be based on the existing facility, and as such the lithium recovery anticipated following this expansion is 71.2% (at SC5.4 grade) and is based on current plant performance and improvements of ore sorting and WHIMS. Future testwork and increased lithium recovery initiatives are planned for the next stage of the project. The recovery methods for the Project were established based on the existing plant, historical operational data, metallurgical testwork as described in Chapter 13 of the report, and equipment information from suppliers. Expansion process design is based on the operational and metallurgical reviews of the past process plant operation and testwork data.

Source: Preliminary Economic Assessment for the North American Lithium Expansion Project, Québec, Canada, Section 17: Recovery Methods, Pages 185-189.