Lola Graphite Project — 2023 Technical Report

The updated feasibility study describes a conventional flotation processing plant designed to treat saprolite and hard rock blends, producing a graphite concentrate grading 95.4% Cg at an overall recovery of 83.6%.

Report context

This NI 43-101 technical report for the Lola Graphite Project, prepared by DRA, is dated April 2023 and constitutes an updated feasibility study (DRA Ref.: J6626-0000-STU-REP-0001, Revision 0). The report presents the process design basis and recovery methods for a mineral processing plant that will treat run-of-mine material from the Lola Graphite Project, owned by SRG Mining Inc.

Processing route

Crushing and storage

Run-of-mine mineralized material will be deposited into a feed hopper using a front-end loader. An apron plate feeder conveys the material to a mineral sizer, where rotating toothed rolls reduce the material from a maximum of 24 inches (600 mm) to 8 inches (200 mm). Crushed material passes a self-cleaning permanent magnet for tramp steel removal and discharges onto a radial stacker. During normal operation, the stacker feeds directly into the crushed ore hopper; a belt feeder delivers material to belt conveyors feeding the SAG mill. An emergency stockpile, reclaimable by front-end loader, is provided.

Grinding and desliming

The SAG mill operates in closed circuit with a single deck screen to remove pebbles larger than 13 mm, which are returned for further grinding. Undersize material is pumped to four multi-deck vibrating screens (three operating, one standby), also in closed circuit with the SAG mill. Screen undersize (-0.8 mm) discharges to a tank. For blended feed, material is pumped directly to rougher flotation. For saprolite-only feed, material is directed to desliming, which comprises two parallel trains, each with two stages of cyclone clusters. The first stage removes fine slime particles; the deslimed underflow reports to rougher flotation. First-stage cyclone overflow is pumped to second-stage cyclones; the overflow from this stage flows to the tailings thickener, and the underflow also reports to rougher flotation.

Rougher flotation

Two parallel rougher flotation trains each process half the material, using diesel as collector and methyl isobutyl carbinol (MIBC) as frother. Each train consists of a bank of eight conventional flotation cells of 16 m³ each (16 cells total). Rougher concentrate is expected to be approximately 36% Cg and is pumped to polishing mills. Rougher tailings are pumped to tailings thickener guard cyclones.

First polishing stage and first cleaner flotation

Rougher concentrate from each train is fed to one of two first-stage polishing mills using ceramic media to scrub gangue minerals from graphite flake surfaces with minimal size reduction. Polished concentrate from both mills is combined and re-split into two trains of first cleaner flotation cells, each with four conventional flotation cells of 10 m³ (eight cells total), expected to upgrade concentrate to 83% Cg. First cleaner tailings are returned to rougher tailings. First cleaner concentrate is pumped to a high-frequency multi-deck vibrating wet screen, splitting into coarse (+100 mesh) and fine (-100 mesh) fractions.

Second stage polishing, second, and third cleaner flotation

The split between coarse and fine fractions from first cleaner flotation is expected to be approximately 50%/50% by weight. Each size fraction is upgraded in dedicated parallel polishing and cleaner flotation circuits. The screen oversize (+100 mesh) and undersize (-100 mesh) streams are polished through dedicated second-stage polishing mills. The fine fraction polishing mill includes dewatering cyclones for solids density control. Second cleaner flotation for each circuit uses dedicated banks of three conventional flotation cells of 2 m³ each; third cleaner flotation uses dedicated banks of two conventional flotation cells of 2 m³ each. The combined third cleaner concentrate grades 95.4% Cg and is pumped to filtration. Second cleaner tails recirculate to first cleaner flotation; third cleaner tails recirculate to second cleaner feed.

Graphite concentrate filtering and drying

Graphite concentrate from third cleaner flotation is pumped to a concentrate holding tank, then to pressure filtration comprising three vertical plate pressure filters, producing a filter cake with 20% moisture. Cake is discharged onto conveyors feeding a common conveyor, then transported to a diesel-fired indirect rotary dryer via a feed hopper and screw conveyor. The dryer reduces concentrate moisture to 0.3% for efficient dry screening and packaging. Filtrate gravitates to a filtrate tank, overflowing to the process water pond.

Graphite dry screening and packaging

Four size fractions are produced from the graphite concentrate: +48 mesh, -48+80 mesh, -80+100 mesh, and -100 mesh. Dry graphite concentrate is pneumatically transported to a bulk bin, then to two sifter screening systems, each consisting of eight sections of 27 sizing screens. Screened fractions gravitate to four dedicated bins. Packaging uses a semi-automatic bagging system loading one-tonne bulk bags; bags are weighed, palleted, and stretch-wrapped for storage and shipment.

Tailings dewatering

Flotation final tailings from rougher and first cleaner flotation are pumped to tailings thickener guard cyclones. Cyclone overflow reports to the 50-metre diameter tailings thickener; cyclone underflow reports to the tailings disposal tank. The thickener also receives desliming cyclone overflow (during saprolite-only operation). Flocculant is added in the thickener feed well. Thickener underflow is pumped to the tailings disposal tank, combining with guard cyclone underflow, and the final tailings are pumped at 50% weight by weight to the tailings pond. Thickener overflow returns by gravity to the process water pond for reuse.

Concentrator reagents

Diesel is used as collector for graphite flotation and as fuel for the rotary dryer, with dedicated storage tanks of 30 m³ and 60 m³, respectively. MIBC frother is delivered in IBC totes and stored in a dedicated 30 m³ tank. Flocculant is delivered in 25-kg bags with an expected consumption of 15 bags per day; a flocculant preparation system provides diluted flocculant.

Concentrator water services

Fresh water from a settling pond is pumped to a fresh water/fire water tank at a nominal rate of 978 m³/d. Gland seal water requires 897 m³/d; 20 m³/d is allocated for plant utility purposes; 61 m³/d is required for flocculant preparation. Fire water is sourced from the freshwater tank through a dedicated distribution network. Process water is recycled from tailings thickener overflow and filtrate tank; make-up water is reclaimed from the tailings pond at a nominal rate of 4,996 m³/d.

Compressed air

High pressure air at 900 kPag is supplied by two compressors (one operating, one standby) for plant and instrument air. The concentrate filtration circuit has two compressors (one operating, one standby) supplying air at 700 kPag. The concentrate pneumatic conveying circuit has one dedicated compressor rated for 690 kPag. Low pressure air for flotation is produced by four air blowers: two units supply air at 23 kPag to rougher and first cleaner cells; two units supply air at 12 kPag to second and third cleaner cells.

Key reported parameters

Technical qualifications

The report states that expected recoveries and concentrate grade are based on applicable testwork results completed on blends of hard rock and saprolite, as well as saprolite-only run-of-mine material. The processing plant equipment has a design factor of 15% above the nominal production rate. The flowsheet and process description are presented for the updated feasibility study; the report does not provide historical operating data from a commercial plant, as this is a proposed design. The tailings pond is not considered as part of the concentrator water system in the water balance summary and is included for illustrative purposes only. The split between coarse and fine fractions for first cleaner flotation concentrate is based on knowledge of graphite flotation circuits and applicable testwork results available to date.

Source: Lola Graphite Project, NI 43-101 Technical Report, Updated Feasibility Study, April 2023, DRA Ref.: J6626-0000-STU-REP-0001, Revision 0. Sections: 17 Recovery Methods, Key Process Design Criteria, Mass Balance and Water Balance, Flowsheet and Process Description, Processing Plant – Reagents and Utilities.