Mont Sorcier Project — 2022 Technical Report

This report details the proposed processing plant design, based on metallurgical testwork, for the Mont Sorcier magnetite concentrate project.

Report context

This technical report presents the recovery methods and processing plant design for the Mont Sorcier Project, as described in the Preliminary Economic Assessment dated 08 September 2022. The process design and flowsheet are based on the various metallurgical test programs presented in Section 13 of the report. The plant is proposed to produce 5.0 Mtpa of magnetite concentrate on average over the Life of Mine, with Run of Mine (ROM) calculated based on a magnetite plant weight recovery of 28.8%. The iron and weight recoveries are based on a recovery model developed from the Mont Sorcier drill hole database. A design factor of 20% is applied on nominal requirements. The design also incorporates knowledge acquired in the processing of magnetite-rich deposits in the Iron Range in Northern USA and comparable projects in Eastern Canada.

Processing route

Crushing Circuit

Run of Mine ore is hauled by trucks and dumped directly into a gyratory crusher feed hopper with a capacity of two truckloads. A rock breaker is provided for oversized boulders. The crushed product from the 750 kW gyratory crusher is conveyed to a cone crusher operating in closed loop with a dry vibrating screening system. Screen oversize reports back to the cone crusher, while screen undersize is conveyed to a 12-hour live capacity crushed ore covered stockpile. The crushing circuit produces a -63 mm crushed product at an average throughput rate of 3,247 t/h and is expected to operate 65% of the time to achieve yearly throughput of 18.5 Mt/y.

Primary Grinding and Cobber Magnetic Separation

Crushed mineralized material is withdrawn from the stockpile by apron feeders to the feed bin of the primary grinding unit, a High Pressure Grinding Roll (HPGR) of 2.6 m diameter by 2 m width. The HPGR reduces the top size from 63 mm to 1 mm and runs in closed circuit with wet vibrating screens. Screen oversize is conveyed back to the HPGR, while screen undersize is pumped to the cobber Low Intensity Magnetic Separation (LIMS) units. The cobber LIMS are 3.6 m long concurrent separators used for coarse feeds in the first magnetic separation step. The magnetic concentrate is pumped to secondary grinding classification cyclones, while the non-magnetic outlet is pumped to dewatering cyclones. The dewatering cyclones decrease water content below 40% before the underflow is pumped to the tailings pond.

Secondary Grinding and Rougher Magnetic Separation

The secondary grinding classification cyclones are the entry point of a closed circuit formed with secondary grinding mills and rougher LIMS. The product exiting the circuit, the classification cyclones overflow, has a P80 of 38 μm. To meet design throughput, three 8.9 m diameter by 14.7 m EGL ball mills, each powered by two 10 MW motors, are required. This design is based on preliminary grinding information and comparable projects. Cyclone overflow reports to finisher LIMS, while cyclone underflow flows to the secondary grinding mill. The secondary grinding mill product is fed to 3.6 m long counter-rotation rougher LIMS to reject non-magnetic particles. The rougher LIMS concentrate is recirculated to the classification cyclones, while rougher LIMS tails report to the tailings thickener.

Finisher Magnetic Separation

Finisher LIMS are fed by the overflow from the secondary grinding classification cyclones. These are 3.6 m long counter-current double drum separators, preferred for producing a high-grade magnetic concentrate from fine feed. The non-magnetic product is sent to the tailings thickener, and the finisher LIMS magnetic product reports to the cleaner flotation circuit or directly to concentrate dewatering and drying.

Cleaner Flotation

The cleaner flotation circuit is fed with the finisher magnetic concentrate. It includes a reverse sulphur flotation circuit to lower the sulphur grade below 0.4% and a reverse silica flotation circuit when low silica concentrate is required. The iron concentrate (flotation tails) is pumped to the concentrate dewatering and drying circuit, while the sulphur- and silica-rich flotation concentrates are pumped to the tailings thickener. This circuit was added in addition to the previous PEA to ensure sulphur levels below 0.4% for all ore types and to increase Fe levels.

Concentrate Dewatering and Drying

The concentrate dewatering and drying circuit removes water from the magnetic concentrate slurry to reduce moisture below 2%. This uses a 60 m diameter high-rate thickener, twelve vacuum disc filters, and two fluidized flash dryers. The concentrate thickener is fed with the finisher LIMS concentrate or the cleaner flotation concentrate, depending on sulphur and silica grade requirements. Flocculant is added to assist thickening. The thickener underflow is pumped to the vacuum disc filters where moisture is reduced to about 10%, then the filter cake is conveyed to the fluidized flash dryers to reduce moisture to 2%. The dried concentrate is conveyed via a covered conveyor to an enclosed concentrate stockpile to avoid exposure to rain and snow.

Tailings Thickening

Rougher and finisher LIMS tails, tailings cyclones overflow, and flotation sulphur- and silica-rich tailings are directed to a 45 m high-rate tailings thickener and thickened to about 65% solids. Flocculant is added to assist thickening. The tailings overflow is pumped to the process water tank, and the underflow is pumped to the tailings management facility together with the tailings cyclones underflow.

Utilities, Services, and Reagents

Two separate water supply systems support the operation: a fresh water tank supplied from a nearby lake system for fire water, reagents preparation, and gland seal water; and a process water tank consisting of concentrate and tailings thickener overflow plus reclaimed water from the tailings pond. Plant and instrument air are provided by compressor and dryer systems. Reagents include sulphur and silica collectors, frother, pH modifier for flotation, and flocculant for concentrate dewatering and tailings thickening. All reagents are prepared in a containment area with appropriate ventilation and fire and safety protection.

Key reported parameters

Technical qualifications

The process plant design is based on testing performed to date (per Section 13 of the report), knowledge acquired in the processing of magnetite-rich deposits in the Iron Range in Northern USA and comparable projects in Eastern Canada. The iron and weight recoveries are based on a recovery model developed from the Mont Sorcier drill hole database. The secondary grinding mill design is based on preliminary grinding information and comparable projects, not on project-specific testwork. The concentrate thickener sizing used typical unit area requirements for this type of duty and materials at this stage of the study. The report notes that the equipment list is based on flowsheet diagrams and equipment sizing is based on the mass balance presented.

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Source: Voyager Metals Inc. – Preliminary Economic Assessment on the Mont Sorcier Project, 08 September 2022, Sections 17.1–17.3.