Casino Project — 2022 Technical Report

The Casino Project is designed as a dual-facility operation processing sulphide ore by conventional flotation to produce copper and molybdenum concentrates, and oxide ore by heap leach and carbon adsorption to produce gold and silver Doré bars and a copper sulphide precipitate.

Report context

The Casino Project technical report is dated 08 August 2022 and covers the design of two processing facilities: one for sulphide ore and one for oxide ore. The report presents process design criteria, major equipment selections, and metallurgical performance projections based on testwork and the proposed mine plan. It does not describe an operating plant; all processing descriptions are for a proposed design.

Processing route

Sulphide ore processing

The sulphide ore processing facility is designed at 120,000 t/d (43,800,000 t/y). The crushing circuit is designed for 80% availability, while grinding and flotation are designed for 93% availability. The crushing rate is 6,667 t/h and the grinding and flotation rate is 5,376 t/h.

Run-of-mine ore at a maximum size of 900 mm is fed to a single 1600 x 3000 TSU Top Service Gyratory Crusher (1,200 kW). Crushed ore to minus 200 mm is stockpiled in a covered conical stockpile containing approximately 75,000 tonnes of live storage. Ore is withdrawn by variable-speed apron feeders to a single grinding line.

Grinding occurs in two stages. A single SAG mill (12.19 m x 8.84 m, 29,000 kW) operates in closed circuit with a trommel, pebble wash screen, and two Raptor XL 1300 pebble crushers (970 kW each). SAG mill product discharges at T80 of 2 to 2.5 mm. Two ball mills (8.5 m x 13.74 m, 22,000 kW each) operate in parallel in closed circuit with hydrocyclones. The final grinding circuit product target is 80% passing 200 microns.

Flotation comprises bulk copper-molybdenum flotation followed by molybdenite separation. The bulk circuit includes 10 copper rougher cells (600 m³ each), 4 pyrite scavenger cells (600 m³ each), 12 first cleaner cells (100 m³ each), 4 second cleaner cells (100 m³ each), and 2 column cells (4.5 m diameter) for third cleaning. Bulk concentrate is reground in two vertical grinding mills (VTM 2250-WB, 1,679 kW each) to 80% passing 25 microns.

The molybdenite flotation circuit receives thickened bulk concentrate. It includes 7 rougher cells (8.5 m³), 7 first cleaner cells (2.83 m³), and column cells for second (2.0 m diameter), third (1.25 m diameter), and fourth (1.0 m diameter) cleaning. Moly concentrate is reground in one SMD 18.5 mill (19 kW) in open circuit. Rougher and first cleaner cells are covered with flotation gas recycling to reduce sodium hydrosulphide and nitrogen consumption.

Copper concentrate (rougher and first cleaner tailings) is thickened in a 45 m diameter high-rate thickener and filtered in three tower-type pressure filters (FLS Pneumapress M30-12, 31.1 m² each). Filter cake is stockpiled and loaded onto highway haul trucks after a wash station. Molybdenum concentrate is filtered in one pressure filter (FLS Pneumapress M19-2, 3.3 m²), dried in a Holo-Flite dryer, and bagged in super-sacks.

Pyrite scavenger concentrate and first cleaner tailing are thickened in a 60 m diameter high-rate thickener and deposited subaqueously in the tailings management facility. Final tailings from pyrite scavenger flotation flow to two 80 m diameter tailings thickeners, then to a cyclone station for sand production or direct deposition.

Process design criteria include life-of-mine plant feed grades of 0.189% copper, 0.023% molybdenum, 0.217 g/t gold, and 1.66 g/t silver. Design head grades are 0.29% copper, 0.024% molybdenum, 0.36 g/t gold, and 2.05 g/t silver.

Reported copper concentrate grade is 28% copper for both supergene and hypogene ores. Molybdenum concentrate grade is 56% molybdenum. Annual concentrate production (life-of-mine) is 264 dry kt copper and 12 dry kt molybdenum. Design annual concentrate production is 390 dry kt copper and 13 dry kt molybdenum.

The sulphide process facility has an estimated total connected load of 146.0 MW and total demand load of 132.0 MW.

Oxide ore processing

The oxide ore processing facility is designed at 9,125,000 t/y. Crushing, conveying, and stacking are designed for 300 days per year at 30,417 t/d (75% availability). Heap leach, ADR, and SART are designed for 365 days per year at 25,000 t/d (98% availability).

Crushing reduces run-of-mine ore (900 mm maximum) to minus 25 mm through three stages: primary gyratory crusher (1100 x 1800 TSU, 450 kW), secondary cone crusher (Raptor XL 1300, 970 kW), and tertiary cone crusher (Raptor XL 1300, 970 kW), with double-deck banana screens at each stage. Lime is added to the fine ore transfer conveyor. Crushed ore is conveyed to a telescoping stacker for placement on the heap leach pad.

The heap leach pad has a storage capacity of 210,000,000 tonnes. Lift height is 8.0 m with a maximum of eight lifts. Leach solution is applied at 12 L/h/m² through drip emitters. Primary leach cycle is 60 days, with secondary leaching through subsequent lifts. Barren solution flow rate averages 1,312 m³/h and pregnant solution flow averages 1,223 m³/h.

Pregnant solution is collected and pumped to a carbon-in-column (CIC) circuit with two parallel trains of five tanks. Gold and silver are adsorbed on activated carbon. A portion of pregnant solution (approximately 150 m³/h) is directed to the SART (Sulphidization, Acidification, Recycling and Thickening) process for copper recovery as copper sulphide precipitate.

Loaded carbon undergoes acid washing, cold stripping to remove copper, and hot pressure Zadra elution. Gold and silver are recovered by electrowinning onto stainless steel mesh cathodes, then smelted in an electric crucible furnace to produce Doré bars. Carbon is regenerated in a horizontal propane-fired kiln.

The SART circuit involves adding sodium hydrosulphide and sulfuric acid to precipitate copper sulphide, which is thickened, filtered, dried, and bagged in super-sacks. The remaining solution is neutralized with lime to precipitate gypsum.

Oxide plant feed grades (life-of-mine) are 0.44 g/t gold, 3.0 g/t silver, and 0.05% copper. Metallurgical performance projections show recoveries of 80% gold, 26% silver, and 18% copper from the heap leach.

The oxide process facility has an estimated total connected load of 12.4 MW and total demand load of 9.8 MW.

Key reported parameters

Technical qualifications

This technical report presents a proposed process plant design, not an operating facility. All metallurgical performance projections are developed from metallurgical test results and the proposed mine plan. No actual operating data from the Casino Project are included. Life-of-mine concentrate production and recovery estimates are based on testwork and projected mine plan grades. Process design criteria, equipment sizing, and availability assumptions are those used for the study presented in the report. The report does not provide current project status, ownership information, or economic analysis.

Source: Casino Project, Form 43-101F1 Technical Report, 08 August 2022, Revision 0, Sections 17 Recovery Methods.