Endako Molybdenum Recovery: Flotation, Regrind & Leaching

Source: Unnamed_Company_87 (2026)
Website: https://moonrivermoly.com/moon-river-moly-ltd-announces-preliminary-economic-assessment-of-potential-restart-of-25-owned-endako-molybdenum-mine/

Critical Data

Overview

The Endako Mine, a joint venture between Moon River (25%) and Centerra Gold Inc. (75%), is a former-producing molybdenum operation located in British Columbia, Canada. With a Preliminary Economic Assessment (PEA) effective November 21, 2025, the project plans to restart processing by reconfiguring and refurbishing two existing facilities—the Old Plant (30,000 tpd) and the New Plant (52,000 tpd)—to achieve a combined capacity of 75,000 tonnes per day (27 million tonnes per annum). Recovery of molybdenum concentrate from mined ore relies on a comprehensive flotation-based flowsheet that integrates crushing, grinding, rougher-scavenger flotation, multi-stage regrinding using IsaMills, column cleaner flotation, and final concentrate leaching with hydrochloric acid. The process achieves an overall molybdenite recovery of 75.8% at a life-of-mine head grade of 0.075% MoS₂. The existing in-pit Kobelco 54-74 gyratory crusher and a new second crusher (54-75) feed a coarse ore stockpile, followed by SAG and ball mill grinding to a target flotation feed size of 200 µm P80. Flotation reagents include diesel oil (collector), pine oil (frother), sodium cyanide (copper depressant), and lime (iron/copper sulphide depressant). Final concentrate is leached, filtered, and dried to 3–5% moisture before shipment to third-party smelters. The restart plan also includes tailings neutralization using alkaline chlorination and dewatering facilities, along with full refurbishment of existing infrastructure. This integrated approach positions the Endako Mine as a significant future producer of high-grade molybdenum concentrate.

Key Process Stages

• Stage 1: Primary Crushing – ROM ore is fed to two gyratory crushers: an existing Kobelco 54-74 (600 kW) relocated to a new building and a new 54-75 crusher (600 kW). Both produce a product with a target P80 of 113 mm. A rock breaker at each dump pocket handles oversize. Crushed material is conveyed via overland conveyors to a 290,000-tonne coarse ore stockpile, providing about 3.6 days of storage at the higher planned throughput.
• Stage 2: Grinding – Ore is reclaimed by four apron feeders and fed to a SAG mill (10.97 m diameter × 5.41 m, 12,750 kW dual pinion) in the New Plant. SAG discharge passes through a 70 mm grate and 19 mm trommel; trommel oversize goes to a pebble crusher (274 kW cone). Combined SAG and ball mill discharge is split: part goes to two main ball mills (6.7 m × 10.36 m, each 8,250 kW) in the New Plant, and a portion is transferred to the Old Plant where six 3.8 m × 4.6 m ball mills (each 1,120 kW) operate in parallel in three sections. All mills run in closed circuit with hydrocyclones to achieve a flotation feed P80 of 200 µm.
• Stage 3: Rougher and Scavenger Flotation – The New Plant houses three parallel banks of 160 m³ flotation cells (two existing, one new row added for the Old Plant feed). Rougher cells (first three per bank) and scavenger cells (remaining four) operate with 21 minutes of design residence time. Cyclone overflow from each mill is fed to dedicated banks. Concentrates from all rows combine by gravity, while tailings report to the tailings management facility.
• Stage 4: Regrinding and Cleaner Flotation – Combined rougher/scavenger concentrate is classified in cyclones; cyclone underflow is reground in two parallel M1000 IsaMills (each 503 kW) to a target P80 of 41 µm (first regrind). The product and cyclone overflow (55 µm P80) feed two parallel first cleaner columns (4.88 m diameter, 14.5 m height). First cleaner concentrate goes to a middlings thickener; tails go to cleaner scavenger cells (three 160 m³). Thickened concentrate is further reground in a second M1000 IsaMill (503 kW) to <16.4 µm P80, then processed in four counter-current cleaner columns (2.44 m diameter, 12.0 m height) operating as second through fifth cleaners. Final concentrate from the fifth cleaner stage is pumped to a 9 m diameter final concentrate thickener, achieving 50% w/w solids.
• Stage 5: Concentrate Leaching, Dewatering, and Drying – Thickener underflow at 50% solids is leached with hydrochloric acid in an agitated tank to remove impurities. The leached slurry is then filtered in a new filter press, producing a cake with 12% moisture. The cake is dried in a new paddle dryer to 3–5% moisture, then packaged for shipment. This new facility is built on the footprint of the former ultra-pure plant and is adjacent to the New Plant. No roasting is used; concentrate is sold to third-party smelters.

Additional Interesting Data and Summary

The Endako Mine’s restart plan leverages existing infrastructure and historical operating experience to deliver a robust processing flowsheet. Key technical parameters include a rougher-scavenger flotation design residence time of 21 minutes, a final concentrate mass pull of 0.06%, and slurry feed flow rates of 7,469 m³/h for rougher flotation. The first regrind mill targets a P80 of less than 55 µm (design 41 µm) and the second regrind mill achieves a P80 finer than 16.4 µm, enabling high-grade final concentrate. Final concentrate cake moisture after filtering is 12% w/w, reduced to 3–5% after drying. The reagent regime uses diesel oil as collector, pine oil as frother, sodium cyanide and hydrated lime as depressants, and flocculant for thickening. Hydrochloric acid is added for concentrate leaching. Tailings are neutralized via alkaline chlorination to oxidize cyanides and thiocyanates, producing non-toxic discharge. The tailings management facility utilizes TP-1 and TP-3 disposal areas with HDPE pipelines and spigots for controlled deposition. Return water from the tailings pond is reclaimed for process use, minimizing fresh water demand from Francois Lake. Process plant manpower is estimated at 118 personnel (operations and maintenance). The site is connected to the BC Hydro grid via a 69 kV, 84 MW substation, with existing electrical infrastructure requiring only minor repairs to a breaker. Environmental considerations include complete tailings detoxification and water recycling. Economically, the project targets an average annual molybdenite production of 15,300 tonnes, driven by a combined processing capacity that was historically demonstrated to exceed 88,000 tonnes milled in a single day. The restart includes installation of a second primary crusher to eliminate crushing bottlenecks, addition of rougher flotation capacity, and reconfiguration of Old Plant rod mills to ball mills. Future outlook for the Endako Mine is positive, with the integrated use of both plants allowing scalable production and the ability to adapt to market conditions. The facility’s significance lies in its proven flotation and regrind technology—including IsaMills and column flotation—combined with modern concentrate leaching and drying, positioning it as a competitive molybdenum producer in North America.

Key Processes: Flotation, Cyanidation, Gravity Separation, SAG Mill, Ball Mill, Crushing

Target Commodities: Gold, Copper