Nussir Copper Processing: Grinding and Flotation Recovery Methods

Source: Blue Moon Metals Inc (2026)
Website: https://bluemoonmetals.com/project/nussir/

Critical Data

Overview

The Nussir Project, operated by Blue Moon Metals Inc., is a significant copper mine development located at Øyen, Norway, utilizing the former Ulveryggen Mine processing facilities from the 1970s. The feasibility study, updated by Worley in 2026, defines a conventional grinding and flotation flowsheet designed to treat 2 million tonnes per annum (Mtpa) of ore. Ore is crushed underground to 80% passing 110 mm and conveyed to a refurbished ore silo with a live capacity of approximately 3,600 m³, providing 24 hours of surge capacity. The processing plant operates 8,000 hours per year at 91.5% availability, with a nominal throughput of 250 tph. The design copper head grade is 1.0% Cu, with an average life-of-mine grade of 0.81% Cu. The recovery method centers on two-stage wet grinding in a SAG mill (6.0 m diameter × 4.5 m EGL, 2.7 MW) and a ball mill (4.7 m diameter × 7.05 m EGL, 2.7 MW) to achieve a primary grind P80 of 100 microns. Subsequent froth flotation, including rougher, regrind, and two stages of cleaner flotation, upgrades the copper minerals to a high-grade concentrate. The concentrate is thickened in a 6 m diameter high-rate thickener and filtered to 8–10% moisture via a pressure filter for bulk shipment. Tailings are thickened in a 25 m diameter thickener and discharged into the adjacent fjord. This modernized plant builds on over a decade of engineering studies, positioning the Nussir Project as a future low-carbon copper producer in Scandinavia.

Key Process Stages

• Stage 1: Underground Crushing and Conveying – Ore is crushed underground to a P80 of 110 mm and transferred by belt conveyors to the existing ore silo. Excess ore is diverted to an uncovered stockpile for front-end loader reclaim. Tramp metal is removed by an overband magnet before the SAG mill feed conveyor.
• Stage 2: Ore Storage and Reclaim – The refurbished ore silo (6,000 m³ nominal, 3,600 m³ live capacity) stores crushed ore. Four variable-speed vibrating feeders reclaim ore onto the SAG mill feed conveyor. A belt weigher and feedback control maintain the set-point feed rate. Stockpile reclaim uses a front-end loader and hopper feeder to deliver ore when silo capacity is exceeded.
• Stage 3: Grinding and Classification – A two-stage wet grinding circuit: SAG mill (6.0 m i/s shell, 4.5 m EGL, 2.7 MW variable speed) with 10–15% charge volume of 125 mm forged steel balls, and ball mill (4.7 m i/s shell, 7.05 m EGL, 2.7 MW variable speed) with up to 36% charge volume of 60 mm balls. The SAG mill trommel undersize combines with ball mill discharge; hydrocyclones (7 × 500 mm, 5 working) classify overflow to P80 of 100 microns at 30–35% solids. Trash screening protects downstream flotation.
• Stage 4: Flotation (Rougher, Regrind, Cleaners) – Rougher flotation uses 7 × 50 m³ forced-air tank cells with reagent conditioning. Rougher concentrate is reground in a stirred mill (355 kW) to a P80 of 25–30 microns using 3 mm ceramic media. First cleaner (3 × 5 m³ cells) and second cleaner (2 × 5 m³ cells) produce final concentrate. Cleaner-scavenger (2 × 5 m³) tailings return to regrind. On-stream analysers monitor grades and particle size.
• Stage 5: Concentrate Dewatering and Tailings Disposal – Final concentrate is thickened in a 6 m diameter high-rate thickener to 60–65% solids, then filtered in a fully automatic pressure filter (26 chambers, 1200×1200 mm plates, 40 mm depth) to 8–10% moisture. Filter cake is stockpiled (5,000 t capacity) for bulk carrier shipment. Tailings are thickened in a 25 m diameter thickener (unit settling rate 0.509 tph/m²) and pumped via pipeline for deep fjord deposition; thickener overflow is recycled to the process.

Additional Interesting Data and Summary

The Nussir process plant is designed to treat 2 Mtpa of copper ore with a nominal throughput of 250 tph and 91.5% annual availability. The grinding circuit sizing was evaluated by SGS, Metso, and Worley, with the selected design based on the 75th percentile Bond ball mill work index and a conservative approach to account for the harder Ulveryggen ore component. The SAG mill is configured for future retrofitting of a pebble crusher. Flotation circuit sizing provides 26.5 minutes of rougher flotation time (scale-up factor 2.2) and 7.5 minutes per cleaner stage. The regrind mill is designed with a specific energy of 15.4 kWh/t for the rougher concentrate. Concentrate dewatering benchmarked against similar projects supports a 6 m thickener and a pressure filter with 26 chambers capable of processing daily concentrate in two shifts. Tailings thickening uses a 25 m diameter thickener based on a unit settling rate of 0.509 tph/m², with thickener overflow water recovered for reuse. The plant is located at Øyen, reusing existing infrastructure from the 1970s Ulveryggen mine, reflecting a sustainable approach to brownfield development. Tailings are disposed via deep fjord deposition, an environmentally managed solution aligned with Norwegian regulations. The Nussir Project aims to produce a high-grade copper concentrate (8–10% moisture) for export by bulk carrier. Future outlook includes potential installation of a pebble crusher and continued optimization of flotation reagents to maintain concentrate quality. The feasibility study, effective April 2026, confirms the project’s technical viability and positions Blue Moon Metals to become a significant European copper supplier with low carbon intensity due to hydropower availability. The processing facility’s design emphasizes reliability, energy efficiency, and compliance with modern environmental standards, supporting the region’s mining heritage while advancing sustainable mineral extraction.

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

Target Commodities: Copper