Copper Flotation Recovery Methods at Black Butte Project

Source: Sandfire Resources America Inc (2026)
Website: https://blackbuttecopper.com/

Critical Data

Overview

Sandfire Resources America Inc., through its wholly-owned Black Butte Copper Project in Montana, USA, is advancing a conventional copper sulphide flotation concentrator to treat underground ore from the Johnny Lee deposit. The plant, designed at a processing rate of 150 dry t/h (1.2 Mt/a), will produce an average of 129,000 t/a of copper concentrate at 22.5% Cu. The project, which forms the basis of a NI 43-101 Preliminary Feasibility Study effective November 5, 2025, leverages industry-standard comminution and flotation technologies to maximize recovery and produce a marketable concentrate for export via road to port. The process flowsheet integrates a primary jaw crusher, a two-stage SAG and ball mill grinding circuit with a target P80 of 38 microns, and a copper flotation circuit using rougher, scavenger, and three stages of cleaning with a Jameson cell operating as a flash cleaner ahead of regrind. Overall copper recovery averages 85.8% over the life of mine at a head grade of 2.9% Cu. The plant operates 24 hours per day with design availabilities of 70% for crushing and 92% for grinding. Tailings are thickened and converted to cemented paste for underground backfill or storage in a Cemented Tailings Facility (CTF), underscoring the project’s commitment to sustainable and responsible mining practices. The recovery methods described are based on extensive test work and simulation by Orway Mineral Consultants, ensuring robust, energy-efficient processing of the massive sulphide ore.

Key Process Stages

• Stage 1: Crushing – Run-of-mine ore is fed to a 90 t ROM bin and discharged via apron feeder onto a 1.12 m wide vibrating grizzly (64 mm bar spacing). Grizzly oversize (67% of feed) reports to a single toggle jaw crusher (CJ411) with a 100 mm closed side setting, producing a crushed product P80 of 99 mm. Grizzly undersize bypasses the crusher. Crushed material is conveyed to a 2,500 t coarse ore bin for 16.7 hours surge capacity. The circuit treats 270 t/h with an impact crush work index of 10.7 kWh/t.
• Stage 2: Grinding – A two-stage SAG and ball mill circuit achieves a primary grind P80 of 38 µm. The SAG mill (6.10 m Ø x 3.05 m EGL) is equipped with a 2,000 kW variable speed motor and grate discharge (25 mm grates; 12 mm trommel apertures). Pebbles are crushed and returned. SAG mill discharge is screened at 2 mm to control transfer size (T80: 600 µm). The ball mill (5.50 m Ø x 8.10 m EGL, 4,600 kW installed, fixed speed, 75% critical speed, 27% ball charge) operates in closed circuit with 250 mm cyclones at 250% circulating load. Cyclone overflow at 35% solids feeds flotation. Total specific comminution energy is 35.4 kWh/t.
• Stage 3: Copper Flotation – Flotation feed (P80 38 µm) enters a conditioning tank then reports to rougher/scavenger circuit: three rougher and four scavenger tank cells (each 30 m³). pH is maintained at 9.5 using lime. Collector Aero 3477 is added stage-wise; depressants sodium monophosphate and dextrin minimize pyrite and carbonaceous gangue recovery. Rougher/scavenger concentrate (9–11% Cu) is pumped to a Jameson cell (E2532/6) acting as a flash cleaner, recovering 53% of copper directly to final concentrate at 26.2% Cu. Jameson tailings are reground in an M5000 IsaMill™ to P80 10–15 µm. Three stages of cleaning follow: first cleaner (five 16 m³ cells plus two cleaner scavenger cells), second cleaner (four 8 m³ cells), third cleaner (three 4.3 m³ cells). Final third cleaner concentrate combines with Jameson concentrate to yield 22.5% Cu at 85.8% recovery (LOM average).
• Stage 4: Concentrate Dewatering – Final copper concentrate is thickened in a 12 m diameter high-rate thickener with auto-dilution and flocculant addition, achieving 57% solids. Thickened concentrate is stored in a 300 m³ agitated tank (18-hour capacity). Filter feed pumps deliver slurry to a Lorax PF60-60 pressure filter (33 mm chamber depth) to produce filter cake at 10% moisture. Filter cake is discharged into sealable containers, loaded onto trucks via front-end loader, and weighed before transport to port. Filtrate returns to the concentrate thickener.
• Stage 5: Tailings Thickening & Paste Backfill – Copper scavenger tailings and cleaner scavenger tailings are thickened in an 18 m diameter high-rate thickener to 55–60% solids. Additional streams from water treatment, paste plant, and CTF decant water also feed the thickener. Overflow is recycled as process water. Thickened tailings are pumped to a 300 m³ paste filter feed tank, then dewatered via two Ishigaki MCDGC 2100 x 100/40 horizontal plate-and-frame filters. Filtered tailings are mixed with granulated blast furnace slag and Portland cement to produce cemented paste for underground backfill or for the Cemented Tailings Facility (CTF), reducing surface tailings storage.

Additional Interesting Data and Summary

The Black Butte Copper Project’s recovery methods are underpinned by a comprehensive process design basis that prioritizes energy efficiency, high metallurgical performance, and environmental stewardship. The flotation circuit employs a selective reagent suite including Aero 3477 collector, MIBC frother, and depressants sodium monophosphate and dextrin to ensure high-grade concentrate while rejecting pyrite and carbonaceous gangue. A six-stream Courier on-stream analyzer provides real-time elemental data for process control, integrated with a Citect SCADA system. Concentrate is dewatered to 10% moisture using a Lorax PF60-60 pressure filter, and final product is transported in sealed containers via road to port for export. Tailings management is a key sustainability feature: thickened tailings (55–60% solids) are filtered and mixed with granulated blast furnace slag and Portland cement to create cemented paste for underground backfill or for placement in a Cemented Tailings Facility (CTF), reducing long-term surface tailings footprint. The process plant includes an 80 t lime silo, automated mixing systems for flocculant and dextrin, and an antiscalant injection system to protect process water lines. Water supply is integrated with underground dewatering treated by a reverse osmosis plant (114 m³/h), with treated water used for process makeup and infiltration gallery recharge. The Preliminary Feasibility Study (effective November 5, 2025) confirms the technical viability of the flowsheet, with a design availability of 92% for the grinding circuit and 70% for crushing. The project’s location in Montana, near existing infrastructure, supports efficient concentrate logistics. Forward-looking statements indicate ongoing optimization of reagent dosing and regrind energy to further improve recovery and concentrate grade. The paste backfill system significantly reduces surface tailings storage requirements, aligning with modern sustainable mining practices. The annual concentrate production of 129,000 t at 22.5% Cu positions Black Butte as a significant domestic copper supplier. The integrated control systems and automated reagent handling ensure consistent metallurgical performance, while the adoption of Jameson cell flash cleaning improves circuit efficiency by recovering over half of the copper before regrind. Overall, the recovery methods demonstrate a robust, conventional yet optimized approach to copper sulphide beneficiation, with strong environmental safeguards and economic viability for long-term operations.

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

Target Commodities: Copper