Processing and Recovery Methods Overview
The Constancia Mine employs a conventional copper-molybdenum flotation circuit designed to process 30.8 Mt/a of ore, with average feed grades of 0.39% Cu and 105 g/t Mo. The plant was designed by Ausenco, incorporating a SABC (SAG-ball mill-pebble crusher) comminution circuit, bulk Cu-Mo flotation, molybdenum separation, and concentrate dewatering.
Key Processing Stages & Equipment
1. Primary Crushing:
– Equipment: FLSmidth 63” x 118” gyratory crusher (1,000 kW motor).
– Output: ROM ore crushed to <125 mm.
– Layout: Hillside location for gravity drainage and reduced ROM pad construction costs.
2. Grinding Circuit:
– SAG Mills: Two 36’ x 26.5’ FLSmidth mills (16 MW total power, twin 8 MW motors each).
– Ball Mills: Two 26.5’ x 41’ FLSmidth mills (16 MW total power, twin 8 MW motors).
– Cyclones: FLSmidth Krebs hydrocyclones (26” diameter, 17 per cluster).
– Target Grind: 80% passing 130 µm.
– Pebble Crushing: Installation deferred to 2023–2024 due to softer Pampacancha ore.
3. Bulk Cu-Mo Flotation:
– Rougher Flotation: Two banks of seven Outotec 300 m³ forced-air cells (pH ~10).
– Regrinding: Glencore IsaMill M10,000 (3 MW) for regrinding rougher concentrate.
– Cleaning Circuit:
– 1st cleaner: Four Outotec 130 m³ cells.
– 2nd cleaner: Three Outotec 130 m³ cells.
– 3rd cleaner: Two Eriez CPT column cells (4.88 m diameter x 12 m tall).
– Recovery Targets: ~88–90% Cu recovery (nominal), with optimization projects targeting +3% recovery via froth crowders and regrind upgrades.
4. Molybdenum Separation:
– Conditioning: NaHS (6,500 g/t) and diesel emulsion (10 g/t) for Cu depression/Mo promotion.
– Flotation Stages:
– Rougher: Ten 10 m³ WEMCO cells.
– Cleaners: Five stages (1st to 5th), including a Jameson cell for final cleaning.
– Final Concentrate: Thickened to 60% solids, filtered (LAROX pressure filters), and dried to 5% moisture.
5. Concentrate Handling:
– Copper Concentrate:
– Thickened in a 24 m diameter thickener.
– Filtered via LAROX horizontal plate filters (91.2 t/h capacity, <8.5% moisture).
– Transported by truck (140 trailers, 36 t capacity) to port.
– Molybdenum Concentrate:
– Bagged in 1 m³ bulk bags for transport.
6. Tailings Management:
– Thickening: 75 m diameter thickener (58% solids underflow).
– Pumping: Five centrifugal pumps in series with HDPE-lined steel pipeline.
– Disposal: Gravity-fed to TMF with 12% max pipeline slope to prevent plugging.
Operational Parameters
– Reagents:
– Lime: 1,000 g/t (grinding), pH 11 in cleaners.
– Collectors: Matcol 251M (17 g/t), D101 (12 g/t).
– Frother: RE-100 (30 g/t).
– Power Consumption: 636,000 MW-h/year.
– Water Usage: 0.88 Mm³/year (average).
Innovations & Challenges
– Pebble Crusher Deferral: Softer ore allowed postponement of pebble crusher installation, saving capital.
– Recovery Optimization: Froth crowders, regrind mill upgrades, and column cell adjustments aim to boost Cu recovery by ~3%.
– Safety Measures: NaHS handling protocols (H₂S risk) and molybdenum plant isolation (downwind location).
Throughput & Capacity
– Design Capacity: 30.8 Mt/a (84,400 t/d).
– Grinding Circuit: 1,875 t/h per train (two parallel trains).
– Copper Concentrate Production: ~12,000 t live storage capacity (7 days).
Technical Challenges & Solutions
– Ore Variability: Geometallurgical studies (500 samples) guide pebble crusher installation timing.
– Tailings Pipeline: Low-slope design (12%) prevents blockages during shutdowns.
– Regrind Limitations: IsaMill power draw increase planned to reduce contaminant locking.
This comprehensive circuit integrates robust equipment selection, gravity-driven layouts, and advanced control systems to maximize recovery while addressing operational and safety challenges.
