Overview of Unit Processes in the Concentrator Circuit
The Morenci concentrator processes sulfide ores, utilizing multiple stages to liberate, concentrate, and separate copper and molybdenum. Each unit process, from crushing to flotation, plays a critical role in efficient recovery.
1. Primary Crushing
Process: Ore is transported from the mine to primary crushers, reducing the ore size for downstream processing. Primary crushers handle large chunks of ore, making it easier to manage and further crush.
Equipment: Includes jaw crushers and cone crushers for initial and secondary crushing.
2. Secondary and Tertiary Crushing
Process: After primary crushing, ore moves to secondary and tertiary crushers for finer particle size reduction.
Equipment: Cone crushers and sometimes hydraulic roll crushers (HRC) perform secondary reduction, enhancing copper and molybdenum mineral liberation.
3. Milling (Primary Grinding)
Process: Fine ore is fed to primary ball mills in closed circuit with spiral classifiers, reducing ore size further and liberating copper and molybdenum particles from gangue.
Equipment: Primary ball mills and spiral classifiers. Spiral classifiers segregate coarse and fine particles for additional grinding or flotation.
4. Cyclone Classification
Process: Cyclone classifiers separate finer particles from coarser particles in mill discharge. Coarse particles return to ball mills, while fine particles proceed to flotation.
Purpose: Ensures optimal particle size distribution for flotation.
5. Rougher Flotation
Process: Chemicals are added to create bubbles that adhere to copper and molybdenum particles, lifting them to the surface and separating them from gangue.
Outcome: Rougher concentrate advances to regrind mills for additional size reduction and purification.
6. Regrinding Mills
Process: Rougher concentrate undergoes regrinding to increase particle surface area, enhancing cleaner flotation.
Equipment: High-energy regrind mills achieve the fine grind needed for effective cleaner flotation.
7. Cleaner Flotation
Process: Concentrate passes through cleaner flotation stages to remove impurities and further concentrate copper and molybdenum.
Stages: Multiple cleaner stages produce higher-grade concentrate with cleaner tailings that can be recirculated.
8. Copper/Molybdenum Separation Circuit
Process: Copper/molybdenum concentrate enters a specialized flotation circuit for metal separation, with flotation conditions adjusted for selective copper or molybdenum flotation.
Products: Copper concentrate and molybdenum concentrate, both thickened and filtered before off-site transport.
9. Thickening and Filtration
Thickening: Tailings and concentrates from flotation are thickened for water recovery, recycled back to the concentrator to enhance water efficiency.
Filtration: Filtered copper and molybdenum concentrates are stored for later transportation.
10. Tailings Management
Process: Flotation tailings are thickened and pumped to tailings storage facilities, where process water is recovered and recycled for sustainability.
Technical report and processing history
The following archived source profiles have been consolidated here to preserve the project’s processing history and study context.
Mineral Processing Circuit of Morenci Mine
The technical report explicitly states that recovery methods for the Van Dyke Copper Project are “Not Applicable” in Section 17, indicating that no active processing or recovery methods were being implemented at the time of the report. However, the document provides contextual insights into historical and adjacent operations that may inform potential future recovery approaches for the Van Dyke deposit.
Historical and Adjacent Recovery Methods
1. In-Situ Leaching (ISL):
– The adjacent Miami Unit (BHP Copper, Inc.) historically employed ISL after underground mining ceased in 1959. The method involved leaching copper from the block-caved underground mine and reprocessing historical tailings via hydraulic mining. Operations were discontinued in 2001, with only limited production thereafter.
– The Inspiration Mine (Freeport McMoRan) utilized solution extraction/electrowinning (SX/EW) for leaching, alongside a smelter and rod mill processing cathodes from other Arizona mines.
2. Regional ISL Practices:
– Arizona has hosted multiple ISL projects, including the Pinto Valley, Miami-East, and San Manuel mines, which combined ISL with conventional mining.
– The Florence Copper Project (Taseko Mines Ltd.), 65 km southwest of Van Dyke, is a pilot-scale ISL operation with 24 injection/recovery wells and an SX/EW plant, focusing on environmentally safe copper recovery.
3. Van Dyke’s Historical ISL Tests:
– Phase 1 & 2 ISL tests (Occidental, 1981–1988) and later work by Kocide (1990) are referenced, though specifics on technical parameters (e.g., lixiviant composition, well spacing, recovery rates) are not detailed in this report.
Technical and Operational Context
– Mineralization: The Van Dyke deposit lies within the Miami-Inspiration trend, characterized by supergene chalcocite and oxide copper zones in fractured Proterozoic schist and Tertiary granite.
– Infrastructure: Historic infrastructure includes a cementation plant, drill sites, and the Van Dyke Shaft, though no active processing facilities exist.
– Challenges:
– Environmental Liabilities: Legacy drill sites and leaching infrastructure (pre-1990) pose unresolved risks.
– Data Gaps: The 2019 re-sampling program (2,193 new assays for TCu, ASCu, CNCU) improved resource confidence, but deposit geometry may evolve with further exploration.
Innovation and Future Potential
– The report hints at ISL as a plausible future method, given its success in adjacent deposits and regional projects like Florence Copper. However, no throughput, recovery efficiencies, or equipment specifications are provided for Van Dyke.
Conclusion
While the report lacks direct details on Van Dyke’s processing circuit, it underscores the deposit’s compatibility with ISL/SX-EW methods, drawing parallels to neighboring operations. Key hurdles include environmental remediation and further geological delineation before selecting a recovery strategy.
