The project is designed to use in-situ copper recovery with conventional solvent extraction and electrowinning to produce LME Grade A copper cathode.
Report context
The Florence Copper Project Technical Report is dated March 2023. Section 17 of the report describes the planned recovery method, comprising in-situ copper recovery (ISCR) well field, process ponds, solvent extraction (SX) plant, tank farm, electrowinning (EW) plant, and water treatment plant. The process is based on injection of a lixiviant raffinate solution into the orebody via injection wells, recovery of pregnant leach solution (PLS) through recovery wells, and conventional SX/EW technology to produce copper cathode.
Processing route
In-Situ Copper Recovery Well Field
Raffinate solutions will be pumped to injection wells from the raffinate pond via a network of high-density polyethylene piping. PLS will be extracted from recovery wells by variable speed electric submersible well pumps, collected in a piping network, and delivered to the PLS Pond. From there, PLS will be pumped to the SX plant. Injection and recovery flow rates will be balanced to maintain hydraulic gradients and produce a nominal flow of 11,230 gpm of PLS to the SX plant.
Hydraulic control pumping will be conducted in a series of perimeter wells using variable speed electric submersible pumps. The hydraulic control solution is collected in a dedicated piping network that can be directed to water treatment or the raffinate pond as required.
After copper recovery in an area is completed, rinsing will commence to restore aquifer water quality. The rinsing process uses the same injection and recovery wells as used for copper recovery. A water treatment plant is utilized during rinsing to minimize freshwater requirements.
All wellheads and process solution pipelines will include secondary containment systems and instrumentation and controls to maintain desired operating conditions.
Process Ponds
The PLS and raffinate ponds are located adjacent to and south of the SX plant. The ponds are designed with 36 hours of retention time. They will be constructed with a double high-density polyethylene liner system in accordance with Arizona's Best Available Demonstrated Control Technology standards. The raffinate pond is equipped with a pumping system to deliver raffinate to the well field and with a raffinate organic skimmer system to recover residual organic. The PLS Pond is equipped with a pumping system to feed PLS to the SX plant.
A storm water and event pond will be constructed to the east of the PLS pond to collect all surface runoff from the plant site. A pumping system will transport collected solutions to water treatment.
Solvent Extraction Plant
The SX plant is designed for a nominal PLS flow rate of 11,230 gpm with a PLS grade of 2 grams per liter (g/L) and consists of four mixer-settlers, two after-settlers, and associated facilities. All mixer settlers are equipped with a pumping and mixing system.
PLS feed to the plant will be split to feed two parallel extraction mixer-settlers where it will be mixed with an immiscible organic solution fed in a counterflow series configuration. The organic phase is composed of an aromatic oxime dissolved in a diluent. Following mixing, solutions are directed to the settler for phase separation. The resultant aqueous solution will feed an after-settler to recover entrained organic, then be directed to the raffinate pond and recycled back to the well field following re-acidification.
Loaded organic from the extraction stage is advanced to the stripping stage where lean electrolyte is mixed with the organic solution in two final mixer settlers in a counterflow series configuration. The stripped organic solution is recirculated back to the extraction stage. The enriched electrolyte solution is routed through an after-settler and multi-media electrolyte filters in the tank farm to become feed for the electrowinning plant.
Tank Farm
The tank farm is located north of the SX plant and consists of process tankage and ancillary processes including reagent tanks, electrolyte recirculation pumping system, electrolyte filters, electrolyte heat exchanger, and organic recovery systems. Electrolyte filters prevent solids or organic from SX entering the EW plant. The organic recovery system processes emulsion that accumulates at the organic/aqueous interface in SX settlers.
Electrowinning Plant
The EW plant consists of 70 EW cells constructed of polymer concrete. Each cell will contain 84 stainless steel cathodes and 85 lead alloy anodes. Filtered and heated electrolyte from the tank farm is pumped through the cells in parallel. Two rectifiers produce direct electrical current passed through the cells in series, causing copper to plate onto stainless steel cathode blanks.
Copper is plated over a cycle of approximately one week. Cathodes are removed and carried by crane to an automatic stripping machine that washes and mechanically removes copper sheets from each side of the cathode blank. Copper sheets are weighed, sampled, and bundled for sale.
Water Treatment Plant
Prior to the start of rinsing, Florence Copper will operate a small neutralization circuit equipped with a lime slaking and dosing system to treat excess process solutions before storage and evaporation in process water impoundments. After rinsing commences, a water treatment plant will be brought online to treat excess water produced in the ISCR process to generate water to support ISCR block rinsing activities.
The water treatment plant will consist of an acidic ultrafiltration circuit and acidic reverse osmosis circuit, generating three process streams: permeate, brine, and wash solution. Permeate will be at a quality suitable for well field rinsing. Brine containing dissolved constituents will be recycled back to the process. Wash solution from membrane cleaning cycles, along with excess water not required for rinsing, will be directed to the process water impoundment for evaporation via mechanical evaporators.
Energy Requirements
At full production, the typical power consumption for the project is estimated to be approximately 103 GWh per year. The EW plant accounts for 67% of total consumption, the well field 12%, the SX plant 10%, water management 7.3%, reagents tank farm and ancillaries 3.5%, and neutralization 1.2%.
Key reported parameters
| Parameter | Units | Value | Basis |
|---|---|---|---|
| Nominal PLS flow rate to SX plant | gpm | 11,230 | Design |
| PLS copper grade | g/L | 2 | Design |
| Extracted PLS copper concentration | g/L | 1.8 | Design |
| SX copper extraction (combined) | % | 90 | Design |
| Plant utilization x availability | % | 98 | Design |
| Organic flow | gpm | 6,690 | Design |
| Stripping flowrate (aqueous) | gpm | 6,310 | Design |
| Nominal copper production | Mlb/yr | 85 | Design |
| EW cells | number | 70 | Design |
| Cathode quality | LME Grade A | Design | |
| Current density (nominal/design) | A/ft² | 28/33 | Design |
| Cathodes per cell | number | 84 | Design |
| Anodes per cell | number | 85 | Design |
| Rectifiers | number | 2 | Design |
| Rectifier voltage (nominal) | V | 150 | Design |
| Total rectifier amps (nominal) | A | 58,840 | Design |
| Cell feed copper concentration | g/L | 40 | Design |
| Cell feed sulfuric acid | g/L | 175 | Design |
| Cell feed flowrate (nominal) | gpm/cell | 127 | Design |
| Process water requirement | gpm | 63 | Design |
| Full production power consumption | GWh/yr | 103 | Design |
Project website: https://florencecopper.com/
Technical qualifications
The report describes the proposed design and does not provide historical operating data from a full-scale facility at this site, nor does it present testwork results. Design criteria are presented as planned parameters for the proposed commercial operation. Performance data and economic outcomes are not included in Section 17 of the report.
Source: Florence Copper Project Technical Report, March 2023, Section 17: Recovery Method.
